| Abstract|| |
This article reports the utilization of exostosis as a source of autogenous bone for the treatment of osseous defects. A patient presented with an exostosis on the mandibular lingual region on the right side of the jaw. Exostosis was surgically removed using a chisel and mallet. The autograft thus obtained was used to treat a shallow osseous crater between 46 and 47. New bone formation was noticed at the grafted site 6 months after grafting. Bone formed in the grafted areas showed comparable clinical features to those of native bone.
Keywords: Autograft, exostosis, osseous crater
|How to cite this article:|
Puttaswamaiah RN, Galgali SR, Gowda VS. Exostosis: A donor site for autograft. Indian J Dent Res 2011;22:860-2
One of the goals of periodontal therapy is to regenerate the periodontium to its pre-disease state. Bone grafts and their synthetic substitutes have been used in an attempt to gain this therapeutic endpoint. Exostosis is a benign bony growth projecting outward from the surface of a bone. This case report describes the successful management of intrabony defect using an autograft harvested from exostosis on the lingual aspect of mandibular alveolar ridge.
| Case Report|| |
A 31-year-old male patient presented with a complaint of loose teeth and bleeding from the gums since 6 months. On clinical examination, generalized periodontal pockets, bleeding on probing, recession and mobility ranging from Grade I to Grade II was noticed. A lingual exostosis was seen at the first molar on the right side of the mandibular arch. Radiographic examination revealed generalized bone loss. Based on the history and clinical findings, the patient was diagnosed as chronic generalized periodontitis.
Six weeks following the initial case, preparation of oral hygiene instruction, scaling and root planing, and minimal occlusal adjustment for gross interferences, the case was reevaluated [Figure 1]. Since the average pocket depth was 6 to 7 mm, treatment consisted of periodontal flap surgery.
Between 46 and 47, an infrabony defect was present, which was 3 to 4 mm apical to the crests of the facial and lingual bony plates. Since there was availability of autogenous graft in the form of exostosis, autogenous bone grafting was planned to treat the osseous crater.
Anesthesia was administered to block the inferior alveolar nerve. Crevicular incision was placed and a full-thickness flap was reflected to expose the entire exostosis [Figure 2].
A surgical length carbide bur in a high-speed handpiece with external saline irrigation was used to make a groove on the superior aspect of the exostosis. The groove was placed close to the normal contour of the alveolar ridge. A chisel was placed in the groove, allowing the exostosis to be cleaved from the alveolar ridge, and a gentle tap was applied to the chisel with a surgical mallet.
The exostosis was cleaved at the groove and separated from the underlying bone as a single piece [Figure 3] and [Figure 4]. The cortical bone, which was removed as a single piece, was cut into smaller particle size using a rongeur [Figure 5]. The autogenous bone graft thus obtained was mixed with saline and placed in the shallow crater present between 46 and 47 [Figure 6]. The flap was repositioned, and sutured using single interrupted sutures.
The patient returned 10 days after surgery with uneventful healing and the sutures were removed. Patient's appointment was scheduled at 3-month interval to check the site. After 3 months, the tissue appeared healed and no signs of inflammation were seen [Figure 7].
Radiographs were taken after 9 months and 18 months. Clinically, there was a reduction in probing pocket depth from 6 to 3 mm. Radiographs also showed radio-opacity between 46 and 47 indicating bone fill [Figure 8].
|Figure 8: IOPA radiographs of the defect site (a) Preoperative radiograph, (b) Immediate Post-operative radiograph, (c) Post-operative radiograph - 9 months, (d) Post-operative radiograph - 18 months|
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| Discussion|| |
Autogenous bone, long considered the gold standard of grafting materials, is currently the only osteogenic graft available to clinical practitioners. Grafted autogenous bone heals into growing bone through the processes of osteogenesis, osteoinduction, and osteoconduction (these stages are not separate and distinct, but overlap each other). 
Autogenous bone can be harvested from the iliac crest or intraoral sites (e.g., mandibular symphysis, maxillary tuberosity, ramus, and exostosis).  It can be harvested, with or without processing, to yield graft materials of different forms, including cortical chips, osseous coagulum, and bone blend (Gara GG et al.,1981). Many investigators have reported on the clinically successful use of autogenous bone grafts harvested from intraoral sites in the treatment of intrabony defects (Nabers CL et al., 1967, Renvert S et al., 1985, Froum SJ et al., 1975, 1983). The majority of literature suggests that regardless of the intraoral donor site, autogenous bone grafts yield regenerative responses superior to those obtained following surgical debridement procedures alone (Froum et al., 1975, 1976). 
In the present case, an interproximal bony crater was present between 46 and 47. Osseous craters are concavities in the crest of the interdental bone confined within the facial and lingual walls.  The interproximal bony crater has been indicted by Pritchard as the most frequent deformity of the alveolar process due to periodontal disease. Black, in 1920, described a combination gingivectomy-osteoplasty-ostectomy procedure for its correction. However, depending on the depth of the defect and the integrity of the tissues facial and lingual to the teeth approximating the crater, these procedures may result in serious problems. These include weakening the support of the proximal teeth, potential furcation involvement due to ostectomy in achieving a harmonious contour, undesirable esthetic considerations in the anterior segments, and possible root sensitivity. 
Barkann, in 1939, described a technique with which she reported regeneration in these crater defects. Beube, in 1947, devised an approach, termed "Interdental Tissue Resection," for interproximal tissue regeneration. Since that time, however, little can be found in the literature reporting successful regeneration of crater defects. A recent series of case reports suggests that the principle of these procedures is still a valuable adjunct to the current therapeutic armamentarium. Quite recently, Ewen described a technique, termed "Bone Swaging," to enhance interproximal fill by fracturing the facial and lingual walls into the defect. Implants of various types for intrabony defects are abundant in the literature. Successful fill-in of defects consisting of three osseous walls, two walls, or even one wall through implants have been reported.  Due to the availability of exostosis as a donor source for autograft, in the present case, the interproximal crater was treated by autogenous bone grafting.
Although, in general, the mandible with its thick cortical plate and fatty marrow is not an optimal donor source; exostosis provides a source of bone without creating a defect at the donor site.  Resecting the exostosis also provides an opportunity to restore the normal bony architecture of the alveolar bone.
Since surgical re-entry and histologic method (which offers clear evidence of the state of the bone crest) were not feasible due to requirement of unnecessary second procedure, radiographs were used to assess the defect fill. Radiographs were standardized using a positioning device. Radiographs showed new bone formation at the grafted site, starting at 6 months after grafting. Bone formed in the grafted areas showed comparable clinical features with those of native bone. Thus, exostosis, if properly handled, can be a source of autograft which could be used to regenerate bone at any infrabony defect.
| References|| |
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|2.||Rosen PS, Reynolds MA, Bowers GM. The treatment of intrabony defects with bone grafts. Periodontol 2000 2000;22:88-103. |
|3.||Carranza FA, Takei HH. Bone loss and patterns of bone destruction. In: Newman MG, Takei HH, Klokkevold PR, Carranza FA, 10 th ed. Carranza's Clinical Periodontology, Missouri: Saunders; 2006. p. 452-66. |
|4.||Schallhorn RG. The use of autogenous hip marrow biopsy implants for bony crater defects. J Periodontol 1968:39;145-7. |
Rajiv N Puttaswamaiah
Department of Periodontics, V.S. Dental College and Hospital, Bangalore
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]