Charles F. Bodecker

Concerning the "Vitality" of the Calcified Dental Tissues

The vitality of the enamel, dentin, and cementum is still an open question. Up to the end of the last century, dental tissues were believed to possess a low degree of vitality and hence were considered subject to systemic metabolic changes. Later, there was a complete reversal of opinion, resulting in the almost general belief that the enamel was an inert, dead structure; some authorities going so far as to include the dentin and the cementum. This point of view seems to carry the non-vitalist conception to the extreme. It is true that both dentin and cementum are composed principally of a matrix, nevertheless cells or cell processes are included in these tissues. The belief that enamel is an inert structure has its justification in the fact that its formative organ is destroyed upon the completion of the crown of the tooth; therefore, no new enamel can be formed. But this fact does not necessarily exclude the possibilities of physical and chemical changes occurring in the enamel after eruption of the tooth. The conception of non-vitality of the dental tissues is slowly undergoing a second reversal, brought about by the observation of the beneficial effect of diet on the teeth. It seems that the entire question of the vitality of the teeth rests upon an exact definition of terms. Churchill (1) presents his conception of the subject in a clear and concise manner. He states: In view of our lack of knowledge concerning vital processes in general, it seems difficult to offer an opinion in a controversy with regard to the vitality of the hard structures of the teeth. And yet, this question is so often the subject of discussion in professional circles that a commitment does not appear out of place.

Odontogenesis of the Rat Molar: Prenatal Stage

THE rat molar has achieved pre-eminence in the field of dental research and at present supersedes the rat incisor in the exploration of the complexities of development and growth. The rat dentition is monophyodont. The molars are teeth of limited growth. There is no formation of enamel over the tips of the cusps so that upon eruption the dentin is exposed.1 They have been successfully used in experimentally induced caries, and have provided material for transplantation4-6 and in vitro studies.711 A chronological table of normal growth and development would be of inestimable assistance in evaluating the results of transplantation and in vitro studies. This information would provide definite stages of normal growth for planning studies and would establish a yardstick for comparison with experimental development. Furthermore, the feasibility of securing material of known age may help resolve some of the intricacies of dental embryology. The process of odontogenesis is continuous from the first invagination of the oral mucosa to the completion of the tooth. To facilitate publication, the report is arbitrarily separated into preand postnatal stages. A complete historical review is available in textbooks, and only where specific aspects of this report are related to the literature will references be given.

Concerning the Vitality of the Calcified Dental Tissues. II The Permeability of Enamel

Previously reported studies (1) in vital staining have established the permeability of dentin and enamel. The passage of stain particles through dentin and enamel of dogs and young human beings was produced by inserting dyes into the dentin or pulp. The particles were transported by a fluid present in the dentin, termed by the authors the dental lymph, which has its origin in the pulp. It is the purpose of this investigation to test the permeability of normal enamel of dogs and human beings from without-inward. The permeability of previously decalcified areas such as incipient caries is not under consideration. In the earlier report (1), the presence of potassium permanganate and other experimentally introduced dyes was demonstrated in the enamel rod sheaths penetrating by way of the dentin, illustrating the permeability of enamel from within-outward (fig. 1). The following report is the result of efforts to determine whether potassium permanganate, silver nitrate or methylene blue can penetrate normal enamel from without-inward. A permeable membrane, generally speaking, permits the passage of substances in both directions, so that one may conceive of, not only the passage of dental lymph into the enamel from the interior, but also the passage of saliva into the enamel and dentin from the surface. Head (2), Pickerill (3), Bunting and Rickert (4), Fish (5), and others suggested that a possible post-eruptive calcification of enamel occurred through the agency of saliva. This was followed by attempts

