top of page

Beyond the Brush: Revealing the Hidden Pathways of Early Childhood Caries Transmission


Early childhood caries (ECC) presents a significant oral health challenge globally, affecting infants and preschool children. Despite being largely preventable, ECC remains a chronic health issue, with recent studies reporting its prevalence in numerous countries. This article delves into the multifactorial etiology of ECC, highlighting the role of Mutans Streptococci (MS) in its transmission. MS, particularly Streptococcus Mutans, is known to colonise the oral cavity, especially post-eruption of the first teeth, and is linked to the development of caries. Vertical transmission of MS from caregivers, especially mothers, is a key route of acquisition by infants. High-density salivary reservoirs of MS in mothers increase the risk of infection in infants, emphasising the importance of reducing maternal MS levels. Horizontal transmission, occurring through interpersonal contact and saliva-sharing activities, also plays a role in nursery school settings. Understanding the transmission of MS is crucial for implementing effective prevention strategies. Targeting vertical transmission by reducing MS reservoirs in mothers and promoting good oral hygiene practices can significantly decrease the risk of ECC in children. Additionally, early identification of ECC and intervention can help prevent its progression.

Keywords: Early Childhood Caries Prevention; Child Dental Health; Toddler Tooth Decay; Baby Teeth Cavities; Cavity Prevention for Kids

Hello there, parents, caregivers, and dental detectives alike! So, picture this: your little one flashes you with the sweetest smile, but all you see beneath the pearly whites is a dental dilemma-early childhood caries (ECC). Now, if I told you that this ECC is not just the work of certain factors and dental behaviors, but rather a hitchhiker, taking the ride from one mouth to another?

Yes, you have heard that right. We are peeling back to the surprisingly transmissible character of ECC, but don't worry—our goal isn't to incite a germophobic frenzy in you. Instead, we're going to explore how simple acts of kindness, generosity, and daily routines can inadvertently facilitate ECC's dissemination of its less-than-endearing charm.

ECC forms the major oral health problems amongst infants and preschool children worldwide with results reported from 29 of 195 countries in a recent 2021 study. Although the condition is preventable essentially it remains a chronic health problem.[1] ECC is defined as the presence of one or more decayed, missing, or filled primary teeth in children aged 71 months (5 years) or younger[2], but has recently been redefined at the Bangkok Declaration by a group of international experts as the presence of a primary tooth with one or more carious (non-cavitated or cavitated lesions), missing (due to caries), or filled surfaces in a child under the age of six years.[3]

You may also have heard of several other terminologies used to describe the condition like nursing bottle caries, baby bottle tooth decay, milk bottle syndrome, and prolonged nursing habit caries. 

So, the question remains, how is this oral health condition transmissible? Well, the etiology of ECC is multifactorial. Let us look at Figure 1 below explaining the influence of various host (human)-microbe (germ)-diet (food eaten by the host) in the etiology and pathogenesis of ECC. 

Figure 1: Mind map explaining the multifactorial etiology of ECC with a focus on Streptococcus Mutans (Strep Mutans circled in red) (Adapted from Anil et al 2017)[4]

Mutans streptococci (MS)

It is a gram-positive coccus predominantly associated with causing dental cavity and found persisting in the mouth of a normal predentate infant by adhering to the colonies of the mucosal surfaces or lying freely in the saliva. They proliferate and multiply faster than the washout rate of salivary fluid and therefore are the culprits behind the transmission of dental caries. Further, the oral flora averages about 2 to 4 divisions per day with swallowing occurring every few minutes, therefore it would also be only reasonable to assume that microorganisms will not be able to sustain in free saliva by only proliferation but instead should be attached to a hard oral surface such as teeth.[5]

Interestingly, previous research has also demonstrated that MS is unable to attach with a good bond to the epithelial surfaces (gums and cheeks) and therefore it could not colonize the infant’s oral cavity before the eruption of teeth.[6] Another longitudinal investigation reported MS presence in 20% of 12 to 16-month-old infants, which were not reported during the first year of life suggesting their presence increases post-eruption of first teeth (lower incisors mostly).[7]

Recent research on the colonization of MS due to technological advancements such as DNA probes shows MS may even form a niche around the rows of tongue of predentate infants.[8]

So, is the early acquisition of MS a major risk factor for the development of ECC and the future experience of a child with caries? The answer is yes! Longitudinal assessments confirm MS presence in plaque at the age of 2 years in children to show the presence of cavities by the age of 4 years.[9,10]

The next question pertains to how the child acquired MS. This can be understood through two potential transmission routes: vertical transmission or horizontal transmission.

