Maximum Daily Ocular Exposure from Three Curing Lights

Objectives: Curing lights emit high intensity blue light that may damage the retina. Threshold limit values below which workers will not be harmed by exposure to blue or ultraviolet light have been set by the American Conference of Governing Industrial Hygienists. This study investigated if dental personnel may be at risk for ocular injury from chronic exposure to blue or UV light from curing lights.

Methods: To simulate a clinical situation, human teeth were mounted in a dentoform on a dental chair. Three dental curing lights, Sapphire (Dent-Mat), SmartLite IQ2 (Dentsply), Optilux 501 (Kerr), were used to cure facial and lingual restorations on the maxillary central incisor. When curing from the lingual, one half of the end of the light guide extended beyond the tooth and the light guide was pointing directly at the detector. The irradiance (mW/cm²/nm) received by the eye at 30, 50, and 100cm from the tooth was recorded using a calibrated spectroradiometer. The irradiance received at each distance was recorded and the weighted irradiance values for retinal damage were calculated to determine the maximum daily exposure times.

Results: There was no risk of UV damage to the eyes. However, there was a significant risk of retinal damage due to blue light at 30 and 50cm away. When curing from the lingual, at 30cm away the maximum daily exposure was as short as 9 seconds.

 Time(seconds) Before Exceeding Maximum Daily Blue Light Exposure

Exposure Direction	Lingual	Lingual	Lingual	Facial	Facial	Facial
Light/Distance	30 cm	50 cm	100 cm	30 cm	50 cm	100 cm
Sapphire	9s	28s	128s	165s	918s	1554s
SmartLite IQ2	53s	124s	720s	514s	1110s	4256s
Optilux 501	76s	270s	864s	532s	1392s	3726s

Conclusion: Protective glasses should be worn when using curing lights. Dalhousie University supported this study.