Comparing the Impact Strength and Transverse Flexure Strength of Three Different Dentures Base Materials
Humam M. Al-Somaiday, Mohammed Moudhaffer and Abdalbseet A Fatalla

Department of Prosthodontics, College of Dentistry, University of Baghdad, Iraq.

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Abstract: Following the rapid development of denture base material and the invention of new materials that used to construct dentures, many studies aimed to test and compare the mechanical and physical properties of the newly developed materials as well as the effect of adding some additive to acrylic resin. As the denture placed in oral environment and subjected to many chemical materials and multiple forces, the denture base materials should have specific properties to full fill as much as possible the needed requirement to made dentures. Flexibility and high impact resistance considered as limitation in conventional heat cured acrylic resin; therefore, new techniques and materials have been introduced to overcome this limitation. In this study, impact strength, and transverse flexural strength and elastic modulus at maximum load of three dentures base materials (heat cured acrylic, polycarbonate and injectable acrylic) were compared. A total of (60) specimens of polycarbonate, injectable acrylic and conventional heat cured acrylic were fabricated according to manufacturer’s instructions and divided into (2) groups, (30) specimens for each testing group i.e. the impact strength and transverse flexural strength at maximum load except for the elastic modulus test at maximum load which was measured concurrently with transverse flexural strength (10 specimens for each testing material). Highly significant differences (P≤ 0.01) between all the (3) experimental materials were noticed after analyzing each test's results with descriptive statistical analysis, one-way ANOVA and post-hoc LSD. The Polycarbonate has the highest mean values of impact strength (233.43 KJ/M2) followed by the (injectable acrylic) with (29.89 KJ/M2) mean value while the lowest mean value was for the (heat cure acrylic) (7.53 KJ/M2). While the heat cured acrylic has the highest transverse flexural strength (77.03 MPa and elastic modulus (4.541 N/M2) at the maximum load, followed by Polycarbonate (69.12 MPa); (2.684 N/M2), then the injectable acrylic (60 MPa); (2.366 N/M2). Scanning electron microscope of fracture line after Charpy's impact test shows that both Polycarbonate and injectable acrylic had ductile fracture, while heat-cured acrylic exhibit brittle fracture. All injectable materials included in this study exhibit higher flexibility, elasticity, ductility and impact resistance. While heat cured acrylic exhibit higher rigidity, brittleness and low impact resistance.

Keywords: Denture Base; Polycarbonate; Thermoplastic Resins; Poly (Methyl Meth Acrylate)

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