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  • Effect of poly(acrylic acid) architecture on setting and mechanical properties of glass ionomer cements
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-25
    R. Wetzel; O. Eckardt; P. Biehl; D.S. Brauer; F.H. Schacher
    更新日期:2020-01-26
  • Elucidating the corrosion-related degradation mechanisms of a Ti-6Al-4V dental implant
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-25
    Xin Chen; Kumar Shah; Shiqi Dong; Lars Peterson; Erika Callagon La Plante; Gaurav Sant
    更新日期:2020-01-26
  • Titanium and zirconium release from titanium- and zirconia implants in mini pig maxillae and their toxicity in vitro
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-25
    Xiuli He; Franz-Xaver Reichl; Stefan Milz; Bernhard Michalke; Xiao Wu; Christoph M. Sprecher; Yang Yang; Michael Gahlert; Stefan Röhling; Heinz Kniha; Reinhard Hickel; Christof Högg

    Objective Titanium (Ti)- and Zirconia (ZrO2)-implants in mini pig maxillae were compared with respect to Ti/zirconium (Zr) release into the surrounding bone tissues, the resulting short term tissue responses and the potential toxicity. Methods Ti/Zr release from Ti- and ZrO2-implants in mini pig maxillae was determined with inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). The spatial distribution of Ti and Zr in maxilla tissues near the implant surface was assessed with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). A histological analysis was performed to investigate the tissue responses after 12 weeks of implantation. The cytotoxicity and DNA damage of Ti particles and ZrO2 particles were studied with XTT and Comet assay. Results The mean Ti content in the bone adjacent to Ti-implants was 1.67 mg/kg-bone weight. The highest Ti content detected was 2.17 mg/kg-bone weight. The mean Zr content in the bone adjected to ZrO2-implants was 0.59 mg/kg-bone weight. The highest Zr content was 0.75 mg/kg-bone weight. The spatial distribution of the Ti and Zr in bone showed mainly a higher intensity of Ti and Zr close to the screw thread outer tip rather. Histological analysis indicated that near both implant-types signs of bone marrow fibrosis were present. EC50 of commercially available ZrO2-nanoparticles (NPs, <100 nm) and ZrO2-microparticles (MPs, <5 μm) was 13.96 mg/ml and 80.99 mg/ml, respectively. ZrO2-NPs and ZrO2-MPs can induce DNA damage at 70 μg/ml and 810 μg/ml, respectively. Significance After 12-weeks of implantation, increased concentrations of Ti and Zr can be detected in bone/tissues near Ti- and ZrO2-implants in mini pig maxillae. Ti content released from Ti-implants is two times higher than the Zr content released from ZrO2-implants. ZrO2-NPs showed lower cytotoxicity and DNA damage compared to results reported for Ti-NPs in human cells.

    更新日期:2020-01-26
  • Load-bearing capacity of CAD/CAM 3D-printed zirconia, CAD/CAM milled zirconia, and heat-pressed lithium disilicate ultra-thin occlusal veneers on molars
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-25
    A. Ioannidis; D. Bomze; C.H.F. Hämmerle; J. Hüsler; O. Birrer; S. Mühlemann

    Objectives The load-bearing capacity of ultra-thin occlusal veneers made of 3D-printed zirconia were compared to the ones obtained by fabricating these reconstructions by CAD/CAM milling zirconia or heat-pressing lithium-disilicate. Methods On 60 extracted human molars, the occlusal enamel was removed and extended into dentin. Occlusal veneers of 0.5 mm thickness were digitally designed. The specimens were divided into 3 groups (n = 20 each) differing in the restorative material and the fabrication technique of the occlusal veneer. (1) 3DP: 3D-printed zirconia (Lithoz); (2): CAM: milled zirconia (Ceramill Zolid FX); (3) HPR: heat-pressed lithium disilicate (IPS e.max Press). After conditioning procedures, the restorations were adhesively bonded onto the conditioned tooth. Thereafter, all specimens were aged in a chewing simulator by exposure to cyclic fatigue and temperature variations. Subsequently the specimens were statically loaded and the load which was necessary to decrease the maximum load by 20% and initiate a crack (Finitial) and the load which was needed to fracture the specimen (Fmax) were measured. Differences between the groups were compared applying the Kruskal-Wallis (KW) test and the Wilcoxon-Mann-Whitney-Test (WMW: p < 0.05). Results The median Finitial values for the groups 3DP, CAM and HPR were 1’650 N, 1’250 N and 500 N. The differences between all three groups were statistically significant (KW: p < 0.0001). The median Fmax values amounted to 2’026 N for the group 3DP, 1’500 N for the group CAM and 1’555 N for the group HPR. Significant differences were found between 3DP and CAM (WMW: p = 0.0238). Significance Regarding their load-bearing capacity, 3D-printed or milled zirconia as well as heat-pressed lithium disilicate can be recommended as restorative material for ultra-thin occlusal veneers to prosthetically compensate for occlusal tooth wear. Despite statistically significant differences between the restoration materials, all load-bearing capacities exceeded the clinically expected normal bite forces.

    更新日期:2020-01-26
  • The bulk compressive creep and recovery behavior of human dentine and resin-based dental materials
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-23
    Xiaodong Wang; Jing Zhou; Dehua Kang; Michael V. Swain; Jaroslav Menčík; Yutao Jian; Ke Zhao

    Objective To evaluate and compare the viscoelastic properties of dentine and resin-based dental materials by bulk compressive test and the Burgers model. Materials and methods Sound dentine, three resin composites as well as a resin-based cement were prepared into cylindrical specimens (n = 8). A bulk compressive creep test was applied with a constant load of 300 N (23.9 MPa) for 2 h, followed by another 2 h recovery. The maximum strain, creep stain, percentage of recovery and permanent set was measured using a linear variable displacement transducer. The viscoelastic properties were characterized via the Burgers model, and the instantaneous elastic, viscous as well as elastic delayed deformation were separated from the total strain. Data were analysed via ANOVA (or Welch's Test) and Tukey (or Games–Howell Test) with a significance level of 0.05. Results Sound dentine presented the lowest maximum strain, creep strain, permanent set and the highest percentage of recovery, followed by 3 resin composites with comparable parameters, while the cement showed a significantly higher maximum strain, permanent set and lower percentage of recovery (p < 0.001). The Burgers model presented acceptable fits for characterization viscoelastic processes of both dentine and resin-based dental materials. Viscous and elastic delayed strain of dentine was significantly lower than those for tested materials (p < 0.001) with the highest instantaneous elastic strain percentage. Similar viscous and delayed strain was found among the 4 resin-based materials (p > 0.05). Significance Sound dentine exhibited superior creep stability compared to resin-based dental materials. The viscous deformation in sound dentine could be ignored when loading parallel to dentine tubules.

    更新日期:2020-01-24
  • Optimization of a real-time high-throughput assay for assessment of Streptococcus mutans metabolism and screening of antibacterial dental adhesives
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-15
    Fernando Luis Esteban Florez; Rochelle Denise Hiers; Yan Zhao; Justin Merritt; Adam Justin Rondinone; Sharukh Soli Khajotia

    Objective The present work shows the optimization of a high-throughput bioluminescence assay to assess the metabolism of intact Streptococcus mutans biofilms and its utility as a screening method for nanofilled antibacterial dental materials. Methods The assay was optimized by monitoring changes in bioluminescence mediated by variation of the experimental parameters investigated (growth media and sucrose concentration, inoculum:D-Luciferin ratio, dilution factor, inoculum volume, luminescence wavelength, replicate and luciferase metabolic activity). Confocal microscopy was then used to demonstrate the impact of biofilm growth conditions on the 3-D distribution of extracellular polymeric substance (EPS) within Streptococcus mutans biofilms and its implications as confounding factors in high-throughput studies (HTS). Results Relative Luminescence Unit (RLU) values from the HTS optimization were analyzed by multivariate ANOVA (α = 0.05) and coefficients of variation, whereas data from 3-D structural parameters and RLU values of biofilms grown on experimental antibacterial dental adhesive resins were analyzed using General Linear Models and Student–Newman–Keuls post hoc tests (α = 0.05). Confocal microscopy demonstrated that biofilm growth conditions significantly influenced the quantity and distribution of EPS within the 3-D structures of the biofilms. An optimized HTS bioluminescence assay was developed and its applicability as a screening method in dentistry was demonstrated using nanofilled experimental antibacterial dental adhesive resins. Significance The present study is anticipated to positively impact the direction of future biofilm research in dentistry, because it offers fundamental information for the design of metabolic-based assays, increases the current levels of standardization and reproducibility while offering a tool to decrease intra-study variability.

    更新日期:2020-01-15
  • Standardization of antimicrobial testing of dental devices
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-09
    J. Camilleri; T. Arias Moliz; A. Bettencourt; J. Costa; F. Martins; D. Rabadijeva; D. Rodriguez; L. Visai; C. Combes; C. Farrugia; P. Koidis; C. Neves

    Objective Dental device is a very broad term that can be used to include any foreign material or product that is introduced in the host oral cavity to replace missing tissues. These devices are subjected to different environments which include dental hard tissues, tissue fluids, blood and saliva. All dental devices are continuously challenged microbiologically and a number of failures in clinical management are related to microbial colonization. Thus, the assessment of the antimicrobial properties of dental devices are extremely important. In this paper, a classification of dental devices is being proposed. This classification distinguishes the devices based on whether they are implantable or not, and also sub-classified based on their specific application and the substrate receiving the device. Methods and Results A literature search was conducted to identify how dental devices have been tested with relation to the microbial strains used and whether the testing has been performed in isolation or reported with other relevant tests such as material characterization and biological activity. The results of the literature review were analyzed and recommendations for antimicrobial testing of dental devices are proposed. These recommendations include the need for the setting up of pre-testing parameters such as ageing and the details of the pre-testing sterilization procedures, as these may affect the material chemistry and the specification for antimicrobial testing to be done with specific single strains or polymicrobial that are native to the region where the device is located are also suggested. Testing can be undertaken in vitro, ex vivo and in vivo. Since the antimicrobial and biological activities influence/condition one another and the material chemistry may affect both the antimicrobial and biological testing this document also makes recommendations regarding biological assessment which can be carried out in isolation or integrated with the microbiological testing and also material testing methods including chemical and physical characterization of bulk, surface, eluted and degraded materials as well as physical characterization methods. Significance The level of standardization of antimicrobial testing for the dental devices needs to be based on the device location and host interaction in order to increase the clinical applicability of the mentioned tests.

    更新日期:2020-01-11
  • Photo-polymerisation variables influence the structure and subsequent thermal response of dental resin matrices
    Dent. Mater. (IF 4.440) Pub Date : 2020-01-07
    Slobodan Sirovica; Yilan Guo; Raymond Guan; Maximilian W.A. Skoda; William M. Palin; Alexander P. Morrell; Dan L. Romanyk; Richard A. Martin; Owen Addison

    Objective The structure of the polymer phase of dental resin-based-composites is highly sensitive to photo-polymerisation variables. The objective of this study was to understand how different polymer structures, generated with different photo-polymerisation protocols, respond to thermal perturbation. Methods Experimental resins were prepared from a series of Bis-GMA/TEGDMA blends (40/60, 50/50 and 60/40 wt.%), with either Camphorquinone/DMAEMA or Lucirin TPO as the photo-initiator system. Resins were photo-polymerised, in a disc geometry, at either relatively ‘high’ (3000 mW cm−2 for 6 s) or ‘low’ (300 mW cm−2 for 60 s) irradiances ensuring matched radiant exposures (18 J cm−2). Specimens were heated, from 20−160 °C at a rate of 5 °C min−1, whilst simultaneous synchrotron X-ray scattering measurements were taken at 5 °C increments to determine changes in polymer chain segment extension and medium-range order as a function of temperature. For each unique resin composition (n = 3), differential scanning calorimetry was used to measure glass transition temperatures using the same heating protocol. A paired t-test was used to determine significant differences in the glass transition temperature between irradiance protocols and photo-initiator chemistry at ɑ = 0.05. Results Resins pre-polymerised through the use of TPO and or high irradiances demonstrated a reduced rate of chain extension indicative of lower thermal expansion and a larger decrease in relative order when heated below the glass transition temperature. Above the transition temperature, differences in the rate of chain extension were negligible, but slower converted systems showed greater relative order. There was no significant difference in the glass transition temperature between different photo-initiator systems or irradiance protocols. Significance The evolution of chain extension and medium-range order during heating is dependent on the initial polymer structure which is influenced by photo-polymerisation variables. Less ordered systems, generated at faster rates of reactive group conversion displayed reduced chain extension below the glass transition temperature and maintained lower order throughout heating.

