Isaac Schour

Studies in Tooth Development I. the 16 Microns Calcification Rhythm in the Enamel and Dentin from Fish to Man

Microscopic examination of ground and decalcified sections of enamel and dentin shows an incremental stratification of pairs of alternating light and dark layers. These layers follow a concentric pattern in transverse sections and resemble the annual rings in trees. The incremental stratifications have been more generally known as the striae of Retzius (enamel) and Owens lines of contour (dentin). They are of physiologic significance because they reflect the nutritional and metabolic variations that occur during the growth and calcification of the dental tissues. Since no calcium withdrawal occurs in the teeth such records are permanent. The purpose of this study was to make a quantitative analysis of the incremental layers and to investigate their constancy and rhythmic nature in the teeth of various species.

Studies in Tooth Development: II. the Rate of Apposition of Enamel and Dentin in Man and Other Mammals

The rate of apposition and calcification of enamel and dentin has in the past been studied mainly by gross, radiographic and histologic observations on jaws of feti and children of known ages that were obtained at autopsy. Such studies yielded approximate data for the chronology of dentition. An indicator to show the site of growth in teeth of living animals was first used by Hunter (1771), who fed madder to pigs. His work was not quantitative but it paved the way for further investigation. Marshall (1920) measured the rate of apposition of the dentin of the incisor in rats that were injected with alizarine, trypan blue or purpurin, and found that the dentin in the incisor of the rat was apposed at the rate of 10 1A per day. PflUger (1931) reported, on the basis of injections of uroporphyrin, that dentin in the young dog grew 10,u per day. Asper (1916) counted the total number of striae of Retzius in ground sections of ten human canines and concluded that one enamel globule and one transverse striation are laid down daily in each enamel rod.

Age Changes in the Periodontal Tissues of the Rat Molar

THE physiologic aging process of the periodontal tissues has been a subject of considerable interest to the dental profession as a whole, and to the periodontist in particular. A knowledge of the physiologic changes of the periodontal tissues with age is essential to an understanding of periodontal diseases. The purpose of this study was to follow in the rat molar the changes that occur from youth to old age in the position of the epithelial attachment, the incidence and degree of gingival inflammation, the position of the alveolar crest, the state of cellular activity at the alveolar crest, the width of the interdental septum, the position of the cellular cementum, and the amount of root resorption. The rat molar, which is a tooth of limited growth, provides a fair comparison with the permanent human tooth, and has been used for that reason in experimental studies. An attempt also was made to establish basic information which would be essential to evaluate the results of experimental studies in the molars of rats of different ages.

The Prevalence, Distribution, and Morphologic Changes of the Epithelial Remnants in the Molar Region of the Rat

T HE PURPOSE of this study is to classify the different forms of epithelial remnants and to investigate the prevalence and incidence of these structures in the periodontal membrane of the molars of the rat. This study is an attempt to provide a base line for later investigations on the fate of the epithelial remnants of the rat molars under different systemic conditions and to serve as a part of a broader study of the biology of epithelium.

Hereditary opalescent dentine (Dentinogenesis imperfecta)

Abstract Several cases of hereditary opalescent dentine are described and analyzed histologically and genetically. The similarity in the dental changes in hereditary opalescent dentine and osteogenesis imperfecta is pointed out, and the characteristic effects are grouped under the general term “dentinogenesis imperfecta.”

Early dentinal and pulpal changes following cavity preparations and filling materials in dogs

T HE primary purpose of this investigation was to study the early dentinal and pulpal response of the teeth of dogs to cavity preparations and different filling materials. A secondary purpose was to develop a comparative histologic evaluation in terms of the degree of pulpal inflammation and degree and type of response of the dentine. Only one comparative study dealing with the early changes in teeth of dogs following dental fillings has been reported. James and Diefenbachl studied twenty-seven teeth which were filled with zinc oxide and eugenol for a period of four to eight days. Pulpal reactions were noted also in open cavities. In cavities filled with zinc oxide and eugenol, however, the reaction was either absent or less severe.