Vertical transmission of MS

This transmission of microbes occurs from the caregiver to the child, with the primary reservoir for infants acquiring MS being their mothers. This is due to saliva contact like tasting or pre-chewing a child’s food. Research shows, that when mothers carried more than 10^5 colony-forming units (cfu) of MS per mL of saliva, the frequency of infant infection stood at 58%. However, if mothers had 10^3 cfu of MS per mL of saliva or higher, the frequency of infant infection dropped drastically to 6%. These results underscore the heightened risk of early-life infant infection when mothers possess high-density salivary reservoirs of MS.[11]

Moreover if the mother’s MS levels are high due to the presence of pre-existing cavities, there is likely to be an increased transmission even before the eruption of first tooth to the child. Reducing the salivary level of MS in highly infected mothers can hinder or postpone the colonization of these organisms in their infant as shown in a study wherein only 11% of babies whose mothers underwent treatment to suppress their MS reservoirs were infected by the age of 23 months. In contrast, 45% of babies in the control group, where mothers' MS levels were not suppressed, were infected by the same age. [12]

It's also worth noting that infants delivered by cesarean section may also acquire MS through vertical transmission, as indicated by a study showing the presence of MS 11.7 months earlier in infants delivered by C-section compared to those delivered vaginally. [13]

Horizontal transmission of MS

This transmission refers to the transmission of microbes between members of a group. For example, in research 2 out of 5 strains of MS were isolated from a cohort of nursery school children (aged 12 to 30 months) due to sharing of food strongly suggesting the presence of horizontal transmission of MS. Transmission is, therefore, most likely to occur by sharing of interpersonal contact, particularly via saliva and the susceptibility of the recipient for colonisation as well. [14]

Why is it important for us to know about this transmission?

  1. Studies have successfully reduced dental caries in young children by targeting the vertical transmission of mutans streptococci (MS) from highly infected mothers.

  2. Habitual consumption of xylitol by mothers has been shown to significantly reduce the probability of vertical transmission of MS and subsequent dental caries in their children.

  3. Efforts to reduce early vertical transmission of MS translate into a decreased risk for dental caries in children.

  4. Paediatric dentists can apply several strategies to decrease caries risk in the pediatric population:

  • Reduce MS reservoirs in mothers, siblings, and caregivers by treating dental caries and using fluorides and chlorhexidine.

  • Avoid saliva-sharing activities and promote good oral hygiene practices.

  • Initiate tooth brushing with fluoridated toothpaste in infants.

  • Discourage decay-promoting feeding behaviours.

  1. Conduct oral health evaluations for infants by a dental professional before their first birthday.

  2. Dental caries is infectious and transmissible, and understanding the acquisition and transmission of infectious agents helps in comprehensive prevention efforts.

Discover a special bonus section dedicated to helping you identify the early signs of ECC development!

Author: Dr. Harshita Sharma, Paediatric Dentist and Medical Writer, India.

Editor: Dr. Sidhant Ochani, MBBS, Khairpur Medical College, Khairpur, Pakistan.


  1. Uribe SE, Innes N, Maldupa I. The global prevalence of early childhood caries: A systematic review with meta-analysis using the WHO diagnostic criteria. Int J Paediatr Dent. 2021;31(6):817-830. 

  2. AAPD. Policy on Early Childhood Caries (ECC): classifications, consequences, and preventive strategies. Pediatr Dent. 2017; 39(7 Suppl): 59-61.

  3. Early Childhood Caries: IAPD Bangkok declaration. Int J Paediatr Dent. 2019; 29(3): 384-386.

  4. Anil S, Anand PS. Early Childhood Caries: Prevalence, Risk Factors, and Prevention. Front Pediatr. 2017;5:157. Published 2017 Jul 18. 

  5. Gibbons RJ, Van Houte H, Dental caries. Bacterial adherence in oral microbial ecology. Annu Rev Microbiol 1975;29:19-44.

  6. Gibbons RJ, Bacteriology of dental caries. J Dent Res 1964;43:1021-1028.

  7. Carlsson J, Grahnen J, Jonsson G. Lactobacilli and streptococci in the mouths of children. Caries Res 1975;9:333-339.

  8. Tanner ACR, et al. The microbiota of young children from tooth and tongue samples. J Dent Res 2002;81:53-57.

  9. Alaluusua S, Renkonen OV. Streptococcus mutans establishment and dental caries experience in children from 2 to 4 years old. Scand J Dent Res 1982; 91:453-457.

  10. Kohler B, et al. The earlier the colonization by mutans streptococci, the higher the caries prevalence at 4 years of age. Oral Microbiol Immunol 1988;3:14-17.

  11. Berkowitz RJ, Turner J, Green P. Maternal salivary levels of Streptococcus mutans: The primary oral infection in infants. Arch Oral Biol 1981;26:147-149

  12. Kohler B, et al. Preventive measures in mothers influence the establishment of Streptococcus mutans in their infants. Arch Oral Biol 1983;28:225-231.

  13. Li Y, Caufield PW, Dasanayake HW, et al. Mode of delivery and other maternal factors influence the acquisition of Streptococcus mutans in infants. J Dent Res 2005;84:806-811.

  14. Emanuelsson I, Wang X. Demonstration of identical strains of mutans streptococci within Chinese families by genotyping. Eur J Oral Sci 1998;106:788-794.

36 views0 comments


bottom of page