Scanning electron microscope and shear bond strength analysis of Biofix and Orthocem two-step fluoridated orthodontic adhesives on human enamel

Introduction: The bonding process in orthodontic treatment is very important. This study aimed to evaluate the shear bond strength (SBS) and bond failure sites of stainless steel brackets bonded with two new two-step adhesives (Biofix (BF) and Orthocem (OC)) and a three-step adhesive (Transbond XT (TXT)). Material & Methods: In this in vitro study, 66 extracted human premolars were collected and randomly divided into three groups (n=22). The brackets were bonded to each tooth with a) TXT, b) BF, and c) OC adhesives according to manufacturers’ instructions. The SBS values of the brackets were measured 24 hours after thermocycling. Adhesive remnant index (ARI), enamel detachment index (EDI) and bond failure locations on bracket surfaces were qualitatively and quantitatively assessed using stereomicroscopic, scanning electron microscope (SEM) and energy dispersive x-ray (EDX) analyses. The data were analyzed using SPSS 22 software and ANOVA test. The significance level was defined at P<0.05. Results: The means and standard deviations of SBS values for TXT, BF and OC adhesives were 22.49±4.58, 17.82±6.43 and 16.20±4.46 MPa, respectively. The SBS in the TXT group was significantly different from the two other groups, but the difference was not significant between the two other groups. Moreover, ARI and EDI were not significantly different between the three groups. The SBS values of BF (P<0.001) and OC (P<0.001) were not significantly different. Conclusion: The adhesive SBS in the BF and OC groups was in the determined ranges to bond the orthodontic brackets. Therefore, these two adhesives can be used as a proper alternative for conventional bonding methods.