Introduction
Oral and dental health plays an important role in people’s general health [1] and is affected by various factors, such as the knowledge and attitude of a person regarding oral and dental health. Improving people’s knowledge and attitude in this regard will lead to more attention toward oral and dental health [5]. Tooth decay is a common and pervasive problem in developed and developing countries, and it is believed that it is increasingly spreading, especially in developing countries, and this causes an increase in treatment costs [9]. Knowledge of the level of decayed, missing, and filled teeth or other indicators allows communities to expand their programs in the direction of education, prevention, and treatment. Before planning for oral and dental health programs in schools, it is better first to check the level of tooth decay and related factors. Therefore, the present study was conducted to determine the rate of tooth decay and its relationship with knowledge, attitude, and performance in high school students in Islamabad-e-Gharb city. 

Materials & Methods
This study was a cross-sectional study conducted among 348 high school students in Islamabad-e-Gharb using Cochran’s formula, 5% error, and 95% confidence level. Students were selected through sampling in two stages, cluster and random. In the first stage, ten schools were selected in different parts of the city. In the second stage, one class was randomly selected from each school for each grade. Data collection was based on clinical examination and using a questionnaire. The equipment used in this study was a mirror, probe, and flashlight. A dental technician in cooperation with health experts performed the dental examination, and to measure other information, a questionnaire designed to measure knowledge, attitude, and performance (KAP) was used, which was designed by Yavari et al. and implemented in schools in Yazd city [14]. This questionnaire has four parts, measuring demographic information, knowledge, attitude, and performance. Data were analyzed using descriptive statistics, independent t-test, one-way analysis of variance, Scheffe’s post hoc test, and Spearman’s correlation coefficient at a significance level of less than 0.05 using SPSS 22.

Results
In this study, the mean and standard deviation of the age of first-, second-, and third-grade students was 12.63±1.65,  13.86±0.58, and 14.78±0.61 years, respectively (range: 13.78±1.37 years). Also, 348 students participated in this study. Of these, 197 students (56.6%) were girls and 151 students (43.4%) were boys, 113 students (32.47%) were first-grade students, 117 students (33.62%) were second-grade students, and 118 students (33.91%) were third-grade students. In this study, 335 students (96.3%) had decayed teeth. The mean and standard deviation of knowledge were 5.40±1.80, the attitude was 37.86±5.18, and performance was 15.71±4.28. The mean of Decay-Missing-Filled Teeth (DMFT index) was 6.07±3.47 and the mean of decayed teeth was 5.31± 2.90 (Table 1). No significant relationship was found between either DMFT index and decayed teeth with gender and parents’ occupation (P>0.05), but the analysis of variance results showed that the number of decayed teeth and DMFT index had a significant relationship with the mother’s education and educational grade of students so that the number of decayed teeth (P=0.023) and DMFT index (P=0.038) among students whose mothers had a diploma and university level of literacy were significantly lower than students with literate or low-literate mothers. The rate of decayed teeth in the second-grade (P=0.012) and third-grade (P<0.001) students was higher than in the first-grade students, and the DMFT index in the first-grade students was higher than in the second- (p=0.005) and third-grade (P<0.001) students (Table 2). There was no significant difference between the DMFT index and the number of decayed teeth with students’ knowledge and attitude regarding oral and dental health (P>0.05). Both the DMFT index (r=-0.124, P=0.021) and decayed teeth (r=-131, P=0.015) had a significant relationship with students’ performance regarding oral and dental health (Table 3).

Discussion  
In this study, the prevalence of tooth decay among students and its relationship with their knowledge, attitude, and performance were investigated. The results of the study showed that 96.3% of students had decayed teeth, which shows a relatively high prevalence and indicates the poor oral and dental health status in the study community. Premature tooth decay in children and adolescents in developing countries has been reported more than in developed countries [15]. The findings of the present study showed that the students had an average performance regarding oral and dental health, which is in line with the results of Mirzaei Alavijeh et al.’ assessing male and female students in Yazd city [1]. Holding training classes by the school health instructors for students and holding meetings with parents may improve the performance of students, which is recommended. The results of the present study showed that tooth decay had no significant relationship with students’ knowledge and attitude, but it had an inverse and significant relationship with students’ performance. This means that with the reduction of health behaviors, the average index of tooth decay increased. Consistent with our results, Shokouhinia et al. showed that girls’ knowledge and attitude had no significant relationship with DMFT, and only health behavior had an inverse and significant relationship with DMFT [25]. In the interpretation of the mentioned results, it can be said that knowledge and attitude alone do not cause performance, because despite the relatively high level of attitude, no correlation was shown with the decayed teeth and DMFT index, and the students’ performance had an inverse and significant relationship with decayed teeth and the DMFT index. It is suggested that future studies focus more on the factors that can improve students’ performance, because prevention is better than treatment, and designing educational interventions in adolescents to prevent teeth decay can be useful.

