Dental The most common cause of fracture at the isthmus of a class II dental amalgam restoration: A Delayed expansion B Inadequate depth at the isthmus area C Inadequate width at the isthmus area D Moisture contamination of the amalgam 💡 Explanation The most common cause of fracture at the isthmus of a class II dental amalgam restoration: ✓ Correct Answer: B. Inadequate depth at the isthmus area