#
Eur J Oral Sci 2001; 109: 20ą26 Copyright Eur J Oral Sci 2001
Printed in UK. All rights reserved
European Journal of
Oral Sciences
ISSN 0909-8836
Pia Gabre1, Thore Martinsson2,
Longitudinal study of dental caries,
Lars Gahnberg3
1
Samariterhemmet Hospital Dental Clinic,
Public Dental Health Services, Uppsala County
tooth mortality and interproximal bone
2
Council, Sweden, Department of Oral
Diagnostics, School of Dentistry, Karolinska
3
loss in adults with intellectual disability Institutet, Sweden, Department of Preventive
Dentistry, Public Dental Health Services,
Uppsala County Council, Sweden
Gabre P, Martinsson T, Gahnberg L. Longitudinal study of dental caries, tooth
mortality and interproximal bone loss in adults with intellectual disability. Eur J Oral
#
Sci 2001; 109: 20ą26. Eur J Oral Sci, 2001
The investigation focused on longitudinal changes of oral health in a group of
adults with intellectual disability. A number of 124 individuals, aged 21ą40 yr in
1990, were followed during 8.5 yr. The incidence and prevalence of caries, incidence
of tooth mortality, and interproximal bone loss were registered from clinical
examinations and bite-wing radiographs. The subjects visited the dental clinic for
preventive dental care on average every third month during the period. The caries
incidence was low, on average 0.51 new lesions per yr. Persons with mild intellectual
Pia Gabre, Samariterhemmet Hospital Dental
disability experienced more caries than other subjects. During the 8.5 yr, the
Clinic, Dragarbrunnsg. 70, S-751-25
subjects had lost on average 1.82 teeth, with periodontitis dominating as the reason
Uppsala, Sweden,
for tooth mortality. Individuals who cooperated poorly with dental treatment had
Telefax: z46ą18ą121060
lost the most teeth. The average annual bone loss in all subjects was 0.03 mm.
E-mail: [e-mail]
Subjects with Down syndrome had a higher bone loss compared to those with other
Key words: dental caries; epidemiology;
diagnoses of intellectual disability. Thus, the major part of the persons with
intellectual disability; periodontal disease; tooth
intellectual disability showed satisfactory oral health. However, subjects with poor
mortality
ability to cooperate with dental treatment and subjects with Down syndrome
showed an increased risk for impaired oral health. Accepted for publication October 2000
In the western world the last couple of decades have seen Genetic impairment and poor oral hygiene have been
important changes in the living conditions for individuals suggested as factors explaining the high prevalence of
with intellectual disability. The policy of normalisa- periodontal diseases (12).
tion, integration, equality and deinstitutionalisation has Longitudinal studies of the progression of oral dis-
been generally accepted (1). Consequently, an increasing eases in individuals with intellectual disability are sparse.
number of intellectually disabled individuals are living A high prevalence of periodontal disease in adolescents
integrated in society, and their right to inŻuence their with Down syndrome has been reported, although the
own lives is acknowledged. Independent living has been disease was less severe and the progression was partly
reported to have an impact on general health as well arrested in the latest study (11, 13). Compared to the
as on oral health in persons with intellectual disability normal Swedish population, the incidence of tooth
(2, 3). Thus, the integration in the community may have mortality was found to be high among institutional-
an impact on the state of health of intellectually disabled ised intellectually disabled subjects during a 10-yr period
individuals. (10). No longitudinal studies have, however, described
The prevalence and incidence of dental caries in the caries prevalence and incidence in people with
persons with intellectual disability living in institutions intellectual disability.
