Objective To explore the effect of gingival retraction cord technique in resin filling treatment of wedge-shaped tooth defect. Methods From January 2023 to May 2025, 80 patients with wedge-shaped tooth defect admitted to Rudong County People 's Hospital were selected, and they were divided into the control group and the study group by the random number table method, with 40 patients in each group. The control group received resin filling treatment, and the study group received resin filling treatment after applying gingival retraction cord technique. The restoration satisfaction, levels of inflammatory factors in gingival crevicular fluid, periodontal tissue stress at different angles, filling detachment rate and overhang rate were compared between the two groups. Results The restoration satisfaction in the study group was higher than that in the control group (P <0.05). After 6 months of treatment, the levels of IL-6, IL-8 and TNF-α in the study group were lower than those in the control group (P <0.05). After 1 year of treatment, the periodontal tissue stress at 30°, 60° and 90° in the study group was lower than that in the control group (P <0.05). The incidence of filling detachment and overhang in the study group was lower than that in the control group (P<0.05). Conclusion The application of gingival retraction cord technique achieves definite efficacy in resin filling treatment of wedge-shaped tooth defect. It can improve restoration satisfaction, relieve inflammatory response of gingival crevicular fluid, reduce periodontal tissue stress, and lower the incidence of filling detachment and overhang, which is worthy of clinical application.