Thursday, April 5, 2012

Posterior Provisional Zimmer Implant Indexing and Crown Fabrication

Many patients report food impaction in the cervical 1/3 of their posterior implant crowns.  This occurs most likely as a result of improper crown emergence profile.  Implants are generally more narrow than the teeth to which they will replace.  The diameter discrepancy results in some difficulty providing ideal implant crown contours.  Proper implant placement guidelines should be followed when planning the surgical placement of a dental implant.  If those implant is placed properly following basic implant placement guidelines the following technique will help ensure your implant crown restorations will have more ideal crown contours, minimized food impaction.

Index implant placement at time of surgery.  Zimmer TSV implants were indexed using a modified surgical guide and the Zimmer carrier provided with the implant for placement.
  • Tighten implant carriers to light hand torque
  • Ensure the implant carriers are seated
  • Ensure the guide/matirx is seated fully on the patient's teeth
  • Ensure the implant carriers do not touch the guide index
  • Apply GC pattern resin carefully around the implant carriers.  
    • Ensure the resin does not enter an undercut area of the adjacent teeth
    • Leave the access hole to the screw of the implant carrier free from resin
    • Ensure sufficient resin is adapted around the carriers to ensure regidity
  • Allow GC Resin to set for 10 min
  • Remove and disinfect appropriately

Preparing cast with Implant Index
  • Remove stone from previous cast to allow room for implant analogs
  • Place index on cast
    • Ensure the index is seated fully and pasively
  • Hand tighten appropriate lab analogs onto index implant carriers
  • Place index with lab analogs onto cast
    • Ensure the lab analogs are free from contacting the stone cast
  • Make a boxing wax matrix around cut out area on cast
  • Mix and pour low expansion stone around the lab analogs
    • Do not cover the junction of the implant and carrier with the stone
    • Ensure the matrix remains fully seated and doesn't move
  • Allow stone to set
  • Remove Index

Provisional Implant Crown Fabrication
  • Modify Zimmer implant carriers to be used as temporary implant abutments
    • Place implant carrier on a implant analog and place it into the Zimmer Implant Lab holder
    • Cut off the coronal section of the implant carrier
    • Sand blast the color off the carrier
    • Place provisional abutment back onto the indexed cast
    • Fill screw access hole with impression material (PVS)
  • Block our undercut areas on cast and under temporary abutment with impression material (PVS) 
  • Place reference lines on the cast indicating the buccal/lingual and mesial/distal location of the implant
  • Fabricate Provisional fabrication matrix from diagnostic wax up
  • Fill provisional matrix with polymethylmethacrylate acrylic of the appropriate shade
  • Place resin filled matrix on cast with and ensure complete seating
  • Place cast with resin filled matrix into a pressure pot with warm water for about 10 minutes at 15 psi
  • Remove form pressure pot
  • Using a 4 round bur expose the implant screw access hole using the previously marked implant location lines
  • Remove the PVS impression material in the screw access hole
  • Remove the provisional implant crowns from the cast
  • Trim provisional implant crowns of excess resin bulk/flash
  • Using a thin diamond disk section between the two implant provisional crowns
  • Brush bead acrylic onto the cervical portion of the provisional abutment to provide proper crown emergence contours
  • Place in pressure pot with warm water at 15 psi for 10 minutes
  • Remove and modify crown contours until you feel the crown exemplifies ideal crown contours
  • Adjust proximal contacts until shims can be pulled through the interproximal with light resistance
  • Polish with pumice and crest shine on a lathe

Preparing Final Impression Transfer Abutments for Final Impression
  • Place finished provisional crowns back on indexed cast
  • Flow impression material (PVS) around the provisional crowns representing the ideal gingival locations
  • Allow 5 minutes to set
  • Remove implant provisional crowns
  • Evaluate Crown cervical contours in impression material
  • Place Open tray impression post onto appropriate implant lab analog
  • Apply flowable composite resin or polyether impression material around the impression analog filling the molded area.  Light cure or allow time to polymerize