This study examined long-term changes in bite force, occlusal contact area, and mean bite pressure in prognathic patients after orthognathic treatment as assessed with the use of a pressure-sensitive sheet (Dental-Prescale, Fuji Photo Film Co.).
One hundred ten prognathic patients were examined. Bite force, occlusal contact area, and mean bite pressure were measured just before surgery and 2 weeks, 6 months, 1 year, 2 years, 3 years, 4 years, and 5 years after surgery. Fourteen untreated prognathic subjects with skeletal class DI malocclusion and 40 control healthy subjects with normal occlusion were also studied.
The bite force and occlusal contact area of the untreated subjects were significantly less than those of the control subjects. The bite force and occlusal contact area of the patients did not differ significantly from those of the control subjects 3 years, 4 years, or 5 years after operation. However, the mean values of bite force and occlusal contact area in the patients were about 80% of those in the control subjects 3 to 5 years after surgery. Mean bite pressure of the patients was significantly higher than that of the control subjects 2 weeks, 6 months, 1 year, and 2 years postoperatively. However, by 3 years after surgery, mean bite pressure of the patients had decreased to the control level, and there were no significant differences between the mean bite pressure of the patients and that of the control subjects 3 to 5 years postoperatively.
In conclusion, there were no significant differences between the levels of the patients and control subjects 3 to 5 years after surgery. These results suggest that orthognathic treatment improves the occlusal function of prognathic patients. However, the mean values of bite force and occlusal contact area in the patients did not reach those in the control subjects even 5 years postoperatively. Longer than 5 years after surgery may be required for postoperative occlusal function in prognathic patients to reach the level of healthy subjects. Facet formation and increased facet number caused by attrition after orthognathic treatment may be the factors allowing postoperative occlusal function in prognathic patients to reach the level of healthy subjects.

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Odontogenic keratocysts have some characteristics distinguishing them from other types of odontogenic cysts. These characteristics include as the development of multiple cysts, occasional association with basal cell nevi syndrome (BCNS), and a high incidence of recurrence clinically, and budding proliferation of the epithelium and the formation of islands of odontogenic epithelium and daughter cysts histopathologically. We studied the growth potential of the epithelial lining of odontogenic keratocysts to gain insight into their biological properties, including potential tumor-like characteristics.
In this study, 51 odontogenic keratocysts in 28 patients were clinically reviewed, and 35 cysts in 20 patients were classified into the following 3 groups and were compared:(1) BCNS and non-BCNS cases, (2) multiple cysts and a single cyst, (3) recurrent and non-recurrent cases after cyst enucleation. Histopathological examinations using hematoxylin and eosin stain were performed to examine budding proliferation of the epithelium and the formation of islands of odontogenic epithelium and daughter cysts. In immunopathological studies using a monoclonal antibody of proliferating cell nuclear antigen (PCNA), the positive cell ratio of PCNA in the cyst epithelium was calculated. Our results were as follows:
1. Clinically 6 cases (21.4%) were associated with BCNS, 10 (35.7%) had multiple cysts, and 5 (17.9%) recurred.
2. Histopathologically the ratios of islands of odontogenic epithelium were higher in BCNS and multiple cyst cases than in non-BCNS and single cyst cases.
3. In immunopathological studies using a monoclonal antibody of PCNA, the ratios of positive PCNA cells in the basal layer of odontogenic epithelium in BCNS and multiple cyst cases were higher than those in non-BCNS and single cyst cases. These results suggest that the epithelium of BCNS and multiple cysts has high growth potential.

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Eight tumors metastasizing to the oral cavity were clinically investigated. The frequency of metastatic oral tumors was 2.6% among all oral malignant tumors (307 cases) treated at our department from 1977 to 1998. Of the 8 patients, 2 were male and 6 were female. At presentation 3 patients had a medical history of treatment for cancer arising in other organs. Four patients had metastasis to the mandible, 3 had gingival metastasis, and 1 had metastasis to the tip of the tongue. Common symptoms of bone metastasis were swelling of the gingiva and alveolar mucosa and pain of the mandible. Gingival and lingual metastasis was associated with a nodular formation resembling epulis. Panoramic radiographs showed infiltrative bony destruction with ill-defined margins or a moth-eaten appearance in 4 cases of mandibular metastasis, and irregular destruction of the alveolar process was observed in 3 cases of gingival metastasis. Three cases were clinically diagnosed as oral cancer, 3 as metastatic tumor, 1 as epulis, and 1 as mandibular osteomyelitis or trigeminal neuralgia. The pathological diagnosis of biopsy specimens or removed tissues was adenocarcinoma in 3 cases, renal cell carcinoma in 1, hepatocellular carcinoma in 1, acinic cell carcinoma in 1, adeno-squamous cell carcinoma in 1, and adenocarcinoma or small cell carcinoma in 1. On the basis of pathological findings and systemic examinations, the primary site was the stomach in 3 cases, the lung in 2, the kidney in 2, and the liver in 1. Surgical removal was performed in 3 cases with gingival or lingual nodular formation, radiotherapy in 3 with mandibular metastasis, and chemotherapy in 1 with mandibular metastasis. One case was not treated after biopsy because the patient and his family refused. The outcome of the patients was very poor, with a mean survival time of 6 months. When treating metastatic oral tumors, the patient's quality of the life must be adequately considered.

