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Year : 2020  |  Volume : 31  |  Issue : 6  |  Page : 957-962
Association between black stains and early childhood caries - A systematic review

Department of Pediatric and Preventive Dentistry, K.S.R. Institute of Dental Science and Research, Tamil Nadu, India

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Date of Submission07-Apr-2020
Date of Acceptance28-Aug-2020
Date of Web Publication22-Mar-2021


Objective: To systematically review the association between black stains and early childhood caries. Methods: Seven electronic databases and hand search were carried out using keywords on black stains and early childhood caries. Articles published in English from January 1947 to January 2020 were included. A total of 38,686 articles were retrieved, and 38,645 duplicate and irrelevant records were removed. Among the 41 articles obtained, 21 articles were excluded after screening the title and abstracts. Fifteen articles were excluded after analyzing the full text. Finally, five articles with cross-sectional study designs were included in this review. Quality analysis was carried out using a modified Newcastle–Ottawa scale. Results: All the five articles included in this review had a low risk of bias. Two articles showed a significant negative association and one article showed a significant positive association between black stains and early childhood caries. Conclusion: Cross-sectional design and heterogeneity of the included articles provide an ambiguous opinion on the association between black stains and early childhood caries. More of longitudinal studies following rigid methodology is needed to establish the association between black stains and early childhood caries.

Keywords: Dental caries, early childhood, stains, tooth discolouration

How to cite this article:
Asokan S, Varshini KR, Geetha Priya P R, Vijayasankari V. Association between black stains and early childhood caries - A systematic review. Indian J Dent Res 2020;31:957-62

How to cite this URL:
Asokan S, Varshini KR, Geetha Priya P R, Vijayasankari V. Association between black stains and early childhood caries - A systematic review. Indian J Dent Res [serial online] 2020 [cited 2022 Oct 7];31:957-62. Available from:

   Introduction Top

Black stain is a type of extrinsic discoloration characterized by the presence of a dark line, or an incomplete coalescence of dark spots formed accompanying the cervical third of crown.[1] The prevalence of black stains in primary dentition ranges from 2.4 to 16%.[2],[3]

Black stains are formed by ferric sulfide, which is a by-product of the reaction between hydrogen sulfide produced by bacteria, the iron present in saliva and gingival exudates.[1] Chromogenic bacteria were proposed as one of the etiological factors in the production of black pigment. Traditional microbiological evaluation of the plaque samples of children with black stains was predominated by Actinomyces Species (spp) mainly Actinomyces naeslundii,[4] whereas lactobacillus count was higher in non-discolored plaque samples.[5] Thus, the bacterial composition of the microbiota may modulate susceptibility and resistance to dental caries.[6]

Pickerill first reported the relationship between extrinsic stains and early childhood caries in 1903. He referred to black stains as a sign of immunity against caries.[7] The existing literature suggests that individuals with black stains have less caries experience.[8],[9] Black stains are considered to be a unique form of dental plaque with a higher tendency for calcification.[8] Spatial chemical analysis of plaque samples of children with black stains revealed a higher concentration of calcium and phosphate along with higher buffering capacity and higher pH of saliva, compared to children without black stains.[10],[4] Increased salivary lactoferrin (iron-binding glycoprotein) concentration was also reported in the saliva of individuals with black stains.[11] However, there is no reliable evidence on how the presence of black stains on the tooth surface reduces susceptibility to caries, and the causative factors of black stains are also not fully understood. A literature search showed very few articles assessing the association between black stains and early childhood caries. Children, less than 6 years do not develop black stains related to beverages like tea, coffee, soft drinks, smoking, tobacco, long-term use of mouthwashes, or exposure to manganese and silver.[12] Hence, the main aim of this systematic review was to find the association between early childhood caries and black stains.

