Principles of tooth preparation /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Fixed Partial
Dentures


CLASSIFICATION OF
CROWNS
1.according to materials

 Complete cast crown (full metal)
 Metal ceramic crown
 all ceramic crown (metal free ceramic)

2.according to surfaces covered
 Full veneer crown
 Partial veneer crown


Inlay
Crown

vs


• An inlay

depends on
internal
retention to
hold it within
the
preparation


• A crown depends

•

on external
retention to
resist removal
External
retention is
provided by
approximation of
the restoration to
the opposing
external axial
walls of the
preparation


Biomechanical principles
of Tooth preparation

1. Preservation of tooth structure
2. Retention and resistance form
3. Structural durability of the

restoration
4. Marginal integrity
5. Preservation of the periodontium

Preservation of tooth structure
 Do not remove excess of tooth

structure , do not over taper
 Tooth becomes weak
 Pulp health gets jeopardised
 Reduction must be adequate , less
reduction will lead to overcontoured
restoration

Two plane reduction for
central incisors


Two plane
reduction
on buccal
aspect of
mandibula
r molar


•


• Retention is

enhanced by
restricting the paths
of insertion
• A—multiple paths of
insertion and
removal , decreased
retention
• B---additon of parallel
sided grooves limits
path of insertion to
one direction ,
increases retention

• To produce an

optimal 6 degree
taper, each opposing
axial wall should have
an inclination of 3
degrees to the path
of insertion


a functional cusp
bevel , in a
plane parallel to
the opposing
cusp , gives
adequate bulk
to the crown
without
sacrificing the
tooth structure

if functional cusp
bevel is omitted ,
crown will be
too thin in this
stress bearing
area


 if crown thickness
is achieved by
overtapering the
axial wall ,
retention is
compromised .

• also health of the
pulp may be
jeopardised

in absence of

functional cusp
bevel , the lab
(technician)
may overbulk
the crown .

this may lead
to


occlusal

A. ---- adequate axial reduction
B. ---- inadequate axial reduction results in
crown with thin , weak walls
C. ---- bulky crown results in promoting plaque
accumulation , jeopardising the health of
periodontium

( niether flat nor fat )

Thank you
For more details please visit


Principles of tooth preparation /certified fixed orthodontic courses by Indian dental academy

Recommended

Recommended

More Related Content

Viewers also liked

Viewers also liked (9)

More from Indian dental academy

More from Indian dental academy (20)

Principles of tooth preparation /certified fixed orthodontic courses by Indian dental academy