Preventive Measures

Relationship between reportedtoothbrushing and dental cariesin adults

MATTI RAJALA*, KALEVI SELKAINAHO* AND ILKKA PAUNIO**

* University of Kuopio, Departments of Dental Public Health and Mathettiatics, Kuopio and

** University of Helsinki, Institute of Dentistry, Helsinki, Eintand

Rajala, M., Selkainaho, K. & Paunio, I.: Relationship between reported toothbrushing anddental caries in adults. Community Dent. Oral Epidemiol. 1980: 8: 128-131.

Abstract - The relationship of toothbrushing to dental deeay has remained unclear. In the presentstudy an effort was made to throw more light on this problem. Glinieal and interview data wereobtained from 212 males. Potential confounding risk indicators were controlled by a multivariateconfounder summarizing score. In general it was found that the values of caries prevalenceindicator were consistently higher for sporadic toothbrushers. It was concluded that the currentstudy provides evidence in favor of a positive association between toothbrushing and low cariesprevalence.

Key words: dental earies, occurrence; epidemiology, dental; toothbrushing.

Matti Rajala, University of Kuopio, P.O. Box 138, 70101 Kuopio 10, Finland. •,

Accepted for publication 10 March 1980. • . '

The relationship of toothbrushing to dental caries isstill equivocal. In an outstanding review article,BiBBY (3) concluded "convincing proof that brush-ing the teeth prevents decay is lacking". Laterresearch has not changed the picture. BRAUNE &ERICSON (4) recommended, however, that the roleof oral hygiene should be further studied eventhough many reports have failed to show a statisti-cally significant t-eduction in the occurrence ofdental caries due to toothcleaning. They suggestedthat the reason for this finding may have been otherfactors, e. g. sugar intake or fluoride exposure.

Also, in most studies, control of such obviousconfounding factors as socio-economic status, suc-rose intake and utilization ofdentai services has notbeen taken into consideration.

In the present study an effort was made toprovide further and more specific informationabout the possible role of toothbrushing in theoccurrence of dental caries.

SUBJECTS AND METHODSData were obtained from 212 male employees of a Finnishpapermill. The data were collected by a dentist under aspecific protocol by interviewing and by clinical diagnosis ofdental deeay according to the criteria WHO (22) has recom-mended. Only those which had progressed to the dentin wereeonsidered. More detailed descriptions of data colleetiontechniques have appeared in previous publications (18).

Potential risk indieators other than toothbrushing werecontrolled by stratification using a muhivariate confoundersummarizing score, based upon a linear discriminant functionstest that separated exposed and non-exposed subjects (10, 15).The method for control of confounding has been detailed byMiETTiNEN (15). The variates included in the model were:number of teeth, age, education, sucrose consumption, pre-vious fluoride exposure, income and utilization of dentalserviees. All were entered as additive terms only. After fitting,the model was not reduced. In computing the particular valueof the score for each subject, the toothbrushing was set to"daily", regardless of actual habits. These scores were thenused as the basis for stratifying daily and sporadic tooth-brushers into four strata in the analysis concerning total cariesprevalence and into three strata when studying facial surfacesonly. Analyses were confined to the range of seores common to

0301-5661/80/030128-04S02.50/0 © 1980 Munksgaard, Copenhagen

Toothbrushing and dental caries 129

both of the compared .series. The occurrence ofdentai carieswas measured as the percentage of decayed tooth surfaces of allsurfaces at risk. Therefore, occlusal surfaces of teeth withcrowns were excluded when total caries prevalence wascalculated.

For testing the differences in rates in stratified analysis, theMantel-Haentzel ehi-square test was applied (12). The stan-dardized prevalence rate difference was eomputed as follows:

where,W'=l/Vo'

Rbj = iate difference in j ' " stratum, Voj = variance ofthe RDj.

For the 95% lower boundary of the RD

R D , 5 % ( + X » / X P )

where, y_^ = pcvcenxilt of chi-square distribution rep-resenting the non-confidence at 95% level; Xp^per- 'centile of chi-square distribution representing the non-eonfidence at the level of actual P-value

RESULTSIntrastratum profiles of the subjects in terms ofcomputed mean values or a selected subset of thepotential confounding factors are shown in Table 1separately for different exposure groups. The Tableshows the degt-ee of intrastratum comparabilitywith legard to selected individual factors con-tt-olled through the composite score. Within eachstratum, the Irequencies were very similar betweentoothbrushing categories. No consistent ttend orsignificant differences can be observed.

Table 2. Mean percentage of deeayed tooth surfaees accordingto frequency of toothbrushing, by level of linear discriminantfunetion score in the range common to both exposurecategories

Stratum ofmultivariate score

InJIIIV

Daily

X

5.26.16.4

21.3

Toothbrushing

s. e.

1.51.33.93.9

Sporadic%

11.28.2

23.723.7

S. 1

3.2.6.6.

Diflerenee between toothbrushing eategories: P<O.OLStandardized prevalence rate differenee: 5.5%.95% lower bound confidence limit for RD: 3.3.

e.

