Lactobacilli and human dental caries: more than mechanical retention.

Lactobacilli have been considered as major contributors to human dental caries for over a century. Recent in vitro model studies have shown that when compared to Streptococcus mutans, a keystone pathogen of human dental caries, the ability of lactobacilli to form biofilms is poor, although differences exist between the different major species. Further studies using molecular and bioinformatics approaches provide evidence that multiple mechanisms, including adhesin-receptor mediated physical contact with S. mutans, facilitate the adherence and establishment of lactobacilli on the tooth surface. There is also evidence that under conditions like continuous sugar consumption, weak acids and other antimicrobials such as bacteriocins from lactobacilli can become detrimental to the microbial community, especially those in the proximity. Details on the underlying mechanisms of how different Lactobacillus sp. establish and persist in the highly complex microbiota on the tooth surface await further investigation.

Assessment of the Silver Penetration and Distribution in Carious Lesions of Deciduous Teeth Treated with Silver Diamine Fluoride.

The aim of this study was to determine the effects of 38% silver diamine fluoride (SDF) on carious lesions of human deciduous teeth. Ten extracted deciduous incisors with caries were collected and treated with SDF. After the treatment, the teeth were sectioned through the center of the carious lesion. The extent of sliver precipitation was examined using quantitative backscattered electron scanning electron microscopy (qBSE-SEM), energy-dispersive X-ray spectroscopy (EDX), and micro-computed tomography (micro-CT). The qBSE-SEM images revealed that the silver particles could penetrate through the pellicle complex, along with the rod sheaths into the demineralized enamel rods and the dentinal tubules, and form silver-enriched barriers surrounding the carious lesions at depths up to 2,490.2 µm (mean 744.7 ± 448.7 µm) within the dentinal tubules of the carious lesions, but less likely in the sound enamel. The EDX spectrum analysis revealed that carbon, oxygen, phosphorus, chlorine, silver, and calcium were the main elements detected in the lesions treated with SDF. Additionally, sodium, magnesium, aluminum, silicon, zinc, sulfur, and fluorine were detected as the minor elements within the SDF precipitation "zone." The micro-CT analysis further showed that in the deep cavitated lesions, the silver precipitation could be observed in the pulp chamber. These findings provide new evidence defining the SDF mode of action for arresting caries and suggest that the application of a highly concentrated SDF solution on deciduous teeth should be used with caution for various carious lesions.

Caries outcome following an intensive fluoride varnish treatment regimen for children at high risk for early childhood caries.

PURPOSE: To evaluate the caries relapse rate for a cohort of 2- to 4-year-old children at high risk of early childhood caries when treated with an intensive fluoride varnish (FV) regimen. METHODS: Eighty paediatric patients were recruited. Forty of these patients were high risk and received the FV treatment (three applications within 2 weeks and additional applications at 1 and 3 months) during 2009-2010. Mutans streptococci (MS) levels in the saliva were evaluated during the treatment period. A comparative group of 40 children, selected from an electronic record search at the New York University College of Dentistry to be of similar age, gender, and ethnicity, but not at elevated risk for ECC, received the standard of care (semi-annual FV treatment). Detailed caries examination and treatment records were obtained for all patients from 2009 to 2014. RESULTS: A significant reduction (P < 0.001) in MS levels was observed in the intensive FV treatment group at the 3-month visit compared with baseline. There was no effect of the intensive FV treatment on caries outcome in the anterior teeth, and the overall caries scores were significantly increased on the posterior teeth. CONCLUSION: The intensive FV regimen appears insufficient to prevent caries relapse in children at high risk for caries.

Impact of parental migration on oral health outcomes of left-behind school-aged children in Luchuan, southern China.

