(Quasi edens, from edo, to eat, or from Dens 2666 ). A tooth. The teeth are usually sixteen in each jaw; they are divided into the body above the gum, and the root, or fang, which is within the socket of the jaw; the neck is the line of division between the root and the body. They are composed of a bony substance and an enamel.

Little attention was paid to the teeth before the period of Eustachius, whose work appeared in 1563. He was followed by a French surgeon, Urban Hemard, about twenty years afterwards; but though the teeth and their diseases were more frequently mentioned in anatomical and chirurgical works, we find no express treatise on the subject till the year 1740, the date of Fouchard's work. This author was followed in 1771 by Mr. J. Hunter; by Dr. Blake in 1798; and Mr. Fox in 1803.

The enamel covers only the body of the tooth, that part which is not covered by the gums, so far as to its neck: it is not vascular, nor capable of being injected: for if animals are fed with madder, the body of the tooth will be coloured, but the enamel will remain unaltered; or, if the enamel be steeped in a weak acid, it will become a powder; but if bone is thus steeped, a soft elastic part remains.

Chemically examined, the enamel consists, like bone, of phosphat of lime, and gelatine, viz. of 29.67 parts of phosphoric acid; 43.3 of lime; and 27.10 of gelatine and water. It is generally agreed that the enamel is never reproduced. It certainly is not when broken to the subjacent bone; but its surface seems to be occasionally supplied, though its hardness prevents injury from attrition.

Each root is hollow, for the admission of vessels and nerves to pass into the substance of the teeth; but these cavities grow less in advanced age.

Ossification begins in the body of a tooth, and is continued to the root; and there are as many points of ossification as there are tubercles in the tooth. Mr. John Hunter suspects that the teeth, when full grown, are not simply bone. He observes, that bones are tinged with the colouring matter of madder when they are complete and perfectly grown, if the animal is fed for a time with this root; and teeth, whilst growing, receive this tinge, but not when they are perfected. In all other bones this red colour is, in time, carried off by absorption, and they return to their original colour; but a growing tooth, if coloured, never loses it. This does not show the want of an absorbent system, for teeth, when their nerves are destroyed, seem to be slowly absorbed; and they certainly continue, while alive, to be vascular. The whole anomaly seems to arise from the minuteness of their vessels. The rickets do not affect the teeth; for we never find them grow soft like the bones, but they remain perfectly hard: lastly, in old age, the other bones become brittle and waste; but the teeth, except when carious, continue in their former state.

The teeth are divided into three classes, viz. the incisures, canini, and molarcs. The incisores, called also denies lactei, and denies risorii, are the four anterior teeth in each jaw; they appear the first. The canini, or dentes oculares, are one on each side of the incisores, in each jaw. The molares arc five on each side of both jaws. Sometimes before twenty years of age, often about five or six and twenty, the last of the grinders appear, and are called dentes sapientiae and dentes genuini. Mr. John Hunter divides and names them as follows; viz. from the symphysis of the jaw on each side, are two Incisores, q. v.; one cuspidatus, (see Canini dentes;) two bicuspides; and three molares, the last of which is the sapientitae dens. See Morales.

The incisores, canini, and the two first of the grinders, are formed at the birth, and are those teeth which are shed. They usually appear about the seventh month, and are shed about the seventh year. The secondary teeth are formed in sockets of their own, which are situated below the other socket. The three dentes molares on each side do not come through the gums until the first set of teeth is shed; then they come through with the second set, and are never shed. Some people never have the last molares. At about three years of age a child hath the whole of its first set of teeth, which are twenty.

There are generally as many protuberances on the body of the teeth as there are roots: but the latter sometimes grow together; at other times they are divaricated, especially in the upper jaw, where, not having a sufficient depth, because of the maxillary sinus, they spread and are extracted with greater difficulty than those on the lower jaw.

The fifth pair of nerves supply the teeth with branches, which, with the blood vessels, are surrounded by a membrane, and, running under the teeth, enter into the cavities through a hole in the roots. From an attention to the fifth pair of nerves, and the parts to which they are distributed, many of the phenomena attendant on disorders of the teeth may be explained. It is in general supposed that the teeth, when a child is born, are lodged in sockets in the jaw-bones, and are covered with, and inveloped by, a thin, very irritable, and sensible membrane, the periosteum of the teeth; so that when the teeth begin to grow, they must necessarily distend, and force their way through this membrane, which, from its sensibility, gives great pain, and occasions fevers, starlings, and all the symptoms of teething. As soon as this membrane is completely divided in that part by the tooth, the child is relieved for the present from the fever and other complaints; which are subject to return upon the successive rising of the other teeth.

