RPD misc

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RPD misc
2013-08-30 09:16:03
RPD misc

RPD misc
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  1. List the basic principles of partial denture design.
    •        Major connectors must be rigid.
    •        Occlusal rest must direct occlusal forces along the long axis of the teeth.
    •        Guide planes are employed to enhance stability and bracing.
    •        Retention must be within the limits of physiologic tolerance of the periodontal ligament.
    •        Maximum support is gained from the adjacent soft tissue denture bearing surfaces.
    •        Designs must consider the needs of cleansibility.
    • The RPD must achieve retention, stability and support via the following.
    • The rests must be positive and direct functional forces in the long axis of the tooth and as close to the center of the tooth as possible.
    • The Major connectors must be rigid in order to achieve cross arch stabilization and must be in intimate contact to soft tissues in order to promote cleansibility.
    • Parallel guiding surfaces allow for passive insertion and bracing utilizing proximal plates.
    • Reciprocation is achieved utilizing minor connectors, proximal plates and retainers.
    • Undue stress to PDL should be minimized w/ rest design and the RPD must not actively engage the dentition in function.
    • Soft tissue support in adjacent edentulous areas maximizes support.
  2. List the 6 requirements of a clasp
    • 1. Retention
    • 2. Bracing
    • 3. Support
    • 4. Reciprocation
    • 5. Encirclement of the tooth over 180 degrees
    • 6. Passivisity
    • 1. Minimal tooth contact 
    • 2. Exact placement of retention contact 
    • 3. Minimal interference with natural tooth contour 
    • 4. Maximum natural cleansing action 
    • 5. Passive functional movement of an extension prosthesis 
    • 6. Reduced display of metal, for better esthetics 
  3. Crowns are necessary as RPD abutments to:
    •     1. establish the proper guide plane if abutment has previous crown
    •     2. reposition the clinical crown
    •     3. restore a badly broken down clinical crown
    •     4. also, a proper rest could be incorporated into the crown which is not normally present on the tooth, such as a cingulum rest on a mandibular canine
  4. Name the three types of “positive” rests that can be used on anterior abutments. 
    • 3 types of positive anterior rests:
    • 1. incisal
    • 2. circular concave
    • 3. cingulum
    • (1)Cingulum rest –
    • a.  Crescent-shaped
    • b. As center as possible when viewed from all directions
    • c.The center is deeper buccal-lingually  (positive rest)
    • (2)Insisal rest- concave mesiodistally and convex buccolabially.
    • (3)Circular concave
    • a)      circular concave rest 
    • i.      #2 or #4 round bur
    • b)      incisal rest
    • i.      two planes preparation with flame shaped bur
    • 1.      incisal plane
    • 2.      labial plane
    • ii.      concave mesiodistally, convex buccolingually
    • iii.      1/3 of mesiodistal incisal width
    • c)      cingulum rest 
    • i.      flamed shape and inverted cone shape burs
    • 1.      use flamed shape bur at 45 to create an outline form
    • 2.      use inverted cone shape bur to create positive rest seat
  5. What type of suprabulge retainer do we recommend at UCLA?  Why?  When do we recommend that such a retainer be used? 
    • Recommendation: Circumferential Clasp (aka: Akers Clasp) because 
    • i. With flexible retentive arm that crosses the height of contour into the undercut and a rigid reciprocating arm that stays above the height of contour 
    • ii. Fulfills the requirements of clasp 
    • 1. Retention 
    • 2. Bracing 
    • 3. Support 
    • 4. Reciprocation 
    • 5. Encirclement 
    • 6. Passivity 
    • Indications for use of a circumferential clasp 
    • b. Bulbous gingival contours 
    • c. Lack of access for an I-bar clasp due to a shallow vestibule, a frenum attachment, or a severe gingival undercut 
    • d. Short teeth with poor or no guide planes 
    • e. Tilted teeth 
    • f. Significant recession and/or abfraction