Chairside Implant Abutments: A Novel CAD/CAM Approach

INTRODUCTION
While dental implants have become a standard of care for various indications, there may still be cause for concern for general dentists or others unfamiliar with the procedures for restoring them, given that the process can be time consuming, difficult, or riddled with options that may at times seem overwhelming. With nearly 80% of those with implants suffering from complications such as inflammation or peri-implantitis at some point following treatment,¹ it is critical for those who place implants to be educated and comfortable with the procedure.

Recent advances in technology include the development of in-office CAD/CAM techniques that permit clinicians to design and mill their own abutments and restorations for implants. These techniques also enable clinicians to design a more suitable alternative to stock or prefabricated abutments that may make placing and restoring implants less appealing.² These CAD/CAM fabricated abutments and/or restorations are highly aesthetic, which is an important factor in designing restorations, particularly in the anterior region.³

CAD/CAM System Recently Introduced
To solve the issues surrounding implant placement, abutment selection, and restoration, Ivoclar Vivadent, in conjunction with Sirona Dental Systems, has developed the IPS e.max CAD Abutment Solutions. This CAD/CAM facilitated system enables clinicians to design, mill, and place abutments and restorations within the comfort of their own practices. At the heart of the system are 2 types of lithium disilicate blocks: the A16 LT (low translucency) and the A14 MO (medium opacity), which are used for fabricating abutments and restorations (Figure 1). Sirona Dental Systems produces the corresponding 5.0-mm TiBases onto which these can be either screw- or cement-retained. Once designed and milled with the appropriate in-office CAD/CAM system, the abutments and crowns (whether milled separately or as one) are then luted onto the TiBase.

The IPS e.max CAD Abutment Solutions feature lithium disilicate, which has been shown to demonstrate a clinical strength of 400 MPa and excellent aesthetics.4 This system is, therefore, perfectly designed for restorations in either the anterior or posterior regions.^5,6

The following case presentation demonstrates the capabilities of IPS e.max CAD Abutment Solutions in providing an advanced and highly aesthetic restoration in a more simplified manner.

CASE REPORT
Clinical Protocol
A patient presented with an implant at No. 19 in need of restoration. The provisional was removed (Figure 2), and the gingiva, which had completely healed, was scanned into the CAD software using the CEREC (Sirona Dental Systems) abutment design mode. This was necessary for developing the proper emergence profile and tissue pressure for the final restoration. Scanning the tissue immediately after removing the provisional was necessary, since the tissue would begin to slump right away.

An implant ScanPost (Sirona Dental Systems) was screwed into the implant (Figure 3) to serve as a digital impression post. A ScanBody (Sirona Dental Systems) was placed on the ScanPost to record the position, angulation, and rotation of the implant. The ScanBody was scanned directly into the software with the CEREC Omnicam (Sirona Dental Systems) (Figure 4). The software displayed a split window on the computer screen; the left window showing a live intraoral view of the patient’s mouth, and the right window showing the full-color virtual model to be built (Figure 5). Scanning powder was not necessary when utilizing the Omnicam.

Figure 1. Image showing the 2 lithium disilicate (IPS e.max [Ivoclar Vivadent]) abutment blocks available for both screw- and cement-retained restorations.	Figure 2. The healing cap was removed, and the gingiva was scanned to determine the correct emergence profile and tissue pressure.
Figure 3. View of the implant ScanPost (Sirona Dental Systems), on which a ScanBody (Sirona Dental Systems) is placed to record the implant position and angulation.	Figure 4. The ScanPost and ScanBody were placed in the mouth for scanning with the CEREC Omnicam (Sirona Dental Systems).

Several images were taken to capture the details required to fabricate the abutment for the restoration. These were dictated by predetermined settings in the software (Figure 6). The mandibular scan included the ScanPost and ScanBody, and the maxillary scan included the opposing arch so as to relate the necessary occlusal information to the software. The buccal bite scan was used to determine the proper occlusion of both arches together. All of these, in conjunction with the gingival scans (performed in the software’s Gingiva Mask Lower mode), were combined to create the entire virtual model of the restoration, on its own and relative to the adjacent teeth (Figure 7).

Once the virtual model was developed, the software proposed a completed restoration based on the gingival contours and natural emergence profile. The amount of tissue pressure was then adjusted in the proposed restoration (Figure 8).

The long axis of the implant was shown relative to the adjacent teeth (Figure 9). This allowed definition of the hybrid abutment in relation to the implant angulation. Angled restorations up to 20° are permitted by the software to compensate for slight angulations in implant placement. Once finalized, the hybrid abutment crown with proper contacts, occlusion, emergence profile, and tissue pressure was displayed (Figure 10). A small red hole on the occlusal surface of the virtual restoration indicated the position of the screw access hole. To finalize the restoration, the gingiva was viewed as transparent and overlaid upon the abutment crown restoration (Figure 11). This was accomplished using the software’s Gingival Mask Lower mode, and the emergence profile and tissue pressure were properly designed and contoured.

