Initial arch wires for tooth alignment during orthodontic treatment with fixed appliances

摘要

Orthodontic treatment is undertaken worldwide, mainly in adolescents and adults to correct crowded, rotated, buried or prominent front teeth. Fixed orthodontic appliances (braces) consist of brackets bonded to the teeth that are connected by arch wires which exert forces on the teeth. The first (initial) type of arch wire, inserted at the beginning of treatment, is for correcting crowding and rotations of teeth.Over recent years a number of new materials (various metal alloys, or mixtures, of nickel and titanium (NiTi)) have been developed which show a range of different properties in the laboratory and which manufacturers claim offer benefits in terms of tooth alignment. Clinical trials of these products in people undergoing orthodontic treatment are required to understand whether different types of initial arch wires actually result in important differences, such as faster alignment, reduced pain or reduced side-effects, during orthodontic treatment. The Cochrane Oral Health Group undertook this review of existing studies to identify and assess the evidence for the effects of initial arch wires of different materials, shape and size of cross-section for alignment of teeth with fixed orthodontic braces in relation to alignment speed, root resorption and pain intensity.The most recent search of studies was done on 2 August 2012. We found nine trials with 571 participants all of whom had upper and/or lower full arch fixed orthodontic appliances. The trials evaluated different initial arch wires, but all of these studies were poorly conducted and/or reported and the results are likely to be biased. All of the trials also varied in a number of other aspects of orthodontic treatment, compared different types of initial arch wires and reported different outcomes at different times. None of the trials reported both potential benefits (alignment) and harms (pain or side-effects such as root resorption). There is no evidence from these studies that any particular initial arch wire material is better than another in people undergoing orthodontic treatment.