Prevalence of dental caries among 12–14 year old children in Qatar

Abstract

Background

To ensure the oral health of a population, clinicians must deliver appropriate dental services, and local communities need to have access to dental care facilities. However, establishment of this infrastructure must be based on reliable information regarding disease prevalence and severity in the target population.

Objectives

The aims of this study were to measure the incidence of dental caries in school children aged 12–14 throughout Qatar, including the influence of socio-demographic factors.

Materials and methods

A cross-sectional study was conducted in Qatar from October 2011 to March 2012. A total of 2113 children aged 12–14 were randomly selected from 16 schools located in different geographic areas. Three calibrated examiners using World Health Organization (WHO) criteria to diagnose dental caries performed the clinical examinations. Data analyses were subsequently conducted.

Results

The mean decayed, missing, and filled teeth index values were respectively 4.62 (±3.2), 4.79 (±3.5), and 5.5 (±3.7), for 12, 13, and 14 year-old subjects. Caries prevalence was 85%. The mandibular incisors and canines were least affected by dental caries, while maxillary and mandibular molars exhibited the highest incidence of dental caries. Dental caries were affected by socio-demographic factors; significant differences were detected between female and male children, where more female children showed dental caries than male children. In addition, children residing in semi-urban areas showed more dental caries than in urban areas.

Conclusion

Results indicated that dental caries prevalence among school children in Qatar has reached critical levels, and is influenced by socio-demographic factors. The mean decayed, missing, and filled teeth values obtained in this study were the second highest detected in the Eastern Mediterranean region.

1. Introduction

1.1. Dental caries

Dental caries is defined as a multi-factorial infectious disease caused by plaque bacteria. When food enters the mouth, bacteria metabolize fermentable carbohydrates, producing acids, which diffuse into hard dental tissue, and demineralize tooth enamel (Featherstone, 2008). In the absence of proper denial hygiene, this process has an increased likelihood of resulting in dental caries. Dental caries currently represents the most common chronic disease among children; it is five times more common than asthma, and seven times more common than seasonal allergies (U.S. Department of Health and Human Services, 2014). Yee et al. (2002) reported in third world countries, dental caries is the fourth most expensive disease to treat. For children of most low-income countries, treating dental caries is estimated at US $3513 per 1000 children, which would exceed the country’s total health budget (Yee et al., 2002). Dental treatment costs could easily exhaust a low-income country’s entire health budget, a budget that is already extended to its capacity, or simply does not exist. However, no country claims to have caries free children (WHO, 2003), and the explanation for why young children develop dental caries is complex.

1.2. Dental caries indicators

Dental caries is commonly measured by the sum of decayed, missing, and filled number of teeth (DMFT index) (WHO, 2000). This value has been widely applied to assess the dental caries status at the population level for public health planning and policy-making purposes (Jakobsen and Hunt, 1990). The DMFT index, first introduced by (Klein et al., 1938), is a cumulative caries measure, which indicates caries occurrence, including past and present dental caries. The DMFT index has been in use for more than 76 years, and it remains the most commonly employed epidemiological index for assessing dental caries (Broadbent and Thomson, 2005).

WHO and Federation Dentaire International (FDI) established the first global oral health goal, as follows: by the year 2000, children reaching the age of 12 will not possess an average of more than three decayed, missing, and filled permanent teeth (DMFT) (Aggeryd, 1983). During the following decades, most high-income countries reached or even exceeded these goals, but for many low-income countries, this remains a remote aspiration (WHO, 2000).

In 2003, the FDI, WHO, and International Association for Dental Research (IADR) issued “Global Goals for Oral Health 2020” (Hobdel et al., 2003). These goals provided guidance for local, regional, and national planners and policy makers to improve the oral health status of their populations. The new oral health goals were not numerically specific. Instead, each country could specify its own targets based on current disease prevalence and severity, local priorities, and oral health systems. Based on DMFT values, WHO generated a scale to classify caries severity: DMFT values between 0.0 and 1.1 were very low; 1.2–2.6 were low; 2.7–4.4 were moderate, 4.5–6.5 were high, and values exceeding 6.6 were very high (WHO, 2000).

Epidemiologic studies from different parts of the world reported that DMFT values and caries prevalence was high among school children (12–14 years old) in some countries, and higher than the figure recommended by WHO goals in Saudi Arabia, Puerto Rico, Peru, Albania, and Lithuania (Table 1).

Table 1.

Selected research studies on caries prevalence and DMFT for different countries.

