RPD DESIGN - BRACING AND RECIPROCATION Flashcards
When are horizontal forces generated
During function by occlusal contacts and by the oral musculature surrounding the denture
What do horizontal forces do to a denture
Displace the denture in the antero-posterior and lateral directions
What are horizontal forces resisted by
Placing rigid components of the denture (bracing components) against suitable vertical surfaces on the teeth and residual ridges
When can bracing only occur
When the denture is fully seated
What are lateral forces capable of doing
conflicting considerable damage on the periodontal tissues and alveolar bone in the edentulous areas
How may bracing on teeth be achieved
by means of rigid portions of clasp arms or plates
How may bracing be achieved on ridges and in the palate
by means of major connectors and flanges
When is a clasp effective in its retention
in the retention distance
What is the retention distance
position when the denture is fully seated to where it escapes over the bulbosity of the tooth
What should a reciprocal element be doing for it ot be effective
should be in continuous contact with the tooth surface as the retentive arm transverses the ‘retention distance’
What can effective reciprocation be achieved by
○ A clasp arm contacting a guide surface of a similar height to the retention distance
○ A plate making continuous contact with the tooth surface as the retentive arm moves through its ‘retention distance’
What happens if a reciprocal arm is not placed on a guiding surface
it will loose contact with the tooth before the retentive arm has passed over the maximum bulbosity of the tooth and fail to provide reciprocation
Why is reciprocation important
The clasp deforms as it goes over the bulbosity - it puts pressure on the tooth which can result in horizontal movement so reciprocation keeps contact with the tooth as the clasp deforms to oppose the horizontal movement and maintain the tooth in its position
