DENTARIA 



DKNTISTUV 



761 



a rasper. There are no eyes, Imt an ear-sac i 



present. Neither In-ill t imr gills <*re developed. 

 The sexes are similar and separate. The larva in 

 ciliated HM<| tiee.-swimming. The ty]>e is of much 

 /o.ilii._;ical inteie-,1, Imt its iiflinitieM are Htill un- 

 certain. Tin- animal liven with the anterior end 

 plunged into tin- sand on the sea-const , at depths 

 of ten to a hundred fathoms. By means of the 

 foot they can creep slowly. They feed mi minute 

 animals, and have an almost ro-mo|iolitan distri- 

 bution. The class includes two or more other 

 genera. D. entitle occurs off British coasts ; and 

 about forty living species are known. The genus 

 occurs as a fossil from Carboniferous strata (or 

 perhaps earlier) onwards. The shells are used for 

 currency and for ornament by the Indians of the 

 northern Pacific coast of America. See Lacaze- 

 Duthiers, Histoire den Dentales (1856-58). 



Hnitaria. or CORAL-ROOT (both names due to 

 knobbed root-stock), is a small genus of Cruciferre, 

 represented in Britain by the rare D. bulbifent, in 

 which the upper leaves bear Bulbils (q.v.), while 

 the pods rarely ripen. The root-stock neing pun- 

 gent, was formerly dried as a remedy for toothache. 

 I), diphylla, a North American species, is called 

 Pepper-root from the same property. The name 

 Coral-root is also applied to the orchid Corallorhiza, 

 while the true Toothwort (q.v.) is Lathrcea sqtta- 

 muria. 



Dentex* a genus of acanthopterous fishes near 

 perches. One species (D. nth/m-ia), the Dentex of 

 the ancient Romans, abounds in the Mediterranean, 



Dentex. 



and has occasionally been taken on the southern 

 shores of Britain. It is an excessively voracious 

 lisli, with large sharp teeth, and attains a large 

 size, sometimes three feet in length, and 20 to 30 

 pounds weight. Great numbers are taken in the 

 mouths of rivers in Dalmatia and the Levant, 

 where they are cut in pieces, and packed in barrels 

 with vinegar and spices, just as the ancients used 

 to treat them. 



Dentifrice* See TOOTH-POWDER, 



Dentine* or IVORY, the principal constituent 

 of mammalian teeth. See TEETH. 



Dentirostres* a somewhat old-fashioned title 

 for one of the subdivisions of singing Passerine birds 

 or Oscines. The term, as equivalent to ' toothed- 

 billed,' is used in opposition to Conirostres ('cone- 

 billed') and Tenuirostres (' slender-billed '). It 

 would include warblers, thrushes, chatterers, crows, 

 \-c., but the character is purely adaptive to the 

 better securing of the prey and the like, and is of 

 little significance in classification. 



Dentistry, the art of the dentist, or that of 

 treating disease in the teeth (Dental .S'M/V^/T.//), and 

 of replacing these organs when lost (M9aUatietU 

 Dentistry). The art is a very ancient one. The 

 Laws of the Twelve Tables (5th century B.C.) -pro- 

 vided for the case of 'teeth bound with gold,' it 

 being lawful in this connection to burn or hnrv 

 gold with the dead person. An Etruscan skull 

 found in 1885 had a set of animal's teeth artificially 

 lixed in it. The dentistry of the l"nit"d States has 

 in recent times become specially celebrated. 



( 1 ) Jh-ntal Surgery. Th disorders to which the 

 teeth are liable are those arising from .!: 

 development, Mich a* Imperfection* iii form or 

 stiu. -lure, irregularity of position, &c. ; t: 

 again, constituting dim-awn more properly o railed, 

 such as caries or dental decay, n-<-r.-i- or death of 

 a tooth, inflammation of the >ft ti*-m-, Mich an 

 the gum, the central pulp or neri-t, AH it in ixtpularlv 

 ailed, neuralgic affection*, &e. ; lastly, thone 

 ari-ing from accidents of various kind-, HUC|I as 

 blows, falls, and the like. For the constitution 

 and diseases of the teeth, see TM.I 11 



The object of the dentist, in treating decayed 

 teeth, is twofold : he either a tempts to arret-t the 

 decay, and repair its ravages ; or he remove* the 

 diseased tooth altogether. These operation*, along 

 with supplying artificial teeth when the natural one* 

 are lost, constitute the main offices of dentistry. 



Scaling. This is a little opeiation, by whicfi the 

 accumulation of a substance termed ' tartar ' is 

 removed from the teeth. Tartar or salivary cal- 

 culus is of different densities and colours, and in a 

 dejKtsit from the saliva. It is most frequently 

 found at the necks of the teeth, and lodges in 

 greatest quantity most commonly behind the lower 

 front -teet b. \\licre it accumulates it is generally 

 accompanied by absorption of the gums, whereby 

 the necks of the teeth are exposed, and they become 

 loosened. Its removal is effected by little hoe- 

 shaped steel instruments, bent in a manner to reach 

 more easily those situations in which the tartar 

 is found. Their mode of use is by inserting the 

 point of any one of them under the free edge of 

 the mass of tartar, at the gum, and lifting it away 

 from the backs of the teeth to which it i- adherent. 

 The teeth are then freed from any particles still 

 sticking about them, and their surface smoothed 

 by being^ rubbed with pumice-powder or chalk. 

 In certain diseased conditions of the structures 

 about the necks of the teeth, considerable purulent 

 discharges occur, and tartar frequently itecomcs 

 largely deposited. 



Regulating. The teeth of the second, or per- 

 manent or adult set, are very liable to le crowded 

 and misplaced, one overlapping the other, or UIOM 

 of the upper jaw falling behind those of the lower 

 when the mouth is closed, thus producing the pro- 

 minent condition of the under jaw denominated 

 4 under-hung.' To remedy these defects, a variety 

 of means have been adopted by dentists ; the prin- 

 ciple upon which all of them act, however, Iwing 

 that of pressing the displaced tooth or teeth into 

 the natural position. This, of course, requires that 

 room or space should exist for them to be thus 

 adjusted ; and where this is not the case, the usual 

 procedure is to remove one or more of the back- 

 teeth, or any others which it is less desirable to 

 preserve. In other cases the dental arch itself is 

 malformed, and may IK- enlarged by regulated 

 pressure so as to afford more accommodation for 

 the teeth, as well as to improve its contour. Siine 

 considerable time is necessary to complete the 

 regulation of misplaced teeth ; and even after they 

 have assumed their proper jtosition, they rebuilt- 

 to be carefully maintained there, otherwise a 

 tendency to K Mime their former irregularity eoon 

 manifests itself. 



Sti>)>imj or Filling. This is one of the most 

 important and delicate n|ierations the dentist has 

 to perform. The first step to U- taken in filling or 

 'stopping' a tooth, is to clear away all deca\ed 

 and dec;>ying substance. For this purpose, a 

 numln'r of slender digging and excavating Meel 

 instruments, termed e\ca\ator,' are required. 

 The 'dental-engine' is another valuable means 

 of preparing the cavity for tilling, and act.* by 

 means of small drills and file-headed point* rapidly 

 rotating, so as to cut away what is desired of 



