The survey was planned as a cross-section evaluation. The study was conducted in Summer 2019. The study population comprised schoolchildren aged 5-17 years.
Study area and population
The study was carried out from July to August 2019 in Zanskar Valley (Ladakh): in Padum city, in some Buddhist monasteries and in some rural areas. The content of fluoride in the water of the examined areas was ≤0.02 ppm/l. The total schoolchildren population aged 5-17 years amounted to 2,407 children. The study gained the approval of all the schools’ authorities. Due to language problems and the low literacy rate of the population, parents or guardians verbal approval was obtained for children’s participation.
Methods
Due to the large number of subjects to be examined, the number of raters was set at four. The team received training and inter-examiner reliability was assessed before the start of the study; sensitivity, specificity, percentage agreement and kappa statistics were recorded. Inter-examiner reliability ranged from 0.75 to 0.84 (K-Cohen) for sound and from 0.82 to 0.88 for caries lesions. Intra-examiner reliability ranged from 0.82 to 0.90 for sound teeth and from 0.84 to 0.91 for caries lesions. One examiner (EC) served as benchmark and conducted the theoretical and calibration sessions. During calibration, the team of examiners was also trained to measure and record the anthropometric indices. Dental caries prevalence (dt/DT) and severity (number of lesions) was recorded with caries at the dentinal lesion level [10]. Every subject was examined using: a plain mirror (Hahnenkratt, Königsbach, Germany) and the WHO CPI ballpoint probe (Asa-Dental, Milan, Italy), under standard light. No bitewing radiographs or fiber-optic trans-illumination were used. The presence of gingival bleeding after probing was evaluated only six teeth [11].
An ad hoc questionnaire was build-up to assess general health, eating habits, oral hygiene and the self-perception of oral conditions, based on previous surveys [12-15]. Direct face to face interviews were conducted with at least one parent of the children under the age of 12, while older children were asked to answer a self‐administered questionnaire. Five items were related to general health: height, weight, waist circumference, heart-rate, oxygen saturation; ten items were related to dietary habits as the consumption of fresh fruit, biscuits, cakes, jam/honey, sweets/candy, meat, cheese, rice, chewing gum, soft drinks, sugared drinks; three items were related to hygiene habits as frequency of oral hygiene, use of a toothbrush and the perception of oral conditions.
The height (cm) was measured using a portable stadiometer (Seca 700, DE, Seca.com) asking the children to stand upright with the back (head, buttocks and heels) touching the device, wearing the school uniform and no cap or shoes were admitted; the weight (Kg) was also measured using a digital weight scale (Seca Clara 803, Seca, DE Seca.com). The waist circumference as the midway between lower ribs and the iliac crest was measured in cm after asking the children to stand with their arms wide open and feet positioned close together. The body mass index (BMI) was calculated dividing the weight by the height squared (kg/cm2). Oxygen saturation and heart-rate were measured using a portable pulse oximetry device (Mindray PM-60, Mindray Medical Italy S.R.L).
Statistical analysis
Data were entered into a database (Excel 2018; Microsoft Corporation, Redmond, WA, USA). Statistical analyses were performed using Stata® 16.0 software (http://www.stata.com). Responses to questionnaire items were treated as categorical or ordinal variables. The BMI data and waist circumference were then considered by the ethnicity of the population, re-coded using the International Obesity Task Force [16-19] and then categorized into three categories each. Oxygen saturation data was divided in two classes under 90% and above 90% [20].
Mean caries data, BMI, waist circumference and oxygen saturation were calculated by age groups (<6,≥6<11,≥11≤14 and >14 years of age). The relation between children’s caries data, gingival bleeding, gender, BMI, waist circumference and questionnaire items were assessed using the Kruskal–Wallis test and a linear trend was calculated to aid the interpretation of data to determine if the measurements indicate an increasing or decreasing trend. Caries severity was evaluated separately for primary and permanent dentition following the distribution frequencies as follows: dt/DT=0 (caries-free subjects), low caries severity dt in the range between 1 and 5 lesions, and DT in the range between 1 and 3 lesions, high caries severity dt >5 and DT >3 caries lesions. Conditional ordinal logistic regression was used to analyse associations among caries severity level (dt/DT), gender, BMI, waist circumference, oxygen saturation and questionnaire items. The Akaike information criterion (AIC) was used to measure the goodness of fit of the statistical model. Multicollinearity might sometimes cause problems with regression results. This problem was solved using the DFBETA command in Stata, dropping the information that have too much influence on the regression line [15, 21].
A forward stepwise logistic regression procedure was also assessed to estimate the ORs of gingival bleeding prevalence and the covariates derived from clinical examination or questionnaire data.