The etiology, pathogenesis and prognosis of internal root resorption in human dentition remain to be better understood. The present study aimed to gain better insight into the pathways by which multinucleated odontoclasts are recruited and activated on the dentin wall, giving rise to resorption lacunae in the disrupted pulp environment after tooth replantation. The upper first molars were luxated and then repositioned in the original socket. Post-treatment events were monitored over 28 days, and tissue specimens were prepared at time intervals. Histologic examination of the mesial and disto-palatal roots of the replanted first molars verified the occurrence of resorption lacunae accompanying TRAP-positive multinuclear cells on the internal dentin wall around day 7 after tooth replantation. Ninety-nine resorption lacunae were detected for the histologically examined 46 roots. These lacunae were classified into A and B types, which appeared to correspond to surface and inflammatory types of external root resorption, respectively. Key events leading to the establishment of odontoclastic resorption of the pulp-side dentin wall were the replacement of the innate pulp tissue with the ingrowth of granulation tissues and the assembly of a new cell population comprising macrophages and fibroblastic stromal cells. The overall results support the hypothesis that the innate pulp of rat molars possesses in potency inhibitory functions against undesirable resorption activities, but after impairment of the innate pulp environment after tooth replantation, a new paradigm of cell-matrices and cell-cell interactions may act cooperatively to induce clastic activities on the internal predentin/dentin wall.

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The purpose of the present study is to investigate the effect of a fine-grained food on the composition and development of the masseter fibers in the rabbits. Masseter fibers were classified as one of three types based on their levels of staining for myofibrillar ATP ase. In Type I (slow) fibers, the diameter and ratio of the fiber was most remarkably decreased by the fine-grained diet. The ratio of type IIa and IIb fibers in the fine-grained diet subjects were increased. The diameter of all fibers in the deep region showed significant decrease. In the superficial region, the diameter of Type I and IIa fibers decreased; however, the diameter of Type IIb increased. These findings suggest that the histochemical characteristics of the masseter muscle are reflected in size and composition of the muscle fibers by decreasing the masticatory loads.

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To clarify the role of cell adhesion molecules in epithelial odontogenic tumors, expression of integrin α₂, α₃ and β₄ subunits and the standard form of CD44 was immunohistochemically examined in 22 ameloblastomas as well as in 1 clear cell odontogenic tumor (CCOT). Integrin α₂ and α₃ subunits were expressed on the cell membrane of peripheral columnar or cuboidal cells in ameloblastomas. Most tumor cells in basal cell ameloblastomas and the CCOT were positive for these subunits. These features suggest that CCOT possesses characteristics similar to those of peripheral cells in main type ameloblastoma or neoplastic cells in basal cell ameloblastoma. Integrin β₄ subunit was found along the basement membrane in ameloblastomas and the CCOT. The expression of these representative epithelial integrins at the epithelialmesenchymal interfaces suggests that they might mediate parenchymal-stromal cell interactions in epithelial odontogenic tumors. CD44 was detected in most tumor cells of ameloblastomas and the CCOT, but keratinizing areas in acanthomatous ameloblastomas showed decreased CD44 expression. These features suggest that CD44 is involved not only in cell adhesion but also in cellular differentiation in epithelial odontogenic tumors.

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DNA topoisomerase type II alpha (Topo IIα) is a nuclear enzyme associated with cell proliferation and chemosensitivity/resistance in various neoplastic lesions. Topo IIα is expressed from the S phase of the cell cycle, peaking in the G2/M phases and decreasing to minimum levels during G0 and G1 phases. In the present study, we examined whether expression of Topo IIα could be reliably localized in proliferative cells in oral squamous cell carcinoma (OSCC), compared with Ki-67 expression in Ki-67 positive proliferative cells. Formalin-fixed, paraffin-embedded blocks of samples from 22 OSCC cases were used. Immunolocalization of Topo IIα and Ki-67 was examined in serial sections using a streptavidin-biotin complex-HRP system. Topo IIα was localized in the basal and parabasal layers in non-pathological squamous epithelium (NPSE). The localization of Topo IIα was perfectly consistent with Ki-67 expression. Also, in OSCC, the immunolocalization for Topo IIa was largely consistent with Ki-67. The labeling index (LI) in NPSE was 5.42±1.89 for Topo IIα and 10.58±3.73 for Ki-67. The LI in OSCC was 25.1±19.23 for Topo IIα and 42.57±20.96 for Ki-67. Significant differences were observed between NPSE and OSCC with regard to LI (P<0.005). In addition, a significant correlation was observed between Topo IIα-LI and Ki-67-LI in NPSE (γ=0.91, P<0.0001) and OSCC (γ=0.65, P<0.001). With regard to tumor differentiation, LIs in poorly differentiated tumor were significantly higher than those in well or moderately differentiated tumors (P<0.01). These findings indicate that expression of Topo IIα is closely associated with cell proliferation. This suggests that Topo IIα immunostaining offers a useful tool for the detection of proliferating cells in NPSE and OSCC.

