title: Evaluation of light-curing units in rural and urban areas.
abstract: OBJECTIVE
  To evaluate the distribution of light-curing units (LCU) used in an urban area (Riyadh) and a rural area (Kharj) of Saudi Arabia, and to compare their irradiance values.
  
  
  METHODS
  The study involved three dental centers in urban areas and two in rural areas, all of which were parts of a single healthcare institution providing dental services. The light outputs (power mW) from 140 LCUs were measured by laboratory-grade spectrometry, and the irradiance (mW/cm(2)) was calculated from the tip area of each LCU. The minimum acceptable irradiance outputs for the quartz-tungsten-halogen (QTH) and light-emitting diode (LED) units were set at 300 and 600 mW/cm(2), respectively. The ages of these units and the protocol used to light-cure the resins were also determined.
  
  
  RESULTS
  The total number of LCUs was 140, 112 (78%) in urban areas, and 28 (22%) in rural areas. In rural areas, only 7 of the 22 (32%) QTH units delivered irradiances greater than 300 mW/cm(2) and were therefore considered clinically acceptable, whereas 4 of the 6 (66.7%) LED units delivered values greater than 600 mW/cm(2). In urban centers, 43 of 61 (70.5%) LED units and 25 of 61 (49%) QTH units were considered clinically acceptable. Irradiance values for both QTH (P < 0.01) and LED (P < 0.05) units were significantly better in urban than in rural areas.
  
  
  CONCLUSIONS
  Urban areas had a greater distribution of LCUs than rural areas. Overall, irradiance values were significantly higher in urban areas.
authors: Department of Restorative Dental Sciences, College of Dentistry, King Saud University, P.O. Box 60169, Riyadh, Saudi Arabia.
authors: Maan M
authors: MM
authors: Alshaafi
keywords: Composite resin; LED; Light-curing unit; QTH; Resin restoration
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