Abstract
Objectives: To assess prevalence and severity of dental caries, examine gender differences and assess the relationship of dental caries to socioeconomic status in a group of Libyan schoolchildren. Design and setting: A cross sectional observational study with cluster sampling within schools. Participants: A random sample of 791, 12-year-olds in 36 elementary public schools in Benghazi. Methods and main outcome measures: Dental caries was assessed using the DMFT and DMFS indices and WHO (1997) criteria. Information about socioeconomic status was collected through a dental health questionnaire. Results: The prevalence of dental caries was 57.8%. The mean DMFT and DMFS indices were 1.68 (SD ± 1.86) and 2.39 (SD ± 3.05) for all subjects and 2.90 (SD ± 1.56) and 4.14 (SD ± 2.97) for subjects with caries experience. Dental caries was more prevalent amongst girls (P = 0.002). There was a statistically significantly negative association between dental caries and the level of father’s education (P = 0.015). Conclusions: While dental caries prevalence in 12 year-old Libyan children was high, the mean DMFT was low compared with other developing countries, but higher than the WHO goal for year 2020. The high level of untreated caries is a cause for concern, representing a high unmet treatment need.
Key words: Caries, prevalence, children, Libya
INTRODUCTION
Dental caries is preventable, but it continues to be a major public health concern. Although the prevalence of dental caries has declined in developed countries during the last 30 years, it remains a significant dental disease and a major public health challenge in children and adults in developing countries1. Significant proportions of children and adults are still affected by caries and it is also still increasing in many countries where preventive therapies such as those involving fluoride are not available and the population has increasing opportunities to consume free sugars2. The World Health Organisation (WHO) had a dental global goal for the year 2000 for children aged 12 years3 to have a DMFT score of ≤3. The WHO global goal for the year 2020 is for a mean DMFT ≤ 1.5 for the same age group4.
The decline in prevalence of dental caries in developed countries is likely to be due to improvement in oral hygiene practices and introduction of fluoride containing dentifrices, along with increased dental awareness and comprehensive preventive programmes since sugars intakes have remained fairly stable in recent decades1., 5.. Furthermore, dental health information provided through schools may have improved the oral health habits and behaviours of the children. In many developing countries children do not benefit from preventive oral health programmes and the prevalence of dental caries in these countries is expected to increase in the future as a result of growing consumption of sugars and limited fluoride exposure6.
Despite the fact that caries is the commonest dental disease in children, little work has been done on determining the prevalence of caries amongst Libyan schoolchildren and only a few studies related to dental caries have been published. Monitoring the prevalence of dental caries is a key element in planning services and determining success or progress towards controlling this dental disease. In Libya, data from a cross-sectional observational study of dental caries in Tripoli involving 10–13-year-old children reported a mean DMFT of 1.587. A study by Hawew et al.8 in 1996 reported the oral health of 6 and 12-year-old children in two cities in Libya with different fluoride concentrations in the drinking water; Benghazi (0.8 ppm) and Jardinah (1.8 ppm). The mean dmft of 6-year-old children in Benghazi private schools was 3.12, and in Benghazi state schools was 2.32. In Jardinah state schools (there were no private schools in Jardinah) the mean dmft for 6-year-olds was 1.07, with 61% caries-free, while in the Benghazi state and private schools 62% and 67% of children respectively were caries-free. The DMFT of 12-year-old children from state (1.17) and private schools (1.12) in Benghazi was very similar, while the DMFT of children in the state schools in Jardinah (0.87), was lower. A study by Al-Shabarti et al.9 of 762, 6–12-year-old schoolchildren in Benghazi showed that the mean DMFT was 1.63, and the prevalence of dental caries was 50%. Similarly, in a younger Libyan population, a 2002 study investigating the prevalence of caries in 685 preschoolers in Benghazi showed that 58% of children had carious primary teeth (mean dmft 2.58)10. These results indicate that dental caries is increasing in children in Libya although it is not clear whether the increase is greater in some population groups. It has been suggested that higher educational levels are related to improved oral health11. The findings of a previous Libyan study of 10–13 year-olds suggested that children whose mothers had a high educational level had a lower caries experience than those children with mothers of low educational level7.
