Human dental plaque microcosm biofilms: effect of nutrient variation on calcium phosphate deposition and growth

Plaque mineralisation is a multi-factorial process involving plaque pH, nucleation, inhibitors and promotors. It is poorly understood because of its complexity. OBJECTIVE: To establish the effects of amino acids and peptones in the simulated oral fluid BMM, a saliva analogue DMM and modifications of these on mineral deposition into dental plaque biofilm microcosms. METHODS: Microcosms were cultured for up to 35 days in an Artificial Mouth pulsed with sucrose, followed by 10 days periodic treatment with a pH 5.0 calcium-phosphate-monofluorophosphate-urea solution (CPMU). RESULTS: Initial biofilm doubling times were 3-7h, which then slowed and varied under the different nutrient conditions although their pH behaviour was similar. In BMM, mineral deposition was 20% that of DMM, but removal of BMM peptones increased deposition 12-fold. Substitution of the amino acids in DMM by casein did not affect deposition levels, but their removal leaving mucin the sole macronutrient, increased mineral deposition three-fold, reaching 40 mmol Ca/g protein. CONCLUSIONS: These substantial increases in mineral deposition when the macronutrient concentration is reduced indicates probable changes in the nucleating, inhibitory and Ca-binding properties of the simulated oral fluids themselves and/or changes in the plaque microbiota and their crystal nucleators and inhibitors.     

Effect of a mouthrinse containing calcium lactate on the formation and mineralization of dental plaque

In this study, a mouthrinse containing calcium lactate was tested for its effect on the accumulation of dental plaque and on the concentrations of calcium and phosphorus therein. Human volunteers rinsed four times per day with a calcium lactate (165 mmol/l) solution for 1 week. Plaque samples, collected 16 h after the last rinse, were analyzed chemically. Calcium lactate rinses had no effect on the plaque score, but resulted in approximately twofold increases of calcium and phosphorus in plaque. The incorporation of monofluorophosphate (5 mmol/l) into the rinsing solution failed to show any significant influence on calcium, phosphorus, and fluoride levels in plaque. Increased mineral deposition in the plaque may provide an explanation for the reduced caries development earlier observed in rats fed a diet containing calcium lactate.     

Immediate and delayed effects of an enzyme-dependent mineralizing mouthrinse on dental plaque

Twenty-two children aged 13 to 14 years rinsed for 3 X 1 min periods with a supersaturated calcium phosphate solution containing urea and monofluorophosphate. Plaque sampled one min after the last rinse showed a marked increase in water-extractable F and a smaller increase in Ca but no increase in water-extractable P. Water-insoluble forms of all three ions were elevated, however. The mean plaque pH was 8.28. Plaque sampled 24 hr after the last rinse showed significant increases in water-insoluble F and Ca only, and no increase in pH. The prompt pH rise and disappearance of water-soluble P suggest that, on exposure to the mineralizing solution, urea and monofluorophosphate are rapidly hydrolyzed by plaque enzymes to provide catabolites which cause the immediate precipitation of fluoridated calcium phosphate.     

A multi-station dental plaque microcosm (artificial mouth) for the study of plaque growth, metabolism, pH, and mineralization

A plaque growth chamber was developed for long-term growth of five separate plaques from the same plaque or saliva sample under identical conditions of temperature and gas phase. Reagent addition and growth conditions for each plaque could be independently controlled, and each was accessible for sequential sampling and electrode insertion. Plaques were cultured for over six weeks on pellicle-coated Lux (TM) 25-mm diameter cover-slips at 35 degrees C under 5% CO2 in N2, and supplied with a medium containing 0.25% mucin (BMM) at 3.6 mL/h, and with periodic 5% sucrose. Electron microscopy and flora analysis of microcosm plaques showed that they had close similarities to reported characteristics of natural dental plaques. Diverse motile bacteria were present. Sucrose-induced Stephan pH curves and urea-induced pH rises were also similar to those reported for natural plaques. Changes in plaque urease, calcium, phosphate concentrations, and the flora were followed over five weeks in a plaque supplied with BMM containing additional 2.5 mmol/L calcium and 7.5 mmol/L phosphate. Despite this high environmental calcium phosphate concentration, there was no continuing increase in calcium levels, although plaque phosphate doubled. Urease levels fluctuated. Changes in the cultivable flora were minor. A urea-containing calcium phosphate/mono-fluorophosphate pH 5 solution, applied for six min every two h for seven days, increased plaque calcium, phosphate, and fluoride to high levels. Thus, plaques grown over several weeks in the multi-station artificial mouth exhibited metabolic and pH behavior typical of natural plaques, could be analyzed during development, and the system allowed manipulation of environmental variables important in plaque pH control and calcification.     

