The inflammation of dental pulp tissue was clearer after the addition of Pg-LPS compared with the ball drill heat-producing group alone, including the increased amount of immune cell infiltration and increased expression of inflammatory factors, which also showed that Pg-LPS triggered the generation of dental pulp tissue inflammation in vivo, in accordance with previous results.19 The level of inflammation in groups treated with LPS+BMP9 was in line with in vitro results, but weaker compared with the group treated with LPS+HCl, which shows that BMP9 has an inhibitory effect on early pulpitis. Here, GDF2 is linked to pulpitis.