Partial Coverage crowns Flashcards
What are inlay?
Intracoronal restorations that fit within the anatomic contour of the clinical crown.
Relies on the strength of the remaining tooth structure for support and retention.
What is an onlay?
Indirect intracoronal restoration with an occlusal veneer (cuspal coverage of at least one cusp) Usually indicated for damaged cusps
How many sessions do onlays typically take?
One for the preparation and second for cementation and adaptation and then one for review.
What materials are typically used for inlays/onlays in clniic?
Ceramic (most common in clinic)
Metal (gold)
Indirect composite resin
Which material has the best survival rate?
All are similar but deterioration rate = Gold < Ceramic < Composite
What are the indications for inlays/onlays?
Class II
Reestablish an adequate contact point
Severely worn tooth but minimal damage
Replacement of a MOD amalgam with aesthetic indirect restoration
Where one or more cusps have been lost or require overlays to protect weakened tooth structure.
What are the contraindications for inlays/onlays?
Severely damaged tooth (less than 2mm of buccal or lingual) If very weak go for full crown (if severely undermined unrestorable)
Insufficient bulk to provide resistance and retention form
MOD inlays
Retainers of FPD
What are the advantages to inlays/onlays?
More durable than direct restorations
Easier to reestablish contact points
More conservative than complete crowns
Onlay - cusp protection
What are the disadvantages of using inlays/onlays?
Less conservative that direct restorations
Risk of cusp fracture especially with inlay
Higher cost and chair time than direct restoration
How to judge between inlay/onlay?
To judge whether onlay or inlay this depends on:
Extension of restoration (when width of an intracoronal catiy exeeds 1/2 the distance of the cusp tips an onlay or crown is probably more suitable. Cuspal coverage is needed)
Onlay if tooth structure less than 2mm or low quality enamel covering the cusp.
Inlay occlusal contacts on the margin (restoration should never finish at the contact point because it is easy to fracture at that point)
What are the features of the inlay/onlay prep?
No sharp internal line angles or points, only curved transitions
The prep extensions depends on the extension the previous restoration or the caries lesion
The cavosurface angle needs to be clear and sharp and should be almost 90 degrees.
No beveling of outer margin
All the axial walls need to be divergent towards the occlusal (opposite of MOD amalgams)
Minimal distance buccolingual should be 2mm (less than this would create a fragile inlay/onlay)
Avoid complex internal geometry to the preparation
Transition of material thickness should be gradual not abrupt
No acute angles within prep
No additional retention features
No tooth structure without support
No aspect of the margin should be locted in an undercut.
Deep chamfer or modified shoulder supra or equigingivally. No feather edge or gutter margin
Ensure all surfaces are smooth
What are the steps for doing inlays/onlay or any idirect restoration in clinic?
1) Get tutor to sign approval (form 26 should be signed before hand)
more in clinic
How is a temporary crown made?
Using The same method as normal crowns
What are the most common types of partial crowns are used?
Most common type of partial coverage is 3/4 crowns or 7/8 crowns
What are the indications of partial coverage restorations?
Restore posterior teeth that lost moderate tooth structure with intact buccal wall
Reestablish the occlusal surface contour with metal allow without compromising aesthetic
Teeth with sufficient bulk to accomdate the necessary retentive features
Retainer of resin bonded bridges (can be used for metal or ceramic)
