Study on Positional Stability of Mini-screw Metal Implant in CBCT

Abstract

Objective The purpose of this study was to perform three-dimensional digital measurement of metal implants in adults and adolescents with CBCT, which is to compare the positional changes of the implants before and after treatment and to explore whether the positional stability of metal implants is reliable. Methods CBCT samples of implants in adults were obtained from 19 adult patients who underwent orthodontic treatment at PKUSS from 2009 to 2013, with an average age of (24±0.7) years, with an observation interval of at least 1.5 years. The CBCT samples of adolescent were obtained from 15 adolescent patients who completed orthodontic treatment at PKUSS from 2013 to 2016. The T1 age was (12.4±0.7) years; the T2 age was (13.3±0.9) years, and the T1 and T2 interval were at least 1 year. CBCT three-dimensional digital measurement was performed in Dolphin Imaging software, and the accuracy of landmark points in CBCT three-dimensional measurement was quantitatively calculated and statistically analyzed to evaluate the sample size. Three-dimensional measurements of implant position in adolescent and adult samples were performed to assess positional stability. The two measurers independently performed the measurement and repeated the process twice. Results The accuracy of the landmark measurement in the CBCT of this study is good, and the measurement error ranges from 0.8 mm to 1.53 mm. The spatial angle change of the two implants before and after the treatment of the adolescent samples is not statistically significant compared with the adult samples (the P values of the four measurements are greater than 0.05), and the four Levene’s tests meet the homogeneity of the variance. At the same time, the variation of all space angles is less than 2°. The distance between the tail points of the implants in the adolescent samples before and after treatment has no statistical significance compared with the adult sample (P<0.05), and the four Levene's tests meet the homogeneity of variance. The distance change of head point shows statistical significance (P<0.05) in 3 out of 4 measurements compared with the adult sample, and only one Levene's tests met the homogeneity requirement of variance. At the same time, the measured values of the distance change of all the points are less than 0.50 mm. Conclusions There is no clinical difference of the positional stability of metal implants between adults and adolescents. The positional stability of metal implants in CBCT is reliable. Key words: Mini-screw implant; 3D digital measurement; Cone-beam CT