    更新日期:2020-01-07
  • A review and current state of autonomic self-healing microcapsules-based dental resin composites
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-26
    Khaled Abid Althaqafi; Julian Satterthwaite; Nikolaos Silikas

    Objective This study systematically reviews the literature on self-healing microcapsule technology and evaluates the biocompatibility of self-healing microcapsules and the efficiency of crack repair within resin-based dental composites. Methods An electronic search was carried out using the following databases: MedLine (PubMed), Embase, the Cochrane Library and Google Scholar. All titles and abstracts of the articles and patents found were analysed and selected according to the eligibility criteria. Only studies published in English were included; the outcomes sought for this review were dental resin composites with self-healing potential. There were no restrictions on the type of self-healing system involved in dental resin composites. Results The search yielded 10 studies and 2 patents involving self-healing approaches to dental resin composites. According to the current literature on self-healing dental resin composites, when a crack or damage occurs to the composite, microcapsules rupture, releasing the healing agent to repair the crack with a self-healing performance ranging from 25% to 80% of the virgin fracture toughness. Significance Self-healing strategies used with resin composite materials have, to date, been bioinspired. So far, self-healing microcapsule systems within dental composites include poly urea-formaldehyde (PUF) or silica microcapsules. The main healing agents used in PUF microcapsules are DCPD monomer and TEGDMA-DHEPT, with other agents also explored. Silica microcapsules use water/polyacid as a healing agent. All self-healing systems have shown promising results for self-repair and crack inhibition, suggesting a prolonged life of dental composite restorations. More investigations and mechanical enhancements should be directed toward self-healing technologies in dental resin composites.

    更新日期:2019-12-27
  • Resin viscosity determines the condition for a valid exposure reciprocity law in dental composites
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-19
    Sri Vikram Palagummi; Taeseung Hong; Zhengzhi Wang; Chang Kwon Moon; Martin Y.M. Chiang

    Objective To provide conditions for the validity of the exposure reciprocity law as it pertains to the photopolymerization of dimethacrylate-based dental composites. Methods Composites made from different mass ratios of resin blends (Bis-GMA/TEGDMA and UDMA/TEGDMA) and silanized micro-sized glass fillers were used. All the composites used camphorquinone and ethyl 4-dimethylaminobenzoate as the photo initiator system. A cantilever beam-based instrument (NIST SRI 6005) coupled with NIR spectroscopy and a microprobe thermocouple was used to simultaneously measure the degree of conversion (DC), the polymerization stress (PS) due to the shrinkage, and the temperature change (TC) in real time during the photocuring process. The instrument has an integrated LED light curing unit providing irradiances ranging from 0.01 W/cm2 to 4 W/cm2 at a peak wavelength of 460 nm (blue light). Vickers hardness of the composites was also measured. Results For every dental composite there exists a minimum radiant exposure required for an adequate polymerization (i.e., insignificant increase in polymerization with any further increase in the radiant exposure). This minimum predominantly depends on the resin viscosity of composite and can be predicted using an empirical equation established based on the test results. If the radiant exposure is above this minimum, the exposure reciprocity law is valid with respect to DC for high-fill composites (filler contents >50% by mass) while invalid for low-fill composites (that are clinically irrelevant). Significance The study promotes better understanding on the applicability of the exposure reciprocity law for dental composites. It also provides a guidance for altering the radiant exposure, with the clinically available curing light unit, needed to adequately cure the dental composite in question.

    更新日期:2019-12-19
  • 更新日期:2019-12-19
  • Cytotoxic and genotoxic potential of respirable fraction of composite dust on human bronchial cells
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-15
    Stevan M. Cokic; Manosij Ghosh; Peter Hoet; Lode Godderis; Bart Van Meerbeek; Kirsten L. Van Landuyt

    Objective To determine the cytotoxic and genotoxic potential of the respirable fraction of composite dust (<4 μm) on human bronchial epithelial cells. Methods Composite sticks of three commercial dental composites (Filtek Supreme XTE, Grandio, Transbond XT) were ground in an enclosed plexiglass chamber with a rough dental bur (grain-size 100 μm) and the generated airborne respirable dust was collected in a personal cyclone on a teflon filter (pore size 5 μm). Immediately after particle collection, the dust was quantified gravimetrically and the particles were suspended in cell culturing medium. Next, human bronchial epithelial cells (16HBE14o-) were exposed to the suspensions (3 μg/ml–400 μg/ml). After 24 h, cell viability (WST-1 assay) and membrane integrity (LDH assay) were evaluated. Furthermore, the genotoxic effect of a sub-cytotoxic concentration (50 μg/ml) of composite dust was evaluated by the comet assay after 3 h exposure and cell cycle disturbances were analyzed by flow cytometry. Cellular uptake of particles was evaluated by transmission electronic microscope (TEM). Results For all three tested composite materials, a decrease in metabolic activity of 10–35% was observed when the cells were exposed to the highest concentrations (100 μg/ml–400 μg/ml). Toxicity was partially linked to membrane disruption especially after 72 h exposure. All tested composites provoked a mild genotoxic effect after short-term exposure compared to the control groups. TEM revealed that respirable particles of all tested composites were taken up by the cells. Significance The respirable fraction of composite dust only showed cytotoxic effects at the highest concentrations, whereas mild genotoxicity was observed after exposure to a sub-cytotoxic concentration.

    更新日期:2019-12-17
  • Effects of S. mutans gene-modification and antibacterial monomer dimethylaminohexadecyl methacrylate on biofilm growth and acid production
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-12
    Hong Chen; Yunhao Tang; Michael D. Weir; Jianghong Gao; Satoshi Imazato; Thomas W. Oates; Lei Lei; Suping Wang; Tao Hu; Hockin H.K. Xu

    Objectives Antibacterial quaternary ammonium monomers (QAMs) are used in resins. The rnc gene in Streptococcus mutans (S. mutans) plays a key role in resisting antibiotics. The objectives of this study were to investigate for the first time: (1) the effects of rnc deletion on S. mutans biofilms and acid production; (2) the combined effects of rnc deletion with dimethylaminohexadecyl methacrylate (DMAHDM) on biofilm-inhibition efficacy. Methods Parent S. mutans strain UA159 (ATCC 700610) and the rnc-deleted S. mutans were used. Bacterial growth, minimum inhibitory concentration (MIC), and minimal bactericidal concentration (MBC) were measured to analyze the bacterial susceptibility of the parent and rnc-deleted S. mutans against DMAHDM, with the gold-standard chlorhexidine (CHX) as control. Biofilm biomass, polysaccharide and lactic acid production were measured. Results The drug-susceptibility of the rnc-deleted S. mutans to DMAHDM or CHX was 2-fold higher than parent S. mutans. The drug-susceptibility did not increase after 10 passages (p < 0.05). Deleting the rnc gene increased the biofilm susceptibility to DMAHDM or CHX by 2-fold. The rnc-deletion in S. mutans reduced biofilm biomass, polysaccharide and lactic acid production, even at no drugs. DMAHDM was nearly 40 % more potent than the gold-standard CHX. The combination of rnc deletion + DMAHDM treatment achieved the greatest reduction in biofilm biomass, polysaccharide synthesis, and lactic acid production. Significance Gene modification by deleting the rnc in S. mutans reduced the biofilm growth and acid production, and the rnc deletion + DMAHDM method showed the greatest biofilm-inhibition efficacy, for the first time. The dual strategy of antibacterial monomer + bacterial gene modification shows great potential to control biofilms and inhibit caries.

    更新日期:2019-12-13
  • Evaluation of alternative photoinitiator systems in two-step self-etch adhesive systems
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-09
    Suzanne M. Almeida, Carine T.W. Meereis, Fernanda B. Leal, Rodrigo V. Carvalho, Peterson O. Boeira, Luiz A. Chisini, Carlos E. Cuevas-Suárez, Giana S. Lima, Evandro Piva

    Objective The aim of this study was to evaluate the effect of different photoinitiator systems on the cell viability and physico-chemical properties of an experimental adhesive resin of a two-step self-etch adhesive system. Methods Eight photoinitiators and coinitiators were evaluated, camphorquinone (CQ); ethyl-dimethylamino benzoate (EDAB); diphenyliodonium hexafluorophosphate (DPIHFP); 1,3-benzodioxole (BDO); piperonyl alcohol (AP); 1,3-diethyl-2-thiobarbituric acid (TBA); bisphenyl phosphinic oxide (BAPO); and diphenyl phosphinic oxide (TPO). Seven experimental adhesive resins (Bis-GMA:TEGDMA – 1:1 by wt%) were formulated by varying the initiation systems: RCQ+EDAB (control), RCQ+EDAB+DPHFP, RCQ+BDO, RCQ+AP, RCQ+TBA, RBAPO and RTPO. The cell viability of the different photoinitiators in their isolated form and after being incorporated into the adhesive resins was evaluated using the MTT assay. The degree of conversion within the hybrid layer (DC in situ) was evaluated by micro-Raman spectroscopy; the polymerization kinetics, by FTIR spectroscopy. The water sorption (Wsp) and solubility (Wsl) were calculated by using percentage of gain and loss of mass. Data were analyzed using One-way ANOVA and Kruskal-Wallis tests (α = 0.05). Results When evaluated in their isolated form, the DPIHFP was considered cytotoxic in all concentrations evaluated. When incorporated into and adhesive resin, RCQ+TBA presented higher cell viability values than control and the highest values of DC in situ (p < 0.05). Additionally, the use of CQ + TBA showed a higher cell viability when compared with the conventional CQ + EDAB system. Significance The pair CQ + TBA could be potentially useful in the development of materials with improved biocompatibility.

