Edmund Applebaum

Age Change in the Permanent Upper Canine Teeth

Histologic study of a graded series of sections of human upper permanent canines revealed that age rather than external irritation is primary factor in production of irregular secondary dentin. The amount of irregular secondary dentin in upper canines is noticeably less than that of upper incisors for same age group.

The Epithelial Sheath: Histogenesis and Function

Epithelium is the primary formative tissue of the human tooth. Starting with the stratum germinativum, the epithelium blazes a trail through the connective tissue, organizing itself and the enclosed connective tissue as it outlines the pattern for a particular tooth. It is our purpose to demonstrate that, in a broad sense, this organization of and by the epithelium takes place in 2 individual units-one of which forms the crown, the other, the root of the tooth. The second unit does not begin to function until the first has virtually completed its functioning. The familiar arrangement of the 4 epithelial layers which constitute the enamel organ serves to complete the formation of the hard tissues of the crown of the tooth up to the cervical line, or the cemento-enamel junction. The epithelial sheath serves to outline the form of the root, and further functions to organize the adjacent connective tissue for the formation of odontoblasts and root dentin. The capacity of the epithelial sheath to stimulate root dentin is not manifested until the enamel is completely formed and calcification is well on the way. During the interval of calcification of the enamel matrix, dentin continues its formation within the crown portion of the tooth.

Effects of Thyroidectomy and Thyroid Stimulation on Growing Permanent Dentition of Rhesus Monkeys

Diets were carefully compounded and the animals were observed regularly. Each animal was given 2 or more injections of a 2 per cent solution of Alizarin red S (Coleman & Bell) pre-experimentally, followed by from 1 to 3 injections during the course of experimentation. The dye was injected intraperitoneally. The dosage ranged from 50 to 75 mg. per kilogram of body weight. One red line for each Alizarin injection is formed in the growing dentin and, on sectioning the teeth, these lines are clearly visible under the microscope. By measuring between the lines with a filar eyepiece micrometer the rate of growth, pre-experimental and experimental, was determined on the same animal. (Some animals, as fig. 1 (ABC) shows, were used as, general controls for studying rate of dentin growth). In addition, the Grenz ray was used for studying calcification. Details are listed in the accompanying Table I.

Histologic changes in jaws and teeth of rats following nephritis, adrenalectomy, and cortisone treatment

Abstract We have described the effects of certain systemic alterations on the jaws and teeth of the rat. A loss of supporting bone was observed in the jaws of rats subjected to cortisone alone or adrenalectomy alone. A similar loss of supporting bone was observed in the jaws of rats subjected to a combination of factors—adrenalectomy, antikidney serum, and cortisone. There was also a marked change in the bone pattern of these rats. Certain vascular changes in the pulps of the molar teeth of these rats were described. After adrenalectomy, the pulpal blood vessels were dilated and there was hemorrhage. Rats given cortisone showed dilated blood vessels in the molar pulps. Similar changes were observed in rats which were adrenalectomized and then given cortisone plus antikidney serum. Rats given antikidney serum alone did not show a severe dilation of the pulpal blood vessels. The factors involved in these changes were discussed.

Lymph Channels in Dentine and Enamel Stained by Amalgam

Although it is customary to study the various tissues of a tooth as distinct entities, nevertheless a broad view is obtained only after these separate ideas are correlated and synthesized and the tooth is regarded as a unit. The object of this paper is to present evidence for the conception of the tooth as a vital organ. The difficulty evidently centers around the notion of life and vitality. Perhaps, in passing, we may say that the vitality of a tissue is a matter of degree rather than definition, for the simplest life processes merge imperceptibly into purely physico-chemical phenomena. It is necessary to bear certain facts in mind when thinking of a tooth. First, it is evident that, since the pulp is an end circulatory organ, it can be affected by vascular conditions throughout the body. And as the formative and nutritive organ of the dentine, it stands in vital relationship to the tooth. Another essential matter is the work of Tomes (1). Waldeyer said that Tomes opened the way to a correct interpretation of the nature of the dentine, for he showed that each of the innumerable canals or tubules that permeate the dentine is occupied by a soft fibril, which is continuous with a cell upon the surface of the pulp. Tomes also discovered the granular layer of the dentine that underlies the cementum, and demonstrated the continuance of the dentinal tubules into these spaces. But Tomes did not believe that the enamel is permeated by organic fibers or tubes, and in 1894 wrote:

