All-trans retinoic acid (ATRA) inhibits matrix metalloproteinase (MMP)-2 and MMP-9 in synovial fibroblasts, skin fibroblasts, bronchoalveolar lavage cells and cancer cells, but activates MMP-9 in neuroblast and leukemia cells. Very little is known regarding whether ATRA can activate or inhibit MMPs in human dental pulp cells (HDPCs). The purpose of this study was to determine the effects of ATRA on the production and secretion of MMP-2 and -9 in HDPCs. The productions and messenger RNA (mRNA) expressions of MMP-2 and -9 were accessed by gelatin zymography and real-time polymerase chain reaction (PCR), respectively. ATRA was found to decrease MMP-2 level in a dose-dependent manner. Significant reduction in MMP-2 mRNA expression was also observed in HDPCs treated with 25 µmol⋅L−1 ATRA. However, HDPCs treated with ATRA had no effect on the pattern of MMP-9 produced or secreted in either cell extracts or conditioned medium fractions. Taken together, ATRA had an inhibitory effect on MMP-2 expression in HDPCs, which suggests that ATRA could be a candidate as a medicament which could control the inflammation of pulp tissue in vital pulp therapy and regenerative endodontics. A strategy for suppressing enzymes involved in inflammation could improve patient response to endodontic repair of damaged pulp tissue, report dental researchers in Korea. Direct pulp capping can preserve the health of an infected tooth, although tissue inflammation can undermine the efficacy of this intervention. Proteins known as matrix metalloproteinases (MMPs) contribute to inflammation in numerous different cell types including dental pulp. Sun-Young Kim and colleagues at Kyung Hee University identified a molecule that may limit MMPs’ effects. They found that all-trans retinoic acid (ATRA), a derivative of vitamin A, can reduce production of MMP-2 at non-toxic doses in cultured human dental pulp cells. Although ATRA did not inhibit production of MMP-9, another enzyme involved in pulp cell inflammation, follow-up experiments using inflamed as well as healthy pulp cells should help clarify ATRA’s anti-inflammatory effects.