Area	Author/year	Country	Sample size	Age	% Of caries	DMFT
Eastern Mediterranean region countries	El-Nadeef et al. (2009)	United Arab	1323	12	54	1.6
		Emirates	1328	15	65	2.5
	Al-Mutawa et al. (2006)	Kuwait		12	26.4	2.6
				14	21.7	3.4
	Al-Sadhan (2006)	Saudi Arabia	205	12–14	93.7	5.94
	Ahmed et al. (2007)	Iraq	392	12	62	1.7
	Pakpour et al. (2011)	Iran	380	12–16	20	2.62
	Nurelhuda et al. (2009)	Sudan	1109	12	30.5	.42
Other countries from different regions of the world	Subedi et al. (2011)	Nepal	325	12–13	53.2	1.6
	Grewal et al. (2011)	India	520	9–12	52.3	.86
	Masood et al. (2012)	Malaysia	1830		70.5	.58
	Yabao et al. (2005)	Philippines	1200	6–12	68.2	2.4
	Casanova-Rosado et al. (2005)	Mexico	1640	12	49.4	3.11
	Jamelli et al. (2010)	Brazil	689	12	71.8	2.9
	Delgado-Angulo et al. (2009)	Peru	90	12	83.3	3.93
	Elias-Boneta et al. (2003)	Puerto Rico	1435	12	81	3.8
	Hysi et al. (2010)	Albania	372	12	85.5	3.8
	Milciuviene et al. (2009)	Lithuania	5910	12	85.5	3.7
				15	92.9	5.6
	Pieper and Schulte (2004)	Germany		12	45.7	1.24
	Campus et al. (2008)	Italy	1333	13–18	59.1	1.94

1.3. Oral health in Qatar and study importance

In Qatar, the oral health care system is in transitional and developmental stages. Systematic data collection is vital to evaluate and plan oral health care for the public. The WHO Global Oral Data Bank (WHO, Oral Health Country/Area Profile, 2013) has collected data on caries prevalence in many countries. Unfortunately, to date, the dental caries status among the school children population in the state of Qatar has never been documented. The absence of dental caries prevalence data in Qatar prevents the organization of any community-oriented oral health promotion programs; therefore a systematic analysis of the dental caries status of Qatar was required. Based on these conditions, the results of the current study are novel, as no similar studies have previously been conducted among Qatar school children.

Therefore, the objectives of the present study were as follows:

• •Measure dental caries prevalence among 12–14 year old school children in Qatar.
• •Compare dental caries in Qatar by socio-demographic factors (gender, ethnicity, age, residence, and school type).
• •Compare dental caries results from Qatar with comparable findings from Eastern Mediterranean regions and other parts of the world.

2. Materials and methods

Ethical approvals for the study were obtained from the following three organizations: (i) Medical Ethics Committee, Research Center (Reference number: RC/11660/2011), Hamad Medical Corporation, State of Qatar; (ii) Research Ethics Sub-Committee, University of Gloucestershire, United Kingdom; (iii) Policy Analysis and Research Office, Supreme Education Council, State of Qatar. The participant pool was drawn from schools throughout Qatar, and schools were officially informed, and assured of confidentiality in the study findings. Following an explanation of the study objectives, written consent was obtained from the schools, and the children and their parents or guardians participating in the study.

2.1. Examiner selection, training, and calibration

Three dentists with previous experience in epidemiological surveys of dental caries were invited to participate in the study. A dental assistant trained in data entry assisted in recording data measured by each dentist during the study. An experienced senior researcher conducted 8 h of training using theoretical and practical activities. During the theoretical discussions, an expert examiner showed photographic slides with clinical examples of each criterion that would be used in the study. The presentation served to instruct dentists and data entry assistants on the criteria and examination methods to be applied, achieve initial standardization protocols, and improve reproducibility among the three dentists and data entry assistants.

Staff training, calibration, and methodological adjustments were performed in a pilot study that involved 30 children, who were not included in the final sample. In this study, the reliability of caries measurements were determined by the test–retest method described by Guilford (1965), and explained in more detail by Rugg-Gunn and Holloway (1974). During the practical phase, each dentist examined thirty children, discussed clinical diagnosis, study codes and criteria, recording, and other errors to reach an acceptable consistency level (Kappa >0.80). The calibration exercises were conducted in two periods of 4 h each, with a 1 week interval between each exercise. Intra-examiner congruency (same examiner in two or more occasions) was evaluated by comparing data from the first and second sessions, respectively. Inter-examiner congruency (variation in disease diagnosis between two or more examiners) was achieved by double-blind duplicated examination of the 30 children.

2.2. Sample size

2.2.1. School selection

The total number of Qatar government and private intermediate schools in the 2011–2012 academic year was 135 (Supreme Education Council, 2012; Qatar Statistics Authority, 2013); with the total number of 12–14 year old school children (Intermediate school children) during the same academic year totaling 40,440 (20,141 males and 20,299 females).

The Supreme Education Council provided a list of intermediate schools (12–14-year-old school children); and 16 schools (8 boy’s and 8 girl’s schools; 12 government and 4 private schools) were randomly selected from 13 different areas (urban and semi-urban) within the state of Qatar. This sample was chosen to ensure appropriate socio-demographic representation from all segments of society (gender, ethnicity, age, area, government, and private schools Fig. 1).

Figure 1.

Map of Qatar including 16 schools location.

