Kasem Ammar T, Elsherbiny Abdallah Ahmed, Abo-Madina Manal, Tribst João Paulo M, Al-Zordk Walid
Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt.
Production Engineering and Mechanical Design Department, Faculty of Engineering, Mansoura University, Mansoura, Egypt.
J Prosthodont. 2023 Mar;32(3):e41-e51. doi: 10.1111/jopr.13626. Epub 2022 Dec 26.
To evaluate the fracture load and stress magnitude of different retainer designs of minimally invasive cantilever resin-bonded fixed dental prostheses (RBFDPs) after artificial aging.
Fifty caries-free human mandibular molars were prepared as abutments for cantilever fixed dental prostheses using different retainer designs: one wing (OW), two wings (TW), inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). Computer-aided design and computer-aided manufacturing were used for milling the RBFDPs using fiber-reinforced composite (FRC), and the restorations were adhesively bonded. The specimens were then subjected to thermomechanical aging and loaded until failure. The 3D finite element analysis (FEA) was performed with five models of retainer designs similar to the in vitro test. Modified von Mises stress values on enamel, dentine, luting resin, and restorations were examined. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (p < 0.001).
A statistically significant difference (p < 0.001) was found between all groups except between IR and LC and between OW and TW designs, with the highest mean failure load detected for OC (534.70 N) and the lowest detected for OW (129.80 N). With regard to failure mode, OW, TW, and LC showed more incidences of favorable failure patterns than IR and OC designs. FEA showed that FRC transmitted low stresses in tooth structure and high stresses to the luting resin.
LC and OC designs can be used to design cantilever RBFDPs in premolar area. IR design transmitted more stresses to the tooth structure and resulted in 30% catastrophic failure. OW and TW were below the normal occlusal force and should be carefully used.
评估人工老化后微创悬臂式树脂粘结固定义齿（RBFDPs）不同固位体设计的断裂载荷和应力大小。
选取50颗无龋的人类下颌磨牙作为悬臂式固定义齿的基牙，采用不同的固位体设计：单翼（OW）、双翼（TW）、嵌体环（IR）、舌侧覆盖（LC）和咬合面覆盖（OC）。使用纤维增强复合材料（FRC）通过计算机辅助设计和计算机辅助制造来铣削RBFDPs，并将修复体粘结。然后对标本进行热机械老化处理并加载直至破坏。使用与体外试验相似的五种固位体设计模型进行三维有限元分析（FEA）。检查牙釉质、牙本质、粘结树脂和修复体上的修正冯·米塞斯应力值。数据采用Kruskal-Wallis检验和Mann-Whitney U检验进行分析（p < 0.001）。
除IR和LC组以及OW和TW设计组之间外，所有组之间均存在统计学显著差异（p < 0.001），其中OC组的平均破坏载荷最高（534.70 N），OW组最低（129.80 N）。关于破坏模式，OW、TW和LC组比IR和OC设计组显示出更多有利破坏模式的发生率。有限元分析表明，FRC在牙齿结构中传递低应力，而在粘结树脂中传递高应力。
LC和OC设计可用于前磨牙区悬臂式RBFDPs的设计。IR设计向牙齿结构传递更多应力，导致30%的灾难性破坏。OW和TW低于正常咬合力，应谨慎使用。
