Advances in light-curing units: four generations of led lights and clinical implications for optimizing their use: part 2. from present to future

Light-activation units are standard items of equipment in contemporary dental practice. An inherent problem for light-cured direct restorations is that materials harden first nearest the light source. Unfortunately, surface hardness, as detected by a dental explorer, does not indicate adequate polymerization. Perhaps even more critically the operator does not know ‘what lies beneath’. The ultimate expression of inadequate polymerization is something that has colloquially been termed as the ‘soggy bottom’ phenomenon!

The ideal light would convert all the electrical power into light of the desired wavelength. As the power conversion improves less heat is generated. Because LED LAUs need less electrical energy for the same optical power output than QTH and PAC lamps, it has meant that small, lightweight battery-operated units have become practical and popular. Broad spectrum QTH and PAC LAUs require wavelength restricting photon and heat filters to suppress dangerous and inactive radiation, such as UV, red and IR. Only about 1–2% of the energy used to power a QTH LAU is converted into useful curing energy. Filters used by traditional lamps return the filtered radiation as heat. Noisy and bulky fans are required to remove this heat and they have the added drawback of consuming energy themselves. LED units are inherently more efficient in this respect. Putting together all these energy losses (heat/fan) or these levels of unused energy (halogen/plasma), a third-generation LED unit with equal power may be assumed to consume between 5 to 10 times less energy than a halogen lamp and 20 times less than a xenon plasma lamp. In these circumstances, a simple battery can replace the mains electricity supply.