The mercury levels in human were measured at various parts of the body. Previously the quantity of mercury in teeth has been investigated in Kitakyushu and other places.
The chronological distribution of mercury in the human body could be detected by the tooth age, which means intraoral exposure period from eruption to extraction. We measured the mercury level in teeth in Seattle, Washington, through precise basic reseach.
The mercury level in the Seattle area is half that of the Japanese. The peak of the histogram from Seattle has a lower level than that of the Japanese.

View full abstract

The fluoride concentration in dental plaque has been shown to be much greater than in saliva. But there have been few studies on distribution of concentration and mode of binding and the physiological significance of fluoride. The content of fluoride, calcium and inorganic phosphate was determined for individual samples of dental plaque collected from 55 school children aged 7-15 years who resided in a low fluoride area.
The relationship among fluoride, calcium, inorganic phosphate and total weight of the plaque was analyzed statistically. The mean fluoride, calcium, and inorganic phosphate concentrations in plaque of junior high school students were higher than those of elementary school children. There was a close relationship between the fluoride and the calcium concentration in plaque (r=0.76, P<0.001). The increase in plaque calcium concentration was very strongly associated with the increase in plaque inorganic phosphate concentration and vice versa (r=0.85, P<0.001). The fluoride concentration was positively correlated with the inorganic phosphate concentration in plaque. Partial correlation analysis, however, showed that the fluoride concentration did not correlate with inorganic phosphate concentration if the calcium concentration factor was fixed. A positive correlation was found between the plaque fluoride and the Ca/P ratio (r=0.53, P<0.001). The fluoride concentration in plaque was negatively correlated with the total amounts of the plaque collected (r=-0.57, P<0.001).
From the results obtained, fluoride could be bound to the calcium or amorphous calcium phosphates in plaque.

View full abstract

An attempt has been made to monitor colonization of S. mutans in fissures of rat molars, and bacterial flora of both fissures and oral cavity have been examined during the progress of tooth eruption.
During this examination S. mutans strains which exhibited unique colony morphology on MS and TYC agar were isolated from fissures of rat molars, and their properties were investigated. S. mutans FA-1 and strains freshly isolated from oral cavity were used as control strains.
Molars extracted from rats were dipped into melted wax to sterilize their surfaces and ground into powder. The powder was sonicated in peptone water, and the resulting suspension wasplated on MS and TYC agar, and then incubated anaerobically for 48 hr at 37°C. The isolated strain and control strains were cultured in both modified Minimal and Complete media of Lederberg (1950). The bacterial growth was determined by the turbidity at OD₆₃₀. Acid production was monitored by pH changes and GLC. The glucosyltransferase (GTase) activity was determined as described by Wenham et al. (1979).
Isolated strains did not synthesize dextran and formed pinpoint colonies on agar plates. Theyformed much longer filamentous chains with cells which were more elongated than control strains.
However, repeated culturing and subsequent plating of the isolated strain on Complete medium revealed increasing numbers of colonies which resembled those of control strains. No difference in lactic acid production and GTase activity was observed between the isolated strain and FA-1, but the freshly isolated strain grew in Minimal medium more rapidly than FA-1 which was inoculated from TYC medium of our stock culture. Repeated culturing of FA-1 in Minimal medium changed its morphology to that of the freshly isolated strain.
This study suggests that the freshly isolated strain may be a mutant of S. mutans, and that the phenotype of S. mutans under the strictly limited conditions in deep fissures may be different from that of S. mutans in the oral cavity.

View full abstract

The activity of bacterial neuraminidase in the oral cavity may have an important role in oral disease, but details of its biological function are unknown. This study deals with the purification and some properties of neuraminidase from culture medium of Bacteroides melaninogenicus ATCC 15930 which was isolated from human gingival crevice. Neuraminidase secreted by the cells into the culture medium was isolated and purified by procedures involving ultra filtration, DEAE-Sephacel column chromatography, fast protein liquid chromatography (FPLC), and high performance liquid chromatography (HPLC). The molecular weight of the purified enzyme was estimated to be 83, 000 by HPLC using a G4000SW column, and the isoelectric point was 5.1. The optimal pH of the purified enzyme activity was pH 4.8. A single protein band having a molecular weight of about 46, 000 was obtained by disc electrophoresis on polyacrylamide gel containing 0.1% sodium dodecyl sulfate. These findings suggest that the purified enzymeis formed of dimers. The substrate specifity of the enzyme is under investigation.

