Comparative Clinical Evaluation of Indirect Ceramic and Composite Restorations Bonded with Fourth- and Eighth-Generation Adhesives Using Dual-Cure Resin Cement

The aim of the present study was to evaluate the clinical performance of indirect aesthetic restorations luted using dual-cure resin cement paired with adhesive systems from two different generations - fourth and eighth. A durable adhesive bond plays a decisive role in the longevity of such restorations by ensuring marginal integrity, retention and resistance to functional stresses. Fourth-generation systems, which have seen extensive clinical use over several decades, demonstrate high predictability due to the separate application of etchant, primer and adhesive, resulting in the formation of a stable hybrid layer. However, the more complex multi-step protocol may increase the risk of operator error. By contrast, eighth-generation adhesives are defined as universal systems, applicable in etch-and-rinse, self-etch, or selective enamel etch techniques. They typically contain functional monomers such as 10-MDP, which enable chemical bonding to hydroxyapatite, as well as nanofillers to enhance mechanical stability. Additional advantages include integrated desensitisers, reduced water sorption and improved resistance to hydrolytic degradation, which collectively may contribute to superior long-term clinical effectiveness. During clinical follow-up, indirect restorations (ceramic and composite) were assessed according to criteria including marginal adaptation, retention, postoperative sensitivity, colour stability, and overall aesthetics. The results indicate that both adhesive protocols - fourth- and eighth generation ? provide a high degree of clinical success, although universal adhesives appear to offer greater versatility and more optimised performance across a range of clinical situations. This study highlights the importance of adhesive system selection for the clinical outcome of indirect aesthetic restorations and provides comparative clinical data that may guide practitioners in optimising restorative protocols.