Disto-angular transmigrated impacted mandibular molar with enostosis: A rare intraoral lesion.

A 29-year-old male patient reported for replacement of missing teeth. The patient gave history of unerupted right lower posterior teeth and the orthopantomogram revealed transmigrated mandibular second molar to the inferior border of mandible just below the root apices of second premolar associated with enostosis distally toward the ramus of mandible with size of about 21 mm Χ 20 mm. This rare interosseous defect plays a vital role in deciding prosthetic treatment options for missing teeth and utmost care should be taken to preserve the health of the patient during such procedures.

Radio opacities are rarely observed in localized areas and diagnosing the etiology behind the lesion is often difficult until the development of modern radiological investigations. These radio opacities because of unknown origin are termed as idiopathic osteosclerosis.[1234] Idiopathic osteosclerosis refers to the anatomic variation observed as an area of increased bone production which is also termed as enostosis or bone island. The lesion is generally asymptomatic and could appear as round, elliptical or irregular in shape.[567] The internal aspect is usually uniformly radiopaque and rarely observed as an intraoral lesion.[7] These lesions remain unnoticed, if not radiologically observed. The present case report identifying island of bone was an accidental finding during routine radiographic investigation for the management of partial edentulous. This rare case report describes the features of enostosis with a transmigrated mandibular second molar, which was observed at the stage of prosthetic replacement and the management of the condition. This condition may complicate the treatment planning if not properly diagnosed.

Case Report

An informed consent was obtained from patient before the utilizing their information for the present case report. A 29-year-old male patient reported with a complaint of missing right lower teeth and reported for prosthetic replacement. Past medical history reveals that the patient is a known case of bipolar disorder and under psychiatric treatment and was on medications for the past 4 years. Patient had a history of extraction of right maxillary and mandibular second molars due to dental caries. On clinical examination, the patient's permanent right mandibular first and second molars and upper right second molar were missing, whereas his lower left third molar was impacted. On the region of missing tooth, mucous membrane looked pale in color and on palpation and probing there was no tenderness or bleeding.

Orthopantomogram revealed a well localized cotton wool radiopaque lesion in relation to 46, 47 and 48 regions and transmigrated mandibular right first molar (46) measuring about 20mm in length and 21 mm height radiologically [Figure 1]. Biopsy was done to find the microscopic and macroscopic features of the lesion. Macroscopic analysis of the lesion showed there were 13 bits of tissues, two hard and 11 soft tissues. The specimens were sent for pathological study. The hard tissues were labeled as A1 and soft tissues were labeled as A2. A1 is hard in consistency, chalky white in color, irregular in surface, texture, and shape. A2 is soft in consistency, grayish-black in color with an irregular surface. Histopathology revealed focal areas of basophilic calcification and dense bony trabeculae with osteocytes in the lacunae along with extravagated red blood cells [Figures 2 and 3].

Figure 1

Radiographic representation of enostosis

Figure 2

Focal areas of basophilic calcification

Figure 3

Dense bony trabeculae with osteocytes in the lacunae along with extravasated red blood cells

Based on the radiographic appearance and biopsy report, the provisional diagnosis was enostosis with transmigrated mandibular second molar. The apex of mandibular second premolar was also in close proximity to the transmigrated tooth and was found to be vital on examination. Surgical removal of the transmigrated tooth was not considered, since the tooth was asymptomatic and close to the inferior border of mandible and mandibular nerve. Patient insisted on fixed restoration and implant prosthesis was not possible due to the asymptomatic bone pathology and a cantilevered fixed prosthesis was done using 44 and 45 as abutments. Canine guided occlusion was maintained in the final prosthesis.

