Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2005  |  Volume : 23  |  Issue : 1  |  Page : 23--26

Dental caries experience and salivary levels of Streptococcus mutans and Lactobacilli in 13-15 years old children of Belgaum city, Karnataka

PP Hegde, BR Ashok Kumar, VA Ankola 
 Department of Preventive and Community Dentistry, KLES Institute of Dental Sciences, Belgaum, India

Correspondence Address:
P P Hegde
Department of Preventive and Community Dentistry, KLES Institute of Dental Sciences, Belgaum


The present cross-sectional study was carried out in 372 school going children of Belgaum aged 13-15 years. The sample was selected by two stage random sampling method. The aim of the study was to estimate the salivary levels of Streptococcus mutans and Lactobacilli and to study the relationship between these microorganisms and dental caries experience. The DMFT was recorded according to the WHO criteria(1997).The microbial load was estimated from a single saliva sample obtained from the children. The mean DMFT recorded was 2.41. Streptococcus mutans was detected in 87.37% and Lactobacilli in only 36.71% of the sample. Statistically, highly significant relation was found between Streptococcus mutans and DMFT categories ( 2 =125.36, P< 0.001), while Lactobacilli was not statistically related to DMFT categories ( χ2 =8.78, P>0.05).

How to cite this article:
Hegde P P, Ashok Kumar B R, Ankola V A. Dental caries experience and salivary levels of Streptococcus mutans and Lactobacilli in 13-15 years old children of Belgaum city, Karnataka.J Indian Soc Pedod Prev Dent 2005;23:23-26

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Hegde P P, Ashok Kumar B R, Ankola V A. Dental caries experience and salivary levels of Streptococcus mutans and Lactobacilli in 13-15 years old children of Belgaum city, Karnataka. J Indian Soc Pedod Prev Dent [serial online] 2005 [cited 2022 Jul 5 ];23:23-26
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In India, children comprise 40% of a rapidly growing population. The prevalence of dental caries varies from 33.7%-90% in children population and is increasing at an alarming rate.[1] The dental caries prevalence among the children of Belgaum (Karnataka) has been reported earlier when the risk profile of dental caries has not been investigated. In view of the multifactorial nature of the dental caries it is impracticable to measure all the risk factors. In this present cross-sectional survey the microbial factor in relation to caries is contemplated. Several microorganisms have been characterized as having high cariogenic potential, but two classes of microorganisms, Streptococcus mutans and Lactobacilli have been extensively studied.[2] The Streptococcus mutans has been strongly associated with the initiation of caries, while Lactobacilli mainly has been connected with the further development of carious lesion.[3]

The aim of this present study was to estimate the salivary levels of Streptococcus mutans and Lactobacilli in school going children and to study the relationship between these organisms and dental caries experience.

 Materials and Methods

Study sample: The sample consisted of 400 high school children; aged 13-15 years. A two stage random sampling was followed.

Stage I: Of the 36 high schools, 4 schools were selected using lottery method, which constituted 10% of the school sample.

Stage II: Among the selected 4 schools, the children were allotted numbers and by using random number table, 100 children per school were selected, thereby yielding a sample of 400.

 Criteria for exclusion:

The school children who were not the resident of Belgaum city by birth.

Children with history of fluoride use.

Those who took antibiotics in the last one month.

Children with orthodontic appliances.

Collection of data: The data was collected on a self-designed proforma. The DMFT recording was done by a single calibrated examiner using mouth mirror and probe according to the criteria for the dentition status assessment outlined in Basic oral health surveys 1997.[4]

Microbial Analysis: Paraffin wax, stimulated whole saliva was collected between 9.30-11.30 am during the school hours. The subject were asked to refrain from eating for one hour before collection. 2 ml of stimulated saliva was collected in a calibrated plastic cup. By means of a sterile disposable syringe 1 ml aliquot of saliva was transferred from the cup to the previously labeled sterile bottle containing 4 ml of transport media (Thioglycollate media) and transported to the Hi-Tech laboratory, Belgaum, where it was processed immediately.

Laboratory procedures: The salivary sample was vortexed, to uniformly mix the saliva and the transport media using a cyclomixer. Using an inoculation loop (4 mm inner diameter) lO uL of the vortexed 1:5 dilution sample was streaked in duplicate on Mitis salivarius bacitracin agar (MSB) selective for Streptococcus mutans and on Rogosa SL agar for Lactobacilli .The MSB agar plates were incubated anaerobically for 48 hours at 37C in 5% COi in nitrogen. The Rogosa SL agar plates were incubated anaerobically for 96 hours at 37C. Following incubation, counts were made of colonies with morphological characteristic for Streptococcus mutans[5] on the MSB agar and of colonies exhibiting the typical morphology of Lactobacilli[5] on Rogosa SL agar. Identification for Streptococcus mutans was confirmed by biochemical tests like mannitol and sorbitol fermentation and catalase test. Gram staining was also performed. Catalase test and Gram staining confirmed the identity of Lactobacilli. Colony counting was done with a magnifying glass and the count of Streptococcus mutans and Lactobacilli was expressed as the number of colony forming units per milliliter (cfu/ml) of saliva. Semiquantitation of the number of colonies was done by multiplying the actual colony count with Ix103 because of the part that the saliva sample was diluted one thousand times (1:5 dilution).

