Objectives

The aim of the present study was to investigate the influence of five different preparation designs and two different ceramic thicknesses on margin quality and fracture resistance of ceramic laminate veneers after thermomechanical loading in vitro.

Materials and methods

Eighty human central incisors were randomly assigned to 10 groups (n = 8) with five different preparation designs: non-prep (NP), minimally invasive (MI) = exclusively enamel-bonded, semi-invasive (SI) = 50% bonded in dentin, invasive (I) = 100% in dentin, and semi-invasive with two additional class III composite resin restorations (SI-C). IPS InLine veneers were fabricated in two thicknesses (L1 = 0.2–0.5 mm; L2 = 0.5–1.2 mm). After adhesive luting (OptiBond FL, Variolink Veneer) with light curing and polishing, specimens were stored in distilled water at 37 °C for 21 days, then thermocycled (2000 cycles between + 5 and + 55 °C), and finally mechanically loaded at the incisal edge at an angle of 45° for 2,000,000 cycles at 50 N und further 1,000,000 cycles at 100 N. Impressions were taken initially, after thermocycling, and after every 250,000 mechanical cycles in order to evaluate cracks and margin quality under a SEM. The veneers were evaluated in a light microscope (× 20) for cracks, chippings, partial, and catastrophic fractures.

Results

Margin quality after three million cycles revealed medians for continuous margin of 82–95% without significant differences among groups, neither at the ceramic/composite (p = 0.943) nor at the tooth/composite interface (p = 0.571). Visual inspection of veneers exhibited 22 cracks, 11 chippings, 4 partial and 4 catastrophic fractures in 38 of 80 veneers. The statistical ranking regarding fracture risk (p ≤ 0.05) was: IL1 = SIL1 = MIL1 = IL2 = CL1 = CL2, MIL2 = NPL1 = NPL2 = SIL2, IL2 = CL1 = CL2 = MIL2 = NPL1 = NPL2 = SIL2.

Conclusions

Even after three million cycles with up to 100 N, all groups showed high survival rates. However, the fracture risk increases with thin veneers and preparations with medium to high dentin portions when compared to thicker veneers with preparations in enamel or partially in dentin (p ≤ 0.05). Preexisting resin composite restorations did not show any significant influence on margin quality and facture risk (p > 0.05).

Clinical relevance

Ceramic laminate veneers are extremely durable with thin veneers and substantial enamel loss being main risk factors for fracture.

中文翻译：

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陶瓷层压板饰面：制备设计和陶瓷厚度对体外抗断裂性和边缘质量的影响。

目标

本研究的目的是研究在体外热机械加载后，五种不同的制备设计和两种不同的陶瓷厚度对陶瓷层压板饰面质量和抗断裂性的影响。

材料和方法

将80例人类中切牙随机分为10组（n = 8），有五种不同的制备设计：非制备（NP），微创（MI）=仅牙釉质粘结，半浸润（SI）= 50％粘结在牙本质中，侵入（I）= 100％粘结在牙本质中半侵入式和两个附加的III类复合树脂修复物（SI-C）。IPS InLine单板的厚度为两种（L1 = 0.2-0.5 mm； L2 = 0.5-1.2 mm）。在用光固化和抛光进行胶粘剂粘合（OptiBond FL，Variolink单板）后，将样品在37°C的蒸馏水中保存21天，然后热循环（在+5到+ 55°C之间进行2000次循环），最后在70°C下机械加载在50 N时以45°角切开边缘2,000,000次，在100 N时再切割1,000,000次。热循环后，每250次，000个机械循环，以便在SEM下评估裂纹和边缘质量。在光学显微镜（×20）中对饰面板进行了裂纹，碎裂，局部和灾难性断裂的评估。

结果

300万次循环后的边际质量显示，连续边际的中位数为82–95％，各组之间无显着差异，在陶瓷/复合材料（p  = 0.943）和牙齿/复合材料界面（p  = 0.571）上均无。目视检查单板的80个单板中有38个单板显示22个裂缝，11个碎裂，4个局部和4个灾难性断裂。的统计排名关于骨折风险（p  ≤0.05）：IL1 = SIL1 = MIL1 = IL2 = CL1 = CL2，MIL2 = NPL1 = NPL2 = SIL2，IL2 = CL1 = CL2 = MIL2 = NPL1 = NPL2 = SIL2。

结论

即使经过300万次循环（最高100 N），所有组的存活率仍很高。然而，当比较薄胶合板，并与中到高的牙本质部分制剂中的骨折风险增加至与搪瓷制剂较厚薄板或部分地在牙本质（p  ≤0.05）。既有的树脂复合材料修复体对边缘质量和制造风险没有显着影响（p  > 0.05）。

临床相关性

陶瓷层压薄板非常耐用，薄薄的薄板和大量的搪瓷损失是造成破裂的主要危险因素。