The association of selected bacteria with the lesions of root surface caries

Plaque from the root surfaces of 165 subjects (mean age 65.5 years, 22-26 teeth/subject) was analysed for specific bacteria. Five subject groups were defined: A (DMFS 16.4), B (DMFS 55.9), C1 (DMFS 55.6), C2 (DMFS 57.0) and C3 (DMFS 48.1). Groups C1 and C2 had unrestored root surface lesions; Group A, B and C3 were free of unrestored root caries and differed in their coronal caries experience. Streptococcus mutans was isolated more frequently from the root lesions in Groups C1 and C2 than from intact root surfaces in Group A. Streptococcus oralis, Streptococcus mitis 1 and Streptococcus sanguis were isolated more frequently from Group A. The percentage contribution that S. mutans made to plaque from lesions in Groups C1 and C2 was higher than that from plaque in Group A and Actinomyces viscosus serovar 2 contributed more to plaque in Group C1 than in samples from Group A. The percentage counts of Lactobacillus in plaque from lesions in Groups C1 and C2 were higher than those from intact roots in Groups A, B, and C3. Subjects were also grouped on the presence of Lactobacillus and S. mutans in plaque samples. Samples with both organisms (n = 17) showed significantly higher isolation frequencies of specific strains of S. mitis 1 and also A. viscosus serovar 2 compared with samples of plaque containing S. mutans or Lactobacillus. Actinomyces naeslundii serovar 1 was not isolated from samples containing both S. mutans and Lactobacillus. The results confirm an association of S. mutans and Lactobacillus with root surface lesions and suggest a relationship between lesions and A. viscosus serovar 2.     

Lactobacillus-mediated interference of mutans streptococci in caries-free vs. caries-active subjects

In order to assess whether naturally occurring oral lactobacilli have probiotic properties, lactobacilli were isolated from saliva and plaque from children and adolescents, with or without caries lesions. The interference capacities of these lactobacilli were investigated against a panel of 13 clinical isolates and reference strains of Streptococcus mutans and Streptococcus sobrinus, as well as against the subject's autologous mutans streptococci, using the agar-overlay technique. Lactobacillus-mediated inhibition differed significantly between the three subject groups (no caries, arrested caries, or active caries), demonstrating increased inhibition in subjects without present or previous caries experience compared to subjects with arrested caries or subjects presenting with frank lesions. Lactobacilli from subjects lacking S. mutans inhibited the growth of the test panel of mutans streptococci significantly better than lactobacilli from subjects who were colonized. Furthermore, subjects without caries experience harbored lactobacilli that more effectively repressed the growth of their autologous mutans streptococci. Twenty-three Lactobacillus spp. completely inhibited the growth of all mutans streptococci tested. Species with maximum interference capacity against mutans streptococci included Lactobacillus paracasei, Lactobacillus plantarum, and Lactobacillus rhamnosus. Naturally occurring oral lactobacilli significantly inhibited the growth of both test strains of mutans streptococci and the subject's autologous mutans streptococci in vitro, and this effect was more pronounced in caries-free subjects.     

The microflora of the erupting first permanent molar

The relationship between microflora, eruption status and caries status in the first permanent molar of young children was investigated in 177 children aged 6-7 years. A significantly greater proportion of fully erupted teeth were classified as sound and plaque-free compared to partially erupted teeth. Fully erupted teeth yielded greater numbers and proportions of mutans streptococci compared with significantly greater numbers and proportions of Actinomyces israelii in partially erupted teeth. Logistical regression analysis showed significant associations between white spot lesions in partially erupted teeth and increased numbers of Streptococcus oralis, mutans streptococci and Streptococcus salivarius whereas the presence of Actinomyces naeslundii was associated with health. Significantly greater numbers and proportions of S. oralis and S. salivarius were isolated from partially erupted teeth with white spot lesions whereas Streptococcus mutans was isolated in significantly greater numbers and proportions from fully erupted molars with white spots. This study suggests that organisms other than mutans streptococci are associated with caries development in erupting permanent molar teeth.     

