Are assessments of damping capacity and placement torque useful in estimating root proximity of orthodontic anchor screws?

• We examined damping capacity to verify the detectability of screw-root proximity.
• Our hypothesis: Periotest values (PTV) cannot be used to estimate root proximity of screws.
• Placement torque and PTV were measured, and root contact was judged with cone-beam computed tomography.
• PTV was strongly related to root contact; the null hypothesis was rejected.
• In addition to PTV, x-ray exploration is recommended for accurate diagnosis.

IntroductionPlacement torque and damping capacity may increase when the orthodontic anchor screws make contact with an adjacent root. If this is the case, root contact can be inferred from the placement torque and damping capacity. The purpose of this study was to verify the detectability of root proximity of the screws by placement torque and damping capacity. For this purpose, we investigated the relationship among placement torque, damping capacity, and screw-root proximity.MethodsThe placement torque, damping capacity, and root proximity of 202 screws (diameter, 1.6 mm; length, 8.0 mm) were evaluated in 110 patients (31 male, 79 female; mean age, 21.3 ± 6.9 years). Placement torque was measured using a digital torque tester, damping capacity was measured with a Periotest device (Medizintechnik Gulden, Modautal, Germany), and root contact was judged using cone-beam computed tomography images.ResultsThe rate of root contact was 18.3%. Placement torque and damping capacity were 7.8 N·cm and 3.8, respectively. The placement torque of screws with root contact was greater than that of screws with no root contact (P <0.05; effect size, 0.44; power, <0.8). Damping capacity of screws with root contact was significantly greater than that of screws with no root contact (P <0.01; effect size, >0.5; power, >0.95).ConclusionsIt was suggested that the damping capacity is related to root contact.