|Year : 2012 | Volume
| Issue : 3 | Page : 182-185
Spontaneous bone regeneration following mandibular resection for odontogenic myxoma
Ezekiel T Adebayo, Benjamin Fomete, Sunday O Ajike
Department of Dental Surgery, Maxillofacial Unit, Ahmadu Bello University Teaching Hospital, Shika, Zaria, Nigeria
|Date of Web Publication||5-Jun-2012|
Ezekiel T Adebayo
General Post Office Box 3338, Kaduna
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Spontaneous bone regeneration is an uncommon condition following traumatic or iatrogenic bone loss. The factors responsible for its occurrence are yet to be fully elucidated. This report presents spontaneous bone regeneration following mandibular resection for a giant odontogenic myxoma in a 16-years-old Nigerian male. New bone formation was observed at the postoperative fourth week and has continued for one year after. Likely factors that favor this occurrence are critically examined. The advantages of spontaneous bone regeneration in resource-poor settings include low biologic and economic costs as compared to bone grafting.
| Abstract in French|| |
La régénération osseuse spontanée est une condition rare suite à la perte osseuse traumatique ou iatrogène. Les facteurs responsables de son occurrence restent encore à être pleinement élucidée. Ce rapport présente la régénération osseuse spontanée après résection mandibulaire pour un myxomatose géant odontogènes chez un homme nigérian âgé de 16 ans. Nouvelle formation osseuse a été observée à la postopératoire quatrième semaine et a continué pendant un an après. Des facteurs susceptibles qui favorisent cette occurrence sont un examen critique. Les avantages de la régénération osseuse spontanée dans des milieux défavorisés comprennent des frais biologiques et économiques faibles par rapport au greffe osseuse.
Mots clés: Mandibule, odontogènes myxomatose, résection régénération osseuse spontanée
Keywords: Mandible, odontogenic myxoma, resection, spontaneous bone regeneration
|How to cite this article:|
Adebayo ET, Fomete B, Ajike SO. Spontaneous bone regeneration following mandibular resection for odontogenic myxoma. Ann Afr Med 2012;11:182-5
| Introduction|| |
Spontaneous bone regeneration (SBR) is an uncommon form of bone healing where bone grows into critical size defects. Apart from the mandible, it has also been reported in the long bones. , In the mandible, SBR has replaced extensive defects up to the entire mandible and bilateral condyles. ,, The exact factors controlling SBR are yet to be identified, but the age of the patient, presence of infection, soft tissue protection of the bone defect, immobilization and genetic factors have been suspected. ,,,,,,, Sub-Saharan Africa reports of SBR are very rare; all previous accounts have come from Nigeria following jaw resection for ameloblastoma. ,, This case report follows mandibular resection for odontogenic myxoma in a 16-years-old Nigerian male with a review on possible factors influencing its occurrence.
| Case Report|| |
A 16-years-old Nigerian male was seen at the Oral and Maxillofacial Clinic for complaint of mandibular swelling of three years duration. Examination revealed surgical scars around the mandible but the parents and the patient could not explain what had been done. Other aspects of the medical history were unremarkable. The lesion was firm, extending from the left lower canine to the left ascending ramus and associated with derangement of teeth. There was limitation of mouth opening from the bulkiness of the swelling as shown in [Figure 1]. Aspiration of the lesion yielded no fluid while jaw radiographs showed a multilocular radiolucency from the region of tooth 43 to the ascending ramus of left mandible as shown in [Figure 2]. Incisional biopsy was done that gave histological diagnosis of odontogenic myxoma of the mandible.
|Figure 1: Photograph showing limitation of mouth opening due to odontogenic myxoma of left mandible|
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|Figure 2: Posterior-anterior radiograph of the mandible showing multilocular radiolucency from odontogenic myxoma|
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The lesion was exposed via a Risdon incision with lip splitting, resection was carried out from tooth 43 to left temporo-mandibular joint. The upper and lower jaws were placed in maxillo-mandibular fixation (MMF) to reduce jaw swinging as delayed reconstruction was proposed. The post-operative course was uneventful and the patient was discharged seven days after surgery with MMF. At the postoperative fourth week, facial profile had improved. At the three months follow-up period, bone was palpated at the surgery site with movement at both temporo-mandibular joints, more on the right side. SBR involving the symphysis, body, ascending ramus and the left condyle was demonstrated on the radiograph as shown in [Figure 3]. A photograph of the patient showing improved facial profile at postoperative review is shown in [Figure 4].
|Figure 3: Radiograph showing spontaneous bone regeneration involving symphysis, body, ascending ramus and condyle of left mandible|
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|Figure 4: Postoperative photograph of case of odontogenic myxoma after left mandibular resection showing improvement in facial profile|
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| Discussion|| |
New bone formation occurs through osteoinduction, osteoconduction and osteogenesis. The committed and uncommitted undifferentiated mesenchymal cells in the periosteum and endosteum contribute to fracture healing. Also, mesenchymal cells in connective tissue can be induced by remaining bone fragments to form new bone and marrow. ,, Osteogenesis is the formation of new bone from osteoprogenitor cells in a wound, it is regarded as responsible for SBR from the periosteum, remnants of resected bone and uncommitted connective tissue cells in the region. 
