Contrary to many advertisements, it is difficult to obtain perfectly white teeth. Natural, healthy teeth have extremely subtle yellow, brown or grey tones. Shine a flashlight behind your front teeth and look in the mirror to see for yourself.
Pure white teeth are like purple hair – they appear synthetic and distracting! However, light tooth shades are extremely attractive. What marketers refer to as “teeth whitening” should more accurately be called “teeth lightening.”
Tooth shade varies between people and even between teeth from the same person. Generally, permanent teeth are darker than primary teeth, and they have a yellow or grey tint to them. This colouration depends upon the natural shade of the outer layer of tooth structure (enamel) and the tooth layer under the enamel dentin). It also depends upon the thickness and translucency of the enamel.
Dentin can be very yellow. If the enamel layer is thin and/or very translucent, the yellow dentin will show through the enamel. These factors help explain why some teeth respond better to bleaching treatments than others.