Flowable Composites for Bonding Orthodontic Retainers

Abstract Objective: To test the null hypothesis that there are no statistically significant differences between flowables and an orthodontic adhesive tested in terms of shear bond strength (SBS) and pullout resistance. Materials and Methods: To test the SBS of Light Bond, FlowTain, Filtek Supreme, and Tetric Flow were applied to the enamel surfaces of 15 teeth. Using matrices for application, each composite material was cured for 40 seconds and subjected to SBS testing. To test pullout resistance, 15 samples were prepared for each composite in which a wire was embedded; then the composite was cured for 40 seconds. Later, the ends of the wire were drawn up and tensile stress was applied until the resin failed. Findings were analyzed using an ANOVA and a Tukey HSD test. Results: The SBS values for Light Bond, FlowTain, Filtek Supreme, and Tetric Flow were 19.0 ± 10.9, 14.7 ± 9.3, 22.4 ± 16.3, and 16.8 ± 11.8 MPa, respectively, and mean pullout values were 42.2 ± 13.0, 24.0 ± 6.9, 26.3 ± 9.4, and 33.8 ± 18.0 N, respectively. No statistically significant differences were found among the groups in terms of SBS (P > .05). On the other hand, Light Bond yielded significantly higher pullout values compared with the flowables Filtek Supreme and Flow-Tain (P < .01). However, there were no significant differences among the pullout values of flowables, nor between Light Bond and Tetric Flow (P > .05). Conclusions: The hypothesis is rejected. Light Bond yielded significantly higher pullout values compared with the flowables Filtek Supreme and FlowTain. However, flowable composites provided satisfactory SBS and wire pullout values, comparable to a standard orthodontic resin, and therefore can be used as an alternative for direct bonding of lingual retainers.