inlays and onlays

Question 1

What is an inlay?

Answer 1

Restorations made indirectly to strengthen and repair decayed or damaged posterior teeth

Question 2

What is an onlay?

Answer 2

Similar to inlay but extends over weakened cusps to provide extra protection
Larger and protects the cusps

Question 3

What was the problem with early ceramic inlays?

Answer 3

Many problems existed regarding marginal integrity - not comparable to gold inlays
Traditional luting cements were used, there was no bond between restorative material and tooth tissue was possible
Luting cement washed out of marginal discrepancies Discolouration, marginal openings and secondary caries
Early ceramic materials were more aggressive to opposing dentition

Question 4

Why would you use an inlay/onlay as an alternative to amalgam?

Answer 4

Concerns for amalgam toxicity
Lichen planus
when composite isn't indicated 
Size of cavity 
Previously failed  composite restorations 
Aesthetic considerations

Question 5

Why else would Inlay and onlay be a good choice?

Answer 5

When a long-lasting aesthetic result is aimed

A conservative type of indirect restoration

Question 6

What are the indicatinos for an inlay?

Answer 6

Low caries rate - all disease must be stabilised in the maintenance phase before going into advanced treatment
Small MO or DO cavities in molars and premolars
Conservative MOD in molars (if really broad will weaken the cusps then will need onlay)

Question 7

what are the indications for an onlay?

Answer 7

Teeth with larger restorations, but sound buccal and lingual walls
Endodontically treated teeth - need cuspal coverage or coronal structure will break away
Wider MOD’s
MOD’s in premolars

Question 8

What are contraindications for inlays/onlays?

Answer 8

Patients with poor OH

Not suitable for patient with excessive occlusal loading

Question 9

What are the different materials inlay/onlays can be made from?

Answer 9

Gold
Ceramic
Resin composites

Question 10

What are the advantages of gold inlay?

Answer 10

Conservative 
Marginal integrity 
Good wear characteristics 
Corrosion resistance 
Relative ease of handling 			Excellent physical and mechanical characteristics 
Excellent survival rates (25-40 years)

Question 11

What are the considerations with gold inlays

Answer 11

Cost
Technique sensitive
Poor aesthetics
Wedge effect of inlay
Other materials were researched as alternatives to gold
Ceramics and resin composites were suggested as alternatives

Question 12

When was the introduction of the acid etch technique?

Answer 12

Buonocore 1955

Question 13

What is the advantage of adhesive technologies?

Answer 13

Aesthetic
Stronger and more stable material - no wear and discolouration
Resin composite used luting is displaced by an inert body
Marginal leakage due to polymerisation shrinkage is minimal
Conservative ceramic

Question 14

What are considerations with adhesive technologies

Answer 14

Ceramic is fragile
Sensitive technique: intraoral adjustment cant be done till bonded, and after bonded adjustments compromise the aesthetics
Bonding indirect composite is an unsolved problem
Wear of luting agent can lead to marginal gaps and secondary caries
Treatment is longer - 2 visits unless using CAD/CAM
Cost

Question 15

What are the different ceramics?

Answer 15

Feldspathic glass ceramic
Leucite reinforces ceramic
Lithium disilicate ceramic

Question 16

What are the different indirect resin composites?

Answer 16

Hybrid composite
Ceromers
Ceramic optimised resins (have higher strength)`

Question 17

What are the 2 ways gold inlays/onlays can be made in the lab?

Answer 17

Lost wax

Casting

Question 18

What are the different ways a resin composite indirect inlay/onlay is made?

Answer 18

Chair side technique: CAD/CAM or impression technique which can be direct or indirect

Question 19

How are ceramic inlays/onlays made?

Answer 19

Conventional techniques: pressable, refractory investment techniques, cast ceramic
or CAD/CAM: lab made or chairside

Question 20

What are the general preparation guidelines for inlays/onlays?

