Prostho 10-19 Flashcards
- Chemical protection of the prepared tooth
Process used for decreasing the dentinal sensitivity of an abutment prepared for crown or for laminate veneer,
by sealing the opened dentin tubules.
Usually coating solutions are used for this purpose.
- Prosthetic protection of the prepared tooth
Process used for decreasing the harmful consequences of abutment preparation for crowns or for laminate veneers,
like dentinal sensitivity, tooth migration, aesthetic, phonetic disadvantages, and changes in occlusal relations.
Usually temporary crowns or bridges are produced for this purpose.
- Scutan method
A method used for creating immediate crowns or bridges.
In essence an elastic impression is taken prior to tooth preparation
and the original shape of the teeth are recorded by this impression.
- Tangential preparation + indications
if a tangent, straight line is fit to the axial walls of the prepared tooth surface, this line has contact with the whole axial surface.
Knife edge praparation is a tapered preparation that has
maximum tooth reduction at occlusal / incisal surfaces and
tapers to zero cutting at the gingival termination.
Indications:
cast metal crown,
metal ceramic crown – with metal collar
13.1 Tangential preparation advantages
Advantages:
- simple, easy to make,
- conservation of tooth structure, the chance for pulp damage is small,
- excess cement can flow out from the crown at insertion
13.2 Tangential preparation disadvantages
Disadvantages:
- it can be difficult to recognize the end of prepared surface on the die (consequence: crown may be to long, too wide – the marginal fit is not precise),
- subgingival preparation line has to be done, consequence: difficult impression taking.
- It doesn’t provide sufficient bulk for the cast crown.
- Shoulder finish line
a finish line design for tooth preparation in which the
gingival floor meets the external axial surfaces at a right or obtuse angle,
this angle can be rounded or cornered.
- 90° shoulder finish line + indications
a finish line design for tooth preparation in which the gingival floor meets the external axial surfaces at approximately a right angle.
Indications:
full ceramic crown (rounded inner angle),
facial margin of metal ceramic crown
15.1 90° shoulder finish line advantages
- distinct margin,
- easy to make relating to chamfer,
- provides optimal aesthetic, - and enough bulk for the restorative material
15.2 90° shoulder finish line disadvantages
- great amount of tooth structure is removed,
- chance for pulp damage is great,
- cannot be carried out on all the teeth
- Chamfer finish line + indications
a finish line design for tooth preparation in which the gingival aspect meets the external axial surface at a rounded obtuse angle.
Indications: first choice in many cases,
cast metal crown,
metal-ceramic crown
16.1 Chamfer finish line advantages
- distinct margin,
- easy to recognize on the die,
- excess cement can flow out from the crown at insertion,
- adequate bulk if the chamfer is deep enough
16.2 Chamfer finish line disadvantages
- care needed to avoid unsupported lip of enamel,
- more difficult preparation,
- if not enough deep, there is not enough place for metal ceramic crown,
- more tooth tissue has to be removed
- Retention form
the feature of a tooth preparation that resists dislodgment of a crown in a
vertical direction or along the path of placement.
Forces are bigger in case of an abutment tooth,
e.g. clasp holding crown, precision attachment.
- Resistance form
the features of a tooth preparation that
enhance the stability of a restoration and
resist dislodgment along an axis other than the path of placement (not vertical forces).
