PURPOSE: The purpose of this in vitro study was to evaluate the SR, tensile strength (TS), and percentage elongation (% E) of different SEs subjected to outdoor weathering in the Malaysian climate.
MATERIAL AND METHODS: Type-II dumbbell-shaped specimens (N-120) (nonweathered=15, weathered=15) were made from 3 room-temperature vulcanized (A-2000, A-2006, and A-103) and 1 heat-temperature vulcanized (M-511) silicone (Factor II). For 6 months, weathered specimens were subjected to outdoor weathering inside a custom exposure rack. Simultaneously, the nonweathered specimens were kept in a dehumidifier. Subsequently, the SR was measured with a profilometer; TS and % E were measured by using a universal testing machine. Two-way ANOVA was used to compare the means of the tested properties of the nonweathered and weathered specimens, and pairwise comparison was carried out between the silicones (α=.05).
RESULTS: After outdoor weathering, the SR, TS, and % E were adversely affected by weathering in the Malaysian environment. Among the silicone materials, A-2000 showed the least TS changes (2.51 MPa), while A-2006 demonstrated significant changes in percentage elongation after outdoor weathering (266.5%). M-511 exhibited the highest mean value (2.50 μm) for SR changes. In addition, A-103 SE showed statistically significant differences in most pairwise comparisons for all 3 dependent variables.
CONCLUSIONS: Based on the evaluation of mechanical properties, A-103 can be suggested as a suitable silicone for maxillofacial prostheses fabricated for tropical climates. However, A-2000 can be a suitable alternative, although significant changes to surface roughness were detected after outdoor weathering.
METHODS: Relevant articles written in English only, before January 15, 2017, were identified using an electronic search in the PubMed, Scopus, and Google Scholar databases. Furthermore, a manual search of the related major journals was also conducted to identify more pertinent articles. The relevancy of the articles was verified by screening the title, abstract, and full text if they met the inclusion criteria. A total of 37 articles satisfied the criteria, from which data were extracted for qualitative synthesis.
RESULTS: Among the 37 included articles, 14 were without aging, 15 were natural or artificial accelerated aging, 7 were outdoor weathering, and 1 contained both artificial aging and outdoor weathering. Only 4 studies out of the 14 without aging had significant observations; whereas 9 articles with natural or artificial aging published significant results, and 3 out of 7 outdoor weathering articles showed significant changes in the evaluated silicone elastomers.
CONCLUSIONS: Despite the varying research, it seems that the single "ideal" maxillofacial prosthetic material that can provide sufficient resistance against different aging conditions is yet to be identified. Therefore, it is imperative for standardization organizations, the scientific community, and academia to develop modified prosthetic silicones possessing improved physical properties and color stability, limiting the clinical problems regarding degradation of maxillofacial prostheses.