Implants

Simplifying Single-Stage Solid Abutments: Techniques for Impressioning and Temporization

Dentistry Today October 1, 20047 Mins read2.5k Views

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Single-stage implants are being utilized more frequently. Currently, Straumann ITI, Lifecore Biomedical, Sulzer Paragon, and 3I offer an implant designed to be used in a single stage with a flared crestal architecture that accepts a solid abutment. Traditional-type implants, whether internal or external platform, typically have the restoration contacting only the abutment head. Restorations fabricated for single-stage type implants have a margin that contacts the implant platform and a central core that is the solid abutment.¹ The implant companies manufacturing single-stage implants have developed plastic impression caps that engage the abutment and seat on the implant platform.²

Restoration of single-stage implants with solid abutments traditionally requires the use of an impression index cap, an analog, and a lab fee commensurate with a more complex restoration. In this article, impression and provisionalization techniques are discussed that utilize standard crown and bridge techniques familiar to all dentists, simplify the laboratory procedure, and reduce the prosthetic costs involved with fabrication of implant-borne crowns.

IMPRESSION TECHNIQUE


Figure 1. Solid abutments are placed into the single-stage implants.	Figure 2. Completed full-arch impression demonstrating details of the margin area of the implants.

Figure 3. Cast fabricated from the full-arch impression.	Figure 4. Lateral view of the cast fabricated from the full-arch impression.

Figure 5. Cast copings fabricated on the ditched dies.	Figure 6. Cast coping on an analog to verify marginal fit.

Figure 7. Porcelain application on the metal coping verified on an analog.	Figure 8. Completed porcelain-fused-to-metal crowns seated on the implants.

Figure 9. Radiograph demonstrating marginal fit of the porcelain-fused-to-metal restorations.

Following the appropriate healing period, the healing screw is removed from the single-stage implant. A solid abutment is threaded into the implant (Figure 1). Modification to the solid abutment can be made to the height or circumferential geometry to accommodate the space restrictions for fixed prosthetics.^3,4

Retrac (Centrix), a nontraumatic retraction material available in an automix syringe, is injected into the sulcular area around the implant with an Access tip.⁵ A cotton Comprecap (Coltène/Whaldent) is inserted over the implant, and the patient is instructed to bite. The compression from the Comprecap serves to fill the sulcus with the Retrac retraction material, physically opening the sulcus and compressing the capillaries within the sulcular tissue. Pressure is maintained for 5 minutes. The Comprecap is removed, and the Retrac is flushed off the abutments and from the sulcus with an air-water syringe and high-volume suction. This technique allows for retraction without disruption of the maturing hemidesmisomal attachment at the gingival titanium connection.

The implant abutment is then air-dried. A tray containing a monophase polyvinyl siloxane impression (PVS, GC America) material is filled by the assistant, while the dentist syringes mono-phase into the sulcular area.6 The tray is inserted and al-lowed to set. Upon impression removal, temporary crowns may be fabricated (Figure 2).⁷

The impression is received at the lab, and 2 models are poured for the arch containing the implants (Figures 3 and 4).^8,9 The first solid model will not be modified and will allow the lab to verify embrasure spaces and proximal contacts. The second model is sectioned, and ditched dies are fabricated in the usual crown and bridge method. Copings are waxed on the second model, with the final margins obtained from a corresponding implant lab analog that perfectly replicates the patient’s situation. Metal copings are cast, and marginal fit is verified on an analog (Figures 5 and 6). Porcelain is applied, and the contours are verified on the first (solid) model (Figure 7).

The restorations are finished and returned to the dentist for try-in and cementation (Figure 8). Vertical bitewing radiographs are taken to verify complete seating of the porcelain-fused-to-metal crown (Figure 9).

TEMPORIZATION
The restorative phase for single-unit implants can be divided into 3 components: impression fabrication, temporization, and final restoration insertion. The majority of the time involved chairside can be in the temporization component.

When a laboratory-fabricated temporary crown is to be utilized, additional patient appointments will be required if indexing was not accomplished at surgical placement. The first patient appointment would involve an impression of the implant to index it with relation to the opposing and adjacent dentition. This would be followed at a subsequent appointment by insertion of the interim restoration. Progressive loading^10-14would then be allowed prior to an impression for the final restoration. Chairside interim crown fabrication can be a time-consuming procedure. An alternative sequence would involve placement of a stock abutment head at the initial restorative visit. An interim crown would then be fabricated chairside, cemented, and the patient dismissed to allow progressive loading.

The following technique will demonstrate a method of fabricating an interim crown to fit a posteriorly placed Straumann ITI (Straumann USA) or Lifecore Stage 1 (Lifecore Biomedical) solid abutment with minimal chairside time.

