Caries incidence in a cohort of primary school students in Lagos State, Nigeria followed up over a 3 years period.
The hallmark for caries management remains prevention. However, cost-effective prevention programs have to be based on evidence, otherwise there is a risk of waste of resources and development of new carious lesions. For children, the attendant problems associated with new caries is high with there being a high risk of adverse outcomes in terms of pain, infection and extraction [Milsom et al., 2002; Pine et al., 2006; Tickle et al., 2008]. These also affect the quality of life of a child [Low et al., 1999; Filstrup et al., 2003; Do and Spencer, 2007]. Efforts directed at implementing effective programs that prevent the development of new carious lesions is therefore a welcome development.
In Nigeria, there is evidence to suggest that attendance at dental care clinics is very poor [Oredugba, 2006]. Most children show up at the clinic for curative services and less so for preventive programs. Yet it is expected the incidence of dental caries will increase particularly as a result of a growing consumption of sugars and inadequate exposure to fluoride [WHO, 2003]. For prevention programs to work, it may therefore be important to move service to the point of care--at the communities.
School-based programs have been shown to be an effective means of implementing preventive oral health care [Axelsson and Lindhe, 1974, 1977; Axelsson et al., 1976; Kerebel et al., 1985]. It may well be one of the critical oral health intervention for school children in Nigeria where there are pointers to poor dental clinic utilisation despite identified oral health needs [Oredugba, 2006]. Yet, prevention programs for caries prevention for school children in Nigeria are important due to the evolving evidence that caries is one of the major oral health issues in children.
However, school based programs have to be designed taking cognisance of the peculiarity of the environment in which they are to be implemented [Klimek et al., 1985]. Also, in order for dentists to offer timely and effective preventive and restorative treatment to pupils, it is important we understand how dental caries in children behaves over time, particularly for children who attend elementary school.
The aim of this study therefore was to describe the progression of dental caries in pupils who had access to an education intervention programme over a three years period.
Materials and methods
This was a school-based epidemiological study designed to assess the incidence of caries in a cohort of school children. The pupils in the study cohort were observed at an individual level at two time points in the study: at baseline and at study completion. The study specifically assessed the number of new cases of carious lesions that developed, the number of teeth extracted because of caries, and the number of filled teeth because of caries over the study period. These parameters were used to assess the incidence, progession and severity of caries over the study period.
The study population was recruited from three primary schools in Lagos State, Nigeria. Lagos State is an urban centre with past reports showing a prevalence of dental caries ranging between 5.7-30.8%, low DMFT ranging between 0.1-0.72, and a high level of untreated caries with a restorative index of 1% [Idiakhoa, 2001; Sho-Silva, 2004; Giwa, 2005; Umesi-Koleosho et al., 2007]. Similarly, the prevalence of early childhood caries ranged between 6.4-22.5% with levels of untreated caries being as high as 95.6% and a dmft of 1.2 [Idiakhoa, 2001; Sowole, 2007; Abiola et al., 2009].
The cohort for the study was recruited in October 2000 and reviewed again in July 2003. Children who were aged 2-10 years old attending the three primary schools selected for the study in the year 2000 (when the baseline assessment was conducted) and who were present in the class on the day the school visit was conducted, were eligible to participate in the study. Children wearing orthodontic appliances or who were using prosthesis were excluded from the study. The schools were selected based on convenience: they were in the vicinity of the principal author's institution, and the school authorities had agreed to have the study conducted in their schools.
Both baseline and follow-up dental examinations were conducted for the pupils under the same conditions: in classroom settings with natural light using a non-magnifying mirror to assess for presence of carious and restored (filled) lesions. Caries was diagnosed using the WHO criteria for diagnosis in epidemiological studies [WHO, 1997]. Children's teeth were not air-dried or cleaned prior to the examinations. Gross debris was however cleared with gauze where necessary before examination of each tooth. The examining dentist followed a protocol for dental examination of the children. Data was recorded in the case record forms. Information recorded included the age at last birthday (in years), sex, and the caries status of each pupil. No radiographs were taken.
Caries status was determined using the deft and DMFT indices. Decay (d and D) were measured as any decayed crown with an unmistakable cavity on the pit or fissure or on a tooth surface. Filling (f and F) were measured as any crown with one or more permanent restorations irrespective of whether or not there was new decay on the tooth. Missing teeth (e and M) were teeth lost as a result of caries either due to an extraction or where retained roots were removed by any other means. The measures were simply recorded as present or absent. The interviewer specifically tried to verify the cause of missing teeth for any child with a missing tooth.
Specific questions asked included history of toothache, visit to the dentist, extraction of teeth at the dentist, recall of tooth exfoliation. Where a history pointed to the cause of a missing tooth being due to extraction as a sequelae to caries, the tooth was then charted as extracted (e) for the primary dentition or missing (M) for the permanent dentition. Otherwise a decision as to the status of a missing tooth was based on the clinical judgement of the dentist. After the conclusion of each child's oral examination, referrals for oral health care were written for all children who required dental treatment.
At the end of the examination, oral health education was provided for the students in each class. The brief 20 minutes discussion on the cause of dental caries, appropriate methodology for oral hygiene, and importance of dental visits for preventive oral health care was given to the pupils in their respective classes. Tooth brushing was also taught to the students using a dental model. The school children were provided with educational information once a year in each of their classes during the follow-up years.
The intra-examiner reliability was measured by comparing examination findings during repeated examinations of 15 children seen at two time points of 1-2 week intervals. Intraexaminer reliability was calculated for year 2000 and 2003 prior to the school visits to conduct the baseline and study exit oral examinations. Both percentage agreement and Cohen's kappa [Cohen, 1960; Hunt, 1986] were calculated from paired observations each year. The kappa value was 0.94 in 2000 and 0.97 in 2003.
The key outcome measure recorded in the study was the development of new cavities in any of the previously caries-free teeth. The presence or absence of caries was represented by the change in deft and or DMFT status.
Descriptive analysis was conducted to describe the study population. The incidence of new cavities was calculated at both the individual and tooth levels. Incidence rates for the development of new caries were calculated for all children who: were caries-free at recruitment; had caries at recruitment; were caries-free at recruitment but developed caries during follow-up. Relative risk (RR) analysis was also computed for caries-risk estimation. Data analysis was conducted using STATA version 0.8. Level of significance was taken as p<0.05.
Prior to the commencement of the study, information about the study was shared with all the eligible students in the schools in the classroom. They were also given information sheets about the study for their parents. Parents were asked to send back a section of the form refusing their child participating in the study if they did not want to participate. All children identified with oral diseases were given referral letters to enable them to access dental clincs of their choice for dental treatment.
A total of 250 children were recruited into the study cohort in 2000. This consisted of 119 males and 132 females. However, only 192 children of these children were seen in year 2003 (92 males and 100 females). A number of the children had transferred from the school during the study period. Retention rate for the study was 76.5%. None of the children were using orthodontic bands or prostheses during the period of the study. Table 1 shows the age and sex profile of the pupils seen in years 2000 and 2003. Data analysis was limited to the 192 children who had available data in the years 2000 and 2003. The profile (age, sex and caries status) of the 251 pupils who were initially recruited for the study and that of the 192 pupils whose data was analysed for this study did not differ significantly (Table 1).
The age range of the cohort at recruitment was 2-10 years. Two children were aged below 3 years. By year 2003, the age range of the cohort was 5-12 years. Table 2 shows the numbers of children in each birth cohort and the proportions of children who had caries in their teeth at recruitment and 3 years later.
Profile of caries in the study cohort in year 2000 In total, 152 (79.2%) children were caries-free at recruitment. Forty children had caries at recruitment in year 2000 as determined by their deft (ranged from 0-9) and DMFT status (ranged from 0-1). Within each birth cohort there was a considerable range in the number of carious teeth recorded, but the proportion of children caries-free was lowest in the oldest age cohort. The mean deft and DMFT of the cohort was 0.52 and 0.02 respectively. The highest deft (0.94) was found in the 7 years old cohort (Tables 1-2).
Profile of caries of the study cohort in year 2003 155 children were caries-free (80.7%) 3 years after the initial contact with the children. The deft ranged from 0-9 while the DMFT range from 0-1. The mean deft was 0.53 while the mean DMFT was 0.01. The highest deft (1.05) was found in the 8 year old cohort.
Caries incidence at the individual level The 152 children in the cohort who were caries-free at recruitment were included in the analysis of the incidence of developing a first cavity in the primary and permanent teeth. Of these, 16 children (10.5%) developed caries by year 2003 (Table 3). The cumulative incidence of caries for the cohort of children who were caries-free at the commencement of the study was 105 new cases per 1,000 children. This was highest for those who were 3 years old at recruitment (148 new cases per 1000 persons). The incidence density for the children who were caries-free at the beginning of the study was 35 new cases per 1000 person years with this highest incidence density found in children who were 3 years old.
Of the 40 children who had caries at the inception of the study, 21 (52.5%) developed new caries lesions (Table 4). The cumulative incidence of caries for the cohort of children who had caries at the commencement of the study was 525 new cases per 1,000 persons. This was highest for the children who were 6 years old at recruitment (909 new cases per 1,000 persons). The incidence density for the children who had caries at the beginning of the study was 175 new cases per 1000 person years with this highest incidence density found in children who were 6 years old.
