Sucrose Rinse Research Articles

Effect of White Cheese and Sugarless Yoghurt on Dental Plaque Acidogenicity

White cheese and sugarless yoghurt are frequently consumed traditional Turkish foods. The aim of this study was to assess their acidogenic potential when eaten alone or following a rinse with sucrose solution. Plaque pH was measured by a pH microelectrode at baseline to determine the resting plaque pH and at time intervals of 1–60 min after rinsing with 10% sucrose solution or eating the test food for 1 min. White cheese consumption for 1 min increased the plaque pH. When white cheese was eaten 5 min after rinsing with 10% sucrose solution, the plaque pH rose rapidly. After sugarless yoghurt consumption, the pH fell to a similar minimum as for sucrose after 5 min but returned to baseline levels after 30 instead of 60 min. Consumption of sugarless yoghurt after a sucrose rinse initially reduced the plaque pH further but did not affect the time taken for pH to regain baseline levels.

Effect of an intensified treatment with 40% chlorhexidine varnish on plaque acidogenicity

Previous work showed that a single application of 40% chlorhexidine varnish, EC40, reduced plaque acidogenicity upon sucrose challenge during less than 3 weeks. It was questioned whether lactic acid production could be reduced significantly longer when the treatment was intensified. Therefore, the effects of three consecutive EC40 applications on plaque acidogenicity were evaluated. Nine subjects who participated in the previous study received three full mouth EC40 applications within 1 week. Before the first application and up to 9 weeks after the third application, plaque samples were taken after a 10% sucrose rinse and analyzed for organic acids with capillary electrophoresis. At baseline, the mean provoked lactic acid concentration was 1.64 (+/-0.69) micromol/mg protein. At the first and seventh day after the third application, there was too little plaque to measure acid concentrations. At 2 weeks after the third application, lactic acid concentrations were significantly reduced (p < 0.05). The acid concentrations 3 weeks after the third application (1.61 (+/-0.99) micromol/mg protein) did not differ from the values at baseline (paired T test, p > 0.05). We conclude that a triple 40% chlorhexidine varnish treatment did not affect plaque acidogenicity for more than 3 weeks. From comparison with a previous study, we conclude that the triple treatment with EC40 within 1 week was not more effective in reducing plaque acidogenicity than the single one.

Dental Plaque pH and Micro-organisms during Hyposalivation

We have previously reported that minor gland and whole saliva flow rates and salivary proteins showed differences in individuals with primary Sjögren's syndrome or head and neck radiation therapy, compared with controls (Eliasson et al., 2005). We now hypothesize that pH and number of acidogenic micro-organisms in dental plaque as well as saliva buffering capacity also differ in these individuals. Plaque pH was measured by the microtouch method up to 60 min after a sucrose rinse. Plaque collected from the same sites was analyzed for counts of total and acidic micro-organisms. Compared with their controls, the irradiated group but not the Sjögren's syndrome group displayed significantly lower plaque pH, increased numbers of lactobacilli and Candida species, as well as reduced buffering capacity. Stepwise regression tests suggested that the buccal minor-salivary-gland secretion rate in the test groups and counts of mutans streptococci in the controls were of significant importance for dental plaque pH.

Effect of xylitol-containing chewing gums on interdental plaque-pH in habitual xylitol consumers

Objective. The aim was to investigate the effect of high and low amounts of xylitol on the interdental plaque-pH, directly and after sucrose challenge, in schoolchildren with habitual consumption. Material and methods. The study group consisted of 11 healthy children (10–15 years) with low caries risk and the experiment had a single-blind crossover (Latin square) design. After a 2-week run-in period with a daily 4.0 g xylitol intake, the children were subjected to single-dose exposures of chewing gums with (i) paraffin (CTR; no xylitol), (ii) low-dose xylitol (LX; 2.0 g xylitol), and (iii) high-dose xylitol (HX; 6.0 g xylitol) in a randomized order separated by a washout period of 1 week. Samples of chewing-stimulated whole saliva were collected prior to and after the experimental period for determination of bacterial counts. The outcome measures were in situ plaque-pH (micro-touch method) and area under the pH curve (AUC). Results. The AUC was significantly greater (p<0.05) in the HX group compared to the LX and control groups during the first 5 min after chewing. After a 10% sucrose rinse, the interdental plaque-pH dropped in all groups but the HX regimen displayed significantly less reduction 0–5 min after chewing (p<0.05). No significant alterations of the total viable counts or mutans streptococci levels in saliva were disclosed during the 4-week experimental period. Conclusions. The present results suggested that a high single dose of xylitol had a short and limited beneficial effect on interdental plaque-pH in habitual xylitol consumers, while a low single dose, resembling normal chewing gum use, did not differ from the control.

