Dental maturity in children with celiac disease: a case–control study

This is a case–control study based on “The Reporting of Observational Studies in Epidemiology (STROBE)” guidelines for reporting case control studies [11]. The sample size was calculated by applying an equation for calculating sample size in case–control studies [12], using 80% power and an alpha level of 0.05. A total number of 190 participants was the minimum requirement (95 for the CD group and 95 for the control group) [13].

The inclusion criteria were the following: children with a CA of 6–14 years with biopsy-proven CD diagnosed according to criteria set out by the European Society of Pediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) [14]. For the control group, only healthy children with ASA 1 status (approved on October 15, 2014 by the American Society of Anesthesiologists) were included. The exclusion criteria were the following: children with mental or physical disabilities or congenital abnormalities and those not having bilateral missing premolars, since DA calculation would not be possible by the traditional method in such cases [15].

CD children were recruited from the Pediatric Celiac Disease Clinic in King Abdulaziz University Hospital (KAUH) in the period between September 2017 and February 2020. Simultaneously, healthy controls were obtained by giving each participant 5 letters of invitation to participate in the study to distribute to their classmates. Parents that replied and agreed to participate were requested to bring their child to King Abdulaziz University Dental Hospital (KAUDH) to be included in the study; this process was iterated until the desired number of healthy controls was obtained.

Ethical considerations in accordance with the Declaration of Helsinki were followed throughout this study. This study was approved by the Research Ethics Committee of the Faculty of Dentistry in King Abdulaziz University (KAU) (Ref: 078-09-17). Parents had to sign an informed parental consent form to give permission for the participation of their child.

A panoramic radiograph was taken in the radiology department. Following this, the parents of the participating children, along with their child, were taken to the dental clinic to complete a personal interview about the child, regarding demographic data, number and sequence of child sibling(s), child dietary habits, and socioeconomic status—specifically parental education and family income. Parental education was categorized as ≤ 12 years or > 12 years of education. Family income was categorized into low [less than 5000 Saudi Arabian Riyals (SAR)], middle (from 5000 to 10,000 SAR), and high (more than 10,000 SAR). Subsequent to the interview, a comprehensive oral clinical examination and dental prophylaxis were carried out.

On a separate day, a non-investigator coded the radiographs, in order for the single trained pediatric dental examiner to be blinded during radiographic DA calculation, to avoid bias. The DA was then measured using the panoramic radiograph, following the Demirjian method [15].

The dietary habits were recorded by interviewing both child and parent, using a checklist. This list corresponds to the frequency intake of the five food groups, as set out by the WHO [16]. For each food group, a rating on dietary intake was recorded on a scale of 1–4, where 1 corresponds to several times a day, 2 is daily, 3 is sometimes, and 4 never. Dietary intake was dichotomized, where ratings of 1 and 2 indicated yes, and ratings of 3 and 4 indicated no.

CA represents the time elapsed since birth, and DA estimates a person’s age based on the magnitude of teeth formation in the jaws [4]. For each participant, the CA was calculated from the date of examination according to his or her date of birth. The DA was calculated by the assessment of the left permanent mandibular teeth in the following order: 2nd molar, 1st molar, 2nd premolar, 1st premolar, canine, lateral incisor, and central incisor. Teeth were rated based on the “A to H” scale, following the given criteria and diagrams at every stage. Each tooth was then given a numerical score that was extracted from predetermined tables for the respective gender. The sum of the seven numerical scores yielded a maturity score, which was subsequently interpreted on the given tables to determine the corresponding DA. In case of a single missing premolar on the left side, the corresponding premolar on the right side was used instead [17]. Participants with bilateral loss of premolars were excluded. The DA was then compared to the CA to assess the state of dental growth and development.

The mean difference between DA and CA was calculated (DM = DA − CA) to assess DM. If the difference was positive, it corresponds with advanced DM, while if it was negative it corresponds with delayed DM [4]. To calculate the difference in months, the mean difference was multiplied by 12. The mean differences were then arranged into three categories: mild (up to 12 months), indicating values within the normal age range, moderate (from 12 to 24 months), and severe (more than 24 months); the latter two categories indicating values outside the normal age range [4, 18].

Inter-rater reliability for the DA calculation was tested using Demirjian’s method by the principal investigator through examining ten panoramic radiographs, under the supervision of a trained pediatric dentist; the process was then repeated two weeks later to calculate intra-rater reliability. For a DA calculation using Demirjian’s method, inter- (with the trainer pediatric dentist) and intra-rater reliability was calculated using the Statistical Package for the Social Sciences (SPSS), version 21 (SPSS, Inc., Chicago, IL, USA)..

Descriptive statistics were used to examine sample characteristics: continuous variables were summerized as means and standard deviations, while counts and percentages were used for categorical variables. The association between the covariates (i.e., personal characteristics and socio-demographic variables, such as family income, parental education, and dietary factors) and the study outcome (DM) were initially evaluated by stratifying the subjects into a CD group and control group. Associations between the covariates and the study outcomes were then evaluated using chi-squared tests, Fisher’s exact tests, independent t tests, or analysis of variance (ANOVA) tests. Post-hoc analysis using Tukey correction was used in cases of significant results in ANOVA tests. After that, mutivariate analyses were carried out (mutiple linear regression models) to predict the DM, to check for interaction, and to control for possible confounding between CD and other covariates. A multiple linear regression analysis was also used to explore possible predictors of DM in CD patients. A P value of < 0.05 was set as statistically significant. The Statistical Package for the Social Sciences (SPSS), version 21 (SPSS, Inc., Chicago, IL, USA) was used for the statistical analysis.

