Written by Jeremy Montrose, DDS, FAGD Wednesday, 30 June 2004 19:00
In reference to prosthetic reconstruction, implants may be placed in poor alignment for a variety of reasons.1 Difficult surgical access, failure to fabricate accurate surgical guides, and the lack of adequate bone height or width are common problems. Often, these complications are identified at the time of surgery when exposure of the surgical site indicates that the proposed alignment is unrealistic.2 Misalignment of implants is a significant problem for restorative dentists.3
|Figure 1a. No. 19 misaligned implant corrected with surgical indexing.||
Figure 1b. UCLA abutment.
Figure 1c. Final radiograph.
|Figure 1d. Final restoration with appealing emergence profile.|
Figure 2a. No. 21 prior to surgery.
|Figure 2b. Implant placement.|
|Figure 2c. Impression coping placed onto an implant during stage I surgery for surgical indexing.||Figure 2d. Custom tray with access hole for coping screw.|
|Figure 2e. Inside of impression; the coping is seen before analog placement.||Figure 2f. Inside of impression; laboratory analog clipped into the coping and secured with the screw from the other side.|
|Figure 2g. Laboratory model with UCLA custom abutment in place.||Figure 2h. The 3 components received from the laboratory: abutment, provisional restoration, and screw.|
Figure 2i. The 3 components fixed together.
|Figure 2j. The abutment and provisional restoration at the time of second stage surgery.|
INDICATIONS FOR SURGICAL INDEXING
Surgical indexing is indicated in the following circumstances:
(1) When 2-stage implant surgery is proposed and the implant team desires to deliver a laboratory-generated abutment and provisional crown at the time of implant uncovery.
(2) When an aesthetic emergence profile cannot predictably be generated from a stock healing abutment.
(3) When the alignment of a stock restorative abutment will not allow for optimal restoration of the occlusion.
Diagnostic radiographs, articulated models, and surgical templates are prerequisites for proper implant treatment planning. For surgical indexing, additional materials and equipment must be available. These include the appropriate impression copings, drivers, impression material, impression trays, adhesive, bite registration materials, laboratory analogs, and shade guides. At the diagnostic visit, a shade should be selected for the provisional restoration.
The laboratory technician generates articulated die models with a laboratory analog, as is performed for restorative implant impressions. Processing the surgical indexing impression differs from that of a conventional restorative implant impression in that (1) the technician must estimate the final soft-tissue margin by mimicking the cemento-enamel junction of the adjacent teeth and (2) only a provisional restoration should be fabricated at this time.
STAGE II (UNCOVERING) SURGERY
After appropriate healing, the implant surgeon uncovers the implant and removes the cover screw. Instead of placing a stock healing abutment, the surgeon places the laboratory-prepared abutment onto the implant with the final restorative screw gently hand-driven into place. A radiograph of the abutment is taken to verify intimate fit with the implant, and the provisional crown is tried in. The provisional occlusion is then checked and adjusted outside the mouth. The implant surgeon then applies the correct final torque to the abutment screw, and with the flaps still open cements the provisional crown with temporary cement. This will provide the surgeon with visual access for cement debris removal. The site is sutured closed and postoperative visits are scheduled. The patient is referred back to the restorative dentist.
Dentists who emphasize either the surgical or restorative phases of implant dentistry find surgical indexing to be a powerful tool. The abutment and provisional restoration facilitated by this procedure allows the case to proceed efficiently while preemptively correcting for implant alignment errors. Surgical indexing is particularly important for advanced cases, such as fabrication of multiple implant abutments and provisional restorations for full-arch reconstruction.
Replacement of missing teeth with implants is now one of the most predictable of all dental procedures. These restorations can last for decades, and an optimum outcome is achievable with proper planning.
The author wishes to acknowledge William “Coach” Bartosiak of North American Dental Laboratory (crown and bridge) and Howard Levy of Horizon Dental Laboratory (removable), the technicians responsible for all of the authors’ restorations.
- Misch CE. Contemporary Implant Dentistry. 2nd ed. St Louis, Mo: Mosby; 1999: Chapter 27.
- Wilson DJ. Ridge mapping for determination of alveolar ridge width. Int J Oral Maxillofac Implants. 1989;4:41-43.
- Lewis S, Avera S, Engleman M, et al. The restoration of improperly inclined osseointegrated implants. Int J Oral Maxillofac Implants. 1989;4:147-152.
- Cranin AN, Klein M, Simons M, et al. Atlas of Oral Implantology. 2nd ed. St Louis, Mo: Year Book Medical Pub; 1999: Chapter 23.
- Assif D, Fenton A, Zarb G, et al. Comparative accuracy of implant impression procedures. Int J Periodontics Restorative Dent. 1992;12:112-121.
- Lewis S, Beumer J III, Hornburg W, et al. The “UCLA” abutment. Int J Oral Maxillofac Implants. 1988;3:183-189.
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