2.2.2. Children selection within the school

A multistage random sample using a stratified random sampling technique with proportion allocation was employed (Levy and Lemeshow, 1980). WHO (1997) recommended the sample size in each age group (12, 13, and 14 years) range from a minimum of 25–50 for each sampling site. In this way, the range of variability in the population is adequately represented, i.e. the sample is representative of the population. Consequently, 40 children from each age at each sampling site were planned for selection; the survey sample size for each age group was calculated as follows:

Urban: six sites in the capital city	6 × 40 = 240
Six sites in two large towns	1 × 2 × 40 = 80
Semi-urban: one site in eight semi-urban locations	1 × 8 × 40 = 320
Total	16 sites × 40 children = 640

The distribution applied to three ages groups (12, 13, and 14 years); consequently, the total sample size that should be selected for the study was 3 × 640 = 1920 children. Attrition was expected during the study period; therefore an additional 280 children were added to the 1920 children. Therefore, 2200 school children were selected, which was sufficient to address the objectives of the study, and exceed the recommended WHO guideline sample size for a national basic oral health survey (WHO, 1997 Fig. 2).

Figure 2.

Sampling and inclusion procedure of school children.

The number of students selected from each school was determined based on total student body at each school. Finally, the classrooms were chosen on a random systemic basis, and each child was selected randomly from each classroom.

It should be noted, however, that in some areas, the desired number of children, i.e. sample size was not always met in the randomly selected schools; consequently the males and females were not equally represented. The variation resulted from an unwillingness to participate, and the number of children in some schools was below the number recommended to fulfill the sample size at each site (Table 2).

Table 2.

Distribution of socio-demographic characteristics by gender.

Variables	Total	Male	Female
	N = 2113 (%)	n = 1125 (53.2%)	n = 988 (46.8%)
Age (in years)
12	698 (33)	436 (38.8)	262 (26.5)
13	706 (33.4)	334 (29.7)	372 (37.7)
14	709 (33.6)	355 (31.6)	354 (35.8)
Nationality
Qatari	1293 (61.2)	756 (67.2)	537 (54.4)
Non-Qatari	820 (38.8)	369 (32.8)	451 (45.6)
Type of school
Public	1509 (71.4)	774 (68.8)	735 (74.4)
Private	604 (28.6)	351 (31.2)	253 (25.6)
Area (16 schools)
Urban
Al Saad	152 (7.2)	152 (13.5)	0
Al Gharafa	175(8.3)	118 (10.5)	57 (5.8)
South Madinat Khalifa	138 (6.5)	0	138 (14.0)
West Bay	230 (10.9)	230 (20.4)	0
Al Thamama	161 (7.6)	161 (14.3)	0
Al Muntaza	150 (7.1)	150 (13.3)	0
Al Waab	237 (11.2)	0	237 (24.0)
Total	1243 (58.8)	811 (72)	432 (43.8)
Semi urban
North
Al Khor	59 (2.8)	0	59(6.0)
South
Al Wakra	154 (7.3)	0	154 (15.6)
Umm Said	141 (6.7)	0	141 (14.3)
West
Al Jumailliah	73 (3.5)	36 (3.2)	37 (3.7)
Al Shahaniyah	313 (14.8)	148 (13.2)	165 (16.7)
Rawdat Rashid	130 (6.2)	130 (11.6)	0
Total	870 (41.3)	314 (28)	556 (56.3)

Visitation permissions and coordination with the schools was obtained from the Supreme Education Council and school principals to arrange a day for data collection.

Each child’s age was confirmed from school registries. School children below 12 or over 14 years of age were not invited to participate. A total of 87 children with in-complete examinations were exempted, and 2113 completed the study (Table 2). The 2113 children represented 5.3% of the total 12–14 year old school children in Qatar during the 2011–2012 academic year.

2.3. Clinical examination of dental caries status

Dental examinations were conducted from October 2011 to March 2012. All children were examined with a disposable mouth mirror, calibrated periodontal probe, tweezers, tray, gloves, mask, and a consistent light source in their school. The collected data were registered in a diagnostic chart for each child. Detailed identifier and socio-demographic information regarding each child, including age, gender, residential area, school name, class, dental examiner, and data recorder names were included in the diagnostic chart.

The examination procedures, instruments, and diagnostic criteria used in this study were based on a WHO (1997) recommended publication, where a tooth was considered decayed if a cavity was present; if a carious lesion and restoration were present, the tooth was recorded as decayed. All teeth were examined in a systematic order using the FDI tooth numbering system.

The examinations were performed in classrooms under florescent lighting with the child sitting on a conventional classroom chair. Based on visual-tactile criteria, caries diagnoses were documented using the DMFT Index (WHO, 2000) as follows: decayed/untreated caries (D); missing teeth/due to caries (M); filled/dental restorations for caries treatment (F), and teeth/index per tooth (T).

