Molars Sentence Examples
These three are therefore reckoned as milk-molars, and their successors as premolars, while the last three correspond to the true molars of other mammals.
Molars in general characters resembling those of Sarcophilus, but of more simple form, the cusps being less distinct and not so sharply pointed.
In the upper molars the two outer columns or tubercles of the primitive tubercular molar coalesce to form an outer wall, from which proceed two crescentic transverse crests, the connexion between the crests and the wall being slight or imperfect, and the crests themselves sometimes tubercular.
In Europe the group is represented by the long-known and typical genus Lophiodon with three premolars in each jaw, of which the upper are simpler than the molars.
In the New World the porcupines are represented by the members of the family Erethizontidae, or Coendidae, which have rooted molars, complete collar-bones.Advertisement
The teeth are usually differentiated into incisors, canines and molars.
The lower molars resemble generally those of the upper jaw, but are narrower.
The skull itself is elongated, with comparatively simple and primitive molars, the latter being relatively short.
In India also occurs Hippohyus distinguished by the extremely complicated structure of its molars.
In the European Miocene we have Hyotherium and Palaeochoerus, and in the Upper Oligocene Propalaeochoerus, which have square molars without any tendency to a selenodont structure in their cusps.Advertisement
Choeropotamus is a European Oligocene genus with bunodont molars which show a conspicuous basal cingulum in the lower dentition; the first premolar is absent.
In the European Miocene Listriodon, which also occurs in the Indian Tertiaries, the molars have a pair of transverse ridges, like those of the proboscidean Dinotherium; but the genus is believed to be related to the Oligocene Doliochoerus and Choerotherium, in which these teeth show a more normal type of structure.
The premolars and molars may be rooted or rootless, with tuberculated or laminated crowns, and are arranged in an unbroken series.
The mouth is divided into two cavities communicating by a narrow orifice, the anterior one containing the incisors and the posterior the molars, the hairy skin of the face being continued inwards behind the incisors.
In this the crowns of the molars are more or less shortened, with their cusps either arranged in longitudinal lines, or forming four upper and three lower more or less distinct oblique ridges.Advertisement
The Nannosciurinae, or second sub-family of Sciuridae, are represented only by the pigmy squirrels (Nannosciurus), characterized by their very short-crowned molars (which approximate to those of dormice in structure) and small premolars, of which the first upper pair is often deciduous, while the upper molars have only three oblique ridges.
The second section, Castoroidea, of the present group includes only the family Castoridae, represented by the beavers, which are large aquatic rodents characterized by their massive skulls, devoid of post-orbital processes, with the angle of the lower jaw rounded, the molars rootless or semi-rooted, with re-entering enamel-folds, and one pair of premolars above and below.
The well-known Indian palm-squirrel, Funambulus palmarum, typifies an Indo-Malay genus allied to Xerus in skull-characters but with molars more like those of Sciurus.
The upper molars are subequal, each with one internal and two external.
The dentition includes one pair of premolars above and below, and rooted or rootless molars with but few enamel folds.Advertisement
Perognathus and Heteromys have rooted molars; the latter genus is distinguished by the presence of flattened spines among the fur, and has species extending into South America.
In general habits and appearance these animals recall large jerboas, from which group they are, however, distinguished by the four pairs of rooted cheek-teeth, the premolars being as large as the molars, and the latter having one outer and one inner enamel-fold.
In the dormice, forming the section Myoxidea, with the single family Gliridae (or Myoxidae), a single pair of premolars may or may not be present; the molars are short-crowned and rooted, with transverse From de Winton.
The Dipodinae, on the other hand, are leaping rodents, with the metatarsals elongated, a small upper premolar present or absent, and the crowns of the molars tall.
The Spalacidae are burrowing types, allied apparently to the ancestral Jaculidae, and characterized by the second and third molars being equal in size, the presence of enamel-folds in all these teeth, and the superiority in size of the claws of the second, third and fourth front toes over the other two.Advertisement
The genus Nesocia is like Mus, but with the incisors and molars broader, and the transverse laminae of the latter more clearly defined.
Australia is the home of the group of jumping species, known as jerboa-rats, characterized by the elongation of the hind limbs, arranged under the genera Notomys, Dipodillus, Ammomys and Conilurus, distinguished from one another by the structure of the molars and the number of teats and foot-pads, the second being further characterized by its long ears.
