- Email: [email protected]
The Capillaries of the Enamel and Their Relation to Mottled Teeth*
THE CAPILLARIES OF THE ENAMEL AND THEIR RELATION TO MOTTLED TEETH* By THEODORE B. BEUST.t
HE word capillary, in the sense used in this contribution, means a fine canal, tube or vessel. The supposition that human enamel contains capillaries has heretofore been generally rejected. It is my intention to present evidence of such a nature that a capil larity of this tissue can no longer be a matter of doubt. Some of you may possibly remember that I began work on the enamel capil laries in 1911.1 D. Caush, in 1904,2 through his staining methods and re search, proved that the assumption of von Ebner, in 1880, that enamel con tained tubes was correct. No attention was given contributions to this subject in our country and American textbook writers failed to consider the capillarity, for the simple reason that J. Leon Wil liams, recognized authority on enamel, rejected the views held concerning their
T
*T h is paper is discussed jointly with Dr. Pierle on page 1009. *Read before the Section on H istology, Physiology, Pathology, Bacteriology and Chemistry (Research) at the Sixty-Seventh Annual Session o f the American Dental Asso ciation, Louisville, K y., Sept. 23, 1925. fW o rk in g under grant from the Research Commission o f the American Dental Associa tion. 1. Beust, T . B .: Dent. Cosmos, 54- : 659 (Ju n e) 1912. 2. V ol.
Caush, D .: T r . Fourth Internat. Cong., 1.
Jour. A .D . A., July, 1926
Louisville, Kentucky
presence. In a recent “re-investiga tion,” he has accepted this view, and his latest work3 presents good pictures of the various tubular elements that had previously been described, whereby the investigations of various observers, carried out between 1900 and the date of publication of his article, were dupli cated. Williams, in this reinvestiga tion, adds nothing to what was disclosed in my publication of 1912.1 His array of illustrations, however, will popu larize the subject. Obviously, the mere demonstration of capillaries in the enamel, then, will only permit of profound conclusions, if it can likewise be shown that these capillaries are continuous with the cir culatory sinuses of the organism. Proof of such continuity would automatically ascribe to them biologic functions. Pickerill4 questioned the validity of my experiments which established such proof in 1914, but as Mummery (1922),5 and, later Bodecker (1923)° 3. (A p r il)
Williams, 1925.
J.
L . : J.
Dent.
Res.,
+. Pickerill, H. P .: Dent. Cosmos, 969 (O ct.) 1913.
55:
5. Mummery, J. H .: Brit. Dent. J., +3: 607 (J u ly ) 1922. 6 . Bodecker, C. F .: Permeability Enamel in Relation to Stains, J .A .D .A ., 60 (Jan .) 1923.
980
1
of 0:
5
Beust-Capillaries
of Enamel in Relation to Mottled Teeth
and Malleson ( 1924),7 have since then confirmed my technic, we may consider this part of my first investigation verified. I n a paper read before the Cleveland Session of the American Dental Association,' I made an attempt to show the distribution of the capillary content of the enamel. I displayed two viewsg of a plaster model, which showed their occurrence in parallel segmented rows.
Fig. 1.-Camera
lucida drawing of
the undersurface of the enamel on a
plaster model. A camera lucida drawing of the enamel undersurface in that contribution showed the row segments in cross-section and displayed variously curved lines marking the points of origin. I n 1924," I attempted to demonstrate the result when such 7. Malleson: Ddntal Histology and Bncteriology, 1924. 8. Beust, T. B.: Physiologic Changes in the Structure of the Enamel After Tooth Eruption, J.A.D.A., 1 1 : 396 (May) 1924. 9. Footnote 8, page 398. 10. Beust, T. B.: Dent. Cosmos, 55 : 6 14 (June) 1924.
981
bundles or sheets of tubes were sectioned, and I contended that the striae of Retzius were produced in that way. T h e figure (No. 4) from that contribution, which showed a ring of enamel represented as a transparent object, gives some idea of the tubular distribution. These vessels I regarded as the avenues through which metabolic fluids must course from the pulp to the enamel periphery.
Fig. 2.-Wire
model of a "spiral."
Recent investigations now permit a more detailed description of these parallel rows of capillaries than was at that time possible, and, in addition, render intelligible some of the hitherto obscure phenomena observable in enamel sections. A description of these systems may well begin with the conditions presented at the amelodentinal junction. Figure 1 shows some of the markings found on the undersurface of the labial enamel shell of a central incisor. T h e lines shown represent the "hila."'l As these 1 1. Beust, T. B. : Dent. Summary, 44: 474 (June) 1924.
