The effect of low‑level light therapy on orthodontic tooth movement rate, heat shock protein 70, and matrix metallopreteinase 8 expression: Animal study

The aim of this study was to determine the effect of low‑level light therapy (LLLT) on orthodontic tooth movement (OTM) rate, heat shock protein 70 (HSP‑70) expression, and matrix metalloproteinase 8 (MMP‑8) expression.

In this experimental study twenty‑four male guinea pigs were randomly divided into three groups (n = 8): control group (K) without orthodontic force and LLLT; treatment group 1 (T1) with orthodontic force, and treatment group 2 (T2) with orthodontic force and LLLT. The labial surfaces of both maxillary central incisors in treatments groups were installed with single‑wing bracket before being inserted with close coil spring to give 10 g/cm2 orthodontic force. For the T2 group, 4 J/cm2 of LLLT was administered in the mesial‑distal and labial‑palatal regions for 3 min every day. On day 14, the gap between teeth was measured and immunohistochemistry staining was done to determine HSP‑70 and MMP‑8 expression. Data were analyzed using (IBM, New York, (ANOVA), followed by Turkey’s HSD test to determine the differences between groups. Nonnormal distributed data would be analyzed using Kruskal–Wallis test, followed by Mann–Whitney test with P < 0.05 being performed.

The gap between teeth in the T2 group was greater compared to T1 group (P = 0.00). However, there was a significant decrease of HSP‑70 and MMP‑8 expression in T2 group compared to T1 group in the tensile and compressive sides.

LLLT intervention during orthodontic treatment could accelerate OTM rate and decreased HSP‑70 and MMP‑8 expression both in tension and in compressive side. Thus, LLLT interventions can be used as adjuvant therapy to shorten orthodontic treatment duration.