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Shifting Smiles and Perspectives by Dr. Bhudsadee Ying Saenghirunvattana

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Shifting Smiles and Perspectives A non-surgical approach to cant correction using TADs

by Dr. Bhudsadee Ying Saenghirunvattana

The correction of asymmetric cases featuring a significant occlusal plane cant in adult patients can be challenging. Surgical intervention has traditionally been regarded as the ideal treatment plan, as it can effectively resolve skeletal discrepancies, decrease treatment duration and mitigate the adverse effects associated with conventional orthodontic mechanics. Nonetheless, not all patients are open to surgical options.

Historically, the management of occlusal plane canting has involved multiple mechanical approaches, such as the use of elastics and asymmetric archwire adjustments. Since miniscrews were introduced for skeletal anchorage, the envelope of discrepancy has expanded, and the array of camouflage treatment possibilities has broadened for these cases. With miniscrew application, orthodontists can selectively intrude or extrude one side or utilize a combination of both techniques to adjust the occlusal plane inclination.

This article presents a case study of an adult Class II patient with a significant occlusal plane cant, treated with a self-ligating metal appliance in conjunction with interradicular miniscrews and intermaxillary elastics.

Diagnosis
A 38-year-old female patient came with a chief complaint of an uneven smile and an uneven dentition. She had visited multiple practices, and most offices suggested orthognathic surgery, which she declined. Clinical examination revealed a right Class I canine and Class II molar and a left Class II canine and molar with 4 mm overjet. Her upper midline deviated to the right 3 mm with a significant occlusal canting to the left. She had orthodontic treatment 17 years previously and her upper right first premolar was extracted during that treatment (Fig. 1).
Shifting Smiles and Perspectives
Fig. 1: Pre-treatment composite.

There was minimal gingival display upon smiling. The patient was not confident in her smile display and could not perform a fully symmetrical smile until the final months of orthodontic treatment. A lateral cephalometric radiograph showed Class II skeletal relationship with high mandibular angle. A postero-anterior cephalometric radiograph showed a maxillary cant to the left. Frontal extraoral pictures showed a lip line cant, good facial symmetry and a minor chin deviation to the right (Figs. 2a-c).
Shifting Smiles and Perspectives
Fig.2a: Pre-treatment radiograph.
Shifting Smiles and Perspectives
Fig. 2b: Pre-treatment radiograph.
Shifting Smiles and Perspectives
Fig.2c: Pre-treatment radiograph.

With severe skeletal asymmetries, a PA radiograph or CBCT is recommended for the diagnosis and treatment plan. Orthognathic surgery is usually the ideal treatment option.

An interpupillary line is used as a reference to quantify the amount of lip cant and occlusal cant. This line is transferred from the original position to the occlusal plane to assess severity. Once the amount of occlusal canting is identified, it is important to determine which side to maintain and which side needs correction. The amount of gingival and incisal display serves as the reference for proper diagnosis (Fig. 3).
Shifting Smiles and Perspectives
Shifting Smiles and Perspectives
     Fig.3: Quantifying the lip cant and occlusal cant using interpupillary line as a reference.


Treatment plan
In this case, the plan was to extract UL4 first to shift the upper midline to match with the left, match with the facial midline, reduce overjet, create arch form symmetry and correct the Class II canine and molar relationship. Two miniscrews were used to correct the occlusal cant by intruding the upper left posterior segment. A 1.6-by-6 mm miniscrew was inserted interradicular between teeth UL2 and UL3 and a 1.8-by-8 mm miniscrew was inserted interradicular between teeth UL6 and UL7.

A self-ligating orthodontic appliance with 0.022-inch MBT prescription brackets was bonded to the upper and lower arches. The detailed treatment sequences are shown at the end of this article (Table 1). After four months, most of the dentition was leveled and aligned. Two TADs were inserted at that time to start occlusal cant correction in 0.019-by-0.025-inch NiTi archwires using a power chain from the miniscrew to the base archwire. The total intrusion time of the upper left posterior segment was approximately three months (Fig. 4).
Shifting Smiles and Perspectives
Fig. 4: Treatment progress from start to finish.

One common side effect of upper arch intrusion is the buccal tipping of the intruded dentition. To avoid this, light intrusion force was used in combination with a large rectangular NiTi archwire.

At the seventh appointment (seven months into treatment), the upper occlusal plane was leveled, with occlusal spaces between the upper and lower left dentition. Quarter inch, 4.5-ounce elastics were used from the lower arch to the upper TADs to help settle occlusion by extruding the lower left posterior segment without causing extrusion of the upper left teeth. This technique helps avoid unnecessary round-tripping.

Continued treatment
By the ninth appointment (10.5 months into treatment), the lower occlusal plane was also leveled, with good occlusion on both sides. The bite was closed, and no occlusal spaces were present at that time.

