The mandible plays a pivotal role in both masticatory function and facial aesthetics¹. As the only movable bone in the facial region, it has less support than other facial bones, and consequently mandibular fractures often result in significant instability². Therefore, treatment of mandibular fractures requires precise reduction of the bone segments to restore the pre-trauma occlusion and normal masticatory function^2,3. Insufficient realignment and fixation of mandibular fractures can result in malocclusion, necessitating revision surgery.

Bone union in an incorrectly reduced position is termed malunion^1,4. The most common causes of malunion are inadequate dental and/or osseous reduction during surgery, imprecise application of internal fixation devices, and/or inadequate stabilization⁵. To prevent postoperative malocclusion due to malunion, proper alignment of the fracture segments based on adequate consideration of the occlusion by oral and maxillofacial surgeons is crucial^2,6.

Mandibular fractures frequently present with a large gap between the fractured ends or require mobilization of the fractured ends owing to bone defects; distraction, displacement, or overlap of fracture fragments; or soft-tissue interposition⁷. In such cases, bone grafting, which provides maximum bone contact by occupying the defect between the bone fragments, can promote adequate healing⁵. In practice, autogenous particulate bone grafts, bone morphogenetic protein, or other growth factors may be considered and packed into the gap⁵.

Herein, we report a case in which revision surgery, including bone grafting to address a defect between the bone fragments, was performed to treat malocclusion secondary to the initial surgery for mandibular fracture.

A 48-year-old man was referred to the Department of Oral and Maxillofacial Surgery at our hospital from a dental clinic with a primary concern of malocclusion. The patient had sustained a mandibular fracture in a motorcycle accident approximately 2 weeks prior and underwent open reduction and internal fixation for the fracture under general anesthesia at the Department of Plastic Surgery in another hospital approximately 1 week before his referral. No significant collaboration with oral and maxillofacial surgeons regarding occlusal reconstruction was noted, and the surgery was performed solely by plastic surgeons.

There was no other relevant medical history. Extraoral examination revealed no remarkable findings; however, intraoral examination revealed a missing right mandibular lateral incisor and malocclusion, with displacement and mobility of the mandibular anterior fragment causing premature contact during mastication.(Fig. 1) Panoramic radiography demonstrated a radiolucent fracture line in the left parasymphyseal region of the mandible and displacement of teeth 31, 32, and 41. Two plates from the initial surgery were observed in the symphysis and left parasymphysis regions.(Fig. 2. A) Three-dimensional computed tomography (3DCT) revealed a mandibular fracture with five deviated bone fragments, three of which were fixed using two plates on the labial side.(Fig. 2. B, 2. C) The clinical diagnosis was malocclusion following the initial surgery for comminuted symphysis/parasymphysis fractures of the mandible. Revision surgery was recommended to properly realign the fracture fragments and restore occlusion, and the patient consented.

Three weeks after the initial surgery, revision surgery, including open reduction and internal fixation, was performed under general anesthesia. An intraoral vestibular incision was made, and a mucoperiosteal flap was elevated to expose the fracture site. The plates used to fix the bone fragments in the initial surgery were removed (Fig. 3. A), and the deviated and malunited bone fragments were refractured, exposed, and cleaned of any fibrous tissue. The separated labial bone and malunited bone that hindered the reduction were harvested for subsequent bone grafting.(Fig. 3. B) Once the fragments were freshened, proper occlusion was established using maxillomandibular fixation (MMF), and the four refractured bone fragments were realigned. For MMF, intermaxillary fixation screws were placed in the maxilla, and arch bars were used on the mandible. Three bone fragments were stabilized using three titanium miniplates, and the anterior teeth were splinted using wires to stabilize the alveolar bone fragment.(Fig. 3. C) Additionally, autogenous particulate bone derived from the harvested bone with no evidence of infection was packed into the defects between the four bone fragments.(Fig. 3. D) The reflected flap was fully closed, and postoperative MMF was not required.

The postoperative course was uneventful, and occlusion was successfully restored. The miniplates were removed approximately 1 year after the revision surgery. Intraoperative findings revealed enhanced bone formation at the bone-grafting sites.(Fig. 4) Two and a half years after revision surgery, the patient had completed dental and prosthetic treatments at another dental clinic, and the occlusion was stable.(Fig. 5) Panoramic radiography showed no evidence of the radiolucent fracture line and reduced displacement of the anterior teeth (Fig. 6. A), and 3DCT confirmed adequate bone formation with disappearance of the defect caused by the comminuted fractures.(Fig. 6. B, 6. C)

The course of this patient, who required revision surgery for comminuted mandibular fractures, highlighted important clinical issues. For the treatment of mandibular fractures, occlusal reconstruction based on the expertise of oral and maxillofacial surgeons is paramount. Furthermore, in cases where revision surgery for comminuted mandibular fractures creates a bone defect, bone grafting may be necessary for favorable bone healing.