    更新日期:2019-12-11
  • Hydroxyapatite-based cements induce different apatite formation in radicular dentin
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-07
    Manuel Toledano-Osorio, Fátima S. Aguilera, Raquel Osorio, Esther Muñoz-Soto, Mayra C. Pérez-Álvarez, Modesto T. López-López, Christopher D. Lynch, Manuel Toledano
    更新日期:2019-12-07
  • Novel riboflavin/VE-TPGS modified universal dentine adhesive with superior dentine bond strength and self-crosslinking potential
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-07
    U. Daood, Salvatore Sauro, Malikarjuna Rao Pichika, Hanan Omar, Seow Liang Lin, A.S. Fawzy

    Objective To modify a universal dentine adhesive with different concentrations of riboflavin and D-Alpha 1000 Succinate polyethylene (VE-TPGS) as a chemical enhancer and to assess the micro-tensile bond strength (24h/12 months), determine resin penetration, measurement of intermolecular interactions and cytotoxicity. Materials and methods An experimental adhesive system based on bis-GMA, HEMA and hydrophobic monomer was doped with RF0.125 (RF – Riboflavin) or RF/VE-TPGS (0.25/0.50) and submitted to μTBS evaluation. Resin dentine slabs were prepared and examined using SEM and TEM. Adhesion force was analysed on ends of AFM cantilevers deflection. Quenched peptide assays were performed using fluorescence scanner and wavelengths set to 320 nm and 405 nm. Cytotoxicity was assessed using human peripheral blood mononuclear cell line. Molecular docking studies were carried out using Schrödinger small-molecule drug discovery suite 2018-2. Data from viable cell results was analyzed using one-way ANOVA. Bond strength values were analysed by two-way ANOVA. Nonparametric results were analyzed using a Kruskal–Wallis test at a 0.05 significance level. Results RF/VE-TPGS0.25 groups showed highest bond strength results after 24-h storage in artificial saliva (p < 0.05). RF/VE-TPGS0.50 groups showed increased bond strength after 12-months of ageing. RF/VE-TPGS modified adhesives showed appreciable presence of a hybrid layer. Packing fraction indicated solid angle profiles describing well sized density and topology relations for the RF/VE-TPGS adhesives, in particular with the RF/VE-TPGS0.50 specimens. Qualitative analysis of the phenotype of macrophages was prominently CD163+ in the RF/VE-TPGS0.50. Both the compounds showed favourable negative binding energies as expressed in terms of ‘XP GScore’. Conclusion New formulations based on the incorporation of RF/VE-TPGS in universal adhesives may be of significant potential in facilitating penetration, distribution and uptake of riboflavin within the dentine surface.

    更新日期:2019-12-07
  • Ex vivo detection and quantification of apically extruded volatile compounds and disinfection by-products by SIFT-MS, during chemomechanical preparation of infected root canals
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-06
    K Ioannidis, C Batty, C Turner, D Smith, S Deb, F Mannocci

    Objectives To assess the release and apical extrusion of toxic volatile compounds and disinfection by-products during instrumentation and irrigation of artificially infected root canal specimens, with sodium hypochlorite and ethylene diamine tetra acetic acid. Methods Forty-two single-rooted human teeth were decoronated to obtain 15 mm-long root specimens and working length was determined 1 mm short of root apex. All specimens were initially preflared, to create sufficient conical space for the development of a nutrient-stressed multispecies biofilm. The specimens were randomly assigned into three groups [Group 1; no endodontic intervention, Group 2; instrumentation with rotary files and irrigation with sterile saline, Group 3; instrumentation with rotary files and irrigation with 2.5% sodium hypochlorite (NaOCl) and 17% ethylene diamine tetra acetic acid (EDTA)]. A customised experimental model apparatus was fabricated for each specimen. The apical root third was inserted in a glass vial filled with sterile ultrapure water, to simulate high-compliance periradicular space. The reaction products of the aliquots obtained from the glass vials were analysed in real time, by selected ion flow tube mass spectrometry (SIFT-MS) in triplicates. Two-way analysis of variance (ANOVA) with post hoc Tukey tests were used for data analysis. The level of statistical significance was set at P < 0.05. Results The group of teeth that were not subjected to endodontic intervention did not show any volatile compounds (VOCs) or disinfection by products (DBPs) whilst instrumentation and irrigation of root canals (Groups 2 and 3) resulted in the apical extrusion of VOCs and DBPs. In Group 3, the aliquots obtained from periradicular space released high concentrations of methanol, propanol, ammonia, chloroform, together with unexpected higher levels of formaldehyde, which were statistically significant compared to Group 2 (P < 0.05). Significance The mechanical preparation and irrigation of artificially infected root canals with rotary files, 2.5% NaOCl and 17% EDTA resulted in the formation of toxic VOCs and DBPs in a water-closed periradicular space. The chemical interaction of NaOCl and EDTA resulted in the generation of high concentrations of formaldehyde. The formation of chloroform and formaldehyde indicate that risk assessment of the potential hazards to health should be carried out.

    更新日期:2019-12-06
  • Dynamic covalent chemistry (DCC) in dental restorative materials: Implementation of a DCC-based adaptive interface (AI) at the resin–filler interface for improved performance
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-04
    Nancy Sowan, Adam Dobson, Maciej Podgorski, Christopher N. Bowman

    Objective Dental restorative composites have been extensively studied with a goal to improve material performance. However, stress induced microcracks from polymerization shrinkage, thermal and other stresses along with the low fracture toughness of methacrylate-based composites remain significant problems. Herein, the study focuses on applying a dynamic covalent chemistry (DCC)-based adaptive interface to conventional BisGMA/TEGDMA (70:30) dental resins by coupling moieties capable of thiol–thioester (TTE) DCC to the resin–filler interface as a means to induce interfacial stress relaxation and promote interfacial healing. Methods Silica nanoparticles (SNP) are functionalized with TTE-functionalized silanes to covalently bond the interface to the network while simultaneously facilitating relaxation of the filler–matrix interface via DCC. The functionalized particles were incorporated into the otherwise static conventional BisGMA/TEGDMA (70:30) dental resins. The role of interfacial bond exchange to enhance dental composite performance in response to shrinkage and other stresses, flexural modulus and toughness was investigated. Shrinkage stress was monitored with a tensometer coupled with FTIR spectroscopy. Flexural modulus/strength and flexural toughness were characterized in three-point bending on a universal testing machine. Results A reduction of 30% in shrinkage stress was achieved when interfacial TTE bond exchange was activated while not only maintaining but also enhancing mechanical properties of the composite. These enhancements include a 60% increase in Young’s modulus, 33% increase in flexural strength and 35% increase in the toughness, relative to composites unable to undergo DCC but otherwise identical in composition. Furthermore, by combining interfacial DCC with resin-based DCC, an 80% reduction of shrinkage-induced stress is observed in a thiol–ene system “equipped” with both types of DCC mechanisms relative to the composite without DCC in either the resin or at the resin–filler interface. Significance This behavior highlights the advantages of utilizing the DCC at the resin–filler interface as a stress-relieving mechanism that is compatible with current and future developments in the field of dental restorative materials, nearly independent of the type of resin improvements and types that will be used, as it can dramatically enhance their mechanical performance by reducing both polymerization and mechanically applied stresses throughout the composite lifetime.

    更新日期:2019-12-04
  • Multifunctional monomer acts as co-initiator and crosslinker to provide autonomous strengthening with enhanced hydrolytic stability in dental adhesives
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-03
    Linyong Song, Rizacan Sarikaya, Qiang Ye, Anil Misra, Candan Tamerler, Paulette Spencer
    更新日期:2019-12-03
  • Effects of ZnO/TiO2 nanoparticle and TiO2 nanotube additions to dense polycrystalline hydroxyapatite bioceramic from bovine bones
    Dent. Mater. (IF 4.440) Pub Date : 2019-12-02
    Luara Aline Pires, Lucas José de Azevedo Silva, Brunna Mota Ferrairo, Rogério Erbereli, João Fiore Parreira Lovo, Orisson Ponce Gomes, José Henrique Rubo, Paulo Noronha Lisboa-Filho, Jason Alan Griggs, Carlos Alberto Fortulan, Ana Flávia Sanches Borges

    Objectives A bovine dense hydroxyapatite ceramic (HA) was produced as new biomaterial, however, the production of a material with consistently high flexural strength remains challenging. The objective of this study was to evaluate the effects of ZnO nanoparticles, TiO2 nanoparticles, and TiO2 nanotubes (1%, 2%, and 5% by weight) on the microstructure and flexural strength of a bovine dense hydroxyapatite ceramic (HA). Methods Discs (Ø = 12.5 mm; thickness = 1.3 mm) were prepared and subjected to X-ray diffraction (XRD), and observation with a field emission scanning electron microscope (FE-SEM), biaxial flexural strength (BFS) testing, and Vickers hardness (VH) testing. The BFS and VH data were subjected to ANOVA and Tukey post-hoc tests (α = 0.05) and Weibull analysis. Results The XRD showed that the addition of nanomaterials caused the formation of a secondary phase when 5% of the ZnO nanoparticles was used, or when all percentages of the TiO2 nanoparticles/nanotubes were used, and the HA crystallographic planes were maintained. Differences were not observed between the higher BFS values obtained with pure HA and those obtained with the 5% addition of TiO2 nanoparticles. However, the results were different compared with the other groups (α = 0.05). The results obtained by Weibull analysis revealed that the 1%, 2%, and 5% addition of TiO2 nanotubes, and the 1% and 2% addition of TiO2 nanoparticles decreased the HA characteristic strength (σ0), while the Weibull modulus (m) increased when 5% of TiO2 nanoparticles, 1% and 2% of ZnO nanoparticles, and 2% of TiO2 nanoparticles were added, but with no statistical difference from the pure HA. The 5% addition of ZnO2 nanoparticles decreased the σ0 without changing m. Moreover, the 5% addition of TiO2 nanoparticles resulted in an m closest to that of pure HA. Regarding the VH results, the blend of HA with 1% and 2% addition of TiO2 nanoparticles exhibited the higher values, which were similar between the different addition ratios (p = 0.102). Moreover, the addition of 5% TiO2 nanoparticles resulted in higher value compared with pure HA. Significance This study demonstrated that the HA blend with 5% of TiO2 nanoparticles has the greatest potential as a bovine HA dense bioceramic reinforcement.

    更新日期:2019-12-03
  • Sulfinates and sulfonates as high performance co-initiators in CQ based systems: Towards aromatic amine-free systems for dental restorative materials
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Julie Kirschner, Florian Szillat, Mariem Bouzrati-Zerelli, Jean-Michel Becht, Joachim E. Klee, Jacques Lalevée
    更新日期:2019-11-30
  • Development of Bis-GMA-free biopolymer to avoid estrogenicity
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Soo-Kyung Jun, Jae-Ryung Cha, Jonathan C. Knowles, Hae-Won Kim, Jung-Hwan Lee, Hae-Hyoung Lee
    更新日期:2019-11-30
  • Vinyl sulfonamide based thermosetting composites via thiol-Michael polymerization
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Jasmine Sinha, Adam Dobson, Osamah Bankhar, Maciej Podgórski, Parag K. Shah, Sheryl L.W. Zajdowicz, Abdulaziz Alotaibi, Jeffrey W. Stansbury, Christopher N. Bowman

    Objective To assess the performance of thiol Michael photocurable composites based on ester-free thiols and vinyl sulfonamides of varying monomer structures and varied filler loadings and to contrast the properties of the prototype composites with conventional BisGMA-TEGDMA methacrylate composite. Methods Synthetic divinyl sulfonamides and ester-free tetrafunctional thiol monomers were utilized for thiol-Michael composite development with the incorporation of thiolated microfiller. Polymerization kinetics was investigated using FTIR spectroscopy. Resin viscosities were assessed with rheometry. Water uptake properties were assessed according to standardized methods. Thermomechanical properties were analyzed by dynamic mechanical analysis. Flexural modulus/strength and flexural toughness were measured on a universal testing machine in three-point bending testing mode. Results The vinyl sulfonamide-based thiol-Michael resin formulation demonstrated a wide range of viscosities with a significant increase in the functional group conversion when compared to the BisGMA-TEGDMA system. The two different types of vinyl sulfonamide under investigation demonstrated significant differences towards the water sorption. Tertiary vinyl sulfonamide did not undergo visible swelling whereas the secondary vinyl sulfonamide composite swelled extensively in water. With the introduction of rigid monomer into the polymer matrix the glass transition temperature increased and so increased the toughness. Glassy thiol-Michael composites were obtained by ambient curing. Significance Employing the newly developed step-growth thiol-Michael resins in dental composites will provide structural uniformity, improved stability and lower water sorption.

