JCDR - Register at Journal of Clinical and Diagnostic Research
Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X
Dentistry Section DOI : 10.7860/JCDR/2020/43086.13513
Year : 2020 | Month : Feb | Volume : 14 | Issue : 02 Full Version Page : ZC23 - ZC28

Quantitative Analysis of Streptococcus Mutans, Streptococcus Sobrinus and Streptococcus Sanguinis and their Association with Early Childhood Caries

Kemthong Mitrakul1, Boontarika Akarapipatkul2, Piamporn Thammachat3

1 Associate Professor, Department of Paediatric Dentistry, Mahidol University, Bangkok, Thailand.
2 Paediatric Dentist, Department of Paediatric Dentistry, Pathumthani Hospital, Pathumthani, Thailand.
3 Paediatric Dentist, Kanchanaburi Hospital, Thailand.

NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR: Kemthong Mitrakul, 6 Yothee Street, Bangkok, Thailand.
E-mail: mkemthong@yahoo.com


Severe Early Childhood Caries (S-ECC) remains highly prevalent worldwide. Streptococcus mutans and Streptococcus sobrinus are causative pathogens of dental caries and strongly involved in plaque or oral biofilm formation. Streptococcus sanguinis has antagonistic relationship with S. mutans and it might delay the colonisation of S. mutans in the oral cavities.


To quantify S. mutans, S. sobrinus and S. sanguinis between 2 groups {S-ECC and Caries Free (CF)} of Thai children and to analyse the association between these bacteria and caries-related factors.

Materials and Methods

Supra-gingival overnight plaque samples were collected from 120 Thai children aged 2-5 years (S-ECC=CF=60) using sterile toothpicks and released in 1 mL of TrisBase and EDTA buffer from January 2015 to December 2017. They were asked to expectorate saliva into a cup, plaque and gingival indices and dmft scores were recorded, parent’s demographic and children’s oral hygiene care and diet were assessed using questionnaire. DNA extraction and quantitative real-time PCR was performed. Different amounts of each bacterium were analysed by Mann-Whitney U test (p<0.05). The correlation between amounts of each bacterium and other clinical factors were analysed by Spearman’s correlation test (p<0.05).


The guardian’s demographic data, habit of milk bottle and breast feedings, oral hygiene care and consumption of cariogenic snacks were different between the two groups. S.mutans and S.sobrinus in plaque were higher in S-ECC. S.sanguinis in saliva and total bacteria were higher in the CF group. Plaque and gingival indices in S-ECC were higher than in the CF group. S.mutans levels in dental plaque and saliva was not significantly different.


S.mutans and S.sobrinus were associated with S-ECC while S.sanguinis was associated with caries-free. Socioeconomics and children’s oral hygiene care and diet were important factors associated with S-ECC.



The S-ECC is one of the most prevalent disease in children worldwide [1]. In Thailand, the prevalence of S-ECC in rural and capital areas is higher than 70% [2]. ECC causes not only local pain but also affects general growth and development, loss of self-esteem and might lead to psychological problems [1,3].

ECC results from an interaction between the acidogenic bacteria, sucrose, and host susceptibility [3,4]. Social and behaviour habits are contributing risk factors [3,4]. In the oral cavity, there are biofilm (dental plaque) which comprises of more than 800 species of microorganisms living in a complex community. It changes over time and the microorganisms population can shift between healthy and pathological environment when factor such as sugar is enhanced [4].

Streptococcus mutans and Streptococcus sobrinus are causative pathogen of dental caries [3-7]. S.mutans is commonly isolated microorganism from dental plaque [6-10]. Not only it is aciduric and acidogenic but also has the capability to adhere and deposit on the tooth surfaces. In the presence glucosyltransferases (Gtfs) (an enzyme of S.mutans), sucrose molecules are cleaved and the glucose component is polymerised into adherent glucans [10]. S.mutans is also able to generate the acid from carbohydrate and tolerate low pH environment [9-11].

S.sobrinus and S.mutans are different in many biochemical characteristics and virulence factors. S.sobrinus has greater acidogenic capacity than S.mutans [10,11]. The attachment of S.sobrinus happens when the pellicles are exposed to sucrose but this does not occur in S.mutans. The cell-associated Gtfs activity of S.sobrinus formed a higher percentage than that of S.mutans [11].

