Dental caries and Streptococcus mutans in a rural child population in Iceland
Sigurdur Runar Saemundsson\ Halldora Bergmann\ Margret O. Magnusdottir^ and W. Peter Holbrook^
v
'Dental Surgery, Vopnafjordur and ^Faculty of Odontology, University of Iceland, Reykjavik, Iceland
Saeimmd.sson SR, Bergtnann H, Magntisdottir MO, Holbrook WP: Dental caries and Streptococcus mutans in a rural child population in Iceland. Scand J Dent Res 1992; 100: 299-303. . ., . . ,., , . .,. ., - ,/, In spite of having a high socioeconomic standing, in Iceland caries prevalence has remained stubbornly high. This study reports findings from a mixed fishing and farming community in East Iceland that has traditionally been associated with the highest prevalence of caries. A total of 188 children aged 3-16 yr (96.4% of residents of that age group) were examined. At 6 yr the mean dmfs score was 4.1, DMFS 0 and 48% were caries-free. The mean DMFS score at 12 yr was 4.7 and 22.6% remained caries-free but at 16 yr the DMFS score was 11.6 and no children were caries-free. Caries was unevenly distributed within each age group and was more prevalent among residents of the fishing town than the surrounding farming district. In a pilot study conducted in 1989 mean counts of Streptococcus mutans for children aged 4-7 yr were 2.6 x 10' cfu/ml and declined to 4.6 x lO"* cfu/ml in 1990 after a program of chlorhexidine brushing had been added to the routine caries preventive measures adopted in this community. It may therefore be possible to screen Icelandic children for caries risk and apply preventive measures to those demonstrated to be most in need.
The prevalence of dental caries in Iceland has been regarded as high (1-3) especially as the decline in caries levels seen in many countries has not been apparent in Iceland (2) until very recently (4, 5). It has been reported by MOLLER (1, 2) that children living in farming communities had less caries than those living in fishing towns or urban areas. Most recent studies of caries among Icelandic children have concentrated on urban populations (4, 6). The link between caries prevalence or incidence and the numbers of cariogenic bacteria present in saliva has been widely investigated (7) in clinical and laboratory studies. Investigations among Icelandic children have been particularly interesting because of the high mean counts of mutans streptococci (8) and the rather high prevalence of S. sobrinus reported (8-10). Furthermore the cariogenicity of at least some Icelandic strains of S. mutans in an experimental hamster model of caries was reported to be high (11). The present investigation reports on the prevalence of dental caries in the Vopnafjordur district of Eastern Iceland. The population is rather isolated and employment is divided between fishing by residents in the town and farming in the surrounding area. Caries prevalences for children from 3 yr to 16 yr of age were recorded and the numbers of
Key vtfords: dental caries, prevaience; Iceland, Streptococcus mutans W. Peter Holbrook, Faculty of Odontoiogy, University of Iceland, Vatnsmyrarvegur 16, 101 Reykjavik, Iceland Accepted for publication 1 November 1991
cariogenic microorganisms in saliva determined. There is no resident dentist in the town and dental services to the child population has been supplied by one of us (S.R.S.) under an agreement with the Local Authority since 1987. Visits have been confined to the summer months and a short visit in December each year. A pilot study was carried out in 1989 (5) to determine the relationship between caries prevalence and mean bacterial counts among preschoolchildren (3-7 yr) and to test the feasibility of sending salivary specimens from the test town to Reykjavik for analysis. A simple program of preventive measures was also instituted for children with a high caries risk. The encouraging results of the pilot study prompted a wider investigation of all children from approximately 3 yr to 16 yr in Vopnafjordur in 1990. Comparison with data obtained by the same investigators from urban areas of Iceland and other communities could then be made and the findings related where possible to those reported from neighboring countries. Material and methods In 1989, the test town Vopnafjordur and surrounding district had a population of 940 with 195 chil-
300
Saemundsson et al.
