Effect of Low-Level Laser Therapy on Stability During Retention Phase.

The biggest problem in the orthodontic process is the pain and the long duration of treatment, which is also generally divided into 2 phases, namely the orthodontic tooth movement (OTM) and the retention phase. In recent decades, low-level-laser therapy has gained attention because it is non-invasive, inexpensive, relieves pain and has no significant adverse effects. Low-level-laser therapy (LLLT) has been proved to effectively induce and accelerate the remodeling process of alveolar bone by increasing the number of osteoblasts and osteoclasts. Therefore, LLLT is widely used in OTM to accelerate tooth displacement, but there are few studies and limited evidence on the stability whether it can strengthen and shorten the retention stage to avoid relapse. Thus, the purpose of this study is to investigate the stability after orthodontic treatment by observing the substantial influence of low-level-laser as during retention phase. Research Question(s) 1\. Does the low-level laser treatment can enhance stability and shorten retention time after orthodontic treatment or not will be demonstrated through 3 aspects： 1. The Incisor Irregularities Index between laser and control group after application of LLLT at debond (0), 6 and 12 months of retention 2. The interarch dimension: intercanine width, intermolar width, interpremolar width, arch length between laser and control group after application of LLLT at debond (0), 6 and 12 months of retention 3. The overjet and overbite between laser and control group after application of LLLT at debond (0), 6 and 12 months of retention Objective General: The goal of this study is to investigate the stability in retention phase after application of LLLT during leveling and alignment with fixed appliances. Specific: 1. To compare the Incisor Irregularities Index between laser and control group after application of LLLT at debond (0), 6 and 12 months of retention 2. To compare the interarch dimension: intercanine width, intermolar