- Anesthetize area.
- Take preliminary impression.
- Remove all defective amalgams and caries.
- Select gingival, body and incisal shades of teeth to be restored
(NOTE: Best accomplished after old dark alloy is gone).
- Prepare teeth as follows:
- reduce facial, lingual and proximal surfaces a minimum of
1.2 mm (1.5 mm is the minimum necessary for esthetic areas,
i.e., the buccal aspect of the preparation).
- allow for no more than 2.5 mm of occlusal reduction.
- all line angles should be smooth and rounded.
- sharp transitions, inner angles, undercuts or feather edges
should be avoided.
- insure there is an adequate path of insertion.
- all gingival margins should be butt shoulder with rounded
axio-cervical line angle. A chamfer preparation is possible
as long as a mechanical support is guaranteed, particularly
when used with reduced tooth structure (e.g., after repeated
crowning).
- flat chamfers, shoulder preparations with angles greater
than 100º, tangential preparations and bevels of the preparation
limit are contraindicated.
- It is necessary to place a proximal box in the preparations
adjacent to the edentulous space, to allow bulking of the framework
at the axio/occlusal line angle.
- Use the preliminary impression to fabricate a well-fitting custom
temporary restoration.
- Take final impression with Panasil vinyl polysiloxane or similar
impression material.
- Secure an adequate interocclusal record.
- Cement temporary restoration.
- Prepare detailed lab prescription with details of nature of
opposing teeth, age of patient, surface occlusal stain required,
etc.
|
 |
Ideal
3-Unit Bridge Preparation |
 |
Ideal
Posterior Preparation (Full Circumferential
Shoulder 90° - 120°) |
|
RECOMMENDED
PREPARATION LIMITS:
 |
 |
Chamfer
preparation (with reduced mechanical
support of the crown). Particularly used with
reduced substance (e.g. after repeated crowning) |
Contraindicated:
flat chamfers, shoulder preparations with angles >100°, tangential
preparations and bevels of the preparation limit
Common Preparation
Errors:
1. Insufficiently
defined and finished preparation margins.
- uneven preparation
limit (so-called gutter preparation, vertical unevenness)
- irregular marginal
reduction of layers (horizontal unevenness)
- wrong shape of
preparation limit
- unnecessarily deep
subgingival preparation
- preparation in
the root dentin
2. Poorly controlled
tooth reduction
- not following proper
reduction guidelines, therefore not allowing sufficient porcelain for
ceramic vitality.
- insufficient reduction
at the palatal side of the upper anterior teeth (malfunctional occlusion)
- excessive taper
Reprinted with
permission of Vident. In-Ceram is a registered trademark of Vita Zahnfabrik.
Return
to In-Ceram® Zirconia product page
|