are low compared to individuals living integrated in Since the knowledge regarding oral health in adults
society (3ą6). Subjects with mild forms of intellectual with intellectual disability is mainly based on cross-
disability living among relatives or in their own apart- sectional studies, the present investigation focused on
ments have, however, a caries experience exceeding that longitudinal changes of oral health in a group of intel-
reported in other intellectually disabled subjects (3, 6). lectually disabled individuals. Our hypothesis was that
Due to poor cooperation with dental treatment in a protracted, systematic, and individualised preventive
intellectually disabled subjects, the therapy chosen has dental care has the potential to equalise di�erences in
often been extraction, resulting in a low number of the prevalence of oral diseases in individuals with intel-
restored teeth and a high number of missing teeth (7ą10). lectual disability. Therefore, in intellectually disabled
Periodontal disease is the dominating reason for tooth adults, given an individualised preventive dental care,
extractions in individuals with intellectual disability, the progression of dental caries, tooth mortality and
especially in subjects younger than 50 yr (10, 11). alveolar bone loss was followed during 8.5 yr. In
Oral health in adults with intellectual disability 21
Table 1
addition, we also wanted to study conditions with a
potential to inŻuence the oral health of these adults. For
Distribution of degree of intellectual disability, age (yr), sex,
that reason, the relationship between oral health and the
medication and Down syndrome (number of subjects)
ability to cooperate with dental treatment and use of
Severe Moderate Mild
medication was analysed.
n~55 n~39 n~30
Age:
Material and methods mean (ĄSD) 39.06 (5.29) 38.74 (5.61) 40.30 (5.34)
median 39.0 39.0 41.5
Subjects
range 30ą49 30ą49 30ą49
Sex:
All patients at a hospital dental clinic who were registered
men 28 25 17
by the Social Services as intellectually disabled and were
women 27 14 13
between 21 and 40 yr of age in 1990ą1991 were examined.
Before the study started in 1990, all patients had had regular Medication:
dental care for 10 yr, including examinations by a dentist neuroleptics 10 6 2
with 9ą15 months interval and frequent visits for prevent- anticonvulsants 10 5 4
ive care, designed on an individual caries and period- combination
neurolepticsz
ontal risk level basis. The care consisted of professional
anticonvulsants 6 1 1
tooth cleaning, and various combinations of scaling, treat-
other drugs 6 6 7
ment with chlorhexidine and/or local applications of
no drugs 23 21 16
Żuoride and counselling to the caregivers. The 132 sub-
Down syndrome 13 16 3
jects investigated showed uniform distribution with respect
to living arrangements (Fig. 1). The degree of intellectual
disability was classi�ed by a simpli�ed method according
Uppsala University. Before collecting data, informed
�
to the system described by KYLEN (14). From clinical
consent was obtained from the subjects' guardians.
examinations and bite-wing radiographs, the caries incid-
ence and prevalence, the number of missing teeth, and the
loss of alveolar bone were noted. A complete description of
Clinical examinations
the methods used was presented in previous papers (3, 6).
Starting in 1990, the oral health of the intellectually
During the period studied, the subjects were examined
disabled individuals was investigated during 8.5 yr (range
annually by a dentist. A mirror and probe were used
7.58ą9.75). Six subjects died during the period. One subject
and, when possible, radiographs were taken. In 1999 all
who was edentulous in 1990 and one subject who declined
examinations included two bite-wing radiographs, unless
dental care were excluded from the study. Thus, 124 sub- the subjects' cooperation was too poor to permit radio-
jects participated in the longitudinal study. Their mean age
graphy. All clinical examinations were performed at
in 1999 was 39.26 (Ą5.39) yr. The distribution by age,
a dental clinic and, with the exception of 5 subjects who
sex, use of medication and Down syndrome related to the
had moved to other cities, by the same dentist as performed
degree of intellectual disability is shown in Table 1. All
the examinations 8.5 yr earlier. To calculate the caries
institutionalised subjects and 18 subjects who lived in their
incidence, all decayed surfaces noted in the patient's
own apartments or among relatives in 1990 had moved to
record during 1990ą1999 were added (DS). The number of
community-based units during the period studied (Fig. 1).
decayed and �lled surfaces (DFS) at the examination in
A majority of the individuals lived in an area with 1 ppm
1999 was registered (15). Only cavities extending into the
Żuoride in the drinking water. The scienti�c and ethical
dentine were included. The number of remaining teeth in
aspects of the protocol of this study were reviewed and
1999 was counted. From the records, the cumulative num-
approved by the Ethics Committee, Faculty of Medicine,
ber of lost teeth between 1990 and 1999 was noted, and
the reason for the tooth loss was noted. In addition, the
number of occasions of topical Żuoride application, profes-
sional tooth cleaning and tooth scaling during the 8.5 yr
was counted. The ability to cooperate was classi�ed
according to the need of physical restraint, premedication
and general anaesthesia to perform dental treatments (10).
Radiographic examinations
Using a standardised long cone technique, two bite-wing
radiographs were taken in 1990 and repeated 8.5 yr later.
From the radiographs, the distance between the cemento-
enamel junction (CEJ) and the alveolar crest (AC) was
measured with a Peak scale loupe (Carton Optic, Tokyo,
Japan) at 7-fold magni�cation (gradation 0.1 mm). When
clearly visible, the interproximal calculus was identi�ed
Fig 1. Changes of living arrangements between 1990 and 1999. from the bite-wing radiographs.
e Institution, % Community-based units of 4ą5 handicapped The mesial surface of the �rst molar, distal and mesial
persons (units), u Own apartments or together with relatives surface of the second premolar, and distal surface of the
(private). �rst premolar in the maxilla and mandible were examined.
22 Gabre et al.
Measurements were performed only in those cases where the
CEJ and AC could be su�ciently identi�ed. The reduction
of alveolar bone height was calculated for each individual
as the mean di�erence between the CEJ to AC distance
in 1999 and 1990 in all readable sites. The methodological
p��������������
error (S) was calculated by using the formula
S � d2=2N
(d~individual di�erences between two measurements,
N~number of repeated determinations; 13). The error of
the method was 0.16.
Statistical analyses
Fig. 2. Distribution of subjects with respect to incidence of
One-factor analysis of variance, ANOVA, was used for
tooth mortality between 1990 and 1999 and reasons for tooth
analysing di�erences between means when more than two
mortality. b Teeth lost due to caries, p Teeth lost due to
groups and large sample sizes (ż30) were tested. Smaller
periodontitis.
sample sizes were analysed by the non-parametric Kruskal
Wallis test. Di�erences between means in two groups
were analysed by the unpaired t-test (sample size ż32)
The alveolar bone loss could be determined in one
and Mann-Whitney U-test. The variable alveolar bone
or more sites at both examinations in 87 individuals.
loss showed a normal distribution (Anderson-Darling test
The total number of sites measured was 1,034. Due to
of normality) and all analyses, regardless of the sample
lack of cooperation, it was not possible to take bite-
size, were made with parametric tests. The analysis was
wing radiographs in 31 subjects. Another reason for
performed using Stat View 4.01 (Abacus, Berkeley, CA,
USA). A 5 % level of signi�cance was used. not measuring alveolar bone loss was poor quality of
the radiographs or di�culties in identifying the CEJ
due to interproximal restorations. Thus, of the teeth
present in the material, 54ą71% could be measured in
both 1990 and 1999.
Results
The proportions of subjects with one or more sites
The subjects had an average of 4.44 (Ą6.66) decayed with a CEJ to AC distance exceeding 2.0 mm at the
surfaces and had lost 1.82 teeth (Ą2.59) during the examinations in 1990 and 1999 were 59% and 71%,
8.5 yr. Ninety subjects experienced caries during the respectively. The corresponding proportions for site level
study, showing a mean number of decayed surfaces of were 15% and 22%. On an individual basis, the mean
6.12 (Ą7.13). The mean number of lost teeth among value of alveolar bone loss during 8.5 yr was 0.24 mm,
the 74 subjects who had lost teeth during the study corresponding to a bone loss of 0.03 mm per yr (Table
was 3.04 (Ą2.74). Subjects with severe intellectual dis- 2). The progression of alveolar bone loss between 1990
ability had a lower caries incidence and prevalence and 1999 is shown in Table 3. The 87 subjects who
compared to subjects with milder forms of intellectual managed the radiographic examination had lost less
disability, even when the number of present teeth teeth than the subjects who were unable to cooperate
was taken into consideration. Individuals with poor (unpaired t-test, P50.001).
cooperation had lost more teeth and, consequently, Those individuals who lived in an institution in 1990
had a lower number of remaining teeth compared to still had a lower caries incidence (ANOVA: institution
those individuals who cooperated well. Although the vs. private P50.05) and prevalence (ANOVA: institu-
preventive dental care was frequent among all subjects, tion vs. units P50.01, institution vs. private P50.0001)
individuals with severe intellectual disability had had after several years of community-based living (Fig. 1).
signi�cantly fewer applications of Żuoride varnish and However, the signi�cant di�erences disappeared when
professional tooth cleaning compared to subjects with caries incidence was related to the number of present
less serious disability (Table 2). teeth. In addition, they had lost more teeth during 8.5 yrs
A total number of 225 teeth were lost between 1990 (ANOVA: institution vs. units P50.01, institution vs.
and 1999, representing 6.8% of the teeth present in 1990. private P50.01) and had a lower number of remaining
Of the teeth lost, 37.3% were lost due to caries, 57.4% teeth in 1999 (ANOVA: institution vs. units P50.01,
due to periodontitis, and in 5.3% the teeth were lost institution vs. private P50.05). Subjects with Down
due to other reasons. More individuals had lost teeth due syndrome had a lower caries incidence and prevalence
to caries (n~43) compared to periodontitis (n~34). If compared to subjects with other diagnoses of intellec-
an individual had lost a large number of teeth, period- tual disability (unpaired t-test: P50.05 and P50.0001
ontitis dominated as the reason. Of the teeth lost due respectively). The number of remaining teeth was lower
to periodontitis, 9 individuals were responsible for 55% in subjects with Down syndrome (unpaired t-test:
(Fig. 2). Sixty-two % of the teeth lost were molars (third P50.05), but they had lost an equal number of teeth
molars included) and 26% anterior teeth. An equal compared to subjects with other diagnoses of intellectual
number of molars were lost due to caries and period- disability during the 8.5 yr. In addition, subjects with
ontitis. In anterior teeth, periodontitis dominated as the Down syndrome had lost more alveolar bone between
reason for tooth mortality (80%). 1990 and 1999 (unpaired t-test: P50.01).
Table 2
Incidence of caries (DS), incidence of tooth mortality and interproximal bone loss during 8.5 yr. Occasions of fluoride varnish application, professional tooth cleaning and tooth scaling per year
between 1990 and 1999. Caries prevalence (DFS) and remaining teeth in 1999. All variables related to degree of intellectual disability and cooperation with dental treatment. Class 1: patient
requires no special consideration in dental treatment. Class 2: patient requires mild physical restraint or premedication. Class 3: patient requires general anaesthesia, conscious sedation or
physical restraint for difficult treatment. Class 4: patient requires general anaesthesia for all kinds of treatment. Mean (ĄSD).
Intellectual disability Cooperation
Total Severe Moderate Mild Class 1 Class 2 Class 3 Class 4
n~124 n~55 n~39 n~30 n~45 n~43 n~25 n~11
Incidence of caries (DS) 4.44 (6.66) 2.67a (5.25) 4.85 (5.17) 7.17a (9.37) 5.73 (8.52) 2.93 (3.84) 3.48 (3.82) 7.27 (10.01)
Caries prevalence (DFS) 17.27 (16.66) 10.11b (10.46) 16.97b (15.53) 30.80b (19.26) 26.33e (21.12) 12.28 (10.86) 13.88 (11.10) 7.46 (6.95)
Incidence of tooth mortality 1.82 (2.59) 2.16 (3.00) 1.77 (2.60) 1.23 (1.48) 1.13f (1.58) 1.49 (2.27) 1.76 (1.94) 6.00 (4.34)
Remaining teeth (32 teeth) 24.89 (5.43) 24.40 (5.65) 24.87 (6.03) 25.80 (4.09) 26.13g (3.98) 26.00 (4.78) 23.68 (4.89) 18.18 (8.62)
Fluoride varnish 2.58 (1.37) 1.99c (1.06) 3.07c (1.46) 3.04c (1.35) 2.88h (0.91) 2.15 (1.05) 3.10 (1.77) 1.88 (2.20)
Professional tooth cleaning 4.47 (1.84) 4.01d (1.65) 4.98d (1.89) 4.66 (1.95) 4.66i (1.89) 4.27 (1.43) 5.12 (1.91) 3.03 (2.29)
Tooth scaling 2.04 (1.83) 2.37 (2.01) 1.68 (1.68) 1.90 (1.59) 1.88 (1.86) 2.35 (1.69) 2.20 (2.09) 1.11 (1.37)
n~87 n~28 n~30 n~29 n~45 n~30 n~10 n~2
Interproximal bone loss 0.24 (0.23) 0.24 (0.26) 0.25 (0.18) 0.24 (0.25) 0.22 (0.22) 0.24 (0.25) 0.37 (0.25) 0.11 (0.11)
a
Signi�cant di�erences: ANOVA severe vs. mild P50.01.
b
Signi�cant di�erences: ANOVA severe vs. moderate P50.05, severe vs. mild P50.0001, moderate vs. mild P50.001.
c
Signi�cant di�erences: ANOVA severe vs. moderate P50.0001, severe vs. mild P50.001.
d
Signi�cant di�erences: ANOVA severe vs. moderate P50.05.
e
Signi�cant di�erences: Kruskal Wallis test P50.0001.
f
Signi�cant di�erences: Kruskal Wallis test P50.01.
g
Signi�cant di�erences: Kruskal Wallis test P50.001.
h
Signi�cant di�erences: Kruskal Wallis test P50.001.
i
Signi�cant di�erences: Kruskal Wallis test P50.05.
Oral health in adults with intellectual disability
23
24 Gabre et al.
Table 3
The progress of the individual means of bone loss between 1990 and 1999, expressed in mm
CEJąAC distance CEJ-AC distance in 1999
in 1990 n 0.0 ą50.5 0.5ą51.0 1.0 ą51.5 1.5 ą52.0 2.0 ą52.5 2.5ą53.0 3.0ą53.5 3.5ą
0.0 ą50.5 5 2 3
0.5 ą51.0 28 18 9 1
1.0 ą51.5 36 25 10 1
1.5 ą52.0 11 5 5 1
2.0 ą52.5 5 1 2 2
2.5 ą53.0 1 1
3.0ą53.5 2 2
In 1990 interproximal calculus was visible in 32% of who were unable to cooperate still had some preventive
the subjects, increasing to 36% in 1999. The calculus dental care (Table 2). Contrary to the preventive care
was visible in 8.3% and 7.8% of the sites in 1990 and given before 1990, the preventive care between 1990
1999, respectively. No correlation between the use of and 1999 was aimed at the subjects with the highest
medication and caries experience, tooth mortality or disease activity. Thus, individuals with moderate and
number of remaining teeth could be observed. Subjects mild intellectual disability more often received Żuoride
taking anticonvulsants showed less alveolar bone loss applications and professional tooth cleaning, and indi-
compared to users of other medication or those who used viduals with severe intellectual disability more often had
no medication at all (unpaired t-test: P50.05). tooth scaling.
The subjects had an average annual tooth mortality
of 0.21 teeth during the study. This result exceeds the
tooth mortality in Swedish populations (16, 20) but is
below that in institutionalised intellectually disabled
Discussion
subjects (10). Ten subjects who lost more than �ve
This study shows a low caries incidence, 0.51 new lesions teeth during the 8.5 yr could, in fact, to a large degree
per yr, among the adults with intellectual disability. explain the di�erences in tooth mortality between the
Compared to the investigation in 1990, the incidence of intellectually disabled and the normal population.
caries had clearly decreased (3, 6). Despite the change More e�cient prevention, improved cooperation with
from institutionalised to integrated living, the indi- dental treatment, and an altered attitude to tooth
viduals who lived in an institution in 1990 still had extractions from caregivers, relatives and dental sta�
a signi�cantly lower caries prevalence compared to other may explain the comparatively lower number of teeth
intellectually disabled individuals, indicating stable lost. Subjects who lived in an institution in 1990 had
habits in individuals with prolonged experience of res- a higher tooth mortality compared to subjects with
tricted living. In line with previous studies, the subjects other living arrangements. A possible explanation may
with Down syndrome had a lower caries incidence be that individuals with the most serious behavioural
and prevalence compared to those with other diagnoses problems remained at the institutions during the pro-
of intellectual disability (3, 4). Of the 10 subjects with- cess of deinstitutionalisation and, consequently, those
out any experience of dental caries at all in the present individuals had the most di�culties cooperating with
study, 9 had the diagnosis Down syndrome. dental treatment. Although the subjects with Down
In comparison with previous reports on subjets with syndrome had a lower number of remaining teeth in
intellectual disability (5, 7ą9) and normal Swedish popu- 1999, they had lost the same number of teeth as other
lations (16ą18), the caries incidence in the present study individuals with intellectual disability between 1990
was low. One explanation for the low caries incidence and 1999. An explanation for the lower number of
in the subjects with intellectual disability may be the remaining teeth may be the high frequency of agenesis
optimal Żuoride concentrations in the drinking water. associated with the diagnosis (21).
