Bacterial adhesion on conventional and self-ligating metallic brackets after surface treatment with plasma-polymerized hexamethyldisiloxane

ABSTRACT Introduction: Plasma-polymerized film deposition was created to modify metallic orthodontic brackets surface properties in order to inhibit bacterial adhesion. Methods: Hexamethyldisiloxane (HMDSO) polymer films were deposited on conventional (n = 10) and self-ligating (n = 10) stainless steel orthodontic brackets using the Plasma-Enhanced Chemical Vapor Deposition (PECVD) radio frequency technique. The samples were divided into two groups according to the kind of bracket and two subgroups after surface treatment. Scanning Electron Microscopy (SEM) analysis was performed to assess the presence of bacterial adhesion over samples surfaces (slot and wings region) and film layer integrity. Surface roughness was assessed by Confocal Interferometry (CI) and surface wettability, by goniometry. For bacterial adhesion analysis, samples were exposed for 72 hours to a Streptococcus mutans solution for biofilm formation. The values obtained for surface roughness were analyzed using the Mann-Whitney test while biofilm adhesion were assessed by Kruskal-Wallis and SNK test. Results: Significant statistical differences (p< 0.05) for surface roughness and bacterial adhesion reduction were observed on conventional brackets after surface treatment and between conventional and self-ligating brackets; no significant statistical differences were observed between self-ligating groups (p> 0.05). Conclusion: Plasma-polymerized film deposition was only effective on reducing surface roughness and bacterial adhesion in conventional brackets. It was also noted that conventional brackets showed lower biofilm adhesion than self-ligating brackets despite the absence of film.

摘要
引言：等离子聚合薄膜沉积技术旨在改性金属正畸托槽的表面性能，以抑制细菌粘附。
方法：采用等离子体增强化学气相沉积（Plasma-Enhanced Chemical Vapor Deposition, PECVD）射频技术，将六甲基二硅氧烷（Hexamethyldisiloxane, HMDSO）聚合物薄膜沉积于传统型（n=10）与自锁型（n=10）不锈钢正畸托槽表面。按照托槽类型将样本分为两组，经表面处理后再划分为两个亚组。通过扫描电子显微镜（Scanning Electron Microscopy, SEM）分析样本表面（槽区与翼区）的细菌粘附情况及薄膜层完整性；采用共聚焦干涉法（Confocal Interferometry, CI）检测表面粗糙度，接触角测量法评估表面润湿性。细菌粘附实验中，将样本置于变形链球菌（Streptococcus mutans）溶液中孵育72小时以诱导生物膜形成。表面粗糙度数据采用曼-惠特尼检验（Mann-Whitney test）进行分析，生物膜粘附情况则通过克鲁斯卡尔-沃利斯检验（Kruskal-Wallis）与SNK检验进行评估。
结果：经表面处理的传统型托槽，以及传统型与自锁型托槽之间，均观察到表面粗糙度降低与细菌粘附减少存在显著统计学差异（p<0.05）；自锁型托槽各组间未观察到显著统计学差异（p>0.05）。
结论：等离子聚合薄膜沉积仅可有效降低传统型托槽的表面粗糙度并抑制其细菌粘附。同时发现，即便未进行薄膜处理，传统型托槽的生物膜粘附量也低于自锁型托槽。