Partial Veneer Crowns , Inlays and Onlays

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Partial Veneer Crowns , Inlays and Onlays
dr shabeel pn
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• Anterior Partial Veneers
• A partial veneer has been described as a
  restoration covering two or more surfaces of a
  tooth.
• There are three types of partial veneer crowns
• Three quarter crown
• Seven eight crown
• Mesial half crown
• All other forms of partial veneers are
  considered variations of the three basic types.

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• Three quarter crown covers three surfaces of
  the crown leaving one surface intact.
• Seven eighth crown used in maxillary molars and
  premolars. It encompasses seven eighth the
  gingival circumference of the tooth.
• Mesial half crown is a three quarter crown
  rotated 90o, preserving the distal surface of the
  tooth. This preparation design is primarily
  indicated for the distal retainer of a mandibular
  FPD with a tilted molar abutment.

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• Indications For Partial Veneers
• Intact or minimally restored teeth.
• Teeth with crown length that is average or
  exceeds average.
• Teeth with normal anatomic crown form, ie,
  without cervical constriction.
• Anterior teeth with adequate labio-lingual
  thickness

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• Contra-indications
• High caries rate
• Short teeth
• Non vital teeth
• Deep cervical abrasion
• Teeth with extensive core restorations
• Bell shaped teeth (severe cervical constriction)
• 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 complete
  crowns
• Electric pulp testing can be done on the intact
  surface
• Complete seating of the restoration can be
  easily verified.

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• Disadvantages
• Retention is less than that of complete veneer
  crown
• 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
• Occlusal or Incisal reduction
• Lingual reduction
• Inter-proximal reduction
• Proximal box or Groove placement
• Occlusal or incisal offset placement
• Facial bevel
• 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 being considered 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 carbide Finishing
• Wheel shaped diamond - Bulk reduction
• Tapered and straight carbide fissure burs -
  preparation of boxes, ledges and pinhole
  finalisation.
• Small round carbide bur
• Finishing stones
• Inverted cone carbide bur preparation 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 45o to the long axis of
  tooth.
• Follow the facial contour of the tooth And
  uniformly remove 1 1.5mm 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
• Lingual surface reduction
• Depth orientation groove placed
• Football or wheel shaped diamond bur used to
  reduce lingual surface.
• Slight ridge left running incisogingivally along
  the centre of the lingual surface.
• Clearance with opposing tooth is atleast 0.7
  1mm
• Do not over reduce cingulum

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• 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 be
  accurately 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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• Inter proximal reduction Three steps are
  involved
• Using a 169L carbide bur, reduce the proximal
  surface by moving bur from lingual to the facial
  surface. Position bur so 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 intact to provide
  aesthetically pleasing results
• Using a narrow chamfer diamond, establish a
  light chamfer finis line on the proximal surface
• 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 plate
• First 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 2 5 degree
  incisal convergence with the lingual gingival
  wall of the preparation.
• 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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• 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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6) Facial bevel Using a fine, flame shaped
diamond bur, develop a narrow bevel lt 0.5mm on
the labioincisal finish line at right angles to
incisal two thirds of the facial surface. 7)
Finishing the preparation Using a carbide
finishing bur, round the angles to ensure
continuity of all the finish lines
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Features of anterior three quarter crown
preparation
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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 occlusion
• Anterior splinting

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• Contra indications
• 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 Le
ss retentive than complete coverage Alignment can
prove difficult Technically demanding Not usable
on non vital teeth
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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 tooth 2 - Pin ledge with proximal
slice 3 Pin ledge with a proximal groove
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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 edge and 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 finish
  line 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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• Ledge preparation
• Two ledges are
  prepared across the reduced lingual surface. The
  provide room for sufficient bulk of metal to
  ensure rigidity. The ledges are prepared parallel
  to the incisal edges of the tooth, as viewed from
  the lingual aspect and parallel to each other as
  viewed from the incisal aspect.
• Indentations
  are made in the two sides of the incisal ledge
  and slightly off centre of the cervical ledge to
  prevent pulp exposure when the pinholes are
  placed.

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• Pinhole preparation -
• Sink
  pilot channels using small round bur or a small
  twist bur. The depth of the completed pinhole
  should be about 2mm. Enlarge and deepen the pilot
  channels with a tapered bur when the placement
  and orientation of the pilot channels have been
  found to be satisfactory. Bevel the junction
  between the pinhole and the ledge with a round
  bur slightly larger than the largest diameter of
  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