17861201
Description
Mind Map by Alice Dolman, updated more than 1 year ago
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Created by Alice Dolman
about 5 years ago
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What factors affect the magnitude
ofclasp retention?
- 1. Type of clasp used
- The type of clasp used determines how it’ll be placed in relation to undercut. Retentive portions of clasps enter
undercuts by approaching from either gingivally (infra bulge) or occlusally (supra bulge). The gingivally
approaching clasps exert a trip action which increases retention. Varying the angle at the contact with tooth
increases or decreases the trip action.
- Circumferential clasp (Circle or Akers) - Ring Clasp - Embrasure Clasp
(Double Akers) - C Clasp (Hair pin or reverse action) - Bar Clasp - RPI
Clasp - RPA Clasp - Combination Clasp
- The type of clasp used determines how it’ll be placed in relation to undercut. Retentive portions of clasps enter
undercuts by approaching from either gingivally (infra bulge) or occlusally (supra bulge). The gingivally
approaching clasps exert a trip action which increases retention. Varying the angle at the contact with tooth
increases or decreases the trip action.
- 2. Axial convergence of tooth surfaces apical to the height of contour
- Size/how far into the angle of convergence (undercut) the clasp terminal is placed - The depth of undercut
engaged or the location of clasps on the undercut of tooth is determined when surveying. The greater undercut,
the greater retention. An undercut too big will strain the clasp and traumatise the teeth. An undercut too small
will give insufficient retention
- Undercut is measured perpendicular to the path or insertion. The
degree of undercut is measured using gauges which considers the
materials MoE
- Size/how far into the angle of convergence (undercut) the clasp terminal is placed - The depth of undercut
engaged or the location of clasps on the undercut of tooth is determined when surveying. The greater undercut,
the greater retention. An undercut too big will strain the clasp and traumatise the teeth. An undercut too small
will give insufficient retention
- 3. Flexibility of the retentive arm: (related to length, diameter, cross sectional form and clasp material)
- - Length, the length of clasp can affect clasp retention, increasing the length increases the flexibility,
measured from the point where the taper begins, may be increased by curving.
- - Diameter - Thicker the clasps, the more rigid they are. The thickness and length of clasps must be related to
the MoE of the alloy used.
- - Cross sectional form - round more flexible
- - Clasp material - wrought wire has greater tensile strength than cast (can be used in smaller diameters)
Materials: gold, steel,chrome all have different MoE. MoE: a greater MoE means a stiffer material. It would
require more force to deflect it to the same degree as a material with a lower modulus. It would require more
force to deflect it to the same degree as a material with a lower modulus.
- - Length, the length of clasp can affect clasp retention, increasing the length increases the flexibility,
measured from the point where the taper begins, may be increased by curving.
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