982
The Journal of the American Dental Association
crevise-like figures admit the vessels, the term hilum appeared appropriate. Two drawings were published in this contri bution. One shows the under surface of the enamel of a third molar. The other shows that each hilum marks the points of entrance of tubes arranged in a row. These radiate as spiral ribbon shaped units (Fig- 2) toward the outer enamel surface, dividing the inner re gions of the enamel into relatively perpendicular plates. The ultimate peripheral distribution of the individual tubal elements of such a ribbon has
Fig. 3.— Spirals seen from the enamel sur face: a, inner or vertical row s; b, outer or horizontal rows.
tinal junction, disposed longitudinally and, at the periphery or enamel surface, it is disposed at right angles to the long axis of the tooth (Fig. 3). As the spiral figures emanating from the hila of adjoining rows thus meet in the outer enamel tissue, we have a series of par allel rows formed which run at right angles to the rows of the inner enamel region. Frequently, these rows are found to be confluent. The external
F ig. 4.— Stereoradiogram o f an in cisor: a, lines (h ila ) showing the points o f origin o f the spiraliform figures; b, horizontal rows form ed by the twist ing o f the figures; c, imbrication lines.
heretofore baffled all attempts at description. It is to the relations of these tubes in the outer regions of the enamel that the following remarks outlet of each series of tubes appears to apply. lie in the valleys between the im In their course toward the enamel brication lines of Pickerill11 (Fig. 4). surface, these spiraliform figures The described turn in the figures ex undergo a peculiar twisting. This turn in the figure is apparently characteristic plains the enamel “whorls,” it being of the enamel of all teeth. At a point assumed that the tubes follow the rods. about midway between the ameloden- These findings are based upon the ob tinal junction and the enamel surface, servation of a large number of sections the elements (tubes) composing the and are supported by facts about to be presented. ribbon, which up to here display con P H O T O M I C R O G R A P H I C E V ID E N C E siderable magnitude, undergo diminu tion in caliber. The figure resulting Although diagrams usually portray from this rotation is, at the ameloden- interpretations better than photographs,
Beust— Capillaries of Enamel in Relation to M ottled Teeth
it is usually very difficult for those not directly engaged with the subject being studied to become oriented. I have, therefore, prepared a number of photo micrographs which will render intelli gible the methods employed and verify the conclusions. In this research, thick cross-sections of enamel, sections vary ing between one-fourth of and the entire enamel covering of the tooth were used. Such relatively opaque ob-
983
The enamel above shown consisted of fragments chipped from dried teeth. The photographs which follow were made from enamel which was never allowed to dry out and which was sub jected to graded concentrations only. We will now consider a series of photographs of an enamel cross-section.
Fig. 5.— Photomicrograph o f the under surface o f labial enamel (trans mitted lig h t ) . •
jects are photographed only with diffi culty. Objectives of low power, with long working distance, must be used. Through their use, it is possible to fol low the tubes in their path through the enamel and catalog the observations by means of the photographic plate. The first photograph (Fig. 5), taken by light transmitted through the entire labial plate of a central incisor, shows some of the hila which were drawn on the plaster model, Figure 1. The next illustration, Figure 6, is a reflectedlight photograph of the same specimen.
Fig. 6.— Specimen shown in Figure 5, by reflected light.
This specimen is mounted between two cover-glasses. Figure 7 shows the lon gitudinal parallel rows as they are seen under the low power of 42 mm. Fig ure 8 gives us a view under the 16 mm. lens. Without moving the preparation, all that lies between the surface here shown and the lower or dentin surface may be studied by simply approximating the lens to the preparation. This was the plan followed in this study. The capillaries were traced in section after
The Journal o f the American Dental Association
Fig. 8.— View (16 m m .) o f parallel rows.
Beust— Capillaries o f Enamel in Relation to M ottled Teeth
section until their definite arrangement was determined beyond question. That
985
which lies far below can be realized from the picture resulting from the
Fig. 9.— Dentin o f the specimen shown in Figure 8, photographed from the enamel side, through the enamel.
Fig.
1 0
.— T he under surface o f the foreg oin g specimen.
one can see and study the space intervening between this surface and that
lowering of the focal plane. (Fig. 9.) This view was made by photographing
986
The Journal of the American Dental Association
through the surface shown in the for mer picture. The view extends down into the dentin, even to the interglobular spaces. The section is now reversed and the former under or dentin surface photographed. Figure 10 shows the nature of the tissue on that side. The
the contained capillaries can be traced from one of the surfaces of the section to the other, and that the parallel rows of hila are not an artefact or that they represent so many cracks. A critical inspection of the dentin surface proves that the specirnen is intact.
Fig. 11.— T he enamel o f the specimen shown in Figure 10, photographed from the dentin side, through the dentin.
focal plane is now transferred, without moving the preparation, to the opposite or enamel side, and an exposure is made through the layer of dentin ex hibited. The result is that the hila shown in the initial photograph become visible (Fig. 11). This series of pho tographs shows that one can photograph through thick sections of enamel; that
In some of these photographs the parallel rows of hila appear continuous. This is not always the case. In Figure 12, long and short hila may be seen. Those appearing continuous are not always so, as the interruption in the segment, owing to the angle at which the tubes leave the dentin, often comes to lie in a shadow.
