The comparative evaluation of physical properties of three different maxillofacial silicone elastomer

Maxillofacial prostheses are used for reconstruction of congenital, developmental and acquired defects of the head and neck. Silicone elastomers are commonly used materials for maxillofacial prosthesis. However, degradation occurs in properties of silicone materials by passage of time. The aim of this study was to evaluate and compare physical properties of three different silicone elastomers before and after accelerated aging.Episil, Multisil and Cosmesil that commonly used materials in practice were included in the study. Molds were prepared according to ISO 37 type 2, ISO 34-1 and A.S.T.M D2240 standards for tensile strength, percentage of elongation, tear strength, hardness; respectively. Specimens were divided into three different groups for each material. Group 1 (n= 30) was consisted of control specimens that were not subjected to aging. Specimens in Group 2 (n= 30) were aged for 300 hours and specimens in Group 3 (n= 30) were aged for 600 hours.Aging was performed in Q.U.V accelerated weathering tester (The Q-Panel Company, Cleveland, USA) at 90% relative humidity. A program cycle of 18 minutes of distilled water spray was used during each 120-minute period. Condensation and exposure to a xenon ultraviolet/visible-light source cycle was performed at 50 ?C ± 2 for 4 hours and 60 ?C ± 2 for 8 hours, respectively and continuously.The specimens were subjected to tensile strength, percentage of elongation, tear strength using testing machine (LR 50K, Lyod intruments ltd, Fareham, UK) and Shore A hardness of the specimens were measured using hardness testing machine (rubber hardness tester, Gauge co.,USA). Results were statistically analyzed by two-way analysis of variance (ANOVA). Tukey test was used to determine any significant differences among the groups.The results of the study indicated that Episil and Cosmesil had similar properties both before and after aging. Multisil showed the weakest properties among three materials. Aging caused poorly changes in hardness, percentage of elongation and tensile strength of the silicone materials. However aging caused increase in tear strength of Cosmesil and Episil materials.Key words: Silicone elastomers, physical properties, accelareted aging