Fluorescence in Direct Dental Resin-Based Composites and Natural Teeth: A Narrative Review

Background/Objectives: Human teeth naturally fluoresce due primarily to organic components within dentine, contributing to their vitality and appearance under ultraviolet (UV) light. Contemporary resin composites increasingly incorporate fluorescent agents to reproduce this property and improve aesthetic integration with natural dentition. This narrative review examines the fluorescence characteristics of natural teeth and direct resin composites, evaluates methods used to assess dental fluorescence, and identifies factors influencing fluorescence stability and biomimetic performance. Methods: Peer-reviewed studies published between 2004 and 2025 investigating fluorescence in human teeth and direct resin-based composites under UV, visible or infrared illumination were reviewed. Studies focused on indirect restorative materials, non-human specimens or caries detection alone were excluded. Results: Natural teeth generally exhibit fluorescence emission peaks between 410 and 500 nm, with dentine demonstrating greater fluorescence intensity than enamel. Composite resins commonly incorporate rare-earth oxide fluorophores and often display similar emission wavelengths (approximately 450-485 nm), although fluorescence intensity varies considerably among brands and shades. Material fluorescence is influenced by composition, aging and environmental exposure. Spectrofluorometry provides highly accurate quantitative assessment, whereas photographic and quantitative light-induced fluorescence (QLF) methods offer greater clinical applicability. Despite advances in fluorescence mimicry, variability among contemporary materials generally continues to permit differentiation from natural tooth. Conclusions: Although substantial progress has been made in reproducing natural tooth fluorescence, significant variability and temporal instability remain among contemporary composite materials. Fluorescence-based methods therefore remain useful for restoration identification. However, continued improvements in biomimetic performance may reduce their future effectiveness. Greater standardisation of fluorescence assessment and investigation of alternative detection approaches are needed to support clinical and forensic applications.