Horizontal transmission of Streptococcus mutans in schoolchildren

Objetive: The aim of this study was to analyze possible horizontal transmission patterns of S. mutans among 6-7-yr-old schoolchildren from the same class, identifying genotypes and their diversity and relationship with caries disease status. Study Design: Caries indexes and saliva mutans streptococci and lactobacilli counts were recorded in 42 schoolchildren. Mutans streptococci colonies were identified by means of biochemical tests and all S. mutans strains were genotyped by arbitrarily primed polymerase chain reaction. A child was considered free of S. mutans when it could not be isolated in 3 samples at 1-week intervals. Results: S. mutans was isolated in 30 schoolchildren: 20 having one genotype and 10 two genotypes. Higher mutans streptococci and caries index values were found in those with two genotypes. Five genotypes were isolated in more than 1 schoolchild and one of these was isolated in 3 schoolchildren. Our results suggest that horizontal transmission may take place. Conclusion: Schoolchildren aged 6-7 yrs may be the source of mutual transmission of S. mutans. Key words:Streptococcus mutans, Horizontal transmission, AP-PCR, genotyping     

Mutans streptococci in subgingival plaque of treated and untreated patients with periodontitis

BACKGROUND: The etiology of root caries is thought to be identical to coronal caries, though root caries seem to be more complicated because of the higher susceptibility of exposed roots (dentin) by periodontal therapy to demineralization than intact enamel. This implies that mutans streptococci are the most likely pathogens in the development of root caries. Although it is known that both the numbers of mutans streptococci and the frequency of isolation in root caries lesions are negatively correlated with the distance from the gingival margin, the subgingival sulcus has not been considered a possible habitat for mutans streptococci. However, subgingival occurrence of mutans streptococci in both untreated and treated periodontal patients has not been documented well in the literature. OBJECTIVE: To investigate the presence and levels of mutans streptococci in the subgingival plaque of patients (n=154) in different stages of periodontal therapy. The subgingival sulcus may be a possible habitat for mutans streptococci. This localisation of mutans streptococci may be of importance in the development of root caries after periodontal surgery. MATERIALS AND METHODS: In this cross-sectional study, subgingival plaque samples from 154 consecutive adult periodontitis patients were tested for presence and levels of mutans streptococci and putative periodontal pathogens by anaerobic cultures. These patients were divided into 4 groups based on their stage of periodontal treatment: (1) untreated patients; (2) patients after initial periodontal therapy only; (3) patients in the maintenance phase who not underwent periodontal surgery; (4) patients after periodontal surgery. RESULTS: The prevalence of mutans streptococci in the 4 study groups varied from 82% in untreated patients to 94% in maintenance patients. The mean proportion of mutans streptococci was 6.65% in maintenance patients versus 1.86% in untreated patients (p=0.005) and 2.51% in patients after scaling and root planing (p=0.041). CONCLUSIONS: The subgingival area is a microbial habitat for mutans streptococci that may be of importance in the development of root caries in periodontitis patients.     

根面龋病灶微生物学研究

作者对13例根面龋患者病灶微生态系中的变形链球菌、乳酸杆菌、粘性放线菌进行定量研究。结果显示,变形链球菌在数量上占绝对优势,乳酸杆菌也较多,而粘性放线菌仅在1例中检出。故支持变形链球菌是根面龋和冠龋共同病原菌的观点。     

The microbiological profiles of saliva, supragingival and subgingival plaque and dental caries in adults with and without type 2 diabetes mellitus

INTRODUCTION: The relationships between suspected bacteria in saliva, yeasts in oral rinse, and supragingival and subgingival plaque versus root surface and coronal caries in adults with type 2 diabetes mellitus and a non-diabetic group were explored. METHODS: One-hundred and five patients with type 2 diabetes and 103 non-diabetic subjects were recruited; their periodontal status, plaque index and magnitude of root surface and coronal caries were assessed. Saliva and an oral rinse were cultured for mutans streptococci, lactobacilli and yeasts. Toothbrush samples of supragingival plaque and curette samples of subgingival plaque were assessed for 17 bacterial species using the checkerboard DNA-DNA hybridization method. RESULTS: Type 2 diabetes patients had significantly more severe periodontitis, a higher plaque index and a higher prevalence and magnitude of root surface caries than non-diabetic subjects. Significantly more diabetic subjects had higher levels of Treponema denticola, Prevotella nigrescens, Streptococcus sanguinis, Streptococcus oralis and Streptococcus intermedius in their supragingival plaque than non-diabetic subjects. No significant difference was found for the organisms in saliva, oral rinse and subgingival plaque between the two groups. After adjustment for diabetic status, root surface caries was associated with an increased count of mutans streptococci, lactobacilli and yeasts in saliva and of Streptococcus mutans in supragingival plaque samples. Coronal caries was only associated with lactobacilli and yeasts in saliva. CONCLUSION: The number of cariogenic organisms in saliva and oral rinse estimated by culture demonstrated a stronger association with both root surface and coronal caries compared to those 17 species assessed with the checkerboard method in supragingival and subgingival plaque.     