During the 10th appointment (12.5 months into treatment), a gingivectomy of teeth UL1 through UL6 was performed to create a symmetrical gingival and incisal display of the upper teeth. Please note that a gingivectomy is usually considered after the treatment is completed. However, in this scenario, the brackets were buried in the gingiva, causing difficulties in elastic placement. Therefore, a gingivectomy was considered at this period.

Over the next 10 months, space closure was performed along with maxillary midline correction. The miniscrew between UL6 and UL7 position was moved more gingivally to allow additional intrusion of UL6 through UL7 over another two-month period. After 22 months of orthodontic treatment, the occlusal cant was corrected along with upper midline correction. A Class I canine and Class II molar were achieved with good stability (Figs. 5 and 6).
Shifting Smiles and Perspectives
Fig. 5: Post-treatment composite.
Shifting Smiles and Perspectives
Fig. 6: Pre-treatment and post-treatment frontal extraoral photograph.

What would I do differently?
The upper left miniscrew between UL6 and UL7 should be placed more gingivally at the infrazygomatic position from the beginning to create more room for intrusion. The patient would also have enough room for better cleaning in the upper left posterior area.

The etiology of occlusal canting in this case is primarily skeletal. After the occlusal plane was leveled, aesthetic crown lengthening would have been a more effective option compared to a gingivectomy to create a symmetrical gingival line between the upper right and left sides. However, because of the cost and the more extensive nature of the surgery, the aesthetic crown lengthening procedure was denied.

During intrusion of the upper left posterior segment, 0.019-by-0.025-inch stainless steel archwires with palatal crown torque would better help prevent the side effects of intrusion. However, in this case report, the intrusion was successfully achieved using 0.019-by-0.025-inch NiTi archwires with light intrusion force.

Conclusion
Correcting severe occlusal canting can greatly improve a patient’s confidence and quality of life. With the introduction of miniscrews into orthodontics, the envelope of discrepancy has expanded, and we, as orthodontists, can correct malocclusion and improve smile aesthetics for our patients to a much greater extent.

Table 1: Orthodontic treatment sequence.
Appointment Number Appointment Intervals Treatment Details
1 Bonding appliance. U/LAW 0.016” NiTi
Refer for UL4 extraction
2 6 weeks UAW 0.018” SS with light powerchain UL3-UL8
LAW 0.018”x0.025” CuNiTi
3 2 weeks U/LAW 0.018”x0.025” CuNiTi with light powerchain UL3-UL8
4 8 weeks U/LAW 0.019”x0.025” NiTi
Insert 2 TADs between UL2-UL3, UL6-UL7
Powerchain from archwire to TAD for intrusion
5 4 weeks UAW 0.019”x0.025” NiTi
LAW 0.017”x0.025” SS
Powerchain from archwire to TAD for intrusion
6 4 weeks UAW 0.019”x0.025” NiTi, PC U6-6
LAW 0.018”x0.025” SS
Powerchain from archwire to TAD for intrusion
7 4 weeks Same AW, PC U7-7, L6-6
Powerchain from archwire to TAD for stabilization
Elastic use from lower teeth to upper TADs
8 6 weeks U/LAW 0.018”x0.025” SS, PC U/L7-7
Powerchain from archwire to TAD for stabilization
Elastic use from lower teeth to upper TADs
9 8 weeks Same AW, PC U/L7-7
Powerchain from archwire to TAD for stabilization
Elastic use for midline correction
10 4 weeks Same AW, PC U7-7
Gingivectomy UL1-UL6 to increase teeth display
11 6 weeks UAW 0.018”x0.025” SS, PC U6-6
LAW 0.016”x0.022” SS
TAD between UL6-UL7 was moved more gingival to the IZC position to allow more intrusion of upper left posterior teeth
Powerchain from archwire to TAD for intrusion
12 8 weeks Reposition of brackets
U/LAW 0.018”x0.025” NiTi
13 8 weeks U/LAW 0.017”x0.025” SS, PC U/L7-7
Settle occlusion
14 6 weeks Same AW, finishing stage
15 4 weeks Same AW, finishing stage
16 6 weeks Debond. Clear retainer
Author Bio
Dr. Bhudsadee-Ying-Saenghirunvattana Dr. Bhudsadee Ying Saenghirunvattana is the owner of Smile Hub dental clinic in Bangkok, Thailand, and a lecturer of orthodontics at the Walailak University International College of Dentistry. Saenghirunvattana graduated as valedictorian and with first-class honors from the Faculty of Dentistry at Chulalongkorn University, Thailand. She obtained a master’s degree in orthodontics and a fellowship in cleft lip and palate from Saint Louis University, and she is an American board-certified orthodontist. Saenghirunvattana has been a speaker at many local and international conferences, including the upcoming 2025 AAO annual conference. Her interests focus on treating complex cases with simplified orthodontic techniques such as miniscrew, self-ligating appliance, clear aligner and early treatment.


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