Objective To explore the effect of all-ceramic onlay restoration on periodontal health indicators in patients with tooth defect. Methods A total of 86 patients with tooth defect admitted to the Department of Stomatology, Taixing Third People's Hospital from March 2023 to November 2024 were selected, and they were divided into group A and group B by the random number table method, with 43 patients in each group. Group A received all-ceramic crown restoration, and group B received all-ceramic onlay restoration. The clinical efffcacy, periodontal health indicators, inffammatory response indicators and aesthetics were compared between the two groups. Results The total effective rate of group B (97.67%) was higher than that of group A (81.40%) (P<0.05). The gingival index and plaque index of group B after treatment were lower than those of group A (P<0.05). The levels of CRP and IL-1β in group B after treatment were lower than those in group A (P<0.05). The scores of restoration shape and color matching in group B after treatment were higher than those in group A (P<0.05). Conclusion All-ceramic onlay restoration technology shows good clinical efffcacy in the treatment of tooth defect. It can not only effectively improve periodontal health, inhibit local inffammatory responses, but also enhance the aesthetic effect of the restored area.