Colonization of Streptococcus mutans and Streptococcus sobrinus genotypes and caries development in children to mothers harboring both species

The major route of early acquisition of mutans streptococci in humans is a vertical transmission from mother to child. The purpose of this longitudinal study was to examine the acquisition, distribution and persistence of Streptococcus mutans and Streptococcus sobrinus in children whose mothers harbored both species and to study the caries incidence in relation to colonization of these bacteria. Fifteen mother-child pairs were followed during the child's first 7 years. Stimulated salivary samples were taken from the mothers and the children. Plaque samples were also collected from the teeth and the tongue of the children. The samples were analyzed by cultivating techniques together with genomic fingerprinting and hybridizing. The caries experience was evaluated on the sampling occasions and retrospectively using the records of caries registrations from the community clinics. During the 7-year period 10 of the 15 children acquired mutans streptococci. Only 4 of them were colonized by both S. mutans and S. sobrinus despite the fact that their mothers harbored both species. In 2 of the children S. sobrinus was found later than S. mutans. A total of 26 genotypes were found in the children and 9 of them were identical to their mothers. New genotypes and a gain-loss pattern were noted especially in the children but also in their mothers. The groups of teeth first positive for the two species were the deciduous molars. The caries experience was low during the study period with 8 children showing no caries.     

A cross-sectional study into the prevalence of root caries in periodontal maintenance patients

Abstract. The aim of this cross-sectional study was to investigate cross-sectionally the prevalence and several risk indicators of root caries in 45 periodontal maintenance patients, who had been actively treated for adult periodontitis 11–22 years ago. These patients were part of a routine 3–6 monthly maintenance schedule. Active and inactive root caries and root fillings were recorded, as well as coronal caries experience. Plaque and bleeding scores, number of exposed root surfaces, rate of saliva secretion, saliva buffering capacity, mutans streptococci counts and Lactobacilli were also scored. From the total of 45 study subjects, 37 patients (82%) showed root lesions (root caries and/or root fillings), while only 8 patients were free of any root lesions. On average, there were 4.3 root lesions per patient (range 0–19) in the present study. 10 patients had active root caries lesions. Of all damaged root surfaces, 9% were active lesions, mostly located on mandibular teeth at lingual and vestibulair sites; 40% were inactive lesions often detected at vestibular sites. The remaining damaged root surfaces (51%) were restored; they were equally divided over both jaws. A higher number of root lesions was observed in those patients with >10⁶mutans streptococci/ ml saliva. Although the actual number of lesions per patient was low in relation to the large number of sites with gingival recession, the results from this cross-sectional study in periodontal maintenance patients indicate that: (1) root caries can be regarded as a complication in periodontal maintenance patients; (2) the individual number of root lesions correlate with individual dental plaque scores; (3) a high number of root lesions is associated with high counts of salivary mutans streptococci; (4) no relation between root caries and coronal caries experience, salivary secretion rate or salivary buffering capacity seems present. Therefore, repeated oral hygiene instructions and adjunctive preventive measures including diet counseling and fluoride rinses, as well as fluoride and chlorhexidine varnishes, should be advocated in high-risk patients.     

Caries prevalence and salivary mutans streptococci in 0–2-year-old children of Japan

The prevalence of caries and the number and species distribution of salivary mutans streptococci in 356 children (aged 0-2 yr old) in Japan were examined twice at an interval of 1 yr. No mutans streptococci were isolated from the predentate children. The detection rate of mutans streptococci and the prevalence of caries increased with age. Mutans streptococci were isolated from 39.9% of the subjects. The majority of isolates were identified as Streptococcus mutans. The concentration of mutans streptococci correlated with the number of erupted teeth (r = 0.339). In addition, the concentration of mutans streptococci was more closely correlated to the caries prevalence of the next year (r = 0.465) than that of the year when the salivary concentration of mutans streptococci was first evaluated (r = 0.368). The children who had no caries but harbored mutans streptococci in the first year showed significantly higher caries prevalence in the next year than did the children with neither caries nor mutans streptococci. These results indicate that the establishment of mutans streptococci is associated with caries initiation in early childhood.     