dren aged between 3 yr and 16 yr. In the summer of 1989, 170 children aged 3-16 yr (87% of the total number of that age group normally resident) were examined and received dental treatment as required. All caries was treated. In a pilot study, 47 children aged 3-7 yr were also examined microbiologically. The main study was conducted in the summer of 1990: 188 children between the ages of 3 yr and 16 yr (96.4% of those normally resident) were examined. Of this total, 144 (76.6%)) resided in the town and the remainder in the country district. Thus point prevalence scores of dental caries for all children were recorded in 1990. From the number of new lesions (d,D) it was also possible to detertiiine the incidence of caries arising between the summer of 1989 and the summer of 1990. For preschoolchildren changes in bacterial counts over the 12 months to 1990 were also assessed. Dental examinations - The study was carried out as part of the ordinary dental service to the community. Children were called in for routine examination according to lists supplied by the local comtiiunity. Residence in the town or surrounding country district was recorded at the time of the visit. Examinations were performed by one operator (H.B.) who then consulted the other operator (S.R.S.) in cases of doubt and for interpretation of bitewing radiographs. Each child was examined in the satne dental chair using the lighting attached to the unit. Dental caries was detected with tnirrors and used probes and the teeth were air-dried prior to examination. The criteria adopted for caries presence and caries scoring were as described by WHO (12) with the exception that the children were also examitied with bitewing radiographs for detection of approximal caries. This was scored if a radiolucency had reached the dentin. A sealed surface was registered as intact unless it obviously covered a posterior composite filling and the presence of fissure sealants was recorded. Initial caries (WHO category 0) was omitted from the registration. . . , , . , . . . .
-
'
. . .
Bacterial sampling - Samples for bacterial analysis were collected frotii the dorsum of the tongue according to the method described by BEIGHTON (13). This method is reliable, gives results comparable with other methods and is easier to use on small children. The 10 ^il samples were dispersed in 1 ml volurnes of Reduced Transport Fluid (14) and sent by express airmail to Reykjavik where they were received and handled within 24 h of the samples being taken. Culture for S. mutans and lactobacilli was on MSB and Rogosa media respectively exactly according to HOLBROOK & BEIGHTON (8). Freventive measures - Dental treatment and preventive measures were performed on these children according to clinical needs. All children received fissure sealing of molar teeth if clinically indicated and fiuoride varnish (Duraphat, Woehlm, Eschwege, Germany) was apphed routinely to all teeth at the end of treatment. After the pilot study (5) chlorhexidine gel (Hibitane Dental Gel, ICI, England) was prescribed for those 15 children thought to be at greatest risk of developing a large amount of caries based largely on the culture of > 10' cfu/ inl S. mutans from the bacterial specimens. Chlorhexidine was applied to the teeth with a new toothbrush by the parents and according to printed instructions from the investigators. The preventive measures were repeated after 6 months. This district has received dental treatment according to the scheme outlined above since spring 1987 with the exception of chlorhexidine therapy, which was only begun in 1989. Results
'
Caries prevalence - Of the children aged 3-16 yr resident in the district, 188 (96.4%) were examined. One child attended a dentist in Reykjavik and five were away from the district for most or all of the study period. The prevalence of dental caries recorded for children is shown in Table 1. Data from 2-yr age groups were combined because the
Table 1
^
_ /
.
\
Prevalence of dented caries (dmfs, DMFS), new lesions (d, D) and proportion of children caries-free examitied al mean ages 4-16 yr in the Vopnafjordttr district of E. Iceland Mean caries scores Mean (SE) d (SE) DMFT % caries-free n D age (yr) DMES dmfs _ _ _ — 0.7 1.7 20 70.0 4 2.1 1.0 0.5 0 0 29 0 48.0 4.1 0 6 0.4 2.2 0.4 0.7 25 0.3 8 1.8 12.5 12.7 — — 0.6 1.6 34 35.3 10 2.8 0.3 — — 1.1 0.4 2.6 22.6 12 31 4.7 — — 1.4 5.7 7.9 14 38 0.8 10.7 2.5 11 6.6 0 11.6 0.2 16 SE = standard error of the mean.
Caries in rural Iceland
301
Table 3
5
5-6y (dmfs) 11-12y(DMFS) 14-15y (DMFS)
a a
CARIES SCORE
Prevalence of dental caries in children in Vopnafjordur district of E. Icetand atiatyied according to residence in town or country district Country Town Caries Caries score % score % (dmfs/ caries(dmfs/ cariesMean DMFS) free DMFS) free age (yr) 0 4.1 38.7 100.0 4-6 2.0 44.7 2.0 7-10 (permanent) 60.0 7.9 3.4 11-13 15.2 30.8 8.3 4.3 13.2 14-16 0
Fig. 1. Distribution of caries scores among children in three age groups in Vopnafjordur.