Statistical Analysis: Means, standard deviation and /or frequencies were calculated for all the variables. For the purpose of analysis, the sample was stratified into three categories based on DMFT values i.e., DMFT=0, DMFT 1-3 and DMFT>3. The counts of Streptococcus mutans and Lactobacilli were dichotomized, as Low and high.[6] The data was statistically analyzed using Students 't' test and x,2 test. Dental caries experience was correlated with Streptococcus mutans and Lactobacilli using Pearson's correlation coefficient.


400 children participated in the study but only 372 could complete the study. Those unable to donate saliva and absent on the day of examination were not included. There were 218 boys and 154 girls. The results of this study is summarized in tables.

Dental caries experience: The dental caries experience ranged from 59.60. The mean DMFT recorded was 2.41. The percentage of caries free children was 41.40%. Earlier study by Kulkarni and Deshpande[7] amongst 2005 school going children in Belgaum aged 11-15 years showed 54.87% to be caries free and the mean DMFT value of 1.18. There was no statistically significant difference observed in the mean DMFT among the males and females (Table 1) and this observation is in accordance with the studies reported by other authors.[3],[8],[9] Also no difference could be found in DMFT values with respect to age (Table 2) which was in association with the studies reported by Parkash et al[1] and Damle and Patel.[10]

Streptococcus mutans: In this study, 87.37% (325) of the sample had detectable levels (>103) of Streptococcus mutans in saliva. The count ranged from 0 - 20x106 cfu/ml of saliva. 246(66.13%) had low level and 126(33.87%) had high level of Streptococcus mutans. A highly significant statistical relation (P<0.001) was obtained between Streptococcus mutans and dental caries experience (Table 3) indicating that the count of Streptococcus mutans varied with respect to the different DMFT categories (Subjects with high caries had harbored high number of Streptococci mutans). The Pearson's correlation coefficient factor r=0.63 which was obtained revealed a very significant statistical correlation (P<0.01) between Streptococcus mutans and dental caries experience, thus corroborating the infectious theory of dental caries. This type of positive relation has been reported earlier.[3],[8],[11]-[18]

Lactobacilli: Lactobacilli was detected in only 36.71% (139) of the total sample. The count ranged from 0-15x105 cfu/ml of saliva. Hoolbrook[6] has stated that the number of Lactobacilli decline as the number of open caries lesion decrease. This can be the basis for explaining the small number of sample carrying Lactobacilli, as in the present study there were only 16(7.3%) subjects with wide open caries lesion and maximum 141(64.6%) demonstrated initial caries lesions and 61(28.1%) had restored cavities. No statistically significant relation was recorded between dental caries experience and Lactobacilli (Table 4) indicating that the Lactobacilli count did not vary with respect to DMFT categories. Such type of relation has been mentioned earlier.[19],[20] However the Pearson's correlation coefficient factor r=0.1608 (P<0.05) obtained was very small, thereby suggesting no statistically significant correlation between them. However strong positive correlation have been reported in other studies.[2],[3],[6],[14],[16],[21],[22] There was no statistically significant difference between boys and girls regarding salivary counts of Streptococcus mutans and Lactobacilli. Similar finding has been reported by Zickert et al.[3]

Comparison of results with other studies was not possible, as disparity between the results exist. This could be attributed to differences in DMFT values, fluoride exposure, dietary pattern, types of oral hygiene practice, genetic factors and several other factors peculiar to the study population. Also distinctness in the technique of sampling saliva and cultivation of bacteria can contribute to variation.

The microbial counts in this study were estimated in stimulated saliva. Questions concerning the reliability of using saliva sample and not plaque can be raised. However the results of the studies by Mundroff et al[23] and Sullivan et al[19] nullify this question, because their results prove that the number of Streptococcus mutans or Lactobacilli in Dental plaque sample does not explain the variation in caries better than the number in stimulated whole saliva.

One issue which requires to be focused at this point is, 'the use of cross-sectional study design which is used in this present study as well as used by other authors[3],[6],[8],[11],[13],[15],[18],[19],[22] to document the correlation between microorganisms and dental caries'. In such a kind of study, a single saliva/plaque sample is taken to record the count of microorganisms, which probably indicates the microbial count at a certain point of time, since dental caries develops over a considerable period of time, during which bacterial count would perhaps fluctuate in response to the changing oral environment. Tukia-Kulmala and Tenovuo have reported that intra-individual variation in salivary factors and microorganisms does exist with respect to time and that single point measurements of salivary factors and microorganisms are unreliable for caries-diagnostic or predictive purposes.[13],[24] Also, Kristila et al,[25] considered longitudinal analysis to be the only way to determine the existence of any saliva-caries relationships with clinical significance, since cross-sectional data do not necessarily reflect the oral situation at the time when the disease process has started. Therefore, it is suggested that longitudinal study design be used, wherein microbial samples are taken at regular intervals. This will in turn help in studying the variation in the count of the microorganisms, as well as the important factor "time" in the Keyes circle of dental caries formation will also be adjusted.

However, the results of the study here, will serve as the baseline data, which will be used to plan a preventive program for the high school children and will serve for evaluating the success of this program. Besides this, the study will be carried forward to construct a reliable caries prediction model for the future.


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