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.
In rare cases, a couple of new teeth come in before the old ones are gone, creating two rows of pearly whites. This is a temporary stage, sometimes called shark's teeth. If your 6- or 7-year-old complains of soreness in the back of his mouth, it's probably the first permanent molars coming in. (He has no baby teeth there to fall out first).