Objectives: The purpose of this investigation was to assess the effect
iveness of five commercially available hand-held dental radiometers an
d a computer-based experimental radiometer. Methods: Light intensity o
f five visible light activation units was determined using the dental
radiometers. The influence of curing light intensity on depth of cure
of a hybrid composite material was determined using a digital penetrom
eter. Results: The radiometers evaluated varied with respect to sensor
aperture diameter, scale readings (analogue or digital) and the units
of measurement (arbitary or mW cm(2)). The experimental computer-base
d radiometer allowed continuous recording of intensity against time; t
hus the light output could be monitored over the entire irradiation pe
riod. Conclusions: When light intensity readings were normalized with
regard to a standardized light sensing device aperture of 4 mm diamete
r, a linear relationship was found between depth of cure and the logar
ithm of the intensity of the light. The results of this investigation
support the use of dental radiometers for periodically monitoring visi
ble light activation units.