Evaluation of the effect of ultraviolet stabilizers on the change in color of a silicone elastomer following aging by three different methods : An in vitro study

Aim and Objective: To compare and evaluate the effect of ultraviolet (UV) stabilizers (UV absorbers [UVA] and hindered amine light stabilizers [HALS]) on the color change of a commonly used silicone elastomer subjected to aging by three different methods. Materials and Methodology: Four groups of 30 samples each were studied; Group A-Control, Group B-Silicone + UVA (Chimassorb 81), Group C-Silicone + HALS (Uvinul 5050), and Group D-Silicone + Combination (UVA + HALS) (Chimassorb 81 + Uvinul 5050). Each group was further divided into groups of 10 samples each based on the method of aging-accelerated weathering chamber (Weather-Ometer), artificial perspiration, and a cleansing agent. Commission Internationale d’Eclairage Lab color values L*, a*, and b* were measured for all samples before and after weathering and change in color (Delta-E) was calculated. One-way ANOVA was applied to compare the mean values of the four groups and the post hoc Tukey test was carried out to compare between two groups. Results: All groups showed a significant color change. For Group A, the color change (average Delta E) for accelerated weathering, artificial perspiration, and cleansing agent was 1.479, 0.617, and 0.62, respectively. Similarly, for Group B, it was 1.109, 0.509, and 0.507; for Group C, it was 1.866, 0.652, and 0.997; and for Group D, it was 1.303, 0.829, and 1.033, respectively. UVA (Chimassorb 81) showed the least change consistently in all three types of aging. Conclusion: Addition of UV stabilizer Chimassorb 81 showed a reduction in color change of the silicone elastomer. Following studies on the effect of these additives on the physical properties of elastomers has shown that they can have a potential use in maxillofacial prosthetic rehabilitation. properties. Current research strategies have been directed toward improving the mechanical properties and color stability of pigmented elastomers. The addition of UV stabilizers, thermochromic pigments, and opacifiers to improve the color stability of pigmented elastomers have been tried in the past with varying results. [13-17] UV degradation occurs on constant exposure to UV rays produced by the sun and depends to a large extent on their duration, extent, and intensity. UV stabilizers have been used extensively in the polymer,[18] paint, cosmetic and plastic industries, as well as for wood[19] and cellulose fabrics[20] to prevent color degradation and increase the life of these products. UV stabilizers are a broad term which includes UV Introduction Silicone elastomers are successfully being used to rehabilitate patients with extraoral defects that are either present congenitally or as a result of trauma, burns, and surgical resections. [1] These elastomers are biocompatible, durable, inert, and easy to manipulate and color to match the natural skin. However, one of the main drawbacks of prostheses made from these elastomers is that they degrade and discolor over a period of time. [2-6] This requires the prostheses to be remade periodically, generally every 6 months-2 years, increasing the cost of rehabilitation. [3,7] The color change has been attributed to factors such as ultraviolet (UV) radiation, temperature changes, humidity, and the use of adhesives, cosmetics, cleansing agents, and exposure to body fluids. [7-12] The popularity and increasing demand for these elastomers have increased the interest of researchers to improve their Department of Prosthodontics, Dr. D Y Pati l Dental Col lege, Pimpri, 2Department of Technical Directorate, CIRT, Pune, Maharashtra, India, 1Department of Maxillofacial Prosthetics, Kings College, London, United Kingdom