牙菌斑pH检测电极技术的研究进展

牙菌斑pH检测技术可检测龋风险,辅助预防龋病,其理论成熟、操作相对简单。由于临床龋风险检测技术的需求提高,微电极技术迅速发展,目前可实现牙菌斑pH检测的微电极种类也逐渐增加。现有电极技术主要包括微型玻璃电极、金属氧化物微电极以及离子敏感场效应晶体管。微型玻璃电极首先被应用于牙菌斑pH值的检测,但其结构薄弱,其中氧化铱微电极以其高强度、响应性优良的特点,成为近年来最具有应用潜力的接触法龋风险检测电极。金属氧化物微电极可以有效弥补玻璃电极强度不足的问题。随着电极技术进一步发展,更加小型、灵敏的离子敏感场效应晶体管受到研究者的关注。另外,为了克服接触法破坏菌斑结构的问题,近年来也有学者提出了光学测定技术,该技术可以实现无接触牙菌斑pH检测。未来的研究将在保证微小化的前提下进一步提高电极的强度及性能,并向无接触检测方向发展。     

Developments in dental plaque pH modelling

OBJECTIVES: The objectives of this review were to give a comprehensive account of the methods used to determine dental plaque pH over the last 50 years, to review how these methods have been used in dental cariology research and to give an update as to how dental plaque pH studies might be developed in the future. DATA: Published, referred papers and abstracts of conference proceedings in the literature were reviewed. SOURCES: A comprehensive search of the electronic databases PubMed and Medline, was undertaken. In addition, a hand search of the Index Denticus was done to identify relevant citations before 1966. STUDY SELECTION: Relevant published literature in peer-reviewed publications was reviewed. No additional inclusion criteria were applied. CONCLUSIONS: This comprehensive review gives an account of the background to, history of, relative merits and demerits of, applications of and future of dental plaque pH technologies.     

Salivary glucose clearance, dry mouth and pH changes in dental plaque in man

The aim was to study the effect of different salivary secretion rates on glucose clearance in saliva and on pH changes in dental plaque in man. Eighteen dental students, 21–33 yr old, participated. Dry mouth was induced by injecting methylscopolamine-nitrate submucosally in the labial sulcus. When dry mouth was established, two variables were measured at l h intervals, while the salivary flow was recovering: (1) secretion rate of resting and paraffin wax-stimulated whole saliva, and (2) glucose clearance in saliva after ingestion of a glucose tablet. pH changes in dental plaque were studied in 9 of the 18 subjects after a mouth rinse with 10% glucose at two separate occasions, once before and once after an injection of methylscopolamine-nitrate. Higher glucose concentration levels in saliva were found at low than at normal salivary secretion rate. After logarithmic transformation of the salivary glucose concentration values, a biphasic elimination pattern could be seen, with a steeper initial phase followed by a slower one. A critical value for the secretion rate with respect to the salivary glucose clearance time was found to be 0.14 ml/min for resting and 0.62 ml/min for stimulated whole saliva (mean values). The pH changes in dental plaque after the mouth rinse with glucose at extremely low secretion rate were significantly more pronounced than at normal flow rate. Thus, salivary secretion rate affects both the glucose clearance in saliva and the pH changes in dental plaque in man.     

用于牙菌斑pH测定的复合型微pH电极的研制

目的　研制可用于测定菌斑pH值的微pH电极。方法　用循环伏安法聚苯胺修饰钨丝电极作为pH指示电极 ,用Ag AgCl丝作为参比电极 ,二者复合于塑料套管内构成复合型pH微电极 ,试用于菌斑pH的测定。结果　在pH3～ 12范围内 ,该电极呈现Nernst响应 ,响应时间 <2min。将该电极试用于菌斑pH测定 ,获得蔗糖含漱后菌斑pH变动曲线。结论　该电极可用于菌斑内pH测定 ,且有望用于体内其它微小环境pH测定。     

Measurement of pH in human dental plaque in vivo with an ion-sensitive transistor electrode

A transistor pH electrode mounted on a removable partial denture was used to measure the pH of 2- and 4-day-old approximal and occlusal plaques in 2 adults. Direct application or a mouth-rinse of sucrose, glucose or maltose to the plaque covering the electrode caused the pH to fall within 2–3 min to approx. 4.4–5.2 in both subjects. Glucosylsucrose and lactose also lowered the pH, but not below 5.5. The transistor pH electrode was found suitable to record the pH of dental plaque in vivo, and to evaluate the fermentability of sugar substitutes.     

Comparison of methods for monitoring changes in the pH of human dental plaque

Changes in human dental plaque pH can be used to obtain estimates of the acidogenic potential of ingested foods. The presence of acid in plaque is influenced by a large number of host, microbial, and substrate factors. Several useful methods have been developed for monitoring changes in plaque pH. Plaque sampling involves repeated removal of small samples of plaque from a number of teeth at intervals after food ingestion, dispersion of the sample, and in vitro measurement of pH. Touch electrode methods utilize glass or antimony microelectrodes, which are placed onto plaque in situ where direct readings can be obtained. Telemetry methods involve placement of glass microelectrodes or ion-sensitive field effect transistors within the dentition. Plaque is allowed to accumulate, and pH changes can subsequently be transmitted with radio or wire. Each of the methods has clear advantages and limitations. The methods have been simultaneously compared in human volunteers using solutions of fermentable carbohydrate. Inter-method differences in response were observed depending upon the site of measurement. Data obtained from caries-prone surfaces via telemetry showed lower pH minima and retarded returns to resting pH levels. The technology is available for controlled comparative plaque pH studies, with the method of choice depending upon the goals of the investigation. It is essential that the results be compared to data obtained with other models designed to evaluate 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。     

Sugar, fluoride, pH and microbial homeostasis in dental plaque.

