(From dentes fricare, to rub the teeth). Dentifrice; called also odontotrimma. Medicines for cleaning the teeth. Many preparations are employed for this purpose, chiefly consisting of scuttlelish bone, bole, bark, myrrh, salt, and soot. Each operator has his receipt, which he highly commends and conceals. Any very fine powder is apparently of equal service, but mastich and myrrh are the general bases: most commonly the former. The powder is flavoured with orris root, with ambergris, etc. and coloured with dragon's blood, bole armoniac, or red sanders, professedly to strengthen the gums, but really to conceal the bleeding from the gums. It was formerly the custom to add common salt or crude sal ammoniac to dentifrices; for what purpose we know not; but both are now disused: and one of the most boasted tooth powders that we have seen, is only magnesia coloured with rose pink. The carbonated dentifrice is merely powdered charcoal, and it has been employed chiefly from its power of destroying the colours of different fluids, discovered by Lowitz. (Sec Charcoal.) Soot is used from the whiteness observed on chimney sweepers' teeth; but it possesses no very peculiar merit. A sufficiently pleasant and efficacious tooth powder is made with two parts of finely powdered mastich, two parts of myrrh, and one part of cassia. It cleans the teeth, preserves them from decaying, and renders the gums peculiarly firm and hard. In fact, however, almost every powder seems equally efficacious, and, if it be impalpable without acidity, equally innocent.

The calculous concretion which forms on the teeth is of singular hardness, and with great difficulty removed; nor has modern chemistry yet discovered a a menstruum which will dissolve it without injuring the enamel. Acids soften this firm covering, and render it transparent. Dentists universally reprobate their use, and we cannot, therefore, encourage it. We suspect, however, that their occasional application will not be injurious: we arc, at least, certain, that the injury acids may do is recoverable. The brushes should be hard and strong; the hairs set at some distance, that they may clean the interstices of the teeth, where the tartar lodges; and the brush should be used more in the longitudinal direction, with respect to the teeth, than across them. If the powders are perfectly fine, no injury can arise from the brush. The preservative tinctures are of little use. Their basis, like the powders, is mastich, and their appellations fanciful.