Cultivation of Rat Molar Tooth Germs in Carrel Flasks. I

HE in vitro culture of tissue is an accepted experimental method which may T be utilized to elucidate problems of growth, differentiation, organizer influence, and function. It has also contributed to studies of malignant cells and the effect of external influences on both normal and pathologic tissue. Tissue culture is concerned with two aspects of growth. Unorganized growth, culturing of a single type of cell, is concerned with survival and proliferation. Organized growth deals with the differentiation of growing tissues and the development of their functional capabilities.1 The in vitro culture of tooth germs is a problem in organized growth. The results of previous investigations of tooth germ culture are both meager and gratifying. The findings verified some existing concepts of dental embryology and made further contributions to the field. Pinkerton and Boyle2 cultured the developing teeth of newborn kittens and observed that the ectoderm and mesoderm grew freely and tended to differentiate. The major contribution to the field was made by Glasstone.3-5 She cultured tooth germs of embryos, which provided sterile tissue from which to dissect the explants. She reported that tooth germs displayed remarkable powers of development. Cultivating rat and rabbit tooth germs, she reported the presence of odontoblasts and dentin formation. In rabbit cultures some enamel had formed. Nuckolls6 and Losee7 cultivated mouse and rat tooth germs. They used the Long and Evans technic to determine the age of the rat embryos. Nuckolls reported a relationship between the enamel organ and the bony crypt. Losee cultured one tooth germ for seventy-eight days and reported that the tissue was viable before fixation. Hay8 is presently culturing tooth germs of mice, and corroborates previous findings. She is also culturing areas of the dental lamina at early stages, and reports development of an incisor with dentin formation on the labial surface. Szabo9 is investigating the growth potency of the cells of the tooth germ by culturing undissected mouse molar tooth germs or the extirpated formative elements of the incisors. He compared fluid media with the hanging drop method and found evidence of differentiation in the enamel epithelium. A preparatory investigation determined the daily progress of growth and development, which established a table of standards for the stages at which the in vitro culture was started. Results of experiments were similarly measured. References to the stage of development and the terminology are those established in the report on the odontogenesis of the rat molar.10

Experimental Papillectomy: Part Ii: Histological Study (Preliminary Report)

INTRODUCTION Transplantation of tooth germs or their elements has long been a subject of experimental investigation (1, 2, 3, 4, 5). Explants have also been grown in vitro (6, 7). The technics of Huggins (4) and Hahn (5) consisted, in part, of transplanting sections of the enamel organ and dental papilla in portions of the body other than the jaws. Glasstone grew whole tooth germs, as well as dissected portions of the enamel organ and dental papilla, in tissue culture. These investigators (4, 5, 6, 7) have established an interrelation between the enamel organ and dental papilla. Their findings reveal that histodifferentiation of odontoblasts occurs only when ameloblasts are present. Thus the initial stimulus for formation of the dental tissues has been shown to be in the enamel epithelium. After differentiation of these two cell layers, the ameloblast apparently loses its ability to influence the formation of the dental papilla and odontoblasts. On transplantation of an isolated dental papilla with odontoblasts, it is capable of independent function in producing dentin. The absence of the enamel epithelium at this time does not impair the normal function of the papilla to form dentin. The ameloblasts, on the other hand, are incapable of independent function. If transplanted alone, they lose their ability to produce enamel. In the absence of the papilla, the enamel organ degenerates into squamous epithelium and forms small cysts. Complete separation of the enamel organ from the already formed enamel is difficult and of questionable value. Tomes process of the ameloblast extends into the young enamel matrix. It is not known whether Tomes process was removed with the enamel organ or remained as part of the young enamel matrix, in the experiments mentioned above. The dependence of the enamel organ on the activity of the dental papilla requires further examination, as does the function of the odontoblasts. Several unsolved problems present themselves. It is known that after formation of the first layer of dentin, the papilla in the area of the odontoblasts is capable of producing dentin without further influ-

Variations in the Lesions and Activity of Dental Caries

It is a common clinical observation that the activity of dental caries varies throughout the different periods of life. Statistics indicate that dental destruction is most active during youth and up to the age of forty. After this time dental caries becomes less and less active and in many persons ceases entirely. Still later, at about the age of fifty or sixty, the teeth of some persons are again affected. The purpose of this paper is to classify dental caries according to the types of lesions and the ages at which they are commonly found. This information may aid in a better comprehension of the mechanism of tooth destruction. In addition to this classification, a changing physical characteristic of the teeth will be discussed which may explain, to a great extent, the reason for the age variations in dental caries.

