Sfondrini Maria Francesca, Cacciafesta Vittorio, Maffia Elena, Massironi Sarah, Scribante Andrea, Alberti Giancarla, Biesuz Raffaela, Klersy Catherine
Department of Orthodontics, University of Pavia, Pavia, Italy.
Angle Orthod. 2009 Mar;79(2):361-7. doi: 10.2319/042108-223.1.
To test the hypothesis that there is no difference in the amounts of chromium released from new stainless steel brackets, recycled stainless steel brackets, and nickel-free (Ni-free) orthodontic brackets.
This in vitro study was performed using a classic batch procedure by immersion of the samples in artificial saliva at various acidities (pH 4.2, 6.5, and 7.6) over an extended time interval (t(1) = 0.25 h, t(2) = 1 h, t(3) = 24 h, t(4) = 48 h, t(5) = 120 h). The amount of chromium release was determined using an atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrometer. Statistical analysis included a linear regression model for repeated measures, with calculation of Huber-White robust standard errors to account for intrabracket correlation of data. For post hoc comparisons the Bonferroni correction was applied.
The greatest amount of chromium was released from new stainless steel brackets (0.52 +/- 1.083 microg/g), whereas the recycled brackets released 0.27 +/- 0.38 microg/g. The smallest release was measured with Ni-free brackets (0.21 +/- 0.51 microg/g). The difference between recycled brackets and Ni-free brackets was not statistically significant (P = .13). For all brackets, the greatest release (P = .000) was measured at pH 4.2, and a significant increase was reported between all time intervals (P < .002).
The hypothesis is rejected, but the amount of chromium released in all test solutions was well below the daily dietary intake level.
检验新的不锈钢托槽、回收的不锈钢托槽和无镍正畸托槽释放的铬含量无差异这一假设。
本体外研究采用经典批次法，将样本在不同酸度（pH 4.2、6.5和7.6）的人工唾液中浸泡较长时间间隔（t(1)=0.25小时，t(2)=1小时，t(3)=24小时，t(4)=48小时，t(5)=120小时）。使用原子吸收分光光度计和电感耦合等离子体原子发射光谱仪测定铬的释放量。统计分析包括重复测量的线性回归模型，计算Huber-White稳健标准误差以考虑数据在托槽内的相关性。事后比较采用Bonferroni校正。
新的不锈钢托槽释放的铬量最大（0.52±1.083微克/克），而回收托槽释放0.27±0.38微克/克。无镍托槽的释放量最小（0.21±0.51微克/克）。回收托槽和无镍托槽之间的差异无统计学意义（P = 0.13）。对于所有托槽，在pH 4.2时释放量最大（P = 0.000），且所有时间间隔之间均有显著增加（P < 0.002）。
该假设被拒绝，但所有测试溶液中释放的铬量均远低于每日膳食摄入量水平。
