Why Do I Have Yellow Teeth Even Though I Brush Them?

Why Do I Have Yellow Teeth? Even Though I Brush Them

White teeth are prized in our society. This is a relatively new outlook, since in the past, some cultures have recognized black teeth or even no teeth as socially advanced. In the modern world, however, the whiter your teeth are the more socially attractive you are regarded.

In pursuit of white teeth, there are many different methods to achieve whitening. Some methods include bleaching. Some teeth may be easily bleached, and some may not be. When teeth are not easily whitened, some other methods include composite bonding, porcelain veneers, or porcelain crowns. These methods involve adding a color-controlled material to the teeth that hides or masks the darker color or defect in size or shape.

When the only problem to be faced is the darker tooth color, then teeth whitening may be a desirable avenue to traverse.

What happens during the whitening process?

Human teeth are made of a surface covering of about 2 mm of enamel. Some other species have thicker enamel coverings. This enamel has a structure of prism like rods which are firmly bound in place by a matrix like cement. When the enamel wears slightly, the matrix which is softer can wear away more rapidly than the enamel rods. This leaves an uneven surface which can attract stains. Because there are small pits in the surface, toothbrushing alone cannot remove these stains. When peroxide bleach is applied to the surface of the enamel, these stains are “oxidized” removing the dark color of the stain. As a result, the teeth will appear whiter.

Another reason that the tooth can appear dark is the color of the layer under the enamel. This is called dentin. The dentin is naturally darker than the enamel, sometimes many times darker. When the bleach is applied for a long enough time, the dentin can be whitened to some degree, but not as readily as enamel. When too much peroxide is applied too quickly this can result in a great deal of tooth sensitivity so the process of whitening should be done under a dentist’s supervision if sensitivity is likely. This occurs with gum recession or if there are cavities that are not treated.

The dentin can only be lightened to a certain degree, so any dentin that is not covered by enamel will appear to be darker. The enamel does not cover the tooth uniformly. It is thicker at the biting edges of the tooth and thins out closer to the gum line. When gums recede, the border or junction of the two materials can be seen readily. There is a ridge that can be felt when the enamel ends. Below the enamel the darker dentin can be seem. The thicker the enamel, the whiter the tooth can be made. The thinner the enamel, the color of the dentin takes over, and the whitening process will not be as effective. So, teeth which are whitened can appear to be lighter toward the biting (or incisal) edge, and darker closer to the gum line.

Since dentin is opaque and enamel is translucent (or allows light to pass through), the incisal edge of the tooth may not have any dentin underneath. When the dentin is present, light is blocked by the opaque dentin and the combination of enamel and dentin color is prevalent. When dentin is not present, the light can pass through the tooth and since the inside of the mouth is darker, the incisal enamel may appear grayish because there is no dentin to reflect light. Also, keep in mind that any porcelain or composite resin in the tooth will not whiten like the natural teeth will.

Every mouth has different circumstances, and it is wise to consult your dentist about your needs before whitening.