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The surface roughness (SR) of the tongue intonguettdicates various aspects of abnormal epithelial hyperplasia, including leukoplakia and squamous cell carcinoma (SCC). Quantification of surface roughness value (SRV) would provide clinicians with more precise estimates of lesions than visual inspection alone. SRV was measured and calculated for 40 tongues with SCC, 20 tongues with leukoplakia and 14 normal tongues, using a non-contact, three-dimensional curved shape measuring and data analysis system. SCC and leukoplakiaaffected tongues showed a higher SRV than normal tongues, and SCC showed the highest SRV (p<0.05). The mean SRVs of normal tongue, leukoplakia and SCC were 51.1 μm, 203.5 (m, and 300.9μm, respectively. Well differentiated SCC showed higher SRV than moderately or poorly differentiated SCC (p<0.05). Our results demonstrate that SRV is an excellent indicator of SR and can be used by clinicians to support the correct diagnosis and proper treatment of abnormal epithelial hyperplasia.

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Irritation fibromas are very common hyperplastic lesions of the oral mucosa, although there have been few studies of large numbers of cases. Clinicopathological features of this type of lesion were examined in 129 lesions in 124 patients, consisting of 47 males and 77 females. The peak incidence of the lesion was in the 6th decade of life. The lesions occurred in the tongue (n=66), the buccal mucosa (n=42), the labial mucosa (n=14), and the hard palate (n=7). All of the lesions were excised totally, and no recurrence was reported in any of the cases. Histologically, the lesions were divided into “radiating” type (n=105) and “circular” type (n=24) according to Barker & Lucas (1967). The incidence of the lesions in the buccal and labial mucosae was higher in the circular type of lesions (83.3%) than in the radiating type of lesions (34.3%), with a significant statistical difference (p<0.05). This supports the hypothesis that a low level of trauma or mechanical irritation might produce a radiating lesion on fixed mucosa and a circular lesion on mobile mucosa.

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Neurothekeoma (NT) including nerve sheath myxoma (NSM), is a benign neoplasm derived from the peripheral nerve sheath that occurs very rarely in the oral cavity. We describe two cases of a distinctive variant of NT arising in the buccal mucosa and the tongue. Histologically, one of the lesions showed the coexistence of ill-circumscribed hypocellular and myxoid lobules and hypercellular fibrous fascicles, and the other demonstrated a scattered distribution of the tumor cells in myxoid matrix in various sizes of nests. These findings, together with immunohistochemical characteristics, suggest that the former lesion is a mixed variant of NT, and the latter is a myxoid variant of it. A review of the literature revealed 16 previous reports of NTs arising in the oral cavity.

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Papillary cystadenoma (PC) is an uncommon benign tumor of the salivary glands, sometimes involving the minor salivary glands. We report a case of PC of minor salivary gland origin located in the hard palate of an 82-year-old woman. The patient complained of swelling of the hard palate, and medical examination of the left side revealed an elastic, hard, painless mass, which was normal in color and measured 8 mm in diameter. After establishing a clinical diagnosis of benign tumor of the hard palate, the lesion was excised under local anesthesia. Histopathologically, the tumor showed papillary proliferations of the lining epithelium, composed of one or two layers of cuboidal or columnar epithelial cells, in multiple cystic spaces. Histogenesis of the tumor was confirmed immunohistochemically, and the lesion was diagnosed as PC.

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