The risk of developing caries over a three year period was significantly higher (RR=4.99; 95%CI = 2.88-8.64; p<0.001) in those who had caries in year 2000 than those who were caries-free in year 2000 (Table 5).
Risk of new caries lesion for caries-free teeth A high proportion of children who had caries developed new cavities when compared to those who were caries-free. The risk of developing new caries in the presence of an existing carious lesion appeared to increase with increasing deft and DMFT. This trend however could not be established as pupils with deft of 5 and 6 has less incidence of new caries when compared with those with deft of 1 to 4 (Table 6).
This study presents data on the caries incidence in a cohort of school children in Lagos State, Nigeria. The data relied on information generated from clinical evaluation of children by a calibrated dentist. The intra-examiner calibration conducted for the dentist in this study was needed for an epidemiological study of this nature. However, like all epidemiological studies, there is the possibility of under-reporting of caries in the study population since radiographs were not taken to rule out incipient or proximal caries.
Most of the children in this study were caries-free at presentation and remained so over the three year study period. In addition, the average deft and DMFT for the study population remained low over the study period. This was consistent with the reports of low caries severity in the study community [Akpata, 1979; Adegbembo et al., 1995; Sofola et al 2004].
Caries incidence was 9.9% over a 3 year period despite some level of preventive intervention in the form of oral health education for the study population. This risk was higher (RR=4.99; 95% CI= 2.88, 8.64) in children with prior carious lesions when compared to those who were caries free. This risk increased with the deft and DMFT though not in a linear fashion. This was confirmation that prior caries experience especially in the primary dentition was a positive predictor of developing new caries lesions later in life especially when specific caries preventive activities targeted at high risk children such as fissure sealing and fluoride therapy were not affected. This may be due to the higher density of caries-initiating organisms in the mouths of those with higher severity of caries which increases the risk of new caries formation [van Houte, 1994]. Also, since dental caries is a dietary carbohydrate-modified bacterial infectious disease [Milsom et al., 2008] one would expect a similar caries development pattern in the same individual especially when the dietary habits remained unchanged. This has significant implication for clinical management as pointed out by Milsom et al.  where the authors noted that children with caries and those without the disease should be considered as two different populations in need of different care strategies. The result of this study not only corroborate the observations of Milsom et al. but also reflects the need for children who are caries-free to be managed as children with low-risk for caries while those with caries should be managed as moderate or high-caries risk patients as specified by Council of Clinical Affairs, America Academy of Pediatric Dentistry . Evidence is however needed on how this risk management profile confers protection for the child taking cognisance of various environmental and social factors that could otherwise modify an individual's response to disease management.
Also, the impact of the dental education programme on caries prevention for this study population was not that clear cut. While the caries severity of the study population remained stable over the study period the analysis of the caries incidence at both the population and tooth levels gave a different result. The fact that new caries lesions were initiated in both the populations that were caries-free and had caries at the inception of the study, implied that there were other determinants of caries occurrence which were not affected by the education intervention. This may not be surprising as the intervention was directed at the children who obviously were not decision makers in their family and therefore may be able to do little or nothing to affect environmental and social factors impacting on their lifestyles.
This study however had limitations. The main drawback was that caries diagnostic criteria in the study were based on exclusion of non-cavitation (enamel caries lesion) for caries-risk prediction. Also, dental caries diagnosis was limited to visual examination. This means proximal caries lesions may have been missed leading to under-reporting of the caries in this study population. However, visual examination was conducted both at baseline and three years later. This should reduce the impact of such under-reporting of caries on the determination of the caries incidence in this study population. Secondly, an analysis of caries-risk based on the primary and permanent dentitions may have been more informative. However, the sample size of children with caries in the permanent dentition was quite small (3 pupils in year 2000 and 2 pupils in year 2003). Each of the pupils had a DMFT of 1. It would therefore have been difficult to conduct any meaningful analysis in terms of showing differences in caries-risk between primary and permanent teeth.
The caries incidence of 9.9% was higher in children who had caries previously compared to those who were caries-free. The risk of developing a new carious lesion was 5 times higher in children with caries when compared with children who were caries-free, increasing with the mean deft and DMFT, though not linear. Public health prevention measures should differ based on caries-risk of children. High-risk caries prevention intervention should be targeted at children who present with dental caries very early and these interventions should start most appropriately by age 2-3 years.
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M.O. Folayan *, O.O. Sofoca **, A.B. Oginni ***
* Department of Child Dental Health, Obafemi Awolowo University, Ile-Ife.
** Department of Preventive Dentistry, University of Lagos, Lagos.
*** Population Council, Abuja, Nigeria
Postal address: M. Folayan, Department of Child Dental Health, Obafemi Awolowo University, Ile-Ife, Nigeria.
