What type of clasps approach the retentive undercut from a gingival or infrabulge direction?

What type of clasps approach the retentive undercut from a gingival or infrabulge direction?

• A. Suprabulge clasps
• B. Infrabulge clasps
• C. Circumferential clasps
• D. Bar clasps

Answer: (B)

Approaching the retentive undercut from the gingival direction means using an infrabulge clasp. Infrabulge clasps engage undercuts from below the height of contour, so the retention is provided by portions that come up from the gingival side to grip the undercut. This is in contrast to suprabulge clasps, which approach from above the survey line and engage the undercut from the occlusal/incisal direction. The term infrabulge specifically describes the path of insertion relative to the tooth’s height of contour, which is why it’s the correct choice for a gingival-direction approach.

Approaching the retentive undercut from the gingival direction means using an infrabulge clasp. Infrabulge clasps engage undercuts from below the height of contour, so the retention is provided by portions that come up from the gingival side to grip the undercut. This is in contrast to suprabulge clasps, which approach from above the survey line and engage the undercut from the occlusal/incisal direction. The term infrabulge specifically describes the path of insertion relative to the tooth’s height of contour, which is why it’s the correct choice for a gingival-direction approach.