In Vitro Studies Of Effect Of Different Factors On Microleakage Of Resin Composite Restorations

ObjectiveSince the composite resin is beautiful, environmentally friendly, minimally invasive, etc., it is widely used in clinic. But there is polymerization shrinkage in composite resin when solidifying, which make the fracture formed between the teeth and resin, and food scraps and other various microorganisms penetrate in the fracture. microleakage of edge is the main defect of composite resin, and microleakage will easily result in the problems, such as edge coloring of filling body, secondary caries, postoperative sensitivity and loosening and dropping out of restorations, etc.Therefore, reducing the composite resin polymerization shrinkage and improving microleakage restorations can improve the quality of restorations, ensure the long-term efficacy of the treatment. This experiment select the new type of clinical material to fill the teeth Class Ⅱ cavity restored, from three aspects of the bonding system, bedding materials and the resin matrix, compare their impacts on the microleakage of composite resin, in order to provide reference for selection of materials more effectively in the clinical work.Method100freshly extracted human molars without defect, caries and cracks were collected, Class Ⅱ cavity according to the standard was prepared on molars. Then the teeth was randomly divided into five groups (A～E):3M self etch adhesive+3M Z250composite resin filling (Group A);37%phosphoric acid+3M total etch adhesive+3M Z250composite resin filling (Group B);3M self etch adhesive+3M UV curing glass ion bottom+3M Z250composite resin filling (Group C);3M self etch adhesive+3M flowing resin bottom+3M Z250composite resin filling (Group D);3M P90bonding system+3M P90composite resin filling (Group E). after thermoeyeling400times,all the test specimens were completely immersed in neutral india ink for7d, maintained at37℃, rinsed thoroughly in running water. All specimens with the hard tissue slicer were divided into two parts along the long axis of teeth form the directions of far, near and middle. The penetrating depth of each observation plane gingival wall dye was observed under the stereomicroscopes at40magnification and measured with the venire caliper, and then took photos. The obtained data was compared between each two groups by t test(P<0.05). One specimen was chosen from each group, after fixed and dewatered treatment, they were soaked and embedded with solidified resin, then after being sawed, grinded, colo red and made into sections, they were placed under the fluorescence microscope to ob serve the condition of the filling materials and the teeth bonding interface as well as to take photos for records.Results1.the microleakage mean of group E (P90) was significantly less than that of r est groups, the difference was statistically significant (P<0.05).2. the microleakage mean of group C (light-cured glass ionomer bottom) was significantly less than the group A, B, D, the difference was statistically significant(P <0.05);3. no statistically significant difference was tested among the microleakage means of group A, B, D (P>005).ConclusionThe microleakage of P90is lowest, which is a well restorative material for posterior restorations; the light-cured glass ionomer bottom can improve the microleakage of composite resin. The differences between the effects of total etch adhesive and self-etching adhesive on the microleakage of composite resin are not statistically significant.