Vital Staining of Growing Bones and Teeth with Alizarine Red S

The increasing use of alizarine Red S as a vital dye prompted this report. In contrast to the method of prolonged madder feeding which gives diffuse effects (2, 5, 13), each injection of alizarine Red S produces a sharp red line in the incremental zones of dentin, cementum and bone (14, 15) that are growing and calcifying at the time. The distance between 2 successive injections thus represents the amount of apposition that has occurred during the intervening period. Sharp effects were not found in the enamel. History. Robiquet and Colin (8) in 1826 reported alizarine to be the principal staining ingredient in madder, which was used in the dyeing of cloth by the early Egyptians. It was synthesized in 1869 (8) and Perkin and Story (18) synthesized 3-iodo-alizarin in 1931. By vital staining with alizarine Red S, studies have been made on bones and teeth of various species ranging from fish to monkey (1, 7, 10, 14, 17, 20). Alizarine has also been used as a non-vital stain in the Spalteholtz method of clearing (25), differential staining of bones (7, 17), and in ground sections of enamel (11). Chemistry. It is important to distinguish between alizarine Red S and other members of the alizarine group. The general formula of the latter is: O OH

Effects of Filling Materials on the Pulp of the Rat Incisor

THIS investigation was designed to study the effects of a variety of commonly used filling materials upon the growing dentin and the pulp of the incisor of the albino rat. One of the important requirements of a dental filling material is that it does not harm the pulp. Investigators and clinicians have, therefore, stressed the need for a rapid and simple method of testing the effects of filling materials on the living pulp before these are used in human teeth. While histologic analysis of the effects of filling materials on the pulp in human teeth is essential to accuracy and objectivity, patients are reluctant to sacrifice teeth for experimental purposes. On the other hand, animal experiments permit the accumulation of relatively large numbers of specimens within a relatively short time. Most important, the conditions of testing can be more accurately controlled. The experiments can then be replicated until the variables are determined and the effects of each material on the pulp can be assessed in an objective and quantitative manner. Until very recently, the dog was the experimental animal of choice, with occasional studies in monkey and man. In 1952, one of us (I. S.) suggested the use of the rat incisor and molar for the analysis of the effects of filling materials on the young and adult pulp. One of the objectives of this study was to establish the validity of using the rat incisor for the bio-assay of new filling materials introduced to operative dentistry.

Dental Caries and Gingivitis in Males 17 to 20 Years Old (At the Great Lakes Naval Training Center)

A LARGE number of enlistees from various parts of the United States were examined at the Great Lakes Naval Training Center. It was felt that the analysis of dental disease in this group would provide a good cross sectional sampling of young adult American men. These young men came predominantly from the Central, Northeastern, and Southeastern states with a few from scattered areas west of the Mississippi River. All enlistees were males between the ages of 17 and 20 years and all were white.

Experimental Cavity Preparations in the Molar of the Rat

THE primary purpose of this investigation was to develop and standardize an experimental method of preparing dentinal cavities in the molar of the rat which could be successfully sealed with a filling material. The effects of such materials upon the pulp could thus be tested. It is essential to develop methods of testing the effects of filling material and medicaments upon the pulp. A number of experimental studies on the effect of various materials upon the pulp have been investigated on the teeth of the dog, monkey, and man. Human teeth would be the most desirable test objects, but for obvious reasons it is difficult to find healthy human teeth which could be used in experimental investigations of this kind. Monkeys and dogs, while available in sufficient numbers for experimental study on their teeth, are expensive to keep and require considerable attention. The rat, on the other hand, is a convenient and less expensive animal for experimental investigations. The molar of the rat is anatomically and biologically similar to the human molar (Schour and Massler3) and therefore well suited for studies of the dental pulp. A careful study of the literature shows no previous investigation on the rat molar as a biologic testing tool for the effects of dental materials upon the pulp.