Epidemiology of dental caries in permanent dentition: evidence from a population-based survey in Egypt

The present cross-sectional study is nested in a national oral health survey conducted in Egypt between September 2013 and May 2014 with the support of the Central Administration of Dentistry, Ministry of Health and Population (MOHP), and the World Health Organization (WHO), country office [9]. The study was carried out according to the principles of the Declaration of Helsinki on experimentation pertaining to human subjects (version 2013) and reported according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

For the population-based survey, the sample size was calculated according to Egypt's Census dataset of 2013, provided by the Egyptian Central Agency for Public Mobilization and Statistics (CAPMAS). Accordingly, 10,144 participants—of which 53% resided in urban areas—were included in the final survey to yield a 95% confidence level, a sample power of 99.32%, and a marginal error of 0.68%.

The survey design included a stratified multistage cluster random sampling approach. Sampling took place in three stages based on the Egyptian administrative divisions. Egypt is geographically divided into four regions; Lower Egypt, Upper Egypt, Desert/Frontier and Civilized regions comprising a total of 27 governorates. Each governorate is further divided into rural and urban areas except for five governorates which include only urban areas. One governorate “North Sinai” was excluded from sample collection due to security reasons. The sampling frame from which the primary sampling units were randomly selected for the survey was obtained from CAPMAS and consisted of a list of all localities in each governorate. The second stage of sampling comprised 160 gathering points including healthcare facilities as well as a few households and workplaces. For the final sampling stage, systematic random sampling was used to select potential participants from individuals present in each gathering point on the day of recruitment. During data collection, edentulous individuals and those seeking dental care—to avoid selection bias—were excluded from the survey. As the current analysis addresses only caries experience in permanent teeth, children in the primary dentition stage were also excluded from the study sample, yielding 9,457 participants.

To test study hypothesis, we investigated the effect of potential determinants on the participants' caries experience using two individual-level dental outcomes: a) past caries experience indicated by the cumulative Decayed, Missing, and Filled Teeth (DMFT) index score; b) untreated caries lesions indicated by the number of decayed teeth (DT component of the index).

Face-to-face interviews were conducted to collect data on sociodemographic characteristics such as age, gender, and place of residence (rural/urban) using a structured questionnaire in simple Arabic language. In the case of minors, the questionnaire was answered by guardians instead. Educational attainment; a combined variable (hereinafter referred to as educational level) comprising the educational level of adults and the paternal educational level of minors was used as an indicator of socioeconomic position (SEP), and included the following categories: analphabetic, high school or less, and two-year academy, college or above. As most Egyptian households are male headed (83%) [10] and given the inverse relationship between a household's poverty risk and paternal educational level, the latter was used to denote the SEP of minors [11].

Source of drinking water, dental anxiety, and frequency of dental visits were examined as further explanatory variables. Sources of drinking water included filtered and unfiltered tap water, as well as bottled, well and mixed-source water. The frequency of dental visits was determined based on whether participants' last dental visit was within 6 months, 6–12 months, 12–24 months, or more than 24 months before participating in the survey or if they have never visited a dentist. Dental anxiety was tested using a single question; “Do you experience any anxiety when going to the dentist?” which was asked to the participants themselves or to guardians in case the participants were minors.

To assess the oral health status of participants, clinical examination was done as per the WHO basic methods for oral health surveys [12]. Visual and tactile examination of the crowns and roots of erupted permanent teeth was performed, excluding third molars. Plane surface mouth mirrors and blunt ball-ended WHO CPI probes were used to remove debris from tooth fissures and assess the presence of fissure sealants or defective restorations without jeopardizing the surface integrity of the undermined enamel overlying early carious lesions.

Teeth were given a score ranging from 0 to 9 only when their incisal edges or occlusal surfaces were completely visible. Sound non-carious teeth were assigned score 0. Teeth showing signs of caries such as enamel breakdown, a distinct cavity, undermined enamel, or an underlying dentin shadow were assigned score 1. Restored teeth were scored according to restoration integrity where restored non-carious teeth were assigned score 2 whereas carious ones were assigned score 3. Missing teeth were scored according to reasons for extraction reported by the participants; teeth missing due to caries were assigned score 4 whereas those missing due to other reasons were given score 5. Sealed non-carious teeth were assigned score 6 while abutment teeth without evidence of caries were given score 7. Unerupted permanent teeth and teeth that could not be examined were given scores 8 and 9 respectively [12]. Assigned scores were then converted using DMFT index scoring where teeth given scores 1 and 3 were assigned to the "Decayed" category, whereas those with scores 2 and 4 were assigned to the "Filled" and the "Missed" categories respectively.

