Diagnostic value of MRI for odontogenic tumours.

OBJECTIVES: To evaluate the diagnostic value of MRI for odontogenic tumours. MATERIALS AND METHODS: 51 patients with odontogenic tumours were subjected to pre-operative MRI examinations. For tumours with liquid components, i.e. ameloblastomas and keratocystic odontogenic tumours (KCOTs), the signal intensity (SI) uniformity of their cystic components (UΣ) was calculated and then their UΣ values were compared. For tumours with solid components that had been examined using dynamic contrast-enhanced MRI (DCE-MRI), their CImax (maximum contrast index), Tmax (the time when CImax occurred), CIpeak (CImax × 0.90), Tpeak (the time when CIpeak occurred) and CI300 (i.e. the CI observed at 300 s after contrast medium injection) values were determined from CI curves. We then classified the odontogenic tumours according to their DCE-MRI parameters. RESULTS: Significant differences between the UΣ values of the ameloblastomas and KCOT were observed on T1 weighted images, T2 weighted images and short TI inversion recovery images. Depending on their DCE-MRI parameters, we classified the odontogenic tumours into the following five types: Type A, CIpeak > 2.0 and Tpeak < 200 s; Type B, CIpeak < 2.0 and Tpeak < 200 s; Type C, CI300 > 2.0 and Tmax < 600 s; Type D, CI300 > 2.0 and Tmax > 600 s; Type E, CI300 < 2.0 and Tmax > 600 s. CONCLUSION: Cystic component SI uniformity was found to be useful for differentiating between ameloblastomas and KCOT. However, the DCE-MRI parameters of odontogenic tumours, except for odontogenic fibromas and odontogenic myxomas, contributed little to their differential diagnosis.

Evaluation of panoramic radiographs taken at the initial visit at a department of paediatric dentistry.

OBJECTIVES: To examine oral and maxillofacial lesions other than those related to the chief complaint in panoramic radiographs taken at the department of paediatric dentistry at our hospital. METHODS: We retrospectively reviewed all 1092 patients who had visited the department of paediatric dentistry at our hospital and had a panoramic radiograph taken between August 1999 and October 2004. The following information was obtained from the patients' files and panoramic radiographs: gender, age, chief complaints and the presence or absence of lesions. RESULTS: Lesions were observed in 140 of the 1092 panoramic radiographs (12.8%). Among the 140 patients discovered to have lesions in the panoramic radiographs, 66 (47.1%, or 6.05% of the entire group of 1092 patients) had different lesions from those underlying the chief complaint. These 66 patients ages ranged from 3 years to 14 years and the lesions involved 39 (59.1%) missing teeth, 20 (30.3%) mesiodentes, 4 supernumerary teeth, 1 odontoma, 1 radicular cyst and 1 impacted tooth. The missing teeth were observed in the central and lateral incisor, canine, and first and second premolar positions of both jaws, especially in the lower lateral incisor and upper central incisor positions. CONCLUSIONS: We were able to detect incidental lesions at a rate of 6.05% (66 of 1092 patients) and at a relatively early age (mean 6.8 years) in the present study. Early treatment of these lesions could avoid maxillofacial deformity and other complications.

A case of recurrent ameloblastoma developing in an autogenous iliac bone graft 20 years after the initial treatment.

A case of recurrent ameloblastoma developing in an autogenous iliac bone graft 20 years after radical resection of primary mandibular ameloblastoma is presented. This case showed extensive bony resorption extending throughout the auto-grafted bone. Seeding to the graft bone was suspected as a cause of the recurrence in the iliac bone graft because wide destruction of the graft bone was observed without any prior signs and symptoms of intraoral mucosa. Consequently, extensive resection of bone as well as adjacent soft tissue was performed. Persistent follow-up examination is essential for management of ameloblastoma.

Bone deformity showing a deep coronoid notch of the mandible in a patient with neurofibromatosis type 1.

