J.H. Shaw

Effects of various sucrose: Casein ratios in purified diets on the teeth and supporting structures of rats

Abstract Purified diets of varying carbohydrate: casein ratios were fed to female rats of the Harvard caries-susceptible strain for a stabilizing period of 28 days and then throughout pregnancy and lactation. Offspring of females fed a low-protein:high-sucrose diet grew more slowly and their molar teeth erupted later than rats born to females fed a control diet with a normal protein content. The molars of the offspring of the protein-deficient females were significantly smaller than those of the controls. This change in size was due to a decrease in the distance between the outer borders of the dentine rather than to a reduction in enamel thickness. Many of the third molars of these rats had missing cusps. The offspring of the deficient females had a significantly higher susceptibility to caries than the offspring of the control females. Rats born to females fed a high-protein: low-sucrose diet had a tendency toward an increased susceptibility to a periodontal syndrome and were significantly less susceptible to dental caries than the offspring of females fed the control diet. There was also a slight tendency for a breakdown of the periodontal structures among the offspring of females fed the low-protein:high-sucrose diet, but the syndrome did not progress as rapidly as among the offspring of females on the high-protein:low-sucrose diet.

Developmental and post-developmental influences on incidence of experimental dental caries resulting from dietary supplementation by various elements

Abstract Caries-susceptible rats of the Harvard strain were used to evaluate developmental and post-developmental influences of dietary supplements of several mineral salts on experimental dental caries. When various levels of sodium chloride, barium chloride, vanadium pentoxide, vanadyl sulphate and ammonium paramolybdate were fed to Harvard caries-susceptible rats, these mineral salts had no consistent, statistically significant influence on the dental caries incidence. Sodium borate and strontium carbonate supplements post-developmentally caused modest but rather inconsistent reductions in the dental caries incidence. Lithium carbonate supplements fed post-developmentally caused consistent reductions in the incidence of dental caries that were significant at the 5 per cent level, while ammonium molybdate supplements under the same experimental circumstances caused reductions that were statistically significant at the 1 per cent level. The various levels of barium chloride, sodium borate, and ammonium molybdate that were provided during pregnancy and lactation in the effort to influence the development of the molars of the offspring had no influence on the dental caries susceptibility of the offspring. Developmental supplements of vanadium pentoxide and vanadyl sulphate resulted in inconclusive findings due to poor reproduction in these experiments, but there seemed to be little evidence that the dental caries susceptibility of the offspring had been altered by either vanadium compound. Developmental supplements of sodium chloride, lithium carbonate, strontium carbonate and ammonium paramolybdate resulted in significant increases in the dental caries susceptibility of the offspring at levels varying from 5 per cent to 1 per cent. Many meticulous experiments need to be conducted before there will be detailed understanding of the role of the minor elements in the development and maintenance of the teeth.

The infectious and transmissible nature of the periodontal syndrome of the rice rat

Abstract The micro-organisms responsible for the periodontal syndrome in the rice rat are readily transmitted from one subject with an actively progressing syndrome to others. Rice rats which are prone to develop the periodontal syndrome when fed diet 700 were rendered relatively inactive with respect to the development of this syndrome by a preliminary period of penicillin supplementation. After cessation of penicillin administration, inoculation of the oral cavity with the micro-organisms in faeces from rice rats with fully developed periodontal lesions resulted in rapid initiation and progression of the destructive processes. Likewise comparable oral inoculations of rice rats of the strain which does not develop this syndrome readily, resulted in a greatly increased rate of initiation and progression of lesions. In both cases, oral inoculation by a thick paste prepared with faeces in physiological saline was more effective than the suspension of faeces in the drinking water. When weanling rice rats from the two strains were caged together, an increased level of the periodontal syndrome was observed in the rice rats from the relatively inactive strain. This method of inoculation appeared to be much less effective than either of the two previous procedures. However for all three procedures for inoculation of the relatively inactive rice rats, despite the highly significant increase in the periodontal syndrome, the rate of progression was still not equal to that observed in rice rats of the strain which is prone to develop the syndrome.

