Correlations of oral bacterial arginine and urea catabolism with caries experience

Background/aim: Alkali generation by oral bacteria plays a key role in plaque pH homeostasis and may be a major impediment to the development of dental caries. To determine if the capacity of oral samples to produce ammonia from arginine or urea was related to caries experience, the arginine deiminase system (ADS) and urease activity in saliva and dental plaque samples were measured in 45 adult subjects. Methods: The subjects were divided into three groups according to caries status; 13 caries‐free (CF) individuals (decayed, missing, and filled teeth = 0); 21 caries‐active (CA) individuals (decayed teeth ≥ 4); and 11 caries‐experienced (CE) individuals (decayed teeth = 0; missing and filled teeth > 0). Real‐time polymerase chain reaction was used to quantify the proportion of certain acid‐ or alkali‐producing organisms in the samples. Results: The amount of ammonia generated from the test substrates by plaque samples was generally higher than that produced by salivary samples in all groups. Significantly higher levels of salivary ADS activity and plaque urease activity were observed in CF subjects compared to CA subjects (P = 0.0004 and P = 0.014, respectively). The proportions of Streptococcus mutans from saliva and dental plaque of CA subjects were significantly higher than those from the CF group (P = 0.0153 and P = 0.0009, respectively). In the CA group, there was an inverse relationship between urease activity and the levels of S. mutans (P < 0.0001). Conclusion: This study supports the theory that increased caries risk is associated with reduced alkali‐generating capacity of the bacteria colonizing the oral cavity; providing compelling evidence to further our understanding of oral alkali‐generation in health and disease.     

The effect of arginine on oral biofilm communities

Alkali production by oral bacteria via the arginine deiminase system (ADS) increases the pH of oral biofilms and reduces the risk for development of carious lesions. This study tested the hypothesis that increased availability of arginine in the oral environment through an exogenous source enhances the ADS activity levels in saliva and dental plaque. Saliva and supra‐gingival plaque samples were collected from 19 caries‐free (CF) individuals (DMFT = 0) and 19 caries‐active (CA) individuals (DMFT ≥ 2) before and after treatment, which comprised the use of a fluoride‐free toothpaste containing 1.5% arginine, or a regular fluoride‐containing toothpaste twice daily for 4 weeks. ADS activity was measured by quantification of ammonia produced from arginine by oral samples at baseline, after washout period, 4 weeks of treatment, and 2 weeks post‐treatment. Higher ADS activity levels were observed in plaque samples from CF compared to those of CA individuals (P = 0.048) at baseline. The use of the arginine toothpaste significantly increased ADS activity in plaque of CA individuals (P = 0.026). The plaque microbial profiles of CA treated with the arginine toothpaste showed a shift in bacterial composition to a healthier community, more similar to that of CF individuals. Thus, an anti‐caries effect may be expected from arginine‐containing formulations due in large part to the enhancement of ADS activity levels and potential favorable modification to the composition of the oral microbiome.     

Effect of arginine on the growth and biofilm formation of oral bacteria

BackgroundAlkali production via arginine deiminase system (ADS) of oral bacteria plays a significant role in oral ecology, pH homeostasis and inhibition of dental caries. ADS activity in dental plaque varies greatly between individuals, which may profoundly affect their susceptibility to caries.ObjectiveTo investigate the effect of arginine on the growth and biofilm formation of oral bacteria.Methods and resultsPolymicrobial dental biofilms derived from saliva were formed in a high-throughput active attachment biofilm model and l-arginine (Arg) was shown to reduce the colony forming units (CFU) counts of such biofilms grown for various periods or biofilms derived from saliva of subjects with different caries status. Arg hardly disturbed bacterial growth of Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis and Streptococcus gordonii in BHI medium, but only inhibited biofilm formation of S. mutans. Scanning electron microscope (SEM) showed S. mutans biofilms harboured fewer cells grown with Arg than that without Arg, even in the initial 2 h and 8 h phase. Confocal laser scanning microscope (CLSM) images of poly-microbial dental and S. mutans biofilms revealed the biofilms grown with Arg had lower exopolysaccharide (EPS)/bacteria ratios than those without Arg (P = 0.004, 0.002, respectively). Arg could significantly reduce the production of water-insoluble EPS in S. mutans biofilms (P < 0.001); however, quantitative real-time PCR (qRT-PCR) did not show significantly influence in gene expression of gtfB, gtfC or gtfD (P = 0.32, 0.06, 0.44 respectively).ConclusionsArg could reduce the biomass of poly-microbial dental biofilms and S. mutans biofilms, which may be due to the impact of Arg on water-insoluble EPS. Considering the contribution to pH homeostasis in dental biofilms, Arg may serve as an important agent keeping oral biofilms healthy thus prevent dental caries.     

