. Elementary biology; an introduction to the science of life . The structure of a human tooth is shown in Fig. 36. The enamel is a hard protective casing. Trouble with the teeth very frequently begins with the breaking of this enamel. The enamel can be cracked by grinding it against some hard sub- stance, as when you try to crack a nut with your teeth ; or it may be cracked by sudden changes of temperature. Drinking very cold water or very hot drinks is likely to be one of the ways of cracking the enamel. Picking the teeth with a needle or some other hard body is also likely to scratch the ena
. Elementary biology; an introduction to the science of life . The structure of a human tooth is shown in Fig. 36. The enamel is a hard protective casing. Trouble with the teeth very frequently begins with the breaking of this enamel. The enamel can be cracked by grinding it against some hard sub- stance, as when you try to crack a nut with your teeth ; or it may be cracked by sudden changes of temperature. Drinking very cold water or very hot drinks is likely to be one of the ways of cracking the enamel. Picking the teeth with a needle or some other hard body is also likely to scratch the enamel and thus to open the way for further damage. In the food that we put into our mouths there are many bac- teria, of many kinds. In par- ticles of food that cling to the teeth these bacteria begin their digestive activities, and some of the substances thus pro- duced act upon the enamel, dissolving away this protec- tive cover. Particles of food in the larger cracks, or fluids in the smaller scratches and cracks, permit the action of the bacteria to continue, and gradually a cavity in the tooth becomes larger and deeper, until it reaches the pulp, and the nerve becomes exposed. A thorough cleaning of the teeth thus becomes necessary at frequent intervals. The most reasonable time to clean the teeth is immediately after each meal. If you get the habit of doing this, it will postpone the rotting of the teeth a good many years. Unfortunately our business and industry are so arranged that most grown-ups cannot manage to look after their teeth after each meal. The best one time a day for
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishe, booksubjectbiology