Comparison of sucrose, lactose, maltose and glucose in the causation of experimental oral diseases

Abstract Complete replacement of sucrose in the periodontal syndrome-producing diet by glucose or by confectioners sugar or one-half replacement by lactose did not have any significant effect on the prevalence and severity of the periodontal syndrome in the rice rat. Replacement of sucrose by maltose caused a significant reduction in the periodontal syndrome; replacement by whole wheat flour or white flour resulted in still greater reductions in the syndrome. Three experiments with different combinations of strains of rats and diets were used to compare the caries-producing ability of sugars. Complete replacement of sucrose by glucose in diet 2700 did not have any effect on incidence of dental caries in rats of the mutant albino strain but did cause moderate reductions in rats of the Harvard caries-susceptible strain. Complete replacement of confectioners sugar by glucose in diet 2000 caused highly significant reductions in initiation and severity of carious lesions, both in the occlusal sulci and on the smooth surfaces. However, replacement of granulated sugar, sucrose, for confectioners sugar also caused significant reductions in both types of lesions. Maltose supported as rapid development of carious lesions as sucrose in all three experiments, but a lower rate of lesions on the smooth surfaces in one out of two experiments. Lactose replacement for half of the sucrose in one experiment led to a lower incidence of carious lesions in the sulci and on the smooth surfaces in one experiment but not in a second experiment. Studies on mixed cultures from rats fed diets containing sucrose, glucose or maltose in one experiment led to the observation that maltose and sucrose seemed to promote somewhat greater synthesis of extracellular material than glucose. Some dextran has been synthesized from each of the carbohydrates. Comparison studies with plaque samples from five humans and oral swabbings from five hamsters led to the observation that extra-cellular slime was synthesized from sucrose alone.

Studies on the protein composition of rodent saliva—I: Application of methods of paper electrophoresis to two strains of laboratory rat

Abstract The basic methods used in the collection, electrophoretic separation, staining and characterization of the protein components of pilocarpine-stimulated whole rat saliva were presented. By these methods ten components were routinely demonstrated. A comparison of the occurrence of these components between a caries-susceptible strain of rat and a caries-resistant strain showed that differences occurred in component 5, which contained most of the amylolytic activity of the saliva, and in component 9, which has the same mobility as crystalline lysozyme. Component 5 was significantly higher in the susceptible rats than in the resistant ones, while component 9 was significantly higher in the resistant than in the susceptible rats. Periodic acid-Schiff staining of patterns revealed positive staining areas of components 1, 2, 5 and 8. Component 8 had the most intense staining for the amount of protein present. Selective sialoadenectomy studies showed that the major amounts of protein were derived from the parotid glands, while the major volume of saliva was obtained from the submaxillary-sublingual complex. The ratio of protein concentrations for the two sets of glands are of the order of 2.9:1.0, respectively. Component I was not usually observed in animals with only their parotids intact, while only an occasional trace of component 9 could be observed in animals with their parotids removed.

Evaluation of the degree of caries-susceptibility in strains of rats

Abstract Two experiments were conducted to determine the influence on dental caries activity of maintaining rats of the Harvard caries-susceptible and caries-resistant strains together for various periods. In the first half of the first experiment, weanling rats of the two strains were caged together, while in the second half, weanling rats of the caries-resistant strain were housed with young adult rats of the caries-susceptible strain which had already developed numerous grossly detectable carious lesions. In the second experiment, half-litters were transferred from caries-susceptible mothers to caries-resistant mothers within 24 hr after birth. These foster offspring were maintained with the half-litter belonging to the mother until weaning at 21 days of age. The rats of the caries-susceptible strain developed high rates of caries activity typical of their predecessors, regardless of the amount of contact with animals of the caries-resistant strain, or the lack of contact with members of their own strain. Three-quarters of the members of the caries-resistant strain which were maintained in direct contact with caries-active members of the caries-susceptible strain remained caries-free throughout the 250 day experimental period. The remaining quarter developed small numbers of slowly progressing carious lesions at a caries-activity level of approximately 10 per cent of that of caries-susceptible rats maintained on experiment for 80 days. The rats of the caries-resistant strain which became caries-active were restricted to a portion of the litters used in the experiments and probably represented the least resistant portion of the caries-resistant strain. These data justify the concept that the caries-susceptibility and resistance of these strains are attributable to genetically inherited characteristics and that the terms caries-susceptible and caries-resistant can be correctly applied to the representatives of the two strains.

Histological studies of the periodontal syndrome in rice rats and the effects of penicillin.