Automutanolysin disrupts clinical isolates of cariogenic streptococci in biofilms and planktonic cells

Introduction:  Dental caries remains one of the most common chronic infectious diseases throughout the world. The formation of dental plaque is one of the caries risk factors. As a consequence, the removal of plaque may reduce the incidence of caries development. We identified an autolysin produced by Streptococcus mutans named auto-mutanolysin (Aml). Aml selectively lyses S. mutans and Streptococcus sobrinus . The specificity towards these cariogenic bacteria suggests that Aml may be used to prevent dental caries. Here, with the aim towards therapeutic application, we investigated the lytic activity of Aml against clinical isolates of S. mutans and S. sobrinus using planktonic cells and biofilms.
Methods:  Planktonic cell suspensions and biofilms of clinically isolated streptococci were treated with Aml in the absence or the presence of Triton X-100. The lytic activity of Aml was monitored as the change in turbidity. The disruption of biofilms was evaluated by detecting the released DNA by polymerase chain reaction and observing the alteration of optical density of treated biofilms.
Results:  Triton X-100 enhances the lytic ability of Aml. Using planktonic cells, Aml had various lysis levels against clinical strains. Repeated Aml treatment showed disruption of the biofilm using the representative clinical strains.
Conclusion:  Our study demonstrates that Aml has an ability to lyse planktonic and biofilm cells of clinically isolated mutans streptococci in the presence of Triton X-100. These results suggest the possibility of using Aml as an alternative or additional approach for caries prevention.     

Salivary gel-forming mucin MUC5B--a nutrient for dental plaque bacteria

Introduction:  Model systems with oral bacteria from dental plaque have demonstrated that the utilization of complex glycoproteins as a food source cannot be undertaken by single species but requires concerted degradation by a multi-species consortium, with each member contributing one or a few hydrolytic enzymes. Unlike previous studies, the aim of the present investigation was to explore the ability of fresh dental plaque to degrade salivary mucin, MUC5B, isolated by methods designed to retain intact the natural polymeric structure and physiological conformation, in an attempt to mimic the naturally occurring interaction between the oral microbiota and salivary mucins.
Methods:  Human salivary MUC5B was isolated from whole saliva by density-gradient centrifugation and incubated with freshly isolated supragingival dental plaque with samples subjected to fluorescent staining for viability and metabolic activity. In addition, the degradation of MUC5B oligosaccharide side chains was studied using a lectin assay, recognizing three different carbohydrate epitopes commonly found on mucin oligosaccharide side chains.
Results:  The addition of purified salivary MUC5B elicited a strong metabolic response from the biofilm cells, whereas individual strains of Streptococcus oralis and Streptococcus gordonii isolated from the same plaque were not able to utilize the MUC5B. The degradation of terminal saccharide moieties on the MUC5B was demonstrated by a marked decrease in both sialic acid and fucose reactivity.
Conclusion:  These results have shown that dental plaque is capable of utilizing human salivary MUC5B as a nutrient source, a process possibly requiring the synergistic degradation of the molecule by a consortium of oral bacteria in the plaque community.     

