Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt.
Fixed Prosthodontics Department, Faculty of Dentistry, Delta University for Science and Technology, Mansoura, Egypt.
J Esthet Restor Dent. 2024 Apr;36(4):652-662. doi: 10.1111/jerd.13130. Epub 2023 Sep 22.
The development of dental adhesives with enhanced bond strength has assisted minimally invasive dentistry. The aim of this study was to evaluate the fracture load and stress distribution pattern of two retainer designs for posterior cantilever resin bonded fixed dental protheses (RBFDPs).
Forty human mandibular molars were divided into two groups according to the retainer design; lingual coverage (LC) and occlusal coverage (OC) retainers. Each main group was then divided according to the number of inlay boxes (n = 10); one inlay and two inlay boxes. High translucency (3Y) zirconia was used to manufacture all restorations, and a dual-polymerizing adhesive resin cement was used for bonding. All specimens underwent 10,000 cycles of thermocycling (5-55°C), 240,000 cycles of dynamic loading (50 N, descending speed v = 30 mm/second, frequency = 1.6 Hz), and failure load test. Both one-way and two-way ANOVA tests were used to analyze the data. The four models included in the in-vitro study are part of the finite element analysis (FEA). When the restorations failed, maximal principal stress values on restorations, enamel, dentin, and luting resin were investigated.
A statistically significant (p = 0.018) higher failure load was recorded for OC1 (627.00 ± 153.4 N) than the other groups; (548.0 ± 75.6 N, 521.20 ± 11.3 N, and 509.20 ± 14.9 N for LC1, LC2, and OC2, respectively). With regard to failure mode, one inlay box designs showed more favorable failure pattern than those of two inlay boxes. FEA showed higher stress magnitude transmitted to the tooth structure in models LC2 and OC2.
Lingual coverage and occlusal coverage retainers are promising designs capable to withstand the normal occlusal force for cantilever RBFDP in premolar area. The use of two inlay boxes decreased the fracture load of the two retainer designs and increased the stress transmitted to the tooth and resulted in high incidence of catastrophic failure.
Monolithic high translucent zirconia RBFDP could be considered as a viable treatment option to substitute missing posterior tooth, with improved esthetics and biocompatibility.
具有增强的粘结强度的牙科粘结剂的发展促进了微创牙科的发展。本研究的目的是评估两种后牙悬臂树脂粘结固定义齿（RBFDP）固位体设计的断裂负荷和应力分布模式。
根据固位体设计（舌侧覆盖[LC]和牙合面覆盖[OC]固位体）将 40 颗下颌磨牙分为两组。每个主组根据嵌体盒的数量进一步分为两组（n=10）；一个嵌体盒和两个嵌体盒。所有修复体均采用高透明度（3Y）氧化锆制造，采用双固化粘结树脂水门汀粘结。所有样本均经历 10,000 次热循环（5-55°C）、240,000 次动态加载（50N，下降速度 v=30mm/秒，频率=1.6Hz）和失效负荷测试。采用单向和双向方差分析对数据进行分析。体外研究中的四个模型均为有限元分析（FEA）的一部分。当修复体失效时，研究了修复体、釉质、牙本质和粘结树脂上的最大主应力值。
OC1 组（627.00±153.4N）的失效负荷明显高于其他组（548.0±75.6N、521.20±11.3N 和 509.20±14.9N，LC1、LC2 和 OC2 分别）（p=0.018）。关于失效模式，一嵌体盒设计的失效模式优于两嵌体盒设计。FEA 显示 LC2 和 OC2 模型中传递到牙齿结构的应力更大。
舌侧覆盖和牙合面覆盖固位体是有前途的设计，可以承受前磨牙区悬臂 RBFDP 的正常咬合力。使用两个嵌体盒降低了两种固位体设计的断裂负荷，并增加了传递到牙齿的应力，导致灾难性失效的发生率增加。
整体高透明度氧化锆 RBFDP 可作为替代缺失后牙的可行治疗选择，具有改善的美观性和生物相容性。