Figure 5. When capturing an image of the ScanBody with the Omnicam, the left window displays a live intraoral view.	Figure 6. This image shows the catalogs that needed to be taken to design a hybrid abutment or crown using the CEREC (Sirona Dental Systems) software.
Figure 7. This virtual model in the CEREC software shows the ScanBody and implant position relative to the adjacent teeth.	Figure 8. The software parameters allow control over the amount of tissue pressure desired in the restoration proposal.
Figure 9. View of the long axis of the implant itself relative to the adjacent teeth.	Figure 10. The final design of the hybrid abutment crown with proper contacts, occlusion, emergence profile, and tissue pressure.
Figure 11. View of the gingiva transparently overlain on the virtual restoration, allowing the user to customize the emergence profile and tissue pressure.	Figure 12. The mill preview shows the virtual hybrid abutment crown positioned in the A16 LT e.max CAD abutment block.
Figure 13. The finalized IPS e.max hybrid abutment crown, large enough to fit the screw without compromising any of the porcelain surface or strength.	Figure 14. The e.max CAD hybrid abutment restoration was bonded to the TiBase (Sironal Dental Systems) with a self-curing resin cement (Multilink Hybrid Abutment; shade HO [Ivoclar Vivadent]).
Figure 15. The restoration was screwed into the implant intraorally and torqued to 25 Ncm.	Figure 16. Occlusal view of the screw access hole of the hybrid abutment crown restored using Teflon tape and a universal nanohybrid composite resin (Tetric EvoCeram [Ivoclar Vivadent]).

A preview of the virtual hybrid abutment crown before milling was viewed (Figure 12). The restoration was virtually positioned in relation to the hole in the abutment block (A3 A16 LT IPS e.max CAD). Because the restoration was designed as a hybrid abutment crown, it would be milled in one piece to be screw-retained to the implant. Once the restoration design was approved, it was milled, stained, glazed, and crystallized (Figure 13). The final crystallized restoration was placed in an ultrasonic bath for 5 minutes to remove any excess debris. The hybrid abutment crown was then prepared for bonding by etching with hydrofluoric acid for 20 seconds, rinsing, and applying a universal primer (Monobond Plus [Ivoclar Vivadent]) to the internal surfaces of the lithium disilicate restoration. The surface primer was allowed to sit for 60 seconds prior to drying, per manufacturer’s instructions.

Next, the TiBase (Sirona Dental Systems) was prepared for bonding by sandblasting the surface above the shoulder with aluminum oxide. To prevent the attachment from being sandblasted as well, the surface below the shoulder was blocked out with wax. Monobond Plus universal primer was then applied to the TiBase and allowed to sit for 60 seconds before drying. Then the IPS e.max CAD hybrid abutment crown was bonded to the TiBase using a self-curing luting composite (Multilink Hybrid Abutment in shade HO [Ivoclar Vivadent]) (Figure 14). After polymerization of the cement was complete, the junction was polished with rubber wheels and polishing points (Universal Gray Knife Edge Polisher and Blue, Pink Gray Polishing Wheel [Brasseler USA]).

Figure 17. Lingual view of the final restoration. This restoration required no adjustments to the tissue, proximal contacts, or occlusion.	Figure 18. Final radiographic image of the completed implant-supported lithium disilicate restoration.

The restoration was then screwed onto the Astra Tech Osseospeed 5.0 implant intraorally and torqued to 25 Ncm (Figure 15). The use of a screw-retained restoration, in addition to simplifying the procedure itself, also eliminated the possibility of extraneous cement that can potentially result in inflammation/peri-implantitis.7 Next, the access hole in the crown was restored using Teflon tape and a universal nanohybrid composite resin (Tetric EvoCeram [Ivoclar Vivadent]) (Figure 16).

Final images of the newly fitted restoration were taken (Figures 17 and 18). No adjustments to the tissue, proximal contacts, or occlusion were necessary, as the software designed a perfect restoration.

CLOSING COMMENTS
Newer, more advanced materials and equipment may enable dental procedures to become more efficient and predictable; however, there are only a select few that, in doing so, alter clinicians’ mindsets about performing the procedure itself. The system demonstrated in this case report (IPS e.max CAD Abutment Solution) allows clinicians to offer and deliver complete implant treatments to their patients with ease and confidence. In the author’s opinion, practitioners and patients alike will benefit from its use, since confusion surrounding implant abutment selection and restoration is eliminated.

References

1. Zeza B, Pilloni A. Peri-implant mucositis treatments in humans: a systematic review. Ann Stomatol (Roma). 2012;3(3-4):83-89.
2. Hamilton A, Judge RB, Palamara JE, et al. Evaluation of the fit of CAD/CAM abutments. Int J Prosthodont. 2013;26:370-380.
3. Khoury F, Happe A. Soft tissue management in oral implantology: a review of surgical techniques for shaping an esthetic and functional peri-implant soft tissue structure. Quintessence Int. 2000;31:483-499.
4. Blanco J, Rego N. Using lithium-disilicate hybrid abutments for implant restorations. Inside Dental Technology. 2013;4:80-81.
5. Kurbad A, Kurbad S. CAD/CAM-based implant abutments. Int J Comput Dent. 2013;16:125-141.
6. Kern M, Sasse M, Wolfart S. Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium disilicate ceramic. J Am Dent Assoc. 2012;143:234-240.
7. Korsch M, Robra BP, Walther W. Predictors of excess cement and tissue response to fixed implant-supported dentures after cementation. Clin Implant Dent Relat Res. Jul 2013. DOI: 10.1111/cid.12122.

Dr. Skramstad is a 2000 graduate of the University of Minnesota School of Dentistry. He is currently faculty in the CAD/CAM department at Spear Education in Scottsdale, Ariz. He also maintains a successful restorative practice in Orono, Minn, focusing on aesthetic, reconstructive, and CAD/CAM dentistry. He is a certified advanced trainer for Patterson Dental, has lectured internationally on technology and digital dentistry, and has published numerous articles on materials and CAD/CAM. He is an Alpha Tester for Sirona Dental Systems focusing on the Chairside, inLab, and Connect digital systems. A product consultant for multiple dental companies, Dr. Skramstad tests and evaluates many products prior to market launch. He can be reached at (612) 385-1740 or via e-mail at the address mike@cerecdoctors.com.

Disclosure: Dr. Skramstad has lectured on behalf of Ivoclar Vivadent and Sirona Dental Systems.