Classic markers of pulpitis, MMP9 [25] and MMP8 [37], were, as expected, significantly increased after pulp exposure and contamination with oral bacteria; however, MMP13 also showed a significant increase in expression (an approximately 1.6-fold increase) of a similar magnitude to MMP8, but not as great as MMP9 (an approximately 6-fold increase), which highlights a potential novel role for MMP13 in inflammation as well as repair within the dentine–pulp complex. The gene discussed is MMP9; the disease is pulpitis.