BACKGROUND: With rapid urbanization in China, an increasing number of rural adults have migrated to cities to seek job opportunities, leaving their school-aged children behind. These left-behind children (LBC) without one or both parents usually receive less attention from their caregivers. Whether the parental migration affects the children's oral health is not well understood. This study aimed to explore the differences in dental caries status and oral health-related behaviors between children with different parental migration experiences in a rural area of Southern China. METHODS: A cross-sectional study was conducted in Luchuan County of Guangxi Province in 2015. A total of 1085 school children aged 8-12 participated in this study. Participants' demographic characteristics, parental migration information, and eating and oral hygiene habits were collected using a self-administered questionnaire. Dental caries of permanent teeth was examined using the decayed, missing, and filled tooth (DMFT) index recommended by the World Health Organization. Dental caries experience and oral health-related behaviors were compared between LBC and non-LBC, as well as children with different experiences of parental migrations. The impact of various parental migration attributes on LBC oral health outcomes was examined by univariate and multivariate analyses. RESULTS: Among the school-aged children examined, 60.9% of them were LBC. Only 29.7% of the children brushed their teeth regularly; 86.5% of them did not know what fluoride toothpaste was. Caries prevalence was 51.4% for LBC and 40.8% for non-LBC (p < 0.001). The LBC experienced a greater DMFT mean (1.20 ± 1.59) compared to the non-LBC (0.85 ± 1.30) (p < 0.001). Oral health-related behaviors were not significantly different between LBC and non-LBC. Dental caries experience and oral health-related behaviors were not related to the type or duration of parental migration. Multiple regression analyses showed that parental migration was one of significant predictors of children's caries outcome; LBC had a higher risk to caries than non-LBC (95% CI =1.26, 2.09). CONCLUSIONS: These findings indicate that parental migration could be a significant risk factor for caries development among 8- to 12-year-old school children in rural China.

HIV infection and microbial diversity in saliva.

Limited information is available about the effects of HIV and subsequent antiretroviral treatment on host-microbe interactions. This study aimed to determine the salivary microbial composition for 10 HIV-seropositive subjects, before and 6 months after highly active antiretroviral therapy (HAART), compared with that for 10 HIV-seronegative subjects. A conventional culture and two culture-independent analyses were used and consistently demonstrated differences in microbial composition among the three sets of samples. HIV-positive subjects had higher levels of total cultivable microbes, including oral streptococci, lactobacilli, Streptococcus mutans, and Candida, in saliva than did HIV-negative subjects. The total cultivable microbial levels were significantly correlated with CD4+ T cell counts. Denaturing gradient gel electrophoresis (DGGE), which compared the overall microbial profiles, showed distinct fingerprinting profiles for each group. The human oral microbe identification microarray (HOMIM) assay, which compared the 16S rRNA genes, showed clear separation among the three sample groups. Veillonella, Synergistetes, and Streptococcus were present in all 30 saliva samples. Only minor changes or no changes in the prevalence of Neisseria, Haemophilus, Gemella, Leptotrichia, Solobacterium, Parvimonas, and Rothia were observed. Seven genera, Capnocytophaga, Slackia, Porphyromonas, Kingella, Peptostreptococcaceae, Lactobacillus, and Atopobium, were detected only in HIV-negative samples. The prevalences of Fusobacterium, Campylobacter, Prevotella, Capnocytophaga, Selenomonas, Actinomyces, Granulicatella, and Atopobium were increased after HAART. In contrast, the prevalence of Aggregatibacter was significantly decreased after HAART. The findings of this study suggest that HIV infection and HAART can have significant effects on salivary microbial colonization and composition.

The Evolving Microbiome of Dental Caries.

Dental caries is a significant oral and public health problem worldwide, especially in low-income populations. The risk of dental caries increases with frequent intake of dietary carbohydrates, including sugars, leading to increased acidity and disruption of the symbiotic diverse and complex microbial community of health. Excess acid production leads to a dysbiotic shift in the bacterial biofilm composition, demineralization of tooth structure, and cavities. Highly acidic and acid-tolerant species associated with caries include Streptococcus mutans, Lactobacillus, Actinomyces, Bifidobacterium, and Scardovia species. The differences in microbiotas depend on tooth site, extent of carious lesions, and rate of disease progression. Metagenomics and metatranscriptomics not only reveal the structure and genetic potential of the caries-associated microbiome, but, more importantly, capture the genetic makeup of the metabolically active microbiome in lesion sites. Due to its multifactorial nature, caries has been difficult to prevent. The use of topical fluoride has had a significant impact on reducing caries in clinical settings, but the approach is costly; the results are less sustainable for high-caries-risk individuals, especially children. Developing treatment regimens that specifically target S. mutans and other acidogenic bacteria, such as using nanoparticles, show promise in altering the cariogenic microbiome, thereby combatting the disease.

Novel Clustering Methods Identified Three Caries Status-Related Clusters Based on Oral Microbiome in Thai Mother-Child Dyads.

