Show Your Work: Anterior Aesthetic Veneers by Dr. Jonathan Ferencz

Bridging the digital–analog divide

by Dr. Jonathan Ferencz

The most critical aspect of any highly aesthetic anterior veneer case is controlling tooth reduction when prepping natural teeth. The goal is to remove a minimal amount of tooth structure to optimize aesthetics and function while still providing enough room for the restorative material and optimal bonding strength. Historically, reduction guide use has been advocated to assist in ensuring adequate reduction and preventing dentists from under- or overpreparing natural teeth.

In an analog workflow environment, the reduction guide fabrication would typically start with a traditional impression. The impression would then be sent to the laboratory with instructions for design and fabrication of a diagnostic wax-up for patient approval of the final treatment outcome. If the patient approves the wax-up of the final design, the laboratory creates a putty impression of the wax-up for the dentist to use as a reduction guide during the tooth preparation appointment. Should the patient demand changes to the wax-up smile design, the dentist would communicate those requests to the laboratory and a new diagnostic wax-up and reduction guide would be created, with associated increased costs, patient visits and chair time.

Digital technologies have significantly streamlined the workflow and eliminated the guesswork from the time-intensive analog processes with intraoral scanning technology and CAD smile design software. However, for veneer cases, the one missing link in today’s digital workflow is the creation and delivery of a reduction guide that exactly duplicates the digital plan.

The risks of working in the aesthetic zone without a reduction guide are either under- or overprepping the natural teeth. If the teeth are underprepared, the final veneers will be overcontoured to hide underlying stump shades. If the teeth are overprepared and enamel removed, the veneers’ bond strength may be significantly compromised. In either case, the provisionals and final restorations may not accurately match the digital diagnostic wax-up and the dentist risks patient rejection of the final restorations, resulting in a remake.

In this case of a 70-year-old patient, who presented with a diastema and failed composite restorations to correct excessive tooth wear and incisal chipping on teeth #8 and #9 (Figs. 1 and 2), we overcame the limitations of the digital workflow process and created a reduction guide that resulted in provisional and final veneer restorations that duplicated the approved digital smile design.

Fig. 1: Retracted view of the patient’s preexisting condition, showing considerable wear to teeth #8 and #9.

Fig. 2: Close-up of the teeth to be restored.

Aesthetic consultation

Intraoral scanners eliminate the need for physical impressions and the inaccuracies inherent in the handling and processing of impression material. The digital impression scan is uploaded to the dental laboratory and used in conjunction with CAD software to create a virtual digital diagnostic wax-up of the proposed case outcome.

In the case presented here, a retracted scan of the patient’s preoperative condition was taken (Fig. 3), sent to the laboratory and uploaded into CAD software (Fig. 4) for a diagnostic wax-up of the proposed final case outcome. Within minutes, the technician proposed two solutions for the patient to view on-screen. One solution proposed lengthening her teeth slightly and fabricating veneers that would close the diastema. The second solution proposed keeping the diastema and repairing her two anterior centrals with highly aesthetic veneers (Fig. 5). After viewing the virtual proposals, the patient expressed that she was less concerned by the aesthetics of her diastema. She declined the proposed design for tooth lengthening and diastema closure, and approved the proposed design for two single central veneers. The patient scheduled a clinical appointment one week later for tooth preparation and provisionalization.

Fig. 3: Scan of pretreatment condition uploaded to CAD software.

Fig. 4: The maxillary scan is articulated with the mandibular scan to allow the technician to do a digital design.

Fig. 5: Preview of virtual digital design shown to patient on-screen. The design is superimposed over the original condition to enable the patient to visualize the anticipated change in tooth contour.

Preliminary fabrications

Before her first scheduled clinical appointment, the laboratory used CAD/CAM technology to design the temporaries and the final restorations in exact accordance to the patient-approved 3D virtual diagnostic wax-up of the final case outcome.

A 3D-printed model of the approved smile design (Figs. 6 and 7) was used to produce an analog silicone putty reduction matrix chairside (Fig. 8). Although this currently is the only analog process in an otherwise digital workflow, I’m confident that future CAD software developments will address the need for a digitally driven 3D reduction guide. One solution would be a virtual 3D-printed reduction guide that is delivered with the 3D-printed diagnostic wax-up model. Another solution would be to design the intraoral scanner software with the ability to compare the preparation to the virtual diagnostic wax-up and identify areas that are underprepared.

Fig. 3: Scan of pretreatment condition uploaded to CAD software.

Fig. 4: The maxillary scan is articulated with the mandibular scan to allow the technician to do a digital design.

Fig. 5: Preview of virtual digital design shown to patient on-screen. The design is superimposed over the original condition to enable the patient to visualize the anticipated change in tooth contour.

First clinical appointment

The patient’s teeth were prepared using the reduction guide to ensure that tooth reduction replicated the digital treatment plan (Figs. 9 and 10). The prepared teeth were then scanned using an intraoral scanner (Fig. 11) and the scans were uploaded to the laboratory for final design of the provisionals and final restorations (Fig. 12).

While the patient waited, the laboratory milled the tooth-colored temporaries from polymethyl methacrylate (PMMA) on an Ivoclar Vivadent PrograMill PM7 mill. The PMMA veneers were delivered and tried in for patient approval. Once the patient approved the aesthetics and fit chairside, we recommended the provisionals be worn for at least a couple of days to test the fit and function before we move on to milling the final definitive veneers. When the patient calls approving the fit and function, we can confidently move forward with milling the final restorations using the same digital file used to fabricate the temporaries (Fig. 13). In this case, the final veneers were milled from IPS E.max CAD on our PrograMill One mill by Ivoclar Vivadent, which is well suited for producing thin margins and thin 0.5mm monolithic veneers. The final veneers are monolithic with no cutback, thus retaining the material’s 500MPa strength.

Fig. 9: Teeth #8 and 9 prepared for ceramic veneers.

Fig. 10: PVS reduction guide positioned over the reduced teeth to check the clearance between the guide and the preparations.

Fig. 11: Intraoral scan of the prepared teeth, #8 and #9.

Fig 12: The pretreatment digital design brought back onto the prepared teeth to create the design of the final restorations.

Fig. 13: The final CAD design is readied to send to the CAM mill.

Second clinical appointment

At the second clinical appointment, the provisionals were removed, the preparations cleaned, and the final veneers seated using Variolink Esthetic dual-cure composite luting cement (Figs. 14 and 15). Patient satisfaction was high because no adjustments were needed, and the final restorations precisely duplicated the proposed and approved provisional restorations.

Fig. 14: The final restorations cemented with Variolink Esthetic.

Fig. 15: Close-up of the cemented veneers.

Conclusion

Digital technologies eliminate the guesswork and inherent inaccuracies of analog processes and improve clinical workflows and efficiencies. From approval of the virtual treatment design and milled provisionals to delivery and seating of the final veneers, the precision of CAD/CAM technologies ensures exact duplication from start to finish. This level of predictability reduces clinical stress and anxiety, eliminates remakes and increases practice profitability.