In vivo measurements of daily UV exposure of human anterior teeth using CaF2:Tb,Sm as a thermoluminescence dosimeter

Abstract

Abstract Ultraviolet radiation (UV) has been indicated as one of the causes of discoloration of dental materials yet the ISO 4049 (2009) standard requires that dental polymers be irradiated with light from a xenon lamp, which includes UV, to evaluate their color stability. It is doubtful that dental polymers in the mouth are exposed to large energy of UV on a daily basis, but there have been no reports concerning exposure. In the present study, we used thermoluminescence (TL) from sintered CaF 2 :Tb,Sm, which is highly sensitive to UV, to measure the daily energy of UV exposure to the labial surface of the maxillary anterior teeth, which are regarded as receiving the maximum exposure among oral tissues. We produced disks of CaF 2 co-doped with Tb 4 O 7 and Sm 2 O 3 (sintered CaF 2 :Tb,Sm) that were 5 mm in diameter and 1 mm thick, and placed them inside glass cases that had a 7-mm external diameter, 3-mm height, and 1-mm thickness of glass made of synthetic silica with ≥90% UV transmittance. These glass cases were fixed in dental mouthpieces in a position corresponding to the central maxillary incisors. These mouthpieces were worn by 11 subjects and UV measurements were carried out over a 24-h period in a uniform environment. The results of these TL measurements showed a TL glow peak in the region of 430 K. This was the same as that seen with irradiation from a xenon lamp as basic illumination. The daily UV radiant energy was 72.2 mJ/cm 2 (32.7–143.8 mJ/cm 2 ), calculated from the relationship between TL intensity and UV radiant energy. This corresponded to 0.02% of the UV radiant energy contained in the light irradiation specified by ISO 4049.