Rare associations of dens invaginatus and mesiodens.

Dens invaginatus is a developmental variation resulting from an alteration in the normal growth pattern of the dental papilla. Synonyms of this disturbance include dens in dente, invaginated odontome, tooth inclusion, and dentoid in dente. Radiographically, it is observed as infolding of a radiopaque ribbon-like structure, with equal density as enamel, extending from the cingulum into the root canal and sometimes reaching the root apex, assigning the appearance of a small tooth within the coronal pulp cavity. This article presents 2 case reports. The first describes an 8-year-old girl with dens invaginatus in a mesiodens; the second report describes a 16-year-old boy presenting with 2 mesiodens, both associated with dens invaginatus.

Enhancement effects of test injection with a small amount of MR contrast medium in the oral and maxillofacial region.

PURPOSE: To examine whether the signal intensity of dynamic contrast-enhanced MRI (DCE-MRI) is altered by test injection of 1 ml of contrast medium, and if so, whether this change affects the DCE-MRI analysis. MATERIALS AND METHODS: Six healthy volunteers were examined by DCE-MRI using a Magnevist syringe and/or an Omniscan syringe for the injection of contrast medium. Each scan was performed 10 times using steady-state free precession (3D-FISP), a sequence for DCE-MRI, before and after intravenous injection of 1 ml of the contrast medium. The internal pterygoid muscle, masseter muscle, tongue, parotid gland, submandibular gland, bone marrow of the mandible, subcutaneous adipose tissue, and common carotid artery were determined to be regions of interest (ROI), and the ROI internal average signal intensity was measured. The 10 data sets obtained before or after contrast medium administration for each ROI were evaluated using the paired t-test. RESULTS: The test injection increased the signal intensities of six of eight ROIs, with all 20 experiments in the submandibular gland showing significant differences. There was no significant difference in the two ROIs corresponding to the carotid artery and subcutaneous adipose tissue of the cheek. CONCLUSIONS: The enhanced signal intensity in the tissue might have been caused by the small amount of contrast medium in the test injection. To eliminate this discrepancy caused by the test injection, a pre-contrast scan should be performed when the average signal intensity of an ROI is measured. We therefore believe that the data obtained before a test injection may be important in the analysis of DCE-MRI.

Usefulness of contrast enhanced-MRI in the diagnosis of unicystic ameloblastoma.

The radiographic features of unicystic ameloblastoma (UA) are typically unilocular and round area of radiolucency. Therefore, this type of lesion is often misdiagnosed as an odontogenic keratocyst or a dentigerous cyst. UA should be differentiated from odontogenic cysts because the former have a higher rate of recurrence than the latter. In the present study, we performed contrast enhanced-MRI (CE-MRI) to diagnose 13 cases of unilocular, round radiolucent lesions visualized on panoramic radiograph and/or CT. In the cases of UA, low signal intensity was observed on T1-weighted images (WIs), and a markedly high signal intensity was observed on T2-WIs; moreover, relatively thick rim-enhancement with/without small intraluminal nodules was observed upon CE-T1WIs. CE-MRI was considered useful in the diagnosis of UA, as characteristic features of this type of lesion i.e., thick enhancement of the tumor wall and small intraluminal nodules were detected only by CE-MRI in the present study.

Assessment of ameloblastomas using MRI and dynamic contrast-enhanced MRI.

We retrospectively evaluated magnetic resonance images (MRI) and dynamic contrast-enhanced MRI (DCE-MRI) of ameloblastomas. MRI and DCE-MRI were performed for 10 ameloblastomas. We obtained the following results from the MRI and DCE-MRI. (a) Ameloblastomas can be divided into solid and cystic portions on the basis of MR signal intensities. (b) Ameloblastomas show a predilection for intermediate signal intensity on T1WI, high signal intensity on T2WI, and well enhancement in the solid portion; they also show a homogeneous intermediate signal intensity on T1WI and homogeneous high signal intensity on T2WI, and no enhancement in the cystic portion. (c) The mural nodule or thick wall can be detected in ameloblastomas lesions. (d) CI curves of ameloblastomas show two patterns: the first pattern increases, reaches a plateau at 100-300 s, then sustains the plateau or decreases gradually to 600-900 s, while the other increases relatively rapidly, reaches a plateau at 90-120 s, then decreases relatively rapidly to 300 s, and decreases gradually thereafter. There was no difference in the CI curve patterns among primary and recurrent cases, a case with glandular odontogenic tumor in ameloblastoma or among histopathological types such as plexiform, follicular, mixed, desmoplastic, and unicystic type.

Role of O6-methylguanine-DNA methyltransferase and effect of O6-benzylguanine on the anti-tumor activity of cis-diaminedichloroplatinum(II) in oral cancer cell lines.

The DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) modulates the effectiveness of alkylating agents. However, the relationship between MGMT and the sensitivities to other agents has not been explored. In the present study, the association between MGMT expression and the cellular sensitivity to the platinum agent, CDDP was examined in four human oral cancer cell lines. CDDP depleted MGMT protein and mRNA levels in all four cell lines. Two cell lines with low MGMT expression were sensitive to an alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine and CDDP, whereas two other cell lines with high MGMT expression were resistant to both agents. Furthermore, the addition of the MGMT inhibitor, O6-benzylguanine (O6-BG), invariably enhanced CDDP sensitivity. CDDP depleted MGMT expression, and CDDP sensitivity was enhanced by O6-BG. These results provide valuable information about the relationship between MGMT expression and CDDP sensitivity in oral cancer chemotherapy.

Effects of histone deacetylase inhibitor FR901228 on the expression level of telomerase reverse transcriptase in oral cancer.

We speculated whether or not the expression level of telomerase reverse transcriptase (hTERT) would be modulated by agents targeting epigenetics in oral cancer cell lines. Although hTERT is known to be targeted by epigenetic changes, it remains unclear how chemoagents targeting epigenetics work on hTERT transcription. In the present study, the epigenetic effects of the histone deacetylase (HDAC) inhibitor FR901228 on hTERT transcription in oral cancer cell lines were analyzed by RT-PCR. The mRNA expression of hTERT was upregulated after exposure to FR901228 in hTERT-negative Hep2 cells, and even SAS and KB cells expressed high levels of hTERT. Moreover, cotreatment of protein synthesis inhibitor cycloheximide (CHX) resulted in the induction of hTERT transcription by FR901228. This suggests that the induction of hTERT by FR901228 requires de novo protein synthesis to some extent and is more likely a direct than an indirect effect on epigenetic changes such as histone acetylation/deacetylation. We further examined the effect of FR901228 on c-myc protein, which is one of the main hTERT transcription activators. FR901228 repressed c-myc protein only in the absence of CHX, and depended on the enhancement of de novo protein synthesis. Our results indicate that c-myc protein is repressed indirectly by FR901228 but may not contribute to FR901228-induced hTERT transcription. The present study showed that the HDAC inhibitor FR901228 induced the hTERT gene by a complex mechanism that involved transcription factors other than c-myc, in addition to inhibition of histone deacetylation.

Assessment of MRI and dynamic contrast-enhanced MRI in the differential diagnosis of adenomatoid odontogenic tumor.

The radiographical differentiation of adenomatoid odontogenic tumor (AOT) from dentigerous cysts, calcifying odontogenic cysts, calcifying epithelial odontogenic tumors, odontogenic keratocysts and amelobastomas is sometimes difficult. We attempted to differentiate AOT from other lesions similar to AOT in radiographic findings using MRI. The MRI features of AOT in our three cases included homogeneous low SI in the cystic portion and homogeneous intermediate SI in the solid portion on T1WI, homogeneous high SI in the cystic portion and intermediate to slightly high SI in the solid portion on T2WI and enhancement of only the solid portion on CE-T1WI although none of the sequences included SI of calcifications. The contrast index curves in the three cases of AOT showed a gradual increase to 300 s, which signified a benign tumor. These MRI features were characteristic features of AOT and might be a basis for differentiating AOT from the above possible lesions in radiographic examinations.

Influence of CpG island methylation status in O6-methylguanine-DNA methyltransferase expression of oral cancer cell lines.

It is known that the O6-methylguanine-DNA methyltransferase (MGMT) gene is susceptible to epigenetic regulation associated with an altered frequency of CpG methylation. To investigate whether epigenetic regulation of the MGMT gene might lead to significant reductions in the expression levels of cancer cells, we sought evidence of a link between the methylation status of the MGMT promoter and the expression levels of seven human oral cancer cell lines. We found two frequently methylated regions: the 5' region extending from nt 690 to nt 893 in the promoter, and the more 3' region extending from nt 1060 to nt 1151 in the untranslated first exon. The 3' region was hypermethylated independently of MGMT expression levels in all cell lines. By contrast, in the three MGMT-downregulated cell lines (SAS, Hep2, HO-1-u-1), the levels of MGMT expression were inversely related to the density of 5' region of the methylated CpGs in the MGMT promoter. Our results implied that the transcriptional inactivation of MGMT might require methylation of the 5' region, but not that of the 3' region in oral cancer cell lines. We further explored the role of methylation in MGMT expression by treating cells with 5-Aza-2'-deoxycytidine (5Aza-dC). 5Aza-dC treatment led to the partial or complete cytosine demethylation of two frequently methylated MGMT regions in all cell lines. 5Aza-dC succeeded in upregulating of the MGMT mRNA levels in only 2 of 7 cell lines (HSC3 and HO-1-u-1), and in fact reduced MGMT mRNA in the other 5 cell lines. Furthermore, 5Aza-dC had an inhibitory effect on MGMT protein levels in all cell lines. Our results suggest that MGMT levels may not revert after 5Aza-dC treatment. Based on our findings, the regulation of MGMT expression appears to be more complex than previously thought, although it is at least partially influenced by CpG methylation. Accordingly, care should be taken interpreting the link between MGMT methylation and expression.

Application of dynamic contrast-enhanced MRI to differentiate malignant lymphoma from squamous cell carcinoma in the head and neck.

Because malignant lymphoma, the second most common malignant tumor of the head and neck, and squamous cell carcinoma (SCC), the most common malignant tumor of the head and neck, require different treatments, it is important to be able to differentiate them. In the present study, we attempted to differentiate malignant lymphomas from SCCs using dynamic contrast-enhanced MRI (DCE-MRI). Seventeen lesions (in 8 cases) of malignant lymphoma and 30 cases of SCC were compared by DCE-MRI. Thirteen of 17 malignant lymphomas (76.5%) showed the maximum contrast index (CI) at 90-180 s, while 26 of 30 SCCs (86.7%) showed the maximum CI at a much faster 60-105 s. There was a statistically significant difference between SCC and malignant lymphoma in the time needed reach the maximum CI (p = 0.0177). There was also significant difference between SCC and malignant lymphoma in their maximum CIs (p < 0.001), with the maximum CIs of 29/30 SCCs (96.7%) above 2.0, while 12/17 malignant lymphomas (70.6%) showed CIs of less than 2.0. We consider these findings to be useful for distinguishing lymphomas from SCCs.

Effects of demethylating agent 5-aza-2(')-deoxycytidine and histone deacetylase inhibitor FR901228 on maspin gene expression in oral cancer cell lines.

Maspin, which belongs to the serine protease inhibitor (serpin) superfamily, has been proposed as a potent tumor suppressor that inhibits cell motility, invasion, angiogenesis, and metastasis. In the present study, we examined the effects of 5-aza-2(')-deoxycytidine (5-aza-dC), a demethylating agent, and FR901228, a histone deacetylase (HDAC) inhibitor, on maspin expression in oral cancer cell lines. The expression levels of maspin mRNA were divided into two groups, which was the maspin low-expressed and high-expressed cell lines in the 12 oral cancer cell lines. The maspin promoter contained only a few methylated CpG sites in the maspin low-expressed cell lines. Moreover, the methylation status was not altered after 5-aza-dC treatment. However, the transcription of the maspin gene was clearly increased following 5-aza-dC treatment in a number of oral cancer cell lines. These results imply that an action of 5-aza-dC is separate from induction of promoter demethylation. Treatment with FR901228 resulted in a time-dependent stimulation of the re-expression of maspin mRNA as early as 4 h after treatment in the maspin downregulated cells. The re-expression of the maspin gene may contribute to the recuperation of biological functions linked to FR901228 such as an inhibitory effect on tumor angiogenesis and cell invasion. These results indicate that maspin and its target genes may be excellent leads for future studies on the potential benefits of FR901228, a HDAC inhibitor, in cancer therapy.

