Measurement of activity concentrations of U-238, Ra-226, Th-232 and K-40 in different dental ceramic materials and assessment of dose given to oral mucosa

摘要

In this study, the beta dose given to oral epithelium was estimated from the activities of radionuclides U-238, Th-232, Ra-226 and K-40 in feldspathic and zirconium dioxide (ZrO2) dental ceramics before and after the sintering process. They were measured using a well-type HPGe detector. Th-232 activity is generally below the minimum detectable level of 1.6 Bq.kg(-1) in all samples and U-238 activity was far below the 1000 Bq.kg(-1) limit stipulated by ISO 6872 standard. However, Ra-226 activity was observed in all samples except for ZrO2 core samples ranged from 8.3 +/- 1.1 to 105 +/- 4 Bq.kg(-1). Considerable K-40 activity was observed in the feldspathic ceramic and ZrO2 veneer ceramic samples (between 1564 +/- 48 Bq.kg(-1) and 2703 +/- 84 Bq.kg(-1)). The beta dose to oral epithelium tissue calculated from the measured activities was determined to be 1.5 mGy/y in a worse-case scenario in which all teeth were restored with dental ceramics. All results indicate that there is no concern about extra beta dose given to oral epithelium due to zirconia used as dental ceramics.