Stability of Surgical Guide Resin After Decontamination and Radiation Cycles

Objectives: To evaluate the effect of combined cycles of radiation, sterilization, and disinfection on surface roughness, flexural strength, and hardness of surgical guide resin for use as a reusable tongue depressor during radiation therapy.
Methods: Eighty 3.2x10 mm discs and forty 12.7x125x3.2 mm prisms were printed in surgical guide resin and divided equally into control (C), 30 (G30), 60 (G60), and 90 (G90) cycles of decontamination and radiation exposure. Radiation was delivered to experimental samples in 2 Gy fractions, totaling 60 Gy (G30), 120 Gy (G60), and 180 Gy (G90). Between each cycle, samples were autoclaved (steam sterilization at 134°C for 20 min) and disinfected (70% isopropyl alcohol for 5 min). Surface roughness (Ra) was measured using the Keyence Digital microscope-VHX-7000 series, flexural strength (MPa) was measured using the Instron 5669A three-point bend test at a strain rate of 5 mm/min, and hardness (D) was measured using the Shore D handheld durometer. One way ANOVA was used to compare sample group means at a 0.05 a priori level of significance.
Results: There were no significant differences in surface roughness (C, 7.4 ± 6.2 Ra; G30, 9.6 ± 6.4 Ra; G60, 9.3 ± 7.2 Ra; and G90, 7.2 ± 7.2 Ra), flexural strength (C, 101.8 MPa; G30, 104.1 MPa; G60, 107.1 MPa; and G90, 102 MPa), or hardness (C, 77.9 ± 3.8 D; G30, 78.8 ± 2.6 D; G60, 78.7 ± 2.9 D; and G90, 77.9 ± 3.2 D) between groups.
Conclusions: The surgical guide resin developed to be used as a reusable tongue depressor maintained its surface and mechanical properties for the conditions proposed in this study, indicating chemical stability through radiation and decontamination.