2020, Number 1
Orthodontic-surgical treatment of Class III malocclusion with severe crowding: A case report
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ABSTRACT
In orthodontics, when malocclusions involve the bony bases, interdisciplinary work with orthognathic surgery is necessary. A clinical case is described of a 17-year-old female patient for orthodontic-surgical treatment, with a diagnosis based on cephalometric and imaging studies and study models indicating skeletal and dental class III, divergent growth, anterior crossbite, non-assessable canine class, severe crowding, and retained third molars. Orthodontic treatment was carried out with the prescription of Roth slot 0.022" × 0.025" appliances, aligning, levelling and decompensating until tripodism was achieved. Extractions of upper and lower first premolars were performed to alleviate crowding. Orthognathic surgery consisted of Le Fort I impaction osteotomy and mandibular body osteotomy.INTRODUCTION
Class III malocclusions, according to Angle, present a mesial position of the lower dental arch with respect to the upper arch and give rise to an abnormal relationship of the incisors with anterior crossbite. In lighter cases, edge-to-edge bite can occur, causing alterations in aesthetics and function. The aetiology of class III malocclusion is multifactorial, it has been identified that genetic predisposition and environmental factors such as pernicious habits (swallowing and mouth breathing) are among the main causes of it.
According to Canut, we can classify this malocclusion as follows:
Class III dental: the molar relationship is class III, it is associated with premature loss of primary molars, eruption anomalies, isolated dental malpositions, and the canines can be found in normal relationships.
Class III skeletal: presents in three forms, maxillary growth deficiency, mandibular prognathism or in combination. Clinically there is a concave profile, mandibular hyperplasia, hyperdivergent growth, increased lower facial height, anterior crossbite, maxillary collapse, prognathism of upper teeth and retrognathism of lower teeth and lip incompetence.
Class III functional: the mandible is forward and forced by occlusal interference that forces the musculature to deviate from the normal mandibular closure pattern, there are no bony discrepancies, however, dental compensations are present.1
The prevalence of class III malocclusion varies considerably among Asians (12%), Europeans (1.5-5.3%) and Caucasians (1-4%).2
The treatment of class III malocclusion represents a major challenge for orthodontists, maxillofacial surgeons and patients. Aesthetic and functional occlusion in patients with class III malocclusion is obtained by growth modification in the primary and mixed dentition, performing orthodontic camouflage when the discrepancy does not exceed the non-parameters, or by orthognathic surgery.
The treatment plan is determined by the patient's age, severity of malocclusion, facial aesthetics, clinical examination and cephalometric analysis.3
Therapeutics commonly used in growing patients with mild to moderate bony discrepancies involve orthopaedic appliances such as the face mask and functional appliances such as Frankel, chinstrap, Bionator and palatal expanders. They redirect or maintain bony growth in a transverse and anteroposterior direction, however, the success of the treatment is dependent on the patient's cooperation in the correct use of the appliance.4
The final treatment decision depends on two factors, the degree of malocclusion and the age of the patient. Obtaining acceptable results with orthodontics alone in adult class III patients is very difficult, treatments are not stable in the long term, tooth movement is limited and, periodontal and functional compromise may occur. This leads orthodontists to evaluate orthodontic-surgical treatment even if the discrepancies are moderate.
The type of surgical procedure will depend on the bony situation both vertically and anteroposteriorly and the expected changes in the soft tissues. The most commonly used procedures are maxillary advancement osteotomy, mandibular recession and in some cases combined with Le Fort I maxillary osteotomy.5
Currently, surgery-first approach is performed prior to orthodontic dental compensation. Researchers claim that these procedures immediately improve the patient's facial aesthetics, oral function and also reduce orthodontic time, however, not all patients are candidates for this type of treatment. Several studies report the instability of these treatments, so the use of these protocols remains controversial.6,7
The main reason for consultation in orthodontic-surgical treatment is to significantly improve facial aesthetics and oral function. Orthognathic surgery is one of the most important methods to treat these malocclusions and facial deformities, improving patients' quality of life and psychological self-perception.8
CLINICAL CASE
A 17-year-old female patient presents to the Orthodontic Clinic of the Justo Sierra University, her main reason for consultation is "I don't like my smile" and in the anamnesis she denies any pathological history.
Extraoral photographs: dolichofacial patient, with slight deviation of the chin to the right, incompetent lips, concave profile, enlarged lower third, lip protrusion, and nasolabial angle 85o (Figure 1).
Panoramic X-ray: we observed pneumatized maxillary sinuses, asymmetric mandibular body and branches, retention of upper and lower third molars, and ectopic upper canines (Figure 2).
