What distinguishes a gingival margin trimmer from an enamel hatchet?

Correct answer: B. The gingival margin trimmer has a curved blade with the cutting edge angled to the blade axis

• A. Both instruments are conventionally supplied double-ended, in mesial and distal pairs.
• B. CORRECT. Both are members of the chisel family, but the ENAMEL HATCHET has a straight blade with its cutting edge in the same plane as the handle, so it planes walls in a straight push. The GINGIVAL MARGIN TRIMMER has a CURVED blade with the cutting edge set at an ANGLE to the blade axis — a bi-angled design that lets it reach the gingival floor of a proximal box and place a bevel there, a location a straight instrument simply cannot access.
• C. Shank length is not the distinguishing feature.
• D. The enamel hatchet is used on posterior preparations as well.

Note: Gingival margin trimmers come in mesial and distal pairs, and in two curvatures — one for the gingival bevel, one for the occlusal. The pairing exists because the instrument must approach from the correct side of the box.