6188

The relationship between toothbrushing and den-tal caries, within categories of the confounder-summarizing score, is shown in Table 2. Theintrastratum value of such a caries pt-evalenceindicator was higher for sporadic toothbrushers.The direction of the difference was consistent butdiffered in amount by stratum. When daily tooth-brushing is contrasted to sporadic toothbrushing,the point estimate of the overall rate difference was5.5%, with 95% lower boundary confidence limit of3.3%. The difference between the toothbrtishinggroups was statistically significant with a one-tailedi^-value less than 0.01. .

When facial surfaces only were analyzed thestratification was reduced to three strata because of

Table 1. Profiles of subjects with daily and sporadic toothbrushing habits in terms of some factors controlled through lineardiscriminant function score, by strata of the score. Shown are means or percentages of subjects in selected categories of thefactors and total number of subjects

Charaeteristie

Mean agePercentage with high

educationMean income in

1000 FMKPercent visiting

dentist irregularlyMean no. of remaining

teethPercent using sucroseProportion consuming

fluoridated drinkingwater over 10 years

Total no. of subjects

Daily

33

82

-€3

15

2342

54

51

1Sporadic

38

67

,22

11

2344

44

9

Daih-

34

47

,17

37

2165

41

46

StratumII

Sporadic

32

70

16

50

2480

29

10

Daily

32

37

14.

63

1870

45

29

IIISporadic

31

25

15

53

2085

17

15

]

Dailv

32

15

13

90

1885

31

29

Sporadic

35

20

14

93

2064

43

16

Daih

33

51

18

44

2161

45

155

TotalSporadic

34

' 41; .

16

57

2174

32

50

130 RAJALA, SELKAINAHO AND PAUNIO

Table 3. Percentage of decayed facial tooth surfaees in subjectswith regular sporadic toothbrushing habits by category ofconfoundei-summarizing score

Stratum ofmultivariate score

IIIIII

Difference between

ToothbrushingDaily

X

3.852.274.02

s. e.

1.450.921.81

toothbrushing groups:

Sporadic

X

3.476.97

11.81

; P<O.Ol.

s.e.

1.621.642.29

the small number of carious lesions on facialsurfaces. Persons with regular toothbrushing habitsshowed lower caries prevalence scores except in thefirst stratum. However, a steadily increasing trendin the rate difference was obset-ved (Table 3). Theoverall difference between toothbrushing groupswas statistically significant with a P-value of 0.01.

DISCUSSIONThe data of this study indicate that caries prev-alence was higher in the sporadic toothbrushinggroup than in daily brushers. Several points re-garding this result must be borne in mind. First, thecross-sectional nature of the data raises the questionof the long-term effect of the toothbrushing habiton dental decay. This possibility, however, wouldmost likely suggest that the observed differences areconservative estimates of the preventive power oftoothbrushing. .

The subjects probably reported their tooth-brushing habits as being more frequent than theyactually are. This affects most survey data. Thismeans that in the group of "daily" brushers theremay be persons whose habit is not so regular. Theremay also be random errors of reporting. Both thesesources of inaccuracy of the results have, however,the effect of diluting the evidence of the associationin the data to an unknown extent.

Limitations of using stratification by a multi-variate confounder-summarizing score have beenpresented by PIKE, ANDERSON & DAY (17). Theystate that one should be cautious if the multiplecorrelation is higher than 0.7. Values exceedingthat level would cause overestimates of signifi-cance. In the present data, the multiple correlationwas 0.4. Thus, the criticism does not apply in thisstudy. On the other hand the purpose of this paper

was not significance testing but rather estimation,to which no such criticisms seem to apply.

Most of the studies reporting a minor or nopieventive effect of toothbi-ushing on dental decayhave included simultaneous exposure to fluoridesor lluoride containing toothpastes and/or dentalhealth education (2, 9, 19, 20). Any possibletoothpaste fluoride effect is probably teduced inthis study because the study population tises fltiori-dated drinking water.

Common indicators of the occurrence of thedental caries have been DMF or DMFS indices (1,5, 6, 11, 16, 21). Here the information about thetoothbrushing has been cross-sectional whet-easdata about the occurrence of dental decay (DMFindex) is longitudinal in nature. Changes in habitsmay have diluted the possible effect of tooth-brushing. These data must, therefore, be inter-preted with caution. DMF indices were not used inthis study because it has been shown (7, 8, 13, 14)that factors other than tooth decay, primarilyperiodontal disease, trauma and feasibility con-siderations in dental treatment, increase the valueof DMF indices as well.

There was an indication in our study that thepositive association between reported daily tooth-brushing and low caries prevalence may be morepronounced in groups with higher overall riskstatus, i. e. in the strata where education andincome was low, frequency of dental visits in-egu-lar, number of teeth small, use of sucrose high andfluoride exposure low. This finding suggests that insituations where the "baseline prevention" is weak,toothbrushing may be useful also in caries pt even-tion,or, vice versa, the true effect of toothbrushingmay be hidden by other, perhaps more powerful,means of caries prevention. This was especiallyobserved on facial surfaces, where toothbrushing 'should logically have its greatest effectiveness.

In conclusion, the current study provides evi-dence in favor of a positive association betweenreported toothbrushing and low caries prevalence,and tends to contradict previous evidence of anegative or no association.

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Toothbrushitig and detital caries 131

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