Comparison of Maximum Insertion Torque Applied to Miniscrew Implants Placed in the Midpalatal Region of Adult Cadavers with and without Torus Palatinus

Abstract The purposes of this study were 1) to compare the maximum insertion torque (MIT) values of miniscrews placed in the midpalatal bone of adult cadavers with and without Torus Palatinus (TP), and 2) to analyze the influence of the TP size on the MIT values. One hundred twenty self-drilling titanium miniscrews (6.0 mm length and 1.6 mm diameter) were placed at anterior median (AM), middle median (MM) and posterior median (PM) sites of the maxilla of 40 adult cadavers. TP sizes (height, width and length) were measured and classified.  MIT values were assessed with a digital torque gauge. The Student t test, one-way analysis of variance (ANOVA) and Pearson correlation were performed for the statistical analysis (P<0.05). MIT values were significantly higher in the group with TP (16.5±6.1 Ncm) than the group without TP (9.6±5.4 Ncm) at all implants sites. The highest MIT value was observed at the MM site of the TP group (20.9±5.8 Ncm) while the MIT value at the AM site was 14.4±4.8 Ncm and that at the PM site was 14.3±5.5 Ncm. No significant differences in MIT values between AM (9.2±6.1 Ncm), MM (10.1±6.2 Ncm) and PM (9.3±3.6 Ncm) sites in the group without TP were observed. MIT values were correlated to the TP height at the MM sites. The presence of TP increased the MIT values during miniscrew insertion in the midpalatal region. TP size (height) is related to the MIT value in the middle median region of large TP. Keywords : Miniscrew implants, Midpalatal Region, Maximum Insertion Torque (MIT), Torus palatinus (TP)