Research and EducationEffect of thixotropic agents as additives on the mechanical properties of maxillofacial silicone elastomers
Section snippets
Material and Methods
Three commercial maxillofacial silicones were used in this study: M511 and Z004 (Technovent Ltd) and A2000 (Factor II Inc). Two thixotropic agents were used, M514 anti-slump agent (Technovent Ltd) and A-300-1 thixotropic agent (Factor II Inc). Silicone part A-to-part B mixing ratios were 10:1, respectively, for M511 and 1:1, respectively, for both Z004 and A2000.
For the tensile strength and elongation specimens, 180 wax patterns were made as dumbbell-shaped specimens to adhere to the conditions
Results
Mean tear and tensile strength values and percentages of elongation at rupture are shown in Table 2. The 3 types of silicone differed significantly (P<.001) in tensile and tear strength values, hardness, and percentages of elongation. The size of this difference depended on whether the thixotropic agent was added. Silicone Z004 showed higher tensile and tear strength followed by A2000 and M511, regardless of the addition of the thixotropic agent. Without the addition of the thixotropic agent,
Discussion
The null hypothesis for the mechanical properties was rejected, except for the tensile strength of all tested silicone types and hardness of M511, which demonstrated no statistically significant difference. The silicone rubber materials tested in this study were all systems which cross-link using an addition reaction. The base contained vinyl-terminated polydimethyl siloxanes, surface-treated silica fillers, and a platinum complex as catalysts. The cross-linker (part B) contained a
Conclusions
Within the limitations of this in vitro study, the following conclusions were drawn:
- 1.
The addition of thixotropic agents (at the level used in this study) to the 3 maxillofacial silicone elastomers reduced some mechanical properties, especially tear strength and percentage of elongation.
- 2.
Silicone Z004 showed superior mechanical properties among the 3 tested silicones; however, tear strength results had a relatively high (>25%) coefficient of variance, which would suggest that larger number of
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