The objective of this study was to develop a mechanical stress model applied to the rat periodontium by means of moving teeth with magnitude- and direction- controlled orthodontic forces for a long period. Three length-differed titanium screw implants (3.0, 3.5 and 4.0mm in length) were used as anchorage for tooth movement. The upper first molars were moved mesially up to 28 days using three newly-developed force-differed super-elastic titanium-nickel (Ti-Ni) alloy closed coil springs (2, 10 and 35gf in load). The survival rate and the pull-out test data for each screw implant revealed that a 4.0mm-long screw implant was the most stable. By tooth displacement evaluation and histological observation, a 2gf-loaded spring provided the minimally detrimental effects on the periodontium and efficiently continuous tooth movement. We developed an effective mechanical stress model applied to the rat periodontium by applying magnitude- and direction-controlled light forces for long durations.

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Immunohistochemical localization of E-cadherin, α-catenin, β-catenin, integrin α₆ and laminin was compared in highly metastatic hamster squamous cell carcinomas termed O-1N. The tumors grew expansively until 4 weeks (expansive stage) and later showed diffuse invasion and induction of stroma which was rich in vascular vessels (invasive stage). Vascular invasion by tumor cell nests was encountered most often in the middle zone at the invasive stage. The size of tumor cell nests remained small in the peripheral zone in all periods, whereas it was significantly larger in the middle and central zones. E-cadherin and laminin expressions were reduced in the periphery, but not in the middle zone. Tumor cell nests penetrated into the vascular lumen without losing expression of adhesion molecules. The results indicate reduced expression of adhesion molecules could be a sign for high invasive and metastatic potency of a tumor, but it is not an essential prerequisite for vascular invasion.

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Odontogenic tumors could be classified into noncalcified tumor such as ameloblastoma; ameloblastic fibroma and squamous odontogenic tumor; and calcified tumors such as calcifying epithelial odontogenic tumor (CEOT), calcifying odontogenic cysts (COC) and adenomatoid odontogenic tumor (AOT). S-100 protein, the EF hand Ca²⁺ binding protein, is involved in a variety of cellular regulations, including Ca²⁺ signaling process. S-100 protein immunoreactivity was observed in CEOT, COC and AOT, and it was expressed either in the focus of calcification or ghost cells and in acellular homogenous areas suggesting precalcification where calcification process may occur. S-100 protein staining was also expressed in tumor epithelial cells in CEOT (1/3) and compact tumor cells in cords and strand structures of AOT. No S-100 protein immunoreactivity was observed in odontogenic tumor cells where they fail to demonstrate areas of calcification within the tumor mass; i.e., ameloblastoma, squamous odontogenic tumors and ameloblastic fibroma lacked S-100 protein staining, except for granular cells of ameloblastoma which were positive for S-100 protein. Odontogenic epithelial islands localized at periphery of the focus in odontoma expressed S-100 protein where the connective tissue cells were also reactive for S-100, suggesting that induction of dental hard tissues or calcification may be associated with the presence of immunoreactive S-100 protein.

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A rare case of mucoepidermoid carcinoma arising in a 15-year-old boy is reported. The patient had palatal swelling with tenderness for two years. After a diagnosis of mucoepidermoid carcinoma was obtained by biopsy and CT scan examinations, the patient underwent a partial maxillectomy. Histopathologically, the tumor arising in the palatal mucosa involved the maxillary bone and the base of the right maxillary sinus. The tumor consisted not only of predominantly clear cells and squamous cells in solid nests but also of mucous cells forming various sized cystic cavities. From a review of the literature, mucoepidermoid carcinoma was shown to be the most frequent salivary tumor in children, comprising 3% to 8% of the total numbers of patients with mucoepidermoid carcinoma. When compared with adult cases, childhood cases more frequently involve the parotid gland and less frequently the minor salivary glands.

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A case of orofacial granulomatosis with buccal mucosal lesion is reported. The patient was a 44-year-old Japanese male who presented with a nodular lesion in the buccal mucosa. Pathology of the resected specimen showed a non-caseating granuloma suggesting Crohn's disease or sarcoidosis. Systemic and biochemical examination showed no evidence of Crohn's disease or sarcoidosis. Finally, based on clinical features and pathological findings, we diagnosed the patient as having orofacial granulomatosis.

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A rare case of Carcinoma in pleomorphic adenoma arising in the left tongue margin in an 88-year-old Japanese woman is reported. Histologically, most of the lesion showed undifferentiated carcinoma composed of clear cells and moderately or poorly differentiated squamous cell carcinoma, with a small area of pleomorphic adenoma. The small number of tumor cells showed a positive immunoreaction for S-100 protein and pan-keratin. From these histological and immunohistochemical findings, the lesion was diagnosed as carcinoma in pleomorphic adenoma.

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Erythroplakia is a very rare lesion of the oral cavity. We report here a large erythroplakia with histologically moderate epithelial dysplasia, occurring on the oral mucosa, of a 56-year-old woman.

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Erythroplakia in the oral cavity is an uncommon lesion which has been known to be a precancerous disease, often showing the features of severe epithelial dysplasia. A significant proportion of these lesions progress to carcinoma. We report a case of extensive erythroplakia which occurred in the oral mucosa of a 56-year-old woman. Immunohistochemical methods were used to elucidate the characteristics and potential for malignant transformation in this lesion. The positive reaction for CK10/13 changed to negative in areas of dysplastic stratified squamous epithelium, while the positive reaction for CK14 was enhanced. Severely dysplastic stratified squamous epithelium exhibited slight immunoreactivity with the MIB-1 antibody against Ki-67 antigen. No staining for p53 was observed. These findings appear to support the view that oral erythroplakia with severe epithelial dysplasia possesses high potential for malignant transformation.

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