Notation for the number of incisors (I), canines (C), premolars (P), and molars (M) in the upper and lower dentition of a species of heterodont mammal, I:C:P:M. In humans, the adult dental formula is usually: 2.1.2.3/2.1.2.3. Since mammalian teeth are usually symmetrical, the total number of teeth is equal to the sum of the upper and lower quadrants, times two; in humans, for example, (8 816) 2 yields a modal number of 32 teeth. The aye-aye has a formula of 1.0.1.3/1.0.0.3, illustrating the need for both upper and lower quadrant counts. Its deciduous dental formula (dI:dC:dM) is 2.1.2/2.1.2. Both the deciduous and adult dental formulas are identical in all extant hominoids.