This general account must be admitted with many restrictions, derived from more minute inquiries. The teeth are formed in the foetus, and even the rudiments of the second set are very early conspicuous. They ossify in distinct points; and, at the period of birth, these ossified points arc nearly contiguous. They are covered with a membrane which is divisible into two layers; most dense and thick near the edge of the jaw, and softer as well as more gelatinous below. The external layer is spongy and vascular; the internal more tender and delicate, without vessels: though Mr. Hunter, perhaps from accident, has inverted this order. The membrane is fastened to the neck of the tooth, which, pressing against it, deprives it of life, and thus occasions its absorption, as well as of the gum above. Laceration seldom takes place, though in some instances it seems to do so, as the ragged edges have been observed. In general, the diseases attributed to dentition do not arise from the distention of this membrane, but to the state of the stomach, and are often relieved by a slight opiate, with the volatile alkali. It has been a too common practice to divide the gum; but this is an unnecessary seve-ritv. and often useless. It is only when the tooth distends it considerably, with violent inflammation, that such an operation is admissible.

Disorders in the teeth, in more advanced age, depend chiefly on a caries, and an inflammation in the membrane which covers their root. When a tooth is carious, it often occasions a fetid breath; and the air passing into, or any warm or cold substance touching it, excites pain. Relief is often obtained by filling the carious part with opium for occasional relief; but with gold or silver laminae for more permanent ease. When the membrane which spreads itself about the roots of the teeth is considerably inflamed, bleeding or purging, according to the state of the constitution, will be needful; warm barley water may also be held in the mouth, and the methods useful in other inflammatory disorders may be employed. Blisters may be applied behind the ears, or on the back; and horse radish or pellitory root may be held between the gums and cheeks, to excite a discharge of saliva. Besides these general causes, scorbutic and venereal complaints will affect the teeth; in which cases, the method of cure will consist in general remedies adapted to them. See Dentifricium.

On the teeth, and their disorders, see Mr. John Hunter's Natural History of the Human Teeth; Eustachius de Dentibus; Hoffman de Dentibus, eorum Morb. et Cura; Hurlock on Breeding of Teeth; Moss on the Management of Children; Bell's Surgery, vol. iv. p. 191; White's Surgery, p. 280; Blake and Fox on the Teeth.

Dens caballinus. See Hyosciamus.

Dens canis. Dog's tooth. Erythronium, dens canis Lin. Sp. Pi. 437. The flower is shaped like that of a lily; the root is long, fleshy, and formed somewhat like the tooth of a dog; the leaves resemble those of the cyclamen. The dried roots are commended as anthelmintic; but are not used with us. Dog tooth spar in mineralogy is one of the original forms of crystals.

Dens leonis, also called taraxacum, urinaria, hie-racium Alpinum, hedypnois. Dandelion". It is the leontodon taraxacum Lin. Sp. Pi. 1122. It is a low plant, with long, narrow, deeply indented leaves, lying on the ground, among which arises a single, naked, hollow pedicle, bearing a large, yellow, flosculous flower, followed by small seeds, covered with a tuft of long down: the root is oblong, slender, yellowish, or brownish, on the outside, and white within. It is perennial, common in uncultivated places, and flowers from April to the end of summer.

The roots, stalks, and leaves, abound with a milky, bitterish juice, but of no particular flavour. They were supposed to be mildly detergent and aperient; but owe their credit chiefly to their milky juice, which was supposed to be saponaceous. Boerhaave highly commends them as a resolvent; but the more immediate and sensible operation of this plant is to loosen the belly, and promote urine; which it does with little stimulus, though in a slight degree; and has been considered as highly efficacious in removing biliary obstructions. Dr. Pemberton, in a late work, speaks of it with commendation in these complaints. Murray observes, that this plant resolves viscid humours, opens obstructed vessels, and is a remedy for various eruptive complaints; and Bergius considers it as an effective, hepatic deobstruent, recommending it in hypochondriasis and jaundice. He recommends it boiled in whey, or formed into broths and apozems. It has also been supposed useful in dropsies, pulmonic tubercles, and some cutaneous disorders; given in decoctions of the plant, and root; or the expressed juice is sometimes administered, from one ounce to four, three or four times a day The plant should always be used fresh; for even extracts of it, as well as the roots and leaves, lose their power by keeping. It may also be taken as part of diet, and eaten fresh. The young leaves blanched resemble in taste the endive, and make a good addition to salads in the spring. The roots are roasted, and used at Got-tingen, by the poorer people, for coffee, from which a decoction of them properly prepared can hardly be distinguished.

See Raii Hist. Lewis's Mat. Mad. It is also a name of the auricula muris, and some other plants.