The comparison of this structure with the dentine of fish-scales signifies the same thing, for in the latter the epidermis is external to the dentine-plates, the hard skeletal structure is in the position of the cutis, not of the cuticle.
In the deeper layers are large spaces, the so-called pulp-cavities leading into narrow canaliculi, the so-called dentine canals.
The structure is {346}looked upon as similar to that of the pulp and dentine canals of many fish-scales.
The scale of enamel gives keenness, the dentine ensures strength, so that the tooth sharpens itself by use, instead of growing dull.
Gnawing wears the dentine much more than the enamel, so that the tooth takes on a bevel resembling that of the chisel which pays frequent visits to a carpenter’s oil-stone.
Defn: A form of dentine which shows sinuous lines of structure in a transverse section of the tooth.
Defn: Pertaining to, or resulting from, the process of growth; as, the incremental lines in the dentine of teeth.
Moreover, the continuous enamel bands on only moderately worn teeth become separated in the final stages of wear into anterior and posterior enamel plates by tracts of dentine that extend toward the crown on the sides of each tooth.
The dentinetracts on the sides of the cheek teeth of Pliogeomys are narrow (see Fig.
But, the enamel cap is thin and the dentine tracts, which are high on the sides of the tooth, are soon revealed by a minimum of wear on the crown.
The enamel investment on the sides of the molariform teeth is interrupted owing to intrusion of tracts of dentine on the sides of each column.
The tracts of dentine of m2 are much narrower than in m1 and the enamel plates are barely separated at the anterolateral margin of the tooth.
A and E), each loop enclosing a core of dentine that had become exposed.
The dentine tracts of m1 are exposed over a relatively wide surface; therefore, the enamel plates are distinctly separated.
Complete enamel plates on the anterior and posterior surfaces are separated by tracts of dentine on the sides of each tooth.
In the molars of modern geomyines, the enamel loop is not continuous but is interrupted on the sides of the crown by vertical tracts of dentine that are exposed at the occlusal surface of the tooth during early stages of wear.
The centre of each tooth is filled with pulp, around which is the bone-like dentine with an outer coat of hard, glossy enamel.
The dentinein many cases partially or completely atrophies, leaving the major part of the scale formed of osseous tissue; such plates often become parts of the internal skeleton.
In the next stage a cap of dentine has become formed, while in the still older tooth this has become covered by a layer of enamel.
A papilla of the dermis makes its appearance, the outer layer of which gradually calcifies to form the dentine and osseous tissue.
In most Teleostei the enamel and dentine layers have disappeared, and the scales are entirely formed of a peculiar calcified tissue developed in the dermis.
Teeth are made up of three different substances, which are known as enamel, dentine and cement.
The dentine is, next to the enamel, the hardest tissue of the tooth, and composes the main body of the tooth.
It merely covers the exposed parts of the teeth of man, but in many animals is intermixed in various ways with the dentine and cement.
The dentine itself has two vertical grooves on each side.
As above mentioned, the dentineis visible on the front of the tooth, since both the cement and the amorphous, calcareous mass are worn away.
The dentine lamellae appear to be identical with what Ray Lankester calls osteodentine.
Anterior tooth conical, with the tip blunt, having been so much abraded that the dentinedoes not extend beyond the coating of cement.
The posterior angle is rounded and the anterior raised into an acute point by the projection of the dentine as a distinct, sharp cusp.
The line of demarcation between cement and dentine is not evident.
Moreover, it is clear that on the front of the tooth the dentine is not covered by enamel.
The tips show what appears to be an inner core of dentine which has been worn down nearly to the cement coating and somewhat fractured.
In this place the outer coating of cement is broken through, showing the underlying dentine or osteo-dentine, which is somewhat corroded or absorbed.
Throughout the tooth the dentine is covered with a very thin layer of shining white enamel.
The dentine at the apex is more nearly white than the cement which surrounds it.
The root is closed, and the apex shows what appears to be a core of dentine surrounded by cement.
