PEEMANENT TEETH. 



Foramen incisivum 



Dentes incisivi 



Dentes Canini. In the four canine teeth, which succeed the incisors in each 

 row (Figs. 881 and 886), the crown is large and conical, corresponding closely in 

 general form to a very large central incisor with its angles cut away, so that 

 the crown assumes a pointed or conical shape. The labial surface is convex, 

 the lingual usually somewhat concave. The root is single and long, particularly 

 in the upper canine, the root of which is longer than that of any other tooth, 

 and produces the canine eminence on the anterior surface of the maxilla. The 

 ; upper canines are larger than the corresponding lower teeth, behind which they 

 bite ; and they are sometimes known as the " eye teeth." 



The upper canine presents on its lingual surface a well-marked cingulum, and often a distinct 

 lingual tubercle; in addition, there is usually a median ridge running from the point of the crown 

 to the apex of the cingulum, which is separated from the lateral part of the cingulum on each 

 jide by a slight depression. These points are neither so well marked, nor so constant, in the 

 lower as in the upper canine. 



Of the two margins sloping away from the apex of the crown, the lateral is the longer in both 

 ;eeth. After it has been a little worn the lower canine is less distinctly pointed than the upper ; 

 its root is also more flattened. On the labial surface of the crown, of both canines and premolars, 

 i wide low vertical ridge (labial 

 ridge) can generally be made out 

 Tig. 882) ; it is most distinct on 



the canine and first upper pre- ^^^^KYyfSX .JT / .^te^ Dens caninus 



molar. 



Dentes Praemolares 



Tigs. 881 and 882). The 

 premolar teeth, eight in 

 aumber, two in each jaw 

 above and below, are placed 

 posterior to the canines, and 

 interior to the molars, as the 

 name indicates. The crown, 

 which, unlike that of the 

 incisors and canines, is flat- 

 tened antero - posteriorly, is 

 characterised by the presence 

 of two tubercles (O.T. cusps) 

 Tig. 883). One of the 

 tubercles, the larger, is placed 

 Dn the labial, the other on 

 the lingual side. The labial and lingual surfaces are both convex. The root 

 is single, but it is, as a rule, flattened antero -posteriorly and grooved, showing 

 in this a tendency to division, which often actually takes place in the first 

 upper premolar. The upper premolars are easily distinguished by the fact that 

 their two tubercles are large and are separated from one another by a distinct 

 antero-posterior fissure (Fig. 883) ; whilst in the lower premolars, on the other 

 hand, the separation between the two tubercles is not effected by a continuous 

 fissure as in the upper teeth, but by two dimple-like depressions separated by 

 a ridge which joins the two tubercles (Fig. 884). In the upper premolars, there- 

 fore, the two tubercles are separated by a fissure, in the lower they are united by 

 a ridge. 



The first upper premolar is often slightly larger than the second ; the reverse is the case in 

 the mandible. The labial surface of the crown is usually somewhat larger than the lingual 

 surface in all premolars. As a general rule in the lower premolars the labial surface of the 

 3wn is sloped medially near the masticating surface. The first can usually be distinguished 

 from the second by the fact that, while the lingual tubercle and surface are smaller than the 

 labial in the first premolar, they are nearly of the same size in the second. In addition, the 

 root of the first upper premolar is bifid or nearly so, and its labial ridge is fairly distinct, but 

 s indistinct in the second. In the first lower premolar the lingual tubercle and surface are very 

 small, in fact the tubercle is quite rudimentary. It should, however, be added that it is often 

 extremely difficult to identify the various premolars. 



Dentes Molares. The molar teeth are twelve in number three on each side 



Spina nasalis 

 posterior 

 Foramen 

 palatinum majus 



Sutnra palatina transversa 



FIG. 883. THE HARD PALATE AND UPPER PERMANENT TEETH, 

 VIEWED FROM BELOW. 





