Shika Hoshasen

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Purpose: To compare effective doses for dental radiography based on tissue doses and the recommendations prescribed by the International Commission on Radiological Protection (ICRP) in 1990 and 2007.
Material and Methods: Effective doses (E) for intraoral and panoramic radiography were calculated using the tissue-dose data reported by Gibbs et al. (Dentomaxillofac Radiol, 1987 & 1988) and the tissue weighting factors recommended by ICRP in 1990 (designated E₁₉₉₀) and in 2007 (designated E₂₀₀₇). The effective doses in intraoral radiography were calculated at 70, 80, and 90 kV for E-speed films using periapical and interproximal projections with round or rectangular collimated beams. The effective doses in panoramic radiography were calculated for three machines at tube voltage and tube current-exposure time product (mAs) settings of 80, 80, 73 kV and 67.5, 225.0, 96.0 mAs, respectively.
Results: The average E₂₀₀₇/E₁₉₉₀ at 70 kV using rectangular collimated beams with a cone length of 40 cm, round beams with a diameter of 7 cm and a cone length of 40 cm, and round beams with a diameter of 7 cm and a cone length of 20 cm were 1.26, 1.28, and 1.08 for periapical projections, and 1.40, 1.54, and 1.43 for interproximal projections, respectively. The average E₂₀₀₇/E₁₉₉₀ for full-mouth radiographic survey with 10 and 14 films at 70 kV using round beams with a diameter of 7 cm and a cone length of 20 cm were 1.13 and 1.10, respectively. E₂₀₀₇/E₁₉₉₀ for the three panoramic machines were in the range of 1.28 to 1.48.
Conclusion: Effective doses in dental radiography as recommended by the ICRP in 2007 were 50 to 170% higher, and 10 to 50% higher with the exception for the extrathoracic region and oral mucosa in the remaining tissues for tissue-weighting factors than the ICRP recommendations of 1990.

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