Ethical Considerations

Compliance with ethical guidelines
This study was approved by the Ethics Committee of the Kermanshah University of Medical Sciences (Code: IR.KUMS.REC.1397.548). 

Funding
Kermanshah University of Medical Sciences approved this research project (code:97555), and the Research Vice-Chancellor of this University has provided all the funds needed for this research.

Authors' contributions
Conceptualization: Nooshin Salimi, Ehsan Bakshi, and Elaheh Ezzati؛ Methodology and data collection: Nooshin Salimi, Ehsan Bakshi, and Faezeh Ezzati؛ Data analysis: Nooshin Salimi, Ehsan Bakshi, and Elaheh Ezzati؛ Editing & review: All authors.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank the respected colleagues of the vice president of research, all education authorities, teachers, school staff, and students of Islamabad-e-Gharb city who participated in this research. 

 

1. Mirzaei Alavijeh M, Jalilian F, Baghiani Moghadam M, Hatamzadeh N, ZinatMotlagh F, Dahaghin N. [Knowledge, attitude and practice of elementary schools students about oral health in Yazd (Persian)]. Iran J Pediatr.Dent. 2013; 9(1):43-50. [DOI:10.29252/ijpd.9.1.43]
2. Halawany HS, Abraham NB, Jacob V, Al-Maflehi N. The perceived concepts of oral health attitudes and behaviors of dental students from four Asian countries. Saudi J Dent Res. 2015; 6(2):79-85. [DOI:10.1016/j.sjdr.2014.09.002]
3. Al Subait AA, Alousaimi M, Geeverghese A, Ali A, El Metwally A. Oral health knowledge, attitude and behavior among students of age 10-18 years old attending Jenadriyah festival Riyadh; a cross-sectional study. Saudi J Dent Res. 2016; 7(1):45-50. [DOI:10.1016/j.sjdr.2015.05.001]
4. WHO. Oral health. Geneva: WHO; 2018. [Link]
5. Farhadtoski K, Bayani M, Sarlak H, Salimi Z. [Factors associated with chronic periodontitis risk: A case-control study (Persian)]. J Arak Uni Med Sci. 2020; 23(2):264-77. [DOI:10.32598/JAMS.23.2.6015.2]
6. Babaei Hatkehlouei M, Tari H, Goudarzian AH, Hali H. Decayed, Missing, and Filled Teeth (DMFT) Index among first-grade elementary students in Mazandaran province, Northern Iran. Int J Pediatr. 2011; 5(6):5069-77. [Link]
7. Shaghaghian S, Malekmakan L, Rahimian V, Savadi N. Dental caries status and its associated factors in pregnant women, Shiraz, Iran, 2014. J Oral Health Oral Epidemiol. 2017; 6(3):165-72. [Link]
8. Mohebi S, RamezaniI A, Matlabi M, Mohammadpour L, Nour Nsa, Hosseini E. The survey of oral-dental health of grade 3 students of Gonabad primary schools in 2007. Intern Med Today. 2009, 14(4):69-76. [Link]
9. Bazrafshan E, Kamani H, Mostafapour FK, Mahvi AH. Determination of the decayed, missing, filled teeth index in Iranian students: A case study of Zahedan city. J Health Scope. 2012; 1(2):84-8. [DOI:10.5812/jhs.5120]
10. Andegiorgish AK, Weldemariam BW, Kifle MM, Mebrahtu FG, Zewde HK, Tewelde MG, et al. Prevalence of dental caries and associated factors among 12 years old students in Eritrea. BMC oral health. 2017; 17(1):169. [DOI:10.1186/s12903-017-0465-3] [PMID] [PMCID]
11. Gao J, Ruan J, Zhao L, Zhou H, Huang R, Tian J. Oral health status and oral health knowledge, attitudes and behavior among rural children in Shaanxi, western China: A cross-sectional survey. BMC Oral Health. 2014; 14:144. [DOI:10.1186/1472-6831-14-144] [PMID] [PMCID]
