In vitro evaluation of the early erosive lesion in polished and natural human enamel Dent. Mater. (IF 4.039) Pub Date : 2018-07-07 P. Mylonas, R.S. Austin, R. Moazzez, A. Joiner, D.W. Bartlett
ObjectiveThis study evaluated the capability of profilometry, microhardness, Optical Coherence Tomography (OCT) and Tandem Scanning Confocal Microscopy (TSM) in characterising the early erosive lesion in polished and natural human enamel in vitro.MethodsPolished (n = 60) and natural (n = 60) human enamel surfaces, were immersed and agitated in 0.3% citric acid erosion at 0 s, 10 s, 30 s, 60 s, 120 s, and 300 s (n = 10). Changes in the surface were measured with 3D-step height change (μm), surface roughness (μm), surface microhardness (KHN), and images were assessed qualitatively with OCT and TSM.ResultsMean (SD) 3D-step height change (μm) was measurable for polished enamel at: 60 s (0.24 ± 0.1), 120 s (1.16 ± 0.71), 300 s (2.01 ± 0.47; p < 0.05); a step height change was not detectable on acid challenged natural enamel surfaces. Mean (SD) surface roughness (μm) of polished enamel was detected at 10 s (0.270 ± 0.013; p < 0.05) and all erosion periods; and in natural enamel detected after 120 s (0.830 ± 0.125) and 300 s (0.800 ± 0.140; p < 0.005). Polished enamel Mean (SD) microhardness (KHN) statistically significantly decreased at all time points (p < 0.001); this was unmeasurable for natural enamel. Qualitative image analysis of both surface types indicated erosive change at the surface level, with progression after increasing erosion time.SignificanceThe early erosive lesion in polished enamel could be characterised quantitatively surface roughness and microhardness and qualitatively using OCT and TSM; whilst in natural enamel only surface roughness could be utilised. Further investigation of early erosion in natural enamel is required to develop new more clinically relevant models.
Antimicrobial photodynamic active biomaterials for periodontal regeneration Dent. Mater. (IF 4.039) Pub Date : 2018-06-30 B.W. Sigusch, S. Dietsch, A. Berg, A. Voelpel, A. Guellmar, U. Rabe, M. Schnabelrauch, D. Steen, B. Gitter, V. Albrecht, D.C. Watts, S. Kranz
ObjectiveBiomaterials for periodontal regeneration may have insufficient mechanical and antimicrobial properties or are difficult to apply under clinical conditions. The aim of the present study was to develop a polymeric bone grafting material of suitable physical appearance and antimicrobial photodynamic activity.MethodsTwo light curable biomaterials based on urethane dimethacrylate (BioM1) and a tri-armed oligoester-urethane methacrylate (BioM2) that additionally contained a mixture of β-tricalcium phosphate microparticles and 20 wt% photosensitizer mTHPC (PS) were fabricated and analyzed by their compressive strength, flexural strength and modulus of elasticity. Cytotoxicity was observed by incubating eluates and in direct-contact to MC3T3-E1 cells. Antimicrobial activity was ascertained on Porphyromonas gingivalis and Enterococcus faecalis upon illumination with laser light (652 nm, 1 × 100 J/cm2, 2 × 100 J/cm2).ResultsThe compressive strength, flexural strength and elastic modulus were, respectively, 311.73 MPa, 22.81 MPa and 318.85 MPa for BioM1 + PS and 742.37 MPa, 7.58 MPa and 406.23 MPa for BioM2 + PS. Both materials did not show any cytotoxic behavior. Single laser-illumination (652 nm) caused total suppression of P. gingivalis (BioM2 + PS), while repeated irradiation reduced E. faecalis by 3.7 (BioM1 + PS) and 3.1 (BioM2 + PS) log-counts.SignificanceBoth materials show excellent mechanical and cytocompatible properties. In addition, irradiation with 652 nm induced significant bacterial suppression. The manufactured biomaterials might enable a more efficient cure of periodontal bone lesions. Due to the mechanical properties functional stability might be increased. Further, the materials are antimicrobial upon illumination with light that enables a trans-mucosal eradication of residual pathogens.
Delayed post-curing stage and oxygen inhibition of free-radical polymerization of dimethacrylate resin Dent. Mater. (IF 4.039) Pub Date : 2018-06-29 Mikke K. Aromaa, Pekka K. Vallittu
Objective It is known that after light-initiated free radical polymerization of a dimethacrylate monomer system, the curing continues for some period of time after the curing light emission has stopped (so-called delayed post-curing stage, DPCS). It is also known that during free radical polymerization, the presence of oxygen effectively inhibits polymerization of monomers. However, less is known of the influence of oxygen inhibition of light initiated polymerization during the DPCS. The aim of this study was to determine some polymerization related properties of a resin system during the DPCS. Methods Monomer systems of BisGMA-TEGDMA (60/40%) with light sensitive initiator-activator (camphorquinone-amine) system were polymerized by light-initiation (wavelength average 430–480 nm) with a radiation intensity of 1200 mW/mm2 for 20 s on the ATR sensor of the fourier transform infrared (FTIR) spectrometer. After light curing, the samples were divided into two groups: the DPCS stage was allowed to continue in air (O2-exposed group) or the samples were protected from the direct effect of air (O2-protected group). The degree of monomer conversion (DC%) was monitored from the sample surface up to 360 min from both groups of samples (n = 6). Sample surfaces were additionally analyzed for surface microhardness (VHN) at four time-points corresponding to time-points of the DC% measurement (n = 6). Results After ending the light-curing of 20 s, i.e. during the DPCS, the DC% still increased from 50% to 65% in the O2-protected group, whereas no increase was seen in the O2-exposed group. Surface microhardness increased from 2.99 to 9.10 VHN of the O2-protected samples and to 4.80 of the O2-exposed samples during a 6-h period. Surface microhardness differed significantly between the groups (p < 0.005). There was significant correlation between the microhardness and DPCS (O2-protected r = 0.950; O2-exposed r = 0.940, p < 0.001). A correlation was also found between degree of conversion values and DPCS time (O2-protected r = 0.941; for O2-exposed r = 0.780, p < 0.001). Significance The results of this study suggested that O2-inhibition of free radical polymerization of dimethacrylate resin occurred after ending the curing light emission. This correlated with a lower surface microhardness of the polymer when the DPCS continued under air-exposure.
On the systematic documentation of the structural characteristics of bovine enamel: A critic to the protein sheath concept Dent. Mater. (IF 4.039) Pub Date : 2018-06-27 Ezgi D. Yilmaz, Jasmin Koldehoff, Gerold A. Schneider
The common structural description of bovine enamel used in materials science studies – nano-sized hydroxyapatite crystallites form micron-sized prisms surrounded by protein sheaths, which in turn build a complex decussation pattern – overlook many important morphological information. This hampers the correct interpretation of the data determined by mechanical analysis. For a profound structural description of enamel morphology, the visualization of its building blocks by high-resolution electron microscopy and focused-ion beam tomography technique, which reveals their form, orientation and configuration at different regions of a tooth (cut in different directions), is undertaken in this work. We adapted here the paleontological classification system and terminology developed for the description of enamel microstructures seen in different species, and accordingly documented the morphological singularities of bovine incisor enamel. The appearance of the boundary regions between crystallites and prisms contradicts to the well-known protein sheath concept. Neighboring crystallites and prisms are not separated by prominent gap zones but they are largely in contact with each other. Proteins might exist within the pores of 20–30 nm in size, which are distributed inhomogeneously through the boundary regions, rather than as protein sheaths covering each crystallite and prism.
Effect of high-intensity curing lights on the polymerization of bulk-fill composites Dent. Mater. (IF 4.039) Pub Date : 2018-06-28 Mindy O. Daugherty, Wen Lien, Michael R. Mansell, Douglas L. Risk, Daniel A. Savett, Kraig S. Vandewalle
ObjectivesThe purpose of this study was to investigate the effect of high-irradiance light-curing-units (LCUs) on the depth-of-cure (DoC) and degree-of-polymerization (DoP) of bulk-fill composites (BFCs).MethodsThe DoC of composites (Beautifil-Bulk, SHOFU; Filtek-Bulk-Fill, 3 M ESPE; Tetric-EvoCeram-Bulk-Fill, Ivoclar; Sonic-Fill-2, Kerr; Venus-Bulk-Fill, Heraeus; Z250, 3M-ESPE) were measured according to ISO-4049 using high-irradiance LCUs (FlashMax-P3, CMS-Dental; SPEC3, Coltene) and conventional LCU (Paradigm, 3M-ESPE) for exposure times: 3/9-s, 3/20-s, and 10/20-s respectively. Using FTIR, the DoP per composite was measured at the bottom surface as a function of post-curing times for the LCUs at the same exposure times. Data was analyzed with nonlinear regression and ANOVA/Tukey.ResultsSignificant differences in DoC were found amongst the LCUs for the various exposure times. All BFCs failed to meet the DoC claimed by manufacturers and failed to satisfy ISO-4049 with the high-irradiance LCUs with 3-s exposures. Standard irradiance and 20-s exposures outperformed all other irradiance-exposure combinations for maximizing the DoC and DoP of BFCs. A minimum of 15.3 J/cm2 radiant exposure was required to achieve an adequate maximum polymerization rate. Venus Bulk exhibited the highest DoC and DoP for any LCU-exposure-time combination.SignificanceAmong the different combinations of BFCs and LCUs, DoC and DoP were always increased with longer exposure time, but there exists a theoretical radiant-exposure limit beyond which DoP or DoC remains unchanged. However, high DoC or DoP are not always associated with one another. Thus, the exposure-reciprocity law must be approached thoughtfully since irradiance and exposure can independently affect DoP and DoC.
Hydration dependent mechanical performance of denture adhesive hydrogels Dent. Mater. (IF 4.039) Pub Date : 2018-06-28 Fengfeng Zhang, Yiran An, Nima Roohpour, Asa H. Barber, Julien E. Gautrot
ObjectiveHydration in denture adhesives regulates the formation of complex morphologies and mechanical function. Multiscale experimental approaches are required to evaluate the impact of hydration on the inherent heterogeneity of denture adhesive-based hydrogels at different length scales and the impact of such phenomena on adhesion performance.MethodsThe morphology of hydrated denture adhesives was examined via cryo-scanning electron microscopy (cryo-SEM). The rheological and thermodynamic behaviour of bulk hydrated deture adhesives was examined by rheology and differential scanning Calorimetry (DSC). The microscopic mechanical properties of the denture adhesives were characterised by atomic force microscopy (AFM) and compared to the properties measured at the macroscopic scale.ResultsThe rheological and mechanical properties of commerically available denture adhesive hydrogels were found to be critically dependent on both the formulation of the adhesives and their hydration level. Clear progression of phase separation was observed in hydrated denture adhesives as hydration increased and changed the mechanical properties of the adhesives at multiple length scales. The adhesives displaying more heterogeneous structures, which were associated with the presence of hydrophobic and organic compounds in the formulation, exhibited more variable mechanical behaviour and weaker rheological properties, but stronger adhesive properties.SignificanceOur results are important in defining the relationships between hydrophilicity, hydration, mechanical and adhesive properties of denture adhesives, allowing the development of improved chemical formulations that control the fixation of dentures.
Post-curing in dental resin-based composites Dent. Mater. (IF 4.039) Pub Date : 2018-06-23 William Germscheid, Louis Gosse de Gorre, Braden Sullivan, Catherine O’Neill, Richard B. Price, Daniel Labrie
Objective To determine the post-curing in six commercial contemporary resin-based composites (RBCs) using axial shrinkage, the degree of conversion, and Vickers hardness. Methods Five Bulk Fill and one conventional RBCs from three companies were selected with a wide range of filler volume content. The axial shrinkage of samples that were 1.00 mm thick by 9–10 mm diameter was measured using a modified bonded disk method over a time between 15 h and 19 h at temperatures of 26 °C and 34 °C (mouth temperature). The degree of conversion (DC) was collected continuously for 10 min using mid-infrared spectroscopy in the attenuated total reflectance geometry. Vickers hardness was measured at 1 h post-irradiation using a load of 300 gf. For all three tests, the samples were irradiated at five exposure times, 20, 5, 3, 1.5 and 1 s with a light curing unit radiant exitance of 1.1 W/cm2. Three samples (n = 3) were used for each experimental condition. Results After light exposure, the axial shrinkage and degree of conversion exhibited a functional time dependence that was proportional to the logarithm of time. This suggests an out-of-equilibrium polymer composite glass that is transitioning to thermal equilibrium. At a sufficiently long time and among the RBCs investigated, the shrinkage related physical aging rate was found to vary between 1.34 and 2.00 μm/log(t). The rate was a function of the filler content. Furthermore, 15 h after light exposure, the post-curing shrinkage was estimated to be an additional 22.5% relative to the shrinkage at 100 s for one RBC at T = 34 °C. The hardness in the photo-cured RBC was varied by using different light exposure times. The first two experimental techniques show that the higher the initial DC 10 min after light exposure, the smaller is the post-curing shrinkage related and DC related physical aging rates. A direct correlation was observed between the shrinkage related and the DC related physical aging rates. Significance Post-curing shrinkage should be evaluated for longer than 1 h. The post-curing shrinkage 15 h after light exposure in dental RBCs can be appreciable. The long-term development of built-in stress within the tooth wall structure may shorten the restoration’s lifespan.
