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17 Cards in this Set
- Front
- Back
What is step one?
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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). |
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How deep should your inlay prep be?
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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. |
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The wall that is slightly divergent is..
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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.
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Is it important to break contact for an inlay?
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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. |
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What's a dovetail?
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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. |
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The finsih line (margin)
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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. |
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What is used to place the bevel?
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Using a flame shaped diamond (red strips) fine.
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How wide is the gingival bevel?
Does the occlusal portion need to be beveled? |
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. |
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For non metal inlays..
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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! |
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Cast gold onlay
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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. |
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Onlay vs. Inlay What's bad about the inlay that is better for the onlay?
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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. |
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Onlay vs. crown?
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Onlay is good unless there is caries on the buccal or lingual.
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"Classic" cast gold onlay preps
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Usually done on teeth that have a history.
-Almost never done since good teeth don't need them. |
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Steps for the onlay
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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 |
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Step 1 for onlay
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1. MOD inlay. Axial walls are the only ones that converge, B and L walls all diverge.
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Step 2 for onlay
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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 |
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what happens if you make your walls to short?
What is a working cusp shoulder? |
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. |