Operative, 11/15/11

Front 1

What is step one?

Back 1

Make sure bur is aligned with long axis of the tooth in all 3 dimensions.
Best instrument to use is tapered diamond with slightly rounded corners.

If lined up slanted, you'll get an undercut. Buccal and lingual walls have 6 - 10 degrees of divergence (metallic inlays).

Front 2

How deep should your inlay prep be?

Back 2

In the middle portion: min portion for gold is 1.5mm.
Ceramic - 2 mm.
Width and depth dependent on path of insertion, thicknss requirements.

Gold inlay - min thickness is central groove (nonworking = 1 mm) + working 1.5 mm min. Prevents wear through, through most of patient's life.

Front 3

The wall that is slightly divergent is..

Back 3

All except for the axial wall, which will actually converge. You need to remove the ivorine occlusal to all of the excavation so you have a nice path of withdrawal.

Front 4

Is it important to break contact for an inlay?

Back 4

Yes. To make a dye from a model that's pour up from the impression, you must break contact. Dye = single tooth model.

Indirect: contact must be broken for extension for prevention + to make sure lab tech can make a dye.

Extension for prevention - there's a thin gap that is filled with cement. Don't want that area to be bathed in plaque.

Front 5

What's a dovetail?

Back 5

Something thats used on the occlusal surface opposite to the side that you are working on.

Ex. if your working on the D, the dovetail is on the M.
-Slight widening of the prep so that the inlay under a lot of force will not rock on the side you are restoring.

-It may be an important resistance form feature since it resists rocking under occlusal forces. Not retention form!
May be = don't need it on all preps, ex: MOD. Molars - 2ndary groove extensions act as dovetail. 2 sided restorations on premolars almost always need a dovetail.

Front 6

The finsih line (margin)

Back 6

For gold inlays, you need to place a bevel.
1. Protect the tissue. Frequently the papilla is in the way. Shrink it with retraction cord that is treated.
-common reason for not getting good impression is having the retraction cord in the way. Tuck the cord into the sulcus and interproximal papilla will shrink.

Front 7

What is used to place the bevel?

Back 7

Using a flame shaped diamond (red strips) fine.

Front 8

How wide is the gingival bevel?
Does the occlusal portion need to be beveled?

Back 8

0.5 mm wide. 3 planes - small bevel, gingival floor, and axial wall.
The bevel should be extended up into the buccal and lingual = also referred to buccal and lingual flares. 30 and 45 degrees cavo surface angle.

Because of the incline, you already have a beveled margin.

Front 9

For non metal inlays..

Back 9

1. must not be 90 degrees - ceramic doesn't do well with bevels.
2. Will be more open than gold. won't seat as well and sealing wont be as good. A better cement usually compensates for that.
3. 70-80 degrees is ideal.
4. J margin are the worst!

Front 10

Cast gold onlay

Back 10

By def, involves all of hte cusp. Inlay-onlay involves some but not all of the cusps.

-Not a crown, since it doesn't cover entire B and L part of the tooth. Intra coronal - resistance and retention come from sets of diverging walls. This is a protective restoration: one that covers all of the cusps and prevents cuspal flexion under function.

Front 11

Onlay vs. Inlay What's bad about the inlay that is better for the onlay?

Back 11

For gold inlay - wedging affect occurs and excess force is on the stresses. This is concentrated at the pulpal floor, B and gingival walls.

This was studied through photoelastic studies and computer modeling.

Front 12

Onlay vs. crown?

Back 12

Onlay is good unless there is caries on the buccal or lingual.

Front 13

"Classic" cast gold onlay preps

Back 13

Usually done on teeth that have a history.
-Almost never done since good teeth don't need them.

Front 14

Steps for the onlay

Back 14

1. path of insertion + undercuts. Line it up so that bur lies along the path of insertion.
2. Retention for gold VS ceramic - slightly more divergent opposing walls than an inlay.
3. Resistance
4. thickness/space
5. Cavo surface

Front 15

Step 1 for onlay

Back 15

1. MOD inlay. Axial walls are the only ones that converge, B and L walls all diverge.

Front 16

Step 2 for onlay

Back 16

Adequate occlusal reduction - depends on balance of
1. conservation
2. make certain you give lab tech enough space.

Working cusps 1.5 mm
Nonworking 1 plane, 1 mm

Front 17

what happens if you make your walls to short?
What is a working cusp shoulder?

Back 17

Less retention form, you negatively affect it. You need to compensate by a working cusp shoulder.
-Done to add resistance and retention. Take flat ended tapered diamond so you create a step going from M to D on the outer aspect of the working cusp.
-Starts off as 1 mm in vertical and 1 mm in horizontal direction like a stair.
- The addition of the vertical form adds to retention form; the horizontal addition adds to resistance form. The horizontal prevents rocking and adds structural integrity = addition of a reinforcing bar. This helps resist gold flexion under function.