The efficacy of a fluoride chewing gum on salivary fluoride concentration and plaque pH in children

Objectives. The purpose of this study was therefore to study the influence of different chewing times on the salivary F concentration and on the recovery of plaque pH directly after a sucrose rinse on both the chewing and the non-chewing side. Methods. For this purpose, one piece of sugar free chewing gum was chewed to 10 healthy subjects (aged 8–10 years, 5 male and 5 female children). Subjects refrained from toothbrushing for 3 days. On the fourth day, they rinsed for 1 min with 10 μl of a 10% sucrose solutions. After 8 min, chewing gum was given and started to chew for either 5, 10, 20, 30, 45 min or control (sucrose rinse). Thus, altogether six test sessions were repeated at one week intervals. Measurements of F concentration in saliva and pH of approximal plaque were carried out at two contralateral sites for up to 60 min. Results. Higher salivary F concentrations were found on the chewing side than on the non-chewing side (expressed as) (p<0.05). But, the difference between the chewing and the non-chewing side was not obvious for the plaque pH (expressed as AUC) (p>0.05). Therefore, this study showed that: (1) the F concentrations in saliva after chewing a F containing chewing gum had only small numerical differences among the various chewing times, with the exception for 5 min. All chewing time periods showed statistically significant differences between chewing and non-chewing side. (2) The prolonged chewing time increased the plaque pH recovery after a sucrose rinse (p<0.05), but there was no statistically significant difference on both of the chewing and non-chewing side (p>0.05). Conclusion. The results of this study indicated that a prolonged chewing time was favorable to the plaque pH recovery after a sucrose rinse and, to a certain extent, to the salivary fluoride concentration. Also it was shown that the F concentration in saliva was strongly dependent on which side the subject chewed on.

Influence of Short-Term Sucrose Exposure on Plaque Acidogenicity and Cariogenic Microflora in Individuals with Different Levels of Mutans Streptococci

The aim was to study the short-term effect of a varying sucrose exposure on plaque acidogenicity and cariogenic microflora in two groups of subjects with different levels of mutans streptococci (MS). Eight subjects with low (<10⁴) and 8 with high (>10⁶) numbers of MS per millilitre saliva participated. Three 7-day test periods were conducted. During two of these, the subjects rinsed either 5 or 10 times daily with 10% sucrose; the third period without any mouth rinses served as control. The subjects refrained from oral hygiene during the last 3 days of each test period. On day 7, the following parameters were measured: plaque pH after a sucrose rinse, numbers of MS, Streptococcus sanguis and lactobacilli in saliva, percent MS in plaque and plaque index. The results revealed that plaque acidogenicity was more pronounced for the high-MS group compared to the low-MS group after all three test periods, i.e. lower resting pH, deeper pH falls and a lower final pH. For both groups, the greatest pH-lowering capacity of plaque was found after the period with 10 sucrose rinses/day. An increase in bacterial counts was noted for both groups during the test periods with the 5- and 10-time rinse regimen; this increase was larger for the high-MS group compared to the group with low MS counts. The highest plaque index was, irrespective of the test period, found for the high-MS group.