DMFT index scores for each child were computed for permanent teeth. Teeth extracted for orthodontic purposes, or those missing due to trauma or congenitally absent were excluded from data processing, and therefore did not contribute to the final missing teeth (M) score. Missing teeth (M) were counted only if the examiner definitively established tooth loss was due to caries. Finally, radiographic and fiber-optic trans-illumination examinations were not performed.

3. Statistical analyses

Data were verified for complete responses prior to data entry and analyses. Statistical Package for the Social Sciences (SPSS Inc., version 20, Chicago, Illinois, USA) was used for all statistical analyses. DMFT index scores were computed for each child. Differences in continuous variables between two groups were measured using a Student’s t-test, and among groups using a one-way Analysis of Variance (ANOVA). Alternatively, a Chi-square test was applied to measure differences between two or more categorical variables.

Binomial logistic regression was employed to identify any association between socio-demographic variables and dental caries. An a priori P < 0.01 level of significance was established, and significant variables were subsequently analyzed in a multinomial logistic regression through best subset method, with a priori P < 0.05 level of significance. Adjusted odds ratios with 95% confidence intervals were calculated for all significant variables in the final model. Model adequacy was assessed through Hosmer and Lemeshow (2000) goodness of fit test.

Inter and intra-examiner reliability was measured through Kappa statistics (Table 3). A Kappa value exceeding 0.80 was considered highly reliable, which was recommended by WHO (1997).

Table 3.

(a) Inter-observer agreement (three examiners) (N = 30). (b) Intra-observer agreement (three examiners) (N = 30).

	Examiner 2	Examiner 3
(a)
Examiner 1	0.89⁎	0.92⁎
Examiner 2	–	0.87⁎

	Agreement between 1st and 2nd observations
(b)
Examiner 1	0.94⁎⁎
Examiner 2	0.92⁎⁎
Examiner 3	0.90⁎⁎

^⁎Kappa coefficient (p < 0.001).

^⁎⁎Kappa coefficient (p < 0.001).

4. Results

4.1. Socio-demographic status

A total 2113 of 2200 school children completed the study; 1125 (53.2%) were males and 988 (46.8%) were females. The study population was composed of 698 (33%) 12-, 706 (33.4%) 13-, and 709 (33.6%) 14-year old children. The following socio-demographic data were collected, about 1293 (61.2%) children were Qatari, and 820 (38.8%) were non-Qatari; 1509 (71.4%) attended public schools, and 604 (28.6%) private schools; and 1243 (58.8%) resided in urban areas, and 870 (41.3%) in semi urban areas. Table 2 summarizes the socio-demographic data by gender.

4.2. Prevalence of dental caries

The number of caries free school children was 317 (15%), indicating the caries prevalence in school children in Qatar was 85% (Table 4). The mean DMFT value for 12-, 13-, and 14-year old children was respectively 4.62 (±3.2), 4.79 (±3.5), and 5.5 (±3.7) (Fig. 3). This indicated that as the age of the children increased from 12- to 14-years old, dental caries increased.

Table 4.

Mean caries indices by socio-demographic and other characteristics among school children in Qatar (N = 2113).

	DT	MT	FT	DMFT	Caries free
	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)	n = 317(15%)
Age (in years) ⁎⁎⁎
12 (n = 698)	3.51 (3.0)	0.11 (0.45)	1.00 (1.6)	4.62 (3.2)	107 (33.8)
13 (n = 706)	3.83 (3.4)⁎	0.13 (0.47)	0.84 (1.47)	4.79 (3.5)⁎	126 (39.7)
14 (n = 709)	4.25 (3.4)⁎	0.15 (0.47)	1.10 (1.86)	5.50 (3.7)⁎	84 (26.5)
Gender⁎⁎
Male (n = 1125)	3.80 (3.3)	0.11 (0.4)	0.83 (1.5)	4.74 (3.4)	185 (58.4)
Female (n = 988)	3.94 (3.2)	0.15 (0.5)	1.14 (1.8)§	5.23 (3.6)§	132 (41.6)
Nationality ⁎⁎
Qatari (n = 1293)	3.79 (3.3)	0.15 (0.5)	0.94 (1.6)	4.89 (3.5)	199 (62.8)
Non Qatari (n = 820)	3.97 (3.2)	0.90 (0.3)	1.03 (1.6)	5.10 (3.5)	118 (37.2)
Area⁎⁎
Urban	3.79 (3.2)	0.12 (0.4)	1.00 (1.7)	4.91 (3.5)	204 (64.4)
Semi urban	3.97 (3.3)	0.14 (0.4)	0.95 (1.5)	5.06 (3.4)	113 (35.6)
Type of school⁎⁎
Public (n = 1509)	3.97 (3.4)	0.14 (0.5)	1.01 (1.7)	5.11 (3.6)	230 (72.6)
Private (n = 604)	3.61 (2.9)§	0.10 (0.3)	0.91 (1.5)	4.62 (3.08)§	87 (27.4)

DT = Decayed teeth, FT = Filled teeth, MT = Missing teeth, DMFT = Decayed, missing and filled teeth.

