Caries detector dyes are used to help you distinguish between affected and infected dentin. Affected dentin is not infused with bacteria, and even though it might be softer than what we usually consider to be good, sound, hard dentin, should not be removed, while infected dentin must be removed before restoring the cavity. The dye evidently works by bonding to denatured collagen in the dentin, which is a byproduct of the decay process. They also help identify cracks and the location of even partially calcified pulpal tissue as an aid in canal identification for endodontic treatment. Keywords: caries detection, dyes, tooth conservation