Oral health status in 12 and 15-year-old schoolchildren

both The health the Klein-Palmer system (D – Decayed, M – Missing, F – Filled The methods of descriptive statistics performed and p-values lower than 0.05 were considered statistically significant. The younger group included 214 children (52.3%) and the older group 195 (47.7%). Individual caries rate was higher in 15-year-old children (81.02%) comparing to 12-year-old (57%). The mean value of decayed teeth for all participants was 2.43 and of total DMFT was 8.99%.


INTRODUCTION
Oral diseases have been identified as one of the global public health issues related to health, psychosocial and economic aspects [1]. Tooth decay is, along with periodontal disease, the most frequent oral disease and represents a chronic, progressive, multifactorial process that leads to loss of dental hard tissues. Its etiology is complex and includes several factors, predominantly the presence of fermentable carbohydrates, host factors, and cariogenic microbial flora [2,3] However, there are also 'micro factors' that are related to individual level and family and 'macro factors' that are referred to social, economic, and cultural features of the country [4]. Caries shares common risk factors with some chronic, non-communicable diseases such as obesity, diabetes, cardiovascular and cerebrovascular disorders [3].
Childhood is a period of constant learning and social, cognitive, emotional, and educational development. Consequently, it is essential to embrace positive habits and attitudes towards oral health and oral hygiene in schoolchildren population. Caries prevalence, strategies for its prevention and diagnosis, treatment, and potential complications of caries lesions are subjects of many epidemiological and clinical studies [2].
Literature data indicate that some European countries and the United States of America have achieved significant results in caries prevention due to effective preventive programs and oral health education. Also, it has been shown that dental caries affects unequally countries with different socioeconomic status, with a higher prevalence in areas with a poorer socioeconomic indicator [5].
Caries prevention programs have the most efficient and long-term results. It is very important to analyze oral health status and identify potential risk factors for caries development in early childhood and adolescence. Obtained epidemiological data is indispensable for creating specific strategies in oral health promotion and preventive treatment [2]. Some authors suggest that the highest caries prevalence in permanent dentition is between 15 and 19 years [6]. Oral health status in 12-yearold children is considered a referent caries indicator in the population and is globally used in different research for evaluation of the success of preventive programs and comparison of the results [3].
The aim of the present study was to evaluate caries prevalence in 12 and 15-year-old schoolchildren in Cukarica, a municipality of Belgrade.

MATERIAL AND METHOD
The retrospective study included 409 schoolchildren of both genders, from two elementary schools located in Cukarica, one of the municipalities of Belgrade. They were all patients of Community health center Sremcica where a specialist in preventive and pediatric dentistry performed regular dental examinations. Their dental charts were analyzed and oral status characteristics gathered and registered using the Klein-Palmer DMFT system (D -Decayed, M -Missing, F -Filled teeth) [7].
Data were analyzed using SPSS Statistics 22 software (SPSS Inc., Chicago, IL, USA). The methods of descriptive statistics and testing statistical hypotheses were performed. For testing statistical significance among numeric variables, t-test was used, while for categorical variables chi-square test was done. P-values lower than 0.05 were considered statistically significant.

RESULTS
The present study included 409 schoolchildren located in Cukarica, one of the municipalities of Belgrade. In the 12-year-old group there were 214 children (52.3%) and in the 15-year-old group 195 (47.7%). Gender distribution in the younger group was 113 males and 101 females and in the older group 104 males and 91 females ( Figure 1).
In total, 31.54 % of children were caries-free (DMFTscore 0) and 68.46% had cavitated caries lesions on the permanent teeth. In 12-year-old schoolchildren, the percentage of children with decayed teeth was 57%. Number of males with all healthy teeth was 48, and females 44. On the other hand, number of children with caries lesions was higher, 65 males and 57 females ( Figure  2). In 15-year-old schoolchildren, only 19.2% of them had all healthy teeth and 82.3% had cavitated caries lesions on their permanent teeth. Number of children with all healthy permanent teeth was similar in males and females, 19 and 18, respectively. Number of schoolchildren with decayed permanent teeth was 85 males and 73 females ( Figure 3).
Individual caries rate, as one of the most important caries prevalence indicators, was higher in 15-year-old children (81.02%) comparing to 12-year-old (57%) and this was statistically significant (p<0.001). Separated analysis in each group showed that in 12-year-old children, individual caries rate was higher in males (57.52%) comparing to females (56.44%), without statistical significance (p=0.839). Similar findings were in the other group; it was also higher in males (81.73%) than in females (80.22). This difference was statistically significant (p=0.026).
The mean value of total DMFT was 8.99%. This value was higher in 15-year-old schoolchildren (11.06%) comparing to 12-year-old children (6.40%). DMFT gender distribution was different between groups, in younger schoolchildren group, this value was slightly higher in males (6.43%) comparing to females (6.35%) and in the older group it was lower in males (10.65%) than females (12.79%). The mean value of decayed teeth for all   participants was 2.43. In 12-year-old children, the mean value of decayed teeth was 1.66 and in the older group it was higher (3.26), and this was found to be statistically significant (t=-6.346, p<0.001). In 12-year-old females the mean value of decayed teeth was 1.65 and males 1.67. In the other schoolchildren group, it was 3.58 for females and 2.98 for males.
The mean value of DMFT in 15-year-old females was significantly higher compared to the 12-yer-old females (t=-4.836, p<0.001). The decayed (D) component of the DMFT index was dominant among other variables (52.08%). The percentage of filled teeth was 37.80% and the percentage of extracted teeth due to caries complications was 6.3%. Decayed permanent teeth were more present in the older group (62.60%) compared to the 12-year-old schoolchildren (42.50%), and it was statistically significant (chi-square=16.420, p<0.001). Even though obtained DMFT values were higher in 15-year-old females than 12-year-old females with statistically significant difference (t=-4.836, p<0.001), that difference was not found in the number of missing teeth among these two groups of schoolchildren even though 15-year-old children had more extracted teeth (13.3%) compared to 12-year-old children (9.8%).
The percentage of filled teeth (F) was higher in the older schoolchildren group (48.7%) than younger group (29.4%) and this difference was statistically significant (chi-square=15.995, p<0.001).

