Predictable Method for Restoring Endodontically Treated Teeth, Comparing Indirect and Direct Methods and Materials in Aesthetic Dentistry.

The goal of this clinical study is to evaluate the long-term clinical performance and cost-effectiveness of different restorative approaches for endodontically treated teeth, with a particular focus on zirconia and glass-ceramic onlays cemented using different resin cementation protocols, as well as direct composite restorations produced using the injection moulding technique. The main questions it aims to answer are: Do zirconia onlays cemented with self-adhesive resin cement show comparable long-term clinical performance to those cemented with conventional adhesive resin cement? Does the choice of cement influence restoration survival, marginal integrity, discoloration, retention, and the occurrence of biological or technical complications? How do zirconia and glass-ceramic onlays compare with direct composite restorations produced using the injection moulding technique? Which treatment approach provides the best balance between clinical performance, cost-effectiveness, and patient satisfaction? The clinical study will include 30 patients requiring restoration of two endodontically treated teeth. A split-mouth design will be used for the indirect restorations, allowing direct comparison of two cementation protocols within the same patient and minimizing the influence of individual patient-related factors. Zirconia and glass-ceramic onlays will be cemented using either a conventional adhesive resin cement or a self-adhesive resin cement. A third group will receive direct composite restorations using the injection moulding technique. Patients will be followed clinically at baseline, 1 year, and 3 years. The evaluations will assess restoration survival and condition, including fractures, cracks, loss of retention, marginal integrity, and discoloration. The condition of the abutment teeth and periodontal tissues will also be assessed, including secondary caries, endodontic complications, probing depth, bleeding on probing, and gingival recession. Patient-reported outcomes, including satisfaction and well-being, will be evaluated using questionnaires. An initial in vitro phase will assess the influence of tooth surface pretreatment on the bond strength of self-adhesive resin cement after artificial aging. The results of this phase will be used to establish the most effective surface pretreatment protocol for the clinical study. This study is expected to provide clinically relevant data on the long-term performance of zirconia, glass-ceramic, and direct composite restorations, as well as the influence of different cementation protocols. By combining clinical outcomes with complication rates, treatment costs, cost-effectiveness, and patient-reported outcomes, the study may help identify predictable, simplified, and economically sustainable restorative approaches for endodontically treated teeth.