    更新日期:2019-11-30
  • Three-dimensional tissue engineering-based Dentin/Pulp tissue analogue as advanced biocompatibility evaluation tool of dental restorative materials
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Christina Hadjichristou, Eleni Papachristou, Ioannis Bonovolias, Athina Bakopoulou

    Objective Two-dimensional (2D) in vitro models have been extensively utilized for cytotoxicity assessment of dental materials, but with certain limitations in terms of direct in vitro-in vivo extrapolation (IVIVE). Three-dimensional (3D) models seem more appropriate, recapitulating the structure of human tissues. This study established a 3D dentin/pulp analogue, as advanced cytotoxicity assessment tool of dental restorative materials (DentCytoTool). Methods DentCytoTool comprised two compartments: the upper, representing the dentin component, with a layer of odontoblast-like cells expanded on microporous membrane of a cell culture insert and covered by a treated dentin matrix; and the lower, representing a pulp analogue, incorporating HUVEC/SCAP co-cultures into collagen I/fibrin hydrogels. Representative resinous monomers (HEMA: 1–8 mM; TEGDMA: 0.5–5 mM) and bacterial components (LPS: 1 μg/ml) were applied into the construct. Cytotoxicity was assessed by MTT and LDH assays, live/dead staining and real-time PCR for odontogenesis- and angiogenesis-related markers. Results DentCytoTool supported cell viability and promoted capillary-like network formation inside the pulp analogue. LPS induced expression of odontogenesis-related markers (RUNX2, ALP, DSPP) without compromising viability of the odontoblast-like cells, while co-treatment with LPS and resin monomers induced cytotoxic effects (live/dead staining, MTT and LDH assays) in cells of both upper and lower compartments and reduced expression angiogenesis-related markers (VEGF, VEGFR2, ANGPT-1, Tie-2, PECAM-1) in a concentration- and time- dependent manner. LPS treatment aggravated TEGDMA-induced and -in certain concentrations (2–4 mM)- HEMA-induced cytotoxicity. Significance DentCytoTool represents a promising tissue-engineering-based cytotoxicity assessment tool, providing more insight into the mechanistic aspects of interactions of dental materials to the dentin/pulp complex.

    更新日期:2019-11-30
  • Influence of collagen cross-linkers addition in phosphoric acid on dentin biomodification and bonding of an etch-and-rinse adhesive
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    D.M. De-Paula, D. Lomonaco, A.M.P. Ponte, K.E. Cordeiro, M.M. Moreira, S.E. Mazzetto, V.P. Feitosa

    Objective To investigate the effects of natural collagen cross-linkers incorporation in phosphoric acid etchant on dentin biomodification, microtensile bond strength (μTBS) and nanoleakage (NL) of a two-step etch-and-rinse adhesive. Methods Experimental aqueous solution of 37% ortho-phosphoric acid were prepared with the addition of 2% biomodification agents: Lignin (LIG) from industrial paper production residue, Cardanol (CARD) from cashew-nut shell liquid, and Proanthocyanidin (PAC) from grape-seed extract. Negative control (NC) was acid solution without cross-linker whilst commercial control (CC) was Condac 37 gel (FGM). Dentin specimens were assayed by FTIR after 15 s etching to detect collagen cross-linking. Extracted third molars were used for μTBS (n = 7) and fracture mode analysis of Optibond S (Kerr), tested after 24 h or 1000 thermal cycles. NL was surveyed by SEM. Statistical analysis was performed with two-way ANOVA and Tukey’s test (p < 0.05). Results FTIR confirmed cross-linking for all agents. μTBS of CC was the highest (46.6 ± 6.2 MPa), but reduced significantly after aging (35.7 ± 5.2 MPa) (p < 0.001). LIG (30.6 ± 3.7 MPa) and CARD (28.3 ± 1.8 MPa) attained similar μTBS which were stable after aging (p > 0.05). Fracture mode was predominantly adhesive. At 24 h, all groups showed presence of silver uptake in hybrid layer, except CARD. After aging, CARD- and LIG-treated specimens exhibited little amount of silver penetration. CC, PAC and NC showed gaps, great nanoleakage at hybrid layer and presence of water channels in adhesive layer. Significance Altogether, ortho-phosphoric acid incorporated with LIG and CARD promotes stable resin-dentin bond strength with minor nanoleakage after aging, thereby achieving therapeutic impact without additional clinical steps.

    更新日期:2019-11-30
  • The effect of temperature and ionic solutes on the fluoride release and recharge of glass-ionomer cements
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Faisal Madi, Sharanbir K. Sidhu, John W. Nicholson

    Objective To determine the effect of storage temperature and the presence of sodium chloride in solution on the fluoride uptake and release of glass-ionomer cements. Methods Several commercial brands were used, and stored at either room temperature (21–23 °C) or 37 °C, in KF solution at a concentration of 1000 ppm F− with and without 0.9% NaCl present. Fluoride levels in the storage solutions after 24 h were measured using a fluoride-ion selective electrode. Specimens were then stored in water, and fluoride release after 24 h was determined. Studies were also carried out to determine chloride levels when specimens were stored in 0.9% NaCl, with or without 1000 ppm fluoride, again using an ion selective electrode. Results All glass-ionomer specimens took up fluoride, and most of the fluoride was retained over the next 24 h when the specimens were stored in water. There was a slight variation in the amount of fluoride taken up with storage temperature and with the presence of sodium chloride. All specimens also took up chloride, with greater uptake at higher temperatures, but little or no effect when KF was also present in solution. Significance The substantial retention of fluoride after 24 h in deionised water confirms previous findings and suggests that an insoluble species, possibly SrF2, forms in situ. Chloride uptake has not been reported previously, and its significance requires further investigation. Fluoride and chloride uptake were apparently independent of each other, which suggests that the ions are taken up at different sites in the cement. This may relate to differences in the respective sizes and hydration states of F− and Cl− ions.

    更新日期:2019-11-30
  • Effect of different materials and undercut on the removal force and stress distribution in circumferential clasps during direct retainer action in removable partial dentures
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    João Paulo Mendes Tribst, Amanda Maria de Oliveira Dal Piva, Alexandre Luiz Souto Borges, Rodrigo Máximo Araújo, João Maurício Ferraz da Silva, Marco Antonio Bottino, Cornelis Johannes Kleverlaan, Niek de Jager

    Objectives This study aimed to evaluate the effect of different materials and undercut on the removal force and stress distribution in the supporting tooth and in the circumferential clasp used in removable partial prosthesis. Methods Upper molars prepared for Akers circumferential clasp with retention and opposing arm were modeled, scanned, elaborated with CAD software and the geometries imported in FEA and analyzed. Six different materials were selected for the clasp (Polyamide, Polyoxymethylene, Polyetheretherketone - PEEK, Gold alloy, Titanium and CoCr) and 3 different undercuts (0.25, 0.50 and 0.75 mm), totaling 18 groups. Results The clasps presented greater stress in their structure and potentially greater damage to the dental enamel when made with rigid materials and with more undercut; however, they presented greater ability to remain in position. Significance Polyamide with a higher undercut is an esthetic alternative to rigid metallic clasps. It showed promising behavior because it strongly reduces the damage to the enamel, and even with an undercut of 0.75, the retention is lower than for CoCr with a 0.25 undercut, and this retention might still be sufficient. Polyoxymethylene and Polyetheretherketone (PEEK) are not suitable materials for the clasps, because the maximum stress occurring during removal with higher undercuts is higher than the material strength.

    更新日期:2019-11-30
  • Composite resin reinforced with fluorescent europium-doped hydroxyapatite nanowires for in-situ characterization
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Lei Li, Dan Li, Wenwen Zhao, Qing Cai, Gang Li, Yunhua Yu, Xiaoping Yang

    Objective The object is to find an easy but efficient way to illustrate the in-situ dispersion of nano-scaled one-dimensional fillers in composite resins, and to correlate their dispersion status with the properties of composite resins. Methods Fluorescent europium-doped hydroxyapatite nanowires (HANW:Eu) were synthesized via the hydrothermal method. The HANW:Eu was mixed into Bis-GMA/TEGDMA (60/40, w/w) at different contents (1–5 wt.%), and different processing methods (kneading, grinding, stirring) were tested to achieve good dispersion of HANW:Eu with the aid of fluorescent imaging system. Then, the mixtures of HANW:Eu and barium glass powder (BaGP) were kneaded into resin at a fixed content (70 wt.%) while at different mixing ratios. In addition to the 3D fluorescent imaging, characterizations were carried out on mechanical properties, fractured surface, wear resistance and polymerization shrinkage, to correlate the composite properties of with the dispersion status of the incorporated HANW:Eu. Results By doping calcium with 5 mol.% of europium, the obtained HANW:Eu displayed strong fluorescence, which made the illustration of its in-situ dispersion status within composites being possible. And this helped to judge that kneading was more efficient to homogeneously disperse HANW:Eu than grinding and stirring. However, it was illustrated vividly that HANW:Eu aggregated severely when it was co-incorporated with BaGP into composites at the total content of 70 wt.%, which had not been previously revealed by other microscope observations. In comparison with composites containing 70 wt.% of BaGP, improvements in the mechanical properties of resulting composites were identified for the cases containing 3 wt.% of HANW and 67 wt.% of BaGP, however, their wear volume loss and the polymerization shrinkage did not decrease as expected due to the HANW aggregations. Significance The fluorescent filler prepared in this study provides a feasible strategy to illustrate the in-situ dispersion status of inorganic fillers, which provides guidance for the processing of composite resins.

    更新日期:2019-11-30
  • Niobium containing bioactive glasses as remineralizing filler for adhesive resins
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Gabriela de Souza Balbinot, Fabrício Mezzomo Collares, Tiago Luis Herpich, Fernanda Visioli, Susana Maria Werner Samuel, Vicente Castelo Branco Leitune
    更新日期:2019-11-30
  • Polymeric scaffolds for dental pulp tissue engineering: A review
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-30
    Hossein E. Jazayeri, Su-Min Lee, Lauren Kuhn, Farahnaz Fahimipour, Mohammadreza Tahriri, Lobat Tayebi

    Objectives The purpose of this review is to describe recent developments in pulp tissue engineering using scaffolds and/or stem cells. It is crucial to understand how this approach can revitalize damaged dentin-pulp tissue. Widespread scaffold materials, both natural and synthetic, and their fabrication methods, and stem-progenitor cells with the potential of pulp regeneration will be discussed. Data and Sources A review of literature was conducted through online databases, including MEDLINE by using the PubMed search engine, Scopus, and the Cochrane Library. Study Selection Studies were selected based on relevance, with a preference given to recent research, particularly from the past decade. Conclusions The use of biomaterial scaffolds and stem cells can be safe and potent for the regeneration of pulp tissue and re-establishment of tooth vitality. Natural and synthetic polymers have distinct advantages and limitations and in vitro and in vivo testing have produced positive results for cell attachment, proliferation, and angiogenesis. The type of biomaterial used for scaffold fabrication also facilitates stem cell differentiation into odontoblasts and the resulting biochemistry of tissue repair for each polymer and cell type was discussed. Multiple methods of scaffold design exist for pulp tissue engineering, which demonstrates the variability in tissue engineering applications in endodontics. This review explains the potential of evidence-based tissue engineering strategies and outcomes in pulp regeneration.