Impact of crystallization firing process on the microstructure and flexural strength of zirconia-reinforced lithium silicate glass-ceramics Dent. Mater. (IF 4.039) Pub Date : 2018-06-23 Hilton Riquieri, Jaiane Bandoli Monteiro, Diogo Cabecinha Viegas, Tiago Moreira Bastos Campos, Renata Marques de Melo, Guilherme de Siqueira Ferreira Anzaloni Saavedra
Objectives The aim of this study was to characterize the microstructure of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics and evaluate their mechanical properties before and after the crystallization firing process (CFP). Methods Field emission-scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed for microstructural characterization. To evaluate the pattern of crystallization and the molecular composition of ZLS glass-ceramics, was used X-ray diffraction (XRD). Vickers hardness, fracture toughness by the indentation method, and biaxial flexural strength were also measured. One hundred and forty ceramic discs were produced (diameter = 12 mm; thickness = 1.2 mm) and allocated among four groups (n = 30): Sfir, Sunf-ZLS Vita Suprinity; and Cfir and Cunf-ZLS Celtra Duo; fired and unfired, respectively. Statistical analysis was performed and Weibull failure probabilities were calculated. Results Cfir showed the highest characteristic strength (251.25 MPa) and hardness (693.333 ± 10.85 GPa). Conversely, Sunf presented the lowest characteristic strength (106.95 MPa) and significantly lowest hardness (597.533 ± 33.97 GPa). According to Weibull analysis, Sunf had the highest structural reliability (m = 7.07), while Sfir presented the lowest (m = 5.38). The CFP was necessary to crystallize zirconia in the partially crystallized ZLS glass-ceramics. Sfir had a lower percentage of crystallized zirconia than did Cfir. Fractographic analyses showed that all failures initiated from an inherent critical defect in Sunf and from processing defects in the remaining groups. Significance The CFP had a direct influence on the flexural strength and microstructural characteristics of both ZLS materials.
Should adhesive debonding be simulated for intra-radicular post stress analyses? Dent. Mater. (IF 4.039) Pub Date : 2018-06-23 Ricardo A. Caldas, Atais Bacchi, Valentim A.R. Barão, Antheunis Versluis
In vitro degradation of a biodegradable polylactic acid/magnesium composite as potential bone augmentation material in the presence of titanium and PEEK dental implants Dent. Mater. (IF 4.039) Pub Date : 2018-06-22 Tycho Zimmermann, Ana Ferrandez-Montero, Marcela Lieblich, Begoña Ferrari, José Luis González-Carrasco, Wolf-Dieter Müller, Andreas Dominik Schwitalla
Objective The aim of this study was to assess the degradation behavior by measuring the H2 release of a biodegradable composite consisting of a polylactic acid matrix reinforced with 30% wt. spherical magnesium microparticles (PLA/Mg) as potential bone augmentation material in combination with dental implants of either titanium or polyetheretherketone (PEEK) in order to evaluate the potential influence of the titanium dental implants on the corrosion behavior of the Mg particles within the PLA matrix. Methods Three PEEK dental implants and three titanium dental implants were put into a central perforation of six PLA/Mg-discs. These samples were incubated at 37 °C for 30 days in McCoy’s 5A modified medium and the H2 release was evaluated. Results Between day 7 and day 16 the average H2 release per cm2 of the surface of the PLA/Mg-samples in combination with the titanium implants was significantly higher than that of the sample group combined with the implants of PEEK (3.1 ± 0.4 ml vs. 2.8 ± 0.4 ml). This significant difference disappeared afterwards, whereas the H2 release was highest at day 30 and amounted 3.5 ± 0.7 ml/cm2 for the group with the titanium implants and 3.2 ± 0.8 ml/cm2 for the group with the PEEK implants. Significance Regarding the similar values of the degradation depending H2 release of the two implant material groups, the co-implantation of a PLA/Mg composite is not only possible with new metal-free implant materials such as PEEK, but also with conventional implants of titanium.
Experimental tricalcium silicate cement induces reparative dentinogenesis Dent. Mater. (IF 4.039) Pub Date : 2018-06-22 Xin Li, Mariano Simón Pedano, Bernardo Camargo, Esther Hauben, Stéphanie De Vleeschauwer, Zhi Chen, Jan De Munck, Katleen Vandamme, Kirsten Van Landuyt, Bart Van Meerbeek
Objectives To overcome shortcomings of hydraulic calcium-silicate cements (hCSCs), an experimental tricalcium silicate (TCS) cement, named ‘TCS 50’, was developed. In vitro research showed that TCS 50 played no negative effect on the viability and proliferation of human dental pulp cells, and it induced cell odontogenic differentiation. The objective was to evaluate the pulpal repair potential of TCS 50 applied onto exposed minipig pulps. Methods Twenty permanent teeth from three minipigs were mechanically exposed and capped using TCS 50; half of the teeth were scheduled for 7-day and the other half for 70-day examination (n = 10). Commercial hCSCs ProRoot MTA and TheraCal LC were tested as references (n = 8). Tooth discoloration was examined visually. After animal sacrifice, the teeth were scanned using micro-computed tomography; inflammatory response at day 7 and day 70, mineralized tissue formation at day 70 were assessed histologically. Results Up to 70 days, TCS 50 induced no discoloration, ProRoot MTA generated gray/black discoloration in all teeth. For TCS 50, 40.0% pulps exhibited a mild/moderate inflammation at day 7. No inflammation was detected and complete reparative dentin with tubular structures was formed in all pulps after 70 days. ProRoot MTA induced a similar response, TheraCal LC generated a less favorable response in terms of initial inflammation and reparative dentin formation; however, these differences were not significant (Chi-square test of independence: p > 0.05). Significance TCS 50 induced reparative dentinogenesis in minipig pulps. It can be considered as a promising pulp-capping agent, also for aesthetic areas.
Correlation of resin viscosity and monomer conversion to filler particle size in dental composites Dent. Mater. (IF 4.039) Pub Date : 2018-06-22 Eric Habib, Ruili Wang, X.X. Zhu
Objective The viscosity of dental resin composites is important in their formulation and clinical use; it depends on the filler particle size and loading. We intend to study the viscosity and conversion of composites made of low dispersity spherical silica fillers. Methods Experimental dental resin composites were formulated using low dispersity spherical silica particles of graded sizes (75, 150, 500, 350, 500, 1000 nm) at several loading levels with resins based on Bis-GMA and UDMA. Their rheological properties and double bond conversion were measured with a rheometer and differential scanning calorimeter, respectively. Results The complex viscosity of the unpolymerized pastes can be fit to an extended Krieger–Dougherty equation that includes an adjustment factor to account for filler particle surface area. This relationship is also extended to estimate the degree of conversion, where the calculated or experimental viscosity is used to predict the resulting conversion. Significance The enhanced understanding of the relationship of filler size, composite viscosity, and monomer conversion will allow improved accuracy in the prediction of the properties of dental resin composite formulations to obtain ideal viscosity for their clinical use and a high degree of conversion.
Fatigue behavior of ultrafine tabletop ceramic restorations Dent. Mater. (IF 4.039) Pub Date : 2018-06-19 F.O. Abu-Izze, G.F. Ramos, A.L.S. Borges, L.C. Anami, M.A. Bottino
Objective The goal of this study was to investigate the fatigue life, failure modes, and stress distribution of partial ultrafine restorations for posterior teeth in different ceramics. Methods Sixty standard tabletop preparations in epoxy resin G10 received lithium-silicate-based zirconia-reinforced (ZLS) or hybrid ceramic (PIC) restorations in 0.5- or 1-mm thickness bonded with resin cement. The same cycling protocol was applied for all specimens, which consisted of 5000 cycles at 200 N, followed by 450-N cycles until the specimens’ fracture or the suspension of the test after 1.5 × 106 cycles. Axial load was carried out with a 4 Hz frequency in Biocycle V2 equipment (Biopdi, São Carlos, SP), with samples immersed in water. The presence of cracks and/or fractures was checked every 2.5 × 105 cycles, and the survival analysis was performed with the number of cycles in which each specimen failed. All specimens were evaluated by stereomicroscopy and scanning electron microscopy (SEM). After data tabulation, Kaplan–Meier and Mantel–Cox (log-rank test) analyses were performed, followed by multiple pairwise comparison, all with a significance level of 5%, and Weibull analysis. Through three-dimensional finite element analysis, stress distribution and maximum principal stresses in the posterior occlusal veneers were evaluated by comparison of different types of substrate (G10, enamel/dentin, enamel), thicknesses, and ceramic materials. Results Zirconium-reinforced lithium silicate restorations with 0.5-mm thickness (ZLS.5) showed lower fatigue strength compared with that of 1.0-mm hybrid ceramic restorations (PIC1), and both were similar to other restorations (PIC.5 and ZLS1) (log-rank test, χ2 = 11.2; df = 3; p = 0.0107 < 0.05). ZLS groups presented random defects that culminated in fracture, whereas PIC groups presented defects that increased with mechanical fatigue after some cycling time. Stereomicroscope images show radial cracks due to the translucency of the material. There was no damage caused by the applicator. MPS (maximum principal stress) distributions were similar for the different substrate types, but the highest modulus of elasticity showed slightly lower stress concentration. Significance PIC is more likely to be used in thinner thickness than indicated by the manufacturer, with fatigue strength similar to that of thicker ZLS restorations.
Influence of different low-pressure plasma process parameters on shear bond strength between veneering composites and PEEK materials Dent. Mater. (IF 4.039) Pub Date : 2018-06-20 Friederike Bötel, Tycho Zimmermann, Mona Sütel, Wolf-Dieter Müller, Andreas Dominik Schwitalla
Objective The aim of this study was to evaluate the impact of oxygen and argon/oxygen low-pressure plasma on the shear bond strength (SBS) between dental PEEK compounds and veneering composites as a function of plasma process time. Methods Of an unfilled PEEK (“Juvora”) and two pigment powder filled PEEK compounds (“DC4420”, “DC4450”), 273 rectangular plates were prepared and polished up to 1200 grit. Afterwards the samples were sandblasted and randomly assigned to five different surface pre-treatment groups (1. No plasma (control); 2. O2 plasma for 3 min; 3. O2 plasma for 35 min; 4. Ar/O2 plasma for 3 min; 5. Ar/O2 plasma for 35 min). Surface roughness and water contact angles were recorded using three samples of each PEEK compound for each of the plasma treatment groups. An adhesive (visio.link, Bredent GmbH & Co KG, Senden, Germany) was applied onto the specimen surfaces and light cured. A mold was used to shape three different veneering composites (a) Vita VM LC, “Vita” (Vita Zahnfabrik, Bad Säckingen, Germany); (b) GC GRADIA, “Gradia” (GC Europe, Leuven, Belgium); (c) GC GRADIA DIRECT Flo, “Gradia Flo” (GC Europe, Leuven, Belgium)) into a cylindrical form on the sample surface before light curing. SBS was measured using a universal testing machine after 24 h of incubation in distilled water at 37 °C. Results The two pigment filled PEEK compounds treated with O2 plasma and veneered with Gradia Flo showed the highest SBS values (34.92 ± 6.55 MPa and 34.2 ± 1.87 MPa) followed by the combination of the unfilled PEEK material with Gradia Flo (29.57 ± 3.71 MPa). The SBS values of the samples veneered with Gradia were lower, but not significantly so. The SBS values of the specimens with Vita were for the most part associated with significantly lower results. Significance A low-pressure plasma process using oxygen plasma for a duration of 35 min, preceded by sandblasting, seems to be the most effective in increasing shear bond strength between veneering composites and PEEK materials.
CAD-FEA modeling and analysis of different full crown monolithic restorations Dent. Mater. (IF 4.039) Pub Date : 2018-06-20 Amanda Maria de Oliveira Dal Piva, João Paulo Mendes Tribst, Alexandre Luiz Souto Borges, Rodrigo Othávio de Assunção e Souza, Marco Antonio Bottino
Objectives To investigate the influence of different materials for monolithic full posterior crowns using 3D-Finite Element Analysis (FEA). Methods Twelve (12) 3D models of adhesively-restored teeth with different crowns according to the material and its elastic modulus were analysed: Acrylic resin, Polyetheretherketone, Composite resin, Hybrid ceramic, pressable and machinable Zirconia reinforced lithium silicate, Feldspathic, Lithium disilicate, Gold alloy, Cobalt–Chromium alloy (Co–Cr), Zirconia tetragonal partially stabilized with yttria, and Alumina. All materials were assumed to behave elastically throughout the entire deformation. Results in restoration and cementing line were obtained using maximum principal stress. In addition, maximum shear stress criteria was used for the cementing line. Results Restorative materials with higher elastic modulus present higher stress concentration inside the crown, mainly tensile stress on an intaglio surface. On the other hand, materials with lower elastic modulus allow stress passage for cement, increasing shear stress on this layer. Stiffer materials promote higher stress peak values. Significance Materials with higher elastic modulus such as Co–Cr, zirconia and alumina enable higher tensile stress concentration on the crown intaglio surface and higher shear stress on the cement layer, facilitating crown debonding.