Previous studies showed that the prevalence of S.mutans in dental plaque of caries-active subjects was higher than S.sobrinus [12-14]. Numerous studies stated that children who were infected with both S.mutans and S.sobrinus have greater incidences of caries than those with S.mutans alone [13-15]. In contrast, study in Thai children found that when subjects were infected by both of them, the caries prevalence was the same as subjects infected by S.sobrinus alone [7].

Previous studies have reported the antagonistic relationship between S. mutans and S. sanguinis. They suggested that S. sanguinis delay the colonisation of S. mutans in the oral cavity and that caries-free children were colonised by high amounts of S. sanguinis. The interaction between S. mutans and S. sanguinis was also associated with caries outcome [16-19]. Previous studies have shown the relationship between S. mutans and S. sobrinus or S.mutans and S.sanguinis in dental plaque and saliva, none of them provided information on both sources in one study especially in Thai children [6,7].

Quantitative real-time PCR provides an accurate result and is a sensitive method for the detection and quantification of bacterial species [15]. This study aimed to detect S.mutans, S.sobrinus and S.sanguinis in dental plaque and saliva samples using real-time PCR from S-ECC and caries-free groups of Thai children, and to analyse the association between these bacteria and other caries-associated factors. The hypothesis is that the quantities of S.mutans, S.sobrinus and S.sanguinis from S-ECC and caries-free groups should be different.

Materials and Methods

This cross-sectional study was conducted between January 2015 to December 2017 at Faculty of Dentistry, Mahidol University, Bangkok, Thailand. The approval from Human Institutional Review Board of the Faculty of Dentistry and the Faculty of Pharmacy, Mahidol University (MU-DT/PYIRB 2009/266.0910, 2013/027.2606) was obtained prior to initiation of the study. Sample size was calculated based on the previous study [6], with α=0.05 and power of 80%, using the software package Primer of Biostatistics (McGraw-Hill, NY, USA).

Subject Selection

Total subjects were 120 (caries-free=60, S-ECC=60) Thai children aged two to five-year-old. All subjects were randomly selected from public schools in Pathumthani province, Thailand. Consent forms were signed. A clinical examination was performed by 2 paediatric dental residents. They were calibrated for clinical examination (kappa co-efficiency=0.85). The diagnosis of S-ECC was based on the AAPD [20]. Children with any systemic disease(s), on any kind of antibiotics, had professional fluoride application or any dental treatment within 3 months prior to the sample collection period were excluded.

Clinical Examination, Plaque Index and Modified Gingival Index

Recorded dmft score and plaque index used a modified debris index of simplified oral hygiene index for deciduous dentition [21-23]. Gingival inflammation was recorded on a 0-4 scale following the modified gingival index [22,23].

The questionnaire: All participants’ parents or caretakers were asked to complete the questionnaire by face-to-face interview. All questions were close ended. Besides the parents’ general information, 3 categories were examined: 1) Child’s general information; 2) Parental attitude towards child’s diet: a) Is your child still bottle feeding?; b) Did your child ever have breast and/or bottle feeding ad lib?; c) Did your child breast and/or bottle feed ad lib and fall asleep?; d) Did you always give your child water after breast or bottle feeding?; e) What type of snacks does your child have per day?; f)Type and frequency of snacks; 3. Parent’s attitude and behaviour in child’s oral hygiene care: a) How many times per day do you brush your child’s teeth?; b) When did you last take your child to the dentist. The Cronbach’s alpha coefficient was 0.7, which is acceptable [6].

Plaque and Saliva Sample Collection

Supra-gingival overnight plaque samples were collected from bucco-gingival surfaces of all teeth using a sterile toothpick and released in 1 mL of TrisBase and EDTA buffer, then they were asked to expectorate saliva into a cup.

DNA Extraction

DNA was extracted based on enzymatic lysis using a commercial kit (Flavogen, Taiwan) as previously described [6]. Extracted DNA concentration and purity were measured by a spectrophotometer at 260 nm/280 nm (Nanodrop 2000C® Thermo Scientific, Delaware, USA).

Culture Condition and Standard Strains

S. mutans ATCC 25175, S. sobrinus ATCC 6715 and S. sanguinis OMZ 2176 strains were cultured in brain heart infusion agar and broth. Genomic DNA was extracted from the overnight culture as described above.