Early childhood caries (ECC) is a disease that globally affects pre-school children. It is important to identify both protective and risk factors associated with this disease. This paper examined a set of saliva samples of Thai mother-child dyads and aimed to analyze how the maternal factors and oral microbiome of the dyads influence the development of ECC. However, heterogeneous latent subpopulations may exist that have different characteristics in terms of caries development. Therefore, we introduce a novel method to cluster the correlated outcomes of dependent observations while selecting influential independent variables to unearth latent groupings within this dataset and reveal their association in each group. This paper describes the discovery of three heterogeneous clusters in the dataset, each with its own unique mother-child outcome trend, as well as identifying several microbial factors that contribute to ECC. Significantly, the three identified clusters represent three typical clinical conditions in which mother-child dyads have typical (cluster 1), high-low (cluster 2), and low-high caries experiences (cluster 3) compared to the overall trend of mother-child caries status. Intriguingly, the variables identified as the driving attributes of each cluster, including specific taxa, have the potential to be used in the future as caries preventive measures.

Association between oral health and gastric precancerous lesions.

Although recent studies have suggested that tooth loss is positively related to the risk of gastric non-cardia cancer, the underlying oral health conditions potentially responsible for the association remain unknown. We investigated whether clinical and behavioral measures of oral health are associated with the risk of gastric precancerous lesions. We conducted a cross-sectional study of 131 patients undergoing upper gastrointestinal endoscopy. Cases were defined as those with gastric precancerous lesions including intestinal metaplasia or chronic atrophic gastritis on the basis of standard biopsy review. A validated structured questionnaire was administered to obtain information on oral health behaviors. A comprehensive clinical oral health examination was performed on a subset of 91 patients to evaluate for periodontal disease and dental caries experience. A total of 41 (31%) cases of gastric precancerous lesions were identified. Compared with non-cases, cases were significantly more likely to not floss their teeth [odds ratio (OR) = 2.89, 95% confidence interval (CI): 1.09-7.64], adjusting for age, sex, race, body mass index, smoking status, educational attainment and Helicobacter pylori status in serum. Among participants who completed the oral examination, cases (n = 28) were more likely to have a higher percentage of sites with gingival bleeding than non-cases [OR = 2.63, 95% CI: 1.37-5.05 for a standard deviation increase in bleeding sites (equivalent to 19.7%)], independent of potential confounders. Our findings demonstrate that specific oral health conditions and behaviors such as gingival bleeding and tooth flossing are associated with gastric precancerous lesions.

Multimodal Data Integration Reveals Mode of Delivery and Snack Consumption Outrank Salivary Microbiome in Association With Caries Outcome in Thai Children.

Early childhood caries (ECC) is not only the most common chronic childhood disease but also disproportionately affects underserved populations. Of those, children living in Thailand have been found to have high rates of ECC and severe ECC. Frequently, the cause of ECC is blamed on a handful of cariogenic organisms, such as Streptococcus mutans and Streptococcus sobrinus. However, ECC is a multifactorial disease that results from an ecological shift in the oral cavity from a neutral pH (~7.5) to an acidic pH (<5.5) environment influenced by the host individual's biological, socio-behavioral, and lifestyle factors. Currently, there is a lack of understanding of how risk factors at various levels influence the oral health of children at risk. We applied a statistical machine learning approach for multimodal data integration (parallel and hierarchical) to identify caries-related multiplatform factors in a large cohort of mother-child dyads living in Chiang Mai, Thailand (N=177). Whole saliva (1 mL) was collected from each individual for DNA extraction and 16S rRNA sequencing. A set of maternal and early childhood factors were included in the data analysis. Significantly, vaginal delivery, preterm birth, and frequent sugary snacking were found to increase the risk for ECC. The salivary microbial diversity was significantly different in children with ECC or without ECC. Results of linear discriminant analysis effect size (LEfSe) analysis of the microbial community demonstrated that S. mutans, Prevotella histicola, and Leptotrichia hongkongensis were significantly enriched in ECC children. Whereas Fusobacterium periodonticum was less abundant among caries-free children, suggesting its potential to be a candidate biomarker for good oral health. Based on the multimodal data integration and statistical machine learning models, the study revealed that the mode of delivery and snack consumption outrank salivary microbiome in predicting ECC in Thai children. The biological and behavioral factors may play significant roles in the microbial pathobiology of ECC and warrant further investigation.

PCR detection of Streptococcus mutans and Aggregatibacter actinomycetemcomitans in dental plaque samples from Haitian adolescents.