Here also may be noticed the huge Philippine long-haired rats of the genus Phlaeomys, characterized by their broad incisors, transversely laminated molars and large claws.
There are three pairs of rooted molars, whose crowns carry transverse plates, decreasing in number from three in the first to one in the last tooth.
The last representatives of the Muridae are confined to Australasia and the Philippines, and constitute the sub-family Hydromyinae, characterized by the very general presence of only two pairs of molars in each jaw.
In the typical Australian and Papuan Hydromys, locally known as water-rats, the molars originally have transverse ridges, the enamel folds between which form cutting edges whose sharpness depends upon the degree to which the teeth have been worn, while the large hind feet are webbed.
Still less specialized are Chrotomys and Xeromys, which include Philippine land-rats, while Crunomys, from the sane area, retains the third molars, and thus connects the group with the Murinae.
Finally, the Philippine Rhynchornys is represented by a rat with two pairs of molars and a long shrew-like nose, the zygomatic arch of the skull being also placed unusually far backward.
At least one pair of premolars is present in each jaw; and these teeth and the molars typically have one outer and one inc_e.
Fore-feet with four digits, hind-feet with three; clavicles imperfect; molars divided by enamel-folds into transverse lobes; milk-teeth shed before birth.
The jugal is without an inferior angle, and extends forwards to the lachrymal; the palate is contracted in front and deeply emarginate behind; the incisors are short, and the molars divided by continuous folds into transverse plates; and the two halves of the lower jaw are welded together in front.
Aconaemys is an allied Chilean genus in which the enamel-folds meet across the molars.
Skull depressed, frontals contracted and without post-orbital processes; p.; or; molars rootless, with transverse enamel-folds.
In America, Paramys, with transversely ridged molars, is allied; and the European Sciuromys should perhaps find a place in the same neighbourhood.
A more advanced phase is represented in the European Lower Oligocene by the Pseudosciuridae, with the genera Pseudosciurus, Sciuroides, Trechomys, Theridomys, &c., in which part of the masseter passes through the broad infra-orbital canal, and the premolars are; the molars being low-crowned, many-rooted and either cusped or ridged.
In general dental characters, especially the retention of three pairs of molars, this genus approximates to the Leporidae, although in the absence of post-orbital processes and the pattern of the molars it departs less widely from the modern Ochotonidae than does Prolagus.
The canine was like a premolar, and in contact with the first tooth of that series; and the cheek-teeth were short-crowned, with the premolar simpler than the molars, and a third lobe to the last lower tooth of the latter series.
The earlier forms had the full series of 44 teeth, with the premolars simpler than the molars; but in the later types the canines and some of the incisors disappear, and at least the hinder premolars become molar-like.
The upper jaw is apparently destitute of incisor and canine teeth, but possesses five molars on each side, with a corresponding number in the jaw beneath.
The molars, and more especially the last, are smaller and simpler than in the pigs of the genus Sus, but the peculiarity of this genus is the extraordinary development of the canines, or tusks, of the male.
The cheek-teeth are low-crowned, with the external cones of the upper molars fused into a W-like outer wall, and the inner ones retaining a regular conical form; while in the lower teeth the crown is formed of crescentic ridges, of which there are three in the last and two each in the other teeth.
Titanotherium, of the Oligocene of the Dakotas and neighbouring districts, was a huge beast, with the hinder upper premolars similar in character to the molars, a pair of horn-cores, arising from the maxilla, overhanging the nose-cavity, four front and three hind toes, only twenty dorso-lumbar vertebrae, and an almost continuous and unbroken series of teeth, in which the canines are short; the dental formula being i.
The skull, which has a longer face than in Titanotherium, lacks horn-cores, while all the upper premolars are simpler than the molars, and the full series of 44 teeth was present.
The first of these is the common shoa 1 tailed field-mouse, or "field-vole," Microtus agrestis, which belongs to the typical section of the type genus, and M S is about the size of a 343 mouse, with a short stumpy body, and a Upper and Lower Molars of the Water-Rat tail about one-third the (or Water-Vole), Microtus amphibius.
