Tatsuo Hashida

Effect of Experimental Hyposalivation on the Induction of Dental Caries in Rats Infected with Streptococcus mutans

The effects of hyposalivation on the induction of dental caries were examined in specific pathogen-free Sprague-Dawley rats infected with Streptococcus mutans MT8148R and fed the caries-inducing diet 2000. Hyposalivation was induced by either irradiation or surgical removal of salivary glands in 30-day-old rats. After either procedure, severe dental caries was induced in the rats when examined at 84 days of age, and a statistically significant correlation was found between caries scores and flow rates of saliva. However, the recovery of strain MT8148R from hyposalivated rats was not always high, and it is possible that microorganisms other than the inoculated S. mutans strain MT8148R may have played a role in promoting dental caries.

Change of Salivary IgA Secretion and Caries Development in Irradiated Rats

Xerostomia is a serious side-effect of radiotherapy for head and neck cancer and often enhances caries activity. However, the relationship between caries induction and the IgA level in saliva in rats subjected to irradiation of the salivary glands is unclear. The effect of salivary gland irradiation on salivary function was examined in specific pathogen-free Sprague-Dawley rats infected with or without Streptococcus mutans MT8148R (serotype c). The flow rate of saliva and the protein concentration in saliva were significantly reduced in irradiated rats, regardless of infection of S. mutans. The caries activity was enhanced in these rats, and an irradiation level of 50 Gy significantly increased the caries score. However, longitudinal study indicated that the salivary concentration of IgA reactive with S. mutans whole cells maintained similar or significantly higher levels in irradiated rats, when compared with those of nonirradiated rats. In addition, there was no negative correlation between the caries score and the salivary concentration of IgA reactive with S. mutans. These findings suggest that the secreted IgA against S. mutans may not play a significant role in the caries induction of hyposalivated rats.

Preliminary nuclear magnetic resonance studies on human saliva

Of gustatory-stimulated human whole, parotid, submandibular and sublingual saliva only parotid saliva, a serous rather than mucous secretion, presented a relatively well-resolved proton NMR spectrum with satisfactory signal-to-noise ratio in a short time (30 min). The proton signal intensities showed significant circadian rhythms related to the circadian rhythms of protein concentrations in saliva. Age- and sex-associated differences in spectra were not observed for healthy saliva. On the other hand, marked differences in the spectra were observed for patients with suspected sialoadenitis.

Effects of Hyposalivation on the Oral Microflora of Rats Fed Sucrose or Wheat Flour Diets

The effects of hyposalivation on the induction of dental caries and on the composition of the oral microflora were examined in specific pathogen-free Sprague-Dawley rats fed either a sucrose or a wheat flour diet with or without inoculation of Streptococcus mutans. Significant dental caries was induced in hyposalivated rats fed diet 2000 containing 56% sucrose, irrespective of infection by S. mutans. Diets containing 56% wheat flour did not induce dental caries in either hyposalivated or sham-operated rats, irrespective of infection by S. mutans. Bacteriological examinations at the end of the experiment demonstrated that the total numbers of lactobacilli and staphylococci increased in hyposalivated rats irrespective of the diet given, while the inoculated stain of S. mutans decreased significantly in hyposalivated rats. These findings suggest that some acidogenic microorganisms such as lactobacilli and staphylococci that can utilize sucrose or glucose but not wheat flour may also promote dental caries in hyposalivated rats.

Dental caries induction in hyposalivated rats.

The effects of hyposalivation on the induction of dental caries and on the oral microflora were examined in SPF Sprague-Dawley rats with or without inoculation of oral streptococci. Significant dental caries was induced in hyposalivated rats, irrespective of the infection with oral streptococci including Streptococcus mutans. In addition, bacteriological analyses demonstrated that the total number of lactobacilli increased significantly at the expense of the inoculated streptococci. These findings suggest that opportunistic infections may be induced in the oral cavity of hyposalivated rats and some acidogenic microorganisms including lactobacilli may promote the induction of dental caries.

