Effect of sodium fluoride on the properties of acrylic resin denture base material subjected to long-term water immersion


Background: Fluoridated acrylic resin material can present more stable properties when compared withconventional one.The most widely used fluoride –containing substance added to dental resin materials is sodiumfluoride (Naf). This study evaluated the effect of Naf in different concentration to the acrylic resin denture basematerial and its effect on tensile strength ,modules of elasticity with long –term water immersion (after 4 monthsimmersion in de-ionized water)Materials and methods: Eighty specimens from dumbbells shaped metal pattern for tensile strength test werepreparedaccording to ISO 527: 1993 plastic –Determination tensile properties ,in dimensions(60mm, 12mm, 3 ±0.2mm) length, width and depth respectively were allocated to two groups according to water immersion therewere 40 specimens before immersion and 40 specimens after water immersion for 4 months in de-ionized water(thede-ionized water was changed every day),these two groups were sub divided in to four groups according to theconcentration of Naf,Naf powder were added to monomer of acrylic in concentrations of 1%,2%and 5% Naf .0%Naf(control group) ,then mixing were done with polymer according to manufacture instructions ,the conventionalflasking ,packing procedure were used following that (fast cycle). For tensile strength test the measuring was doneby Instron machine, the values of modulus of elasticity were obtained from tensile test.Results: Results showed that the addition of sodium fluoride to acrylic resin material werelower the tensile strengthand modules of elasticity with highly significant differences p<0.01 when compared to control group regardless theconcentration of Naf,But after immersion (for 4 month ) the tensile strength and modules of elasticity increased incomparison to groups before immersion (with highly significance differences p <0.01 ), highly significance differences(p <0.0)were found between groups after and before immersion in all concentrations except for tensile strengthbetween 1%Naf and 2%Naf after immersion there was no significant differences(p>0.05), and for modules ofelasticity between control and 1%Naf, 1% Naf and 2%Naf( after immersion ),there was only significant differencesbetween them(p<0.05).Conclusions: Addition of fluoride to acrylic resin material lower the tensile strength and modules of elasticity whencompared to control group regardless the concentration of Naf, But after immersion (for 4 months ) the tensilestrength and modules of elasticity increased in comparison to groups before immersion (with highly significancedifferences p <0.01)