Background: Edgewise fixed orthodontic appliances are available in two different brackets slot sizes (0.018-inch and 0.022-inch). Both systems are used by clinicians worldwide with many orthodontists claiming clinical advantages and superiority of one system over the other. However, the scientific evidence supporting this area is scarce and weak. This leaves the clinician's choice of bracket slot system to be based mainly on empirical clinical preferences.~Aim: To compare the 0.018-inch and 0.022-inch conventional ligation pre-adjusted orthodontic bracket slot systems in terms of the effectiveness of treatment.~Methods/Design: Prospective, multi-centre randomised clinical trial, undertaken in the secondary care hospital environment in NHS (National Health Service) Tayside in the United Kingdom. Two hundred and sixteen orthodontic patients will be recruited in three secondary care centres in NHS Tayside, United Kingdom. The participants will be randomly allocated to treatment with either the 0.018-inch or 0.022-inch bracket slot systems (n= 108 for each group) using Victory conventional ligation pre-adjusted bracket systems (3M Unitek, Monrovia, California). Baseline records and outcome data will be collected both during and at the end of orthodontic treatment and will be assessed as follows:. Primary outcome measures: The duration of orthodontic treatment for the maxillary and mandibular arches. Secondary outcome measures: The number of scheduled appointments for the maxillary and mandibular arches, occlusal outcome (Peer Assessment Rating index), orthodontically induced inflammatory root resorption using periapical radiographs and the patient perception of wearing orthodontic appliances.
The purpose of this study is to compare the 0.018-inch and 0.022-inch bracket slot systems to determine which is more effective for orthodontic treatment .