With this background in mind, the aims of this study were to determine the prevalence and severity of dental caries and examine gender differences in relation to the prevalence of caries and severity amongst 12-year-old schoolchildren in Benghazi, Libya. In addition, the relationship of dental caries and parents’ education levels, which was considered as a proxy measure of socioeconomic status was investigated to help focus the attention of the Libyan government for future planning and monitoring of dental services in Benghazi. The objectives were to undertake a dental examination of 12-year-old Libyan schoolchildren in Benghazi in order to assess the prevalence of dental caries and to ask these children to complete a dental health questionnaire on factors associated with dental caries.
MATERIALS AND METHODS
Ethical clearance and permissions from the Libyan Health Ministry, Education Ministry and local authorities to conduct the study in Benghazi were secured. Written informed consents were received from the parents/guardians and participant children.
The sample
This cross-sectional observational study was conducted in schools in Benghazi, Libya. There were 7,682 eligible schoolchildren in the target age group registered at 81 elementary schools in 15 districts in Benghazi. The government-funded public schools comprised 90% of the total number of schools in Benghazi. A cluster sampling method with schools as cluster was used, with a random selection of boys and girls from each selected elementary school made. The final sample was 791, 12-year-old schoolchildren (397 boys and 394 girls) resident in Benghazi, studying at the sixth grade in 36 elementary public schools which educated pupils of both genders. The sample size provided a 95% Confidence Interval of ±4% (standard error 2.04%).
Dental examination
Clinical dental examinations of participant subjects were conducted in the schools with the child seated in an ordinary classroom-type chair and using artificial lighting and a headlamp. The criteria were visual, limited to dentine caries and no further diagnostic aids were employed. One calibrated examiner (RH) dentally examined all erupted maxillary and mandibular teeth for dental caries in the children, using the DMFT and DMFS indices and WHO diagnostic criteria12. Data collection forms were based on those recommended by the WHO12.
Reproducibility of the study
To ensure the reproducibility of the application of diagnostic criteria between children and schools, two subjects in each school were re-examined on the same day as their initial dental examination. Overall, 70 subjects, 10% of the total sample, were re-examined, the examiner being blind to the identity of the subjects re-examined.
Questionnaire
There is no governmental classification of geographical areas based upon socioeconomic information in Libya, therefore, parents’ education levels were considered as an alternative measure of socioeconomic status. Information on factors associated with dental caries and socioeconomic information was collected through a questionnaire completed by the children, with instructions in how to complete the questionnaire given to subjects prior to completion.
Statistical analysis
Dental caries data were imported into MS Excel files by Newcastle University’s Data Preparation Service and the dental caries indices calculated using a programme developed in the School of Dental Sciences, Newcastle University 13. The derived data were then analysed using the Statistical Program for Social Sciences-SPSS 14.0 for Windows statistical programme (SPSS 14.0 for Windows) (SPSS Inc, Chicago, Illinois, US). Cohen’s Kappa12 was used to measure the level of intra-examiner agreement and the reproducibility of the application of diagnostic criteria for dental caries.
Prevalence of dental caries was calculated as the number and proportion of subjects with caries experience in the permanent dentition. Severity of dental caries was assessed using DMFT and DMFS indices and a Kolmogorov–Smirnov Z test used to assess the normality of distribution of the data. Measures of central tendency (mean, median) and dispersion (SD and IQR) of the DMFT and DMFS indices were calculated for all subjects and for subjects with caries experience. The subjects were categorised into three groups (without caries; lower caries experience (DMFT 1–3), higher caries experience (DMFT ≥ 4)) using the 50th percentile of the distribution of the DMFT amongst subjects with caries experience as the cut-off point between subjects with lower and higher caries experience. In the same way the subjects were also categorised into three groups based on their DMFS index: DMFS = 0, DMFS = 1–4 and DMFS ≥ 5. In addition, the subjects were also categorised into six groups using the DMFT distribution used by the WHO at 12 years14: without caries experience (DMFT = 0), very low caries experience (DMFT = 0–1.1), low caries experience (DMFT = 1.2–2.6), moderate caries experience (DMFT = 2.7–4.4), high caries experience (DMFT = 4.5–6.5) and very high caries experience (DMFT ≥ 6.6).