MR imaging of epithelial cysts of the oral and maxillofacial region.

The aim of the present study was to review the magnetic resonance (MR) appearance of primary epithelial cysts in order to distinguish the cysts from other possible lesions. MR images were obtained in 27 cases of epithelial cysts, including 7 odontogenic keratocysts, 3 dentigerous cysts, 1 glandular odontogenic cyst, 10 radicular cysts, 4 nasopalatine duct cysts, and 2 nasolabial cysts. In addition, contrast enhanced MR imagings were performed in 12 cases, including 3 odontogenic keratocysts, 1 dentigerous cyst, 1 glandular odontogenic cyst, and 7 radicular cysts. We obtained the following results on the basis of the above MR and contrast enhanced MR findings. (a) Odontogenic keratocysts had a predilection for intermediate-high signal intensity (SI) on T1-weighted images (WI) and heterogeneous low-high SI on T2WI. (b) Dentigerous cysts, glandular odontogenic cyst, radicular cysts and nasolabial cysts showed the same predilection with the SI, which were homogeneous intermediate SI on T1WI and homogeneous high SI on T2WI. (c) The MR images of the nasopalatine duct cysts, which showed homogeneous high SI on T1WI, were specific. (d) The Gd-T1WI would be useful in decisively differentiating odontogenic cysts, which showed rim-enhancement, from tumors consisting of solid components. In conclusion, we were able to obtain more information from the MR and contrast enhanced MR images than from conventional radiograph findings.

The value of dynamic contrast-enhanced MRI in diagnosis of malignant lymphoma of the head and neck.

In this study, we attempted to diagnose malignant lymphoma on the basis of magnetic resonance imagings (MRIs) and dynamic contrast-enhanced MRI (DCE-MRI). Eighteen lesions (in eight patients), all of which had been proven histopathologically, were detected on MRI. The eight patients included five patients with diffuse large B-cell lymphoma, one with B-cell low-grade MALT lymphoma, one with follicular lymphoma, and one with Hodgkin's lymphoma. Nine lesions were located in the submandibular region, three in the buccal region, two in the orbit region, two in the submental region, and one each in the palatal and tonsil regions. The diameter of the lesions ranged between 9 and 42.2 mm (average: 22.4 mm). The signal intensities (SIs) of the 18 lesions were examined on T1-weighted (T1WI), T2WI, and gadopentetate (Gd)-T1WI. One lesion in case 8 was excluded from DCE-MRI findings, i.e., the regions of interest could not be adequately set on DCE-MRIs. The contrast index (CI) curves of the remaining 17 lesions were prepared. All 18 lesions showed almost the same images on T1WI, T2WI, and Gd-T1WI, although they represented four types of lymphoma. The images showed homogeneous SI that was intermediate to slightly high SI on T1WI, slightly high SI on T2WI, and moderately enhanced on Gd-T1WI. Thus, the cases of malignant lymphoma in this study showed relatively characteristic features based on MRI; however, these features might be non-specific. The CI curves in this study showed a relatively rapid increase, reaching a maximum CI at 45-120 s, and a relatively rapid decrease in most lesions (14/17; 82.4%); on the other hand, the curves of 3 of the 15 lesions (17.6%) showed relatively rapid increase, sustenance of a plateau, and a gradual decrease thereafter. These patterns of CI curves may indicate characteristic features useful for distinguishing malignant lymphomas from other lesions.

Incidentally found and unexpected tumors discovered by MRI examination for temporomandibular joint arthrosis.

We examined the frequency of incidentally found or unexpected tumors discovered at the time of magnetic resonance imaging (MRI) examinations in the temporomandibular joint (TMJ) region for patients with suspicion of TMJ arthrosis. Five MR images (T1-weighted transverse scout image and proton density and T2-weighted oblique sagittal images at the open and closed mouth) were acquired. In 2776 MRI examinations of TMJ arthrosis, two tumors were discovered. They consisted of an adenoid cystic carcinoma in the deep portion of the parotid gland, and a malignant tumor extending from the infratemporal fossa to the parapharyngeal space. The rate of incidentally founded or unexpected tumors in TMJ examinations was low (0.072%), but the two tumors found were malignant tumors, and therefore, scout image should be carefully examined, not only used for positing the slice.