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.     

Saturation of human saliva with respect to calcium salts

It may be assumed that free ionic concentrations of calcium and phosphate in resting saliva tend to equilibrate with those in plaque fluid, and that salivary data can therefore be used to illustrate chemical conditions in both saliva and plaque. In the present study, salivary data collected from the literature or obtained in our laboratory were used to calculate degrees of super- and undersaturation with respect to apatites, brushite, beta-tricalcium phosphate, octacalcium phosphate, calcium carbonate and calcium fluoride in the pH range from 3 to 9. Concentrations of calcium, phosphate, fluoride, carbonate, and background ion strength of resting parotid saliva, resting submandibular saliva, and resting and stimulated whole saliva were entered into a computer program, and curves illustrating saturation in the pH range 3-9 constructed. It was found that oral fluids are supersaturated with respect to apatites above pH 5.3 and with respect to octacalcium phosphate and beta-tricalcium phosphate above pH 6. Parotid saliva was undersaturated with respect to brushite whilst submandibular saliva was supersaturated with respect to that salt in the pH range 6-8. Stimulated whole saliva with 25 mmol/l carbonate became supersaturated with respect to calcium carbonate only above pH 7.3, which may explain the absence of this salt in the human oral cavity. To maintain the saturation of oral fluids with respect to calcium fluoride, i.e. to ensure its survival in the mouth required 6 ppm fluoride in the aqueous phase. Therefore, this salt, the outcome of topical fluoride therapy, will inevitably dissolve in the oral fluids.     

The effect of sucrose application frequency and basal nutrient conditions on the calcium and phosphate content of experimental dental plaque

A reduced pool of calcium in dental plaque would be expected to increase the ability of plaque fluid to dissolve the underlying enamel when the pH falls during sugar exposure. We have examined the relationship between frequency of sugar application and Ca and P(i) concentrations in artificial mouth plaque microcosm biofilms. Ten plaques were grown simultaneously from a human saliva inoculum using a continuous flow of simulated saliva, DMM, supplemented with either urea or glucose to modulate the resting pH. In addition the plaques received sucrose applications of varying frequency: 12-, 8-, 6-, or 4-hourly, or not at all. After 15 days the plaques were sampled by taking 4 full-thickness specimens of each, and acid-extractable Ca and P(i), and alkali-soluble protein and carbohydrate were determined. Ca and P(i) concentrations were in a range comparable with those in human plaque, except in the DMM + urea plaque receiving no sucrose, when concentrations were higher. Plaque Ca concentration decreased significantly as sucrose application frequency increased. Increasing sucrose application frequency also reduced the protein, i.e. the cell biomass, content of the plaques and, in the case of DMM + urea plaques, increased the water-insoluble hexose content, presumably extracellular polysaccharide. Reduced biomass was partly due to the bulking of plaque with extracellular polysaccharide, but the marked effect of urea on polysaccharide formation is not understood. This study shows that increasing frequency of sugar application alters dental plaque by reducing its mineral protection capacity.     

