When disc brakes for high performance cars arrived on the scene we began to hear of warped brake discs on road going cars, with the same analyses and diagnoses. Typically, the discs are resurfaced to cure the problem and, equally typically, after a relatively short time the roughness or vibration comes back.
As a result, the cheek teeth, like the incisors, have evolved to continuously grow throughout life. In other rodents, the diet of tubers, seeds, and grain requires little chewing, resulting in little wear of the cheek teeth.
This is called the period of mixed dentition, because for much of the time, children will have both primary and permanent teeth. Teeth form under the gum before they erupt (emerge through the gum). The crown, or visible part of the tooth, forms before the roots do. Before the roots form, the developing tooth is called a tooth bud.. Eventually, the 20 primary teeth are replaced by 32 permanent teeth.