Effects of root contact length on the failure rate of anchor screw

Purpose: This study aimed to evaluate the causal relationship between root contact and root contact length of orthodontic miniscrew implants (miniscrews), and assessed factors for implant failure through cone-beam computed tomography (CBCT) images. Methods: First, a logistic regression analysis was performed to investigate the most relevant factors for implant failure based on sex, age, vertical skeletal pattern, horizontal skeletal pattern, and presence of root contact in 59 patients (mean age: 21.2, age range: 13-54 years) who had miniscrew implants. Next, 38 miniscrews (1.6 mm in diameter and 8.0 mm in length) with root contact were investigated in the patients. Root contact length was measured using CBCT taken after miniscrew implant placement. Results: The results showed that root contact was the most critical risk factor for failure of miniscrew implants in patients. Logistic regression analysis showed that the risk approximately doubled as the root contact length increased by 1.0 mm. Conclusion: Avoiding proximity to the root during miniscrew implant placement is essential to prevent implant failure.