numbers of children per year were rather small (ca. 15). A large proportion of children in the youngest age groups were caries-free whereas the older children had considerable past experience of caries. Caries was unevenly distributed among children in all age groups but particularly in the younger children. The distribution of caries among children aged 5-6 yr, 11-12 yr and 14-15 yr is shown in the Figure. Children aged 14-15 yr showed a distribution of caries resembling a normal curve. In the younger age groups the distribution of caries was skewed to the left of the graph with many children having little or no caries. Table 2 shows the proportion of the total caries scores (dmfs or DMFS) attributable to the 25% of each age group most affected by dental decay. For both primary and permanent dentitions 25% of the younger children account for about 70% of the total caries score but this declines to about 50% of the total caries score when the teeth have been erupted for about 8 yr. The differences in caries prevalence between children living in the town and the surrounding country district are given in Table 3. There was a lower mean caries score among all age groups of children resident in the country district. The differences in the proportion of children caries-free is most strikTable 2 Distribution of caries among children in each age group Proportion (%) of total caries score (dmfs or DMFS) represented by the 25% of children most affected by caries Mean age (yr) % of DMFS l of dmfs 4 70.4 6 69.8 8 87.5 52.2 67.8 to 64.6 12 53.3 14 50.8 16
ing for the youngest children but this difference declines with age and is not seen by 14 yr. Incidence of caries - The incidence of caries in tooth surfaces for primary teeth (d) and permanent teeth (D) is shown in Table 1. Many 4-yr-old children were attending the dentist for the first time. For all other age groups the incidence of new lesions was !0' cfu/ml (y) 4-5 dmfs 4.1 1.8 ds 0.3 0.4 6-7 5.5 dmfs 3.1 0.3 ds 8-9
DMFS DS
0.4 0.1
•
10-11
DMFS DS
2.7 0.4
-
12-13
DMFS DS
3.7 0.4
14-15
DMFS DS
11.6 0.9
lj
;o.7
/
2.7 0.2 4.9 6.5 9.6 0.8
^:
•:
Table 6 Comparison of bacterial parameters in pilot study with those recorded in main study Pilot study Main study Age (yr) 4-7 4-7 Mean count S. mutans cfu/ml 2.6x10' 4.6x10-'* Mean count lactobacilli cfu/ml 1.9 X IO" 3.5x10' Proportion with 5. mutans (%) 77.1 55.1^^ Proportion with lactobaeilli (%) 29.2 20.4 P
Sigurdur Runar Saemundsson\ Halldora Bergmann\ Margret O. Magnusdottir^ and W. Peter Holbrook^
v
'Dental Surgery, Vopnafjordur and ^Faculty of Odontology, University of Iceland, Reykjavik, Iceland
Saeimmd.sson SR, Bergtnann H, Magntisdottir MO, Holbrook WP: Dental caries and Streptococcus mutans in a rural child population in Iceland. Scand J Dent Res 1992; 100: 299-303. . ., . . ,., , . .,. ., - ,/, In spite of having a high socioeconomic standing, in Iceland caries prevalence has remained stubbornly high. This study reports findings from a mixed fishing and farming community in East Iceland that has traditionally been associated with the highest prevalence of caries. A total of 188 children aged 3-16 yr (96.4% of residents of that age group) were examined. At 6 yr the mean dmfs score was 4.1, DMFS 0 and 48% were caries-free. The mean DMFS score at 12 yr was 4.7 and 22.6% remained caries-free but at 16 yr the DMFS score was 11.6 and no children were caries-free. Caries was unevenly distributed within each age group and was more prevalent among residents of the fishing town than the surrounding farming district. In a pilot study conducted in 1989 mean counts of Streptococcus mutans for children aged 4-7 yr were 2.6 x 10' cfu/ml and declined to 4.6 x lO"* cfu/ml in 1990 after a program of chlorhexidine brushing had been added to the routine caries preventive measures adopted in this community. It may therefore be possible to screen Icelandic children for caries risk and apply preventive measures to those demonstrated to be most in need.
