Juan M. Navia

Caries experience in deciduous dentition of rural Chinese children 3-5 years old in relation to the presence or absence of enamel hypoplasia.

The association of enamel hypoplasia (EHP) with dental caries of the deciduous dentition was determined in 1,344 rural Chinese children aged 3-5 years. The degree of EHP was determined using a modified DDE Index. Number of decayed, missing, and filled teeth and tooth surfaces were determined for all subjects. Anthropometric assessment of body weight and height was done as an indirect measure of the nutritional status of the children. Results from the study showed that the prevalence of EHP was 22.3% in the total study population. The prevalence of dental caries was 82.3%. There was no difference in the caries experience between males and females. Significantly greater caries experience was observed among the children living in a low socioeconomic county and children with low height for age. Children with low birth weight showed a slightly higher percentage of caries than those born with normal birth weight. Children with enamel hypoplasia demonstrated a significantly higher caries experience than those who did not have such defects. The results of this study consistently support previous studies that found nutritional deficiency to have an important impact on tooth development and susceptibility to dental diseases. This study also indicates that the presence of enamel hypoplasia may be a predisposing factor for initiation and progression of dental caries, and a predictor of high caries susceptibility in a community, particularly if fluoride programs are not implemented.

Colonization by mutans streptococci in the mouths of 3- and 4-year-old Chinese children with or without enamel hypoplasia

This case-control study compared the prevalence and concentration of mutans streptococci (MS) in saliva between children with and without enamel hypoplasia (EHP). A total of 486 3- or 4-year-old Chinese children were initially screened for EHP, then distributed into two groups: 234 children diagnosed as having EHP were assigned to the case group; 252 who were free of EHP were included in the control group. The concentration of MS in saliva was assayed for each child. Nutritional status was deduced from body height and weight. Birth weight, prematurity, and nursing history were also determined. MS were found in 94.7% of the study population. The differences in MS concentrations were not associated with low birth weight, prematurity, length of breast feeding, or body height and weight. A statistically significant association existed between the presence of EHP and high counts of MS (p < 0.001). High MS counts were correlated with severity of enamel defects (p < 0.001). When the caries status of the children was controlled as the confounding factor in statistical analyses, the association between EHP and MS decreased but still remained significant (p = 0.025). This study shows that high MS counts are correlated with EHP, suggesting that irregularities in enamel surfaces could be a contributing factor that fosters the increased colonization of MS in the mouths of children.

Effect of Undernutrition During the Perinatal Period on Caries Development in the Rat: II. Caries Susceptibility in Underfed Rats Supplemented with Protein or Caloric Additions During the Suckling Period

The specific role of protein deficiency in altering dental caries incidence in rat pups was investigated. A 10% protein supplement given to undernourished rats during development allowed them to overcome weight deficiencies and reversed dental caries to the low incidence found in well-nourished control rats. Caries in undernourished rats supplemented with an isocaloric, proteinfree solution, was as high as that of undernourished rats intubated with distilled water.

Effect of Undernutrition During the Perinatal Period on Caries Development in the Rat: V. Changes in Whole Saliva Volume and Protein Content

Rats malnourished during development show increased susceptibility to caries. During this time molars mineralize and salivary glands undergo rapid development. Nutritional stress could affect either or both of these processes, thus determining caries susceptibility. Present studies show drastically reduced protein content and volume of saliva in rats undernourished during development.

Effect of Undernutrition During the Perinatal Period on Caries Development in the Rat: III. Effects of Undernutrition on Biochemical Parameters in the Developing Submandibular Salivary Gland

Undernutrition imposed on rats during the suckling period led to diminished levels of the biologic compounds associated with protein biosynthetic pathways in the submandibular salivary gland. DNA, RNA, protein concentration, and total wet weight in undernourished rats did not return to control amounts after intubation with a supplement containing no protein. However, supplements of a solution containing 10% protein during early development completely restored control amounts.

