Comparative evaluation of plasticization of composite resin by preheating, sonic, and ultrasonic activation on its...

By reducing the viscosity of composite resin, its adaptability to the tooth surface can be improved.

This study aims to comparatively evaluate the efficacy of plasticization of composite resin by preheating, sonic, and ultrasonic activation on the marginal adaptation to the tooth surface.

Standardized box-shaped Class I cavities (3 mm × 3 mm × 2 mm) were prepared on 32 extracted mandibular molars. Following etching and bonding, samples were divided into four groups depending on the technique used to plasticize the composite resin (n = 8 each): Group 1 - hand instrument (no plasticization done), Group 2 - preheated composite resin, Group 3 - sonically driven plasticization, and Group 4 - ultrasonically driven plasticization. Further, composite resins were compacted using a hand instrument and light-cured for 20 s. Samples were then stored in an incubator at 37°C and 100% humidity for 24 h to allow complete polymerization. Models were split in buccolingual direction to expose the bonding interface. Marginal adaptation was analyzed using FESEM (Field Emission Scanning Electron Microscope) at ×5000-×20,000.

The data were statistically analyzed using one-way ANOVA and post hoc test.

Post hoc pairwise comparison of marginal adaptation revealed statistically significant differences between Group 1 - hand instrument (no plasticization) with all other groups adapted using the plasticization technique. Ultrasonic plasticization demonstrated the best marginal adaptation, followed by preheated composite, then sonic plasticization, while the hand instrument placement technique showed the least favorable results.

Plasticization of composite resin enhances the marginal adaptation to the tooth surface and produces gap-free margins.