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 μm 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?