Effect of thiourethane filler surface functionalization on stress, conversion and mechanical properties of restorative dental composites Dent. Mater. (IF 4.039) Pub Date : 2018-06-20 André L. Faria-e-Silva, Andressa dos Santos, Angela Tang, Emerson M. Girotto, Carmem S. Pfeifer
Objectives This study evaluated the efficacy of a thiourethane(TU)-modified silane agent in improving properties in filled composites. Methods The TU-silane agent was synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene and 3-(triethoxysilyl)propyl isocyanate with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiol and alkoxy silane groups. Barium glass fillers (1 μm average particle size) were functionalized with 5 wt% TU-silane in an acidic ethanol solution. Commercially available 3-(trimethoxysilyl)propyl methacrylate (MA-silane) and (3-mercaptopropyl)trimethoxysilane (SH-silane), as well as no silane treatment (NO-silane), were used as controls. Composites were made with BisGMA-UDMA-TEGDMA (5:3:2), camphorquinone/ethyl-4-dimethylaminobenzoate (0.2/0.8 wt%) and di-tert-butyl hydroxytoluene (0.3 wt%) and 70 wt% silanated inorganic fillers. Polymerization stress (PS) was measured using a cantilever beam apparatus (Bioman). Methacrylate conversion (DC) and rate of polymerization (RP) during photoactivation (800 mW/cm2) were followed in real-time with near-IR. Flexural strength/modulus (FS/FM) were evaluated in three-point bending with 2 × 2 × 25 mm. Statistical analysis: 2-way ANOVA/Tukey’s test (α = 5%). Results DC, Rpmax and E were similar for all groups tested. FS was similar for the TU- and MA-silane, which were statistically higher than the untreated and SH-silane groups. Stress reductions in relation to the MA-silane were observed for all groups, but statistically more markedly for the TU-silane material. This is likely due to stress relaxation and/or toughening provided at the filler interface by the oligomeric TU structure. Significance TU-silane oligomers favorably modified conventional dimethacrylate networks with minimal disruption to existing curing chemistry, in filled composites. For the same conversion values, stress reductions of up to 50% were observed, without compromise to mechanical properties or handling characteristics.
Effect of an acidic sodium salt on the polymerization behavior of self-adhesive resin cements formulated with different adhesive monomers Dent. Mater. (IF 4.039) Pub Date : 2018-06-21 Pedro Paulo Albuquerque Cavalcanti de Albuquerque, Ezequias Costa Rodrigues, Luis Felipe Schneider, Rafael Ratto Moraes, Paulo Francisco Cesar, Leonardo Eloy Rodrigues Filho
Objective To determine the influence of benzenesulfinic acid sodium salt 98% (BAS) and the activation mode on the polymerization behavior of experimental self-adhesive resin cements (SARCs) formulated with distinct self-etch methacrylates. Materials and methods Three catalyst-pastes using different self-etch methacrylates (2MP — bis 2-(methacryloyloxy) ethyl phosphate; 4META — 4-methacryloxyethyl trimellitic acid anhydride; and GDMAP — 1,3-glycerol dimethacrylate phosphate) and four base-pastes were formulated from the incorporation of different amounts of BAS associated to N-N-dihydroxyethyl-p-toluidine (DHPT). BAS/DHPT ratios were blended respectively based on the following final weight (wt%): control (0.0;2.0%), BP1 (0.5;1.5%), BP2 (0.8;1.2%) and BP3 (1.0;1.0%). Real-time polymerization kinetics (KP) was assessed for 10 min by FTIR spectroscopy. Maximum rate of polymerization (Rpmax) was obtained from the first derivative of the curve conversion versus time. Degree of conversion (DC) was determined over 10 min and after 24 h. SARCs were tested in self and dual activation modes. Data of Rpmax and DC 24 h were respectively analyzed by two-way ANOVA followed by Tukey’s method (α = 0.05). Results All factors and their interactions were statistically significant (p < 0.01). BAS caused an increase in DC in the first minutes of the KP analysis, especially in self-activated groups. After 24 h, all groups showed higher DC than those observed in the first 10 min. In general, the addition of BAS increased the Rpmax. The GDMAP-based materials group showed the highest Rpmax values when exposed to light but self-activated formulations with GDMAP or 2MP showed the lowest Rpmax. Significance The addition of BAS increased the degree of conversion of SARCs in the first minutes and 24 h after the polymerization reaction. This finding showed the importance of adding this type of salt during resin cement production to achieve better polymerization in the first minutes of the luting procedure specially when light exposure is not possible.
Novel magnetic nanoparticle-containing adhesive with greater dentin bond strength and antibacterial and remineralizing capabilities Dent. Mater. (IF 4.039) Pub Date : 2018-06-21 Yuncong Li, Xiaoyi Hu, Yang Xia, Yadong Ji, Jianping Ruan, Michael D. Weir, Xiaoying Lin, Zhihong Nie, Ning Gu, Radi Masri, Xiaofeng Chang, Hockin H.K. Xu
Objectives A nanoparticle-doped adhesive that can be controlled with magnetic forces was recently developed to deliver drugs to the pulp and improve adhesive penetration into dentin. However, it did not have bactericidal and remineralization abilities. The objectives of this study were to: (1) develop a magnetic nanoparticle-containing adhesive with dimethylaminohexadecyl methacrylate (DMAHDM), amorphous calcium phosphate nanoparticles (NACP) and magnetic nanoparticles (MNP); and (2) investigate the effects on dentin bond strength, calcium (Ca) and phosphate (P) ion release and anti-biofilm properties. Methods MNP, DMAHDM and NACP were mixed into Scotchbond SBMP at 2%, 5% and 20% by mass, respectively. Two types of magnetic nanoparticles were used: acrylate-functionalized iron nanoparticles (AINPs); and iron oxide nanoparticles (IONPs). Each type was added into the resin at 1% by mass. Dentin bonding was performed with a magnetic force application for 3 min, provided by a commercial cube-shaped magnet. Dentin shear bond strengths were measured. Streptococcus mutans biofilms were grown on resins, and metabolic activity, lactic acid and colony-forming units (CFU) were determined. Ca and P ion concentrations in, and pH of biofilm culture medium were measured. Results Magnetic nanoparticle-containing adhesive using magnetic force increased the dentin shear bond strength by 59% over SBMP Control (p < 0.05). Adding DMAHDM and NACP did not adversely affect the dentin bond strength (p > 0.05). The adhesive with MNP + DMAHDM + NACP reduced the S. mutans biofilm CFU by 4 logs. For the adhesive with NACP, the biofilm medium became a Ca and P ion reservoir. The biofilm culture medium of the magnetic nanoparticle-containing adhesive with NACP had a safe pH of 6.9, while the biofilm medium of commercial adhesive had a cariogenic pH of 4.5. Significance Magnetic nanoparticle-containing adhesive with DMAHDM and NACP under a magnetic force yielded much greater dentin bond strength than commercial control. The novel adhesive reduced biofilm CFU by 4 logs and increased the biofilm pH from a cariogenic pH 4.5–6.9, and therefore is promising to enhance the resin–tooth bond, strengthen tooth structures, and suppress secondary caries at the restoration margins.
Endocrown restorations: Influence of dental remnant and restorative material on stress distribution ☆ Dent. Mater. (IF 4.039) Pub Date : 2018-06-21 João Paulo Mendes Tribst, Amanda Maria de Oliveira Dal Piva, Camila Ferreira Leite Madruga, Marcia Carneiro Valera, Alexandre Luiz Souto Borges, Eduardo Bresciani, Renata Marques de Melo
Objective The goal of this study was to evaluate the stress distribution in a tooth/restoration system according to the factors “amount of dental remnant” (3 levels) and “restorative material” (2 levels). Methods Three endodontically treated maxillary molars were modeled with CAD software for conducting non-linear finite element analysis (FEA), each with a determined amount of dental remnant of 1.5, 3, or 4.5 mm. Models were duplicated, and half received restorations in lithium disilicate (IPS e.max CAD), while the other half received leucite ceramic restorations (IPS Empress CAD), both from Ivoclar Vivadent (Schaan, Liechtenstein). The solids were imported to analysis software (ANSYS 17.2, ANSYS Inc., Houston, TX, USA) in STEP format. All contacts involving the resin cement were considered no-separation, whereas between teeth and fixation cylinder, the contact was considered perfectly bonded. The mechanical properties of each structure were reported, and the materials were considered isotropic, linearly elastic, and homogeneous. An axial load (300 N) was applied at the occlusal surface (triploidism area). Results were determined by colorimetric graphs of maximum principal stress (MPS) on tooth remnant, cement line, and restoration. Results MPS revealed that both factors influenced the stress distribution for all structures; the higher the material’s elastic modulus, the higher the stress concentration on the restoration and the lower the stress concentration on the cement line. Moreover, the greater the dental crown remnant, the higher the stress concentration on the restoration. Thus, the remaining dental tissue should always be preserved. Significance In situations in which few dental remnants are available, the thicker the restoration, the higher the concentration of stresses in its structure, protecting the adhesive interface from potential adhesive failures. Results are more promising when the endocrown is fabricated with lithium disilicate ceramic.
An analytical model to design circumferential clasps for laser-sintered removable partial dentures Dent. Mater. (IF 4.039) Pub Date : 2018-06-21 Ammar A. Alsheghri, Omar Alageel, Eric Caron, Ovidiu Ciobanu, Faleh Tamimi, Jun Song
Objective Clasps of removable partial dentures (RPDs) often suffer from plastic deformation and failure by fatigue; a common complication of RPDs. A new technology for processing metal frameworks for dental prostheses based on laser-sintering, which allows for precise fabrication of clasp geometry, has been recently developed. This study sought to propose a novel method for designing circumferential clasps for laser-sintered RPDs to avoid plastic deformation or fatigue failure. Methods An analytical model for designing clasps with semicircular cross-sections was derived based on mechanics. The Euler–Bernoulli elastic curved beam theory and Castigliano’s energy method were used to relate the stress and undercut with the clasp length, cross-sectional radius, alloy properties, tooth type, and retention force. Finite element analysis (FEA) was conducted on a case study and the resultant tensile stress and undercut were compared with the analytical model predictions. Pull-out experiments were conducted on laser-sintered cobalt–chromium (Co–Cr) dental prostheses to validate the analytical model results. Results The proposed circumferential clasp design model yields results in good agreement with FEA and experiments. The results indicate that Co–Cr circumferential clasps in molars that are 13 mm long engaging undercuts of 0.25 mm should have a cross-section radius of 1.2 mm to provide a retention of 10 N and to avoid plastic deformation or fatigue failure. However, shorter circumferential clasps such as those in premolars present high stresses and cannot avoid plastic deformation or fatigue failure. Significance Laser-sintered Co–Cr circumferential clasps in molars are safe, whereas they are susceptible to failure in premolars.
Influence of fluoride on the mineralization of collagen via the polymer-induced liquid-precursor (PILP) process Dent. Mater. (IF 4.039) Pub Date : 2018-06-21 Neha Saxena, Maegan A. Cremer, Evan S. Dolling, Hamid Nurrohman, Stefan Habelitz, Grayson W. Marshall, Laurie B. Gower
Bonding to caries affected dentine Dent. Mater. (IF 4.039) Pub Date : 2018-06-08 Naghmeh Meraji, Mohammad H. Nekoofar, Kazem Ashofteh Yazdi, Mohammad Reza Sharifian, Noushin Fakhari, Josette Camilleri
Objectives Dentine replacement materials are often placed over caries affected dentine (CAD). The aim of this study was to compare the bonding characteristics and interactions of selected hydraulic calcium silicate-based dentine replacement materials to CAD and sound dentine. Methods Three hydraulic calcium silicate-based dentine replacement materials were assessed: Retro MTA, Biodentine and Theracal LC. Material characterization was done by scanning electron microscopy and X-ray diffraction analyses. Blocks of sound and CAD were prepared and standardized by Vickers microhardness testing. Half of the affected and sound dentine blocks were pretreated with 5.25% NaOCl prior to material placement. The materials were stored either for 1 week or 24 weeks in 37 °C in fully saturated conditions. Shear bond strength was assessed at both time periods. Radiopacity of the interfacial dentine was also evaluated to assess the remineralization potential of the dentine replacement materials. Results The reaction of Theracal was slower than that of the water-based materials. The bond strengths of different materials did not differ after 1 week (P > 0.05). The bond strength of Biodentine and Retro MTA increased over time but no change was observed for Theracal. NaOCl pre-treatment deteriorated the bond strength to sound dentine but improvement was observed in affected dentine. Radiopacity changes were observed after 24 weeks. Significance Biodentine and Retro MTA showed better bonding to CAD. Pretreatment with NaOCl improved the bond strength of dentine replacement materials to CAD.
Modal analysis for implant stability assessment: Sensitivity of this methodology for different implant designs Dent. Mater. (IF 4.039) Pub Date : 2018-06-08 Elisabetta Maria Zanetti, Stefano Ciaramella, Michele Calì, Giulia Pascoletti, Massimo Martorelli, Riccardo Asero, David C. Watts
Objective To investigate the influence of implant design on the change in the natural frequency of bone-implant system during osseointegration by means of a modal 3D finite element analysis. Methods Six implants were considered. Solid models were obtained by means of reverse engineering techniques. The mandibular bone geometry was built-up from a CT scan dataset through image segmentation. Each implant was virtually implanted in the mandibular bone. Two different models have been considered, differing in the free length of the mandibular branch (‘long branch’ and ‘short branch’) in order to simulate the variability of boundary conditions when performing vibrometric analyses. Modal analyses were carried out for each model, and the first three resonance frequencies were assessed with the respective vibration modes. Results With reference to the ‘long branch’ model, the first three modes of vibration are whole bone vibration with minimum displacement of the implant relative to bone, with the exception of the initial condition (1% bone maturation) where the implant is not osseointegrated. By contrast, implant displacements become relevant in the ‘short branch’ model, unless osseointegration level is beyond 20%. The difference between resonance frequency at whole bone maturation and resonance frequency at 1% bone maturation remained lower than 6.5% for all modes, with the exception of the third mode of vibration in the ‘D’ implant where this difference reached 9.7%. With reference to the ‘short branch’, considering the first mode of vibration, 61–68% of the frequency increase was achieved at 10% osseointegration; 72–79% was achieved at 20%; 89–93% was achieved at 50% osseointegration. The pattern of the natural frequency versus the osseointegration level is similar among different modes of vibration. Significance Resonance frequencies and their trends towards osseointegration level may differ between implant designs, and in different boundary conditions that are related to implant position inside the mandible; tapered implants are the most sensitive to bone maturation levels, small implants have very little sensitivity. Resonance frequencies are less sensitive to bone maturation level beyond 50%.
