Merging Clear Aligner Therapy With Digital Smile Design to Maximize Esthetics and Minimize Tooth Reduction

Ryan Tak On Tse, BDS

Ceramic veneers are highly esthetic restorations with predictable outcomes.^1-3 They have excellent success rates when bonded to enamel.^4-8 However, as the amount of tooth structure removed increases, typically the success rate of the restoration declines and the biomechanical risk rises. Digital smile design (DSD) protocols allow the clinician to plan the final position and shape of the teeth before any irreversible changes are made.⁹

Combined with the use of an esthetic pre-evaluative temporary, DSD provides a highly reliable clinical process to minimize the removal of tooth structure when ceramic veneers are being placed.^1,10-12 Once the smile is designed using DSD, a preoperative temporary restoration is made and placed in the mouth. Esthetics, phonetics, and function are then evaluated, and when these are acceptable to the patient and clinician the teeth are prepared through the temporary material, preventing unnecessary removal of tooth structure.

In situations where patients present with poorly positioned teeth, clear aligners (eg, Invisalign^®, Align Technology, invisalign.com) may be used to properly position the teeth based on the desired end result, allowing for an esthetic outcome without significant removal of tooth structure. This article describes how to merge DSD with clear aligner therapy so that the clinician can know where to position the teeth using orthodontic movement, enabling tooth structure removal to be minimized while allowing the desired esthetic design to be achieved. Patients often are motivated to accept clear aligner treatment as a means of accomplishing their esthetic goals while maintaining tooth structure integrity.

Clinical Case Overview

A 29-year-old woman presented for dental care, unhappy with the appearance of her smile. Intraoral examination revealed peg lateral incisors, teeth Nos. 7 and 10, with spaces between adjacent teeth; lower incisors angled to the patient's right and crowded; and cross-bite at Nos. 7 and 26 due to No. 26 being positioned labially (Figure 1).

The patient's medical history showed she was in good health with no contributory medical issues. Regarding the patient's dental history, her only concern was the appearance of her smile.

Diagnosis and Risk Assessment

Periodontal: Radiographic evaluation revealed no attachment loss or bone loss. Bleeding on probing was evident on the lingual side of the lower anterior teeth. The patient was diagnosed as American Academy of Periodontology (AAP) 1.
Risk: Low
Prognosis: Good

Biomechanical: The patient had no caries and a few small composite restorations.
Risk: Low
Prognosis: Good

Functional: Despite anterior misalignment, with cross-bite on Nos. 7 and 26, the patient had acceptable function. There was no obvious attrition. The upper anterior teeth had mild crowding.
Risk: Low
Prognosis: Good

Dentofacial: When smiling, the patient fully revealed the upper gingival contours. The incisal edges of teeth Nos. 8 and 9 were well-positioned. However, the midline tilted to the left side, and these teeth had discoloration in the gingival one third.
Risk: High
Prognosis: Poor

Treatment Plan

The treatment plan was to modify the patient's smile using veneers in a minimally invasive approach. The DSD and mock-up would be utilized to test-drive the treatment outcome. This would afford the patient the opportunity to not only give the smile a trial period but also to see the value of the aligner therapy before the veneer preparation. After the patient agreed to the clear aligner therapy, teeth Nos. 6 through 11 would be moved to the desired position and minimally prepared for the final veneers.

While alternative plans utilizing veneer treatment without clear aligner therapy were also presented to the patient, she chose the full treatment plan after being motivated by the mock-up and gaining an understanding of the treatment goal using the DSD.

Phase 1: DSD and Motivational Mockup

The standard DSD protocol requires four extraoral photographs to be taken: retracted view (Figure 1), smile view (Figure 2), lateral view, and 12 o'clock view (Figure 3).^13,14 The retracted and smile views are used to establish the dentofacial midline, proper incisal edge position, smile curve, and smile design. The 12 o'clock view provides a reference for the incisal edge position in relation to the wet-dry border of the lower lip. The lateral view (not shown) offers a reference for the incisor position and angulation.

Smile design begins by determining the upper incisal edge position, as proposed by Spear¹⁵ and Kois.¹⁶ Tooth size, tooth proportion, and gingival contours are then designed in sequential steps once a digital ruler is calibrated (Figure 4).

Next, the upper incisor position in relation to the patient's lower lip is determined, using the lateral smile view and 12 o'clock view (Figure 5) photographs. In this case, after the DSD was completed, teeth Nos. 7 through 10 were planned for the addition of 1 mm labially and incisally. The technician fabricated the wax-up according to the DSD, and a silicone index was then fabricated for the mock-up. Temporization material (Protemp^™, 3M ESPE, 3M.com) was injected into the silicone index and applied intraorally without any tooth preparation.

The patient was highly motivated by the mock-up and did not want it removed (Figure 6); however, she became aware that the esthetic lengthening on tooth No. 7 prevented her from closing her teeth together. This realization allowed the patient to understand the need to correct her cross-bite with the use of clear aligner therapy (Invisalign).

