Treatment decision in adult patients with class III malocclusion: surgery versus orthodontics

Class III malocclusion is characterized by a variety of skeletal and dental components, including a large or protrusive mandible, retrusive maxilla, protrusive mandibular dentition, retrusive maxillary dentition, and combinations of these components [1]. Its diagnosis, prognosis, and treatment have always been a challenge for clinicians [2]. A normal occlusion and improved facial esthetics of skeletal class III malocclusion can be achieved by growth modification [3], orthodontic camouflage, or orthognathic surgery [4]. The age of the patient, severity of the malocclusion, patient’s chief complaint, clinical examinations, and cephalometric analysis will delineate the treatment of choice [5]. Growth modification should begin before the pubertal growth spurt [6–10], after which only orthodontic camouflage or orthognathic surgery are possible. The severity of class III malocclusion in adult cases would define whether the patient is suitable for surgery or orthodontic treatment [11]. Kerr et al. [12] suggested that surgery should be performed in patients with ANB and incisor mandibular plane angles of lower than − 4° and 83°, respectively. Eisenhauer et al. [13] also conducted a study to separate class III patients who can be properly treated orthodontically from those who require orthognathic surgery. They suggested a predictive model including Wits appraisal, SN, maxillary/mandibular ratio, and lower gonial angle variables for correct classification of class III malocclusion in adult cases. However, problem would arise when distinguishing between borderline surgical-orthodontic class III malocclusion cases. Rabie et al. [14] evaluated borderline class III patients who had undergone camouflage orthodontic treatment or orthognathic surgery and suggested that Holdaway angle can be a reliable guide in determining the treatment modality of these patients. They further suggested that patients with a Holdaway angle greater than 12° can be successfully treated by orthodontics alone while patients with Holdaway angles less than 12° would require surgical treatment. In a similar study conducted in 2011 by Benyahia et al. [15] found a threshold or borderline value of 7.2°, thus suggesting that patients with Holdaway angles above this value can be successfully treated by orthodontics without the need for orthognathic surgery. Although both studies have shown the correlation between Holdaway angle values and the need for orthognathic surgery, the big difference between the findings of Rabie et al. [14] and Benyahia et al. [15] in estimation of the threshold value prompted us to conduct another study. Therefore, the aim of this study was to delineate diagnostic measures in borderline class III cases for choosing proper treatment modality and also to compare the treatment effects between them.

This retrospective study was carried out in accordance with the ethical standards set forth in the 1964 Declaration of Helsinki. Informed written consent was obtained from each patient and a parent or guardian. Ethical approval with the number of 95A11181 was obtained from the Craniomaxillofacial Research Center before patient recruitment.

Lateral cephalograms of all of class III patients who had attended the private practice orthodontic office from 2011 to 2016 and met the inclusion criteria were selected for the study.

By placing the significance level at 0.05 and the power at 90%, a sample size of 58 patients would be needed [16].

Out of a total number of 430 class III patients, 65 met the inclusion criteria and were selected to participate in this study. The camouflage group comprised of 36 patients (15 males and 21 females) with the mean age of 23.5 (SD 4.8) years old and confidence interval 25.6–21.2, and the surgery group comprised of 29 patients (12 males and 17 females) with the mean age of 24.8 (SD 3.1) and confidence interval 26–22.3. There was no spastically significant difference in age between groups P < 0.9.

Treatment of the camouflage patients included treatment with fixed orthodontic appliances in both jaws. While the majority of camouflage group patients were treated without teeth extractions, 6 of them underwent the extraction of the lower first premolars and the upper second premolars. The treatment of all of these patients was focused on flaring of the upper incisors and retraction of the lower incisors throughout class III mechanics, specially by application of class III elastics.

The patients of the surgery group also received fixed orthodontic treatment in both jaws. Nine patients had also undergone extractions of the upper first premolar and the lower second premolar teeth, while the rest were treated without extractions. Their surgical treatments were performed in the forms of either bimaxillary surgery (5 patients), maxillary advancement (16 patients), or mandibular setback (8 patients).

The pretreatment records (containing panoramic and lateral cephalograms, intra- and extra-oral photographs, and plaster models) were presented to three board-certified orthodontists. They were asked to divide the patients into the camouflage and surgery groups solely based on these records. Based on their judgment, the camouflage and surgery group consisted of 34 and 31 patients, respectively.

No statistically significant differences were found in relation to VAS scores regarding the satisfaction of dental and facial appearance subjects (P < 0.855).