Microbiology of root surface caries in humans

Studies on the microbiology of root surface caries between 1970 and 1975 placed emphasis on Gram-positive pleomorphic filamentous rods, particularly Actinomyces viscosus and Actinomyces naeslundii. Both of these species had been shown to produce root surface caries in experimental animals. Since this time, studies have placed more emphasis on Streptococcus mutans, and S. mutans and Lactobacillus are significant in prediction of root surface caries risk in patients. Subsequent studies confirmed an association between S. mutans and 'soft' or 'initial' root lesions. Thus, it is important when determining the microflora of root surface lesions to make careful characterization of the state of the lesion. A second important aspect of the analysis of bacterial communities associated with root surface caries is better definition of the organisms. Most studies have concentrated on 'target organisms' S. mutans, S. sanguis, A. viscosus, A. naeslundii, Lactobacillus, and Veillonella. However, it has been known for 17 years that the Actinomyces associated with the lesions may be variants of A. viscosus and A. naeslundii. Such strains (intermediate strains) have been described in taxonomic studies of Actinomyces, yet little is known of the differences in physiology of these strains or their relationship to root surface caries. A similar situation exists with oral Streptococcus where new taxonomic divisions are being proposed. Recognition of the potential diversity within the 'target' genera of root surface caries could yield valuable data. Recent studies suggest that this is so, since samples from root surface lesions which contain S. mutans and Lactobacillus show a high isolation of S. mitis 1 and no isolations of A. naeslundii. Careful definition of the lesions of root surface caries and the flora will allow analysis to relate a specific bacterial community to the state fo the lesion and assist in monitoring the control of the lesion through fluoride and antibacterials.     

Microbial flora associated with presence of root surface caries in periodontally treated patients

Abstract — Examination of saliva and dental plaque was carried out in 35 adults who had been treated for periodontal disease 3 yr earlier. Plaque samples were collected from approximal and buccal sound and carious root surfaces. The samples were analyzed for the presence and proportions of members of Streptococcus, Lactobacillus and Actinomyces. The results showed a low prevalence of root surface caries and a low level of salivary mutans streptococci and lactobacilli. From subjects with root caries there was a not statistically significant tendency to higher proportional levels of mutans streptococci in plaque from carious root surfaces than from caries-free surfaces. An inverse significant relationship between noncarious and carious root surfaces was noted for S. sanguis. The population of A. viscosus and A. naeslundii was similar in plaque samples from sound and carious sites but showed elevated levels in the subjects with five or more new root surface lesions.     

Microbial flora associated with presence of root surface caries in periodontally treated patients

Examination of saliva and dental plaque was carried out in 35 adults who had been treated for periodontal disease 3 yr earlier. Plaque samples were collected from approximal and buccal sound and carious root surfaces. The samples were analyzed for the presence and proportions of members of Streptococcus, Lactobacillus and Actinomyces. The results showed a low prevalence of root surface caries and a low level of salivary mutans streptococci and lactobacilli. From subjects with root caries there was a not statistically significant tendency to higher proportional levels of mutans streptococci in plaque from carious root surfaces than from caries-free surfaces. An inverse significant relationship between noncarious and carious root surfaces was noted for S. sanguis. The population of A. viscosus and A. naeslundii was similar in plaque samples from sound and carious sites but showed elevated levels in the subjects with five or more new root surface lesions.     

Identification of mutans streptococci by restriction fragment length polymorphism analysis of polymerase chain reaction-amplified 16S ribosomal RNA genes

Mutans streptococci are frequently isolated from dental plaque and carious lesions. These bacteria have been identified by conventional methods such as biochemical and serologic tests followed by the isolation of colonies on the mitis-salivarius agar, which are sometimes inconsistent. Recently, species-specific polymerase chain reaction (PCR) has been reported to rapidly identify Streptococcus mutans and Streptococcus sobrinus. However, in the case of identification and classification into several species, e.g. within the group of mutans streptococci consisting of seven species, the identification using species-specific PCR seems somewhat inefficient because of need for the development and preparation of specific primers for each species. Therefore, in this study we developed a simple method using restriction fragment length polymorphism analysis of PCR-amplified 16S ribosomal RNA genes (16S rRNA genes PCR-RFLP) for the identification of seven different species included in the group of mutans streptococci. We amplified 16S rRNA gene sequences from genomic DNA samples by PCR using universal primers and digested the PCR products with the restriction endonucleases, HpaII and HaeIII. HpaII produced six RFLP patterns for eight reference strains, since the patterns for S. sobrinus, Streptococcus downei and Streptococcus ferus were similar. RFLP patterns produced with HaeIII could separate these three species. Furthermore, the RFLP patterns predicted from the 16S rRNA gene sequences in the GenBank database agreed with the actual RFLP patterns produced in the present study. The 16S rRNA sequence comparisons can be used to identify oral mutans streptococci; however, the identification by sequencing is sometimes difficult in large-scale studies and for small laboratories. Therefore, 16S rRNA genes PCR-RFLP, using HpaII and HaeIII, could be an alternative method for the identification of mutans streptococci, and may be applicable for large-scale studies on the cariogenicity of mutans streptococci.     

