The microbiology and biochemistry of plaque, saliva, and drinking water from two communities with contrasting levels of caries in Colombia, S.A

Do we need to be concerned about dental caries in the coming millennium?

Dental caries continues to be a pubic health problem despite claims that 50% of schoolchildren are caries-free. There are widespread variations in the prevalence of caries worldwide. Caries lesions are the clinical manifestation of a pathogenic process that may have been occurring on the tooth surface for months or years. Acid production by bacteria embedded in a biofilm termed "dental plaque" is a key aspect of the pathogenesis of dental caries; nevertheless, the ability of micro-organisms to survive in a hostile acid milieu and the influence of fluoride and additional agents on this acid tolerance receive scant attention. Study of cariogenic micro-organisms largely has been limited to observations made on them in the planktonic state; clearly dental caries is essentially a surface phenomenon, and micro-organisms behave distinctively when grown on a surface. Although significant progress has been made in our understanding of the etiology, pathogenesis, and prevention of dental caries, it still remains a scientific and clinical enigma worthy of the attention of the best scientists.

Trends in dental caries in Latin American and Caribbean 5-6- and 11-13-year-old children: a systematic review

OBJECTIVES

To determine trends in dental caries prevalence and severity in Latin America and Caribbean.

METHODS

A systematic review was done of studies published between 1970 and 2000 among 5-6- and 11-13-year-old children that used WHO caries diagnostic criteria.

RESULTS

Over the last 30 years, there has been a significant decrease in caries severity for children 5-6 years old and also a significant decrease in caries prevalence and severity for children 11-13 years old. The same broad trends were observed when caries prevalence and severity was analyzed for the last 20 and 10 years but these were not statistically significant.

CONCLUSIONS

Evidence of a decrease in dental caries in Latin American and Caribbean children has been shown, although the decrease was less prominent in the past few years.

Does variability in salivary protein concentrations influence oral microbial ecology and oral health?

Salivary protein interactions with oral microbes in vitro include aggregation, adherence, cell-killing, inhibition of metabolism, and nutrition. Such interactions might be expected to influence oral ecology. However, inconsistent results have been obtained from in vivo tests of the hypothesis that quantitative variation in salivary protein concentrations will affect oral disease prevalence. Results may have been influenced by choices made during study design, including saliva source, stimulation status, control for flow rate, and assay methods. Salivary protein concentrations also may be subject to circadian variation. Values for saliva collected at the same time of day tend to remain consistent within subjects, but events such as stress, inflammation, infection, menstruation, or pregnancy may induce short-term changes. Long-term factors such as aging, systemic disease, or medication likewise may influence salivary protein concentrations. Such sources of variation may increase the sample size needed to find statistically significant differences. Clinical studies also must consider factors such as human population variation, strain and species differences in protein-microbe interactions, protein polymorphism, and synergistic or antagonistic interaction between proteins. Salivary proteins may form heterotypic complexes with unique effects, and different proteins may exert redundant effects. Patterns of protein-microbe interaction also may differ between oral sites. Future clinical studies must take those factors into account. Promising approaches might involve meta-analysis or multi-center studies, retrospective and prospective longitudinal designs, short-term measurement of salivary protein effects, and consideration of individual variation in multiple protein effects such as aggregation, adherence, and cell-killing.

Associations of microbiological factors and plaque index with caries prevalence and water fluoridation status

Plaque indices, numbers of mutans streptococci, lactobacilli and total viable flora in plaque and saliva were assessed as part of a large-scale cross-sectional study designed to determine the factors that are associated with high caries activity in children. Subjects, 12 to 15 years old, residing in areas where the water supplies were either fluoridated (n = 140) or fluoride-deficient (n = 173) were studied. Mutans streptococci and lactobacilli numbers in saliva were positively correlated with plaque index. Plaque indices were significantly higher in the high-caries group than in the zero-caries group of the fluoride-deficient community. In the fluoridated community, there was no difference in the plaque index between the zero- or high-caries groups. In each community, pooled dental plaque and saliva harbored fewer mutans streptococci and lactobacilli in the zero-caries than the high-caries group. Greater numbers of mutans streptococci were found in the dental plaque and saliva of the zero-caries subjects in the fluoridated community than in the fluoride-deficient community, suggesting that a greater caries challenge can coexist with zero-caries status in the fluoridated community.

Caries prevalences among geochemical regions of Missouri

Our objectives were to determine how the prevalences of caries in elementary school children vary between geochemically defined regions of the state of Missouri and to compare this variation with that found for prehistoric Missouri inhabitants (Hildebolt et al.: Am. J. Phys. Anthropol. 75:1-14, 1988). Caries data on 6,584 school children were used in the study of second and sixth graders drinking optimally and suboptimally fluoridated water. Geochemical regions were based on maps recently published by the United States Geological Survey. Differences in mean caries scores and proportions of children with caries were tested by analysis of covariance, analysis of variance, Student t, and chi-squared tests. We found that caries prevalences do vary between the geochemical regions of the state. In the total sample, however, there were no significant differences between those children drinking optimally fluoridated water and those drinking suboptimally fluoridated water. We conclude that there is variation in caries rates among geochemically defined regions of the state and that geochemical factors associated with young parent materials may be antagonizing the action of fluoride.

Antimicrobial systems of human whole saliva in relation to dental caries, cariogenic bacteria, and gingival inflammation in young adults

The association of salivary antibody (total IgA, IgG, and IgM and antibodies reactive with Streptococcus mutans) and non-antibody (lysozyme, lactoferrin, salivary peroxidase, myeloperoxidase, hypothiocyanite, thiocyanate) defense factors with oral health (past and present dental caries, gingival bleeding, the number of salivary S. mutans and lactobacilli) were studied in 50 naval recruits. Dental caries was significantly associated with large amounts of S. mutans, lactobacilli, and total salivary immunoglobulins and with low salivary flow rate and buffer capacity. Salivary anti-S. mutans antibodies did not correlate with dental caries or S. mutans levels. Moreover, none of the salivary non-antibody factors alone had any strong relationship to dental caries or S. mutans levels. Gingival inflammation was associated with elevated levels of lysozyme in whole saliva. It is concluded that in adults the associations between single-point measurements of most salivary antimicrobial constituents and the factors describing oral health are weak.

The effect of geochemical factors on prevalences of dental diseases for prehistoric inhabitants of the state of Missouri

In previous epidemiological studies, it has been suggested that geochemical factors besides fluoride may affect the prevalences of dental diseases. Our objective in this study was to determine whether the prevalences of periodontal diseases, coronal caries, and root caries for prehistoric inhabitants vary between geochemical regions of the state of Missouri. Burial sites were located on unique maps that depict geochemical variation among regions of the state. Data on dental caries and alveolar bone loss were gathered from 179 of the best preserved skeletal remains of the Late Woodland (A.D. 400-900) and Mississippian (A.D. 900-1700) periods. Mean caries scores and proportions of individuals with caries were calculated for these geochemical regions. Average alveolar bone loss was regressed on age for the individuals of these regions. Significant differences in caries and bone loss were found between several regions. These differences cannot be adequately explained by fluoride concentrations or by diet. It is suggested that geochemical factors, in addition to fluoride, may have affected the prevalences of dental diseases.

Antimicrobial factors in saliva: ontogeny and relation to oral health

Antimicrobial agents (antibody and non-antibody) present in human saliva protect oral tissues by a variety of mechanisms, such as prevention of bacterial adhesion, agglutination of micro-organisms, and inhibition of multiplication and metabolism. However, studies in which the concentrations of various salivary antimicrobial agents have been correlated to the presence and severity of oral diseases--of dental caries, in particular--have produced controversial data, and it seems evident, also on the basis of the present study, that no single salivary antimicrobial factor (except flow rate) affects oral health to a significant degree. In the present study, we report the levels of some selected salivary antimicrobial agents in predentate and dentate human infants, with a comparison to the levels found in young adults' saliva. Salivary lysozyme, peroxidase, and hypothiocyanite concentrations were already at the adult level at the time when the primary teeth erupt, whereas immunoglobulin (IgA, IgG, and IgM), lactoferrin, myeloperoxidase, and thiocyanate concentrations were significantly lower in children than in adults. Dentate children had more IgG, thiocyanate, and protein in whole saliva than did predentate children.

Calcium and phosphate in human dental plaque and their concentrations after overnight fasting and after ingestion of a boiled sweet

The concentrations of ionized and total Ca inorganic and total phosphate were determined in the same pooled samples of fluid separated from 24 h plaque collected from volunteers at least 1 h after a mid-morning snack. About half the total concentration of Ca was ionized (1.53 mM, SD 0.73, n = 36). The mean total Ca concentration (2.88 mM, SD = 0.89, n = 34) was about half that reported previously. The inorganic phosphate was in the range reported previously and comprised about 80 per cent of the total pool of soluble phosphate. A small but significant pool of organic phosphate comprised about 20 per cent of the total phosphate. There were no differences in any of these measurements between plaque-fluid samples pooled from upper buccal posterior teeth and from other sites. The product ([Ca ion] X [inorganic phosphate]) in plaque fluid greatly exceeded saturation levels with respect to potential solid phases present at the enamel surface. Five adults provided overnight-fasted dental plaque for one year to examine the effects of ingesting a boiled sweet on the plaque Ca and phosphate when collected 15 min later. There were no significant differences between fasting control and post-sweet levels of plaque-fluid Ca (ionized and total) and phosphate (inorganic and total). In the post-sweet residue, there were lower total phosphate but not Ca concentrations; the variability in these measurements may explain the unexpected depletion of the organic pool of phosphate in the residue.

Structural integrity of host defense factors in dental plaque

The structural integrity of immunoglobulin A (IgA), IgG, and IgM and lactoferrin in dental plaque fluid samples from two populations of Colombian children with contrasting levels of dental caries was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electrophoretic transfer to nitrocellulose. The immune factors or their fragments or both were detected with monospecific antibody conjugated with horseradish peroxidase. All the immune factors examined were extensively degraded, although there appeared to be small amounts of intact IgA and IgG in some samples. Analysis of the samples with antibody to secretory component showed that secretory IgA as well as serum IgA was degraded. IgG appeared to be cleaved into two major fragments, one fragment having a relative mobility similar to the F(ab')2 fragment of IgG and the other a relative mobility slightly greater than Fc. IgM and lactoferrin were virtually completely degraded. There was no apparent relationship between the fragmentation patterns of IgA and IgG in the plaque fluid samples from the two communities and their susceptibility to dental caries.

Specific and nonspecific immune factors in dental plaque fluid and saliva from young and old populations

Separate samples of supragingival dental plaque overtly free of blood were centrifuged to obtain the free fluid phase (plaque fluid). Bound protein was eluted from the plaque bacteria and matrix by washing the plaque with a low-pH buffer. The plaque fluid, low pH eluate, and whole saliva were assayed for immunoglobulins A, G, and M, the third component of complement, lysozyme, lactoferrin, and lactoperoxidase. Concentrations of total protein and albumin were also determined. Antibody reactive with specific plaque bacteria was detected by indirect immunofluorescent microscopy. Specific and nonspecific immune proteins were present in plaque fluid from adult subjects at significantly greater concentrations than in their saliva, which suggests that these proteins are concentrated in dental plaque. The results indicate that both saliva and gingival exudate contribute to the immunological proteins found in the free fluid phase of dental plaque. The observation that immunoglobulin A antibody reactive with plaque bacteria could be detected in plaque fluid suggests that a wide variety of immunological reactions may occur in the dental plaque. These potential interactions between host, plaque bacteria, and their products could serve to influence the plaque flora and its ability to induce disease.

