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http://jdr.sagepub.com/ Journal of Dental Research

http://jdr.sagepub.com/content/89/3/307The online version of this article can be found at:

DOI: 10.1177/0022034509356779

2010 89: 307 originally published online 21 January 2010J DENT RES

W.M. Thomson, S.M. Williams, J.M. Broadbent, R. Poulton and D. LockerLong-term Dental Visiting Patterns and Adult Oral Health

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307

DOI: 10.1177/0022034509356779

Received December 18, 2008; Last revision August 3, 2009;

Accepted September 22, 2009

W.M. Thomson1*, S.M. Williams2, J.M. Broadbent3, R. Poulton2, andD. Locker4

1Department of Oral Sciences, Sir John Walsh Research

Institute, Faculty of Dentistry, University of Otago, Dunedin,

New Zealand; 2Department of Preventive and Social Medicine,

Dunedin School of Medicine, University of Otago, Dunedin,

New Zealand; 3Dunedin Multidisciplinary Health and

Development Research Unit, Department of Preventive

and Social Medicine, Dunedin School of Medicine, University

of Otago, Dunedin, New Zealand; and 4Community

Dental Health Services Research Unit, Faculty of Dentistry,

University of Toronto, ON, Canada; *corresponding author,

[email protected]

J Dent Res 89(3):307-311, 2010

AbAcTo date, the evidence supporting the benefits of

dental visiting comes from cross-sectional studies.

We investigated whether long-term routine dental

visiting was associated with lower experience of

dental caries and missing teeth, and better self-

rated oral health, by age 32. A prospective cohort

study in New Zealand examined 932 participants’

use of dentistry at ages 15, 18, 26, and 32. At each

age, routine attenders (RAs) were identified as

those who (a) usually visited for a check-up, and

(b) had made a dental visit during the previous 12

months. Routine attending prevalence fell from

82% at age 15 to 28% by 32. At any given age,routine attenders had better-than-average oral

health, fewer had teeth missing due to caries, and

they had lower mean DS and DMFS scores. By

age 32, routine attenders had better self-reported

oral health and less tooth loss and caries. The lon-

ger routine attendance was maintained, the stron-

ger the effect. Routine dental attendance is

associated with better oral health.

KEY WOD: oral health, utilization, dental

visiting.

INODUcION

he adult users of dental services can be categorized into routine attenders and

problem-oriented attenders (Gilbert et al., 2000). Promoting regular dental

visits is one of the cornerstones of preventive dentistry (Axelsson et al., 1991;

Murray, 1996; Richards and Ameen, 2002), but, typically, only about half of

the adult population in most Western countries are routine attenders (Roberts-

Thomson et al ., 1995; Jamieson and Thomson, 2002), with rates being lower

among men and in particular social, ethnic, or age groups (Roberts-Thomson

et al., 1995; Dixon et al., 1999; Green et al ., 2003), and higher in Scandinavia

(Hjern et al., 2001). There is epidemiological evidence showing that problem-

oriented attenders have poorer oral health than routine attenders, even after

adjustment for putative confounders such as social class, age, gender, and

ethnicity, but almost all of that comes from cross-sectional studies. One excep-

tion, a cohort study of young New Zealand adults, found that problem-oriented

attenders were three times more likely to experience caries-associated tooth

loss over an eight-year period (Thomson et al., 2000). Such differences are not

confined to clinical measures: A recent UK study of a representative sample

of adults found that problem-oriented attenders had poorer oral-health-related

quality of life (McGrath and Bedi, 2001). A US study of older adults reported

that the prevalence of “oral disadvantage” (defined according to a range of self-

reported measures) was greater among problem-oriented attenders, even after

adjustment for clinical measures (Gilbert et al., 1997).

It is currently unclear whether the difference between problem-oriented

and routine attenders is due to the routine visiting itself—that is, that dental

attendance and the associated preventive (and interceptive) care and advice

are efficacious—or whether it is because of a “healthy user” effect (Posthuma

et al ., 1994): Routine attenders have better oral health and health behaviors

anyway. A recent systematic review was inconclusive (Davenport et al.,

2003), owing to a shortage of appropriate, high-quality studies. It would be an

unusual society which permitted random allocation of its citizens to particular

dental attendance patterns for the purposes of a randomized control trial.

Thus, the most useful higher-level source of information on the issue is likely

to be a prospective cohort study where a (preferably representative) sample is

followed for long enough to determine whether routine dental attendance is

contributing to routine attenders’ better oral health over and above their better

oral health behavior.

