Shear Bond Strength of Fixed Retainer Bonded with Different Types of Composites

Aim: Aims of the study were to measure shear bond strength of different composite types used in bonding fixed retainer. Subjects and methods: The sample of this study consists of sixty extracted sound human premolar teeth that were divided into three wire groups and three fiber-reinforced composite groups. In wire and fiber-reinforced composite groups, one group is bonded with control conventional composite and two groups bonded using different types of flowable composites. Each sample was etched, bonded and then inserted into the universal testing machine. The resulted data were collected and then analyzed to obtain the mean values of shear bond strength of each sample. Results: In wire groups, the results demonstrated that the difference between groups was statistically non-significant (p value>0.05) as indicated by one way ANOVA. In FRC groups, the results demonstrated that the difference between groups was statistically significant (p value>0.05) as indicated by one way ANOVA. There was a statistically significant difference between conventional composite and Tetric-N flowable composite when used, respectively. Conclusion: In all FRC groups the results of shear bond strength were less than the results of wire groups. It was found that the FRC weakens instead of strengthens the fiber/composite complex. INTRODUCTION Retention is usually necessary following orthodontic treatment to overcome the elastic recoil of the periodontal supporting fibers and to allow remodeling of the alveolar bone. With the possibility of acid etching and bonding, it has become common practice to apply bonded fixed retainers for long-term retention of the achieved orthodontic results.(1) Bonded lingual retainers are fabricated in various designs that consist of combinations of different wires in different sizes and different composites.(2) Spiral or multistrand wires appear to be the most popular for direct bonded retainers. The main advantage of the use of multistrand wire is the irregular surface that offers increased