الفهرس 
MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
This study aimed to evaluate the effect of human extra-oral and environmental aging conditions on the mechanical properties (tensile strength and percentage, elongation, tear strength and shore A hardness) of maxillofacial silicon elastomer MED-4210, a commercially-available poly (dimethylsiloxanes) reinforced with different proportions of TiO2 nanoparticles.
Specimens were fabricated using MED-4210 maxillofacial silicon elastomer(Factor II Inc.) according to (ASTM) for recording (tensile strength and percentage elongation, shore A hardness and tear strength),and they were divided into four equal groups(15 specimens/ group) according to TiO2 (US Research Nanomaterials, Inc.) NPs weight percentage (w/w%). Un modified silicone elastomer (Blank silicone elastomer) was served as control group and nano-TiO2 at 1.5%, 2% and 2.5% were mixed into the MED-4210 maxillofacial silicon elastomer. Specimens were subjected to different aging conditions groups (30 specimens/group) dry storage in dark for 6 months , storage in simulated sebum solution for 6 months, storage in simulated acidic perspiration for 6 months , accelerated artificial daylight weathering for 360 hours , storage in antimicrobial silicone-cleaning solution for 30 hours and mixed aging of sebum under UV light 360 hours.
The mechanical testing was investigated on two stages, stage one, before aging conditions for the four groups (control ,1.5% ,2% , 2.5% TiO2 NPs groups ) and stage two after conditioning, for 0% (control group) and 2.5% nano-TiO2 silicone elastomers composite only.
Chapter 6 Summary, Conclusion and Recommendations
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The conditioning period selected simulated a silicone prosthesis in service for 12to 18 months. Type 2 dumbbell-shaped specimens were prepared using a prefabricated copper molds for tensile strength test according to ASTM D 412 and for tear strength test, type C trouser- shaped specimens and 90º angle were used according to ASTM D624.While shore A hardness test was assessed by the use of square shaped specimens (25 × 25 ×6 mm) according to ASTM D 2240. The hardness was measured by the Digital Shore A durometer.
The results of the present study proved that, TiO2 nanoparticles addition improved the mechanical properties in terms of tensile strength and percentage elongation, tear strength and shore A hardness of MED-4210 maxillofacial silicon elastomer before and after extra-oral aging conditions. This was evident through the significant changes ((p < 0.05) among all the properties tested. All the ageing methods had more effect on control group (blank silicone elastomer) regarding the mechanical properties, but 2.5% nano-TiO2 silicone elastomers composite exhibited significant differences according to the mechanical properties after aging. So, reinforcement of MED-4210 maxillofacial silicon elastomer with TiO2 nanoparticles introduces a favorable material with physical and anti-ageing properties in our in vitro study.