The mammalian teeth are placed in the muscular sockets in the jaw bones. This type of dentition is called Thecodont. The teeth are ‘diphyodont’. Two sets of teeth develop during life lime. The first set of teeth develop in the young and known as ‘milk or deciduous teeth’, after certain age these are replaced by the second set of permanent teeth. But in bats ‘and, guinea pigs the milk teeth are shed before birth. In platypus, toothed whales, sloths and sirenians the monophyodont dentition’ is present. Milk dentition is reduced by the replacement of the third premolar in marsupials.
All the teeth are not alike in all mammals. Mostly mammals exhibit ‘heterodont dention’. The teeth are modified in the form and function. But in Dolphins and porpoises it is homodont (all teeth are alike). There are four types of mammalian teeth.
1) Incisors: These are present on the premaxillae bones of the upper jaw and dentary bones of the lower jaw. They have only one ro and sharp cutting edges. So this type of teeth is used in sizing and cuffing.
2) Canine: These are present between the incisors and premolar. There is a single such troth in each half of each Jaw. These are long, conical teeth with a single root and simple, sharp-pointed crown.
3) Premolars : These follow the canines. They have double root and compressed crown with one or two cusps. These possess grinding and crushing surfaces. Premolars are replaced once in life time.
4) Molars: These are next to the premolars. They have more than two roots and cusps. These do not have predessors and always develop in the permanent set. Molars are used for crushing and mastica lion.
Both prermolars and molars are collectively knows, as cheek teeth and are borne on maxillae and dentaries. These have broad crushing and grinding surfaces or cusps.