Clasp Designs

There are three commonly used clasp designs for NMCDs.¹²

1. Standard clasp: The "standard" or the "main" clasp is the most common and efficient clasp design (Figures 7, 8A). An improper clasp design will lead to the fabrication of a large and/or bulky clasp. Few millimeters of the tooth (1-2mm) and tissue contact are all that is required for achieving optimal clasp retention and stability.¹²

   Figure 7 - Standard clasp

   

   Figure 7 - Standard clasp

2. Circumferential clasp: It is commonly indicated for a free-standing mesially-tipped distal abutment tooth. This claps design helps in eliminating the broad flat cantilever and strengthens itself by encircling the tooth (Figure 8B). When the circumferential clasp encircles multiple teeth, it is termed as a "continuous circumferential clasp” (Figure 8C). The continuous circumferential clasp design helps in improving its rigidity.¹²

   Figure 8 - Animations depicting the standard clasp, circumferential clasp, and the continuous clasp (from left to right)

   

   Figure 8 - Animations depicting the standard clasp, circumferential clasp, and the continuous clasp (from left to right)

3. Combination clasp: A circumferential clasp used along with a standard clasp is termed a combination clasp.¹² A clasp should passively fit on the tooth surface without exerting excessive stresses on the abutment tooth.² Occasionally, minor reshaping of the tooth in the area of the survey line and/or guide planes may be required to accomplish the same.² Tapered diamonds followed by fine finishing diamonds (with copious amounts of water) may be used to prepare and finish the tooth preparations (Figure 9).²

Figure 9 - Tapered diamond point may be used to prepare the tooth surfaces

Figure 9 - Tapered diamond point may be used to prepare the tooth surfaces

Clasp thickness recommendations:

Recommendations for the thickness of the clasp are based on the depth of the undercut and the material used for its fabrication.³³ A 1.0 mm thickness Estheshot clasp is indicated when a 0.25 mm undercut is present, however, a 1.0 mm thickness Valplast clasp is indicated when a 0.5 mm undercut is present.³³ A 0.5 mm thickness Reigning clasp is recommended for a tooth having a 0.5 mm undercut.³³