Impact of different light curing modes on the cuspal deflection of maxillary premolars restored with nanohybrid resin restoration: An in vitro study

INTRODUCTION: The influence of various light-curing modes may lead to polymerization shrinkage resulting in contraction stresses in composite resin. These stresses leads to linear movement of the cusp tips of the tooth as a result of interactions between polymerization shrinkage stress of the composite and adherence of the cavity wall of the tooth. That may lead to restoration failure. AIM: Comparative evaluation of the effect of different light-curing modes on the cuspal deflection of class II Mesio-occlusal-distal cavity restored with Nano-hybrid composite resin restorative material. METHOD: Thirty-six standardized MOD preparations were prepared on maxillary first premolars. Three groups(n=12) were divided according to different light-curing modes of Blue phase LED curing light- Group 1: soft-start curing mode; Group 2: pulse curing mode; Group 3: continuous curing mode. 1mm diameter glass beads were fixed to each cusp tip as a reference point for intercuspal distance to measure initial cuspal deflection for each group. MOD Preparations were etched and bonded with adhesive resin to provide micromechanical attachment and restored with Nano-hybrid composite restoration using the incremental technique. The cuspal deflection was then measured with the Digital micrometer gauge and the mean difference was measured for each group