Beust— Capillaries of Enamel in Relation to M ottled Teeth
In an earlier contribution,11 I contended that the hila were composed of
987
attempt has been made as yet, to my knowledge, to determine their distribu-
Fig. 12.— Long and short “ hila.”
rows of individual tubes. Figure 13 which was taken with the 4 mm. lens, is an example of the tube rows, the ele ments, the tubes, being clearly seen. Near their points of origin, they com municate with one another by means of membranous or thornlike processes. In my 1912 contribution,1photographs of these, the main avenues of capillary flow into the enamel, were shown. The finer avenues were in this article described as “half-moon shaped lines partially enveloping the rods.” Re cently J. Leon Williams dwells on this point. He seems to have over looked my discovery of these canals. Two photographs in his recent work show them beautifully. T H E S P IR A L I F O R M
tion. The problem at first seemed beset with insurmountable difficulties, and it was only by evolving a scheme of graded sectioning that the relations
Fig. 13.— Tubes entering a hilum.
F IG U R E S
Although the spiraliform figures are seen in every specimen of enamel, no
could be definitely ascertained. As I propose to show, they exhibit as much
988
The Journal o f the American Dental Association
consistency in distribution as the fibersleave the hila in alternate rotation, of a muscle. To comprehend their(Fig. 14.) One sheet of tubes is
Fig. 14.— Alternation in direction o f the tubes.
form, the figure of the spiral already shown, which was represented as ema nating at right angles from the long axis of the tooth, must be borne in mind. The capillaries, as may be seen,
Fig. 15.— M odel showing distribution o f the spirals.
directed to the right, the next row to the left. In common with the rods, they leave the dentin in most parts of
Fig. 16— Right and left turns o f the tubes.
Beust— Capillaries o f Enamel in Relation to M ottled Teeth
989
the tooth at an acute angle, as is seen in .Figure 15. By examining this model carefully, it will be seen that the lower half of the lower row of spirals turn to the right, while the upper half of the lower row rotates to the left. The top row ( a) of spirals on this model is
tinuous ribbon. Those leaving the hila above the line are deflected toward the left, while those below are deflected toward the right, as the arrows indi cate. A similar phenomenon is shown in Figure 17. The upper or outer third of the spirals, I should judge, has here
twisted on itself. Both forms are found. We will now see how the photomi crographs agree with these interpreta tions. Figure 16 represents an enamel cross-section. The surface here shown belongs to the inner regions, the tubes being sectioned near their points of ori gin. It will be seen that the capillaries here shown emanate as an almost con
been removed in grinding. The alter nate rotation of the figures is here also evident. The next photograph (Fig. 18) is marked for better orienta tion. On sections of this kind, the tubes can be traced from the surface down to their points of origin at the amelodentinal junction. For example, there is dentin underlying the spirals on this preparation. By lowering the ob-
990
The Journal of the American Dental Association
jective, it is easily seen. Figure 19 preparation, the hila showing through shows this to be the case. It was photo- a layer of dentin.
Fig. 18.— Arrows indicating alternation in capillary distribution.
Fig. 19.— Dentin underlying the enamel shown in Figure 8 (photographed through the enam el).
graphed through the spiraliform figures and is therefore rather blurred. Figure 20 is taken from the dentin side of this
It will now seem probable that the enamel is vascular to an extreme degree. The next photomicrograph
Beust— Capillaries of Enamel in Relation to M ottled Teeth
Fig-. 21.— Capillary distribution (1 6 mm. v ie w ).
992
The Journal o f the American Dental Association
(Fig. 21), taken with the 16 mm. lens, is another exposition of the wealth of
will admit colloidal fluids and, there fore, lymph. Any chemicophysicist will understand what this fact implies. J. Leon Williams is in error in calling these sinuses defects. As they are an
Fig. 24.— Portion o f mm. v ie w ).
the cingulum
(16
integral part of enamel, without them there would be no enamel. Fig. 22.— Naturally mottled teeth, stained with fuchsin.
THE
C A P I L L A R IE S IN TO
capillaries present. The vessels that permeate the enamel in countless sheets
M OTTLED
T H E IR
R E L A T IO N
ENAM EL
In a paper read before the Research Section of the American Dental Asso
Fig. 23.— The cingulum o f the specimen shown in Figure 22.
