Fig. 32 —Photograph of teeth not kept clean, showing how germs and a sour substance called acid eat holes in them and thus cause decay and toothache.
Toothache.—Toothache is a common ailment, and yet it can be entirely prevented. A tooth does not ache until it has a hole in it. The tender nerve within gives us warning that it is being hurt. The dentist can stop the ache and mend the tooth so that it will not ache again. Look at your teeth every month and feel about them with a wooden tooth-pick to know when the decay begins. If the little holes are mended as soon as found, you will never have toothache, and you can keep your teeth as long as you live.
Fig. 33 —Slice down through a tooth showing f, the enamel, and d, the soft pulp with nerves and blood tubes from the root at h.
How to keep the Teeth Sound.—Every tooth is covered with a layer of hard shining substance called enamel ([Fig. 33]). So long as this is unbroken the softer bony part of the tooth cannot decay. At the base of the tooth where the gum joins it the enamel is very thin, so that the scratch of a pin or other instrument may break it.
Never pick the teeth with a pin or needle. The biting off of thread, finger nails, and other hard material may crack the enamel. It may also be softened and eaten away by acid formed where food remains about a tooth. For this reason a quill or wooden pick or piece of tough thread, called dental floss, should be used to clear the teeth of food after each meal. Slimy matter collects over the whole surface of the teeth, and is likely to cause decay in spots unless it is cleaned off night and morning with brush and water. The chewing of dry crusts of bread or crackers strengthens the teeth and keeps off decay.
Why Candy and other Sweets cause the Teeth to Decay.—A sour substance called acid usually starts the decay of a tooth by eating through the enamel. Germs change sugar and other sweets into an acid. The acid is not made at once. An hour or more is needed for the germs to grow to form the acid. If, after eating sweet foods, the mouth is well cleaned, no acid will be formed. Sugar and candy do not, therefore, spoil the teeth unless it is left sticking about them.
How to brush the Teeth.—Every boy and girl should own a toothbrush. The teeth should be brushed every night and morning and kept white. Yellow or gray slimy teeth are very ugly. The teeth should be brushed on the inside as well as on the outside. It is best to brush the teeth crosswise for two minutes and then spend another two minutes brushing the upper teeth downwards and the lower teeth upwards. This prevents pushing the gum away from the teeth. Plenty of water should be used with the brush, and a little good powder is helpful once a day.