Expression of procollagen A1 type 1 induced by two different dentine bonding systems in human pulp fibroblasts

This study aimed to evaluate the effects of two different dentine bonding systems (DBSs) on primary cultures of human pulp fibroblasts (HPFs). Cell viability and procollagen alpha 1 type I expression were investigated. Polymerised resin disks of the bonding agent from a two-step self-etch system and of the primer/bonding agent from a two-step etch-and-rinse system were used to condition culture medium for 24 or 96 h. HPFs were incubated in control (untreated) or DBSs-conditioned medium for 24 h. HPF viability was determined using the 3-dimethylthiazol-2,5-diphenyltetrazolium bromide (MTT) assay. Western blot analysis was used to analyse procollagen alpha 1 type I expression. Statistical analyses were performed using Student's t-tests. The results showed that HPFs incubated with DBSs-conditioned medium for 24 h demonstrated a significant reduction in the percentage of viable cells versus cells incubated with control medium (45% for self-etch DBS and 30% for etch-and-rinse DBS; p < 0.05), whereas this percentage increased significantly after exposure to the 96h DBSs-conditioned medium (62% and 77%, respectively; p <0.05). Procollagen alpha 1 type I expression in HPFs was strong for control specimens, but decreased in 24 h-DBSs-conditioned medium, and was abolished with 96 h-DBSs-conditioned medium. In conclusion, HPF exposure to medium containing eluates of the different DBSs led to an early cytotoxic effect (24 h) that decreased after a conditioning time of 96 h, whereas procollagen alpha 1 type I expression decreased at 24 h and was absent after 96 h. Procollagen alpha 1 type I expression may be a useful parameter for evaluating DBSs biocompatibility.