Answer 20

Box shaped cavities
Divergent walls to allow path of insertion
No undercuts
Limit path of insertion
Occlusal isthmus should not exceed 1/4 intercuspal width
Resistance to occlusal forces
Specific guidelines apply for gold or ceramic/composite

Question 21

What’s the preparation for gold inlay?

Answer 21

1.5mm occlusal reduction
Proximal box 1mm width
isthmus 1/3 of intercuspal width
Block out undercuts with restorative material

Question 22

What’s the preparation for Gold onlay?

Answer 22

Intracoronal the same an inlay
1.5-2mm cuspal reduction
1mm occlusal shoulder

Question 23

When may you need to include cusps and make an onlay?

Answer 23

Look at the stress distribution, wedging stresses produced by inlays by photoelastic analysis
With cuspal protection it stops the cusp fracture
With an onlay, the stress concentrations are more evenly distributed - forces are directed through the tooth

Question 24

What is the preparation for ceramic inlay?

Answer 24

similar to old but no bevels - as this can create thin areas of ceramic which may fracture
Box shaped cavity
Parallel and slightly divergent walls
Round internal line angles
90 degrees cavo-surface angle
2mm deep occlusal
No grooves or slots as the restoration will be bonded
Outline of cavity should avoid occlusal contacts to avoid loading at the margins

Question 25

What is the preparation for ceramic onlay?

Answer 25

Same as inlay
One or more cusps also prepared
provide 1.5mm occlusal reduction
Need 2mm thickness at the cusp

Question 26

Why should the cavity avoid occlusal contacts?

Answer 26

to aoid unnecessary load at margins that could lead to deterioration of cement and marginal openings

Question 27

What is the basic set up for restorative procedures?

Answer 27

Burs - medium grit tapered and straight diamond burs
Retraction cord and packer - put it in before take impressions to separate gingiva from the margin of restorations
Provisional material - systemp, protemp

Question 28

What are the direct methods of temporisation?

Answer 28

Composite based temporary material e.g. systemp
Shape with flat plastic
No impression required
No temp cement

Question 29

What are the indirect methods of temporisation

Answer 29

Preoperative impression or lab made vacuform shell
Self-curing acrylic material
Composite based acrylis material e.g. protemp
TempBond NE to cement (no eugenol)

Question 30

Why does the TempBond have to be NE?

Answer 30

Eugenol interferes with setting of composite

Question 31

Why should cementation be done under RD?

Answer 31

if adhesive cement is used, very sensitive to moisture

Question 32

What cement do we tend to use more now?

Answer 32

Resin cements - still have mechanical retention but not adhesive

Question 33

What are the options for cementation of gold restoration?

Answer 33

Traditional: GIC or zinc phosphate

Resin cements: Panavia or Rely X

Question 34

What is the choice of cementation for aesthetic inlays/onlays?

Answer 34

Resin luting agents preferred over traditional cements

Compomers are contraindicated due to expansion - fracture of ceramic

Question 35

How is glass ceranic cemented/fitted on to the tooth?

Answer 35

Fitting surface is treated with HF acid or sandblasting
Coating of fitting surface with silane coupling agent
Resin cement for cementation: Calibra, Rely X unicem, nexus, Variolink II
Effectively the restoration and tooth will act as one piece

Question 36

How is the cementation for composite different?

Answer 36

roughening of the fitting surface isn’t eough
Resin cement for cementation
But the bond of composite to composite inlays is still an unsolved problem

Question 37

How can high viscosity resin composite be used for cementation?

Answer 37

The thickness of cermaic cant be more than 2mm to ensure curing of the material
Colour of inlay can also affect the setting

Question 38

What are the 2 ways the inlay/onlay can fail?

Answer 38

Bulk fracture - in areas of cuspal coverage less than 2mm thick
Marginal breakdown - resin cement not heavily filled, wears more quickly - need to repair margin

Question 39

What needs to be checked for inlays/onlays

Answer 39

Good cementation technique
Preparation guidelines
Thickness of ceramic
Bonding to tooth structure