This report describes the use of miniscrew-assisted customized lingual fixed appliances in a patient with severe skeletal Class II malocclusion. The patient was a 12-year-old Chinese girl with the chief complaint of protrusive lips and anterior teeth. Her diagnosis included a skeletal Class II relationship with maxillary protrusion, a backward-rotated mandible, a full Angle Class II molar relationship, and severe deep overjet and overbite. Four premolars were extracted, and miniscrew anchorage was placed in the maxillary posterior lingual segment to provide maximum anchorage and to achieve vertical control of the intruding molars. The customized lingual fixed appliance and temporary anchorage devices created a smooth and invisible treatment progress, resulting ultimately in a well-aligned dentition with ideal intercuspation and a dramatically improved profile. The 3-year follow-up examination indicated that the excellent treatment outcome was stable.
Highlights
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We report a skeletal Class II patient with severe deepbite and mandibular retrusion.
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Customized lingual appliance and miniscrews created smooth treatment progress.
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Final occlusion and inclination of incisors were better than predicted in the setup model.
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Obvious retraction, complete leveling, and vertical control were achieved.
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The significantly improved profile and solid occlusion are stable in the long term.
A skeletal Class II malocclusion with severe anterior deep overbite, excessive overjet, and high mandibular plane angle is among the most complex and difficult malocclusions to treat with an orthodontic strategy alone, because of the simultaneous existence of a skeletal discrepancy and the sagittal and vertical discrepancies in the dental arch. In Chinese people, a skeletal Class II malocclusion is often accompanied by a retrusive and clockwise-rotated mandible and micrognathism, leading to a convex facial profile and excessive lower facial height.
The fundamental and most effective treatment for a skeletal Class II malocclusion and a retrusive mandible is surgical relocation of the jaw bone. However, such invasive surgical methods are difficult for many families to accept because of the possible surgical risks and high costs. Moreover, this patient, a 12-year-old girl, could have faced a long wait before receiving such surgery.
The demand for esthetic orthodontic appliances and procedures has increased recently. Patients prefer lingual fixed appliances because of their invisibility. Customized lingual appliances have become more convenient for orthodontists because of the availability of preadjusted data and the predictability of the procedures, resulting in tooth movement toward the expected target. Moreover, a customized archwire can minimize the work of archwire bending for clinicians.
Like the labial technique, temporary miniscrew anchorage has played a role in expanding the applications of lingual appliances, particularly in patients who require maximum anchorage. Miniscrews facilitate anterior tooth retraction and the achievement of anchorage control to correct molar relationships. Miniscrews have also been reported to be useful for vertical control in high-angle patients. Intrusion of the molars enables counterclockwise rotation of the mandible; this aids in the control of the mandibular plane angle, improving the facial profile.
In this case report, we describe the use of a customized Incognito lingual appliance (Incognito, Bad Essen, Germany) and miniscrews with extraction of 4 premolars to resolve a skeletal Class II malocclusion, severe anterior deep overbite, excessive overjet, retrusive mandible, and high mandibular plane angle in an adolescent patient. The treatment plan involved primarily anterior retraction and posterior vertical control to improve the overall appearance, including the frontal and lateral views, using miniscrew-assisted nonsurgical correction with a customized lingual fixed appliance. See Supplemental Materials for a short video presentation about this study.
Diagnosis and etiology
The patient was a 12-year-old girl with the chief complaint of protrusive mouth and teeth. She denied any oral habit. Photographs taken before treatment showed a mild asymmetric mandible. A convex profile caused by mandibular retrognathism and maxillary protrusion was noted. The patient’s profile also showed increased lower facial height ( Fig 1 ). Intraoral photographs and the dental casts showed that the patient had a full Class II molar relationship, with severe deep overbite, excessive overjet, and mild crowding in the maxillary and mandibular dentitions ( Fig 2 ).
The lateral cephalometric analysis showed a skeletal Class II jaw relationship with mandibular retrusion (ANB, 7.9°) and a high mandibular plane angle (MP/SN, 40.58°). The maxillary incisors were proclined. Both the upper and lower lips were obviously in front of the E-line ( Fig 3 ). No symptom of a temporomandibular disorder was detected. This patient was diagnosed with Class II malocclusion with a skeletal Class II base, high mandibular plane angle, severe deep overbite, and excessive overjet.
