The results of this study indicate that the amount of polymerization shrinkage and cuspal deflection were highly correlated. The materials that showed a lower shrinkage value also demonstrated lower cuspal deflection. As cuspal deflection increases, the chances of crack formation in a tooth would also increase and may also cause clinical symptoms such as temperature sensitivity and pain on biting. Therefore, in large class II cavities, resin composite with a low polymerization
shrinkage value should be used to reduce cuspal deflection.