Direct Custom Implant Impression Copings: A Method for Accurate Impression of Highly Shaped Peri-Implant Gingiva

Implant treatment in the aesthetic zone benefits significantly from the use of well-designed screw-retained implant provisional restorations. This protocol allows the clinician and patient to evaluate the periodontal response to the implant treatment before proceeding to the definitive restorations.

Soft-Tissue Considerations
Following maturation of the soft tissue around the implant and provisional (generally 3 to 6 months following the last surgical procedure), the gingiva should have attained a natural and aesthetically acceptable state. The gingiva should have a reasonable appearance to the free-gingival margin and the papilla, based on reported expectations for papilla volumes and heights.^1-4
Minor modifications to the emergence profile of the abutment and the apical extent of the interproximal contact⁵ may need to be modified to accomplish the aesthetic goals for the treatment,^6,7 but significant efforts should be made to minimize the number of connections (and disconnections) to the head of the implant.⁸ This will ensure that the tissue being manipulated is fully mature and at a significantly lower risk for peri-implant bone and soft-tissue loss. Generally, the subgingival emergence of the abutment should be kept as narrow as possible, while achieving the desired results.^9-11 When modifications to the provisional are required to achieve the desired result, removal of the abutments should be delayed until at least 3 months following the last surgical procedure.

Figure 1. The screw-retained implant provisional is removed from the implants. Note the highly polished, narrow subgingival area with a 2-mm titanium collar.	Figure 2. The straight-body, open-tray impression copings are quickly attached. With the screw post slightly loosened, an attempt to rotate the body is made to quickly verify that the coping is properly indexed. The screw post is then retightened.
Figure 3. Low viscosity, dual-polymerizing resin cement is gently injected into the area around the impression coping. (DUO-LINK [BISCO Dental Products] was used for this case.)	Figure 4. A narrow cannula tip is used to ensure that the resin reaches to the full depth of the peri-implant sulcus.
Figure 5. The resin is connected across the pontic site (if applicable) and polymerized. This process should be accomplished in no more than 2 minutes to prevent changes to the soft tissue. At this point the tissue contours are “frozen” in the exact positions they were in at removal of the provisional.	Figure 6. A floss bridge will act as a scaffold across which the low shrinkage resin (Pattern Resin LS [GC America]) will be incrementally built to ensure interimplant accuracy in the impression.
Figure 7. The floss is gently woven between the impression copings to support the resin without applying tension.	Figure 8. The completed floss-based scaffold.
Figure 9. Note that the soft tissue remains completely unchanged, even after several minutes without the provisional in place. Compare to Figure 2.	Figure 10. The completed resin splint will ensure accuracy of the impression. Note: space was left under the resin splint to ensure that the copings will be picked up in the impression.

Figure 11. The tissue surface of the impression clearly illustrates the accuracy of the direct custom implant impression coping technique.

THE FINAL IMPRESSION
When the soft tissue has reached a satisfactory state¹² or the maximum expected volume, it is time to make the final impression. The ideal cast made from the impression should be a nearly exact replica of the form of the gingiva immediately after the provisional was removed. The difficulty lies in that immediately following removal of the provisional, the papilla will begin to flatten significantly, and the subgingival emergence will occlude. The rate at which these changes happen varies, and is largely dependent on the maturity of the soft tissue and the thickness of the periodontium. In the author’s clinical experience, these changes appear to begin as early as one or 2 minutes after removal of the provisional restoration. The flattening of the gingiva has the potential to significantly compromise the aesthetic potential of the treatment, and overall predictability. If the gingiva and papilla do flatten prior to the setting of the impression material, the resulting cast will have to be modified by the technician in an attempt to restore an ideal shape to the emergence and papilla. Unfortunately, the effect these modifications will have on the stone model may differ significantly from the gingival response once the definitive restoration and abutment are delivered. This may result in open gingival embrasures (“black triangles”), unaesthetic pontic emergence, recession of the facial gingival margin, and exposure of metal abutments.

THE DIRECT CUSTOM IMPRESSION COPING TECHNIQUE
The direct custom impression coping technique¹³ allows the clinician to efficiently and accurately capture the mature gingival positions without flattening or remodeling. Other implant impression techniques have been widely used (including indirect pattern resin custom copings,^14,15 flowable composite with closed tray copings,¹⁶ and using the provisional as a transfer coping^17-19), but most involve significant time in the laboratory, extended appointment times, or duplicate provisionals.

The direct custom implant impression coping technique protocol:

1. Prepare impression copings (the copings should be open-tray, and straight or narrow emergence) and appropriate driver.
2. Remove implant provisional (Figure 1).
3. Quickly attach impression copings and hand tighten (Figure 2).
4. Loosen the screw post a quarter turn and attempt to rotate the impression body; if it will not rotate, it is likely that the coping is properly indexed.
5. Retighten the screw post.
6. Dry the copings and adjacent gingiva.
7. Using a narrow tip, inject a dual-polymerizing resin cement (such as DUO-LINK [BISCO Dental Products]; Kerr Maxcem Elite [Kerr], RelyX Unicem 2 [3M ESPE], SpeedCEM [Ivoclar Vivadent], etc) into the emergence area around the copings and pontic receptor sites (Figures 3 to 5).
8. Polymerize the resin for 20 seconds.

This technique is easily performed in less than 2 minutes; after which, the gingiva will be accurately held in the exact position it was in with the provisional in place. Radiographs should now be made to ensure that the copings are fully seated. If treatment will involve multiple adjacent or splinted implant restorations, they should be properly splinted with a low shrinkage acrylic resin (ie, Pattern Resin LS [GC America]) to maximize accuracy (Figures 6 to 10).^20-23 This will ensure that the interimplant positions are as accurate as the gingival positions.
The direct custom impression coping technique is simple to perform and provides an accurate and efficient impression of the desired gingival position (Figure 11). This results in a laboratory cast that is a proper representation of the positions of the free-gingival margin, the papilla, and the subgingival emergence of the abutment. An accurate cast saves the technician the difficult task of adjusting the emergence in the laboratory with no evidence of how the soft tissue will ultimately respond.

CONCLUSION
The accuracy of the direct custom impression coping dramatically increases the predictability of implant treatment in the aesthetic zone, where the gingival aesthetics contribute significantly to the overall success of the treatment.

References

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Dr. Schoenbaum is an assistant clinical professor in the University of California, Los Angeles (UCLA) Division of Restorative Dentistry, assistant director of the UCLA continuing education department, and the assistant director for the UCLA Center For Esthetic Dentistry. He has lectured internationally and published numerous papers on implants and aesthetics. He is a Fellow in the AGD and the American College of Dentists. Dr. Schoenbaum also maintains a private practice within the UCLA faculty group dental practice with an emphasis on aesthetics and implant prosthetics. He can be reached at (310) 267-3380 or at tschoenbaum@dentistry.ucla.edu.

Disclosure: Dr. Schoenbaum reports no disclosures.