William Lefkowitz

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.

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

Histological Evidence of the Harmful Effect of Cement Under Orthodontic Bands

Dental cements are used universally for securing bands during orthodontic treatment. These preparations-contain a high content of phosphoric acid and may be a responsible factor in the decalcification of the enamel. An indication that this danger is real was noted in a recent report (1) which showed that dyes penetrated the enamel of the teeth of dogs only in those areas which were subjected to the action of oxyphosphate cement. It appeared evident that the action of the cement made the enamel abnormally permeable from without, so that the dye could penetrate the enamel, and, in certain areas, also the dentin. The normally impermeable surface of enamel is considered a barrier to dental caries and this property should be maintained to insure good dental health. It has been observed clinically that small islands of decalcification, usually white in character, may be present on the enamel after the removal of anchor bands. They are particularly noticeable when the tooth is dry. Many clinicians removed bands periodically with the expectation that the saliva would not only arrest the etching of the enamel but would also recalcify it. Etching of enamel has been produced experimentally through the action of weak acids, lactic acid being the most common. Mummery (2) and Bunting and Palmerlee (3) reported that the enamel was unevenly decalcified by acids. The work of Enright, Friesell and Trescher (4) verified these earlier reports. They demonstrated that decalcifications occurred with relatively weak acids and that the enamel had a variable resistance to the action of acid, i.e., certain isolated areas were more susceptible than others.

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-

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).

The formation of cementum

C EMENTUM may be defined as a bony covering of the roots of the teeth. It consists of a matrix composed of calcified collagenous fibrils and may be either cell-free or contain cement corpuscles, sometimes called cementocptes. The first formed layer is acellular or hyaline cementum. Subsequently formed layers may be either cellular or acellular. Generally, the imprisoned cells are found in the apical area and in the bifurcation of multirooted teeth. The cementum also contains imbedded fibers of the periodontal membrane. At the surface of cementum there is an uncalcified layer called prccementum. It may be observed in histologic sections between the cementohlasts and calcified cementurn. It stains pink with eosin, demonstrating its lack of calcification. A similar uncalcified layer, predentine, may bc obserrcd between the odontoblasts and calcified dentine. Cementum and bone are similar in appearance. The basic difference is that cementum is deposited throughout life, whereas bone is constantly being resorbed and replaced. Furthermore, there is no inclusion of blood vessels in cementum as is common in bone. The bone changes result in very little alteration of substance. Because of the continuous deposition of cementurn there is a constant increase of this tissue with age. The primary function of cementum is to provide a means of attachment of the principal fibers of the periodontal membrane to the root. It further serves to repair resorbed areas of the root. It is associated with active eruption by continuous deposition. The importance of cementurn has long been recognized. Studies in comparative anatomy, old and youn, tr teeth of human beings, have contributed much to our present knowledge of cementum.l Recently, as a result of Gottlicb’s investigations, the phrase “biology of the cementum” became prominent in the literature.2 From his findings, one may conclude that the cementum possesses vitality. These physiologic studies have proved a valuable aid to understanding normal as well as pathologic cementum. The cementurn is a product of the periodontal membrane, from which it derives its nourishment. This may be observed by histologic examination of the cementocytes in cellular cementum. In the deeper layers regressive changes of the cementocytes are evident. Irregular staining of the nucleus demonstrates pyknotic changes. Frequently, the nucleus is chromophobic and does not stain at all. In the superficial layers the cement,ocytes appear normal, indicating an increased vitality toward the surface.