Long-term Dental VisitingPatterns and Adult Oral Health

EEAcH EPOclinial









308 Thomson et al. J Dent Res 89(3) 2010

The aim of this study was to determine whether long-term rou-

tine dental attenders had (a) better self-rated oral health and (b)

lower experience of dental caries and missing teeth by age 32.

MAEIAL & MEHOD

The Dunedin Multidisciplinary Health and Development Study

is a longitudinal study of a birth cohort born in Dunedin (NewZealand) between 1 April 1972 and 31 March 1973 (Silva and

Stanton, 1996). The sample that formed the basis for the longi-

tudinal study was 1037 children assessed within a month of their

third birthdays and is considered to be broadly representative of

its age group in the South Island population. Periodic collections

of health and developmental data have since been undertaken,

and this study uses data collected from assessments conducted

at ages 15, 18, 26, and 32. Over 90% of the cohort self-identified

as European. Ethical approval for the study was obtained from

the Otago Ethics Committee, and informed consent was obtained

from each participant (and also from parents at the assessments

conducted during adolescence).

Use of Dental ervies

Information on use of dental services was collected at ages 15, 18,

26, and 32, and was determined differently as participants aged.

The assumption was made that all were routine attenders before age

15, since the New Zealand School Dental Service provided routine

care to almost all children at that time (and the small number who

had opted out are believed to have routinely sought private dental

care) (Thomson, 2001). At ages 15 and 18, participants were asked

whether they were enrolled with the General Dental Benefit scheme

(whereby NZ adolescents were entitled to receive free routine den-

tal care) and about the time since their last dental visit (and the

reason for it). At ages 26 and 32, use of dental services was deter-

mined by asking participants whether they usually visited the den-tist for a check-up or only when a dental problem arose, together

with the number of months since the last visit. For each of ages 15,

18, 26, and 32, routine attenders were identified as those who (a)

usually visited for a check-up, and (b) had made a dental visit dur-

ing the previous 12 months.

Dependent Variales

At each age, dental examinations for caries (collected as sur-

face-level data) and missing teeth were conducted by calibrated

dental examiners, who obtained an estimate of accumulated

tooth loss due to caries by observing the presence or absence of

each tooth, and ascertaining the reason for its absence. In thisstudy, third molars were not included in the computation of

tooth loss; only those teeth which had been lost because of car-

ies were included. Self-rated oral health was measured by ask-

ing participants to rate their oral health in comparison with that

of other persons their age (with response options: ‘among the

nicest’, ‘better than average’, ‘worse than average’, or ‘among

the worst’). The dependent variables used in the current study

were mean DMFS and mean DS, the prevalence of 1+ teeth

missing due to caries, and self-reported oral health (as a binary

variable) by age 32.

covariates

We measured socio-economic status (SES) by using data col-

lected on parental socio-economic status, using standard New

Zealand occupationally based indices (Irving and Elley, 1977;

Elley and Irving, 1985), which involve a 6-category classifica-

tion (where, for example, a doctor scores ‘1’ and a laborer scores

‘6’). Childhood SES was calculated as the average of the highest

SES level of either parent, assessed repeatedly from birth to 15

years. Participants were classified as having low (groups 5 and

6), medium (groups 3 and 4), or high (groups 1 and 2) childhood

SES. SES in adulthood was classified the same way, but using

the participant’s occupation at age 32.

Dental plaque accumulation was measured at ages 15, 18, 26,

and 32 according to the Simplified Oral Hygiene Index (Greene

and Vermillion, 1964). Because we had no direct measure of

self-care at any age (other than self-reported toothbrushing fre-

quency), plaque scores were used to represent self-care (as one

directly observable measure of the efficacy of that self-care) to

determine whether a “healthy user” effect existed.

Data Analysis

Following the computation of descriptive statistics, we fitted mod-

els using generalized estimating equations (GEE) methods in Stata,

according to a recently described approach (Pepe et al., 1999). The

aim was to estimate the strength of the association between regular

dental visiting and the outcome variable of interest (the “univariate

association”) at each assessment. A non-standard GEE with an

independent correlation matrix provided an appropriate covariance

matrix for these comparisons to be made. Further analyses adjusted

for sex and SES (and for plaque score in subsequent modeling) at

each assessment. Because pairwise comparisons of the 4 assess-

ments involved 6 statistical tests, the Bonferroni inequality test was

used to adjust the type 1 error rate, so comparisons in the modelswere regarded as statistically significant for P < 0.008.

