Orthodontic Root Resorption was Associated with the Secretion of IL-6 and IL-8 Stimulated by IL-17in Dental Pulp Cells

Abstract

Orthodontically induced inflammatory root resorption (OIIRR) is a common complication associated with orthodontic tooth movement. The aim of this study was to investigate how dental pulp contributes to root resorption during orthodontic tooth movement. Fifteen male 8-week-old BALB/c mice were subjected to an excessive orthodontic force of 25 g to induce a mesially tipping movement of the upper first molars for nine days. The expression levels of the TRAP, interleukin(IL)-17, IL-17 receptor(IL-17R), IL-6 and keratinocyte chemoattractant (KC; IL-8-related protein in rodents) proteins were determined in dental pulp (DP) by an immunohistochemical analysis. Furthermore, the effects of IL-17 on the production of IL-6 and IL-8 were investigated using human dental pulp (hDP) cells in vitro.Resorption lacunae with multinucleated cells were observed in the 25 g group during the in vivo experimental tooth movement study. Immunoreactivity for IL-17, IL-17R, IL-6 and KC was detected in all of the DP tissues subjected to the orthodontic force on day nine.Moreover, IL-17 increased the release of IL-6 and IL-8 from hDP cells. The results of this study suggest that the IL-17 may aggravate the process of root resorption by increasing the production of IL-6 and IL-8 from hDP cells.