THE MOUTH, ORAL OR BUCCAL CAVITY 1209 



The root is single, oval, or elliptical on transverse section, and is longer and more 

 prominent than the roots of the incisors. 



The upper canines, popularly called the eye teeth, are larger and longer than the 

 two lower, and in occlusion are distal to them to the extent of half the width of the 

 crown. 



The lower canines, popularly called the stomach teeth, have the general form of 

 the upper canines, but their lingual surfaces are much more flattened, owing to 

 the absence of the elevations marking the upper teeth. Their roots are more 

 flattened and may be bifid at their apices. 



The bicuspid teeth, or the premolars (denies premolares), are eight in number, 

 four in each jaw; they are placed distal to the canine teeth, two upon each side 

 of the jaw. 



The crown is surmounted by two cusps, one buccal and one lingual, separated 

 by a groove, the buccal being more prominent and larger than the lingual. The 

 lower bicuspids are not truly bicuspid, the first having but a primitive lingual 

 cusp, the second having the lingual cusp divided into two sections i. e., it is 

 usually tricuspid. The necks of the teeth are oval ; the roots are single and later- 

 ally compressed, that of the first upper bicuspid being frequently bifid. The 

 first upper bicuspid is usually the largest of the series. The roots of the lower 

 bicuspids are less compressed and more rounded. 



The Molar Teeth (denies molares) are the largest and strongest teeth of the per- 

 manent set, and are adapted by their forms for the crushing and grinding of the 

 food. They are twelve in number, six in each jaw, three being placed posterior 

 to each second bicuspid. 



The crowns are cuboidal in form, are convex buccally and lingually; they are 

 flattened proximally and distally. They are formed by the fusion of three primi- 

 tive cuspids in the upper and four in the lower. To these are added in the first 

 and second upper molars a distolingual tubercle, and in the first and third 

 molars of the lower jaw a distobuccal tubercle. The unions of the primitive 

 forms are marked by sulci. The necks of these teeth are large and rhom- 

 boidal in form. The roots of the upper molars are three in number one large 

 lingual or palatal root, and two smaller buccal roots. In the lower molars, two roots 

 are found, a proximal and a distal, each of which is much flattened from before 

 backward. 



The first molar teeth are the largest of the dental series; they have four cusps 

 on the upper and five in the lower three buccal and two lingual. The second 

 molars are smaller; the crowns of the uppe^r are compressed until the distolingual 

 cusp is reduced. The crowns of the lower are almost rectangular, with a cusp 

 at each angle. The third molars are called the wisdom teeth, or dentes sapientiae 

 (denies serolini), from their late eruption; they have three cusps upon the upper and 

 five upon the lower. The three roots of the upper are frequently fused together, 

 forming a grooved cone, which is usually curved backward. The roots of the lower, 

 two in number, are compressed together, and curve backward. 



Of the permanent teeth, all but the molars represent succedaneous teeth, 

 that is, teeth that succeed those of the temporary set. The molars are primary 

 teeth, as they possess no forerunners in the temporary set. 



Arrangement of the Teeth. 1 The human teeth are arranged in two parabolic 

 arches, the upper row or arch (arcus denlalis superior] being larger, its teeth over- 

 lapping the lower row or arch (arcus denlalis inferior}. The average distance 

 between the centres of the condyles of the mandible is about four inches, which 

 is also the distance from either of these points to the line of junction between the 

 lower incisor teeth. Whether the jaw be large or small, the equilateral triangle 



> After Dr. W. G. A. Bonwill. 



