Effect of Preheating on Fracture Resistance of Bis-GMA Free and Containing Resin Composite After Cyclic Loading (In-Vitro Study)

Aim: Evaluation of preheating effect on fracture resistance of Bis-GMA free and containing resin composite after cyclic loading.
Materials and Methods: Two different resin composite were used, Bis-GMA free composite (Admira Fusion) and Bis-GMA containing composite (Grandio). One hundred sound maxillary premolars were selected, MOD cavity prepared in 90 teeth of them, and 10 teeth remained intact (control gp.). The prepared teeth classified into 9 groups according to type of resin composite used, heating temperature (room temperature (23°C) & 54±1°C) and cyclic loading time (24 hours & 3 months). The mechanical ageing test was carried out utilizing a four-station multi-modal ROBOTA chewing simulator, and universal testing machine was used to determine fracture resistance, The amount of force required to fracture was measured in Newtons. IBM® SPSS® Statistics Version 20 for Windows was used to perform the statistical analysis.
Results: At varied temperatures and cyclic loading, the mean value of fracture resistance of teeth restored by Admira (A1) was higher than that of teeth restored by Grandio (A2). Teeth restored with heated composite at 54±1 °C had stronger fracture resistance than teeth restored at room temperature. After 24 hours of cyclic loading, the mean fracture resistance load of all groups tested was higher than that observed after three months (P<0.001).
Conclusion: Even without preheating, Bis-GMA-free resin composite restorative materials restored the fracture resistance of maxillary premolars with MOD preparation under cyclic stress. Preheating, on the other hand, improves the fracture resistance of teeth repaired with the two resin composites evaluated.