Certain articles of food affect the teeth badly. The continued use of acid medicines works direct harm, as do also the fruit acids ingested when undergoing a grape-cure. In such cases double vigilance in caring for the cleanliness of mouth and teeth becomes necessary. Sugary and starchy foods are likewise harmful to the teeth, especially when eaten in the form of sticky sweets. If remnants of such foods be allowed to remain for any length of time between the teeth, lactic acid, which is very destructive to the teeth, develops. Sugar, chocolate, etc., are otherwise nourishing and wholesome articles of food ; and if the mouth and teeth be thoroughly cleansed after eating such substances no harm will ensue.
Smoking has no detrimental effect on the teeth. The brownish dis coloration often noticed on the teeth of constant smokers is only external, and may be easily removed. In certain respects the smoke prevents decay and stems fermentation. On the other hand, it acts as a corrosive on the gums and mucous membrane, and for this reason excessive smokers rarely have healthy mucous membranes in the mouth.
The chief care of the teeth consists in cleansing or brushing them regularly. Chewing hard bread thoroughly tends to clean and preserve the teeth. For this reason some uncivilised races, and persons who eat coarse food, have beautiful teeth without resorting to any mechanical care of them. In rinsing the mouth, warm water is preferable to cold water, because the former more readily dissolves and removes tough and fatty remnants of food. To remove particles of food from the spaces between the teeth, a tooth-brush is necessary. The shape of the tooth-brush is less important than its skilful handling. Brushing should be done, not only on the visible surfaces, but over all the surfaces that can be reached. The chewing-surfaces should be well brushed, as should also the furrows in the molars, where food remnants which cannot be removed by the tongue are most likely to become lodged. Also the back surfaces of the teeth (facing the tongue) should be carefully brushed (see Fig. 412). The tooth-brush should not be passed over the teeth from side to side, but with up and down movements, the upper row being brushed from above downward, and the lower row from below upward (see Figs. 413 and 414). If the teeth be brushed sideways, it tends to force the food remnants into the interspaces instead of removing them. By brushing the teeth in the proper direction, the gums also derive the benefit of a mild massage which makes them firm and tense. Otherwise they are apt to become flabby, inflame readily, and bleed at every touch. At first the
brushing of the gums may cause them to bleed, it is true ; but this will be for a few days only, and afterward they will be healthier and firmer.
The tooth-brush should not be too hard, since this may cause injury to the gums. Bristles of medium stiffness are to be preferred. After using, the tooth-brush should be thoroughly rinsed, and dried in the fresh air. Air-tight tooth-brush holders are very inappropriate, as they keep the bristles damp and cause them to rot. It is much better to hang up the tooth-brush on a nail. No two persons should ever use one tooth-brush in common.
A tooth-pick is useful for removing food remnants which cannot be reached by the tooth-brush. Soft, quill tooth-picks are preferable to wooden ones. After using a tooth-pick it is advisable to rinse the mouth with warm water in order to remove the loosened particles of food. When the teeth are so close together as to prevent the introduction of a tooth-pick, a waxed silken thread is effectual.
A good tooth-powder enhances the effects produced by water and brush. The powder must be very finely pulverised, and should contain no gritty substances. The main basis of all tooth-powders is an alkaline carbonate which, in addition to its mechanical effect, also serves to neutralise the effects of acids and the dangerous consequences caused by the presence of the bacillus of caries. The more powerful alkalies, soluble in water, are not adapted for use in tooth-powders, as they corrode the mucous membrane. For this reason great caution is necessary when selecting tooth-soap or tooth paste, as even the best soap develops free alkali when brought in contact with spring-water containing lime. Tooth-paste consists principally of tooth powder and soap, with an admixture of glycerine. The colour of the tooth powder is immaterial, since it is due merely to an admixture of colouring matter. Tooth-powder containing linden-wood coal renders the gums black or blue along the edges, and the discoloration rarely disappears. Pulverised oyster-shells, cuttlebone, pumice and cigar ashes are too coarse and gritty, and affect the enamel too severely. Tooth-powders that in a very short time give the teeth a dazzling white appearance, contain free acids which dissolve the enamel, and should, therefore, be particularly avoided. The addition of an antiseptic to the tooth-powder is of little value, since it does not dissolve completely in the short period of time it takes to brush the teeth.