Dental Caries Experience in Elementary School Students in Quebec: Surveillance Study Using ICDAS II

Introduction

In 2010, the Ministère de la Santé et des Services sociaux in Quebec entrusted the Institut national de santé publique du Québec (INSPQ) with the task of updating oral health surveillance data for elementary school students. The most recent oral health studies dated back to the late 1990s,^1,2 and the lack of more recent clinical data was a barrier to updating Quebec’s public dental health program.

In 2012–2013, the INSPQ conducted a province-wide study of the oral health of elementary school students, entitled Étude clinique sur l’état de santé buccodentaire des élèves québécois du primaire (ÉCSBQ 2012–2013).^3,4 This study had 2 distinctive features: its data collection system was different from that used in previous provincial studies, and a caries indicator combining primary and permanent dentitions was developed.

ÉCSBQ 2012–2013 was the first surveillance study in Quebec to generate findings on dental caries that included the first signs of enamel demineralization. In earlier studies, the visual detection threshold for dentin involvement was used in the clinical assessment of dental caries, as recommended by the World Health Organization (WHO).⁵ In ÉCSBQ 2012–2013, caries were assessed using the International Caries Detection and Assessment System II (ICDAS II).⁶ This made it possible to provide a more complete picture of the level of tooth decay among elementary school students. All stages on the continuum of dental caries, from involvement of the surface layer of enamel to deep lesions, were thus taken into account. In addition, knowledge of the prevalence of dental caries at the early stages of the disease represents a substantial asset in terms of identifying public health preventive measures.

Traditionally, dental caries have been reported separately for each type of dentition, that is, primary and permanent teeth. However, in our opinion, the prevalence of caries in both dentitions combined provides a more comprehensive measure of the burden of dental caries from a surveillance standpoint.

The objective of this article is to provide an overall picture of dental caries in Grade 2 and Grade 6 students in Quebec. More specifically, it aims to compare the prevalence of caries at different stages of the disease in different types of dentition.

Methods

The target population of this cross-sectional descriptive study included all Grade 2 and Grade 6 students enrolled in public and private, French- and English-language elementary schools in Quebec. It excluded students attending schools on Indigenous reserves, specialized schools and schools located in northern regions. Some students were also excluded for logistic or medical reasons. Three levels of sampling — regions, schools and students — ensured that the study would be representative of the province. For the first level, we selected 10 regions among all admissible administrative regions categorized into 3 strata (populous, sparsely populated and other). The second sampling level was aimed at identifying schools in the selected regions according to educational system (public or private schools), the socioeconomic status index of the schools as defined by the Ministère de l’Éducation et de l’Enseignement supérieur of Quebec or the geographic area. At the student level, Grade 2 and Grade 6 students from the chosen schools were selected using a simple, random method without replacement.

Before oral health examinations were carried out, parents were required to read and sign a consent form and complete a health questionnaire for their child. They were also asked to complete a questionnaire designed to gather sociodemographic information. Afterward, each student was given a summary statement regarding his or her oral health and was referred to a dentist in case of obvious need.

In late October and early November 2012, 16 dentist-examiners received theoretical training followed by practical training to standardize their clinical assessments, in accordance with recommendations of the ICDAS Foundation experts who were consulted. Clinical assessments of 1 of the dental trainers was used as a gold standard for evaluating examiner reliability regarding coding of clinical condition of about a dozen students. This reference dentist had previously been trained by ICDAS Foundation experts who had come to Montréal in spring 2012 for this purpose.

Simple and weighted kappa statistics as well as percentage of agreement were used to determine the reproducibility of the clinical assessments of the gold standard dentist compared with those of the dentist-examiners.⁷ Agreement scores were calculated according to data collected under the same conditions as in the field study, as suggested by the founders of ICDAS II.

Two other methods were used to determine the level of interexaminer agreement: (1) approximately 10 of the students examined by each dentist-examiner were seen again by a gold standard dentist about midway through the data collection process; and (2) each dentist-examiner examined 5% of the students twice during the data collection process. Agreement scores for each of the 16 examining dentists as assessed before and during the data collection were satisfactory.

Between November 2012 and June 2013, clinical data were gathered by intraoral examinations conducted without radiographs in elementary schools using portable equipment. Headlamps (Storm 100 lumens; Black Diamond, Utah), disposable dental mirrors (model 1006640; Henry Schein, New York), and dental probes (model 5009532U0 WHO 23/6; Brasseler, Canada) were used. The ICDAS II system was applied for each tooth surface, although the activity of carious lesions was not assessed.⁶ To distinguish between code 1 and 2 carious lesions, the surface of the tooth was dried with an air syringe. Clinical data were entered directly into a computerized data collection tool. SAS 9.3 software was used to create the final database. The results were weighted, so that the final sample would be truly representative of the target population. To account for sampling design, the accuracy of estimates was calculated using the bootstrap weighting technique.

