Lingual orthodontics with customized functional appliance

Investigations

Extra-oral and intra-oral photographs, study models, lateral cephalometric radiograph, panoramic radiograph, functional examination and video recording of the patient were conducted. She had an atypical swallowing pattern, the mandible moved upwards and backwards on closure, and there was 4 mm of incisal exposure at rest and 100% incisor exposure during smiling.

Diagnostic focus and assessment

Study model analyses confirmed the clinical findings with the mandibular midline shifted 2 mm towards the patient's right side. Cephalometric analyses revealed a Class II skeletal relationship (ANB = 7°), maxillary prognathism (SNA = 86°) and an orthognathic mandibule (SNB = 79°) in relation to the anterior cranial base. Both maxillary and mandibular incisors were protruded in relation to their alveolar base (Table 1). The case was diagnosed as an Angle's Class II division l malocclusion on a Class II skeletal base attributed to a prognathic maxilla and an orthognathic mandible with a horizontal growth pattern associated with proclined upper and lower incisors and protrusive upper lips.

Therapeutic focus and treatment

The main goals of the treatment were to correct the deep bite, to rotate the mandible clockwise to open the bite, retract the maxillary anterior teeth to correct the protrusion, retract the proclined mandibular incisors and eliminate the functional retrusion of the mandible. The patient was concerned about aesthetics and was apprehensive about the visibility of brackets. The patient and her parents were also cautious regarding invasive procedures like implant-assisted orthodontics and orthognathic surgery. The patient insisted on ‘invisible’ fixed orthodontic therapy, to hide the presence of the device completely. It was decided to avoid extractions and mini implants for the patient and to treat with lingual orthodontics and a customized functional appliance to eliminate lip trap and functional retrusion.

The decision taken by young adults to commit themselves to orthodontic treatment is a more complex issue than for the younger age groups, as they have the demands of their work and broader social needs to consider. With increasing number of adult patients seeking orthodontic treatment,¹ lingual orthodontics has become the ‘aesthetic’ solution for meeting the needs of these patients.² The 7th generation lingual brackets are edgewise brackets specifically designed for the lingual surface of the teeth.³ The maxillary anterior brackets have a built-in bite plane which helps minimize accidental debonding from the lower incisors. The bite plane effect also allows efficient bite opening in deep bite cases. It is difficult to visualize and accurately position the lingual brackets if they are directly bonded. Indirect bonding is therefore the standard in lingual orthodontics and the CLASS (Custom Lingual Appliance Set-up Service) system was employed for this patient. A full archwire of 0.016” Copper Nickel Titanium (Cu-NiTi) followed by 0.017” x 0.017” Cu-NiTi was used for alignment of the teeth. Torque establishment of the anterior teeth is necessary prior to en mass retraction, 0.017” x 0. 025” TMA archwires were used for torque levelling. Sliding mechanics was used for closure of the space (Figure 2). Compensating curves and gable bends were placed in the archwires to counteract the bowing effects. In the detailing stage, 0.016” TMA archwire was used.

A functional appliance can be defined as a removable or fixed appliance which changes the position of the mandible so as to transmit forces generated by the stretching of the muscles, fascia and/or periosteum, through the acrylic and wirework, to the dentition and underlying skeletal structures, and favourably changes the soft tissue environment.⁴ Deciding which functional appliance to use can be difficult with lingual orthodontics. It was therefore decided to follow the component approach advocated by Vig and Vig.⁵ The occlusal bite block of Clark's twin block was also incorporated⁶ (Figure 2). A construction bite with a sagittal advancement of 3 mm and vertical opening of 3 mm was recorded. The wire components included were a labial bow for the maxillary arch, which will provide a retrusive effect to the maxilla. Connecting wires between buccal shields and lip pads, as well as interconnecting wire between the lip pads, were also incorporated. Lip pads in the mandible, bilateral buccal shields and occlusal blocks holding the mandible in advanced position, along with the wire components, made up the customized functional appliance. The patient was instructed to wear the functional appliance for 2–4 hours for the first two weeks, followed by night-time wear for the next two weeks. Full-time wear was recommended after one month of acclimatization to the functional appliance.

Follow-up and outcome

Favourable clinical results were observed within 9 months (Figure 3). Bite opening was evident with reduction in overjet and improvement of the profile. The bite planes on the maxillary incisor brackets cause rapid bite opening, making the lingual appliance most effective in deep bite cases,^7,8 and this patient has certainly benefited from this. At the end of the treatment, functional occlusion was observed with normal overjet, overbite and adequate intercuspation, with Class I molar relation and Class I canine relation bilaterally, nearly coincident midlines, normal maxillary and mandibular incisor inclination (Figure 4). Vertical skeletal dysplasia with deep bite was eliminated and cephalometric measurements showed maxillary clockwise rotation and mandibular clockwise rotation, contributing to improved facial profile. Maxillary and mandibular incisor axial inclinations were corrected (Figures 5 and 6; Table 1). The patient was extremely satisfied with the treatment results.