Modification of the restoration protocol for resin-based composite (RBC) restoratives (conventional and bulk fill) on cuspal movement and microleakage score in molar teeth Dent. Mater. (IF 4.039) Pub Date : 2018-05-30 I. Politi, L.E.J. McHugh, R.S. Al-Fodeh, G.J.P. Fleming
Objective To modify the resin-based composite (RBC) restoration protocol for standardised Class II cavities in third molar teeth restored using conventional RBCs or their bulk fill restorative counterparts. Employing cuspal deflection using a twin channel deflection measuring gauge (during) and microleakage to determine marginal integrity (following) RBC restoration, the modified restoration protocol results were compared with traditional (oblique) restoration of Class II cavities. Methods Thirty-two sound third molar teeth, standardised by size and morphology, were subjected to standardised Class II cavity preparations and randomly allocated to four groups. Restorations were placed in conjunction with a universal bonding system and resin restorative materials were irradiated with a light-emitting-diode light-curing-unit. The cumulative buccal and palatal cuspal movements from a twin channel deflection measuring gauge were summed, the restored teeth fatigued thermally prior to immersion in 0.2% basic fuchsin dye for 24 h, before sectioning and examination for microleakage. Results Teeth restored using conventional RBC materials had significantly higher mean total cuspal movement values compared with bulk fill resin restorative restoration (all p < 0.0001). Teeth restored with Admira Fusion and Admira Fusion x-tra had significantly the lowest microleakage scores (all p < 0.001) compared with Tetric EvoCeram and Tetric EvoCeram Bulk Fill restored teeth. The microleakage scores for the range of RBC materials tested were significantly reduced (all p < 0.001) when the modified RBC restoration protocol was employed compared with the traditional Class II restoration technique. Significance Modification of the RBC restoration protocol of some conventional RBCs and bulk fill resin restoratives significantly improve bond integrity and could be translated as a validation of the limited clinical studies available on bulk fill materials in the dental literature where Class II cavities perform less well than Class I cavities following extended follow-up. Clinical significance The results of the current study add further weight to experimental protocols employing cuspal movement (during) and cervical microleakage (following) RBC restoration of standardised cavities in natural dentition to provide an indication of polymerization shrinkage stress at the tooth/RBC restoration interface in a ‘clinically meaningful context’.
Internal adjustments decrease the fatigue failure load of bonded simplified lithium disilicate restorations Dent. Mater. (IF 4.039) Pub Date : 2018-05-28 Camila da Silva Rodrigues, Luís Felipe Guilardi, Andressa Cargnelutti Follak, Catina Prochnow, Liliana Gressler May, Luiz Felipe Valandro
Objective To investigate the effect of intaglio surface adjustment of simplified lithium disilicate ceramic restorations adhesively cemented to a dentin-like material on its fatigue behavior. Methods Ceramic discs (IPS e.max CAD) were prepared and an in-Lab simulation of machining roughness was performed by grinding with SiC paper (#60). Ceramic discs were divided into 4 groups according to the internal adjustment of the cementation surface: no adjustments (CTRL); adjustment with a medium (M), fine (F), or extra fine (FF) diamond bur. Dentin-like material discs were also produced. Ceramic disc intaglio surfaces were etched (5% hydrofluoric acid; 20 s) and received a silane coating. Dentin-like material discs were etched (10% hydrofluoric acid; 1 min) and received a primer coating. Pairs of ceramic/dentin-like material were adhesively cemented (Multilink Automix), and fatigue failure load tests were performed using the Staircase approach (250,000 cycles; 20 Hz). Roughness, topographic and fractographic analyses were performed. Statistical analyses were carried out through ANOVA tests. Results All ground groups (M = 521.3 N; F = 536.9 N; FF = 676.2 N) presented lower fatigue failure load values than the control (1241.6 N). M diamond bur created a rougher surface than F (Ra and Rz parameters). However, FF was similar to F and M for Ra, and similar to F for Rz. Significance Bur adjustments on the intaglio surface of simplified lithium disilicate ceramic restorations greatly decreased the fatigue failure load even using an extra-fine diamond bur. Care should be taken when internal adjustments are needed.
The effect of desiccation on water sorption, solubility and hygroscopic volumetric expansion of dentine replacement materials Dent. Mater. (IF 4.039) Pub Date : 2018-05-24 Ruba Mustafa, Ruwaida Z. Alshali, Nick Silikas
Objective To evaluate water sorption, solubility and hygroscopic expansion and the effect of desiccation for a calcium silicate-based material, a conventional glass ionomer, and a resin-modified glass ionomer. Methods Water sorption, solubility and hygroscopic expansion of Biodentine™ (BD), GC Fuji IX GP® FAST (FJ), and Ionolux (IO) were tested under two pre-storage conditions: with desiccation and without desiccation. Disc-shaped samples (n = 5) were immersed in water and weighed at different time intervals (1 h, 24 h, 3 d, 7 d and 30 d) and hygroscopic expansion was recorded at 7 d and 30 d. Data were analysed using Factorial repeated measures ANOVA, one-way/two-way ANOVA, Independent samples t-test and Tukey’s post hoc test (α = 0.05). Results With desiccation, sorption of IO and FJ was 124.33 μg/mm3 and 79.97 μg/mm3 respectively. Solubility was −12.36 μg/mm3 for IO and −20.19 μg/mm3 for FJ. Hygroscopic expansion was 3.01% for IO and −2.35% for FJ. Without desiccation, sorption was in the order: IO ˃ BD ˃ FJ (130.35 μg/mm3, 122.07 μg/mm3, and 107.21 μg/mm3 respectively), while solubility order was: BD ˃ FJ ˃ IO (154.83 μg/mm3, 88.82 μg/mm3, and 25.67 μg/mm3 respectively). IO and FJ showed significant difference in sorption and solubility between the two pre-storage treatment groups (p ˂ 0.005). Hygroscopic expansion was in the order: IO ˃ BD ˃ FJ. Significance BD had the highest solubility while IO had the least. The relatively stable polymeric resin in IO may contribute to its low solubility but high hygroscopic expansion. Desiccation had significant effect on sorption, solubility and volumetric expansion of water-based materials.
Structure–properties relationships in dental adhesives: Effect of initiator, matrix monomer structure, and nano-filler incorporation Dent. Mater. (IF 4.039) Pub Date : 2018-05-22 Elham Azad, Mohammad Atai, Mojgan Zandi, Parvin Shokrollahi, Laleh Solhi
Objectives This is a confirmatory study to evaluate the effect of photoinitiator type and concentration, matrix monomer chemical structure, and nanoparticle incorporation on the physical and mechanical properties of an experimental dentin bonding agent. Materials and methods Different concentrations of camphorquinone-amine (CQ-A) system, butanedione (BD), and phenylpropanedione (PPD), as photoinitiator, BTDMA, as a comonomer containing carboxylic acid groups, and silica nanoparticles as reinforcing inorganic filler were incorporated into a methacrylate base experimental dental adhesive. The effect of these ingredients, as independent variables, on the shrinkage kinetics, flexural strength and modulus, and microshear bond strength of the adhesives were then investigated. The results were analyzed using one-way ANOVA and Tukey’s post-hoc test at the significance level of 0.05. Results The results indicate that the efficiency of CQ-A initiator system is diminished in the presence of the acidic monomer BTDMA while the photopolymerization is efficiently progressed with BD as initiator. PPD shows the lowest efficiency in the photopolymerization of the adhesives. BTDMA as a monomer with the capability of interaction with tooth structure provides adhesive with improved microshear bond strength to dentin. Incorporation of silica nanoparticles at low concentrations enhances the flexural and microshear strength of the dentin bonding agent. Significance Understanding the structure–property relationship in dental adhesives may help the material selection in clinical dentistry. The study elucidates the relationship between monomer structure, initiator type, and nanofiller and physical and mechanical properties in dental adhesives.
Effect of selective carious tissue removal on biomechanical behavior of class II bulk-fill dental composite restorations Dent. Mater. (IF 4.039) Pub Date : 2018-05-21 Paula Fernanda Damasceno Silva, Lais Rani Sales Oliveira, Stella Sueli Lourenço Braga, Cácia Signori, Steve R. Armstrong, Carlos José Soares, Maximiliano Sérgio Cenci, André Luis Faria-e-Silva
Objectives This study aimed to develop a method to induce carious lesions in the pulpal floor dentin of a class II cavity preparation, and to determine the effects of this carious lesion on the biomechanical behavior of the dental composite restoration. Methods The pulpal floor dentin of class I cavities in sound third molars were demineralised with acetic acid for 35 days followed by a 7-day exposure to pooled human saliva biofilm and demineralization was verified by micro-CT. Subsequently, the proximal walls were removed forming a class II cavity and the caries lesion was left intact or was completely removed prior to restoration with a bulk-fill dental composite (n = 10). Cuspal deflection was assessed by strain-gauge and micro-CT imaging. The presence of enamel cracks was assessed by transillumination before and after restoration, and again after 1,200,000 cycles of mechanical fatigue in a chewing simulator. Finally, resistance to fracture by axial compressive loading and failure mode was determined. Data were analyzed by 2-way repeated measures ANOVA, Fisher’s exact test, and t-test (α = 0.05). Results The presence of carious lesions had no significant effect upon cuspal deflection, formation of enamel cracks, and fracture strength of the dental composite restorations. The restorative procedure increased the number of enamel cracks, which was not affected by mechanical cycling. Significance Maintaining carious lesions does not affect the biomechanical behavior of class II restorations performed with bulk-fill dental composite.
Mechanical behavior of CAD/CAM occlusal ceramic reconstruction assessed by digital color holography Dent. Mater. (IF 4.039) Pub Date : 2018-05-21 H. Xia, P. Picart, S. Montresor, R. Guo, J.C. Li, O. Yusuf Solieman, J.-C. Durand, M. Fages
Synthesis of silver-containing calcium aluminate particles and their effects on a MTA-based endodontic sealer Dent. Mater. (IF 4.039) Pub Date : 2018-05-19 Luiza Helena S. Almeida, Rafael R. Moraes, Renata D. Morgental, Sérgio S. Cava, Wellington Luiz O. Rosa, Patrícia Rodrigues, Anderson S. Ribeiro, Marcus Só, Fernanda G. Pappen
Objective To synthetize calcium aluminate (C3A) and silver-containing C3A particles (C3A + Ag) testing their effects on the properties of a MTA-based endodontic sealer in comparison to an epoxy resin- and a calcium silicate-based sealer. Methods Pure C3A and C3A + Ag particles were synthesized by a chemical method and characterized using XRD to identify crystalline phases. SEM/EDS analysis investigated morphology, particle size, and elemental composition of particles. Setting time, flow, radiopacity, water sorption and solubility of commercial and modified sealers were evaluated according to ISO 6876/2012. The pH and ions release were measured using a pHmeter and a microwave induced plasma optical emission spectrometer. The inhibition of biofilm growth was evaluated by confocal laser scanning microscopy (CLSM). Data were rank transformed and analyzed by ANOVA and Tukey test (P < 0.05). Results The C3A particles showed an irregular grain agglomerated structure with voids and pores. In C3A + Ag particles, Ag modified the material morphology, confirming the deposition of Ag. The physicochemical properties of the modified MTA-based sealer were similar to the commercial material, except for the significant increase in Ca+2 release. However, there was no Ag release. Setting time, flow, radiopacity, water sorption and solubility were adequate for all materials. All the materials showed alkaline pH. Antibiofilm effect was improved in the presence of C3A particles, while the biofilm inhibition was lower in the presence of Ag. Significance The modified sealer presented improved antibiofilm properties and calcium release, without dramatic effects on the other characteristics. It is expected a positive effect in its antimicrobial behavior.
Biodegradation of resin–dentin interfaces is dependent on the restorative material, mode of adhesion, esterase or MMP inhibition Dent. Mater. (IF 4.039) Pub Date : 2018-05-19 Bo Huang, Dennis G. Cvitkovitch, J. Paul Santerre, Yoav Finer
Objective To measure the effect of simulated human salivary esterases (SHSE) and metalloproteinases (MMP) inhibition on the integrity of restoration–tooth interfaces made from traditional or polyacid-modified resin composites bonded to human dentin by either total-etch or self-etch adhesives. Methods Resin–dentin specimens, made from traditional (Z250) or polyacid-modified (Dyract-eXtra) composites were bonded to human dentin using total-etch (TE-Scotchbond) or self-etch (SE-EasyBond) adhesives. TE was applied with or without the MMP inhibitor galardin. Specimens were incubated in phosphate-buffer or SHSE (37 °C/pH = 7.0) for up to 180 days, then suspended in a continuous flow biofilm fermenter cultivating biofilms of Streptococcus mutans UA159. Interfacial bacterial penetration, biofilm biomass and viability were measured by confocal laser scanning microscopy and biomarker dyes and used as interfacial biodegradation markers. Results All specimens showed increased biofilm penetration and biomass with time regardless of incubation condition. SHSE increased bacterial penetration in all experimental samples after 180 days (p < 0.05). Galardin reduced interfacial bacterial ingress and bacterial biomass vs. non-MMP-inhibited TE-bonded specimens (p < 0.05). TE interfaces showed lower interfacial bacterial biomass vs. SE after 90-day and 180-day (p < 0.05). Dyract-eXtra specimens showed lower bacterial cell viability within the interface vs. Z250 (p < 0.05). Significance The biodegradation of resin–tooth interfaces is accelerated by esterases, modulated by MMP inhibition and is dependent on the material’s chemistry and mode of adhesion. The in vitro bacterial growth model used in this study facilitates the elucidation of differences in interfacial integrity and biostability between different materials and techniques and is suitable for assessment of their performance prior to clinical evaluation.