EUL

Participation rates in the Dunedin Study are high, with 972 partici-

pants (96%) taking part in the age-32 assessment; 932 (96%) of

those were dentally examined. The 40 who were not dentally exam-

ined did not differ from the latter in terms of gender, but there was

a slight difference by childhood SES group (high 98.1%; medium

96.3%; low 92.9%; P = 0.04). The current analyses involved those

932 individuals (51.1% of whom were male). Complete service-use

data were available for 739 individuals at age 15, 823 at age 18, 904

at age 26, and 916 at age 32.The prevalence of routine attending fell from just over four-

fifths at age 15 to about one in four by age 32 (Table 1). Just over

one in ten were routine attenders at each of ages 15, 18, 26, and 32

(“long-term routine attenders”). An age-associated divergence was

apparent between men and women, and more of the latter were

long-term routine attenders. All three SES groups showed a decline

in routine attendance with age: An apparent lack of a SES differ-

ence at age 15 had become quite a gradient by age 18 (whereby it

was lowest among low-SES individuals and highest among those

of high SES), and it was marked by ages 26 and 32.









J Dent Res 89(3) 2010 Visiting Patterns and Oral Health 309

ale 1. Dental Visiting Status at Ages 15, 18, 26, and 32, by Sex and Socio-economic Status (brackets contain percentages)

Sex Socio-economic statusa

Number (%)b Female Male High Medium Low

Age 15Routine attenders 604 (81.7) 304 (83.3) 300 (80.2) 105 (84.0) 391 (81.0) 107 (82.3)Non-routine attenders 135 (18.3) 61 (16.7) 74 (19.8) 20 (16.0) 92 (19.0) 23 (17.7)

Age 18Routine attenders 549 (66.7) 271 (66.9) 278 (66.5) 99 (74.4) 367 (68.6) 80 (53.0)c

Non-routine attenders 363 (33.3) 134 (33.1) 140 (33.5) 34 (25.6) 168 (31.4) 71 (47.0)Age 26

Routine attenders 282 (31.2) 151 (33.9) 131 (28.5) 58 (38.7) 179 (31.2) 44 (25.0)c

Non-routine attenders 622 (68.8) 294 (66.1) 328 (71.5) 92 (61.3) 394 (68.8) 132 (75.0)Age 32

Routine attenders 254 (27.7) 139 (30.9) 115 (24.7)c 55 (36.4) 160 (27.5) 38 (21.3)c

Non-routine attenders 662 (72.3) 311 (69.1) 351 (75.3) 96 (63.6) 422 (72.5) 140 (78.7)Ages 15 to 32

Routine attenders 102 (10.9) 65 (14.3) 37 (7.8)b 18 (11.8) 69 (11.7) 15 (8.2)Non-routine attenders 830 (89.1) 391 (85.7) 439 (92.2) 134 (88.2) 522 (88.3) 169 (91.8)

All combined 932 (100.0) 456 (48.9) 476 (51.1) 152 (16.4) 591 (63.8) 184 (19.8)

a Five cases unable to be classified.b Numbers with complete service-use data: 739 at age 15; 823 at age 18; 904 at age 26; and 916 at age 32.c P < 0.05.

ale 2. Oral Health or Disease at Age 32 by Dental Visiting Status at Ages 15, 18, 26, and 32

Self-rated Oral Health‘better than average’ (%)a

1+ Teeth Missing Dueto Dental Caries (%)

Mean Number ofDecayed Surfaces (SD) Mean DMFS (SD)

Age 15b Routine attenders 336 (55.9) 123 (20.4)c 1.9 (3.7)c 15.9 (14.1)c

Non-routine attenders 56 (41.5) 35 (25.9) 2.8 (5.1) 18.8 (18.6)Age 18b

Routine attenders 311 (57.0)c 99 (18.0)c 1.7 (3.6)c 15.1 (14.0)c





Non-routine attenders 288 (43.6) 174 (26.3) 2.7 (5.1) 17.3 (12.8)Ages 15 to 32

Always a routine attender 82 (80.4)c 12 (11.8)c 1.1 (2.8)c 15.1 (14.7)c

Others 350 (51.5) 146 (21.4) 2.0 (4.0) 16.0 (14.2)Never a routine attender 47 (32.0) 61 (41.5) 4.9 (7.5) 21.3 (19.8)

All combined 479 (51.6) 219 (23.5) 2.4 (4.8) 16.8 (15.4)

a Four missing cases.b Numbers with complete service-use data: 739 at age 15; 823 at age 18; 904 at age 26; and 916 at age 32.c P < 0.05.

