INLAYS AND ONLAYS

Question 1

inlay

Answer 1

intracoronal restoration made indirectly to strengthen and repair decayed or damaged posterior teeth

Question 2

onlay

Answer 2

similar but extends over weakened cusps to provide extra protection

Question 3

crown

Answer 3

provides full coverage over tooth

onlay only provides cuspal protection

Question 4

indications for inlays and onlays

Answer 4

1) As an alternative to amalgam
- concerns for amalgam toxicity
- lichen planus (can be due to the amalgam)
2) When composite isn’t indicated
- eg size of cavity
- previous failed composite restorations
- aesthetics considerations
3) when a long lasting aesthetic result is aimed
4) a conservative type of indirect restoration

Question 5

indications for onlays

Answer 5

teeth with larger restorations but sound buccal and lingual walls
endo treated teeth
wider MODs
MODs in premolars

Question 6

indications for inlays

Answer 6

small MO or DO in molars/pre

conservative MOD molar

Question 7

contraindicaitons of inlays/onlya

Answer 7

patients with poor OH

not sutible for pts with excessive occlusal loading

Question 8

materials

Answer 8

gold
ceramic
resin composite

Question 9

gold ad and dis

Answer 9

ad
- conservative
marginal integrity 
good wear characteristics
corrosion resistance
relative ease of handling
excellent phyical and mechanical characteristics

dis
- cost
technique sensitive
poor aesthetics
wedge effect of inlay

Question 10

ceramic ad and dis

Answer 10

ad

• aesthetic
• stronger and more stable material ( no wear; discoluratiom)
• resin composite luting agent
• marginal leakage due to polymerisation shrinkage is minimal
• conservative ceramic restoration

dis

• sensitive technique (intraoral adjustment is contra indicated until the restoration is bonded, after bonding adjustments can compromise aesthetics)
• wear of the luting agents can lead to marginal gaps and secondary caries
• longer treatment: indirect restorations – 2 visits are required unless chairside CAD/CAM used
• cost

Question 11

common ceramics used

Answer 11

feldspathic glass ceramic
leuctie reinforced glass ceramic
lithium disilicate glass ceramic

Question 12

fabrication technique for each material for inlay/onlay

Answer 12

1) gold
- lab made , lost wax or casting
2) composite
- CAD/CAM chairside
- labmade
3) ceramic
- conventional – pressable, refractory, casting
- CAD/CAM – chairside or lab

Question 13

gold inlay measurements

Answer 13

1.5mm occlusal reduction
proximal box 1mm width
isthmus 1/3 intercuspal width

Question 14

gold onlay

Answer 14

intracoronal prep as inlay
1.5-2mm cuspal reduction
1mm occlusal shoulder

Question 15

onlays and occlusal force

Answer 15

biting forces pushed through long axis of tooth

cusps are protected

Question 16

stress distribution for inlays

Answer 16

occlusal forces are placed which spread occlusally and laterally
overtime can break the buccal cusp

Question 17

prep for ceramic inlay

Answer 17

similar to gold inlay but no bevels (bevels would thin the enamel and be liable to fracture)
- box shaped cavity
- parallel and slightly divergent walls
- rounded interal line angles (to prevent stress concentrations)
- 90 degree cavosurface angle (to prevent any unsupported enamel or thins of ceramic)
- 2mm deep occlusally
no grooves or slots

Question 18

prep for ceramic onlay

Answer 18

• Same as inlay
• addition of one or more cusps also prepared
• Provide 1.5mm occlusal reduction
• Cusp reduction 2mm

Question 19

direct temporarys for inlays

Answer 19

• composite based temporary material
• mainly for inlays
• shape with flat plastic instruments within the cavity
• no impression required
• no temp cement needed
• check occlusion and adjust as necessary

Question 20

indirect temporary

Answer 20

• pre operative impression required
  or lab made vacuform shell
• composite based material
• temp bond NE to cement, no eugenol based material

Question 21

what cements are preferred

Answer 21

resin luting agents over traiditonal (GIC) as they provide adhesive bond to tooth structure

Question 22

how to cement glass ceramic

Answer 22

fitting surface treated with HF acid
coat fitting surface with sialine coupling agent
resin cement for cementation

Question 23

failure or the inlay or onlay

Answer 23

bulk fracture
- often in areas of cuspal coverage esp if ceramic material less than 2mm thick
marginal breakdown
- resin cement not heavily filled
wear more quiclly