INBDE Dentistry Practice Test 2026 – Complete Exam Prep

Ferrule is the term for the minimum amount of natural tooth structure that must remain coronal to the finish line to encircle the tooth with a crown and resist fracture. Having about 1.5–2 mm of tooth structure around the circumference provides resistance to functional and parafunctional forces, distributes stresses, and helps prevent fracture, especially when a post and core is used. Margin and finish line describe where the crown meets the tooth and the boundary of reduction, not the amount of coronal structure needed. Dentin thickness matters for strength, but it’s not the term for the required encircling tooth structure.