Indiana University-Purdue University Indianapolis (IUPUI) / Background: VST-50 (a room temperature-vulcanizing silicone (RTV) by Factor II Inc.) has long been proposed as a potential alternative material for MDX4-4210, another RTV by Dow Corning Corp. and the current material of choice for maxillofacial prosthesis. Though VST-50 has similar chemistry and flexibility as MDX4-4210, its mechanical properties is still too low for it to be used in the clinic. An improvement in the mechanical property of VST-50 is a critical step to bring the material to clinical application. Objective: To investigate the effect of AEROSIL® R 812S (colloid silica) addition on the mechanical properties of VST-50 and compared to that of MDX4-4210. Methods: The VST-50 was mixed with AEROSIL® R 812S at 2 or 4 parts per hundred parts of rubber. That material was mixed with the catalyst under vacuum. The mixture was poured onto a machined plastic mold to produce a silicone sheet 3.0 ± 0.2 mm thick. All samples were prepared by manufacturer recommended method. Testing samples were prepared and tested following ISO 37 for tensile strength, ASTM D624 for tear strength and ASTM D2240 for shore A hardness test. One way ANOVA was used to compare the groups (Alpha=0.05). Result: Significant differences (P<0.001) were found between MDX4-4210 and modified VST-50 groups. The mean value of tensile strength, tear strength and hardness of VST-50 (4phr colloid silica) were 7.43(MPa), 34.82(N/mm) and 40.4 respectively, compared to MDX4-4210 were 3.67(MPa), 5.48(N/mm) and 31.5, respectively. Conclusion: Modified VST-50 with 4phr silica revealed improved mechanical properties to use as a maxillofacial prosthetic silicone elastomer.

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study was to investigate the effect of nano ceramic fiber fillers on the physical properties of VST-50HD silicone maxillofacial prosthesis. Nano alumina fibers at 2 percent, 4-percent, and 6-percent wt were mixed into the VST-50HD silicone elastomer (Factor II Inc., Lakeside, AZ), a commercially-available poly(dimethylsiloxanes). Ten dumb-bell-shaped specimens were used to determine the tensile strength according to ISO 37:2005 and elongation at fracture. Ten trouser-shaped test pieces were used to determine the tear resistance according to ISO 34-1:2004. Shore A test method was used to measure the hardness of the material. The data collected from all quantitative studies of the modified silicones were analyzed using one-way ANOVA with concentration of nano ceramic fiber as the main variable. Specimens from VST- 50HD were also made and tested as control. Results: The mean values for tensile strength (MPa) of control group, 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers were from 3.43 ± 0.12 to 5.48 ± 0.71. Tear strength (MPa) were from 2.34 ± 0.37 to 5.01 ± 0.39. Elongations at fracture were from 699.66 ± 43.69 to 793.51 ± 57.27. Shore A hardness were from 25.76 ± 2.18 to 38.76 ± 1.83. Conclusion: There was a significant difference (p < 0.001) in the mean tensile, tear and Shore A hardness strengths between the control group and 2-percent, 4-percent, and 6-percent percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. There was a significant difference (p < 0.001) in the mean elongation at fracture between the 2-percent and control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. The properties of the experiment were all lower than the control. Further research is needed to determine the appropriate material and amount of dispersing agent, coupling agent, and determination of the hydprophilicity of the nano ceramic fiber fillers with great emphasis on the dispersing agent.

Indiana University-Purdue University Indianapolis (IUPUI) / Fabrications of desirable fixed or removable dental prostheses depend upon accurate casts or dies. Recently, the most frequently used impression materials have been polyether (PE) and polyvinyl siloxane (PVS). However, both have their limitations: PVS is inherently hydrophobic, and PE is rigid. In order to take advantage of the desirable qualities of both PVS and PE impression materials, a new generation of impression material is being developed called vinyl polyether silicone (VPES, GC). The purpose of the present study was to compare the properties of hydrophilic PVS, PE, and VPES in regard to surface detail reproduction, contact angle, and tear strength. The hypotheses to be tested were: 1) VPES will show a significant superiority insurface detail reproduction compared with PVS and PE impression materials; 2) VPES will show a significant superiority in wettability compared with PVS and PE impression materials; 3) VPES will show a significant superiority in tear strength compared with PVS and PE impression materials. In order to test the surface detail reproduction, impressions were made of stainless steel dies with a parallel series of 15 different width lines on the surface and tested under dry and moist conditions. The wettability was assessed by contact angles of saturated CaSO4 aqueous solution drops on flat impression surfaces. A trouser tear test was employed to test the tear strength. The trouser-shaped specimens were prepared and tested in the Instron Universal Testing Machine. The data were analyzed by one-way ANOVA and Pearson‘s Chi square, (p < 0.05). All the materials showed better detail reproduction under the dry conditions than the moist conditions. There were no differences between the three materials in detail reproduction when impressing under either moist conditions or dry conditions. All the materials showed good wettability in the contact angle test. PVS rendered a contact angle as low as 34.19º. The contact angle of VPES was 44.84º, which was lower than 54.76º for PE. In the tear strength test, PE showed nearly two time higher tear strength than the other two impression materials. VPES showed slightly lower tear strength than PVS. The tear strength of the three materials tested in increasing order was VPES, PVS, PE. VPES showed comparable detail reproduction to PVS and PE and better wettability than PE, but showed the lowest tear strength compared with PE and PVS.