Harry H. Shapiro

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-

Spread of infection of dental origin; anatomic and surgical considerations.

Abstract 1. 1. The fasciae and fascial spaces of the head and neck are reviewed. 2. 2. The basic anatomy is related to infections of dental origin. 3. 3. The direct spread of infections by fascial pathways is discussed and illustrated. 4. 4. Principles in the management of cases originating in abscessed teeth are stressed and the general treatment of dental infections outlined.

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).

Growth in the Mandibular Dental Arch

In a previous study on the growth of the dental arches in the cat (1), the rate of percentage growth increase in anterior-posterior and lateral dimensions was found to vary. The direction of growth also was shown to be accelerated during certain periods of development. Because the dentition of the cat follows the human curve so closely (2) (3), and because it is accepted that the growth of the dental arch may be taken as an indication of growth in the jaws. it was thought that a similar study made upon the human dental arch might show comparable findings. In this study, the dental arches of 544 individuals between the ages of 5 and 25 were measured in 3 directions. All measurements were made upon the mandible from plaster casts of the dentition of children and young adults, and on living subjects. The following points were selected for measurement (fig. 1). Lines A and B represent the anterior-posterior dimension from the median line, immediately anterior to the incisor teeth, to the distal gingival margins of the last molar teeth (Dimensions A and B are represented by a single line as they are identical). Line C represents the dimension across the mandible, using the distal gingival margins of the canine teeth as points of measurement. Line D represents the dimension across the mandible in the region of the last molar teeth, using the distal gingival margins as measuring points. Table I is a compilation of the growth measurements described above and includes a calculation of the percentage growth based on maturity and the earliest age dimensions studied.

Experiments Dealing with Factors Influencing the Shedding of Deciduous Teeth Part I. Radiographic Study

Shedding of the deciduous teeth has been attributed to pressure caused by the erupting permanent teeth. If this were always true, it would be logical to expect that when there is a failure of the permanent tooth germ to develop, resorption would not occur. In cases of congenital loss of permanent tooth germs, it is often noted that the root of the deciduous tooth is resorbed, despite the fact that there is no permanent tooth germ (1) present which might cause pressure. Since there are no experimental data which have come to our attention regarding the accepted theory of resorption, experimental means were devised for testing the validity of the theory of pressure. Permanent tooth germs of cats were removed at several stages during their development, before the onset of resorption of the deciduous root. This form was selected because the curve of the developing dentition is similar to that of man, and also because it has been shown previously that the cat is especially suited for experimental work on dentition (2, 3). The permanent canine tooth was selected for study because of its accessibility and large size. The germ was removed on one side of the mandible, and the unoperated side served as a control.

The effect of alterations of the facial musculature on the facial skeleton and dental arch form of the rat; a preliminary study.

ORTHODONTISTS, on the basis of clinical observations, have long felt that the facial musculature plays an important role in the establishment of alveolar arch form and dental occlusion. The influence of the buccal and labial muscles in determining the direction of alveolar growth and the eruption of the teeth has been discussed by Brodie,1 and the clinical significance of the lips and cheeks has been noted by him and others.2 For many years myofunetional therapy has been used in orthodontic treatment as a means of altering unfavorable patterns of muscle function.3 There has been little experimental evidence reported concerning the effect of the facial musculature upon the bony architecture of the face and alveolar arches. Washburn4 produced asymmetries in the nasal and maxillary bones of rats and rabbits by unilateral sectioning of the seventh nerve; this procedure, of course, was not designed to study the effect of individual muscles upon the bony skeleton, but rather the effects of total unilateral paralysis of the facial muscles. The intertwining and decussation of the oral musculature interfere with evaluation of these structures as individual units. In this preliminary study we have endeavored to overcome this obstacle by altering the function of various components of the oral musculature in order to evaluate effects of such procedures on the developing facial skeleton.

Growth in the Dental Arches of the Cat

Previous studies on the dentition of the cat (1) (2) indicate that this animal, for a number of reasons, is especially suitable for studies related to human dentition. The life cycle of the cats dentition follows closely that of the human. There are no teeth present at birth, and the deciduous teeth and permanent teeth both develop and erupt in the same relative order as those of the human dentition. In this study, the relative growth values of the maxillary and mandibular dental arches, during their development from birth to the time of completion of the permanent dentition, were made from measurements of plaster models of the jaws of the cat. These measurements were compared with similar ones made directly on the jaws at intervals during the progress of the study, and demonstrated their accuracy (Jig. 1). TECHNIQUE