Cariogenic potential of foods. II. Relationship of food composition, plaque microbial counts, and salivary parameters to caries in the rat model.

A series of rat caries experiments was carried out to test the relative cariogenic potential and to identify the major carcinogenic elements of 22 popular snack foods. Parameters that were measured included rat caries, number of cariogenic bacteria in plaque, salivary parameters including flow rate, buffering capacity, total protein, lysozyme and amylase content, and composition of test foods including protein, fat, phosphorus, calcium, fluoride, galactose, glucose, total reducing sugar, sucrose, and starch. Many interesting relationships were observed between food components, numbers of plaque bacteria, salivary components, and specific types of carious lesions. Protein, fat, and phosphorus in foods were all associated with inhibition of both sulcal and buccolingual (smooth-surface) caries. Food fluoride was associated with inhibition of buccolingual caries, whereas calcium was related to inhibition of sulcal caries. Glucose, reducing sugar, and sucrose in foods were all related to promotion of both sulcal and smooth-surface caries. The numbers of Streptococcus sobrinus in plaque were associated with promotion of smooth-surface caries only, whereas lactobacilli, non-mutans bacteria, and total viable flora were related to promotion of both smooth-surface and sulcal caries. The salivary flow rate was associated with inhibition of both buccolingual and sulcal caries. Salivary buffering capacity (at pH 7) and salivary lysozyme delivery were associated with inhibition of number and severity of sulcal caries, while the salivary amylase content was related to the promotion of the number of sulcal lesions.

Caries risk assessment by a cross-sectional discrimination model.

Although the prevalence of dental caries is continuing to decline, it still affects a majority of the US population and can be a serious problem for those afflicted. The objective of this project was to develop and perfect a model for assessment of risk of dental caries onset in children. In the first study, reported herein, a set of clinical, microbiological, biochemical, and socio-demographic variables was identified that distinguished, with an acceptable level of sensitivity and specificity, between children who had no previous caries experience and children who had high caries levels. A total of 313 children--age 12-15 years, 140 from a fluoridated community and 173 from a fluoride-deficient community--was selected on the basis of previous caries experience, either zero DMFS or high DMFS (> or = 6 in the fluoridated or > or = 8 in the fluoride-deficient community). Clinical exams for DMFS, dental fluorosis, and plaque were conducted. Stimulated whole saliva was collected for analysis of mutans streptococci, lactobacilli, total viable flora, and fluoride concentration. A questionnaire was used for collection of demographic data as well as information on prior fluoride exposure, dietary habits, and oral hygiene practices. By means of discriminant analyses, with use of seven key clinical and laboratory variables, it was possible for zero-DMFS subjects to e classified correctly (specificity) in 77.6% of cases in the fluoridated community and in 86.1% of cases in the fluoride-deficient community. High-caries subjects were classified as such (sensitivity) in 79.3% and 88.1% of cases, respectively.

Caries risk assessment in a longitudinal discrimination study.

Our objective was to develop and perfect a model for the assessment of risk of dental caries onset in children. Even though dental caries prevalence in children is continuing to decline, there is still a significant minority for whom it is a problem. In this study, we sought to ascertain whether a set of variables selected in a previous cross-sectional study could be used to differentiate between caries-free six-year-olds who would or would not subsequently present with clinically-detectable caries. A total of 472 caries-free six-year-olds--286 from a fluoridated community and 186 from a fluoride-deficient community--was selected. Clinical examinations for DMFS, dental fluorosis, and plaque were conducted. Stimulated whole saliva was collected for analysis of mutants streptococci, lactobacilli, total viable flora, and fluoride, calcium, and phosphate concentrations. A questionnaire was used for collection of demographic data as well as information on prior fluoride exposure, dietary habits, and oral hygiene practices. By means of linear discriminant analyses, it was possible to predict correctly which children would develop caries within six to 12 months (sensitivity) in 82.8% of cases and which children would not develop caries during that period (specificity) in 82.4% of cases.

Control of microbial contamination with commercially available cleaning solutions.

The elimination of cross-contamination from operatory to laboratory is required for effective infection control. This study determined whether microbial cross-contamination occurs during cleaning of dental prostheses with an ultrasonicator and examined ways to reduce or eliminate the contamination that might occur. The antimicrobial activities of a temporary cement remover and tartar and stain remover were compared with deionized water and a known strong antimicrobial agent. All solutions were assessed without and with ultrasonication. The microbicidal strains were cultured in brain-heart infusion broth, with and without acrylic resin slabs, and the organisms were killed either without or with sonication and without or with acrylic resin slabs. Further testing with natural plaque-contaminated denture materials is warranted.

