Blue-Light Exposure in Dental Photopolymerization: Ocular, Thermal, and Occupational Safety Considerations for Contemporary Light-Curing Units: Review Article

Abstract

Dental light-curing units are indispensable for the polymerization of resin-based restorative materials, adhesives, sealants, luting agents, and orthodontic bonding systems. The progression from quartz-tungsten-halogen technology to high-intensity light-emitting diode systems has improved photopolymerization efficiency, but it has also increased operator and patient exposure to concentrated blue-violet radiation and procedure-related heat. To provide a structured review of the optical and thermal hazards associated with contemporary dental light-curing units, with emphasis on retinal phototoxicity, soft-tissue and pulpal heating, protective eyewear, and chairside risk mitigation. A structured narrative review was performed to assess the ocular and thermal hazards associated with contemporary dental light-curing units. A systematic literature search was conducted using PubMed, Scopus, and Google Scholar databases for publications between 2000 and 2024. Search keywords included “dental light-curing units,” “blue light hazard,” “retinal phototoxicity,” “LED curing lights,” “pulpal temperature rise,” and “occupational exposure in dentistry.” Inclusion criteria comprised in vitro studies, clinical investigations, review articles, and international safety guidelines focusing on optical radiation hazards, thermal effects, and protective strategies in dentistry. Articles not published in English or lacking direct relevance to dental photopolymerization were excluded. A total of 45 studies were initially identified, of which 20 relevant articles were included following title screening, abstract evaluation, and full-text assessment. Data were analyzed qualitatively to synthesize current evidence on biological risks and clinical safety protocols. Most contemporary curing units emit predominantly within the 400–500 nm spectrum, with the greatest retinal blue-light hazard reported around 420–455 nm. Modern LED devices commonly deliver irradiance two to three times greater than earlier quartz-tungsten-halogen units, and some high-power units have claimed outputs approaching 5,000 mW/cm². Repeated direct or reflected exposure may contribute to cumulative retinal photochemical injury, whereas prolonged irradiation, inadequate tip positioning, and misuse can elevate pulpal and soft-tissue temperatures sufficiently to increase the risk of biological injury. Blue-light curing should be regarded not only as a materials-processing step but also as an occupational and patient-safety issue. Clinical safety depends on wavelength-compatible eye protection, strict adherence to manufacturer instructions, routine output monitoring, and procedural techniques that minimize unnecessary ocular and thermal exposure.