A technique for assessment of the cariogenic potential of foods by plaque pH changes on enamel surfaces of rat molars

Plaque pH changes on rat molars subjected to cariogenic challenge were measured with an antimony microelectrode. Measurements were made after feeding one of seven different reference or snack foods. Resting plaque pH was measured after fasting and minimum plaque pH after feeding the various foods. This reproducible technique may be of use in determining the cariogenic potential of foods.     

微型pH电极的制备及其在牙菌斑pH检测中的应用

目的研制可用于牙菌斑pH原位检测的化学修饰性微型pH电极。方法采用氧化铱为氢离子敏感膜,以极化电解的方式将敏感膜附着于铂丝上,制备铂-氧化铱化学修改性微型pH电极,筛选性能优良的电极用于菌斑pH的原位检测,并与蜂式微型pH电极的检测进行对比。结果自制电极在pH值为1~11范围内呈线性响应,斜率为55.8mV/pH,响应时间为15~20s,电极在8h内的漂移为0.5~1.0mV,使用寿命大于1年。在对牙菌斑pH的原位检测中,自制电极与蜂式pH电极在漱糖后1h内各时间点测得的菌斑pH值差异均无显著性(P>0.05)。结论自制的铂-氧化铱化学修饰性微型pH电极对H+选择性好、性能稳定、响应范围广、响应时间短,在牙菌斑pH的原位检测中显示了良好的可行性。     

The Effect of Common Infant Foods on Plaque pH

Purpose: To evaluate the effect of cow's milk, milk plus sugar, milk plus honey and formula on plaque pH when compared to a 10% sucrose solution in 8- to 12-year-old children. Materials and Methods: Plaque pH was measured using a pH microelectrode at baseline to determine resting plaque pH and at intervals between 1 and 60 min after rinsing with the test liquids. Plaque pH data were analysed using repeated- measure ANOVA and paired t tests. Results: The study findings showed that 10% sucrose has the greatest cariogenic potential, followed by milk plus honey, milk plus sugar, formula and cow's milk. Except for the control group, the evaluated foods did not reduce the pH below 6. Conclusion: Although the test groups appear to be non-cariogenic as compared with sucrose, they still lead to considerable acidogenic response in the dental plaque. When bottle feeding is essential, it was confirmed that frequently use of these beverages may cause enamel demineralisation.     

The cariogenic potential of foods--a critical review of current methods

Current methods used in examining the cariogenic potential of foods are plaque pH measurements, measurements of adhesiveness of foods, experimental caries models and animal tests. pH measurements can be used for separating the non-acidogenic foods from the acidogenic ones but they are not suitable for separating foods with different levels of caries inducing potential. This is illustrated by the fact that virtually all foods which contain carbohydrates cause the pH of human plaque to fall below 5.5. Cooked rice and beans also give such a pH drop but these foods have a very low caries-inducing potential, as shown in studies of persons with hereditary fructose intolerance. Furthermore, experimentation has shown that acid formation and enamel dissolution are not directly correlated. Animal models exist in which various test foods can be examined under identical conditions. By using the same microbial challenge and a reference food, for example sucrose, the relative cariogenic potential of a test food can be calculated. One limitation with these animal models is that the foods have to be given in powdered form and not in the physical form in which they are consumed by humans. The main objection against most of the current methods is that they reflect important factors in our concept of the pathogenesis of dental caries only to a limited extent. For example, only the animal tests can be used to illustrate the extent to which foods support the colonization of S. mutans on teeth. The qualitative composition of the plaque is practically never considered. A series of tests can, however, be combined to give more relevant information about the caries-inducing potential of foods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plaque sampling and telemetry for monitoring acid production on human buccal tooth surfaces

The plaque sampling method and wire telemetry using miniature, glass pH electrodes on the buccal surface of mandibular first permanent molars, compared human dental plaque pH responses to a 10 per cent solution of sucrose. Nine subjects abstained from oral hygiene and were tested in morning sessions on 5 consecutive days. The mean resting plaque pH value for all sessions by plaque sampling was 6.60 +/- 0.18 (mean +/- SD) and by telemetry was 6.56 +/- 0.19. After a 1 min sucrose rinse, 1-day-old plaque showed a decrease in pH approx. 5.5 by both methods. The 2-, 3-, 4- and 5-day-old plaque, the mean minimum pH achieved was 4.69 +/- 0.28 as measured by sampling and 3.94 +/- 0.49 as determined by telemetry. The times taken to reach minimum pH as determined by the two methods were almost identical. The electrode calibration data showed that all the telemetry electrodes responded consistently for all 5 days of study. Scanning electron microscopy and microbiological analysis of electrode tips and enamel replicas revealed that plaque accumulated on glass at the same rate with a similar bacterial composition to plaque formed on clean enamel. It is proposed that glass microelectrodes and wire telemetry are a reasonable means for continuously monitoring plaque pH in situ. Comparison with plaque sampling suggested that telemetric responses reflect the type of plaque which accumulates at particular sites on the dentition.     

