Conservative Midline Correction

Minimal tooth reduction to correct a midline cant

Courtney Lavigne, DMD, FAGD

Today, cosmetic dentistry requires conservative approaches and thinking beyond traditional porcelain veneer preparations to achieve patients’ esthetic goals in a responsible manner.

A midline cant is a prominent esthetic concern, even to the layperson. While a midline shift is not recognizable to dental professionals or the layperson until it is quite significant, even the slightest midline cant is easily detectable.

A midline cant correction often requires restorations on multiple teeth. When one or both of the teeth affected by the cant are in otherwise healthy condition without additional esthetic concerns, more conservative approaches than traditional porcelain veneers should be considered. Esthetic composite bonding is one option. When porcelain is the material of choice, a non-prep or minimal-prep “chip” veneer is a valid option and should be considered.

Case Presentation

A 34-year-old woman presented to our office in good dental health, having seen a dentist for routine cleanings and examinations every 6 months throughout her life. She came to our office with a chief complaint of poor esthetics of teeth Nos. 8 and 9. The patient didn’t like the poor esthetics of the composite, the canted midline, or the tooth size discrepancy between the two teeth (Figure 1). Her goals were to have symmetrical, natural-looking front teeth that matched the rest of her smile. She wanted to fix the midline, the shade, and the shape. The patient was frustrated with how many times she had replaced the bonding on tooth No. 8 without improved results, and desired porcelain veneers based on her own research.

Diagnosis and Treatment Plan

The patient desired a porcelain veneer to fix the unesthetic bonding on tooth No. 8. We discussed possible treatment options, including redoing the composite bonding on tooth No. 8, as well as composite bonding on tooth No. 9 to address the cant. We also discussed porcelain options; because of the patient’s history with composite replacement on tooth No. 8, she wanted to move forward with porcelain veneers. While porcelain could achieve the cosmetic result she was looking for, tooth No. 9 was a non-restored tooth in very good condition. A veneer preparation seemed aggressive, and because the patient was comfortable with porcelain moving forward, a chip non-prep veneer on tooth No. 9 and a porcelain veneer on tooth No. 8 were proposed. After showing the patient several before and after photo examples of similar treatment, we were both comfortable moving forward with a porcelain veneer to replace the composite bonding on tooth No. 8, and a porcelain non-prep chip veneer to correct the canted midline (Figure 2).

Treatment Description Prior to preparation

The patient’s initial appointment involved intra- and extraoral photographs and diagnostic alginate impressions. From these impressions, we made two sets of models. One set was used for a diagnostic wax-up to establish the proposed shape and size of the teeth for the final restorations. The second set of models was used to create a preparation guide. From the diagnostic wax-up, three putty matrices were established. One matrix was used for temporization, one was used for an incisal edge guide, and one was used as a reduction guide. Prior to the patient’s preparation appointment, she completed 3 weeks of at-home whitening with KöR Whitening (www.korwhitening.com) custom trays. The patient was satisfied with the results prior to in-office whitening and opted to move forward with treatment. After 3 weeks of shade stabilization, we had the patient return for shade analysis. The shade was taken using shade guides and photography.

Preparation

The preparation appointment began with administration of one cartridge of 2% Xylocaine (DENTSPLY Pharmaceutical, www.dentsply.com) 1:100,000 epinephrine. An OptraGate (Ivoclar Vivadent, www.ivoclarvivadent.com) was used during preparation with a plastic tongue retractor. Tooth No. 8 was prepared with Brasseler (https://brasselerusa.com) medium-coarseness diamonds, followed by fine diamonds. The preparation was finished with greenies. Tooth No. 9 was not prepared, but a series of medium to fine coarseness interproximal finishing strips were used to reduce any surface abnormalities and smooth the incisal edge while eliminating the sharp corner. Tooth No. 9 was finished with white stones. The matrices were used to confirm the incisal edge position of the preparation and that sufficient reduction had been achieved.

Impression and Temporization

For the final impression, retraction cords in size 0 and 00 were soaked in astringent and placed. The final impression was taken with Impregum™ Polyether (3M Oral Care, www.3m.com) in a full-arch tray. A bite registration was taken with Occlufast Zhermack (http://en.zhermack.com).

Photographs were taken of the prepared teeth and communicated with the lab to verify the stump shade. Stump shade tabs were used.