Streptococcus mutans and Aggregatibacter actinomycetemcomitans are oral pathogens associated with dental caries and periodontitis, respectively. The aim of this study was to determine the colonization of these two microorganisms in the dental plaque of a group of Haitian adolescents using two different polymerase chain reaction (PCR) methods, standard PCR, and quantitative real-time PCR (qPCR) assays. Fifty-four pooled supra-gingival plaque samples and 98 pooled sub-gingival plaque samples were obtained from 104 12- to19-year-old rural-dwelling Haitians. The total genomic DNA of bacteria was isolated from these samples, and all participants also received caries and periodontal examinations. Caries prevalence was 42.2%, and the mean decayed, missing, and filled surface (DMFS) was 2.67 ± 5.3. More than half of the adolescents (53.3%) experienced periodontal pockets (Community Periodontal Index score ≥3). S. mutans was detected in 67.3% by qPCR and 38.8% by PCR of the supra-gingival plaque samples (p < 0.01), and 36.6% by qPCR and 8.1% by PCR of the sub-gingival samples (p < 0.01). A. actinomycetemcomitans was detected in 85.1% by qPCR and 44.0% by PCR of the sub-gingival samples (p < 0.01), but the prevalence was similar, 67.3% by qPCR and 59.2% by PCR, in the supra-gingival plaque samples. Neither age nor gender was significantly correlated to the bacterial colonization. The results demonstrated a moderate-to-high prevalence of S. mutans and A. actinomycetemcomitans in the Haitian adolescent population, and qPCR is more sensitive than standard PCR in field conditions. These findings suggest that qPCR should be considered for field oral epidemiologic studies and may be necessary in investigations having major logistic challenges.

Genomic island TnSmu2 of Streptococcus mutans harbors a nonribosomal peptide synthetase-polyketide synthase gene cluster responsible for the biosynthesis of pigments involved in oxygen and H2O2 tolerance.

The oral biofilm community consists of >800 microbial species, among which Streptococcus mutans is considered a primary pathogen for dental caries. The genomic island TnSmu2 of S. mutans comprises >2% of the genome. In this study, we demonstrate that TnSmu2 harbors a gene cluster encoding nonribosomal peptide synthetases (NRPS), polyketide synthases (PKS), and accessory proteins and regulators involved in nonribosomal peptide (NRP) and polyketide (PK) biosynthesis. Interestingly, the sequences of these genes and their genomic organizations and locations are highly divergent among different S. mutans strains, yet each TnSmu2 region encodes NRPS/PKS and accessory proteins. Mutagenesis of the structural genes and putative regulatory genes in strains UA159, UA140, and MT4653 resulted in colonies that were devoid of their yellow pigmentation (for strains UA140 and MT4653). In addition, these mutant strains also displayed retarded growth under aerobic conditions and in the presence of H(2)O(2). High-performance liquid chromatography profiling of cell surface extracts identified unique peaks that were missing in the mutant strains, and partial characterization of the purified product from UA159 demonstrated that it is indeed a hybrid NRP/PK, as predicted. A genomic survey of 94 clinical S. mutans isolates suggests that the TnSmu2 gene cluster may be more prevalent than previously recognized.

Prospective study of potential sources of Streptococcus mutans transmission in nursery school children.

Transmission of Streptococcus mutans, a major dental caries pathogen, occurs mainly during the first 2.5 years of age. Children appear to acquire S. mutans mostly from their mothers, but few studies have investigated non-familial sources of S. mutans transmission. This study prospectively analysed initial S. mutans oral colonization in 119 children from nursery schools during a 1.5-year period and tracked the transmission from child to child, day-care caregiver to child and mother to child. Children were examined at baseline, when they were 5-13 months of age, and at 6-month intervals for determination of oral levels of S. mutans and development of caries lesions. Levels of S. mutans were also determined in caregivers and mothers. A total of 1392 S. mutans isolates (obtained from children, caregivers and mothers) were genotyped by arbitrarily primed PCR and chromosomal RFLP. Overall, 40.3 % of children were detectably colonized during the study, and levels of S. mutans were significantly associated with the development of caries lesions. Identical S. mutans genotypes were found in four nursery cohorts. No familial relationship existed in three of these cohorts, indicating horizontal transmission. Despite high oral levels of S. mutans identified in most of the caregivers, none of their genotypes matched those identified in the respective children. Only 50 % of children with high levels of S. mutans carried genotypes identified in their mothers. The results support previous evidence indicating that non-familial sources of S. mutans transmission exist, and indicate that this bacterium may be transmitted horizontally between children during the initial phases of S. mutans colonization in nursery environments.

