Lower incisor proclination is a frequently observed adverse effect during the alignment and levelling stages of fixed orthodontic treatment. This is partly attributed to the inadequate torque control provided by the initial round wires with the Conventional Archwire Sequence (CAS). While rectangular archwires offer improved torque control, the higher forces they generate often limit their application at this stage.

Recently, braided rectangular Nickel Titanium archwires have emerged as a promising alternative, offering low force levels and enabling their application as the initial archwire. Hence, it is now possible to both initiate the treatment and complete the alignment and leveling stage with rectangular archwires. 

In this context, we propose the Three Rectangular Archwires Sequence (TRAS) of 0.017 x 0.025-inch braided NiTi, 0.017 x 0.025-inch NiTi, 0.017 x 0.025-inch SS for use in 0.018 slot appliances. The study aims to evaluate the alignment and levelling efficiency of this TRAS and compare it with the CAS (0.014-inch NiTi, 0.016-inch NiTi, 0.016 x 0.022-inch NiTi, 0.016 x 0.022-inch SS, 0.017 x 0.025-inch SS) in the mandibular arch.

Patients to be started on fixed appliance therapy at the Orthodontic Clinic, JIPMER, Puducherry, will be screened for eligibility. Thirty-eight individuals who meet the selection criteria and willing to participate will be included in the study. They will be bonded with 0.018-inch slot MBT prescription brackets and tubes using the standard bonding protocol. Based on a computer-generated random sequence, the participants will be allocated to receive either of the two archwire sequences. 

The primary outcomes are alignment and levelling efficiency (estimated as change in the Little’s Irregularity Index and Curve of Spee measured from study models made at baseline and at the end of alignment and levelling). The secondary outcomes include lower incisor position change (estimated using linear and angular variables from lateral cephalograms made at baseline and at the end of alignment and levelling), the number of bond failures during the assessment period (recorded from history and clinical examination), and root resorption assessed from intra-oral periapical radiographs at baseline and at the end of alignment and levelling.

Per Protocol analysis will be followed for group comparisons. Paired T-test /Wilcoxon signed rank test will be used for the intra-group comparisons of alignment and levelling efficiency, incisor inclination changes, and root resorption. The inter-group differences in the same will be analysed with the Independent Samples T-test/ Mann-Whitney test. The difference in the proportion of bond failures between the groups will be compared with Chi-square/ Fisher’s exact test. All the tests will be two- tailed with p<.05.