Tooth Condition, a Factor in Experimental Isotope Absorption

Experiments with radio-active phosphorus have not given uniform results. Differences of opinion still exist concerning a minimal degree of metabolism in the enamel and the role of the pulp in this respect. The reason may be that there is a general tendency to regard all teeth as being closely similar in structure, physical character and physiological activity. The present paper shows evidence that the permeability of the teeth is variable, a quality closely related to physiological phenomena. This physical characteristic is affected by a number of conditions: 1. Tooth age, 2. Type of animal, 3. Degree of attrition, 4. Secondary dentin, 5. Degree of protective metamorphosis, 6. Degree of activity of the dental pulp. The first 4 conditions are known generally to histologists; they are mentioned only briefly so as to present all known factors which may affect the permeability of the teeth. The degree of protective metamorphosis (1) and activity of the dental pulp, however, have received no consideration and will be discussed in detail.

Concerning Defects in the Enamel of Teeth of Ancient American Indians

Enamel fissures, or flaws in the protective covering of the teeth, are considered to be of modern origin. It has been thought that the unbalanced diet of civilized man, or possibly his changed mode of life, has some evil influence on the formation of dental enamel, resulting in defects in the protective covering of the teeth. This, however, does not seem to be the case. An interesting light was thrown upon this subject by an examination of teeth of Pueblo Indians of New Mexico, who are supposed to have lived 800 or 900 years ago.2 This examination disclosed the rather startling fact that many of these teeth contained typical enamel fissures. Doubt consequently arose temporarily in my mind as to the correctness of the claim of Thaddeus P. Hyatt, who maintains that enamel fissures predispose teeth to decay. Such a supposition appeared to be disproved, for this collection of 317 teeth showed less than 3 per cent of dental decay! The paradox of the presence of enamel fissures, and of a very low incidence of dental caries, will be explained in this paper. The twenty occlusal surfaces of the teeth of civilized man show a frequency of decay greater than on all the remaining one hundred twenty-eight surfaces! Enamel fissures, being real defects in the protective covering of the teeth, are commonly found on the occlusal areas, and are held responsible for the increased liability of these sur-

The Lipin Content of Dental Tissues in Relation to Decay

Dental decay is chiefly a disease of childhood and of youth. Its activity is usurally greatly reduced after the age of twenty-five to thirty years according to the health of the individual. Millers commonly accepted chemico-parasitic theory of dental decay offers no explanation for this and other clinical observations. Only if we accept the views of Bunting (3), Rodriguez (7), McIntosh and Barlow (6), and others, that dental decay is an infectious disease dependent upon the presence of specific organisms, can we comprehend such a change in the activity of this malady. With such a thesis we may assume that, after the age of twenty-five or thirty, oral conditions are such that the proliferations of the specific organisms of decay cannot develop as readily as in youth. This would result in -the reduced activity of the disease. That specific organisms, however, are not entirely responsible for this disease is shown by the following clinical observation. Decay is most common at the contact points of two closely adjoining teeth, and it is usual that both surfaces are attacked. This is what we would anticipate if we accepted the thesis that decay results from the bacterial fermentation of carbohydrate food lodged between the teeth. When, however, we encounter cases in which only one of the two closely contacting teeth decays, Millers chemico-parasitic theory, including its modification of specific dental infection, does not hold.

Role of the Dental Papilla in Early Tooth Formation: Part 1-Roentgenographic Study

The interdependence of the enamel, dentin and pulp has long been a subject of experimental investigation [Legros and Magitot (1), Tomes (2), von Brunn (3), Huggins, McCarroll and Dahlberg (4), Hahn (5), and others]. Most of the studies of relations of the component tooth parts deal with the formation and calcification of the tissues at the very earliest stage of development. Relations of the component parts after complete formation of the tooth have also been studied (6, 7, 8, 9). However, very little work has been done, in vivo, to determine the influence of the dental papilla on the newly formed tissues after the formation of the enamel matrix, the latter described by Chase (10) as the acid resistant enamel, and by Diamond and Weinman (11), as the enamel first formed in the organic state which later becomes calcified. In order to learn more about the role of the dental papilla in tooth development after formation of the enamel but previous to its complete calcification, and also the effect of the papilla upon the growth of bone in the surrounding structures, a technic was devised for the removal of the intact dental papilla, leaving the remaining portions of the tooth undisturbed in the jaw. The cat was selected for this experimental study because it has been shown previously that the dentition has a growth curve similar to that of man, and completes its cycle of development within a relatively short period of time, about nine months (12, 13).