Onlays Flashcards
1
Q
What principles govern gold inlay preps?
A
- Tapered intracoronal walls about 6 degrees
- No undercuts or undercuts blocked out
- Flat floors with rounded internal line angles
- Bevel: gingival, proximal, occlusal
2
Q
What are some contraindications of inlays/onlays? What are some of their disadvantages?
A
Contraindications
- Lack of surface area to bond to or resistance/retention form
- Lack of dimensions
- Tooth periodontally unsound
Disadvantages:
- Unaesthetic (gold)
- Unconservative vs direct
3
Q
What are some methods of placing pins?
A
Vertical channel:
- Cut with 700 tapered fissure bur
- Take impression with rubber base material
Cast pin system
- Pin channel cut with special drills
- Use plastic impression pins
4
Q
How is an MOD ceramic onlay prepared? (sim clinic)
A
MOD cavity with 856
- Depth 2.5mm; width 2.0mm
- Taper occlusal and proximal walls 6-10 degrees
- Locate proximal gingival floor in enamel, 1mm above CEJ
- Flare proximal box walls mesio-distally (i.e. so that walls splay outwards in a mesio-distal direction)–>avoids sharp line angles in ceramic as if crack at stress area this tends to propogate)
- Clear contact (by extending 0.25mm into B/L embrasures)
Reduce Cusps (856)
- 2mm functional cusp + functional cusp bevel 1.0mm wide
- 1.5mm non-functional cusp
Final finishing and smoothing (8877 and L10)
- Smooth margins
- Round internal line angles (this is more so important in ceramic than gold, again due to crack propogation)
- No undercuts
Basically in clinic:
- Remove caries, assess adequate occlusal depth (2mm, isthmus width 1.5mm)
- Taper walls
- Flare proximal box mesio-distally
- Reduce cusps (Functional 2mm + 1mm bevel, non functional 1.5mm)
- Finish and smooth + round angles, ensure no opposing tooth contact with margins and no unsupported enamel
- NO BEVELS, 90 degree butt joint required at cavosurface margins as:
(1) thin sections of ceramic are difficult to fabricate and can crack easily
(2) Margins can not be burnished into place to fix defects
5
Q
How is an MOD gold onlay prepared? (sim clinic)
A
Occlusal using 856
- Depth 2.5mm; width 2.0mm
- Taper occlusal and proximal walls 6-10 degrees
- Locate proximal gingival floor in enamel, 1mm above CEJ
- Clear contact (by extending 0.5mm into B/L embrasures)
- DO NOT FLARE PROXIMAL like in ceramic (i.e. don’t make the walls splay outward in mesio-distal direction, as you need it more square to create mechanical retention since gold can not bond to tooth structure via the cement)
Reduce cusps (856)
- 1.5mm functional cusp + functional cusp bevel (1.0mm)
- 1.0mm non functional cusp (in buccal cusp of upper premolar can reduce by 0.5mm to avoid excessive gold showing in aesthetic zone)
Finalise proximal boxes
- Place proximal box flares using L10 in path of draw (in this case refers to taper outwards towards occlusal to avoid undercuts)
- Place 0.25mm bevel at gingival margin (removes unsupported enamel and protects tip of non-functional cusp–>can place in gold as margins can be burnished and gold can survive in thin sections)
- ‘square up’ internal proximal box using Fiz10 and use 169L to place grooves in line angles (axio-buccal and axio lingual)–>creates more mechanical retention to avoid total dependance on resin cement
Place contra-bevel in non-functional cusp using 8877 to ensure the margin flows along all surfaces of tooth
Final finish
-check all margins are smooth
Basically in clinic:
- Remove caries, assess adequate occlusal depth (2mm, isthmus width 1.5mm)
- Taper walls, do not flare proximal walls mesio-distally (as need more retention with gold due to no bonding)
- Reduce cusps (Functional 1.5mm + 1mm bevel, non-functional 1mm but 0.5mm in upper premolars for aesthetics)
- Bevel all along the margins
- Finishing and smoothing, ensure no opposing tooth contact with margins and no unsupported enamel
6
Q
What are the indications (uses) of inlays and onlays? What are the prerequisites to doing an inlay/onlay?