    更新日期:2019-11-30
  • Bonding to industrial indirect composite blocks: A systematic review and meta-analysis
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-27
    Hao Yu, Mutlu Özcan, Keiichi Yoshida, Hui Cheng, Takashi Sawase
    更新日期:2019-11-28
  • Remineralization effectiveness of the PAMAM dendrimer with different terminal groups on artificial initial enamel caries in vitro
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-27
    Menglin Fan, Min Zhang, Hockin H.K. Xu, Siying Tao, Zhaohan Yu, Jiaojiao Yang, He Yuan, Xuedong Zhou, Kunneng Liang, Jiyao Li

    Objective Disruption of the demineralization–remineralization balance could trigger the development of dental caries, making it challenging for enamel to “self-heal”. Thus, extrinsic assistance is needed to restore enamel lesions and stop undermining progression. The aim of this study was to investigate enamel remineralization in a simulated oral environment via poly (amino amine) (PAMAM) dendrimers quantitatively. Methods Bovine enamel specimens were shaken in demineralization solution (pH 4.5, 37 °C, 50 rpm/min) for 72 h to create initial enamel carious lesions. The subsurface-demineralized specimens were then divided into four groups: enamel treated with PAMAM-NH2, enamel treated with PAMAM−COOH, enamel treated with PAMAM−OH, and enamel treated with deionized water. The treated specimens underwent subsequent 12-day pH cycling. Enamel blocks were analyzed by transverse microradiography (TMR), surface microhardness testing and scanning electron microscopy (SEM) before and after demineralization and pH cycling. Results Groups treated with PAMAM dendrimers showed lower lesion depth and less mineral loss, attained more vertical-section surface microhardness recovery, and adsorbed more mineral deposits (p < 0.05). The enamel lesion remineralization values of PAMAM-NH2, PAMAM-COOH, and PAMAM-OH groups were 76.42 ± 3.32%, 60.07 ± 5.92% and 54.52 ± 7.81%, respectively. Significance In conclusion, PAMAM with different terminal groups could induce enamel remineralization, among which PAMAM-NH2 showed the most prominent competence, followed by PAMAM-COOH and PAMAM-OH, in that order.

    更新日期:2019-11-28
  • Comparison of various 3D printed and milled PAEK materials: Effect of printing direction and artificial aging on Martens parameters
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-27
    Alexander Prechtel, Marcel Reymus, Daniel Edelhoff, Reinhard Hickel, Bogna Stawarczyk

    Objectives The aim of this study was to investigate the effect of artificial aging on the Martens parameters of different 3D printed and milled polyaryletherketon (PAEK) materials. Methods In total 120 specimens of 4 different polyetheretherketon (PEEK) materials (Essentium PEEK, KetaSpire PEEK MS-NT1, VICTREX PEEK 450 G and VESTAKEEP i4 G) were additively manufactured via fused layer manufacturing (FLM) in either horizontal or vertical directions (n = 15 per group). 75 specimens were milled out of prefabricated PAEK blanks from the materials breCAM.BioHPP, Dentokeep, JUVORA Dental Disc 2 and Ultaire AKP ( = 15 per group). Martens hardness (HM), indentation hardness (HIT) and indentation modulus (EIT) were determined initially and longitudinally after thermocycling (5−55 °C, 10,000x) and autoclaving (134 °C, 2 bar). In each case, the surface topography of the specimens was examined for modifications using a light microscope. Data were analysed with Kolmogorov-Smirnov test, univariate ANOVA followed by post-hoc Scheffé test with partial eta squared (ηp2), Kruskal–Wallis-, Mann–Whitney-U-, Friedman- and Wilcoxon-Test. A value of p < 0.05 was considered as significant. Results Milled specimens showed higher Martens parameters than printed ones (p < 0.001). Artificial aging had a negative effect on the measured parameters (p < 0.001). Horizontally printed specimens presented higher Martens parameters than vertically printed ones, regardless of material and aging process (p < 0.001). Essentium PEEK and breCAM.BioHPP showed the highest and VICTREX PEEK 450G as well as Ultaire AKP the lowest values of all investigated PAEK materials initially, after thermocycling and after autoclaving (p < 0.001). Microscopic examinations showed that artificial aging did not cause any major modifications of the materials. Significance Additively manufactured PEEK materials showed lower Martens parameters than milled ones, whereas horizontally printed specimens presented higher values than vertically printed ones. Artificial aging had a negative effect on the Martens parameters, but not on the surface topography.

    更新日期:2019-11-28
  • Retrospective analysis on the repair vs. replacement of composite restorations
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-26
    Philipp Kanzow, Annette Wiegand

    Objective Our retrospective study aimed to assess the impact of repairs on the longevity of anterior and posterior direct composite restorations and to compare longevity of repaired and replacement restorations. Methods Patient records were retrospectively screened for anterior and/or posterior composite restorations with 2+ surfaces placed in permanent teeth between 2000 and 2015. During follow-up, repaired and replaced restorations were assessed and mean annual failure rates (mAFR) calculated. Outcome was considered in three levels: Success (no further intervention), survival 1 (first repair = survival, second repair = failure) and survival 2 (more than one repair = survival, all surfaces repaired = failure). Statistical analysis was performed using Kaplan–Meier statistics, log-rank tests, and multi-variate Cox-regression analyses with shared frailty (p < 0.05). Results 8542 initial restorations placed in 3239 patients were included (4.7 ± 4.4 years follow-up, 2.5 ± 0.7 surfaces). Longevity of initial restorations was prolonged by repair(s) (after 10 years: success: 68.3%, mAFR: 3.7%; survival 1: 77.3%, mAFR: 2.5%; survival 2: 80.4%, mAFR: 2.2%; p < 0.001). 616 repaired restorations (4.9 ± 4.2 years follow-up, 3.5 ± 1.0 surfaces) and 264 replacement restorations (5.6 ± 4.1 years follow-up, 3.0 ± 0.8 surfaces) were analyzed. Success of repaired restorations amounted to 43.4% after 10 years (mAFR: 8.0%), further repair(s) prolonged survival (survival 1: 65.7%, mAFR: 4.1%; survival 2: 74.8%, mAFR: 2.9%; p < 0.001). Success of replacement restorations amounted to 48.6% after 10 years (mAFR: 7.0%), repair(s) prolonged survival (survival 1: 67.4%, mAFR: 3.9%, p = 0.044; survival 2: 74.1%, mAFR: 3.0%, p = 0.003). Significance Repairs are suitable to increase the survival of restorations; repaired restorations last as long as replacements.

    更新日期:2019-11-27
  • Synthesis of sol–gel derived calcium silicate particles and development of a bioactive endodontic cement
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-26
    Gabriela de Souza Balbinot, Vicente Castelo Branco Leitune, Julia Silveira Nunes, Fernanda Visioli, Fabricio Mezzomo Collares

    Objective The aim of this study is to produce sol-gel derived calcium silicate particles (CS) and evaluate the influence of different concentration of calcium tungstate in the physical, chemical, mechanical and biological properties of developed cements. Methods Sol-gel route were used to synthesize calcium silicate particles that were characterized with x-ray difraction, Fourier transformed infrared spectroscopy, scanning electron microscopy, laser diffraction and nitrogen absorption. Cements were formulated with the addition of different concentrations of calcium tungstate (CaWO4), resulting in four experimental groups according to the CS:CaWO4 ratio: CS100 (100:0), CS90 (90:10), CS80 (80:20), CS70 (70:30). The setting time, radiopacity, compressive strength, pH, calcium release, cell proliferation and cell differentiation were used to characterize the cements. Results CS particles were succesfully sinthesized. The addition of CaWO4 increased the radiopacity and did not influenced the setting time and the mechanical properties of cements. The pH of distilled water was increased for all groups and the CS100 and CS90 groups presented incresed calcium release. Reduced cell viability was found for CS70 while CS100 and CS90 presented higher ALP activity and % of mineralized nodules after 21 days. Significance Sol-gel derived CS particles were sucssfully developed with potential to applied for the production of bioactive ceramic cements. The addition of 10% of CaWO4 resulted in cements with adequate properties and bioactivity being an alternative for regenerative endodontic treatments.

    更新日期:2019-11-27
  • Micropatterned hydrogels and cell alignment enhance the odontogenic potential of stem cells from apical papilla in-vitro
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-25
    Michael Ha, Avathamsa Athirasala, Anthony Tahayeri, Paula P. Menezes, Luiz E. Bertassoni

    Introduction An understanding of the extracellular matrix characteristics which stimulate and guide stem cell differentiation in the dental pulp is fundamental for the development of enhanced dental regenerative therapies. Our objectives, in this study, were to determine whether stem cells from the apical papilla (SCAP) responded to substrate stiffness, whether hydrogels providing micropatterned topographical cues stimulate SCAP self-alignment, and whether the resulting alignment could influence their differentiation towards an odontogenic lineage in-vitro. Methods Experiments utilized gelatin methacryloyl (GelMA) hydrogels of increasing concentrations (5, 10 and 15%). We determined their compressive modulus via unconfined compression and analyzed cell spreading via F-actin/DAPI immunostaining. GelMA hydrogels were micropatterned using photolithography, in order to generate microgrooves and ridges of 60 and 120 μm, onto which SCAP were seeded and analyzed for self-alignment via fluorescence microscopy. Lastly, we analyzed the odontogenic differentiation of SCAP using alkaline phosphatase protein expression (ANOVA/Tukey α = 0.05). Results SCAP appeared to proliferate better on stiffer hydrogels. Both 60 and 120 μm micropatterned hydrogels guided the self-alignment of SCAP with no significant difference between them. Similarly, both 60 and 120 μm micropattern aligned cells promoted higher odontogenic differentiation than non-patterned controls. Significance In summary, both substrate mechanics and geometry have a statistically significant influence on SCAP response, and may assist in the odontogenic differentiation of dental stem cells. These results may point toward the fabrication of cell-guiding scaffolds for regenerative endodontics, and may provide cues regarding the development of the pulp-dentin interface during tooth formation.

    更新日期:2019-11-26
  • Theoretical prediction of dental composites yield stress and flexural modulus based on filler volume ratio
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-16
    Yoan Boussès, Nathalie Brulat-Bouchard, Pierre-Olivier Bouchard, Hazem Abouelleil, Yannick Tillier

    Objective A costly advantageous approach in composites development process is to limit experimental tests by predicting mechanical properties with respect to their filler ratio. Models exist for other fields than dentistry. They have been compared to 3-point bending test experimental results for yield stress, flexural modulus and flexural strength. Methods Five formulations of the same experimental material were made. They were composed of an organic matrix and different ratios of silanated barium glass particles. The samples were stored in distilled water for 24 h at 37 °C prior to the 3-point bending test. The Turcsányi model for yield stress was notably investigated, and SEM was used to complete data analysis. Results The yield stress showed reproducible results and a good fit with Turcsányi model with respect to filler ratio. The flexural modulus data are not scattered but did not fit with the existing models. No trend could emerge for flexural strength and strain because of scattering; these properties are more unpredictable. The SEM observations of fracture areas confirm a good matrix-filler interface quality. Significance SEM pictures validated the numerical parameter obtained from Turcsányi model. The latter therefore seems to be applicable to dental composites. Firstly, it enables to predict the evolution of the material yield stress without testing all filler ratios. Secondly, this model provides a good way to get micro-information on the matrix-filler interface from macroscopic tests. The discrepancy between flexural modulus results and theory highlighted the necessity to include an “interface quality” parameter in accurate predictive models.

