The Effect Of Post-irradiation,Temperature And Solvent On Surface Hardness Of Bulk Fill And Traditional Resin-based Composites

Objective:To determine the effect of post-irradiation aging,different temperatures,different solvents and their interactions on the changes in surface hardness of three traditional resin-based composites and three bulk fill resin-based composites.Materials and methods:Three bulk fill resin-based composites(X-tra Fil,Sure Fil SDR,Filtek bulk fill flowable)and three traditional resin-based composites(Filtek Z350 XT,Filtek Z250 XT,Grandio)were selected and were made into circular samples(6mm diameter and4 mm height).30 specimens of each composite resin were prepared and randomly assigned to different groups(23℃,37℃)and subgroups(dry aging,deionized water aging,75% ethanol/water solution aging)(n=5).A total of 7 time points including 0h,1h,24 h,7d,1m,3m and 6m were chosen to measure the composites’ surface and subsurface hardness with microhardness tester.In order to investigate long-term change of the surface hardness of composite resin under the condition of various factors.Results:The surface hardness of the composite resin under the conditions of dry aging and deionized water increased firstly,then remained stable,and finally decreased.The percentages increase of surface hardness of the 6 composite resins were shown as drying aging > deionized water aging > 75% ethanol/water solution aging.Under dry condition,Sure Fil SDR showed the greatest increase in surface hardness within 24 hours,reaching 34.6 to 78.4 percent of the initial hardness value,higher than the other five kinds.Followed by Filtek bulk fill flowable,with minimal Grandio changes.Compared with dry condition,the surface hardness of 6 composite resin soaked in deionized water changed less.At 24 h,the biggest percentage increase in bulk fill resin-based composites surface hardness was Sure Fil SDR(13.2%-15.5%)and the smallest was FBF(8.7%-10.6%).within 1month,the largest percentage increase in surface hardness of traditional resin-based composites was seen as Grandio(10.2%20.2%),and the smallest is Filtek Z250 XT(6.7% 15.7%).Under the condition of75% ethanolethanol/water solution aging,surface hardness decreased significantly at24 hours,especially Sure Fil SDR fell by 42.1%-61.1%,and Grandio decreased obviously at 1 hour,both the Filtek Z350 XT and Filtek Z250 XT increased firstly and then decreased,reaching a maximum at approximately 24 h.The surface hardness of composite resin specimens stored at 37℃increased by a larger percentage than that of23℃,up to 2 times or more.Conclusion:The surface hardness of bulk fill and traditional resin-based composites increased continuously with time after light irradiation,lasting for about 1 month.The change is closely related to temperatures and storage solvents.As a traditional composite resin,curing depth of Grandio can be up to 4 mm.And the surface hardness increased minimum to confirm stable clinical applications.As bulk fill resin-based composites,Filtek bulk fill flowable and Sure Fil SDR had a curing depth of up to 4mm,but their hardness were low and they need to be used in combination with other resins.Moreover,water and 75% ethanolethanol/water solution aging have a significant impact on the surface hardness of these two materials,which should be fully considered in clinical applications.