Angle Class III malocclusion, subdivision right, treated without extractions and with growth control

Fernandes, Sérgio Henrique Casarim

doi:10.1590/S2176-94512010000600017

Abstracts

Angle Class III malocclusion is characterized by anteroposterior dental and facial discrepancies usually accompanied by skeletal changes associated with a genetic component. Early, accurate diagnosis and appropriate treatment are of paramount importance to promote growth control and prevent relapse. This article reports the two-phase treatment of a female patient, aged 12 years, with an Angle Class III, subdivision right malocclusion with anterior crossbite in maximum intercuspation (MIC) and end-on bite in centric relation, further presenting with lack of maxillary space. The case was treated without extractions and with growth control. This case was presented to the Brazilian Board of Orthodontics and Facial Orthopedics (BBO) as representative of Category 1, i.e., Angle Class III malocclusion treated without tooth extractions, as part of the requirements for obtaining the BBO Diploma

Angle Class III; Maxillary protraction; Interceptive orthodontics

A Classe III de Angle é uma má oclusão caracterizada por discrepâncias anteroposteriores dentárias e faciais, normalmente acompanhadas por alterações esqueléticas, com componente genético associado. O diagnóstico precoce e correto e o tratamento adequado são de suma importância para promover o controle do crescimento e evitar recidivas. Este artigo relata o tratamento, executado em duas fases, de uma paciente do sexo feminino de 12 anos de idade, apresentando uma má oclusão de Classe III de Angle, subdivisão direita, com mordida cruzada anterior em máxima intercuspidação habitual (MIH) e topo em relação cêntrica (RC), apresentando, ainda, falta de espaço na maxila, que foi tratada sem exodontias e com controle de crescimento. Esse caso foi apresentado à Diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), representando a categoria 1, ou seja, uma má oclusão Classe III de Angle, tratada sem exodontias e com controle de crescimento, como parte dos requisitos para a obtenção do título de Diplomado pelo BBO

Classe III de Angle; Protração maxilar; Ortodontia interceptativa

BBO CASE REPORT

Angle Class III malocclusion, subdivision right, treated without extractions and with growth control^*

Sérgio Henrique Casarim Fernandes

M.Sc. and Specialist in Orthodontics and Facial Orthopedics, COP/PUC-Minas Gerais State, Brazil. Coordinator, Specialization Program in Orthodontics, Brazilian Dental Association (ABO), Juiz de Fora, Minas Gerais State, Brazil. Diplomate of the Brazilian Board of Orthodontics and Facial Orthopedics (BBO)

Contact address

ABSTRACT

Angle Class III malocclusion is characterized by anteroposterior dental and facial discrepancies usually accompanied by skeletal changes associated with a genetic component. Early, accurate diagnosis and appropriate treatment are of paramount importance to promote growth control and prevent relapse. This article reports the two-phase treatment of a female patient, aged 12 years, with an Angle Class III, subdivision right malocclusion with anterior crossbite in maximum intercuspation (MIC) and end-on bite in centric relation, further presenting with lack of maxillary space. The case was treated without extractions and with growth control. This case was presented to the Brazilian Board of Orthodontics and Facial Orthopedics (BBO) as representative of Category 1, i.e., Angle Class III malocclusion treated without tooth extractions, as part of the requirements for obtaining the BBO Diploma.

Keywords: Angle Class III. Maxillary protraction. Interceptive orthodontics.

HISTORY AND ETIOLOGY

The female Caucasian patient presented for orthodontic consultation at age 12, with good general health, reporting no history of serious illness and/or trauma. She had no sucking or postural habit and had normal swallowing and speech.

She was in the permanent dentition phase with second maxillary molars still missing. Menarche had occurred five months earlier, suggesting that the patient was in the deceleration phase of pubertal growth spurt. She had no relevant carious lesions and no periodontal problems. In centric relation (CR) she presented with an end-on bite in the anterior region, and maximum intercuspation (MIC), severe anterior crossbite (Figs 1, 2 and 3). In researching the family history it was found that the mother had an end-on dental relation in the anterior region. The patient's chief complaint was esthetics-related. According to her, she was greatly disturbed by the protrusion of her lower teeth.

DIAGNOSIS

The patient showed facial symmetry, a straight profile, proportional vertical thirds, lip competence and a predominantly nasal breathing pattern (Fig 1).

