The Chairside Instructor 21 Tooth Decay Decay, Cavities and Restorations Progress of Tooth Decay Abscess Healthy teeth and roots without signs of decay. If not treated, tooth decay can cause an abscess (arrow) and can lead to serious infections. Image ©Elsevier Inc. All rights reserved. Early decay may not be easy for you to notice. Abscess If not treated, tooth decay can cause an abscess and can lead to serious infections. Decay under the surface may be larger than it looks from the outside. Decay in tooth grooves Decay under filling Decay between teeth Root decay Abscess