The Level Of Ions Released From Digitized Metallic Dental Prosthesis And Metabolism:an In Vivo Study

Objective:This study aimed to explore the metal ion precipitation level and metabolism in the mouth of the selective laser melting(SLM)of cobalt-chromium alloy restorations and computer numerically controlled milled(CNC-milled)commercial pure titanium restorations,and provide guidance for digitized metallic dental prosthesis in clinical work.Methods: In this study,six eighteen-month-old beagle canines were divided into CNC-milled CP-Ti group and SLM Co-Cr alloy group according to their weight and the random number table.The upper jaw impressions were made by silicone rubber and then,we made corresponding metal brackets according to the impressions.The palate mucosa in contact with the mental brackets,blood and hair samples are collected on day 0,day 3,week 1,week 2,month 1,month 2,month 3,month 4,month 5,and month 6 of wearing the metal brackets.After the relevant pretreatment and nitration,the metal ion species and concentration are detected by inductively coupled plasma mass spectrometry(ICP-MS).Results: By comparing the time points of the beagle canines themselves,the total metal ion concentration of the palatine mucosa of the two groups of beagle canines was significantly different at different time points(CNC-milled CP-Ti group P=0.000<0.05,SLM Co-Cr alloy group P=0.009<0.05),and the total metal ion concentration reached a peak at month 1 and then decreased.In the detection of hair,the difference in total metal ion concentration of the two groups was statistically significant at different time points(CNC-milled CP-Ti group P=0.004<0.05,SLM Co-Cr alloy group P=0.000<0.05),the total concentration of metal ions in the CNC-milled CP-Ti group fluctuated and was at the lowest value at month 4;the total concentration of metal ions in the SLM Co-Cr alloy group reached its peak at the month 1 and then declined.In the detection of whole blood,the difference in total metal ion concentration of the two groups was statistically significant at different time points(CNC-milled CP-Ti group P=0.004<0.05,SLM Co-Cr alloy group P=0.002<0.05),the total metal ion concentration of the CNC-milled CP-Ti group reached a peak between month 2 and month 4,and then decreased;while the total metal ion concentration of the SLM Co-Cr alloy group reached a peak between month 1 and month 2,and then decrease.In the detection of plasma,the difference in total concentration of metal ions in the CNC-milled CP-Ti group was statistically significant at different time points(P=0.002<0.05),and the total ion concentration is in a fluctuating state with a low peak between month 2 and month4;while the difference in total concentration of metal ions in the SLM Co-Cr alloy group was not statistically significant at different time points(P=0.052>0.05),there is no obvious difference in the total concentration of metal ions among each time point.Correlation analysis showed that the correlation of the various samples in the CNCmilled CP-Ti group was not significant or the correlation was low;in the SLM Co-Cr alloy group,the total mucosal metal ion concentration was moderately positively correlated with the total hair metal ion concentration(r=0.674,P=0.000<0.05),the total concentration of mucosal metal ions was moderately positively correlated with the total concentration of plasma metal ions(r=0.646,P=0.000<0.05)Conclusion: Under the experimental conditions,wearing CNC-milled CP-Ti brackets and SLM Co-Cr alloy brackets in the beagle canine’s mouth will produce a certain amount of metal ion precipitation,and can cause an instantaneous increase of metal ions in the oral mucosa.The two groups reach a peak at month 1.There are differences in the effects on the blood and hair of the two groups: in the CNC-milled CP-Ti group,the metal ion concentration of the whole blood remained at a high peak between month 2 and month 4;while the hair and plasma did not detect the peak point.In the SLM Co-Cr alloy group,the hair metal ion concentration remained at a high peak from week 2 to month 1;the metal ion in the whole blood remained at a high peak from month 1 to month 2;while the plasma metal ion concentration was not detected the peak point.