Docs, use the standard criteria to control your preps( they can be slight different but if you stick to them you ll be all right). practice. for more info about preps use Shillinburg Fundamentals of tooth preparation.
Criteria for Amalgam Preparation:
1. The preparation should be approximately 1.5-2.0 mm deep at the pulpal floor.
2. The preparation should be approximately 1.5 mm deep at the proximal axial wall.
3. The buccal, lingual, and gingival extensions of the mesial box must be free of contact with the adjacent tooth.
4. The cavosurface margins should be near 90 °, with no unsupported enamel.
5. The walls in the occlusal portion of the class II should be near parallel. The walls of the box portion should be slightly undercut in order to provide mechanical retention for the alloy.
6. Retention grooves may be optionally laced in the buccal and lingual walls at the bucco-axial and linguo-axial line angles.
7. Extensions fo the occlusal outline are as described in the clinical conditions.
8. A bevel at the axial/pulpal line angle is optional. If placed, it should not be greater then 0.5 mm wide.
Criteria for the Full Cast Crown Preparation (typically full gold)
1. The occlusal reduction should ideally provide for 1.5 mm of clearance from the opposing occlusal surface.
2. The occlusal reduction should generally presere the occlusal anatomy of the tooth, providing for uniform reduction.
3. The axial walls should be free from undercuts and tapered approximately 8-10 degrees from the long axis of the tooth.
4. The finish line should be a champfer profile, equal in diameter to ½ the diameter of the largest champfer diamond that you are provided.
5. The finish line should be between 0.5 and 1.0 coronal to the free gingival margin and follow the contour of the free gingival margin. It should smooth, continuous, even, and well-defined.
6. Extension of the proximal should allow for visual clearance between the margin and the adjacent tooth.
Criteria for Porcelain Fused to Metal Crown Preparation:
1. The cervical margin should be smooth, continuous, and well defined. The cervical bevel, when used, is 0.5-10 mm in width and is well defined.
2. The appropriate path of insertion varies less than 10° parallel to the long axis of the tooth on all axial surfaces and a line of draw is established.
3. Axial tissue removal is optimally 1.5 mm to be sufficient for convenience, retention and resistance form.
4. There is full visual taper 6° - 16°
5. The facial shoulder is optimally 1.2 mm wide. A shoulder finish line shall be placed on the buccal from the mesial buccal line angle to the distal buccal line angle.
6. Occlusal reduction is optimally 2 mm and the general occlusal anatomy is maintained.
7. The margins should be 0.5 mm occlusal to the CEJ or simulated free gingival margin, whichever is most coronal.
watch how to do a temporary crown
http://www.youtube.com/watch?v=wSu_Opy6TRw
remember you will have a shell and you will need to adjust it( I used scissors), fill with acrylic and remove some access.
