A Case Report on Surgical–Orthodontic Correction of Skeletal Class III Malocclusion with Severe Prognathic Mandible and Retrognathic Maxilla

Abstract

Mandibular prognathism combined with a retrognathic maxilla is a skeletal discrepancy that is difficult to correct. We report a case of a 25-year-old Saudi male patient with skeletal class-III malocclusion due to severe prognathic mandible who was referred to an orthodontist at Prince Sultan Military Medical City. Complete clinical examination, radiographic assessment, and study models revealed class-III malocclusion due to anteroposterior deficiency of the maxilla and severe prognathic mandible. Orthognathic surgery was performed 18 months after the presurgical orthodontic phase. A 10-mm LeFort I advancement of the maxillary arch, with impaction of 3 mm, was performed with a bilateral sagittal split osteotomy (BSSO) of 11 mm. Stable occlusion and superior aesthetics were observed at the 1-year follow-up. Surgical–orthodontic treatment endows an adult patient with a class-III malocclusion or mandibular prognathism with a stable occlusion and superior aesthetics.

INTRODUCTION

In dentistry, mandibular prognathism is one of the most challenging conditions to treat, requiring a combination of orthodontic and surgical treatments.[1] The global prevalence of mandibular prognathism varies widely, ranging from as low as 1% in Caucasians to as high as 15% in Asian populations.[2] The incidence of mandibular prognathism in Saudi Arabia was reported to be 9.4%.[3]

Severe malocclusions affect the physical health of patients, and the major impacts include difficulties in mastication, breathing, and speech; temporomandibular joint dysfunction; and compromised oral hygiene.[4] Additionally, the compromised aesthetics cause a negative psychosocial impact.[5] The resultant functional, esthetic, psychological, and social discrepancies negatively affect the quality of life of patients.

Mandibular prognathism or skeletal class-III malocclusion with a retrognathic maxilla and prognathic mandible is a severe maxillofacial deformity that requires an optimal treatment plan for achieving satisfactory results. It exhibits numerous cephalometric features such as an extremely low anterior face height, retrognathic maxilla, short anterior cranial base length, obtuse gonial angle, acute cranial base angle, proclined maxillary incisors, and retroclined mandibular incisors.[6] The aim of the treatment of this deformity is to allow the patient to achieve structural balance, functional efficiency, and aesthetics and thus lead a normal life.[7]

Maxillofacial discrepancies that exhibit both a skeletal and dental component can be corrected with early growth modification and orthodontic treatment and camouflaging or with a combination of surgical and orthodontic treatments.[8] Growth modification is possible only in prepubertal patients, whereas isolated orthodontic treatment does not give an optimal outcome. Therefore, an increasing number of adult patients are opting for a combination of orthognathic surgery and orthodontic treatment to correct a severe malocclusion.[9] The present case study reports a case of severe mandibular prognathism corrected using the surgical–orthodontic treatment.

CASE REPORT

A 25-year-old Saudi male patient presented to the orthognathic clinic in the Maxillofacial Surgery Department of the Prince Sultan Military Medical City in Riyadh, with the chief complaint of an unesthetic facial appearance caused by a prominent lower jaw. He had no specific past illness. The patient did not have a history of smoking or drinking alcohol. He had no remarkable family medical history. No significant abnormalities on physical examination. His temperature was 36.5°C, pulse rate was 75 beats/min, and blood pressure was 129/83 mm Hg.

Lateral and oblique views exhibited anteroposterior deficiency of the maxilla and severe prognathic mandible with concave facial profile. Intraorally, the molar relationship was class III with complete anterior crossbite. A negative overjet of 17 mm was observed [Figures 1 and 2]. A final diagnosis of class-III molar malocclusion with anterior crossbite was made. Orthognathic surgery was decided as a treatment plan after consultation with orthodontists and taking informed consent from the patient. Bilateral sagittal split osteotomy (BSSO) with presurgical and postsurgical orthodontics was planned to achieve aesthetically acceptable and functionally optimum occlusion, with straight facial profile and minimum traumatic surgical exposure to the patient. The patient underwent presurgical orthodontic treatment for 1 year for leveling and alignment, following which decompensation was performed [Figure 3]. The patient was reevaluated in the orthognathic combined clinic before surgical treatment. LeFort I osteotomy maxillary advancement of 10 mm, with 3-mm impaction, was performed. Allograft augmentation was performed for all bony gaps to support the large amount of maxillary advancement and prevent relapse. This was combined with a BSSO with a mandibular setback of 9 mm, which was performed after release of the pterygomassetric sling. A reduction genioplasty of 3 mm with chin advancement of 3 mm was performed. All the osteotomies were stabilized with rigid fixation by using 3-mm miniplates and screws. The patient was admitted in the hospital for 1 day after surgery and then discharged in a stable condition. The patient was followed up on a regular basis in the maxillofacial surgery clinic [Figure 4].

