Objective To investigate the clinical effect of modified crown lengthening in the repair of maxillary anterior teeth defect. Methods A total of 86 patients with maxillary anterior teeth defect admitted to our hospital from January 2023 to March 2024 were randomly divided into control group and observation group, with 43 patients in each group. The control group was directly treated with post-core crown restoration, and the observation group was treated with modified crown lengthening before post-core crown restoration. The repair effect, tooth aesthetics and bite force were compared between the two groups. Results The total effective rate of repair in the observation group was 95.35%, which was higher than 81.40% in the control group, and the difference was statistically significant (P<0.05). The proportion of class Ⅰ and class Ⅱ of dental aesthetics in the observation group was higher than that in the control group, and the proportion of class Ⅲ and class Ⅳ was lower than that in the control group, the difference was statistically significant (P <0.05). The bite force of the two groups after treatment was higher than that before treatment, and the observation group was higher than the control group, the difference was statistically significant (P<0.05). Conclusion The application of modified crown lengthening in the repair of maxillary anterior teeth defect is effective, which can effectively improve the occlusal ability of patients, help to improve the aesthetics of teeth and the total effective rate of repair, and is worthy of clinical application.