Flares in dental crown preparation /certified fixed orthodontic courses by Indian dental academy

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


Flares
• A flame diamond
and carbide bur is
used to make the
mesial and facial
flares which are
narrow at the
gingival end and
wider occlusally.

Occlusal
• No: 171 bur is used Offset
to produce a 1.0 mm
wide ledge on the
lingual incline of the
facial cusp
connecting the
grooves, assuming
the shape of an
inverted V. Its floor
is perpendicular to
the path of insertion

Occlusal Finishing Bevel
• A flame diamond or
no: 170 bur is used
for creating an
occluso facial
finishing bevel. The
bevel is rounded up
to the proximal
occlusal line angle
to blend with the
proximal flares.

Completed seven eigth crown preparation


Features of the Seven-Eighth
Crown Preparation


Proximal Half Crowns


• Round end tapered
Occlusal Reduction
diamond and no: 171
bur.
• Depth orientation
grooves on the distal
aspect of the occlusal
surface 1.5mm deep.
Since the mesial
segment of the tooth is
dropped below the
occlusal plane the
grooves may not be as
deep.
• The tooth structures
between the orientation
grooves are removed

Functional
• Is done using roundCusp Bevel
end tapered diamond
and no: 171 bur.
Depth orientation
grooves are placed
across the facial
occlusal line angle of
the mandibular
molar. The bevel will
be shorter and
shallower on the
mesial cusp than on
the distal.

• Torpedo diamondAxial Reduction
Mesial is
used for the axial
reduction by making the
path of insertion of
mesial surface parallel
with the long axis of the
premolar abutment.
• The end of the diamond
will eventually make
contact with the tooth in
the gingival area of the
mesial surface and
produce a chamfer finish
line.

Facial and Lingual Axial
Reduction
• Is done with a
tropedo diamond
producing a definite
chamfer finish line
at the same time.
End the extension
1.0 mm or more
mesial to the distofacial embrasure.

Axial Finishing
• Torpedo bur is used
to produce a distinct
finish line and
round of the angles
of the preparation.


Occlusal Isthmus and
Countersink
• No: 171 bur is used
to make an occlusal
isthmus and a
countersink in the
distal fossa to
supplement
retention, resistance
and structural
durability.

Facial and Lingual
• No: 171 bur is used to
make parallel grooves on
the facial and lingual
surfaces with in 1.0 mm
of the vertical distal
extension of preparation.
• The grooves should be
parallel to the mesial
surface of the tooth and
the long axis of the other
abutment.

Grooves

Distal Occlusal Offset
• A V-shape offset
0.5 to 1.0 mm from
the distal occlusal
finish line
connecting the
lingual groove to
the countersink to
the facial groove is
made using no: 171
bur.

Flares and
• A flame diamond is Occlusal
used to place flares
distal to the facial
and lingual grooves.
• A bevel is cut along
the distal marginal
ridge with the flame
diamond taking care
not to extend into the
distal occlusal
embrasure.

Bevel

Completed proximal half crown preparation


Features of the Proximal Half
Crown Preparation


Five-Eighths Crown

 The five-eighths veneer crown
restoration is less frequently used
than those preparations previously
described.

FINISH BEVEL

COUNTER
SINK

 It is indicated where a single
proximal
surface of a maxillary molar tooth is
involved and occlusal and lingual
coverage is indicated due to
involvement of these areas.
 It provides a more conservative
design for single tooth restorations
and abutment preparations for short

FLARE LINGUALGROOVE

MAXILLARY MOLAR

REVIEW OF LITERATURE
• Anthony H.L Tjan et al (1979) have discussed
the functions of grooves and offset of a three
quarter crown and the types of groove flare
design possible. They have established a practical
guide to planing the grooves on a three quarter
crown which fulfills biologic, mechanical &
structural requirements.

• Mitsuo Kishimoto et al (1983) studied the
retention and resistance of four variations of
three quarter crown variations. Preparation
with boxes or four grooves were found to
be the most retentive of three quarter
crowns used in the study. Lingual
placement of proximal groove enhanced
retention. Three quarter crowns with V
shaped groovewww.indiandentalacademy.com
had least resistance.

• Shillingburg HT Jr.(1976). Partial veneer
crowns still play a role in modern restorative
dentistry.
• They must be used in the right situation with
thoughtful treatment planning, and they must
be done well in accordance with certain
principles.
• Three-quarter crowns are less retentive than
full crowns, but they can be used successfully
as single unit restorations and retainers for
short span bridges. Retention can be enhanced
by the use of proximal boxes.

• Potts RG, Shillingburg HT Jr, Duncanson
MG Jr. (1980). Five preparation designs were
tested for retention and resistance.
• Retention values for all partial veneer crowns
were significantly lower than those for the
complete veneer crown.
• Resistance values increased significantly with
the addition of grooves and/or extension of
axial surface coverage.
• Addition of grooves and/or extension of axial
surface coverage produced small increases in
retention values but marked increases in
resistance values

Conclusion
Tooth preparation for the various types of
partial veneer crowns was described.
•
Although retention and resistance of partial
veneer crowns is less but the conservative design
makes them a restoration of choice wherever
possible. Addition of retentive grooves and other
features increases the retention and resistance;
still it remains less than the complete coverage
crown.
•
A thorough clinical and radiographic diagnosis
and treatment planning is an utmost need for long
term success of the restoration.
•

REFERENCES
•
•
•
•

Fundamentals of fixed prosthodonticsH.T.Shillingberg
Contemparary fixed prosthodonticsS.F.Roseintiel.
Tylman’s theory of practice of fixed
prosthodontics.
Fundamentals of tooth preparations
-H.T.Shillingberg, Jacobi, Brackett



Tjan AHL and Miller GD. Biometric guide to groove
placement on three quarter crown preparations. J Prosthet
Dent. 1979; 42: 405-410.



Kishimoto M, Shillingburg T, and Duncanson MG.
Influence of preparation features on retention and
resistance. Part II: Three quarter crown. J Prosthet Dent.
1983; 49: 188-192.



Shillingburg HT Jr. Conservative preparations for cast
restorations. Dent Clin North Am. 1976 Apr; 20(2):25971.



Potts RG, Shillingburg HT Jr, Duncanson MG Jr
Retention and resistance of preparations for cast
restorations.J Prosthet Dent. 1980 Mar; 43(3):303-8.

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Flares in dental crown preparation /certified fixed orthodontic courses by Indian dental academy

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