Onlays Flashcards
What is an inlay?
Indirect restoration that lies inside the tooth cusps
Why do you use an onlay?
To provide cuspal coverage to the tooth
When do you use an overlay?
To cover all occlusal surfaces of the tooth
When do we use onlays?
Replace tooth structure loss
Increase vertical height
Correction of contacts
Denture abutments (rests)
Heavy occlusal loads
1/2-2/3rds tooth structure loss (if > 2/3rds loss = crown)
What are the advantages of onlays?
Majority of the restoration is supragingival
Conservative - preserves as much tooth structure as possible
Prevention from fracture
Restoration of contacts
Resistance to occlusal loads
If the tooth is vital - allows for sensibility testing
What are the disadvantages of crowns?
Technique sensitive - moisture control, accurate impression
Multiple visits
Time consuming restoration
Debonding of onlay
How to ensure success of restoration?
Occlusal reduction
Contact clearance
Margin on all sound tooth structure
Resin based restorations as core
Retraction cord, elastomeric impression
How much can MOD teeth weaken abutment teeth?
59%
How do wide preps in molars change the Tsai-wu strength ratio index?
Lowers the inverse
Where do the lowest stresses occur in the onlays?
At the rounded margin
Where do the highest stress levels occur?
In the inlay with bevelled margins
What is used to cement temp onlay and why?
Tempbond
Spot etch
Poly F
Little resistance/retention form
What must be checked before cementing an onlay?
Marginal fit
Contact point
Occlusion
What cement is used for the definitive restoration
Resin based cement
