Purpose: To investigate how light intensity changes as the distance increases from the tip of the light guide.
Materials and methods: Ten different curing light/light guide combinations were used. Light intensity was measured at 0, 3, 6, and 10 mm from the tip of the light guide with a radiometer. Measurements were repeated in five separate trials and the mean light intensity +/- standard deviation was calculated. The fiber density was measured at the entrance and exit of all ten light guides and the light dispersion patterns were recorded.
Results: Light intensity decreased as distance increased for all lights tested; however, the rate and extent of this decrease was not similar for all lights (p < 0.0001). Turbo light guides exhibited a more rapid decrease in intensity as the distance increased than standard light guides. At 10 mm, all the turbo light guides had lost over 80% of their intensity recorded at 0 mm.
Conclusion: 1. The rate and extent of the decrease in intensity is not similar among curing lights (p < 0.0001). 2. It is not possible to predict light intensity at 10 mm from measurements made at 0 mm. 3. Curing light manufacturers should state intensity over clinically relevant distances (0 to 10 mm).