Changes in Lactate and Other Ions in Plaque and Saliva after a Fluoride Rinse and Subsequent Sucrose Administration

The purpose of this study was to examine plaque and saliva composition after a fluoride rinse and subsequent sucrose application. Fifteen subjects accumulated plaque for 48 h, and then rinsed with a fluoride rinse based on 228 µg/g (ppm) Na₂SiF₆ and some received no rinse. After 60 min, upper and lower buccal molar plaque samples and 1-min saliva samples were collected. The subjects then rinsed with 10% g/g sucrose solution, and 7 and 15 min later, a second and a third set of samples were collected. Plaque fluid and clarified saliva were then recovered from these samples by centrifugation, and the remaining plaque acid extracted. The plaque fluid, centrifuged saliva, and plaque extract samples were then analyzed using micro techniques for pH, free calcium, phosphate, organic acids (plaque fluid and saliva only) and fluoride. Considering both the fluoride rinse and no-rinse groups, the most notable compositional changes in saliva 7 min after the sucrose rinse were pH –0.40 unit, free calcium 0.42 mM, lactate 5.2 mM, phosphate –1.3 mM, and fluoride 2.8 µM; while in plaque fluid, the corresponding changes were pH –1.59 unit, free calcium 1.5 mM, lactate 35 mM, phosphate –1.6 mM and fluoride –26 µM. After sucrose rinsing, undersaturation was found with respect to dicalcium phosphate dihydrate in saliva and plaque fluid and with respect to tooth enamel in some plaque fluid samples. Plaque fluid composition appeared to be strongly influenced by salivary clearance, diffusive loss of ions into the water phase of the rinse, and lower jaw pooling of the sucrose and fluoride components of the rinses. After the experimental rinse, the fluoride concentration in plaque fluid [86 ± 22 mM (upper molar site), 162 ± 150 mM (lower molar site)], saliva (26 ± 18 mM), and whole plaque [99 ± 97 µg/g (upper molar site), 197 ± 412 µg/g (lower molar site)] was comparable to the values in previous studies using this rinse. These very high plaque fluid fluoride concentrations, compared with the ‘no-rinse’ samples, induced an approximately 0.3-unit increase in the plaque fluid pH 7 min after the sucrose rinse, a small decrease (approximately 20%) in lactate production and a modest increase in enamel saturation. Although these changes were all statistically significant, no correlation was found between the decrease in lactate concentration and plaque fluid fluoride, pH or whole plaque fluoride.

Association of caries activity with the composition of dental plaque fluid.

This study tests the hypothesis that caries activity is associated with lower degrees of saturation with respect to enamel mineral in dental plaque fluid following sucrose exposure. Plaque fluids were obtained from caries-free, caries-positive, and caries-active subjects. Samples were collected before and at 3 and 7 min after a sucrose rinse on consecutive weeks and analyzed for organic acids, inorganic ions, pH, calcium activity, and, in selected samples, total protein. After sucrose, pH values were significantly lower in the caries-active group in comparison with the caries-free and caries-positive groups. Total and free calcium concentrations increased with decreasing pH, with free calcium being about one-third of total calcium. The caries-active group exhibited significantly lower degrees of saturation with respect to enamel mineral, after sucrose, and had significantly higher mutans streptococci levels in plaque than did the caries-free samples. Thus, saturation levels in post-sucrose plaque fluids reflect the cariogenic potential of dental plaque.

Release of mineral ions in dental plaque following acid production

The release of appreciable amounts of calcium, phosphate and fluoride found in whole plaque into the plaque-fluid phase, following bacterial acid production, can potentially reduce the driving force for tooth demineralization. However, limited information is available on this topic, particularly on the release of fluoride. This study sought to determine the change in calcium, phosphate and fluoride concentrations in plaque fluid after sucrose exposure. 48 h overnight-fasted supragingival plaque samples were collected from all tooth surfaces (with the exception of the lower lingual anterior teeth) of one half of an individual mouth, following a 1 min water rinse. Plaque samples were then collected from the other half of the same mouth, following a 292 mM sucrose rinse. Plaque fluid was isolated by centrifugation and analysed for total calcium and phosphate (ion chromatography) and for free fluoride (ion-specific electrode). Samples were collected from seven individuals. Following sucrose exposure, plaque-fluid pH decreased significantly from 6.5±0.3 to 5.4±0.2; calcium concentrations (mmol/l) also increased significantly ( p<0.01) from 1.9±0.5 to 5.0±2.1. Fluoride and phosphate concentrations in plaque fluid, however, did not increase significantly after sucrose exposure: mean concentrations (mmol/l) of fluoride after the water and sucrose rinses were 0.006±0.003 and 0.005±0.002, respectively, and mean phosphate concentrations (mmol/l) were 11.0±2.0 and 12.0±3.0, respectively. When results were expressed per wet plaque weight, phosphate concentrations were also found to increase significantly. The same trends were observed when additional plaque samples were treated in vitro with sucrose: fluoride-ion activity did not increase in plaque under in vivo-like conditions.

