During radiotherapy for head and neck tumours, the oral cavity and cheek area would be inevitably exposed to high energy radiation; thus, the material surface of the teeth, dental restorations with high atomic number, or alloy prosthodontics would generate backscatter electrons that cause the buccal mucosa adjacent to these materials to receive localized high dose enhancement, which primarily leads to side effects or oral mucositis. Based on the size of the adult oral cavity, this study aimed to use acrylic resin to create an oral phantom with two grooves on the left and right sides for placement of three molars. Moreover, the distance between the inner cheek and the side surface of the teeth could be accurately adjusted every 1 mm from 0 to 5 mm. This enhanced the dose in the buccal mucosa during head and neck radiotherapy and made the distribution measurement of the radiation dose simple and feasible at different depths (0-5 mm). Meanwhile, the study employed the film type optically stimulated luminescent dosimeter with a thickness of 0.3 mm to measure the absorbed dose inside the buccal mucosa to reduce the dose interference from radiotherapy. The study fixed three real molars in a row located at the left side of the phantom and employed 6 MV photons and intensity-modulated radiotherapy (IMRT) to treat and simulate oral cancer and measure the attenuation of the molar's backscatter dose from 0 to 5 mm in an up beam direction. The result showed that, in every 3 mm, the phantom had attenuated the enhancement of backscatter dose <3%. The irradiation dose enhancement in a single direction was twice higher than that through IMRT 7 field treatment. These measurement results were consistent with the results of previous studies.
Keywords: Oral cavity; backscatter dose; dental restoration; mucositis; optically stimulated luminescent dosimeter.