Figure 1.

Showing the pre-surgical OPG of the patient

Figure 2.

Showing the pre-surgical extra-oral photo for the right and left lateral view with a smile

Figure 3.

Showing the intra-oral frontal view photo

Figure 4.

Showing the steps of LeFort I advancement with bone graft

OUTCOME AND FOLLOW-UP

The patient was referred back to the orthodontic clinic to complete the postsurgical orthodontic phase. The post-surgical orthodontic treatment was completed in 6 months, and class-I canine and class-I molar relationships were achieved. The patient was followed up regularly in the orthognathic clinic. The patient exhibited high satisfaction and stable occlusion at the 1-year postoperative follow-up [Figures 5-8].

Figure 5.

Showing the post-surgical OPG of the patient

Figure 8.

Showing the intra-oral photo for the frontal view

Figure 6.

Showing the post-surgical extra-oral photo for the left and right lateral view with a smile

Figure 7.

Showing the intra-oral frontal view photo

DISCUSSION

Mandibular prognathism associated with a retrognathic maxilla is a challenging maxillofacial deformity that requires a precise treatment plan to achieve optimal results. The therapeutic alternatives available for mandibular prognathism treatment include early growth modification, orthodontic treatment, or a combination of surgical and orthodontic treatments. Facial growth modification can be an effective method for resolving skeletal class-III jaw discrepancies in prepubertal children with dentofacial orthopedic appliances such as the face mask, chin cup, maxillary protraction combined with chin cup traction, and Fränkel functional regulator III appliance.[10,11,12,13,14] However, because the age of the patient in the present case report was 25 years, growth modification could not be performed. According to a study, even in children who have undergone growth modification for maxillofacial discrepancies, continued growth results in the relapse of the results obtained in childhood.[1] Isolated orthodontic treatment can be used to camouflage minor discrepancies. However, our patient had a severe discrepancy with a negative overjet of 17 mm, which contraindicated the use of isolated orthodontic treatment. Therefore, a combination of orthognathic surgery and orthodontic treatment was considered appropriate for the patient.

Mandibular prognathism may be treated through a mandibular setback, a maxillary advancement, or a combination of these two methods. Because of the large negative overjet and retrognathic maxilla in the patient, we opted for a combination BSSO and LeFort I advancement surgeries.

A class-III malocclusion often leads to dentoalveolar compensation in both maxillary and mandibular arches. The skeletal malocclusion in mandibular prognathism is often compensated by the retroclination of mandibular incisors and the proclination of maxillary incisors with respect to the alveolar process. The retroinclination of the mandibular incisors may be due to the increased pressure of the orbicularis oris musculature on the prognathic mandible.[15] The tongue locates forward and is larger than normal in mandibular prognathism.[16] The force exerted by the enlarged tongue on the lingual surfaces of the maxillary teeth may cause proclination of the maxillary incisors. The dental changes may also be due to the natural tendency of the body to attain normal occlusion. Preoperative orthodontic decompensation must be performed to gauge the actual discrepancy and allow maximal repositioning of the mandible. This allows better surgical planning and yields optimal therapeutic results.[1] Therefore, orthodontic decompensation was performed in the present case.

Relapse after orthognathic surgery is a distressing complication. The musculature, in particular the pterygomassetric sling, is the most vital factor for postoperative relapse following mandibular setback.[17] Thus, the pterygomassetric sling must be released intraoperatively, which we achieved in the present case. Additionally, rigid fixation, as was performed in this particular case, provides stability of the postoperative position and reduces relapse.[18]

Bone grafting was performed in the interpositional gap of the LeFort I maxillary advancement because of the large advancement (10 mm) performed. Bone grafting of the interpositional gap creates a mechanical stop to prevent relapse, provides a scaffold for secondary ossification, inhibits soft tissue herniation, and accelerates bony union.[19]

The present case has certain limitations. We did not fabricate a surgical guide, which would have made the intraoperative procedure more precise. However, the grafting of interpositional gaps and release of the pterygomassetric sling ensured good postoperative stability even at 1-year follow-up.

CONCLUSION

Surgical–orthodontic treatment endows an adult patient with a class-III malocclusion or mandibular prognathism with a stable occlusion and superior aesthetics. Presurgical orthodontic decompensation must be performed to gauge the actual discrepancy and allow maximal repositioning of the mandible, whereas the postsurgical orthodontic treatment facilitates normal occlusal rehabilitation by correcting any dental discrepancy.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.