Bond strength of different bracket bonding materials to the enamel subjected to thermal cycling

OBJECTIVE: The aim of this study was to evaluate in vitro the shear bond strength of metallic orthodontic brackets to enamel using different bonding materials followed by thermal cycling. METHODS: A fluid composite resin (Transbond XT / 3M Unitek) and a resin-modified glass ionomer (Fuji Ortho LC / GC America Inc.) were evaluated. Eighty sound human premolars were randomly divided into eight experimental groups (n = 10), according to the material used and the number of thermal cycles: zero, 1000, 2000 and 3000 cycles. Bracket bonding was performed on the buccal surface of the teeth. After 24 hours, they were subjected to thermal cycling at temperatures ranging between 5° C and 55° C for 15 seconds each immersion. Shear bond strength was performed using a universal testing machine with a chisel-type tip at a speed of 0.5 mm / min. The bond strength data was analyzed using two-way ANOVA. RESULTS: No difference on shear bond strength was observed regarding the number of thermal cycles for each specimen (p = 0.873). A significant difference was found in shear bond strength between the bonding materials (p = 0.022), with significantly higher values for Transbond XT regardless of the number of thermal cycles. CONCLUSION: The number of thermal cycles did not significantly affect the bond strength of the adhesive materials investigated. The bonding agent Transbond XT showed higher bond strength than Fuji Ortho LC regardless of the number of thermal cycles.

研究目的：本研究旨在体外评估不同粘接材料经热循环处理后，金属正畸托槽与牙釉质间的剪切粘接强度（shear bond strength）。
研究方法：本研究共评估两种粘接材料：流动复合树脂（Transbond XT / 3M Unitek）与树脂改性玻璃离子水门汀（Fuji Ortho LC / GC America Inc.）。选取80颗健康人类前磨牙，根据所使用的粘接材料类型及热循环次数（0、1000、2000、3000次）随机分为8个实验组，每组n=10。托槽粘接操作均在牙齿颊面完成。样本静置24小时后，置于5℃至55℃的循环水浴中进行热循环处理，每次浸泡时长15秒。采用带有凿型头的万能试验机（universal testing machine），以0.5mm/min的加载速度开展剪切粘接强度测试。采用双因素方差分析（two-way ANOVA）对粘接强度数据进行统计学分析。
研究结果：结果显示，对于各组样本而言，热循环次数对剪切粘接强度均无显著影响（p=0.873）。不同粘接材料间的剪切粘接强度存在显著差异（p=0.022）：无论热循环次数如何，Transbond XT的剪切粘接强度均显著更高。
研究结论：热循环次数对本研究所考察的两种粘接材料的粘接强度均无显著影响。无论热循环次数多少，Transbond XT的粘接强度均高于Fuji Ortho LC。