Preventive and reparative effects of low‐level laser therapy on orthodontically induced inflammatory root resorption—An animal study

Abstract Background Orthodontically induced inflammatory root resorption (OIIRR) is one of the most important side effects of orthodontic treatment. Low‐level laser therapy (LLLT) is a useful way to reduce the orthodontic treatment duration and may have some effect on preventing and repairing OIIRR. However, the specific effects of LLLT on OIIRR remain unknown. Objective Our research aimed to evaluate the Dentin Sialophosphoprotein (DSPP) expression level and root resorption volume during treatment and retention to explore the role of LLLT in preventing and repairing OIIRR. Methods Thirty‐seven 6‐week‐old male Sprague–Dawley rats were selected to establish an OIIRR model; the rats were divided into Group B (blank), Group F (force), Group F(LLLT) (force and LLLT), Group F+R (force and retention) and Group F+R(LLLT) (force, retention and LLLT). The root resorption volume of the distal buccal root and mesial root in the maxillary left first molar was calculated by micro‐CT, and the DSPP expression level on the compression side of the periodontal ligament was analysed by immunohistochemical staining. Results The resorption volume in Group F was greater than that in Group F(LLLT). For the mesial root, the volume in Group F was greater than that in Groups F+R and F+R(LLLT). For the distal buccal root, the volume in Groups F and F+R was greater than that in Group F+R(LLLT). The DSPP level in Group F(LLLT) was greater than that in Group F and there was no difference between Groups F+R and F+R(LLLT). Conclusions LLLT has a certain preventive effect and a limited reparative effect on OIIRR in rats.