Composition of human plaque fluid

The composition of pooled resting plaque fluid was determined in four groups of college-age students (18-22 years), each composed of 50 individuals, who abstained from oral hygiene for 36 hours and did not eat or drink for at least one hour prior to plaque collection. Plaque samples from each group were pooled under mineral oil in small centrifuge tubes and centrifuged at 37,000 g for one hour at 4 degrees C. Supernatants were then combined under mineral oil and centrifuged at 5000 g (4 degrees C) for 15 minutes. In general, the inorganic composition of plaque fluid in the four groups was quite similar and in agreement with values reported by other investigators, but quite different from those of saliva or serum. The mean composition was: Ca, 7.07 +/- 0.51 mmol/L; P, 23.2 +/- 5.3 mmol/L; Na, 18.6 +/- 2 mmol/L; K, 85.1 +/- 5.3 mmol/L; Mg, 3.9 mmol/L; Cl, 42.8 +/- 9 mmol/L; F, approximately 0.004 mmol/L; pH, 5.69 (5.63-6.01). Acetate, propionate, succinate, butyrate, lactate, and formate were determined in two samples analyzed, with acetate and propionate being the predominant acids found. It was also demonstrated, through the titration of one of the plaque fluid samples, that the observed buffer capacity in plaque fluid was mostly related to its organic acid composition. It was noted, however, that when the initial pH in plaque fluid exceeded 6.5, phosphate contributed significantly to the buffer capacity. The contribution of other soluble species (proteins, peptides, amino acids) to the observed buffering in plaque fluid appeared to be small.(ABSTRACT TRUNCATED AT 250 WORDS)     

pH responses to sucrose and the formation of pH gradients in thick 'artificial mouth' microcosm plaques.

Artificial microcosm plaques were grown in a five-plaque culture system for up to 6 weeks, reaching a maximum depth of several mm. Procedures for long-term pH measurement with glass electrodes were established; they showed that the application of 5 or 10% sucrose for 6 min with a slow continuous flow of a basal medium containing mucin (BMM) generated the pH changes characteristic of in vivo Stephan curves. These pH responses were reproducible between plaques. Plaque mass and thickness were critical variables. Successive, sucrose-induced pH curves in plaques up to 4 mm thickness showed minor reductions only in the amplitude and rates of pH change. In plaques over 4 mm thick there was a pronounced reduction in pH response to successive sucrose applications, indicating increased diffusion limitations--a result of plaque growth to seal in the freshly-inserted pH electrode. In plaques of 6 mm maximum thickness, 10% sucrose induced a decrease to below pH 5.5 lasting 24 h, compared to the pH response in 2 mm thick plaque, which returned to the resting pH in 2 h. Differences in pH of up to 0.9 units were identified in thick plaques between inner and outer layers. The BMM flow rate was a critical determinant of the amplitude of the pH response to sucrose and subsequent return to resting pH. These results confirm, for microcosm plaque, the importance of clearance dynamics and diffusion-limited gradients in regulating plaque pH.     

Relationship between calcium and inorganic phosphorus concentrations of both resting and stimulated saliva and dental plaque in children and young adults

Calcium and inorganic phosphorus concentrations of both resting and paraffin-wax stimulated whole saliva and dental plaque were estimated in 39 young adults and 98 children aged 12-14 yr. Plaque was collected from the adults after 48 h without tooth-brushing and consumption of a standardized diet. Plaque was collected from the children without any dietary or oral hygiene restrictions. The results from the study with children provided consistent evidence for a statistically significant relationship between salivary and plaque concentrations of both calcium and inorganic phosphorus. However, multiple regression indicated that only the concentrations in the stimulated secretion were directly associated with concentrations in plaque. The apparent relationship between concentrations in resting saliva and plaque was due to correlation between resting and stimulated saliva. These relationships were less apparent in the young adults, in whom the controlled conditions resulted in a narrower range of mineral concentrations in dental plaque.     

