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Introduction
Class III malocclusion is characterized by the mandibular dental arch displaced in a forward direction from the maxillary arch. It can be categorized into two types: skeletal class III and pseudo-class III malocclusion. Skeletal class III malocclusion can result from both conditions maxillary deficiency and mandibular overgrowth, or from a combination of skeletal maxillary deficiency and mandibular prognathism. On the other hand, pseudo-class III malocclusion may be due to premature contact during the normal path of closure of the mandible, habitual established crossbite, or visceral interferences.1 class III malocclusions also have a strong genetic basis, with global distribution of approximately 6%.2
It is worth mentioning that the effective treatment of patients with class III anomalies requires that the skeletal profile must be fully established. Moreover, its objectives must be strictly defined to prevent treatment errors.3
Currently, there are two broad approaches to the correction of jaw mal-relationship in non-growing patients with severe skeletal class III malocclusion. One of them is the conventional three-stage method (CTM), which comprises the steps of preoperative orthodontic treatment, orthognathic surgery, and postoperative orthodontic treatment. This approach is still considered a standard method due to its stability and predictability. However, there are several disadvantages related to CTM, such as prolonged treatment time and unaesthetic appearance in the decompensation period.4,5
The other method is the surgery-first orthognathic approach (SFOA), which was officially proposed by Nagasaka et al. 6 in 2009. According to this method, the orthognathic surgery for mandibular prognathism is performed without pre-surgical orthodontic treatment. In that case, the orthodontic treatment is performed only after surgery. Different studies indicate advantages of this approach compared with CTM, including the shortening of the overall treatment duration7 and early improvement in facial esthetics.8
Given that current evidence on the management of class III malocclusion still needs to be expanded,7 we describe in this paper the management of a case of severe skeletal class III malocclusion by SFOA based on the experience of the Tamil Nadu Government Dental College and Hospital, Chennai, India.
Case report
Diagnosis
A 19-year-old female patient reported to the Department of Orthodontics and Dentofacial Orthopedics of the Tamil Nadu Government Dental College and Hospital, Chennai, India, with a chief complaint of forwardly placed lower jaw. The patient did not present with any significant prenatal, postnatal, medical, or dental history. There was no history of trauma and even the familial history was negative for this disorder.
Extraoral examination of the patient revealed leptoprosopic face with facial asymmetry. The nasal septum was deviated towards the right side. The nasal bridge was depressed. The patient had, moreover, a concave profile, anterior divergence, acute nasolabial angle, shallow mentolabial sulcus, protruded chin, and an increased Frankfort-mandibular plane angle (FMA) (Figure 1).
Upon functional examination, we found that the patient was a nasal breather without any temporomandibular joint problems. The path of closure was upwards and forwards and the lower jaw was deviated to the left by 2-3 mm during maximal mouth opening. Perioral muscle activity was normal and the incisor exposure during smile was 80% (Figure 1).
Intra-oral examination of the patient revealed normal gingival and frenal attachments. The tongue was normal in size, but it was low-lying and anteriorly positioned. Patient had a full complement of teeth present in both the arches (8 permanent teeth erupted on each hemiarch). The maxillary arch was ovoid and asymmetric, with multiple rotated and abnormally inclined teeth. Occlusal wear facets were present on buccal cusp tips of 16, 17, and 13. The mandibular arch was broad, ovoid, and asymmetric, with multiple rotated and abnormally inclined teeth. Occlusal wear facets were present on buccal cusp tips of 46.
Inter-arch examination showed bilateral Angle’s class III molar relationship, canines and incisors in class III relationship on both the sides with reverse overjet of 10 mm (overjet = -10 mm), anterior open bite and complete crossbite. Curve of spee was within normal limits (Figure 2).
Model analysis suggested 2 mm and 4 mm of space discrepancy in the lower and upper dental arches, respectively. No need for arch expansion was required. Bolton’s analysis was suggestive of a mandibular anterior as well as overall mandibular tooth material excess of 1.2 mm and 2.5 mm, respectively.
Radiographic assessment of the patient revealed the absence of severe anomaly in the dentition (after orthopantomogram examination). The results of the cephalometric analysis indicated class III skeletal base due to orthognathic maxilla, and prognathic mandible, with vertical growth pattern and proclined upper, and retroclined lower incisors (Figures 3A, 3B and e 1).
The diagnosis of the malocclusion presented by the patient was Angle’s class III malocclusion on a class III skeletal base attributed to the orthognathic maxilla, and prognathic mandible, with vertical growth pattern, protruded chin, proclined upper incisors, retroclined lower incisors, reverse overjet, complete crossbite, acute nasolabial angle, protruded lower lip, and depressed nasal bridge.
Treatment planning
A surgery first approach followed by orthodontic treatment using a pre-adjusted edgewise appliance (MBT prescription with 0.022 MBT bracket slot), along with rhinoplasty for nasal bridge augmentation was planned for the patient.
The objectives of treatment included:
• correction of skeletal jaw mal relationship (by surgery);
• correction of crossbite, profile, and lip incompetence;
• optimum functional occlusion and good esthetics results.
