Assessment of zirconium oxide nano-fillers incorporation and silanation on impact, tensile strength and color alteration of heat polymerized acrylic resin

Abstract

The mechanical strength and color stability of poly methylmethacrylate (PMMA) remains far from ideal for maintaining the longevity of denture. The purpose of this study was to assess impact, tensile strength and color stability of heat polymerized denture base after addition of salinated and non-salinated zirconium oxide (ZrO2) nano- fillers. Materials and methods: zirconium oxide nanofillers were incorporated into (PMMA) denture base by free radical bulk polymerization. The nano-particales were Silanated by coating with a layer of trimethoxysil ypropylmethacrylate (TMSPM) before dispersed and sonicated in monomer (MMA) in two percentages of 3% and 5% by weight. Then it was mixed with acrylic powder as general conventional method. One hundred and seventy five specimens were prepared for this study. fifty bar shapes specimens (80mm x 10mm X 4mm) for impact strength test, another fifty dumbbell shaped specimens (75mm × 12.75mm × 2.5mm ) were prepared for tensile strength test. On the other hand, seventy five disc shaped specimens (50mm diameter and 0.5mm thickness) were prepared for color stability test. They were divided into two groups according to the nanofillers used ; silanated and non-silanated ZrO2 nanofillers, for each group Three subgroups were prepared (one control and two(3% and 5%) for the silanated and non-silanated ZrO2 nano-fillers. Impact strength test was carried out with charpy type impact testing instrument. While tensile strength test were done by using Jain Qiao equipment system. . On the other hand, color stability was objectively assessed by using a spectrophotome ter device after 48 hours immersion in three different solutions (distilled water, cola and tea) and the amount of light absorption was calculated. Impact and tensile strength means (in MPa) and color stability means (in nm) were analyzed statistically by analysis of variance and the comparative T-test and least significance test (LSD). Result: Significant increase in impact strength occur in acrylic reinforced with 5% wt silanated (ZrO2) nanofillers , but non significant increase was observed at 5% wt non-silanated (ZrO2) nanofillers when compared with control group. On the other hand, there were non-significant improvements in the tensile strength for all groups of (ZrO 2) reinforcements. While for the color stability test data showed significant increase in the light absorptions for specimens reinforced with (ZrO2) nanofillers when compared with control group. on the other hand, there were no significant difference observed between specimens reinforced with non-silanated and silanated (ZrO2) nanofillers. Conclusion: the findings of this study showed that Silanaized ZrO2 nano-fillers is effective in improving impact strength while it was not effective in improving the tensile strength, the maximum increase in impact strength was observed in denture base nano composite containing 5% wt of silanated ZrO2 nano-fillers. On the other hand, significant color differences were detected between control group and specimens incorporated with zirconium oxide nano-fillers at