Table 1. Age, sex and average deft/DMFT of the study cohort Age Male Female p value Average (years) (n) (n) deft/ DMFT Year 2000 (n=251) 2 4 3 0.0/0.0 3 14 13 0.0/0.0 4 12 25 0.51/0.0 5 18 26 0.41/0.0 6 29 23 p=0.21 0.52/0.02 7 17 23 0.63/0.0 8 12 14 0.50/0.04 9 5 2 0.0/0.0 10 8 3 0.18/0.5 Total 119 132 0.40/0.03 Year 2000 (n=192) 2 0 2 0.0/0.0 3 14 13 0.0/0.0 4 12 20 0.53/0.0 5 18 25 0.42/0.0 6 27 21 p=0.41 0.63/0.02 7 15 17 0.94/0.0 8 3 2 0.20/0.20 9 1 0 0.0/0.0 10 2 0 0.5/0.5 Total 92 100 0.52/0.02 Year 2003 (n=192) 5 9 14 0.17/0.0 6 10 24 0.74/0.0 7 19 26 0.36/0.0 8 25 15 1.05/0.03 9 19 17 p=0.20 0.42/0.0 10 7 2 0.0/0.11 11 2 2 0.0/0.0 12 1 0 0.0/0.0 Total 92 100 0.53/0.01 Table 2. Number of children in each age cohort and the deft and DMFT age (years) Number of decayed, extracted, filled or missing teeth children (deft and DMFT) in age category 0 1 2 3 4 5 6 7 9 Year 2000 2-2.99 2 2 0 0 0 0 0 0 0 0 3-3.99 27 27 0 0 0 0 0 0 0 0 4-4.99 32 26 3 1 1 0 0 0 0 1 5-5.99 43 34 4 3 1 0 1 0 0 0 6-6.99 48 37 3 2 3 1 1 1 0 0 7-7.99 32 22 3 4 0 0 0 2 1 0 8-8.99 5 2 2 0 0 0 0 0 0 0 9-9.99 1 1 0 0 0 0 0 0 0 0 10-10.99 2 1 0 1 0 0 0 0 0 0 Total 192 152 15 12 5 1 2 3 1 1 Year 2003 5-5.99 23 20 2 1 0 0 0 0 -- 0 6-6.99 34 28 1 0 2 1 1 0 -- 1 7-7.99 45 36 5 1 3 0 0 0 -- 0 8-8.99 40 28 1 2 1 5 3 0 -- 0 9-9.99 36 30 3 0 2 0 0 1 -- 0 10-10.99 9 8 1 0 0 0 0 0 -- 0 11-11.99 4 4 0 0 0 0 0 0 -- 0 12-12.99 1 1 0 0 0 0 0 0 -- 0 Total 192 155 13 4 8 6 4 1 -- 1 Table 3. Age specific incidence of caries among children that had no caries in year 2000 Age (years) Cohort (year 2000) Number of children developing new cavities (year 2003) 2 2 0 3 27 4 4 26 2 5 34 4 6 37 3 7 22 3 8 2 0 9 1 0 10 1 0 Total 152 16 Age (years) Cumulative incidence Incidence density (new cases per 1000 (new cases per 1000 persons) in year 2003 person-years) 2 0 0 3 148 49 4 77 26 5 118 39 6 81 27 7 136 45 8 0 0 9 0 0 10 0 0 Total 105 35 Table 4. Age specific incidence of caries among children that had caries in year 2000 Age (years) Cohort (year 2000) Number of children developing new cavities (year 2003) 4 7 5 5 9 3 6 11 10 7 10 3 8 3 0 Total 40 21 Age (years) Cumulative incidence Incidence density (new cases per 1000 (new cases per 1000 persons) in year 2003 person-years) 4 714 238 5 333 111 6 909 303 7 300 100 8 0 0 Total 525 175 Table 5. Relative risk of caries over the 3-year period Cumulative incidence Relative Risk Had caries in (new cases per 1000 (95%CI) of caries year 2000 persons) of caries No 105 1.00 Yes 525 4.99 (2.88, 8.64) Table 6. Number and percentage of children developing new cavities in previously caries-free teeth according to the number of carious teeth recorded at recruitment A B C 0 152 16 (11.0) 1 15 5 (33.3) 2 12 6 (50.0) 3 5 5 (100.0) 4 1 1 (100.0) 5 2 1 (50.0) 6 3 1 (33.3) 7 1 1 (100.0) 9 1 1 (100.0) A = Number of carious teeth at recruitment (deft and DMFT). B = Number of children. C = Number (%) developing new cavities in previously caries-free teeth
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|Author:||Folayan, M.O.; Sofola, O.O.; Oginni, A.B.|
|Publication:||European Archives of Paediatric Dentistry|
|Date:||Dec 1, 2012|
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