Comparison of the shear bond strength between metal brackets and Transbond™ XT, Filtek™ Z250 and Filtek™ Z350 before and after gastroesophageal reflux: An in vitro study.

ABSTRACT

PURPOSE: To evaluate in vitro the effect of gastroesophageal reflux, before and after bonding of metal brackets on composite resin surface. MATERIALS AND METHODS: Two hundred and ten resin discs were divided into 5 groups (n=42), according to the time and medium of storage 24h, 7- and -30 days in artificial saliva (AS) and hydrochloric acid (HCL). Twelve samples from each group were submitted to surface roughness analysis (n=60). The other one hundred and fifty samples were divided into 3 groups (n=50) according to the bonding material: Transbond™ XT (TXT), 3M™ Filtek™ Z250 (Z250) and 3M™ Filtek™ Z350 XT (Z350). After bonding, the samples were subdivided, one more time, into 5 groups (n=10) according to the time (24h, 7, and 30 days) and medium storage (AS, HCL). Following, the shear bond strength (SBS) analysis was accomplished. Erosive challenge was performed for 7 or 30 days, before and after bonding of orthodontic brackets, for 1min, 4 times a day. SBS was performed in a universal testing machine (Instron) at 0.5mm/min. SBS data were subjected to two-way ANOVA and Tukey's test (α=0.05). RESULTS: TXT showed higher SBS values in all conditions (AS - 10.9±2.0 (24h); 10.5±4.9 (7 days); 9.4±2.2 (30 days); HCL - 11.5±3.7 (7 days); 8.0±2.1 (30 days)) - (P<0.0001). No statistical difference was detected in SBS between Z250 and Z350 composite resins (Z250 SBS AS - 7.1±1.9 (24h), 5.2±1.8 (7 days), 4.5±1.5 (30 days); HCL - 5.2±2.3 (7 days), 5.0±2.5 (30 days)) - (P<=0.063)/Z350 SBS AS - 7.4±1.0 (24h); 3.7±1.7 (7 days); 3.4±1.7 (30 days); HCL - 3.5±3.3 (7 days); 4.4±1.2 (30 days)) - (P<=0.167), respectively). Storage times and media did not statistically influence the SBS of TXT and Z250 composite resins (P>0.05), but did influence the Z350 SBS (P<0.05). CONCLUSION: Regardless of time and storage medium, TXT was the best composite resin for bonding brackets. Furthermore, the erosive challenge did not lead to surface changes in the Z250 resin at 7 and 30 days, unlike the Z350 resin.