Treatment progress
The surgery first approach was planned for the patient because of her severe skeletal discrepancy, nearly aligned dental arches, and severely compromised esthetics. First of all, the surgical treatment objectives were planned by prediction tracing keeping in mind two approaches to surgery: 1) bilateral sagittal split osteotomy (BSSO) with mandibular set back, and 2) bi-jaw surgery with mandibular set-back and maxillary advancement. The first approach would require a mandibular set-back of 12 mm which could have yielded an unstable result as well as severe encroachment into tongue space. Thus, we decided to perform a second approach with bi-jaw surgery (Le-fort1 with maxillary advancement of 5 mm and BSSO with a mandibular set back of 7 mm). After a satisfactory outcome of the prediction tracing, facebow transfer (Figures 4 and 5) and mock surgery (Figure 6) were done. Surgical splints were fabricated to stabilize the jaws during two stage surgical procedures of bi-jaw surgery (Figure 7). Surgeries in both jaws, i.e. BSSO with mandibular set back and Le-Fort 1 osteotomy with maxillary advancement was performed (Figures 8A, 8B, and 9). The patient and her parents did not consent to rhinoplasty. Four weeks after the surgery, the patient reported back to our Department, and the orthodontic phase of treatment was started (Figure 10).
Pre-adjusted Edgewise Appliance with MBT bracket prescription (0.022 slot) was chosen and bonding was done (Figure 10). After initial alignment and leveling with 0.016 NiTi and 0.016 SS wires, different stage wires were used at proper time intervals. The used wires included 0.017 x 0.025 NiTi, 0.017 x 0.025 SS, 0.019 x 0.025 NiTi, and 0.019x 0.025 SS. Class III elastics were employed (Figure 11). Settling of occlusion was done and, proper intercuspation and good root parallelism were achieved.
The treatment was complete and brackets were de-bonded after almost 10 months of the total treatment time. The patient had an acceptable profile and an improved esthetic appearance with lip competency was also observed (Figure 12). However, her esthetics could have been enhanced more if she had been willing for rhinoplasty. Other favorable outcomes such as, optimum dental occlusion with Angle’s class I molar relationship bilaterally, canines in class I relationship with proper overjet and overbite were achieved at the end of treatment (Figure 13). Finally, the patient was given an activator along with a chin cup for retention (Figure 14).
Treatment results
The treatment duration was 10 months. Dental class I occlusion on skeletal class I jaw bases, with ANB = 10 (Figure 14 and e 1) was achieved at the end of the treatment. We found also a mild increase in mandibular plane angle by 20, but the mandible achieved a relatively stable position as depicted by the articular angle value of 1350. The maxillary and mandibular incisors were placed at the best possible position and with acceptable inclination (Figure 14 and e 1). Root parallelism was obtained as well (Figure 15 and 16).
Discussion
Orthodontic treatment is essential for many patients. Among its goals are the achievement of an adequate occlusion along with a satisfactory and healthy functioning of the stomatognathic system’s physiological routine, for an optimal facial, oral, and dental esthetics, and thus resulting in a long‑term stability.9 Skeletal Class III malocclusion can be treated differently in growing children and in non-growing adults. Since there is a natural tendency of dentoalveolar compensation for the underlying skeletal discrepancy (depending upon the severity of malocclusion), surgical or camouflage treatment are the available options for non-growing patients with Class III malocclusion. Kerr et al.10 developed some cephalometric yardsticks and reported that surgery should be performed for patients with an ANB angle of < -4°, a maxillary/mandibular (M/M) ratio of 0.84. Considering that the ANB angle of the patient in this case report was -110, the surgery was indicated.
In our patient, the dental compensations were far too small compared to the degree of a skeletal discrepancy, and individually the dental arches were more or less aligned, which was a clear indication for SFOA.11 In this sense, it is worth noting that recent researches have demonstrated that, compared with the traditional scheme, surgery-first protocols seem to reduce total treatment time12 and obtain an immediate improvement of the facial profile or upper airway constriction. This, in turn, may result in good patient satisfaction, improved cooperation throughout the treatment,11 self-confidence,13 and an immediate increase of quality of life after surgery.14
We observed in the present case report that the achieved outcomes corroborate the benefits of SFOA that have been described in the literature.11-14 Very little effort was needed to achieve optimal occlusion and the orthodontic phase was completed in a record time of 9 months, with a total treatment duration of only 10 months for our patient.
The total treatment time was shorter than for CTM with similar postoperative stability of the mandible and maxilla, similar surgical movements, and other surgical results.5 The total duration of orthodontic treatment was also shorter, which should be related to more efficient postoperative orthodontics and partial resolution of dentoalveolar compensation after surgery, leading to less complex orthodontic treatment.15
Furthermore, another important aspect is that the orthodontic tooth movement may be facilitated by the surgically induced regional acceleratory phenomenon.11,15,16 Such process corresponds to a complex physiologic event involving accelerated bone turnover and decreased regional mineral density.16 The benefits inherent in surgery first have led to increased use of SFOA by surgeons and orthodontists.
Few studies suggest that orthognathic surgery can be done at the earliest of 16.5 years of age in boys and 14.9 years of age in girls, given that the circumpubertal growth can be incomplete,17 however chances of late mandibular growth cannot be denied up to the age of 18-20 years. Therefore, long-term retention was advised for our patient.
Finally, based on the hierarchy of stability of orthognathic procedures, simultaneous “both jaw surgery” with rigid internal fixation is considered more stable than a mandibular setback.18 In addition, according to the results of the study of Busby et al. bimaxillary surgery was more stable beyond 2 years postoperatively than single jaw surgery.19 Both considerations were extremely relevant to the surgical planning of the presented case report.
Conclusion
SFOA is a new treatment paradigm for the treatment of dento-maxillofacial deformities. In certain cases, with precise treatment planning as in our case report, SFOA has been acknowledged to reduce total treatment time significantly and to achieve high levels of patient and orthodontist satisfaction. However, there are limitations related to this approach, particularly on later mandibular growth. Thus, a careful case selection, adequate diagnosis, predicting, and simulating correction with the model setup is essential to its success. Furthermore, a well-planned, well-timed and well-executed treatment should lead to the best possible results in this context, always take this into account!
