E06. Identify which compounds that are needed for visible light-curing and in which wavelength region the light is located that is used for light-curing.

The compounds needed for light-curing are different ketones (often champheroquinone) and a tertiary amine (often dimethylaminoethylmethacrylate. If champheroquinone is used, a wavelength of 468 nm is needed, while other ketones may need another wavelength. This is important to be aware of.

Different light sources produce different wavelength intervals. Thus, if a light-source that produces a wavelength of  468  nm will cure a champheroquinone based composite well, but if the ketone in the composite is activated at another wavelength (e.g. 430 nm), the composite will not cure well. In other words, make sure that the composite you use matches your light source. The first light sources that were available on the market consisted of a light box and a rather long fiber optic cord (black cord shown below)  

Because of the length of the cord the light intensity of these units rarely exceeded 200 mW/cm². Another drawback was that after some time, the cord tended to degrade. The degradation consisted of broken fibers. By looking along the length of the cord with the other end of the cord in front of a regular light source, one can detect the broken fibers, because these fibers show up as black dots (see below).

By developing light units with the lamp inside the hand-held "gun", it was possible to develop light sources with light intensities exceeding 500 mW/cm² (see below).

These units have solid fiber optic rods of different sizes and shapes (see below) that can be attached to the hand-held gun.

By looking carefully at the above light tips, you may be able to see that some of them have pieces of a composite resin on the light tip, contaminations that have been "glued" to the tip surface when the tip was placed in contact with a composite resin during cure. To make sure that the lamp produces an acceptable amount of light, the lamp should be checked regularly with a light meter (see below). 

A lower than normal value may suggest that the reflector of the lamp has oxidized (see below).  

Other potential explanations behind a decrease in light intensity may be that some of the filters have degraded. Such degradation may occur if the lamp is cold sterilized and the sterilizing agent leaches into the lamp and contaminates the filters.

The reason there are filters inside the lamp is twofold. First, any UV light needs to be filtered out to avoid potential tissue damages. Second, infrared light must also be filtered out, because the infrared light generates heat that might damage the pulp.

When you use the light source, be aware that the light intensity is so high that it can cause eye damages. Therefore, never ever look straight into the light