Conventional PCR

All extracted DNA samples were confirmed with 16srRNA universal primers [Table/Fig-1] [24-27]. Each reaction mixture (total volume of 25 μL) contained 2 μL of DNA sample, 16.5 μL of nuclease-free water, 1 μL of 10 mM deoxynucleoside triphosphate (dNTP), 1 μL of each primer, 1.5 μL of 50 mM MgCl2, 2.5 μL of 10X PCR buffer minus Mg, and 0.5 μL of Taq DNA polymerase (KAPA Biosystems, USA) using Thermocycle (GeneAmp PCR System 9600 PCR machine, PerkinElmer, CA, USA) as previously described [28].

Primers used in this study [24-27].

Primer nameNucleotide sequence (5’ to 3’)Expected amplicon (bp)Annealing Temp (°c)Ref
Universal 16SBACF5-TGG AGC ATG TGG TTT AAT TCG A-3′16056.7Sinsimer D et al., [24]
S. mutansF55’-AGCCATGCGCAATCA ACA GGT T-3’41559Yano A et al., [25]
S. sobrinusSobF5’-CGCACTTGCTCCAGTGTTACTAA-3’54651Sato T et al., [26]
S. sanguinisMKP-F5’-GGATAGTGGCTCAGGGCAGCCAGTT-331361.5Hoshino T et al., [27]

Quantitative Real-time PCR

Using specific primers [Table/Fig-1], the reaction mixture (total volume of 20 μL) contained 8.2 μL of water, 10 μL of 2X KAPA SYBR® FAST qPCR Master Mix, 0.4 μL of 10 μM forward and reverse primer, and 1 μL of standard bacteria DNA. We set the thermocycler (C1000™ Thermal cycler and CFX 96 Real-time System) for 40 cycles. Each cycle consisted of enzyme activation at 95°C for 3 minutes, denaturing at 95°C for 3 seconds, annealing for 20 seconds and extension for 30 seconds. Melting curves were generated from 60°C to 95°C and read every 0.5°C for 5 seconds [6].

Agarose Gel Electrophoresis

Amplified PCR products were checked with 1.5-2% agarose gel which stained with ethidium bromide and gel image were captured with a digital imaging system [Table/Fig-2] (Molecular Imager ®Gel docTM Systems, Bio-Rad Laboratories Inc., CA, USA) [6].

Agarose gel electrophoresis of real-time PCR products (a) universal primers, (b) specific primers for S. sanguinis and (c) specific primers for S. mutans (d) specific primers for S. sobrinus.

Statistical Analysis

SPSS 16.0 software (Microsoft Corporation, USA) was used to record and analyse the data. Kolmogorov-Smirnov and Shapiro-wink tests (p<0.001) were used to assess data distribution. The different amounts of each bacterium were analysed by Mann-Whitney U test (p<0.05). The correlation between amounts of each bacterium and other clinical factors were analysed by Spearman’s correlation test (p<0.05). The association between caries status and demographic, socioeconomic, diet, and other factors were analysed by Pearson’s Chi-Square test (p<0.05).



Total subjects were 120 (S-ECC=60, CF=60). Mean age of the children was 3.56±0.53 years. [Table/Fig-3,4 and 5] showed that the guardian’s demographic data, habit of milk bottle and breast feedings, oral hygiene care and consumption of cariogenic snacks were different between two groups.

Demographic characteristics of subjects in both groups.

n (%)n (%)
Children’s gender
Male28 (46.7)28 (46.7)1.0
Female32 (53.3)32 (53.3)
Guardian’s education levels
Primary school4 (6.7)16 (26.7)0.001*
High school or diploma23 (38.3)35 (58.3)
≥Bachelor degree33 (55)9 (15)
Guardian’s occupation
Worker for government or private company32 (53.3)14 (23.3)0.001*
Merchant17 (28.4)13 (21.7)
Employee5 (8.3)23 (38.3)
Housekeeper6 (10)10 (16.7)
Relationship with the child
Parents50 (83.3)37 (61.7)0.02*
Grandparents or senior relative10 (16.7)21 (35)
Babysitters0 (0)2 (3.3)
Monthly family income
<10,000 baht5 (8.3)10 (16.7)0.001*
10,001-20,000 baht17 (28.3)37 (61.6)
≥20,000 baht38 (63.4)13 (21.7)
Family member’s smoking
Yes11 (18.3)38 (63.3)0.011*
No49 (81.7)22 (36.7)

1Pearson’s Chi-square test. *p-value <0.05

Feeding pattern and oral hygiene care in 2 groups.

