The Effects Of Amorphous Calcium Phosphate On Permeability,Color Stability And Micro Hardness Of Resin Infiltration

Background and Objective:Dental caries is clinical common and frequently occurring disease in endodontics, treatment of the disease is a research hotspot currently, The progress of treatment technology is often influenced by development of science of dental caries material.Tissue engineering and materials science were developing rapidly in twentieth Century 90’s, promoting the development speed of dental materials. The use of low viscosity resin which infiltrated into the body of the lesion and form a diffusion barrier was seen as a caries therapy now. This therapies is effective in halting the disease progression, and avoid removing large amounts of healthy tooth tissue painlessly and non-invasively.Amorphous calcium phosphate was found in the process of synthesize hydroxyapatite by wet chemical method. Amorphous calcium phosphate is regarded as amorphous mesophase, which prevention and treatment caries by increasing the mineral content of enamel effectively, inhibiting demineralization and promoting remineralization.The purpose of this experiment was to use a nano amorphous calcium phosphate as the permeability of dental resin filler for the prophylactic treatment of early caries.Research and development of the material and technical success will greatly improve the therapeutic effect of early caries, improve people’s quality of life, reduce secondary caries problems of economic investment.At the same time, the technology promotion, will bring better social and economic benefits.The final clinical application is to provide a new way for the prevention and treatment of early caries, while other hard tissue engineering and clinical repair will get wide application. Amorphous calcium phosphate will be added into resin infiltration in this experiment, to research the effects of amorphous calcium phosphate on permeability, color stability and micro hardness of resin infiltration on the basis of increased mineralizationMethods:Experiment 1:The effects of amorphous calcium phosphate on permeability of resin infiltrationArtificial dentin caries lesion was established by demineralization fluid. The specimens were infiltrated by resin infiltration agent(A group) and amorphous calcium phosphate agent(B group). Utilizing visible-light to cure resin after permeate and double fluorescent staining. The specimens were embed by denture base resins. Using the slow cutting machine slicing out 1 mm thick sheet along the longitudinal direction. The sections were observed under the confocal laser scanning microscopy (CLSM) and the electron microscope. To compare the permeability of two groups by measure and observe the depth of resin into the enamel fracture in two groups.Experiment 2:The effects of amorphous calcium phosphate on color stability of resin infiltrationArtificial dentin caries lesion was established by demineralization fluid. The specimens were infiltrated by resin infiltration agent(A group) and amorphous calcium phosphate agent(B group) and obtaining two groups of samples. And then placed in the ultraviolet aging test box for aging treatment, measuring the colour of samples in 6,12,24,48hours. Record the each Lx*,ax*,bx* values(X represents different irradiation time). Using chromatic aberration formula to calculate the value of chromatism(ΔE),ΔEx*=[(Lx*-Lo*)2+(ax*-ao*)2+(bx*-bo*)2]1/2. Researching the effects of amorphous calcium phosphate on color stability of resin infiltration by calculating AEExperiment 3:The effects of amorphous calcium phosphate on micro hardness of resin infiltrationArtificial caries model was embedded in the base resin after the resin infiltration, exposing the resin infiltration surface only and maintain the level. Polishing the surface with buffing wheel and then placed under the micro hardness tester. Loading 100g and holding for 15 seconds to get impression. Measuring the length of the diagonal under the light microscope. Recording the corresponding Knoop hardness and then averaging. This average value was regarded as the micro hardness value of the sample to evaluate the effects of amorphous calcium phosphate on micro hardness of resin infiltration.Finally, the polished surface of enamel was observed by using scanning electron microscope to assess the impact on polishing performance when amorphous calcium phosphate adding to resin infiltration.Results:The experimental observations found that permeability of resin infiltration was reduced after amorphous calcium phosphate added with the help of confocal laser scanning microscopy (CLSM) and scanning electron microscope. The colours of resin infiltration(A group) and amorphous calcium phosphate resin(B group) were changed after ultraviolet irradiation. The value of chromatism(AE) increased with the extension of irradiation time, the colour of two groups tend to be stable after 24 hours. The value of chromatism(ΔE) of two groups had no statistical difference at the same irradiation time(P>0.05). After micro hardness test, the micro hardness of resin infiltration group (group C) increased significantly compared with demineralized group (group B), but there were statistical differences (P<0.05) in the micro hardness value compared with normal enamel group (group A),there were no statistical differences(P>0.05) between nano amorphous calcium phosphate group (group D) and normal enamel group (group A). Scanning electron microscope observation showed that,the enamel surface were smooth with small amount of slide mark,the pores were small and little in resin infiltration group (group C), howere, when nano amorphous calcium phosphate group (group D) after the polishing, the surface is not regular, big pore, the surface is rougher than group C.Conclusion:Ultraviolet light can accelerating resin’s aging and cause changes in resin’s color, adding amorphous calcium phosphate into resin infiltration does not affect the color stability of resin. Resin infiltration can restore the micro hardness of demineralized enamel surface, but there were differences between normal enamel, amorphous calcium phosphate can compensate for this short-coming, but the amorphous calcium phosphate can reduce the permeability and the polishing performance of the resin infiltration.