During treatment of mandibular fractures, complications such as malocclusion may arise owing to inadequate or incorrect treatment, iatrogenic causes, or lack of treatment³. Although mild malocclusion in patients with good dental and periodontal health can be treated with occlusal equilibration, prosthetic reconstruction, or orthodontics⁸, severe malocclusion may require revision surgery. Previous studies found that approximately 0.5%-3% of patients require revision surgery⁹. However, revision surgery is usually a significant burden for the patient because of increased pain, prolonged recovery time, higher hospitalization costs, and interruptions to daily life^2,6. In the present case, the patient required revision surgery for severe malocclusion following inadequate treatment of a mandibular fracture. Due to the patient’s good compliance with the additional surgical procedure, the treatment proceeded smoothly without any complications.

Bone healing typically requires 4-8 weeks; however, nonunion can occur because of several reasons, including mobility at the fracture site, inaccurate reduction, the presence of teeth in the fracture line, or the surgeon’s lack of skill^2,10,11. Various complications, such as malocclusion or facial deformity, may occur when a maxillofacial fracture is malunited or improperly resolved⁴. In particular, malunited mandibular fractures frequently result in malocclusion^1,12. In the present case, the fractured anterior fragment with teeth exhibited mobility and nonunion because only 3 weeks had passed since the initial unsatisfactory reduction. This free fragment, along with the other malunited fragments that were inaccurately reduced, resulted in malocclusion. Patients who develop abnormal union due to surgeon’s inexperience often exhibit unsatisfactory reduction or instability soon after treatment⁷. Revision surgery increases the risk of technical difficulties, such as the need for wide exposure to visualize bony irregularities, make precise incisions, and reconnect soft tissues¹; however, in this patient, the expert knowledge and experience of the oral and maxillofacial surgeons helped achieve accurate and satisfactory reduction, restoring the original occlusion and promoting favorable wound healing.

Malunion can be attributed to an unfavorable mechanical or biological environment². The mechanical environment is affected by bone defects and/or displacement or overlap of bone segments, whereas decreased vascular supply, nutritional disorders, inflammation, and factors that inhibit bone healing may result in an unfavorable biological environment^2,7. In the present case, malunion after the initial surgery was likely caused by a bone defect and displacement of bone fragments owing to unsatisfactory reduction. Regarding bone defects, some authors have stated that segments separated by more than 1.5 cm generally do not heal without the insertion of a bone graft¹. Other authors have described that, in young patients with well-vascularized tissue and a bone gap of less than 1 cm, bone grafting may not be necessary³. Nonetheless, larger bone gaps may require particulate cancellous bone and marrow from the iliac crest confined using mesh trays, or allogenic and/or autogenous rib, iliac crest, or mandibular bone grafts³. Autogenous bone has been the gold standard bone grafting material in maxillofacial surgery; however, this material is associated with harvest-site morbidity¹³. Recent advances in biomedical engineering, such as resorbable synthetic grafting materials, have shown promise and will most likely lead to shifts in the bone grafting philosophies of clinicians¹³. In the present case, which involved a middle-aged patient, the separated labial bone and excess malunited bone were excised during reduction, creating a bone defect >1 cm. Because autogenous bone was harvested from the surgical field, it was used to pack the defect instead of resorbable synthetic grafting materials. Regarding bleeding enhancement procedures, refracture of the deviated and malunited bone fragments resulted in sufficient bleeding, and other techniques, such as drilling holes to promote marrow bleeding, were not required.

Displacement of the alveolar bone and teeth and severe malocclusion are indications for revision surgery. In addition, bone grafting may be necessary to address the defect caused by revision surgery of mandibular comminuted fractures and enhance bone healing. In treating jaw fractures, the skills and techniques of oral and maxillofacial surgeons are essential⁷, although collaboration with plastic surgeons may be necessary for aesthetic concerns. For maxillofacial fractures, a team approach, relying on the interdisciplinary cooperation of surgeons from various surgical specialties, is crucial.

The authors would like to thank the patient for consenting to publication of this report.

T.W. participated in data collection and wrote the manuscript. M.H. participated in study design and helped draft the manuscript.

Written informed consent was obtained from the patient for publication of this article and accompanying images.

No potential conflict of interest relevant to this article was reported.