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Compensatory orthodontic treatment of skeletal Class III malocclusion with anterior crossbite

Introduction This case report describes the orthodontic treatment of an adult patient with skeletal Class III malocclusion and anterior crossbite. A short cranial base led to difficulties in establishing a cephalometric diagnosis. The patient's main complaint comprised esthetics of his smile and difficulties in mastication. Methods The patient did not have the maxillary first premolars and refused orthognathic surgery. Therefore, the treatment chosen was orthodontic camouflage and extraction of mandibular first premolars. For maxillary retraction, the vertical dimension was temporarily increased to avoid obstacles to orthodontic movement. Results At the end of the treatment, ideal overjet and overbite were achieved. Conclusion Examination eight years after orthodontic treatment revealed adequate clinical stability. This case report was submitted to the Brazilian Board of Orthodontics and Facial Orthopedics (BBO) as part of the requirements to become a BBO diplomate.

Compensatory orthodontic treatment of skeletal Class III malocclusion with anterior crossbite BBO Case Report introduction A 22-year and 10-month-old male patient arrived for his initial examination in good general health, complaining about his smile, particularly an anterior crossbite and maxillary diastemas, as well as difficulties associated with mastication. His dental history included the extraction of maxillary first premolars at the age of 12, carried out by a clinical dentist due to lack of adequate space for eruption of maxillary canines.  Facial examination revealed balanced characteristics: mesofacial pattern, symmetric features and adequate lip seal. However, a sagittal maxillomandibular deficiency was also noted. The patient had narrow nostrils, slightly ptotic nasal tip, paranasal deficiency, marked grooves at rest and when smiling, a short mentocervical line and an obtuse mentocervical angle, which confirmed the diagnosis. There was also a discrete predominance of maxillary deficiency (Fig 1).
The examination of temporomandibular joints revealed bilateral clicking at mandibular opening and closing, maximal mouth opening of 43 mm and an irregular path, but no pain. Intraoral clinical examination revealed adequate oral hygiene. Malocclusion was classifi ed as Angle Class I with anterior crossbite, absence of maxillary fi rst premolars, canines in full Class III relationship, anterior mandibular crowding, rotated maxillary central incisors and anterior diastemas (Figs 1 and 2). There were no diff erences between usual maximal intercuspation and centric relation. Radiographs showed that the patient had good dental and periodontal health and no endodontic problem or bone loss (Figs 3 and 4).   Compensatory orthodontic treatment of skeletal Class III malocclusion with anterior crossbite BBO Case Report Cephalometry revealed that the maxillomandibular relationship was apparently normal (ANB = 2°) and that a few angles were slightly greater than normal (Conv. = 5.5°; SNA = 86°; SNB = 84°) ( Fig 5). However, the ANB angle is known to be markedly aff ected by geometrical factors. 1 When the cranial base is short, maxillomandibular discrepancies cannot be evaluated on the sagittal plane using the ANB angle (Fig 6). Other cephalometric parameters (Wits = -8 mm; S-N = 71.5 mm) and particularly facial analysis should be used to elucidate this confounding factor. 2,3 When evaluated by cephalometry and having the cranial base as reference, maxillary and mandibular incisors showed buccal inclination and marked protrusion (1-NA = 25°, 1-NA = 7 mm) in mandibular teeth (1-NB = 34°, 1-NB = 11 mm). In contrast, the inclination of mandibular incisors in relation to the mandibular plane was good and met the Brazilian standards (IMPA = 94°). 2

treatment plan
The fi rst treatment plan presented to the patient was the orthodontic combined with orthognathic surgery, which the patient promptly refused. For this reason, an alternative plan was suggested. It included orthodontic camoufl age with orthodontic appliances in both arches and extraction of mandibular fi rst premolars. The patient had undergone extraction of maxillary fi rst premolars and, therefore, our aim was to achieve normal molar and canine occlusion. Mandibular extractions followed by retraction of anterior teeth should be supported by adequate anchorage control.
The dentist and the patient agreed on the following objectives for the treatment selected: preservation of maxillary and mandibular bones position; alignment and reduction in maxillary diastemas; alignment of mandibular teeth; normal occlusion, correction of negative overjet and functional occlusion; esthetic improvement aft er lower lip retraction; and achievement of a pleasant smile.
Treatment plan was divided into the following phases: modifi ed Nance lingual arch (away from mandibular incisors); fi xed orthodontic appliances in both arches using the straight-wire system and 0.022 x 0.028-in slots; extraction of mandibular fi rst premolars; tooth leveling and alignment with treatment progression Treatment progression was in accordance with the plan. Mandibular second molars were included in initial leveling to aggregate an anchorage unit for the retraction of incisors. Maxillary second molars were bonded and included in leveling during orthodontic finishing.
The vertical dimension had to be temporarily increased with glass-ionomer cement built-up on posterior teeth. This procedure was used for retraction of mandibular anterior teeth because anterior crossbite and marked overjet were obstacles to movement (Figs 7A, B and C). Spaces were closed by means of sliding mechanics (0.019 x 0.025-in wire) and hooks were soldered between canines and lateral incisors. Class III intermaxillary elastics (¼-in, medium force) were used to control anchorage together with the lingual arch which was removed after retraction of anterior teeth and closing of extraction spaces. No skeletal anchorage was used. Treatment was completed with 0.018-in archwires, elastic chains in both arches to retain interproximal contacts, and Class II intermaxillary elastics (5/6-in, medium force) to retain the movement achieved (Figs 7D, E and F). After orthodontic completion, intercuspation was good, and canine and molar occlusion relationships, as well as overjet, were normal (Fig 8, 9). Maxillary (2 x 2) and mandibular (4 x 4) V-looped braided bonded lingual archwires were placed for retention.   The final radiograph showed that root parallelism was good after space closure and that root size was preserved (Figs 10 and 11).
In the maxillary arch, diastemas were reduced, molars were slightly extruded, intercanine distance (35.5 mm) was preserved and intermolar distance was shortened (from 43.5 mm to 42.0 mm). A marked cephalometric effect was found in the mandibular arch with anterior retraction, intrusion and mesial movement of mandibular molars (Fig 12 and Table 1). However, intercanine (21.5 mm) and intermolar (33.0 mm) distances did not change.
There were no significant changes in the position of the maxilla or the mandible (Fig 13). Facial esthet-   ics improved due to less marked lower lip protrusion, confi rmed by reduction of 2.5 mm in the cephalometric variable that describes the lower lip (S line) (Fig 14 and Table 1). The relationship between the maxilla and the mandible showed good intercuspation and coordination, although sagittal skeletal discrepancy was camoufl aged by dental compensation. Overjet and overbite were fully corrected, and the criteria for ideal functional occlusion were met. The positive results, confi rmed by clinical stability eight years aft er treatment completion, were favored by the lack of remaining facial growth, the use of fi xed retention and patient's satisfactory occlusal relationship (Fig 15).

Final considerations
Cranial base abnormalities strongly affect the interpretation of cephalometric variables in this region, particularly SNA, SNB, ANB and convexity angle. Other cephalometric parameters, correction factors and, above all, facial analysis findings contributed to making the diagnosis and developing a treatment plan. In adults, Class III skeletal patterns may often be treated with either orthodontic camouflage or orthognathic surgery. 4,5 In the case reported here, the treatment chosen was orthodontic camouflage with extraction of mandibular first premolars. Treatment results were satisfactory, and the occlusal objectives were achieved. The final harmonious smile pleased the patient and improved his selfesteem and quality of life.