Objective To analyze the effect of iRoot BP Plus root apical barrier combined with warm gutta-percha obturation technique in the treatment of patients with permanent teeth root tip open under oral microscope. Methods A total of 60 patients with permanent teeth root tip open admitted to our hospital from January 2022 to February 2024 were selected and divided into reference group and experimental group by the random number table method, with 30 patients in each group. The reference group was treated with conventional warm gutta-percha obturation technique under oral microscope, and the experimental group was treated with iRoot BP Plus root apical barrier combined with warm gutta-percha obturation technique under oral microscope. The treatment effect, gingival crevicular fluid inflammatory factors (interleukin-6, interleukin-1β, tumour necrosis factor-α), occlusal force and pain were compared between the two groups. Results The total effective rate of treatment in the experimental group (96.67%) was higher than that in the reference group (76.67%) (P <0.05). After treatment, the levels of interleukin-6, interleukin- 1β and tumor necrosis factor-α in the experimental group were lower than those in the reference group (P <0.05). After treatment, the occlusal force in the experimental group was higher than that in the reference group (P <0.05). After treatment, the score of pain in the experimental group was lower than that in the reference group (P <0.05). Conclusion The application of iRoot BP Plus root apical barrier combined with warm gutta-percha obturation technique under oral microscope in patients with permanent teeth root tip open is helpful to improve the therapeutic effect, reduce the inflammatory reaction of the affected teeth, improve patients’ occlusal force and relieve pain. It is worthy of application.