Dental caries

 Dental caries (tooth decay) 

      Dental caries is the most common disease of dental tissues,mainly of premolars and molars. It is more common in those children and adult persons whose diets are rich in carbohydrates which need less chewing and generally stick to the teeth. 

                           

**1 causative agent- 

                                          It is caused by acidogenic (acid- producing) bacteria of mouth,steptococcus mutans,in the presence of high proportion of sugar. The bacteria cause anaerobic decomposition of sugars into organic acids. 

 

                          

*** 2 symptoms - 

Dental caries is characterized by gradual softening of enamel and dentine due to decalcification. before this, the masses of bacterial cell and food particles stick to the teeth and form dental plaques to cover the teeth.finally,it leads to apperance of cavities in the teeth leading to inflammation and necrosis of pulp,called pulpits.

**** 3 prevention

1 avoid sugar- rich eatables .

2 regular brushing of teeth after meals.

3  vigorous chewing of fibrous food s.

4  consumption of water containing 1 ppm (parts per milion) of flouride reduces the rate of tooth decay in the children. 

5 clearing of food particles from between the teeth by dental floss. 

Note

*  Teeth help in physical digestion of food, while salivary glands help in chemical digestion. 

*  The length of the small intestine depends upon the mode of feeding of the animals. It is longer in herbivores like rabbit, cow,deer, etc, compared to carnivores like tigers,lions,etc, because it is easier to digest near than cellulose.

* Peristalsis is involuntary contraction and relaxation of gut muscles to move the food downwards. 

*  Period of gastric digestion depends upon nature of food. It is 1-2 hours for carbohydrates but 5-6 hours for fats. 

* Secretion of digestive enzymes is controlled by hormones of endocrine cells.

* Egestion is a partly voluntary and partly involuntary process.