The light-curing unit: An essential piece of dental equipment

Introduction This article describes the features that should be considered when describing, purchasing and using a light-curing unit (LCU). Methods The International System of Units (S.I.) terms of radiant power or radiant flux (mW), spectral radiant power (mW/nm), radiant exitance or tip irradiance (mW/cm(2)), and the irradiance received at the surface (also in mW/cm(2)) are used to describe the output from LCU. The concept of using an irradiance beam profile to map the radiant exposure (J/cm(2)) from the LCU is introduced. Results Even small changes in the active tip diameter of the LCU will have a large effect on the radiant exitance. The emission spectra and the effects of distance on the irradiance delivered are not the same from all LCUs. The beam profile images show that using a single averaged irradiance value to describe the LCU can be very misleading. Some LCUs have 'hot spots' of high radiant exitance that far exceed the current ISO 10650 standard. Such inhomogeneity may cure the resin unevenly and may also be dangerous to soft tissues. Recommendations are made that will help the dentist when purchasing and then safely using the LCU. Conclusions Dental manufacturers should report the radiant power from their LCU, the spectral radiant power, information about the compatibility of the emission spectrum from the LCU with the photoinitiators used, the active optical tip diameter, the radiant exitance, the effect of distance from the tip on the irradiance delivered, and the irradiance beam profile from the LCU.