The earlier the colonization by mutans streptococci, the higher the caries prevalence at 4 years of age

Seventy-eight 4-year-old children, examined earlier for the presence of mutans streptococci at 4-month intervals from 15 months of age, were recalled for recording of dental caries and salivary sampling. The saliva samples were analysed for the presence of mutans streptococci, including the species Streptococcus mutans and Streptococcus sobrinus and lactobacilli. The results showed that the earlier the mutans streptococci had been detected in the children, the higher the caries experience. Eighty-nine percent of the children colonized at 2 years of age had experienced caries and had a mean dfs of 5.0 compared with 25% of the non-colonized 4-year-olds with a mean dfs of 0.3. S. mutans was the predominant species. S. sobrinus was usually found in combination with S. mutans , except in 2 children where S. sobrinus was the only species detected. More children with multiple species had higher numbers of total mutans streptococci and a tendency to higher caries prevalence than children with only S. mutans.     

The predominant aciduric microflora of root-caries lesions

The etiology of root caries is not fully understood, and although mutans streptococci, lactobacilli, and A. naeslundii have been implicated in its initiation and progression, this study was designed to determine the potential role of other microbial species and the nature of predominant aciduric microflora in the root caries process. We isolated the predominant aciduric microflora from root-caries lesions (n = 14) and sound root surfaces in subjects with (n = 13) or without (n = 10) root caries, using both a "most probable numbers" method and conventional plating methods. The predominant aciduric bacteria from root lesions were lactobacilli and A. israelii, while from sound root surfaces in subjects with root caries, A. gerencseriae comprised over 60% of aciduric isolates. Mutans streptococci were not among the aciduric isolates. Subjects without root caries harbored fewer bacteria, and S. anginosus (pH 4.8) and S. oralis (pH 5.2) were the predominant aciduric bacteria. The microbial etiology of root caries is more complex than was previously appreciated, and factors underlying the microbial succession occurring during the disease process are not known. Taxa with previously unrecognized aciduric characteristics have been isolated routinely, and the role of these organisms in the root caries process requires further investigation.     

Humoral IgG antibodies to oral microbiota in a population at risk for root-surface caries.

Mutans streptococci have been strongly implicated in the initiation of dental caries on coronal surfaces. Their role in development of root-surface caries is less clear. The etiologic agents of both types of dental caries are likely to elicit systemic immune responses. The objective of the present study, therefore, was to study the association of clinical variables of disease with humoral IgG antibodies to nine oral micro-organisms in 314 adult subjects, aged 45-65 years, who were at risk for root-surface caries. Antibody activity to Streptococcus mutans strain Ingbritt, S. mutans/S. sobrinus GTFs, S. faecalis strain 19433, Actinomyces viscosus strain WVU 626, Actinomyces naeslundii strain 12, Lactobacillus casei, Actinobacillus actinomycetemcomitans strain Y4, Porphyromonas gingivalis strain 381, Eikenella corrodens strain 1073, and Wolinella recta strain 371 was measured by ELISA. Pearson correlation coefficients among log10 antibody levels within subjects revealed marked positive correlations among subgingival bacteria, generally weak positive correlations among supragingival micro-organisms, and no correlations between elements of the supragingival battery with the subgingival battery. IgG antibody levels to mutans streptococcal antigens were significantly correlated with subject DMF scores (r = 0.23; p less than 0.0001). No significant correlation was seen between DMF scores and antibody to any other supragingival micro-organism tested. Further relationships between levels of S. mutans antibody and individual clinical variables were analyzed by step-wise multiple linear regression, resulting in a model that was highly significant (p = 0.0001), with an r2 = 0.14. Numbers of missing teeth, coronal caries, root-surface caries, and root-surface restorations were each positively associated with antibody levels to mutans streptococci.(ABSTRACT TRUNCATED AT 250 WORDS)     

The predominant microflora of nursing caries lesions.