The prevalence of dental caries in Iceland has been regarded as high (1-3) especially as the decline in caries levels seen in many countries has not been apparent in Iceland (2) until very recently (4, 5). It has been reported by MOLLER (1, 2) that children living in farming communities had less caries than those living in fishing towns or urban areas. Most recent studies of caries among Icelandic children have concentrated on urban populations (4, 6). The link between caries prevalence or incidence and the numbers of cariogenic bacteria present in saliva has been widely investigated (7) in clinical and laboratory studies. Investigations among Icelandic children have been particularly interesting because of the high mean counts of mutans streptococci (8) and the rather high prevalence of S. sobrinus reported (8-10). Furthermore the cariogenicity of at least some Icelandic strains of S. mutans in an experimental hamster model of caries was reported to be high (11). The present investigation reports on the prevalence of dental caries in the Vopnafjordur district of Eastern Iceland. The population is rather isolated and employment is divided between fishing by residents in the town and farming in the surrounding area. Caries prevalences for children from 3 yr to 16 yr of age were recorded and the numbers of
Key vtfords: dental caries, prevaience; Iceland, Streptococcus mutans W. Peter Holbrook, Faculty of Odontoiogy, University of Iceland, Vatnsmyrarvegur 16, 101 Reykjavik, Iceland Accepted for publication 1 November 1991
cariogenic microorganisms in saliva determined. There is no resident dentist in the town and dental services to the child population has been supplied by one of us (S.R.S.) under an agreement with the Local Authority since 1987. Visits have been confined to the summer months and a short visit in December each year. A pilot study was carried out in 1989 (5) to determine the relationship between caries prevalence and mean bacterial counts among preschoolchildren (3-7 yr) and to test the feasibility of sending salivary specimens from the test town to Reykjavik for analysis. A simple program of preventive measures was also instituted for children with a high caries risk. The encouraging results of the pilot study prompted a wider investigation of all children from approximately 3 yr to 16 yr in Vopnafjordur in 1990. Comparison with data obtained by the same investigators from urban areas of Iceland and other communities could then be made and the findings related where possible to those reported from neighboring countries. Material and methods In 1989, the test town Vopnafjordur and surrounding district had a population of 940 with 195 chil-
300
Saemundsson et al.
dren aged between 3 yr and 16 yr. In the summer of 1989, 170 children aged 3-16 yr (87% of the total number of that age group normally resident) were examined and received dental treatment as required. All caries was treated. In a pilot study, 47 children aged 3-7 yr were also examined microbiologically. The main study was conducted in the summer of 1990: 188 children between the ages of 3 yr and 16 yr (96.4% of those normally resident) were examined. Of this total, 144 (76.6%)) resided in the town and the remainder in the country district. Thus point prevalence scores of dental caries for all children were recorded in 1990. From the number of new lesions (d,D) it was also possible to detertiiine the incidence of caries arising between the summer of 1989 and the summer of 1990. For preschoolchildren changes in bacterial counts over the 12 months to 1990 were also assessed. Dental examinations - The study was carried out as part of the ordinary dental service to the community. Children were called in for routine examination according to lists supplied by the local comtiiunity. Residence in the town or surrounding country district was recorded at the time of the visit. Examinations were performed by one operator (H.B.) who then consulted the other operator (S.R.S.) in cases of doubt and for interpretation of bitewing radiographs. Each child was examined in the satne dental chair using the lighting attached to the unit. Dental caries was detected with tnirrors and used probes and the teeth were air-dried prior to examination. The criteria adopted for caries presence and caries scoring were as described by WHO (12) with the exception that the children were also examitied with bitewing radiographs for detection of approximal caries. This was scored if a radiolucency had reached the dentin. A sealed surface was registered as intact unless it obviously covered a posterior composite filling and the presence of fissure sealants was recorded. Initial caries (WHO category 0) was omitted from the registration. . . , , . , . . . .
-
'
. . .
Bacterial sampling - Samples for bacterial analysis were collected frotii the dorsum of the tongue according to the method described by BEIGHTON (13). This method is reliable, gives results comparable with other methods and is easier to use on small children. The 10 ^il samples were dispersed in 1 ml volurnes of Reduced Transport Fluid (14) and sent by express airmail to Reykjavik where they were received and handled within 24 h of the samples being taken. Culture for S. mutans and lactobacilli was on MSB and Rogosa media respectively exactly according to HOLBROOK & BEIGHTON (8). Freventive measures - Dental treatment and preventive measures were performed on these children according to clinical needs. All children received fissure sealing of molar teeth if clinically indicated and fiuoride varnish (Duraphat, Woehlm, Eschwege, Germany) was apphed routinely to all teeth at the end of treatment. After the pilot study (5) chlorhexidine gel (Hibitane Dental Gel, ICI, England) was prescribed for those 15 children thought to be at greatest risk of developing a large amount of caries based largely on the culture of > 10' cfu/ inl S. mutans from the bacterial specimens. Chlorhexidine was applied to the teeth with a new toothbrush by the parents and according to printed instructions from the investigators. The preventive measures were repeated after 6 months. This district has received dental treatment according to the scheme outlined above since spring 1987 with the exception of chlorhexidine therapy, which was only begun in 1989. Results
'
Caries prevalence - Of the children aged 3-16 yr resident in the district, 188 (96.4%) were examined. One child attended a dentist in Reykjavik and five were away from the district for most or all of the study period. The prevalence of dental caries recorded for children is shown in Table 1. Data from 2-yr age groups were combined because the
Table 1
^
_ /
.
