| Objective: To study the biomechanical properties of composite bone cement,which consists of polymethyl methacrylate(PMMA)and ?-calcium phosphate(?-TCP)with different total mass ratios plus a certain total mass ratio of gentamicin(GM),to screen composites bone cement suitable for clinical applications.Method: The powder of ?-TCP bone cement was added to the powder of the corresponding proportion of PMMA bone cement at a total mass ratio of 15%,25%,and 35% and mixed well.The GM powder was added to the above three sets of composite bone cement powders at a total mass ratio of 4%.Fully mixed and then kept in separate bottles,numbered as group a,group b and group c.According to the manufacturer's recommended solid-liquid ratio of 2:1,polymethyl methacrylate monomer compound liquid and composite bone cement powder were mixed and sampled.48 samples were prepared for each group.Each group was randomly selected 6 times during sample preparation.The injection time of each group of composite bone cement was measured with a sterile syringe.Each group of samples was dried and then stored in bottles for use.Each group of samples was randomly divided into 8 groups of 6 in each group.A small group was randomly selected from each group of bone cement,and the compressive strength of each group of samples before immersion was measured using a WDW-20 microelectronic universal testing machine.The remaining 7 groups of samples of each group of composite bone cement were weighed using an electronic balance.Immerse in a centrifuge tube filled with phosphate buffered saline at a ratio of 1:5 and randomly numbered as a-1d,a-3d,a-5d,a-1w,a-2w,a-3w,a-4w;b-1d,b-3d,b-5d,b-1w,b-2w,b-3w,b-4w;c-1d,c-3d,c-5d,c-1w,c-2w,c-3w,c-4w,and placed in a constant temperature and humidity oscillator,respectively,on the 1d,3d,5d,1w,2w,3w,4w take out each group of composite bone cement corresponding number group sample.After drying the samples in each group,the mass of the composite bone cement soaked in each group was weighed after being dried,and the degradation rate was calculated from the difference between the masses before soaking and the soaking.The Ph value was used to measure the Ph value of the soaking solution for each group.Ultravioletspectrometer was used to measure the cumulative release of GM in each group of infusions.The compressive strength of each group after soaking was measured with a WDW-20 Microcontroller Electronic Universal Tester.Statistics and analysis of the data in each group were used to screen out the ideal ratio of composite bone cement.Result:1.The injection time of cement in group c was significantly longer than that of group a and b,and there was a significant difference between the three groups.The difference have statistically significant(p<0.01).2.The compressive strength of bone cement in group c before soaking was significantly higher than that in group a and b,and there was a significant difference between the three groups.The difference was statistically significant(p<0.01).The compressive strength of the three groups of cement after soaking decreased with the increase of soaking time,and no significant difference was found between the three groups,the difference was not statistically significant(p> 0.05).3.The degradation rate of bone cement in group c was significantly higher than that of group a and b.The degradation rate of each group increased with the prolongation of soaking time,and there was a significant difference between the three groups.The difference was statistically significant(p <0.01).4.The Ph value of the bone cement soaking solution in the c group was significantly lower than that in the a and b groups.Ph value of the soaking solution in each group decreased as the soaking time prolonged,and there was a significant difference between the three groups.The difference was statistically significant(p<0.01).5.The cumulative release of GM in bone cement soaking solution in group c was significantly higher than that in group a and b.The cumulative release of GM in soaking solution in each group increased with the soaking time,and there was a significant difference between the three groups.The difference was statistically significant(p<0.01).Conclusion: Statistical analysis of the experimental results shows that the biomechanical properties of the c-composite bone cement are more suitable for clinical use.When the content of ?-TCP is 35% in the composite cement,the performance of the two groups of cement can be combined to the utmost degree.Ithas ideal injectable time,compressive strength,in vitro degradation rate,GM release in vitro,Ph value.It is the ideal mixing ratio. |
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