View full abstract

The purpose of this study was to gain more definitive information on the placental transfer of fluoride in rats at low maternal intake level.
Wistar rats (8 week-old) were used in this study, and they received a low fluoride diet (F=0.3 ppm) and distilled water. They were mated after being kept a week under the experimental conditions. Female offspring born from them were randomly assigned to nine groups with various levels of fluoride intake at 3 weeks of age. They received a low fluoride diet and 0-10 ppmF (as NaF) solution, or an ordinary breeding diet (F=33ppm) and tap water (F≅0.1 ppm). The nine groups were called the 0, 0.1, 0.2, 0.5, 1, 2, 5, 10ppm group, and tap water group. They were mated with male rats at 12 weeks of age. Females were killed immediately after delivery. Plasma and left femurs were obtained from 158 females, and plasma and tibiofemoral bones of the newborn pups were taken from each litter. Plasma inorganic fluoride and bone fluoride were analyzed with the electrode method following diffusion procedures. Total plasma fluoride in females was analyzed with the electrode method following ashing and diffusion procedures.
Close agreement was found between inorganic and total values of plasma fluoride in females. Plasma inorganic fluoride in females of the 0-1 ppm groups was constant, ranging from 2-4 ppb, but it rose from 4 ppb to 74 ppb in proportion to fluoride intake in the 1-10ppm and tap water groups. The fluoride in pups of all groups were ranging 2-6 ppb. Bone fluoride concentrations in adult females rose from 7 ppm to 763 ppm, and those in pups rose from 7 ppm to 56ppm in proportion to fluoride intake in all groups.
These findings suggest that (1) there is little organic fluorine in rat plasma, (2) plasma fluoride in rats may be maintained at a lead above about 3 ppb, (3) the amount of fluoride transferred to rat fetuses increases in proportion to fluoride intake even at low maternal intake levels, and (4) bone fluoride in newborn pups is an excellent index of the amount of fluoride transferred to fetuses.

View full abstract

HEPA filters are widely used for air cleansing in hospital wards for operatory and blood disease patients. In recent years need has been felt for a convenient and small bioclean room, and the HEPA filter has come to be attached to a compact air purifier in actual clinical environments.
We have studied a small air purifier, “Enviracaire”, equipped with a HEPA filter (abbreviated E.V.C.) in a series of basic experiments on dust removal and bacterial elimination capacity. We obtained the following conclusions.
1. The wind velocity of the E.V.C. at high speed operation was 0.4 m/sec and the wind volume was 0.07m/sec.
2. When box A was installed on the dispersion outlet of the E.V.C, for the purpose of shutting off the flow of contaminated air from other parts, removal of dust particles under 0.42-0.62μm was 99.97-99.99%, and of particles over 0.62 pm, 100%. The weight of dust particles was 100% in all cases. Air-borne bacteria were removed 100% in all cases. Even when a high concentration of Serratia marcescens was sprayed into the air, removal was 100 % as observed by a SY type pinhole sampler (the SY method).
3. When box A was removed and experiments were conducted as in actual conditions, at the center of the E.V.C. outlet dust particles over 0.62μm were found at distances greater than 50 cm. Particle weight also increased at distances greater than 50cm. With the SY method removal at different distances was 75.0-100%, and with the HV method removal was 69.7-100% with 15 minute suction, 64.3-100% with 30 minute suction, and 78.4-100% with 60 minute suction. At distances less than 60cm the existance of bacteria was quite small.
4. It is to be concluded that though this apparatus is highly effective in removal of dust and bacteria and, in the future, may have practical application.

