The effects of low-level laser therapy as a novel adjunctive approach in orthodontic treatment of periodontally compromised patients

Abstract

Tooth displacement associated with compromised periodontal support results in a growing orthodontic treatment demand but presents special challenges of pain management and inflammation control. Low-level laser therapy (LLLT) shows effects on orthodontic pain relief and periodontal inflammation control respectively. But there is no evidence regarding its application as part of a joint orthodontic-periodontal treatment strategy. This study therefore aims to investigate the effects of LLLT as a novel adjunctive approach in orthodontic treatment of periodontally compromised patients. We first systematically reviewed the effects of LLLT on pain management for orthodontic patients, and then the adjunctive effects of LLLT on periodontal inflammation control. Based on the evidence achieved, a randomised controlled trial (RCT) with a split- mouth design was subsequently conducted with 27 adult patients to investigate the analgesic and inflammation-modulatory effects of LLLT in orthodontic patients with compromised periodontium. The laser side (laser group) was repeatedly irradiated with a 940 nm diode laser at 8.6 J/cm2 and the non-laser side (placebo group) received pseudo laser treatment throughout 1 year of fixed appliance therapy. Subjective pain assessment (primary outcome) and periodontal clinical examination were carried out at multiple follow-ups. The levels of cytokines in gingival crevicular fluid (GCF) and periodontopathic bacteria in supragingival plaque samples were assessed respectively. Alveolar bone dimension changes were evaluated in 19 patients with cone beam computed tomography (CBCT). In the RCT conducted with orthodontic patients with compromised periodontium, the subjective pain assessment showed a significant reduction in pain intensity following placement of the initial archwire in the laser group at 6-hour (P=0.03) and 24-hour (P=0.02) follow-ups as reported by the pain diary, and at 24-hour (P=0.04), 1-week (P=0.03) and 9-week (P=0.02) follow-ups as triggered by chairside archwire activation. According to the pain diary, pain subsided 1 day earlier (P=0.03) in the laser group, with a lower peak value (P=0.02) during the first week. The laser group exhibited less reduction in bite force, which was significant during the first month (P=0.02 at 1-week and P=0.04 at 1-month follow-ups). Regarding periodontal indices, a significantly lower increase in the plaque index was observed in the laser group at 1-month follow-up (P=0.01) and in the gingival index at 3-month follow-up (P=0.01). LLLT inhibited the elevation of interleukin-1ß level in GCF at 1-day (P=0.01) and 1-month (P=0.01) follow-ups, of prostaglandin E2 level at 1-day (P=0.02) and 1-week (P=0.00) follow-ups and of substance P level at 1-day follow-up (P=0.00). However, there was no significant effect of LLLT on the prevalence or quantity of Porphyromonas gingivalis or Treponema denticola in supragingival plaque. The CBCT measurements showed no significant intergroup differences in alveolar bone level or thickness changes over 12 months. This thesis presents the first evidence for the effectiveness of LLLT in a joint orthodontic-periodontal treatment strategy. LLLT exhibited benefits in pain relief and inflammation control, which were particularly noticeable in the early stage of adjunctive orthodontic treatment. Further studies with long-term follow-up and comprehensive assessments are required to confirm these effects.