Comparison of Long-Term Clinical Outcomes of Zirconia and Lithium Disilicate Prostheses: A Retrospective Cohort Study

<b>Objectives</b>: This study aimed to compare the 5-year cumulative survival rates and clinical outcomes of zirconia and lithium disilicate restorations in both tooth- and implant-supported prostheses, focusing on survival, technical and biological complications, as well as patient-reported satisfaction. <b>Materials and Methods</b>: A retrospective cohort of 200 patients treated with either zirconia (n = 100) or lithium disilicate (n = 100) fixed restorations between 2020 and 2024 was analyzed. Only cases with a minimum follow-up of 5 years were included. Clinical parameters (fracture, chipping, retention loss, secondary caries, peri-implant complications), radiographic outcomes (marginal bone loss, periapical stability), and patient satisfaction (VAS scores for esthetics and function) were evaluated. Kaplan-Meier survival analysis and subgroup analyses (anterior/posterior, tooth-/implant-supported) were performed. <b>Results</b>: At 5 years, the cumulative survival rate was 94.0% for zirconia and 89.0% for lithium disilicate (<i>p</i> = 0.210). Technical complications were lower with zirconia (14.0% vs. 21.0%, <i>p</i> = 0.182), including fewer fractures (6.0% vs. 12.0%, <i>p</i> = 0.126). Chipping (5.0% vs. 7.0%) and debonding (3.0% vs. 2.0%) showed no significant differences. Biological outcomes were comparable: secondary caries (7.0% vs. 11.0%, <i>p</i> = 0.332), endodontic issues (4.0% vs. 6.0%, <i>p</i> = 0.516), peri-implant mucositis (9.0% vs. 12.0%, <i>p</i> = 0.495) and peri-implantitis (3.0% vs. 5.0%, <i>p</i> = 0.470). Radiographically, periapical stability was preserved in most cases (93.0% vs. 89.0%, <i>p</i> = 0.317), and the mean marginal bone loss was slightly lower with zirconia (0.46 ± 0.25 mm vs. 0.53 ± 0.30 mm, <i>p</i> = 0.148). Patient-reported outcomes were favorable in both groups, with esthetic VAS scores of 8.6 vs. 8.2 (<i>p</i> = 0.072) and functional scores of 8.4 vs. 8.0 (<i>p</i> = 0.085). Zirconia was rated higher in posterior/implant-supported cases, while lithium disilicate was preferred in anterior restorations. <b>Conclusions</b>: Both zirconia and lithium disilicate restorations demonstrated favorable long-term outcomes, with zirconia trending toward superior mechanical reliability in posterior and implant-supported restorations, and lithium disilicate excelling in esthetic performance, particularly in anterior regions. Material selection should be guided by clinical indication, occlusal load distribution, and esthetic requirements.