n (%)n (%)
Milk bottle
Yes18 (30)45 (75)0.001*
No42 (70)15 (25)
Frequency of milk bottle feeding
1 time/day7 (38.9)13 (28.9)0.555
2-3 times/day8 (44.4)19 (42.2)
>3 times/day3 (16.7)13 (28.9)
Duration of milk bottle feeding
<10 minute/each feeding11 (61.1)14 (31.1)0.043*
10-30 minutes/each feeding5 (27.8)13 (28.9)
>30 minute/each feeding2 (11.1)18 (40)
Breast milk
Yes4 (6.7)18 (30)0.001*
No56 (93.3)42 (70)
Frequency of breast feeding
1 time/day3 (75)13 (72.2)0.751
2-3 times/day1 (25)3 (16.7)
>3 times/day0 (0)2 (11.1)
Duration of breast feeding
<10 mins/time4 (100)12 (66.7)0.400
10-30 mins/time0 (0)5 (27.8)
>30 mins/time0 (0)1 (5.5)
Sleep with bottle of milk
Yes13 (21.7)41 (68.3)0.001*
No47 (78.3)19 (31.7)
Brushing frequency
>1 time/day53 (88.3)33 (55)0.001*
once a day6 (10)20 (33.3)
once in 2 days1 (1.7)7 (11.7)
Drinking water after milk feeding
Always39 (65)20 (33.3)0.002*
Sometimes18 (30)31 (51.7)
Never3 (5)9 (15)
Dental treatment
Regular23 (38.3)5 (8.3)0.001*
Irregular6 (10)18 (30)
Never31 (51.7)37 (61.7)

1Pearson’s Chi-square test. *p-value <0.05

Type and frequency of snacks consumption in both groups.

n (%)n (%)
Frequency of protein
None11 (18.3)5 (8.3)0.092
Only in meal33 (55)30 (50)
Between meal ≥1 time/day16 (26.7)25 (41.7)
Frequency of fruit
None7 (11.7)13 (21.7)0.069
Only in meal32 (53.3)18 (30)
Between meal ≥1 time/day21 (35)29 (48.3)
Frequency of sugar coated snacks
None13 (21.7)6 (10)0.001*
Only in meal37 (61.6)21 (35)
Between meal ≥1 time/day10 (16.7)33 (55)
Frequency of soft drink in one day
None27 (45)3 (5)0.001*
Only in meal14 (23.3)15 (25)
Between meal ≥1 time/day19 (31.7)42 (70)
Frequency of hard candies in one day
None32 (53.3)12 (20)0.001*
Only in meal15 (25)12 (20)
Between meal ≥1 time/day13 (21.7)36 (60)
Frequency of potato chip in one day
None10 (31.3)2 (6.7)0.008*
Only in meal13 (40.6)9 (30)
Between meal ≥1 time/day9 (28.1)19 (63.3)
Frequency of Thai dessert in one day
None19 (59.3)8 (26.7)0.034*
Only in meal6 (18.8)11 (36.7)
Between meal ≥1 time/day7 (21.9)11 (36.6)

1Pearson’s Chi-square test. *p-value <0.05

Conventional PCR and Quantification Real-Time PCR of S. mutans, S. sobrinus and S. sanguinis

There was a 100% detection rate by the universal primers. [Table/Fig-6] shows the comparison of bacterial levels between the two groups. Both plaque and gingival indices were different between the two groups [Table/Fig-7]. [Table/Fig-8] shows the correlation of clinical parameters and microbial finding between two groups. When compared between plaque and saliva, S. mutans levels were not significantly different.

Comparison of bacterial levels between caries free and S-ECC groups.

S. mutan
Mature plaque2.87×104±7.96×1041.90×105±5.75×1050.005*
Total bacteria
Mature plaque5.33×107±4.24×1073.85×107±3.51×1070.017*
S. mutans/total bacteria
Mature plaque6.91×10-4±2.23×10-35.65×10-3±1.36×10-20.003*
S. sobrinus
Mature plaque59.34±1.58×1027.45×102±1.59×103<0.001*
S. sobrinus/total bacteria
Mature plaque3.9×10-6±1.27×10-54.67×10-5±1.24×10-4<0.001*
S. sanguinis
S. mutans
S. sanguinis/S. mutans
S. sanguinis/total bacteria
S. mutans/total bacteria

1Nonparametric Mann-Whitney U test. *p<0.05

Measurement of plaque and gingiva indices in both groups.

Plaque score1.21±0.0721.171.74±0.0831.670.001*
Gingival score0.17±0.0600.001.34±0.3391.000.001*

1Nonparametric Mann-Whitney U test. *p<0.05

Correlation of clinical parameters and microbial finding in both groups.

