Effect of Siwak on Certain Mechanical Properties of Acrylic Resin

Background: (PMMA) has been used in dental prosthetic devices for almost 70 years; three features have contributed for its success: excellent appearance, simple processing technique and easy repair. However, the resistance to impact and fracture of PMMA during function is low. Various methods for enhancing strength of the acrylic resin denture bases have been reported. This study was designed to evaluate the effect of adding Siwak powder with average particle size of (75 μm) in three different concentrations by weight to PMMA on certain mechanical properties. Material and Methods: Tensile strength, elongation, transverse strength, impact strength, compressive strength and the surface roughness of heatpolymerized acrylic resin specimens were evaluated for both the control group A (0%) and the experimental groups. These groups consisted of acrylic resin mixed with different proportions of Siwak powder B (3%), C (5%) and D (7%) by weight. Stainless steel samples with dimensions of (65 mm, 12.5 mm, 2.5 ± 0.03 mm) length, width, and thickness were constructed for testing tensile strength and elongation of acrylic resin. Other uniform molds were made by investing machined stainless steel standards (65 mm 10 mm, 2.5 mm) for testing denture base materials in surface roughness and these specimens were reused for transverse deflection test. For testing the impact strength and compressive strength of acrylic resin, wax patterns (60 mm,10 mm, 10 mm) and (20 mm,10 mm, 10 mm) length, width, thickness were prepared. Results: Siwak powder (5%) did not greatly affect the tensile strength and compressive strength (P = 0.05). The addition of Siwak powder at ratio of (3%) did not greatly affect impact strength of the experimental group in comparison to the control group, while the addition of (7 %) Siwak powder revealed a significant decrease in tensile strength, impact strength and compressive strength in comparison to the control group. Conclusion: Addition of low concentrations (3%, 5%) Siwak to the heat polymerizing acrylic resin did not affect significantly the tested mechanical properties.