Which type of direction do infrabulge clasps use to approach the retentive undercut?

Which type of direction do infrabulge clasps use to approach the retentive undercut?

• A. Gingival direction
• B. Occlusal direction
• C. Buccal direction
• D. Lingual direction

Answer: (A)

Infrabulge clasps engage the retentive undercut from the gingival direction because the undercut they rely on is located apical to the height of contour, toward the gingival margin. Seating the clasp from the gingival side allows the retentive arm to slide into that undercut properly and maintain retention without lifting the tooth crown or interfering with the occlusion. Approaching from other directions would miss the undercut’s location and compromise seating and retention. This is different from suprabulge clasps, which are designed to engage undercuts from an occlusal (or incisal) direction.

Infrabulge clasps engage the retentive undercut from the gingival direction because the undercut they rely on is located apical to the height of contour, toward the gingival margin. Seating the clasp from the gingival side allows the retentive arm to slide into that undercut properly and maintain retention without lifting the tooth crown or interfering with the occlusion. Approaching from other directions would miss the undercut’s location and compromise seating and retention. This is different from suprabulge clasps, which are designed to engage undercuts from an occlusal (or incisal) direction.