Beust— Capillaries o f Enamel in Relation to M ottled Teeth
99.3
These facts are opposed to the devel ciation at Dallas,11 my conception of a chemicotraumatic origin of mottled opmental hypothesis entertained by enamel was supported by the following Black, Williams and others. We will now consider some photo histologic observations: 1. The agency causing the lesionmicrographic evidence verifying my enters the enamel from without centri- paper read at Dallas. petally, traverses these capillaries* Figure 22 shows a stained section of
Fig. 25.— An amplification o f the specimen shown in Figure 24.
etches their walls and apparently dilates a mottled incisor. Figure 23 shows its cingulum. Figure 24 is a higher power them. 2. The agency attacks the rod from photomicrograph of the cingulum just the lumen of the capillary, gradually shown and gives a view of a portion in which the healthy tissue mingles with breaking it down. th e mottled tissue, the agency having 3. The lesion can be duplicated ex entered between the rods, through the perimentally by exposing teeth to vari capillaries. ous solutions. Figure 25 shows an amplification of 4. The agency follows the enamel a part of the foregoing. Figure 26 capillaries, reaches and follows the den shows where the agency has penetrated tinal tubules and attacks the interfibril- the morphologically intact enamel and lar dentin or matrix, producing mottling entered the dentin tubules and is attack ing the interfibrillar dentin matrix. of the dentin.
994
The Journal of the American Dental Association
Fig. 27.— An artificially mottled specimen showing a duplication o f phenomena exhibited by the foregoin g.
Beust— Capillaries of Enamel in Relation to Mottled Teeth
Figure 27 shows artificially mottled enamel. The agency has penetrated
995
stratifications seen in longitudinal sections o f enamel. In the sections here
Fig. 28.— Characteristic markings o f the enamel sta in ed /ed with fuchsin.
the morphologically intact enamel and shown, the striae o f Retzius are stained the dentin. By morphologically intact red. The healthy rod substance failed enamel, I mean enamel that still retains to take the stain. As these teeth were
Fig. 29.'— A specimen showing duplication o f the same phenomena.
its form and contours. The rods, o f course, are partially decomposed. Figures 28 and 29 show the familiar
stained in bulk and afterward sectioned, it must be assumed that the stain penetrated the tubes and that the striae are
The Journal of the American Dental Association
996
the sectioned capillary sheets. A like interpretation was advanced by Caush in 1904.
Fig. 30.— Plaster model carv ' after a camera lucida drawing by Dr. A. E. Lang.
E X P E R IM E N T S
W IT H
E T C H IN G
F L U ID S
In further support o f the theories here presented concerning the microstructure o f the enamel, I shall outline the results
o f experiments at etching enamel with acids o f modified concentration. It will be evident that these harmonize with the interpretation regarding the tube distribution. I f enamel is alternately etched with 5 per cent lactic acid and brushed with a soft brush, a peculiar phenomenon is observable. The acid entering the tube sheets attacks the tissue in their imme diate vicinity first, a peculiar ridging resulting, which corresponds to the above outlined distribution o f the sheets. First, we shall study a plaster model (Fig. 30) carved by an assistant after the camera lucida drawing. It will be observed that the model is covered with a series o f furrows. Those forming in the outer regions of the enamel, where the removal o f tissue by the acid has not progressed so far are
Fig. 31.— Photomicrograph o f the original specimen treated (reflected lig h t).
Beust— Capillaries of Enamel in Relation to Mottled Teeth
disposed at right angles to the long axis o f the tooth and may be termed hori-
enamel, the furrows become perpen dicular or longitudinal. A represents the inner regions, nearest the amelodentinal
Fig. sure. Fig. 32.— Appearance margin.
near
the gingival
zontal furrows. As calcification pro ceeds to the deeper regions, we find that the furrows are more deeply scal loped, the scalloping corresponding to the described twist in the spirals. The
997
33.— Appearance at the lingual fis
boundary. A 1 shows the region o f scal loped furrows. B illustrates the tissue in the outer third and C shozus intact enamel, which was protected by wax during the experiment. D represents the dentin, which also displays perpen dicular ridging (longitudinal with the long axis o f the tooth). These mark-
Fig. 34.— Appearance o f the deeper enamel regions (row s now perpendicular).
obliquity increases as the tissue is farther removed until, in the inner onefourth, relatively speaking, o f the
ings exhibited by the dentin will be made the objects o f special study, W e will now see how the photo-
998
The Journal of the American Dental Association
micrographs o f the tooth after which this model was carved agree with this representation. Figure 31 gives a view o f the lingual surface o f the lower second . molar, which was the tooth used in the experi ment. It shows the occlusal third and corresponds to our model. Figure 32
region o f the parallel rows emanating from the hila. C O N C L U S IO N
The new and important points that have been revealed in this research may be briefly expressed as follows: 1. The prevalence o f the capillaries has been determined.
Fig. 35.— Innermost enamel region (perpendicular row s).
is a photomicrograph o f the tissue nearer the gingival margin. In its lower parts, the perpendicular rows (out o f focus) are faintly visible. Figure 33 shows the region o f the lingual fissure. Figure 34 was made with the lens focused on the scalloped furrows, both the scalloped and perpendicular rows being in evidence. Figure 35 shows the innermost part of the enamel, the
2. Their exact mode o f distribu tion has been shown. 3. The arrangement o f the enamel rods in human enamel has been ascer tained, for it must be assumed that the canals follow the rods. 4. The histologic studies have con tributed farther evidence in support o f the view that the agency producing mottled enamel must enter the capil laries from without.
