Abstract

Spontaneous bone regeneration of the reconstructed mandible in children is rarely reported. Most of previous reports discussed the role of periosteum in regeneration of bone. Alternatively, other factors such as mechanical stress and muscle attachment have also been implicated in spontaneous bone regeneration. This paper presents spontaneous-regeneration of the reconstructed mandible in a young girl, undergone a segmental mandibulectomy, and discusses the factors associated with regeneration based on the results of image examinations and Finite Element Analysis (FEA). The patient was an 11 year-old girl diagnosed as ossifying fibroma in the mandible. A segmental mandibulectomy and immediate mandibular reconstruction using a Ti-mesh tray and particulate cancellous bone and marrow was planned. The spontaneousregeneration of the coronoid process was observed on the reconstructed mandible. On the CT slabs, the reattachment of the masseter and temporal muscle was confirmed. Before treatment, the transversal growth of her maxilla was asymmetrical. After the mandibular reconstruction and prosthodontic treatment, her maxilla grew back with bilateral symmetry. The occlusal loading on her mandible appeared symmetrically via an FEA. In addition, the stress was concentrated in the external oblique ridge, and the graft bone remodeled into the anatomical configuration. Through this case, it is suggested that the reattachment, the healthy growth of masticatory muscles, and the rehabilitation of oral function contributed to spontaneous bone regeneration and remodeling in the mandible, as well as the preservation of periosteum.

Introduction

Even in children, various oral and maxillofacial tumours develop. In 1997, Sato et al. [1] reported incidences and diagnosis of 250 oral and maxillofacial tumours in children. They reported that 232 patients (93%) had benign tumours and 18 (7%) were malignant. In some cases, the tumours disappear without treatment as the child is growing. On the other hand, depending on the type of tumor, surgical ablation may be needed.

Spontaneous bone regeneration of the reconstructed mandible in children is rarely reported in the previous literatures. In 2012, Ahmad et al. [2] presented a case with spontaneous regeneration following hemimandibulectomy, and discussed the theories pertaining to the mechanism, and source of the new bone formation in the light of previous literature. They focused on the role of periosteum in regeneration of bone. Other literature [3] has also described that the reservation of periosteum, coupled with the age of the patients, possible genetic factors, and infection may play important roles in rapid bone regeneration. Alternatively, other factors such as mechanical stress and muscle attachment have also been implicated in spontaneous bone regeneration.

Materials and Methods

The patient was an 11 year-old girl. She complained of facial swelling and visited our hospital. As for 3 years history, she slowly had an enlargement of painless swelling on the left cheek. Visual inspection showed severe swelling from the left mandibular angle to the ramus region. Manual examination showed diffuse, non-tender, hard-texture swelling. An intraoral examination showed buccolingual expansion of the mandibular alveolus in the left molar region with overlying of normal mucosa. Her left molars were vital and inclined to the lingual side. There was no neural disturbance.

On the initial panoramic examination there was a large oval radiolucent lesion from the left molar region to the ramus (Figure 1). CT examination showed the lesion extending anteriorly from the left second premolar to the coronoid process and notch posteriorly, sparing the condylar process (Figure 2). The biopsy confirmed the provisional diagnosis of an ossifying fibroma. We planned a segmental mandibulectomy of the left mandible from the second premolar to the mandibular notch, including the coronoid process, and immediate mandibular reconstruction using a custom-made Timesh tray and autogenous Particulate Cancerous Bone And Marrow (PCBM) harvested from posterior iliac crest.

Our treatment plan of attempting a mandibular reconstruction, incorporating a custom-processed Ti-mesh tray, was reviewed and approved by the Ethics Committee at Tsurumi University (Approval number:915). This study followed the Declaration of Helsinki on medical protocol. Informed consent was obtained from the patient and her parents.

Conclusion

Through this case, it is suggested that the reattachment, the healthy growth of masticatory muscles, and the rehabilitation of oral function contributed to spontaneous bone regeneration and remodeling in the mandible, as well as the preservation of periosteum.