Fatigue failure load of an adhesively-cemented lithium disilicate glass-ceramic: Conventional ceramic etching vs etch & prime one-step primer Dent. Mater. (IF 4.039) Pub Date : 2018-05-19 Maitê Munhoz Scherer, Catina Prochnow, Andressa Borin Venturini, Gabriel Kalil Rocha Pereira, Thiago Augusto de Lima Burgo, Marília Pivetta Rippe, Luiz Felipe Valandro
Objectives To evaluate the effect of different glass-ceramic surface treatments and aging on the fatigue failure load of a lithium disilicate glass-ceramic adhesively cemented to a dentin analogue material. Methods One hundred and twenty (120) disc-shaped lithium disilicate specimens (Ø = 10 mm, thickness = 1.5 mm) were produced and randomly allocated (n = 20) into 6 groups, considering 2 study factors: “surface treatment” in 3 levels (SIL—silane application only; HF5+SIL—5% hydrofluoric acid etching and silane application; ME&P—etching with an one-step ceramic primer), and “storage” in 2 levels (baseline—storage for 7 days; aging—storage for 90 days + 12,000 thermal cycles). Ceramic discs were adhesively cemented to discs of a dentin analogue material (Ø = 10 mm, thickness = 2.0 mm) following the manufacturers’ instructions. The fatigue failure load was determined by the staircase approach (250,000 cycles; 20 Hz; initial load = 1050 N [∼70% of mean load-to-failure]; step size = 52.5 N [5% of initial load]). Micro-morphologic, fractographic, and atomic force microscope analysis were also performed. Fatigue failure load data were evaluated by one-way ANOVA, Bonferroni and t-tests for independent samples. Results HF5+SIL presented higher fatigue failure load in both conditions (baseline and aging); ME&P presented intermediary mean values, while the SIL group presented the worst performance. All groups had a statistically significant decrease in the fatigue performance after aging. Significance Hydrofluoric acid followed by silane application showed the best fatigue performance for an adhesively-cemented lithium disilicate ceramic. Aging negatively influenced the fatigue performance for all tested groups.
Promoting porcelain–zirconia bonding using different atmospheric pressure gas plasmas Dent. Mater. (IF 4.039) Pub Date : 2018-05-18 Yi-Chuan Liu, Jung-Pei Hsieh, Yung-Chung Chen, Li-Li Kang, Chii-Shyang Hwang, Shu-Fen Chuang
Stability and reactivity of γ-ΜPTMS silane in some commercial primer and adhesive formulations Dent. Mater. (IF 4.039) Pub Date : 2018-05-18 Maria Dimitriadi, Angeliki Panagiotopoulou, Maria Pelecanou, Konstantina Yannakopoulou, George Eliades
Objectives To evaluate the stability and reactivity of γ-methacryloxypropyl trimethoxysilane (MPTMS) in commercially available primers and adhesives. Methods Four representative primer formulations [Calibra Silane Coupling Agent/Dentsply (CLB), G-Multi Primer/GC (GMP), Kerr Silane Primer/Kerr (KSP), Monobond Plus/Ivoclar Vivadent (MBP)] and a universal adhesive [Scotchbond Universal/3M ESPE (SBU)] containing MPTMS were analyzed spectroscopically. For the stability study, the silanol content was evaluated in bulk solutions as received (reference-RE) and after aging (AG, 48 °C/1 month) by 1H, 13C, 31P NMR and in fresh films by transmission FTIR analysis (TIR, films applied on Ge windows after solvent evaporation). The reactivity, as expressed by the siloxane formation capacity of the RE products, was evaluated by micro-multiple internal reflectance FTIR analysis (MIR, films applied on Ge crystals) after drying and ethanol rinsing (t0) and following 1 (t1) and 24 h (t24) storage (air/37 °C). Results NMR and TIR showed ∼60% MPTMS silanol groups in RE-CLB, with the other (∼40%) groups being methylated or ethoxylated. In AG-CLB, the silanol peaks further decreased, while ethoxylation and siloxane derivatization increased. In all other products and aging conditions no silanols were traced and formation of small- and large-size MPTMS derivatives was evident. Apart from the 10-MDP molecule, phosphorous impurities were identified in all RE specimens (2–5%), which after AG reached a maximum value of 15% (MBP). MIR analysis showed siloxane formation in all products, regardless the presence of free silanols (t1), which further increased at t24 especially in CLB, GMP and MBP. Significance MPTMS silanols are very sensitive to mild thermal aging. Incorporation of MPTMS in the same vials with adhesive and conventional methacrylate monomers, results in derivatization with no detectable silanols, even in fresh materials. The condensates formed may induce additional siloxane formation due to residual activity, which greatly varies among the materials tested. These may have a detrimental effect on MPTMS silanol chemisorption and bonding capacity.
In vitro assessment of ribose modified two-step etch-and-rinse dentine adhesive Dent. Mater. (IF 4.039) Pub Date : 2018-05-17 U. Daood, J.K.H. Tsoi, P. Neelakantan, J.P. Matinlinna, H.A.K. Omar, M. Al-Nabulsi, A.S. Fawzy
Objective Collagen fibrils aid in anchoring resin composite restorations to the dentine substrate. The aim of the study was to investigate effect of non-enzymatic glycation on bond strength and durability of demineralized dentine specimens in a modified two-step etch-and-rinse dentine adhesive. Methods Dentine surfaces were etched with 37% phosphoric acid, bonded with respective in vitro ethanol and acetone adhesives modified with (m/m, 0, 1%, 2% and 3% ribose), restored with restorative composite–resin, and sectioned into resin–dentine slabs and beams to be stored for 24 h or 12 months in artificial saliva. Bond-strength testing was performed with bond failure analysis. Pentosidine assay was performed on demineralized ribose modified dentine specimens with HPLC sensitive fluorescent detection. The structural variations of ribose-modified dentine were analysed using TEM and human dental pulpal cells were used for cell viability. Three-point bending test of ribose-modified dentine beams were performed and depth of penetration of adhesives evaluated with micro-Raman spectroscopy. The MMP-2 and cathepsin K activities in ribose-treated dentine powder were also quantified using ELISA. Bond strength data was expressed using two-way ANOVA followed by Tukey’s test. Paired T tests were used to analyse the specimens for pentosidine crosslinks. The modulus of elasticity and dentinal MMP-2 and cathepsin K concentrations was separately analyzed using one-way ANOVA. Results The incorporation of RB in the experimental two-step etch-and-rinse adhesive at 1% improved the adhesive bond strength without adversely affecting the degree of polymerisation. The newly developed adhesive increases the resistance of dentine collagen to degradation by inhibiting endogenous matrix metalloproteinases and cysteine cathepsins. The application of RB to acid-etched dentine helps maintain the mechanical properties. Significance The incorporation of 1%RB can be considered as a potential candidate stabilizing resin dentine bond.
Fluoride containing bioactive glass composite for orthodontic adhesives — Apatite formation properties Dent. Mater. (IF 4.039) Pub Date : 2018-05-17 N.A. Al-eesa, A. Johal, R.G. Hill, F.S.L. Wong
Objectives Dental materials that can form apatite offer the potential to not only prevent demineralisation but enhance remineralisation of the enamel. The objective of this study was to investigate the ability of a novel BAG-resin adhesive to form apatite in 3 immersion media. Methods A novel fluoride containing BAG-resin adhesive described previously, with 80% by weight filler load, was used to fabricate 90 disks. Each disk was immersed in 10 ml of either tris buffer (TB), or artificial saliva at pH = 7 (AS7) or pH = 4 (AS4). At ten time points (from 6 h to 6 months), three disks were taken from each of the solutions and investigated by ATR-FTIR, XRD and SEM. Results The BAG-resin formed apatite on the disk surface, which increased with time, especially in AS4 and AS7. The apatite crystals formed in AS7 were highly oreintated and the oreintation increased with time. Significance This novel BAG-resin adhesive differs from the currently used adhesives by promting apatite formation, particularly under acidic conditions. Thus, applied in the clinical situation to bond orthodontic brackets, it may discourage the frequent occurrence of white spot lesion formation around the brackets.
Synthesis and characterization of a new methacrylate monomer derived from the cashew nut shell liquid (CNSL) and its effect on dentinal tubular occlusion Dent. Mater. (IF 4.039) Pub Date : 2018-05-08 Madiana Magalhães Moreira, Lucas Renan Rocha da Silva, Talita Arrais Daniel Mendes, Sérgio Lima Santiago, Selma Elaine Mazzetto, Diego Lomonaco, Victor Pinheiro Feitosa
Objective The aim of this study was to synthesize, to characterize and to evaluate the effects on tubular occlusion of new monomer derived from cashew nut shell liquid (CNSL), also studying the effects of acid challenge (AC) on dentin surfaces treated with desensitizers. Methods The intermediary cardanol-epoxy (CNE) was synthesized through epoxidation of CNSL, followed by synthesis of cardanol-methacrylate-epoxy (CNME) through methacryloyl chloride esterification. Products were purified through chromatography column and characterized by Fourier transform infrared spectrometry and nuclear magnetic resonance. Resinous dentin desensitizers were formulated containing either unsaturated cardanol (CNU), CNE or CNME. Dentin disks were divided into seven groups: SL — Smear-layer, EDTA — EDTA-treated only, GLUMA — Gluma Desensitizer, OCB — One Coat Bond, CNU — CNU desensitizer, CNE — CNE desensitizer and CNME — CNME desensitizer. Dentinal fluid rate (DFF) was obtained using a Flodec equipment and tubular occlusion employing a scanning electron microscope (SEM), before and after AC. Data of DFF were submitted to two-way ANOVA and Tukey’s test (p < 0.05). Results GLUMA showed the lower reduction in DFF when compared to the other products, which were statistically similar. Even after AC, CNME presented the most homogenous and occluded surface, while CNE and CNU were partially removed, GLUMA was completely removed and OCB keep an occluded, but irregular surface. Significance CNME showed a great reduction of DFF and a homogenous occluded surface, suggesting that it may be a suitable and acid-resistant treatment option for dentine hypersensitivity.
In-vitro subsurface remineralisation of artificial enamel white spot lesions pre-treated with chitosan Dent. Mater. (IF 4.039) Pub Date : 2018-05-08 Jing Zhang, Victoria Boyes, Frederic Festy, Richard J.M. Lynch, Timothy F. Watson, Avijit Banerjee
Objective To test the null hypothesis that chitosan application has no impact on the remineralisation of artificial incipient enamel white spot lesions (WSLs). Methods 66 artificial enamel WSLs were assigned to 6 experimental groups (n = 11): (1) bioactive glass slurry, (2) bioactive glass containing polyacrylic acid (BG + PAA) slurry, (3) chitosan pre-treated WSLs with BG slurry (CS-BG), (4) chitosan pre-treated WSLs with BG + PAA slurry (CS-BG + PAA), (5) remineralisation solution (RS) and (6) de-ionised water (negative control, NC). Surface and cross-sectional Raman intensity mapping (960 cm−1) were performed on 5 samples/group to assess mineral content. Raman spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were used to identify the type of newly formed minerals. Surface and cross-sectional Knoop microhardness were implemented to evaluate the mechanical properties after remineralisation. Surface morphologies and Ca/P ratio were observed using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Data were statistically analysed using one-way ANOVA with Tukey’s test. Results BG + PAA, CS-BG, RS presented significantly higher mineral regain compared to NC on lesion surfaces, while CS-BG + PAA had higher subsurface mineral content. Newly mineralised crystals consist of type-B hydroxycarbonate apatite. CS-BG + PAA showed the greatest hardness recovery, followed by CS-BG, both significantly higher than other groups. SEM observations showed altered surface morphologies in all experimental groups except NC post-treatment. EDX suggested a higher content of carbon, oxygen and silicon in the precipitations in CS-BG + PAA group. There was no significant difference between each group in terms of Ca/P ratio. Significance The null hypothesis was rejected. Chitosan pre-treatment enhanced WSL remineralisation with either BG only or with BG-PAA complexes. A further investigation using dynamic remineralisation/demineralisation system is required with regards to clinical application.
