Objective To investigate the clinical effects of plastic fiber post and preformed fiber post in the treatment of oral post and core restoration. Methods From January 2021 to December 2023, 88 patients with severe dental defect who needed post and core restoration admitted to Xuzhou Central Hospital were selected. According to the random number table method, they were divided into control group and study group, with 44 patients in each group. The control group was treated with plastic fiber post, and the study group was treated with preformed fiber post. The clinical efficacy, periodontal condition [periodontal pocket depth (PD), bleeding index (BI), plaque index (PLI)], masticatory efficiency, occlusal force and adverse events were compared between the two groups. Results The total effective rate of treatment in the study group was 97.73%, which was higher than 84.09% in the control group (P <0.05). After treatment, the masticatory efficiency and occlusal force in the study group were higher than those in the control group (P <0.05). After treatment, PD, BI and PLI in the study group were lower than those in the control group (P <0.05). The incidence of adverse events in the study group was lower than that in the control group (P <0.05). Conclusion Compared with plastic fiber post, preformed fiber post has better clinical effect, which can effectively improve masticatory efficiency and occlusal force of patients, improve periodontal condition and reduce the incidence of adverse events.