The Third International Intercomparison on EPR Tooth Dosimetry: part 2, final analysis.

The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.

A method to differentiate between the levels of ESR signals induced by sunlight and by ionizing radiation in teeth from atomic bomb survivors.

Electron spin resonance (ESR, or electron paramagnetic resonance, EPR) analysis of tooth enamel is an effective method for the retrospective estimation of individual radiation doses. One problem with this technique is that the observed ESR signal may include a contribution from ultraviolet (UV) light exposure from sunlight, especially in front teeth. Thus there has been a need to find ways to estimate the UV-light effect in the total signal so that the net ESR dose from ionizing radiation can be determined. To examine this issue, we measured 96 teeth of various types, but with buccal and lingual parts measured separately, from a control group of atomic bomb survivors (estimated dose <5 mGy). We found that, except for molars, the mean ESR-estimated dose for the buccal halves was, on average, nearly twice that from the lingual side, which indicates that the UV-light-induced lingual dose equals the difference between the two halves. Using these corrections for UV-light exposure to front teeth that had been exposed to both ionizing radiation and UV light, it was found that the estimated radiation doses closely approximated the previously estimated ESR dose to molars from the same donors or the estimated dose arrived at with cytogenetic methods. We concluded that, when using ESR to estimate radiation dose, measuring molars is the first choice, but if only front teeth are available, separate measurements to the buccal and lingual parts can provide an estimation of the mean UV-light contribution to the ESR-determined dose.

The 3rd international intercomparison on EPR tooth dosimetry: Part 1, general analysis.

The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.

Comparison of three methods of numerical procedures for ESR dosimetry of human tooth enamel.

Three numerical methods were employed to examine how gamma ray doses ranging from 100 mGy to 1Gy could be reconstructed using five human molar teeth. For samples above 28 0mGy, the obtained doses are consistent with each other within the errors but slightly larger than actually given doses. Background doses range from 20 to 170 mGy depending on the methods and samples. Further precise studies would be needed to characterize each method, but it would be recommended to apply several methods to check the reliability of the obtained doses.

Analyses of absorbed dose to tooth enamel against external photon exposure.

Absorbed dose to tooth enamel was examined against external photon exposure by measurements with thermoluminescence dosemeters (TLDs) and Monte Carlo calculations. TLDs were placed in a realistic physical phantom to measure dose to the teeth region in a head. A voxel-type phantom was constructed from computed tomography (CT) images of the physical phantom. Monte Carlo calculations with this voxel-type phantom were performed to analyse the results of the experiments. The data obtained were compared to the enamel doses, which were calculated with a modified MIRD-type phantom and already given in a previous paper. It was confirmed that the data derived with the MIRD-type phantom are applicable for retrospective individual dose assessments by electron spin resonance (ESR) dosimetry using teeth for the photon energy region above 300 keV. The analysis, however, indicated that the configuration of the head can affect the enamel dose relative to external exposure to photons with energy below 100 keV.

Relations between tooth enamel dose and organ doses for electron spin resonance dosimetry against external photon exposure.

An analysis of doses to tooth enamel and to organs was carried out to develop a method that can predict the organ doses and the effective dose by electron spin resonance (ESR) dosimetry using tooth samples for external photon exposure. Absorbed dose to tooth enamel and organ doses were obtained by Monte Carlo calculations using the EGS4 code in combination with a mathematical human model with a newly defined teeth part. The calculations gave quantitative relations between tooth enamel dose and organ doses for some cases of external photon exposure. It was also found that tooth enamel dose depends more significantly on energy of incident photons than the other organ dose or the effective dose. The obtained data are to be useful for the assessment of individual dose in past exposure events by the ESR dosimetry using tooth enamel.

EPR dose reconstruction for Russian nuclear workers.

The present paper describes results of the first independent evaluation of the accuracy of the dose-reconstruction technique by electron paramagnetic resonance using tooth enamel. Each of twenty-four teeth donated by Mayak nuclear workers with known occupational radiation exposure histories was cut into two parts so that each tooth could be shared for blind electron paramagnetic resonance examination by at least two of the four laboratories participating in the study. The mean difference (+/- SD) between electron paramagnetic resonance estimates of the paired samples of each tooth shared by the two laboratories in best agreement was 0.02 +/- 0.15 Gy. Mayak workers can be classified into two groups: modern workers (after 1961) having reliable official dose information and earlier nuclear workers whose dose information is less reliable because they were exposed mainly before 1961. Film badges did not contain filters until 1954. Doses in this earlier group are much higher (up to 5 Gy). Comparison of the electron paramagnetic resonance results with tooth doses calculated from official film-badge doses showed a close agreement for the first group, whereas in the second group, official doses appeared to be slightly higher than the electron paramagnetic resonance doses. The results suggested a possibility that the official doses were somewhat overestimated among the high-dose-exposed workers. Consequently, cancer risks derived from this high-dose group might tend to be slightly underestimated.

Contamination from possible solar light exposures in ESR dosimetry using human tooth enamel.