   Methodology Top

PRISMA statement for reporting systematic reviews was used to prepare this review ( The step-wise search strategy has been explained in the flow chart [Figure 1].
Figure 1: PRISMA Flowchart

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Literature search

An extensive literature search was done, which included all the articles published from January 1947 to January 2020. The following search strings were used in databases like PUBMED, MEDLINE, IndMED, Cochrane, EMBASE, and Google scholar using the keywords “black stains,” “tooth discoloration,” “extrinsic stains,” “early childhood caries,” “nursing bottle caries,” “baby bottle decay,” “dental caries,” “tooth decay.”

The PubMed search included the terms (((((dental caries) OR early childhood caries) OR nursing bottle caries) OR baby bottle decay) OR tooth decay) AND black stains.

(((((dental caries) OR early childhood caries) OR nursing bottle caries) OR baby bottle decay) OR tooth decay) AND Extrinsic stains.

(((((dental caries) OR early childhood caries) OR nursing bottle caries) OR baby bottle decay) OR tooth decay) AND tooth discoloration.

The IndMED database was searched by the terms “Black stains AND Dental Caries.” The Cochrane database was searched by the terms “Early childhood caries in All Text OR nursing bottle caries in All Text OR baby bottle tooth decay in All Text OR dental caries in All Text AND black stains in All Text - in Trials.” The google scholar database was searched by the terms “association of black stains and dental caries black OR stains OR dental OR caries,” “Black stains and dental caries,” “Association of black stains and dental caries.” Grey literature search and manual search of the reference list of selected articles were also carried out.

Criteria for article selection

  1. Observational studies (case-control, cohort, and cross-sectional studies)
  2. The human trial which recorded dental caries and black stains
  3. Articles which included children till six years of age
  4. Articles published in the English language.

Exclusion criteria

  1. Articles on children with congenital anomalies
  2. Articles on children with dentofacial anomalies
  3. Articles on medically compromised children or children with special health care needs.

Data extraction

Two investigators independently evaluated the titles, abstracts, and full text of all the articles obtained through various searches. The third investigator resolved a disagreement between the two investigators. Full-text articles were retrieved for the potentially eligible articles.

The following data from each of the included articles were extracted

  1. Citation characteristics (year of publication, journal, title, authors)
  2. Study characteristics (study design, study setting, location)
  3. Demographic characteristics (age, gender, sample size)
  4. Outcome characteristics (index used to measure dental caries, diagnostic criteria used for black stains, the reported prevalence and association)

Quality appraisal

A version of the Newcastle–Ottawa Scale, modified for cross-sectional studies was used for quality assessment.[13] The scale uses a star rating system, in which the stars were allocated across three categories. The first category in the scale addresses the selection of the sample for which a maximum of 5 stars can be given. The second category addresses the comparability for which a maximum of two stars can be given. The third category addresses the measure of outcome for which a maximum of 3 stars can be given. If fewer than six stars were scored, the study was considered to be at a high risk of bias while the articles with seven or more stars were considered to be at low risk of bias.

   Results Top

An initial literature search yielded 38,682 articles through various search engine databases: PubMed –732, Google scholar-18,300, Medline - 14,716, Cochrane - 4,934 and manual search of the reference list of selected articles yielded four articles. A total of 38,641 duplicate records were removed. Forty-one articles were screened for their titles and abstracts. Twenty-one articles were excluded, and the remaining 20 articles were included for full-text analysis. After the full-text analysis, 15 articles were excluded because of the following reasons:

  1. Articles did not include the specified age group limit,
  2. Articles not concerned with both dental caries and black stains,
  3. In vitro studies.

Finally, five articles were included in this systematic review, and they were subjected to qualitative analysis.

