Class II malocclusion treatment with a customized dual force distalizer

Intraoral distalizers associated with skeletal anchorage provide the major benefit of promoting molar distalization with minimum anchorage loss and patient cooperation. This case report presents the treatment of a 17-year-old female with Class II Division 2 malocclusion, maxillary dentoalveolar protrusion, mild mandibular retrusion, increased overjet, deepbite, and lip incompetence. The treatment plan involved initial maxillary molar distalization with a customized version of the skeletally anchored dual force distalizer (DFD). The customized DFD used smaller mini-implants and included a fixed anterior biteplane. The device applied simultaneous forces from the buccal and palatal sides directly to the molars using nickel-titanium coil springs and allowed orthodontic mechanics in the mandibular teeth. An overcorrected Class I molar relationship was obtained after 6 months. After the distalization phase, retraction mechanics began with retraction loops and using a modified transpalatal bar reinforced with the mini-implants as anchorage. Moreover, the finishing phase was performed with multiloop edgewise archwires and intermaxillary elastics to enable an individualized control of each tooth. Total treatment time comprised 2 years 4 months, and significant improvements regarding the facial and occlusal perspectives were noticed. Similarly, these favorable changes remained stable during the 2-year follow-up period. The customized version of the skeletally anchored DFD followed by fixed appliances showed effectiveness and stability in Class II malocclusion treatment.

Highlights

  • Intraoral distalization is a viable alternative for Class II malocclusion treatment.

  • In this patient, molar distalization was performed with the dual force distalizer anchored in 2 mini-implants.

  • The distalizer applied simultaneous forces from the buccal and palatal sides directly to the molars.

  • The skeletally anchored dual force distalizer showed effectiveness and stability in Class II malocclusion treatment.

Nonextraction protocols for Class II malocclusion treatment in patients without or with a small residual growth usually include maxillary molar distalization and/or Class II elastics. However, patient cooperation remains the most important parameter to obtain successful results. ,

Therefore, the use of compliance-free protocols with fixed functional appliances or intraoral distalizers has been increasing because they significantly reduce the need for patient cooperation, allowing more predictable results. , In patients in which the Class II malocclusion is predominantly dentoalveolar and the mild skeletal impact is not the main complaint, intraoral distalizers can be considered as a treatment alternative. , ,

Despite their effectiveness in obtaining maxillary molar distalization, the use of conventional distalizers is controversial because it is related to undesirable effects such as premolars mesialization, anterior anchorage loss, and distal tipping. , To overcome some of these side effects, intraoral distalizers have been associated with mini-implants. , ,

Various protocols for maxillary molar distalization associated with mini-implants have been reported. In general, they include buccal or palatal mini-implants. Mini-implants could be used as direct or indirect anchorage, and the distalization force could be applied by the buccal or the palatal sides. , When used as an indirect anchorage, some anchorage loss of premolars has been reported. , , , , Furthermore, a smaller amount of distal tipping has been described after molar distalization with palatal appliances because they applied the force closer to the center of resistance of the molar. , ,

Some molar rotation is expected if the distalization force is applied only by 1 side (buccal or palatal). , , , To decrease the molar rotational effect, the distalization force should be applied simultaneously from the buccal and palatal sides. , , The skeletally anchored dual force distalizer (DFD) is characterized by the application of a distalizing force from both sides and includes the use of 2 palatal mini-implants associated with a Nance button as anchorage. Greater bodily tooth movement with minimal rotational and angulation effects has been described after maxillary molar distalization with this appliance. Orthodontic mechanics on the mandibular teeth could be performed during the distalization phase. Then, some adaptations to the original appliance design may be performed depending on each patient’s need.

Thus, this case report presents a compliance-free alternative for Class II malocclusion treatment with a customized version of the skeletally anchored DFD associated with fixed appliances.

Diagnosis and etiology

A 17-year-old female patient attended the orthodontic clinic of the School of Dentistry, Universidad Nacional Mayor de San Marcos, Lima, Perú. The absence of incisors contact and smile dissatisfaction were her chief complaints.

The clinical examination showed a convex profile, horizontal growth pattern, increased buccal corridors on smiling, lip incompetence at rest, and subclinical facial asymmetry. Intraoral examination evidenced a Class II Division 2 malocclusion with one half of Class II and one quarter of Class II molar relationships on the right and left sides, respectively, , maxillary dentoalveolar protrusion, increased overjet, deepbite, mild maxillary crowding (1.5 mm), moderate mandibular anterior crowding (5.0 mm), Bolton discrepancy of the mandibular anterior teeth (excess tooth mass of 3.5 mm), dentoalveolar constriction at the premolar region in the maxillary and mandibular arches, mandibular dental midline deviation to the right, moderate curve of Spee, and moderate rotation and distoangulation of the mandibular right canine ( Figs 1 and 2 ).