Lateral skull X-ray: class III bone, the open goniac angle is observed and in the ANB the dental compensations characteristic of a dental class III such as proinclined upper incisors and retroinclination of the lower incisors, via a permeable area, mandibular prognathism, and lower lip protrusion (Figure 2).
Intraoral photographs: deviated midline, ectopic upper canines, healthy periodontal tissues, oval and transversely collapsed arches, negative horizontal and vertical overbite, severe crowding in both arches, with prognathism of upper incisors and retroinclination of lower incisors, class III molar on both sides, and non-assessable class canine (Figure 1).
TREATMENT
In the pre-surgical orthodontic phase, Roth slot 0.022" × 0.025" brackets were placed, first upper and lower premolars were extracted to relieve the crowding of both arcades, the prescribed sequence of archwires for this technique was followed 0.014", 0.016", 0.016" × 0.022", and 0.017" × 0.025", flexible archwires for alignment and levelling, double key steel archwires (DKL) until the space closure was achieved and reach at 0.019" × 0.025" steel arches necessary for the placement of surgical posts.
Alignment, levelling and dental decompensations were achieved, which at the moment aggravates class III (Figure 3) but the crowding was released and the tripodism necessary for surgical stability was achieved and monitored with several model shots.
Prior to surgery we ensured root parallelism to obtain treatment stability (Figure 4).
In the post-surgery phase, we changed the archwires to TMA 0.017" × 0.025" and intermaxillary elastics, to obtain maximum intercuspidation. In this case, post-surgical tooth movement was limited by the periodontal conditions in the lower arch, as the roots approached the vestibular cortex.
Radiographically, we can observe the bone and soft tissue changes achieved after surgery. Clinically, it was achieved the correct dental and root position, correction of crowding and obtaining class I molar on both sides, as well as class I canine, the dental midline, correction of horizontal and vertical overbite, achieving correct interarch function and this provided an improvement in the patient's facial aesthetics. The retention was fixed with dead wire and circumferential retainers (Figures 5 and 6).
In the final sagittal cephalometry we observed advancement and impaction of the maxilla and little mandibular retrusion improving the intermaxillary relationship, we also observed improvement in the inclination of the upper and lower incisors with respect to their bony bases, vertically there were no significant changes (Table 1).
DISCUSSION
The correction of class III bone by orthodontics and maxillofacial surgery remains a challenge for orthodontists and surgeons, and complete knowledge of the case by both parties improves treatment control.
Today the concept of surgery first continues to be controversial in terms of stability, although it is requested by patients since the results in facial aesthetics are immediate and it reduces time in orthodontic treatment. The use of this procedure will depend entirely on the complexity of the case, the orthodontist's ability to resolve the dental compensations, and the patient's cooperation.
Due to the increasing frequency with which patients seek this procedure, it is important that the orthodontist in training is aware of the limitations of this procedure. Mahmood et al,8 highlights the main conditions that a patient undergoing orthognathic surgery prior to orthodontics should have, including: minimal arch length discrepancy, mild to moderate transverse, vertical and sagittal discrepancies, with normal incisor inclinations and minimal dental compensations, to avoid interference during surgical correction.
In this case we decided to start with orthodontic control due to the severe crowding. The decision to perform premolar extractions will depend on various factors such as: the degree of crowding, the need to eliminate pre-existing dental compensations, how limited dental movements can be without causing periodontal damage, the expected results in the dental inclinations with respect to their bony bases and above all the impact they will have on soft tissues,9,10 in order to obtain long-term stability.
In a study by Ni et al11 mentions that the quality of life of patients with class III malocclusion improves significantly after orthodontic-surgical treatment, while pre-surgical orthodontic treatment has no effect on quality of life, and that, on the contrary, temporarily worsens facial aesthetics and mastication.
It has been reported that orthodontic-surgical treatments regardless of the protocol used, whether pre- or post-surgical orthodontics, drastically improve the quality of life of patients, the functional, aesthetic and psychological effect, exceeds the expectations in most of those who undergo these treatments.
CONCLUSION
Although there are different treatment alternatives in class III patients, in adult patients the treatment possibilities are reduced. Dental camouflage is a widely used option, but it has limitations in terms of tooth movement and soft tissue changes are few. Although the vast majority of patients are primarily looking for dental and facial aesthetics, the only means to obtain drastic and stable changes is still the combination of orthodontics and orthognathic surgery.
REFERENCES
AFFILIATIONS
1 Alumna de Maestría en Ortodoncia. Universidad Justo Sierra. México.
2 Docente de Maestría. Universidad Justo Sierra. México.
CORRESPONDENCE
Alejandra Jurisira Carrillo Rodríguez. E-mail: ajcr21@hotmail.comReceived: Noviembre 2019.Accepted: Febrero 2020.