Relapse and failure rates between CAD/CAM and conventional fixed retainers: a 2-year follow-up of a randomized controlled clinical trial

Retention has been always considered a major challenge in orthodontics. Recently computer-aided design/computer-aided manufacturing (CAD/CAM) fixed retainers (FRs) have been introduced as a marked development in retainer technology, offering potential advantages. The objective of this study was to compare the differences in relapse and failure rates in patients treated with FRs using CAD/CAM technology, lab-based technique, and chairside method. A double-blinded, prospective, randomized controlled clinical trial was conducted over a 2-year period at a single centre. These patients were divided into three groups: CAD/CAM group with multistranded Stainless Steel wires (CAD/CAM, n = 14), lab group with the same multistranded wires (lab, n = 15), and a chairside group with Stainless Steel Ortho-FlexTech wires (chairside, n = 14). Inter-canine width (ICW) and Little's irregularity index were digitally measured from scans at the orthodontic debonding (T1), 6-month retention (T2), 1-year retention (T3), and 2-year retention (T4) visits. All forms of failure were documented and analyzed. Participants were randomly assigned to the three groups using online randomization software (randomization.com) by a statistician who was not involved in the study. Patients were blinded in terms of the FR group to which they were each randomly assigned. The principal investigator was blinded upon data analysis since patients' records were coded to minimize observer and measurement bias. Initially 81 patients were assessed for eligibility. Seventy-five patients were randomly allocated into the three study groups. After 2-year follow-up, 43 patients came back for the follow-up and were analyzed. The CAD/CAM group showed significantly less reduction in ICW compared to the chairside group at all time intervals (P