In addition, the Decay Index (DT/DMFT × 100%), the Missing Index (MT/DMFT × 100%) and the Care Index (FT/DMFT × 100%) were calculated for all subjects and dental caries data were cross-tabulated with gender. Associations between the experience of dental caries and socioeconomic variables were tested through a process of bivariate and multivariate analysis.
RESULTS
Written consents were obtained from 2,662 of the total of 3,014 subjects aged 12 years attending the 36 randomly selected schools all of whom were invited to participate in the study. This represented a response rate of 88.3%. From those children providing written consents, lists by school were made and the required sample number (791 pupils; 29.7% of the consenting children) was selected randomly and included in the study.
The levels of intra-examiner agreement in the assessment of dental caries, as measured by Cohen’s Kappa12 for the DMFT and DMFS indices were 0.95 and 0.93, respectively.
As Table 1 shows, 457 children (57.8%) had experience of dental caries and 334 (42.2%) were caries free. For all subjects (n = 791), the mean (SD) DMFT and DMFS was 1.68 (±1.86) and 2.39 (±3.05), respectively. The mean for the decayed component of DMFT and DMFS was 1.60 (±1.79) and 2.12 (±2.59), respectively. The D (decayed) component comprised the greatest proportion of the caries experience seen. The mean for the missing component (teeth missing due to dental caries) of DMFT and DMFS was 0.05 (±0.24) and 0.21 (±1.18) respectively. The mean F (filled) component comprised the lowest of all components of the indices at 0.03 (±0.28) and 0.06 (±0.54), respectively.
Table 1.
Mean (SD) DMFT and DMFS for all children (n = 791) and for children with caries experience (n = 457)
| Index | No. of subjects | Mean | SD | Decayed | Missing | Filled | |||
|---|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | ||||
| For all subjects | |||||||||
| DMFT | 791 | 1.68 | 1.86 | 1.60 | 1.79 | 0.05 | 0.24 | 0.03 | 0.28 |
| DMFS | 791 | 2.39 | 3.05 | 2.12 | 2.59 | 0.21 | 1.18 | 0.06 | 0.54 |
| For subjects with caries experience | |||||||||
| DMFT | 457 | 2.90 | 1.56 | 2.78 | 1.52 | 0.07 | 0.31 | 0.05 | 0.37 |
| DMFS | 457 | 4.14 | 2.97 | 3.69 | 2.43 | 0.35 | 1.53 | 0.10 | 0.71 |
For subjects with caries experience (n = 457), the mean (SD) DMFT and DMFS was 2.90 (±1.56) and 4.14 (±2.97), respectively. The mean for the decayed component of DMFT and DMFS was 2.78 (±1.52) and 3.69 (±2.43), respectively. The mean of missing component of DMFT and DMFS was 0.07 (±0.31) and 0.35 (±1.53), respectively. The mean for the filled teeth in the DMFT and DMFS was 0.05 (±0.37) and 0.10 (±0.71), respectively (Table 1).
For all subjects, the Decay Index was 95.2%, the Missing Index was 3.0% and the Care Index was 1.8%. While for subjects with caries experience, the Decay Index was 95.9%, the Missing Index was 2.4% and the Care Index was 1.7% (Table 2).
Table 2.
Mean (SD) DMFT and Decay, Missing and Care Indices for all subjects (n = 791) and for subjects with caries experience (n = 457)
| Index | Mean | SD | Decay Index (%) | Missing Index (%) | Care Index (%) |
|---|---|---|---|---|---|
| DMFT for all subjects | 1.68 | 1.86 | 95.2 | 3.0 | 1.8 |
| DMFT for subjects with caries experience | 2.90 | 1.56 | 95.9 | 2.4 | 1.7 |
Dental caries was more prevalent amongst girls (63.5%) than boys (52.1%); the difference was statistically significant (Fisher’s Exact Test; P = 0.002) (Table 3). The mean DMFT and DMFS was also statistically significantly higher in girls than boys (P = 0.002) (Table 4). When the association between the severity of dental caries and gender was tested according to the grouping systems for the DMFT index 14, similar statistically significant differences were observed. The proportion of subjects with very low, moderate and high caries experience was greater amongst girls than boys, while the proportion of subjects without, with low and very high caries experience was higher in boys. This association was also statistically significant (P = 0.002) (Table 5).