In vitro demineralization of enamel by F-sensitive and F-resistant mutans streptococci in the presence of 0, 0.05, or 0.5 mmol/L NaF.

Lactate production and accompanying enamel demineralization by fluoride-sensitive and fluoride-resistant mutans streptococci were studied in an in vitro demineralization model in the presence of 0, 0.05, or 0.5 mmol/L NaF. The fluoride-resistant strains were derived from laboratory strains or were recently isolated strains from xerostomic patients on high-dose fluoride therapy. The demineralization model was composed of a cell suspension in a glucose-agarose gel overlying a bovine enamel block. Lactate and calcium content of the agarose were determined after 22-hour incubations at 37 degrees C. Fluoride-resistant variants of Streptococcus sobrinus 6715-15 produced less lactate and caused less demineralization than did the parent strain even in the presence of fluoride. On the other hand, fluoride-resistant variants of Streptococcus mutans C180-2 and of S. mutans GS-5 produced more acid and caused greater demineralization than did their respective parent strains, both in the absence and presence of fluoride. Two recently isolated fluoride-resistant S. mutans strains produced more lactate and demineralized enamel more than did two recently isolated S. mutans strains from normal human subjects, both in the presence of 0 and 0.05 mmol/L NaF. It is concluded that adaptation to fluoride resistance does not invariably reduce the cariogenicity of mutans streptococci nor the effectiveness of fluoride in preventing demineralization.

Oral yeasts, mucosal health, and drug use in an elderly denture-wearing population.

Drug use among the elderly may be a factor in oral mucosal pathology and the prevalence of oral yeasts. This study was designed to evaluate the relationship between oral yeast, denture-bearing mucosal health and drug use, especially drugs with known hyposalivatory side effects. There was an inverse relationship between denture-bearing mucosal health, and hyposalivatory drug use r = -0.41 P less than 0.04. Use of drugs with a hyposalivatory side effect was related to increased numbers of Candida glabrata but not Candida albicans in saliva and at denture stomatitis and denture sore sites.

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.

Use of an intra-oral model to evaluate 0.05% sodium fluoride mouthrinse in radiation-induced hyposalivation.

The present study was undertaken to evaluate the effect of a twice-daily topical application of a 0.05% NaF mouthrinse on de- and remineralization in the oral cavities of subjects suffering from radiation-induced hyposalivation. Six subjects each wore a bonded intra-oral appliance containing a sound and a demineralized human enamel slab for four weeks. During that period, the subjects used 0.05% NaF rinses, twice daily, instead of the 1.1% NaF gel that had previously been a part of their preventive regimen. Salivary flow rates, plaque pH profiles following a 10% sucrose rinse, S. mutans and lactobacillus counts, fluoride clearance, and enamel microhardness were determined during the study. Sound enamel samples displayed no evidence of demineralization, and the previously demineralized enamel showed remineralization in the outer 50 microns in three of the six subjects. The results suggest that a twice-daily oral rinse with 0.05% NaF can prevent demineralization and enhance remineralization in subjects with radiation-induced hyposalivation.

Effects of fluoride, lithium, and strontium on growth and acid production of mutants streptococci and Actinomyces viscosus.

Eight strains of mutants streptococci and two strains of Actinomyces viscosus were studied to determine (1) their relative sensitivities to fluoride, lithium, and strontium and (2) whether lithium or strontium interact to enhance the known antimicrobial effects of fluoride. Analyses of variance of the data revealed a major inhibition of growth and acid production by fluoride, but not by lithium or strontium. Fluoride (5 mg/l) inhibited cell growth of all strains tested by a mean of 17% and total titratable acid production by a mean of 31%. However, there were marked differences between the strains. Mean total titratable acid was inhibited by fluoride least with the A. viscosus strains (15%) and most with the mutans streptococci (34%). Although interactions among the elements were statistically significant, they were generally slight in magnitude.

Interactions of sanguinarine and zinc on oral streptococci and Actinomyces species.

Sanguinaria extract, which contains benzophenanthridine alkaloids, has been used as a folk medicine for many years. Minimum inhibitory and minimum bactericidal concentrations (MIC and MBC values) for sanguinarine were determined for common and etiologically important plaque bacteria. Because the efficacy of sanguinarine is believed to be enhanced by zinc, isobolograms were assessed to determine their mode(s) of interaction. Hydrogen ion concentration influenced the inhibitory activity of both sanguinarine and zinc. For sanguinarine, at the optimum pH (6.5), MIC values were 4 or 8 micrograms/ml for Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguis, Actinomyces viscosus and Actinomyces naeslundii. MIC values were 0.125-0.50 mmol Zn/ml. MBC values ranged from 1 to 8 mmol Zn/ml at pH 5.5. Isobologram data revealed that sanguinarine and zinc interacted synergistically. Viadent oral rinse, which contained 300 micrograms sanguinaria extract/ml and 0.2% zinc chloride (14.9 mmol Zn/l), was inhibitory to all strains tested. MIC values were 1 or 2% (ml Viadent oral rinse/100 ml aqueous solution) for all strains except A. viscosus for which the MIC value was 12% (vol/vol).

Effects of contrast agents on the fallopian tube in a rabbit model.

The authors evaluated the effect of different iodinated contrast agents on the fallopian tube and adnexal tissue in 15 rabbits. Ethiodized oil, an oil-soluble agent, was used in five rabbits. The following water-soluble agents were used: iothalamate meglumine 30% (n = 3), iothalamate meglumine 60% (n = 3), and ioxilan (n = 4). The agents were injected through catheters placed in the fallopian tubes. Fallopian tubes and peritoneal cavities were histologically evaluated. The contralateral tube served as a control. Ioxilan and iothalamate meglumine 30% produced no pathologic response in the tube or peritoneal cavity. Iothalamate meglumine 60% was associated with mild inflammatory infiltrate, mucosal edema, giant cell reaction, and periovarian adhesions that were bilateral but more pronounced on the injected side. Use of ethiodized oil resulted in papillary fibrous adhesions on the ovarian surface, and fat granulomas were seen in the periovarian tissues. The safety of oil-based contrast agents for use in hysterosalpingography is therefore questioned. No significant differences were found among the water-soluble contrast agents.

Interactions of selenium and fluoride on growth, glycolysis and survival of Streptococcus mutans GS-5.

The effects of low concentrations (1.0 mmol/l of selenite and seleno-dl-cystine were tested alone, or in combination with NaF, on growth, glycolysis, and survival of Streptococcus mutans GS-5. In batch culture, both selenium-containing compounds (1.0 mmol/l) inhibited the growth rate and final cell yield by 92% or greater; glycolysis, however, was not affected. The observed bactericidal action of selenite at 0.1 mmol/l was pH-dependent. Fluoride reduced the killing effect of SeO3 in the culture medium and in a lactate-acetate buffer system at pH 6.5, 5.0 and 4.0. These data indicate that selenium-containing compounds exert an antibacterial action on cells of S. mutans in a manner which leaves glycolysis unaffected.

Correlations between numbers of microflora in plaque and saliva.

An epidemiologic investigation to reliably identify caries-susceptible subjects by microbiological and chemical assessment of plaque and saliva is currently in progress. As part of that study, the numerical relationships of mutans streptococci, lactobacilli and total viable microflora in plaque and saliva among 12- to 15-year-old children in a fluoridated community were determined. Paraffin-stimulated whole saliva and pooled dental plaque were collected. Each sample was suspended in reduced transport fluid, chilled on ice, and assayed. The bivariate normal distribution was found to be a suitable model for the distribution of the pairs [numbers of bacteria in plaque (log10), numbers of bacteria in saliva (log10)]. Statistically significant positive correlations were found between numbers of mutans streptococci in plaque and saliva, and between lactobacilli in plaque and saliva.

Cariogenic potential of foods. I. Caries in the rat model.

As part of a major study to identify cariogenic elements of foods, the cariogenic potential of 22 foods relative to sucrose (confectioners' sugar) was determined over six intubation rat caries experiments. Cariogenic potential indices were calculated for each food from sulcal and buccal-lingual caries based on both number and severity. Those foods with the lowest cariogenic potential indices were peanuts, gelatin dessert, corn chips, yoghurt, and bologna; with the highest cariogenic potential indices were sucrose, granola cereal, french fries, bananas, cupcakes, and raisins. There was no simple relationship between food sucrose content and caries. Enhanced cariogenic potential was associated with foods containing approximately 1% or more hydrolyzable starch in combination with sucrose or other sugars.

AUR memorial award--1988. MRI enhancement of perfused tissues using chromium labeled red blood cells as an intravascular contrast agent.

