Effect of mandibular molar anatomy on the buccal Class I cavity preparation

In mandibular molars, enamel dramatically increases in thickness at the buccal pit area and progresses occlusally due to an extensive concavity in the buccal dentinal core. In order to comply with the principles of operative dentistry, this anatomic variance dictates that, if the ultimate restoration is to be placed in dentin, the axial wall of a Class I buccal pit preparation should incline medially rather than follow the external contour of the tooth. The occlusal cavosurface angle of the preparation should be obtuse to coincide with enamel rod direction. Retention, when needed, should be placed at the mesio-axial and disto-axial line angles to avoid undermining occlusal intercuspal enamel, especially as the preparation approaches 2 mm occlusal to the buccal pit.