Table 3.
Significance of association (P values, Odds Ratio and 95% CI) between the number (N) and proportion (%) of subjects with or without dental caries experience and gender
| Experience of dental caries | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Gender | Girls | Boys | Both | ||||||
| Yes | No | Total | Yes | No | Total | Yes | No | Total | |
| No. subjects | 250 | 144 | 394 | 207 | 190 | 397 | 457 | 334 | 791 |
| % | 63.5 | 36.5 | 100 | 52.1 | 47.9 | 100 | 57.8 | 42.2 | 100 |
Fisher’s Exact Test; P = 0.002. OR = 1.594 (95% CI 1.199, 2.118).
Table 4.
Mean (SD), median, and interquartile range (IQR) for DMFT and DMFS and the significance of differences (P*) when categorised by gender
| Index | Gender | No. of subjects | Mean | SD | Median | IQR | P* |
|---|---|---|---|---|---|---|---|
| DMFT | Girls | 394 | 1.88 | 1.94 | 1.00 | 3.00 | 0.002* |
| DMFT | Boys | 397 | 1.48 | 1.76 | 1.00 | 3.00 | |
| DMFS | Girls | 394 | 2.71 | 3.28 | 2.00 | 4.00 | 0.002* |
| DMFS | Boys | 397 | 2.08 | 2.77 | 1.00 | 4.00 |
Mann–Whitney U test, statistically significant at P < 0.01.
Table 5.
Significance of association (P) between the number (N) and proportion (%) of subjects (i) without caries experience, with lower and higher caries experience (DMFT and DMFS), and gender, based on 50th percentile of distribution of DMFT and DMFS; and (ii) without, with very low, low, moderate, high and very high caries experience and gender based on DMFT categories used by WHO14
| Severity of dental caries experience | Girls N (%) |
Boys N (%) |
P (Linear Association Exact test) |
|---|---|---|---|
| (i) | |||
| No caries DMFT = 0 | 144 (36.5) | 190 (47.9) | 0.002* |
| Lower caries DMFT = 1–3 | 153 (38.8) | 133 (33.5) | |
| Higher caries DMFT ≥ 4 | 97 (24.6) | 74 (18.6) | |
| Total | 394 (100) | 397 (100) | |
| No caries DMFS = 0 | 144 (36.5) | 190 (47.9) | 0.001* |
| Lower caries DMFS = 1–4 | 161 (40.9) | 142 (35.8) | |
| Higher caries DMFS ≥ 5 | 89 (22.6) | 65 (16.4) | |
| Total | 394 (100) | 397 (100) | |
| (ii) | |||
| No caries DMFT = 0 | 144 (36.5) | 190 (47.9) | 0.002* |
| V. low caries DMFT = 0–1.1 | 55 (14.0) | 42 (11.0) | |
| Low caries DMFT = 1.2–2.6 | 56 (14.0) | 59 (15.0) | |
| Moderate caries DMFT = 2.7–4.4 | 108 (27.0) | 85 (21.0) | |
| High caries DMFT = 4.5–6.5 | 24 (6.0) | 19 (5.0) | |
| V. high caries DMFT ≥ 6.6 | 7 (2.0) | 2 (5.0) | |
| Total | 394 (100) | 397 (100) | |
Statistically significant at P < 0.005.
With regard to level of parental education, the highest proportion of caries-free subjects was observed amongst those children whose fathers were educated to higher education levels, representing a statistically significant negative association (P = 0.015) between caries experience and father’s educational level (Table 6). When fathers’ educational level was included as a variable in the multivariate analysis it was found to be independently associated with caries experience of their children (P = 0.008; OR 0.699, 95% CI 0.536, 0.912).
Table 6.