    更新日期:2019-11-18
  • Pulp ECM-derived macroporous scaffolds for stimulation of dental-pulp regeneration process
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-15
    Hengameh Bakhtiar, Mohammad Pezeshki-Modaress, Zahra Kiaipour, Mahdieh Shafiee, Mohammad Reza Ellini, Amir Mazidi, Sarah Rajabi, Soheila Zamanlui Benisi, Seyed Naser Ostad, Kerstin Galler, Pardis Pakshir, Amir Azarpazhooh, Anil Kishen

    Objective Recent studies suggest xenogeneic extracellular matrices as potential regenerative tools in dental pulp regeneration. This study aimed to fabricate and characterize a novel three-dimensional macroporous pulp-derived scaffold that enables the attachment, penetration, proliferation and differentiation of mesenchymal stem cells. Method Bovine pulp was decellularized and characterized with histological and DNA content methods. This scaffold was prepared using finely milled lyophilized decellularized pulp extracellular matrix (ECM) digested with pepsin. Three different concentrations of ECM (1.50, 2.25 and 3.00 mg/ml) were freeze-dried and were tested with/without chemical crosslinking. The specimens were subjected to physicochemical characterization, cell viability and quantitative real time polymerase chain reaction assessments with human bone marrow mesenchymal stem cells (hBMMSCs). All scaffolds were subcutaneously implanted in rats for two weeks and histological and immunostaining analyses were performed. Results Histological and DNA analysis confirmed complete decellularization. All samples demonstrated more than 97% porosity and 1.50 mg/ml scaffold demonstrated highest water absorption. The highest cell viability and proliferation of hBMMSCs was observed on the 3.00 mg/ml crosslinked scaffolds. The gene expression analysis showed a significant increase of dmp-1 and collagen-I on 3.00 mg/ml crosslinked scaffolds compared to the other scaffolds. Histological examination of subcutaneous implanted scaffolds revealed low immunological response, and enhanced angiogenesis in cross-linked samples compared to non-crosslinked samples. Significance The three-dimensional macroporous pulp-derived injectable scaffold developed and characterized in this study displayed potential for regenerative therapy. While the scaffold biodegradability was decreased by crosslinking, the biocompatibility of post-crosslinked scaffold was significantly improved.

    更新日期:2019-11-15
  • Self-cured resin modified by quaternary ammonium methacrylates and chlorhexidine: Cytotoxicity, antimicrobial, physical, and mechanical properties
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-14
    Karina de Paula Lopes Campos, Gil Mendes Viana, Lucio Mendes Cabral, Maristela Barbosa Portela, Raphael Hirata Junior, Larissa Maria Cavalcante, Eduardo José Veras Lourenço, Daniel de Moraes Telles

    Objective To evaluate the addition of dimethylaminohexadecyl methacrylate (DMAHDM) and chlorhexidine diacetate on cytotoxicity, antimicrobial activity, physical, and mechanical properties of a self-cured resin. Methods 132 disk-shaped and 48 rectangular specimens were divided into four experimental groups as described: Control Group (CG – no addition), dCHX (1%), DMAHDM (5%), and DMAHDM + dCHX (5% + 1%). The biofilm viability, flexural strength (FS - ISO 20795-1:2013), surface roughness (SR), and color stability (ΔE) were analyzed after being stored for 4 weeks in distilled water and immersed for 72 h in coffee. Cytotoxicity was measured after 24 h, 3, and 7 days of elution using an MTT test on L929 cells (ISO 10993-5:2009). SR and ΔE were measured by a contact profilometer and a spectrophotometer using the CIELab parameter. Data were submitted to ANOVA and Bonferroni’s/Tukey’s tests (p ≤ 0.05). Results Significant antimicrobial activity against Streptococcus mutans and Candida albicans was detected in all groups when compared to the CG (p < 0.05). Only the dCHX group, in 24 h of elution, demonstrated no cytotoxicity effects. There was a statistical difference for FS on the tested groups (p < 0.05). No differences were detected in the initial roughness’ measurements among the groups (p > 0.05). However, after storage and immersion in coffee, the groups containing DMAHDM presented with rougher surfaces and significantly lower color stability compared to the control (p < 0.05). Significance The addition of dCHX and DMAHDM in self-cured resin presented antimicrobial properties; however, cytotoxicity, physical, and mechanical properties were compromised.

    更新日期:2019-11-14
  • Probing the interfacial strength of novel multi-layer zirconias
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-12
    Marina R. Kaizer, Nantawan Kolakarnprasert, Camila Rodrigues, Herzl Chai, Yu Zhang

    Objectives The rapidly increasing use of zirconia-based CAD/CAM multi-layer structures in dentistry calls for a thorough evaluation of their mechanical integrity. This work examines the effect of the multi-layering architecture as well as variations in composition and inclusion of pigments among the layers on the flexural strength of multi-layer zirconias. Methods A modified 4-point bending test, aided by a Finite Element Analysis (FEA), was used to probe the interfacial strength of 3 classes of yttria-partially-stabilized zirconia: Ultra Translucent Multi-Layer (UTML—5Y-PSZ), Super Translucent Multi-Layer (STML—4Y-PSZ), Multi-Layer (ML—3Y-PSZ). In accord with the size limitation (22-mm height) of CAD/CAM pucks, test samples were prepared in the form of “long” (25 × 2 × 3 mm) and “short” (17.8 × 1.5 × 2 mm) beams. Homogeneous beams (both long and short) were produced from either the Enamel (the lightest shade) or Dentin (the darkest shade) layer, whereas multi-layer beams (short beam only) were obtained by cutting the pucks along their thickness direction, where the material components of various shades were stacked. Results The Enamel and Dentin layers exhibited similar flexural strength for a given material class, with ML amassing the highest strength (800–900 MPa) followed by STML (560–650 MPa) and UTML (470–500 MPa). The 3 classes of multi-layer zirconia showed a trade-off between strength and translucency, reflecting different yttria contents in these materials. The failure stress of the cross-sectional multi-layer beams was, however, ∼30% lower than that of their Enamel or Dentin layer counterparts, regardless of material tested. Significance The weakness of interfaces is a drawback in these materials. Additionally, when measuring strength using short beam flexure, friction between the specimen and supporting pins and accuracy in determining loading span distances may lead to major errors.

    更新日期:2019-11-13
  • High-translucent yttria-stabilized zirconia ceramics are wear-resistant and antagonist-friendly
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-12
    Fei Zhang, Benedikt C. Spies, Jef Vleugels, Helen Reveron, Christian Wesemann, Wolf-Dieter Müller, Bart van Meerbeek, Jérôme Chevalier

    Objectives To evaluate two-body wear of three zirconia ceramics stabilized with 3, 4 and 5 mol% yttria and to compare their wear behavior with that of a lithium-disilicate glass-ceramic. Methods Sixteen rectangular-shaped specimens made from three grades of zirconia ceramics and a lithium-disilicate glass-ceramic were polished and dynamically loaded in a chewing simulator (2 kg vertical load, 2.1 Hz) under water at 90 °C for 1.2 × 106 cycles (about 7 days) in the ball-on-plate mode against steatite antagonists. Surface roughness was measured before and after wear testing. Wear tracks were scanned with a non-contact 3D profilometer and super-impositions were used to determine wear loss of the antagonists. Wear surfaces were imaged by SEM. XRD and micro-Raman spectroscopy were used to characterize phase transformation and stress status in the worn and unworn areas of the zirconia ceramics. Results Independent of fracture toughness, strength and aging-susceptibility, the three zirconia ceramics showed a similar and limited amount of wear (∼10 μm in depth) and were more wear-resistant than the lithium-disilicate glass-ceramic (∼880 μm in depth). Abrasive wear without obvious cracks was observed for all investigated zirconias, whereas the glass-ceramic with a lower fatigue threshold and high susceptibility to surface dissolution exhibited significant abrasion, fatigue and corrosion wear. All three zirconia ceramics yielded a lower antagonist wear than the glass-ceramic and no significant differences were found between the zirconia ceramics. Significance In the context of this study, high-translucent zirconia ceramics stabilized with a higher yttria content, recently introduced in the dental field, were as wear-resistant and antagonist-friendly as conventional high-strength zirconia and suitable for monolithic restorations.

    更新日期:2019-11-13
  • The digital factory in both the modern dental lab and clinic
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-12
    David Leeson

    Objective Significant technological advances are occurring in the dental industry that are complementary to the introduction of monolithic restorative materials. Glidewell Laboratories has been at the forefront of innovation of these developments and these internal developments may be instructive of future trends in dentistry. Methods This paper examines internal Glidewell data from 2010 to 2019 about zirconia-related technology and provides context for some technological advancements at Glidewell Laboratories. Results The trend towards increased use of monolithic zirconia in both, posterior and anterior regions continues to grow. With the advent of intraoral scanners and chairside CAD/CAM technologies, more and more dentists are able to provide same day dentistry. Despite the many clinicians that have made the leap to digital dentistry the low rate of growth in ownership and utilization means PVS impression will be common place long into the future. Glidewell Laboratories has an advanced, automated impression scanning, AI crown design, automated milling and glazing system extending the advantages of digital dentistry to all dentists and pushing the bounds of the technology further. Significance This paper describes the first use of AI GAN to design dental crowns and also shows the strong path monolithic zirconia restorations are paving into the future. Supporting technologies will continue to evolve around zirconia and this paper provides a snapshot of those that exist and a few that are in development.

    更新日期:2019-11-13
  • SEM observation of novel characteristic of the dentin bond interfaces of universal adhesives
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-12
    Toshiki Takamizawa, Arisa Imai, Eizo Hirokane, Akimasa Tsujimoto, Wayne W. Barkmeier, Robert L. Erickson, Mark A. Latta, Masashi Miyazaki

    Objective The aim of this study was to observe the resin/dentin interfaces of universal adhesives by using scanning electron microscopy (SEM), and to compare their morphologies with conventional etch & rinse (ER) and self-etch (SE) adhesive systems. Methods Two three-step and one two-step ER adhesives and two two-step and two single-step SE adhesives were used for comparison with seven universal adhesives in ER mode and SE mode, respectively. Bonded surfaces with bovine teeth were longitudinally sectioned and mirror-polished. Half of the samples were treated with HCl and NaOCl solutions. The interfaces were subjected to argon ion beam etching and then observed by scanning electron microscopy. Results The thickness of the adhesive layer (AL) of most of the seven universal adhesives and single-step SE adhesives was similar. Universal adhesives in SE mode formed a hybrid smear layer as a high-density zone between the AL and dentin. The thickness of the hybrid layer (HL) of the universal adhesives in ER mode was ∼1–2 μm, with a high-density zone (reaction layer [RL]) below the HL. Conclusion The morphological features of most universal adhesives in SE mode and single-step SE adhesives are similar. Although resin–dentin interfaces of universal adhesives in ER mode resemble those of ER adhesives, universal adhesives have a distinctive feature, an RL. Significance The RL might be a sign of chemical bonding even when using universal adhesives in ER mode.

    更新日期:2019-11-13
  • Three-body wear of 3D printed temporary materials
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-12
    Andreas Kessler, Marcel Reymus, Reinhard Hickel, Karl-Hein Kunzelmann

    Objective The aim of this study was to investigate the three-body wear of different additively manufactured temporary materials, one temporary PMMA material for CAD/CAM milling and one resin-based composite for direct restorations as a control group by using an ACTA machine. Methods Specimens (n = 8) of the 3D printing materials 3Delta temp, NextDent C&B, Freeprint temp were additively manufactured by DLP 3D printer. Postprocessing was carried out according to the manufacturer's specifications. Telio CAD were cut out of blocks, Tetric EvoCeram was applied directly and light cured. Three-body wear was simulated with an ACTA machine. Data were statistically analysed (ANOVA, post hoc test: Tukey, p < 0.05). The worn surfaces of the specimens were examined with a FE-SEM. Results The average mean wear was 50 ± 15 μm for Tetric EvoCeram < 62 ± 4 μm for 3Delta temp < 236 ± 31 μm for Telio CAD < 255 ± 13 μm for NextDent C&B < 257 ± 24 μm for Freeprint temp. After 200,000 cycles, the wear and wear rates for Tetric EvoCeram and 3Delta temp were significantly lower than those for the other materials. SEM revealed that 3Delta temp has a higher filler proportion than the other 3D printing materials but less than Tetric EvoCeram. Significance The filler content influences the wear behaviour of additively manufactured materials as well as dental restorative composite materials. While most 3D printing materials have a low inorganic filler load, which qualifies the materials for temporary use only, one 3D printing material has an optimized composition that would qualify the material for longer clinical service time if wear is considered as the outcome variable.

