Enamel is the thin outer covering of the tooth. This tough shell is the hardest tissue in the human body. Enamel covers the crown which is the part of the tooth that visible outside of the gums.
Because enamel is translucent, you can see light through it. But the main portion of the tooth, the dentin, is the part that responsible for your tooth color -- whether white, off white, grey, or yellowish.
Sometimes coffee, tea, cola, red wine, fruit juices, and cigarettes stain the enamel on your teeth. Regular visits to your dentist for routine cleaning and polishing can help remove most surface stains and make sure your teeth stay healthy.
What does tooth enamel do?
Enamel helps protect your teeth from daily use such as chewing, biting, crunching, and grinding. Although enamel is a hard protector of teeth, it can chip and crack. Enamel also insulates the teeth from potentially painful temperatures and chemicals.
Unlike a broken bone that can be repaired by the body, once a tooth chips or breaks, the damage is done forever. Because enamel has no living cells, the body cannot repair chipped or cracked enamel.
A group of researchers in Australia and Taiwan has developed a new way to analyze the health of human teeth using lasers. As described in the latest issue of Optics Express, the Optical Society's (OSA) open-access journal, by measuring how the surface of a tooth responds to laser-generated ultrasound, they can evaluate the mineral content of tooth enamel -- the semi-translucent outer layer of a tooth that protects the underlying dentin.
This is the first time anyone has been able to non-destructively measure the elasticity of human teeth, creating a method that can be used to assess oral health and predict emerging dental problems, such as tooth decay and cavities.
Enamel demineralization is caused by bad oral hygiene. Not brushing, for instance, can lead to the build-up of dental plaques, and bacteria in these plaques will absorb sugars and other carbohydrates a person chews and produce acids that will dissolve the minerals in tooth enamel.
Quantifying the mineral content of tooth enamel can help dentists determine the location and the severity of developing dental lesions. Existing methods for evaluating enamel are limited, however. Dentists can visually assess the teeth, but dental lesions can be hard to spot in certain parts of the mouth because they are obscured by dental plaque, saliva, or the structure of a tooth itself. Dentists can use sharp dental instruments to probe the enamel, but this can be destructive to the teeth and gums. X-ray scans can reveal dental lesions, but they give no information on the level of mineralization.
For research purposes, "nano-indentation" is commonly used for gaining information on the elasticity of tooth enamel -- a measure of its mineral content -- but nano-indentation destroys the measured regions of the enamel in the process and is only used to look at extracted teeth.
What Wang, Fleming, and their colleagues wanted to do was to develop a clinical method that would give as much information as nano-indentation and could be used to assess tooth enamel in actual patients while being completely non-destructive. So they developed a way to measure the elasticity of tooth enamel by adapting laser ultrasonic surface wave velocity dispersion, a method similar to what industrial engineers use to evaluate the integrity of thin films and metals.