Evaluation of early resin luting cement damage induced by voids around a circular fiber post in a root canal treated premolar by integrating micro-CT, finite element analysis and fatigue testing Dent. Mater. (IF 4.039) Pub Date : 2018-05-07 Yen-Hsiang Chang, Hsuan-Wen Wang, Pei-Hsun Lin, Chun-Li Lin
Objective This study utilizes micro-CT image combined with finite element (FE) analysis and in vitro fatigue testing to investigate the mechanical behavior associating with early resin luting cement damage induced by voids around a circular fiber post in a root canal treated premolar. Methods Six similar mandibular first premolars with root canal treatment were scanned with high resolution micro-CT before and after fatigue testing. Micro-CT images of all teeth were processed to identify various materials (dentin, luting cement and void) to evaluate the volume/position of the void in each reconstructed tooth root canal model. Six corresponding mesh models from CT images were generated to perform FE simulations under receiving oblique concentrated loads (200 N) to evaluate the luting cement layer mechanical behavior. All teeth were subjected to the fatigue test with 240,000 load cycles simulating chewing for one year to compare results with those in FE simulations. Results The result showed that most voids occurred adjacent to the apical third of the fiber post. Voids induced the fiber post to pull out, creating a stress concentration at the void boundary. Fatigue life in the experimental testing was found decreased with the stress value/micro-motion increasing in FE analysis. Significance This study establishes that micro-CT, FE simulation and fatigue testing can be integrated to understand the early de-bonding mechanism at the luting cement layer in a root canal treated premolar, suggesting that attention must be paid to resin luting cement dissolving/debonding easier when voids occur in the apical and peri-apical areas of fiber posts.
Fracture loads and failure modes of customized and non-customized zirconia abutments Dent. Mater. (IF 4.039) Pub Date : 2018-05-05 Izabela Cristina Maurício Moris, Yung-Chung Chen, Adriana Cláudia Lapria Faria, Ricardo Faria Ribeiro, Alex Sui-Lun Fok, Renata Cristina Silveira Rodrigues
Objective This study aimed to evaluate the fracture load and pattern of customized and non-customized zirconia abutments with Morse-taper connection. Methods 18 implants were divided into 3 groups according to the abutments used: Zr — with non-customized zirconia abutments; Zrc — with customized zirconia abutments; and Ti — with titanium abutments. To test their load capacity, a universal test machine with a 500-kgf load cell and a 0.5-mm/min speed were used. After, one implant-abutment assembly from each group was analyzed by Scanning Electron Microscopy (SEM). For fractographic analysis, the specimens were transversely sectioned above the threads of the abutment screw in order to examine their fracture surfaces using SEM. Results A significant difference was noted between the groups (Zr = 573.7 ± 11.66 N, Zrc = 768.0 ± 8.72 N and Ti = 659.1 ± 7.70 N). Also, the zirconia abutments fractured while the titanium abutments deformed plastically. Zrc presented fracture loads significantly higher than Zr (p = 0.009). All the zirconia abutments fractured below the implant platform, starting from the area of contact between the abutment and implant and propagating to the internal surface of the abutment. All the zirconia abutments presented complete cleavage in the mechanical test. Fractography detected differences in the position and pattern of fracture between the two groups with zirconia abutments, probably because of the different diameters in the transmucosal region. Significance Customization of zirconia abutments did not affect their fracture loads, which were comparable to that of titanium and much higher than the maximum physiological limit for the anterior region of the maxilla.
Challenges in luting fibre posts: Adhesion to the post and to the dentine Dent. Mater. (IF 4.039) Pub Date : 2018-05-01 Adriana Lemos Mori Ubaldini, Ana Raquel Benetti, Francielle Sato, Renata Corrêa Pascotto, Antonio Medina Neto, Mauro Luciano Baesso, Anne Peutzfeldt
Objective To investigate the relationship between physicochemical interactions of resin luting cements with dentine and retention of fibre posts in root canals. Methods Retention of fibre posts (RelyX Fiber Post) was assessed by the pull-out method. The diffusion zone of the cements and their chemical interaction with dentine were estimated by micro-Raman spectroscopy. Resin luting cements employing etch-and-rinse (Rely X Ultimate and Variolink II), self-etch (Rely X Ultimate and Panavia F2.0), or self-adhesive (RelyX Unicem 2) modes were investigated. Data were analyzed by analysis of variance followed by Tukey HSD tests. Results The retention of the fibre posts decreased in the following order: RelyX Ultimate, etch-and-rinse mode > RelyX Unicem 2 ≥ RelyX Ultimate, self-etch mode ≥ Panavia F2.0 ≥ Variolink II (p < 0.05). One of the etch-and-rinse mode cements presented the deepest diffusion zone, while the other, along with the self-adhesive cement, produced the shallowest zone. Cements used in the self-etch mode showed intermediary diffusion into dentine (p < 0.05). All resin luting cements showed some degree of chemical interaction with dentine, the highest recorded for RelyX Ultimate used in the etch-and-rinse mode and the lowest for Panavia F2.0 (p < 0.05). The retention of fibre posts in the root canal could be attributed neither to the mode of interaction of the luting cements with dentine nor to their ability to diffuse into dentine. Significance Chemical interaction between the resin luting cement and the dentine paired with adequate post pretreatment contribute positively to the retention of fibre posts.
Chemical interaction of glycero-phosphate dimethacrylate (GPDM) with hydroxyapatite and dentin Dent. Mater. (IF 4.039) Pub Date : 2018-04-30 Kumiko Yoshihara, Noriyuki Nagaoka, Satoshi Hayakawa, Takumi Okihara, Yasuhiro Yoshida, Bart Van Meerbeek
Objectives Although the functional monomer glycero-phosphate dimethacrylate (GPDM) has since long been used in several dental adhesives and more recently in self-adhesive composite cements and restoratives, its mechanism of chemical adhesion to hydroxyapatite (HAp) is still unknown. We therefore investigated the chemical interaction of GPDM with HAp using diverse chemical analyzers and ultra-structurally characterized the interface of a GPDM-based primer formulation with dentin. Methods HAp particles were added to a GPDM solution for various periods, upon which they were thoroughly washed with ethanol and water prior to being air-dried. As control, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was used. The molecular interaction of GPDM with HAp was analyzed using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Crystal formation upon application of GPDM onto dentin was analyzed using thin-film XRD (TF-XRD). Its hydrophobicity was measured using contact-angle measurement. The interaction of GPDM with dentin was characterized using transmission electron microscopy (TEM). Results XRD revealed the deposition of dicalcium phosphate dihydrate (DCPD: CaHPO4·2H2O) on HAp after 24 h. NMR confirmed the adsorption of GPDM onto HAp. However, GPDM was easily removed after washing with water, unlike MDP that remained adhered to HAp. Dentin treated with GPDM appeared more hydrophilic compared to dentin treated with MDP. TEM disclosed exposed collagen in the hybrid layer produced by the GPDM-based primer formulation. Significance: Although GPDM adsorbed to HAp, it did not form a stable calcium salt. The bond between GPDM and HAp was weak, unlike the strong bond formed by MDP to HAp. Due to its high hydrophilicity, GPDM might be an adequate monomer for an etch-and-rinse adhesive, but appears less appropriate for a ‘mild’ self-etch adhesive that besides micro-retention ionically interacts with HAp, or for a self-adhesive restorative material.
Hygroscopic expansion of self-adhesive resin cements and the integrity of all-ceramic crowns Dent. Mater. (IF 4.039) Pub Date : 2018-04-27 Magdalena Kirsten, Ragai Edward Matta, Renan Belli, Ulrich Lohbauer, Manfred Wichmann, Anselm Petschelt, José Zorzin
Objective Low pH neutralization and subsequent remnant hydrophilicity can lead to hygroscopic expansion of self-adhesive resin cements (SARCs) after water storage. The aim of this in vitro study was to investigate the effects of hygroscopic expansion of SARCs, used as luting and partial core build-up material, on integrity and cement gap thickness increase of all-ceramic CAD/CAM crowns. Methods Human third molars (n = 48) were prepared and anatomical all-ceramic CAD/CAM crowns were manufactured (VITABLOCS Mark II, VITA Zahnfabrik). Crowns internal surfaces were HF etched and silanized. The prepared teeth with their respective crowns were divided into 6 groups (n = 8). In groups 1, 3 and 5 the coronal dentin was removed to simulate a partial core build-up. Groups 1 and 2 were luted with iCEM (Heraeus Kulzer), 3 and 4 with RelyX Unicem 2 Automix (3M), 5 and 6 with Variolink Esthetic DC (Ivoclar Vivadent). All specimens were dual cured and stored in distilled water at 37 °C. Crown integrity was controlled at baseline and in regular intervals until 180 days. Cement gap thickness was measured using an optical 3D scanner (ATOS Triple scan, GOM) at baseline and after 180 days. Crown integrity was statistically analysed using Kaplan–Meier survival analysis and cement gap thickness increase using two-way ANOVA (α = 0.05). Results After 180 days storage, crack formation was observed in all specimens of group 1 (mean survival time of 85.5 days), in one specimen of group 2 and in two specimens of group 4. Two-way ANOVA analysis revealed a statistically significant interaction between material type and build-up on cement gap size increase for iCEM. Significance Within the limits of this study, the application of SARCs with low pH neutralization as partial build-up material under CAD/CAM crowns is not recommended for clinical use.
In vitro and in vivo studies of anti-bacterial copper-bearing titanium alloy for dental application Dent. Mater. (IF 4.039) Pub Date : 2018-04-27 Rui Liu, Yulong Tang, Lilan Zeng, Ying Zhao, Zheng Ma, Ziqing Sun, Liangbi Xiang, Ling Ren, Ke Yang
Objective A novel copper-bearing titanium alloy (Ti–Cu) was fabricated for dental application that is expected to efficiently restrain the growth of bacteria and discourage biofilm formation. The aim of this study was to investigate both the antibacterial activity and biofilm inhibition of Ti–Cu alloy in vitro, and the antibacterial effect of Ti–Cu implant in early stage of peri-implantitis in vivo. Methods Staphylococcus aureus and Escherichia coli were selected to evaluate the antibacterial activity of Ti–Cu alloy and Ti served as control. The antibacterial rate, attached bacteria and developed biofilms were studied from quantitative antibacterial test, biofilm observation and bacterial morphological examination. Electrochemical tests were used to investigate the corrosion property of Ti–Cu alloy. Furthermore, both Ti and Ti–Cu dental implants were manufactured and then implanted in the mandibular premolar sites of beagle dogs for 3 months with ligature-infected treatment. Implant-tissue samples were prepared for radiographic analysis, Micro-CT evaluation and histological examination. Results Ti–Cu alloy was found to efficiently kill the attached bacteria by ways of damaging cell membranes and cell walls and strongly inhibit the biofilm formation. However, Ti–Cu alloy had excellent corrosion resistance similar with Ti. Further, Ti–Cu dental implants showed superior capacities of inhibiting the bone resorption caused by bacterial infection and enhancing bone formation. Significance Ti–Cu alloy strongly inhibited biofilm formation in vitro and prevented bacterial infection associated with dental implant in vivo, making it great potential for application in dental implants with excellent antibacterial viability and positive effect against bone resorption induced by peri-implantitis.
Does translucency influence cure efficiency and color stability of resin-based composites? Dent. Mater. (IF 4.039) Pub Date : 2018-04-25 Vinícius Esteves Salgado, Guilherme Ferreira Rego, Luis Felipe Schneider, Rafael Ratto de Moraes, Larissa Maria Cavalcante
Objective To determine if material’s translucency influences the cure efficiency and color stability of resin-based composites (RBCs). Methods Four commercially-available RBCs indicated for aesthetic restorations were selected in different translucent/opaque shades: IPS Empress Direct (IED) A3 Dentin, A3 Enamel, Trans 20, and Trans 30; Filtek Z350 XT (FZX) A3D, A3B, A3E, and CT; Estelite ∑ Quick (EQ) OA3, A3, and CE; and Opallis (OP) DA3, EA3, and T-Neutral. Color was obtained in the L′C′h′ system at three distinct periods: 24 h after photoactivation (baseline), after 30 d of water storage (WS), and after 30 d of coffee storage (CS). The translucency parameter (TP) of each RBC was calculated at baseline. The degree of C C conversion (DC) was obtained by Fourier-transform infrared spectroscopy at 0.05 mm (top) and 2 mm (bottom) surfaces; the cure efficiency considered the bottom/top ratio. The CIEDE2000 color difference (ΔE00) was calculated considering the WS–baseline and CS–baseline values. Data were submitted to two-way ANOVA and Tukey’s post-hoc test (α = 0.05). Pearson’s tests were used to analyze the correlations between TP and DC, and between TP and ΔE00. Results For all RBCs, cure efficiency was not affected by materials’ translucency. A positive, significant correlation was observed between TP and DC at the bottom surface for FZX only. For all RBCs, the higher the TP, the higher the ΔE00. The ΔE00 was higher after CS than after WS, except for EQ A3. Positive correlation between TP and ΔE00 were observed for all materials. Conclusion The translucency did not influence the cure efficiency but affected the color stability for all RBCs. Clinical significance High-translucent RBCs presented lower color stability and should be used carefully.
