Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2) on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n = 21). One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624), tensile strength (ASTM D412), percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (α = 0.05). Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer.

INTRODUCTION: Maxillofacial defects are located in a highly visible body area that is identified with one's identity. An aesthetic and comfortable maxillofacial prosthesis relieves many concerns of the patient and may improve quality of life. Silicone elastomers are more color stable than other materials used in maxillofacial prostheses thus many authors investigated the color stability of those materials under weathering conditions. OBJECTIVES: This study evaluates the effects of two types of nano-oxides particles at different concentration on the color stability of pigmented silicone MDX4-4210 maxillofacial prosthetic elastomers after artificial aging. MATERIALS AND METHODS: MDX4-4210 silicone elastomer specimens were fabricated. The control group was incorporated with intrinsic coloring agents, one of nanoparticles group was incorporated with intrinsic coloring agents and titanium oxide nanoparticles (TiO2) at different concentration (2%, 2.5 and 3%), other nanoparticles group was incorporated with intrinsic coloring agents and aluminum oxide nanoparticles (AL2O3) at different concentration (2%, 2.5% and 3%). All specimens were exposed to sunlight, sweat and ultraviolet light for one months. Easy shade spectrophotometer was used to determine the CIELAB (L*a*b*) parameter before and after aging of each specimen, and the values were noted. RESULTS: The majority of the color changes in all groups were above 3.3 ΔE* units, which indicates that they were visually observed color change. After one month aging period TiO2 group was more stable than Al2O3 regarding ultraviolet light. Regarding sweat TiO2 group showed more color alteration. Al2O3 group showed lower color alteration on exposure to sunlight. CONCLUSIONS: Artificial aging procedures affected the color stability of the maxillofacial silicone with or without nanoparticles incorporation.

INTRODUCTION:Dental implants are currently one of the main pillars of restorative dentistry. Titanium and its alloys were and still are the gold standard for dental implant materials. However, Titanium is not a perfect material and has many drawbacks thus the search for a more ideal material is ongoing. Zirconia and Polyetheretherketone are two viable alternatives to titanium as dental implant materials. They show different mechanical behavior invitro and invivo, so they are investigated and compared to each other. OBJECTIVES: Evaluate and compare the different material properties of Polyetheretherketone and yttrium-stabilized tetragonal polycrystalline zirconia when used as dental implant material. MATERIALS AND METHODS: Microbars of zirconia and Polyetheretherketone were prepared using precision cutter and low speed micro motor under water cooling and used to assess the following properties for the two materials: 1) Vickers Microhardness 2) Flexural strength before and after cyclic loading RESULTS: There was a highly significant difference between hardness of zirconia and Polyetheretherketone. There was also a highly significant difference between flexural strength of zirconia and Polyetheretherketone (both before and after cyclic loading). There was significant decrease in flexural strength of zirconia after cyclic loading. No significant difference was found for Polyetheretherketone after cyclic loading. CONCLUSIONS: Polyetheretherketone is a promising alternative to titanium and zirconium as a dental implant material.

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