Tag: experiments on digestive enzymes

In general teeth of reptiles (except crocodile) are acrodont. Thus, teeth are fixed over bone and not embedded in sockets in jaws. The fangs of snakes are modified maxillary teeth of upper jaw. If pulled out these teeth can be replaced.

Humans have two sets of teeth- the deciduous or milk teeth and the permanent teeth. The milk premolars are absent in infants. Thus, dental formula of infants are 2102/ 2102 as against 2123/ 2123 in adult humans.

Majority of mammals including human being forms two sets of teeth during their life, a set of temporary, milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont. An adult human has 32 permanent teeth, which are of four different types, namely, incisors (I), canine (C), premolars (PM) and molars(M). Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in humanis 2123/ 2123. In children the premolars and last molar are absent. Hence the child has dental formula 2102/ 2102. The number of teeths according to this dental formula will be 20. These teeth will be diphyodont and (32-20) or 12 teeth will be monophyodont.

Enamel is the hardest substance in the human body and contains the highest percentage of minerals, 96%, with water and organic material. The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate.

Majority of mammals including human being forms two sets of teeth during their life, a set of temporary, milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont. An adult human has 32 permanent teeth, which are of four different types, namely, incisors (I), canine (C), premolars (PM) and molars(M). Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in human is 2123/ 2123. The premolars and last molars are absent in children. Thus the teeth which grow twice are incisors, canines and two molars i.e., a total of 20 teeth.

Enamel is the hardest material of animal kingdom. Enamel is ectodermal. It is secreted by Ameloblast cells of the ectoderm. lt has maximum amount of inorganic salt (96%) in It. Inorganic salt are mainly found in the form of phosphate and carbonate of Ca, Mg, Na and K. 3% of water is found in the enamel. Along with it Keratin and  ossein are also found in teeth. Ossein is a protein of bones, remaining part of tooth develops from mesoderm of embryo.

Cheek teeth or post canines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many cusps or tubercles). Mammals have multicuspidate molars.

Teeth appear to have first evolved in sharks, and are not found in the more primitive jawless fish. Lampreys do have tooth-like structures on the tongue, these are in fact, composed of keratin, not of dentine or enamel, and bear no relationship to true teeth. 

• The premaxilla is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. 
• In humans, they are fused with the maxilla and usually termed as the incisive bone (the portion of the maxilla adjacent to the incisors). Hence,  Incisor is present in premaxilla of the human jaw.