| THE RELATION OF THE INNER BORDER OF BACTERIAL FILM ON THE TOOTH WITHIN THE GINGIVAL CREVICE TO THE ZONE OF DISINTEGRATING EPITHELIAL ATTACHMENT CUTICLE |
Fig. 9 is a good example of a band of hard calculus, at this time located along the course of the cementoenamel junction. The course of the zdeac conforms to the general course of the inner border of the calculus. Along the middle of the picture the deeper part of the calculus consists of separate knobs or lumps, not so close to the zdeac.
Higher magnification of selected fields permits more accurate presentation of the relation of the zdeac and the inner border of calculus. Although all the specimens were brushed off as described previously, to remove soft cellular and bacterial material, some of them still had enough stained material (bacterial) left on the calculus and in cracks and depressions on it to make the calculus photograph dark.
Several of the specimens were allowed to dry for long periods of time. These were photographed direct or were mounted in Clarite before photographing. Long drying causes surface cracking. Any such cracks shown in these pictures should be disregarded.
In photographing, no attempt was made to orient the picture taken exactly perpendicular or crosswise to the tooth. Some of the fields are at the very bottom of the lesion, but others are at other locations along the quite variable course of the zdeac on such different tooth specimens.
Fig. 10 is a higher magnification of an area on enamel in Fig. 2. Now the
remnants of bacterial film can be seen at protected areas where this was not dislodged by the brushing. Note the ragged outer edge of the zdeac and its projection somewhat between lumps of calculus. Perhaps this indicates that the progressive change and receding apexward is caused or promoted by the encroachment of the continuously building and advancing calculus.
Fig. 11 shows heavier or thicker calculus crowding the zdeac on enamel and corresponds to the fairly early stage of the periodontoclasia disease process.
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| Fig. 9, 10 & 11 |
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Figs. 12 and 13 are further examples of calculus crowding down the zdeac on enamel. In Fig. 12, at left, calculus is advancing toward the zdeac which is giving way to it. Fig. 13 shows the usual gap or space between calculus and the zdeac. Before brushing off, this space is filled with microorganismal material which overlaps the outer border of the zdeac.3
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| Fig. 12, 13 & 14 |
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The rough, knobby calculus crowding down the zdeac is seen at two places, especially in Fig. 16. At the left the calculus was cracked off just above the zdeac. Fig. 17 shows a heavy, thick lump of calculus which is made up of somewhat smooth knobs or bumps. This is not unusual and suggests some different factor or influence in its formation as compared with some other rough surface calculi. The zdeac is heavily stained and shows somewhat the laminated appearance of this (disintegrating) part of the epithelial attachment cuticle from which the epithelial cells had been removed in the disease process.
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| Fig. 15, 16 &17 |
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Fig. 18 shows two lumps of rough-surfaced calculus that have nearly closed in the space between them. The piece on the left has encroached closely upon, and has forced back, the zdeac at this location. In Fig. 19 the space between the inner border of the calculus and the zdeac appears to be of approximately uniform width all along except at one place where a knob of calculus projects and encroaches more upon the zdeac.
In Fig. 20 the inverted V of the zdeac extends high between two thick, well-separated lumps of calculus. At the upper part of the space between these lumps a thin, smaller scale has started to form. In Fig. 21 the inverted V projection of the zdeac between lumps of calculus and the characteristic ragged and jagged appearance of the occlusalward side of the zdeac are shown.
Figs. 22 and 23 show knobs of calculus that have been built onto or into the zdeac which tends to give way at these places especially. One should visualize inflamed crevicular epithelial tissue resting against and constantly irritated by these hard knobs of calculus (foreign material).
Fig. 24 is an example of a condition that is only occasionally seen, in which there is considerable distance from the inner border of the calculus to the zdeac. Although the specimen was brushed off as usual, some remaining fringe of bacterial material can be seen at the edge where it was somewhat protected by the thickness of the calculus. This specimen and field would tend to discount, to some extent, the idea that encroachment of the forming calculus is an essential factor in the shifting, or change apexward, of the location of the zdeac.
Fig. 25 (The apparent white granules in this picture are high lights on the dry specimen and should be disregarded.) shows a well-stained and sharply outlined zdeac with heavy, thick, knobby calculus at quite variable distances from it. The course of the zdeac is influenced, however, by the approaching projections of calculus.
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| Fig. 18 & 19 |
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| Fig. 20 & 21 |
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| Fig. 22, 23 & 24 |
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| Fig. 25, 26 & 27 |
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Fig. 26 shows large lumps or projections of calculus apparently made up of roundish knobs which are smooth on the outer surface. Note the usual depression of the zdeac in advance of the calculus as it builds downward, and the space in the middle where the two large lumps have not yet come together.
Fig. 27 shows thick, rough-surfaced calculus approaching the zdeac all along. At the right side of the picture a large piece of the calculus was cracked off, but a small scale, about in the center of the area, remained. This was firmly attached and considerable force was required to remove it. This is an example of what is likely to happen when large pieces of calculus are torn off by the dentist and the area is not thoroughly cleaned or smoothed. Small pieces such as this, remain and are the nucleus onto which more calculus may be built later.
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Discussion
Almost all adults (and many younger persons) have more or less subgingival calculus on from a few to many of their teeth. In most instances it extends very close to the zdeac, which is always located at the outer border of the receding epithelial attachment. The rough, hard calculus against which the inflamed crevicular epithelial tissue rests not only promotes further progress of' the disease, but it also is very much in the way of effective application of the method of personal oral hygiene which is necessary4 for prevention of lesions and for prevention of further progress of lesions that have already developed.
Successful prevention and control of periodontoclasia, therefore, requires a clear knowledge and application of the information presented in this paper, and in addition information as to the relation of the inner border of bacterial film on the tooth, within the gingival crevice, to the zdeac, which was presented in a previous paper.3 Dental students who do not have the opportunity to examine and study large numbers of specimens prepared as indicated herein simply cannot know and fully comprehend the conditions at the locations where the lesions of this most important disease advance.
Summary
It has been shown that the inner border of subgingival calculus is closely related to the zdeac. In general the course of the zdeac about the tooth parallels that of the advancing calculus.
As the calculus builds and advances apexward the zdeac moves correspondingly, and the space between them tends to be about the same width all the way along.
The constancy of these conditions tends to support the idea of a cause and effect relationship.
References
1. Bass, C. C.: A Demonstrable Line On Extracted Teeth Indicating the Location of the Outer Border of the Epithelial Attachment, J. D. Res. 25: 401, 1946.
2. Bass, C. C., and Fullmer, H. M.: The Location of the Zone of Disintegrating Epithelial Attachment Cuticle in Relation to the Cemento-Enamel Junction and to the Outer Border of the Periodontal Fibers on Some Tooth Specimens, J. D. Res. 27: 623, 1948.
3. Bass, C. C.: The Relation of the Inner Border of Bacterial Film On the Tooth Within the Gingival Crevice to the Zone of Disintegrating Epithelial Attachment Cuticle, Oral. Surg., Oral Med., and Oral Path. 2: 1580, 1949.
4. Bass, C. C.: The Necessary Personal Oral Hygiene for Prevention of Caries and Periodontoclasia, New Orleans M. & S. J. 101: 52, 1948.
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