The enamel is derived from the outer layer of the embryonic dog-fish, the epiblast, which also gives rise to the epidermis; while the dentine and bony base arise in the underlying mesoblast, the dermis.
Dentine forms the main bulk of the teeth; it is sometimes of the normal type, but generally differs from that in higher vertebrates in being vascular, and is known as vasodentine.
When examined microscopically dentine is seen to be traversed by great numbers of nearly parallel branching tubules which radiate outwards from the pulp-cavity.
In all living forms they are without enamel, consisting merely of dentine and cement, and are never found in the front part of the mouth in the situation occupied by the incisors of other mammals.
The teeth are pointed and often have the dentine remarkably folded.
The exoskeleton of the dogfish is mainly composed of placoid scales, each of which consists of a little bony base imbedded in the skin, bearing a small backwardly-directed spine formed of dentine capped with enamel.
The incisors are composed entirely of dentine and have the form of conical tusks projecting greatly from the mouth.
The external layer of the dental papilla is composed of long nucleated cells, the =odontoblasts=, and it is by these that the dentine is formed.
The dentine of the basal part of the larger teeth is in some genera very greatly folded, causing the structure to be highly complicated.
The body is elongated and closely covered with small scales consisting of dentine enamelled at the surface.
The outer layer of the dermal papilla then gradually becomes converted into dentine and bone, while enamel is developed on the inner side of the Malpighian layer, forming a cap to the scale.
Vasodentine is found below the dentinein Iguanodon.
In all the figures the enamel is black, the pulp white, the dentine represented by horizontal lines, and the cement by dots.
Each tooth, as has been already described, consists of three distinct tissues, dentine and cement of dermal origin, and enamel of epidermal origin.
The grinding teeth are six on each side of the jaw, and are composed of alternate convolutions of enamel, dentine and cement, which wear unequally by the lateral motion of grinding, and so form the necessary inequality of surface.
In the case of the incisors a considerable portion of the crown of each tooth is totally devoid of enamel, and its dentine is also deficient to some extent, so that the teeth are thin, sharp-edged, and of a dirty yellowish color.
At the bottom of this notch the enamel is deficient and the dentine exposed, but there is no irregular pitting, as in stomatitis teeth.
Syphilis only plays the part of a diathetic state profoundly affecting the maternal constitution at the time of dentine development; while these teeth may be due to secondary results of syphilis, they do not demonstrate syphilitic heredity.
The enamel organs of the first set appear during the seventh week of foetal life; the dentine bulb during the ninth week.
This models the enamel cap which fits over the dentine like a glove.
The enamel organs and dentine bulb for the permanent teeth form just before birth (Fig.
Any deviation in size or contour of the permanent teeth from the normal must hence be due to defect in nutrition in the dentine bulb, between the fifteenth and twenty-fifth week of foetal life.
Klein reports, "less than half the enamel, but the greater part of the dentine decalcified.
Klein reports, "a great deal of enamel and the greater part of the dentine decalcified.
The decalcified dentine was now so tender that it was torn into shreds merely by the force of the re-expanding tentacles.
The enamel was not at all, and the dentine only slightly, softened.
The angles or projections of the fibrous basis of the enamel and dentine (except, perhaps, in No.
The enamel anddentine both now somewhat softened; and Dr.
With enamel and dentine (the former of which contains only 4 per cent.
Each ridge consists of a core of dentine surrounded by a coat of enamel.
All Marsupials (except the Wombats) to some extent, and the Macropods especially, are characterised by the prolongation of the tubes of the dentine into the clear enamel.
The pulp becomes inflamed, irregular calcification ensues, and osteo-dentine is formed around the ball.
The pulp then resumes its healthy state and functions, and coats the osteo-dentine enclosing the ball, together with the root of the conical cavity into which the mass projects, with layers of normal ivory.
In the most primitive family, the Thelodontidae,[154] the head and trunk are covered with small scales or tubercles of dentine and not fused into large plates.
The teeth are usually of large plates of dentine covered with enamel, and are present on the pterygo-palatine and splenial bones.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "dentine" in a variety of sentences. We hope that you will now be able to make sentences using this word.