Discoloration of the teeth in patients with cystic fibrosis of the pancreas: Histologic studies☆

Abstract Detailed histologic studies of teeth obtained from thirty-two patients with cystic fibrosis of the pancreas were undertaken with regard to the presence, distribution, and nature of the peculiar discoloration of the teeth observed in such patients. A yellow discoloration in dentine was usually observed in ground sections of these teeth when viewed by tungsten incandescent light. Fluorescence microscopy of these sections revealed fluorescent patterns which appeared to parallel the yellowish patterns observed under tungsten light. No such abnormalities were discernible in decalcified sections studied under tungsten light.

Grenz Ray Studies of the Calcification of Enamel

V. von Ebner (1906) attempted to classify the changes in enamel from the soft embryonic state to the stone-hard condition it finally reaches. On the basis of its appearance in polarized light he proposed 4 terms to describe the stages of enamel in passing from its original soft condition to the finished, hard state: primary, young, transitional and hard. It may be advisable to discuss some terms especially since they have been used with different meanings or emphasis by many investigators. Thus, development of enamel implies the formative processes associated primarily with cellular activity of the ameloblasts. Calcification on the other hand deals with subsequent processes superposed on development or formation namely, the deposition and precipitation of mineral salts. The calcification of the enamel has been described by Beust (1928) as occurring in several stages. Beust demonstrated this by staining and by x-ray studies. Kitchin confirmed this by polarized light studies, while more recently Chase employed the decalcification method to show that enamel which has just been formed (organic) resists solution in acids. Later on, it is relatively acid soluble. The difference must be due to some transformation taking place after enamel has been deposited by the ameloblasts.

Concerning the Permeability of Human Enamel

For many years considerable discussion has arisen as a result of the work of various investigators concerning the question of enamel permeability. The opinions of these men have been reviewed in recent publications. A thorough and cautious consideration of the evidence presented seems to warrant a belief in the permeability of the enamel. However, this permeability is not a very simple matter, since it involves the question of membrane charge and pore-wall phenomena. Any discussion of the permeability of the enamel must, as a result, take cognizance of its complexity as a membrane structure. It is probably because of the electrical properties of the enamel that many workers have been disappointed in their attempts to force dyes into the structure. Then again, the failure in these experiments was due, possibly, to the fact that the color ion of the organic dye was too large to penetrate the small channels in the enamel. In the experiments described in this paper, the writer tried to delineate by a staining method the channels in enamel through which a salt or water might pass during the process of electroendosmosis. This is simply a movement of water through the pores of a membrane with the application of an electric current. Many considerations are involved in this conception of the enamel membrane. Bechold2 introduces the conception of a membrane by discussing diffusion

Enamel of Shark's Teeth

There is an old controversy among histologists concerning the outer layer of sharks teeth; some claiming that it is enamel, others that it is dentin. A good case can be made out for either side, if the microscope alone is used. But before deciding this question it is necessary that a broad picture be drawn of the process of enamel and dentin formation and calcification, including the paleontologists idea of gradual tissue specialization. Richard Owen (4), was particularly interested in observing the same organ in different animals under every variety of form and function. He first used the terms, homology and analogy. In his monumental work on dental forms in vertebrates he wrote:

Decalcification Versus Mechanical Injury in Caries

The results of the experiments of several workers have indicated a relationship between dental caries production and physical character of the diet. Rosebury, Karshan, and Foley (1) have shown 3 distinct types of experimental dental lesions in rats, all produced with diets containing coarsely ground cereal particles: 1) Beginning in enamel at base of molar fissures, 2) Resulting from fracture of cusp, 3) Beginning in dentin at the cusp summit. Only the first seems comparable to human caries. Four degrees of progress of the fissurecaries lesion have been described, which were later (2) extended to comprise ten stages: 1) Penetration of the enamel diffusely or through enamel lamellae (stage 1), 2) Spread at dentino-enamel junction (stages 2 to 4), 3) Penetration of dentin by infiltration of the tubules and disintegration of the dentin matrix (stages 5 to 7) and 4) Loss of surface continuity and formation of a cavity (stages 8 to 10). These workers have reported that the occurrence of fissure caries seems to be independent of the calcified state of the tooth (1, 2, 3). They stated that: