Dental curing lights polymerize light-activated resin composites for fillings, sealants, veneers, and bonding by emitting blue light (430-480nm) that triggers photoinitiators like camphorquinone, hardening materials in seconds for durable restorations. Types include LED (efficient, cool 1000-5000mW/cm², cordless, 4000+hr lifespan, polywave for all composites), halogen/QTH (broad spectrum but hot, bulky, shorter bulb life), plasma arc (fastest 3s cures, high heat/expensive), lasers (precise, rare). Use: Position tip 1-2mm from material, cure 20-40s in 2mm layers; eye shields prevent retinal damage. LEDs dominate 90%+ practices for speed, ergonomics, and depth up to 6mm.