Finishing the casting Flashcards
can you make a margin disappear in a finshed casting
no you cant
Eval the gold cast
in good light
look first for nodules or other irregularirites that might be an impediment to full seating
magnification
Six zones foor casting eval
- Itaglio surface- most critical because if it doesnt work or fit then the margin which is the most important will be off.
- Sprue area : cut it off slightly larger, leave a little more gold where the wax up was..then with stones or disk
- Proximal contacts : where solid model comes in. Becareufl on solid model that you cleaned the model up to the margins. You will feel it go smoothly margin to margin if no issues.
- Occlusal surface
- axial walls
- external margin. (dont go past margin and dont abrade it since so thin (dont over finish it!!) gotta cover prepped tooth structure
Intaglio surface
zone 1
Begin with the internal margin
Most critical area of the entire casting
Were you careful during waxing and investing?
Evaluate this area first, because a defect here might mean…
You guessed it!
Start over
Examine for nodules, especially small ones
DO NOT try on die until entire area is free of irregularities
only place casting should come in contact with tooth or solid model is
AROUND THE MARGINS
OBJECTIVES
There should be no interferences to complete seating of the casting on the die.
If the casting were to be placed, either on a die model without die spacer or the tooth, no contact should exist between the die and the internal surface of the casting, except at the margins.
There should be a uniform space of 25 to 35 µm.
The marginal area only ( ~ 1-2 mm) of the casting should create a tight seal at the die margin (10 µm or less gap)
How to remove intaglio surface
- Use small carbide burr
- Remove slightly more than the defect itself
- Micro-etch entire intaglio surface
- Exercising extreme care at the Margins
internal marking agents
- Liqua-Mark (water-soluble die)
- AccuFilm IV (solvent-based die)
- Occlude (powdered spray)
- Rouge in Turpentine
- Fit Checker (elastomeric detection paste)
Sprue area
2
- Section sprue circumferentially with carborundum disc.
- Bend and twist remaining attachment until sprue and button can be removed.
- Adjust casting with stones and sandpaper discs to re-establish proper coronal contours.
proximal contacts
#3 area where proximal surface if not shaved on die model to give extra space, when you polish and get to interprox surface dont spend time there or you loose contact.
Exercise caution not to remove proximal contacts by polishing them away.
Better left heavy than light
It is always easier to remove excess material chairside than to add material in the lab.
A solid model can be helpful.
Shaving proximal contacts prior to the wax-up can also be helpful.
Proximal contacts should be broad in all directions.
Occlusal surface
4
Before adjusting, check thickness of casting in multiple areas with Iwanson thickness gauge.
Care during the waxing phase should translate into minimal occlusal adjustments in the casting.
A smooth and polished wax-up pays dividends at this stage.
Occlusally, A Satin finish is acceptable and easier to read and adjust intraorally.
Centrum type contacts.
No contacts on inclines, either in MI or excursions.
if you error then
error on being taken off more than not
Occlusal surface is ok to have a satin finish?
yes but jjust the occlusal..its easier tor ead.
axial walls
5
Axial walls are now smoothly contoured and highly polished.
A series of progressively finer grades of abrasives are utilized, each removing the scratches made by the previous grade.
Time is wasted if the progression to a finer grade abrasive is too rapid.
The resulting highly polished surface enables the patient to carry out optimum plaque control.
(polsih in sequence!!)
External margin
#6 dont over finish!
Special attention must be paid to finishing and polishing the marginal areas of the casting.
Under-finishing/polishing results in rough surfaces that harbor plaque.
Over-finishing/polishing results in margins that do not cover all of the prepared tooth surfaces.
This can result in unnecessary post-operative sensitivity and an irregular surface that is more inclined to trap plaque.
The best marginal adaptation can occur when gold alloy margins are finished directly on the tooth, an advantage of partial coverage inlays, onlays, 3/4 and 7/8 crowns.
7/8 crown
done on max molars. sneaks on top of cusp, seen as gold.
everything buccal surface of one cusp