While the exact explanation for SBR is unknown, the relative youthfulness of patients (age between 3 and 11 years) at the time of bone loss to resection or trauma has often been noted. ,,,, According to Shuker, when similar bone loss occurs in older persons, SBR may not occur even when other factors similar to that in the relatively young are present.  While Park et al., noted the high osteogenic potential in young people, Ogunlewe et al., explain that children are favored for SBR due to high cellular activity and the availability of abundant mesenchymal cells to form osteogenic tissue. , However, since not all children experience SBR after bone loss, age may not be the only factor. Also, cases have been reported in people between 27 and 58 years old. , The patient being presented was 16 years old. In view of the preponderance of SBR in young people, youthfulness is certainly beneficial.
Infection was believed to encourage periosteal bone regeneration. ,,, Diffuse sclerosing osteomyelitis, condensing osteitis and proliferating osteitis are inflammatory conditions that cause additional bone formation.  Hata et al., reported that SBR occurred following resection for chronic diffuse sclerosing osteomyelitis in a 41-year-old man. It is possible that the inflammatory process contributed to SBR in this fourth decade.  This appears contradictory as Azumi et al., believe that substance P released during the inflammatory process inhibits osteoblastic activity of laying new bone.  Some other cases of SBR in the mandible occur in the absence of frank infection. ,, Our case also had no evidence of frank infection; however, we believe that the absolute absence of infection in jaw tumors is difficult to establish due to the close relationship of the dentate jaw to the polymicrobial oral environment. Hence, infection may have the capacity to stimulate new bone growth.
Soft tissue protection of the bone defect is regarded as essential for new bone growth into critical size defects as seen in SBR. ,, This can be through preservation of periosteal cover of the defect by suturing it back in position to prevent granulation tissue in-growth as was done by Ogunlewe et al.  In experimental animals, Lemperle et al., showed that when active osteogenic periosteum is present, defect protection using a macro porous titanium mesh was enough to allow SBR to fill sizeable bone defects.  In the absence of periosteum, limited spontaneous bone regeneration occurred with contributions from cancellous bone grafts and osteo-inductive materials. 
Immobilization of bone stumps has been regarded as important for SBR. , While some authors suggested that it promotes osteogenesis, Ogunlewe et al., reported no stumps to immobilize even though an arch bar was placed to maintain the jaw shape but SBR still occurred replacing the entire mandible and both condyles. ,, Our case had MMF to prevent jaw swinging and achieve some immobilization. Stability can also conferred by titanium implant plate, orthopedic external fixator, stainless steel plate, over contoured reconstruction plate, and arch bar. ,,,, Whether immobilization is essential for SBR is controversial as Shuker suggested that continuous functional stresses on the regenerating area could serve as a mechanical factor in promoting osteogenesis.  Therefore, it is doubtful that limited mouth opening contributes to the regeneration process, but rather it may be the stability provided by the various appliances. According to Webb et al., the appliances placed in the jaw wound for stabilization may also act as scaffold along or within which new bone may be formed, analogous to developmental ossifying centers that develop at the forks of branched nerves during embryonic ossification. 
This report of SBR occurring following mandibular resection in a 16-years-old Nigerian male exemplifies the benefits of SBR. According to Chiapasco et al., SBR decreases the economic and biologic costs, and reduces the risk of postoperative complications following treatment of bone lesions.  In developing countries like Nigeria, many patients do not return for bone grafting after resection for economic reasons; hence, SBR when it occurs is very important in this environment. The acceptable facial profile based on the radiologic finding of SBR in [Figure 3] and the physical appearance in [Figure 4] attests to its benefit. Therefore, further investigations into the factors influencing SBR are necessary.
| Conclusion|| |
This report presents a 16-years-old Nigerian male treated for mandibular odontogenic myxoma by means of resection. SBR was observed from the 4 th postoperative week. Factors encouraging SBR such as relative youth, immobilization of the bone stumps and the possible influence of osteogenic factors in the soft tissues of the mandible were reviewed. The benefit of SBR in this environment includes reduced economic and biologic costs and lower risk of complications as compared to the use of grafts.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]