Inlays/Onlays

Question 1

What is the defintion of an inlay?

Answer 1

Is an indirect intracoronal restoration, places in a prepared cavity space

Question 2

Name the 3 principles of inlays?

Answer 2

Wedge retention
Stress proportionak to cusp height and width of isthmus
No reinforcement of remaining tooth structure
- marginal leakage
- cusp fracture
- loss of restoration

Question 3

Name the indications of inlays?

Answer 3

Same as for direct restorations

Question 4

Name the 3 contraindications of inlays?

Answer 4

Caries; MOD on premolars and wide isthmus MOD on molars
Root filled teeth

Question 5

What is the defintion of wedge retention?

Answer 5

The stress should be transmitted to tooth tissue
Effective height of the lingual cusp
- possible fracture of vulnerable cusp

Question 6

What is the definition of an onlay?

Answer 6

Is an indirect extracoronal restoration, usuallynplaced after tooth surface reduction

Question 7

Name the indications of onlays?

Answer 7

Cuspal coverage
Restoration of Functional cusp
Restoration of lost tooth tissue

Question 8

What isnthe difference between a direct and indirect restorations?

Answer 8

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

Question 9

Name the 3 types of materials for inlays and onlays?

Answer 9

Metal
Composite
Porcelain

Question 10

What are the advantages and disadvantages of using precious metal for an inlay or onlay?

Answer 10

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)

Question 11

What are the advantages and disadvantages of non-precious metal?

Answer 11

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

Question 12

What are the advantages of indirect composite?

Answer 12

Good aesthetics
Less expensive
Easier to repair
Poor wear resistance

Question 13

Name the 4 ways in which a inlay/onlay is retained in a cavity?

Answer 13

Luting cements
Mechanical retention
Binding
Micro-mechanical retention

Question 14

What is the defintion of a luting cement?

Answer 14

Fills hap between restoration and cavity

Question 15

What is the defintion of mechanical retention?

Answer 15

Parallex axial walls and resistance form

Question 16

What is the defintion of bonding?

Answer 16

Chemical adhesion between restoration and cavity

Question 17

What is the defintion of micromechanical retention?

Answer 17

Retention due to adhesive nagerial locking into surface irregularities

Question 18

Mechanical retention and resistance?

Answer 18

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

Question 19

How to bond tooth tissue to the restoration?

Answer 19

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

Question 20

Name 2 types of surface treatments?

Answer 20

Sandblasting metal
HF to etch ceramic

Question 21

Explain enamel bonding?

Answer 21

Etching of enamel surface
Micromechanical retention
However sensitive to contamination

Question 22

Explain dentine bonding?

Answer 22

Conditioning of dentine
Adhesion to the hybrid layer
However sensitive to contamination
Requires hydrated dentine

Question 23

How important is surface roughness?

Answer 23

Is important when trying to create micromechanical retention
- which is why surfaces are treated to increase the roughness

Question 24

What are the principles of ceramic onlays?

Answer 24

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

Question 25

Describe the requirements of gold inlays/onlays (cavity prep)

Answer 25

1-1.5mm occlusal clearance
Sharp internal angles
Bevelled shoulders in box and on functional cusps (onlay)
Proximal flare
6-10 degrees occlusal divergence in isthmus and boxes
Isthmus bevel (inlay)
Minimal proximal extension
Luted to tooth

Question 26

Describe the requirements of ceramic inlays/onlays (cavity prep)

Answer 26

1.5-2mm occlusal clearance
Rounded internal angles
90 degree finish lines in box and on all cusps
No bevels
1mm shoulder
12-15 degree occlusal divergence in isthmus and boxes
Greater proximal extension
Bonded to tooth

Question 27

Explain the step by step guide to create a cavity for an inlay indirect restorations?

Answer 27

Matrix for temp/guide reduction
Place dam
Remove old reato
Evaluate tooth for appropriate restoration - block out minor undercuts in GIC
Prepare occlusal portion
Prepare proximal boxes
Pcclusal clearance
Finish margins
Temporaries
Impressions

Question 28

Describe the requirements of a metal MOD onlay cavity?

Answer 28

Proximal box
Proximal flare
Isthmus
Buccal bevel
Occlusal reduction
Functional cusp bevel
Occlusal bevel
Lingual bevel
Ginguval bevel

Question 29

Describe the cavity requirements for a metal onlay?

Answer 29

1mm planar occlusal reduction
1.5 mm for functional cusp
Buccal cusp needs a bevel
Functional cusp line = shoulder or heavy chamfer
Sharp internal angles
Proximal bevel and flare

Question 30

Describe the cavity preparation for a cermaic/composite onlay?

Answer 30

1.5 mm planar occlusal reduction
2 mm for functional cusp
Buccal cusp needs a butt finish
Functional cusp finish needs a shoulder
Rounded internal angle
No proximal bevel or flare

Question 31

Explain how to create a temporary restoration?

Answer 31

Apply vaselune to plastic teeth
Mix composite - ProTemp/integrity
Place composite in matrix
Seat over prep
Follow manufactures instructions
Add flowable composite to fill any voids
Trim excess with soft flex discs

Question 32

Manufacturers instructions for ProTemp?

Answer 32

49 second working time
1:40 m for setting in mouth
2:50 m for matrix removed
5:00 m removal from matrix and finishing

Question 33

Notes for clinic?

Answer 33

Full arch impression required
- light and medium bodied silicone
- opposing arch in alginate
Biscuit try in (ceramic)
Return to lab for glazing
Try in
Cement