Effects of Low-Level Laser Therapy as an Adjunct for Orthodontic Retention: A Systematic Review of Human and Animal Studies

Abstract

Background: Low-level laser therapy (LLLT) has been verified effective in tooth-movement acceleration and pain alleviation during active orthodontic treatment, but its function remains inconclusive post-treatment. This systematic review aims to evaluate the effects of LLLT as an adjunct retention regimen following active orthodontic tooth movement (OTM).Methods: This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Six databases (Cochrane Central Register of Controlled Trials, MEDLINE, Embase, Pubmed, Scopus, ProQuest) were comprehensively searched for human and animal studies published till December 2019 and screened according to our eligibility criteria. The risk of bias was assessed based on the Cochrane Handbook for Systematic Reviews of Interventions and Systematic Review Center for Laboratory Experiment Tool. Two independent reviewers performed all procedures in duplicate. Any disagreement was resolved by discussion or consultation with a third reviewer.Results: A total of 394 records were identified from the initial search. Following screening, 15 full-text articles were reviewed for eligibility (ĸ>0.90), and ultimately, eight studies (three human studies and five animal studies) were included in this review. The key outcomes considered were ‘preventing tooth relapse’ and ‘rehabilitating root resorption’. Two controlled clinical trials (CCTs) and one animal study supported the preventive effects of LLLT on the relapse of post-orthodontic tooth positions. In contrast, two animal studies reported opposing findings. Regarding the rehabilitation of root resorption, evidence supported the reparative potential of LLLT in orthodontic force-induced root resorption. Overall, there was a high risk of bias among studies, except for one randomised controlled trial. Due to the substantial heterogeneity among studies in terms of their types, participants, designs, LLLT settings and variables of interest, it was not feasible to conduct a meta-analysis; therefore, a qualitative synthesis is presented.Conclusion: The quality of evidence for LLLT contributing to the maintenance of orthodontic outcomes or a better treatment prognosis remains low. There is considerable controversy over the effects of LLLT on orthodontic relapse. However, the use of LLLT after OTM has promising reparative effects for root resorption and is generally recommended.