From Classical Enamel/Dentin Bonding to Self-Adhesive Composites: A Narrative Review of Current Clinical Aspects

Adhesive dentistry has undergone a significant evolution, transitioning from classical multi-step adhesives to simplified single-bottle or universal adhesives and now towards self-adhesive composites that no longer require a separate adhesive. This review focused on clinical applications, recent developments, and future trends in peer-reviewed articles identified through database searches in PubMed, Web of Science Core Collection, EBSCO DOSS, and Google Scholar without date restrictions. Reference mining of the identified articles was also used. Significant advances in the clinical performance of simplified adhesives are challenging the status of "gold standard" adhesives, although their long-term reliability in load-bearing (Class II) composite restorations remains uncertain due to a lack of longitudinal real-world data and extended survival metrics. Integration of acidic functional monomers like 10-MDP is becoming a standard to create a more stable chemical bond with dentin hydroxyapatite, rather than relying solely on micromechanical retention. Ensuring long-term stability of the hybrid layer against degradation remains a challenge. When enamel is present, etching with phosphoric acid is still recommended, while the necessity of enamel beveling is being questioned. As the clinical success of self-adhesive flowable composites is limited to non-load-bearing areas, further developments are moving toward self-adhesive bioactive composites for bulk-filling that combine self-adhesive properties with load-bearing capacity.