Clinical characteristicsS. sanguinisS. mutans (saliva)S. Mutans (Plaque)S. sobrinus (plaque)

1Spearman correlation. *p<0.05

CC: Correlation coefficient


This is the first study in Thai children which determined the amount of S. mutans, S. sobrinus and S. sanguinis from both dental plaque and saliva. Previous studies reported that S. mutans and the ratio of S. mutans to total bacteria were higher in S-ECC [8,15]. Another research in Thai children found that the severity of ECC correlated with high levels of S. mutans and S. sobrinus [29]. Corresponding with this study, we found that S-ECC children had higher levels of S. mutans, S. sobrinus, S. mutans/total bacteria and S. sobrinus/total bacteria than caries-free children. From previous studies, S. mutans was detected in high level while S. sobrinus was detected in lower level in S-ECC than S. mutans [7-10]. Martinez-Martinez RE et al., compared the distribution of oral streptococci from saliva of caries-free and caries-affected Mexican children. They reported that S. mutans was identified in 80% of the caries-affected while S. sobrinus was detected 70% in the caries-affected children [16]. Contrast to the previous study in Thai Children, present study indicated that when subjects were infected by both S.mutans and S.sobrinus, the caries prevalence was the same as subjects infected by S.sobrinus alone. There might be a high possibility that S.sobrinus was not found without the presence of S. mutans [7].

In this study, it was found that in S-ECC dental plaque, mean level of S.mutans was higher than S.sobrinus which corresponds to other studies [7-10]. However, previous study reported that the acidogenicity of S. sobrinus was greater than S. mutans [30]. Several studies in children found that increasing S.sobrinus colonisation in dental plaque was correlated with aggravated caries activity as well as that in saliva [8,31,32]. From previous study, there was high baseline count of S.sobrinus in children with recurrent caries. This indicated that besides S.mutans, S.sobrinus can be used as a part of caries risk assessment, especially in high-risk group [33].

There are numerous studies about bacteria composition in dental plaque of caries-free and caries-active children. Li Y et al., analysed the diversity of microorganism in different caries status. They found that the diversity of microorganism in caries-free group was higher than that of caries active [34]. Other study reported that bacterial diversity was decreased when caries progress from healthy to active lesion [35]. Correspond to the present study, which found that total bacteria level in dental plaque of caries-free is higher than those in S-ECC group. From ecological plaque hypothesis, dental caries is the result from imbalance of oral micoorganisms. This results in shifting of bacterial community from healthy bacteria to acid tolerant bacteria. The new condition promotes the proliferation of cariogenic bacteria but decreases the diversity of the plaque community [34]. It can imply that the higher diversity of bacteria in caries-free condition can suppress the condition promoting dental caries [34,35].

Choi EJ and colleagues found that the level of S.mutans showed low correlation with dmfs scores while the ratio of S.mutans to total bacteria, the level of S.sobrinus and the ratio of S.sobrinus to total bacteria had positive correlation with dmfs score [8]. In this study, we found that the level of S.mutans, the ratio of S.mutans to total bacteria and the ratio of S.sobrinus to total bacteria in mature plaque were positively correlated with dmft scores. Various studies reported that the presence of dental plaque was associated with dental caries, but some studies did not [36,37]. We found that the level of S. sobrinus and the ratio of S. sobrinus to total bacteria in mature plaque was positively correlated with plaque index. Law V and Seow WK reported that S.mutans and S.sobrinus infection was correlated with dental plaque amount [37]. Prevalence of S.mutans was higher in children with visible plaque than that of plaque-free group [38-40]. This study showed that the level of S.mutans and the proportion of S.mutans to total bacteria in dental plaque correlated with gingival index. This is similar to previous study which reported that the prevalence of S.mutans was positive correlated with visible dental plaque, gingival inflammation and bleeding [38]. Beighton D et al., also reported that level of S.mutans and S.sobrinus in saliva showed correlation with gingival scores [41].

For S.sanguinis, in this study, its level in saliva was different and higher in caries-free group. Previous study from Thai children also demonstrated that S.sanguinis level was higher in caries-free group when compared with those of S-ECC [6]. Moreover, S.sanguinis level was inversely correlated with dmft scores. This study corresponded with previous studies [6,42,43].

