Recurrent decay is tooth decay that forms under existing fillings, crowns, or onlays Because of leakage around a dental restoration, constant pressure from chewing or stress from grinding and clenching can loosen crowns and onlays and cause fillings to crack, chip, or wear away. These problems can leave gaps and allow harmful bacteria to get underneath the crown, onlay, or filling. You may have marginal leakage if a restoration feels loose or if you have tooth sensitivity or pain on a restored tooth. Having food gets stuck in the filling or around the gum line of a crown can also be an indication of marginal leakage. As decay worsens and weakens the underlying natural tooth structure, cracks, breakage, or the loss of the tooth may occur, and if left untreated, more serious procedures like a root canal, bridge, or dental implant may be needed. However, if caught early enough, your doctor can typically remove the decay and provide you with a new restoration.