Objective To explore the effect of TriLuxe onlay combined with digital intraoral scanning (IOS) technology in the treatment of patients with molar defect. Methods A total of 120 patients with molar defect (all in the final form after tooth preparation) admitted to our hospital from March 2021 to February 2023 were selected. According to the random number table method, they were divided into the control group and the observation group, with 60 patients in each group. The control group was treated with conventional resin fflling, and the observation group was treated with TriLuxe onlay combined with IOS technology. The restoration accuracy, aesthetic effect, masticatory function, complication rate and satisfaction were compared between the two groups. Results The marginal gap and proximal contact pressure in the observation group were less than those in the control group (P<0.05). The scores of color matching, morphological naturalness and marginal adaptability in the observation group were higher than those in the control group (P<0.05). After restoration, the uniformity of occlusal force distribution and masticatory efficiency in the observation group were better than those in the control group (P<0.05). The incidence of complications in the observation group (3.33%) was lower than that of the control group (18.33%) (P<0.05). The satisfaction rate of the observation group (98.33%) was higher than that of the control group (83.33%) (P<0.05). Conclusion TriLuxe onlay combined with IOS technology has a favorable therapeutic effect in the treatment of molar defect. It can improve the aesthetic effect and accuracy of restorations, and effectively enhance patients' masticatory function after restoration, with a low incidence of complications and high patient satisfaction.