Evaluation of efficiency of low-level laser on relapse after orthodontic treatment: a randomized controlled clinical trial

Introduction
The retention is a critical stage after the active orthodontic treatment which has been always aimed at being shorter and more effective and acceptable.

Objectives
The purpose of this study was to evaluate the effectiveness of 3 protocols of fixed and removable retainers, and to investigate the effect of low-level laser (LLL) on the amount of relapse and the duration of the retention phase.

Material and methods
A total of 54 straightening and alignment patients’ casts and radiographs as well as debond of orthodontic appliances and 1-year recall were evaluated using the American Board of Orthodontics (ABO) discrepancy index. These patients were equally divided into 3 retention protocol groups, including upper and lower bonded retainers (BRs), upper and lower vacuum-formed retainers (VFRs), and upper and lower VFRs with LLL application. A continuous wavelength (Ga-Al-As) semi-conductor laser was applied in the third group, with an 808 nm wavelength of special protocol.

Results
Only VFR LLL group improved in total cast radiograph evaluation (CRE) scores, while in the other two groups, total CRE scores decreased insignificantly for BRs and significantly for VFRs. At the end of observation period, lowest rate of relapse was noted among the patients of laser group, followed by BRs and VFRs groups, respectively. The average time required to reach 12 hours of retainer’s use in laser group was 8.33 weeks, whereas the required time to reach intermittent use was 25 weeks.

Conclusions
During retention phase, only buccolingual inclination among CRE variables improved significantly. While alignment, overjet, interproximal contact, and total CRE worsened significantly, changes in marginal ridges, occlusal contacts, occlusal relationship, and root angulation were insignificant. Both BRs and VFRs are effective methods to prevent a relapse, with clinically insignificant post-treatment changes. Applying LLL with VFRs would significantly reduce the number of relapses, enhance the total CRE as well as decrease the required time of retainers’ wearing and overall retention phase.