From a dental perspective, she presented,in CR, an Angle Class III malocclusion, right subdivision, end-on incisor relationship and, on the right side, bilateral posterior open bite, maxillary and mandibular crowding with rotations, lack of space for tooth 13 with slight impingement, permanence of tooth 53 and midline shift greater than 3.5 mm to the right (Figs 1, 2). When in MIC, the Angle Class III malocclusion worsened with severe anterior and right lateral crossbite, as well as deep overbite (Fig 3).

The analysis of periapical radiographs revealed the presence of all permanent teeth, in addition to tooth 53, and the early formation of third molars. No changes capable of compromising orthodontic treatment were found (Fig 4).

The dental pattern featured retroclined lower incisors (1-NB = 15.5º and IMPA = 84º), slightly protruding and inclined maxillary incisors (1-NA = 6.5 mm and 1-NB = 24), which was consistent with her Class III malocclusion (Table 1).

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Cephalograms in CR (Fig 5) exhibited a Class III skeletal pattern, especially due to maxillary retrusion (WITS = -7 mm; ANB = -2º, with SNA = 75º and SNB = 77º), with an increased lower facial third (SN-GoGn = 34.5º; FMA = 32º and Y Axis = 67). It is noteworthy that these values were influenced by the end-on relation of the incisors during projection in CR. The cephalometric measurements can be evaluated in Table 1.

TREATMENT GOALS

Since this patient was still growing, the key objective was to redirect mandibular growth, improving the relationship between the upper and lower lips. As regards the dental aspects, space was required for the correction of crowding, rotations and midline. The purpose was to maintain the inclination of maxillary incisors and enhance lower incisor inclination buccally, as well as achieve appropriate canine and molar relationships. From a skeletal standpoint, the aim was to reduce the anteroposterior discrepancy by maxillary protraction and redirection of mandibular growth with the purpose of enabling a more harmonious growth, expanding the upper arch and controlling the vertical direction of growth.

TREATMENT PLANNING

To attain the desired results, the patient and her parents were informed of the importance of compliance in wearing the appliances and the need to perform the treatment in two phases.

In the first phase, a removable "Skyhook" type appliance (600 g) would be used in conjunction with a Hyrax-type palatal expansion appliance with two daily activations to correct the crossbite. In addition to the expander, brackets would be bonded to the upper incisors (Roth prescription, 0.022x 0.028-in slot) to start the alignment and leveling phase, and if necessary, slightly protrude these teeth.

In the second phase, the expander would be removed and a chin cup prescribed for night use. The complete fixed orthodontic appliance would be set up to proceed with alignment and leveling using 0.012-in nickel-titanium (NiTi) and 0.014-in to 0.020-in stainless steel archwires. If necessary, from the moment archwire progression reached 0.018-in archwires, Class III intermaxillary elastics would be used on the right side. Rectangular 0.019x0.025-in stainless steel archwires would then be used in both arches to finish the case. After the end of active treatment, a 0.8 mm lower fixed canine-to-canine lingual retainer would be bonded and in the upper arch a removable wraparound type appliance to be worn 24/7 for six months, and then nights only for six months. The patient and her parents were also informed in writing of the need for careful hygiene and proper care of the appliances to ensure the normal development of treatment and retention.

TREATMENT PROGRESS

Initially, bands were contoured for the first molars and an impression of the upper arch and chin were taken for fabrication of the appliances planned for the case. The Hyrax-type appliance was installed with two buccal extensions in the canine region for attachment of the protraction elastics, with a recommendation of two daily activations (0.5 mm per day). The Skyhook was also set up (to be used at least 16 hours per day), with a maxillary traction force of 300 g on each side (heavy 3/16-in elastics). The elastics were placed at an angle of 30º to the occlusal plane so as to offset a counterclockwise rotation likely to occur in the maxilla. Expansion proceeded as expected and after ten days of activation the screw was stabilized. After 21 days, Roth prescription straight wire metal brackets were bonded to the maxillary incisors for leveling and alignment while creating space for tooth 13. Six months later, the expander and protraction appliance were removed. The patient's anterior and posterior crossbites were corrected, along with the dental Class III. At this point, the remaining upper and lower appliances were installed and the first NiTi 0.012-in archwire inserted for alignment and leveling. This was followed by a sequence of 0.014-in, 0.016in, 0.018-in and 0.020-in stainless steel archwires. From this point on, Class III elastics began to be used (5/16-in with 200 g force) to control the Angle Class III malocclusion. In the lower arch interproximal stripping was performed on the incisors to correct the crowding. Next, rectangular 0.018x0.025-in archwires were used to correct the torque of tooth 12 and adjust its root position, which was palatally tipped. After the final correction of the torques with an ideal 0.019x0.025in archwire and the assurance that the intended goals had been achieved, the brackets were removed and the retainer bonded. A lower bonded canine-to-canine retainer was made with 0.8 mm stainless steel wire and was used, along with an upper wraparound-type removable appliance, and the patient was instructed to wear the removable retainer 24 hours a day during the first six months and then nights only for another six months.