On account of an important difference in the structure of its molars, it is now very generally referred to a distinct genus, under the name of Evotomys glareolus; these teeth developing roots at a certain stage of existence, instead of growing permanently.
Fossil voles from the Pliocene of England and Italy with molars which are rooted as soon as developed form the genus Mimomys.
As a general rule, the molars, and more especially the first, are partially brachyodont (short-crowned); although they are taller in the chital (Cervus axis).
As we descend in the geological series the deer have simpler antlers, as in the European Miocene Dicrocerus; while in the Oligocene Amphitragulus, Dremotherium and Palaeomeryx, constituting the family Palaeomerycidae, antlers were absent, and the crowns of the molars so low that the whole depth of the hollows between the crescentic columns is completely visible.
As a rule the molars are tall-crowned (hypsodont).
The crowns of the molars belong to the crescentic or selenodont type, and are tall-crowned or hypsodont; but one or more of the anterior premolars is usually detached from the series, and of simple pointed form.
The teeth of the cheek-series which are in contact with each other consist of two small premolars (the first almost rudimentary) and three broad molars, constructed generally like those of Camelus.
Next to the latter is a curved, sub-erect canine, followed after an interval by an isolated minute and often deciduous simple conical premolar; then a contiguous series of one premolar and three molars, which differ from those of recent species of Camelus in having a small accessory column at the anterior outer edge.
The dentition comprises the typical 44 teeth, of which the molars are short-crowned, with four crescentic cusps on those of the upper jaw (selenodont type).
The molars are less completely selenodont than in the type genus.
Homacodon was an animal of the size of a rabbit, with five toes (of which only five were functional to each foot) and 44 teeth, of which the molars are tuberculated (bunodont), with six columns on those of the upper jaw; the premolars being of a cutting type.
The dental formula, when completely developed, is incisors i, canines o, premolars 31 molars - on each side, giving a total of 34 teeth.
The last premolar and the molars have quadrate crowns, provided with two strong transverse ridges, or with four obtuse cusps.
In Macropus giganteus and its immediate allies, the premolars and sometimes the first molar are shed, so that in old examples only the two posterior molars and the incisors are found in place.
The milk-dentition, as in other marsupials, is confined to a single tooth on each side of each jaw, the other molars and incisors being never changed.
The dentition of the kangaroos, functionally considered, thus consists of sharp-edged incisors, most developed near the median line of the mouth, for the purpose of cropping herbage, and ridged or tuberculated molars for crushing.
The molars are usually not longer (from before backwards) than the anterior premolars, and less compressed than in the next section.
The crowns of the molars have two prominent transverse ridges.
They crush or grind the food, and are hence called " molars."
These three, then, are grouped as the " molars."
Of the five teeth between the incisors and molars the most anterior, or the one usually situated close behind the premaxillary suture, very generally assumes a lengthened and pointed form, and constitutes the " canine " of the Carnivora, the tusk of the boar, &c. It is customary, therefore, to call this tooth, whatever its size or form, the " canine."
With regard to the lower teeth the difficulties are greater, owing to the absence of any suture corresponding to that which defines the incisors above; but since the number of the teeth is the same, since the corresponding teeth are preceded by milk-teeth, and since in the large majority of cases it is the fourth tooth of the series which is modified in the same way as the canine (or fourth tooth) of the upper jaw, it is reasonable to adopt the same divisions as with the upper series, and to call the first three, which are implanted in the part of the mandible opposite to the premaxilla, the incisors, the next the canine, the next four the premolars, and the last three the molars.
When, as is the case among nearly all existing mammals with the exception of the members of the genera Sus (pigs), Gymnura (ratshrew), Talpa (moles) and Myogale (desmans) the number of teeth is reduced below the typical forty-four, it appears to be an almost universal rule that if one of the incisors is missing it is the second, or middle one, while the premolars commence to disappear from the front end of the series and the molars from the hinder end.
When there is a marked difference between the premolars and molars of the permanent dentition, the first milk-molar resembles a premolar, while the last has the characters of the posterior molar.
In the specialized forms the premolars tend to become more or less completely like the molars; and, contrary to what obtains among the Carnivora, the whole series of cheek-teeth (with the occasional exception of the first) is very strongly developed.
