Evaluation of ocular hazards from 4 types of curing lights.
OBJECTIVE
To assess the risk of ocular damage from 4 types of light curing units (LCUs) and to estimate the maximum permissible ocular exposure times from each LCU during an 8-hour workday.


METHODS
Extracted human maxillary teeth were mounted in a dentoform. Four types of LCUs (plasma arc, low-power and high-power light-emitting diode, and quartz-tungsten-halogen) were used to cure a simulated restoration in the maxillary central incisor from the facial and palatal aspects. To simulate ocular exposure, the spectral irradiance (W/[cm2 · nm]) from the LCUs was measured 5 times at each of 3 distances (30 cm, 50 cm and 100 cm) from the tooth, using a cosine-corrected probe attached, via a fibre optic cable, to a calibrated spectroradiometer. The weighted blue-light and effective ultraviolet (UV) irradiances that would be received by the eye from each LCU were calculated.


RESULTS
The maximum permissible daily exposure limits for UV light exceeded 8 hours at all distances and orientations. The maximum permissible cumulative daily exposure time to blue light was as low as 6 seconds when curing from the palatal aspect with the plasma arc LCU and as high as 1.5 hours when the low-power light-emitting diode LCU was used from the facial aspect.


CONCLUSIONS
The 4 LCUs tested did not pose a risk of UV-mediated ocular damage. The higher-powered lamps showed potential to cause blue-light-mediated ocular damage at shorter distances, with damage potentially occurring after cumulative viewing of only 6 seconds at the 30-cm distance during an 8-hour workday.
Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS.
Daniel
D
Labrie
Justine
J
Moe
Richard B T
RB
Price
Mitchell E
ME
Young
Christopher M
CM
Felix
D000465:Algorithms; D055117:Curing Lights, Dental / Q000009:adverse effects* / Q000145:classification; D003726:Dental Assistants; D003793:Dental Restoration, Permanent / Q000295:instrumentation / Q000379:methods; D003815:Dentists; D005128:Eye Diseases / Q000209:etiology*; D006801:Humans; D008027:Light / Q000009:adverse effects; D008422:Materials Testing; D008452:Maximum Allowable Concentration; D009784:Occupational Diseases / Q000209:etiology*; D011829:Radiation Dosage; D012307:Risk Factors; D013057:Spectrum Analysis; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects