BRITISH DENTAL JOURNAL VOLUME 196 NO. 2 JANUARY 24 2004
Dental caries experience in older people over
time: what can the large cohort studies tell us?
W. M. Thomson1
Background Little was known of the natural history of dental caries
among older adults until recently, but reports from a number of large
cohort studies have now enabled better understanding of the nature
and determinants of dental caries in older people. The aim of this review
is to examine and compare findings from established population-based
longitudinal studies of older adults in order to determine their
Methods The dental literature was reviewed in order to identify reports
on dental caries incidence from large, population-based dental
longitudinal studies of older adults (age 50+) with at least 3 years of
Results Reports were identified from four studies (in Iowa, North
Carolina, Ontario and South Australia) which met the criteria; four
reports dealt with coronal caries, and five with root surface caries.
When annualised, coronal and root surface caries increments were
combined and compared with those reported for adolescents, the caries
experience of older people over time (between 0.8 and 1.2 new surfaces
affected per year) exceeded that reported from cohort studies of
adolescents (between 0.4 and 1.2 surfaces per year). The only caries risk
factor common to all four studies was the wearing of a partial denture
(for root surface caries only).
Conclusions Older people are a caries-active group, experiencing new
disease at a rate which is at least as great as that of adolescents.
Practice implications Dentate older people should be the target of
intensive monitoring and preventive efforts at both the clinical practice
and public health levels. There is no easily identifable ‘magic bullet’ for
preventing caries in that age group, but the use of evidence-based
preventive interventions (such as fluoride) should suffice.
As well as undergoing a demographic transition, whereby the
number and proportion of older people in the population are
increasing steadily,1industrialised countries are also undergoing
a ‘dental transition’, marked by a steady reduction in edentulism
and missing teeth among older people.2The dental profession is
now faced with the challenges of treating and preventing dental
1Associate Professor, Dental Public Health, School of Dentistry, The University of Otago,
PO Box 647, Dunedin, New Zealand
Correspondence to: W. M. Thomson
Received: 06.01.03; Accepted: 11.04.03
© British Dental Journal 2004; 196: 89–92
caries in an age group in which little is known or understood of the
disease. Moreover, there is a perception among dental profession-
als and policy-makers that dental caries is, for the most part, only
active in younger people.3Over a decade ago, a clear need was
identified for information on the natural history of dental caries
among older people,4,5in order to provide clarification of issues
such as: (a) whether root surface caries is, in fact, the predominant
form of caries experienced; (b) whether coronal caries increments
continue in dentitions which are already heavily restored; and (c)
the nature and timing of possible interventions to prevent those
diseases or arrest their progression.
Studying the natural history of chronic, progressive diseases
such as dental caries, requires the use of the longitudinal study
design, whereby repeated examinations are made on the same
individuals over time. It also requires that the people being studied
have been randomly selected from the general population; find-
ings from studies involving samples of dental patients (termed
‘clinical convenience samples’) may not necessarily be generalis-
able, because people who are regular users of dental care tend to
differ in several important respects from those who are not.6
In recent years, a number of reports have appeared from
dental longitudinal studies (‘cohort studies’) of population-
based samples of older people, and these are making a substan-
tial contribution to our knowledge of the natural history of
dental caries in that age group. The aim of this brief review is to
examine and compare the findings of those studies in order
to consolidate our current knowledge of the natural history of
dental caries among older people.
The MEDLINE bibliographic database was searched (via Ovid and
PubMed) for eligible studies using the key terms ‘aged’, ‘dental
caries’ and ‘cohort studies’. The searches were repeated substitut-
ing, in turn, ‘follow-up studies’, ‘longitudinal studies’ and
‘prospective studies’ for the term ‘cohort studies’. The EMBASE
bibliographic database was searched in the same manner. The
reports obtained in this way were further limited by applying the
following criteria for inclusion:
1. They had to have been published in English
2. Participants had to be at least 50 years old and number at least
500 at baseline (for reasons of statistical efficiency)
3. A probability-based population sample was used, rather than a
● More and more people are retaining their teeth into old age. This paper examines the
findings of a number of large studies which have followed older people over time in order
to examine the natural history of dental caries in that age group.
● Surprisingly, the dental decay rate over time among older people is at least as great as
that among adolescents.
● Interventions aimed at improving the oral health of older people should take into account
and use a broad combination of clinical and population-based strategies, as there is no
‘magic bullet’ which will eliminate the problem.
90 BRITISH DENTAL JOURNAL VOLUME 196 NO. 2 JANUARY 24 2004
convenience or clinical sample (in order to be able to gener-
alise from the study estimates)
4. Data were reported separately for both the incidence and incre-
ment of both coronal and root surface caries, and
5. The observation period was at least 3 years, considered to be
the minimum length of follow-up time for (a) sufficient disease
experience to be observed, and for (b) satisfactory elucidation
of risk factors.
In addition, the databases were searched again using the names
of the authors of the papers identified in the first search, after
which the same criteria were applied. Baseline data from the stud-
ies concerned were obtained in the same manner.
In the second part of the study, the identified reports were scru-
tinised for evidence of multivariate modelling of caries occurrence,
in order to identify common risk markers and risk factors which
might provide a convenient focus for preventive interventions.
The MEDLINE search via Ovid resulted in 45 ‘hits’, while that via the
PubMed search using the same keywords resulted in 324. The
EMBASE search retrieved none. From those reports, dental longitu-
dinal studies of older people in Iowa, North Carolina, Ontario and
South Australia were identified which met the entry criteria for this
study (extending the searches substituting, in turn, ‘follow-up stud-
ies’, ‘longitudinal studies’ and ‘prospective studies’ for the term
‘cohort studies’ resulted in no further studies being found which met
those criteria). There were seven reports identified from those
included in the current study, of which two described coronal
caries,7,8three described root surface caries,9–11and two presented
data on both types of caries.12,13All but two of the reports described
changes over 3 years; the remaining two covered a 5-year period.9,13
A summary of the baseline estimates for caries prevalence
and severity from earlier reports in the Iowa,14North Caroli-
na,15 Ontario16and South Australian17studies is presented in
Table 1. Overall, the dental characteristics at baseline were
quite similar, with the notable exception of the North Carolina
blacks, who had (on average) fewer teeth present and lower
A summary of the caries incidence and increment estimates
from the studies is presented in Table 2. In order to enable cal-
culation of a combined caries increment and facilitate compari-
son with the other studies, the five-year report from the North
Carolina study9is not included in the table; however, the South
Australian study13is included because it reported data on both
coronal and root surface caries. Estimates were reported sepa-
rately for blacks and whites in the North Carolina (NC) study.
Table 1 Coronal and root surface caries prevalence and severity at baseline
Coronal cariesRoot surface caries
StudyMean DFS% with DFS>0Mean DFS % with DFS>0
520 18.814.590.0 2.363.2
Table 2 Reported incidence and increments of coronal and root surface caries from cohort studies of older people with 3+years of follow-up
Coronal caries Root surface cariesBoth combined
*Brackets contain the annualised increment, computed by dividing the combined caries increment by the number of years of follow-up,
then rounding the result to 1 decimal place
56%2.4 (0.8)44%1.1 (0.4)3.5 (1.2)
NC (B) = North Carolina Blacks
NC (W) = North Carolina Whites
SA = South Australia
Fig. 1 Reported annualised caries increments from longitudinal studies of
older people (gold bars) and adolescents (purple bars)
BRITISH DENTAL JOURNAL VOLUME 196 NO. 2 JANUARY 24 2004
with greater root surface caries experience in a cross-sectional
study;19it is unclear whether this is due to their having a role in
causing the disease, or whether it merely reflects the higher disease
rate which led to wearers losing teeth in the first place. However,
the consistency of the finding across the longitudinal studies
means that partial denture wearers should be the target of inten-
sive clinical preventive efforts. Other than partial dentures, no sin-
gle characteristic or behaviour was uncovered which would be
easily amenable to change through intervention at either the clini-
cal or public health levels, indicating that population-based
approaches to preventing caries (such as water fluoridation) are as
appropriate for older people as they are for children and adoles-
cents.20However, it is possible that differences in approach may
also have limited the extent to which the studies unearthed risk
factors. For example, the primary focus of the South Australian
report14was the role of medications as putative risk factors for
dental caries, while that of the North Carolina study8was the
relationship of ethnicity and caries risk.