Electron spin resonance (ESR) measurement data of 98 teeth from atomic-bomb survivors who received various radiation doses were analyzed in terms of possible solar light exposure by tooth position. Each tooth was divided into buccal and lingual parts for independent ESR measurement. We found that average buccal doses were larger than their corresponding lingual doses by 0.48 +/- 0.30 Gy (first incisors), 0.33 +/- 0.38 Gy (second incisors), 0.20 +/- 0.23 Gy (canines), 0.24 +/- 0.26 Gy (first bicuspids), 0.17 +/- 0.51 Gy (second bicuspids) and 0.04 +/- 0.18 Gy (large molars and wisdom teeth). Such a clear declining trend following tooth position in the mouth is readily appreciated as due to solar light exposures. Comparisons of lingual doses of multiple teeth from the same five donors suggest that lingual doses of first incisors were also overestimated by 0.34 +/- 0.18 Gy. From the results presented, we deduce that the buccal doses of first incisors are, on the average, overestimated by nearly 0.8 Gy. Therefore, use of front teeth for biodosimetry requires special caution. How to estimate the contribution from exposure to solar light in ESR biodosimetry is discussed.

A close correlation between electron spin resonance (ESR) dosimetry from tooth enamel and cytogenetic dosimetry from lymphocytes of Hiroshima atomic-bomb survivors.

PURPOSE: To estimate gamma-ray doses received by Hiroshima atomic bomb survivors using electron spin resonance (ESR) of tooth enamel and to compare the results with cytogenetic data. MATERIALS AND METHODS: Tooth enamel ESR was performed for 100 teeth donated from 69 Hiroshima survivors, and conventional cytogenetic examinations were conducted for 61 of the tooth donors. To evaluate possible contamination from dental X-ray exposure, which primarily affects the tooth's buccal surface, each tooth was divided into buccal and lingual parts for subsequent independent enamel isolation and ESR measurement. RESULTS: Almost 20 teeth showed considerably larger buccal doses than lingual doses, but most of these discrepant teeth were incisors and canines. The results are probably attributable to solar light exposure. In contrast, the buccal and lingual doses found in molars were similar. Conventional translocation data of lymphocytes and ESR-estimated doses of 40 donors of molars showed the dose-response for translocations to be almost the same as that expected from in vitro gamma-ray irradiation experiments. CONCLUSIONS: Both tooth enamel ESR and lymphocyte cytogenetics are useful measures for individual biodosimetry of acute radiation exposure, even half a century after the exposure occurred.

Alkaline denaturation of dentin--A simple way to isolate human tooth enamel for electron spin resonance dosimetry.

Electron spin resonance (ESR) of tooth enamel is a recently developed method for the retrospective dose estimation of human radiation exposures. The assay requires isolation of enamel from dentin, which is difficult because the boundary between enamel and dentin is not easily discernible. Here we describe a simple method for isolating enamel by alkaline denaturation of dentin. The method requires 4 weeks, but scratching of the denatured and hence softened dentin is needed only once a week. Above all, no special skill is required. We found that the alkaline treatment did not cause deterioration of the ESR signal recorded in enamel exposed to 2 Gy of gamma rays prior to its isolation. The assay is particularly suited for teeth containing many cracks that were generated during long-term storage after extraction of the teeth. Such teeth tend to disintegrate during enamel isolation processes, which poses difficulties to isolate enamel mechanically from individual small pieces.

Biodosimetry: chromosome aberration in lymphocytes and electron paramagnetic resonance in tooth enamel from atomic bomb survivors.

One hundred enamel samples isolated from extracted teeth donated by atomic bomb survivors were subjected to free radical measurement by means of electron paramagnetic resonance (ESR). Results comparing ESR with the chromosome aberration frequency in lymphocytes of the tooth donors, and with the physically estimated DS86 dose suggested that ESR data correlated more closely with chromosome data than with the estimated DS86 doses, probably because DS86 may depend on erroneous memory in some cases.

Effects of propolis on dental caries in rats.

Propolis, the resinous hive product collected by bees, is important in the defense of the hive. The effects of propolis on growth and glucosyltransferase activity of Streptococcus sobrinus 6715, Streptococcus mutans PS14 and Streptococcus cricetus OMZ61 in vitro, and on dental caries in rats infected with S. sobrinus 6715 were investigated. Propolis had antimicrobial activity against S. sobrinus, S. mutans and S. cricetus, and inhibited both water-insoluble glucan synthesis and glucosyltransferase activity. In rats inoculated with S. sobrinus, about half of their fissures were carious, while dental caries was significantly less (p = 0.01) in rats given propolis. Dental caries was markedly decreased by the multiple actions of propolis which had antimicrobial activity, inhibited water-insoluble glucan synthesis, and inhibited glucosyltransferase activity. No toxic effects of propolis on the growth of rats were observed under experimental conditions in this study. These results suggest that propolis can control dental caries in the rat model system.

