2. A - Cast Gold Onlays Flashcards
What is the definition of a metal onlay?
- Overlays one or more of the cusps of a tooth and is designed to strengthen a tooth that has been weakened by caries or previous fillings
What parts of the tooth does an onlay cover?
- All portions of the tooth involved in occlusal function
- Caries, fracture, and defects
- Adequate retention and resistance form
- Covers all cusps
- Keep margins supragingival
What teeth do you not want to do onlays on?
Mandibular 2nd molars - hard to get good retention
What are some indications for gold onlays?
- Incomplete tooth fracture
- Deep and wide MOD amalgams
If inadequate tooth structure remains for sufficient retention and resistance form, what do you do?
Change the treatment plant to a FVC
What are some important characteristics of inlays?
- Divergent walls toward the occlusal
- They don’t protect or reinforce the cusps from fracturing
For a maxillary bicuspid onlay prep, what is the pulpal depth and the isthmus width?
- 2.0 mm pulpal depth
- 2.0 mm isthmus width
What are the occlusal reduction depths for an onlay?
- At least 1.5mm for centric-bearing cusps (lingual - max, facial - mand)
- At least 1.0 mm for working cusps (facial - max, lingual - mand)
How wide should the bevels be for the functional and non-functional cusps?
- Functional - 1.0-1.5 mm wide
- Non-functional - 0.75 - 1.0 mm wide
What is needed on the prep when the functional cusp is weak or the centric contact compromises the bevel placement?
A shoulder (hood) will be required to provide adequate reduction and strength for the structural cusp
Where should the shoulder be located?
Gingival to the pulpal floor, but occlusally to the gingival floor
Which 2 walls on an inlay/onlay prep are not divergent, but convergent?
The mesial and distal axial walls
Do you blend the bevels, why or why not?
Yes - so there’s no sharp corners, less chance for undercuts, easier to wax and less chance of an open margin
Why reduce the occlusal before finishing the inlay divergence?
- Shorter walls
- Easier access
- Assess retention/resistance form needed
What is the hood placed on the functional cusps?
- Stamp cusp reinforcement
- Increases occlusal clearance on stamp cusp for centric and working contacts of opposing tooth
- Increases retention
What is skirting and what does it do?
- An extension onto the facial or lingual surface just past the proximal line angle of the tooth
- It braces the tooth against forces that might split it and adds retention and resistance
- Usually placed just mesial to the distal facial line angle
Why are triple trays called triple trays?
It provides:
- Impression of the prep
- Opposing tooth
- The registration
What are the practical advantages of the double bite impression?
- Minimizes errors in occlusion
- Time efficient
- Cost efficient
What are the appropriate uses of the double bite impression technique?
- Patient exhibits a type I restorative case
- Stable, positive, and reproducible centric occlusion/MIP
- Sufficient number of positive natural tooth stops in quad
- Adequate space to place the tray without impinging on the teeth or soft tissues
When do you not want to use a double bite impression technique?
- Type II or type III restorative case
- Occlusion in unstable
- Inadequate number of mesial and distal unprepared teeth
- Casting will be used as a component of a removable partial denture
- A lack of centric stops in the quad
- Impingement on the tray preventing centric closure
What are the requirements for provisionals?
- Wont irritate the tooth
- Protects tooth from injury/microleakage
- Maintains perio health and contacts
- Provides esthetic and chewing function
- Strength and retention as needed