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Small cell carcinoma rarely arises from the salivary glands. It more commonly occurs in the lung.
A 72-year-old man was referred to the Oral and Maxillofacial Surgery of Shimane Medical University Hospital for a painless tumor (approximately 31×28mm) on the floor of the mouth. Microscopic examination of hematoxylin and eosin stained biopsy tissues revealed malignant lymphoma or undifferentiated carcinoma (small cell carcinoma) because proliferating atypical small round cells were observed and formed tumor nests. We then performed immunohistochemical staining of the tissue to clarify the nature of the tumor. On immunohistochemical staining, epithelial marker (EMA) and endocrine marker (synaptophysin) were positive and lymphocyte markers (LCA, L-26, and UCHL) were negative. On the basis of these results, we judged that this malignant tumor was small cell carcinoma with endocrine differentiation arising from the sublingual salivary gland.
After electron-microscopic observation, we concluded that the small cell carcinoma in our case was small cell ductal carcinoma.

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An increasing number of studies have shown that patients with Fanconi's anemia (FA) are at risk for the development of malignancies. We report a case of carcinoma of the tongue in a patient with persistent FA.
The patient was treated for aplastic anemia at 9 years of age. At 14 years of age, a chromosome fragility test revealed a diagnosis of FA. The patient received an HLA-compatible bone marrow transplant from his brother, and showed marked improvement, although chronic graft-versus-host disease and stomatitis developed.
Nine years later, at the age of 23 years, the patient was referred to our department because of pain on the left side of the tongue. On clinical examination, a 46×32 mm ulcerating mass was noted. The histological diagnosis on biopsy was a well-differentiated squamous cell carcinoma.
The patient was treated surgically by resection of the tongue carcinoma. Cervical lymph node metastases were found in 8 nodes on the same side of the tongue as the lesion.
Disease recurred 9 months after surgery, and he died of complications of pneumonia 3 months later.

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We have reported that most malignant melanomas of the oral mucosa are clinically and histologically identical to acral lentiginous melanoma (ALM) of the skin. There have been many studies of precusors of cutaneous melanoma, but few have mentioned oral melanoma.
We describe our experience with a case of precancerous melanosis occurring in the hard palate. A 68-yearold woman was referred to our hospital because of a pigmented lesion of the palate, which her dentist had noticed accidentally. Clinical examinations revealed brownish-black plaque in the center of the lesion and adjacent light brown pigmented macules with no apparent borderline. She underwent surgical resection of the lesion via an intraoral approach for a diagnosis of a benign or premalignant melanocytic lesion. Histological examination revealed lentiginous or pagetoid proliferation of atypical melanocytes in the epithelial layer in the plaque lesion, with proliferation of dendritic melanocytes or simple hyperpigmentation in the macular lesion. These findings were identical to those of the radial growth phase of acral lentiginous melanoma of the oral cavity, which we reported previously. A diagnosis of a precursor lesion of ALM was made. She is free from disease 12 months after operation.

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Vascular leiomyoma, first reported by Stout in 1939, is a benign tumor of smooth muscle. It frequently occurs in the skin and subcutaneous tissues, especially the lower extremities, but seldom arises in the oral cavity.
We report a case of vascular leiomyoma arising in the upper lip. An 82-year-old man was referred to our clinic because of a painless tumor of the upper lip. He had had the lesion for more than 10 years. Sonographic examination revealed a 21×13×9mm benign tumor with calcification. Clinically, it was diagnosed as a calcifying epithelial tumor, and enucleation of the tumor was performed. Microscopically, the tumor was composed of numerous blood vessels surrounded by smooth-muscle-like tumor cells, with some areas of calcification. The histopathological diagnosis was vascular leiomyoma. The postoperative course at 21 months has been uneventful.
A review of 55 cases of oral vascular leiomyoma reported in Japan indicated frequent disagreement between the preoperative and pathological diagnoses, suggesting difficulty in clinical diagnosis of this tumor.

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Benign symmetrical lipomatosis (BSL, Madelung's disease) is a rare disease characterized by symmetrical and diffuse adipose tissue deposits over the neck. Its etiology is unknown. Alcoholism, liver disease, hyperuricemia, diabetes, and hyperlipidemia have been described in association with this condition. The Mediterranean region seems to have the highest incidence of BSL. We report a case of BSL in a 64-year-old man referred to our hospital because of disfigurement of the neck. The patient showed a characteristic appearance, with multiple symmetrical fat tissue deposits over the neck, back, and arms. He had a high intake of alcohol over the past 30 years, and laboratory examinations revealed elevation of transaminases. Hyperlipidemia was also observed. There was no family history of similar disorders. Surgical excision of the mass in the left side of his neck was done under general anesthesia. Histological examination of the neck mass revealed unencapsulated adipose tissue with no evidence of malignancy.

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