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      Frequency, biofilm formation and acid susceptibility of streptococcus mutans and streptococcus sobrinus in saliva of preschool children with different levels of caries activity

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          Abstract

          Background:

          One of the causative factors in development of dental caries is microorganisms. Two species of Mutans streptococci including Streptococcus mutans and Streptococcus sobrinus are associated with dental caries in human beings. The aim of this study was to investigate the frequency of S. mutans and S. sobrinus in saliva of children with different caries activity and ability to form biofilm and acid susceptibility of these microorganisms.

          Materials and Methods:

          This analytical case-control study was performed on 83 preschool children, 4-6 years old. Children were divided into two groups including 41 caries-active and 42 caries-free children. Non-stimulated saliva samples were collected and culture and polymerase chain reaction techniques were used. Statistical analysis was performed using t-test, Chi-square, ANOVA, and Kappa tests.

          Results:

          S. mutans and S. sobrinus were found in 65% and 21.6% of the samples respectively. S. mutans was isolated from 75.6% of caries-active and 54.8% of caries-free children. Figures for S. sobrinus were 29.2% and 14.3% respectively. Acid susceptibility of microorganisms isolated from saliva was 87.43 in caries-active children and 94.30 for caries-free children. Biofilm formation of microorganisms in caries-active and caries-free children was 0.77 and 0.73, respectively.

          Conclusion:

          Frequency of S. mutans in caries-active children was significantly higher than caries-free children, but the difference in frequency of S. sobrinus was not significant. Acid susceptibility of microorganisms in caries-active children was significantly lower, but the ability to form biofilm was not significantly different in two groups.

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          Most cited references24

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          Longitudinal study of dental caries incidence associated with Streptococcus mutans and Streptococcus sobrinus in pre-school children.

          Streptococcus mutans and Streptococcus sobrinus are known to be associated with the development of dental caries. In this study these bacteria were detected in pre-school children (each with primary dentition, age range 3-5 years, n = 60) using a PCR method, and then their presence was compared with the incidence of dental caries over a 1-year period. Plaque samples were collected from all erupted tooth sites using a sterile toothbrush. Dental examinations at the beginning of the study (baseline) and after 1 year were also performed to determine decayed, missing, filled teeth (dmft) scores using WHO caries diagnostic criteria. The prevalences of S. mutans and S. sobrinus across all the subjects were 61.7% and 56.6%, respectively; 13 subjects (21.7%) were positive for S. mutans alone, 10 (16.6%) were positive for S. sobrinus alone and 24 (40.0%) were positive for both S. mutans and S. sobrinus, whereas 13 (21.7%) were negative for both S. mutans and S. sobrinus. dmft scores of subjects positive for both S. mutans and S. sobrinus at baseline and after 1 year were significantly higher than of those positive for S. mutans alone at the same stages (P < 0.01 and P < 0.001, respectively). The caries incremental increase was also significantly greater in those with both bacteria detected (P < 0.05). Our results indicate that pre-school children harbouring both S. mutans and S. sobrinus have a significantly higher incidence of dental caries than those with S. mutans alone.
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            The final pH of bacteria comprising the predominant flora on sound and carious human root and enamel surfaces.

            Acidogenesis at low pH appears to be an important bacterial cariogenic trait. However, most information in this regard pertains to only a few of the acidogenic dental plaque bacteria. Therefore, the 'final' pH in sugar broth was determined for a wide variety of oral bacteria. Their source was: (1) carious material from advanced root lesions (ARL), (2) plaque from sound root surfaces of root-caries-free subjects (SRS), (3) plaque from "white spot" coronal lesions and sound coronal surfaces of caries-active subjects, and (4) plaque from sound coronal surfaces of caries-free subjects. Strains from groups 1 and 2 (ARL, 389 strains; SRS, 358 strains) were previously identified (van Houte et al., 1994) to the genus/species level and belonged to the predominant cultivable flora (PCF). Strains from groups 3 and 4 also belonged to the PCF but were not identified. All strains were placed in one of 4 final pH categories: or = 4.6. The main findings were: (1) ARL samples contained many strains with a final pH < 4.2 (mean percentage of 25.7). They included all strains of Lactobacillus and mutans streptococci (MS), most Bifidobacterium strains and non-mutans streptococci (non-MS), and about 20% of the Actinomyces strains. By contrast, SRS samples contained far fewer strains with a final pH < 4.2 (mean percentage of 8.4) which were nearly all non-MS. (2) Organisms with a final pH < 4.4 constituted mean percentages of 41.5 and 32.1 for the ARL and SRS samples, respectively. (3) The final pH distribution of strains in samples from coronal surfaces showed a tendency relative to caries activity (group 3 vs. group 4) similar to that for groups 1 and 2. Our findings further support the concept that increased cariogenic conditions are associated with increased proportions of organisms capable of acidogenesis at a low pH and that this shift involves organisms other than the MS and lactobacilli.
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              Quantitative real-time polymerase chain reaction for Streptococcus mutans and Streptococcus sobrinus in dental plaque samples and its association with early childhood caries.

              Streptococcus mutans and Streptococcus sobrinus are closely associated with the development of early childhood caries (ECC). Recently, quantitative real-time polymerase chain reaction (qRT-PCR) has been used for rapid and accurate quantification of these bacterial species. This study aims to detect quantitatively the levels of S. mutans and S. sobrinus in plaque samples by qRT-PCR, and to assess their association with the prevalence of ECC in Korean preschool children. One hundred and five children (71 months old or younger) were examined and classified into three groups (caries-free, ECC, severe ECC). Dental plaque samples were collected and qRT-PCR was conducted using oligonucleotide primers specific for glucosyltransferase gene (S. mutans-gtfB, S. sobrinus-gtfU) and universal primer. Pearson's correlation test was conducted to evaluate the relationship between the dmfs (decayed, missing, or filled surfaces primary teeth) scores and the microbiological findings. There was a significant difference between the levels of S. mutans and S. sobrinus in the plaque samples of the three groups (P < 0.05). The proportion of S. sobrinus to S. mutans showed strong correlation to the dmfs scores (r = 0.748, P < 0.05). The qRT-PCR results of this study showed that children with ECC had higher level of S. mutans and S. sobrinus in their dental plaque samples. The children with higher ratio of S. sobrinus to S. mutans in their dental plaque showed higher incidence of ECC.
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                Author and article information

                Journal
                Dent Res J (Isfahan)
                Dent Res J (Isfahan)
                DRJ
                Dental Research Journal
                Medknow Publications & Media Pvt Ltd (India )
                1735-3327
                2008-0255
                Jul-Aug 2013
                : 10
                : 4
                : 440-445
                Affiliations
                [1 ]Department of Pediatric Dentistry, Babol University of Medical Sciences, Babol, Iran
                [2 ]Department of Microbiology, Babol University of Medical Sciences, Babol, Iran
                [3 ]Dentist, Babol University of Medical Sciences, Babol, Iran
                Author notes
                Address for correspondence: Dr. Mahtab Hamzeh, Department of Pediatric Dentistry, Babol University of Medical Sciences, Babol, Iran. E-mail: dr.mh61@ 123456yahoo.com
                Article
                DRJ-10-440
                3793405
                24130577
                571cc129-648d-45d8-be0e-0b6057e57f67
                Copyright: © Dental Research Journal

                This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : November 2012
                : March 2013
                Categories
                Original Article

                Dentistry
                acid susceptibility,biofilm,streptococcus mutans,streptococcus sobrinus
                Dentistry
                acid susceptibility, biofilm, streptococcus mutans, streptococcus sobrinus

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