Estimation of radiation dose from porcelain teeth containing uranium compound.

Uranium concentrations of porcelain teeth were determined using the fission track method. The uranium contents of each brand range 0.33-10 ppm, 0.69-81 ppm, 2.5-14 ppm, and 11-205 ppm, respectively. In addition, corresponding dose equivalents to the oral mucosa were calculated.

Presurgical evaluation for dental implants using a reformatting program of computed tomography: maxilla/mandible shape pattern analysis (MSPA).

A new analysis technique that provides a shape pattern of the maxilla or mandible is described. This technique uses a software program of computed tomography multiplanar reformation (CT/MPR). The successive cross-sectional images obtained by the CT/MPR are numbered, and the height and width of the maxilla and mandible at each of these cross-sectional images at specified levels are measured. The measured height and width are plotted against the number of the cross-section. This technique, termed maxilla/mandible shape pattern analysis (MSPA), creates an easy profile of the shape of the maxilla and mandible, and it enhances treatment planning for the placement of dental implants.

[Non-destructive neutron activation analysis of dental porcelain powders (author's transl)].

Determination of 15 elements in the dental porcelain powders (Vita VMK 68) marketed in Japan was done by means of non-destructive neutron activation analysis. The potassium and sodium contents showed less variations from powder to powder, and the uranium contents varied from a few ppm to 1090 ppm in a wide range. The high contents of uranium (345--1090 ppm) were detected in the powders of Enamel, Dentin, Effect, Color and Gum which were used for the superficial parts of a porcelain crown, while the low contents of uranium (1.6--2.7 ppm) were detected in those of Opaque and Translucent which were used for the core part and the top of the crown. Cerium and samarium were also detected in each powder in the amounts similar to those of uranium. The main radionuclides present in the porcelain powders were 238U, 235U, 234U, 234mPa, 234Th, 231Th and 40K. The activities of these nuclides were calculated and discussed.

[Distribution of uranium in dental porcelains by means of the fission track method (author's transl)].

Porcelain teeth, some of which contain uranium compounds for aesthetic purpose, have been widely used in dental clinics. Hazardous effects due to uranium radiation have been suggested by recent publications. In the previous study, the authors reported the uranium content of porcelain teeth and radiation dose by it. In this study, using the fission track method, the authors examined spatial distribution of uranium in dental porcelain teeth (4 brands) which were marketed in Japan. From each sample of porcelain tooth, a 1-mm-thick specimen was sliced, and uranium content was measured at every 0.19 mm from labial side to lingual side for making a uranium distribution chart. Higher uranium concentration was found in Trubyte Bioblend porcelain teeth (USA) and they showed almost uniform distribution of uranium, while those of the Japanese three brands indicated, in most case, comparatively lower concentration and found to be non-uniform distributions. Range of uranium concentration in these brands were N.D. approximately 5.2 ppm (Shofu-Ace), N.D. approximately 342 ppm (Shofu-Real), N.D. approximately 47 ppm (G.C. Livdent) and N.D. approximately 235 ppm (Trubyte Bioblend), respectively.

Differential diagnosis between cyst and tumor. Dentigerous cyst and ameloblastoma containing teeth.

A study was conducted on 21 cases of ameloblastoma (a type of tumor containing an embedded tooth) and 87 cases of dentigerous cyst. The former cases were selected from among those which had been diagnosed histopathologically. Using radiographs of these lesions, the following parameters were measured: 1) the distance between the cement-enamel junction of the embedded tooth and its attachment to the cystic wall; 2) the area of the radiolucent image (similar to the area with a cystic appearance). From measurements of the former parameter, it appeared that the embedded tooth extends more toward the root apex in ameloblastoma than in dentigerous cyst, whereas the latter parameter indicated that the radiolucent area varies in size slightly in ameloblastoma, but tends to be smaller in dentigerous cyst. Moreover, with regard to clustering between ameloblastoma and dentigerous cyst, no definite tendency was detected on distance, whereas only ameloblastoma without dentigerous cyst was seen above 20 cm2 of area.

Uranium content in porcelain denture teeth and in porcelain powders for ceramic crowns.

Some porcelain denture teeth and porcelain powders marketed in Sweden haven been analyzed for the content of uranium. The fission track method and the delayed neutron technique were the methods used. Compared to results published previously the content of uranium was generally found to be lower in the brands analyzed. The denture teeth contained 23-186 ppm for Anatoform, 35-137 ppm for Myerson, 15-45 ppm for Candulor G and 20-53 ppm for Vivopearl. The baked and fired porcelain powders showed values of about 2.8 ppm at most, those in the form of powder about 25 ppm at most. The radiation dose to the mucosa of the upper lip was calculated and is discussed.

Determination of uranium in human teeth, bones and tissues by the fission track method.

The uranium content of several human tooth, bone and soft tissue samples was determined by the fission tract method. The average uranium content in teeth, bones and soft tissues were 6.7, 8.4 and 64 ppb ash, respectively. The distribution of uranium in bones is less uniform than that of teeth, and the uranium content of soft tissues is generally higher than that of teeth and bone. The presence of thorium does not interfere with the uranium determination in most cases.

[Activation analysis of mercury in head hair of dentists (author's transl)].

Mercury contents in head hair of 58 dentists, working at the hospital of Nihon University School of Dentistry were determined using neutron activation analysis. The values ranged from 2.47 ppm to 13.7 ppm. The frequency distribution of the mercury contents increased steeply at about 2 ppm to the maximum of 4 approximately 5 ppm, and decreased to about 11 ppm, its distribution pattern followed a log-normal one with a median of 5.46 ppm. The dentists were divided into two groups and the mercury contents in head hair of them were compared with each other. The arithmetic and geometric means of the values for dentists who handled amalgam in dental practice were 5.66 ppm (SD +/- 1.80) and 5.40 ppm (SD multiplied/divided by 1.36), while those for the dentists who did not handle amalgam in dental practice were 5.96 ppm (SD +/- 2.82) and 5.38 ppm (SD multiplied/divided by 1.59). The values of them agreed well with each other. The arithmetic mean for all dentists was 5.79 ppm (SD +/- 2.28) and the geometric mean of them was 5.40 ppm (SD multiplied/divided by 1.46). They were much lower than the values reported by Suzuki, Miyazawa or Sairenji, et al. in the past year, and they agreed well to those for normal Japanese men with the same age. Therefore it is concluded that proper mercury handling might be established in the dental office.

A case of osteoporosis with bilateral defects in the mandibular processes.

We carried out a detailed total body examination of a 62-year-old woman with osteoporosis who had bilateral defects in the mandibular processes. It was inferred that the defects in both articular heads were caused by resorption of small bone fragments following fracture. The quantity of bone salt was determined by microdensitometry, and a diagnosis of osteoporosis was then established. An improved bite was obtained by treatment consisting of tooth extraction and the preparation of partial dentures.