Objective: To investigate the clinical and aesthetic effects of all-ceramic inlay restoration versus direct resin filling on dental defects in adolescents and their impact on masticatory function. Methods: Patients with extensive molar defects treated at our hospital from June 2024 to June 2026 were enrolled and divided into an inlay group and a filling group according to the treatment modality chosen, with 20 cases in each group. Both groups received root canal therapy. The filling group underwent composite resin filling restoration, while the inlay group received all-ceramic inlay restoration. The restoration outcomes were assessed using the USPHS criteria. Masticatory function (bite force and masticatory efficiency) was compared between the two groups before treatment and at 3 months post?treatment. Dental defects and aesthetic outcomes (AC scores) were recorded within 12 months after restoration. Results: The success rate of restoration in the inlay group was 100.00%, which was significantly higher than that in the filling group (90.00%, P<0.05). At 3 months post?treatment, bite force and masticatory efficiency significantly increased in both groups, with the inlay group showing significantly greater improvements than the filling group (all P<0.05). At 12 months post?treatment, AC scores (tooth morphology, color, and aesthetics) significantly improved in both groups, and the inlay group had significantly higher scores than the filling group (all P<0.05). Conclusion: All?ceramic inlay combined with root canal therapy is effective in treating extensive molar defects, restoring tooth morphology and function, and offers superior aesthetic outcomes with greater durability and stability. It is worthy of clinical promotion.