See also:part or
See also:crown covered by
See also:enamel, a
See also:neck where the
See also:gum surrounds it, and one or more roots or fangs fitting into sockets (alveoli) in the
See also:bone . For surgery of the teeth see
See also:DENTISTRY . There are
See also:thirty-two permanent teeth in man, sixteen in the upper and sixteen in the
See also:lower jaw; they are also arranged in symmetrical sets of eight teeth on each side . The two teeth on each side of the
See also:line in front are " incisors " and have
See also:chisel-shaped crowns . The mesial or central incisor of the upper jaw is broader than any of the others, consequently it bites against the central and lateral incisors of the lower jaw, and the same want of exact adaptation continues throughout the series, so that every tooth in the upper jaw except the last molar bites against its corresponding tooth of the lower jaw and the tooth behind that . ninth
See also:month, or even later; then, after a few months, come the central and lateral upper incisors; again a few months' and the lower lateral incisors appear, followed closely by first molars . After another
See also:rest of four or five months come the canines, the eruption of which is a slow
See also:process, while by about the end of the second
See also:year the second molars have appeared, and the milk dentition is
See also:complete . It will be seen from the above that the milk teeth are cut in batches with resting intervals between . As C . S . Tomes points out, we do not know what causes the eruption of the teeth; the growth of the roots is not of itself enough to account for it .
It is possible, however, that
See also:blood-pressure may be the determining cause . The first permanent tooth to be cut is the first molar, and this happens during or soon after the
See also:sixth year . It does not displace any of the milk teeth, but comes down behind the second milk molar . During the seventh year the central milk incisors fall out and their place is taken by the permanent ones; the
See also:shed teeth are mere shells of the crown, all the
See also:root having been absorbed, though not, as might be thought, owing to
See also:direct pressure of the succeeding tooth . The lateral incisors succeed their milk predecessors at about eight years old, the first premolar takes the place of the first temporary molar about nine, the second pre-molar that of the second temporary molar about ten, Fro. r.—The Permanent Teeth of the Right Side, Inner or the canine about eleven, while the second molar comes Lingual Aspect. down behind the first about twelve, and so is known as The upper
See also:row shows the upper teeth, the lower row the lower teeth . The the "twelve-year-old tooth." The third molar, or wisdom cingulum is distinct on the upper incisors and both canines, the lingual tooth, usually appears between eighteen and twenty, but
See also:cusp on the upper lateral incisor and the upper canine. may be much later, indeed it is sometimes never cut at all, and when it is, it often does not come down to a level with the other teeth . It is believed that man is gradually undergoing a suppression of his last molar teeth, which, if the process continue, will lead to our successors having a different dental
See also:formula from our own . It is interesting to
See also:notice that 1st molar Next to the incisors comes the " canine tooth," the crown of which is somewhat peg-shaped, while behind this are the two " premolars " or " bicuspids," whose crowns are flattened from before backward and bear two cusps, the larger of which is the
See also:external or labial cusp, while the smaller is the
See also:internal or lingual . As a
See also:rule there is a single root, though sometimes in the first upper premolar it is
See also:double . The three " molars " are placed behind the premolars, and the upper and lower sets can be easily distinguished because the upper have three roots -while the lower have only two . Of the three roots which the upper molars bear two are lateral or external and one mesial (see fig. r), so that it is easy to tell the
See also:outer from the inner side of an upper molar . The front can, as a rule, be identified by the fact that the roots are gene-rally bent a little backward at their tips, and this applies to other teeth than the upper molars .
In the lower jaw, owing to the two fangs being anteroposterior, it is not possible to tell the lateral from the mesial
See also:surface of the molars by them, although the backward inclination of their tips shows the front from the back . When it is remembered that the upper teeth overlap the lower externally it is reasonable to expect that the lower molars would show some rounding due to wearing away of the edge of the crown on the outer side, and this is the case . The grinding surface of the crowns of the upper molars shows three or four cusps, while on that of the lower four or five are found . Of the three molars the first is the largest, and the third, or wisdom tooth, the smallest, while the upper wisdom tooth is smaller than the lower . In the " milk teeth " or temporary dentition of the
See also:child there are only twenty teeth, ten in each jaw and five in each segment . They are two incisors, one canine, and two so-called molars . These molars occupy the position which the permanent premolars later on take, and it is held by many that the adult molars really belong to the milk dentition, although they cannot appear until the jaw has grown backward sufficiently far to make
See also:room for them . The temporary teeth differ from the permanent in their smaller
See also:size, their whiter
See also:colour, the greater constriction of their necks, and in the fact that the roots of the molars are widely splayed . The
See also:dates at which the milk teeth are cut are very variable . The lower central incisors come first between the sixth and Canine Lateral incisor 1 A Central incisor 1 in molar From
See also:Birmingham, in
See also:Cunningham's Text-
See also:Book of Anatomy . The masticating surfaces of the two upper molars are shown above . In the second row the upper teeth are viewed from the outer or labial side .
In the third row the lower teeth are shown in a similar manner; and below are the masticating surfaces of the two lower molars . In the specimen from which the first upper molar was
See also:drawn the two outer or buccal cusps were not distinctly separated, as is often the case . in some of the lower races of mankind the last molar tooth is nearly as large as those in front of it, and this is the case in the anthropoid apes . A .
See also:Keith and D . Braden Kyle have pointed out that the second and third molar teeth are successively formed in the posterior
See also:wall of the maxillary antrum and molar Central incisor Canine sand premolar 2nd molar From Ambrose Birmingham, in Cunningham's Text-Book of Anatomy . Lateral incisor 1st premolar rest the .Central incisor Canine and premolar Lateral incisor zst premolar ist molar 3rd molar F I 11 11 1st molar 2nd molar crown Central incisor Lateral incisor Canine and their crowns look backward . It is owing to the gradual growth backward of this antrum and the maxilla that they are rotated
See also:round a quarter of a circle and so at last look down-
See also:ward (see A . Keith,
See also:British Journal of Dental Science, vol. xlv.,
See also:June 16, 1902) . Extra teeth are occasionally met with in the incisor, premolar and molar regions; their significance will be better realized after the
See also:embryology and
See also:comparative anatomy of the subject have been sketched . For an accurate and detailed description of man's teeth see A
See also:Manual of Dental Anatomy, by C . S .
See also:London, 1904 .
There are no comments yet for this article.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.
Links to articles and home page are encouraged.