PREPARATION GUIDE
Shade Selection
Recommended Shade Guides: Ivoclar Chromascop®.
General Considerations
Ensure even reduction of the anatomic form.
Avoid sharp internal edges, angles and undercuts. Create rounded internal
line and point angles, particularly at the linguoincisal line angle.
Create a shoulder preparation of 1.2 mm at a 90-110º angle. Maintain
shoulder preparation with butt joint margins. Avoid tapered margins, feathered
edges and bevelled margins.
Incorporate taper of 8 to 10 degrees (never more than 12º)
Tooth preparation length should reflect a 1.5 to 2.0 mm occlusal (incisal) reduction.
Uniform Facial Preparation
A medium grit, round-ended, diamond bur is used to remove a uniform thickness
of facial enamel by joining the depth-cut grooves.
Join the depth grooves in three places by angling the diamond bur to the corresponding gingival, middle or incisal plane of the tooth.
Chamfer Margins
Correct preparation of the chamfer margins interproximally
allows appropriate bulk of porcelain.
Using the same round-ended diamond bur, the interproximal
preparation is extended from the gingival chamfer margin into the proximal
space. NOTE: Eliminate all discolored enamel in the interproximal.
The diamond bur is angled to eliminate undercuts and establish a deep chamfer on the lingual aspect of the preparation to ensure a passive fit. The incisal edge should be rounded. Avoid all sharp angles.
Inlay Preparation
Smooth prep walls and trim excess lining material with finishing diamond or bur
Do not include undercuts
Create a 5º to 15º divergence in the proximal walls from the floor to the occlusal margin of the preparation.
Ensure all walls end in a butt margin.
With onlays, cuspal reduction of a minimum of 1.5 mm is required.
Smooth prep walls and trim excess lining material with finishing diamond or bur.
Do not include undercuts.
Create a 5º to 15º divergence in the proximal walls from the floor to the occlusal margin of the preparation.
Ensure all walls end in a butt margin.