inlays and onlays Flashcards
What is an inlay?
Restorations made indirectly to strengthen and repair decayed or damaged posterior teeth
What is an onlay?
Similar to inlay but extends over weakened cusps to provide extra protection
Larger and protects the cusps
What was the problem with early ceramic inlays?
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
Why would you use an inlay/onlay as an alternative to amalgam?
Concerns for amalgam toxicity Lichen planus when composite isn't indicated Size of cavity Previously failed composite restorations Aesthetic considerations
Why else would Inlay and onlay be a good choice?
When a long-lasting aesthetic result is aimed
A conservative type of indirect restoration
What are the indicatinos for an inlay?
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)
what are the indications for an onlay?
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
What are contraindications for inlays/onlays?
Patients with poor OH
Not suitable for patient with excessive occlusal loading
What are the different materials inlay/onlays can be made from?
Gold
Ceramic
Resin composites
What are the advantages of gold inlay?
Conservative Marginal integrity Good wear characteristics Corrosion resistance Relative ease of handling Excellent physical and mechanical characteristics Excellent survival rates (25-40 years)
What are the considerations with gold inlays
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
When was the introduction of the acid etch technique?
Buonocore 1955
What is the advantage of adhesive technologies?
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
What are considerations with adhesive technologies
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
What are the different ceramics?
Feldspathic glass ceramic
Leucite reinforces ceramic
Lithium disilicate ceramic
What are the different indirect resin composites?
Hybrid composite
Ceromers
Ceramic optimised resins (have higher strength)`
What are the 2 ways gold inlays/onlays can be made in the lab?
Lost wax
Casting
What are the different ways a resin composite indirect inlay/onlay is made?
Chair side technique: CAD/CAM or impression technique which can be direct or indirect
How are ceramic inlays/onlays made?
Conventional techniques: pressable, refractory investment techniques, cast ceramic
or CAD/CAM: lab made or chairside
What are the general preparation guidelines for inlays/onlays?
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
What’s the preparation for gold inlay?
1.5mm occlusal reduction
Proximal box 1mm width
isthmus 1/3 of intercuspal width
Block out undercuts with restorative material
What’s the preparation for Gold onlay?
Intracoronal the same an inlay
1.5-2mm cuspal reduction
1mm occlusal shoulder
When may you need to include cusps and make an onlay?
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
What is the preparation for ceramic inlay?
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
What is the preparation for ceramic onlay?
Same as inlay
One or more cusps also prepared
provide 1.5mm occlusal reduction
Need 2mm thickness at the cusp
Why should the cavity avoid occlusal contacts?
to aoid unnecessary load at margins that could lead to deterioration of cement and marginal openings
What is the basic set up for restorative procedures?
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
What are the direct methods of temporisation?
Composite based temporary material e.g. systemp
Shape with flat plastic
No impression required
No temp cement
What are the indirect methods of temporisation
Preoperative impression or lab made vacuform shell
Self-curing acrylic material
Composite based acrylis material e.g. protemp
TempBond NE to cement (no eugenol)
Why does the TempBond have to be NE?
Eugenol interferes with setting of composite
Why should cementation be done under RD?
if adhesive cement is used, very sensitive to moisture
What cement do we tend to use more now?
Resin cements - still have mechanical retention but not adhesive
What are the options for cementation of gold restoration?
Traditional: GIC or zinc phosphate
Resin cements: Panavia or Rely X
What is the choice of cementation for aesthetic inlays/onlays?
Resin luting agents preferred over traditional cements
Compomers are contraindicated due to expansion - fracture of ceramic
How is glass ceranic cemented/fitted on to the tooth?
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
How is the cementation for composite different?
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
How can high viscosity resin composite be used for cementation?
The thickness of cermaic cant be more than 2mm to ensure curing of the material
Colour of inlay can also affect the setting
What are the 2 ways the inlay/onlay can fail?
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
What needs to be checked for inlays/onlays
Good cementation technique
Preparation guidelines
Thickness of ceramic
Bonding to tooth structure