We present a case of a 10-year-old girl with neurofibromatosis type 1 related skeletal dysplasia. In the present case, a unilocular radiolucency at the left coronoid notch visible on a panoramic radiograph was suspected to be a neurofibroma. However, only the presence of bone deformities was observed on CT. Fat-like tissue adjacent to the bone deformities inside the left mandibular ramus was revealed, and the presence of neurofibroma was unequivocally denied on the MR images. However, biopsy of the lesion suggested neurofibroma. The diagnostic imaging 18 months after the first visit did not revealed a tumourous mass. However, careful follow up is required even though we could not prove the presence the lesion on the basis of imaging.

Radiographic examination of mesiodens and their associated complications.

OBJECTIVES: To examine mesiodens with regard to their status, their influence on adjacent teeth and their alteration during the follow-up period. METHODS: From retrospective reviews of all patients who visited our institution from 1990-2001, we identified 200 patients (256 mesiodentes) who were shown to have mesiodentes on the basis of a periapical radiograph, a panoramic radiograph or an axial radiograph. RESULTS: The number of supernumerary teeth was one in 146 cases (73%), two in 52 cases (26%) and three in 2 cases (1%). Of 256 mesiodentes, the direction of the crown of the mesiodens was inverted in 172 (67%), in a normal direction in 69 (27%) and in a horizontal direction with regard to the tooth axis in 15 (6%). Of the 147 mesiodentes for which axial radiography was performed, 131 (89%) were located at a palatal site against the dental arch, 16 (11%) overlapped the dental arch and none were at a labial site. Of our 200 cases, a delay of eruption of the permanent central incisor was seen in 12 (6%), malposition or rotation of the central incisor in 5 (2.5%) and dentigerous cyst formation arising from mesiodens in 22 (11%). Marked movement of the mesiodens was seen in 10 cases during the follow-up period of 5-7 years. Some complication arising from mesiodens was seen in 19.5% of all cases in our research. CONCLUSION: Although mesiodentes are not caused by malocclusion, they may cause it. A long period of impaction of mesiodentes may bring about dentigerous cyst formation or movement of the mesiodentes.

Radiographic examination of dentigerous cysts in the transitional dentition.

OBJECTIVES: To examine radiographically the relationship between the deciduous tooth and dentigerous cyst of the permanent successor during the transitional dentition. METHODS: From a retrospective review of all patients who visited our institution from April 1988 to August 2001, 70 patients under 16 years of age who had histologically confirmed dentigerous cysts that had developed from the central incisor to the second premolar were identified. These 70 patients were investigated using panoramic and periapical radiographs. RESULTS: In most cases (54 cases; 77.1%) the cyst was in the premolar region. Of the 54 premolars with dentigerous cysts, the overlying deciduous tooth had already been lost in 7 cases. Of the 47 remaining premolars with associated deciduous tooth, 35 (74.5%) had bone resorption of the periapical or bifurcation region, or irregular resorption of the associated deciduous tooth. Of the remaining 12 deciduous teeth with no periapical lesions, 9 had been treated with root canal therapy. Thus, 44 of these 47 cases (93.6%) had the possibility of inflammation at the deciduous tooth associated with the dentigerous cyst. Evidence from one case in the present study suggesting the process by which cyst development occurs is also given. CONCLUSION: Inflammatory change at the apex of the deciduous tooth may bring on a dentigerous cyst of the permanent successor.

Comparison of radiographic and MRI features of a root-diverging odontogenic myxoma, with discussion of the differential diagnosis of lesions likely to move roots.

Lesions that can produce divergence of the roots of teeth in the mandible include odontogenic cysts (odontogenic keratocysts, lateral periodontal cysts and radicular cysts), ameloblastomas, odontogenic myxomas, central giant cell granulomas, adenomatoid odontogenic tumors and aneurismal bone cysts, and other tumors. Moreover most benign jaw lesions can do this occasionally. However, when lesions--which show interradicular tear-shaped radiolucencies--are small it is often difficult to interpret them radiographically, because they do not show characteristic radiographic features. We describe a comparison of radiographic and magnetic resonance (MR) features of a root-diverging odontogenic myxoma, with discussion of the differential diagnosis of lesions likely to move roots. In addition, we discuss radiographic and MR features of possible lesions, which show similar radiographic findings to odontogenic myxoma.