It has been demonstrated that chromium (Cr) labeling significantly decreases the relaxation times of packed red blood cells (RBCs). In this study, the spin-lattice relaxation time (T1) of human red cells was shortened from 836 ms to 29 ms and the spin-spin relaxation time (T2) shortened from 134 ms to 18 ms, when the cells were labeled at a Cr incubation concentration of 50 mM. Labeling of canine cells at 50 mM resulted in a T1 of 36 ms and a T2 of 26 ms. A labeling concentration of 10 mM produced similar relaxation enhancement, with uptake of 47% of the available Cr, and was determined to be optimal. The enhancement of longitudinal and transverse relaxation rates (1/T1,-1/T2) per amount of hemoglobin-bound Cr are 6.9 s-1 mM-1 and 9.8 s-1 mM-1 respectively, different from those of a pure Cr+3 solution. Labeling cells at 10 mM decreased the survival half-time in vivo from 16.6 days to 4.7 days in dogs. No difference in red cell survival was found with the use of hetero-transfusion versus auto-transfusion of labeled RBCs. Significant shortening of the T1 (912 ms to 266 ms, P = .03) and T2 (90 ms to 70 ms, P = .006) of spleen and the T1 (764 ms to 282 ms, P = .005) and the T2 (128 ms to 86 ms, P = .005) of liver occurred when 10% of the RBC mass of dogs was exchanged with Cr labeled cells. Liver and spleen spin density changes (P greater than 0.23) and muscle spin density and relaxation changes (P greater than 0.4) were insignificant. The in vivo T1 of a canine spleen which had been infarcted did not change following transfusion with labeled cells, where the T1 of liver did shorten. We believe this preliminary study suggests that Cr labeled red cells may have the potential to become an intravascular magnetic resonance imaging contrast agent.

Peritoneal reaction resulting from iodinated contrast material: comparative study.

A consensus does not exist as to the optimal contrast agent for hysterosalpingography. This study was undertaken to evaluate the early and delayed inflammatory responses of the peritoneal surfaces to various types of iodinated contrast media. Guinea pigs received intraperitoneal injections of lactated Ringer solution, iothalamate meglumine, diatrizoate sodium, ioxilan, or ethiodized oil. The inflammatory response of the peritoneal surfaces was assessed at 1,7, and 30 days. Five animals were studied at each time point for each agent. No animals that received Ringer lactate or iothalamate meglumine had inflammation at any time. Ioxilan produced inflammation in two of five animals at 7 days and no inflammation at 1 or 30 days. Ethiodized oil produced no inflammation at 1 day; however, three animals had inflammation at 7 days, and all five had inflammation at 30 days. The 30-day group showed striking inflammatory response with granulomatous features. The authors recommend the continued use of meglumine-based water-soluble ionic contrast material for hysterosalpingography.

Interactions of zinc with fluoride on growth, glycolysis and survival of Streptococcus mutans GS-5.

Effects of zinc and/or fluoride on growth, glycolysis and survival of Streptococcus mutans GS-5 were examined in vitro. Zinc inhibited growth and glycolysis, and enhanced the antimetabolic activity of fluoride. Zinc alone had little effect on cell survival. During cell growth without pH control a protection from cell death was mediated by fluoride, which appeared to be caused by a higher final pH in the culture medium. When cell death was observed under controlled pH conditions in a lactate-acetate buffer at pH 6.5, 5.0 or 4.0, fluoride was bactericidal only at pH 4.0. However, the combination of zinc plus fluoride was strongly bactericidal at all pH values that were tested.

Effect of metronidazole on development of subgingival plaque and experimental periodontitis.

Active tissue destruction in experimental periodontitis has been positively correlated with subgingival spirochetes and total number of organisms. The present study was designed to inhibit spirochete populations and evaluate the effect upon periodontal destruction. Metronidazole was administered orally to four squirrel monkeys (100 mg/kg/bwt) for 17 days. After 3 days, marginal periodontitis was induced around bicuspids and molars by tying silk ligatures at the gingival margins. Subgingival plaque samples were taken baseline and 14 days after ligature placement. Dark-field microscopy quantitated motile forms, spirochetes, straight and curved rods, filament, cocci and fusiforms. Periodontal destruction was evaluated at 2 weeks by histometric analysis of connective tissue attachment, crestal alveolar bone and infiltrated connective tissue. Bacterial and histometric comparisons were made with experimental periodontitis data from four animals (control) which had not received metronidazole. Subgingival plaque prior to periodontitis induction was dominated by cocci, but fusiforms and straight rods were also present. Straight rods formed a greater proportion of the plaque which developed in metronidazole-receiving animals. The absence of spirochetes and motile rods contrasted with the control group where spirochetes were the predominant type. The total number of bacteria was also larger in the control animals. Histometric analysis showed that areas of infiltrated supracrestal connective tissue were similar in both groups. Loss of connective tissue attachment and alveolar bone was significantly less in experimental animals, and the latter values did not differ significantly from baseline dimensions. The results indicated that the subgingival bacterial populations which developed during metronidazole administration did not result in an experimental periodontitis.