^⁎p < 0.01 vs. group 1.

^§p < 0.01

^⁎⁎By student’s t-test.

^⁎⁎⁎By One way ANOVA test.

Figure 3.

Bar diagram showing mean DMFT among different age group children by gender.

DMFT analysis showed mean DT values were 3.51 (±3.0), 3.83 (±3.4), and 4.25 (±3.4), respectively for 12, 13, and 14 year old children. The mean MT values were 0.11 (±0.45), 0.13 (±0.47), and 0.15 (±0.47), respectively for 12, 13, and 14 year olds. The mean FT values were 1.00 (±1.6), 0.84 (±1.47), and 1.10 (±1.86), respectively for 12, 13, and 14 year old children. Results indicated due to the increased mean values, the DT component was the major constituent of the DMFT index.

Female children exhibited a higher mean DMFT value 5.23 (±3.6) than male children 4.74 (±3.4). Qatari children showed a lower mean DMFT value 4.89 (±3.5) than non-Qatari children 5.10 (±3.5). Children residing in urban areas had a lower mean DMFT value 4.91 (±3.5) than children residing in semi urban areas 5.06 (±3.4). Results indicated private school children had lower mean DMFT values 4.62 (±3.08) than public school children 5.11 (±3.6).

Decayed teeth (D) distribution by arch and tooth number is shown in Table 5. Caries lesions were not evenly distributed among different tooth types. The most commonly affected teeth in the maxilla were the first molars (29.9%), followed by second molars (11.8%), central incisors (5.5%), second premolars (4.9%), lateral incisors (4.5%), and second premolars (3.6%). The most commonly affected teeth in the mandible were the first molars (26.3%), followed by second molars (10%), second premolars (1.51%), first premolars (0.61%), central incisors (0.26%), and lateral incisors (0.20%). The least affected teeth were the canines in the maxilla (0.77%) and mandible (0.10%). A comparison of the maxillary and mandibular arch showed a higher caries frequency in the maxilla (60.9%) relative to the mandible (39.1%).

Table 5.

Distribution of decayed teeth (N = 5032) by arch and tooth number.

Tooth	Decayed teeth
	Right	Left	Total
Maxilla
1	166 (3.3)	111 (2.2)	277 (5.5)
2	130 (2.6)	99 (1.9)	229 (4.5)
3	20 (.39)	19 (.38)	39 (.77)
4	153 (3)	96 (1.9)	249 (4.9)
5	110 (2.2)	70 (1.4)	180 (3.6)
6	802 (15.9)	706 (14)	1508 (29.9)
7	300 (6)	292 (5.8)	592 (11.8)
Total			3074 (60.9)
Mandible
1	7 (.14)	6 (.12)	13 (.26)
2	6 (.12)	4 (.08)	10 (.20)
3	3 (.06)	2 (.04)	5 (.10)
4	16 (.32)	13 (.29)	29 (.61)
5	40 (.80)	36 (.71)	76 (1.51)
6	677 (13.4)	648 (12.9)	1325 (26.3)
7	270 (5.4)	230 (4.6)	500 (10)
Total			1958 (39.1)

The distribution of missing teeth (M) by arch and tooth number is shown in Table 6. The most commonly missing teeth in the maxilla were the first molars (54.7%), followed by second premolars (5.08%), first premolars (3.9%), second molars (1.17%), central incisors (0.78%), and lateral incisors (0.39%). The most commonly missing teeth in the mandible were the first molars (19.5%), followed by second premolars (4.3%), second premolars (6.64%), second molars (2.73%), and central incisors (0.39%). None of the subjects were missing the lateral incisors in the mandible. The least affected teeth were canines in the maxilla and mandible, in which none of the subjects were missing in the maxilla, and only one tooth in the mandible. A comparison of the maxillary and mandibular arch showed an increased frequency of missing teeth in the maxilla (66.1%) compared to the mandible

Table 6.

Distribution of missing teeth (N = 256) by arch and tooth number.

Tooth	Missing teeth
	Right	Left	Total
Maxilla
1	1 (.39)	1 (.39)	2 (.78)
2	1 (.39)	0 (0)	1 (.39)
3	0 (0)	0 (0)	0 (0)
4	9 (3.52)	4 (1.56)	13 (5.08)
5	5 (1.95)	5 (1.95)	10 (3.9)
6	75 (29.3)	65 (25.4)	140 (54.7)
7	1 (.39)	2 (.78)	3 (1.17)
Total			169 (66.1)
Mandible
1	0 (0)	1 (.39)	1 (.39)
2	0 (0)	0 (0)	0 (0)
3	0 (0)	1 (039)	1 (.39)
4	5 (1.95)	6 (2.34)	11 (4.3)
5	11 (4.30)	6 (2.34)	17 (6.64)
6	27 (10.5)	23 (9)	50 (19.5)
7	3 (1.17)	4 (1.56)	7 (2.73)
Total			87 (33.9)

The distribution of filled teeth (F) by arch and tooth number is shown in Table 7. The most commonly filled maxillary teeth were the first molars (47.1%), followed by second molars (7.5%), first premolars (2.96%), second premolars (2.70%), central incisors (0.79%), lateral incisors (0.63%), and canines (0.22%). The most commonly filled mandibular teeth were the first molars (31.2%), followed by second molars (3.92%), second premolars (1.85%) and first premolars (0.90%). The mandibular central incisors, lateral incisors, and canines were not filled in any of the study subjects. A comparison of the maxillary and mandibular arch showed an increased frequency of filled teeth in the maxilla (62%) compared to the mandible (38%).