\
Prevalence of dented caries (dmfs, DMFS), new lesions (d, D) and proportion of children caries-free examitied al mean ages 4-16 yr in the Vopnafjordttr district of E. Iceland Mean caries scores Mean (SE) d (SE) DMFT % caries-free n D age (yr) DMES dmfs _ _ _ — 0.7 1.7 20 70.0 4 2.1 1.0 0.5 0 0 29 0 48.0 4.1 0 6 0.4 2.2 0.4 0.7 25 0.3 8 1.8 12.5 12.7 — — 0.6 1.6 34 35.3 10 2.8 0.3 — — 1.1 0.4 2.6 22.6 12 31 4.7 — — 1.4 5.7 7.9 14 38 0.8 10.7 2.5 11 6.6 0 11.6 0.2 16 SE = standard error of the mean.
Caries in rural Iceland
301
Table 3
5
5-6y (dmfs) 11-12y(DMFS) 14-15y (DMFS)
a a
CARIES SCORE
Prevalence of dental caries in children in Vopnafjordur district of E. Icetand atiatyied according to residence in town or country district Country Town Caries Caries score % score % (dmfs/ caries(dmfs/ cariesMean DMFS) free DMFS) free age (yr) 0 4.1 38.7 100.0 4-6 2.0 44.7 2.0 7-10 (permanent) 60.0 7.9 3.4 11-13 15.2 30.8 8.3 4.3 13.2 14-16 0
Fig. 1. Distribution of caries scores among children in three age groups in Vopnafjordur.
numbers of children per year were rather small (ca. 15). A large proportion of children in the youngest age groups were caries-free whereas the older children had considerable past experience of caries. Caries was unevenly distributed among children in all age groups but particularly in the younger children. The distribution of caries among children aged 5-6 yr, 11-12 yr and 14-15 yr is shown in the Figure. Children aged 14-15 yr showed a distribution of caries resembling a normal curve. In the younger age groups the distribution of caries was skewed to the left of the graph with many children having little or no caries. Table 2 shows the proportion of the total caries scores (dmfs or DMFS) attributable to the 25% of each age group most affected by dental decay. For both primary and permanent dentitions 25% of the younger children account for about 70% of the total caries score but this declines to about 50% of the total caries score when the teeth have been erupted for about 8 yr. The differences in caries prevalence between children living in the town and the surrounding country district are given in Table 3. There was a lower mean caries score among all age groups of children resident in the country district. The differences in the proportion of children caries-free is most strikTable 2 Distribution of caries among children in each age group Proportion (%) of total caries score (dmfs or DMFS) represented by the 25% of children most affected by caries Mean age (yr) % of DMFS l of dmfs 4 70.4 6 69.8 8 87.5 52.2 67.8 to 64.6 12 53.3 14 50.8 16
ing for the youngest children but this difference declines with age and is not seen by 14 yr. Incidence of caries - The incidence of caries in tooth surfaces for primary teeth (d) and permanent teeth (D) is shown in Table 1. Many 4-yr-old children were attending the dentist for the first time. For all other age groups the incidence of new lesions was !0' cfu/ml (y) 4-5 dmfs 4.1 1.8 ds 0.3 0.4 6-7 5.5 dmfs 3.1 0.3 ds 8-9
DMFS DS
0.4 0.1
•
10-11
DMFS DS
2.7 0.4
-
12-13
DMFS DS
3.7 0.4
14-15
DMFS DS
11.6 0.9
lj
;o.7
/
2.7 0.2 4.9 6.5 9.6 0.8
^:
•:
Table 6 Comparison of bacterial parameters in pilot study with those recorded in main study Pilot study Main study Age (yr) 4-7 4-7 Mean count S. mutans cfu/ml 2.6x10' 4.6x10-'* Mean count lactobacilli cfu/ml 1.9 X IO" 3.5x10' Proportion with 5. mutans (%) 77.1 55.1^^ Proportion with lactobaeilli (%) 29.2 20.4 P