FE analysis of conceptual hybrid composite endodontic post designs in anterior teeth Dent. Mater. (IF 4.039) Pub Date : 2018-04-24 Antonio Gloria, Saverio Maietta, Massimo Martorelli, Antonio Lanzotti, David C. Watts, Pietro Ausiello
Objectives To assess conceptual designs of dental posts consisting of polyetherimide (PEI) reinforced with carbon (C) and glass (G) glass fibers in endodontically treated anterior teeth. Methods 3D tessellated CAD and geometric models of endodontically treated anterior teeth were generated from Micro-CT scan images. Model C-G/PEI composite posts with different Young’s moduli were analyzed by Finite Element (FE) methods post A (57.7 GPa), post B (31.6 GPa), post C (from 57.7 to 9.0 GPa in the coronal–apical direction). A load of 50 N was applied at 45° to the longitudinal axis of the tooth, acting on the palatal surface of the crown. The maximum principal stress distribution was determined along the post and at the interface between the post and the surrounding structure. Results Post C, with Young’s modulus decreasing from 57.7 to 9.0 GPa in the coronal–apical direction, reduced the maximum principal stress distribution in the restored tooth. Post C gave reduced stress and the most uniform stress distribution with no stress concentration, compared to the other C-G/PEI composite posts. Significance The FE analysis confirmed the ability of the functionally graded post to dissipate stress from the coronal to the apical end. Hence actual (physical) C-G/PEI posts could permit optimization of stress distributions in endodontically treated anterior teeth.
Effect of hydration and crack orientation on crack-tip strain, crack opening displacement and crack-tip shielding in elephant dentin Dent. Mater. (IF 4.039) Pub Date : 2018-04-22 Xuekun Lu, Shelley D. Rawson, Philip J. Withers
Objectives To quantify the extent of crack-tip plasticity, crack opening displacement (COD) and crack bridging for crack growth perpendicular (HAH) and parallel (RAR) to the tubules in elephant dentin under both hydrated and dry conditions to better understand their influence on intrinsic and extrinsic toughening during crack growth. Methods Compact tension test-pieces were prepared from a tusk of African elephant ivory. Crack-tip strain mapping and COD measurements by digital image correlation (DIC) technique were made under incremental loading and unloading of cracks for hydrated and dry dentin of different orientations. Results For the RAR test-piece the plastic zones were significantly larger in the hydrated condition compared to when dry. By contrast, the plastic strains in the HAH test-piece were negligible in both wet and dry conditions. In the RAR condition the crack front was broken up into overlapping longitudinal ‘fingers’ with crack bridging regions in between, the ligaments extending 400 μm behind the crack front in the dry case. This could only be seen in 3D by X-ray CT. Extrinsic shielding reduces the crack-tip stresses by 52% and 40% for hydrated and dry RAR test-pieces respectively. No significant bridging was found in the HAH case. Significance For crack growth parallel to the tubules, collagen plasticity determines the intrinsic toughening, whereas microcracking from the tubules governs extrinsic shielding via ligament bridging, which is maintained further behind the crack in the hydrated case. For cracks grown perpendicular to the tubules, neither toughening mechanisms are significant.
Chairside CAD/CAM materials. Part 3: Cyclic fatigue parameters and lifetime predictions Dent. Mater. (IF 4.039) Pub Date : 2018-04-17 Michael Wendler, Renan Belli, Diana Valladares, Anselm Petschelt, Ulrich Lohbauer
Objectives Chemical and mechanical degradation play a key role on the lifetime of dental restorative materials. Therefore, prediction of their long-term performance in the oral environment should base on fatigue, rather than inert strength data, as commonly observed in the dental material’s field. The objective of the present study was to provide mechanistic fatigue parameters of current dental CAD/CAM materials under cyclic biaxial flexure and assess their suitability in predicting clinical fracture behaviors. Methods Eight CAD/CAM materials, including polycrystalline zirconia (IPS e.max ZirCAD), reinforced glasses (Vitablocs Mark II, IPS Empress CAD), glass-ceramics (IPS e.max CAD, Suprinity PC, Celtra Duo), as well as hybrid materials (Enamic, Lava Ultimate) were evaluated. Rectangular plates (12 × 12 × 1.2 mm3) with highly polished surfaces were prepared and tested in biaxial cyclic fatigue in water until fracture using the Ball-on-Three-Balls (B3B) test. Cyclic fatigue parameters n and A* were obtained from the lifetime data for each material and further used to build SPT diagrams. The latter were used to compare in-vitro with in-vivo fracture distributions for IPS e.max CAD and IPS Empress CAD. Results Susceptibility to subcritical crack growth under cyclic loading was observed for all materials, being more severe (n ≤ 20) in lithium-based glass-ceramics and Vitablocs Mark II. Strength degradations of 40% up to 60% were predicted after only 1 year of service. Threshold stress intensity factors (Kth) representing the onset of subcritical crack growth (SCG), were estimated to lie in the range of 0.37–0.44 of KIc for the lithium-based glass-ceramics and Vitablocs Mark II and between 0.51–0.59 of KIc for the other materials. Failure distributions associated with mechanistic estimations of strength degradation in-vitro showed to be useful in interpreting failure behavior in-vivo. The parameter Kth stood out as a better predictor of clinical performance in detriment to the SCG n parameter. Significance Fatigue parameters obtained from cyclic loading experiments are more reliable predictors of the mechanical performance of contemporary dental CAD/CAM restoratives than quasi-static mechanical properties.
Antibacterial photocatalytic activity of different crystalline TiO2 phases in oral multispecies biofilm Dent. Mater. (IF 4.039) Pub Date : 2018-04-17 Heloisa N. Pantaroto, Antonio P. Ricomini-Filho, Martinna M. Bertolini, José H.D. Silva, Nilton F. Azevedo Neto, Cortino Sukotjo, Elidiane C. Rangel, Valentim A.R. Barão
Objective Titanium dioxide (TiO2) incorporation in biomaterials is a promising technology due to its photocatalytic and antibacterial activities. However, the antibacterial potential of different TiO2 crystalline structures on a multispecies oral biofilm remains unknown. We hypothesized that the different crystalline TiO2 phases present different photocatalytic and antibacterial activities. Methods Three crystalline TiO2 films were deposited by magnetron sputtering on commercially pure titanium (cpTi), in order to obtain four groups: (1) machined cpTi (control); (2) A-TiO2 (anatase); (3) M-TiO2 (mixture of anatase and rutile); (4) R-TiO2 (rutile). The morphology, crystalline phase, chemical composition, hardness, elastic modulus and surface free energy of the surfaces were evaluated. The photocatalytic potential was assessed by methylene blue degradation assay. The antibacterial activity was evaluated on relevant oral bacteria, by using a multispecies biofilm (Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum) formed on the treated titanium surfaces (16.5 h) followed by UV-A light exposure (1 h) to generate reactive oxygen species production. Results All TiO2 films presented around 300 nm thickness and improved the hardness and elastic modulus of cpTi surfaces (p < 0.05). A-TiO2 and M-TiO2 films presented superior photocatalytic activity than R-TiO2 (p < 0.05). M-TiO2 revealed the greatest antibacterial activity followed by A-TiO2 (≈99.9% and 99% of bacterial reduction, respectively) (p < 0.001 vs. control). R-TiO2 had no antibacterial activity (p > 0.05 vs. control). Significance This study brings new insights on the development of extra oral protocols for the photocatalytic activity of TiO2 in oral biofilm-associated disease. Anatase and mixture-TiO2 showed antibacterial activity on this oral bacterial biofilm, being promising surface coatings for dental implant components.
Antibacterial quaternary ammonium compounds in dental materials: A systematic review Dent. Mater. (IF 4.039) Pub Date : 2018-04-17 Pooyan Makvandi, Rezvan Jamaledin, Mostafa Jabbari, Nasser Nikfarjam, Assunta Borzacchiello
Objective Quaternary ammonium compounds (QACs) represent one of the most effective classes of disinfectant agents in dental materials and resin nanocomposites. This reviews aims to give a wide overview on the research in the field of antibacterial QACs in dental materials and nanocomposites. Method An introduction to dental materials components as well as the microorganisms and methods of evaluation for the antimicrobial assays are presented. Then, the properties and synthesis route of QACs, as monomer and filler, are shown. Finally, antimicrobial monomers and fillers, specifically those contain quaternary ammonium salts (QASs), in dental materials are reviewed. Results QACs have been used as monomer and micro/nanofiller in restorative dentistry. They possess one or more methacrylate functional groups to participate in polymerization reactions. QACs with multiple methacrylate groups can also be used as crosslinking agents. Furthermore, QACs with chain length from ∼12 to 16 have higher antimicrobial activity in cured dental resins. In general, increasing the chain length leads to a threshold value (critical point) and then it causes decrease in the antimicrobial activity. Significance The current state of the art of dental materials and resin nanocomposites includes a wide variety of antimicrobial materials. Among them, QACs presents low cytotoxicity and excellent long-term antimicrobial activity without leaching out over time.
Preparation and characterization of Bis-GMA-free dental composites with dimethacrylate monomer derived from 9,9-Bis[4-(2-hydroxyethoxy)phenyl]fluorene Dent. Mater. (IF 4.039) Pub Date : 2018-04-13 Jingwei He, Hilde M. Kopperud
Objective Synthesize a new BPA-free monomer for use in methacrylate-based materials and evaluate critical properties of resin and composite materials based on the monomer. Methods Bis-EFMA was synthesized through reaction between 9,9-bis[4-(2-hydroxyethoxy)-phenyl]fluorene and 2-(methacryloyloxy)ethyl isocyanate. Experimental Bis-EFMA-based resin (Bis-EFMA/TEGDMA = 50/50, wt./wt.) and composite were prepared. Critical properties were investigated according to standard or referenced methods Bis-GMA/TEGDMA (50/50, wt./wt.) resin system, Bis-GMA-based composite and 3 M ESPE Filtek™ Z250 were used as controls. Results FT-IR and 1H NMR spectra confirmed the structure of Bis-EFMA monomer. Cured resin materials: Bis-EFMA-based and Bis-GMA-based resins had nearly the same degree of conversion (p > 0.05); Bis-EFMA-based resin had significantly lower shrinkage, water sorption and solubility, and cytotoxicity than Bis-GMA-based resin (p < 0.05); flexural properties of Bis-EFMA-based resin were all higher than those of Bis-GMA-based resin (p < 0.05). Cured composite materials: There was no significant difference in conversion (p > 0.05); Bis-EFMA-based composite had significantly lower shrinkage and solubility (p < 0.05); water sorption of Bis-EFMA-based composite and Z250 were similar (p > 0.05), but lower compared to Bis-GMA-based composite (p < 0.05); Bis-EFMA-based composite had the deepest curing depth (p < 0.05); Before water immersion, there was no significant difference in flexural strength between Bis-EFMA-based composite and each control composite (p > 0.05), while FS became lower than that of Z250 (p < 0.05), but higher than that of Bis-GMA-based composite (p < 0.05) after water immersion; Flexural modulus of Bis-EFMA-based composite and Z250 were nearly the same (p > 0.05), higher than that of Bis-GMA-based composite (p < 0.05); Bis-EFMA-based composite showed less cytotoxicity than Bis-GMA-based composite and Z250 (p < 0.05). Significance Bis-EFMA has potential as a substitute for Bis-GMA to prepare Bis-GMA-free dental composites.
The effect of DLC-coating deposition method on the reliability and mechanical properties of abutment’s screws Dent. Mater. (IF 4.039) Pub Date : 2018-04-10 Dimorvan Bordin, Paulo G. Coelho, Edmara T.P. Bergamo, Estevam A. Bonfante, Lukasz Witek, Altair A. Del Bel Cury
Objective To characterize the mechanical properties of different coating methods of DLC (diamond-like carbon) onto dental implant abutment screws, and their effect on the probability of survival (reliability). Methods Seventy-five abutment screws were allocated into three groups according to the coating method: control (no coating); UMS – DLC applied through unbalanced magnetron sputtering; RFPA-DLC applied through radio frequency plasma-activated (n = 25/group). Twelve screws (n = 4) were used to determine the hardness and Young’s modulus (YM). A 3D finite element model composed of titanium substrate, DLC-layer and a counterpart were constructed. The deformation (μm) and shear stress (MPa) were calculated. The remaining screws of each group were torqued into external hexagon abutments and subjected to step-stress accelerated life-testing (SSALT) (n = 21/group). The probability Weibull curves and reliability (probability survival) were calculated considering the mission of 100, 150 and 200 N at 50,000 and 100,000 cycles. Results DLC-coated experimental groups evidenced higher hardness than control (p < 0.05). In silico analysis depicted that the higher the surface Young’s modulus, the higher the shear stress. Control and RFPA showed β < 1, indicating that failures were attributed to materials strength; UMS showed β > 1 indicating that fatigue contributed to failure. High reliability was depicted at a mission of 100 N. At 200 N a significant decrease in reliability was detected for all groups (ranging from 39% to 66%). No significant difference was observed among groups regardless of mission. Screw fracture was the chief failure mode. Significance DLC-coating have been used to improve titanium’s mechanical properties and increase the reliability of dental implant-supported restorations.
Numerical fatigue analysis of premolars restored by CAD/CAM ceramic crowns Dent. Mater. (IF 4.039) Pub Date : 2018-04-10 Ehsan Homaei, Xiao-Zhuang Jin, Edmond Ho Nang Pow, Jukka Pekka Matinlinna, James Kit-Hon Tsoi, Khalil Farhangdoost
Objectives The purpose of this study was to estimate the fatigue life of premolars restored with two dental ceramics, lithium disilicate (LD) and polymer infiltrated ceramic (PIC) using the numerical method and compare it with the published in vitro data. Methods A premolar restored with full-coverage crown was digitized. The volumetric shape of tooth tissues and crowns were created in Mimics®. They were transferred to IA-FEMesh for mesh generation and the model was analyzed with Abaqus. By combining the stress distribution results with fatigue stress–life (S–N) approach, the lifetime of restored premolars was predicted. Results The predicted lifetime was 1,231,318 cycles for LD with fatigue load of 1400 N, while the one for PIC was 475,063 cycles with the load of 870 N. The peak value of maximum principal stress occurred at the contact area (LD: 172 MPa and PIC: 96 MPa) and central fossa (LD: 100 MPa and PIC: 64 MPa) for both ceramics which were the most seen failure areas in the experiment. In the adhesive layer, the maximum shear stress was observed at the shoulder area (LD: 53.6 MPa and PIC: 29 MPa). Significance The fatigue life and failure modes of all-ceramic crown determined by the numerical method seem to correlate well with the previous experimental study.