The antibacterial effect of photodynamic therapy in dental plaque-derived biofilms

Background and Objective:  Photodynamic therapy has been advocated as an alternative to antimicrobial agents to suppress subgingival species and to treat periodontitis. Bacteria located within dense biofilms, such as those encountered in dental plaque, have been found to be relatively resistant to antimicrobial therapy. In the present study, we investigated the ability of photodynamic therapy to reduce the number of bacteria in biofilms by comparing the photodynamic effects of methylene blue on human dental plaque microorganisms in the planktonic phase and in biofilms.
Material and Methods:  Dental plaque samples were obtained from 10 subjects with chronic periodontitis. Suspensions of plaque microorganisms from five subjects were sensitized with methylene blue (25 μg/mL) for 5 min then exposed to red light. Multispecies microbial biofilms developed from the same plaque samples were also exposed to methylene blue (25 μg/mL) and the same light conditions as their planktonic counterparts. In a second set of experiments, biofilms were developed with plaque bacteria from five subjects, sensitized with 25 or 50 μg/mL of methylene blue and then exposed to red light. After photodynamic therapy, survival fractions were calculated by counting the number of colony-forming units.
Results:  Photodynamic therapy killed approximately 63% of bacteria present in suspension. By contrast, in biofilms, photodynamic therapy had much less of an effect on the viability of bacteria (32% maximal killing).
Conclusion:  Oral bacteria in biofilms are affected less by photodynamic therapy than bacteria in the planktonic phase. The antibacterial effect of photodynamic therapy is reduced in biofilm bacteria but not to the same degree as has been reported for treatment with antibiotics under similar conditions.     

Mechanisms of inhibition by fluoride of urease activities of cell suspensions and biofilms of Staphylococcus epidermidis, Streptococcus salivarius, Actinomyces naeslundii and of dental plaque

BACKGROUND/AIMS: Fluoride is known to be a potent inhibitor of bacterial ureases and can also act in the form of hydrofluoric acid as a transmembrane proton conductor to acidify the cytoplasm of intact cells with possible indirect, acid inhibition of urease. Our research objectives were to assess the inhibitory potencies of fluoride for three urease-positive bacteria commonly found in the mouth and to determine the relative importance of direct and indirect inhibition of ureases for overall inhibition of intact cells or biofilms. METHODS: The experimental design involved intact bacteria in suspensions, mono-organism biofilms, cell extracts, and dental plaque. Standard enzymatic assays for ammonia production from urea were used. RESULTS: We found that ureolysis by cells in suspensions or mono-organism biofilms of Staphylococcus epidermidis, Streptococcus salivarius or Actinomyces naeslundii was inhibited by fluoride at plaque levels of 0.1-0.5 mm in a pH-dependent manner. The results of experiments with the organic weak acids indomethacin and capric acid, which do not directly inhibit urease enzyme, indicated that weak-acid effects leading to cytoplasmic acidification are also involved in fluoride inhibition. However, direct fluoride inhibition of urease appeared to be the major mechanism for reduction in ureolytic activity in acid environments. Results of experiments with freshly harvested supragingival dental plaque indicated responses to fluoride similar to those of S. salivarius with pH-dependent fluoride inhibition and both direct and indirect inhibition of urease. CONCLUSION: Fluoride can act to diminish alkali production from urea by oral bacteria through direct and indirect mechanisms.     

Caries-free subjects have high levels of urease and arginine deiminase activity

Objectives

This study investigated the relationship between urease and arginine deiminase system (ADS) activities and dental caries through a cross-sectional study.

Material and Methods

Urease and ADS activities were measured in saliva and plaque samples from 10 caries-free subjects and 13 caries-active. Urease activity was obtained from the ammonia produced by incubation of plaque and saliva samples in urea. ADS activity was obtained from the ammonia generated by the arginine-HCl and Tris-maleate buffer. Specific activity was defined as micromoles of ammonia per minute per milligram of protein. Shapiro-Wilk statistical test was used to analyze the distribution of the data, and Mann-Whitney test was used to determine the significance of the data.

Results

The specific urease activity in saliva and plaque was significantly higher in individuals with low DMFT scores. ADS activity in saliva (6.050 vs 1.350, p=0.0154) and plaque (8.830 vs 1.210, p=0.025) was also higher in individuals with low DMFT scores.

