The Chairside Instructor 22 Chewing surface decay (Occlusal decay) Decay in between teeth (Interproximal decay) Decay at the gum line (Cervical decay) Root decay (Radicular decay) Tooth decay can form under fillings. X-ray of tooth with decay under a filling. Common Sites of Decay Decay Under fillings Tooth Decay Decay, Cavities and Restorations