Yoichiro Kameyama

Pulpal and periapical tissue reactions after experimental pulpal exposure in rats

The purpose of this study was to investigate histologically and histometrically the changes in pulpal and periapical tissues after pulpal exposure in rats. All animals received a pulpal exposure in the left mandibular first molar. Animals were killed at 1 to 56 days after pulpal exposure, and their mandibles were evaluated histologically and histometrically. Histologically, pulpal necrosis extended gradually from the upper part of the pulpal tissue to the apex, with inflammation starting in the periapical tissue at an early stage. As the periapical lesion developed, alveolar bone and cementum resorption was also found. Histometrically, the length of pulpal necrosis increased gradually from 1 to 28 days. The vertical length of the periapical lesion after 14 days was significantly increased, while the horizontal length and the overall area after 7 days were also significantly increased. The periapical lesion extended in a mesiodistal direction at first and then in a vertical direction before expansion ceased.

Distribution of fluoride concentration in the rat's bone.

SummaryThe present study was undertaken to determine the fluoride distribution profile in the rat femur. Male Wistar rats were divided into four groups and given water containing 0, 25, 50, and 100 ppm of fluoride, respectively, for 10 weeks. The fluoride distribution from the periosteum to the endosteum was determined in each specimen after sampling using the abrasive microsampling technique [5]. In the outer circumferential lamellae, the concentration of fluoride was relatively high in the periosteal layer and then decreased gradually towards its interior. In the haversian and interstitial lamelae, it was lower and roughly constant through the tissue. In the inner circumferential lamellae, it rose again to reach the highest level towards the endosteal surface. Fluoride concentration throughout the cortex increased significantly with increasing intake of fluoride. These increases were especially marked at periosteal and endosteal surfaces.

Human papillomavirus type 38 infection in oral squamous cell carcinomas.

In this study, 53 paraffin-embedded oral squamous cell carcinoma (OSCC) biopsy specimens were used. Human papillomavirus type 38 (HPV-38) infection was demonstrated in OSCCs using the PCR technique, DNA sequencing analysis, in situ hybridization, and immunohistochemical techniques. Additionally, the correlation between HPV-38 infection and expressions of proliferating cell nuclear antigens (PCNA) or p53 protein was analyzed immunohistochemically. Using consensus primers for the L1 region (L1-PCR), we identified 35 of 53 specimens (66%) as positive for HPV-38 DNA. Furthermore, specimens from patients over 60 years of age revealed a lower prevalence for the HPV-38 (56.7%) than did those below that age (78.3%). Immunohistochemically, positive stainings for PCNA and p53 protein were more frequently detected in HPV-38 positive OSCCs than HPV negative ones. These results indicate that HPV-38 positive OSCCs were higher in proliferative cellular activity than HPV negative ones. Moreover, the findings suggest that HPV-38 infection may cause malignant transformation of the oral mucosal epithelium.

Human papillomaviruses in the normal oral cavity of children in Japan

The purpose of this study was to determine the frequency of human papillomavirus (HPV) infections in the normal oral cavity of children in Japan. Oral squamous cell specimens were collected from 77 children (44 boys and 33 girls), aged 3 and 5 years. Extracted DNA was evaluated for HPV infections by polymerase chain reaction (PCR) methods, using consensus primers for the L1 region, specific primers, and direct DNA sequencing analysis. Thirty-seven of 77 specimens (48.1%) were positive for HPV DNA. Positive rates of boys and girls in all specimens were 28.3 (22/77) and 19.5 (15/77)%, respectively. The positive rate in 3-year-old children was 45.2 (14/31)%, and positive rates in boys and girls were 52.6 (10/19) and 33.3 (4/12)%, respectively. The positive rate in 5-year-old children was 50.0 (23/46)%, and positive rates in boys and girls were 48.0 (12/25) and 52.4 (11/21)%, respectively. HPV types were determined by specific PCR and direct DNA sequencing analysis. Frequent HPV types in the specimens of all children were HPV-16 (11/37; 29.7%),-1 (6/37; 16.2%),-2 (6/37; 16.2%),-75 (6/37; 16.2%). The results of the present investigation indicate that many HPVs, including HPV-16 (a high-risk type for cancer), are present in the oral cavity of 3- and 5-year-old children. It is suggested, therefore, that the oral cavity is already a reservoir of HPVs in childhood where later HPV-associated diseases, such as oral cancer and other oral lesions, may develop.

A clinicopathological study of ameloblastomas

72 cases of ameloblastoma were obtained from the files of the Department of Pathology, School of Dentistry, Aichi-Gakuin University for the years January 1970 through December 1983. The cases were analyzed with respect to sex, age, duration, site histopathology, and treatment. Of 72 patients, 63 had no previous therapy, while 9 received their initial treatment elsewhere. There were 38 males and 34 females, a ratio of 1.2: 1. At the time of diagnosis, the ages of all patients ranged from 11 to 71 years, with an average of 36.6 years. About 65% of patients were in the 2nd, 3rd, and 4th decades of life. The duration of symptoms varied from 2 days to 5 years, with an average of 12.6 months. 69 cases occurred in the mandible, with the molar-ramus region being the most frequent site of involvement. Only 3 were found in the maxilla. The left side of the mandible was affected 1.6 times more frequently than the right. Histopathologically, 44 cases were of the plexiform type, 15 the follicular, 10 the acanthomatous, and 2 the basal cell type. Only 1 case was of the granular cell type. Most of the findings in the present study agreed with previous available data from the literature on ameloblastomas.

