Figure 1. More severe molar cusp wear and increased reactionary dentin (RD) formation in the Mmp9−/− mice.

(A,B) Slight wear of one cusp (arrows) and no RD formation was seen at M1.5 in both Mmp9−/− and wild-type molars. (C–G) At M4.5 and (H,I) M7.5, the heights of the cusps (arrows) in the Mmp9−/− mice were reduced compared with the controls. (J–Q) More amount of RD (dashed lines) was seen in the Mmp9−/− molars at M4.5, M7.5 and M13.5. At M13.5, dentin on top of RD (arrows) was worn off in the Mmp9−/− mice but not in the wild-type mice. WT, wild-type; M1, the first mandibular molar; M2, the second mandibular molar, M3, the third mandibular molar; RD, reactionary dentin. Scale bars: 100 μm. (A,B,J–Q) HE staining images; (C–I) Stereomicroscopy images.