A
Indications:
- Aesthetic alternative to alloy based restorations
- Access for direct restoratives a problem
- Protection of teeth with cusps at risk of fracture or heavily worn teeth
- Conservative modification of tooth shape (occlusal reconstruction)
- Retainers for some types of bridges
Prerequisite:
- Large cavity: sufficient dimensions for thickness of material
- Sufficient area for bonding
- Periodontally sound
7
Q
What are some advantages of inlays/onlays?
A
- Aesthetics (ceramic)
- Better contact and higher strength vs direct fillings
- If all ceramic: good tolerance by gingiva, higher durability than resin, good clinical record
- More conservative than a crown
- Longevity
- Low creep and corrosion
- Not lead to tooth discoloration
Onlay only:
-Support cusps, reduce risk of tooth fracture
8
Q
What are the principles for a prep design for inlays/onlay?
List the steps you would take to create ceramic onlay prep and a gold onlay prep.
A
- Adequate occlusal depth (at least 2mm)
- Adequate isthmus width (1.5-2mm)
- Divergent walls
- Rounded line angles
- Shoulder finish on gingival margins
- Remove unsupported enamel
- Block out undercuts with GIC
- No bevels at margins (ceramic onlays, gold and ceramic inlays)
- No opposing cusp contact with margins
- Similar principles for onlays
Ceramic:
- Remove all the caries
- Assess for adequate occlusal depth and isthmus thickness, adjust if necessary
- Create 6-10 degree divergence in the walls to avoid undercuts. Ensure there is no opposing cusp contact with the margins
- If proximal box involved, flare proximal box walls mesio-distally (i.e. so that walls splay outwards in a mesio-distal direction)–>avoids sharp line angles in ceramic as if crack at stress area this tends to propogate)
- Reduce Cusps with 856 bur:
- 2mm functional cusp + functional cusp bevel 1.0mm wide
- 1.5mm non-functional cusp - Final finishing and smoothing: smooth margins, round internal line angles (very important in ceramic due to crack propagation), no undercuts, no u/s enamel
Gold:
- Remove all the caries
- Assess for adequate occlusal depth and isthmus thickness, adjust if necessary
- Create 6-10 degree divergence in the walls to avoid undercuts. Ensure there is no opposing cusp contact with the margins
- Reduce cusps (856)
- 1.5mm functional cusp + functional cusp bevel (1.0mm)
- 1.0mm non functional cusp (in buccal cusp of upper premolar can reduce by 0.5mm to avoid excessive gold showing in aesthetic zone) - Square up’ internal proximal box using Fiz10 and use 169L to place grooves in line angles (axio-buccal and axio lingual)–>creates more mechanical retention to avoid total dependance on resin cement
- Place 0.25mm bevel at gingival margin and continue all the way along the entire margin (removes unsupported enamel and protects tip of non-functional cusp–>can place in gold as margins can be burnished and gold can survive in thin sections)
- Final finishing and smoothing: smooth margins, round internal line angles (less critical for gold than ceramic but nonetheless important), no undercuts, no u/s enamel
*Differences in steps highlighted in google docs
9
Q
What should be checked at the insertion appointment?
A
- Passive fit
- Good proximal contact
- Good margins
- Good aesthetics
10
Q
What cement is generally suggested with gold inlays/onlays?
A
-Rely X Unicem
11
Q
What is the procedure to cement CEREC?
A
- Same steps as porcelain
- Note that HF etch is done in laboratory, unnecessary to do in clinic.
- Clinic steps are:
- Apply silane to inside of CEREC
- Etch/wash/dry tooth
- Apply Optibond to tooth for 15 seconds, air dry for 3 seconds + light cure for 20 seconds
- Apply cement to CEREC, seat, light cure
- Finish and check occlusion