Those who were routine attenders at a given age had a higher

proportion reporting better-than-average oral health and a lower

proportion with caries-associated tooth loss (Table 2). For example,

at age 32, 67.4% of those who were routine attenders at age 26—

but only 45.4% of those who were not—rated their oral health as

better than average. Similarly, routine attenders had fewer untreated

decayed surfaces (on average) and lower mean DMFS scores by

age 32. When the patterns from ages 15 to 32 were examined, long-

term routine attenders had more favorable scores on all indicators,

particularly in comparison with those who were never routine

attenders. For example, the latter’s mean number of untreated

decayed surfaces by age 32 was more than 4 times that of the long-

term routine attenders; the overall mean DMFS difference was just

over 5 surfaces, and there were also marked gradients in tooth-loss

experience and self-rated oral health.

Some 147 (15.8%) were routine attenders at none of the 4

ages, 220 (23.6%) at 1 age, 308 (33.0%) at 2 ages, 155 (16.6%)

at 3 ages, and 102 (10.9%) at all 4 ages. This categorization by

the number of ages of routine attendance was strongly associ-

ated with self-reported oral health and caries-associated missing








310 Thomson et al. J Dent Res 89(3) 2010

0

10

20

30

40

50

60

70

80

90

100

1+ teeth missing due to caries Self-rated oral health ‘better than average’

%

0 ages 1 age 2 ages 3 ages 4 ages

Figure a. Gradients in age-32 prevalence of caries-associated toothloss and better-than-average self-rated oral health by the number ofassessment ages at which participants were routine attenders [147(15.8%) were routine attenders at no age, 220 (23.6%) at 1 age, 308

(33.0%) at 2 ages, 155 (16.6%) at 3 ages, and 102 (10.9%) wereroutine attenders at all 4 ages; error bars depict standard errors].

0

5

10

15

20

25

Mean DMFS at 32 Mean DS at 32

M e a n

0 ages 1 age 2 ages 3 ages 4 ages

Figure . Gradients in age-32 mean DMFS and DS scores, by thenumber of assessment ages at which participants were routine attenders[147 (15.8%) were routine attenders at no age, 220 (23.6%) at 1 age,308 (33.0%) at 2 ages, 155 (16.6%) at 3 ages, and 102 (10.9%) wereroutine attenders at all 4 ages; error bars depict standard errors].

teeth (Fig., a) and with mean DMFS and DS scores by age 32

(Fig., b): There were generally less-favorable scores among

those who had been routine attenders at fewer ages.

The models comparing the associations between the 4 oral

health outcomes and routine attendance at the 4 ages (Table 3) first

controlled for sex and SES, after which plaque scores for each of

ages 15, 18, 26, and 32 were also entered (as proxies for self-care,

in an attempt to adjust for a “healthy user” effect). In interpreting

the model outcomes, it is important to bear in mind that the ORs

and IRRs for each age represent the univariate estimate, adjusted

for the covariates. Thus, someone who was a routine attender at age

15 had 1.70 times the odds of an age-15 non-routine attender of

reporting better-than-average oral health by age 32. Moreover, with

the exception of age 18, the closer the age was to 32, the greater the

OR, with an age-32 routine attender having 3.36 times the odds.

Similarly, the odds of having caries-associated tooth loss by age 32

were lower for routine attenders regardless of age, but they were

lowest for age-26 routine attenders. The models for age-32 DS and

DMFS confirmed that routine attendance predicted lower scores,

but there were no clear patterns with respect to age, other than age-

32 routine attenders having the lowest IRR for mean DS.

DIcUION

This study aimed to determine whether long-term routine dental

attenders had better self-rated oral health and lower experience of

dental caries and missing teeth by age 32 than those with less-

favorable visiting patterns. We found that routine attenders have

better self-reported oral health and less tooth loss and dental caries.

We also observed that the differential was greater with longer expo-

sure to routine attendance, with long-term routine attenders having

the best oral health by age 32. Analysis of the data also suggested

that, for decayed surfaces and self-rated oral health, more proximal

exposure to routine attendance is beneficial.

It is appropriate to consider first the weaknesses and strengths of

the study. For example, the dental attendance data were self-

reported, and we were unable to verify each participant’s dental

utilization independently. Moreover, the collected information per-

tained to the individual’s usual dental visiting pattern at that age,

and it is possible that some may have changed their pattern (e.g.,

from non-routine to routine and back to non-routine between

assessments); thus, there is likely to be a degree of inaccuracy in

exposure measurement. Underlying the entire approach is the

assumption (unable to be tested here) that the benefits of routine

attendance are similar regardless of who the dentist is. The study’s

strengths lie in its prospective design, high retention rate after three

decades, and its mix of clinical and self-report outcome measures.