DISCUSSION
This study, conducted in the scope of the Belgrade municipality of Cukarica, included schoolchildren aged 12 and 15. Oral status of 12-year-olds has been the subject of many studies around the world since, according to the recommendation of the World Health Organization (WHO), children of this age are considered a standardized group for monitoring oral health, both due to the presence of permanent dentition and the fact that habits of preserving oral health are already formed [7]. In order to understand epidemiological situation of oral health better, it was important that children aged 15 were included in this research as the consequences of bad habits can already be noticed at this age [8]. Of the total number of children examined, 31.54% had all healthy teeth present. This data coincides with the research conducted on the territory of our country, that analyzed the state of oral health in children and youth [3]. If these results are compared with those in developed countries of Europe, such as Germany (ACI only 0.5 and with the tendency to decrease), Spain, where the value of the ACI index for 12-year-olds is 0.82, and for 15-yearolds 1.38, that is, countries in Asia, e.g. China (1.14), and Malaysia (1.36), it is quite clear that the Republic of Serbia is still in the group of countries with a high distribution rate of caries. [9.10] Among the countries with low values, the ACI particularly singles out Nigeria with a score of 0.16 [11]. However, it should be noted that compared to the countries in the environment, Serbia is showing significant progress. The average value of ACI in Montenegro is 3.43, in Bosnia and Herzegovina it is 4.89 in urban areas, and up to 6.74 in rural areas of BiH [12,13]. Also among the countries with high values of the average caries index is Poland with a value of 4.2 and Iran with 3.35 [14,15].
The Average Caries Index (ACI) for both age groups was 2.43, which indicates that caries in our area is permanently present and that fact represents a serious social and medical problem affecting the country.
If we compare these results obtained in the scope of one Belgrade municipality (2.43) with those recorded in the southern Serbia (4.22), it can be concluded that there is a difference between the caries index in children living in urban areas and children from rural areas [16]. It should be taken into account that many measures have been taken in the past decade to improve oral health of children in Serbia, especially in the field of prevention [17]. WHO expectations were that by 2020, the value of ACI in twelveyear-olds would be below 1.5 [18]. Our results obtained from the systematic review of the 2019/2020 school year, indicated that we are approaching the achievement of the set goal and that the average values of the caries index, in respondents aged 12, was 1.66.
WHO's study on the health behavior of young people aged 11, 13 and 15 (Health Behavior in School-aged Children; HBSC) was implemented in 49 countries around the world, including Serbia. According to the data for Serbia from 2018, 70.9% of the respondents stated that they brush their teeth more than once a day (82.6% girls and 59.9% boys), which goes in favor of schoolchildren in Serbia who have higher level of brushing culture compared to their peers from other countries in our region [19].

CONCLUSION
The results of this retrospective study showed that the presence of caries in schoolchildren aged 12 and 15 years was found in two-thirds of respondents (68.46%). In the group of 12 years, caries was present in 122 subjects (57%), while in 15-year-old children it was found in 158 subjects (82.3%).
The strategy of education, promotion of oral health, as well as the application of preventive and prophylactic measures should be implemented in less developed parts of Serbia. Intensive education of young parents is necessary for raising health awareness to achieve the same level of oral health as in developed countries of the world.