Radiobiological risk estimation in dental radiology - a comparison between intra-oral full mouth and panoramic radiography

Dental radiological procedures form about 25% of diagnostic X-ray applications. ICRP 60 report stipulates that the radiation doses should be optimized. Measurements of entrance radiation doses (ESD) were made in patients undergoing peri-apical (70 KVp, 8 μ A) and panoramic (70 KVp, 12 μA) radiography. Calibrated LiF thermoluminescent chips are used in 50 patients and humanoid phantom. Effective doses are calculated from measured phantom doses. Stochastic effect probability factor is taken as 7.3 x 10-2 Sv-1. The patient ESDs ranged from 444 to 1850 μGy and 322 to 615 μGy; phantom organ doses ranged from 71 to 2210 μGy and 67 to 537 μGy for peri-apical and panoramic radiography respectively. Differences in patient doses for infra-orbital, parotid gland, and sub-mandibular glands were significant (p<0.001). Differences in phantom doses for lens, sub-mandibular gland, bone marrow, thyroid and second cervical vertebra were significant (p<0.01). The effective dose for full mouth x-ray technique is 425 μSv and for pantomography technique effective dose is 132 μSv. The radiobiological probability of stochastic effects for these two techniques are estimated as 31.0 x 10-6 (10 film study) and 9.6 x 10-6 which compares with the risk 0.37 to 10.95 x 10-6 quoted by Avendanio et al (1996). (author)