It is impossible for the naked eye to identify differences between the types of light sources, variations in wavelength and changes in pulse and intensity. The light intensity is directly proportional to the number of photons that stimulate the photoinitiator, which is responsible for initiating the resin polymerization reaction (66,67). Therefore, frequent evaluation of the light intensity and care in the maintenance of light sources used for polymerization are among the ways of preventing post-operative sensitivity (65).