Creating restorations that stand the test of time
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.
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.
Case 1’s 18-month follow-up
More than a year later, the same patient returned
for treatment on Tooth 25
Fig. 5: Preoperative view of the Class V defect on Tooth 25.
Fig. 6: Adding Omnichroma composite to the facial of #25 before light-curing.
Fig. 7: After light-curing.
Fig. 8: The initial contouring of the facial and the gingival margin was done with a flame-tip diamond bur.
Fig. 9: The facial surface was smoothed and evenly reduced with a coarse disc.
Fig. 10: A polishing cup was used to obtain a high polish.
Fig. 11: The completed restoration can be compared to the composite restorations done more than a year before on Teeth 23, 24 and 26.
Fig. 12: Smile view of the completed restorations on Teeth 23–26.
The second clinical case features a 55-year-old patient who also had several noncarious cervical defects on #11–13. Tooth 12 had a previously treated Class V composite that needed to be replaced. A history of bruxism was evident by the wear of the incisal edges of his teeth. The patient admitted to a reluctance to wear his night guard (Fig. 13). The patient was encouraged to wear the night guard to decrease the incisal wear as well as preventing the cervical erosion/abfraction lesions.
The teeth were anesthetized with 1.7ml (one carpule) of Lidocaine HCl 2% with 1:100,00 epinephrine. Packing cord (00 Ultrapak, Ultradent) was placed below the gingival margin of the teeth to provide retraction of the gingival tissue and some moisture control at the gingival tissue margin. Once the composite is cured, the cord also acts as a landmark to locate the gingival margin.
The facial margins on the teeth were beveled to increase the enamel bond and to help blend the color of the composite material seamlessly into the enamel of the tooth. The old restoration on #12 was completely removed to ensure the greatest bond to the tooth. A slow-speed round bur was then used to remove the surface dentin layer from #11 and #13. The teeth were then acid-etched, rinsed and dried before the bonding agent (Bond Force, Tokuyama Dental) was applied to all three teeth and light-cured. Omnichroma was applied in a single layer one tooth at a time and evenly spread out with a thin IPC sculpted, taking time to make sure the gingival margin is sealed. A #3 brush is helpful to evenly spread out the composite; there is no need to rush because the composite material is very sculptable and holds its shape. Next, the composite was light-cured (Fig. 14).
As with the first clinical case, a flame tip diamond bur on a high-speed handpiece was used to contour the gingival margin area. If there is a large excess of composite material, then the diamond bur can be used to reduce the composite close to the final contour. The final contour is best done with a thin, coarse disc (e.g., Soflex-XT, 3M) to achieve a smooth and uniform contour (Fig. 15). Once this contour has been achieved, a higher polish can be accomplished with a medium and then a fine rubber cup polisher (e.g., Blue & Pink Flexicups, Cosmedent, Fig. 16). To achieve an even higher polish, use a Jiffy brush or a felt buff wheel (FlexiBuff, Cosmedent). If there is still an over-contoured gingival margin, a #12 Bard Parker scalpel can also be used to trim the excess composite (Fig. 17, demonstrated here on a Typodont). A high polish is always desirable, but it is more important to achieve an even and smooth surface with a nicely sealed gingival margin. Fig. 18 shows an immediate postprocedure result; Fig. 19 was taken after 11 months.
Postoperative photos taken at 8-, 10- and 12-month follow-up appointments show that these restorations can hold polish and color. For direct veneers and large Class IV restorations with a high polish, it is advised to have the hygienist either skip these surfaces when using a coarse prophy paste or use fine polishing paste.