The Microbial Generation of Nitric Oxide in the Human Oral Cavity

Nitric oxide a potent antimicrobial agent and vasodilator, may be synthesized in the human mouth due to the bacterial reduction of salivary nitrate. The purpose of this study was to determine whether intra-oral pH changes produced by the oral flora may augment the production of nitric oxide. To test this hypothesis a sucrose mouthrinse was administered to human volunteers who were free from caries and periodontal disease and production of oral nitric oxide was related to intra-oral pH changes. Baseline measurements consisted of pooled supragingival plaque and anterior and posterior tongue scrapings for microbiological analysis. Additional samples of saliva were collected for nitrate and nitrite analysis. Intra-oral pH measurements were recorded with a microelectrode at selected sites and NO intra-oral levels were measured by chemiluminescence. In addition selected members of the oral flora were tested for their ability to reduce nitrate to nitrite. A decrease in pH produced by the sucrose rinse was significantly associated with an increase in the intra-oral generation of NO after 5 min (p=0.006). The most frequently recovered nitrate reducing organisms were Veillonella spp. and Actinomyces spp. whilst the acidogenic Streptococcus spp. were negative nitrate reducers. The oral generation of NO appears to be influenced by pH levels within the oral cavity. Keywords: nitric oxide, nitrate, nitrite, saliva, nitrate reductase, intra-oral pH.

A Mathematical Model of the Influence of Salivary Urea on the pH of Fasted Dental Plaque and on the Changes Occurring during a Cariogenic Challenge

Urea diffusing from saliva into dental plaque is converted to ammonia and carbon dioxide by bacterial ureases. The influence of normal salivary urea levels on the pH of fasted plaque and on the depth and duration of a Stephan curve is uncertain. A numerical model which simulates a cariogenic challenge (a 10% sucrose rinse alone or one followed by use of chewing-gum with or without sugar) was modified to include salivary urea levels from 0 to 30 mmol/l. It incorporated: site-dependent exchange between bulk saliva and plaque surfaces via a salivary film; sugar and urea diffusion into plaque; pH-dependent rates of acid formation and urea breakdown; diffusion and dissociation of end-products and other buffers (acetate, lactate, phosphate, ammonia and carbonate); diffusion of protons and other ions; equilibration with fixed and mobile buffers; and charge-coupling between ionic flows. The K_m (2.12 mmol/l) and V_max (0.11 μmol urea/min/mg dry weight) values for urease activity and the pH dependence of V_max were taken from the literature. From the results, it is predicted that urea concentrations normally present in saliva (3–5 mmol/l) will increase the pH at the base of a 0.5-mm-thick fasted plaque by up to 1 pH unit, and raise the pH minimum after a sucrose rinse or sugar-containing chewing-gum by at least half a pH unit. The results suggest that plaque cariogenicity may be inversely related to salivary urea concentrations, not only when the latter are elevated because of disease, but even when they are in the normal range.

