Cure monitoring systems for and methods of monitoring polymerizable material to determine the degree of curing of the polymerizable material. A monitoring light source delivers visible monitoring light at one or more different visible wavelengths and a visible light detector detects the monitoring light diffusely reflected by the polymerizable material. The monitoring light has a wavelength of maximum emission (λmax-mon) that does not effectively induce polymerization of the polymerizable material. Change in intensity of the monitoring light reflected from the polymerizable material is used to determine when a selected degree of curing is reached in the polymerizable material.