2) Define resistance form and identify the specific features and criteria that address it in the class II cavity preparation Resistance form- internal form; shape and placement of the preparation walls enabling tooth to withstand masticatory forces, preventing fracture of the tooth or restorative material.
- -pulpal/gingival walls perpendicular to long axis of the tooth; flat pulpal/gingival walls buccolingually
- -pulpal depth - 1.5 - 1.9 mm
- -axial depth - 1.0 - 1.5 mm (0.5 mm into dentin clinically)
- -strong cusps/ridges with sufficient dentinal support
- -divergent dovetail wall
- -s-curve- increase strength of amalgam and tooth structure at the junction of the occlusal step and proximal box, exit angle 90degrees
- -round internal line angles (inc. rounded axiopulpal line angle and gingival "bevel" that follows enamel rods, which increases the bulk and decreases the stress concentration within the restorative material)