Circumferential Clasp - Cast Clasp Design
Posted on 12/01/2011
The circumferential clasp is a clasp design where both the buccal and lingual arms originate from a common source and the undercut is engaged from the opposite side of the tooth (mesial-distal) from the point of origin. One arm acts as the retentive arm while the other acts as the bracing/reciprocating arm. This suprabulge clasp design can be designed with either both clasps cast or one cast and one wrought wire.
The design with cast buccal and lingual arms offers the advantages of excellent retention, rigidity and long term durability. As such it is ideally indicated for tooth supported RPDs (i.e. RPDs where abutment teeth lie distally to the circumferential clasp).
However, there are several important disadvantages to this design including:
1. Aesthetics: the cast clasps are prominent
2. Food Deflection: the cast clasps often disrupt normal food deflection patterns that are needed for stimulation of the gingivae.
3. Adjustment Difficulty: the cast clasps can only be adjusted at the final third of the clasp closer to the clasp tip - just where the arm crosses the height of contour.
4. Distal Extension RPD: Contraindicated for distal extension RPDs dues to torque applied to the abutment teeth.
Due to the above mentioned disadvantages, an alternative design where one of arms is wrought wire is often utilized. This design will be discussed in tomorrow's blog.
The design with cast buccal and lingual arms offers the advantages of excellent retention, rigidity and long term durability. As such it is ideally indicated for tooth supported RPDs (i.e. RPDs where abutment teeth lie distally to the circumferential clasp).
However, there are several important disadvantages to this design including:
1. Aesthetics: the cast clasps are prominent
2. Food Deflection: the cast clasps often disrupt normal food deflection patterns that are needed for stimulation of the gingivae.
3. Adjustment Difficulty: the cast clasps can only be adjusted at the final third of the clasp closer to the clasp tip - just where the arm crosses the height of contour.
4. Distal Extension RPD: Contraindicated for distal extension RPDs dues to torque applied to the abutment teeth.
Due to the above mentioned disadvantages, an alternative design where one of arms is wrought wire is often utilized. This design will be discussed in tomorrow's blog.
