Effect Of High Energy X-ray Irradiation On The Nano-mechanical Properties And The Wear Behaviour Of Human Enamel

Objective:To investigate the effects of high energy X-ray irradiation on the mechanical properties friction properties of human enamel,analysis of the possible mechanism of human enamel irradiation damage from surface microstructure.Materials and Methods:The enamel samples of milk and permanent teeth were prepared and simulated by high energy X-ray irradiation in vitro.The mechanical properties including hardness and Young's modulus of the prepared samples were evaluated on a TI-950 Tribolndenter.Mineralization of the enamel samples.High speed reciprocating friction testing machine(UMT-2),scanning electron microscope(SEM)were used to observe the wear resistant.The surface morphology of enamel was observed by atomic force microscope(AFM),and the surface roughness and Young's modulus of individual enamel post were calculated.The crystal structure was analyzed by XRD.Results:1.Effect of X-ray irradiation on mechanical properties of enamel:With the increase of irradiation dose,the nanoscale hardness and Young's modulus of the human enamel surface decreased after irradiation.The results of enamel of primary teeth were more obvious.When the cumulative irradiation dose was up to 70 gy,the nano-hardness and elastic modulus of primary enamel decreased from 5.08 GPa and 92.3GPa to 1.57 GPa and 54.39 GPa.The hardness and modulus of elasticity of permanent enamel decreased from 5.52 GPa and 103.8GPa to 1.634 GPa and 61.19 GPa.The Young's modulus of single glaze post decreased gradually,and the elastic modulus of permanent enamel post decreased by 41.07% and 32.97%,respectively.2.Effect of X-ray irradiation on the friction properties of enamel:(1)Friction behavior change: With the increase of irradiation dose,the friction coefficient of permanent enamel increased after irradiation.When irradiated by 30 Gy,the friction coefficient of enamel increased by 12.9% and 9.7% respectively.When irradiated by 50 Gy,the friction coefficient of enamel increased by 23.6% and 13.3%respectively.When the cumulative irradiation dose was up to 70 Gy,the friction coefficient of enamel increased by 46.9% and 35.6% respectively.(2)Wear behavior change: With the increase of irradiation dose,the wear of enamel increased and the wear scar became deeper and wider.When irradiated with30 Gy,the wear of enamel in breast and permanent tooth increased by 0.6 and 0.125 times.When irradiated by 50 Gy,the wear of enamel increased by 0.88 and 0.438 times.When the cumulative irradiation dose was up to 70 Gy,the wear of enamel increased by 2.6-fold and 1.58 times.3.Effect of X-ray irradiation on the surface micro-structure of enamel of enamel:As the dose of radiation increases,the enamel columns were gradually disarranged,honeycomb and cracked structure appeared on the surface,the structure of enamel pillars dissolved gradually,and the edges were blurred,especially the enamel of primary teeth.With the increase of irradiation dose,the surface roughness of enamel increased and the tendency of primary teeth increased significantly after irradiation.When irradiated by 30 Gy,the surface roughness of enamel and enamel increased by 16.57%and 7.94%.When irradiated by 50 gy,the surface roughness of enamel and enamel increased by 23.46% and 9.94%,respectively.The surface roughness of permanent enamel increased by 43.46% and 32.94% respectively when the cumulative dose of irradiation reached 70 Gy.Conclusion:1.With the increase of irradiation dose,the nano-mechanical properties and friction and wear properties of permanent enamel decreased gradually,but the tendency of enamel decreased obviously.2.With the increase of irradiation dose,the enamel of the permanent tooth appeared different degree of crystal structure change,the arrangement of the enamel column was gradually disordered,the honeycomb and crack structure appeared on the surface,the structure of the enamel pillar dissolved gradually,and the edge was blurred.The crystallinity decreased and the crystal size increased,especially the enamel of primary teeth.3.High energy irradiation caused direct damage to the enamel of breast and permanent tooth.