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 sorbitol gum chewing on plaque pH response after ingesting snacks containing predominantly sucrose or starch

The purpose of this study was to determine the effect of chewing a sorbitol gum (Trident) for 10 minutes on interproximal plaque pH changes following ingestion of selected sucrose- or starch-containing foods. The snacks containing predominantly sucrose (and/or simple sugars) were chocolate bar, cream-filled cupcakes, cream-filled sandwich cookie, cherry pie and raisins. The snacks containing predominantly starch were oat cereal, granola bars, pretzels, potato chips and corn chips. Plaque pH responses were monitored using an indwelling wire-telemetry system in five adult panelists. The test design involved two sets of 5 x 5 Latin square randomization in which each set consisted of two series of tests. In the first series of tests, the fasted, resting plaque pH was recorded for 5 minutes, panelists ingested the designated snacks for 2 minutes, and the pH response was monitored for the remainder of a 2-hour period. In the second series of tests, the same procedure was followed through the snack ingestion. After the pH response to the snack was monitored for 15 minutes, the panelists were asked to chew one stick of sorbitol gum for 10 minutes and the pH response was then monitored for the balance of the 2-hour period. Results indicated that both the sugar- and starch-containing snacks tested in this study caused significant decreases in interproximal plaque pH. Chewing a sorbitol gum after ingestion of the snacks significantly reduced the demineralizing potential of the plaque. The chewing of sorbitol gum following the ingestion of snacks can be recommended as an adjunct to other caries-preventive oral hygiene measures.     

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.     

与窝沟龋有关的优势耐酸菌构成的分析

目的　分析不同患龋状态窝沟中的优势耐酸菌构成,了解其在龋病发病中的作用。方法　第一年轻恒磨 牙窝沟新发早期龋儿童10名,2年无龋儿童10名。取新发龋窝沟处菌斑和同口正常第一恒磨牙窝沟菌斑及无龋 儿童第一恒磨牙窝沟菌斑,用平皿培养法分析菌群构成;用最可能数法(MPN)分离优势耐酸菌;API 20 Strep试剂盒 鉴定链球菌。结果　变形链球菌是无龋组窝沟的优势耐酸菌,且中性条件下检出较多;血链球菌是新龋组正常窝 沟和新龋窝沟处的优势耐酸菌;革兰阳性杆菌在酸性条件下占总检出菌比例(82%)显著高于中性条件下(61%)。 结论　菌斑生态构成非常复杂,在各个生态阶段,菌群组成不同。菌斑内局部pH值伴随菌群构成的变化推动着龋 病过程。     

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)     

The effect of miswak extract on plaque pH. An in vivo study

The aim of this study was to document changes in plaque pH when an acidic challenge was followed by rinsing with miswak extract (Salvadora persica), and to evaluate the effect of miswak rinse on parotid gland secretion rate. Plaque pH was measured in 3-day-old plaque using the microtouch electrode. Rinsing with miswak extract, compared with water rinsing, resulted in protracted elevation of plaque pH (>6.0). The difference in plaque pH between miswak extract and water rinse was statistically significant at 30 min (p < 0.001). Rinsing with miswak extract stimulated parotid gland secretion (p < 0.01). In conclusion, miswak extract raised the plaque pH, suggesting a potential role in caries prevention.     

The acidogenic potential of reference foods and snacks at interproximal sites in the human dentition

Telemetry was used to evaluate changes in plaque pH at interproximal sites in the dentition of five human subjects following the ingestion of a variety of reference foods and snacks. Short-term telemetry (30 min) revealed that most of the substrates yielded both pH minima and total responses similar to that obtained with a 10% sucrose rinse. Aged Cheddar cheese and skim milk were much less acidogenic than were the other foods.     

Oral food clearance and the pH of plaque and saliva

Carbohydrate clearance, plaque pH, and saliva pH resulting from eating foods containing high levels of sugar or starch were measured in the same experimental runs on the same test subjects. Foods with a higher content of sugar were removed more rapidly and depressed the pH of the plaque for a shorter time than did starchy foods containing less sugar. This finding suggests that retention of food in the mouth may be as important an indicator of its cariogenic potential as is the level of the pH it produces in plaque.     

The effect of previous diet on plaque pH response to different foods

In this study we investigated the effect of previous diet on the response of plaque pH to three test foods. The study population consisted of 11 dental students. Plaque pH was measured, by means of the touch electrode method, on the first two upper molars. The study was conducted at two sessions, one week apart. Subjects followed a 48-hour high-sugar diet before the first test session and a 48-hour low-sugar diet before the second test session. During both 48-hour periods, students refrained from all oral hygiene practices and fluoride utilization. At each session, three foods were ingested at one-hour intervals: cola, beer, and chocolate bar. pH measurements at baseline and at selected times after food ingestion were recorded and analyzed. Multivariate analysis of variance revealed significant independent effects of food, previous diet, and their interaction on plaque pH. After the same foods were ingested, plaque pH response after a previous high-sugar diet was significantly more acidic than after a previous low-sugar diet.     

