Effect of increased packing pressure on various properties of denture base acrylic resins

Thesis (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2014 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 102-105.Objectives: The purpose of this study was to investigate the effect of increased packing pressure prior to and during polymerization of different denture base materials on the denture base's flexural strength and abrasion resistance. Furthemore, this study evaluated the effect of using chemically polymerized luting acrylic resins on the shear-bond strength between acrylic resin artificial teeth and denture base materials. Lastly, the study aimed to assess the effects of increased packing pressure prior to and during polymerization of different denture base materials and different surface treatments on the shear bond strength between acrylic resin artificial denture teeth and denture base materials. Methods: Three heat-polymerizing denture base acrylic resins were tested: Impact 2000 (Harry J. Bosworth Company), Lucitone 199 (DENTSPLY International Inc.), and Premium Denture Base (Patterson Dental). Two different pressures were applied to each material prior to and during polymerization: (1) conventional (Conv.), 3,500 psi and (2) high pressure (HP), 24,462 psi. Circular specimens OV(20/group) measuring 16 × 2 mm were prepared for biaxial flexural-strength testing in an Instron universal testing machine. For abrasion resistance, rectangular specimens (N=10/group) measuring 40 × 15 × 3 mm, were fabricated and polished (mean surface roughness = 0.02 Mum ± 0.004) and then subjected to 200,000 simulated tooth-brushing cycles with a denture brush (Archtek) and a denture paste (Polident Dentu Creme; GlaxoSMithKline). Surface roughness (Ra) was measured with a profilometer (Surftest SJ-201 ; Mitutoyo), and volume loss was calculated from weight and density measurements. For shear-bond strength testing, denture base specimens were circular and measured 16 × 2 mm while artificial tooth specimens were cylindrical and measured 3 mm in height and 3.3 in width (N=10/group). Five groups were obtained from each material and differed according to the polymerization pressure of the denture base, bonding method (heat vs. autopolymerizing acrylic resins) and surface treatments (None [No], airborne particle abrasion [Airborne] or acrylic resin primer application [Primer]). After the artificial teeth were bonded to the denture bases, the shear-bond strength test was conducted in the Instron machine. Data were analyzed by using ANOVA and multiple comparison tests ([alpha] [less or equal to].05). [TRUNCATED