Department of Dental Materials and Prosthodontics, Araçatuba Dental School, Universidade Estadual Paulista, Araçatuba Dental School, São Paulo, Brazil.
Int J Oral Maxillofac Implants. 2011 Mar-Apr;26(2):251-6.
The aim of this study was to evaluate the effect of retightening and mechanical cycling on the maintenance of preload in the retention screws of implant-supported crowns.
Five groups (n = 12 in each group) of implant-crown assemblies were created according to different abutments and veneering materials: Gold UCLA abutments cast in gold alloy veneered with ceramic (group 1) and light-curing resin (group 2), UCLA abutments cast in titanium veneered with ceramic (group 3) and light-curing resin (group 4), and zirconia abutments with ceramic veneering (group 5). The crowns were attached to implants by gold retention screws. The assemblies were submitted to mechanical cycling for a total of 1 million cycles. Removal torque measurements were performed initially and after each period of 100,000 cycles; this was followed by screw retightening with 35 Ncm of torque. Data were evaluated with analysis of variance, the paired t test, and the Student t test.
All groups exhibited reduced removal torque values in comparison to insertion torque initially and after all periods of mechanical cycling. Analysis of variance revealed statistically significant differences among the groups, but there were no differences among the periods of mechanical cycling or for the interaction between groups and cycling. Group 1 was the only group that did not show a difference between removal torque values of different cycling periods. The Student t test did not reveal statistically significant differences between mean removal torque values obtained before and after mechanical cycling, except for group 4.
Torque maintenance allowed screw joint stability in the present study. Mechanical cycling associated with the retightening of abutment screws did not influence the maintenance of insertion torque.
本研究旨在评估固位螺钉预载荷的维持效果，以重新拧紧和机械循环。
根据不同的基台和饰面材料，创建了五组（每组 12 个）种植体-冠组件：金 UCLA 基台铸造金合金饰面陶瓷（组 1）和光固化树脂（组 2）、UCLA 基台铸造钛饰面陶瓷（组 3）和光固化树脂（组 4）、氧化锆基台与陶瓷贴面（组 5）。通过金固位螺钉将冠固定到种植体上。这些组件总共经历了 100 万次机械循环。初始时和每 10 万次循环后进行移除扭矩测量，然后用 35 Ncm 的扭矩重新拧紧螺丝。采用方差分析、配对 t 检验和学生 t 检验对数据进行评估。
与初始插入扭矩相比，所有组的移除扭矩值均降低，且所有机械循环周期后均降低。方差分析显示组间存在统计学差异，但机械循环周期或组间和循环交互作用无差异。只有第 1 组在不同循环周期的移除扭矩值之间没有差异。除第 4 组外，学生 t 检验未显示机械循环前后平均移除扭矩值存在统计学差异。
在本研究中，扭矩维持允许螺钉接头稳定。机械循环与基台螺钉的重新拧紧不会影响插入扭矩的维持。