The peculiar mode of displacement of the teeth from behind forwards in some members of both groups may perhaps indicate a relationship, although in the case of the Sirenia the replacement takes place by means of a succession of similar molars, while in the Proboscidea the molars remain the same numerically, but increase greatly in size and number of transverse ridges."
Moreover, the Szechuen jumping-mouse differs from the typical Zapus by the closer enamel-folds of the molars, the shorter ears, and the white tail-tip, and is therefore made the type of another sub-genus.
The anterior premolars are quite rudimentary, sometimes not developed at all, and generally fall by the time the animal attains maturity, so that there are but six functional cheek teeth, - three that have predecessors in the milk-dentition, and hence are considered as premolars, and three molars, but otherwise, except the first and last of the series, not distinguishable in form or structure.
In Merychippus, on the other hand, the milk-molars have short crowns, without any cement in the hollows, thus resembling the permanent molars of the under-mentioned genus Anchitherium.
The general characteristics of this progenitor of the horses are those given above as distinctive of the group. The cheek-teeth are, however, much simpler than those of Anchitherium; the transverse crests of the upper molars not being fully connected with the outer wall, while the premolars in the upper jaw are triangular, and thus unlike the molars.
In this study, none of the first maxillary molars show occlusal surface caries.
The other ten concluded that there was a lack of evidence to support prophylactic removal of impacted third molars.
He is approximately 29 years old and has few back molars now, but he is able to manage hay.
I haven't visited a dentist in four years (fruit gums extract dodgy molars better than most Harley Street crooks ).
Additionally, cavities were noted on the first and second deciduous molars of one child and were associated with a dental abscess.
Twelve general reviews did not conclude with a clear message about the management of third molars.
The archeological first maxillary molars show an even higher tendency to posses fused roots, especially in female teeth.
Hooks most commonly form on the front edge of the upper first premolars and the back edge of the lower last molars.
It also shows that the anterior molars of elephants do not correspond to the premolars of other ungulates, but to the milk-molars, the early loss of which in consequence of the peculiar process of horizontal forward-moving (From Owen.) FIG.
In elephants there are only two, the last milk-molar and the first true molar (or the third and fourth of the whole series), which are alike in the number of ridges; whereas in mastodons there are three such teeth, the last milk-molar and the first and second molars (or the third, fourth and fifth of the whole series).
Canine very small; a considerable interval between it and the first premolar, which is as long from before backwards but not so broad as the molars, and has a cutting edge, with a smaller parallel inner ridge.
The cheek-teeth are short-crowned, generally with no cement, the upper molars having a W-shaped outer wall, from which proceed two oblique transverse crests, while the lower ones carry two crescents.
In Xerus itself, which is represented by the terrestrial African spiny squirrels, the ears are short, there are only two teats, and flat spines are mingled with the fur; while the skull, and more especially the frontals, is elongated, with a very short post-orbital process, and the crowns of the molars are taller than usual (see Spiny Squirrel).
In the circumpolar Evotomys (represented in England by the red-backed field-mouse) and the nearly allied North American Phenacomys, the molars develop roots in old age; but in Microtus (which includes the water-rat, and is circumpolar) they are rootless throughout life, the genus being' one of the largest in the mammalian class (see Vole).
The masseteric ridge of the lower jaw is obsolete, the palate broad, the incisors long and the molars semi-rooted, with external and internal enamel-folds (see Agouti).
When fully developed, the number of cheek-teeth is, however, seven; and it is probable that, as in placentals, the first four of these are premolars and the remaining three molars, although it was long held that these numbers should P. ? ??
They should pay special attention to the molars, as these teeth have lots of tiny grooves and crevices where food particles can hide.
The points of the molars fit into the grooves of the opposite molars.
Bands encircling the molars also can be used for attachments.
Localized juvenile periodontitis usually affects the molars (back grinding teeth) and incisors.
Pericoronitis is a condition found in children whose molars are in the process of erupting through the gum.
The first permanent teeth, the six-year-molars that become the first permanent molars, erupt behind each of the four second baby molars, usually between the ages of five and six.
Teething (the eruption of the primary teeth through the gums) may cause discomfort or pain, particularly with the large molars.
Eruptions of the permanent teeth are usually much less distressing, although the eruption of the first four broad permanent molars may cause discomfort.