Comparative study on mineralization-related intraoral parameters in periodontitis-affected and periodontitis-free adults

Abstract – The parameters related to an intraoral mineralization tendency in periodontitis-affected (P+) and periodontitis-free (P-) study subjects (16 adults, 46–74 yr, matched for sex and age) were compared. For this purpose the calcium (Ca) and phosphate (P) concentration of both plaque and saliva, resting pH and the acidogenic response of interdental plaque, plaque wet weight, salivary flow rate, buffering capacity and sucrase activity, interdental and salivary S. mutans levels as well as salivary lactobacilli and yeast levels were estimated. Plaque Ca (μg/mg protein, P <0.025) and P (μg/mg protein, P <0.05), saliva Ca (μg/ml, P <0.005) and the saliva Ca:P ratio ( P <0.005) were higher in the P+ than in the P- group. The resting pH values were higher ( P <0.025) and the acidogenic response of the interdental plaque was lower ( P <0.025) in the P+ group than in the P- group. The P+ group had lower S. mutans levels in saliva and interdental plaque. No differences were found in the wet weight of plaque and in the flow rate, buffering capacity or sucrase activity of saliva between the groups. The findings of the mineralization-related parameters in the two "extreme" groups of periodontal status suggest a higher intraoral mineralization tendency in periodontitis-affected persons than in periodontitis-free subjects. Ca and P accumulation of supragingival plaque seem to be connected with low acidogenicity of plaque and high salivary Ca concentration.     

A comparison of human dental plaque microcosm biofilms grown in an undefined medium and a chemically defined artificial saliva

The growth and pathogenic properties of dental plaque result from interactions between the microbiota and the oral environment and have been studied in laboratory experimental systems ranging from single or a few species (such as in chemostats) to dental plaque microcosms. Microcosm plaque is an in vitro version of natural plaque and has been explored as a microflora model because it is sited a more manipulable and controllable environment. It is obtained as microcosm biofilms in an 'artificial mouth' plaque culture system by culturing the bacteria in natural plaque-enriched saliva (i.e. salivary bacteria where a whole-saliva donor has abstained from oral hygiene for 24 h to increase the plaque bacteria in the saliva). The aim here was to examine whether a new, chemically defined analogue of saliva (defined medium mucin, DMM) could substitute for a previously used, chemically undefined medium (basal medium mucin, BMM) as an analogue of saliva for large-scale biofilm culturing. DMM contains various ions, mucin, amino acids, vitamins and growth factors at concentrations generally similar to those in saliva, whereas BMM contains yeast extract, peptones and mucin. To model the nutrient functions of salivary proteins, amino acids equivalent to 5 g/l casein were also included in DMM. In earlier studies, BMM-grown plaques were similar to natural plaques in structure, composition, growth rate and pH response to substrates. Their doubling-time patterns over a 20-day period were similar, except that the DMM-grown plaques showed biphasic growth patterns that were more pronounced than with BMM. Variation in enzyme profiles between BMM- and DMM-grown plaque, measured using the API-ZYM technique, provided evidence of nutritional effects on plaque composition. It was concluded that realistic growth rates and patterns are generated in microcosm plaque biofilms by supplying both DMM and BMM. However, the use of DMM enables specific modifications to be made to nutrient conditions during large-scale culture in our 'artificial mouth' biofilm system.     

Effect in vitro acidification on plaque fluid composition with and without a NaF or a controlled-release fluoride rinse

Plaque fluid ion concentration changes, especially fluoride, in response to the pH decrease associated with a cariogenic episode are important components of the caries process. A "controlled-release" (CR) fluoride rinse, based on the controlled release of fluoride in the presence of calcium, has been shown to form large fluoride reservoirs in resting plaque. In this study, the in vitro acid-induced release of fluoride, and other ions, was examined in 48-hour-fasted plaque fluid from subjects (n = 11) who received no rinse, or who used a 228-ppm CR or NaF fluoride rinse 1 hr before being sampled. After collection, the plaque was centrifuged to yield plaque fluid, acidified (0.1 microL of 0.5 mol/L HCl per milligram plaque), and then re-centrifuged before a second sample was obtained. Although previous studies indicated a higher plaque fluid fluoride after the new rinse relative to NaF, no statistically significant difference was observed here. Average fluoride release after acidification (average pH, 5.2) was statistically greater following the use of the CR rinse (153 micromol/L) compared with the NaF rinse (17 micromol/L). No fluoride release was seen in the no-rinse samples. The pH, free calcium, phosphate, acetate, propionate, and buffer capacity were not affected by the different amounts of fluoride deposited in the plaque. However, following acid addition, an increase in free calcium and phosphate was observed, which was also independent of the rinse. The large release of fluoride following acidification suggests that the new rinse may provide an improved cariostatic effect.     