HE word capillary, in the sense used in this contribution, means a fine canal, tube or vessel. The supposition that human enamel contains capillaries has heretofore been generally rejected. It is my intention to present evidence of such a nature that a capil larity of this tissue can no longer be a matter of doubt. Some of you may possibly remember that I began work on the enamel capil laries in 1911.1 D. Caush, in 1904,2 through his staining methods and re search, proved that the assumption of von Ebner, in 1880, that enamel con tained tubes was correct. No attention was given contributions to this subject in our country and American textbook writers failed to consider the capillarity, for the simple reason that J. Leon Wil liams, recognized authority on enamel, rejected the views held concerning their
T
*T h is paper is discussed jointly with Dr. Pierle on page 1009. *Read before the Section on H istology, Physiology, Pathology, Bacteriology and Chemistry (Research) at the Sixty-Seventh Annual Session o f the American Dental Asso ciation, Louisville, K y., Sept. 23, 1925. fW o rk in g under grant from the Research Commission o f the American Dental Associa tion. 1. Beust, T . B .: Dent. Cosmos, 54- : 659 (Ju n e) 1912. 2. V ol.
Caush, D .: T r . Fourth Internat. Cong., 1.
Jour. A .D . A., July, 1926
Louisville, Kentucky
presence. In a recent “re-investiga tion,” he has accepted this view, and his latest work3 presents good pictures of the various tubular elements that had previously been described, whereby the investigations of various observers, carried out between 1900 and the date of publication of his article, were dupli cated. Williams, in this reinvestiga tion, adds nothing to what was disclosed in my publication of 1912.1 His array of illustrations, however, will popu larize the subject. Obviously, the mere demonstration of capillaries in the enamel, then, will only permit of profound conclusions, if it can likewise be shown that these capillaries are continuous with the cir culatory sinuses of the organism. Proof of such continuity would automatically ascribe to them biologic functions. Pickerill4 questioned the validity of my experiments which established such proof in 1914, but as Mummery (1922),5 and, later Bodecker (1923)° 3. (A p r il)
Williams, 1925.
J.
L . : J.
Dent.
Res.,
+. Pickerill, H. P .: Dent. Cosmos, 969 (O ct.) 1913.
55:
5. Mummery, J. H .: Brit. Dent. J., +3: 607 (J u ly ) 1922. 6 . Bodecker, C. F .: Permeability Enamel in Relation to Stains, J .A .D .A ., 60 (Jan .) 1923.
980
1
of 0:
5
Beust-Capillaries
of Enamel in Relation to Mottled Teeth
and Malleson ( 1924),7 have since then confirmed my technic, we may consider this part of my first investigation verified. I n a paper read before the Cleveland Session of the American Dental Association,' I made an attempt to show the distribution of the capillary content of the enamel. I displayed two viewsg of a plaster model, which showed their occurrence in parallel segmented rows.
Fig. 1.-Camera
lucida drawing of
the undersurface of the enamel on a
plaster model. A camera lucida drawing of the enamel undersurface in that contribution showed the row segments in cross-section and displayed variously curved lines marking the points of origin. I n 1924," I attempted to demonstrate the result when such 7. Malleson: Ddntal Histology and Bncteriology, 1924. 8. Beust, T. B.: Physiologic Changes in the Structure of the Enamel After Tooth Eruption, J.A.D.A., 1 1 : 396 (May) 1924. 9. Footnote 8, page 398. 10. Beust, T. B.: Dent. Cosmos, 55 : 6 14 (June) 1924.
981
bundles or sheets of tubes were sectioned, and I contended that the striae of Retzius were produced in that way. T h e figure (No. 4) from that contribution, which showed a ring of enamel represented as a transparent object, gives some idea of the tubular distribution. These vessels I regarded as the avenues through which metabolic fluids must course from the pulp to the enamel periphery.
Fig. 2.-Wire
model of a "spiral."
Recent investigations now permit a more detailed description of these parallel rows of capillaries than was at that time possible, and, in addition, render intelligible some of the hitherto obscure phenomena observable in enamel sections. A description of these systems may well begin with the conditions presented at the amelodentinal junction. Figure 1 shows some of the markings found on the undersurface of the labial enamel shell of a central incisor. T h e lines shown represent the "hila."'l As these 1 1. Beust, T. B. : Dent. Summary, 44: 474 (June) 1924.
