Objective To analyze the effect of onlay restoration versus full crown restoration on dental aesthetics and restoration integrity in patients with tooth defect after root canal treatment. Methods A total of 100 patients with tooth defect after root canal treatment admitted to Yinchuan Stomatology Hospital from January 2022 to December 2022 were selected as the research subjects, and they were divided into the control group and the observation group by the random number table method, with 50 patients in each group. The control group was treated with full crown restoration, and the observation group was treated with onlay restoration. The clinical efficacy, dental aesthetics, restoration integrity and periodontal health indexes were compared between the two groups. Results There was no significant difference in clinical efficacy between the two groups (P >0.05). The scores of color matching, marginal staining, surface gloss and total score in the observation group were higher than those in the control group (P <0.05). The restoration integrity rate in the observation group (88.00%) was higher than that in the control group (68.00%) (P <0.05). The GI and PLI in the observation group at 1 and 2 years after operation were lower than those in the control group (P <0.05). Conclusion The two treatment methods demonstrate comparable clinical efficacy two years postoperatively, but compared with full crown restoration, onlay restoration for with tooth defect after root canal treatment can effectively improve dental aesthetics and restoration integrity, and improve patients' periodontal health.