Discussion

Idiopathic osteosclerosis refers to the anatomic variation observed as an area of increased bone production which is also termed as enostosis or bone island. These manifestations have a congenital or developmental origin and are usually missed out in macroscopic examinations. Its findings are usually shown up in X-rays or radiographs while assessing for other purposes.[8] On imaging, it usually projects itself as a radiopaque area. Since the advent of computed tomography, a difference is recognized between an enostosis growing inward from the periodontium and an enostosis (opacity) within the spongy bone. In present case report also, the enostosis was identified as a part of a diagnostic investigation for implant supported prosthesis and patient was asymptomatic and was unaware of the lesion. The size of enostosis in the present case report was around 21 mm in length. Though the biggest of the lesion was identified by Smith[9] in 1993 in tibia at a size of 50 mm × 50 mm, it has been elucidated that the size of the idiopathic osteoscelerosis (IO) ranges from 1 to 10 mm.

The prevalence rate of radiopaque lesions from the literature evidence ranges from 3.3% to 31.0%.[410] observed 5.4% frequency of idiopathic osteosclerosis in 1921 full mouth intraoral radiograph surveys[4] observed 6.1% on 1047 patients. Despite the fact that the women had a predominant higher ratio than men, the female to male ratio of the prevalence of IO was 1.5:1 and 2:1 as per the studies of Geist and Katz,[17] our present case report has been observed in male patient. Similarly, a number of cases with radiopaque lesions were marked increase in number among female patients as per the studies.[11] In contrast, the studies of,[46] found no significant difference in the ratio of women and men.

The present case showed the occurrence of enostosis in the mandibular posterior region and this is accordance with the previous study which reported a predilection for the mandible in the posterior region.[1412] This might be partially explained by the fact that when the panoramic radiographs were examined and assessed, there were fewer problems with the superimposition of anatomic structures in the mandible than in the maxilla, besides the fact of difference in bone anatomy and blood supply.[13] In addition, the lesion was in association with impacted molar tooth. This is evident from the literature that the cause and biologic behavior of idiopathic osteosclerosis is unknown, the suggested causes include retained primary root fragments, bone deposited in response to unusual occlusal forces or anatomic variations analogous to tori.[1415] Hence, it is possible that microscopic root fragments may act as a nidus for bone proliferation in some cases. The present case report also proves the impacted molar teeth appeared to be the nidus for the development of idiopathic osteosclerosis.

The biopsy of the lesion was hard in consistency and was chalky white in color with irregular surface texture and shape. Previous case reports have suggested that enostosis could appear as round, elliptical or irregular in shape, generally asymptomatic and without any obvious etiological agent. The internal aspect is usually uniformly radiopaque, consisting of a ground glass/stippled appearance,[6] or coarse trabeculae that may extend beyond the area of increased density.[10] These lesions may need a treatment and a biopsy if it gradually increases in size.[16]

As these lesions in the jaw are often found in association with missing tooth, prosthetic replacement becomes questionable prognosis. Though previous studies have not suggested any pathological association of enostosis, implant supported prosthesis cannot be opted due to hard consistency of the bone and also literature evidence of osseointegration in enostosis is lacking. Though enostosis represent type I bone to provide good cortical anchorage, it has a lack of vascularity,[17] hence, osseointegration would be delayed. Invasive treatment option could be surgical removal of lesion and the associated tooth followed by grafting. However, in our case, removal of tooth with the lesion has a high probability of fracture of mandible due to proximity of the tooth to the mandibular basal bone. Hence, considering the age of patient, it was recommended for cantilevered fixed treatment option with passive contact.[18] Regular follow-up of the case is required to identify an early diagnosis of pathological changes in the impacted tooth.

Conclusion

Despite the fact that enostosis is asymptomatic and nonpathological lesion, care to be taken to distinguish idiopathic osteosclerosis from a condensing osteitis or more significant lesions such as per apical cemental dysphasia or ossifying fibroma. In addition, we conclude that regular follow-up is required, though not for the lesion per se, but for the associated deformities which could occur due to impacted tooth, root fragments, etc. Careful treatment planning is also necessary if enostosis is related with missing tooth.