Two-hundred and eight participants (104 children with CD, and 104 healthy controls) were included in the analysis. A total of 149 CD patients were contacted, and 520 letters of invitation were distributed to the classmates of CD children. The response rate of the CD group was 69.80%, while the response rate of the control group was 20%. In both the CD and control groups, 50% of the participants were girls. No statistically significant differences were found between the socioeconomic distribution of the two groups with respect to family income (P = 0.874), mother education (P = 0.052), and father education (P = 0.781). Children in the CD group were less likely to report daily intake of protein (76.0%), compared to the control group (80.8%) and the difference was statistically signifcant (P = 0.027). Thirteen of the children with CD were taking growth hormones (GHs) (Table 1).

The mean CA was 10.67 ± 2.40 (95% CI 10.21–11.14) years in the children with CD, and 10.69 ± 2.37 (95% CI 10.23–11.15) years in the healthy controls (P = 0.958). Children with CD had significantly lower mean DA compared to controls (10.01 years ± 2.05; 95% CI 9.62–10.41 vs. 11.27 years ± 2.42; 95% CI 10.81–11.75, P < 0.001) (Fig. 1). Therefore, children with CD had a delayed DM of 0.66 ± 0.91 years, corresponding to 7.94 ± 10.94 months, while the healthy controls had an advanced DM of 0.58 ± 0.73 years, corresponding to 6.99 ± 8.77 months (P < 0.001). The DM categories among all participants showed that 95.60% were CD children in the category of delayed DM, (P < 0.001). In the category of advanced DM, 82.50% were healthy controls (P < 0.001) (Fig. 2).

In the CD group, 65 patients (62.5%) had delayed DM, 22 patients (21.2%) had normal DM, and 17 patients (16.3%) had advanced maturity. In the control group, only 3 participants (2.9%) had delayed DM, 21 participants (20.2%) had normal DM, and 80 participants (76.9%) had advanced DM.

Grading the DM for the CD group, 22 patients (21.2%) had normal maturity, 35 patients (33.7%) had mild delay, 26 patients (25%) had moderate delay, 4 patients (3.8%) had severe delay, 12 patients (11.5%) had mild advanced, only 5 patients (4.8%) had moderate advanced, and none had severe advanced. Grading the DM for the healthy controls showed that 21 participants (20.2%) had normal maturity, 45 participants (43.3%) had mildly advanced, 31 participants (29.8%) had moderately advanced, 4 participants (3.8%) had severly advanced, 3 participants had mild delay, and none had moderate or severe delay (Fig. 3).

A bivariate analysis of the DM in months (difference between DA and CA) by demographic, SES, and dietary variables was carried out speparately for CD and control groups. Boys in the control group had signifcantly higher mean DM of 8.77 ± 9.27 months (95% CI 6.19–11.35), compared to girls (5.22 ± 7.94 months; 95% CI 3.01–7.43) (P = 0.034). Moreover, the youngest age category (6–7 years) in general had higher DM of 5.65 ± 7.66 months (95% CI 1.71–9.59), corresponding to an advanced DM, which was significantly different from the other two age groups (P < 0.001); the middle age group (8–10 years) had a mean DM of − 8.52 ± 07.50 months (95% CI − 11.18 to − 5.86), corresponding to a delayed DM; and the oldest age group (11–14 years) had a mean DM of -11.85 ± 10.28 months (95% CI − 14.66 to − 9.05), corresponding to a delayed DM.

Family income was found to be associated with the DM in the CD group (P = 0.016). The middle-income group (between 5000 and 10,000 SAR) had a mean DM of − 11.32 ± 9.70 months (95% CI − 14.66 to − 7.99), corresponding to a delayed DM, which was significantly different from the highest-income group (> 10,000 SAR), which had a mean DM of − 4.07 ± 10.90 months (95% CI − 7.70 to − 0.43), corresponding to a delayed DM. Mother education was also associated with DM in the CD group (P = 0.042). Children whose mothers had less than 12 years of education had a mean DM of − 9.24 ± 10.16 months (95% CI − 11.91 to − 6.57), corresponding to delayed DM, which was significantly different from those whose mothers had more than 12 years of education, with a mean DM of − 6.29 ± 11.75 months (95% CI − 9.78 to − 2.80), corresponding to a delayed DM.

In the control group, daily intake of vegetables was significantly associated with DM (P = 0.048). The mean CA and DA and the mean DM did not show a significant difference between children with CD that were taking growth hormones (GHs) and those that were not taking them (P = 0.783). The mean DM of children taking GH was 5.64 ± 9.36 months (95% CI 0.036–11.4), while the mean DM of those that were not taking GHs was 6.48 ± 10.44 months (95% CI 4.32–8.76) (Table 2).

A multiple linear regression model was applied to confirm the relationship between CD and DM, while controlling for confounding variables. Children with CD had a signifcanlty delayed DM by about 15 months on average (β ± SE, − 14.84 ± 1.31; 95% CI − 17.41 to − 12.26, P < 0.001) compared to control subjects, after controlling for other variables. Children aged 6–7 years had advanced DM by 9.32 ± 1.88 months (95% CI 5.61–13.03, P < 0.001) in comparison with the 11–14 year-old children after controlling for other variables (Table 3).

A multiple linear regression model was used to explore possible predictors of DM in the CD group (n = 104). Young age was found to be the only significant predictor for DM. Children in the youngest age group (6–7 years) had significantly advanced DM by 16.21 ± 2.58 months (95% CI 11.09–21.32, P < 0.001) compared to 11–14 year-old children (Table 4).

Intra-class correlation coefficient (ICC) for inter-rater agreement was carried out for each tooth separately on the lower left quadrant; the score ranged from 0.96 to 1, which indicated excellent reliability [19]. Also, intra-rater reliability was performed for each tooth separately; the score ranged from 0.95 to 1, which likewise indicated excellent reliability [19].