the effect of intrusive orthodontic force on dental pulp of adults versus adolescents

background: there is no conclusive evidence on the effect of orthodontic force application on dental pulp tissue. the aim of this study was to compare early and delayed histological effects of intrusive forces on dental pulp of adolescents and adults. materials and methods: patients referred to the department of orthodontics of mashhad university of medical sciences participated in this study. they were assigned to adult (25–32‑year‑old) and adolescent (13–18‑year‑old) groups. a cantilever spring made of 16 × 22 steel wire was used to apply intrusive force to upper first premolars (11 teeth in adolescents and 11 teeth in adults) and the opposing teeth were considered as control group. in each group, 6 pairs of teeth were extracted after one week, and the remaining 5 pairs were extracted after one month of intrusion. histologic changes were compared between the control and intrusive groups and also between the adults and adolescents after 7 days and 1 month. statistical analysis was performed using statistical package for the social sciences and wilcoxon and mann–whitney u‑tests. p ≤ 0.05 was set as statistically significant. results: significant difference was not found in any histological parameters between intrusive and control groups 1 week and 1 month after intrusion in adolescents and adults ( p > 0.05). one month after intrusion, inflammatory cell response intensity ( p = 0.032) and frequency of chronic inflammation ( p = 0.032) were significantly higher in adults compared to adolescents. conclusion: mild intrusive force in closed apex teeth causes no significant histologic changes in adolescents and adults. however, it seems that inflammatory‑related histologic pulpal changes are more severe in adults after one month of intrusion. key words: dental pulp, histology, intrusion