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Partial VeneerCrowns , Inlays
and Onlays
Dr shabeel pn
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Anterior Partial Veneers
A partial veneer has been described as arestoration covering two or more surfaces of a tooth.
There are three types of partial veneer crowns:
1. Three quarter crown
2. Seven eight crown
3. Mesial half crown
All other forms of partial veneers are
considered variations of the three basic types.
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Indications For Partial Veneers:
1) Intact or minimally restored teeth.
2) Teeth with crown length that is average or exceeds
average.
3) Teeth with normal anatomic crown form, ie,
without cervical constriction.
4) Anterior teeth with adequate labio-lingual
thickness
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Contra-indications:
1. High caries rate2. Short teeth
3. Non vital teeth
4. Deep cervical abrasion
5. Teeth with extensive core restorations
6. Bell shaped teeth (severe cervical constriction)
7. Thin teeth
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Advantages:
Conserves tooth structure
Easy access to margins for finishing (for dentist)
Less gingival involvement than with complete cast
crown
Aesthetics are superior to that of the completecrowns
Electric pulp testing can be done on the intact
surfaceComplete seating of the restoration can be easily
verified.
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Disadvantages:
Retention is less than that of complete veneercrown
Skilful preparation is crucial to avoid metal display
Preparation is limited to teeth with normally
shaped, average length clinical crown.
It is not indicated for use in cases of non vital teeth
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Steps for Preparation of Tooth for Partial Veneer
Crowns
There are seven steps for tooth preparation for partial
veneer crowns:
1. Occlusal or Incisal reduction
2. Lingual reduction
3. Inter-proximal reduction
4. Proximal box or Groove placement
5. Occlusal or incisal offset placement6. Facial bevel
7. Finishing the preparation
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The technique for each step may vary according to
whether the tooth is in the maxilla or in the mandible.
In the following discussion the tooth that is beingconsidered is the maxillary canine.
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Armamentarium:
Narrow (0.8mm) round tipped , tapered diamond
For bulk reduction
Regular size (1.2mm) round tipped tapered diamond
or carbideFinishing
Wheel shaped diamond - Bulk reduction
Tapered and straight carbide fissure burs -
preparation of boxes, ledges and pinhole finalisation.
Small round carbide burFinishing stones
Inverted cone carbide burpreparation of incisal
offset
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1 ) Incisal Reduction:
Depth orientation grooves are placed at about 1
1.5mm depth.
Using tapered round ended diamond bur reduce
the incisal edge 1mm at 45oto the long axis of tooth.
Follow the facial contour of the tooth And
uniformly remove 11.5mm of enamel
Design of incisal bevel should prevent contact with
opposing teeth and incisal margin
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2) Lingual Reduction:
Accomplished in two stages:
a. Lingual surface reduction
Depth orientation groove placed Football or wheel shaped diamond bur used to
reduce lingual surface.
Slight ridge left running incisogingivally along thecentre of the lingual surface.
Clearance with opposing tooth is atleast 0.71mm
Do not over reduce cingulum
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b. Lingual gingival reduction -
Using tapered round ended diamond, a chamfer of 0.5mm
deep is made at the cervical finish line. Reduction parallels long axis of the preparation (in this case
the incisal two thirds of the labial surface)
The path of placement of the restoration must beaccurately determined before axial reduction
Mesiodistally it should be parallel to the long axis of the
tooth , buccolingually , it should parallel the middle third or
incisal third of the tooth.
to enhance the retention and resistance form, a slightly
exaggerated chamfer is placed in the lingual aspect and a
guiding groove is placed in the middle of the lingual surface
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3) Inter proximal reduction: Three steps are involved ;
a) Using a 169L carbide bur, reduce the proximal surface by
moving bur from lingual to the facial surface. Position burso that the tip of the bur is further facial than the shank. Do
not break contact with the adjacent teeth. The facial line
angles must remain intacet to provide aesthetically pleasing
results
b) Using a narrow chamfer diamond, establish a light chamfer
finis line on the proximal surface
a) Using a hatchet instrument, the contact with the adjacent
tooth is broken to establish labial proximal extensions. A
flame shaped bur is used to finish the flare. Axial reduction
is now complete
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4) Proximal grooves:
These are placed as far labially as possible without
undermining the labial enamel plateFirst groove is begun by cutting a 1mm deep template
with a 170L bur. This groove is extended gingivally in
increments to the full length.
Second groove is cut parallel to the first on the
opposite side.
Lingual wall of the groove has a 25 degree incisal
convergence with the lingual gingival wall of thepreparation.
Facial wall of the groove should be continuous with the
proximal flare to contribute bulk to the facial margin.
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The grooves are parallel to the incisal half or two
thirds of facial surface.
Boxes may be used as substitutes for the grooves
where there are existing proximal restorations or
caries. Boxes must be narrow to resistant, hence
lingual wall of the box shortens as it moves lingually.
The grooves are a minimum of 3mm long and
terminate within 0.5mm of the gingival finish line.
)
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5) Incisal groove
Using 37 inverted cone bur, develop a 0.5 to 1mm
groove connecting the proximal groove . This
should be in the dentin and parallel to the DEJ.
Groove is not placed at the expense of the incisal
edge.
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Features of anterior three quarter crown preparation
Pi M difi d Th Q
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Pin Modified Three Quarter crown
Indications:
Undamaged anterior teeth in caries free mouth
Alteration of lingual contour of the maxillary
anterior teeth or the alteration of occlusionAnterior splinting
C t i di ti
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Contraindications:
Large pulp
Thin teeth
Non vital teeth
Carious involvement
Problems with proposed path on withdrawal of FPD
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Advantages:
Minimal tooth reduction
Minimal subgingival margins, hence periodontally
preferable
Optimum access for margin finishing and hygiene
Adequate retention
Disadvantages:
Less retentive than complete coverage
Alignment can prove difficult
Technically demanding
Not usable on non vital teeth
Pi l d ti
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Pin ledge preparation
Three designs of pin ledge preparations have been
describes:
1- Conventional Pin ledge involving only the lingual
surface of the tooth2 - Pin ledge with proximal slice
3Pin ledge with a proximal groove
Conventional pin ledge preparation
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Conventional pin ledge preparation
Lingual reduction
This is done similar to conventional anterior
two third crown preparation with a few additional features. A
lingual incisal bevel is prepared with a wheel bur , about
1.5mm in width. It should be parallel to the uncut incisal edgeand should end lingual to the labio-incisal angle to avoid
display of metal.
The lingual axial wall should be parallel to the
gingival two thirds of the labial surface. The chamfer finishline should stop lingual to the contact of the tooth surface
adjacent to the edentulous space inorder to improve
accessability to operator and patient (for maintenance)
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Proximal reduction
Only one proximal surface is prepared.The proximal surface adjacent to the edentulous
ridge is only prepared. The diamond is held either
parallel to the path of placement or slight lingual
inclination is given. The primary purpose of this step
is to provide adequate bulk of the metal in area for
subsequent connector. Reduction includes contact
area , but should not be extended too facially.
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Pinhole preparation
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Pinhole preparation -
Sink pilot channels using small
round bur or a small twist bur. The depth of thecompleted pinhole should be about 2mm. Enlarge
and deepen the pilot channels with a tapered bur
when the placement and orientation of the pilotchannels have been found to be satisfactory. Bevel
the junction between the pinhole and the ledge with
a round bur slightly larger than the largest diameterof the pinhole. Inspect all areas of the preparation for
smoothness and evaluate the margins
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Features of pinledge anterior three quarter crown
