Effect Of Er:YAG Laser Etching Combined With MDP On The Bond Strength Between Y-TZP Ceramics And Resin

Aim: The purpose of this paper is to investigate the effect of different pulse widths of Er:YAG laser etching on the surface roughening of zirconia ceramics,and to select the best pulse width laser in combination with phosphate monomer MDP to investigate its effect on the bond strength and durability between zirconia ceramics and resin.Materials and Methods: Two types of zirconia porcelain blocks and zirconia porcelain columns were designed and produced,with sizes of 5mm×5mm×2mm and2mm×2mm×10mm,respectively,and were ultrasonically cleaned after grinding the bonded surfaces with 600,800,1000,1500,and 2000 mesh water sandpaper in turn.In Experiment 1,the porcelain blocks were randomly divided into seven groups,blank group(A),sandblasting group(B)Er:YAG laser treatment group(C),and five different pulse widths named as 50μs-SSP group,100μs-MSP group,300μs-SP group,600μs-LP group,and1000μs-VLP group,respectively.The surface morphology of the zirconia specimens was observed under scanning electron microscope and surface profiler,and qualitative and quantitative analyses were performed in parallel to derive the optimal pulse width laser dominance group.In Experiment 2,the porcelain columns were divided into three groups: laser dominance group(600 μs-LP group),sandblasting group and blank group to produce resin columns and surface treated zirconia porcelain column specimens for bonding.The tensile strength of the specimens in the laser advantage group(600μs-LP group),the sandblasting group and the blank group were tested using a universal testing machine,and the failure modes of the fracture surfaces were observed under a body microscope.Experiment 3 was selected on the basis of experiments 1 and 2 for the laser dominant group(600μs),and configured with 10wt% MDP primer for the experiments.The porcelain columns were randomly divided into four groups: blank group,laser dominant group(600μs),laser(600μs)combined with MDP group and MDP alone group for bonding the resin columns to the surface treated zirconia porcelain column specimens.zirconia-resin bonded specimens were made and each group was divided into two subgroups(initial bonding group and aging group)with the same storage conditions as in Experiment 2.four groups of specimens were tested using a universal testing machine for tensile The tensile strength of the four groups was tested using a universal testing machine,and the failure modes of the fracture surfaces were observed under a body microscope.The surface treatment factors were statistically analyzed using Kruskal-Wallis test and post hoc multiple comparisons(Bonferroni post hoc test);then Mann Whitney U test was performed between the tensile strength values of the aging/initial bonding groups for the same surface treatment.The test level was set at α=0.05.Result: The surface roughness Sa values of each group were measured by optical profilometer.Among the laser groups,the laser group with 600 μs pulse width had the highest Sa value and was significantly higher than the sandblasted group(P<0.05).The tensile bonding test results of Experiment 2 showed that under the water storage and aging test conditions,the tensile strength values of the 600-μs pulse width laser group were higher than those of the sandblast group,and the difference between them was statistically significant(P<0.05).After the aging test,the bonding strength of each experimental group was significantly reduced(P<0.05).The results of tensile bonding test in Experiment 3 showed that under the conditions of water storage and aging test,the 600μs pulse width laser combined with MDP group had the highest tensile strength value,which was higher than that of MDP and laser treatment group alone,and the difference was statistically significant(P<0.05).After the aging test,the bond strength of all experimental groups decreased significantly,but the laser combined with MDP group still had the highest tensile bond strength(P<0.05).Conclusion: The 600μs pulse width laser etching can effectively promote the surface roughness of zirconia ceramics and obtain the tensile bond strength better than the sandblasting group;and the 600μs pulse width Er:YAG laser etching combined with MDP treatment is more favorable to the bonding bond and bond durability between zirconia ceramics and resin.