Student, Post-Graduate Program in Dentistry, Atitus Education, Passo Fundo, RS, Brazil.
Student, Post-Graduate Program in Dental Sciences, Federal University of Santa Maria (UFSM), Santa Maria, RS, Brazil.
J Prosthet Dent. 2022 Dec;128(6):1335.e1-1335.e8. doi: 10.1016/j.prosdent.2022.10.008. Epub 2022 Nov 18.
Zirconia has been reported to be suitable for multiunit monolithic restorations. However, as the connector region is the weakest part of the system, studies are needed to determine the optimal connector geometry.
The purpose of this in vitro study was to evaluate the load-bearing capacity under fatigue of implant-supported fixed partial prostheses made of monolithic zirconia with different connector cross-sectional geometries.
Three-unit monolithic fixed partial prostheses (from mandibular second premolar to the second molar) were fabricated in zirconia (Zenostar T) by computer-aided design and computer-aided manufacture (CAD-CAM). Different connector cross-sectional geometries, with an area of 9 mm, were tested (n=10): round, square with rounded angles, or trapezoid with rounded angles. The prostheses were screwed over 2 implants and inserted into acrylic resin bases. The specimens were submitted to a mechanical fatigue test until failure, with load applied to the pontic using the stepwise stress methodology (initial load of 100 N for 5000 cycles, followed by an increase to 200 N for 20 000 cycles, with a subsequent increase of 50 N each step). For data analysis, fatigue failure load (FFL) and cycles for fatigue failure (CFF) were recorded. Failed structures were analyzed by fractography. The Kaplan-Meier test followed by a log-rank Mantel-Cox post hoc test was used to analyze FFL and CFF (α=.05). Weibull analysis was also performed.
The round (1065 N) and trapezoid (1010 N) groups presented higher FFL values than the square one (870 N) (P≤.05). For CFF, the round connector (358 777) was better than the square (280 310) (P=.006), and the trapezoid (337 773) was statistically similar to both (P>.05). No difference among groups was observed in Weibull modulus either for CFF or FFL data. All failures were catastrophic, originating at the base of the connector and propagating toward the occlusal surface of the pontic (region under loading).
The connector cross-sectional geometry significantly influenced the mechanical fatigue performance of implant-supported fixed partial prostheses made of monolithic zirconia.
氧化锆已被报道适用于多单位整体修复体。然而，由于连接体区域是系统中最薄弱的部分，因此需要研究确定最佳的连接体几何形状。
本体外研究的目的是评估不同连接体横截面几何形状的整体氧化锆制造的种植体支持固定局部义齿在疲劳下的承载能力。
通过计算机辅助设计和计算机辅助制造（CAD-CAM）制造了三单位整体固定局部义齿（从下颌第二前磨牙到第二磨牙），采用氧化锆（Zenostar T）制成。测试了不同的连接体横截面几何形状（面积为 9mm），包括圆形、带有圆角的方形或带有圆角的梯形（n=10）。将义齿拧在 2 个种植体上，并插入丙烯酸树脂基底中。使用逐步应力方法对试件进行机械疲劳试验直至失效，通过对桥体施加负载（初始负载为 100N，循环 5000 次，然后增加到 200N，循环 20000 次，随后每次增加 50N）。记录疲劳失效负载（FFL）和疲劳失效循环（CFF）。通过断口形貌分析来分析失效结构。采用 Kaplan-Meier 检验和对数秩 Mantel-Cox 事后检验分析 FFL 和 CFF（α=.05）。还进行了威布尔分析。
圆形（1065N）和梯形（1010N）组的 FFL 值高于方形组（870N）（P≤.05）。对于 CFF，圆形连接器（358777）优于方形连接器（280310）（P=.006），而梯形连接器（337773）在统计学上与两者相似（P>.05）。对于 CFF 或 FFL 数据，连接器的横截面几何形状对威布尔模量均无影响。所有的失效都是灾难性的，起始于连接器的底部，并向桥体的咬合面（受载区域）扩展。
连接体的横截面几何形状显著影响了整体氧化锆制造的种植体支持固定局部义齿的机械疲劳性能。
