Smear Layer

The smear layer is a thin, amorphous layer of debris composed of dentin collagen, hydroxyapatite crystals, and microbial remnants that forms on tooth surfaces during cavity preparation with rotary instruments. It typically obstructs dentinal tubules (1-5 ¿m deep) and reduces dentin permeability by 86%, acting as both a mechanical barrier and potential substrate for bacterial growth. While it may provide short-term occlusion of tubules and decrease sensitivity, its interference with bonding (reducing adhesive strength by 30-50%) makes removal/modification essential for durable restorations. Common smear layer management approaches include total etch (phosphoric acid) for complete removal, self-etch adhesives for partial dissolution/integration or EDTA or citric acid in endodontics. Its dual nature-protective vs. adhesive-inhibiting-remains a key consideration in restorative and endodontic procedures. This book focuses on the structural, physiological and bacterial considerations of smear layer and the controversy of smear layer- to retain or to remove?