Table 7.

Distribution of filling teeth (N = 1890) by arch and tooth number.

Tooth	Filling teeth
	Right	Left	Total
Maxilla
1	10 (.53)	5 (.26)	15 (.79)
2	7 (.37)	5 (.26)	12 (.63)
3	2 (.11)	2 (.11)	4 (.22)
4	30 (1.58)	26 (1.37)	56 (2.96)
5	24 (1.27)	27 (1.43)	51 (2.70)
6	453 (24)	438 (23.1)	891 (47.1)
7	70 (3.7)	71 (3.8)	141 (7.5)
Total			1175 (62)
Mandible
1	0 (0)	0 (0)	0 (0)
2	0 (0)	0 (0)	0 (0)
3	0 (0)	0 (0)	0 (0)
4	10 (.53)	7 (.38)	17 (.90)
5	16 (.85)	19 (1)	35 (1.85)
6	298 (15.8)	291 (15.4)	589 (31.2)
7	41 (2.17)	33 (1.75)	74 (3.92)
Total			715 (38)

4.3. Binomial logistic regression analysis

DMFT index scores were classified as binary data; i.e. children with and without dental caries. Binomial logistic regression was employed to identify any association between different exposure variables and dental caries (Table 8). Female children showed a significantly higher incidence of dental caries than male children (P < 0.05). Children residing in semi-urban areas showed a significantly higher incidence of dental caries than children residing in urban areas (P < 0.05).

Table 8.

Univariable logistic regression analysis of predictors for dental caries among children in Qatar (N = 2113).

Variables	Crude OR (95% CI)⁎	P-value⁎⁎
Gender
Male	1	0.048
Female	1.23(1.10–1.63)
Residential area
Urban	1	0.030
Semi-urban	1.32(1.03–1.69)

^⁎Outcome variable (1 = caries, 0 = caries free). Odds ratios based on univariable logistic regression analysis.

^⁎⁎Two sided P values based on −2 log likelihood ratio.

4.4. Multinomial logistic regression analysis

Variables significant at the P < 0.01 level of significance at the binomial level were analyzed in the multinomial logistic regression analysis using the best subset method (Table 9). One variable remained in the final multinomial logistic regression analysis for dental caries among children in Qatar. Children residing in semi-urban areas showed a significantly higher incidence of dental caries than children residing in urban areas and the difference was statistically highly significant (P < 0.006).

Table 9.

Multivariable logistic regression analysis for dental caries among children in Qatar (N = 2113).

Variables	Adj. OR (95% CI)⁎	P-value⁎⁎
Type of residential area
Urban	1	0.006
Semi-urban	1.48(1.12–1.96)

^⁎Model adjusted for age, Outcome variable (1 = caries, 0 = caries free). Adjusted odds ratios based on multivariable logistic regression analysis (Adjusted OR, By Hosmer and Lemeshow goodness of fit test).

^⁎⁎2 Sided p values based on −2 log likelihood ratio.

5. Discussion

To best of our knowledge, this is the first comprehensive overview based on empirically derived dental caries data among 12–14-year old school children in Qatar.

A 12–14-year old school children study group was selected based on the following criteria: (i) it is likely at these ages all permanent teeth, except third molars, will have erupted; and (ii) these age groups are considered the caries and disease trend global monitoring ages for international comparisons and monitoring (Aggeryd, 1983; WHO, 1997).

The DMFT index using WHO diagnostic criteria to identify dental caries was applied in the current study. However, WHO criteria grouped different stages of dental caries processes into one code (decayed), without differentiating the various dental caries stages, i.e. initial and advanced carious lesions; non-cavitated and cavitated carious lesions, which may subsequently under- or over-estimate dental caries and its severity (Pine and Harris, 2007). Braga et al. (2009) reported different diagnostic criteria to identify dental caries, such as the International Caries Diagnosis and Assessment System (ICDAS), which have shown utility in differentiating between the various dental caries stages not classified by WHO (Braga et al., 2009). The DMFT index using WHO diagnostic criteria to identify dental caries was employed in the present study for two primary reasons: (i) the majority of the published literature followed WHO criteria in diagnosing dental caries; consequently for comparative purposes across global populations, we adhered to the same methodology; and (ii) WHO excludes initial lesions from diagnostic criteria due to concerns over reliability in diagnosis, citing attempts to identify initial lesions increases examiner variability, resulting in unreliable data (Kidd et al., 2003); however including initial lesions (non-cavitated) in epidemiological surveys can be extremely valuable in early caries detection. Kidd et al., 2003; raised doubts in the reliability of including initial lesions (non-cavitated lesions) in determining caries prevalence.

