SU-E-T-89: Characterization of Dental Restoration Material for Cs-137 Radiation Dosimetry

The purpose of this work is to characterize the radiation-induced thermoluminescence properties of a dental restoration material and to see if the material might be feasible for use in retrospective radiation dosimetry.

Retrospective, or accidental, dosimetry is the study of using nearby materials to measure radiation received by individuals. In this project we obtained samples of Ivoclar Vivadent e.max CAD material, a glass-ceramic used for making dental restorations such as full or partial crowns. The samples were machined into square chips .32 cm × .32 cm × .089 cm and annealed in the same furnace used by the dentist. The samples were exposed to a Cs-137 source using a PMMA source holder and then read in a Harshaw 3500 TLD reader. The samples were read without nitrogen gas flux using heating rates of 5 degrees C/s or 10 degrees C/s up to a maximum temperature of 400 degrees Celsius. The glow curves were analyzed using Systat PeakFIT peak-fitting software and Microsoft Excel spreadsheets. The authors gratefully thank Dr. Aaron Imdieke and the staff of River City Dental, St. Cloud, MN for the dental restoration materials and the use of their dental furnace.

A sample subjected to a radiation exposure of .04 C/kg exhibits a glow curve with a prominent peak at approximately 140 degrees Celsius, which is well-modeled by the first order glow curve deconvolution formula developed by Kitis, Gomez-Ros, and Tuyn. The activation energy corresponding to this peak is approximately 1 eV. The thermoluminescent signal fades with time after exposure.

Ivoclar Vivadent e.max CAD dental restoration material has the potential to be used as a material for retrospective Cs-137 radiation dosimetry. Future work could look at its thermoluminescent dosimetry properties in more detail and also at other dental restoration materials. The authors would like to thank Dr. Aaron Imdieke and the staff of River City Dental, St. Cloud, MN, for the donation of scrap dental restoration materials and the use of their dental furnace.