TREATMENT RESULTS

In evaluating the results (Figs 6 to 10) on completion of treatment and six years after removal of the appliance (Figs 11 to 15), one can observe that both the intended goals and the stability of treatment were rather successfully achieved. The posterior crossbite was corrected and the redirection of growth in the anteroposterior direction was also successful. In the mandible there was an increase of 1.5º in SNB, from 77º to 78.5º during treatment while the maxilla showed an increase of 2.5º in SNA, from 75º to 77.5º. Thus, there was an increase of 1º in the ANB,which rose from -2º to -1º (Fig 10,Table 1).

The vertical dimension was controlled, maxillary position maintained and mandibular plane angle (SN-GoGn) decreased from 34.5º to 31º. Although it may seem a considerable decrease, it is important to remember that the first cephalometric radiograph was performed in CR, and in this position the incisors had an end-on relationship, which led to further opening of the mandibular plane. Regarding dental positions, appropriate alignment and leveling were attained as well as correction of the Angle Class III, crossbite, midline, overbite and overjet, in addition to establishing correct disocclusion guidance. Unfortunately, the upper incisors had to be tipped labially by 15º, from 24º to 39º. The upper molars however were moved mesially, providing normal occlusion according to Andrews' six keys. A slight intrusion of the maxillary incisors and small 4º lower incisor tipping toward labial, from 15.5º to 19º (Fig 10, Table 1) were also performed. Despite these changes, the intermolar and intercanine widths remained stable except for a slight 1 mm decrease in mandibular intermolar width (Table 1). The face exhibited a slight improvement in profile with a slight protrusion of the upper lip while chin position and vertical dimension were preserved. Regarding stability, it was noted that six years after completion of treatment the patient's occlusion was well established with well preserved molar and canine relationships, disocclusion guidance, adequate overbite and overjet, and facial aesthetics (Figs 11 and 12). From a cephalometric standpoint one can note that the measurements relating to the position of the maxilla and mandible underwent minor changes, consistent with the pattern of growth, while the dental measurements remained fairly stable (Fig 15, Table 1).

FINAL CONSIDERATIONS

Angle Class III malocclusion is difficult to plan and control as it may have a powerful genetic component.^1-10Moreover, there are several other etiological factors to consider, such as poor individual tooth positions, mandibular overgrowth, inadequate maxillary growth, vertical problems or a combination of several of these factors.^2,3,4,6Planning should consider all these factors in addition to patient age to try to predict treatment outcome and stability.^1,8,9In this particular case, it is important to remember that cephalometric radiographs, photographs and initial models were performed in CR, which may have diminished mandibular cephalometric measurements in an anteroposterior direction, and augmented them in terms of vertical relations, masking a more severe Class III. In MIC, the patient had a fully functional crossbite with the upper incisors being covered by their lower counterparts. The reason why all records were taken in CR was to show that even in CR the patient had indeed a genuine Angle Class III malocclusion relationship. Therefore, the goals were achieved, i.e. the molar relationship, anterior and posterior crossbites and midline shift were all corrected. The skeletal pattern also improved with greater maxillary growth in relation to the mandible, and although the cephalometric results showed only minor changes, one must remember again that the initial radiograph was performed in CR, which may have minimized the problem presented by the patient. However, in order to establish a correct relationship in the anterior region, the maxillary incisors had to be excessively tipped, in line with the compensatory treatment used for Class III malocclusion, which was intended in this case. Treatment stability, both esthetic and functional, was verified during a sixyear follow-up period. There was slight extrusion of incisors and molars but the growth pattern remained fairly stable. It is thus possible to confirm that the mechanics used in this case was effective and well indicated.

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