Amongst the 22 modules, the darkgray module was determined as the most pivotal module for pulpitis, from which 5 core genes, A HMOX1, LOX, ACTG1, STAT3 and GNB5, were selected, and assumed to exert pivotal effects on the pathophysiologic causal links of pulpitis. The gene discussed is HMOX1; the disease is pulpitis.