الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
Maxillofacial prostheses made of medical grade silicone elastomers are routinely used to replace facial parts lost through disease or trauma. The most serious problems encountered with silicone include: discoloration of the prosthesis; deterioration of its physical and mechanical properties; difficulties related to the repair process; and a relatively short service life of the prosthesis, depending on the patient’s habits, the climate, and the environment. Fillers are nanosized particles added to the silicone elastomer to improve the physical properties, mechanical properties and viscosities of silicone elastomers. The fillers fulfill the task of supporting the cross-linked matrix by diffusing to the matrix. Different techniques of application of the nanoparticles are being implicated to test their effect on the silicone elastomer. Recent studies have shown that nanoparticles can be extrinsically coated on the surface of maxillofacial silicone elastomer A-2186.
The aim of the study: is to evaluate the bonding between the maxillofacial silicone elastomer and the extrinsically coated nanoparticles; assessment of the color stability of the surface coated maxillofacial silicone elastomer.
Material and Methods: Silicon elastomer with a skin like intrinsic pigment was tested with a total of 72 specimens prepared. group I including 24 specimens with no titanium dioxide nanoparticles, group II including 24 specimens with nanoparticles internally mixed with the elastomer; moreover, 24 specimens of group III which were surface coated with titanium dioxide nanoparticles solution. FTIR and SEM testing to evaluate bonding between silicone and TiO2 nanoparticles. Color measurements were recorded before and after artificial aging through ultraviolet irradiation, artificial eccrine solution and outdoor daylight weathering. Evaluation of surface morphology for the specimens was verified through scanning electron microscopy.
Results: FTIR showed new peaks at 1531, 1641, stretch band at 3200-3600. SEM images revealed that TiO2 nanoparticles were adherent to the surface despite aging conditions and preparation methods. Regarding color stability, all specimens suffered color alteration following the three artificial aging conditions. As for ultraviolet irradiation, the least ΔE value was recorded by group II (ΔE=2.49). Regarding daylight weathering condition, the least ΔE value was recorded by group I (ΔE=3.24), which was comparable to group II (ΔE=3.27). Both groups had values below acceptability threshold and slightly higher than perceptibility threshold value. However, when specimens were dipped into the artificial eccrine solution, the least value was recorded by group I (ΔE=3.63) being solely below the acceptability threshold value. In addition, SEM verified the presence of titanium dioxide nanoparticles within the elastomeric composite despite being subjected to artificial aging.
Conclusion: Titanium dioxide nanoparticles can be surface coated to the maxillofacial silicone elastomer which is verified through FTIR and SEM. Mixing titanium dioxide nanoparticles internally with silicon elastomer yields a better result in decreasing color alteration when exposed to ultraviolet irradiation. However, adding titanium dioxide nanoparticles has little or no effect as regards to outdoor daylight weathering or artificial eccrine solution.