Principles of tooth preparation/ orthodontic continuing education

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

Fixed PartialFixed Partial
DenturesDentures

CLASSIFICATION OFCLASSIFICATION OF
CROWNSCROWNS
1.1.according to materialsaccording to materials
 Complete cast crown (full metal)Complete cast crown (full metal)
 Metal ceramic crownMetal ceramic crown
 all ceramic crown (metal free ceramic)all ceramic crown (metal free ceramic)
2.according to surfaces covered2.according to surfaces covered
 Full veneer crownFull veneer crown
 Partial veneer crownPartial veneer crown

Inlay vsInlay vs
CrownCrown

•An inlayAn inlay
depends ondepends on
internalinternal
retention toretention to
hold it withinhold it within
thethe
preparationpreparation

• A crown dependsA crown depends
on externalon external
retention toretention to
resist removalresist removal
• ExternalExternal
retention isretention is
provided byprovided by
approximation ofapproximation of
the restoration tothe restoration to
the opposingthe opposing
external axialexternal axial
walls of thewalls of the
preparationpreparation

Biomechanical principlesBiomechanical principles
ofof Tooth preparationTooth preparation
1.1. Preservation of tooth structurePreservation of tooth structure
2.2. Retention and resistance formRetention and resistance form
3.3. Structural durability of theStructural durability of the
restorationrestoration
4.4. Marginal integrityMarginal integrity
5.5. Preservation of the periodontiumPreservation of the periodontiumwww.indiandentalacademy.comwww.indiandentalacademy.com

Preservation of tooth structurePreservation of tooth structure
 Do not remove excess of toothDo not remove excess of tooth
structure ,structure , do not over taperdo not over taper
 Tooth becomes weakTooth becomes weak
 Pulp health gets jeopardisedPulp health gets jeopardised
 Reduction must be adequate , lessReduction must be adequate , less
reduction will lead toreduction will lead to overcontouredovercontoured
restorationrestoration

Two plane reduction forTwo plane reduction for
central incisorscentral incisors

Two planeTwo plane
reductionreduction
on buccalon buccal
aspect ofaspect of
mandibulamandibula
r molarr molarwww.indiandentalacademy.comwww.indiandentalacademy.com

•

• Retention isRetention is
enhanced byenhanced by
restricting the pathsrestricting the paths
of insertionof insertion
• A—multiple paths ofA—multiple paths of
insertion andinsertion and
removal , decreasedremoval , decreased
retentionretention
• B---additon of parallelB---additon of parallel
sided grooves limitssided grooves limits
path of insertion topath of insertion to
one direction ,one direction ,
increases retentionincreases retentionwww.indiandentalacademy.comwww.indiandentalacademy.com

• To produce anTo produce an
optimal 6 degreeoptimal 6 degree
taper, each opposingtaper, each opposing
axial wall should haveaxial wall should have
an inclination of 3an inclination of 3
degrees to the pathdegrees to the path
of insertionof insertion

a functional cuspa functional cusp
bevel , in abevel , in a
plane parallel toplane parallel to
the opposingthe opposing
cusp , givescusp , gives
adequate bulkadequate bulk
to the crownto the crown
withoutwithout
sacrificing thesacrificing the
tooth structuretooth structure

if functional cuspif functional cusp
bevel is omitted ,bevel is omitted ,
crown will becrown will be
too thin in thistoo thin in this
stress bearingstress bearing
areaarea

 if crown thicknessif crown thickness
is achieved byis achieved by
overtapering theovertapering the
axial wall ,axial wall ,
retention isretention is
compromised .compromised .
• also health of thealso health of the
pulp may bepulp may be
jeopardisedjeopardised

in absence ofin absence of
functional cuspfunctional cusp
bevel , the labbevel , the lab
(technician)(technician)
may overbulkmay overbulk
the crown .the crown .
this may leadthis may lead
to occlusalto occlusalwww.indiandentalacademy.comwww.indiandentalacademy.com

A. ---- adequate axial reductionA. ---- adequate axial reduction
B. ---- inadequate axial reduction results inB. ---- inadequate axial reduction results in
crown with thin , weak wallscrown with thin , weak walls
C. ---- bulky crown results in promoting plaqueC. ---- bulky crown results in promoting plaque
accumulation , jeopardising the health ofaccumulation , jeopardising the health of
periodontiumperiodontium
(( nietherniether flatflat nornor fatfat ))

Principles of tooth preparation/ orthodontic continuing education

Recommended

Recommended

More Related Content

More from Indian dental academy

More from Indian dental academy (20)

Recently uploaded

Recently uploaded (20)

Principles of tooth preparation/ orthodontic continuing education