View full abstract

The environmental problems in dental clinics claim our attention because of the special nature of dental treatment such as cutting and grinding of the teeth and prosthetic material. In recent years, the air turbine engine developed as a super high speed apparatus for the cutting of teeth has come to be widely used in dental treatment. But because the cutting of teeth has become highly effective, dental cuttings, saliva and bacteria from the mouth of patients cause pollution of the air inside dental clinics.
The present study was made of the air-borne bacteria in various clinics at dental hospital N. Pure cultures were made of the bacteria and their bacteriological characteristics were investigated. The following conclusions were obtained.
1. Bacterial counts in the clinics were 0.41-2.13/l in April, 0.41-1.41/l in July and 0.30-2.27/l in December. The bacterial count in clinic A for five days was 0.26-1.12/l. The number of air-borne bacteria during dental treatment was to 3.1 to 7.6 times more than during the pre-treatment stage.
2. The correlation between the number of patients and bacterial counts in the various clinics was 0.406-0.777. The correlation for five days in clinic A was 0.971. Thus a high correlation was observed between the density of patients and bacterial counts.
3. Bacteriological characteristics.
1) The air-borne becteria at dental hospital N consisted of 12.4% Myces, 34% bacilli, and 53.6% cocci.
2) From the pure cultures of air-borne bacteria, we found that gram-positive cocci were 117 (51.5%), gram-negative cocci were 22 (9.7%), gram-positive bacilli were 71 (31.3%), and gram-negative bacilli were 17 (7.5%).
3) Those which proved to be positive in hemolytic reaction either to human or horse blood were 70 (30.8%). Of them, a hemolytic types were 12 and 9 hemolytic types were 55, and 3 proved to be a hemolytic to human blood and β hemolytic to horse blood.
4) 5 Gram-positive bacilli were proved to from spores, accounting for 7.0%.
5) Among the air-borne bacteria in the clinics, the existence of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Micrococcus, Bacillus subtilis and Serratiawas confirmed.

View full abstract

Glycoproteins in saliva play an important role in dental plaque formation. This study deals with the binding of oral bacteria with the sialic acid-rich glycoprotein purified from human submandibular-sublingual saliva. Sialoglycoprotein was isolated and purified from human submandibular-sublingual saliva by fast protein liquid chromatography followed by high performance liquid chromatography (HPLC). The molecular weight of the purified sample, consisting of four subunits, was estimated to be 440K daltons by both the HPLC and SDS-disk electrophoresis. Both Streptococcus sanguis and Bacteroides gingivalis had high binding affinity to sialoglycoprotein. When the cell surfaces of both bacteria were treated with trypsin at 37°C for 90minutes, the decrease of radioactivity was less in Streptococcus sanguis than Bacteroides gingivalis. No radioactivity was detectable in the 2 pieces of bacteria after heating at 100°C for 10minutes, indicating the lost of binding ability.

View full abstract

In order to estimate the influence of diagnostic reversals on the evaluation of dental health program, we investigated the data from 9276 school children's first molars, which had been examined annually by school dentists. The results were as follows:
1. A high rate of diagnostic reversals were found in the lower school grades. The rate of the reversal decreased in the higher grades.
The upper first molars showed a higher rate of reversal than the lower first molars.
2. Almost all of the diagnostic reversals were from the first degree of dental caries. The rate of the reversal from the first degree of dental caries of upper first molar was about 40.9-47.7% in the lower school grades and about 20% in the higher grades. The reverse rate of lower first molar was about 20% in the lower school grades and about 10% in the higher grades. The rate of the reversal from the second degree of dental caries was about 20% for the upperand 10% for the lower first molar, and there were no differences between the lower and higher school grades.
3. There was no influences of diagnostic reversals on the evaluation of the dental health program when we used the decayed teeth having more than the second degree of dental caries. But we found some influence of diagnostic reversals on the dental health program when weused the first degree of dental caries and above.