Chemotherapeutic effect of zinc on Streptococcus mutans and rat dental caries

Abstract Streptococcus mutans growth and plaque formation on nichrome wires (McCabe, Keyes and Howell, 1967) were studied using a chemically-defined medium containing either 0.5, 5, 8 or 16 parts/106 Zn as ZnSO4. Acid production from glucose by washed cells was evaluated in a pH stat using the same medium without nitrogen sources. Zn depressed bacterial growth and initial plaque formation, but had no effect on continued growth and production of plaque initially formed in the control medium (0.5 parts/106 Zn). Acid production was inhibited at Zn:cell ratios of 2 and 4 μg Zn per mg cell wet weight. Rats were infected with Strep. mutans at the time of tooth eruption and provided with 0, 25, 50, 100 or 200 parts/106 Zn in drinking water or in topically-applied solutions (0, 500, or 1000 parts/106) of Zn swabbed twice daily. Buccal caries scores were reduced in rats drinking water containing 200 parts/106 Zn, or receiving 500 parts/106 topical application. No further caries reduction was observed when 1000 parts/106 Zn was applied. Zinc had no effect on rat oral flora; Strep. mutans 6715 and Strep. sanguis were the predominant members of the cultivable flora. Zn:cell ratios lower then previously reported interfered with some metabolic activities of Strep. mutans in vitro. The weak effect of Zn in vivo may be due to factors such as dilution, chelation effects and tooth-site.

Collaborative Evaluation of a Rat Caries Model in Six Laboratories

When highly controlled parallel rat caries studies were run simultaneously in six laboratories, a similar pattern of caries developed in every laboratory with a range in mean values such that the results of no investigator were significantly different from those of at least two others. These results indicate that the major factors influencing development of rat caries have been recognized and can be controlled within reasonable limits.

A Case-Control Study of Plasma Ascorbate and Acute Necrotizing Ulcerative Gingivitis

Data from animal studies and from studies of patients with acute necrotizing ulcerative gingivitis (ANUG) have provided suggestive evidence for an association between ascorbate deficiency and disease risk. Further, there is biological plausibility for such an association, due to the role of ascorbate in collagen synthesis and leukocyte function. A case-control study of plasma ascorbate and ANUG was performed on 60 patients with a history of ANUG infection and 60 age-race-sex-matched controls. No cases had had active lesions for at least two months prior to their vitamin assay to avoid any potential reduction of dietary intake of ascorbic acid due to the presence of painful mouth lesions. According to results obtained by use of a modification of the 2,4-dinitrophenylhydrazine method for determination of total plasma ascorbate, the mean and standard error of the mean of plasma ascorbate for all ANUG cases was 0.07 ± 0.006 mmol/L; the mean for all controls was 0.10 ± 0.006 mmol/L. Paired differences in plasma ascorbic acid concentrations between cases and controls were significantly different from zero (p < 0. 001). The unadjusted relative risk (RR) of ANUG as obtained by conditional logistic regression for subjects whose plasma ascorbic acid concentration was at or below the median value for controls, relative to subjects with higher values, was 7.3 (90% confidence interval, 3.0 - 17.4; one-sided p value < 0.001). Patients with a history of ANUG ingested a daily average of 1.2 ± 0.2 servings of dietary ascorbic acid, as compared with a daily average of 1.9 ± 0.2 servings for healthy controls. The significant RR of ANUG for decreased plasma ascorbate persisted after data were adjusted for dietary intake (RR = 6.6 ; 2.7 - 16.1; p = 0.016). Similarly, smoking status only partly explained ascorbate differences, with a RR of ANUG of 4.4 (0.9 - 20.2 ; p = 0.057) adjusted for smoking. Adjusting for social class differences between cases and controls, however, explained the observed differences (RR = 1.00). We conclude that the significant association between decreased plasma ascorbate and ANUG even after healing of initial lesions was as hypothesized, although a causal interpretation of the findings was obscured by social class differences between cases and controls.

Rat Caries Assay of Reference Foods and Sugar-containing Snacks

Using standard reference snack foods, we tested a method, using rats fed in a programed feeding machine, to evaluate the caries-promoting properties of foods. Results, which were expressed in relation to a control food, indicate that the method distinguished differences in caries potential among a number of different snack foods. Buccal and sulcal caries scores of rats fed snack foods varied in their responses. A gel diet used to provide essential nutrients for the rat growth in this approach contributed minimally to the caries response which was related principally to the food being tested.

A microanalytical technique for the estimation of fluoride in rat molar enamel

Circumscribed areas of 1 mm diameter were demarcated on the mesio-buccal cusps of rat maxillary molars by punched adhesive tape. The areas were etched with 0.4 μl of 1.0 M or 0.5 M perchloric acid (HClO4) and the resultant solutions mixed with 0.1 M sodium acetate buffer. Fluoride was determined with a combination fluoride electrode modified to allow measurements in 2.5 μl aliquots. The depth of etching obtained with 1.0 M HClO4 was 6.3 ± 0.2 μm and with 0.5 M HClO4, 3.1 ± 0.1 μm. Twice daily topical applications of NaF solutions containing 1000 μg F/ml and 2000 μg F/ml respectively, to the molars of weanling rats resulted in a significant (p < 0.05) increase in fluoride uptake by rat first maxillary molar enamel surfaces.