Genetic classification of severe early childhood caries by use of subtracted DNA fragments from Streptococcus mutans.

Streptococcus mutans is one of several members of the oral indigenous biota linked with severe early childhood caries (S-ECC). Because most humans harbor S. mutans, but not all manifest disease, it has been proposed that the strains of S. mutans associated with S-ECC are genetically distinct from those found in caries-free (CF) children. The objective of this study was to identify common DNA fragments from S. mutans present in S-ECC but not in CF children. Using suppressive subtractive hybridization, we found a number of DNA fragments (biomarkers) present in 88 to 95% of the S-ECC S. mutans strains but not in CF S. mutans strains. We then applied machine learning techniques including support vector machines and neural networks to identify the biomarkers with the most predictive power for disease status, achieving a 92% accurate classification of the strains as either S-ECC or CF associated. The presence of these gene fragments in 90 to 100% of the 26 S-ECC isolates tested suggested their possible functional role in the pathogenesis of S. mutans associated with dental caries.

Reduction in bacterial contamination of toothbrushes using the Violight ultraviolet light activated toothbrush sanitizer.

PURPOSE: This two armed, self-controlled, investigator blinded, clinical study tested the efficacy of an ultraviolet (UV) light toothbrush holder (Violight) to decrease toothbrush bacterial contamination. METHODS: 25 subjects were randomly assigned to control or experimental groups and received two toothbrushes for home use on either even or odd days. The control group rinsed both toothbrushes after use in cold tap water with no mechanical manipulation. The experimental group rinsed one toothbrush in cold running water while storing the other toothbrush in the Violight toothbrush holder after use. The toothbrushes were returned after 2 weeks use in sealed plastic bags and were analyzed for the number of colony forming units (CFU) of S. mutans, S. salivarius, lactobacilli, E. coli, and other coliforms, and total bacterial counts by culture. An additional analysis of the total bacterial profile was performed using denaturing gradient gel electrophoresis (DGGE). RESULTS: The Violight toothbrush holder reduced total CFU by an average of 86% (ANCOVA, P = 0.037). In addition, a tendency was noted for a reduction in total bacterial population as detected by DGGE.

Promoting oral health from birth through childhood: prevention of early childhood caries.

Early childhood caries (ECC) is the single most common chronic childhood disease in the United States. Associated with a characteristic clinical presentation, ECC results from a culmination of risk factors, including cariogenic bacteria, inappropriate feeding practices, and social variables. It is essential that nurses become knowledgeable about ECC health promotion and prevention interventions to facilitate their efforts in everyday patient encounters and improve the overall oral health status of infants and children. This article provides an overview of ECC along with suggestions for actions that nurses can take to improve the oral health of children.

Association of mutans streptococci between caregivers and their children.

The purposes of this literature review were to: (1) review the sources of mutans streptococci (MS) colonization in children and the effect of MS levels of primary caregivers on children's MS colonization; and (2) evaluate studies examining interventions to reduce transmission of MS from caregivers to their children. Forty-six studies were reviewed. Strong evidence demonstrated that mothers are a primary source of MS colonization of their children. A few investigations showed other potential sources of children's MS colonization, notably fathers. The role of other factors influencing transmission, such as socioeconomic status (SES) and specific cultural or behavioral practices, are unclear. There were at least 12 reports of microbiological interventions to reduce transmission of MS from caregivers to their children. Even though most studies found a reduction of MS in the children and 2 showed significant caries reduction, these studies generally lock consistent findings regarding caries reduction, hove a small sample size and inadequate control groups, and lock blindness of investigators and subjects. The efficacy of microbiological approaches on the caregivers to reduce caries risk in children still needs to be established through more rigorously designed clinical trials.

Developmental defects of enamel increase caries susceptibility in Chinese preschool children.