    更新日期:2019-11-13
  • Characterization of the bioactivity of two commercial composites
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-05
    Melissa Tiskaya, N.A. Al-eesa, F.S.L. Wong, R.G. Hill

    The aim of this study was to characterize the ion release, pH changes and apatite formation ability of two potentially bioactive composites Cention N (CN) and Activa (ACT). Ion release and apatite formation was investigated in three different immersion media: Tris buffer pH 7.3 (TB), Artificial Saliva pH 4 (AS4) and Artificial Saliva pH 7 (AS7) in order to mimic the conditions present in the mouth. Fluoride release was followed using an ion selective electrode, whilst all other ions were determined by inductively coupled plasma optical emission spectroscopy. Apatite formation was followed by FTIR and XRD. SEM was used to follow glass degradation and apatite formation on both polished cross-sections and surfaces of the composites. ACT released very few ions including fluoride upon immersion in TB and AS7, but released more ions including significant quantities of Al in AS4. This would suggest the glasses in ACT are acid degradable fluoro-alumino-silicate glasses similar to the glasses used in glass ionomer cements. There was no evidence of any apatite formation with ACT. CN released more ions in TB and AS7 than ACT and formed an apatite like phase in AS7. The calcium fluoro-silicate glass in CN was observed to degrade significantly in AS4. CN has bioactive properties that may explain the low incidence of secondary caries found clinically with this composite.

    更新日期:2019-11-06
  • Shear bond strength vs interfacial fracture toughness — Adherence to CAD/CAM blocks
    Dent. Mater. (IF 4.440) Pub Date : 2019-11-02
    Nicoleta Ilie, N. Dorin Ruse

    Objective To compare shear bond strength (SBS) and interfacial fracture toughness (IKIC) results when assessing the effect of surface roughness and thermocycling on the adherence of a resin composite luting agent (RCLA) to a CAD/CAM resin composite block (RCB). Methods Tetric CAD HT along with the recommended bonding system, Adhese Universal and Variolink Esthetic LC, were used. Surface roughness was achieved with 600/320/60 grit SiC papers. Samples were stored 24 h in 37 °C water or thermocycled 10000× (5 °C–55 °C) prior to testing. Results were analyzed by univariate ANOVA and Scheffé modified t-tests (α = 0.05). Fractured specimens were viewed with a stereo microscope and selected specimens with a scanning electron microscope. Results SBS results showed a significant difference between the 60 grit group and the other groups, both after 24 h and thermocycling. A large number of SBS samples showed cohesive fracture or subsurface damage in RCB. Thermocycling led to a significant decrease in SBS in all groups. IKIC results showed no significant differences due to surface preparation after 24 h storage in 37 °C. After thermocycling, there was a significant difference between the 60 and the 600 grit groups. All KIC samples fractured adhesively at the RCB surface. KIC of the RCLA was significantly higher than IKIC of all groups. Significance The results endorse the use of fracture mechanics methodology for the assessment and characterization of adherence, while identifying difficulties in its implementation. The results suggest also that adherence to CAD/CAM RCB may be limited by the strength of the resin composite block — adhesive interface.

    更新日期:2019-11-04
  • The Academy of Dental Materials: Providing roots and wings
    Dent. Mater. (IF 4.440) Pub Date : 2019-10-31
    Grayson W. Marshall, Sally J. Marshall, Stephen C. Bayne

    Objectives The long history of the Academy of Dental Materials (ADM) is documented with its strategies (a) to rapidly communicate science among its members, (b) to establish special awards to stimulate new science, and (c) to develop new dental materials scientists. Methods We searched the history of the last 35 years of the ADM newsletters, transactions, journals, and officer notes. We document the (a) presidents, (b) meeting history, (c) membership growth, and (d) development of special awards through 2019 with the recent creation of the ADM Marshall Post-Doctoral Award. Results There are 36 years of recent ADM history, 42 international meetings, membership growth to 400 individuals from 15 countries, service of 19 presidents, Paffenbarger annual Awardees since 1989, induction of >200 fellows, and recognition of the first winner of Marshall Post-Doctoral Award in 2018. New directions for recruiting members are suggested. Three potential new thrusts for the organization are presented: artificial intelligence, genetic engineering, and intensive member mentoring. Significance These suggestions for the ADM provide a path for the ADM to continue to adapt to the ever changing scientific landscape.

    更新日期:2019-11-01
  • Incorporating N-acetylcysteine and tricalcium phosphate into epoxy resin-based sealer improved its biocompatibility and adhesiveness to radicular dentine
    Dent. Mater. (IF 4.440) Pub Date : 2019-10-11
    Carlos Henrique Ribeiro Camargo, Laís Carolina Landim Gomes, Monique Costa Moreira França, Tatiane Sampaio Bittencourt, Marcia Carneiro Valera, Samira Esteves Afonso Camargo, Marco Cicero Bottino

    Objective This in vitro study was designed to evaluate the biocompatibility, adhesiveness, and antimicrobial activity of epoxy resin-based sealer associated with N-Acetylcysteine (NAC) or beta-tricalcium phosphate nanoparticles (β-TCP) as an experimental retro-filling material. Methods Cytotoxicity was assessed using 2,3-Bis-(Methoxy-4-Nitro-5-Sulphophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) and Sulforhodamine B (SRB) assays after exposing human periodontal ligament fibroblasts to extracts of the materials for 1, 3, or 7 days. For the adhesive resistance test, root canals (48 single-root teeth) were instrumented with Reciproc #40 files (VDW GmbH, Germany) and obturated. After 7 days, the apices were sectioned and a retrograde cavity prepared and filled with the experimental materials (Mineral trioxide aggregate, Epoxy sealer, Epoxy sealer + NAC, and Epoxy sealer + β-TCP). For the push-out test, one 2-mm thick slice was obtained from the apical third of each specimen. Antimicrobial activity was performed using agar diffusion method. Biofilms were grown in microplates and exposed to the extracts of retro-filled materials, followed by analysis of growth inhibition on agar plates. Results Epoxy sealer in association with β-TCP or NAC showed better bond strength while Mineral trioxide aggregate allowed for the lowest adhesion. Mineral trioxide aggregate, Epoxy sealer + β-TCP, and Epoxy sealer + NAC showed low cytotoxicity. Epoxy sealer was the most cytotoxic. In antimicrobial activity assays, all materials had no effect on Candida albicans. Addition of NAC improved the antimicrobial property of Epoxy sealer against Enterococcus faecalis compared to unmodified Epoxy sealer (P < 0.05). Significance Incorporating β-TCP or NAC with Epoxy sealer could improve the adhesiveness and biocompatibility for better use in endodontic therapy.

    更新日期:2019-10-12
  • Optimization of 3D bioprinting of periodontal ligament cells
    Dent. Mater. (IF 4.440) Pub Date : 2019-10-08
    Nimal Thattaruparambil Raveendran, Cédryck Vaquette, Christoph Meinert, Deepak Samuel Ipe, Saso Ivanovski

    Three-dimensional (3D) bioprinting of cells is an emerging area of research but has been not explored yet in the context of periodontal tissue engineering. Objective This study reports on the optimisation of the 3D bioprinting of periodontal ligament cells for potential application in periodontal regeneration. Methods We systematically investigated the printability of various concentrations of gelatin methacryloyl (GelMA) hydrogel precursor using a microextrusion based three-dimensional (3D) printer. The influence of different printing parameters such as photoinitiator concentration, UV exposure, pressure and dispensing needle diameter on the viability of periodontal ligament cells encapsulated within the 3D bioprinted construct were subsequently assessed. Results This systematic evaluation enabled the selection of the most suited printing conditions for achieving high printing resolution, dimensional stability and cell viability for 3D bioprinting of periodontal ligament cells. Significance The optimised bioprinting system is the first step towards to the reproducible manufacturing of cell laden, space maintaining scaffolds for the treatment of periodontal lesions.

    更新日期:2019-10-10
  • Effect of cleaning protocol on silica deposition and silica-mediated bonding to Y-TZP
    Dent. Mater. (IF 4.440) Pub Date : 2019-10-04
    Renally Bezerra Wanderley Lima, Suelem Chasse Barreto, Beshr Hajhamid, Grace Mendonça de Souza, Mario Fernando de Goes

    Objectives To evaluate the effect of cleaning methods on the deposition of silica on yttria-stabilized zirconium dioxide (Y-TZP) surface and on the silane-silica mediated bond strength between Y-TZP and resin cement. Methods Y-TZP slabs were air-abraded with 30 μm silica-coated alumina particles and distributed in three groups: no cleaning, cleaning with a stream of oil-free air/water spray for 5 s and cleaning with an ultrasonic bath in water for 10 min. The distribution of Si on the Y-TZP surfaces was recorded using energy dispersive spectroscopy (EDS). After the treatment was applied, Y-TZP slabs (n = 20) received a primer application and resin cement cylinders were built on the surface. After storage (24 h) in water storage or 3 months plus thermocycling; n = 10), microshear bond strength test (μSBS) was performed. X- ray Photoelectron Spectroscopy (XPS) characterized the chemical bonds between the silica layer and the silane-containing primer. Data were analyzed using ANOVA and Tukey test, as well as Weibull analysis (α = 0.05). Results Cleaning method had a significant effect on the amount of Si deposited on zirconia surface (p < 0.001) and, consequently, on bond strength (p < 0.001). Storage/aging also had a significant effect on bond strength (p < 0.001). Low values of Weibull moduli for bond strength were observed for all groups after aging. XPS showed silane-silica chemical interaction for all groups. Significance The silica deposited by tribochemical coating to Y-TZP was removed by the cleaning methods evaluated, compromising bond strength. Stability of the bonding is also a concern when no cleaning method is applied.

    更新日期:2019-10-04
  • Morphological and elemental analysis of silver penetration into sound/demineralized dentin after SDF application
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-30
    Mahmoud Sayed, Naoko Matsui, Motohiro Uo, Toru Nikaido, Masakazu Oikawa, Michael F. Burrow, Junji Tagami

    Objective The aim of this study was to evaluate the penetration depth of silver into sound and demineralized dentin after application of silver diamine fluoride (SDF). Methods Two hundred and eighty-eight dentin specimens were used. The specimens were divided into 3 groups: (1) sound dentin (control), (2) 30 min EDTA-treated dentin; and (3) 13 h EDTA-treated dentin. SDF was applied to all specimens. Each group was divided into 3 subgroups according to storage time into: 24 h, 2 weeks and 1-year storage time. Each subgroup was further divided into four subgroups (n = 8) according to different examinations as optical microscope (OM) observation, scanning electron microscopic (SEM) observation, elemental analysis with energy dispersive spectroscopy (EDS) and Micro-PIXE test. Results The OM showed discoloration in the superficial layer after 24 h and keep extending deeper after 2 weeks and 1-year. SEM showed silver crystals within dentinal tubules after 2 weeks and 1-year. EDS analysis can detect silver penetration only in the 1-year group reaching around 1200 μm inside dentin. Micro-PIXE test detected silver at all time intervals, confirming the EDS depth results. Significance It can be concluded that silver ions can completely infiltrate the demineralized dentin lesion with further penetration into the underlying mineralized dentin.