982
The Journal of the American Dental Association
crevise-like figures admit the vessels, the term hilum appeared appropriate. Two drawings were published in this contri bution. One shows the under surface of the enamel of a third molar. The other shows that each hilum marks the points of entrance of tubes arranged in a row. These radiate as spiral ribbon shaped units (Fig- 2) toward the outer enamel surface, dividing the inner re gions of the enamel into relatively perpendicular plates. The ultimate peripheral distribution of the individual tubal elements of such a ribbon has
Fig. 3.— Spirals seen from the enamel sur face: a, inner or vertical row s; b, outer or horizontal rows.
tinal junction, disposed longitudinally and, at the periphery or enamel surface, it is disposed at right angles to the long axis of the tooth (Fig. 3). As the spiral figures emanating from the hila of adjoining rows thus meet in the outer enamel tissue, we have a series of par allel rows formed which run at right angles to the rows of the inner enamel region. Frequently, these rows are found to be confluent. The external
F ig. 4.— Stereoradiogram o f an in cisor: a, lines (h ila ) showing the points o f origin o f the spiraliform figures; b, horizontal rows form ed by the twist ing o f the figures; c, imbrication lines.
heretofore baffled all attempts at description. It is to the relations of these tubes in the outer regions of the enamel that the following remarks outlet of each series of tubes appears to apply. lie in the valleys between the im In their course toward the enamel brication lines of Pickerill11 (Fig. 4). surface, these spiraliform figures The described turn in the figures ex undergo a peculiar twisting. This turn in the figure is apparently characteristic plains the enamel “whorls,” it being of the enamel of all teeth. At a point assumed that the tubes follow the rods. about midway between the ameloden- These findings are based upon the ob tinal junction and the enamel surface, servation of a large number of sections the elements (tubes) composing the and are supported by facts about to be presented. ribbon, which up to here display con P H O T O M I C R O G R A P H I C E V ID E N C E siderable magnitude, undergo diminu tion in caliber. The figure resulting Although diagrams usually portray from this rotation is, at the ameloden- interpretations better than photographs,
Beust— Capillaries of Enamel in Relation to M ottled Teeth
it is usually very difficult for those not directly engaged with the subject being studied to become oriented. I have, therefore, prepared a number of photo micrographs which will render intelli gible the methods employed and verify the conclusions. In this research, thick cross-sections of enamel, sections vary ing between one-fourth of and the entire enamel covering of the tooth were used. Such relatively opaque ob-
983
The enamel above shown consisted of fragments chipped from dried teeth. The photographs which follow were made from enamel which was never allowed to dry out and which was sub jected to graded concentrations only. We will now consider a series of photographs of an enamel cross-section.
Fig. 5.— Photomicrograph o f the under surface o f labial enamel (trans mitted lig h t ) . •
jects are photographed only with diffi culty. Objectives of low power, with long working distance, must be used. Through their use, it is possible to fol low the tubes in their path through the enamel and catalog the observations by means of the photographic plate. The first photograph (Fig. 5), taken by light transmitted through the entire labial plate of a central incisor, shows some of the hila which were drawn on the plaster model, Figure 1. The next illustration, Figure 6, is a reflectedlight photograph of the same specimen.
Fig. 6.— Specimen shown in Figure 5, by reflected light.
This specimen is mounted between two cover-glasses. Figure 7 shows the lon gitudinal parallel rows as they are seen under the low power of 42 mm. Fig ure 8 gives us a view under the 16 mm. lens. Without moving the preparation, all that lies between the surface here shown and the lower or dentin surface may be studied by simply approximating the lens to the preparation. This was the plan followed in this study. The capillaries were traced in section after
The Journal o f the American Dental Association
Fig. 8.— View (16 m m .) o f parallel rows.
Beust— Capillaries o f Enamel in Relation to M ottled Teeth
section until their definite arrangement was determined beyond question. That
985
which lies far below can be realized from the picture resulting from the
Fig. 9.— Dentin o f the specimen shown in Figure 8, photographed from the enamel side, through the enamel.
Fig.
1 0
.— T he under surface o f the foreg oin g specimen.
one can see and study the space intervening between this surface and that
lowering of the focal plane. (Fig. 9.) This view was made by photographing
986
The Journal of the American Dental Association
through the surface shown in the for mer picture. The view extends down into the dentin, even to the interglobular spaces. The section is now reversed and the former under or dentin surface photographed. Figure 10 shows the nature of the tissue on that side. The
the contained capillaries can be traced from one of the surfaces of the section to the other, and that the parallel rows of hila are not an artefact or that they represent so many cracks. A critical inspection of the dentin surface proves that the specirnen is intact.
Fig. 11.— T he enamel o f the specimen shown in Figure 10, photographed from the dentin side, through the dentin.
focal plane is now transferred, without moving the preparation, to the opposite or enamel side, and an exposure is made through the layer of dentin ex hibited. The result is that the hila shown in the initial photograph become visible (Fig. 11). This series of pho tographs shows that one can photograph through thick sections of enamel; that
In some of these photographs the parallel rows of hila appear continuous. This is not always the case. In Figure 12, long and short hila may be seen. Those appearing continuous are not always so, as the interruption in the segment, owing to the angle at which the tubes leave the dentin, often comes to lie in a shadow.