Conclusions

Caries-free subjects had a higher ammonia generation activity by urease and arginine deiminase system for both saliva and plaque samples than low caries-active subjects. High levels of alkali production in oral environment were related to caries-free subjects.     

Effects of mouthrinses with triclosan, zinc ions, copolymer, and sodium lauryl sulphate combined with fluoride on acid formation by dental plaque in vivo

Bacteriological tests demonstrated a slight synergistic effect of triclosan and sodium lauryl sulphate (SLS) on the growth of Streptococcus mutans NCTC 10449 and Streptococcus sanguis ATCC 10556 in vitro. A single mouthrinse with SLS (17.4 mM) or SLS plus triclosan (3.5 mM) significantly decreased the number of salivary mutans streptococci in a group of 12 subjects up to 90 min after rinsing. The effect on plaque pH of a mouthrinse with either 12.0 mM NaF, NaF plus 10.0 mM zinc acetate, NaF plus 17.4 mM SLS, or NaF plus SLS plus 3.5 mM triclosan with or without the addition of zinc ions or 0.65% w/v of a polyvinylmethyl ether/maleic acid copolymer was investigated. The plaque pH responses to a 10% w/v sucrose mouthrinse were measured in 2-day-old plaque with microtouch pH electrodes in six groups of 10 subjects 90 min after a single mouthrinse with test solution. There was no significant difference in plaque pH between the various mouthrinses. In conclusion, triclosan enhanced the growth-inhibitory activity of SLS against oral streptococci in vitro but not against salivary mutans streptococci in vivo. Neither triclosan incorporated into a mouthrinse containing SLS plus fluoride, nor the addition of zinc ions or copolymer affected acid formation by dental plaque in vivo.     

Detection of oral bacteria in cardiovascular specimens

Background/aims:  Oral bacteria, including cariogenic and periodontal pathogens, are thought to be etiological factors in the development of cardiovascular diseases. To define this relationship, we analyzed the distribution of oral bacterial species in cardiovascular specimens.
Method:  Following acceptance into the study, 203 consecutive patients were analyzed, from whom 82 aortic valve specimens, 35 mitral valve specimens, and 86 aortic aneurysmal wall specimens, of which 16 contained aneurysmal thrombus tissues, were obtained. In addition, a total of 58 dental plaque specimens were collected from the same group of patients who underwent heart valve replacement or removal of aortic aneurysms. Bacterial DNA was extracted from both cardiovascular tissues and dental plaque in those cases and then species-specific polymerase chain reaction assays were used to analyze the occurrences of six oral streptococcal and six periodontal bacterial species.
Results:  Streptococcus mutans was the most frequently detected species in the cardiovascular specimens, followed by Aggregatibacter actinomycetemcomitans . As for dental plaque specimens from patients who underwent cardiovascular operations, most of the tested periodontitis-related species as well as oral streptococci were detected at high frequencies. Furthermore, the positive rate of S. mutans in cardiovascular specimens from patients whose dental plaque specimens were also positive for S. mutans was 78%, which was significantly higher than any other tested species when the same analysis was performed.
Conclusion:  Our results suggest that specific oral bacterial species, such as S. mutans and A. actinomycetemcomitans , are related to bacteremia and may be etiologic factors for the development of cardiovascular diseases.     

Improving toothbrushing behaviour in an institution for the disabled in Lisbon, Portugal

Abstract:  The oral health of disabled persons is strongly associated with oral hygiene practices. However, many difficulties limit them from removing dental biofilms (plaque).
Purpose:  This pilot study evaluates changes in toothbrushing capability among 135 disabled individuals enrolled in an institution for the disabled.
Methods:  Direct observation of toothbrushing behaviour of the disabled was used to recommend changes required in daily toothbrushing programme. The simplified Debris Index (DI-S) was used to compare plaque removal outcomes over a 3-month period.
Results:  At baseline, of the 135 participants, 114 completed a routine toothbrushing procedure and 10 (8.8%) of them brushed all tooth surfaces. At the end of the study, 52 (48.6%) brushed all tooth surfaces. The mean difference between the initial and final DI-S was 0.62 ( P  < 0.01).
Conclusion:  Toothbrushing was not a common procedure at this institution. This study shows that it is possible to implement daily oral hygiene maintenance in disabled individuals. Furthermore, most participants will adopt more efficient toothbrushing behaviour when monitored daily.     

