Fig. 4

A heavy orthodontic force promotes the formation of tertiary dentine. A–D Hard tissue milling slides show that the width of the tertiary dentine of the coronal pulp increased after orthodontic tooth movement. The yellow-colored rectangles indicate areas shown at higher magnification in (A-i–D-i), the white-colored rectangles indicate areas shown at higher magnification in (A-ii–D-ii). E Quantitative analysis showing that the width of tertiary dentine of the coronal pulp increases in a force-dependent manner, the heavy force group (100 g) exhibits a wider tertiary dentine compared with the control group (P < 0.05), F while no significant change was observed for the width of tertiary dentine of the root (P > 0.05). M: mesial, D: distal, P: pulp; D: dentine. All results are representative of three repeated experiments. *p < 0.05. The scale bars in (A–D) are 100 μm, while those in (A-i–D-i, A-ii–D-ii) are 50 μm