Analyses such as this are rare because of the scarcity of prospective

oral health studies of birth cohorts (particularly through adulthood).

Turning to the research question, what are the effects of long-

term routine dental attendance? Does repeated exposure to dental

check-ups and advice (and whatever one-on-one prevention is

available) over many years actually have an effect, or are there ten-

able alternative hypotheses which might explain the findings? The

strength of the observed association between long-term routine use

and better oral health is indisputable, particularly with missing

teeth, self-rated oral health, and untreated caries. The findings with

respect to the overall caries experience represented by age-32

DMFS are not quite as straightforward, with little difference among

those who were routine attenders at 2, 3, or 4 ages, a finding which

is most likely attributable to routine attenders’ higher likelihood of

receiving restorative treatment (Baelum, 2008).

However, the crux of the issue is the extent to which the

“healthy user” effect was responsible for at least some of the

observed differences between routine attenders and the remain-

der: They probably differ in ways that are hard to measure but

likely to result in better oral health. Sex and SES are two such

factors, and we controlled for those accordingly. It might also be

expected that (all other factors being equal) routine attenders are

likely to have cleaner teeth than problem-oriented attenders, and

so we controlled for that using plaque scores measured at each








J Dent Res 89(3) 2010 Visiting Patterns and Oral Health 311

ale 3. Estimates (and 95% confidence intervals) for the Association between Routine Dental Attendance at Ages 15, 18, 26, and 32 (adjustedfor sex and socio-economic status) and Oral Health Outcomes by Age 32

Routine Attendance at Age:

15 18 26 32

Models without plaque scoresSelf-rated oral health ‘better than average’a 1.78c (1.22, 2.60) 1.73d (1.29, 2.32) 2.49e (1.85, 3.34) 3.51c d e (2.54, 4.84)1+ teeth missing due to dental cariesa 0.73c (0.46, 1.16) 0.54d (0.38, 0.76) 0.30c d e (0.20, 0.46) 0.50e (0.33, 0.75)Mean number of decayed surfacesb 0.65 (0.44, 0.95) 0.59 (0.44, 0.78) 0.53 (0.37, 0.75) 0.48 (0.35, 0.65)Mean DMFSb 0.84 (0.71, 1.01) 0.78 (0.69, 0.89) 0.82 (0.71, 0.93) 0.89 (0.79, 1.01)

Models with plaque scoresSelf-rated oral health ‘better than average’a 1.70c (1.16, 2.50) 1.52d (1.12, 2.05) 2.24e (1.65, 3.03) 3.36c d e (2.42, 4.66)1+ teeth missing due to dental cariesa 0.75c (0.47, 1.20) 0.66d (0.46, 0.95) 0.35c d e (0.23, 0.54) 0.54e (0.36, 0.82)Mean number of decayed surfacesb 0.64 (0.42, 0.96) 0.67 (0.49, 0.90) 0.60 (0.43, 0.84) 0.54 (0.40, 0.73)Mean DMFSb 0.86 (0.71, 1.02) 0.83 (0.73, 0.95) 0.86 (0.75, 0.98) 0.93 (0.82, 1.05)

a Estimates are odds ratios (OR).b Estimates are incidence rate ratios (RR).c,d,e Estimates with different symbols are significantly different from each other (by post hoc criteria).

of the 4 assessment ages. After adjustment for those effects, the

beneficial effect of routine dental attendance persisted; that thedifference made by adjustment for plaque scores (as directly

observable measures of dental self-care at each of the 4 ages)

was not a great one suggests perhaps that dental visiting has a

relatively strong effect. It may, of course, be that the routine

attenders’ regular exposure to the dental care environment and

associated oral health messages influenced their self-care behav-

ior (and consequently their plaque scores); however, investigat-

ing this issue is beyond the scope of the current study.

In conclusion, this prospective study supports the notion that

routine dental attendance is associated with better oral health

outcomes. It is therefore appropriate for current oral health mes-

sages to strongly promote regular dental visiting.

AcKNOWLEDGMEN

This work was supported by: Grant R01 DE-015260 from the

National Institute of Dental and Craniofacial Research, National

Institutes of Health, Bethesda, MD 20892, USA; and by a program

grant from the Health Research Council of New Zealand.

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