Although a plethora of published studies on dental caries among different age groups in different regions around the world is available, data on dental caries have not been published from Qatar. Hence, the present study examined the prevalence of dental caries and the influence of socio-demographic factors in Qatar. The study showing dental caries data among 12–14-year old school children in Qatar raises great concerns as dental caries incidence in the study sample was 85%; and only 15% of the examined children were caries-free. If the results of the study group are used as proxy for the total Qatar population, and the high percentage of dental caries in the country is not immediately addressed and remains untreated, the severity of disease is likely to increase in the future. Our results might reflect poor oral hygiene, and the absence of oral health education. Additionally, current estimates indicated that WHO, 2000 goals have not been achieved for Qatar children (WHO, 2000).

Moreover, mean DMFT was 4.62 (±3.2), 4.79 (±3.5), and 5.50 (±3.7), respectively for 12-, 13-, and 14-year old children. These DMFT mean values are within the WHO (2000) “high” category (DMFT 4.5–6.5), and exceed the global goal of three or less decayed, missing, or filled teeth for the year 2000 (WHO, 2000). Interestingly, we found as age increased from 12- to 14-years, more carious teeth were observed; thus, the incidence of dental caries increased. These results were congruent with other studies (Wyne, 2004; Yabao et al., 2005; Shingare et al., 2012), and might result from poor oral hygiene, inadequate oral hygiene procedures, and neglect of dental treatment.

In addition, the present study revealed higher caries prevalence and mean DMFT compared to studies from other countries (Table 1). A comparison with data from other Eastern Mediterranean region countries showed the mean DMFT value for 12–14-year old school children in Qatar was among the second highest in Eastern Mediterranean region countries, and was only exceeded by Saudi Arabia in which the DMFT value was 5.94 (Al-Sadhan, 2006).

Furthermore, the DMFT score for 12-year olds was 4.79 (±3.2), higher than reports from other regions of the world, including Nepal (1.6), India (0.86), Malaysia (0.58), Philippines (2.4), Mexico (3.1), Brazil (2.9), Peru (3.9), Puerto Rico (3.8), Albania (3.8), and Italy (1.9) (Table 1). However, due to different sample sizes and varying age ranges of participating children, comparisons among all study results must be conducted with caution. The decay component (DT) was the primary contributor to the DMFT value in this study. This is consistent with results from other studies conducted on similar age groups in Saudi Arabia and Sudan (Al-Sadhan, 2006; Nurelhuda et al., 2009), emphasizing an immediate requirement to provide restorative dental services to these age groups.

Results indicated female children had a higher mean DMFT value 5.23 (± 3.6) than male children 4.74 (±3.4). Therefore, female children showed a significantly higher incidence of dental caries than male children (P < 0.05) and the difference was marginally significant. Similar findings were reported among Egyptian (Abdel-Aziz, 1999) and Indian children (Shingare et al., 2012). Dietary habits, and frequent snacking by female children during food preparation might explain these observations. The observation of higher caries risk among females could also be related to fluctuating hormonal levels during puberty (Lukacs and Largaespada, 2006). However, this is incongruent with results obtained for Saudi Arabian children, where males exhibited higher mean DMFT values relative to female children (Al-Sadhan, 2006). Moreover, a technical report by FDI (1988) attributed the higher caries prevalence in girls to earlier permanent teeth eruption; teeth were exposed for longer periods of time, which increased decay risk.

Children residing in urban areas had a lower mean DMFT value 4.91 (±3.5) than children in semi urban areas 5.06 (±3.4). Children who resided in semi-urban areas exhibited significantly increased risk for dental caries than children in urban areas (binomial, P < 0.05; multinomial, P < 0.01 logistic regression analyses). In Qatar, advanced dental service clinics (dental specialty services) in semi-urban areas are fewer than in urban areas. Increased dental caries in this geographic area might also be due to eating habit and lifestyle differences between the two groups. In addition, children in semi-urban areas have more access to and consume more sweetened snacks and drinks than children residing in urban areas (Bener et al., 2013).

In Qatar, children from higher socioeconomic backgrounds were generally enrolled in private schools, and children from lower socioeconomic backgrounds primarily attended public schools. Therefore, school type was chosen to assess children from different socioeconomic backgrounds. The results of the study showed that private school children had a lower mean DMFT value 4.62 (±3.08) than public school children 5.11 (±3.6), consistent with results reported by Piovesan et al. (2011). The children from private schools were presumably from higher socioeconomic levels, increasing their opportunity to access dental care clinics. Differences in respective mean DMFT values between Qatari 4.89 (±3.5) and non-Qatari children 5.10 (±3.5) were not observed. This might be due to substantial lifestyle differences.

