RPD Tooth Modifications

Question 1

What should the dentist have before beginning tooth modifications?

Answer 1

• Surveyed preliminary cast
  
  • guide

Question 2

Guide Plane Prep

Answer 2

• Always prepped 1st
• Parallel to planned path of insertion
• Sweeping motion
  
  • follow natural curvature of tooth
    
    • not straight cut
• Reduced Height of Contour
  
  • no large spaces b/w teeth→Food traps & Black Triangles
• Polish All Adjusted Areas

Question 3

Guide Plans for Tooth Supported Abutment vs Free-end Extension

Answer 3

• Tooth Supported Abutment
  
  • reduce 2-4mm in occlusogingival direction
• Free-end extension:
  
  • reduce 1.5-2mm in occlusogingival direction
  • allows slight rotation to ⇣ Forcep Action

Question 4

Guide Planes for Anterior Teeth provide:

Answer 4

• Prallelism
• Stabilization
• Decrease
  
  • wedging
  • undesirable space (esthetic)
• Increase Frictional retention
• restore normal width to edentulous space

Question 5

Retentive Undercut for Claps

Answer 5

• Helps retain RPD
• Gentle Depression on tooth surface
  
  • Depth: 0.25 mm
    
    • depth of 1st undercut gauge
  • Mesial-Distal x Occlusal-Gingival Size:
    
    • 4x2 mm
  • avoid ledges or shoulders
• move handpiece in anteroposterior direction
  
  • near the line angle or mid facial
• Polish w/rubber wheel or point

Question 6

Enameloplasty:

Answer 6

• Changes the Height of Contour
  
  • Lowered
    
    • enhances position of clasp arm→does not interfere w/occlusion
  • No higher than the Jxn of gingival & middle ⅓
  • enhances ethetics & retention
  • Thickness of enamel determines amount of adjustment

Question 7

Occlusal Rests:

Answer 7

• Directs forces down the long axis of the abutment tooth
• prepared after guideplanes
• Depth: 1-1.5 mm
• Facial-Lingual Width: ⅓-½
• Spoon shaped floor of prep

Question 8

What should you do if you are prepping an occlusal rest in a filling or crown?

Answer 8

• Tell patient that the filling/crown might break or fracture
  
  • requires replacement

Question 9

Embrasure Rest

Answer 9

• Prepped over interproximal of 2 adjacent teeth
  
  • never break contact
  • keep marginal ridges even
• Depth: 1-1.5 mm
• Width: 1.5-2.0 mm
• Cut Sluiceway at facial & lingual embrassure
  
  • allows room for clasp arms

Question 10

Anterior Rests

Answer 10

• Canine=Top choice
  
  • due to shape and strength
• Cingulum rest:
  
  • canine or lateral incisor
  • favored over incisal rest
  • inverted cone or diamond disc used
    
    • disc: might hit adjacent tooth
    • inverted cone=best
  • Half Moon Shape or upside down V
  • Depth: 1-1.5 mm
  • Rounded edges

Question 11

Minor Connectors