As the permanent molars push through the gums, they often leave a flap of tissue over the tooth.
The points of the molars fit into the grooves of the opposing molars.
Both the baby teeth and the permanent teeth are usually affected, particularly the eight front teeth and the six-year or first molars.
Swelling or infection occurs during eruption of the molars.
Children should get sealants on their first permanent "six-year" molars, which come in between the ages of five and seven, and on the second permanent "12-year" molars, which come in between the ages of 11 and 14.
These teeth are distinguished as "intermediate" molars.
On the other hand, there are those who believe that the functional dentition (other than the replacing premolar and the molars) correspond to the milk-dentition of placentals, and that the rudimentary tooth-germs represent a "prelacteal" dentition.
Premolars compressed, pointed; and the molars with quadrate tuberculated crowns.
The three pairs of molars in each jaw are, like the last premolar, quadritubercular oblong teeth.
In the lower jaw there are also one or two small and early deciduous premolars; third premolars of both jaws formed on the same type as that of the rat-kangaroos, but relatively much larger; molars rudimentary, tubercular.
The broad molars are either bluntly tuberculated or transversely ridged; the outer side of the hind part of the lower jaw has a deep pocket; and the hind-limbs are generally very long, with the structure of the foot similar to that of the bandicoots.
In the more typical Lemuridae there are two pairs of upper incisor teeth, separated by a gap in the middle line; the premolars may be either two or three, but the molars, as in the lower jaw, are always three on each side.
Unlike the early horses, the later premolars are as complex as the molars; and although there is a well-marked gap between the canine and the premolars, there is only a very short one between the former and the incisors.
The full series of forty-four teeth was developed; and the upper molars were short-crowned, or brachyodont, with six low cones, two internal, two intermediate.
There are but three pairs of incisor teeth in each jaw, and the upper molars are tricuspid.
The cheek-teeth (premolars and molars) form a A B C FIG.
There is usually a short gap between the canine and first premolar; the upper molars are short-crowned and transitional between the bunodont (tubercular) and selenodont (crescentic) types, with two outer concave tubercles and two inner conical ones; while the lower molars are crescentic, with three lobes in the last of the series..
Each of the lower molars carries two crescentic ridges.
In the earlier short-crowned forms these teeth are unlike the molars, and the first of the series is separated by a gap from the second.
The upper cheek-teeth are short-crowned and without cement, and show distinct traces of the primitive tubercles; the two outer columns form a more or less complete external wall, connected with the inner ones by a pair of nearly straight transverse crests; and the premolars are originally simpler than the molars.
Outer columns of upper molars similar, the hinder ones not flattened; ridges of lower molars oblique or directly transverse, a third ridge to the last molar in the earlier forms. The Lophiodontidae, which date from the Eocene, come very close to Hyracotherium in the horse-line; and it is solely on the authority of American palaeontologists that the division of these early forms into equoids and tapiroids is attempted.
In North America the earliest representative of the group is Systemodon of the Lower Eocene, in which all the upper premolars are quite simple; while the molars are of a type which would readily develop into that of the modern tapirs, both outer columns being conical and of equal size.
The other upper premolars and molars all formed on the same plan and of nearly the same size, with four roots and quadrate crowns, rather wider transversely than from before backwards, each having four columns, connected by a pair of transverse ridges, anterior and posterior.
Nearly related is the extinct family Lophiodontidae (inclusive of the American Helaletidae), in which both the upper and lower first premolar may be absent, while the upper molars present a more rhinoceros-like form, owing to the lateral compression and consequent lengthening of the outer columns, of which the hinder is bent somewhat inwards and is more or less concave externally, thus forming a more complete outer wall.
Finally, in the Oligocene Colodon the last three upper premolars are like the molars, and the first pair of lower incisors is lost.
As regards the dentition of the existing species, the cheek-series consists of the four premolars and three molars above and below, all in contact and closely resembling each other, except the first, which is much smaller than the rest and often deciduous; the others gradually increasing in size up to the penultimate.
The upper molars present a characteristic pattern of crown, having a much-developed flat or more or less sinuous outer wall, and two transverse ridges running obliquely inwards and backwards from it, terminating internally in conical eminences or columns, and enclosing a deep valley between.