The effect of X-ray irradiation-induced hyposalivation on caries induction in SPF rats infected withStreptococcus mutans

The effects of X-ray irradiation to the salivary glands on the induction of dental caries and on the oral microflora were examined in specific pathogen-free Sprague-Dawley rats fed a sucrose diet and inoculated with a strain ofStreptococcus mutans. Hyposalivation was induced by irradiation of 35 Gy and dental caries was significantly enhanced in irradiated rats infected withS. mutans. Bacteriological examinations at the end of the experiment demonstrated that the recoveries of lactobacilli and staphylococci significantly increased in hyposalivated rats with 50 Gy of irradiation. However, the recovery of the strain ofS. mutans from hyposalivated rats were not significantly higher than that of non-irradiated rats. These findings suggest that some acidogenic microorganisms such as lactobacilli and staphylococci may have played some role in promoting dental caries.

Myxoma of the Jaws—report of six cases

SummaryClinical-radiographical analysis of six cases with myxoma of the jaws diagnosed histopathologically was attemped, and the following summary was obtained.1.All patients presented with either painless swelling or no symptoms, and it is suggested that myxoma of the jaws is not a rapidly growing and is a benign lesion according to their histories and clinical-radiographical findings.2.Radiographs of six cases showed rather variable appearances and needed to be differentiated from that of ameloblastoma, hemoangioma, giant cell tumor, fibrous dysplasia or dentigerous cyst.3.Though most of myxomas in the jaws are considered to be of odontogenic origin, odontogenic epithelium was found histopathologically in only one of five cases.

Large recurrent ameloblastoma

The ameloblastoma is the most common odontogenic tumor. It is usually described as a locally malignant lesion, because it has been characterized as a benign tumor with a marked tendency to recur. In a recent survey of the literature, t reatment by curettage was found to have resulted in a 50-90 per cent recurrence rate 1,2) and hemiresection in about a 10 per cent recurrence rate% The following two cases are unusual due to the long period elapsed before their recurrence after a hemimandibulectomy and in that they showed large recurrent lesions.

The effect of X-ray irradiation on the function and saliva composition of rat parotid and submandibular/ sublingual glands

Radiation therapy to the head and neck area frequently causes severe salivary gland dysfunction and xerostomia. Morphological studies of irradiated salivary glands have suggested that the submandibular/sublingual gland may be less radiosensitive than the parotid gland. The purpose of this study was to evaluate the effect of radiation on major salivary gland functions in rats with radiation-induced xerostomia.The effect of salivary gland irradiation on salivary function was examined in specific pathogen-free Sprague-Dawley rats. The animals were irradiated with a single exposure of either 22 Gy or 32 Gy. Stimulated saliva excretion time was measured for the parotid and submandibular/ sublingual glands, and the total protein in saliva was analysed.Our results showed that the saliva flow rate and protein concentration of parotid saliva were significantly reduced in the 32 Gy-irradiated rats.

Dentigerous cyst of an impacted mesiodens

Dentigerous cysts are usually associated with the crowns of unerupted or developing teeth, and which is the common odontgenic cyst in the jaws. The patient, a 37-year-old man was refered to Osaka University Dental Hospital complaining of alveolar bone swelling at the left upper anterior region. About six months previously, the dentigerous cyst happend to be disclosed on a panoramic radiograph taken for dental treatment, although the patient had not noticed any symptom. Clinical examination showed a diffuse swelling in the region of the left side of the ala of the nose. Intraorally, there was a swelling extending labially from the upper right incisor to the upper left first premolar. The covering mucosa seemed to be normal or slightly reddish. He was in good health, and general oral condition was good. Panoramic r ad iog raph and in t raora l r a d i o g r a p h s revealed a large round radiolucency of the anterior maxil la including the apex of the left incisors, but also in continuity with an inpacted mesiodens (Fig. 1, 2). The frontal tomograph showed a well-defined unilocular