Dental The instrument formula of a Gingival margin trimmer is 12 1/2-100-7-14. This instrument cannot be used for: A Distal gingival preparation B Mesial gingival preparation C Inlay preparation with steep gingival bevel D Onlay preparation with steep gingival bevel 💡 Explanation The instrument formula of a Gingival margin trimmer is 12 1/2-100-7-14. This instrument cannot be used for: ✓ Correct Answer: B. Mesial gingival preparation