View full abstract

The purpose of this study was to elucidate whether the hepatitis B virus infection of practicing dentists occurrs through saliva. I investigated the mechanism of HBs antigen occurrence in saliva and the possibility of contamination from saliva containing by hepatitis B virus during dental treatments.
1. From the analysis of the relationship between the amount of HBs antigen in serum and saliva and the amount of occult blood in saliva in HBV carriers, I found that the HBs antigen found in saliva might come from direct contamination by blood. Therefore, the amount of HBs antigen in saliva can be estimated by the amount of occult blood.
2. The occult blood was measured with Hemastix in 245 cases of general dental treatment. Bleeding was found to increase more than 90% in cases of tooth extraction, scaling, and crown & bridge preparation. These cases gave a veading of more than positive “+++” in the Hemastix test.
The results suggested the possibility that minimum infective dose (according animal experiments) was released into the mouth as HBs antigen. This comfirmed the possibility that practicing dentists are exposed to danger of infection with HBV through the HBV carriers' saliva.
It might be possible to decrease the efficacy of hepatitis B virus by frequent washing of the oral cavity during dental treatments.

View full abstract

The effects of NaF on the growth of Streptococcus mutans (St. mutans) and the activity of dextransucrase purified from St. mutans were examined in vitro. The minimum inhibitory concentrations (MIC) for a fluoride provided as NaF were lower than 180 ppmF without regard to St. mutans serotypes (a-g). NaF arrested bacterial growth at the concentrations of 180 and 360 ppmF bacteriostatically. No effects of fluoride on the synthesis of water-insoluble dextran were observed in the cell-freesystem.

View full abstract

A protease derived from Streptomyces globisporus strain 1829 diminished the activity of glucosyltranferase (EC 2. 4. 1. 5) produced by Streptococcus mutans to synthesize water-insoluble polysaccharide, as determined turbidimetrically in a salivary mixture. Mouth rinses containing the protease interfered with the formation of dental plaque in humans. This protease had no effect on the activitiy of salivary peroxidase, α-amylase, and lysozyme. The possible clinical application of the protease for the control of dental plaque was discussed.

View full abstract

In order to understand regional differences in situation and incidence rate per year of HBV infection for Japanese dentists, we surveyed anti-HBs antibody positive rate for dental practitioners at Nerima (Tokyo), Utsunomiya (Tochigi), and Hachinohe (Aomori). A longitudinal survey of conversion rate positive with the anti-HBs/c antibodies was also done for dentists at Hachinohe.
The anti-HBs antibody positive rate for dentists at Hachinohe was found to be noticeably higher than those at Nerima and Utsunomiya. However, the rate of anti-HBs antibody in the districts of Nerima, Utsunomiya and Hachinohe was the same level as those in other districts previously reported (see ref. 4, 5, 6, 15), implying that there is little regional difference of the HBV infection in Japanese dentists. It also seems that the regional difference was not related to the kind of HBs-Ag subtypes, period of the survey, and ages of the subjects.
During the year of December of 1982 to 1983, the antibody positive conversion rate was found to be only one case (2.3% of the incidence rate per year) out of 43 dentists in the Hachinohe district. Furthermore, it was implied by the longitudinal survey that HBV infection was much related to the length of clinical work These results indicate that preventive treatments of HBV infection in Japan shoud be done either before or immediately after clinical work

View full abstract

To measure the adhesive force when pulling an explorer from a carious pit or fissure, a system consisted of a load cell, a DC amplifier, and an electromagnetic oscillograph was devised.
277 carious portions of pits and fissures of 99 extracted premolar and molar teeth were probed with an explorer, and were allocated to three groups according to the tactile sensations, “not adhesive”, “questionably adhesive”and“discernibly adhesive”when pulling out the explorer. The mean pressure when inserting an explorer into a pit or fissure was 819.1 (S.D. =40.0) g. When pulling out the explorer, the ranges of the adhesive forces judged“not adhesive”, “questionably adhesive”and“discernibly adhesive” were from 0 to 36.8g, from 0 to 96.7g, and from 27.6 to 387.7g, respectively.
These results suggest that it is difficult to distinguish“questionably adhesive”from“not adhesive”by tactile sensation, but that it will be possible to distinguish“discernibly adhesive”from“not adhesive”if the standard of judgment as discernibly adhesive force is clearly defined.

View full abstract