Shear bond strength and adhesive remnant index of orthodontic brackets bonded to enamel using adhesive systems mixed with TiO2 nanoparticles

ABSTRACT Introduction: It is recently suggested that titanium dioxide (TiO2) nanoparticles can be added to bracket luting agents in order to reduce bacterial activity and protect the enamel. However, it is not known if this addition can affect the shear bond strength (SBS) below clinically acceptable levels. Therefore, this study examined this matter within a comprehensive setup. Methods: This in vitro experimental study was conducted on 120 extracted human premolars randomly divided into four groups (n=30): in groups 1 and 2, Transbond XT light-cured composite with or without TiO2 was applied on bracket base; in groups 3 and 4, Resilience light-cured composite with or without TiO2 was used. Brackets were bonded to teeth. Specimens in each group (n=30) were divided into three subgroups of 10 each; then incubated at 37°C for one day, one month, or three months. The SBS and adhesive remnant index (ARI) were calculated and compared statistically within groups. Results: The SBS was not significantly different at one day, one month or three months (p>0.05) but composites without TiO2 had a significantly higher mean SBS than composites containing TiO2 (p<0.001). The SBS of Transbond XT was significantly higher than that of Resilience (p<0.001). No significant differences were noted in ARI scores based on the type of composite or addition of TiO2 (p>0.05). Conclusions: Addition of TiO2 nanoparticles to Transbond XT decreased its SBS to the level of SBS of Resilience without TiO2; thus, TiO2 nanoparticles may be added to Transbond XT composite for use in the clinical setting.

摘要 引言：近期有研究提出，可将二氧化钛（TiO₂）纳米颗粒添加至托槽粘接剂中，以降低细菌活性、保护牙釉质。但目前尚不明确，该添加是否会使剪切粘接强度（SBS）降至临床可接受水平以下。因此，本研究通过全面的实验设计对该问题展开了探究。
方法：本体外实验研究纳入120颗拔除的人前磨牙，随机分为4组（每组n=30）：第1、2组采用含或不含TiO₂的Transbond XT光固化复合树脂涂覆于托槽基底；第3、4组采用含或不含TiO₂的Resilience光固化复合树脂。将托槽粘接于牙齿表面。每组（n=30）的标本均分为3个亚组，每组10个；随后分别置于37℃环境下孵育1天、1个月或3个月。对剪切粘接强度与粘接残留指数（ARI）进行计算，并在组内开展统计学比较分析。
结果：在1天、1个月及3个月三个时间点，剪切粘接强度无显著差异（p>0.05）；但不含TiO₂的复合树脂的平均剪切粘接强度显著高于含TiO₂的复合树脂（p<0.001）。Transbond XT的剪切粘接强度显著高于Resilience（p<0.001）。不同复合树脂类型及是否添加TiO₂对粘接残留指数得分无显著影响（p>0.05）。
结论：向Transbond XT复合树脂中添加TiO₂纳米颗粒后，其剪切粘接强度降至不含TiO₂的Resilience复合树脂的水平；因此，可在Transbond XT复合树脂中添加TiO₂纳米颗粒以用于临床场景。