Microleakage beneath orthodontic brackets in high field magnetic resonance imaging (MRI) AT 1.5 & 3 Tesla

Abstract

Objectives: The aim of the present study was to evaluate the effects of 1.5T and 3T MRI on the adhesion between the orthodontic brackets and the teeth by evaluating the microleakage between the enamel, adhesive and brackets interfaces. Methods: 58 extracted human premolars which were received a standard bracket bonding procedure were randomly divided into three groups; control group (n = 20; no MRI), 1.5T MRI group (n = 19; 20min MRI exposure of 1.5T) and 3T MRI group (n = 19; 20min MRI exposure of 3T). The teeth were kept in distiled water for 2 weeks, and thereafter subjected to 500 thermal cycles. Then, specimens were sealed with nail varnish, stained with 0.5% basic fuchsin for 24h, sectioned and photographed under a stereomicroscope. Microleakage was scored with regard to the adhesive–enamel and bracket–adhesive interfaces at the occlusal and gingival levels. Statistical analysis was accomplished by Kruskal–Wallis and Bonferroni–Dunn tests. Results: All of the groups exhibited statistically similar microleakage scores in the adhesive– enamel interface along occlusal margins (p>0.05, p = 0.331). The mean microleakage scores along gingival margins in the 3T MRI group was significantly higher compared to the control group both in the adhesive–enamel and bracket–adhesive interfaces (p<0.05, p = 0.019 and p = 0.020 respectively). The microleakage scores along the gingival margins were also significantly higher than the occlusal margins in the 3T MRI group (p<0.05, p = 0.029). Conclusions: 3T MRI may weaken the adhesion between the enamel and the stainless steel orthodontic bracke