Fixed Prosthodontics Lecture 21

Front 1

What are onlays?

Back 1

-Intracoronal cast metal restorations that only cover the clinical crownthat requires at least one or more cusps are invovled in preparation

Front 2

Onlays are recommended for FPD retainers due to their increase in retention (T/F)

Back 2

False: Onlays are not recommended for FPD retainers due to their reduced retention

Front 3

What is the benefits of only vs. crown?

Back 3

-More conservative
-Can cap all cusps for posterior teeth
-Provides less gingival irritation
-Successful in eliminating future tooth fracture

Front 4

What are the indication of onlays?

Back 4

-Large, failing amalgam or composite that extends 2/3 the distance from central groove to facial and lingual cusps tips
-Grossly worn dentition
-Existing amalgams with one or more fractured cusps

Front 5

What are the contraindications for onlays?

Back 5

-Insufficient tooth structure to provide proper retention and resistance form

Front 6

What is the advantage of onlay?

Back 6

-Low creep translates into no edge deterioration
-No corrosion means no discoloration, as opposed to amalgam
-Excellent mechanical properties provide for long life of the restoration
-Support cusps which leads to reduced risk of tooth fracture

Front 7

What is the disadvantages of onlay?

Back 7

-Not a conservative restoration but still more convservative than a full gold crown
-Must get rid of undercuts
-Need extension for impression materials, wax pattern and gold

Front 8

Describe the step in MOD gold onlay?

Back 8

-Occlusion reduction 2mm (2/3 the height of 271 bur)
-Cusp reduction: use side of 271 to reduce cusps 1.5 mm
-Outline: extend to central groove F/L and all faulty grooves.
-Cutting proximal boxes: extend into proximal boxes w/o removing marginal ridges

Front 9

What is the purpose of gingival beveling?

Back 9

-Removes weak enamel
-Creates 'lap sliding fit'
-Create 30 degree bevel at gingival margin, which is burnishable
-0.5-1.0mm wide

Front 10

Purpose of collars?

Back 10

-Enhance R&R form on overly weakened cusps, especially centric holding cusps
-All cusps can be collared, if needed (Exception: facial cusps of maxillary teeth)
-2-3 mm high occluso/gingivally and 0.8 mm in axial depth
-Blend with proximal box
-Facial bevel and blend with gingival bevel

Front 11

What type of material is used to make onlay?

Back 11

-Type II or Type III gold
-Silver, copper, platinum, palladium, sometimes zinc

Front 12

Bevel on facial and lingual enamel margins. If you don't have canine guidance, make sure bevel ends past excursive contacts (T/F)

Back 12

True

Front 13

What are some advantages and disadvantages of gold onlays vs amalgams?

Back 13

-Advantages: There will be no edge deterioration or corrosion as seen w/ amalgam
-Disadvantages: Not as conservative as amalgams b/c we must get rid of undercuts. We also have to extend the prep for impression material, wax pattern, and gold.

Front 14

What are two clinical indications for a gold onlay?

Back 14

-Restoration of severely worn dentition w/ preserved buccal and lingual cusps
-Replacement of an MOD restoration w/ sufficient tooth structure for proper R7R form

Front 15

Advantages of cast onlays?

Back 15

-Supports cusps and thus reduces risk of tooth fracture
-Longevity
-High strength

Front 16

What are the main criteria for the design of the onlay?

Back 16

-Include central, buccal, and lingual grooves
-Be 1.8 mm deep
-Follow curvature and anatomic contours of the original tooth
-Provide adequate dentin for resistance and retention

Front 17

All weakened cusps can be collared to enhance R7R form (T/F)

Back 17

False: Except is facial cusps of maxillary teeth

Front 18

How should the retention grooves in proximal boxes be placed?

Back 18

-0.3 mm into dentin w/ 169L
-Along the long axis of the tooth.