A case of complex odontoma associated with an impacted lower deciduous second molar and analysis of the 107 odontomas.

OBJECTIVE: Odontoma is a comparatively common odontogenic tumor, and it may lead to interference with the eruption of its associated tooth. Odontomas are mostly associated with permanent teeth, and they are rarely associated with deciduous teeth. The purpose of this report is to analyze 107 odontomas and to present a case of complex odontoma associated with a lower deciduous second molar. SUBJECT AND METHODS: The 106 cases were analyzed with regard to the following parameters: age, gender, location, erupted teeth, congenital missing teeth, radiological features, histopathological features and prognosis. RESULTS: Of the 106 cases, 41 were complex odontoma, 62 were compound odontoma, and three were immature odontoma. Compound odontoma had a predilection for the anterior. Complex odontoma occurred more often at the mandible. CONCLUSION: Odontoma located above the tooth crown of lower deciduous molar did not behave clinically different from that associated with permanent tooth. An odontoma could be related with a supernumerary tooth or a missing tooth. If odontomas, which interfered with tooth eruption, were extirpated early, the impacted teeth would probably erupt normally and be normal in shape.

MR imaging of nasopalatine duct cysts.

We describe the magnetic resonance (MR) features of two cases of nasopalatine duct cyst (NPDC), including the first presentation of T1-weighted images (WI). The signal intensity of the cases of NPDC showed homogeneous high signal intensity on both on T1 and T2WI, although most cysts of maxillofacial regions demonstrate low to intermediate signal intensity on T1WI. NPDC may commonly be of high signal intensity on T1WI, which is consistent with keratin and viscous fluids.

CT and MR imaging of localized amyloidosis.

The localized form of amyloidosis affecting the head and neck region is rare. The characteristic features of localized amyloidosis appeared as multiple nodules on the tongue, lip, and cheek on computed tomography (CT) and magnetic resonance imaging (MRI). Contrast-enhanced CT scans represented this lesion as a marked nodular enhancement. MR features of this lesion appeared slightly low on T1-weighted images and slightly high on T2-weighted images compared with T1-T2 images of residual normal tongue. Time contrast intensity curves obtained from dynamic MRI rapidly increased to reach a plateau and gradually decreased during the late and delayed phases. MR findings suggest that such lesions might be comprised of fibrous tissue with abundant vessels. This report suggests that dynamic MRI might be helpful for diagnosing localized amyloidosis.

Odontogenic myxoma of maxillary sinus: CT and MR-pathologic correlation.

We showed the characteristic features of odontogenic myxoma in the maxillary sinus with computed tomography (CT), magnetic resonance imaging (MRI), and histopathological findings. CT images showed a multilocular soft tissue mass with bone destruction and thinning, and the characteristic finding of this lesion as strands of fine lacelike density. MRI revealed intermediate signal intensity on T1-weighted image and high signal intensity on T2-weighted image. MRI showed the erosive extent of the lesion into the adjacent structures. In contrast T1-weighted image, the peripheral portion of the lesion with a relatively large quantity of collagen bundles was enhanced, while the central portion with only mucoid component was not. The CT and MRI appearances correlated well with the histologic features and therefore were considered to be a useful tool for diagnosis of myxoma.

Two cases of polyostotic eosinophilic granuloma.

We report two cases of polyostotic eosinophilic granuloma (EG). Both plain radiographs and CT showed diffuse osteolytic lesions which suggested malignant tumors. Although EG was polyostotic, the prognosis was relatively good. Both cases developed new lesions over a follow-up period of 4-5 years and therefore further long-term review is needed.

A case of glandular odontogenic cyst associated with ameloblastoma: correlation of diagnostic imaging with histopathological features.

The glandular odontogenic cyst (GOC) is a rare odontogenic cyst. There has only been one reported case of the simultaneous presence of GOC and ameloblastoma. The radiographic features of GOC are well established but the MR findings have not been described. We report a case of GOC associated with ameloblastoma with special reference to the correlation of the diagnostic imaging with the histopathological features.