Dental caries in South African black and white high school pupils in relation to sugar intake and snack habits

DMFT scores, total sugar intakes and snacks habits were determined in 1918 South African Black pupils (923 rural, 995 urban) and 724 White pupils (English and Afrikaans speaking) aged 16-18 years inclusive. Mean DMFT scores of school groups of Black pupils (both sexes) ranged from 0.9 and 2.0 in rural areas, to 4.2-6.7 in urban areas (where data were far higher than such obtained 7 years ago), and were 9.2 and 10.2 for White pupils. Corresponding mean daily sugar intake were - rural Blacks, 69 g and 97 g, urban Blacks 118-141 g, respectively (all slightly higher than previously); and Whites 102 g and 123 g. Mean DMFT scores of girls were higher than those of boys; yet while mean sugar intakes of Blacks girls and boys were somewhat similar, White girls' intakes were much lower than those of White boys. In the ethnic-sex groups studied, mean DMFT scores for pupils in upper, compared with lower, third of sugar intake, were higher in nine of the 14 sub-groups. Mean DMFT scores in upper, compared with lower, third of exposure to snack practices were higher in 11 of the 14 groups. However, most of the differences were slight. In further research, more intensive enquiries should be pursued on roles of ethnic and familial factors, as well as on roles of inter-acting dietary components additional to sugar and sugar-containing foods.

Prevalence of Streptococcus mutans serotypes, Actinomyces, and other bacteria in the plaque of children

Selected microbial components in dental plaque were determined for children in Biddeford, Maine and Colombia, South America. Using cultural methods, Streptococcus mutans was detected in 51.4% of the Colombian children and 63.3% of the Maine children. Serotype c was predominant in both populations. The greatest difference between the two groups occurred with serotypes d and g which were present in 25% of the Colombian children with S. mutans and were not detected in the Maine children. In the specimens examined with specific FA conjugates. Actinomyces was the predominant genus, present in all individuals and comprising an average of 52% of all cells.

Thiol groups and reduced acidogenicity of dental plaque in the presence of metal ions in vivo

Metal ions are known to influence the cariogenicity of dental plaque. Inhibition of acid metabolism in plaque may be of importance in this respect. Metal ions inhibit the acidogenicity of dental plaque to a different extent and it has been suggested that an enzyme inhibition based on oxidation of thiol groups may explain this observation. The aim of the present study was to evaluate the significance of oxidation of thiol groups in the inhibition of acid production in plaque by silver, tin and zinc salts. Nine subjects with 3-d sucrose induced plaque received topical applications of the metal ions. Cysteine or glutathione, which are known to reverse thiol oxidations, were then applied in one side of the mouth. Plaque pH measurements, in the presence of sucrose, were performed prior to and up to 2 h after treatment. The results showed that the acid production inhibited by the metal ions was reactivated by cysteine or glutathione. Iodoacetamide and p-chloromercuribenzoate were also shown to inhibit acid formation in dental plaque. The high affinity silver, tin and zinc have for SH groups, the observed inhibitory effect of these metals, the reactivation of the metabolism by monothiols and the fact that organic sulfhydryl reagents inhibit acid formation in plaque indicate that oxidation of thiol groups may be the mechanism by which these metals exert their effect.

Microflora and chemical composition of dental plaque from subjects with hereditary fructose intolerance

We compared the microbiological and chemical composition of dental plaque from subjects with hereditary fructose intolerance who restrict their dietary sugar intake with that of control subjects who do not. The two groups showed no significant differences in chemical composition of plaque: the mean protein, carbohydrate, calcium, magnesium, and phosphate contents were similar. Dental plaque from both groups contained similar numbers of total colony-forming units per microgram of plaque protein, and Streptococcus sanguis, an indigenous nonpathogen, was isolated with equal frequency from plaque samples of both groups. However, potentially odontopathic Streptococcus mutans and Lactobacillus were isolated three to four times more frequently from plaque samples of control subjects than from plaque samples of subjects with hereditary fructose intolerance. Clearly, diet (sucrose in particular) influences the colonization and multiplication of specific cariogenic organisms in dental plaque.