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Types of clasps
Transcript of Types of clasps
prepared by: Razan Burhan
• 1. Simple circlet clasp
Most versatile and widely used. Best for tooth supported partial denture. It approaches the undercut from the edentulous space. It engages the undercut, located away from the edentulous space.
• It is a combination of two simple circlet clasps joined at the terminal end of the reciprocal arms.
• It is used for sharing the retention with additional teeth on the. same teeth on the same side of the arch when the principle abutment tooth has poor periodontal support. It is a mode of splinting weakened teeth.
4. Embrasure clasp or modified crib clasp
It is a combination of two simple circlet clasps joined at the body. It is used on the side of the arch where there is no edentulous space.
Indications: It is used in kennedy’s class 2 and class 3 cases without any modifications. Occasionally, a very small edentulous space can be closed by a modified embrasure clasp called a pontic clasp
5. Ring clasp
Indicated in tipped molars In Distal edentulous conditions with distolingual undercut - the retentive arm is extended all around the tooth from the disto buccal end to terminate in the distolingual undercut across the mesial side of the tooth
• 6. fishhook or hairpin or reverse action clasp
Type of simple circlet clasp. retentive arm – crosses the facial surface of the tooth from its point of origin, loops back in a hairpin turn to engage a proximal undercut below its point of origin
• 7. • Onlay clasp
• Extension of a metal crown or onlay with buccal and lingual clasp arms. Used in occlusal surfaces of submerged abutment teeth – thus restoring the occlusal plane with an onlay.
• If onlay clasp is made of chrome alloy – the opposing tooth should. be protected with a gold crown to avoid attrition of enamel. Used in caries resistant mouth.
Types of Cast Circumferential Clasps
• 2. Reverse circlet clasp or reverse approach clasp
This clasp is used when the retentive undercut on the abutment tooth is located adjacent to the edentulous space. Used in distal extension denture base to control the stresses acting on the terminal abutment teeth.
3.Multiple circlet clasp
8. combination clasp
A cast circumferential clasp can’t be used – when an undercut is adjacent to the edentulous space since it produce destructive rotatory forces on the distal abutment A flexible wrought wire retentive arm is used to replace the rigid cast alloy retentive arm.
It has a retentive arm arising from one direction and Half and half clasp a reciprocal arm arising from another direction. Two minor connectors are needed for this design. The first minor connector attaches the occlusal rest and the retentive arm to the major connector. The second minor connector connects the reciprocal arm which is similar to the bar clasp with or without an auxiliary rest.
9 • Back-action clasp
It is a modification of the ring clasp Here the minor connector is connected to the end of the clasp arm and the occlusal rest is left unsupported. Disadvantages : Lack of support to the occlusal rest reduces its function. It has both biological and mechanical unsound principles
10 • Grasso’s clasp or VRHR clasp
• Developed by Grasso, This clasp consists of vertical reciprocal arm, an occlusal rest and a horizontal retentive arm arising separately from the major connector.
• Minimizes tooth contact
• Advantages . Grasso’s clasp or VRHR clasp Does not require the preparation of guidewithout compromise in efficacy. The placement Suitable for posterior teeth with high survey lines. planes of the retentive arm is more aesthetic.
The RPA clasp
is a. Rest-proximal plate – Akers retentive arm (RPA) clasp modified circumferential clasp The circumferential arm arises from the proximal plate adjacent to the edentulous base area. The retentive component of this direct retainer - engages a retentive undercut located on the facial surface of the abutment tooth away from the edentulous area.
Circumferential clasp Aker’s clasp
Vertical projection or bar clasp
11. Half and half clasp
Its have a retentive arm arising from one direction and the reciprocal from the another
This type intended to provide dual retention
Its have 2 minor connector
Types Vertical projection or Roach or Bar type
Modified T clasp
Infra bulge clasp or mirror view clasp