Use of Digital Technology to Fabricate an Anterior Fixed Restoration Supported by a Dental Implant and Natural Teeth

Dentistry is experiencing an explosive growth of digital technology, including digital dental laboratory technology. These technologies are aimed at decreasing patient operating time, streamlining dental laboratory fabrication processes, and producing results that are at least equal to, if not better than, those achieved with previous procedures.¹ Ongoing debate centers on whether or not the dental profession has arrived at the point where clinicians can reliably count on digital imaging, digital impressioning, and digital laboratory workflow for dependable accuracy and esthetic quality of dental restorations.² Few dental professionals, however, doubt that that day will eventually arrive if it hasn't already.

Intraoral digital impression scanning continues to evolve rapidly. New, state-of-the-art scanners accompanied by enhanced software are appearing on the market regularly. As an example, the intraoral scanner (Carestream CS 3600, Carestream Dental, carestreamdental.com) used for this case report is an open-source, portable, handheld optical scanner with no accompanying trolley. It utilizes rapid image capture and requires no powdering or other surface application to the teeth being scanned. A recent in vitro study showed this scanner to be significantly better in "trueness" for image capture on partially edentulous models when compared with three other systems.³ "Trueness" refers to the ability of a measurement to match the actual value of the quantity being measured.⁴ It should be noted that all four systems in the study performed less effectively on fully edentulous models, and no significant differences were found between them in that phase of the experiment.³

Further demonstrating the growth in digital technology, new V3 software developed for the intraoral scanner used in this report offers enhanced refinement capabilities, enabling the operator to quickly and easily "clean up" extraneous flashings and fill in small voids. The scanner system also has high-definition color capabilities, as can be seen in the scanned images presented in this case report. Additionally, the unit's image capture is considerably faster than the previous version (CS 3500).⁵

The patient in this case was a 75-year-old woman who presented with a three-unit fixed prosthesis with the maxillary right lateral incisor and maxillary left central incisor as abutments. Gingival swelling with accompanying discomfort had developed on the labial aspect of the left central incisor abutment (Figure 1), and the radiographic image suggested vertical root fracture (Figure 2). Subsequent extraction of the left central incisor confirmed this diagnosis.

A 5-mm x 11.5-mm dental implant (ETIII SA [no-mount], Hiossen, hiossen.com) was placed immediately in the socket with no grafting (Figure 3) as in the protocol described by Crespi et al.⁶ A 5-mm x 2-mm stock transfer abutment (Hiossen) was secured to the implant (Figure 4), and an acrylic four-unit provisional bridge prosthesis (with the maxillary right and left natural lateral incisors as terminal abutments) was cemented with a light application of a mixture of Durelon^™ luting cement (3M ESPE, 3m.com) and Vaseline^® petroleum jelly (Unilever, vaseline.com) on the natural abutments only. Tooth No. 10 was prepared for a full-crown restoration.

No attempt was made to lessen the normal incisal contact and function of this provisional prosthesis, congruent with the aforementioned Crespi study.⁶ Figure 5 shows the labial aspect of the provisional restoration/dental implant interface at 1 week postoperative, with a good early gingival healing response evident.

At approximately 6 weeks postoperative the provisional bridge was removed to evaluate the healing response (Figure 6). The implant was cleansed with 2% chlorhexidine, and the provisional prosthesis was recemented with a light coating of Durelon/Vaseline mixture on all three abutments. The emergence profile of the extracted tooth had changed rather profoundly from a somewhat triangular shape, as seen in Figure 4, to conform to the rounded emergence profile of the dental implant transfer abutment, as seen in Figure 6.

At approximately 10 weeks postoperative the provisional restoration was removed for the impression scanning procedure. The transfer abutment was removed (Figure 7), and scans with and without a scan body were made, according to the sequence required and prompted by the scanner software (Figure 8 through Figure 10). The ovate pontic receptor site for the upper right central incisor was surgically enhanced prior to the scan.⁷ The dental laboratory (Natural Esthetics Dental Lab, naturalestheticslab.com) chose to generate a hard model from the STL file to fabricate the titanium custom abutment and the porcelain-fused-to-zirconia final fixed prosthesis (Figure 11 through Figure 13). The four-unit fixed prosthesis offered the patient a conservative design in that no additional dental implant fixtures were required, and the challenge of trying to achieve optimal soft-tissue esthetics between adjacent central incisor implants was avoided.^8,9

The final restoration prior to insertion/cementation is shown in Figure 14 and Figure 15. The custom abutment was placed and torqued to 40 Ncm, and the final restoration was cemented (RelyX^™ Luting Plus Cement, 3M ESPE) at approximately 6 months post implant placement. Only a light amount of cement was applied to the incisal portion of the intaglio surface of the dental implant retainer. Surface treatment of all units was performed by using 5 seconds of sandblasting with 5-micron aluminum oxide followed by surface application of priming agent (Z-Prime^™, BISCO, bisco.com) to prepare the zirconia surfaces for cementation.

The final restoration at 1 week post cementation is shown in Figure 16 and Figure 17. The patient's final smile esthetics at 2 weeks post cementation is shown in Figure 18.

Performing restorative dentistry in cases that involve teeth and dental implants is especially challenging in the patient's anterior esthetic zone. When the patient's smile reveals the interface between teeth, dental implants, dental restorations, and marginal gingival tissues, the clinician is obliged to strive to satisfy all parameters of health, biometrics, and function.¹⁰

The clinical situation presented here involved natural teeth adjacent to a pontic space and dental implant. In such a case the success of the final restoration is highly dependent on the practitioner having the ability to capture the individual aspects of tooth preparations, gingival form, and dental implant components, then relate these various aspects to each other, and, finally, accurately communicate this information to the dental laboratory.

The digital impression scanner used in this case was able to capture the necessary information from the patient's mouth and convey it electronically to the dental laboratory for fabrication of: a custom dental implant abutment and compatible zirconia-based ceramic crown (for the maxillary left central incisor implant), two zirconia-based ceramic crowns for natural teeth (for the maxillary right and left lateral incisors), and a zirconia-based ceramic pontic (for the maxillary right central incisor space). An accurate relationship among teeth and implants was also captured to allow the dental technician to connect all four crowns in a rigid four-piece fixed dental prosthesis.

While the author favors the CS 3600, other intraoral impression scanners are available for accomplishing these tasks,⁵ such as TRIOS^® (3Shape, 3shape.com), iTero^® Element (Align Technology, Inc, itero.com), 3M^™ True Definition Scanner (3M), and Planmeca Emerald^™ (Planmeca, planmeca.com).

This case report demonstrated the use of a contemporary intraoral impression scanner to capture tooth and soft-tissue positions for a four-unit fixed prosthesis and accompanying custom dental implant abutment. Controlled studies should be done before dentists can rely on the consistency of these procedures and to evaluate their efficiency and long-term efficacy. In the present case, no savings of operator or dental team time or patient chairtime were realized.

The author thanks Mr. John Aguirre of Carestream Dental for his technical assistance in preparing some of the images used in this article.

The author periodically receives product and technical support from Carestream Dental.

Joseph R. Greenberg, DMD
Clinical Professor of Restorative Dentistry, Kornberg School of Dentistry, Temple University, Philadelphia, Pennsylvania; Clinical Professor of Periodontics, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania; Private Practice, Villanova, Pennsylvania