Phase 2: Merging the Software Treatment Plan With DSD

An intraoral scan (CEREC^®, Dentsply Sirona, dentsplysirona.com) was taken and sent to an Invisalign facility. Instruction was given to the technician, and the ClinCheck^® software (Align Technology) treatment plan model was prepared. Using Invisalign, the primary treatment objectives were to correct the anterior cross-bite, minimize removal of sound tooth structure, and create space bilaterally around the peg lateral incisors to accommodate ideal contour and angulation.

Currently, there is no software available to digitally combine DSD with Invisalign ClinCheck, so the images from each were superimposed using three reference lines marked on each photograph: the dental midline, a line between the highest points of the incisal surfaces of teeth Nos. 8 and 9, and a line between the cusp tips of teeth Nos. 6 and 11 (Figure 7 and Figure 8).¹³ The clinician then reoriented the software treatment plan to match these three lines and captured the view for Invisalign as a reference (Figure 9). This is a critical step because the technician must match the software model with the patient's face.

The next step was to confirm the software model by superimposing the pretreatment ClinCheck photograph to the DSD photograph (Figure 10). If the former does not match the latter, the technician must reorient the software model; otherwise, the teeth will move to undesirable positions.

Phase 3: Verify Software Model Result With DSD; Create Invisalign Plan

Once the ClinCheck photograph was matched with the DSD, the image of the predicted Invisalign result was then superimposed to the DSD photograph. This allowed the clinician to verify the ClinCheck result with the patient's face (Figure 11 and Figure 12). This merging procedure is necessary so that the tooth movement caused by Invisalign therapy may be facially driven.

From the occlusal view, 0.5 mm space was planned on the mesial surfaces of teeth Nos.7 and 10, and 0.2 mm space was planned on the distal aspects. With more mesial than distal space available, the restorations would be able to create a visually pleasing mesial angulation to the lateral incisors (Figure 13), whereas if the spaces were greater distally, the lateral incisors would be angled distally, generating an unsightly result. Teeth Nos. 8 and 9 were retracted by 1 mm to achieve ideal tooth position that would allow the restorations to be placed with minimal tooth structure removal (Figure 14 through Figure 16).

Phase 4: Clear Aligner Treatment

Fourteen aligners were used to complete the Invisalign treatment in 8 weeks (Figure 17 and Figure 18). A photobiomodulation device (OrthoPulse^®, Biolux Research, orthopulse.com) was utilized to accelerate movement of the teeth.^17,18 The patient's use of a dental monitoring application (Dental Monitoring, dental-monitoring.com) allowed tooth movement to be remotely monitored and aligners to be efficiently sequenced when movement was complete.

Phase 5: Final Restorations

New photographs were taken to update the DSD after completion of Invisalign treatment. Veneers were planned for teeth Nos. 7 through 10, and composite layering was planned as an additive strategy for tooth No. 6. The wax-up was fabricated and a "trial smile" was used to test-drive the new smile. The trial smile was also used as the esthetic pre-evaluative temporary and preparation guide for the final restorations.^1,10-12

The preparation margins were smoothed using an air scaler (SONICflex^®, KaVo Dental, kavousa.com). Then, with the use of a two-cord retraction technique, the preparations were scanned with an intraoral scanner (CEREC), and acrylic temporaries (Protemp) were fabricated using a stent created from the wax-up. The veneers were milled with the aid of the CEREC biocopy function based on the wax-up.

The final restorations were created using e.max^® HT ingot A1 shade (Ivoclar Vivadent, ivoclarvivadent.com) with ceramic layering. The veneers were cemented with a light-cured nanofilled composite resin (Filtek^™ Supreme Ultra, shade CT, 3M ESPE). The composite was preheated in a composite warmer prior to cementation. The final restorations are shown in Figure 19 and Figure 20.

Discussion

By merging clear aligner therapy with DSD, teeth can be "moved" digitally, providing directional control and quantification. For basic, non-complicated cases the three-line technique shown here is a simple and economical way to perform this merger. In the present case, symmetry and angulation of the peg laterals were able to be visualized in three dimensions, the cross-bite correction was planned and executed accurately, and minimal tooth structure was removed on the central incisors. As carefully as the DSD and Invisalign data were merged, margin for error still existed, which will be the case until the two technologies are truly integrated. The author looks forward to this in the future.

Conclusion

This case illustrated a method to systematically diagnose, plan, and stage treatment for a smile makeover. The use of DSD allowed the clinician to preoperatively plan various approaches to treatment and visualize the outcome of each. The merging of Invisalign and DSD enabled the clinician to move the teeth to ideal positions for veneer restorations and achieve the desired esthetic results using minimally invasive dentistry. The new veneers were in harmony with the face and lower lip, and the spaces were impeccably closed.

The additive approach used in this case minimized tooth preparation and also made the teeth more prominent in the patient's smile. The patient was satisfied with not only the excellent esthetics but also the minimal removal of tooth structure.

Acknowledgment

The author thanks Lamberto Villani of Oral Design, Dubai, UAE, for his laboratory assistance, cooperation, and excellent work on this case.

About the Author

Ryan Tak On Tse, BDS
Instructor, University of Southern California Esthetic Dentistry training program,Hong Kong and China; Private Practice specializing in Implant and Esthetic Dentistry, Hong Kong

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