In fish, Hox gene expression regulates mechanisms for tooth initiation.
Shark teeth form from modified scales near the tongue and move outward on the jaw in rows until they are eventually dislodged.
The variations usually lie in the morphology, number, development timeline, and types of teeth.
In addition, rodent incisors consist of two halves, known as the crown and root analogues.
The mineral distribution in rodent enamel is different from that of monkeys, dogs, pigs, and humans.
Horses start to "run out" of erupting tooth in their early 30s and in the rare case they live long enough, the roots of their teeth will fall out completely in the middle to latter part of their third decade.
Elephants have six sets of molars in their life, all of which grown from the back of their mouth and are then pushed forward.
[15] All members of the order Tubulidentata have no incisors or canines, their teeth have no enamel, and their molars grow continuously from the root.