Effects of a carbohydrate-free diet and sugar substitutes on dental plaque accumulation

Abstract Plaque accumulation and characteristics were determined gravimetrically, planimetrically, visually, and microbiologically in 24 human subjects who consumed a carbohydrate-free diet for 4 days. In addition, the effects of xylitol-, sorbitol- and sucrose-containing can dies upon plaque formed during consumption of the diet were ascertained. Experimental design was such that all 24 subjects traversed each 4-day test period; a 9-day interval between test periods was observed. All plaque measurement methods demonstrated that the subjects in all groups, including a control group which received no candies, accumulated significant amounts of dental plaque. No significant differences in plaque amount could be detected among the xylitol, sorbitol and control groups. However, subjects receiving sucrose-containing candies clearly exhibited larger amounts of plaque. The bacteriological investigations corroborated the clinical observations. The number of microbial colonies from plaque samples taken from the sucrose test group was clearly higher than in the other three groups. In addition, the number of bacteria in plaque samples from the sorbitol group was higher than in the xylitol group. A statistically significant increase in the proportion of anaerobic sorbitol-and xylitol-fermenting bacteria was detected in the sorbitol and xylitol test groups during the 4-day test periods.     

The relationship between plaque pH, plaque acid anion profiles, and oral carbohydrate retention after ingestion of several 'reference foods' by human subjects

The primary aim of this study was to rank several reference foods (apple drink, caramel, chocolate, cookie, skimmed milk powder, snack cracker, and wheat flake) according to their plaque pH response as monitored in a panel of 12 volunteers by the plaque-sampling method for comparison with data previously reported with other methods used to assess cariogenicity potential. Secondary experiments (using subsets of the panel of subjects) were undertaken in an attempt to elucidate some of the reasons for the observed plaque pH changes. Oral carbohydrate retention was measured at a single time period after food use as total anthrone-positive carbohydrate material, and as specific acidogenic sugars by gas-liquid chromatography after gel-exclusion chromatography. The concentrations of acid anions in the plaque fluid after food consumption were measured by isotachophoresis eight min after food use. According to the plaque pH response, apple-flavored fruit drink and chocolate were the most acidogenic foods and skimmed milk powder the least acidogenic. There were significant correlations (p less than 0.05) between the plaque pH data and lactate-plus-acetate concentrations in plaque fluid, but the correlations between the pH data and any of the carbohydrate retention parameters were not significant.     

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.     

Assessment of denture plaque pH in subjects with and without denture stomatitis

abstract — To evaluate the "resting" pH and induced pH changes in denture plaque, soft deposits were collected from the fitting surface of the denture, pooled and suspended in water. Plaque pH was determined with microelectrode equipment before and after mouth rinsing with a sucrose solution. A characteristic level in the "resting" pH of denture plaque was found in most of 12 subjects tested. pH values below the baseline level were recorded for more than 2 h after a rinse. The pH depressions were more pronounced in maxillary than in mandibular plaque. Further, the pH minima tended to be lower in subjects with denture stomatitis than in. controls. No clear relationship could be established between the "resting" pH and the concentration of Candida hyphae in denture smears or palatal inflammation.     

微型pH电极直接测试人牙菌斑pH的应用研究

目的：进一步探讨微型ｐＨ电极在原位检测人牙菌斑ｐＨ的可行性，了解漱糖后对菌斑ｐＨ的影响。方法：采用微型蜂式ｐＨ指示电极直接测试人牙邻面菌斑ｐＨ变化。结果：微型ｐＨ电极与玻璃ｐＨ大电极所测结果基本一致；漱糖后菌斑ｐＨ呈下降趋势，２０ｍｉｎ时达到最低点；无龋组与龋敏感组之间的ｐＨ改变无显著性差异。结论：微型ｐＨ电极适用于在原位直接测试菌斑ｐＨ；漱糖后菌斑ｐＨ发生改变，但龋坏与否的个体之间未见明显不同     

Assessment of denture plaque pH in subjects with and without denture stomatitis.

To evaluate the "resting" pH and induced pH changes in denture plaque, soft deposits were collected from the fitting surface of the denture, pooled and suspended in water. Plaque pH was determined with microelectrode equipment before and after mouth rinsing with a sucrose solution. A characteristic level in the "resting" pH of denture plaque was found in most of 12 subjects tested. pH values below the baseline level were recorded for more than 2 h after a rinse. The pH depressions were more pronounced in maxillary than in mandibular plaque. Further, the pH minima tended to be lower in subjects with denture stomatitis than in controls. No clear relationship could be established between the "resting" pH and the concentration of Candida hyphae in denture smears or palatal inflammation.