Biochemical comparison of plaque fluid on tooth and acrylic surfaces during a sucrose challenge

Previous studies have investigated variations in dental plaque fluid composition within a single mouth after a sucrose exposure. The purpose of this study was to determine a potential source of calcium and phosphorus in plaque by comparing the pH, calcium and phosphorus concentrations in plaque fluid obtained from an acrylic appliance with samples taken from supragingival tooth surfaces within the same individual after a sucrose challenge. Separate plaque samples from 14 individuals were collected from an acrylic appliance or tooth surfaces within same individual before and 15 min after a 20% sucrose rinse. Each plaque sample was centrifuged and nanolitre samples of plaque fluid were analysed for pH with a pH microelectrode, for total calcium concentration by atomic absorption in a graphite furnace, and for phosphorus concentration by spectrophotometry. There was an increase in the calcium and phosphorus concentration in the plaque after the sucrose challenge and a significant increase in calcium and phosphorus concentrations in the plaque taken from the teeth compared to the acrylic surfaces. The results indicate that the increased total calcium and phosphorus in plaque during a sucrose challenge is probably derived from the demineralization of enamel or extracellular demineralized components.

The role of microbiology in models of dental caries.

Models of dental caries (laboratory, animal, and human in situ models) vary markedly in their microbiological complexity. Laboratory models range from mono-cultures of cariogenic species providing an acidic challenge to enamel, to the development of diverse mixed cultures growing on a habitat-simulating medium in an artificial mouth or chemostat. The latter systems are of value in determining either mechanisms of action or cause-and-effect relationships--e.g., between dietary components or antimicrobial agents and the microflora. Laboratory models have also shown that the sensitivity of oral bacteria to inhibitors is markedly reduced when growing in biofilms such as dental plaque. Animal models have proved unequivocally that caries is an infectious and transmissible disease. Their use has enabled comparisons to be made of (a) the cariogenic potential of different bacterial species, (b) the role of the diet, and (c) the effects of potential anti-caries agents. It has been claimed that no caries-protective agent currently in use has failed a rodent test. In situ human models have been designed to permit the development of "natural" plaque on standardized enamel surfaces freely exposed to the human oral environment. The microflora that develops on unadulterated surfaces is similar in composition to that found at comparable sites on vital teeth. Demineralization can be accelerated by the inoculation of additional cariogenic bacteria coupled with either intra- or extra-oral sucrose rinses. The increased realism associated with the transition from laboratory to human in situ models is countered by a reduced ability to control or manipulate the system for experimental purposes. Thus a hierarchy of tests is needed for the study of anti-caries agents, each requiring a varying degree of microbiological complexity.

Effects of lactate dehydrogenase and nicotinamide adenine dinucleotide on human dental plaque pH and acid anion concentrations

The effect of sucrose rinses supplemented with L-LDH and NAD was investigated. When LDH or NAD were added to the sucrose rinse, the pH fall was less marked than with rinsing with sucrose alone. Significant differences ( p < 0.05) in mean minimum pH and cH areas were observed when sucrose rinses were supplemented with LDH, NAD or with a combination of LDH and NAD, when compared with sucrose alone. Plaque fluid concentrations of lactate and acetate significantly decreased with all rinses when compared with sucrose alone. Phosphate levels also decreased, although not significantly, when NAD was the sole supplement. No significant decreases were observed in succinate, formate or propionate concentrations. The results confirm the beneficial effect of LDH in reducing the accumulation of lactate in plaque following a sucrose rinse. The inclusion of NAD in the rinse demonstrated the role of extracelluar hydrogen acceptors in the reaction. Further work is required to identify endogenous hydrogen receptors and to clarify the fate of pyruvate resulting from the oxidation of lactate before the potential role of LDH as a cariostatic agent can be fully understood.