All the five included articles were in cross-sectional study design which evaluated the association of dental caries and black stains in the primary dentition. These articles were carried out in Brazil,[9] Greece,[3] Spain,[14] China,[15] and India.[7]

Assessment methods

Out of 5 articles, three articles used Theilade et al. and Koch et al. criteria for evaluating black stains.[9],[14],[15] Boka et al. 2013[3] did not use any specific diagnostic criteria for the evaluation of black stains. They only mentioned the presence or absence of black stains based on visual assessment. Muthu et al. 2019 used Lobene and modified Lobene index for evaluating black stains. The dental caries status was evaluated by WHO criteria (1997) in 4 of the included articles[9],[3],[14],[15] and International Caries Detection and Assessment System was used in one of the articles.[7]

The summary of included articles has been shown in [Table 1]. All the included articles demonstrated a negative association between black stains and dental caries except one article.[7] Among the four articles, Boka et al., 2013[3] (P < 0.001) and Chen et al., 2014[15] (P < 0.01) showed a significant negative association. Muthu et al., 2019[7] demonstrated a significant positive association (OR = 1.132) between black stains and early childhood caries.
Table 1: Summary of included studies

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[Table 2] shows the quality assessment of the included articles. Non-respondents category under the selection criteria of the Newcastle–Ottawa scale was not applicable and hence was not scored. Therefore, the maximum number of stars that can be given for quality assessment was 9. All the five articles had a star rating of 6 and above, indicating a low risk of bias.
Table 2: Risk of bias analysis using the Newcastle-Ottawa scale adapted for cross-sectional

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All the articles except Garcia Martin et al., 2013[14] received three stars (out of 4) in the selection category. In comparability category, all articles received two stars and in outcome category maximum of 3 stars was received by Chen et al., 2014,[15] and remaining other articles received two stars.

   Discussion Top

This systematic review assessed the association between black stains and early childhood caries. Majority of the included articles demonstrated that children with black stains experienced lower caries status than those without black stains. To summarize the results of the included articles, black stains may have a protective role in children. The protective role may be due to dietary factors, iron supplementation, water content, salivary characteristics, and microbial content of black stains.

Each article highlighted certain factors responsible for the protective role of black stains against dental caries. Franca-Pinto et al., 2012[9] described the role of water content. Garcia Martin et al., 2013[14] and Chen et al., 2014[15] mentioned about dietary factors, and additionally, Garcia Martin et al., 2013[14] also explained about oral iron supplements. Muthu et al., 2019[7] described the role of microbes. Apart from these factors, salivary characteristics may also play an important role.

Dietary habits

Dietary habits could have a cariostatic and modulating effect on the virulence of cariogenic bacteria. Consumption of vegetables, fruits, dairy products, eggs, legumes, and soy sauce may promote the growth and colonization of bacteria related to black stains, which, in turn, may alter the growth and survival of cariogenic bacteria leading to lower caries status.[14] Chen et al., 2014[15] concluded that children who were never fed with the nursing bottle during sleep tend to have less growth of cariogenic bacteria and higher pH, thus, creating a favorable environment for the bacteria related to black stains. Thus alteration in oral microbiota could lead to a reduction in caries experience.

Oral iron supplements

Oral iron supplements fortified with folic acid and/or Vitamin B12 are routinely prescribed to children below 5 years of age.[16] Iron salts are also incorporated in infant cereals and multivitamin formulas.[17] They get attracted on to the organic portion of the tooth surface by various forces like electrostatic, van der wall, hydrophobic interaction, and hydrogen bonds.[18] They reduce the acidogenic potential of dental plaque[19] and protects from acidic by-products.[20] Thus, the presence of iron in the black stain may contribute lower caries experience in children.[14]

Water content

Water with high iron content and high pH are associated with a higher incidence of black stains. According to Claudia et al., 2018, three factors were found to be associated with black dental stains-”consuming water with high iron content, consuming water with high pH and having a high salivary pH. In another study by Tirth A et al., 2009, water consumed by the children with black stains showed the presence of ferric ions of about 1.2 mg/lit which is more than the tolerable dose that is 0.3 mg/lit prescribed by Indian Standard Drinking Water – Specification. In a study by Franca-Pinto CC et al., 2011[9] children who drank tap water had more black stains than those who consumed mineral water and natural well water. Children who drank water from natural wells presented higher caries prevalence than those who consumed mineral water or tap/filtered water. Higher iron content and higher pH in consumable water may alter the normal microbiota leading lesser caries experience in children with black stains.


