(a–f) 3D microCT images of (a,d) Control, (b,e) Osx-PPR conditional Het and (c,f) Osx-PPR conditional KO molars at P18 are shown. Upper panels: 3D reconstructed microCT images of the mandible, lower panels: individual slices of microCT images at an interval of 6 μm. Scale bars: 1 mm. (g,h) Sections of (g) Control, (h) Osx-PPR conditional Het and (i,j) Osx-PPR conditional KO molars at P18 were stained for nuclei and anti-periostin (ABT280) at 0.5 μg ml−1. Osx-PPR conditional KO mice with long roots (Mouse #1) (i) and short roots (Mouse #2) (j) are shown. Red: Periostin-Alexa546, blue: DAPI, grey: DIC (differential interference contrast). Yellow arrowheads: periostin+ PDL cells in the middle portion of the dental root. Scale bars: 200 μm. (k) Body weight measurement of Control (blue line), Osx-PPR conditional Het (green line) and Osx-PPR conditional KO (red line) mice between P0 and P25. n=4–16 per group, data are represented as mean±s.d.