OBJECTIVES: The present epidemiological study aimed to compare the prevalence and severity of developmental defects of enamel (DDE) and dental caries between urban and suburban Chinese preschool children. METHODS: A total of 1351 3- to 6-year-old children were invited to participate in this study and received dental examinations. A modified DDE index was used to assess the prevalence and severity of DDE. The dental caries diagnosis was based on the World Health Organization (WHO) health survey methods for field studies and was recorded using the decayed, missing and filled tooth (dmft) index. The caries status was further classified as caries or severe caries according to a modification of the American Academy of Pediatric Dentistry definition. RESULTS: Overall, the DDE prevalence was 48.3% among the 1351 preschool children. The DDE prevalence was higher in innercity children (54.1%) than in suburban children (42.0%; P < 0.001). In contrast, the suburban children had a higher prevalence of dental caries (65.2% vs 57.5%; P = 0.004) and a higher mean dmft score (3.5 ± 4.2 vs 2.9 ± 3.8; P = 0.005) than the innercity children. Only 23.9% of the children were free of both DDE and caries. The caries risk increased significantly and independently as DDE severity increased (linear trend, 95% confidence interval = [1.32, 1.69], age [1.60, 1.88], urban residence [1.18, 2.15] and breastfeeding experience [1.04, 1.60]) after controlling for other demographic risk factors. CONCLUSIONS: The study provides new evidence that DDE is a significant contributing factor for the highly prevalent and progressive dental caries observed in Chinese preschool children. These results highlight the importance of including DDE in caries risk assessments.

A screening method for gastric cancer by oral microbiome detection.

Gastric cancer is the second most common malig-nancy and one of the principal causes of cancer­related mortality worldwide. Early diagnostic and screening methods for gastric cancer are limited at present, most of them involving invasive procedures. We aimed to investigate the characteristics of the oral microbiome in gastric cancer individuals and to conduct a screening method for gastric cancer by oral microbiome detection. We used high­throughput sequencing to examine the total bacterial profile of saliva and plaque samples of 50 subjects, including 37 individuals with gastric cancer and 13 controls. The Venn diagram and species abundance clusters were generated from the data. The results indicated that the oral bacteria were more complex in patients with gastric cancer. Based on the characteristics of the oral microbiome in individuals with gastric cancer, a scoring system was designed to screen gastric cancer. In the present study, 36 out of 37 individuals in the gastric cancer group were identified as a high­risk population, giving a sensitivity rate of 97%. One out of 13 individuals in the control group was identified as a high­risk population, providing a false-positive rate of 7.7%. The scoring system we designed may be a potential method for screening suspected gastric cancer patients by oral microbiome detection. Further calibration of this scoring system is needed by recruiting a larger study population.

Diagnosing Developmental Defects of Enamel: Pilot Study of Online Training and Accuracy.

PURPOSE: The purpose of this study was to assess dentists' ability to correctly identify and classify development defects of enamel (DDE). METHODS: The modified DDE (MDDE) index was used to classify enamel defects into two types: (1) enamel hypoplasia-pitted, grooved, or missing enamel; or (2) enamel opacity-translucency of enamel not caused by dental caries or fluorosis (can be either demarcated or diffuse). A panel of six experts selected and scored 36 images using the MDDE, and the consensus score was used as the gold standard score in the evaluation of survey respondents. A short training table was developed to match training images to descriptors for the MDDE. A survey, including the training table, was then distributed electronically to 2,036 U.S. dentists and expanded function dental assistants from the Indian Health Service and 6,174 members of American Academy of Pediatric Dentistry. The percent of correct responses was evaluated for each image. RESULTS: Survey respondents (348 total) showed great variability in correct responses for each image, ranging from 41 to 97 percent, for each category of the MDDE. CONCLUSIONS: Enhanced training and calibration on the ability of dental providers is needed to identify the different types of development defects of enamel.

Development of species-specific primers for detection of Streptococcus mutans in mixed bacterial samples.

Streptococcus mutans is the major microbial pathogen associated with dental caries in children. The objectives of this study were to design and evaluate species-specific primers for the identification of S. mutans. Validation of the best primer set, Sm479F/R, was performed using seven S. mutans reference strains, 48 ATCC non-S. mutans strains, 92 S. mutans clinical isolates, DNA samples of S. mutans-Streptococcus sobrinus or S. mutans-Streptococcus sanguinis, and mixed bacterial DNA of saliva samples from 33 18-month-old children. All of the S. mutans samples tested positive, and no PCR products were amplified from members of the other streptococci or nonstreptococci strains examined. The lowest detection level for PCR was 10(-2) ng of S. mutans DNA (c. 4.6 x 10(3) copies) in the test samples. The results of this study suggest that the Sm479F/R primer pair is highly specific and sensitive for identification of S. mutans in either purified or mixed DNA samples.