Station 2: Dentition and Dental Formula Mammals have four types of teeth: incisors, canines, premolars, and molars. The number of each teeth in the jaws of mammals can be described by the dental formula. The first number refers to the number of incisors, the second number to the number of canines, the third is premolars, and the fourth are molars. Here are some examples: Humans: 2123 (feel your teeth from one half of your jaw) Old World monkeys: 2123 New World monkeys: 2133 2. Write the opossum dental formula below. Opossum dental formula: