Orthodontic-Surgical Treatment of Class III Malocclusion with Mandibular Asymmetry

Class III skeletal malocclusion may result from mandibular prognathism, maxillary retrusion or a combination of both (1). Maxillary deficiency is more frequent, accounting for 60% to 63% of the causes of this type of malocclusion (2). Maxillary skeletal deficiency can also be associated with deficiency of the middle third of the face, confirmed by the contour of the zygomatic bone, orbital ridge and subpupillary area (3). Intraoral examination reveals increased axial inclination of the maxillary incisors and decreased axial inclination of the mandibular incisors in an attempt to mask the real maxillomandibular discrepancy (4). Bone discrepancy is reflected in the facial soft tissues, causing an unfavorable esthetic impact, which may be aggravated by the facial asymmetric present in most cases. Patients with these disharmonies are usually treated with a combination Orthodontic-Surgical Treatment of Class III Malocclusion with Mandibular Asymmetry


INTRODUCTION
Class III skeletal malocclusion may result from mandibular prognathism, maxillary retrusion or a combination of both (1).Maxillary deficiency is more frequent, accounting for 60% to 63% of the causes of this type of malocclusion (2).Maxillary skeletal deficiency can also be associated with deficiency of the middle third of the face, confirmed by the contour of the zygomatic bone, orbital ridge and subpupillary area (3).Intraoral examination reveals increased axial inclination of the maxillary incisors and decreased axial inclination of the mandibular incisors in an attempt to mask the real maxillomandibular discrepancy (4).Bone discrepancy is reflected in the facial soft tissues, causing an unfavorable esthetic impact, which may be aggravated by the facial asymmetric present in most cases.Patients with these disharmonies are usually treated with a combination

Orthodontic-Surgical Treatment of Class III Malocclusion with Mandibular Asymmetry
maxillary hypoplasia, malar deficiency, and increased lower one third of the face.Clinical examination revealed Angle's Class III, subdivision right malocclusion, with narrow maxilla, left posterior open bite, deviation of the maxillary midline to the right and the mandibular midline to the left, and accentuated crowding in the maxillary anterior region, with palatal displacement of the maxillary right lateral incisor (Fig. 1).
The analysis of plaster models confirmed narrow maxilla with unilateral left posterior crossbite, negative dentoalveolar discrepancy in both arches (maxillary: -9.0 mm and mandibular: -2.0 mm), Bolton discrepancy with 2.0 mm maxillary excess in total, being 0.2 mm in the anterior teeth, maxillary midline shifted 2 mm to the right, negative overjet of 5.0 mm, absence of overbite, and palatally displaced maxillary right lateral incisor.
Periapical radiographs showed malformed root of the mandibular left second premolar, narrow roots of the maxillary and mandibular incisors, indicating need of periodic radiographic follow up for control of root resorption.Panoramic radiograph (Fig. 2) showed horizontal resorption of the bone crests and the posteroanterior cephalometric radiograph of the face confirmed skeletal asymmetry.

Treatment Objectives
The main goals of the orthodontic-surgical treatment were to promote maxillary advancement and mandibular retrusion for correction of the dental relationship, Class III skeletal malocclusion and accentuated mandibular asymmetry with deviation to the left.The aim of the presurgical orthodontic preparation was to correct the dental disharmonies.Slow maxillary expansion and extraction of the maxillary first premolars on both sides were planned for correction of the maxillary midline shift and retroclination of the maxillary incisors, maintaining the anchorage with the use of Class II intermaxillary elastic mechanics.In the mandibular arch, proclination of the mandibular incisors was performed by increasing their axial inclination, thus accentuating the negative overjet in order to permit skeletal correction.

Treatment Progress
Initially, a Haas palatal expander was fabricated to promote slow expansion of the maxilla with two activations per week.After assembling of the orthodontic appliance (Edgewise prescription -slot .022"x 0.28"), extraction of the maxillary premolars on both sides was performed.A sequence of 0.014" to 0.020" stainless steel alignment and leveling archwires was used and correction of the maxillary midline based on the median sagittal plane was done to permit alignment and leveling of the maxillary right lateral incisor.Alignment and leveling of the mandibular dental arch (0.014" to 0.020" archwires) was performed by moving the incisors buccally.Subsequently, retraction of the maxillary incisors was performed, maintaining the anchorage with Class II intermaxillary elastics.
The mandibular arch was slightly contracted by increasing the buccal root torque to the molars.In the maxillary arch, buccal root torque to the molars was decreased, thus contributing for correcting the transverse relationship between the dental arches.The intercuspation was checked by occluding the plaster models that were obtained periodically until satisfactory occlusion was attained for performing the surgery.After obtaining satisfactory intercuspation of the plaster models, soldered hooks were placed on a 0.019 x 0.025 stainless steel archwires in all inter-bracket spaces and the patient was forwarded to orthognathic surgery.
The third molars were extracted 6 months before the orthognathic surgery to permit bone formation in the extraction wounds.Figure 3 shows the presurgical orthodontic preparation.
The surgical procedure included maxillary  advancement and intrusion as well as retrusion and anticlockwise rotation of the mandible.Mandibular asymmetry was corrected with sagittal osteotomy of the mandible ramus, which permitted the adequate intercuspation of the dental arches with the repositioned maxilla and decrease of the angle of the mandibular plane, thus reducing the lower one third of face.Surgery was planned according to facial analysis, predictive cephalometric tracing, and preparation of the surgical guide.After surgery, the patient returned for orthodontic finishing for obtaining Class II molar relationship and Class I canine relationship, normal overjet and overbite and coincident midlines.After the active treatment phase, a wraparound-type retention plate was used in the maxillary arch and a stainless steel 3x3 lingual canine-to-canine retainer was placed in the mandibular arch.