Results are presented according to 3 stages of caries: stage 1–3 caries (non-obvious caries); stage 4–6 caries (obvious dental caries); and stage 1–6 caries. Although various combinations are possible, it was decided to group codes 1–3 and 4–6 to allow comparison of our results with those of previous Quebec studies that assessed the presence of caries at a corresponding ICDAS II code 4 threshold.

The presence of fillings is reported in the F component of the DMFT or DMFS index (upper or lower case for permanent and primary dentition, respectively), as well as the FS component of the ICDAS index, as in the study by Guedes de Amorim et al.⁸ The caries experience index, primarily at stages 1–6, underestimates the number of surfaces that are filled because, when this index is calculated, a surface that has both a carious lesion and a filling is considered carious. To estimate the average number of filled surfaces, without taking into account the simultaneous presence of carious lesions, it is more appropriate to use the FS-ICDAS index.

The research protocol for this study was approved by a public health ethics committee. Confirmation of collaboration by the Ministère de l’Éducation, des Loisirs et du Sport, as well as the passive consent of all school boards, their public schools and all the private schools involved in the study was obtained.

Results

The participation rate of schools was approximately 93%, while that of Grade 2 and 6 students was 69% and 64%, respectively. During the data collection phase, the dentist-examiners visited 475 schools and examined 2875 Grade 2 students and 2788 Grade 6 students. A detailed description of the sample is provided in Table 1.

Grade 2

Among students in Grade 2, the mean number of primary teeth was 13.06 out of a possible 20, while the mean number of permanent teeth was 10.13 out of a possible 28. When both dentitions were combined, the mean number of teeth observed was 23.19. With regard to primary dentition, students usually had second molars (> 98%) and first molars (> 95%), as well as canines (> 94%). With regard to permanent dentition, lower central incisors were observed in 98–99% of the students and first molars in > 96%.

Table 2 shows the caries experience of Grade 2 students by tooth or surface, index components and dentition. At the tooth level, the mean caries experience for Grade 2 students was 3.96 d_1-6mft and 1.88 D_1-6MFT or 5.84 for primary and secondary dentitions combined. At the surface level, the mean caries experience of the same children was about 8.33 for d_1-6mfs, 2.96 for D_1-6MFS and 11.28 combined. For dmfs + DMFS, nearly 7 surfaces (6.57) had a carious lesion, with lesions on 5.79 of those surfaces at stage 1–3 and lesions on 0.77 at stage 4–6; few surfaces were missing (0.31) and 4.40 surfaces were filled. However, irrespective of the presence or absence of carious lesions, the mean number of filled surfaces (fs-icdas + FS-ICDAS) was 4.92.

Table 3 reveals that about 80% of Grade 2 students had stage 1–6 caries in their primary dentition, while 69% had stage 1–6 caries in their permanent dentition. For combined dentitions, almost all students (90%) had stage 1–6 caries. In addition, the proportion of students with non-obvious carious lesions in their combined dentitions (d_1-3s + D_1-3S > 0) was high (85%), while the proportion of students with obvious carious lesions in both dentitions (d_4-6s + D_4-6S > 0) was lower (20%).

Grade 6

For Grade 6 students, several primary teeth had already been replaced by permanent teeth. On average, only about 2.56 primary teeth were present, compared with 23.19 permanent teeth out of a possible 28. For combined dentitions, the mean number of teeth was 25.75. Of all the teeth normally present, the students most frequently had permanent first molars (all students) and permanent lateral and central incisors (almost all students).

At the tooth level, Grade 6 students had, on average, a d_1-6mft of 1.94, a D_1-6MFT of 4.98 and a d_1-6mft + D_1-6MFT of 5.98 (Table 4). At the surface level, the mean caries experience was 4.04 for d_1-6mfs, 7.86 for D_1-6MFS and 9.96 for d_1-6mfs + D_1-6MFS. Close to 8 surfaces (7.88) had a carious lesion: 7.49 surfaces had stage 1–3 caries and 0.39 surfaces had stage 4–6 caries. There were almost no missing surfaces (0.06) and 2.01 filled surfaces. The fs-icdas + FS-ICDAS index revealed 2.48 filled surfaces.