Summary

The orthodontic diagnosis must be carried out broadly, aiming to define the characteristics and severity of the malocclusion, in order to obtain and ensure a therapeutic occlusion that satisfies the functional and aesthetic requirements of orthodontic treatment. The treatment of Class III with dental and skeletal components can vary according to the objectives established for the case, which may be compensatory, with orthodontic camouflage of the skeletal discrepancies, or surgical, involving one or two bony bases, depending on the etiology of the problem and the severity of the skeletal discrepancy. It is important to emphasize the significance of mandibular manipulation for the correct diagnosis of the occlusal relationship, since altering the position of the mandible from habitual maximum intercuspation (MIH) to centric relation (CR) can lead to changes in occlusal parameters. The diagnostic elements of the present clinical case revealed a dentoskeletal Class III malocclusion. There was a significant difference between MIH and CR, with anterior displacement of the mandible, without signs and symptoms of temporomandibular joint dysfunction. The recommended treatment would be orthognathic surgery due to the severity of the observed discrepancy; however, the case was alternatively treated through dental compensation.

Introduction

Throughout orthodontic history, different schools of occlusion have emerged. Many clinicians rely on these principles that have been routinely incorporated into diagnosis and clinical practice. Currently, gnathological concepts aim to achieve an organic occlusion, characterized by a mutually protected occlusion.

Roth introduced this thinking in the 1970s, warning that failing to achieve gnathological principles may predispose individuals to the development of temporomandibular disorders (TMD). Therefore, it is essential for the clinician, during the case diagnosis, to manipulate the mandible in an attempt to get as close as possible to the centric relation (CR), checking for differences between this position and the habitual maximum intercuspation (MIH), thus avoiding errors in diagnosis.

A stable and reproducible mandibular position, which can be used as a reference, is the basis from which an accurate orthodontic diagnosis can be made. This position is known as centric relation, which has gained acceptance as a preferred position, as it is the only reproducible maxillomandibular relationship.

Therefore, it is essential for the clinician to master the technique of manipulating the mandible, which will allow it to be gently moved to the therapeutic position of CR when it is displaced in another position.

If it is necessary to measure the discrepancy of the heads of the mandible in the horizontal, vertical, or transverse planes, it will be necessary to add to the diagnosis the use of a semi or fully adjustable articulator with a condylar position indicator. Thus, it will also be possible to evaluate the changes obtained with orthodontic treatment. The orthodontist must carefully examine the TMJ of their patients, regardless of the growth stage, especially in the presence of signs and symptoms of dysfunction.

The treatment of Class III with dental and skeletal components with mandibular asymmetry is complex, and orthopedic, orthodontic, or surgical resources may be used. Therefore, correct diagnosis is of utmost importance to recommend the appropriate therapy for each case and to achieve the best results.

Case Report

14 years and 9 months old female patient. The frontal facial analysis indicated an increase in the lower third, deviation of the chin to the left, competent lips, low smile height with evident dental asymmetry. In the profile analysis, a convex facial profile was observed with protruded lower lip and chin (Figure 1). In the intraoral examination, good morphology of dental crowns was noted, several amalgam restorations, anterior crossbite, and little development of the alveolar process of the maxilla in the anterior region (Figure 2). The model analysis indicated an Angle Class III dental relationship, moderate crowding in both dental arches, extrusion of lower and upper incisors, anterior reverse bite, deep Spee curve, lower midline deviated to the left by 6 mm, ovoid arch form in the lower arch and square in the upper arch (Figure 3). The panoramic radiograph showed complete permanent dentition with developing third molars, good bone height, multiple dental organs with dilacerated roots (Figure 4). In the interpretation of the cephalometry by Fonseca6 (2016), a Class III was observed combined with upper incisors inclined to the vestibular, increased occlusal plane, and extruded lower incisors. The lower lip and soft pogonion were enlarged in relation to the subnasal vertical line (Figure 5 and Table 1). The inspection of the TMJ revealed that they were asymptomatic, and manipulation of the mandible with the 3-finger technique showed a significant discrepancy from MIH to RC (Figure 7). This last finding changed the patient's treatment plan from surgical to conservative treatment. Her diagnostic synthesis is described in Table 2 (Figure 6).

