CLASPS DESIGNS IN RPD

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Clasp Design

Direct retainers may come in various designs:
Cast circumferential clasp (suprabulge) Akers’
Half and half
Back-action
Ring clasp

Wrought wire clasp
Roach clasp (infrabulge) I-bar
T-bar
Y-bar
7-bar

Both cast circumferential and wrought wire clasps are suprabulge clasps, in that they engage an undercut on the tooth by originating coronal to the height of contour, while Roach clasps are infrabulge clasps and engage undercuts by approaching from the gingival.

In addition there are a couple of specific theories which include the clasp design:
RPI: mesial rest, distolingual guide plate, I-bar Described by Kratochvil in 1963 and modified by Kroll in 1973
An illustration of the RPI design function

RPA: mesial rest, distolingual guide plate, Akers’ clasp-style retentive arm
RPC: mesial rest, distolingual guide plate, other type of cast circumferential clasp So named in response to the RPI Philosophy introduced by Kratochvil and Kroll

        

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“I need a denture – what are my options?”

• Conventional removeable partial dentures
• Precision and semi-precision partial dentures
• Conventional over-denture
• Implant over-denture
• Immediate dentures – what to expect
• Wearing a new denture – what to expect
• Why consider a metal base denture?

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• Conventional Removable Partial Dentures

A partial denture is useful for a person missing some teeth, but still having a number of natural teeth.

This device is also called a removable prosthesis, and is a means by which artificial replacement teeth are held in the mouth. The prosthesis is commonly kept in place by means of clasps. These are thin finger-like structures, usually made of a special resilient metal alloy or sometimes plastic, that rest upon and wrap around some remaining natural teeth. Clasps keep the prosthesis securely in place but still allow a person to easily take it out for regular cleaning and proper brushing of remaining natural teeth.

Some reasons for having a partial denture made

• Replace missing teeth

• Improve ability to chew more naturally

• Chew food with confidence

• Make it possible to eat certain favorite foods

• Maintain a healthier and socially acceptable mouth

• Aids in the preservation of remaining natural teeth

• Help prevent or treat problems of the TMJ (the jaw joint)

• Often improve speech

• Helps develop a more pleasing and confident smile

• Support the face – – often with a more youthful appearance

• Enhance self esteem

• An economical way to replace missing teeth

• Many times an additional tooth may be added to an existing partial denture if a natural tooth is lost

• In most cases crowning teeth is not necessary to fit a partial denture

• Partial dentures are usually easy to repair if they are broken

Esthetics and the conventional partial denture

Generally, clasp design is reasonably esthetic, and often it is possible for them not to be seen. However, depending upon partial denture design, which is based on mouth conditions, there may be some show of clasps. Often this is not an appearance problem. However, if avoiding an unacceptable show of clasps would compromise optimal partial denture design, various special attachments may sometimes be employed to do away with conventional clasps. These attachments are more technically complex and often are referred to as precision or semi-precision attachments.

How long will a partial denture last?
Accidents happen, and the mouth is constantly changing. Partial dentures may no longer fit properly, can break or bend or simply wear out. In fact there is nothing made for the mouth that is permanent. Fractured clasps and so forth may often be repaired.

On average, a partial denture may be expected to last about five years. Depending upon circumstances, a certain removable prosthesis can last a shorter or longer time

        

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