Treatment alternatives
Three treatment options were considered for this patient. Because she was a deaf-mute dancer and her parents had high expectations regarding her facial esthetics, a comprehensive orthodontic treatment plan aiming to resolve the malocclusion and skeletal discrepancy was considered. The first option was 2-phase treatment with a functional appliance to move the mandible forward, correcting the mandibular retrusion. Twin-block and Herbst appliances were recommended. However, the patient had passed menarche, and a pretreatment cephalogram showed a degree of cervical vertebral maturation that most likely followed the pubertal growth spurt (stage 3), indicating that she had passed the best time for functional orthodontic treatment. Moreover, a Twin-block appliance is more suitable for patients with an average or low mandibular plane angle. The second option was a labial esthetic fixed appliance with extraction of the maxillary right and left first premolars and retraction of the maxillary anterior teeth to decrease overjet and establish a Class I canine relationship and a full Class II molar relationship, without Class II elastics or mandibular forward movement. Genioplasty might also be considered to improve the lower facial esthetics, if necessary. The third option was a miniscrew-assisted labial esthetic fixed appliance or lingual fixed appliance with extraction of the maxillary right and left first premolars and the mandibular right and left second premolars to retract the maxillary arch, correcting the deep overbite and excessive overjet, and establishing Class I canine and molar relationships. Considering the invisibility of the appliance, convenience, and high expectations for facial esthetics, the patient and her parents chose the third option with a lingual fixed appliance. The difficulty with this option was that the patient had a high mandibular plane angle with downward and backward rotation of the mandible. An extruding effect on the molars during leveling and the use of Class II elastics to correct the molar relationship were inevitable; however, extruded molars would increase the mandibular plane angle, worsening the patient’s profile. Thus, vertical control of the molars was necessary. Furthermore, precise control of the dentition is challenging in cases involving extractions and the use of lingual appliances. With the third option, the use of miniscrew anchorage was explained fully to the patient.
Treatment progress
The patient consented to the final treatment plan, and it was approved by the ethics committee of Peking University School and Hospital of Stomatology, Beijing, China. Her orthodontic treatment began in August 2008. Under local anesthesia, the maxillary first premolars and mandibular second premolars were extracted before bonding. A fully customized Incognito lingual appliance (Incognito) was placed using indirect bonding with a customized bonding tray on both arches.
Nickel-titanium archwires (0.014, 0.016, and 0.016 × 0.022 in) were placed for initial alignment and leveling of both arches ( Fig 4 , A ). When the 0.016 × 0.024-in stainless-steel archwire (without extra torque ordered) was placed in both arches, miniscrews (diameter, 1.5 mm; length, 9 mm; Zhongbang Medical Treatment Appliance, Xi’an, China) were inserted on the lingual side of the maxillary posterior segment under local infiltration anesthesia to provide skeletal anchorage.
Classic sliding mechanics with a 0.016 × 0.024-in stainless-steel archwire were used to close the spaces in both arches ( Fig 4 , B ). The anterior teeth were moved together with a straight archwire guided by the posterior brackets and tubes. All tiebacks in the maxillary arch were placed on the miniscrews to close the extraction spaces ( Fig 5 , A ), or the maxillary first molars were rigidly ligated to the miniscrews to prevent mesial movement and extrusion of the molars ( Fig 5 , B ). Class II elastics extending from the buccal buttons of the mandibular second molars to the gingival hooks of the maxillary canines were placed to adjust the molar and canine relationships. After the space-closing stage, final detailing was achieved with 0.0182 × 0.0182-in beta-titanium wires ( Fig 6 ). This full-sized wire provided good torque delivery and second-order expression. We achieved excellent intercuspation and occlusal relationship. The overall active treatment lasted 35 months. At the end of active treatment, the miniscrews were removed. After debonding of the lingual brackets, complete records were taken for treatment assessment ( Figs 7-10 ). Full-time wear of vacuum-formed retainers was suggested.
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