Effect of various dental restorations on dose distribution of 6 MV photon beam

Aim: The purpose of this study is to evaluate the effect of various dental restoration materials on dose distribution in radiotherapy of head and neck cancer with 6 MV photon beam of a medical linac. Setting and Design: The dental restorations include tooth, tooth with amalgam, tooth with Ni-Cr alloy, and tooth with Ceramco. Dose perturbation due to the dental restorations on 6 MV beam of Siemens Primus linac was calculated by MCNPX Monte Carlo code. These dental materials were separately simulated in a cubic water phantom. Materials and Methods: Photon percentage dose change in the presence of tooth, tooth with amalgam, tooth with Ni-Cr alloy, and tooth with Ceramco was calculated at various depths on the central axis of the beam relative to the dose in water. In another evaluation, the absolute dose (cGy) for water, tooth, tooth with amalgam, tooth with Ni-Cr alloy, and tooth with Ceramco was obtained by calculating 100 cGy dose at 0.75 cm depth in the water phantom. Results: Based on the calculations performed, maximum percentage dose change due to backscattering was 11%, 8%, 6%, and 4% for amalgam, Ni-Cr alloy, Ceramco and tooth at depth of 0.75 cm, respectively. The maximum dose perturbation by amalgam is due to its higher mass density and atomic number. Conclusion: Ignoring the effect of dental restoration compositions on dose distribution causes discrepancy in clinical treatment planning system calculations.