PURPOSETo evaluate the effect of various metal oxides on impact strength (IS), fracture toughness (FT), water sorption (WSP) and solubility (WSL) of heat-cured acrylic resin.MATERIALS AND METHODSFifty acrylic resin specimens were fabricated for each test and divided into five groups. Group 1 was the control group and Group 2, 3, 4 and 5 (test groups) included a mixture of 1% TiO2 and 1% ZrO2, 2% Al2O3, 2% TiO2, and 2% ZrO2 by volume, respectively. Rectangular unnotched specimens (50 mm × 6.0 mm × 4.0 mm) were fabricated and droptower impact testing machine was used to determine IS. For FT, compact test specimens were fabricated and tests were done with a universal testing machine with a cross-head speed of 5 mm/min. For WSP and WSL, discshaped specimens were fabricated and tests were performed in accordance to ISO 1567. ANOVA and Kruskal-Wallis tests were used for statistical analyses.RESULTSIS and FT values were significantly higher and WSP and WSL values were significantly lower in test groups than in control group (P<.05). Group 5 had significantly higher IS and FT values and significantly lower WSP values than other groups (P<.05) and provided 40% and 30% increase in IS and FT, respectively, compared to control group. Significantly lower WSL values were detected for Group 2 and 5 (P<.05).CONCLUSIONModification of heat-cured acrylic resin with metal oxides, especially with ZrO2, may be useful in preventing denture fractures and undesirable physical changes resulting from oral fluids clinically.

It may be concluded that the glazed specimens showed a better color stability, although the staining observed in the polished specimens was not clinically noticeable.

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The aim of this study was to evaluate the stress distribution in the bone around dental and zygomatic implants for 4 different implant-supported obturator prostheses designs in a unilaterally maxillary defect using a 3-dimensional finite element stress analysis. A 3-dimensional finite element model of the human unilateral maxillary defect was constructed. Four different implant-supported obturator prostheses were modeled; model 1 with 2 zygomatic implants and 1 dental implant, model 2 with 2 zygomatic implants and 2 dental implants, model 3 with 2 zygomatic implants and 3 dental implants, and model 4 with 1 zygomatic implant and 3 dental implants. Bar attachments were used as superstructure. A 150-N vertical load was applied in 3 different ways, and von Mises stresses in the cortical bone around implants were evaluated. When the models (model 1-3) were compared in terms of number of implants, all of the models showed similar highest stress values under the first loading condition, and these values were less than under model 4 conditions. The highest stress values of models 1-4 under the first loading condition were 8.56, 8.59, 8.32, and 11.55 Mpa, respectively. The same trend was also observed under the other loading conditions. It may be concluded that the use of a zygomatic implant on the nondefective side decreased the highest stress values, and increasing the number of dental implants between the most distal and most mesial implants on the nondefective side did not decrease the highest stress values.