Salivary mutans streptococci in 6-year-old children from a multicultural suburban area after attending an oral health program.
Dental caries (Prevention)
Oral health (Education)
Streptococcus (Physiological aspects)
|Publication:||Name: European Archives of Paediatric Dentistry Publisher: European Academy of Paediatric Dentistry Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2008 European Academy of Paediatric Dentistry ISSN: 1818-6300|
|Issue:||Date: June, 2008 Source Volume: 9 Source Issue: 2|
|Geographic:||Geographic Scope: Denmark Geographic Code: 4EUDE Denmark|
Aim: To investigate the prevalence of salivary mutans streptococci (MS) in children from a low socioeconomic multicultural suburban area and to evaluate if a 3-year comprehensive oral health education (OHE) program, initiated at the age of two years, had an impact on the saliva levels. Study Design: Prospective clinical trial. Methods: The material consisted of two cohorts of 6-year-old children from a suburban area in southern Sweden. One cohort (n=804) had participated in a OHE program with a focus on tooth brushing with fluoride toothpaste and flouride tablets added to the regular preventive care provided by the Public Dental Service. The second cohort (n=217) consisted of reference children only attending for regular dental care. Both cohorts were dominated by children with Arabic background. Salivary MS were evaluated by a chair-side test and caries was scored through clinical examinations. Statistics: Analyses were performed with chi-square tests, Pearson correlation coefficients and odds ratio calculations. Results: The prevalence of salivary MS was high in both cohorts with approximately 90% harbouring the bacteria. One third of the children exhibited high counts (>106 CFU/ml) and there were no statistically significant differences between the groups. A statistically significant positive relationship between the levels of MS colonisation and caries prevalence was found in both cohorts. Conclusions: A 3-year OHE program implemented at the age of two years did not affect the high levels of salivary MS displayed in 6-year-olds living in a multicultural high-caries area.
Key words: Bacteria, Caries, Immigrants, Prevention
It is well known that the prevalence of dental caries in childhood is linked to poverty and social deprivation [Locker, 2000] and an early colonisation of cariogenic bacteria is associated with an increased caries risk [for a review, see Thenisch et al., 2006]. Studies on the prevalence of mutans streptococci (MS) in children from different socioeconomic and ethnic groups have however displayed somewhat inconsistent results. Beighton and co-workers  reported that preschool children living in deprivation harboured more MS than non-deprived and similar findings have been suggested in infants [Grindefjord et al., 1991] and young schoolchildren [Angulo et al., 1994; Seibert et al., 2002]. Other studies were however unable to demonstrate a relationship between social background and oral colonisation of caries-associated microorganisms [Radford et al., 2000; Habibian et al., 2002]. Another question of interest is whether or not the MS colonisation can be affected by education and/or early oral health information activities. Seow et al.  reported a significant decrease in MS counts following a single dental health education session with tooth brushing instruction to mothers while a long-term dental health education program conducted in a low socioeconomic high caries suburb of Leeds failed to affect the salivary MS levels [Kowash et al., 2002].
The implementation of an oral health education (OHE) program in a high-caries immigrant area in Sweden from early pre-school ages offered a possibility to further investigate the above mentioned issues. The first aim was to investigate the prevalence of salivary MS in a low socioeconomic multicultural Swedish area and secondly, to evaluate if a comprehensive OHE program could influence the salivary levels. The null hypothesis was that no differences would be demonstrated between the intervention group and a reference group subjected to the conventional preventive care provided by the Public Dental Service.
Material and Methods
The study groups and the oral health project have been described previously [Wennhall et al., 2005]. Out of the 804 children that started the oral health education program at 2 years of age, 651 (81%) remained in the project by age of 5 years. Those children were recalled for a clinical examination and saliva sampling at the age of 6 years and 507 (78%) showed up after one reminder. The distribution between the sexes was even; 52% were boys and 48% girls. The original reference group consisted of 217 children (51% boys and 49% girls) and 172 of them (79%) were available for follow-up at 6 years. Both cohorts were dominated by Arabic-speaking families ([approximately equal to] 50%), followed by first generation immigrants from Albania ([approximately equal to] 10%) and Bosnia ([approximately equal to] 6%).
Oral health program in brief. The OHE program started at the age of two years with tooth brushing training and diet counselling every third month. The children were supplied with free samples of toothbrushes and fluoridated toothpaste. Fluoride tablets were prescribed as a daily 0.25 mg NaF supplement. Between three and five years, the children were recalled semi-annually and the fluoride tablet recommendation was increased to 0.5 mg per day. Approximately 96% of the families complied satisfactorily with the program (4-6 visits) which gave a 30% relative caries reduction compared with the reference group [Wennhall et al., 2008].
Microbial cultivation and enumeration. The number of salivary MS was estimated with a chair-side technique, the Dentocult SM Strip Mutans (Orion Diagnostica, Helsinki, Finland), as described earlier [Jensen and Bratthall, 1989]. The children were asked to chew on a standardized piece of paraffin for one minute before a plastic strip was rotated on the dorsum of the tongue and withdrawn through closed lips. After a 48-hour cultivation period at 37[degrees]C in a selective MSB-broth, the strips were dried and the colony forming units (CFU), identified by morphology, were counted by one single examiner in a stereo microscope with aid of a special squared lattice device [Twetman and Frostner, 1991]. The following scores were used: 0 = 0-4 CFU; 1 = 5-29 CFU; 2 = 30-199 CFU; 3 = 200-499 CFU; 4 = >500 CFU. An intra-examiner reproducibility test was performed by re-scoring 100 strips after one month and the Kappa value obtained was 0.87.
In the reference group, 87.7% of all children exhibited detectable growth of salivary MS and the corresponding value in the OHE group was 90.4%. The distribution of the MS scores is shown in Table 1. In both groups, around 40% displayed low counts (score 0 + 1) while high counts (scores 3 + 4) were demonstrated in approximately 27% of the children. There were no statistically significant differences between the groups (p>0.05). Likewise, there were no significant differences in the distribution of MS in the different ethnic groups or between the sexes. The relationship between caries, MS levels and some background dietary variables is summarized in Table 2. A statistically significant positive relationship (p<0.05) was found between the salivary MS levels and the prevalence of caries at the age of 5 years in both groups. A positive correlation (p<0.05) between frequent consumption of "sweets in-between meals" and MS levels was also evident in the intervention and the reference groups while a statistically significant relationship between "sweet drinks at night" and MS scores only was displayed in the reference group.
This study was performed as an adjunct and follow-up of a 3-year OHE program carried out between 2 and 5 years of age in an immigrant high-caries suburban area in southern Sweden [Wennhall et al., 2008]. The chair-side test was considered as a robust endpoint since it has been used in numerous field trials and validated against conventional cultivation [Karjalainen et al., 2004]. The bacterial scoring was carried out by one single experienced investigator with the aid of a special device that allowed a high degree of precision. Consequently, the intra-examiner agreement was excellent.
An obvious finding was the relatively high number of children (88-90%) harbouring salivary MS. Elevated MS counts in low-income and immigrant families has generally been attributed to impaired tooth brushing and dietary habits and previous studies have indicated detection levels of 46%-83% in saliva samples of preschool children from various socioeconomic areas [Thibodeau et al., 1993; Twetman et al., 1996; Pienihakkinen and Jokela, 2002; Seibert et al., 2002]. On the other hand, the proportion of children with high counts was more comparable or even lower than previously reported [Thibodeau et al., 1993; Twetman et al., 1996]. It is however important to emphasise that the studies varied somewhat concerning age groups, sampling and cultivation procedures which may have influenced the recorded levels. The positive relationship between MS prevalence and dental caries has been demonstrated in numerous cross-sectional and prospective studies [Thenisch et al., 2006]. To further explore if this group of immigrant children harbours more salivary MS than non--immigrants or children with a higher socioeconomic background, additional cohorts of the same age are required, sampled and analysed with the present methodology.
The OHE program was planned and implemented according to the "common risk factor" approach. In spite of considerable efforts, we largely failed to improve the oral hygiene and dietary habits in the intervention group [Wennhall et al., 2005; 2008], an interesting question was whether or not the OHE program would have an influence on the MS levels in saliva. Theoretically, a diminished colonisation would reduce the risk for future caries development but we found no significant differences in the colonisation pattern between the two cohorts. Thus, the null hypothesis could not be rejected. This finding was in agreement with a previous project based on outreach OHE focusing on oral hygiene, fluoride tooth paste and dietary habits [Kowash et al., 2002]. Furthermore, the result was not unexpected considering the weak scientific support for the assumption that gained knowledge is an effective tool in changing a non-healthy dental behaviour [Kay and Locker, 1996]. An "earlier" estimation of the MS levels would have increased the chances of detecting a possible effect of the intensive intervention between 2 and 3 years but unfortunately no such data were collected. Interestingly, the OHE program turned out to be reasonable successful in spite of the unaffected MS levels and this was most likely explained by the increased use of fluoride toothpaste and tablets among the children. Thus, the present findings reinforce previous assumptions that the fluoride levels obtained in plaque by normal toothpaste and tablet use are too low to have a significant influence on the composition of the caries-associated microflora.
A 3-year oral health education program implemented at the age of two years did not affect the levels of salivary mutans streptococci in 6-year-olds living in a multicultural low-income area in southern Sweden. A high prevalence of the bacterium was found with almost 90% exhibiting detectable levels but further studies are needed to explore a possible relationship to the socioeconomic level.
The study design was approved by the ethical committee at Lund University, Sweden. The authors would like to thank Mrs. Inger Sjostrom, Department of Odontology, Pediatric Dentistry, Faculty of Medicine, Umea University, for skilful technical assistance. The study was supported by grants from the Public Dental Service in Skane, The Region Skane Research Council for Health and Medical Service, and Radet for halso- och sjukvardsforskning i sodra Sverige (HSF), Lund, Sweden. The authors have no competing interests to declare.
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I. Wennhall *, **, L. Matsson *, S. Twetman ***
* Dept. Paediatric Dentistry, Faculty of Odontology, Malmo University; Malmo, ** Public Dental Service, Region Skane, Sweden *** Dept. Cariology and Endodontics, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
Postal address: Prof. Svante Twetman. Dept. Cariology and Endodontics, Faculty of Health Sciences, University of Copenhagen, Norre Alle 20, DK 2200 Copenhagen N, Denmark. Email: email@example.com
Table 1. Prevalence and distribution of salivary mutans streptococci in two cohorts of 6-year-old children from a low income immigrant area in southern Sweden. OHE denotes oral health education. mutans streptococci score (%) Group 0 1 2 3 4 OHE intervention (n=507) 21 22 30 12 15 Reference (n=172) 18 22 33 12 15 Table 2. Association between caries, some dietary habits and salivary mutans streptococci (MS) levels in two cohorts of 6-year-old children from a low-income immigrant area in southern Sweden. reference group Variable MS score n yes Manifest caries (defs) low (0+1) 66 55% medium (2) 61 66% high (3+4) 45 78% OR (95% CI) 12.3 (1.1-5.2) Sweet drinks at night low (0+1) 66 0% (yes/no) medium (2) 61 8% high (3+4) 45 13% OR (95% CI) 13.8 (1.1-13.0) Frequent small eating low (0+1) 66 8% (>3/day) medium (2) 61 27% high (3+4) 45 34% OR (95% CI) 2.5 (1.2-5.5) intervention group Variable n yes Manifest caries (defs) 220 26% 157 55% 130 64% OR (95% CI) 12.9 (1.9-4.5)1 Sweet drinks at night 220 2% (yes/no) 157 2% 130 5% OR (95% CI) 12.6 (0.9-7.8; NS) Frequent small eating 220 12% (>3/day) 157 18% 130 29% OR (95% CI) 3.1 (1.9-4.9) NS = not significant; Odds ratio (OR) with 95% confidence interval is given for MS score 0-2 vs. 3-4.
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