Dental caries prevalence among intermediate and secondary school students in Thamar – Yemen

Aims: To determine the prevalence of dental caries among intermediate and secondary school students 13–16 years old to determine the age and sex difference and to obtain data that can help in planning preventive dental health programs for school students in Yemen. Materials and Methods: A random sample of 512 intermediate school students,449 secondary school students were examined. Intermediate school student sample was divided into 3 age groups namely 13,14,15 and secondary school student sample was divided into 3 age groups namely 16,17,18 years old. The WHO methodology (1997) was used to assess the individual tooth status. Results: The mean DMFT for the total sample was 5.2±0.13; which increased with the increasing of age from 4.54 to 4.84 to 6.47 for the age groups 13,14,15 years old respectively; without significant sex difference as total 5.44 for males and 5.14 for total females. Results of dental caries for the secondary school students showed that the mean DMFT for the total sample was 5.98± 0.14, which decreased with the increasing of age from 5.60 to 6.49 to 5.85 for the age groups 16,17,18 years old respectively, with peak value at 17 years old without significant sex difference, 5.74 for total males, 6.21 for total females. Conclusion: The mean DMFT for both intermediate, secondary schools increased with increasing age with statistical significant difference with no sex differences.


INTRODUCTION
Dental caries is a highly prevalent chronic sugar dependent infectious disease, affecting calcified tissue of the tooth and causing demineralization of the inorganic portion with subsequent destruction of the organic substance.The carious tooth never returns to its original state, even if it is treated. (1)hree factors (the epidemiological triad) play a role in the development of dental caries: the host (genetic predisposition, malnutrition during teeth formation and behaviour, such as dietary habits and oral hygiene practices); the agent (mainly streptococcus mutans); and finally the environment (lack of fluoride in water, lack of vitamin D and high consumption of refined sugars) (2)(3)(4) .These factors interact to produce a variety of dental diseases at varying rates and intensities.The factors contributing to these variations could be cultural, genetic, geographic and/or environmental in nature.Caries can be controlled by different measures, but it can never be truly prevented (5) .Dental caries has a worldwide distribution, regardless of sex, age, race and socioeconomic level (6) .
In many Arab countries, dental caries is increasing overtime, especially since the relatively recent economic growth, which has resulted in an increased consumption of refined sugar (7)(8)(9)(10)(11) higher than in other developing countries (10) .Lack of awareness about oral health practices has also contributed to the increase in dental caries.In Morocco, Sudan, Jordan and Lebanon, for example, the decayed, missing, filled teeth indices (DMFT) were 2.6,1.1,0.2 and 3.6 respectively in the 1970s and increased to 4.5, 2.1,1.7 and 5.0 respectively in the 1980s and 1990s (WHO unpublished data  1974, 1979,1984)  (12,13) .However, there is no study conducted on Yemen Republic concerning prevalence of dental caries except the present study concerning prevalence of dental caries among primary school children in Thamar which revealed a mean dmft for the primary dentition was 3.40±0.15.It was decreased with increas-Dental caries prevalence among intermediate and secondary school students in Thamar-Yemen ing age with significant sex difference (males was higher than females, while for the permanent dentition the mean DMFT was 3.35±0.12,which increased with increasing the age which statistically significant age difference, but with no sex variation. (14)he aims of this study were to determine the prevalence of dental caries in intermediate and secondary school students in Thamar Governorate.To determine age and sex differences in the prevalence of dental caries.To obtain data that can help in the planning preventive dental health programs for school children in republic of Yemen.

Oral Examination:
Examination of teeth was performed according to the basic method of oral health survey of WHO for the year 1997 assessing tooth status, DMFT index was used (15) .
The examination was carried out using plane mouth mirrors and sharp sickle shaped dental caries explorers.The examination was performed in classrooms.Students chosen randomly from the list were examined under natural day light.All teeth present in the mouth were examined in a systematic approach starting from the last upper right molar proceeding in an orderly manner from one tooth or tooth space till the last lower right molar.Information regarding name, age, sex of the child was registered on a special case sheet prior to the examination.
The data were analyzed using SAS program.The complete randomized design (CRD) were used for analysis of variance of data.Means were tested for their significant differences by using Duncan's Multiple Range Test at 0.05 level for 13, 14 and 15 years, and for 16, 17 and 18 years old school students.

RESULTS
Table (1)  The mean DMFT and standard error for the total sample were found to be 5.2 + 0.13, mean DT= 5.12 + 0.13, mean MT= 1.8 + 0.14 and mean FT= 1.86 + 0.21.Ratios of the components to DMFT were found to be DT/DMFT= 98.46%, M T/DMFT= 0.34%, FT/DMFT= 0.36%.So the highest percentage is for the decayed teeth followed by filled teeth.The mean DMFT appears to be increasing from 4.54 at 13 years old to 4.84 at the 14 years to 6.47 at the age 15 years old with statistically significant difference between them.
The mean DMFT for females in the total sample was 5.14, which is slightly lower than for males (5.44).This sex difference was found to be statistically not significant.
The mean MT for total males was 2.0 which is slightly higher than that of females (1.29) with statistically significant difference between them.
While the mean DMFT for secondary school students and its components were shown in Table (4).The mean DMFT for the total sample and its standard error were found to be 5.98 + 0.14, mean DT= 5.77 + 0.13, mean MT= 1.53 + 0.12 and mean FT= 2.26 + 0.35.Ratios of the components to the DMFT were found to be DT/DMFT= 96.48%, MT/DMFT= 0.25%, FT/DMFT= 0.6%.The highest proportion was for the decayed teeth.The mean DMFT appears to be increasing for the first two ages with statistically significant difference between them.The mean DMFT for females in the total sample was 6.21 which is higher than that for total males (5.74) but with no statistical significant difference between them.

DISCUSSION
The present study shows that the mean DMFT for intermediate school students for the total sample was 5.2 (4.54 at the age of 13 years, 4.84 at the age of 14 years, and 6.47 at the age of 15 years).The caries prevalence and severity among permanent dentition of this age group is increasing with advancing age.No significant difference was found between 13 and 14 years old, but significant difference was found between the ages 14 and 15 years old.This is attributed to the irreversibility of the caries process and accumulative nature of the disease.This finding is in agreement with many studies in the developed coun-tries (16-19) and in developing countries (19)(20)(21)(22)(23) .
The results reveled no statistical significant difference found between total males and females.This is in accordance with studies conducted in developed and developing countries (24)(25)(26) .The result of the mean DMFT at 13 years old was 4.54, according to WHO DMFT range at 12 years of 1995 (27).This DMFT is considered a high level (4.5-6.5), which is higher than many developed countries like Austria (4.2), Canada (3.7), Italy (2.9), Japan (3.6) and Russian Federation (3.5) and some developing countries like India (3.8) and Madagascar (27) .The result is higher than most of the Arab countries level except Lebanon, which is the highest for this age group ( DMFT=5) (27) .
According to WHO DMFT range at 12 years old for Yemen in 1987-1990 (27) which was (1.6-3.1) is considered low moderate) this range is much higher than that due to accumulative nature of the disease, lack of dental awareness and resources.
Among the studies carried out in Iraq the result of this study is higher than that of Khamrco and Al-Salman (28) in Mosul City Centre which revealed the mean DMFT for 10-14 years old was 3.75, also this mean is higher than that reported by Salman (29) among primary school children in Mosul City Centre which revealed the mean DMFT for 12 years was 2.84.
The differences in the two studies with this one may be due to the increasing age of the student and the accumulative nature of the disease which leas to increase in DMFT with increasing age.
Results of this study showed that the ratios of the components to the DMFT for the total sample of the intermediate school students were as follows: DT/DMFT=98.46%, MT/DMFT=0.34%,FT/DMFT= 0.35%.the highest proportion was for the decayed teeth.This may indicate that therapeutic dental services are limited due to inadequacy and lack of awareness.
The ratios of the components to the DMFT are nearly the same with that recorded by Salman (14) for primary school children indicating very little increase in the prevalence for the intermediate school students.
The mean DMFT for secondary school students for the total sample was 5.98 (5.60 at the ages 16 years, 6.49 at the ages 17 years and 5.85 at the ages 18 years.The caries prevalence and severity among this age group is increasing with advancing age.Significant difference was found between 16 and 17 years old but not significant difference was found between 17 and 18 years old.This is attributed to the irreversibility of caries process and accumulative nature of the disease.This finding is in agreement with many studies in the developed countries (21,24,30) and in developing countries (5,10,20,23,31) .
The results revealed no statistical significant difference was found between total males and females.This is in accordance with many studies conducted in developed and developing countries (20,24,30) .
The result of the mean DMFT at 18 years old was 5.85, accordance to WHO DMFT range at 18 years of 1995 (27) , this DMFT is considered a high level, which is more than that repeated for many developed countries like Austria (4.2), Canada (3.7), Italy (2.9), Japan (3.6) an Russian Federation (3.5) and some developing countries like India (3.8) and Madagascar (27).This result is higher than most of the Arab countries, and it is nearly the same as Lebanon (DMFT=5) (27) .
Results of this study showed that ratios of the components to the DMFT were as follows: DT/DMFT=96.48%, MT/DMFT=0.25%,FT/DMFT= 0.42%, the highest proportion was for the decayed teeth this may indicate that therapeutic dental services are limited due to inadequacy i.e. the need for services is far greater than the demand.The percentage of population seeking treatment on demand varied between (3-6%) (32);in Yemen.The main concern of the existing services is to satisfy the curative demands.This does not comply with the philosophy of a prevalence approach which concentrates on the primordial prevention including dental health education tooth brushing and the use of fluoridated dentifrice to achieve improvement in oral health.

CONCLUSION
The mean DMFT for the total sample for intermediate, secondary school students was 5.2, 5.98 respectively which increased with increasing age with statistical significant difference.The highest ratios of the components to the DMFT was for the decayed teeth followed by filled teeth then missing teeth.No significant sex differences between total females and total males were present concerning intermediate and secondary school students.
shows the distribution of the sample by age and sex.The sample of intermediate school students compose of 512 student.252 males (49.21%), 260 females (50.78%) divided into 3 age groups 13,14,15 years old.

Table ( 4
): Mean DMFT and its components ± SE by age and sex for secondary school students Means with the same letters are statistically not different (p> 0.05); SE: standard error Capital letters compare between total males and females (age).Small letters between brackets compare between total females and males (sex).Small letters without brackets compare between males and females within the same age group.