    更新日期:2019-10-01
  • Effect of extrinsic pigmentation and surface treatments on biaxial flexure strength after cyclic loading of a translucent ZrO2 ceramic
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-29
    Breno Fortes Bittar, Jean Soares Miranda, Arthur Chaves Simões, Nathália de Carvalho Ramos, João P.B. Machado, Yu Zhang, Rodrigo Othávio Assunção Souza, Fabíola Pessôa Pereira Leite

    Objective To evaluate the influence of extrinsic pigmentation on the biaxial flexural strength and surface topographic of translucent Y-TZP (InCoris TZI – Sirona – USA) subjected to several surface treatments. Methods Sintered zirconia discs-shaped specimens (n = 120) (ø:12 mm; thickness:1.2 mm; ISO 6872) were prepared and divided (n = 15) according to various factors: “extrinsic pigmentation” (n: without; p: with) and “surface treatments” (C: control — as sintered; A: abraded with silica-coated alumina particles (30 μm); G: glazed with a thin film of low-fusing porcelain glaze; GH: glazed and etched with 10% hydrofluoridric acid for 60 s. Mechanical cycling (1.2 × 106 cycles, 200 N, 3.8 Hz) and flexural strength test (1 mm/min — 1000 kg cell) were performed. Two-way ANOVA and Tukey’s were used for statistical test (α = 0.05). Weibull analysis was used to evaluate the strength reliability. Samples were analyzed via (1) an optical profilometer to determine the surface roughness (Ra); (2) an X-ray diffraction (XRD) to evaluate phase transformations; and (3) a SEM equipped with an energy dispersive X-ray spectroscopy (EDX) to elucidate morphological properties and chemical compositions. Results Regardless of the surface treatment (p = 0.5459) (Cn: 560.16 MPa; Gn: 573.36 MPa; An: 643.51 MPa; GHn: 542.94 MPa; Cp: 628.04 MPa; Gp: 641.90 MPa; Ap: 554.47 MPa; GHp :602.84 MPa) and extrinsic pigmentation (p = 0.1280) there was no difference in the flexural strength among the experimental groups. According to the XRD analysis, phase transformations occurred in the An group (t → m) and in Ap group (t → c). Surface roughness was affected by surface treatments (An — p = 0.001) and extrinsic pigmentation (Gp — p = 0.001). Significance The biaxial flexural strength of the tested samples was not affected neither by surface treatments nor by pigmentation, although it can cause phase transformation and promote surface roughness.

    更新日期:2019-09-29
  • Zirconia toughened mica glass ceramics for dental restorations: Wear, thermal, optical and cytocompatibility properties
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-28
    Sivaranjani Gali, RaviKumar K

    Background In an effort to design novel zirconia reinforced mica glass ceramics for dental restorations, clinically relevant properties such as wear, coefficient of thermal expansion, optical transmittance, and cytocompatibility with human gingival fibroblast cell lines were investigated in the present study. Materials & Methods Microstructure analysis of two body wear of heat treated mica glass ceramic ceramics (47.2 SiO2–16.7 Al2O3–9.5 K2O–14.5 MgO–8.5 B2O3–6.3 F wt.%) reinforced with 20 wt.% YSZ, were evaluated against a steatite antagonist in a chewing simulator following Willytec Munich method. In addition, Coefficient of thermal expansion (CTE), total transmittance, scattering coefficient and cytocompatibility on human gingival fibroblast cell lines were performed and compared to the commercially available dental ceramic systems. Results The experimental mica glass ceramic demonstrate micro-ploughing, pull out and debris formation along the cutting surface, indicating abrasive wear mechanism. Thermal expansion of mica glass ceramic composite was recorded as 5 × 10−6/°C, which is lower than the thermal expansion of commercially available core and veneering ceramics. Further, significant differences of transmittance and scattering coefficient of mica glass ceramics with 20 wt.% YSZ with commercial dental ceramics was found and extensive fibroblast cell spreading with filopodial extension, cell-to-cell bridges and proliferation with human gingival fibroblast cell lines. Conclusion With acceptable cytocompatibility with human gingival fibroblast cells and better wear properties with respect to commercial IPS emax Press, the mica glass ceramic composites (47.2 SiO2–16.7Al2O3–9.5 K2O–14.5 MgO–8.5 B2O3–6.3 F wt.%) with 20 wt.% YSZ have the potential for dental restorative applications as machinable veneering ceramics.

    更新日期:2019-09-29
  • A comparative evaluation of ion release characteristics of three different dental varnishes containing fluoride either with CPP-ACP or bioactive glass
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-26
    Ahmed Sleibi, A.R. Tappuni, Natalia G. Karpukhina, Robert G. Hill, A. Baysan

    Objective To compare ion release characteristics of three different dental varnishes either containing CPP-ACP and fluoride (CPP-ACPF, MI Varnish GC, Japan), bioactive glass and fluoride (BGAF, Dentsply Sirona USA) or fluoride alone (NUPRO White, Dentsply Sirona USA) using fluoride-Ion Selective Electrode (F-ISE), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), 19F and 31P Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). Methods A thin layer (0.0674 ± 0.0005 g) of each varnish (20 × 25 mm in area) was spread on a roughened glass slide (n = 7). They were separately immersed in 10 ml Tris buffer (0.06 M, pH = 7.30), and changed after 1, 2, 4, 6, 24 and 48 h. Fluoride-ion concentration at each time using the F-ISE, whilst calcium and phosphate release were investigated using ICP-OES. XRD, FTIR. MAS-NMR analyses were also performed before and after immersion. Results The cumulative F-ion release was significantly higher in CPP-ACPF (1.113 mmol/g) > BGAF(0.638) > F(0.112) (p < 0.001). The cumulative calcium and phosphorus were higher in the CPP-ACPF (0.137 mmol/g, 0.119) than BGAF (0.067, 0.015) (p < 0.001) respectively. The XRD and 19F MAS-NMR confirmed the presence of NaF peaks in all cases before immersion. There were less prominent signal and appearance of fluorapatite crystals after immersion. 19F MAS-NMR revealed CaF2 formation after immersion in both CPP-ACPF and BGAF. 31P MAS-NMR showed phosphate signals in both CPP-ACPF and BGAF before immersion. FTIR failed to show any signs of apatite formation. Significance Both CPP-ACP and bioactive glass enhanced ion release without compromising the bioavailability of fluoride. The CPP-ACPF varnish had the most promising ion release.

    更新日期:2019-09-26
  • Polymerization shrinkage of resin-based composites for dental restorations: A digital volume correlation study
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-22
    Marta Gallo, Hazem Abouelleil, Jean Marc Chenal, Jérôme Adrien, Joël Lachambre, Pierre Colon, Eric Maire
    更新日期:2019-09-22
  • Experimental composites of polyacrilonitrile-electrospun nanofibers containing nanocrystal cellulose
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-21
    Bernardo U. Peres, Adriana P. Manso, Luana D. Carvalho, Frank Ko, Tom Troczynski, Hugo A. Vidotti, Ricardo M. Carvalho

    Objective To test the effects of addition of polyacrilonitrile (PAN) nanofibers and nanocrystal cellulose (NCC)-containing PAN nanofibers on flexural properties of experimental dental composites. Methods 11 wt% PAN in dimethylformamide (DMF) solution was electrospun at 17.2 kVA and 20 cm from the collector drum. NCC was added to the solution at 3 wt%. Fiber mats were produced in triplicates and tested as-spun. Strips (5 cm × 0.5 cm) were cut from the mat in an orientation parallel and perpendicular to the rotational direction of the collector drum. Tensile tests were performed and ultimate tensile strength (UTS), elastic modulus (E) and elongation at maximum stress (%) were calculated from stress/strain plots. Fiber mats were then infiltrated by resin monomers (50/50 BisGMA/TEGDMA wt%), stacked in a mold (2 × 15 × 25) and light-cured. Beams (2 × 2 × 25 mm) were cut from the slabs and tested in a universal testing machine. Data were analyzed by multiple t-test and one-way ANOVA (α = 0.05). Results Addition of 3% NCC resulted in higher tensile properties of the fibers. Fibers presented anisotropic behavior with higher UTS and E when tested in perpendicular orientation. The incorporation of 3% NCC–PAN nanofibers resulted in significant increase in work of fracture and flexural strength of experimental dental composite beams. Significance NCC was found to be a suitable nanoparticle to reinforce experimental dental composites by incorporation via nanofiber. This fundamental study warrants future investigation in the use of electrospun nanofibres as a way to reinforce dental composites.

    更新日期:2019-09-22
  • Novel nanotechnology and near-infrared photodynamic therapy to kill periodontitis-related biofilm pathogens and protect the periodontium
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-21
    Manlin Qi, Xue Li, Xiaolin Sun, Chunyan Li, Franklin R. Tay, Michael D. Weir, Biao Dong, Yanmin Zhou, Lin Wang, Hockin H.K. Xu
    更新日期:2019-09-22
  • Enhanced teeth whitening by nanofluidic transport of hydrogen peroxide into enamel with electrokinetic flows
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-20
    Chenhui Peng, Sohyun Park, Frederico Barbosa de Sousa, HiongYap Gan, Sang J. Lee, Wei Wang, Stacey Lavender, Shira Pilch, Jongyoon Han

    Tooth whitening, a routine procedure in dentistry, is one of the examples of medical procedures that are limited by the challenge of delivering molecules into various types of nanoporous tissues. Current bleaching methods rely on simple diffusion of peroxides into enamel nano channels, therefore requires sufficient contact time with peroxides. In-office treatments often involve enamel etching or light activation which often results in patient sensitivity and potential soft tissue damage. Objective To demonstrate a robust method to transport hydrogen peroxide to greater depths into enamel nanopores through nanofluidic flows driven by electrokinetics, with the intention to increase efficacy while reducing treatment time. Methods Freshly extracted human teeth were subjected to electrokinetic flow treatment with hydrogen peroxide under different electric fields with varying operation times. Pre- and post-operative shade matching was done using a photospectrometer. Results It is demonstrated that the operation time for the same concentration of hydrogen peroxide can be shortened by 10 times. The proposed method showed significant improvements in whitening effects over control groups and thus offers promising clinically-viable chairside applications with efficacy. Significance The demonstrated nanofluidic transport of hydrogen peroxide into enamel has a potential to be applied for enhancing tooth whitening, compared to simple diffusion, without heating the hard dental tissues.

    更新日期:2019-09-21
  • Alternative model for cathepsin K activation in human dentin
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-20
    A. Bafail, M. Azizalrahman, T. Vilde, A. Kishen, A. Prakki

    Objective To evaluate the protease activity in dentin matrices subjected to lactic acid (LA) in comparison to polyacrylic acid (PAA) challenge model at cathepsin K (CT-K) optimum pH 5.5 to assess effectiveness of inhibitors in dentin collagen degradation. Methods Dentin disks measuring 0.5 mm prepared from human molars were completely demineralized in 10% H3PO4. Demineralized dentin disks were challenged with 0.1 M LA, 1.1 mM PAA, artificial saliva (AS), or deionized water (C) for 24 h or 7-days. Dentin collagen properties were tested by measurement of %dry mass change, and ultimate tensile strength (UTS). Degradation of dentin type I collagen was measured by telopeptide assays measuring the sub-product release of C-terminal cross-linked telopeptides (ICTP) and C-terminal peptide (CTX) in the incubation media in relation to total protein concentration, which correlates with matrix metalloproteinases (MMPs) and CT-K activities. Results Gravimetric analysis showed statistically significant difference between C and other groups (p < 0.04) at 24 h. LA specimens showed significantly higher weight loss from 24 h to 7-days (p = 0.02). UTS revealed statistically significant difference between AS and LA at 24 h and 7-days. UTS at 24 h and 7-days for C and AS had significantly higher mean values compared to LA and PAA. Telopeptide assays reported that CTXtp results showed that LA at 24 h had significantly higher mean values compared to C and AS. Significance LA has the ability to activate endogenous CT-K in dentin as measured by the release of CTX (CT-K specific telopeptide). This LA based model has the potential application for further investigations on the activity and possible inhibitors of CT-K in human dentin.

    更新日期:2019-09-21
  • Osteogenic potential of human dental pulp stem cells cultured onto poly-ε-caprolactone/poly (rotaxane) scaffolds
    Dent. Mater. (IF 4.440) Pub Date : 2019-09-20
    N.K. Oliveira, T.H.C. Salles, A.C. Pedroni, L. Miguita, M.A. D’Ávila, M.M. Marques, M.C.Z. Deboni
    更新日期:2019-09-21
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