Cariogenic potential of pooled plaque fluid from exposed root surfaces in humans

The composition of pooled plaque fluid from exposed root surfaces of five population samples was determined before and at selected times (3, 7 and 15 min) after a 5 and 10% sucrose rinse. Subjects were 45–65 yr old, had exposed, sound root surfaces, and were grouped according to root caries status [caries-free (CF), no root caries history; caries-positive (CP), recorded root caries experience]. Samples were obtained only from the sound surfaces of the CF and CP subjects after overnight fasting. Plaque samples from each subgroup were pooled under mineral oil and maintained on ice. Plaque fluid was then isolated by centrifugation and analysed for organic acids and inorganic ions (ion chromatography), and pH (microelectrodes). From these data, the degree of saturation [DS (TM)]in plaque fluid with respect to tooth mineral (TM) was calculated. Before exposure to sucrose, plaque fluids from the CF and the CP subgroups had similar ionic compositions. These fluids were also found to be supersaturated with respect to tooth mineral. After exposure to sucrose, a rapid decrease in plaque fluid pH was observed, which corresponded primarily to lactic acid production. For all times examined, mean pH and DS (TM) values were lower and lactic acid concentrations were higher in the CP than the CF samples. Lower values of DS (TM) suggest that plaque fluid from CP subjects had a measurably greater cariogenic potential. Calcium concentrations also increased significantly and to comparable levels in all plaque fluid samples after sucrose exposure, despite lower acid production in CF samples. These results appear to be associated with the further finding that whole plaque from the CF subgroups contained significantly more calcium than that from the CP subjects. Thus the presence and availability of mineral ions such as calcium within plaque may play an important part in controlling enamel demineralization. In general, the chemical composition of plaque fluid from root surfaces before and after sucrose exposure was similar to that previously found for samples from coronal surfaces. Taking these results into consideration, along with the fact that dentine mineral is more soluble than enamel mineral, it can be concluded that the driving force in plaque fluid for the demineralization of exposed root tissue is greater than that for enamel demineralization.

Effect of Chewing Xylitol Chewing Gum on Salivary Flow Rate and the Acidogenic Potential of Dental Plaque

Ten adults participated in the study which consisted of four experimental periods each lasting 2 weeks, during each of which subjects were assigned to one of four gum-chewing regimens: no gum, sucrose gum, sorbitol gum and xylitol gum. At the start and end of each test period unstimulated and stimulated salivary flow rates were determined. At the end of each test period the acidogenic potential of 48-hour dental plaque was measured using a Beetrode pH microelectrode. No statistically significant (p < 0.05) effect on salivary flow rate was observed. The xylitol chewing gum regimen resulted in significantly higher plaque pH than no gum, sucrose gum and sorbitol gum at 2, 10, 20, 30 and 60 min following a 10% sucrose rinse. In addition, xylitol gum regimen exhibited a significantly higher minimum pH and smaller area of the curve below pH 6. The results suggest that the regular use of xylitol-sweetened gum may serve to reduce the acidogenic potential of dental plaque.

Effect of sucrose rinses on the oral microflora and on salivary sucrase activity.

The effect of sucrose rinses on the salivary microflora and on bacterial sucrose cleaving, i.e., sucrase activity, was studied in 11 dental students with high salivary counts of mutans streptococci (> or = 10(5) CFU/ml). The subjects rinsed for 1 min with a 10% (w/v) sucrose solution every 4-h during waking hours on 2 consecutive days. Four paraffin-stimulated saliva samples were collected as follows: one before the rinses and then 12 h and 5 and 8 days after the rinses. Commercial dip-slide methods were used to determine viable counts of mutans streptococci, lactobacilli, and yeasts; mutans streptococci were also enumerated using MSB agar, while blood agar was used to recover the total facultative and anaerobic bacteria. The sucrase activity was determined using both whole (mainly cell-associated) and centrifuged (extracellular) saliva samples. The proportions of facultative bacteria (p = 0.007) and mutans streptococci (p = 0.001) increased as a result of the sucrose rinses. No changes were detected in the number of lactobacilli or yeasts. The sucrose rinses increased both the cell-associated (p = 0.049) and the extracellular (p = 0.011) sucrase activities. The measurement of sucrase activity may be of value in assessing dietary habits and sucrose consumption.

Composition of pooled plaque fluid from caries-free and caries-positive individuals following sucrose exposure.