Data collection was carried out by 20 investigators recruited from the MOHP and the Faculty of Dentistry, Ain Shams University, Cairo, Egypt. All investigators partook in a five-day training session on the examination procedures. Multiple calibrations were performed during data collection where investigators examined the same sample of individuals and variability among examiners was assessed. Inter-examiner reliability was deemed satisfactory at kappa values of 0.75 or greater [13].

Multivariable logistic regression models were created for past caries experience (all DMFT index components) and untreated disease (DT index component) for which the odds ratios (OR) and 95% CI were estimated as measures of association. Both models were adjusted for well-known caries risk factors including frequency of sugar consumption, tooth brushing, and smoking as well as other covariates such as age, gender, educational level, place of residence, source of drinking water, dental anxiety, and frequency of dental visits.

Descriptive statistics of the study sample are shown in (Table 1). The sample included 9,457 participants of which 1,731 participants had both primary & permanent teeth including 52 five-year-old participants who had at least one fully erupted permanent tooth. The mean sample age was 28.8 ± 16.0 (range 5–85), 50.90% were females and 46.60% resided in rural settings. Dental anxiety was reported by 46.52% of the participants and 39% stated visiting the dentist recently (i.e., within the past six months). 78.20% of the study sample had DMFT > 0 with total mean value 5.5 ± 5.7, 70.30% had at least one untreated carious permanent tooth (DT > 0) with mean value 3.0 ± 3.4.

The prevalence and mean scores of past caries experience (DMFT > 0) and mean scores for untreated caries (DT > 0), filled and missing teeth due to caries are also provided in Table 1 stratified by age, gender, geographic location, place of residence, educational level, frequency of dental visits, source of drinking water and dental anxiety.

A significant negative association was detected between mean DMFT scores and level of education for both genders (Fig. 1). In Fig. 2, while mean DMF scores were significantly higher among dentally anxious female participants, dental anxiety was negatively associated with caries experience in males.

Tables 2 and 3 show the results from the multivariable logistic regression analysis for past and present caries experience respectively. The likelihood of having a DMFT score > 0 was lower in young age groups; (6–15 yrs.) (OR 0.03, 95% CI [0.01; 0.08]), (16–20 yrs.) (OR 0.09, 95% CI [0.04; 0.23]), (21–35 yrs.) (OR 0.22, 95% CI [0.09; 0.53]) than among participants ≥ 60 years. On the other hand, the differences in odds of having untreated caries (DT > 0) were non-significant across age groups (16–20) years (OR 0.70 95% CI [0.47; 1.05]), (21–35) years (OR 1.09 95% CI [0.75; 1.58]), (36–45) years (OR 1.18 95% CI [0.80; 1.74], or (46–59) years (OR 0.92, 95% CI [0.63; 1.35]) when compared to participants ≥ 60 years.

Prevalence odds ratios showed that analphabets had significantly higher DMFT > 0 and DT > 0 than people with a college education and above; (OR 1.54, 95% CI [1.20; 1.98]) and DT >0 (OR 1.62, 95% CI [1.32; 2.00] respectively in the multivariable logistic regression analysis. Dental anxiety was also positively associated with caries experience where dentally anxious participants had significantly higher odds of worse past and present caries experience; (OR 1.29, 95% CI [1.14; 1.46]) and (OR 1.32, 95% CI [1.19; 1.46]) respectively. Besides, gender differences were significant, with lower odds (OR 0.75, 95% CI [0.67; 0.85]) and (OR 0.81, 95% CI [0.73; 0.90] for DMFT > 0 and DT > 0 respectively among males.

Dental caries remains a major health issue in Egypt particularly among vulnerable groups namely women and people with a low SEP. Given the high proportion of untreated carious lesions among young Egyptian adults, preventive approaches such as regular screening and provision of interim or conservative restorative techniques are highly recommended in early years of life as proposed by the life course approach. Routine screening of different public water systems throughout the country is also warranted to adjust fluoridation levels and promote substantial caries prevention at national level.