inlays and onlays Flashcards
What is the difference between inlay and onlay?
INLAY- Intracoronal restoration made indirectly to strengthen and repair decayed or damaged posterior teeth
ONLAY- Similar but extends over weakened cusps for extra protection
What are the indications?
Alternative to amalgam (concerns due to toxicity and lichen planus)
When resin composite not indicated (cavity size, aesthetics etc)
Longlasting, aesthetic and conservative
Inlays- small MO or DO cavities, conservative MOD in molars
Onlays- larger restorations but sound buccal and lingual walls, endo treated, wider MODs
What are contraindications?
Patients w poor oral hygiene or excessive occlusal loading
What materials are used to construct these?
GOLD
Conservative, marginal integrity, good wear characteristics, corrosion resistance, ease of handling, excellent physical/mechanical props, excellent survival rates (25-40yrs)
Cost, technique sensitive, poor aesthetics, wedge effect of inlay
CERAMIC
Aesthetic, stronger and more stable, resin composite luting agent, marginal leakage due to p. shrinkage is minimal, conservative
Sensitive technique, intra oral adjustment contraindicated, can have marginal gaps due to wear, 2 visits unless CADCAM, cost
Eg. Feldspathic, leucite reinforced, lithium disilicate
RESIN COMPOSITE
Not as popular, no p. shrinkage when fitting
What are the fabrication techniques?
Gold- lab made- lost wax or casting
Ceramic- conventional (pressable, refactory, casting), CADCAM (chairside/lab)
Composite- CADCAM chairside of lab made
What are the general rules of prep?
Box shaped cavities
Divergent walls for path of insertion
No undercuts
Limit path of insertion
Occlusal isthmus should not >1/4 intercuspal width
Resist occlusal forces
What should a gold inlay prep look like?
1.5mm occlusal reduction
Proximal box 1mm width
Proximal flare for marginal integrity
Isthmus 1/4 of intercuspal width
Isthmus and gingival bevel for marginal integrity
Dovetail for retention, resistance and structural durability
What should a gold onlay prep look like?
Same as inlay but
1.5-2mm cusp also reduction
1mm occlusal shoulder for structural integrity
Lingual, buccal and functional cusp bevel
What does the stress distribution look like for a gold inlay?
Wedging stresses produced by photoelastic analysis
Can weaken cusp—> fracture
What does a prep for a ceramic inlay look like?
Similar to gold but no bevels (thin areas of ceramic may fracture)
Box shaped cavity
Parallel and slightly divergent walls
Round internal line angles
90 degree cavosurface angle
2mm deep occlusally
No grooves or slots
Cavity margins should avoid occlusal contacts so no unnecessary loading (deteriorates cement and marginal openings)
What should a ceramic onlay prep look like?
Same as inlay
One or more cusps also prepped
1.5mm occlusal reduction
Cusp reduction 2mm
Check occlusal contacts
Undercuts can be blocked out w GIC/RMGIC/composite
What equipment is needed?
Medium grip tapered and straight diamond burs
Special bur kits can give box shaped cavities
Provisional material eg. pro temp
Retraction cord and packer/gingival retraction paste
What is the direct method of temporisation?
Composite based materials eg. Systemp
Shaped w flat plastic
No impression or temp cement required
What is the indirect method of temporisation?
Preop impression/lab made vacuform shell
Composite based material eg. Protemp
TempBond NE to cement
How are inlays/onlays cemented?
When adhesive cement is used, should use rubber dam
Gold- traditional (GIC), resin (Panavia, Rely X Unicem)
Ceramic- resin luting agents preferred (self/dual cured- Calibra, Nexus, Variolink II)
Fitting surface treated w HF acid/sandblasted then coated w silane coupling agent
