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Rests Rest Seats - PowerPoint PPT Presentation


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Rests & Rest Seats. Rest. A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface Provides vertical support. Rest Seat. Portion of a tooth prepared to receive a rest. Functions. Direct forces along long axis of abutment. Slides down incline.

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Presentation Transcript
slide2
Rest
  • A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface
  • Provides vertical support
rest seat
Rest Seat
  • Portion of a tooth prepared to receive a rest
functions
Functions
  • Direct forces along long axis of abutment
functions5

Slides down incline

Functions
  • SUPPORT - prevents denture base from moving cervically & impinging gingiva

Fractured abutment, no rest seat

functions8
Functions
  • Maintain a clasp -tooth relationship
functions9
Functions
  • Prevent extrusion of abutments
  • Provide reference for relines or impressions
functions10
Functions
  • Act as indirect retainer
    • Prevents rotation (Class I or II RPD’s only)
preparation of rest seats
Preparation of Rest Seats
  • Light pressure
  • High-speed handpiece
  • +/- Waterspray
  • Minimal heat is generated
preparation of rest seats12
Preparation of Rest Seats
  • Keep in enamel
  • No anesthesia
preparation of rest seats13
Preparation of Rest Seats
  • Occlusal Rest Seats
    • Diamonds
      • 8801- 014
      • 38006 -135
    • Medium round carbide burs
      • #2, #4

8801- 014

preparation of rest seats14
Preparation of Rest Seats

8837K-014

  • Cingulum Rest Seats & Guiding Planes
    • Long, medium diameter cylindrical bur or diamond (e.g. #57L; 8837K-014)
rest seat form
Rest Seat Form
  • Smooth flowing outline form (i.e. no sharp line angles)
occlusal rest seat form
Occlusal Rest Seat Form
  • Rounded triangular shape
    • Apex near center of tooth
occlusal rest seat form17
Occlusal Rest Seat Form
  • Base of triangle should be one third the bucco-lingual width of the tooth
occlusal rest seat form18
Occlusal Rest Seat Form
  • Marginal ridge must be lowered and rounded 1-1.5mm
    • Bulk of metal to prevent fracture
occlusal rest seat form19
Occlusal Rest Seat Form
  • Floor inclined towards the center
  • Angle formed by rest and minor connector should be less than 900
occlusal rest seat form20
Occlusal Rest Seat Form
  • Deepest portion is central
occlusal rest seat form21
Occlusal Rest Seat Form
  • Floor should be concave or spoon shaped ball-&-socket joint
  • Prevents horizontal stresses & torque
occlusal rest seat form22
Occlusal Rest Seat Form
  • Directs the occlusal forces along the long axis of the tooth
  • Prevent orthodontic movement
positive rest seats
“Positive” Rest Seats
  • An explorer tip will not slide off the rest seat
occlusal rest seat form24
Occlusal Rest Seat Form
  • Conventional Form
occlusal rest seat form25
Occlusal Rest Seat Form
  • Adjacent Tooth
    • Rest not flared to facial line angle
    • Lingual flared more - space for minor connector
double embrasure rest seat form
Double Embrasure Rest Seat Form
  • Adjacent teeth, the form is also modified
  • Flared more dramatically on facial and lingual line angles
double embrasure rest seat form27
Double Embrasure Rest Seat Form
  • Provides space for the retentive & bracing arms
  • Ensure all line angles are smoothed
lingual rest seats
Lingual Rest Seats
  • Usually the canine, due to its well-developed cingulum
  • When canine is not available, an incisor may be used
cingulum rest seat form
Cingulum Rest Seat Form
  • Inverted “V”
  • < 900
cingulum rest seat form30
Cingulum Rest Seat Form
  • Slightly rounded to avoid sharp line angles
  • Test as ‘positive’ with explorer tip
  • 1mm depth
cingulum rest preparation
Cingulum Rest Preparation
  • Do not create an enamel undercut
  • Cylindrical bur along the long axis of the tooth
cingulum rest seat placement
Cingulum Rest Seat Placement
  • Place in sound tooth structure or restorations
  • Not on amalgam restorations
  • If not prominent or large pulp
    • Use different tooth
    • Bonded rest seat
    • Onlay or crown
maxillary cingulum rest seats
Maxillary Cingulum Rest Seats
  • Avoid opposing occlusion
maxillary cingulum rest seats37
Maxillary Cingulum Rest Seats
  • 1.5 - 2.0 mm clearance for metal
  • Check with articulated models
bonded cingulum rests
Bonded Cingulum Rests
  • Flat emergence profile
  • Pumice, rinse, etch, bond using rubber dam
  • Ensure cervical composite well adapted
composite bonded rest seat form
Composite Bonded Rest Seat Form

Correct

Overcontoured

Overcontoured

Open margin

round lingual rest seat form
Round Lingual Rest Seat Form
  • Mesial of the canine teeth when typical cingulum rest contraindicated
    • Large restoration
    • Lack of clearance with the opposing teeth
    • Poor cingulum
round lingual rest seat form41
Round Lingual Rest Seat Form
  • Spoon shaped, similar to occlusal rest seat
  • More difficult due to the incline of the lingual surface
  • Easily incorporated into crowns
incisal rests
Incisal Rests
  • Inferior mechanically & esthetically
  • Lingual rest is nearer to the center of rotation
    • Less torquing potential
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