The present study investigated and focused on successfully treated borderline class III patients in order to provide some guidelines which can assist the clinicians in choosing the best treatment modality for them, namely, surgical or camouflage correction. Treatment success was assured through using cases in which the patients were satisfied with the end results. Furthermore, three board-certified orthodontists had also approved the treatment course and results of the selected cases. The severity of class III malocclusion ranges from mild dentoalveolar to severe skeletal problems. Generally, orthognathic surgery is recommended to non-growing patients with larger dentoskeletal discrepancies, while dentoalveolar compensation or camouflage is recommended for milder discrepancies; however, the decision as to which treatment should be chosen is not always an easy task specially in borderline cases. Borderline cases refer to patients with mild to moderate skeletal problems that can be treated by either orthodontic or surgical means. Also, this important fact should not be overlooked that this decision primarily belongs to the patients. Cassidy [19] defined “borderline cases” as those patients who were similar with respect to the characteristics on which the orthodontic/surgical decision appeared to have been based.

In practice, the treatment decision is based on the clinical examination and the cephalometric analysis by assessing the amount of sagittal and vertical discrepancy, dentoalveolar compensations, and facial esthetics. The results of this study confirmed the importance of facial esthetics in the class III decision-making process. The Holdaway H angle was singled out by discriminant analysis as being the decisive parameter. The threshold or borderline value for Holdaway and Wits appraisal were 10.3° and − 5.8 mm, respectively. In 1983, Holdaway [20] defined this angle as being formed by the soft tissue H line and the soft tissue facial plane (Na-Pog). Ideally, its value is 10° when facial convexity is normal. This angle quantifies the protrusion of the upper lip relative to soft tissue profile and is independent of the skeletal discrepancy of the bases (ANB angle). Consequently, it is perfect for characterizing the profile of borderline surgical skeletal class III, in whom esthetics and facial appearance might be of greater importance than occlusion or skeletal discrepancy.

Therefore, the finding of this study implies that a new borderline class III malocclusion patient with a Holdaway angle greater than 10.3° would be treated successfully by camouflage alone, while a new patient with a Holdaway angle of less than 10.3° should be treated by combined surgery. This study also showed that Wits appraisal greater than − 5.8 mm would be effectively corrected by camouflage and less than − 5.8 mm must be treated by surgery. In this way, 81.5% of our patients were properly classified. On the contrary, Rabie et al. [14] suggested that patients with a Holdaway angle greater than 12° can be successfully treated by orthodontics alone while patients with Holdaway angles less than 12° would require surgical treatment. In a similar study, Benyahia et al. [15] reported this critical angle as 7.2°. The differences between these results could be due to different inclusion criteria. Selection bias with recruitment was avoided by including consecutive cases from database of completed cases of a clinic. Moreover, this study was a retrospective one, and all the samples met the inclusion criteria. All the patients were treated by one orthodontist, and one surgeon operated on them.

The treatment of all patients in camouflage group was focused on flaring of the upper incisors and retraction of the lower incisors throughout class III mechanics, specially by application of class III elastics. No bone-anchored appliance was used in this group. One of the weaknesses of this study is the variety in the surgical procedures. Further research is needed with no variety in the surgical procedures.

Kerr et al. [12] tried to establish cephalometric yardsticks to objectify the decision for treatment. The important factors that differentiated the surgery and orthodontic patients in their study were the size of the antero-posterior discrepancy, the inclination of the mandibular incisors, and the appearance of the soft tissue profile. Also, Ghiz [21] presented a logistic equation with four variables to predict the future success of early orthopedic treatment and could correctly classify 95.5% of the successfully treated infants but only 70% of the unsuccessfully treated infants.

In a similar study, Eisenhauer showed that the Wits appraisal is the most decisive parameter for determining orthodontic therapy or orthognathic surgery in adult patients with class III malocclusion [13]. Recently, Martinez reported that Wits appraisal, lower incisor inclination, and inter-incisal angle were indicative in treatment of camouflage or orthognathic surgery [22].

This study found that borderline class III malocclusion patients who have a Holdaway angle greater than 10.3° would be treated successfully by camouflage alone, while surgery should be the treatment of choice in borderline class III malocclusion patients with a Holdaway angle of less than 10.3°. This study also showed that Wits appraisal greater than − 5.8 mm would be effectively corrected by camouflage and less than − 5.8 mm must be treated by surgery.