Transient acid-impairment of growth ability of oral Streptococcus, Actinomyces, and Lactobacillus: a possible ecological determinant in dental plaque

Introduction:  Dental plaque pH decreases to about 4 through bacterial fermentation of carbohydrates and this low pH is maintained for from several minutes to about an hour. Repeated acidification causes demineralization of the tooth surface, resulting in caries formation. The acidification also influences plaque bacteria. Severe acidification kills bacteria efficiently, while physiological acidification, the condition occurring in plaque, kills bacteria partially and may impair growth ability. We, therefore, investigated the effects of physiological acidification on representative caries-related bacteria.
Methods:  Streptococcus mutans , Streptococcus sobrinus , Streptococcus sanguinis , Streptococcus oralis , Lactobacillus paracasei , and Actinomyces naeslundii were used. Effects of physiological acidification at pH 4.0 on cell viability and growth ability, as well as the growth rate of these bacteria at pH 4.0–7.0, were investigated.
Results:  Mutans streptococci and Lactobacillus grew at pH 4.0 but the growth of S. sanguinis and S. oralis ceased below pH 4.2 and pH 4.2–4.4, respectively. Acidification at pH 4.0 for 1 h killed 43–89%, 45% and 35–76% of S. sanguinis , S. oralis , and Actinomyces , respectively. Furthermore, assessment of bacterial growth curves revealed that the growth ability of the surviving cells of S. sanguinis , S. oralis and Actinomyces was impaired, but it was recovered within 2–5 h after the environmental pH had returned to 7.0. The acidification neither killed nor impaired the growth of mutans streptococci and Lactobacillus .
Conclusions:  These results indicate that physiological and transient acidification is not sufficient to kill bacteria, but it causes a temporary acid-impairment of their growth ability, which may function as an ecological determinant for microbial composition in dental plaque.     

O12 Volatile markers of oral malodor in the breath

In the early 1990s, a break-through toothpaste, known as Colgate^® Total™, was launched with documented long-lasting activity against plaque, gingivitis, calculus, tooth decay and bad breath. The technology behind this toothpaste is the combination of triclosan, a polyvinyl methyl ether maleic acid (PVM/MA) copolymer and sodium fluoride (TCF). The function of the copolymer is to ensure optimal oral retention and prolonged release of the antibacterial triclosan. Effective levels of triclosan have been measured in the oral cavity 12 h after brushing the teeth. This allows prolonged control of oral bacteria that can lead to the formation of dental plaque and gingivitis and bad breath. Similarly, the retention of triclosan to oral surfaces during 2 years regular use of the product has led to a significant reduction in incremental coronal caries compared to an ADA-approved anti-cavity fluoride toothpaste. Furthermore, significantly less calcium phosphate has been shown to be present in dental plaque after brushing the teeth with the triclosan/copolymer toothpaste, and this has resulted in the reduced formation of tartar. A new variant of the triclosan/copolymer/fluoride toothpaste, having the numerous therapeutic and aesthetic benefits of the original formula, has been made available to consumers. The new dentifrice, which contains an impactful breath freshening flavor, has been documented to be significantly better ( P  < 0.05) than a control toothpaste in providing sustained control of bad breath over 12 h. After 12 h, breath odor was reduced from 51% compared to the control. The long term retention and subsequent release of triclosan by the copolymer in the TCF formula provide consumers protection against plaque, gingivitis, tartar, caries and bad breath.     

Alkali production in the mouth and its relationship with certain patient’s characteristics

Objectives

To assess the relationships among alkali production, diet, oral health behaviors, and oral hygiene.

