Investigate Adhesive Strength After Different Er:YAG Laser Irradiation Time Treatment Of Dentin

ObjectiveCompare different Er:YAG laser irradiation time to analyze relation of the laserirradiation time to the adhesive strength of regular dentin. Optimal irradiation time forthe highest dentin adhesive strength was obtained, which would significantly improvethe crown life span.Method1.60pieces of premolars which belong to15to30years old were chosen. Theseteeth are full ripe, no restoration and also no fold crack. Then, these teeth wererandomly divided into six group which were A, B, C, D and E.10pieces of teethwhich soft tissue and girmir were removed, were allocated to each group.2.The enamel of these60pieces of teeth were removed in water spraysurrounding. The essence of occlusal surface dentin were retain and turned into60pieces of4mm×4mm×4mm cubes. Then, length2/3of the tooth was packed by self-curing plastic (the occlusal surface dentin should not be touch). After that, all thesample teeth were furbished into uniform modern.3.These60teeth samples were allocated into6groups, which were A, B, C, D, E,and F. These samples groups were irradiated under laser radiation which was set to6HZ,6J/cm2, and laser beam spot diameter of1mm. These six groups of samples wereplaced vertically ca.17mm from the laser source and forming a4mm x4mmirradiation region under water spraying condition. The irradiation time of group A, B,C, D, E and F were0s,1s,2s,3s,4s, and5s, respectively. 4.Take a straw with5mm diameter and cut into60small straws that were4mmheight each. After photo-curable resin cement splash into straws, all the samples werestick with the straws to made resin piece by using the resin cement bond.5.8teeth from each group were taken and fasten in the universal tensile testingmachine to recording data for statistical analysis.6.The rest2teeth from each group were horizontally slivered and adhered on ametal bar. Then metallized film in a vacuum evaporator. After that, a S4700scanningelectron microscope was used to observe and take photo in representative areas ofthese teeth.7.SPSS13.0software was used to analysis the result. Er:YAG of group A, B, C,D, E, and F were compared by using SNK-q method.ResultsThe group of resin bond strength of Er:YAG laser irradiation significantly greaterthan the blank space group. Adhesive strength of resin of group D, E significantlygreater than group B,C,F. The highest adhesive strength of six groups that havemaximum difference is (P <0.01), group D, E have no statistical difference which is（P＞0.05）, adhesive strength of group B, D are steadily increase. The tension ofgroup D,E reach to the highest. However, adhesive of group F decreases along withthe irradiation time prolonged.ConclusionThe optimal irradiation time of regular dentin under Er:YAG laser irradiation is3s to4s.