Inlay/Onlay Preparation Flashcards
What is the difference between an inlay and an onlay?
Inlay = no cusp missing Onlay = covers cusp
What are the two types of inlays/onlays?
- metal
2. esthetic (composite or ceramic)
What are the indications for METAL inlay/onlays? (6)
- Large restorations
- endodontically treated teeth (posterior in particular)
- Teeth at risk for fracture (craze lines)
- Dental Rehabilitation (rebuilding entire occlusion)
- Diastema Closure/Occlusal Plane Correction
- Removable Prosthodontic Abutment (rest seat stability)
What are the contraindications for METAL inlay/onlays? (4)
- High Caries Rate (get them under control first)
- Young Patients (large pulp, still growing)
- Esthetics
- Small Restoration (conservative approach)
The advantages of METAL inlay/onlays include: strength, Low wear, _______, and control of ______.
biocompatibility
control contours/contacts (easier)
Why is “chair time/number of appointments” a disadvantage to using METAL inlays/onlays?
can’t make gold chairside…need for a temporary restoration
Why is “cost” an issue with METAL inlay/onlays?
lab bills
True or False: METAL inlay/onlays are very technique sensitive because you must bevel all the way around the preparation margins.
True
Why are “splitting forces” an important consideration with METAL INLAYS?
The path of insertion is slightly divergent…could act as a wedge and break off the cusp
What is the conventional degree of divergence for a METAL inlay preparation?
4 degrees
6 to 8 would be fine, just make SURE it is NOT converging
What is the preparation depth and width for a METAL inlay?
- 5 - 2.0 mm wide
- 5 mm deep
*do NOT weaken the marginal ridge
What is the purpose of a 40-45 degree Sweep Bevel?
reduce microgap leakage
What is the occlusal reduction for a METAL ONLAY preparation?
Functional Cusp: 1.2 - 1.5 mm
NonFunctional: 1.0 mm
True or False: Axial wall defects are acceptable for inlay/onlay preparations because they will be filled with cement.
FALSE, the creation of an undercut to fill the void would cause the restoration not to seat
What does it mean to “hood” a cusp?
to extend the onlay up the ridge to the tip of a cusp without fully encompassing the entire cusp = hold the onlay/tooth together
What are the indications for indirect TOOTH-COLORED inlay/onlays? (3)
- Esthetics
- Large Defects (less shrinkage than direct filling)
- Large Previous Restorations
What are the contraindications for indirect TOOTH-COLORED inlay/onlays? (3)
- Heavy Occlusal Forces (bruxism/clenching)
- Inability to maintain a dry field (needed for bonding)
- Deep subgingival preparations
What are the advantages of indirect TOOTH COLORED inlay/onlays?
- improved physical properties
- variety of materials/techniques available
- wear resistance
- reduced polymerization shrinkage (cement still shrinks)
- support of remaining tooth structure
- more precise control of contours/contacts
- biocompatibility and good tissue response
- increased auxillary support (EFDA can design it)
What are the disadvantages to indirect TOOTH-COLORED inlay/onlays?
- increased cost and time
- technique sensitivity
- difficult try-in and delivery
- brittleness of ceramics
- wear of opposing dentition and restorations
- short clinical track record
- low potential for repair (you would have to etch with acid…in their mouth)
What are five types of tooth-colored inlay/onlays?
- Feldspathic porcelain
- Pressed Glass-ceramics
- Lithium Disillicate
- CAD/CAM Leucite Reinforced Glass
- Composite Restorations
How does a ceramic inlay preparation differ from metal preparation?
deeper (2 mm functional, 2 mm central, 1.5 mm nonfxnl)
more rounded
no bevels
True or False: Ceramic Inlay/Onlay preparations should exit at a 45 degree angle.
False, 90 degrees for strength
Why are all internal and external line angles rounded for Ceramic Inlays?
- prevent stress points
- ease of placement/fit
What type of rotary instrument is typically used for ceramic inlay or onlay tooth preparations?
diamond
(for example: there is a diamond bur that measures 1.5mm wide and 2.0mm tall which gives perfect dimensions when used in the central groove)
True or False: Ceramic Inlays & Onlays are more conservative than metal.
False, need a bulk of ceramic material for strength!
Why must exit angles for Ceramic inlays/onlays be close to 90 degrees?
ensures bulk of ceramic at the margins
True or False: A ferrule margin must be placed for adequate retention of Ceramic onlays.
False, avoid ferrule margins
What is the ideal wall taper for ceramic inlays/onlays?
6-8 degrees
metal inlays ~4
Why must you avoid over-tapering the occlusal walls?
leads to thinner occlusal margins and increased margin stress as the margin approaches the cusp
True or False: Ceramic inlays & onlays should have bevels at the margin.
False, should have “rollercoaster margins” that smoothly transitions
The occlusal preparation for ceramic inlays & onlays should be smooth with broad rounded corners that are ______ in diameter.
1 mm
The box should be a minimum reduction of ______ axially and _______ facial lingually.
1.5 mm
2 mm
True or False: Always onlay cusps that are at risk for fracture.
True
What is the desired ceramic thickness?
2 mm
After excavating the caries, how is it determined whether or not a cusp is preserved?
- thickness of axial wall
- internal stress cracks(?)
- location of crack
- color
- holding cusp (?)
- Excursive interferences (?)
True or False: If a functional cusp is undermined, it must be onlayed.
True
True or False: If a nonfunctional cusp is undermined, it must be onlayed.
False, could place GI