Methods

Data from 52 subjects including demographics, diet, and oral hygiene scores were analyzed against the level of arginine and urea enzymes in plaque and saliva samples. An oral habit survey was completed that included: use of tobacco (TB), alcohol (AH), sugary drinks (SD), and diet. Alkali production through arginine deiminase (ADS) and urease activities were measured in smooth-surface supragingival dental plaque and un stimulated saliva samples from all subjects. ADS and urease activities were measured by quantification of the ammonia generated from the incubation of plaque or saliva samples. Spearman correlations were used to compute all associations.

Results

Participants in the lowest SES (Socio-economic status) group had the habit of consuming sugary drinks the most and had the highest rate of tobacco use. Males consumed significantly more alcohol than females. No significant relationship was found between age or gender and alkali production. Higher rates of sugary drink consumption and tobacco use were significantly related to lower alkali production.

Conclusion

The study showed a relationship between alkali production and oral hygiene, diet, and certain oral health behaviors. Poor oral hygiene was significantly associated with age, lower SES, tobacco use, and alcohol, and sugary drinks consumption.

Clinical relevance

Certain oral health behaviors have an impact on oral hygiene and on alkali production; it is important to address these factors with patients as a strategy for caries control.     

Could alkali production be considered an approach for caries control?

This study investigated the relationship of arginine deiminase (ADS) and urease activities with dental caries through a case-control study. ADS and urease activities were measured in dental smooth-surface supragingival plaque and whole saliva samples from 93 subjects, who were in three different groups: caries-free (n = 31), caries-active (n = 30), and caries-experienced (n = 32). ADS activity was measured by quantification of the ammonia generated from the incubation of plaque and saliva samples in a mixture containing 50 mM arginine-HCl and 50 mM Tris-maleate buffer, pH 6.0. ADS-specific activity was defined as nanomoles of ammonia generated per minute per milligram of protein. Urease activity was determined by quantification of ammonia produced from 50 mM urea. For bacterial identification and enumeration real-time qPCR analysis was used. Groups were compared using Kruskal-Wallis tests. Spearman correlations were used to analyze plaque metabolic activity and bacterial relationships. The results revealed significantly higher ammonia production from arginine in saliva (1.06 vs. 0.18; p < 0.0001) and plaque samples (1.74 vs. 0.58; p < 0.0001) from caries-free subjects compared to caries-active subjects. Urease levels were about 3-fold higher in the plaque of caries-free subjects (p < 0.0001). Although higher urease activity in saliva of caries-experienced and caries-free subjects was evident, no significant difference was found between the groups.     

Helicobacter pylori in the oral cavity is associated with gastroesophageal disease

Background:  In Mexico, more than 80% of the population is infected with Helicobacter pylori . The frequency of H. pylori detection in the oral cavity is unknown, as its relationship with gastroesophageal pathology.
Aim:  To detect the presence of H. pylori in the oral cavity in Mexican population by PCR and to determine its association with gastroesophageal disease.
Methods:  Patients were divided into two groups with different clinic conditions from whom gastric biopsy, dental plaque, and saliva samples were taken and analyzed. The first group comprised of hospitalized patients, the majority of whom were diagnosed with gastroesophageal disease, while the second group was selected from a dental clinic (ambulatory population) the majority of whom appeared to be healthy subjects.
Results:  H. pylori was detected in gastric biopsy, dental plaque and saliva samples by PCR using a set of specific primers for the signal sequence of the vacuolating cytotoxin gene; detection of H. pylori in general was higher in gastric biopsy and dental plaque samples than in saliva samples. Detection of H. pylori in the oral cavity is significantly ( P  = 0.0001) associated with patients presenting gastroesophageal disease, while healthy subjects and those with other non-gastric disease do not present with H. pylori in their oral cavity.
Conclusions:  H. pylori detection in the oral cavity is associated to gastroesophageal disease. In addition, it is suggested that all patients presenting gastric symptoms and H. pylori detection in the oral cavity would begin bacterial treatment immediately.     