It is worthwhile to investigate how the observed increments
compare with those reported for adolescents. Older people may be
considered to be even more at risk than children and adolescents
because root surface caries can also contribute to their caries
increment, whereas it is extremely uncommon among individuals
under 20 years of age.21In Figure 1, the annualised combined
caries increments from the reviewed studies have been plotted
against annualised data available from longitudinal studies of
adolescents which have reported caries increments from: age 12 to
15 among 655 Swedes;22age 12 to 15 among 583 Finns;23and age
15 to 18 among 690 New Zealanders.24That the caries experience
of older people over time was at least as great as that of adoles-
cents should provide considerable food for thought, given Western
industrialised countries' concentration of dental public health,
clinical and preventive resources upon children and adolescents,
rather than older people.25
It is possible (but not probable) that the decision to limit the lit-
erature search to MEDLINE, PubMed and articles in English may
have resulted in the omission of studies which should have been
included. This is unlikely, however, given (a) the status of English
as the lingua franca of science, and (b) the relative rarity of obser-
vational cohort studies of the oral health of older people.
In summary, review of the published outcomes of recent large
cohort studies shows that older people are a caries-active group,
with coronal caries making the major contribution to ongoing dis-
ease experience. No single, over-arching risk factor for caries
among older people has been identified, emphasising the need for
multi-strategy preventive efforts, including the use of fluorides in
both population- and individual-level prevention.
1. Berkey D, Berg R. Geriatric oral health issues in the United States. Int Dent J 2001; 51
(3 Suppl): 254-264.
Douglass C W, Shih A, Ostry L. Will there be a need for complete dentures in the
United States in 2020?J Pros Dent 2002; 87: 5-8.
Drake C W, Beck J D. Models for coronal caries and root fragments in an elderly
population. Caries Res1992; 26:402-407.
Gershen J A. Geriatric dentistry and prevention: research and public policy. Adv Dent
Res1991; 5: 69-73.
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Locker D. Response and non-response bias in oral health surveys. J Public Health Dent
Drake C W, Beck J D, Lawrence H P, Koch G G. Three-year coronal caries incidence and
risk factors in North Carolina elderly. Caries Res1997; 31: 1-7.
Hawkins R J, Jutai D K G, Brothwell D J, Locker D. Three-year coronal caries incidence
in older Canadian adults. Caries Res 1997; 31: 405-410.
Lawrence H P, Hunt R J, Beck J D, Davies G M. Five-year incidence rates and intraoral
distribution of root caries among community-dwelling older adults. Caries Res 1996;
10. Lawrence H P, Hunt R J, Beck J D. Three-year root caries incidence and risk modelling
in older adults in North Carolina. J Public Health Dent 1995; 55:69-78.
11. Locker D. Incidence of root caries in an older Canadian population. Community Dent
Oral Epidemiol1996; 24: 403-407.
The incidence estimate is the proportion of participants who
experienced new caries in one or more surfaces during the obser-
vation period, while the increment is the mean number of surfaces
which were affected. Thus, in the Iowa study, 56% of participants
had one or more coronal surfaces affected by caries during the
three years, with a mean 2.4 surfaces affected.
Reported 3-year coronal caries incidence ranged from 45% to
59%, with a mean increment of between 0.5 and 0.8 surfaces per
year. The coronal caries estimates from the North American studies
were similar (with the exception of the NC blacks), and, while the
longer period covered by the South Australian (SA) study makes
direct comparison difficult, the rates appear to be consistent. The
lower increment observed among the NC blacks may be at least
partly accounted for by their greater reported incidence of tooth
There was more variation in the incidence estimates for root
surface caries, with between 29% and 44% of individuals experi-
encing new disease over a 3-year period. The mean increment
ranged from 0.2 to 0.4 surfaces per year. For all studies, the contri-
bution of coronal caries to the combined increment was greater,
ranging from just over half (in the SA study) to three-quarters (in
the Ontario study).