Abstract Three experiments involving histological studies of periodontal disease in rice rats were performed: 1. 1. Studies of the initiation and progression of the periodontal syndrome in ninetyone susceptible rice rats have demonstrated that the lesions of the soft and mineralized tissues of the periodontium were first evident at approximately 5 weeks of age. Deterioration of the periodontium progressed rapidly until extensive periodontal disease and degeneration were present at 15 weeks. 2. 2. Similar studies of seventeen rice rats from a periodontal syndrome-inactive strain of rice rat showed that these rice rats did not develop any noticeable lesions of the soft tissues of the periodontium even at 45 weeks, but did develop small areas of alveolar bone resorption. 3. 3. One hundred periodontal syndrome-susceptible rice rats were used in the study of the effect of penicillin administered by various routes on the prevention of the periodontal syndrome. Penicillin, regardless of the route of administration, almost completely prevented soft tissue lesions and caused highly significant reduction in the number and extent of areas of alveolar bone resorption.

Further studies on the microbial agent or agents responsible for the periodontal syndrome in the rice rat

Abstract The periodontal syndrome in rice rats was produced as a result of oral inoculations with a pooled culture containing four micro-organisms isolated from the oral cavities in rice rats with rapidly developing, advanced periodontal lesions. Inoculations with the single micro-organisms from this mixture did not result in conclusive identification of the aetiologic agent although a gram-positive, thick, spore-forming rod may have been responsible. Penicillin pre-treatment among rice rats from the syndrome-inactive strain did not result in oral circumstances whereby the periodontal syndrome-producing agent or agents could establish themselves more readily than without a preliminary period of penicillin administration. Oral inoculations of white rats with faecal paste or microbial cultures from rice rats did not result in a demonstrable periodontal syndrome.

Dietary phosphate supplementation and its effects on dental caries and salivary and serum concentrations of calcium and inorganic phosphate in the rat.

Abstract An attempt has been made to determine the mechanism whereby dietary phosphate supplements act to reduce the incidence of caries in rats. Experiments were also done to determine the influence of weight, sex and rate of flow on the concentrations of calcium, inorganic phosphate and bicarbonate in pilocarpine-stimulated saliva from rats of the Harvard caries-susceptible strain. Bicarbonate was found to be the main buffer in rat saliva. The rate of salivary flow was higher in males than females. Saliva from female rats contained a higher concentration of inorganic phosphate than saliva from males and the concentration was independent of flow rate. Salivary calcium concentration was independent of sex but increased at higher flow rates. For the phosphate feeding experiment, eighty-one rats were divided into three groups of which Group 1 received a cariogenic diet alone while Groups 2 and 3 received supplements of 2% Na2HPO4 and 2·2% commercial Na phytate, respectively. Groups 2 and 3 had a reduced incidence of caries. By elimination, a direct effect of phosphate on the teeth is postulated as serum and salivary calcium and inorganic phosphate analyses did not differ significantly among the three groups.

The comparative influence of thyroid imbalance and limited body weight gain on submandibular gland weight, the protein components of saliva and dental caries in the rat

Abstract Hyperthyroidism in the rat, produced by dietary desiccated thyroid, resulted in an absolute increase in submandibular gland weight, a relative decrease in prevalence of dental caries (when increased food consumption is considered), and specific changes in pilocarpine-stimulated protein components of saliva, notably a decrease in component 5 and an increase in component 9 compared to rats with hypothyroidism produced by dietary 6-n-propyl-2-thiouracil. The latter exhibited an absolute decrease in gland weight, a relative increase in caries (when decreased food consumption is considered), and an increase in component 5 and decrease in component 9. Total salivary protein secretion was slightly decreased in the former and markedly decreased in the latter, compared to that secreted by pair-weight control rats. Changes in salivary protein components did not appear to reflect changes in serum protein components among any of the groups. A comparison of pair-weight control animals whose rates of growth were limited to those of the experimental groups by caloric restriction (12 per cent and 38 per cent below the normal level of food consumption) demonstrated progressively smaller gland weights and lower caries experiences and progressive decreases in salivary component 5 and increases in salivary component 9. It is concluded that factors other than rate of growth and food intake are responsible for the changes in thyroid imbalance. This study supports the view that salivary gland function and caries experience are closely related to thyroid physiology.