How Visible Light Curing came into Dentistry

Visible light curing − activation of the polymerization of a material by means of light included in the visible spectrum, followed in the wake of ultraviolet light activated materials suffering a demise, largely caused by concerns over the hazards of exposure to ultraviolet radiation¹ and limited depth of cure.² The motivation to find an acceptable, user friendly means of light-activation in dentistry stemmed from market appeal for the desirable qualities of photo-activated materials, notably a one component formulation, as distinct from two components − base and catalyst − in chemically-cured systems, an opportunity for extended working time, and a ‘command set’.

In the early 1970s, two chemists at the ICI Petrochemical and Polymer Laboratory in Runcorn, Edward (Ed) Dart and Joseph (Joe) Nemcek, developed a visible light-activated (alpha)-diketone/amine catalyst system − an innovation which was granted a patent in 1976.³ Ed and Joe had been looking for a novel way to cure acrylic resins, specifically acrylic paint to be used to paint car bodies. Subsequent to the approach having been found difficult to apply, in particular in difficult to access, rust-prone areas of car bodies, new applications were sought for the Dart/Nemcek catalyst system. These included the development of resins used in fibre optic systems and in the manufacture of fan blades for jet engines.