As stated above, the lower molars have the crown formed by a pair of crescents; the last having no third lobe.
It differs from typical rats of the genus Mus by its broader incisors, and the less distinct cusps on the molars.
The tall upper molars have inner columns.
The molars, as in other elephants, are six in number on each side above and below, succeeding each other from before backwards.
The full typical series of 44 teeth was developed in each, but whereas in the Periptychidae the upper molars were bunodont and tritubercular, in the Pantolambdidae they have assumed a selenodont structure.
The primitive Artiodactyla thus probably had the typical number (44) of incisor, canine and molar teeth, brachyodont molars, conical odontoid process, four distinct toes on each foot, with metacarpal, metatarsal and all the tarsal bones distinct, and no frontal appendages.
The upper molars, which may be either selenodont or buno-selenodont, carry five cusps each, instead of the four characteristic of all the preceding groups; and they are all very low-crowned, so as to expose the whole of the valleys between the cusps.
The Dichobunidae include the genus Dichobune, of which the species were small animals with buno-selenodont molars.
Xiphodon and Dichodon represent another type with cutting premolars and selenodont molars; while Caenotherium and Plesiomeryx form yet another branch, with resemblances to the ruminants.
The molars are partially selenodont in the typical genus Anthracotherium, with five cusps, or columns, on the crowns of those of the upper jaw, which are nearly square.
In Ancodon (Hyopotamus) the cusps on the molars are taller, so that the dentition is more decidedly selenodont; the distribution of this genus includes not only Europe, Asia and North Africa, but also Egypt where it occurs in Upper Eocene beds in company with the European genus Rhagatherium, which is nearer Anthracotherium.
On the other hand, in Merycopotamus, of the Lower Pliocene of India and Burma, the upper molars have lost the fifth intermediate cusp of Ancodon; and thus, although highly selenodont, might be easily modified, by a kind of retrograde development, into the trefoil-columned molars of Hippopotamus.
Finally, we have in the Pliocene of India the genus Tetraconodon, remarkable for the enormous size attained by the bluntly conical premolars; as the molars are purely bunodont, this genus seems to be a late and specialized survivor of a primitive type..
These are for the most part large antelopes, with long cylindrical horns, which are present in both sexes, hairy muzzles, no face-glands, long tufted tails and tall thick molars of the ox-type.
The subfamily is characterized by the narrow crowns of the molars, which are similar to those of sheep, and' the hairy muzzle.
These are medium-sized or large antelopes with naked muzzles, narrow sheep-like upper molars, fairly long tails, rudimentary or no face-glands, and pits in the frontal bones of the skull.
The duikers, or duikerboks (Cephalophus), of Africa, which range in size from a large hare to a fallow-deer, typify the subfamily Cephalophinae, characterized by the spike-like horns of the bucks, the elongated aperture of the face-glands, the naked muzzle, the relatively short tail, and the square-crowned upper molars; lateral hoofs being present.
All these are large and generally more or less uniformly coloured antelopes with horns in both sexes, long and more or less hairy tails, high withers, small face-glands, naked muzzles, tall, narrow upper molars, and the absence of pits in the frontal bones.
With the single exception of the Indian sloth-bear, all the species have forty-two teeth, of which the incisors and canines closely resemble those of purely carnivorous mammals; while the molars, and especially the one known as the " sectorial " or " carnassial," have their surfaces tuberculated so as to adapt.
The first and second molars have quadrate crowns, with four principal obtuse conical cusps, around which numerous accessory cusps are clustered.
The milk-dentition, and even the early condition of the permanent dentition, is formed on the same general type as that of Sus, except that certain teeth are absent, the formula being 13 i cl, total 34; but as age advances all the teeth have a tendency to disappear, except the canines and the posterior molars, but these, which in some cases are the only teeth left in the jaws, attain an extraordinary development.
In all cases a more or less full series of teeth is developed, these being differentiated into incisors, canines, premolars and molars, when all are present; but only a single pair of teeth in each jaw has deciduous predecessors.
It may be added that the division of these teeth into premolars and molars in figs.
They are heavily built ruminants, with horns of nearly equal size in both sexes, short tapering tails, large hoofs, narrow goat-like upper molars, and usually small face-glands.