[A problem with ESR dosimetry utilizing human tooth enamel in low dose region].

Experiments were made to determine the dependence of CO3(3-) signal intensity on radiation dose in the low dose region from 3.1 x 10(-4) C/kg to 865.6 x 10(-4) C/kg. After all human tooth enamel samples were crushed into 350-500 micrometers particles, they were irradiated with 60Co gamma rays. Irradiated samples were measured with the ESR instrument, and the CO3(3-) signal appearance and the true signal have been determined. It is confirmed that the relation between the true intensity of the CO3(3-) signal and the exposure have linearity from 25.0 x 10(-4) C/kg to 865.6 x 10(-4) C/kg. It is difficult to confirm this in the case of less than 25.0 x 10(-4) C/kg due to the effect of organic signal and noise.

Relation between the weight of human tooth enamel and the CO3(3-) signal intensity on the ESR dosimetry.

Experiments were made to determine the dependence of CO3(3-) signal intensity on enamel weight in the ESR dosimetry utilizing teeth. After all human tooth enamel samples were crushed into 500-840 micrometers particles, they were irradiated with various doses of 60Co gamma rays at the same dose rate. Irradiated samples were distributed into 10-500 milli-grams weights and were measured with ESR instrument. The relation between CO3(3-) signal intensity and enamel weight have linearity up to 300 mg weight under the same dose as shown by measurements.

[Report on dental health activities in Konan-town, Koriyama-city].

Konan-town in Fukushima-pref. has high-level decay of deciduous teeth of the young. The individual level (guardians of the young), the professional level (the medicalcare and the administration), and the dental health activities level (the systematist and the residents of the district) all together have practiced dental health activities by "Shiroi-ha Kyoshitsu" for 73 one-year-old infants starting in 1986 for three years. This report is based on the results of the activities which have been conducted for the first 18 months. "Shiroi-ha Kyoshitsu" has practiced activities such as surveys on oral hygiene practice, teaching how to chose snacks and mouth cleaning and dental examination. The information on improving dental hygiene was given to the district level to stress the importance of good dental practices. In the study group, the rate of high-level caries increased from 2.4% to 58.6% (over 18 month period); however, it decreased to 4.6% if we compared with the rate among the comparative group of infants (at the age of 2 to 4 as of 1985) when they were 18 months old. The rate of B or C type caries is 3.2% which was only a half of what it was before. On the other hand, when using the dmft index for the study group of infants, the rate of the dmf index changed from 0.05 teeth (at date started) to 2.45 teeth (over an 18 month period).(ABSTRACT TRUNCATED AT 250 WORDS)

[Dental health measures to psychopathic patients. II. The improvement of toothbrushing habit and its related factors].

This study was designed for an oral prophylaxis program to remedy the oral condition of the mentally subnormal patient who required treatment at an open type mental hospital. The subjects consisted of 115 inpatients. The mean age was 45.5 years. The mean number of teeth functioning in mastication was 19.6. In order to improve their oral health they were given guidance and their oral hygiene condition was inspected every month. "STPI" was applied to investigate the toothbrush behavior in these patients. After six months, oral condition improved. Relationship between toothbrush behavior and mental illness was analyzed by principle component analysis and rotated by normal valimax method. Four factors were designed as follows. (1) Depressional state; (2) Personality disorders; (3) Hypochondric factor; (4) Manic state. Dental health of chronically mentally ill patients related to suppressive toothbrush behavior. The other hand the findings of this study showed that it was possible to improve their oral health by improving their living condition.

Effect of black-pigmented Bacteroides gingivalis on cytotoxic activity of linolenic acid against mouse macrophages.

The effects of sonicates of black-pigmented Bacteroides gingivalis (Bg-sonicates) on the cytotoxicity of linolenic acid (LA) against mouse macrophages were examined. Treatment of macrophages with LA alone or in combination with Bg-sonicates resulted in the release of lactate dehydrogenase (LDH) from the cells. This observation suggests the cytotoxicity of LA. Also, an increase in thiobarbituric acid-reactive materials was observed in experimental systems of the addition of Bg-sonicates to LA. The cytoplasm of macrophages treated with LA was not stained with May-Grünwald-Giemsa solution, while neither the nucleus nor the cytoplasm was stained when the cells were treated with LA and Bg-sonicates. The above cytotoxicity was nearly abolished when LA and Bg-sonicates were preincubated before the addition to macrophages. B. gingivalis is considered to increase the extent of the cytotoxic effects of LA to the cell nucleus by promoting peroxidation of LA.

Human tooth dosimetry for gamma-rays and dental x-rays using ESR.

The effect of secondary electron equilibrium on the ESR dosimetry of x- and gamma-ray irradiation has been studied by using acrylic plates to simulate the soft tissue of the human mouth. Dental x-rays create a different ESR signal pattern at the front surface of the tooth vs the back surface. The effect on radiation build-up of the acrylic plate on gamma-irradiation is dominant at the front but is not appreciable at the back side of the tooth.