Micrographic evaluation of different widia compositions of orthodontic pliers submitted to peracetic acid and intensive use

Abstract Introduction The sterilization and disinfection procedures should be adapted to the chemical profile of the metal alloys present in the instruments. Objective This study aimed to perform a micrographic assessment on the surface characteristics of the widia of orthodontic pliers with two alloy compositions subjected to the action of 0.2% peracetic acid and intensive use. Material and method Twenty distal cutting pliers were divided into two groups (n=10) according to widia composition (%wt): W1- 85% to 87% of tungsten carbide (TC) and other components in the proportion of 13% to 15% and W2 – 87.5% to 88.5% of tungsten carbide and 11.5% to 12.5% for other components. All the pliers were assessed in a stereoscopic magnifying glass (32x) after three treatments: before use (T0); after cutting 100 segments of rectangular stainless-steel wires – intensive use (T1); and after 100 sterilization cycles in 0.2% peracetic acid and intensive use (T2). The cutting sites of all pliers were standardized. Widia regions were defined by line “A” representing T1 and line “B” representing T2. A frequency distribution table and Fisher’s exact test (α=0.05) was performed. We assessed two widia from each composition and treatment in SEM and energy-dispersive X-ray spectroscopy (EDS/SEM). Result The results showed that W1 pliers presented significantly fewer defects after the sterilization cycles with peracetic acid and intensive use than W2 pliers (p=0.0198). There were no differences between both pliers after intensive use (p=1.000). Conclusion The SEM images and EDS analyses showed changes in widia surfaces after the different treatments. Widia composition affected the resistance of the orthodontic pliers after sterilization cycles with 0.2% peracetic acid and intensive use.摘要 引言：灭菌与消毒操作应适配器械中所含金属合金的化学特性。 目的 本研究旨在对两种不同合金成分的正畸钳硬质合金（widia）表面特性，在0.2%过氧乙酸作用与高强度使用后的显微形貌进行评估。 材料与方法 选取20把远端切断钳，根据硬质合金的质量分数成分分为两组（n=10）：W1组含85%~87%碳化钨（Tungsten Carbide, TC），其余成分占比13%~15%；W2组含87.5%~88.5%碳化钨，其余成分占比11.5%~12.5%。所有钳具分别在三个阶段完成评估：使用前（T0）、切断100段矩形不锈钢丝后（高强度使用，T1）、经0.2%过氧乙酸完成100个灭菌循环并联合高强度使用后（T2）。所有钳具的切削部位均进行标准化处理。硬质合金区域以代表T1的A线与代表T2的B线划定。采用频数分布表与Fisher确切概率法（检验水准α=0.05）进行统计分析。此外，对每种成分与处理组的2个硬质合金样本开展扫描电镜（Scanning Electron Microscope, SEM）与能量色散X射线能谱（energy-dispersive X-ray spectroscopy, EDS/SEM）分析。 结果 结果显示，经过氧乙酸灭菌循环联合高强度使用后，W1型钳的表面缺陷显著少于W2型钳（p=0.0198）；仅高强度使用后，两组钳具的表面缺陷无显著差异（p=1.000）。 结论 扫描电镜图像与能谱分析结果表明，不同处理后硬质合金表面均发生了改变；硬质合金成分会影响正畸钳经0.2%过氧乙酸灭菌循环联合高强度使用后的抗损性能。