Effects of Curing Lights on Human Gingival Epithelial Cell Proliferation

 

TAKE-HOME MESSAGE

  • This in vitro study was designed to determine the effects of blue light generated from light-emitting diode (LED) and quartz-tungsten-halogen (QTH) curing lights on the proliferation of human gingival epithelial cells. Both lights generate heat, but the LED light generates significantly less heat than the QTH light at 1 mm (P = .004) and reduces curing time by two-thirds. The LED light inhibited cell proliferation at a 39-second exposure at 6 mm and at 1 and 6 mm for 60-, and 120-second exposures (P < .05). The QTH light inhibited cell proliferation at 72 hours after 120-second exposure at a distance of 1 mm.

  • While insufficiently cured dental materials cause cytotoxicity, it has been shown that prolonged exposure to curing lights inhibits the proliferation of human gingival epithelial cells and may damage oral tissues. The authors concluded that an appropriate curing time suitable for the curing light unit and power output be used and that a balance be struck between allowing composites to fully cure while minimizing unnecessarily prolonged light exposures.
–  Laurie C. Carter, DDS, PhD

BACKGROUND

Light-emitting diode (LED) and quartz-tungsten-halogen (QTH) curing lights are used commonly in clinics. The aim of this study was to assess the effect of these lights on the proliferation of human gingival epithelial cells.

METHODS

Smulow-Glickman (S-G) cells were exposed to a VALO LED (Ultradent) or an XL3000 QTH (3M ESPE) light at 1 millimeter or 6 mm distance for 18, 39, 60, and 120 seconds. Untreated and Triton X-100 treated cells were used as controls. At 24, 48, and 72 hours after light exposure, cell proliferation was evaluated via a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

RESULTS

The authors first evaluated the performances of these 2 lights. Both LED and QTH lights generated heat. The LED light generated less heat than the QTH light and could save approximately two-thirds of the curing time. When used for 18 seconds at a 6 mm distance, the LED light did not inhibit the proliferation of S-G cells. However, if the exposure time was longer (for example, 39, 60, or 120 seconds), the LED light inhibited cell proliferation. The inhibitory effect increased when the exposure time was increased to 39, 60, or 120 seconds. The QTH light did not inhibit S-G cell proliferation if the exposure time was less than 120 seconds.

CONCLUSIONS

Prolonged exposure to a blue curing light (both LED and QTH) inhibits the proliferation of gingival epithelial cells and may cause damages to oral soft tissues.

PRACTICAL IMPLICATIONS

In dental practices, a balance should be struck in consideration of curing time not only to cure the composites completely but also to minimize unnecessarily prolonged light exposure.

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