الفهرس 
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Abstract
Facial prostheses made of silicone elastomer material are universally considered the ultimate reliable treatment option to rehabilitate disabling facial defects caused by traumatic injuries, congenital abnormalities or tumor ablative surgery when reconstructive surgery is contraindicated. Although silicone facial prostheses have achieved high patients satisfaction aesthetically and functionally, there are matters that affect these prostheses performance.
Microbial biofilms that are difficult to be cleaned can be easily formed on silicone facial prostheses surface as the hydrophobicity and roughness of silicone elastomer material surface increase the liability of colonization of opportunistic microorganisms present in the microenvironment close to facial prostheses on its surface e.g. candida albicans. In addition, suitable conditions for growth of these colonized microorganisms are available due to occlusion of the skin by prostheses for long time per day. These biofilms affect the performance and decrease the lifetime of facial prostheses because they irritate the skin and bring about degradation and discoloration of the silicone elastomer material by using it as a nutrient source. Serious systemic diseases may also be provoked in immunocompromised hosts.
Therefore, the general aim of this thesis was to make a necessary improvement in silicone elastomer facial prosthetic material to prevent biofilms formation on facial prostheses to enhance longevity of prostheses and to improve quality of life.
In this study, A total of sixty six specimens were prepared and divided into six groups each of elevn specimens. One control group of silicone elastomer (MED-4210, Factor II Inc., USA) without adding TiO2 nanoparticles and five study groups by combining the silicone elastomer with various weight percentages of the TiO2 nanoparticles (Aeroxide® TiO2 P25, Sigma-Aldrich Inc., USA) : 2 - 10 wt %. Scanning laser microscopic imaging was used to evaluate the uniformity of dispersion of titanium dioxide nanoparticles within the processed silicone elastomer matrix. Then, all elastomer specimens were tested for antifungal activity against Candida albicans at 30, 60, 90 and 120 min follow‑up using impregnated culture and inhibition zone methods.
Scanning laser microscopic examination revealed uniform dispersion as the filler loading was increased to 6 wt% and signs of agglomeration appeared as the filler loading increased to 8 wt% and 10 wt%. The data were subjected to one way analysis of variance and tuckey’s test for comparison. Results of the performed antimicrobial testing revealed statistically significant difference in antifungal property tested was observed by impregnated culture test at 60, 90 and 120 min between the control group and 10wt%. The precents of candida albicans reduction after 120 min were found to increase from 0%, 82%, 87%, 94% and 97% respectively for the control group- with increasing the nano-Titanium loading till reaching maximum value at 10wt% (99.9%).
Considering the limitations of the present in vitro study, the following conclusions can be drawn:
1. Scanning laser microscopy images showed adequate dispersion of nanoparticles in silicone elastomer in 2%, 4%, 6 % (w:w) concentrations.
2. The incorporation of Aeroxide Titanium dioxide P25 nanoparticles to silicone elastomer MED-4210 can impart efficient antifungal activity to the silicone elastomer against candida albicans under UVA exposure, owing to the photocatalytic properties of nano‑TiO2.
3. The antifungal rates increased with increasing concentrations of Titanium dioxide nanoparticles up to 10 wt%.
4. 6 wt% of TiO2 nanoparticles was considered, for economic reasons to the end user and less effect on the mechanical properties of silicone elastomer.