Release of mercury from dental amalgam fillings in pregnant rats and distribution of mercury in maternal and fetal tissues.

Mercury vapor released from a single amalgam restoration in pregnant rats and mercury concentrations in maternal and fetal rat tissues were studied. Dental treatment was given on day 2 of pregnancy. Mercury concentration in air sample drawn from the metabolism chamber with the rat was measured serially for 24 h on days 2, 8 and 15 of pregnancy. An average mercury concentration in the air samples from the rats given amalgam restorations was 678.6+/-167.5 ng/day on day 2. The average mercury concentration in the air samples tended to decline as time elapsed but a marked amount (423.2+/-121.5 ng/day) was observed even on day 15. The amount of mercury in the air samples increased 7--20-fold after chewing. The placement of the single amalgam restoration (3.8--5.5 mg in weight) increased the levels of mercury approximately three to 6 times in the maternal brain, liver, lung, placenta and 20 times in the kidneys. The highest mercury concentration among fetal organs was found in the liver, followed by the kidneys and brain. Mercury concentrations in maternal organs and fetal liver were significantly higher than those of the controls, and concentrations in maternal whole blood, erythrocytes and plasma, and in fetal whole blood were also significantly higher. Mercury concentrations in the fetal brain, liver, kidneys and whole blood were lower than those of the maternal tissues.

The Effect of High Sugar Intake on the Development of Periradicular Lesions in Rats with Type 2 Diabetes

Diabetes mellitus is associated with depression of natural defenses against infection and increases the risk of periodontal disease. However, the effects of diabetes on periradicular tissue, which differs structurally from periodontal tissue, are not known. In this study, we evaluated the effects of type 2 diabetes on the development of periradicular lesions after exposure of the pulp in the left mandibular first molar through the occlusal surface in rats. GK rats with spontaneous non-insulin-dependent diabetes mellitus and Wistar rats (controls) received a normal laboratory diet and either water or a 30% sucrose solution. At both 2 and 4 weeks after pulp exposure, histologic analysis showed that alveolar bone resorption was most severe and the periradicular lesions were largest in diabetic rats given the sucrose solution. These results suggest that the metabolic conditions produced by type 2 diabetes enhance the development of periradicular lesions in rats.

DNA Vaccine against Hamster Oral Papillomavirus-associated Oral Cancer

Previously we developed a carcinogenesis model involving the combination of 9, 10-dimethyl-1, 2-benzanthracene (DMBA) application with physical wounding of hamster lingual mucosa. The presence of a novel hamster oral papillomavirus (HOPV) was demonstrated and its genome sequenced. In the present study, this HOPV hamster model was used to test whether vaccination with the L1 gene could prevent the development of oral carcinoma. DNA plasmids encoding the L1 gene or the vector alone were injected intramuscularly into 20 vaccinated and 20 control hamsters, respectively. The lingual tips of the hamsters were painted with DMBA for 8 weeks. A portion of the lingual tips was excised, and the tips were then painted daily with DMBA until the animals were killed 13 days later. All control hamsters developed lingual carcinoma, whereas 12 of the L1-vaccinated hamsters showed no lesions. These results suggest that immunization with L1 DNA vaccines may prevent the development of papillomavirus-associated oral cancer.

Verruciform xanthoma of the gingiva: Report of three cases

Forty-seven English and Japanese cases (including three new cases) of verruciform xanthoma of the gingiva were analyzed. Males were affected more frequently than females, and the average age of the patients was 40.9 years. Both maxillary and mandibular gingivae were affected. The most frequent site of involvement in both jaws was the premolarmolar gingiva. Simple surgical excision was the treatment of choice.

Ultrastructure of the congenital epulis

This report presents the ultrastructural features of a congenital epulis. The granular cells of the epulis were packed with numerous membrane bound cytoplasmic granules containing particles, small vesicles, and electron-dense materials. These granules were negative in immunohistochemical reaction for CEA (DAKO PAP KIT). Cytoplasmic organelles such as mitochondria, rough surfaced endoplasmic reticulum, and Golgi apparatus, were absent. Nuclei were markedly indented. Occasionally, banded intracellular collagen fibrils were observed within the cytoplasm. Some of these fibrils were surrounded by a limiting membrane, whereas others appeared to lie free in the cytoplasm. The collagen fibrils were also seen within a deep invagination of the cell surface. There was no basal lamina around the granular cells. Sporadically, mast cells with many granules containing lamellar formations were found between the granular cells. These observations support the idea that granular cells of the congenital epulis are derived from mesenchymal cells, probably fibroblasts.