**Figure 1 (A-C) –** Initial extraoral photographs.

**Figure 2 (A-F) –** Initial intraoral photographs.

**Figure 3 (A-E) –** Initial study models.

**Figure 4–** Initial panoramic radiograph and deep right and left spee curve.

**Figure 7 (A-D) –** Intraoral clinical appearance of habitual occlusion in centric relation.

An MBT Gemini bracket system was used with torque -7° and -6° in upper and lower canines, respectively, with a 0.022” slot (3M Unitek). Initially, a lower plate was used to facilitate the correction of the anterior crossbite, associating with Class III elastics of ¼” diameter and 115gf to maintain the position of the mandible in CR for the first 3 months. Subsequently, the force vector of the elastics was changed to vertical for 2 months (Figure 8). Then, the lower appliance was installed, continuing the sequence of round arches of the first phase of treatment 0.014”, 0.016” and 0.018” of classic NiTi (Figure 9). In the second phase, rectangular arches 0.017” x 0.025” and 0.019” x 0.025” classic NiTi were used, while correcting the lower midline to the right and achieving leveling of the dental arches (Figure 10). The third phase used rectangular arches 0.019” x 0.025” of stainless steel without hooks (Figure 11) and in the fourth phase of treatment, braided rectangular arches 0.019” x 0.025” of stainless steel were used (Figure 12).

In the final results, an improvement in facial appearance was observed, reducing the initial asymmetry, along with an improvement in the smile (Figure 13). Regarding occlusion, the dental arches were shaped and coordinated, and the deviation of the lower midline was corrected (Figure 14). A mutually protected occlusion was achieved (Figure 15). A fixed lower retainer from 3 to 3 and a removable upper retainer were used (Figure 16).

In the final cephalometric analysis, better harmony in the position of the incisors and soft tissues of the lower third of the face was observed (Figure 17 and Table 3).

**Figure 8 (A-F) –** Intraoral photographs, occlusal protections, Class III and vertical elastics.

**Figure 9 (A-C) –** Bonding of MBT 0.022” appliances and first orthodontic phase, 0.014”, 0.016” and 0.018” classic nitinol arches.

**Figure 10 (A-C) –** Second orthodontic phase, 0.017 x 0.025” and 0.019 x 0.025” classic nitinol arches.

**Figure 11 (A-C) –** Third orthodontic phase, 0.019 x 0.025” stainless steel arches without posts.

**Figure 12 (A-F) –** Fourth orthodontic phase, 0.019 x 0.025” Braided steel arch.

**Figure 13 (A-C) –** Final extraoral photographs.

**Figure 14 (A-F) –** Final intraoral photographs.

**Figure 15 (A-C) –** Correct mandibular functional movements.

**Figure 16 (A-B) –** MBT retention protocol, fixed lower retainer from 3 to 3 and removable upper retainer from 7 to 7.

**Figure 17 (A-B) –** Final panoramic radiograph.

Discussion

The orthodontic literature classifies Class III malocclusion as dental, skeletal, or functional. The latter refers to the adaptation that the mandible undergoes due to dental interference, which can be introduced by the loss of one or more dental organs, causing a displacement of the mandibular condyles forward and upward, reinforcing the importance of evaluating the TMJ and manipulating the mandible. Incorrect diagnosis can lead to inadequate treatments.

Conclusions

The results obtained in the present clinical case were considered satisfactory, taking into account the conformation of the dental arches, mutually protected occlusion, and the therapeutic location of the heads of the mandible. The relationship of the soft tissues improved substantially, with a significant change in the smile and facial profile.

Authors: Franco Fonseca Balcázar, Khiabet Fonseca Esparza, Franco Fonseca Esparza

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Professional articles about dentistry: Skeletal support in orthodontics