Dental hygiene work in a clinical trial

Abstract:  Dental hygiene activities were developed as part of a randomized clinical trial designed to assess the safety of low-level mercury exposure from dental amalgam restorations. Along with dental-hygiene clinical work, a community programme was implemented after investigators noticed the poor oral hygiene habits of participants, and the need for urgent action to minimize oral health problems in the study population.
Objectives:  Clinical and community activity goal was to promote oral health and prevent new disease. Community activities involved participants and their fellow students and were aimed at providing education on oral health in a school environment.
Methods:  Dental hygienists developed clinical work with prophylaxis, sealants application and topical fluoride and implemented the community programme with in-class sessions on oral health themes. Twice a month fluoride mouthrinses and bi-annual tooth brushing instructional activity took place. Participation at dental-hygiene activities, sealed teeth with no need of restoration and dental-plaque-index were measures used to evaluate success of the programme for the participants.
Results:  Improvement in dental hygiene is shown by the decrease in dental plaque index scores ( P  < 0.0001); also sealants integrity is achieved in 86.3% of teeth. 888 (13.7%) teeth with sealants had to be restored or were lost. Children participated actively on dental hygiene activities. Teachers became aware of the problem and included oral-health in school curricula.
Conclusion:  Dental hygiene activities have shown to be helpful to promote dental hygiene, promote oral health and to provide school-age children with education on habits that will be important for their future good health.     

三氯羟苯醚漱口液作用特点的研究

目的 研究新型三氯羟苯醚（triclosan）漱口液－力博漱口液的作用特点。方法 ①检查并记录受检者用药前后的牙菌斑指数和牙龋出血指数,观察临床疗效。②采集受检者用药前后受检者的龋下菌斑标本,厌氧环境下培养,计数菌落数（CUF／L）。对比用药前后的抑菌效果。③选择变形链球菌C、牙龋卟啉单胞菌等为实验菌株,以倍比稀释后的三氯羟苯醚漱口液和酸氯己定漱口液为抑菌物,厌氧培养后,观察抑菌环大小,对比两种漱口液对不同菌株的最低抑菌浓度。④在光滑附着板上培养变形链球菌,形成细菌斑膜后,将附着板置于三氯羟苯醚漱口液、醋酸氯己定漱口液和生理盐水中,观察细菌脱落情况。结果 ①三氯羟苯醚漱口液含漱治疗牙龋炎症临床有效,可降低牙菌斑指数及牙龋出血指数。②使用三氯羟苯醚漱口后,口腔致病菌的培养计数有所减少。③三氯羟苯醚漱口液对变形链球菌C的最低抑菌浓度低于醋酸氯己定漱口液,对牙龋卟啉单胞菌的最低抑菌浓度高于醋酸氯己定漱口液。④在三氯羟苯醚漱口液中,附着板上的细菌膜最容易脱落,三氢羟苯醚漱口液的抗细菌附着作用强于醋酸氯己定漱口液和生理盐水。结论     

A long-term effect of caries-related factors in initially caries-free children

Aim.  The aim of this study was to examine the rate and pattern of early childhood caries development in caries-free children based on their dental plaque accumulations, salivary Streptococcus mutans levels, maternal sharing, oral hygiene, and feeding attitudes at baseline and at 24-month follow-up period.
Design.  A total of 92 children, aged between 15 to 35 months, comprised the study group. The children's dental examinations were first carried out at baseline, and 56 of them were re-examined 24 months later to determine the changes in dental status. The mothers were also interviewed at each examination based on a prepared questionnaire.
Results.  The prevalence of caries incidence was 45% at 24-month evaluation period among initially caries-free children. The new caries formation was mostly observed on occlusal and aproximal surfaces of maxillary molars (28% and 26%) followed by mesial, distal and buccal surfaces of anterior teeth, respectively. Significant correlations between dental caries formation and maternal sharing, S. mutans levels, and plaque scores were found.
Conclusion.  The results indicated that early S. mutans colonization, high plaque accumulation, and maternal sharing were important factors on a child's caries development.