Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt.
Production Engineering and Mechanical Design Department, Faculty of Engineering, Mansoura University, Mansoura, Egypt.
Clin Oral Investig. 2023 May;27(5):2109-2123. doi: 10.1007/s00784-022-04813-2. Epub 2022 Dec 2.
To study the fracture resistance and stress distribution pattern of translucent zirconia and fiber-reinforced composite cantilever resin-bonded fixed dental prostheses (RPFDPs) with two retainer designs.
Forty human mandibular molars were divided into two groups according to the retainer design. The restorations included a premolar pontic and 2 retainer designs: (D1) inlay ring retainer and (D2) lingual coverage retainer. Each main group was then divided according to the material used (n = 10): zirconia (Z) or fiber-reinforced composite (FRC) (F). Restorations were cemented using dual polymerizing adhesive luting resin. All specimens were thermo-cycled (5-55 °C for 10,000 cycles), then subjected to dynamic loading (50 N, 240,000, and 1.6 Hz) and fracture resistance test. The finite element analysis includes the two models of retainer designs used in the in vitro test. Modified von Mises stress values on enamel, dentin, luting resin, and restorations were examined when the restorations failed.
A significantly higher failure load was recorded for zirconia groups (505.00 ± 61.50 and 548.00 ± 75.63 N for D1Z and D2Z, respectively) than for FRC groups (345.00 ± 42.33 and 375.10 ± 53.62 N for D1F and D2F, respectively) (P = 0.001). With regard to failure mode, D2 showed a more favorable failure pattern than D1. Model D2 resulted in lower stresses in tooth structure than model D1, and zirconia transmitted more stresses to the tooth structure than FRC.
The lingual coverage retainer (D2) enhanced the biomechanical performance of the restoration/tooth complex. Considering the failure mode and tooth stress, FRC is a promising treatment option when constructing a cantilever RPFDP.
Dentists should be aware of the biomechanical behavior during the selection of the material and for the replacement of a single missing mandibular premolar tooth with minimally invasive RBFDP.
研究两种固位体设计的半透明氧化锆和纤维增强复合悬臂树脂粘结固定义齿（RPFDP）的抗折能力和应力分布模式。
根据固位体设计，将 40 个人类下颌磨牙分为两组。修复体包括一个前磨牙桥体和两种固位体设计：（D1）嵌体环固位体和（D2）舌侧覆盖固位体。每个主组根据材料的不同（n=10）进一步分为两组：氧化锆（Z）或纤维增强复合材料（FRC）（F）。修复体使用双固化粘结树脂粘结。所有样本均经过热循环（5-55°C，10000 次循环），然后进行动态加载（50N，240000 次，1.6Hz）和抗折能力测试。有限元分析包括体外试验中使用的两种固位体设计模型。当修复体失效时，检查牙釉质、牙本质、粘结树脂和修复体上的修正 von Mises 应力值。
D1Z 和 D2Z 组的氧化锆组（505.00±61.50 和 548.00±75.63N）的失效负荷明显高于 FRC 组（345.00±42.33 和 375.10±53.62N）（P=0.001）。就失效模式而言，D2 比 D1 显示出更有利的失效模式。模型 D2 导致牙体结构的应力低于模型 D1，氧化锆向牙体结构传递的应力高于纤维增强复合材料。
舌侧覆盖固位体（D2）增强了修复体/牙体复合体的生物力学性能。考虑到失效模式和牙体应力，纤维增强复合材料是构建悬臂 RPFDP 的一种有前途的治疗选择。
牙医在选择材料和微创 RBFDP 替换单个下颌前磨牙时，应注意生物力学行为。
