Illuminating the invisible: translational biophotonics for contemporary caries detection and biological decision-making.

Dental caries remains the most prevalent chronic condition globally, yet conventional diagnostic methods often fail to detect early lesions. Biophotonics, the study of light-tissue interactions, provides a new diagnostic pathway by exploiting the inherent optical properties of enamel and dentin. Over the past decades, research has connected laboratory spectroscopy, molecular chemistry and clinical imaging to define how light-based diagnostics can reveal the earliest biochemical signatures of demineralization. Conventional diagnostic methods, including visual examination and radiography, remain indispensable but are limited in their ability to detect early subsurface lesions, assess lesion activity and characterize the biological status of affected tissues. Recent advances in biophotonics can be exploited to generate clinically relevant biomarkers of disease initiation and progression. This review examines the translational pathway linking fundamental photonic phenomena in dental hard tissues to contemporary caries detection technologies and biologically guided treatment strategies. Emphasis is placed on light transmission and fluorescence-based technologies, fluorescence spectroscopy, Raman spectroscopy, multiphoton microscopy, second harmonic generation (SHG), two-photon excited fluorescence (2PEF) and optical coherence tomography (OCT). Experimental investigations have demonstrated that dentinal collagen degradation is associated with a progressive reduction in the SHG/2PEF ratio, while fluorescence and Raman studies have identified porphyrin derivatives and advanced glycation end-products as major contributors to the red fluorescence observed in active carious lesions. Beyond diagnosis, contemporary developments in minimally invasive dentistry increasingly integrate photonic biomarkers into the Bioactive Dental Concept, where lesion activity, cavitation status and individual caries risk guide the selection of preventive, minimally invasive and restorative interventions. Within this framework, photonic technologies may serve not only as diagnostic adjuncts but also as biological decision-support tools. Future integration of multimodal imaging, artificial intelligence and bioactive restorative materials may further enhance the precision and personalization of caries management. This evolution exemplifies the broader potential of biophotonics to bridge fundamental optical science and clinical oral healthcare.