Technique


Figure 10. Acrylic coping fabricated on an analog to duplicate the margins of the single-stage implant.	Figure 11. Acrylic coping tried on the single-stage implant intraorally to verify fit.

Figure 12. DirectCrown temporary tried in intraorally over the acrylic coping to verify clearance circumferentially.	Figure 13. DirectCrown temporary filled with self-polymerizing acrylic inserted over the acrylic coping intraorally to develop proximal contacts.

Figure 14. Temporary crown upon removal intraorally.	Figure 15. Acrylic flash has been removed and gross shaping has been performed. The margin is indicated in red pencil.

Figure 16. Completed temporary showing margin detail.	Figure 17. Buccal view of the completed temporary.

Figure 18. The completed temporary placed intraorally.

The Straumann ITI implant and Lifecore Stage 1 implant provide 3 solid abutments that vary from 4, 5.5, and 7 mm in height.¹⁵ This allows selection of a solid abutment to accommodate the available interarch space. These abutments may be modified when needed if the available sizes are not adequate.⁹ If a height less than 4 mm is required, selection of a screw-retained prosthesis should be considered in lieu of a cement-retained restoration.

Following selection of the proper abutment height and prior to the patient appointment, a corresponding analog is selected. The abutment head and analog are color-coded to prevent confusion and im-proper selection. The analog has a corresponding shoulder that matches the implant with the selected abutment head inserted. A bead-and-brush technique utilizing the self-cure acrylic included in the DirectCrown kit (Direct-Crown) is applied to the analog to form a thin coping down to the margins.^16,17 The circumferential surfaces of the coping need to be approximately 2 mm thick to resist breakage upon placement to complete the interim restoration. The occlusal surface should be kept very thin to avoid interference with the next step. Excess acrylic is removed prior to set of the material to prevent locking onto the analog. Margins are marked with a pencil, and the coping is trimmed (Figure 10). The coping should snap off the analog and have a snap fit intraorally.

The preselected abutment head is placed on the implant following healing screw removal. The prefabricated acrylic coping is snapped over the solid abutment head, and a DirectCrown shell is selected that will cover the coping buccal-lingually (Figures 11 and 12).

The DirectCrown shells do not have a proximal contact, and this will be built out intraorally with self-cure acrylic. A mix of acrylic from the Direct-Crown kit is placed into the shell, and the shell is then inserted over the prefabricated coping that has been placed on the solid abutment (Figure 13). After setting, the interim coping is removed from the solid abutment (Figure 14). Margins are examined and marked with a pencil prior to finishing (Figure 15). Proximal surfaces are adjusted for proper shape and contour, and the interim restoration is polished (Figures 16 and 17). The final step is placement of the interim restoration intraorally and adjustment of the occlusion (Figure 18).^18,19

CONCLUSION
Complexity of restoring dental implants may hamper dentists from adding implant treatment modalities to their armamentarium. Simplifying the restorative portion of treatment for fixed prosthetics via incorporating common techniques used daily for crown and bridge will allow more general practitioners to restore implants in their practices.

When techniques are utilized that do not require special components (ie, impression caps, positioning cylinders) or laboratory parts (ie, mulitiple implant analogs), the costs and complexity of restoring implants becomes easily incorporated into any dental practice. The advantage of lowering office overhead expenses with easier techniques for the restorative doctor will be an additional benefit. The average savings utilizing these techniques (depending on which single-stage implant has been placed) is approximately $45 per unit with the elimination of im-plant impression components.

The prefabricated coping made to fit the single-stage implant in the posterior region combined with the Direct-Crown acrylic shell provides an accelerated method for interim crown fabrication. This same technique can be modified to other prefabricated abutments for other implant systems. The intimate fit of the interim restoration is ensured when the coping is fabricated extraorally. Margins and a lack of voids in the acrylic can be accomplished by dental auxiliary prior to the patient appointment, decreasing valuable chairside time. The Direct- Crown acrylic shell assists in development of the basic contours of the final interim restoration, as the occlusal, buccal, and lingual surfaces are prefabricated. Minimal time is required to shape the proximal surfaces and adjust the occlusion.

References

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Dr. Schneider is in private practice in Springfield, Va, and is an adjunct instructor at Tufts University School of Dental Medicine Restorative Department. He is also a consultant to the Martinsburg Veterans Administration hospital in implant dentistry, as well as an international speaker and consultant to various dental companies. He can be reached at aldds@aol.com.

Dr. Kurtzman is in private practice in Silver Spring, Md, and is an associate clinical professor at the University of Maryland School of Dentistry Department of Restorative Dentistry. He is an evaluator for several dental companies and an international speaker. He can be reached at drimplants@aol.com.