Due to the existing demands for methods independent of patient co-operation in preventing and overcoming the incidence of white spot lesions (WSLs) and caries in fixed orthodontic treatments, several studies have considered the modification of orthodontic composites using antimicrobial nanomaterials. In this regard, the aim of this study is to investigate the effect of the addition of chitosan nanoparticles (NPs) and TiO₂ NPs on Streptococcus mutans (S. mutans) counts and the enamel mineral content in fixed orthodontic patients. A double-blind randomized clinical trial study was carried out in 24 patients (i.e., 48 upper second premolars and 48 maxillary lateral incisors) who were candidates for fixed orthodontic treatment. In the case of the control group, the bracket was bonded to the tooth with an orthodontic adhesive (Transbond XT, 3M Unitek, USA) while, in the experimental group, the bracket was bonded to the tooth with Transbond XT containing 1% chitosan NPs and 1% TiO₂ NPs. For the maxillary lateral incisor and upper second premolar teeth, the S. mutans counts around the brackets were measured, through the usage of real-time PCR, at the time points of 1 day, 2 months, and 6 months after bonding the brackets to the tooth. Furthermore, the enamel mineral content measurement was also performed around the brackets at 1 day, 2 months, and 6 months after bonding the brackets to the tooth. The S. mutans counts were analyzed using Friedman and Mann–Whitney U tests. The Repeated measures ANOVA test and Independent samples T-test were also applied, in order to evaluate the mineral content. According to the results, there was a significant reduction in the S. mutans counts of experimental group at the time points of 1 day, 2 months, and 6 months in both maxillary lateral incisor and upper second premolar teeth. However, we did not observe any significant differences in the control group between the reports at 1 day, 2 months, and 6 months in both maxillary lateral incisor and upper second premolar teeth. The outcomes of this study indicate that, with regard to maxillary lateral incisor teeth, there were no significant differences between the results of the experimental group and control group at the time points of 1 day, 2 months, and 6 months. Furthermore, with respect to the upper second premolar teeth, no significant differences were observed between the two groups at 1 day and 2 months; however, S. mutans counts were significantly lower in the experimental group than in the control group at the time point of 6 months. Moreover, our gathered data confirmed the absence of any significant differences between the experimental group and control group, in terms of enamel mineral content, at the time intervals of 1 day, 2 months, and 6 months. In conclusion, the incorporation of chitosan NPs and TiO₂ NPs in orthodontic composites induces an antibacterial property in the resultant adhesive to be used for fixed orthodontic treatment.

由于现有的对独立于患者合作的方法的需求，以预防和克服固定正畸治疗中白斑病变 (WSL) 和龋齿的发生率，一些研究已经考虑使用抗菌纳米材料对正畸复合材料进行改性。在这方面，本研究的目的是研究添加壳聚糖纳米颗粒（NPs）和TiO ₂ NPs对变形链球菌（S. mutans ）的影响。) 计数和固定正畸患者的牙釉质矿物质含量。一项双盲随机临床试验研究在 24 名适合进行固定正畸治疗的患者（即 48 颗上第二前磨牙和 48 颗上颌侧切牙）中进行。在对照组的情况下，托槽用正畸粘合剂（Transbond XT，3M Unitek，美国）粘合到牙齿上，而在实验组中，托槽用含有 1% 壳聚糖 NPs 的 Transbond XT 粘合到牙齿上和 1% TiO ₂ NPs。对于上颌侧切牙和上第二前磨牙，S. mutans在托槽与牙齿粘合后的第 1 天、2 个月和 6 个月的时间点，通过使用实时 PCR 测量托槽周围的计数。此外，在托槽与牙齿粘合后 1 天、2 个月和 6 个月，还在托槽周围进行了牙釉质矿物质含量测量。使用Friedman 和 Mann-Whitney U 检验分析变形链球菌计数。还应用了重复测量方差分析检验和独立样本 T 检验，以评估矿物质含量。根据结果​​，变形链球菌显着减少实验组上颌侧切牙和上第二前磨牙分别在第1天、第2个月和第6个月的时间点计数。然而，我们没有观察到对照组在 1 天、2 个月和 6 个月的报告中上颌侧切牙和上第二前磨牙的任何显着差异。本研究结果表明，在上颌侧切牙方面，实验组和对照组在第1天、第2个月和第6个月时间点的结果没有显着差异。此外，在上第二前磨牙方面，两组在第 1 天和第 2 个月时无显着差异；然而，变形链球菌在 6 个月的时间点，实验组的计数明显低于对照组。此外，我们收集的数据证实，在 1 天、2 个月和 6 个月的时间间隔内，实验组和对照组之间在牙釉质矿物质含量方面没有任何显着差异。总之，在正畸复合材料中加入壳聚糖纳米粒子和_二氧化钛纳米粒子会在所得粘合剂中诱导抗菌性能，用于固定正畸治疗。