WIKTORSSON et al. (19) reported a signi�cantly lower caries More teeth were lost due to periodontitis, but more
experience, although higher than that found in the pres- individuals had lost teeth due to caries. This result is in
ent study, among individuals aged 30ą40 yr living in an line with our previous �ndings in subjects with intellec-
area with optimal water Żuoride concentration compared tual disability (10). In normal Swedish populations,
to individuals in a neighbouring city with low water however, caries is the main reason for tooth mortality in
Żuoride concentrations. persons aged under 50 yr (20, 22).
The preventive dental care given at the dental clinic The annual alveolar bone loss was low, 0.03 mm,
was frequent. The subjects received professional tooth among the 87 subjects who managed bite-wing radio-
cleaning approximately every third month. Due to poor graphs, a result similar to or lower than the bone loss
cooperation, however, on some occasions an attempt at in adolescents with Down syndrome (13) and normal
preventive dental care would have been a more correct Swedish populations (16, 23). An explanation for the
description of the treatment. This explains why subjects apparent limited bone loss in the present study may be
Oral health in adults with intellectual disability 25
that the 2nd molars, which have been found to be most caries lesion per year, and only 4% had more than two
a�ected by alveolar bone loss, were not included in the new lesions per year. The high caries incidence among
registrations (23). The reason for not including the 2nd the individuals with mild intellectual disability found
molars, distal surfaces of the 1st molars, and mesial in the investigation in 1990 was decreased by 43%. Less
surfaces of 1st premolars was a too small proportion of than 10% of the subjects had serious tooth mortality
readable sites among these surfaces. When calculating (44 lost teeth during 8.5 yr). An annual alveolar bone
means of bone loss on an individual basis, the number of loss of 0.06 mm or more was registered in 10% of the
missing teeth may result in an underestimation of the subjects. Thus our data give support to the hypothesis
prevalence and severity of the periodontal disease. The that a protracted, systemic, and individualised preventive
subjects investigated in the present study lacked more dental care could equalise the di�erences in the pre-
teeth than a normal population when the study started, valence of oral diseases in individuals with intellectual
and, consequently, the underestimation may have been disability. However, special attention needs to be focused
more signi�cant in our study compared to studies of on two subgroups of intellectually disabled individuals
normal populations. Smoking is the most important with an obvious risk of deteriorated oral health, namely
explanatory factor for periodontal disease progression, subjects with poor ability to cooperate with dental
even more important than supragingival plaque (22). In treatment and subjects with Down syndrome. With the
the present study, only 2% of the subjects were smokers, exception of these groups, the prevalence of oral diseases
compared to the smoking prevalence reported in Swedish can be kept low in individuals with intellectual dis-
populations of 20ą25% (18), and 2% su�ered from ability who receive an individualised preventive dental
diabetes mellitus, another risk factor for periodontal care using generally available measures.
disease (22).
Although almost half of the subjects used medication
with a potential to cause hyposalivation, it was, due to
Acknowledgements ą We thank John Gulliver for revising the
English text and Bertil Andersson for help with the statistical
poor ability to deliver saliva among the subjects, not
analyses. We also thank Dr. Monica Barr Agholme for valuable
possible to measure if the salivary Żow rate in fact was
criticism. This study was supported by VaĘ rdalsstiftelsen,
decreased. However, no correlation between use of
Karolinska Institutet, and Uppsala County Council.
medication and dental caries could be observed in the
present study. In a previous study individuals with
intellectual disability who used neuroleptics had lost
signi�cantly fewer teeth than other intellectually disabled
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