Relationship between the number (N) and proportion (%) of subjects with and without caries experience and parents’ educational level
| Parents’ education | Total no. of subjects | Experience of caries | P* | Contingency coefficient | +/−† | |
|---|---|---|---|---|---|---|
| Yes N (%) |
No N (%) |
|||||
| Mother’s educational level | ||||||
| Illiterate | 51 | 31 (6.8) | 20 (6.0) | 0.924 | ||
| Up to secondary school‡ | 454 | 260 (56.9) | 194 (58.1) | |||
| Higher§ | 286 | 166 (36.3) | 120 (35.9) | |||
| Total | 791 | 457 (100) | 334 (100) | |||
| Father’s educational level | ||||||
| Illiterate | 17 | 11 (2.4) | 6 (1.8) | 0.015* | 0.088 | −ve |
| Up to secondary school‡ | 367 | 228 (49.9) | 139 (41.6) | |||
| Higher§ | 407 | 218 (47.7) | 189 (56.6) | |||
| Total | 791 | 457 (100) | 334 (100) | |||
Linear Association Exact Test. Statistically significant at P < 0.05 (OR: 0.699; 95% CI: 0.536, 0.912).
Direction of association.
Elementary school and intermediate school.
College/postgraduate.
DISCUSSION
The study sample was from Benghazi which is the second largest city in Libya after the capital, Tripoli. The study sample included 36 schools drawn from 15 different districts with different socioeconomic groups and cultures and was sufficiently large (n = 791), to make the study sample reasonably representative of 12-year-olds in Benghazi and other urban regions of Libya.
The present study provided useful information about the prevalence and severity of dental caries in 12-year-old Libyan schoolchildren in Benghazi and these findings contribute to the overall picture of Libyan schoolchildren’s dental health, although they may be an underestimate of the disease present as clinical radiographic examinations were not included.
The prevalence of dental caries in these Libyan 12-year-olds was high; 457 subjects (57.8%) had experience of dental caries. When compared, the prevalence of dental caries observed was higher than that found in a similar age group in Tunisia (48.3%), Uganda (40.2%), Iran (36.2%), the UK (32.7%), Italy (43.1%) and India (10%)15., 16., 17., 18., 19., 20.. Conversely, the prevalence of dental caries found in the present study was lower than that in Riyadh and Qaseem, Saudi Arabia (92.3% and 87.9% respectively), in the Philippines (74.9%) and Brazil (78%)21., 22., 23..
The mean DMFT of the 12-year-olds in the present study was 1.68 (SD 1.86) therefore, the study population met the WHO goal for 20003, but not for the Year 20204. The overall mean DMFT in the present study was much lower than that reported by previous studies conducted in other developing countries, in Hungary (3.8), Saudi Arabia (5.06), Oman (3.23), Kuwait (2.6), the Philippines (3.68) and Brazil (3.95)21., 22., 23., 24., 25., 26..
The decayed component (D) was the highest component of the DMFT index, representing 95.2% of the DMFT for all subjects and 95.9% for subjects with caries experience. This was higher than that observed in studies of 12 year-old children in Mexico (82.3%), Tunisia (44.7%), Iran (58.7%), in Iraq (54.8%), India (73%) and Romania (89%)15., 16., 19., 27., 28., 29.. This could be due to exposure to caries-associated risk factors such as poor oral hygiene, less exposure to fluoride through limited tooth brushing30, absence of dental hygienists in Benghazi, and frequent consumption of free sugars. Furthermore, the absence of dental health education and public caries prevention programmes in Libya may have contributed to the high prevalence of dental caries.
High levels of caries are usually related to high treatment needs and the high level of untreated caries which dominated the observed DMFT and represented unmet treatment need is a cause for concern and may be an indicator of the inability of dental services to cope with a dental caries problem. In Libya, dental services within communities and within the school dental services are not able to provide all the dental treatment needed by children9 and therefore children may be forced to seek dental treatment from private dental services, which are expensive.
The Missing index was 3.0% for all subjects and 2.4% for subjects with caries experience. This figure was lower than that found for similar age groups of children in France (11%), in Iran (3.4%), Iraq (3.6%) and India (7%)16., 19., 27., 31.. In contrast, the lowest component of the index was the filled (F) component. The Care index which reflects the restorative care of those who have suffered dental caries was 1.8% in present study; less than that found in the UK (42% and 48%), Tunisia (5%), Oman (3%), Iran (37.9%), three surveys in Brazil (50.5%, 66.4%, 56.3%) and in India (13%)15., 16., 19., 20., 25., 32., 33.. This may have arisen because of poor access to oral health services, with the low ‘Filled’ component being an indicator of the inability of current dental services to adequately treat children’s decay. Other factors such as lack of parental dental awareness of the importance of treating caries in childhood due to their erroneous belief that children’s teeth are replaceable and not important may have contributed to this pattern of caries experience. Most oral health services in Libya provide symptomatic treatment rather than restoration and prevention9.
