James A. English

Oral manifestations of ionizing radiation. II. Effect of 200 KV. x-ray on rat incisor teeth when administered locally to the head in the 1,500 R. dose range.

A SERIES of three experiments was performed to observe, among other things, the effects of a single dose of irradiation on growing incisor teeth of white rats during a relatively long period of time following irradiation (100 days). In the first experiment, the animals were divided into three groups, and different doses were given to each group. This was done to determine what dosage level might have an effect on the growth of the incisor teeth and still provide an adequate number of surviving animals for observation during the selected study period. An indication of the dosage range to be tried was obtainable from previous related studies on dental growth, made by Leist,1 Burstone,2 and Medak, Schour, and Klauber.3 However, since we used different physical factors of radiation, with local head radiation only, using our own strain of rats, an actual trial was necessary. The second and third experiments were made to verify the changes observed in the 1,500 r. group of the pilot study.

Oral manifestations of ionizing radiation. I. Oral lesions and effect on developing teeth of swine exposed to 2000 K. V. total body X-ray irradiation.

THIS is a report of an investigation of the oral tissues and developing teeth of 41 swine which were exposed to 2000 kv. total body x-ray irradiation. These swine were selected for study from a group of 120 animals that were being used in an experiment to determine the lethal dose of high voltage x-ray irradiation on large animals. In addition the experiment was to determine the effects of x-ray applied to one side of the body as compared to a bilateral exposure with the same dose of x-ray. Certain general pathologic responses will be published later; this publication is limited to a description of oral lesions and the effects of irradiation upon developing teeth, the tongue, and salivary glands. The number of swine used in this study was not sufficient to provide good quantitative data. No statistical analyses have been attempted and the extent of quantitating has been resolved in simply stating how many animals responded in a certain way. There are some interesting factors about developing teeth which make them especially valuable for radiobiologic study. They provide a means for the study of the effects of ionizing irradiation on cells of varied embryonal origin, in several stages of proliferation, growth, and differentiation. The enamel of teeth is produced by ameloblasts which differentiate from the inner enamel epithelium, which in turn is a product of the invagination of the oral epithelium. In the process of differentiation, these basal epithelial cells change their polarity27 and become secretary in function. That is, the Golgi apparatus of the ameloblast moves to what was formerly the distal or outer end of the cell, and the enamel matrix is formed at the end of the cell which originally was its base (Fig. 1). This single cell type can, therefore, be studied in proliferation, differentiation (including polarity change), and productive metabolism. With these changes one naturally expects an alteration in its susceptibility to irradiation, for it has been shown that the same cell will respond to stimuli according to its metabolic activity, its state of growth, and its age.6 Other portions of the developing tooth also offer valuable material for similar comparative studies. The dentin of the tooth is formed by the activity of odontoblasts, which are differentiated from connective tissue contained in the dental papilla, and by the fibers of von Korff which occur among these connective tissue cells.33 Here, then, is a connective tissue counterpart, in

Experimental effects of thiouracil and selenium on the teeth and jaws of dogs.

HE purpose of this paper is to report certain changes in the dentition and bone of the jaws of a litter of dogs treated with two goitrogenic compounds: thiouracil and organic selenium. No other published accounts of experimental studies relating these drugs to oral structures have been found in the literature. The very limited amount of endocrinologic data of any kind pertaining to the dentition has served to make this investigation more interesting and more worth while. It first became apparent that this study might be fruitful when certain gross changes were noted in the teeth of a litter of dogs which had been treated with thiouracil and selenium compounds at the Wyeth Institute of Applied Biochemistry, Philadelphia, Pa., in an experiment directed by Dr. Joseph Seifter.t The investigation reported herein began after the sacrificing of the dogs, when the heads were made available for study. The practical significance of studying these particular drugs is twofold. Both of these compounds fall into a large group of commonly used drugs that have an effect on the thyroid gland, and it is important to know any structural changes that may result from using them. One of the compounds contains the element selenium which is found in sufficient quantities in nature to be of significance in certain areas of the United States and throughout the world.

Examiner Standardization for Caries Studies

Examiners in clinical control programs customarily undergo an intensive period of training to standardize their interpretation of diagnostic criteria. Data are presented summarizing examiner error rates in calibration examinations and reversal rates in a field study.

The encouragement of international research co-operation in dentistry

Abstract The speaker discusses suggestions made by scientists from many countries regarding improving international relationships in dental research. Many people believe that periodic international dental research meetings should be held that are of greater scope that those that have been held to date. There appears to be a real hope that existing research organizations could be banded in such a way that each would not lose its identity. Perhaps a single area where improvement is most desired by all is in publication of research findings. The speaker presents the viewpoint of the International Association for Dental Research and asks for discussion from members of other organizations.

International Aspects of Dental Research

an important subject, and I have solicited comments from a number of people on how they believe our Association is serving an international purpose, whether they believe it is possible for us to become a -better international organization and how this might be accomplished. I suspect that the majority of the persons in this banquet hall have given little thought to the internationality of our Association, that relatively few recognize that there are any serious problems related to international membership, and that there will be a number of our most active members who will be in varying degrees of disagreement with the suggestions and conclusion I shall present this evening. I do not intend to do much more than give an outline of my inquiries into the question of internationality for I realize that a long discourse would be out of place following the social activities we have had so far this evening, but I do hope that what I say may lead to some action in subsequent council meetings. MIost of all, I hope you will be interested in what I have to say. I believe a good way of introducing my discussion is to read a letter I received four weeks ago from a friend in Bristol, England: