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Effect of Mutans Streptococcal Colonization onPlaque Formation and Regrowth in Young Children –A Brief CommunicationChristian Lee, DDS, MS; Norman Tinanoff, DDS, MS; Glenn Minah, DDS, PhD;Elaine Romberg, PhD

Abstract

Objectives: Visible plaque on the maxillary anterior teeth of young children hasbeen identified as a risk indicator for early childhood caries. The present studyexamined whether this plaque is related to the colonization of children’s teeth withMutans streptococci (MS) or toothbrushing frequency. Methods: Thirty-nine chil-dren, aged 12 to 36 months, had plaque scores, and plaque samples were takenfrom the labial surfaces of the maxillary incisors at baseline and repeated 3 daysafter suspended oral hygiene (plaque regrowth). Results: A positive correlation wasfound between the baseline percent MS and regrowth plaque score and betweenbaseline and regrowth plaque scores. Plaque scores of those that brushed zero toone time a day were not different from those who brushed two or more times a day.Conclusions: This study suggests that the presence of plaque on the anterior teethof young children is consistent and related to MS colonization.

Key Words: plaque, mutans streptococci, children

IntroductionPersonal oral hygiene measures

are generally considered the main-stays of oral disease prevention, anddental professionals include oralhygiene instruction for patients,especially for those who present withhigh levels of dental plaque. Whilethe importance of this aspect ofhealth education is not in question,many clinicians may be making theassumption that higher levels ofplaque are solely the result of thepatient’s poor skill or motivation inremoving plaque deposits. In con-trast to this conventional wisdom,there is evidence that individualsmay experience higher levels ofplaque for reasons other than oralhygiene effort.

Differential plaque formationbetween individuals is well docu-mented. Studies have consistentlyplaced subjects into “high” or “low”

plaque-forming groups (1,2). Whileseveral factors play a role in differ-ential plaque formation rates, no onevariable alone is believed to beresponsible for these differences (2).

Mutans streptococci (MS), thegroup of organisms most oftenetiologically associated with theinitiation of dental caries, produceextracellular polysaccharides thatmay aid in dental plaque formation(3). The water-insoluble glycosidiclinkage unique to MS-derived poly-mers, makes MS-containing plaquemore resistant to removal (4), and MSmutants defective in synthesizingthese polymers have a decreasedability to form plaque and inducecaries (5).

With regard to the association ofdental caries with visible dentalplaque on the teeth, several reportshave shown that the presence ofvisible plaque on incisors in young

children is highly correlated withcaries prevalence (6,7).

Linking these concepts together,we hypothesized that MS coloniza-tion in young children promotes theformation and accumulation ofdental plaque. The principal objec-tive of this investigation was to deter-mine if such MS colonization wasrelated to the presence of visibledental plaque and plaque regrowthin 12- to 36-month-old children.Additional objectives were to inves-tigate the relationship betweentoothbrushing frequency and base-line plaque levels, and to determineif a relationship exists betweenbaseline and regrowth values ofboth plaque levels and percent MS indental plaque.

MethodsAfter the Institutional Review

Board approval was obtained, 39children, 12 to 36 months old, wererecruited for this prospective clinicalstudy from the University of Mary-land Dental School and three affili-ated clinics. Inclusion criteria werethe presence of all four maxillaryprimary incisors; exclusion criteriaincluded cavitations and/or restora-tions on the facial surfaces of themaxillary incisors, as well as anyunderlying medical conditions whichwould have contraindicated partici-pation in the study. Children whohad taken systemic antibiotic therapywithin 2 weeks of the first visit wereeither excluded or rescheduled.

Send correspondence and reprint requests to Dr. Norman Tinanoff, Department of Health Promotion and Policy, University of Maryland DentalSchool, 650 W. Baltimore St. Room 2221, Baltimore, MD 21201. Tel.: 410-706-7970; Fax: 410-706-3028; e-mail: Ntinanoff@umaryland.edu. ChristianLee is with the Dental School, University of Maryland. Norman Tinanoff, Glenn Minah, and Elaine Romberg are with the Department of HealthPromotion and Policy, Dental School, University of Maryland. Glenn Minah is with the Basic Medical Sciences, Dental School, University ofMaryland. Manuscript received: 2/1/07; accepted for publication: 6/5/07.

Vol. 68, No. 1, Winter 2008 57

©2007, American Association of Public Health DentistryDOI: 10.1111/j.1752-7325.2007.00050.x

Participation consisted of twovisits, spaced 3 days apart. Duringthe baseline visit (Visit 1), informedconsent was obtained and a seven-item questionnaire was administeredthat asked about parental tooth-brushing frequency and dietarybehavior. Mean plaque scores foreach child were obtained by onetrained examiner using a modifiedSilness–Loe Plaque Index (8), scoringonly the mesiobuccal, straightbuccal, and distobuccal surfaces ofthe four maxillary incisors. Followingplaque scoring, a sterile cotton swabwas run along the labial gingivalmargin of the four incisors to obtainthe plaque sample for culture. Tomaximize the sample yield, anyplaque adhering to the explorerduring the plaque scoring was alsowiped onto the sampling swab.Following the clinical data collec-tion, a toothbrush prophylaxis using

fluoride-free dentifrice was per-formed by one dentist to bring eachsubject to a zero plaque level. Car-egivers were then instructed tosuspend oral hygiene efforts for 3days until after the follow-up visit(Visit 2). They were also instructedto temporarily remove any tooth-brushes from the child’s reach toavoid the child from brushing his/herteeth without the caregiver’s knowl-edge. At Visit 2, the caregivers wereasked if they had complied with theabstinence in oral hygiene for theprior 3 days. Regrowth plaquescoring and the microbiologic proto-col were repeated identically tothat for the baseline sample. Atoothbrush prophylaxis was alsorepeated.

For the microbial analysis, theheads of cotton swabs containingthe plaque samples were placed into5-mL screw-top sample vials con-

taining 1 mL of sterile saline. Sam-ple vials were serially diluted andplated onto brain–heart infusion(BHI) agar (Difco, Detroit, MI) andalso mitis salivarius kanamycin baci-tracin (MSKB) agar (9). Dilutionswere incubated at 37 °C in air con-taining 10 percent CO2 for 3 days(MSKB plates) or 1 week (BHIplates). Colony-forming units (CFUs)on the BHI plates were used toassess total bacteria counts, whileCFUs on MSKB plates were used toassess MS counts. The percent MS oftotal flora was calculated for eachsubject visit from the MS and totalbacterial count ratio.

For data analysis, independentt-tests were used to determine sig-nificant differences in plaque scorebased on toothbrushing frequency.Additionally, correlations (Pearson’sr) were determined between base-line percent MS versus regrowthplaque scores, between the subjects’baseline and regrowth plaque scores,as well as for the subjects’ baselineand regrowth percent MS.

ResultsThirty-nine eligible subjects, with

a mean age of 24.7 ± 8.22 months,participated in this investigation.Twenty-one subjects were male and18 were female. The mean baselineplaque score for all subjects was0.93 ± 0.74, and the regrowth plaquescore was 1.20 ± 0.70. Concerninginitial plaque scores related to tooth-brushing frequency, those childrenwho reportedly brushed zero or onetime a day had a mean plaque scoreof 1.11 ± 0.86 versus a mean plaquescore of 0.76 ± 0.57 (nonsignificant)for those that reportedly brushed twoor more times a day.

A positive correlation was foundbetween the percent MS of total floracultured from the incisors at baselineversus the regrowth plaque scores[Pearson’s r = 0.34 (P = 0.036)](Figure 1). The correlation betweenbaseline percent MS of total floraversus regrowth plaque was repeatedjust for the MS positive subjects(n = 23), yielding a correlation ofr = 0.51 (P = 0.013) (figure notshown).

Figure 1Correlation between the percent mutans streptococci (MS) of totalflora from the maxillary incisors at baseline examination versusregrowth plaque scores (Silness–Loe) after 3 days of suspendedoral hygiene in 12- to 36-month-old children. (Those childrenwith percent MS = 0 are not shown.) Pearson’s r test: r = 0.34;

P = 0.036

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Correlation analyses were alsoperformed to determine if a relation-ship existed between an individual’sbaseline plaque score or percent MSof total flora score, and their subse-quent 3-day regrowth plaque scoreor percent MS score. There was apositive correlation between thesubjects’ baseline plaque scores andregrowth plaque scores (Pearson’sr = 0.79, P < 0.01) (Figure 2). Simi-larly, a correlation was foundbetween the subjects’ percent MSfrom the baseline samples and thatcultured during the regrowth period(Pearson’s r = 0.78, P < 0.01) (figurenot shown).

