Immediate reports of Post-Operative Sensitivity (POS) reported after restoring teeth with direct composite resin restoration is a perplexing issue experienced by most dentists. This review hopes to look at some of the causes of post-operative sensitivity and the plausible solution and / or prevention to this arcane issue. In most studies on POS, the three most commonly cited reasons are: polymerization shrinkage of the resin, microleakage around the margins of the restoration and build-up of residual stress in the fabric of the tooth after placement of direct composite restoration. Knowledge gained by this review points towards soft start mode of polymerization using low light-cure intensities may help to reduce polymerization shrinkage and possibly postoperative sensitivity.