The putty matrix was used to fabricate the temporaries. The matrix was loaded with Luxatemp (DMG America, www.dmg-america.com) in shade BL, and the temporaries were left connected because of the fragility of tooth No. 9. The temporaries were finished, polished, and cemented with clear TempBond™ (Kerr Dental, www.kerrdental.com).

Laboratory Communication

The laboratory was instructed to fabricate two feldspathic veneers—one chip veneer on unprepared tooth No. 9 and a porcelain veneer on tooth No. 8. The final shade selected was 1M1 from a bleaching shade guide. The lab was given preoperative photographs as well as photos of the prepared teeth, two sets of upper and lower impressions (the uppers were of the prepared teeth), an impression of the provisionals, and written details of the required outcome and the patient’s goals. Figure 3 and Figure 4 show the porcelain restorations.

Try-in

There were two try-in appointments prior to final cementation. The initial try-in appointment resulted in the restorations being sent back to the lab for hue adjustment of tooth No. 8. The initial veneer appeared too pink intraorally. The second try-in appointment was successful, and the patient felt her goals had been met (Figure 5 and Figure 6). Because of visual fatigue from evaluating the restorations in several different lighting scenarios, the patient returned for a separate appointment for final cementation.

Cementation

At the final cementation appointment, the patient was anesthetized with 2% Xylocaine 1:100,000 epinephrine. The teeth were isolated with a rubber dam. The temporaries were easily removed with a scaler. The teeth were lightly pumiced with NADA prophylaxis paste and we placed a retraction cord in size 0 soaked in Astringedent (Ultradent, www.ultradent.com).

The restorations were treated with hydrofluoric acid prior to being silanated with Kerr silane primer.

Tooth No. 9 was etched with 35% phosphoric acid for 15 seconds. Veneer No. 9 was delivered first. We etched the surface of tooth No. 9 with ExciTE® F (Ivoclar Vivadent) and light-cured. The veneer was then seated with a thin line of Variolink Veneer cement (Ivoclar Vivadent) in shade 0. While stabilizing the veneer with a plastic instrument, a microbrush was used to initially remove the excess, and the veneer was tack-cured and the remaining excess removed. The veneer was then light-cured on each side for 40 seconds while spraying air to keep the tooth cool.

Tooth No. 8 was then etched with 35% phosphoric acid for 15 seconds. We used Optibond™ XTR primer with Optibond XTR adhesive (Kerr Dental) and light-cured. Veneer No. 8 was seated with Kerr NX3 cement (shade-white) loaded around the margins. The veneer was held in place and tack-cured. Excess was removed and the veneer was then light-cured for 40 seconds from each side while spraying air to keep the tooth cool. Two different cements were used because the amount of reduction on the incisal edge of tooth No. 8 was slightly greater than 2 mm as a result of the composite/tooth junction from the initial fracture, and a dual-cure cement was indicated. The retraction cords were then removed, and the interproximal contacts, occlusion, and margins were verified.

Finishing and Polishing

Finishing was necessary after delivering tooth No. 9. The incisal edge was finished with a fine diamond from Brasseler. The veneer was then polished with porcelain finishing burs to fully blend the vanishing finish line. A goat-haired brush on the slow speed handpiece was used with Diamante polishing paste (Olivier Tric, www.oliviertric.com).

Discussion

We were able to accomplish all of the goals of the case with a minimally invasive approach. Tooth No. 9 was polished and it was confirmed that there were no undercuts. As a result, preparation was not necessary for fabrication of the final restoration. This is an unconventional approach to porcelain, but with proper case selection, a highly effective one. Having a highly skilled ceramist with knowledge and experience with feldspathic chip veneers is imperative.

Conclusion

This accreditation case type II was about case selection and laboratory communication. Though using two conventional veneers may have been an easier route to accomplish the desired outcome, it would have been far more aggressive. We were able to accomplish a highly esthetic outcome and meet the patient’s desires while only removing minimal additional tooth structure on the preparation of tooth No. 8. In this particular case, the patient began with a nice smile and normal gingival zeniths and nice symmetry throughout her dentition with the exception of teeth Nos. 8 and 9. At the end of the case we had conservatively improved the color/value, shape, and esthetics of these teeth while correcting the canted midline.

References

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About the Author

Courtney Lavigne, DMD, FAGD
New England Academy of Cosmetic Dentistry
Affiliates Committee of the American Academy of Cosmetic Dentistry
Private Practice
Wayland, Massachusetts