Mammals including human being forms two sets of teeth during their life, first set of temporary milk or deciduous teeth [milk teeth] replaced by second set of permanent or adult teeth [permanent teeth].
· An adult human has 32 permanent teeth which are of four different types, namely,
- Incisors (I),
- Canine (C),
- Premolars (PM)
- 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 [2-I,1-C,2-PM,3-M]
· The hard chewing surface of the teeth, made up of enamel (Enamel is the hardest substance in the human body and contains the highest percentage of minerals), helps in the mastication (chewing) of food.
· Our mouth has the salivary glands which secrete saliva. The saliva breaks down the starch into sugars.
· The saliva secreted into the oral cavity contains electrolytes (Na+, K+, Cl", HCOs) andenzymes, salivary amylase and lysozyme.
· The chemical process of digestion is initiated in the oral cavity by the hydrolytic action of the carbohydrate splitting enzyme, the salivary amylase.
· 30 per cent of starch is hydrolysed here by this enzyme (optimum pH 6.8) into a disaccharide - maltose.
· Lysozyme present in saliva acts as an antibacterial agent that prevents infections.