菌斑pH值、游离钙和总蛋白水平与根龋易感性的关系

目的　分析菌斑液成分的动态变化与根龋易感性的关系。方法　比较无根龋组和有根龋组根面牙菌斑液在糖溶液漱口前后 ,所测定pH值、游离钙 (微电极法 )和总蛋白水平 (分光光度法 )的差异。结果　静止状态下 ,无根龋组和有根龋组的pH值 (无根龋组 6 2 4± 0 74,有根龋组 5 96±0 70 )和游离钙 [无根龋组 (0 6 0± 0 46 )mmol/L ,有根龋组 (0 89± 0 5 4)mmol/L]两项指标差异无统计学意义 ;糖漱口后 ,有根龋组的pH(5 14± 0 19)和游离钙 [(1 73± 0 74)mmol/L]水平均低于无根龋组[pH 5 2 8± 0 16 ,游离钙 (2 73± 1 2 5 )mmol/L],差异有统计学意义。总蛋白水平与游离钙含量之间没有相关性。同一个体牙根面与冠面之间菌斑液的三项指标均有显著的相关关系。结论　有根龋组的菌斑液有较强的致龋倾向 ,在细菌酵解糖产酸方面 ,牙根面 (牙骨质 )菌斑与牙冠面 (牙釉质 )菌斑无根本差别     

Dental plaque fluoride and pH in children exposed to different water fluoride levels.

The aims of this study were to determine plaque fluoride concentrations in children not exposed to topical fluorides but to different fluoride levels in the drinking water (0.1 and 2.0 ppm), and to observe whether plaque fluoride was related to plaque pH. Twenty-five children (6 to 7 years old) were selected from two rural villages in Brazil. A sub-set of subjects was examined for resting and fermenting plaque pH before sampling. A maximum of 14 sites was studied in each subject (vestibular and interproximal of first molars and central incisors). Plaque fluoride was extracted and measured with an inverted fluoride electrode under oil. Amounts of plaque were determined by protein analysis. Mean values in the 0.1 ppm village were 1.3 ngF/mg of plaque wet weight (SD = 1.1) and in the 2.0 ppm village 2.5 ngF/mg (SD = 2.1) and were not statistically different (Kruskal-Wallis test, P = 0.09). Plaque fluoride varied considerably from site to site in the same mouth. Combining sites in all subjects, plaque fluoride concentrations were positively related to resting and fermenting pH (regression analysis, P< 0.01-0.001, adjR2 = 0.12-0.31). On an individual basis the same trend was found for fermenting, but not for resting pH. In conclusion, our findings showed a moderate influence of water fluoride upon dental plaque fluoride concentrations and give some support to the theory that low fermenting pH may contribute to the release of bound plaque fluoride.     

In vivo effects of fluoride, chlorhexidine and zinc ions on acid formation by dental plaque and salivary mutans streptococcus counts in patients with irradiation-induced xerostomia

Irradiation therapy including major salivary glands may result in xerostomia and enhanced susceptibility to dental caries. The present aim was to assess the ability of mouthrinses with F-, Zn2+, and chlorhexidine (CH), in various combinations, to reduce acidogenic potential of dental plaque and salivary mutans streptococcus counts (SMSC) in 7 patients with xerostomia secondary to irradiation. The patients rinsed twice daily for 3 weeks with the following test solutions: (1) 12 mmol/l NaF (F; control), (2) NaF + 20 mmol/l ZnCl2 (F-Zn), and (3) NaF + 1.1 mmol/l CH (F-CH). Resting periods (F) of varying lengths were incorporated. Acid formation by dental plaque was monitored as plaque pH response to a sucrose mouthrinse, at the end of each test period, 4 h after mouthrinsing with test solution. Plaque pH was measured repeatedly at 2-8 sites in each patient before, and up to 60 min after the sucrose mouthrinse using touch microelectrodes. SMSC were determined using Dentocult SM-Strip mutans. Compared with F, F-CH significantly (P < or = 0.02) reduced acid formation by plaque and SMSC, whereas F-Zn did not affect acid formation or SMSC significantly. Pilot experiments in 4 patients showed mouthrinses with NaF + 0.55 mmol/l CH + 10 mmol/l Zn2+ to be ineffective, whereas NaF + 2.2 mmol/l CH was highly effective, but no better than F-CH. Twice daily mouthrinses with 12 mmol/l NaF in combination with 1.1 mmol/l CH may be an effective regimen to prevent post-irradiation caries.     