Results also detected a marked variation in caries distribution by tooth number and arch (Table 5). The mandibular incisors and canines were least affected by dental caries, while dental caries was most frequently recorded in the maxillary and mandibular molars. Udoye et al. (2009) reported similar findings in Nigerian, and El-Nadeef et al. (2009) in United Arab Emirates children. Due to the molar anatomy (deep pits and occlusal surface fissures and wide proximal surfaces), cariogenic food particles and plaque can more readily be retained, and access for effective oral hygiene can be challenging, therefore more prone to dental caries. On the other hand, incisors and canines have smooth labial and lingual surfaces, and therefore exhibit low retention to cariogenic food particles and plaque.

Results indicated that dental caries was more common in the maxillary (60.9%) relative to the mandibular arch (39.1%). Demirci et al. (2010) evaluated caries prevalence in individual teeth among patients attending a university dental clinic in Turkey, and reported results consistent with the present study.

This epidemiological study indicated that the incidence of dental caries in Qatar’s children aged 12–14 is alarming. Many factors might explain high dental caries in the pre-teen to teenaged population, including changing population lifestyles, inadequate use of dental health services, lack of family support in dental health care, absence of good oral health habits in children, high sugar consumption, and inadequate awareness of the positive effects of fluoride toothpaste. Bener et al. (2013) reported that insufficient educational outreach on oral health in the country has exacerbated the problem.

Qatar has not yet developed a system where routine dental visits are the accepted norm. In addition, oral health education programs have not been launched in the school curriculum. It is clear the population must be educated regarding the advantages of regularly visiting a dentist. For dental caries among children to be reduced, and oral health improved, responsible policymakers must develop and implement appropriate oral health promotion and care programs for use in schools and primary healthcare centers.

Oral health authorities should also focus attention on policies that promote behavioral changes in dietary habits at a national level, which can be achieved through restrictions on advertising and legislation to control unhealthy foods, and bans on unhealthy and sugary food sales in and around schools with enhanced accessibility to healthy foods.

Finally, cumulatively the Supreme Council of Health, dentists, school teachers, the media, parents, and children themselves must arrest caries progression, and decrease caries prevalence throughout Qatar.

Notwithstanding its strengths, clear limitations were identified in this study. It is therefore appropriate to identify and discuss these limitations, and any effects on the results, interpretations, conclusions, and recommendations.

First, dental caries were identified by clinical examinations; no radiographs were taken, which might over- or under-estimate the actual magnitude of the problem. This limitation applies to most studies using WHO criteria for dental caries diagnoses (Al-Sadhan, 2006; Campus et al., 2008; Tramini et al., 2009; Mtaya et al., 2009).

Second, the DMFT index was based strictly on WHO diagnostic criteria to identify dental caries. However, WHO criteria are binary presence/absence data, i.e. presence or absence of decay, and does not differentiate among the various stages of dental caries (initial and advanced carious lesions, and non-cavitated and cavitated carious lesions), which might subsequently under- or over-estimate dental caries incidence and severity (Pine and Harris, 2007).

Third, in the present research only affected teeth were recorded on a diagnostic chart, without determining the tooth surfaces affected by caries. Additional studies that include decayed, missing, and filled surfaces (DMFS) should be conducted.

Finally, the study design was cross sectional; therefore, evidence regarding casual relationships could not be confirmed. Undoubtedly, further longitudinal studies are required to overcome this limitation. Therefore, the data derived from our analysis should be interpreted with caution, considering all previous limitations.

The following recommendations can be drawn from this research:

Dental caries has reached serious levels in Qatar among children, and results of this study emphasize an urgent need to expand the available dental services in the country. Efforts should focus on strengthening dental services, including building the required infrastructures for optimal dental care throughout the country. If dental service expansion is not initiated, serious negative impacts on the future of oral health in Qatar might occur.

The province health authorities should be encouraged to develop nationally oriented oral health care promotion strategies aimed at increased improvement of oral self-care practices, regular dental visits for children, and enhanced control of oral disease.

Implementation of community-based preventive oral health programs focused on healthy diet and adequate oral hygiene practices should be promoted in school curricula and services to combat the growing dental caries problem.

6. Conclusions

The following findings include the important summary highlights of this study:

• 1.Dental caries prevalence among school children in Qatar was 85%. Mean DMFT values were respectively 4.62 (±3.2), 4.79 (±3.5), and 5.5 (±3.7) for 12-, 13-, and 14-year old children.
• 2.
  Dental caries was affected by socio-demographic factors, but significant differences were observed for the following variables:

  • •
    Female children were more at risk for dental caries than male children.
  • •
    Children residing in semi-urban areas were significantly more at risk for dental caries than children residing in urban areas.
• 3.A comparison of these results with data from other Eastern Mediterranean region countries showed mean DMFT values for 12–14-year old school children in Qatar was the second highest in the Eastern Mediterranean region.

Conflict of Interest

The authors have no conflict of interests to declare.