Asian patients tend to have a higher percentage of extraction cases due to lateral profiles and dentoalveolar patterns. Patients look for beautiful smiles – not just straight teeth. Esthetic orthodontic treatment with clear aligners aspire to help patients achieve this goal. But despite research and technological advancements in artificial intelligence and aligner software technology, extraction cases using aligners remain unpredictable. There are limitations in controlling teeth movement in three dimensions.
The 3M™ Incognito™ Appliance System is a popular customized individually fabricated lingual orthodontic appliance. It has several advantages, including an easy rebonding protocol with individually fitted bracket bases. It minimizes wire bending with pre-fabricated arch wires and improves incisors’ torque control. Incognito Appliances are suitable for treatment of all malocclusions for all ages. Of all the invisible orthodontic appliances, lingual fixed appliances rise above in terms of controlling teeth movements three dimensionally. An extraction case of a Chinese teenager is presented here.
Alex was a 14-year-old Chinese boy presenting with Class II Division 1 malocclusion on a skeletal Class I base and increased Lower Incisor-to-APog line. He had a convex profile. Intraorally, he had a Class I molar relationship on both sides, Class II canine relationship on left, midline shift and anterior crossbite. There was crowding in upper and lower arches, increased curve of Spee, and proclined incisors. The orthodontic treatment plan included extraction of upper first bicuspids and lower second bicuspids, then Incognito lingual fixed appliance treatment.
The patient’s chief complaints were malaligned upper and lower teeth which were “sticking out.” He had no apparent facial asymmetry; normal incisors showed at rest and he had normal lower facial height. He had a convex profile, incompetent lips and normal naso-labial angle. The lips are protrusive with upper and lower lips 3-4mm above the esthetic line. The temporomandibular joints were normal. Alex went to boarding school in the U.K. so he came to see me every 8-12 weeks.
Intraorally, all permanent teeth were present. There was mild crowding in upper arch and moderate crowding in lower arch. Class II division 1 incisor relationship with a severe increased overjet of 8mm, and the overbite was 4mm. Lower midline was 2mm to the right. Class I molar relationships were on both sides. Click here for Figure 1. Pre-treatment photographs: extra-oral
Figures 2-3. Pre-treatment photographs and radiograph
Full permanent dentition was present. No other obvious pathology was noted. Click here for Figure 4. Cephalometric tracing: pre-treatment.
The SNA and SNB values were both within the normal range. ANB value indicated Class I skeletal base. Maxillary and mandibular plane angles were within normal range. Lower facial height ratio and value were normal. Upper incisors and lower incisors’ angulations were proclined. Lower incisor to A-Pogonion line was increased at 7.5mm. The lips were above the norm with respect to Ricketts E-Plane.
Class II division 1 malocclusion on a skeletal Class I base. He had a convex profile with protrusive lips, but nasolabial angle was normal. Intraorally, he had a Class I molar relationship on both sides, midlines shift. There was crowding in both arches, increased curve of Spee, proclined upper and lower incisors.
Treatment plan and retention strategy
The objectives of the treatment included improving patient’s profile and lips competence, normalizing the overjet and overbite, alignment of teeth and arch form coordination. The treatment plan included extraction of upper first bicuspids and lower second bicuspids, then custom-made Incognito lingual fixed appliances with 0.028” X 0.022” vertical ribbon-arch self-retaining slots in lower canine to canine brackets, 0.022” X 0.028” horizontal-slot edgewise brackets for premolars to first molars, and lingual tubes for second molars.
The proposed retention strategy included fixed lingual retainers from canines-to-canines. The prognosis for stability is good as growth has almost ceased for the patient and can contribute to incisal relationship stability, as well as fixed retainer.
Treatment mechanics and issues encountered
1. Wire sequences:
2. Light Class II elastics from upper canines to lower first molars were worn at nighttime only for 12 months during space closures.
Alignment and levelling - 8 months
Space closures - 22 months (appointments were about a 12-week interval as the patient was studying abroad in a boarding school)
Finishing and detailing - 8 months
3. Patient went to study at a boarding school in England 14 months after the start of treatment.
4. We were only able to see him once every 3 to 4 months, and more regularly when he was back to Hong Kong for summer vacation.
5. Emergency contact information was given to the patient at the school area in case of orthodontic treatment emergency. There were no debonding of brackets or wire discomfort during his study. The only problem was the extension of the treatment which the patient and family understood if the source was the 12-week interval.
Figure 5. Mid-treatment photographs 014 NiTi wire
Figure 6. Mid-treatment photographs. 16x22 NiTi
Figure 7. Mid-treatment photographs. 16x24 SS extra torque 13-23
Figure 8. Mid-treatment photographs. 18.2x18.2 TMA
Figure 9. Mid-treatment photographs. .014 NiTi using the self-retaining slots
Figure 10. Mid-treatment photos. 16x22NiTi
Figure 11. Mid-treatment photos. 16x24 SS
Figure 12. Mid-treatment photos. 18.2 x 18.2 TMA
The panoramic radiograph shows that all permanent teeth except third molars were present. The wisdom teeth were extracted during the treatment due to pericoronitis.
All roots are reasonably parallel, and no root contacts were found. Root resorptions were found but less than 2mm. There was no pathology detected. Click to view additional Post Treatment Photographs
Cephalometric superimposition Overall superimposition of pre- and post-treatment cephalometric radiographs registered on anterior cranial base. (Melsen, 1974; Nelson, 1960)
Cephalometric tracing: superimposition of pre- and post-treatment
Figure 17. Cephalometric tracing: superimposition of pre- and post-treatment
Table 1. Cephalometric assessment
Figure 19. Post-treatment photographs: intra-oral
Figure 20. Post-treatment photographs: extra-oral
Figure 21. Post-treatment photographs: extra-oral
Mandibular growth was seen during the treatment which is normal as patient has not finished growth. Upper incisors have been retroclined and normalised, while lower incisors’ inclination has increased slightly. Overjet and overbite, Lower incisors to A-Pogonion line has been normalised. Vertical dimension has slightly decreased after the treatment.
Figure 22-23 Post-treatment photographs: intra-oral.
1. Proffit WR, Fields HW, Sarver DM. Contemporary orthodontics. St. Louis, Mo.: Mosby Elsevier; 2007.
MOrth, MOrthRCS (Edin), BDS, BSc, MBA, MRACDS (Ortho), AdvDipOrtho (HK), FCDSHK (Orthodontics), FHKAM (Dental Surgery)
Dr. Wilson Lee obtained his dental degree, Master of Orthodontics and specialist training from the University of Hong Kong (HKU). He was awarded the Gold Medal at the Conjoint Examination of the Membership in Orthodontics, Royal College of Surgeons of Edinburgh and the College of Dental Surgeons of Hong Kong. He is a Member in Orthodontics of the Royal Australasian College of Dental Surgeons and is one of the first orthodontists to use Incognito Lingual Appliance in Hong Kong, and is the first batch of Key Opinion Leader (KOL) of Incognito since 2010. He has been invited to speak in UK, USA, Japan, Singapore, Taiwan, Malaysia, Nepal, India, Indonesia, Cambodia, Nepal, Ukraine, as well as conducting Incognito certification courses. He has obtained the Titular Membership of ESLO in 2018. He is Honorary Clinical Assistant Professor of the postgraduate program in Orthodontics at The University of Hong Kong. His clinical interests include Incognito lingual appliance, non-surgical orthodontic treatment of borderline surgical cases with Temporary Anchorage Devices and Esthetics in Orthodontics.
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