Study Of Three Different Caries Preparation Methods On Deciduous Teeth

Objective Cavity preparation is the first step of restoration,its basic principle was first proposed by Black GV in 1893,who believed that extension for prevention was necessary.But with the application of new filling material and bonding technology,changes in epidemiology of dental caries,and so on,the Black Theory has been modified by scholars,and the new concept of "minimally invasive dentistry" comes true.It mainly includes the following aspects:(1)early diagnosis of dental caries;(2)individual dental caries susceptibility assessment and plaque control;(3)non-surgical treatment of dental caries;(4)caries surgical treatment improvements: smaller cavity preparation,the use of minimally invasive technique to rot bonding repair materials,and fill the failed backfill without completely removing it or filling it again,etc.Minimally invasive cavity preparation technology includes four categories: motor mechanical method,non-motor mechanical method,chemical mechanical method and photolithography method.The aim of this study is to look for better preservation method and better restoration filling material.Methods In this study we aim to compare different cavity preparation methods on deciduous teeth.So we divide deciduous teeth into three groups: motor mechanical group(high speed turbine dental caries cavity preparation group),ultrasonic group and Carisolve group(chemical mechanical method).This study include three parts.In the first part,we compared the difference of surface roughness and cleanness among three groups by scanning electronic microscope.Each group contains 5 decay deciduous teeth.In the second part,we fill cavities with stir-in resin for each group and test shear strength difference among three groups.Each group contains ten decay deciduous teeth.In the third part,we fill cavities with two kinds of filling materials,glass ionomer cement(GIC)and composite resin and test between motor mechanical group and ultrasonic group and test micro leakage.Each group contains 20 non-decay deciduous teeth,and every 10 of them for one kind of filling materials separately.Results 1.With scanning electronic microscope we find that cavity walls show totally different.In motor mechanical group cavity surface seems most smoothly,and we do not find any fractures in this study.In ultrasonic group cavity surface seems most roughness and we find some fractures.In Carisolve group cavity surface are less smoothly and we do not find any fractures.2.The tensile tests after filling showed that the highest shear strength value occurred in the motor mechanical group,Carisolve group showed least shear strength value.Differences among these three groups were statistically.3.In micro leakage test we find in motor mechanical group GIC and composite resinshow similar edge leakage.And in ultrasonic group there is no statistical difference between GIC and composite resin.But edge leakage in ultrasonic group seems significant seriously than that in motor mechanical group.Conclusion Electronic microscopy shows that cavity surfaces of motor mechanical group are more smoothly with thick smear layer,and the filling material shows highest filling shear strength value,with less micro leakage.In Carisolve group cavity surfaces are clean with opening dentin tubules.In terms of shear strength test,this group shows lest filling shear strength value.Cavity surfaces in ultrasonic group are rough with partly smear layer.And the filling material shows moderate shear strength value,but the microleakage was the worst among three groups.