Objective: To investigate the physical properties of tensile strength and modulus, elongation, tear strength, hardness, colour change and light transmittance, of a new maxillofacial-silicone elastomer after accelerated light-aging.
Methods: For each property (tensile strength, tear strength, hardness and colour change) 16 specimens were fabricated of TechSil 25 silicone-elastomer. Half of the specimens served as control (Group1) and the remaining were aged in environmental chamber (Group2), exposing them to filtered Xenon light of 150 klx, and irradiance of 475 W/m2 under controlled moisture conditions for 360 h.
Tensile and tear tests were conducted according to ISO specifications no. 37 and 34 respectively, in a Zwick testing machine. Shore A hardness measurements were run according to ASTM D 2240. Colour change was determined in the CIE LAB system using a Minolta chromameter, and light transmittance was determined using Ocean Optics USB 4000 Fibre optic spectrometer operated by SpectraSuite software.
Statistical t-test for independent data was used to analyse significant differences (p<0.05) between both groups (1 and 2) in tensile strength, tensile modulus, elongation, tear strength, hardness, and light transmittance. Colour change (ΔE) greater than 3 was considered visually perceivable.
Results: Mean (SD) values of all measurements of both groups are presented in the following table.
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No statistically-significant differences
were present between groups (p>0.05) in the analysed properties. However, high
colour change was evident.
Conclusions: Silicone specimens light-aged for 360 h, which simulate 6-12 months of clinical service, showed no changes with respect to the properties studied. However, colour change was significant and perceivable necessitating replacement of such prosthesis within that period of service.