Assessment of pleomorphic adenomas using MRI and dynamic contrast enhanced MRI.

We evaluated magnetic resonance images (MRI) and the value of dynamic contrast enhanced MRI (DCE-MRI) of pleomorphic adenomas retrospectively. MRI was performed for 18 pleomorphic adenomas, including 11 cases with DCE-MRI. We obtained the following results on the MRI and DCE-MRI. (a). Pleomorphic adenomas showed a predilection for homogeneous intermediate signal intensity on T1-weighted images (T1WI), heterogeneous high signal intensity on T2-weighted images, and heterogeneous enhancement on Gd-T1WI. (b). Of 11 contrast index (CI) curves of pleomorphic adenomas, nine CI curves (81.8%) increased gradually to 600 s or increased gradually, reached a plateau, and sustained the plateau to 600 s. The remaining two (18.2%) increased gradually and decreased gradually thereafter. (c). CI curves reached the maximum CI index at 135-300 s.

Effects of p53 gene therapy in radiotherapy or thermotherapy of human head and neck squamous cell carcinoma cell lines.

We report herein the effects of p53 gene therapy in the radiotherapy or thermotherapy of eight human head and neck squamous cell carcinoma (SCC) cell lines. The discrepancy between radiosensitivity combined with p53 gene therapy than that without p53 gene therapy increased among the eight SCC cell lines. The discrepancy increased in the thermosensitivity at 43 degrees C and decreased in that at 44 degrees C among the eight SCC cell lines. Thus, the p53 gene therapy did not always improve the discrepancy between radiosensitivity and thermosensitivity in the eight SCC cell lines. In the radiotherapy combined with adenoviral p53 gene therapy, the survival rates of three of eight SCC cell lines decreased, and that of only one cell line increased compared with radiotherapy alone. In thermotherapy combined with p53 gene therapy, the survival rates of three at 44 degrees C and five at 43 degrees C of the eight SCC cell lines decreased, although only one cell line at 43 degrees C increased its survival rate compared with thermotherapy alone. The p53 gene therapy decreased the survival rates of both radiotherapy and thermotherapy in three of eight SCC cell lines. Further, the distribution of plots on the basis of the time for 10% survival of radiotherapy and the dose for 10% survival of thermotherapy with p53 gene therapy shifted to the lower left side of the plots compared with those without p53 gene therapy. These findings indicated that p53 gene therapy improves the effects of both radiotherapy and thermotherapy.

Evaluation of tumor proliferation using dynamic contrast enhanced-MRI of oral cavity and oropharyngeal squamous cell carcinoma.

We investigated the relationship between the enhanced patterns acquired by dynamic MRI and the tumor cell proliferation estimated by immunostaining proliferating cell nuclear antigen (PCNA) in oral squamous cell carcinoma (SCC). Thirty patients with primary oral SCC underwent dynamic contrast enhanced (DCE)-MRI using a three-dimensional fast imaging with steady-state precession sequence. Tumor cell proliferation of all surgical specimens was evaluated using immunohistochemical staining with the anti-PCNA antibody. The relationship between the dynamic MRI parameters (maximum CI and maximum CI gain) and the PCNA labeling index was statistically analyzed using regression analysis. The time contrast index curves of all cases showed a rapid and high uptake pattern. The PCNA labeling index showed a significant correlation with maximum CI and maximum CI gain (P<0.0001, r=0.866 and P=0.0019, r=0.544, respectively). The assessment of DCE-MRI parameters may provide valuable information for tumor cell proliferation of the patients with oral cancer.

Thermoradiotherapy combined with adenoviral p53 gene therapy in head and neck squamous cell carcinoma cell lines.

