A tooth has only 0.5 mm of tooth structure remaining above the gingival margin. What is the PRIMARY concern for crown restoration?

The ferrule effect is the encirclement of tooth structure by the crown's axial walls above the finish line. A minimum of 2 mm of sound tooth structure above the finish line is required to provide adequate ferrule for resistance to fracture and displacement. With only 0.5 mm remaining, there is grossly inadequate ferrule, making the restoration biomechanically unsound. Options include crown lengthening, orthodontic extrusion, or extraction and implant. The ferrule effect is the most critical biomechanical factor in post-core-crown restorations.