Thermo-setting glass ionomer cements promote variable biological responses of human dental pulp stem cells Dent. Mater. (IF 4.039) Pub Date : 2018-04-09 Mar Collado-González, Miguel R. Pecci-Lloret, Christopher J. Tomás-Catalá, David García-Bernal, Ricardo E. Oñate-Sánchez, Carmen Llena, Leopoldo Forner, Vinicius Rosa, Francisco J. Rodríguez-Lozano
Objective To evaluate the in vitro cytotoxicity of Equia Forte (GC, Tokyo, Japan) and Ionostar Molar (Voco, Cuxhaven, Germany) on human dental pulp stem cells (hDPSCs). Methods hDPSCs isolated from third molars were exposed to several dilutions of Equia Forte and Ionostar Molar eluates (1/1, 1/2 and 1/4). These eluates were obtained by storing material samples in respective cell culture medium for 24 h (n = 40). hDPSCs in basal growth culture medium were the control. Cell viability and cell migration assays were performed using the MTT and wound-healing assays, respectively. Also, induction of apoptosis and changes in cell phenotype were evaluated by flow cytometry. Changes in cell morphology were analysed by immunocytofluorescence staining. To evaluate cell attachment to the different materials, hDPSCs were directly seeded onto the material surfaces and analyzed by scanning electron microscopy (SEM). The chemical composition of the materials was determined by energy dispersive X-ray (EDX) and eluates were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). Statistical analysis was performed with analysis of variance (ANOVA) and Student’s t-test (α < 0.05). Results Undiluted Equia Forte extracts led to a similar cell proliferation rates than the control group from 72 h onwards. There were no significance differences between Equia Forte and Ionostar Molar in terms of cell apoptosis and phenotype. However, in presence of Equia extracts the migration capacity of hDPSCs was higher than in presence of Ionostar Molar (p < 0.05). Also, SEM studies showed a higher degree of cell attachment when Equia Forte extracts were used. Finally, EDX analysis pointed to different weight percentages of C, O and Ca ions in glass ionomer cements, while other elements such as La, Al, Si, W, Mo and F were also detected. Significance In summary, Equia Forte promoted better biological responses in hDPSCs than Ionostar Molar.
Clinical evaluation of the bulk fill composite QuiXfil in molar class I and II cavities: 10-year results of a RCT Dent. Mater. (IF 4.039) Pub Date : 2018-04-07 Katrin Heck, Juergen Manhart, Reinhard Hickel, Christian Diegritz
Objective The objective of this RCT was to compare the 10-year clinical performance of QuiXfil with that of Tetric Ceram in posterior single- or multi-surface cavities. Methods 46 QuiXfil (Xeno III) and 50 Tetric Ceram (Syntac classic) composite restorations were placed in 14 stress bearing class I and 82 class II cavities in first or second molars. Clinical evaluation was performed at baseline and after up to 10 years by using modified US Public Health Service criteria. At the last recall period, 26 QuiXfil and 30 Tetric Ceram restorations in 11 stress bearing class I and 45 class II cavities, were assessed. Results Ten failed restorations were observed during the follow-up period, four Tetric Ceram restorations failed due to secondary caries (2), tooth fracture (1) and bulk fracture combined with secondary caries (1) whereas six QuiXfil restorations failed due to secondary caries (1), tooth fracture (2), secondary caries combined with restoration fracture (1), restoration fracture (1) and postoperative sensitivity (1). Fisher’s exact test yielded no significant difference between both materials (p = 0.487). Significance Both materials, bulk fill QuiXfil restorations and Tetric Ceram restorations, showed highly clinical effectiveness during the 10-year follow-up.
In-vitro and in-vivo design and validation of an injectable polysaccharide-hydroxyapatite composite material for sinus floor augmentation Dent. Mater. (IF 4.039) Pub Date : 2018-04-07 J.C. Fricain, R. Aid, S. Lanouar, D.B. Maurel, D. Le Nihouannen, S. Delmond, D. Letourneur, J. Amedee Vilamitjana, S. Catros
Objective Polysaccharide-based composite matrices consisting of natural polysaccharides, pullulan and dextran supplemented with hydroxyapatite (Matrix-HA) have recently been developed. The principal objective of this study was to evaluate the capacities of this composite material to promote new bone formation in a sinus lift model in the sheep. Secondary objectives were to evaluate in vitro properties of the material regarding cell adhesion and proliferation. Methods In this report, once such composite matrix was prepared as injectable beads after dispersion in a physiological buffer, and evaluated using a large animal model (sheep) for a sinus lift procedure. Results In vitro studies revealed that these microbeads (250–550 μm in diameter) allow vascular cell adhesion and proliferation of Endothelial Cells (EC) after 1 and 7 days of culture. In vivo studies were performed in 12 adult sheep, and newly formed tissue was analyzed by Cone Beam Computed Tomography (CBCT scanning electron microscopy (SEM) and by histology 3 and 6 months post-implantation. CBCT analyses at the implantation time revealed the radiolucent properties of these matrices. Quantitative analysis showed an increase of a dense mineralized tissue in the Matrix-HA group up to 3 months of implantation. The mineralized volume over total volume after 6 months reached comparable values to those obtained for Bio-Oss® used as positive control. Histological examination confirmed that the Matrix-HA did not induce any long term inflammatory events, and promoted direct contact between the osteoid tissue and lamellar bone structures and beads. After 6 months, we observed a dense network of osteocytes surrounding both biomaterials as well as a newly vascularized formed tissue in close contact to the biomaterials. Significance In conclusion, the absence of animal components in Matrix-HA, the osteoconductive property of Matrix-HA in sheep, resulting in a dense bone and vascularized tissue, and the initial radiolucent property to follow graft integration offer great promises of this composite material for clinical use.
Wear measurement of dental tissues and materials in clinical studies: A systematic review Dent. Mater. (IF 4.039) Pub Date : 2018-04-04 C. Wulfman, V. Koenig, A.K. Mainjot
Objectives This study aims to systematically review the different methods used for wear measurement of dental tissues and materials in clinical studies, their relevance and reliability in terms of accuracy and precision, and the performance of the different steps of the workflow taken independently. Methods An exhaustive search of clinical studies related to wear of dental tissues and materials reporting a quantitative measurement method was conducted. MedLine, Embase, Scopus, Cochrane Library and Web of Science databases were used. Prospective studies, pilot studies and case series (>10 patients), as long as they contained a description of wear measurement methodology. Only studies published after 1995 were considered. Results After duplicates’ removal, 495 studies were identified, and 41 remained for quantitative analysis. Thirty-four described wear-measurement protocols, using digital profilometry and superimposition, whereas 7 used alternative protocols. A specific form was designed to analyze the risk of bias. The methods were described in terms of material analyzed; study design; device used for surface acquisition; matching software details and settings; type of analysis (vertical height-loss measurement vs volume loss measurement); type of area investigated (entire occlusal area or selective areas); and results. Sinificance There is a need of standardization of clinical wear measurement. Current methods exhibit accuracy, which is not sufficient to monitor wear of restorative materials and tooth tissues. Their performance could be improved, notably limiting the use of replicas, using standardized calibration procedures and positive controls, optimizing the settings of scanners and matching softwares, and taking into account unusable data.
Influence of Class V preparation on in vivo temperature rise in anesthetized human pulp during exposure to a Polywave® LED light curing unit Dent. Mater. (IF 4.039) Pub Date : 2018-03-29 Driellen Christine Zarpellon, Patrício Runnacles, Cristiane Maucoski, Dayane Jaqueline Gross, Ulisses Coelho, Frederick Allen Rueggeberg, Cesar Augusto Galvão Arrais
Objective This in vivo study evaluated pulp temperature (PT) rise in human premolars having deep Class V preparations during exposure to a light curing unit (LCU) using selected exposure modes (EMs). Methods After local Ethics Committee approval, intact first premolars (n = 8) requiring extraction for orthodontic reasons, from 8 volunteers, received infiltrative and intraligamental anesthesia and were isolated using rubber dam. A minute pulp exposure was attained and sterile probe from a wireless, NIST-traceable, temperature acquisition system was inserted into the coronal pulp chamber to continuously monitor PT (°C). A deep buccal Class V preparation was prepared using a high speed diamond bur under air-water spray cooling. The surface was exposed to a Polywave® LED LCU (Bluephase 20i, Ivoclar Vivadent) using selected EMs, allowing 7-min span between each exposure: 10-s in low (10-s/L), 10-s (10-s/H), 30-s (30-s/H), or 60-s (60-s/H) in high mode; and 5-s-Turbo (5-s/T). Peak PT values and PT increases over physiologic baseline levels (ΔT) were subjected to 1-way, repeated measures ANOVAs, and Bonferroni’s post-hoc tests (α = 0.05). Linear regression analysis was performed to establish the relationship between applied radiant exposure and ΔT. Results All EMs produced higher peak PT than the baseline temperature (p < 0.001). Only 60-s/H mode generated an average ΔT of 5.5 °C (p < 0.001). A significant, positive relationship was noted between applied radiant exposure and ΔT (r2 = 0.8962; p < 0.001). Significance In vivo exposure of deep Class V preparation to Polywave® LED LCU increases PT to values considered safe for the pulp, for most EMs. Only the longest evaluated EM caused higher PT increase than the critical ΔT, thought to be associated with pulpal necrosis.
Aging resistance, mechanical properties and translucency of different yttria-stabilized zirconia ceramics for monolithic dental crown applications Dent. Mater. (IF 4.039) Pub Date : 2018-03-26 E. Camposilvan, R. Leone, L. Gremillard, R. Sorrentino, F. Zarone, M. Ferrari, J. Chevalier
Objectives The dental market moves towards high-translucency monolithic zirconia dental crowns, which are usually placed either with – or without – a thin glaze layer. The microstructural features and the mechanical performances of these materials are still controversial, as well as their susceptibility to aging. This paper aims at studying these aspects in the current generation of zirconia dental crowns showing different degrees of translucency. Methods Four different commercial zirconia materials were investigated, including one standard ‘full-strength’ 3Y-TZP and three grades with improved translucency. The microstructural features (phase composition and assemblage, grain size) were carefully studied, as well as mechanical properties (biaxial bending strength and indentation toughness), translucency and aging behavior (in autoclave at 134 °C). Aging was conducted on crowns with and without glaze to better represent clinical uses. Results Important differences are found in terms of microstructures among the materials in terms of cubic phase content and yttria in the tetragonal phase, leading to different optical, mechanical and aging resistance properties. We show that higher cubic phase content leads to better translucency and stability in water steam, but at the expense of strength and toughness. A compromise is always inevitable between translucency and aging resistance on one side and mechanical properties on the other side. Significance - Even so called ‘high translucent’ zirconia ceramics tested in this work should be considered as medium translucency materials. - Aging occurs in standard state-of-the-art dental zirconia and glazing does not fully avoid this issue. However, aging did not compromise strength even after prolonged duration. - Aging is null in the ‘highly translucent’ zirconia grades but at the expense of strength, which is then comparable to glass-ceramics.
Fatigue failure load of two resin-bonded zirconia-reinforced lithium silicate glass-ceramics: Effect of ceramic thickness Dent. Mater. (IF 4.039) Pub Date : 2018-03-24 Jaiane Bandoli Monteiro, Hilton Riquieri, Catina Prochnow, Luís Felipe Guilardi, Gabriel Kalil Rocha Pereira, Alexandre Luiz Souto Borges, Renata Marques de Melo, Luiz Felipe Valandro
Objectives To evaluate the effect of ceramic thickness on the fatigue failure load of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics, adhesively cemented to a dentin analogue material. Methods Disc-shaped specimens were allocated into 8 groups (n = 25) considering two study factors: ZLS ceramic type (Vita Suprinity — VS; and Celtra Duo — CD), and ceramic thickness (1.0; 1.5; 2.0; and 2.5 mm). A trilayer assembly (ϕ = 10 mm; thickness = 3.5 mm) was designed to mimic a bonded monolithic restoration. The ceramic discs were etched, silanized and luted (Variolink N) into a dentin analogue material. Fatigue failure load was determined using the Staircase method (100,000 cycles at 20 Hz; initial fatigue load ∼60% of the mean monotonic load-to-failure; step size ∼5% of the initial fatigue load). A stainless-steel piston (ϕ = 40 mm) applied the load into the center of the specimens submerged in water. Fractographic analysis and Finite Element Analysis (FEA) were also performed. Results The ceramic thickness influenced the fatigue failure load for both ZLS materials: Suprinity (716 N up to 1119 N); Celtra (404 N up to 1126 N). FEA showed that decreasing ceramic thickness led to higher stress concentration on the cementing interface. Significance Different ZLS glass-ceramic thicknesses influenced the fatigue failure load of the bonded system (i.e. the thicker the glass ceramic is, the higher the fatigue failure load will be). Different microstructures of the ZLS glass-ceramics might affect the fatigue behavior. FEA showed that the thicker the glass ceramic is, the lower the stress concentration at the tensile surface will be.
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