The Journal of Occupational and Environmental Hygiene recently published at study entitled The Dental Curing Light: A Potential Health Risk. The authors were Richard B.T. Price, Daniel Labrie, Ellen M. Bruzell, David H. Sliney & Howard E. Strassler. This study measured the effect of magnification loupes on the blue light hazard when the light from a dental curing light was reflected off a human tooth.
Powerful blue-light emitting dental curing lights are used in dental offices to photocure resins in the mouth. In addition many dental personnel use magnification loupes.
In this study, loupes with magnifications of 3.5x and 2.5x were positioned at the entrance of an integrating sphere (equivalent to the human eye) connected to a spectrometer. A model of the mouth with human teeth was then placed 40 centimeters away and in line with the sphere. The light guide tip of a broad-spectrum curing light was positioned at a 45-degree from the facial surface of the model’s central incisor. With the loupes over the entrance into the sphere, the spectral radiant power was recorded five times.
Using guidelines set by the American Conference of Governmental Industrial Hygienists (ACGIH), the maximum permissible cumulative exposure times in an eight-hour day were calculated. At a 40-centimeter distance, the maximum cumulative daily exposure time to light reflected from the tooth was about 10 minutes with magnification loupes. The weighted blue irradiance values were significantly different for each brand of loupe and LED light curing units.
This study found that all loupes increased the radiant flux entering the sphere. The radiant flux received by the sphere, or equivalently by the eye, was greater when loupes were used. In addition, the beneficial effect of eye movements to reduce the time-averaged retinal irradiance for a small source may need to be reduced, because when loupes are used, the eyes are more fixed looking at one spot on a tooth. Thus, these maximum exposure times may need to be shortened.
The study concludes that the light emitted from a light-curing unit may be potentially hazardous to a clinician’s eyes. Without a magnification loupe, the maximum daily exposure time to light reflected from a tooth was 11 minutes. All of the magnification loupes tested increased the weighted blue light irradiance received by the eye. Furthermore, the lack of eye movement when using a loupe may increase the risk of damage to the retina from the effects of higher radiant exposure.
Therefore, the authors of the study recommend that anyone using a dental light curing unit should wear protective eyewear that have been specifically designed to filter out harmful wavelengths.
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