There were many researchers who studied the interaction between oral streptococci in saliva and dental plaque, few studies reported the antagonism action between S.sanguinis and S.mutans. In this study, S. mutans level was higher in S-ECC groups than those of caries-free group which corresponded to previous studies that S. mutans is the main cariogenic microorganism and they might inhibit the growth of S. sanguinis [44,45]. Kreth J et al., investigated the molecule mechanism of the antagonism interaction between S. mutans and S. sanguinis, they reported that S. sanguinis could inhibit the growth of S. mutans by hydrogen peroxide (H2O2) whereas mutacins produced by S. mutans are involved in S. sanguinis growth inhibition and the mutacins mutants had reduced ability to inhibit the growth of S. sanguinis [45]. In this study, we found positive correlation between level of S. sanguinis and dmft score. S. sanguinis might also be used as an indicator with S. mutans for predicting dental caries. From previous studies, they also suggested that the ratio of S. mutans/S. sanguinis can indicate the risk of caries [46,47]. Loesche WJ and Syed SA reported that the percentages of S. sanguinis decreased as the plaque score increased [23]. The proportions of S. sanguinis steadily declined as the gingivitis developed [44]. Corresponded with this study where plaque and gingival scores were higher in S-ECC group. Furthermore, S. sanguinis was inversed correlated with plaque and gingival indices [44].

In the present study, we found the relationships between caries status and related factors from questionnaire. Several studies reported that ECC are commonly found in children with low economic status [42,43,46]. Sarumathi T et al., found that low socioeconomic children had higher risk of developing dental caries than those in middle or high socioeconomic status [43]. The result of this study found that caries-free children had greater proportion of high household income than S-ECC group. Correlation between caries status and parent’s education level has been reported. Various studies suggested that ECC was commonly found in children whose guardians have low literacy level [42,46]. Sarumathi T et al., study found that the children whose parents had high educational level had lower caries prevalence similar to this study [43].

The results of this study found that S-ECC group had more smokers in the house than caries-free group. Household tobacco smoke increased risk of ECC [44,45]. Infection is caused by chemical toxin in tobacco which suppresses or modulates immune system [44]. In-vitro study mentioned that phagocytes acitivities of neutrophils and monocytes were inhibited by nicotine [44]. Vitamin C in blood levels of smokers and children with second-hand smoking were decreased [47-49]. This condition prefers the growth of S. mutans [49]. Second-hand smoked children received the same toxins as the active smoker but in lower doses, so they might receive the same oral health affect as those in active smoking. Previous study reported that the levels of S. mutans were increased in active smoking [50]. Same as the study from Sakki T et al., which mentioned that nicotine in tobacco increased the growth of S. mutans and it was transmitted from guardians to their children [47]. Another possible factor is that active smoking parent might have poor dietary behaviour, unhealthy lifestyle and lack of oral health awareness. This condition might affect their children’s oral health.

In this study, we found that S-ECC group had frequent consumption of food in every types of dietary except fruit and protein. Various studies mentioned about the correlation between high frequency of food and beverage consumption and dental caries [51,52]. The frequency and amount of beverage consuming in S-ECC children were greater than that of caries-free children [53].

Numerous studies found the association between bottle feeding and dental caries [3-5]. In this study, we found that S-ECC had more duration of bottle feeding than caries-free children and S-ECC was associated with history of sleeping with bottle or breast feeding. Furthermore, S-ECC children had history of sleeping with bottle or breast feeding more than caries-free children. The relation between bottle sleeping and caries was found [3]. Du M et al., study stated that bottle-fed children were five times higher risks in developing early childhood caries than breast-fed children [54]. There were various advantages from breast-feeding. Infant received nutrition and immunological protection through human milk. In contrast, the association between breastfeeding and dental caries was inconclusive. From systematic review of epidemiological evidence mentioned that children who breast-fed longer than 1 year or at night might had higher prevalence of dental caries [55]. Dissimilarly, other systematic review stated that there was no scientific evidence about the cariogenicity of human milk [56].


The cross-sectional design of the study limit in finding out the predicting factor in questionnaires. In addition, this study used the subjects from the district that have similar socioeconomics and demographic information. The result need to be interpreted carefully so as to generalise the representatives of Thai children.


S.mutans and S.sobrinus were associated with S-ECC while S.sanguinis was associated with caries-free group. Socioeconomics and children’s oral hygiene care and diet were important factors which were found associated with S-ECC.

Author declaration: This study was partially presented at the IADR Meeting 2018 (https://iadr2018.zerista.com/event/member/491734).


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