Fig. 3

A heavy orthodontic force promotes the expression of RANKL in periodontal tissues, but does not affect OPG expression in dental pulp or periodontal tissues. A–D To further evaluate the expression of RANKL in dental pulp and periodontal tissues, we performed immunohistochemical staining. The results show that orthodontic forces promote the expression of RANKL on the compressive side of periodontal tissues. The orange-colored rectangles indicate areas shown at higher magnification in (A-i–D-i). E Semi-quantitative analysis of the percentage of RANKL-positive cells in pulp tissues, the RANKL expression was very low in pulp tissues, there was no significant difference among groups. The blue-colored rectangles indicate areas shown at higher magnification in (A-ii–D-ii). F Semi-quantitative analysis of the percentage of RANKL-positive cells in periodontal tissues on the pressure side of the first molar. The percentage of RANKL-positive cells on the compressive side of periodontal tissues in the experimental groups increased in a force-dependent manner (P < 0.01). G–J Immunohistochemical staining showing that there is no significant difference in the expression of OPG in dental pulp and periodontal tissues. The orange-colored rectangles indicate areas shown at higher magnification in (G-i–J-i). The blue-colored rectangles indicate areas shown at higher magnification in (G-ii–J-ii). K, L Semi-quantitative analysis of the percentage of OPG-positive cells in periodontal tissues on the pressure side of the first molar. The percentage of OPG-positive cells in dental pulp (K) and periodontal tissues (L) did not change significantly (P > 0.05). M: mesial, D: distal, T: tooth, AB: alveola bone. All results are representative of three repeated experiments. *p < 0.05; **p < 0.01. The scale bars in (A–J) are 100 μm, while those in (A-i–J-i, A-ii–J-ii) are 50 μm