Inlays/Onlays Flashcards
(33 cards)
What is the defintion of an inlay?
Is an indirect intracoronal restoration, places in a prepared cavity space
Name the 3 principles of inlays?
Wedge retention
Stress proportionak to cusp height and width of isthmus
No reinforcement of remaining tooth structure
- marginal leakage
- cusp fracture
- loss of restoration
Name the indications of inlays?
Same as for direct restorations
Name the 3 contraindications of inlays?
Caries; MOD on premolars and wide isthmus MOD on molars
Root filled teeth
What is the defintion of wedge retention?
The stress should be transmitted to tooth tissue
Effective height of the lingual cusp
- possible fracture of vulnerable cusp
What is the definition of an onlay?
Is an indirect extracoronal restoration, usuallynplaced after tooth surface reduction
Name the indications of onlays?
Cuspal coverage
Restoration of Functional cusp
Restoration of lost tooth tissue
What isnthe difference between a direct and indirect restorations?
Direct:
- places by operator chair side - plastic material
- no conventional or digital impression needed
Indirect:
- fabricated outside the mouth in a lab and cemented as a rigid unit
- impression required
Name the 3 types of materials for inlays and onlays?
Metal
Composite
Porcelain
What are the advantages and disadvantages of using precious metal for an inlay or onlay?
Low corrosion
Low wear to opposing teeth
Relatively easy to cast and adjust
Can be considered aesthetic
Expensive
Difficult to bond directly to surface (surface treatment required)
What are the advantages and disadvantages of non-precious metal?
Very hard metal and so difficult to adjust
Greater wear to opposing teeth
Some alloys have low corrosion resistance
Not much cheaper than precious
Silver in colour
Bond well to composite
What are the advantages of indirect composite?
Good aesthetics
Less expensive
Easier to repair
Poor wear resistance
Name the 4 ways in which a inlay/onlay is retained in a cavity?
Luting cements
Mechanical retention
Binding
Micro-mechanical retention
What is the defintion of a luting cement?
Fills hap between restoration and cavity
What is the defintion of mechanical retention?
Parallex axial walls and resistance form
What is the defintion of bonding?
Chemical adhesion between restoration and cavity
What is the defintion of micromechanical retention?
Retention due to adhesive nagerial locking into surface irregularities
Mechanical retention and resistance?
Load applied to lingual cusps, lead to the buccal cusps to lift off, and creater a point of rotation at the base of the lingual wall
How to bond tooth tissue to the restoration?
Most need resin based cements
Base metal - MDP or 4 META
Ceramic - silane coupler
Noble metal - high Cu, Sn plating with MDP
Augmented by surface treatments
- sandblasting
- HF to etch ceramic
Name 2 types of surface treatments?
Sandblasting metal
HF to etch ceramic
Explain enamel bonding?
Etching of enamel surface
Micromechanical retention
However sensitive to contamination
Explain dentine bonding?
Conditioning of dentine
Adhesion to the hybrid layer
However sensitive to contamination
Requires hydrated dentine
How important is surface roughness?
Is important when trying to create micromechanical retention
- which is why surfaces are treated to increase the roughness
What are the principles of ceramic onlays?
Compared with metal restorations, ceramic or composite indirect restorations:
- requires bulk for strength
- greater extension on proximal (finishing)
- rounded internal angles (reduces stress concentration)
- greater taper of walls (less retention required because bonded; manufacturing technique)
- are bonded to tooth tissue