The predominant microflora recovered from infected dentine of 52 carious teeth from 14 children with nursing caries was determined using both selective and non-selective media for the isolation of specific genera and acidified media (pH 5.2) to isolate the predominant aciduric microorganisms, and compared with the microflora of sound enamel surfaces in caries-free children. Streptococcus mutans formed a significantly greater proportion of the lesion flora while Streptococcus oralis, Streptococcus sanguis and Streptococcus gordonii formed a significantly greater proportion of the plaque flora from sound tooth surfaces. The proportions of Actinomyces naeslundii and Actinomyces odontolyticus were significantly greater in the plaque samples than in the lesion samples. Actinomyces israelii formed 18.2% of the flora from the lesions, but was not isolated from the plaque samples. The proportions of Candida albicans, Lactobacillus spp. and Veillonella spp. were also significantly greater in the carious dentine than in the plaque samples. The most frequently isolated lactobacilli were Lactobacillus casei, Lactobacillus fermentum and Lactobacillus rhamnosus. The predominant aciduric flora was S. oralis, S. mutans and A. israelii and these taxa were also isolated from a similar proportion of the lesions at pH 7.0. Strains of S. mutans, L. casei, L. fermentum and L. rhamnosus isolated from individual carious teeth were genotyped using PCR-based methods. Each species was genotypically heterogeneous and different genotypes were recovered from different carious teeth in the same child. These data indicate that the microflora of lesions in the same child is microbiologically diverse and support a non-specific aetiology for nursing caries in which the physiological characteristics of the infecting flora, not its composition, is the major determinant underlying the disease process.     

Caries-associated micro-organisms in infants from different socio-economic backgrounds in Scotland

OBJECTIVES: The aims of this study were: (1) to compare the frequency of isolation of mutans streptococci, (Streptococcus mutans, Steptococcus sobrinus), lactobacilli and yeasts (caries-associated micro-organisms) in the saliva of 1-year-old infants with and without dental caries; and (2) to determine if socio-economic background influenced the frequency isolation of bacteria and caries status. METHODS: 1393 1-year-old consented infants, who comprised 70. 3% of children born in Dundee during a 1year period, had saliva samples taken (tongue-loop method) for microbiological culture and were examined for dental caries (d(1)-threshold: enamel and dentine diagnostic threshold). Thirty-nine infants were diagnosed with caries and the frequencies of isolation of caries-associated micro-organisms (and absolute microbial counts) were compared with infants who were caries-free. In addition, associations were sought between the infants' socio-economic background, the frequency of isolation of caries-associated micro-organisms and caries status. RESULTS: Streptococcus mutans, lactobacilli and yeasts were isolated more frequently from those infants with caries compared to those who were caries-free (S. mutans: 29.7 vs 9.8%, P=0.0008; lactobacilli: 15.4 vs 4.3%, P=0.0073; yeasts: 23.7 vs 10.4%, P=0.0016-Fisher's exact test). There were no significant differences between the isolation frequencies of S. sobrinus (2.7 vs 1.3%, P=0.39) from those with and without caries. Significantly, more infants living in areas of high deprivation had caries compared to those from more affluent areas (DEPCAT 6 and 7 vs 1-5: 3.6 vs 1.9%, P=0.049), but, apart from yeasts, socio-economic background was not significantly associated with the isolation frequencies of any of the caries-associated micro-organisms. CONCLUSIONS: In infants as young as 1year of age, salivary S. mutans, lactobacilli and yeasts but not S. sobrinus were isolated significantly more frequently from those with caries compared to those who were caries-free. Apart from yeasts, socio-economic background did not influence the frequency of isolation of caries-associated micro-organisms. However, infants living in areas of highest deprivation had significantly higher frequencies of caries compared to those from more affluent areas.     

Human strains of mutans streptococci show different cariogenic potential in the hamster model

The cariogenic potential of fresh humans strains of Streptococcus mutans and Streptococcus sobrinus was examined in hamsters maintained on a high sucrose diet. The strains 1B 16 (S. mutans) and B13 (S. sobrinus) isolated 20-25 yrs ago served as positive controls. Three series of experiments were run. Some strains were tested once and some strains were tested in all 3 experiments. The animals infected with S. sobrinus strains generally showed lower caries scores than those infected with S. mutans strains. Among the groups infected with the different strains of S. mutans the caries scores varied. In one of the experiments the caries score of the animals infected with one of the Icelandic S. mutans strains was significantly higher than that of the positive control group and the group infected with one of the fresh Swedish isolates. Thus, different strains of mutans streptococci where shown to induce varying caries activity in the hamster model.