12. Peyman N, Samiee Roudi K. [The effect of education based on the theory of planned behavior on caries prevention of permanent teeth in fifth grade students in Khaf city (Persian)]. J Mashhad Dent Sch. 2015; 39(2):123-36. [doi:10.22038/jmds.2015.4065]
13. Yousofi M, Behrouzpour K, Kazemi S, Afroughi S. [Dental caries and related factors among 7-12 year-old school children in Yasuj, Iran, in 2014 (Persian)] . Armaghane Danesh. 2015; 20(9):836-47. [Link]
14. Yavari M, Morowatisharifabad M, Haghi M, Rezaeipandari H, Hatamzadeh N, Azad E. [Study of knowledge, attitude, practice and oral health status among high school students in Yazd (Persian)]. J Tolooe behdasht. 2016; 14(6):261-75. [Link]
15. Oleksyn K, Rozhko M. Prevalence of dental caries among young people living in the regions with low fluoride levels. Galician Med J. 2018; 25(3):1-9. [DOI:10.21802/gmj.2018.3.7]
16. Basir L, Khanehmasjedi M, Araban M, Khanehmasjedi S. [Caries risk factors in students in Ahvaz, Iran (Persian)]. Payesh. 2020; 19(3):311-8. [DOI:10.29252/payesh.19.3.311]
17. Myint ZCK, Zaitsu T, Oshiro A, Ueno M, Soe KK, Kawaguchi Y. Risk indicators of dental caries and gingivitis among 10− 11-year-old students in Yangon, Myanmar. Int Dent J. 2020; 70(3):167-75. [DOI:10.1111/idj.12537] [PMID] [PMCID]
18. Mohammadi M, Vaisi Raiegani AK, Jalali R, Ghobadi A, Salari N. [The prevalence of dental caries in deciduous and permanent teeth in iranian children: A systematic review and meta-analysis (Persian)]. J Res Dent Sci. 2018; 15(3):180-9. [DOI:10.29252/jrds.15.3.10]
19. Eskandarizadeh A, Sajadi FS, Torabi M, Sharifi M, Amini Z, Sahebghalam B, et al. [Caries free prevalence among 6, 12 & 15-year old school children in Kerman during 2000-2005 (Persian)]. J Health Dev. 2015; 4(1):42-51. [Link]
20. Asdagh S, Nuroloyuni S, Amani F, Sadeghi Mazidi T. [Dental caries prevalence among 6-12 years old school children in Ardabil city, 2012 (Persian)]. J Ardabil Univ Med Sci. 2015; 15(1):39-45. [Link]
21. Shyam R, Manjunath B, Kumar A, Narang R, Ghanghas M. Relationship of sociodemographic factors on dental caries experience among 11-14-year-old schoolchildren in India. Indian J Dent Res. 2019; 30(6):948-53. [DOI:10.4103/ijdr.IJDR_380_17] [PMID]
22. Hemmati N, Setarehdan SK, Noubari HA. Multi-channel Near-Infrared Spectroscopy (NIRS) system for noninvasive monitoring of brain activity. Proceedings of 2012 IEEE-EMBS International Conference on Biomedical and Health Informatics. Jan 5 2012; Hong Kong, China. [DOI:10.1109/BHI.2012.6211548]
23. Shirzaiy M, Mohageri G. Evaluation DMFT and CPTIN Indices and related personal behaviors in the 12-years-old students. Dent Clin Exp J. 2018; 3(1):e65179. [DOI:10.5812/dcej.65179]
24. Maharani DA, Zhang S, Gao SS, Chu CH, Rahardjo A. Dental caries and the erosive tooth wear status of 12-year-old children in Jakarta, Indonesia. Int J Environ Res Public Health. 2019; 16(16):2994. [DOI:10.3390/ijerph16162994] [PMID] [PMCID]
25. Shokouhinia E, Mohammadi NK, Marashi T, Ghorbani Z. [Comparison of tooth brushing related knowledge, attitude and health behavior as well as dental health status among boy and girl students in elementary schools in district 4 of Tehran in 2015 (Perrsian)]. J Health Field. 2016; 4(1):11-7. [Link]