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A histologic study was conducted in 121 albino rats to determine the effect of experimentally induced diabetes upon the periodontal structures. Diabetes was induced by subcutaneous injection with a 5 per cent aqueous solution of alloxan in a dosage of 200 mg./kg. body weight. Blood sugar levels were regularly determined in all the animals. Subcutaneous injection with alloxan produced hyperglycemia, pancreatic disturbances, and symptoms comparable to those which occur in human diabetes. In twenty-five animals, no hyperglycemia or apparent diabetes followed injection with alloxan. The seventy-eight diabetic animals could be divided into an acute and a chronic group on the basis of survival beyond the initial acute stage which in forty-five cases terminated in death after an average of only 3.6 days. The experimental period in the chronic group ranged from three to thirty-two weeks. The mandible, maxillae, tibiae, ribs, vertebrae, pancreas, and kidneys removed at the termination of the experimental period were examined microscopically. In the periodontal structures, no notable pathologic changes were observed in the animals which succumbed after a brief acute response to alloxan or in the animals in which there was no response to injection with alloxan. The following conclusions regarding the periodontal structures of albino rats with experimentally induced chronic diabetes were established by the findings: (1) The nature and incidence of gingival disease are not peculiarly altered in diabetes. (2) A tendency toward varying degrees of nonspecific osteoporosis of alveolar bone is a feature in individual cases of diabetes. (3) In diabetes, severe changes generalized throughout the alveolar bone are accompanied by comparable alterations in other bones of the skeletal system. (4) In individual cases of diabetes the alveolar bone may present no significant alteration. (5) In diabetes, hyperglycemia and pancreatic changes are not associated with osteoporotic bone tendencies in a specific cause and effect relationship. (6) Notable pathologic changes in the periodontal membrane or cementum are not associated with diabetes.

Two complete fixed prostheses built with the occlusion in centric relation and with occlusion in the subject's existing centric occlusal position were tested with telemetry under conditions of actual use. The findings indicate that the subject did not use the centric relation position but accepted the prosthesis built to her preexisting centric occlusion. These findings are consistent with our previous results of telemetric studies conducted on patients with three-unit fixed prostheses.

Although surgical treatment is an effective method of eliminating many periodontal conditions, surgery is no panacea; it cannot be relied on to produce the desired results without employing other treatment methods indicated by the requirements of individual cases. Only infrequently is it necessary to employ surgical procedures to create soft tissue and bone contours artificially.

The keratotic process was studied microscopically and histochemically in eighty oral lesions diagnosed clinically as leukoplakia. In all lesions the stratum corneum was thickened and presented varied degrees of hyperkeratosis or parakeratosis, separately or in combination. Several histochemical differences between the hyperkeratotic and parakeratotic lesions were noted. Of particular interest was the observation that hyperkeratotic lesions were characterized by an increase in disulfides and a diminution in sulfhydryls in the stratum corneum which did not occur in parakeratotic lesions. An intermittent type of keratosis was also described.

Recordings of tooth contacts produced by an intraoral miniature electronic telemetry system placed in the natural teeth during chewing and swallowing have been presented and explained.

An intraoral occlusal telemetry system has been developed utilizing a miniature multifrequency transmitter which broadcasts at three different frequencies, registers tooth contacts on three different surfaces of the same tooth, and coordinates tooth contacts with swallowing. The transmitter is small enough to fit into a pontic replacing a single mandibular molar.

An experiment was conducted in the albino rat to evaluate the changes in the periodontal tissues associated with protein deprivation and to compare these changes with those observed in other areas of the skeletal system. The following changes resulted from protein deprivation: 1. a. 1.1. I. In the periodontal area, degeneration of connective tissue of the gingiva and periodontal membrane, osteoporosis of the alveolar bone, and retardation in the deposition of the cementum. 1.2. II. In the femur and vertebra, osteoporosis, marked inhibition of the endochondral and periosteal bone formation. 2. b. The changes observed in the periodontal membrane and alveolar bone were identical with those observed in the periosteum and bone in other areas of the skeletal system. 3. c. Osteoporosis in protein deprivation results from the following changes: reduced deposition of the osteoid, reduction in number of osteoblasts, and retardation in the morphodifferentiation of connective tissue cells to form osteoblasts. 4. d. Protein deprivation impedes endochondral bone formation by retarding the maturation and degeneration of cartilage cells and formation of osteoid.

An external covering over the completed enamel surface is described in the literature as a cuticular formation (1), an amorphous pellicle (2), a hornlike substance (3), or a combination of an organic membrane which may be calcified and keratinous cuticle (4). This covering is presented as consisting of a single layer (3), and as consisting of two layers (1, 5, 6). Its origin is attributed to the ameloblasts (3), the entire enamel organ (1, 5), and a combination of ameloblasts and epithelial attachment (6). It has been termed "Nasmyth's membrane", "enamel cuticle" (3), or "primary" and "secondary enamel cuticle". An additional cuticle which is frequently found covering the cementum has been described as a continuation of the secondary enamel cuticle and a derivation of the epithelial attachment. It has been termed the "dental cuticle" (6). A study of approximately 1400 decalcified sections of 64 erupted teeth in situ in human adult jaws offered an opportunity to establish more definitely whether or not cuticular structures actually exist in relation to the teeth and periodontal tissues. Three unerupted teeth completely embedded in the maxilla were included in the series studied. In general, the histological technique used in the preparation of the material was that presented in a previous publication (7). The term cuticle when used here refers to a thin, strandlike, non-cellular structure with a clear eosin-staining matrix of varying widths enclosed within smooth linear margins.