title: Light intensity decay in quartz-tungsten-halogen polymerization units.
abstract: OBJECTIVE
  The aim of this study was to determine the effect of ageing on the light intensity of quartz-tungsten-halogen (QTH) polymerization units in dental schools and dental clinics.
  
  
  METHODS
  Two dental schools and multiple public health dental clinics were visited and the light intensity of curing units was assessed. The age, make, model and service history were recorded. A calibrated radiometer (range 0-1000 nm) was used to measure the light intensity of 171 QTH units. At the end of each visit, the team members provided each dental clinic with a verbal report of the test results and recommendations on maintenance of light polymerization units.
  
  
  RESULTS
  The 171 units tested were from seven different manufacturers. The mean light intensity was 373.1 mW/cm(2), the lowest intensity being 95.3 and the highest 526.60 mW/cm(2). Only 29 QTH units recorded more than 500 mW/cm(2); 102 units showed readings that ranged between 300 and 500 mW/cm(2) and 39 units recorded readings below 300 mW/cm(2). It was not able that one unit had light intensity reading of less than 100 mW/cm(2). The age distribution was as follows: 35 units were more than 10 years old, 79 were from 5 to 10 years old and 57 were less than 5 years old. There was a high statistical significant relation between the mean light intensity and age (P = 0.001).
  
  
  CONCLUSIONS
  Light intensity values used in some dental clinics were to be found lower than what is recommended for optimum polymerization of resin-based composite restorations. Awareness among dentists of the value of QTH light curing units and their commitment to care and maintenance are crucial to achieving optimum restoration properties. How to cite this article: Al-Samadani KH, Al-Dharrab A, Wahbi MA , Algizani L. Light Intensity Decay in Quartz-Tungsten-Halogen Polymerization Units. J Int Oral Health 2013; 5(1):23-30.
authors.affiliation: Department of Restorative Dental Science, College of Dentistry, Taibah University, Al Madinah Al Munawwarah - 43353, Kingdom of Saudi Arabia.
authors.forename: Khalid
authors.initials: K
authors.lastname: H Al-Samadani
authors.forename: Al-Dharrab
authors.initials: AD
authors.lastname: Ayman
authors.forename: A Wahbi
authors.initials: AW
authors.lastname: Mohammed
authors.forename: I Algizani
authors.initials: IA
authors.lastname: Loay
keywords: Intensity; Light unit; Polymerization; Quartz-tungsten