The mean DMFT in girls (1.88) was statistically significantly higher (P < 0.002) than in boys (1.48), similar to the findings of some studies18., 22. but not others11., 16., 29.. In the present study, the prevalence of dental caries experience was slightly lower in boys as compared with girls even though girls generally pay greater attention to hygiene and aesthetics than boys. This might be partially explained by the fact that generally there is a trend towards earlier permanent tooth eruption in girls than boys and they are exposed to risk factors for dental caries for a longer period of time than in boys. However, the differences in eruption times are only a few months which may result in little clinical difference.
The Decay Index was 95.2% in the present study, similar to other dental epidemiological surveys in the same age groups in Libya; 71.8%, 84.8%, 90.6%, 77%7., 8., 9., 34., respectively and increased over time, being greater in the more recent studies. In addition, the Care Index was low in this study (1.8%) and showed a downward trend over time when compared with similar age groups in Libya; 15%, 1.9%, 5%, 1%, respectively7., 8., 9., 34.. This downward trend in the Care Index might be due to limited access to dental services, despite the growing number of children in Libya.
When comparing the mean DMFT found in the present study (1.68), a similar figure (1.7) was observed in Iraq27, while lower DMFTs have been observed in Portugal (1.5)35, Tunisia (1.3)15, and in Egypt (1.2)15. An almost similar figure was reported in Mangalore, India (1.83)36, but, the prevalence of dental caries (82.5%) was much higher than that observed in the present study.
On the other hand, contrary to the relatively low mean DMFT in the present study, most studies undertaken in developing countries have shown relatively high mean DMFTs; 2.6, 2.3, 3.2, 3.7, and 3.31 in 12-year-old schoolchildren in Kuwait, Syria, Jordan, the Philippines and Romania, respectively23., 24., 29., 37., 38.. Similarly, the mean DMFT in the present study was lower than that found in Sudan (2.6), Jordan (4.74), two regions in Saudi Arabia (5.06 and 4.53), Oman (3.23), Saudi Arabia (5.2) and Brazil (3.95), respectively21., 22., 25., 39., 40., 41.. The authors suggested that these high figures were due to caries-related risk factors such as oral hygiene and dietary practices. In contrast, the DMFT found in Uganda (0.98) and in Iran (0.77)18., 19. in 2006 were lower than that found in the present study. Downward trends in caries experience have been reported in 16 developing countries from 1970 to 2000 in Latin America and the Caribbean42, while the mean DMFT declined from 5.0 in 1985 and 4.3 in 1991 to 3.8 in 1996 in the East European country of Hungary26. The mean DMFT in 12-year-old Libyan schoolchildren in the present study was still substantially lower than the mean DMFT reported in these developing countries and nearer that reported in the UK43., 44. In the present study, the experience of caries decreased with fathers’ increasing educational level. The highest caries-free proportion however, was observed among children whose fathers were educated to college/postgraduate level and this negative association was statistically significant. These results suggest a strong influence of a parents’ educational level on the pattern of dental health of their children and confirm the findings of a previous Libyan7 and UAE45 study. In contrast, a study conducted in Iraq in 2007 reported that caries experience rose significantly with higher education of the mother27.
In conclusion, although the prevalence of dental caries in 12-year-old Libyan children was high at 57.8%, the mean DMFT was low compared with other developing countries and met the WHO goal for year 20003, but was higher than the WHO goal for year 20204. Statistically significantly more caries occurred in girls than boys. Higher parental educational levels were statistically significantly associated with a lower prevalence of dental caries in their children. The high level of untreated caries was a cause for concern. It represented a high level of unmet treatment need and demonstrated the necessity to target oral health services towards prevention programmes and oral health promotion in order to improve the oral health status of children in Libya and to achieve the WHO goals for oral health.
Acknowledgements
This study was sponsored by the Ministry of Higher Education, Libya. The authors would like to thank all children, parents, schools staff and local authorities in Benghazi for their cooperation with the study. We would also like to thank Professor June Nunn for calibration of the researcher in the use of the dental caries index.
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