Introduction to Fixed Prosthodontics Forth Year

1. • PARTIAL VENEER CROWNS

2. Definition
“An extracoronal restoration
that restores all but one
coronal surface of a tooth or
dental implant abutment,
usually not covering the
facial surface”
GPT 8thEd,JPD July2005

3. Partial veneer crown
Types :
Post. teeth
3/4th crown
Modified 3/4th
7/8th crown
Reverse 3/4th
Proximal ½ crown
Ant.teeth
3/4th crown
Pin-ledges
Porcelain
Laminates

4. Indications
• Posterior Teeth that have lost moderate amount of
tooth structure, provided buccal wall is intact
• Commonly used as retainers for FPD’s
• Where restoration or alteration of the occlusal surface
is needed
• Anterior partial veneer crowns can be used as
retainers, to re-establish anterior guidance & to splint
teeth.

5. Indications continued
• Teeth with crown length that is average or that
exceeds average
• Teeth with normal anatomic crown form
• Anterior teeth with adequate labio-lingual thickness

6. Contraindications
• Short clinical crown
• Retainers for long-span FPD’s
• Rarely suitable for RC-treated teeth especially anteriors
• Posterior-.RC-treated teeth where cusps are weakened
• Active caries & periodontal diseases.

7. Contraindications continued
• Deep cervical abrasion
• Teeth with extensive core restoration
• Bell shaped teeth
• Thin teeth
• Poorly aligned abutment

8. Advantages
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Conservation of tooth structure
Reduced pulpal & periodontal insult
Access to supra-gingival margin is easy
Better seating of the restoration
Cement removal is simple
Permits electric vital testing
Good esthetic

9. Disadvantages
• Less retention & resistance
• Skillful preparation is critical to avoid metal display
• Limited to fairly intact teeth

10. Principles Of Tooth Preparation
1.Preservation of tooth structure
2.Retention & resistance form
3.Structural durability of the restoration
4.Marginal integrity
5.Preservation of the restoration

11. Maxillary Premolar
3/4th Crown
Occlusal Reduction
 Mark the proposed location of
the margin of the completed
preparation
 Depth grooves are made with a
tapered carbide or narrow
diamond.
 Initial depth holes are placed in
the mesial and distal fossae
approximately 0.8 mm deep &
centric cusp: 1.3mm.

12. b.Initial depth holes are
connected by a guiding groove
that extends through the central
groove. Additional guiding
grooves are placed on the lingual
cusp similar to those for a
complete cast crown .
The depth cut placed on the
triangular ridge of the buccal
cusp becomes shallower as it
approaches the cusp tip
lingual

13. Recommended minimum clearance for
reduction of a partial veneer crown
preparation.
c.Half the occlusal reduction
is completed.
Note the centric cusp bevel.

14. d. Occlusal reduction completed

15. E, After guiding grooves are placed in the
lingual surface of the tooth parallel to the
proposed path of withdrawal, the proximoaxial
and linguoaxial reductions are initiated.
Simultaneously a smooth and even-width
cervical chamfer is created.,
Proximal and lingual axial reduction is
performed with a round-tipped
diamond. The proximal reduction is
stopped short of the proposed
location of the buccal
margin.

16. F, When the axial
reduction of the first
half is considered
acceptable, the other
half can begin.

17. G, Proximal grooves are placed
perpendicular to the prepared
surface, and the buccal wall of
each groove is flared to leave no
unsupported enamel.
The proximal flares are
connected with a narrow
contrabevel. After rounding of
the line angles, the preparation is
complete.

18. H, The interproximal clearance relative to adjacent
teeth extends cervically as well as near the occlusal
aspect of the buccal flares of the proximal grooves.

19. Groove placement
• Done with tapered
carbide bur
• By 3 stages:
1.shallow occlusal
template
2.extension to half
length
3.Completion to
full length

20. • Grooves should be placed as far facially as possible
• Grooves are done first on the more inaccessible
proximal surface
• Length of the groove should be at least 4mm
• Groove need not be deeper than 1mm at it’s cervical
end
• Groove should resist lingual displacement

21. Contd.
•
Walls of the grooves should not be
undercut relative to the selective
path of withdrawal
•
Walls should be flared towards
intact buccal surface
•
900 angle between lingual walls of
proximal groove will resist lingual
displacement
•
Buccal wall of each groove is flared
to leave no unsupported enamel
•
Proximal flares are connected with
a narrow contra bevel
•
0.6mm clearance with adjacent
teeth

22. Bucco-occlusal contra-bevel
• Formed by connecting
mesial & distal flares
• It’s primary purpose to
remove any unsupported
enamel
• If group function is planned,
a heavier bevel will be
needed
• The bevel should remain
within the curvature of cusp
tip
OCCLUSAL OFFSET
When additional bulk is
needed to ensure rigidity

24. Mandibular Premolar Modified
3/4th crown
• Additional retention is required
• Functional cusp bevels are placed on
buccal cusp
STEPS
 0.8 mm depth holes
 Depth holes connected by guiding groove

25. 1/2 the occlusal reduction completed
Occlusal reduction & mesial
1/2 of axial surface
completed

26. Axial reduction completed &
proximal grooves prepared
 Mesial groove has been flared &
centric cusp chamfer placed

27. Facial view of complete prepn

28. 3/4th Prepn on a Mandibular Molar/PM
• Location of occlusal finish
line
• No need for an offset on
the lingual inclines of the
buccal cusp

29. Reverse 3/4th Crown
• Mandibular molar with
intact lingual surface ,with
severe lingual inclination
• Occlusal offset on the
buccal slopes of lingual
slopes

30. THANK YOU