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 microg/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 microM; 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 microM. 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 microg/g (upper molar site), 197 +/- 412 microg/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.     

Effect of monofluorophosphate on calcium phosphate formation in supersaturated solutions

The effect of purified monofluorophosphate (MFP) on the formation of hydroxyapatite (HA) in supersaturated calcium phosphate solutions was determined. In solutions initially at pH 7.4 and seeded with HA crystals, MFP was hydrolysed to a small extent, releasing F-. Once the crystal growth-enhancing property of this F- was compensated for, 4 mmol/l MFP could be shown to inhibit precipitation by 40%. Without compensation for F-, MFP appeared to inhibit precipitation by only 18%. This inhibition was weaker than that caused by pyrophosphate or ethane-1-hydroxy-1,1-diphosphonic acid. Because MFP is hydrolysed on apatite surfaces to F-, use of sodium MFP as an anticaries agent is unlikely to cause significant inhibition of enamel remineralization.     

The effect of calcium beta glycerophosphate on phosphatase activity in plaque from monkeys (Macaca fascicularis)

Plaque was assayed for phosphatase activity using the following substrates (a) disodium α and β glycerophosphate; (b) calcium α and β glycerophosphate; (c) inositol hexaphosphoric acid sodium; (d) p-Nitrophenyl phosphate. Optimum pH values for acid and alkaline phosphatase were 5.5 and 8.5. The enzymes were labile, losing 50 per cent activity within 3 hr of plaque collection. Zinc and magnesium stimulated both acid and alkaline phosphatase activity. The results show that (1) plaque from monkeys can release small amounts of phosphate from a variety of organic phosphates, and (2) plaque from animals fed calcium β glycerophosphate has a smaller capacity, which is not significant to break down organic phosphates than plaque from control animals at alkaline pH. The available evidence suggests that the cariostatic effect of calcium β glycerophosphate is not dependent on its breakdown by microorganisms.     

Comparative study on mineralization-related intraoral parameters in periodontitis-affected and periodontitis-free adults

The parameters related to an intraoral mineralization tendency in periodontitis-affected (P+) and periodontitis-free (P-) study subjects (16 adults, 46-74 yr, matched for sex and age) were compared. For this purpose the calcium (Ca) and phosphate (P) concentration of both plaque and saliva, resting pH and the acidogenic response of interdental plaque, plaque wet weight, salivary flow rate, buffering capacity and sucrase activity, interdental plaque, plaque S. mutans levels as well as salivary lactobacilli and yeast levels were estimated. Plaque Ca (micrograms/mg protein, P less than 0.025) and P (micrograms/mg protein, P less than 0.05), saliva Ca (micrograms/ml, P less than 0.005) and the saliva Ca:P ratio (P less than 0.005) were higher in the P+ than in the P- group. The resting pH values were higher (P less than 0.025) and the acidogenic response of the interdental plaque was lower (P less than 0.025) in the P+ group than in the P- group. The P+ group had lower S. mutans levels in saliva and interdental plaque. No differences were found in the wet weight of plaque and in the flow rate, buffering capacity or sucrase activity of saliva between the groups. The findings of the mineralization-related parameters in the two "extreme" groups of periodontal status suggest a higher intraoral mineralization tendency in periodontitis-affected persons than in periodontitis-free subjects. Ca and P accumulation of supragingival plaque seem to be connected with low acidogenicity of plaque and high salivary Ca concentration.