Fig 1
Pretreatment facial and intraoral photographs.

Fig 2
Pretreatment digitized models.

Panoramic radiograph evaluation confirmed the moderate mesial angulation of the mandibular right canine root and showed agenesis of the mandibular right third molar ( Fig 3 ). The cephalometric examination showed a mild skeletal Class II sagittal relationship, horizontal mandibular plane angle, palatal inclination and retrusion of the maxillary incisors, increased overjet, deepbite, and a reduced nasolabial angle ( Fig 3 ; Table ). The temporomandibular joint showed no pathologic symptoms. In addition, she presented a noncontributory medical background and no sign of active periodontal disease.

Fig 3
Pretreatment radiographs and lateral cephalometric tracing.

Table
Cephalometric variables
Measurement Norm Pretreatment Postdistalization Posttreatment
SNA (°) 82.0 82.2 82.2 82.6
SNB (°) 80.0 75.7 75.7 75.9
ANB (°) 2.0 6.5 6.5 6.7
FMA (°) 25.0 22.9 22.9 23.7
SN-GoGn (°) 32.0 26.2 25.7 26.5
SN-U1 (°) 104.0 88.6 102.3 99.8
U1-NA (°) 22.0 6.5 18.3 17.2
U1-NA (mm) 4.0 1.7 3.0 0.5
U6-PTV (mm) 18.2 15.8 13.0 13.4
PP-U6 (mm) 24.7 19.9 18.9 19.2
IMPA (°) 90.0 99.7 103.1 107.9
L1-NB (°) 25.0 26.7 29.8 35.6
L1-NB (mm) 4.0 4.5 4.6 6.7
Nasolabial angle (°) 102.0 95.2 93.1 97.0
UL-E Line (mm) −4.0 0.5 0.8 0.2
LL-E Line (mm) −2.0 3.0 3.0 3.2

Treatment objectives

The primary orthodontic treatment objectives were to correct the Class II molar relationships, reduce the maxillary dentoalveolar protrusion, obtain adequate overjet and overbite, correct mandibular anterior crowding, improve mandibular dental midline deviation, obtain a functional occlusion, decrease the buccal corridor widths, and improve facial and smile esthetics.

Treatment alternatives

The following treatment options were considered: (1) maxillary first premolar extractions, (2) Class II elastics associated with fixed appliances, (3) fixed functional appliances associated with fixed appliances, (4) distalization of the maxillary molars with a skeletally anchored appliance (anchored to palatal mini-implants) followed by fixed appliances, and (5) distalization of the entire maxillary arch with extra alveolar mini-implants or miniplates on the infrazygomatic crest. All options included dentoalveolar posterior expansion for buccal corridor decrease and stripping of the mandibular anterior teeth for moderate crowding correction.

These treatment alternatives were discussed with the patient, and she preferred to avoid premolar extractions because of esthetic concerns during treatment, a long phase wearing elastics, and did not accept the use of fixed functional appliances. In addition, she refused the idea of using miniplates. Thus, the fourth option was chosen because of the greater stability reported for palatal mini-implants , and a short period of elastics.

Treatment progress

The treatment was performed in different phases: (1) leveling and alignment of the maxillary teeth, (2) bite opening with a palatal acrylic anterior plate associated with the leveling and alignment of mandibular canines, (3) maxillary molar distalization with the customized skeletally anchored DFD associated with leveling and alignment of the remaining mandibular teeth, (4) retraction of the maxillary anterior teeth, and (5) finishing.

Preadjusted MBT brackets, slot 0.022 × 0.028-in (Clarity metal-reinforced ceramic brackets; 3M Unitek, 3M Dental Products, Monrovia, Calif) were used. Brackets were firstly placed in the maxillary arch ( Fig 4 , A ). Leveling and alignment was achieved with 0.014-in, 0.016-in, 0.020-in, 0.017 × 0.025-in, and 0.019 × 0.025-in nickel-titanium (NiTi) archwires. Then, a 0.018 × 0.025-in stainless steel archwire was placed. An acrylic plate was used in the anterior region of the maxillary arch to open the bite and allow mechanics in the mandibular arch. Because of the severe root mesial angulation and rotation of the mandibular right canine, initial leveling and alignment included only bands on mandibular molars and brackets on the canines. Copper NiTi 0.016-in and 0.017 × 0.025-in were used ( Fig 4 , B ). During this phase, the extraction of third molars was decided because of their initial angulation and position.

Oct 30, 2021 | Posted by in Orthodontics | Comments Off on Class II malocclusion treatment with a customized dual force distalizer
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