Factors that may contribute to the maintenance or breakdown of the oral microflora have been studied in the laboratory using a mixed culture chemostat system. Carbohydrate type had relatively little influence of the proportions of individual species at neutral pH. In contrast, when the pH was allowed to fall following carbohydrate metabolism, the stability of the microflora was markedly perturbed. The proportions of Streptococcus mutans, Lactobacillus casei and Veillonella dispar increased and they became the predominant species, while levels of other Gram-negative organisms and S. gordonii declined. Low levels (1 mmol/l) of sodium fluoride (NaF) had little effect on the microflora at neutral pH. However, when the pH fell following carbohydrate metabolism, 1 mmol/l of NaF slowed acid production and, in so doing, reduced the inhibition of acid-sensitive species, and suppressed the selection of S. mutans under otherwise favourable conditions. These data (and others) suggest that the mode of action of fluoride in human beings might include a subtle but clinically significant antimicrobial effect. These findings have also led to the proposal of a modified hypothesis (the "ecological plaque hypothesis") to explain the role of the resident oral microflora in dental disease. The hypothesis also has implications for treatment and prevention strategies.     

The pH of dental plaque in its relation to early enamel caries and dental plaque flora in humans

Dental caries appears to result from the action of multiple, interrelated factors. A companion study dealt with the plaque-flora/caries relationship (van Ruyven et al., 2000). The plaque-pH/caries relationship is the subject of this study. Since both studies involve the same subjects, plaques, and tooth surfaces, data on the examined factors have also been integrated. In vivo plaque pH determinations (microelectrode) were done on buccal sound (s) and "white-spot" (ws) caries surfaces in a selected dentition area in a low-caries (no ws) and higher-caries subject group. The pH response to sugar was evaluated before and after a sugar rinse, a local sugar application, or sucking on a sugary lozenge. pH profiles with sugar rinsing and normal or limited salivary flow conditions, showed progressively decreasing plaque pH values at various time points in the order of: low-caries subjects (s sites), higher-caries subjects (s sites), higher-caries subjects (s + ws sites), and higher-caries subjects (ws sites). The minimum pH values showed the same trend. Analyses of all data indicated only a statistical difference for minimum values for s sites in low-caries subjects vs. ws sites in higher-caries subjects, and for s and ws sites in the latter. Local sugar application and sucking on a sugary lozenge induced smaller pH drops than sugar rinsing; such suboptimal sugar exposure caused a disappearance of the difference between the minimum pH values for s and ws sites observed with sugar rinsing in the higher-caries subjects. Initial plaque pH values were similar regardless of subject or tooth caries status. The values were also not correlated with the plaque levels of strongly iodophilic polysaccharide-storing bacteria. Collectively, both studies indicate that increasing subject caries status is characterized by increasing plaque levels of highly-acid-tolerant, acidogenic bacteria and an increasing plaque-pH-lowering potential and support the dynamic relationship between these parameters.     

Gingivitis and dental plaque in relation to dental fluorosis in man in Morocco

A survey of 254 boys aged 12–14 yr from a fluorosis area (Khouribga) and a nonfluorosis area (Beni Mellal) in Morocco demonstrated no differences in level of gingival inflammation. The level of plaque accumulation was consistently lower in the fluorosis area compared to the non-fluorosis area. This difference was less pronounced on teeth with a relatively low level of dental fluorosis (lower incisors) than on teeth with a relatively high level of dental fluorosis (canines and premolars).     

pH changes in dental plaque caused by sweetened, iron-containing liquid medicine.

Five commercially available liquid iron medicines and a 5% aqueous sucrose solution were tested in a randomized cross-over study with six subjects at intervals of 3-4 d. The pH in plaque was measured in minute samples taken 5 min before and 5, 10, 20, and 40 min after oral intake of 10-ml volumes of the test solutions. The iron-containing medicines differed with respecto to pH (2.8-7.0), buffer capacity, viscosity, and iron content; two contained sorbitol (28 and 42%) and three sucrose (9, 17, and 47%). As expected, all sucrose-containing preparations produced a significant decrease in pH while no appreciable pH changes followed those with sorbitol. The pH readings after 5 min were affected by the sucrose content rather than the initial pH of the solutions. The decrease in pH was of shorter duration after exposure to the sucrose-containing iron medicines than after the 50% aqueous sucrose solution.     

Influence of sugar content in soft bread on pH of human dental plaque.

Quantitative determination of monosaccharides, disaccharides and sorbitol by use of gas-liquid chromatography (GLC) was performed on thirty-three samples of different commercial soft bread. Maltose was found in all the bread samples. Fructose and glucose were found only in samples of sweetened bread. Sucrose was detected in 5 samples, lactose in 2, and sorbitol in 2. Up to 20 per cent of the fresh bread weight was found to be low-molecular weight carbohydrates. Plaque pH-changes were studied in 18 persons following a 30-second month rinse with each of 3 solutions: (1) 50% sucrose, (2) water extract of sweetened bread, and (3) water extract of unsweetened bread. Mouth rinsing with the extract of sweetened wheat bread (sucrose 7.7 per cent of the dough weight) caused pH-decreases in plaque which were significantly more pronounced than those induced by the water extract of unsweetened wheat bread.