Saliva plays a vital role in maintaining the oral health of an individual. Salivary parameters such as pH, buffering capacity, calcium and phosphate ion concentrations are well-known caries-protective factors. Analysis of salivary parameters by Surdacka et al., 1989 concluded that significantly higher levels of calcium, inorganic phosphates, copper, sodium, total protein, and lower levels of glucose were found in patients with black stains. Notably, greater buffering capacity and high calcium levels were reported in children with black stains.[10],[4] Salivary calcium indirectly regulates the aggregation of microorganism in saliva to help to maintain the globular structure of salivary micelles and act as a reservoir for remineralization. The micelles are composed of salivary immune system proteins such as low molecular weight mucin, sIgA, lactoferrin, amylase, proline-rich proteins, and lysozyme.[21] Higher buffering capacity may neutralize the acids produced by bacteria leading to lower caries status.

Salivary lactoferrin

Nordbo et al., 1987[11] reported a higher concentration of salivary lactoferrin (iron-binding glycoprotein) in the saliva of individuals with black stains. Lactoferrin (Lf), an 80-kDa iron-binding glycoprotein belonging to the transferrin family, is a component of human secretions including saliva. Lactoferrin binds to phosphorylated acidic glycoproteins in acquired pellicle[22] and has a high affinity for acidic macromolecules. This may contribute to increased adsorption of iron to the tooth surface, which promotes the bacteriostatic action by sequestering the iron necessary for the bacterial growth.[23] Bactericidal action of lactoferrin is by binding to lipopolysaccharide (LPS) of gram-negative or lipoteichoic acid of gram-positive bacteria.[24] Huo L, et al., 2011 found that lactoferrin possesses antibacterial activity against  Streptococcus mutans Scientific Name Search its binding with bacterial DNA. Lactoferrin concentrations were found to be lower in children with early childhood caries and higher in caries-free children.[25] Hence it confers a cariostatic effect in children with black stains.


Children with black stain exhibit a reduced microbial diversity with altered plaque microbiota. Actinomyces species mainly  Actinomyces naeslundii Scientific Name Search d Aggregatibacter actinomycetemcomitans were more abundant in plaque samples of children with black stains compared to children without black stains.[26],[5] Actinomyces species were one among the early colonizers in infants' mouth, and Actinomyces naeslundii were detected by 1 year of age.[27] The increased Actinomyces antibody level associated with increased Actinomyces colonization may lead to lower caries experience.[28] Greater diversity in the genetic pattern of S. mutans exist between children with active caries and black stains.[29] The overall plaque genome suggests that Actinomyces may not be the only microorganism involved in black stain formation. Porphyromonas gingivalis, Cardiobacterium, Haemophilus, Corynebacterium, Tannerella and Treponema were also more abundant in plaque samples of children with black stains.[4] The microorganisms associated with black stains create a competitive environment for cariogenic bacteria which impairs its adhesion to tooth surfaces.[7] Thus, the bacterial composition of the microbiota may modulate susceptibility and resistance to dental caries.

Surface specificity

The surface-specific distribution of black stains seems to influence the occurrence of dental caries. Fissure surfaces associated with extrinsic stains had a higher incidence of caries compared to smooth surfaces. It was hypothesized that the presence of black stains on fissure surfaces might have a deleterious effect due to morphology of deep pit and fissures. This may have a higher tendency for dental plaque retention, thereby increasing the caries susceptibility of the tooth.[7]

   Conclusion Top

Among the five articles included in this review, three articles showed a significant association between black stains and early childhood caries. However, only two articles showed a negative association and one article showed a positive association. Since all the included articles were cross-sectional studies, more of longitudinal studies are required to prove the association between black stains and early childhood caries.

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Conflicts of interest

There are no conflicts of interest.

   References Top

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[PUBMED]  [Full text]  

Correspondence Address:
Dr. Sharath Asokan
Department of Pediatric and Preventive Dentistry, KSR Institute of Dental Science and Research, Tiruchengode - 637 215, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijdr.IJDR_327_20

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