Endodontics · single question
Which property IMPROVES the 'ferrule effect'?
Show answer and explanation
Correct answer: A. Dowels/posts in the core
Dowels/posts in the core (A) improve the ferrule effect by providing retention for the core buildup. However, the TRUE ferrule is provided by encircling the tooth structure WITH THE CROWN MARGIN — a 2mm band of sound dentin circumferentially above the finish line.
• The ferrule effect: a metal collar (crown margin) that encircles sound vertical tooth structure. It prevents crown fracture and root fracture by distributing occlusal forces along the long axis.
• Minimum ferrule: 2mm of sound dentin height + 1mm of dentin thickness.
• Option B: A metal band placed CORONAL to (not apical to) the finish line — this IS the ferrule concept. If placed apical to the core/crown margin, it doesn't create the ferrule effect.
• Post alone does NOT create a ferrule — the crown margin does.
• The ferrule effect: a metal collar (crown margin) that encircles sound vertical tooth structure. It prevents crown fracture and root fracture by distributing occlusal forces along the long axis.
• Minimum ferrule: 2mm of sound dentin height + 1mm of dentin thickness.
• Option B: A metal band placed CORONAL to (not apical to) the finish line — this IS the ferrule concept. If placed apical to the core/crown margin, it doesn't create the ferrule effect.
• Post alone does NOT create a ferrule — the crown margin does.