We examined effects of recombinant p53-expressing adenovirus combined with thermoradiotherapy in 8 head and neck squamous cell carcinoma (SCC) cell lines to improve the outcomes of the treatment of advanced head and neck cancer. The p53 gene therapy did not improve the discrepancy between thermoradiosensitivities among the 8 SCC cell lines. However, p53 gene therapy improved the effects of thermoradiotherapy in all 8 cell lines, and there were significant differences in four situations of the HSC4 44 degrees C (p=0.032), SAS at 44 degrees C (p=0.029), the KB at 43 degrees C (p=0.025), and the Ca9-22 43 degrees C (p=0.020). In comparing the survival rates of thermoradiotherapy with those of thermotherapy and radiotherapy, thermoradiotherapy demonstrated actual survival rates less than theoretical survival rates based on the survival rates of thermotherapy multiplied by the survival rates of radiotherapy in almost all treatments of thermoradio-gene therapy of the 8 SCC cell lines. These results demonstrate that thermoradiotherapy combined with p53 gene therapy may be a useful tool in treating SCC cells.

MR features of aneurysmal bone cyst of the mandible and characteristics distinguishing it from other lesions.

Aneurysmal bone cyst (ABC) is a relatively rare, non-neoplastic expansile lesion of bone. Bleeding may occur during an operation or biopsy for ABC, as this cyst is an aneurys with numerous pools of blood. Therefore, it is necessary to diagnose ABC before treatment or biopsy. In the present report, we describe the characteristic computed tomography (CT) and magnetic resonance imaging (MRI) features of ABC in the mandible. Based on the literature and on our own experiences, we compare with the features of ABC with the corresponding features of other lesions showing similar conventional radiographic appearances. In the present case, bone-targeting CT showed the characteristic feature, which reflected the histopathological appearance of a partially cystic meshwork divided by coarse septa. MRI showed almost homogeneous intermediate signal intensity, including a partial slight low-signal-intensity area on the T1-weighted image, and homogeneous high signal intensity, which showed a 'bubbly' appearance, on T2-weighted image. On the enhanced T1-weighted image, the intermediate signal intensity areas apart from the areas that showed slight low-signal intensity on the non-enhanced T1-weighted image, were well enhanced. This creates a 'honeycomb' appearance. The 'meshwork' appearance on bone-targeting CT, the 'bubbly' appearance on the T2WI and the 'honeycomb' appearance on Gd-T1WI may be the characteristic features of ABC.

Thermoradiotherapy combined with p53 gene therapy of human salivary gland adenocarcinoma cell line.

We report on thermoradiotherapy combined with p53 gene therapy in the human salivary gland adenocarcinoma cell line HSG. HSG cells were successfully infected at a rate of 62.3% with MOIs of 20 of either AxCAip53 or AxCAiLacZ. The AxCAiLacZ did not inhibit the survival of the HSG cells. The survival fractions of AxCAip53-infected HSG cells were lower than those of the AxCAiLacZ-infected HSG cells, but there was no significant difference (p=0.30). AxCAip53 decreased the survival rates of thermotherapy (43 degrees C; p=0.084 and 44 degrees C; p=0.18), radiotherapy (6 Gy; p=0.20) and thermoradiotherapy (6 Gy plus 43 degrees C; p=0.24 and 6 Gy plus 44 degrees C; p=0.96), but there were no significant differences. In comparing the survival rates of thermoradiotherapy with those of thermotherapy and radiotherapy, thermoradiotherapy, regardless of the combination with p53 gene therapy, demonstrated actual survival rates lower than theoretical survival rates based on survival rates of thermotherapy multiplied by survival rates of radiotherapy. This result indicates that thermoradiotherapy is effective in the treatment of HSG cells. Thermoradiotherapy combined with p53 gene therapy was the most effective therapy among the combinations of therapies demonstrating that thermoradiotherapy combined with p53 gene therapy may be a useful tool in the treatment of HSG cells.

Adenoviral p53 gene therapy in head and neck squamous cell carcinoma cell lines.

We reconstructed the recombinant p53-expressing adenovirus and examined its infections and effects in head and neck squamous cell carcinoma cell lines. Eight human head and neck squamous cell carcinoma cell lines were infected by the recombinant adenovirus harboring the lacZ gene (AxCAiLacZ) or the wild-type p53 gene (AxCAip53), and the effects were investigated. The eight cell lines were successfully infected by AxCAiLacZ at a level of more than 50%. The survival of all 8 squamous cell lines were inhibited in the range from 8 to 26.7% by only one treatment of the AxCAip53 infection. This result suggested that p53 gene therapy might become a useful tool in head and neck squamous cell carcinoma treatment.