Beust— Capillaries of Enamel in Relation to M ottled Teeth
In an earlier contribution,11 I contended that the hila were composed of
987
attempt has been made as yet, to my knowledge, to determine their distribu-
Fig. 12.— Long and short “ hila.”
rows of individual tubes. Figure 13 which was taken with the 4 mm. lens, is an example of the tube rows, the ele ments, the tubes, being clearly seen. Near their points of origin, they com municate with one another by means of membranous or thornlike processes. In my 1912 contribution,1photographs of these, the main avenues of capillary flow into the enamel, were shown. The finer avenues were in this article described as “half-moon shaped lines partially enveloping the rods.” Re cently J. Leon Williams dwells on this point. He seems to have over looked my discovery of these canals. Two photographs in his recent work show them beautifully. T H E S P IR A L I F O R M
tion. The problem at first seemed beset with insurmountable difficulties, and it was only by evolving a scheme of graded sectioning that the relations
Fig. 13.— Tubes entering a hilum.
F IG U R E S
Although the spiraliform figures are seen in every specimen of enamel, no
could be definitely ascertained. As I propose to show, they exhibit as much
988
The Journal o f the American Dental Association
consistency in distribution as the fibersleave the hila in alternate rotation, of a muscle. To comprehend their(Fig. 14.) One sheet of tubes is
Fig. 14.— Alternation in direction o f the tubes.
form, the figure of the spiral already shown, which was represented as ema nating at right angles from the long axis of the tooth, must be borne in mind. The capillaries, as may be seen,
Fig. 15.— M odel showing distribution o f the spirals.
directed to the right, the next row to the left. In common with the rods, they leave the dentin in most parts of
Fig. 16— Right and left turns o f the tubes.
Beust— Capillaries o f Enamel in Relation to M ottled Teeth
989
the tooth at an acute angle, as is seen in .Figure 15. By examining this model carefully, it will be seen that the lower half of the lower row of spirals turn to the right, while the upper half of the lower row rotates to the left. The top row ( a) of spirals on this model is
tinuous ribbon. Those leaving the hila above the line are deflected toward the left, while those below are deflected toward the right, as the arrows indi cate. A similar phenomenon is shown in Figure 17. The upper or outer third of the spirals, I should judge, has here
twisted on itself. Both forms are found. We will now see how the photomi crographs agree with these interpreta tions. Figure 16 represents an enamel cross-section. The surface here shown belongs to the inner regions, the tubes being sectioned near their points of ori gin. It will be seen that the capillaries here shown emanate as an almost con
been removed in grinding. The alter nate rotation of the figures is here also evident. The next photograph (Fig. 18) is marked for better orienta tion. On sections of this kind, the tubes can be traced from the surface down to their points of origin at the amelodentinal junction. For example, there is dentin underlying the spirals on this preparation. By lowering the ob-
990
The Journal of the American Dental Association
jective, it is easily seen. Figure 19 preparation, the hila showing through shows this to be the case. It was photo- a layer of dentin.
Fig. 18.— Arrows indicating alternation in capillary distribution.
Fig. 19.— Dentin underlying the enamel shown in Figure 8 (photographed through the enam el).
graphed through the spiraliform figures and is therefore rather blurred. Figure 20 is taken from the dentin side of this
It will now seem probable that the enamel is vascular to an extreme degree. The next photomicrograph
Beust— Capillaries of Enamel in Relation to M ottled Teeth
Fig-. 21.— Capillary distribution (1 6 mm. v ie w ).
992
The Journal o f the American Dental Association
(Fig. 21), taken with the 16 mm. lens, is another exposition of the wealth of
will admit colloidal fluids and, there fore, lymph. Any chemicophysicist will understand what this fact implies. J. Leon Williams is in error in calling these sinuses defects. As they are an
Fig. 24.— Portion o f mm. v ie w ).
the cingulum
(16
integral part of enamel, without them there would be no enamel. Fig. 22.— Naturally mottled teeth, stained with fuchsin.
THE
C A P I L L A R IE S IN TO
capillaries present. The vessels that permeate the enamel in countless sheets
M OTTLED
T H E IR
R E L A T IO N
ENAM EL
In a paper read before the Research Section of the American Dental Asso
Fig. 23.— The cingulum o f the specimen shown in Figure 22.