Predictors of caries over time
Multivariate modelling of caries occurrence had been reported
from three of the cohort studies (NC, Ontario and SA), and had
been done for both coronal7,8,13and root surface10,11,13caries. The
outcomes of those models are summarised in Table 3. Partial den-
ture wearing was a predictor for root surface caries for every group
except the NC whites. No other common risk factor was found.
Caries incidence data from five different large-scale, longitudi-
nal studies have been reviewed and found to be remarkably con-
sistent in their findings. The data suggest that older people are
indeed a caries-active group. While both coronal and root sur-
face caries contributed to the observed increments, there was a
consistent pattern whereby coronal caries made the greater con-
tribution to the overall increment. Clinical preventive measures
for older people should clearly be directed at both types of
caries, as the widespread perception that root surface caries is
their only problem is erroneous.
The only caries risk factor common to all four studies was the
wearing of a partial denture, and that was for root surface caries
only (and it did not emerge as a risk factor among NC whites). Par-
tial dentures have been previously identified as being associated
Table 3 Reported risk factors and risk markers for dental caries from
cohort studies of older populations
Study/groupCoronal cariesRoot surface caries
WhitesLow socio-economic status
Gingival recession > 3mm
Mean probing depth > 2mm
Partial denture wearing BlacksBaseline coronal DFS
Number of teeth at baseline Irregular dental attendance
Greater severity of
loss at baseline
Antiasthma drugs long term Not taking long-term aspirin
Partial denture wearing
South AustraliaPartial denture wearing
RESEARCH Download full-text
92BRITISH DENTAL JOURNAL VOLUME 196 NO. 2 JANUARY 24 2004
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19. Steele J G, Walls A W G, Murray J J. Partial dentures as an independent indicator of
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20. Burt B A. Prevention policies in the light of the changed distribution of dental caries.
Acta Odont Scand 1998; 56: 179-186.
21. Galan D, Lynch E. Epidemiology of root caries. Gerodontology 1993; 10: 59-71.
22. Mattiasson-Robertson A, Twetman S. Prediction of caries incidence in schoolchildren
living in a high and a low fluoride area. Community Dent Oral Epidemiol 1993; 21:
23. Hausen H, Karkkainen S, Seppa L. Application of the high-risk strategy to control
dental caries. Community Dent Oral Epidemiol2000; 28: 26-34.
24. Kruger E, Thomson W M, Poulton R, Davies S, Brown R H, Silva P A. Dental caries and
changes in dental anxiety in late adolescence. Community Dent Oral Epidemiol 1998;
25. Chen M, Andersen R M, Barmes D E, Leclercq M-H, Lyttle C S. Comparing oral health
care systems. A second international collaborative study.Geneva: World Health
A BDA member wishing to make a point on the subject of ‘Door -
TO THE EDITOR OF THE "JOURNAL OF THE BRITISH DENTAL ASSOCIATION."
DEAR SIR-The question whether a dentist putting Member of the British Dental
Association on his door-plate is guilty of unprofessional conduct or not, was brought
before the Representative Board. It is a question of taste, or what is good form and
what is not good form. Professional bodies have certain canons of good taste, and an
observance of unwritten laws is one of them. Just how far unwritten laws may be dis-
regarded with impunity is a nice question. As long as the medical profession refrain
from indicating the college or university from which they have received their diplo-
mas or degrees, on their door-plates, I shall hold it snobbery for a dentist to affix
Eng., London, I., or Ed., after the letters L.D.S. on his door-plate. Whenever I see a
door-plate embellished as follows, M.R.C.S., L.R.C.P.(London) L.D.S; L..D.S (Eng.);
D.D.S. (U.S.A., America) - I wonder why photographic enlargements of the various
diplomas are also not hung out. A galaxy of letters is apt to confuse. Why not make it
clear to the passers by?
Br Dent J1902, 23: 576
One Hundred Years Ago