Treatment Results
At the end of treatment, it was observed functional occlusion, normal overjet and overbite, and adequate intercuspation, with Class II molar relationship and Class I canine relationship, coincident midlines, normal lateral and protrusive excursions.Mandibular prognathism and asymmetry were eliminated and facial esthetics was considerably improved.The cephalometric measurements showed maxillary advancement, contributing to improve the patient's profile.The maxillary incisors were retruded and the mandibular incisors were protruded and had their axial inclination increased.Figures 4 and 5 show the results obtained with the orthognathic surgery and orthodontic finishing stage.Total and partial superimposition of initial and final cephalometric tracings revealed the changes occurred with the treatment (Fig. 6).

DISCUSSION
It is very important to understand the components of facial asymmetry in order to outline an accurate and effective treatment plan (7)(8)(9)(10).The analysis of posteroanterior cephalometric radiographs determines if the asymmetry is related to the maxilla, mandible or both, in the sagittal or transverse directions, and if the anomaly is also associated with dental compensations.
Most studies have demonstrated that transverse dental compensation is correlated with skeletal asymmetry (8,(10)(11)(12).Inclinations of the occlusal plane greater than 4 o and mentum deviations observed in the posteroanterior cephalograms are important characteristics to determine the presence and extension of facial asymmetry (13,14).
The patient of this case presented significant facial asymmetry with occlusal plane inclination, mandibular asymmetry and mentum deviation to the left.Haraguchi et al. (14) and Severt and Proffit (15) have reported that in patients with dentofacial deformities with mandibular occlusion and pleasant facial esthetics.The orthodontic treatment may provoke some undesirable alterations such as root resorptions.In the present case, root resorptions were not observed, in spite of the presence of with narrow root apices and anomaly of form in the mandibular left second premolar.There was gingival recession in the maxillary left canine.The causes of recessions may be predisposing factors, such as anatomy and morphology, and precipitating factors that induce or accelerate gingival inflammation and the occurrence of bone dehiscence (17)(18)(19).During the treatment, the patient received a gingival graft with success and the recession is currently under control.
Eighteen months after removal of the orthodontic appliance, the treatment can be considered as successful.The goals of the orthodontic-surgical treatment, namely having coincident the maxillary and mandibular midlines, correlating the mentum with the sagittal midline, leveling the lip commissures, giving a symmetric appearance to the maxillary canines, aligning and leveling the maxillary and mandibular teeth, and obtaining ideal anteroposterior, transverse and vertical occlusion, overjet and overbite, were completely achieved.
When the skeletal problem compromises the facial esthetics, the surgical-orthodontic treatment is the most indicated for patients who do not present facial growth potential and mainly for those who have facial asymmetry.A correct diagnosis and planning as well as an appropriate execution of the treatment plan are determinant factors for having success and long-term stability.In the case presented in this report, the orthodontic-surgical treatment was well indicated for correction of the Class III skeletal malocclusion and the patient's facial asymmetry, proving adequate masticatory function and pleasant facial esthetics.deviation, lateral excursion to the left was present in over 85% of the studied population.According to Haraguchi et al. (14), the mandible is more asymmetrical than the maxilla because of its greater growth potential.While the mandible is a movable bone, the maxilla is rigidly connected to the adjacent skeletal structures by means of sutures and synchondroses.
The patient presented narrow maxilla associated with posterior crossbite in the left side.According to Haraguchi et al. (14), it is difficult to determine if the posterior crossbite is a consequence of narrow maxilla or if it simply results from the mandibular deviation.In the present case, posterior crossbite was treated with slow expansion in order to permit dentoalveolar remodeling.Surgically assisted disjunction was discarded due to the possibility of compromising the postsurgical stability (16).The maxillary right and left first premolars were extracted to correct the maxillary midline, dental compensations and negative dentoalveolar discrepancy.The inclination of the mandibular teeth was increased to promote satisfactory postsurgical interincisal relationship.
The objectives of the presurgical orthodontic treatment were achieved and only small corrections were necessary after surgery, obtaining adequate functional