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 processingtechnique and easy repair. However, the resistance to impact and fracture of PMMA duringfunction is low. Various methods for enhancing strength of the acrylic resin denture baseshave been reported. This study was designed to evaluate the effect of adding Siwak powderwith average particle size of (75 µm) in three different concentrations by weight to PMMAon certain mechanical properties. Material and Methods: Tensile strength, elongation,transverse strength, impact strength, compressive strength and the surface roughness ofheat- polymerized acrylic resin specimens were evaluated for both the control group A(0%) and the experimental groups. These groups consisted of acrylic resin mixed withdifferent proportions of Siwak powder B (3%), C (5%) and D (7%) by weight. Stainlesssteel samples with dimensions of (65 mm, 12.5 mm, 2.5 ± 0.03 mm) length, width, andthickness were constructed for testing tensile strength and elongation of acrylic resin. Otheruniform 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 werereused for transverse deflection test. For testing the impact strength and compressivestrength of acrylic resin, wax patterns (60 mm,10 mm, 10 mm) and (20 mm,10 mm, 10mm) length, width, thickness were prepared. Results: Siwak powder (5%) did not greatlyaffect the tensile strength and compressive strength (P = 0.05). The addition of Siwakpowder at ratio of (3%) did not greatly affect impact strength of the experimental group incomparison to the control group, while the addition of (7 %) Siwak powder revealed asignificant decrease in tensile strength, impact strength and compressive strength incomparison to the control group. Conclusion: Addition of low concentrations (3%, 5%)Siwak to the heat polymerizing acrylic resin did not affect significantly the testedmechanical properties.