Beust— Capillaries o f Enamel in Relation to M ottled Teeth
99.3
These facts are opposed to the devel ciation at Dallas,11 my conception of a chemicotraumatic origin of mottled opmental hypothesis entertained by enamel was supported by the following Black, Williams and others. We will now consider some photo histologic observations: 1. The agency causing the lesionmicrographic evidence verifying my enters the enamel from without centri- paper read at Dallas. petally, traverses these capillaries* Figure 22 shows a stained section of
Fig. 25.— An amplification o f the specimen shown in Figure 24.
etches their walls and apparently dilates a mottled incisor. Figure 23 shows its cingulum. Figure 24 is a higher power them. 2. The agency attacks the rod from photomicrograph of the cingulum just the lumen of the capillary, gradually shown and gives a view of a portion in which the healthy tissue mingles with breaking it down. th e mottled tissue, the agency having 3. The lesion can be duplicated ex entered between the rods, through the perimentally by exposing teeth to vari capillaries. ous solutions. Figure 25 shows an amplification of 4. The agency follows the enamel a part of the foregoing. Figure 26 capillaries, reaches and follows the den shows where the agency has penetrated tinal tubules and attacks the interfibril- the morphologically intact enamel and lar dentin or matrix, producing mottling entered the dentin tubules and is attack ing the interfibrillar dentin matrix. of the dentin.
994
The Journal of the American Dental Association
Fig. 27.— An artificially mottled specimen showing a duplication o f phenomena exhibited by the foregoin g.
Beust— Capillaries of Enamel in Relation to Mottled Teeth
Figure 27 shows artificially mottled enamel. The agency has penetrated
995
stratifications seen in longitudinal sections o f enamel. In the sections here
Fig. 28.— Characteristic markings o f the enamel sta in ed /ed with fuchsin.
the morphologically intact enamel and shown, the striae o f Retzius are stained the dentin. By morphologically intact red. The healthy rod substance failed enamel, I mean enamel that still retains to take the stain. As these teeth were
Fig. 29.'— A specimen showing duplication o f the same phenomena.
its form and contours. The rods, o f course, are partially decomposed. Figures 28 and 29 show the familiar
stained in bulk and afterward sectioned, it must be assumed that the stain penetrated the tubes and that the striae are
The Journal of the American Dental Association
996
the sectioned capillary sheets. A like interpretation was advanced by Caush in 1904.
Fig. 30.— Plaster model carv ' after a camera lucida drawing by Dr. A. E. Lang.
E X P E R IM E N T S
W IT H
E T C H IN G
F L U ID S
In further support o f the theories here presented concerning the microstructure o f the enamel, I shall outline the results
o f experiments at etching enamel with acids o f modified concentration. It will be evident that these harmonize with the interpretation regarding the tube distribution. I f enamel is alternately etched with 5 per cent lactic acid and brushed with a soft brush, a peculiar phenomenon is observable. The acid entering the tube sheets attacks the tissue in their imme diate vicinity first, a peculiar ridging resulting, which corresponds to the above outlined distribution o f the sheets. First, we shall study a plaster model (Fig. 30) carved by an assistant after the camera lucida drawing. It will be observed that the model is covered with a series o f furrows. Those forming in the outer regions of the enamel, where the removal o f tissue by the acid has not progressed so far are
Fig. 31.— Photomicrograph o f the original specimen treated (reflected lig h t).
Beust— Capillaries of Enamel in Relation to Mottled Teeth
disposed at right angles to the long axis o f the tooth and may be termed hori-
enamel, the furrows become perpen dicular or longitudinal. A represents the inner regions, nearest the amelodentinal
Fig. sure. Fig. 32.— Appearance margin.
near
the gingival
zontal furrows. As calcification pro ceeds to the deeper regions, we find that the furrows are more deeply scal loped, the scalloping corresponding to the described twist in the spirals. The
997
33.— Appearance at the lingual fis
boundary. A 1 shows the region o f scal loped furrows. B illustrates the tissue in the outer third and C shozus intact enamel, which was protected by wax during the experiment. D represents the dentin, which also displays perpen dicular ridging (longitudinal with the long axis o f the tooth). These mark-
Fig. 34.— Appearance o f the deeper enamel regions (row s now perpendicular).
obliquity increases as the tissue is farther removed until, in the inner onefourth, relatively speaking, o f the
ings exhibited by the dentin will be made the objects o f special study, W e will now see how the photo-
998
The Journal of the American Dental Association
micrographs o f the tooth after which this model was carved agree with this representation. Figure 31 gives a view o f the lingual surface o f the lower second . molar, which was the tooth used in the experi ment. It shows the occlusal third and corresponds to our model. Figure 32
region o f the parallel rows emanating from the hila. C O N C L U S IO N
The new and important points that have been revealed in this research may be briefly expressed as follows: 1. The prevalence o f the capillaries has been determined.
Fig. 35.— Innermost enamel region (perpendicular row s).
is a photomicrograph o f the tissue nearer the gingival margin. In its lower parts, the perpendicular rows (out o f focus) are faintly visible. Figure 33 shows the region o f the lingual fissure. Figure 34 was made with the lens focused on the scalloped furrows, both the scalloped and perpendicular rows being in evidence. Figure 35 shows the innermost part of the enamel, the
2. Their exact mode o f distribu tion has been shown. 3. The arrangement o f the enamel rods in human enamel has been ascer tained, for it must be assumed that the canals follow the rods. 4. The histologic studies have con tributed farther evidence in support o f the view that the agency producing mottled enamel must enter the capil laries from without.