The composition of pooled plaque fluid from five population samples was determined before and at selected times (7, 15, 30, and 60 min) after a 10% sucrose rinse. Subjects were grouped according to caries status (caries-free, CF, DMFS = 0; caries-positive, CP, DMFS > 10). Samples were also studied from white-spot surfaces and from sound surfaces of the same mouths of two additional CP groups. Plaque fluid was isolated by centrifugation and analyzed for organic acids, inorganic ions (ion chromatography), and pH (microelectrodes). Prior to sucrose exposure, plaque fluids from the CF subgroups and from sound surfaces of the CP subjects had higher pH values than samples from CP subgroups and from white-spot surfaces, respectively; the ionic compositions were otherwise similar. Starved plaque fluids were also found to be supersaturated with respect to enamel and to a significantly greater degree in the CF samples, suggesting that CF plaque fluid may have a greater remineralization potential than CP samples. Following sucrose exposure, a rapid decrease in plaque fluid pH was observed, which corresponded primarily to lactic acid production. For all times examined, mean pH and DS(En) values were lower and lactic acid concentrations were higher in the CP samples than in the CF samples; noted differences were statistically significant at 7 min for pH and DS(En), and at 7, 15, and 30 min for lactic acid. Lower values of DS(En) suggest that plaque fluid from CP subjects had a measurably greater cariogenic potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of intra-oral demineralization of enamel after single exposures to sodium fluoride.

Studies demonstrated the effects of single rinses with low concentrations of NaF on the intra-oral demineralization of enamel. Blocks of bovine enamel were covered with Streptococcus mutans IB1600, mounted in palatal appliances, and worn in the mouths of volunteers for specified times. Subjects rinsed with solutions of NaF, with or without sucrose. Demineralization was determined as changes in iodide penetrability (delta Ip) of the enamel, while the pH and F of the streptococcal plaque, and enamel F, were determined with ion-specific electrodes. Delta Ip was reduced by about 80% (from 14.5 +/- 2.7 to 2.8 +/- 2.3 units) when 250 micrograms F/mL was added to the sucrose rinse. Corresponding plaque pH's were 4.1 +/- 0.5 and 4.2 +/- 0.3, consistent with a lack of effect on bacterial acidogenesis. Protection against mineral loss was concentration-dependent. Administration of sucrose at different times after NaF revealed that the effect of F persisted for at least 60 min. Analyses of plaque F demonstrated an initial elevation and concentration within the cells, followed by a drop to stable, baseline values. Enamel F increased slowly to almost 500 micrograms/g enamel after 105 min. The protective effect of F appeared to be manifested in two stages, the first related to a high plaque F and the second to F that became incorporated into the enamel. Analysis of the data suggested that F was transferred from plaque to enamel during the experimental period.

Effect of timing of administered calcium lactate on the sucrose-induced intraoral demineralization of bovine enamel

A number of soluble calcium salts are known to reduce the demineralization of enamel in the mouth. The present study was undertaken to examine the effects of rinses containing different concentrations of calcium lactate, and the time of giving the rinses with respect to sucrose challenges. Subjects wore palatal appliances containing blocks of bovine enamel whose surfaces were covered with Streptococcus mutans IB 1600, and rinsed with 10% sucrose for 1 min. Changes in iodide penetrability of the enamel, and the pH and extracellular ion concentrations of the streptococcal plaque were determined. When added to the sucrose rinse, 100 or 150 mM calcium lactate reduced demineralization by about 35%, although the plaque pH was not affected. Plaque calcium was elevated but diffused away rapidly so that concentrations after 45 min were close to control values. Plaque inorganic phosphate and lactate were not affected. Ongoing demineralization appeared to be stopped when 100 mM calcium lactate was given 15 min after the sucrose rinse. When the lactate was given 15 min before the sucrose rinse, demineralization was reduced by only about 25%, consistent with the rapid diffusion of plaque calcium. The combination of (i) pretreatment with calcium lactate and (ii) admixture of calcium lactate with sucrose was most effective. Demineralization was reduced about 55% with 100 mM calcium lactate under these conditions, and protective effects were seen with as little as 25 mM. In summary, the findings demonstrate the enamel-protective effect of relatively low concentrations of calcium lactate, and point to the need to sustain a high plaque calcium during periods of maximum acidogenicity.