DiscussionThe objectives of this investiga-

tion were to determine whetherthere was a relationship between achild’s level of MS colonization andthe quantity of dental plaque for-mation, whether a child’s plaqueforming rates are constant, andwhether reported oral hygiene pro-cedures affect plaque levels. The

results of this investigation maychallenge the hypothesis that plaquelevels in children primarily are afunction of oral hygiene effort and/orskill. Such differences between theconcept of whether plaque formationon teeth is primarily a result of oralhygiene techniques or the result ofbiologic factors (colonization of spe-cific bacteria and constant correla-tions) are important regarding howwe interpret the findings of plaquepresence in young children as a riskfactor for caries (6,7).

We found a positive correlation inthese young subjects between theirpercent MS of total flora and theirplaque scores, which is in accord withthe concept that the MS colonizationin a child’s mouth affects his or herplaque levels. Physiologically, MSproduce extracellular polysaccha-rides that may aid in dental plaqueformation by adding to the mass ofplaque (3) and by strengthening theattachment of these adsorbed bacteriato the enamel (4). It is interesting tospeculate that, at least in young chil-

dren, the presence of visual plaqueon the maxillary anterior teeth mayindicate an elevated level of MS.

Our results did not support aneffect of toothbrushing frequency onvisual plaque scores on the maxillaryincisors in young children. No sig-nificant difference in plaque scoreswas observed with different parentaltoothbrushing frequency levels. Ofcourse, it is possible that the smallsample size may have resulted ininsufficient statistical power to dem-onstrate an effect from brushing fre-quency on plaque levels in subjects,or that issues of questionnaire valid-ity regarding oral hygiene proce-dures could confound such findings.

In the present study, a positivecorrelation between baseline andregrowth plaque scores is consistentwith earlier works that could classifya given individual as a “high” or“low” plaque former (1,2). There wasalso a strong positive correlationbetween the baseline and regrowthpercent MS. This correlation indicatesthat MS regrowth are minimallyaffected by the toothbrush prophy-laxis performed by the examiner orthe 3-day abstinence in oral hygienemeasures. The public health implica-tion of these results (the positivecorrelations between MS levels andplaque scores, baseline and regrowthplaque scores, and baseline andregrowth MS levels, but the absenceof a relationship between plaquescores and toothbrushing frequency)is that the presence of visual plaquein young children is a caries riskfactor that may not be affected byimproving the oral hygiene behav-iors performed by the children’scaretakers.

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2. Zee KY, Samaranayake LP, Attstrom R.An in vivo replica study of microbialcolonization in “rapid” and “slow” dentalplaque formers. Acta Pathol MicrobiolImmunol Scand. 2000;108:113-21.

3. Gibbons RJ, Fitzgerald RJ. Dextran-induced agglutination of Streptococcus

Figure 2Correlation of baseline plaque scores with regrowth plaque

scores. Pearson’s r = 0.79; P < 0.01

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Effect of Mutans Streptococci on Plaque Formation 59

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4. Guggenheim B. Enzymatic hydrolysisand structure of water-insoluble glucanproduced by glucosyl transferases from astrain of Streptococcus mutans. HelvOdontol Acta. 1970;14:89-108.

5. Tanzer JM, Freedman RJ, Fitzgerald J,Larson RH. Diminished virulence of

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6. Alaluusua S, Malmivirta R. Early plaqueaccumulation – a sign for caries risk inyoung children. Community Dent OralEpidemiol. 1994;22:273-6.

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8. Silness J, Loe H. Periodontal disease inpregnancy II: correlation between oralhygiene and periodontal condition. ActaOdontol Scand. 1964;22:273-6.

9. Kimmel L, Tinanoff N. A modified mitissalivarius medium for a caries diagnostictest. Oral Microbiol Immunol. 1991;6:275-9.

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