Prevalence of gingivitis and calculus in 12-year-old Puerto Ricans: a cross-sectional study

This research is part of a comprehensive cross-sectional study that assessed the oral health status of 12-year-olds attending public and private schools in the eleven government health insurance regions (GHI) of Puerto Rico, using a multi-stage sampling methodology. The study design and sampling methodology have been previously described [26].

This study was conducted in schools, and the GHI regions were selected, as in 1997, to allow comparison with other oral health indicators assessed in a previous study [27]. The universe of public and private, urban and rural, schools was used as the sampling frame for this island-wide study. Schools were stratified according to their GHI region and, within each stratum, schools were organized according to their geographic proximity and poverty level. School level clustering reasonably assumed a social-cultural homogeneity at the school level. In Puerto Rico public/private school attendance is considered a proxy measure for SES, with private school attendance representing a higher family SES compared to public school attendance [26‐29].

Study recruitment occurred during October–November 2010 and January–April 2011. The study’s clinical procedures were conducted between November 2010–May 2011. After obtaining permission from the Department of Education and approval from the Institutional Review Board of the Medical Sciences Campus, University of Puerto Rico (MSC-UPR), the project director visited the selected schools in the sample. During each visit, the project director explained the study aims to the school principal and home-room teachers, and requested a list of 12-year-olds enrolled in 5th to 7th grades. Twenty 12-year-olds, 10 boys and 10 girls, were then randomly selected using a computer-generated random number. The project director and the home-room teacher explained the aims and methods of the study to the selected children, emphasizing that their participation was voluntary. A letter of invitation, informed consent form, medical history questionnaire and a demographic information form were sent to the parents of potential participants. The medical history questionnaire asked for details of any medical conditions suffered by the child, medications being taken and food allergies. Demographic information collected included the date of birth, gender, ethnicity, dental insurance information and home address.

Inclusion criteria were as follows: 1) classification with a physical status ASA I and/or ASA II as defined by the American Society of Anaesthesiologist [30]; 2) being 12 years of age at the time of recruitment. The exclusion criteria were: 1) participants with conditions requiring antibiotic prophylaxis; 2) those who demonstrated an inability to comply with study protocol requirements.

Prior to the study, the two study examiners were trained by a periodontist and an experienced reference examiner in gingivitis and calculus assessment. During the study, 10% of the examinations were repeated, and the examiners demonstrated 83.33% inter-examiner agreement on BOP scores and 88.89% agreement for calculus.

All clinical procedures were conducted in a single visit to the child’s school, after confirming proper parental and child consent, in the following sequence: 1. medical history review; 2. height and weight measurements; 3. soft tissue examinations; 4. cumulative caries experience (DMFS) and pit and fissure sealants; 5. dental fluorosis assessment; 6. gingival evaluations (BOP); 7. dental calculus assessment. As part of the main study, a sub-sample of the participants (n = 823) completed an oral health knowledge and habits questionnaire [see Additional file 1] and a 24-h dietary assessment [29]. A study procedure flowchart is included (Fig. 1).

The day the clinical exams were scheduled, qualifying children were asked to brush and floss their teeth under the home-room teacher’s supervision. As a significant number of children in public schools participate in the school breakfast and lunch programs, these oral hygiene procedures were useful in removing food debris and allowed better visualization of the oral hard and soft tissues.

The examiners conducted oral examinations and evaluated the presence of gingival bleeding and dental calculus using a modified version of the Oral Health Surveys of the National Institute of Dental Research Diagnostic Criteria and Procedures [31]. The portable equipment used consisted of a dental chair, external light source, and an air compressor. All processes complied with Occupational Safety and Health Administration (OSHA) infection control procedures. Oral examinations were conducted on all the erupted teeth in two selected quadrants (one maxillary and one mandibular) that were chosen using a computer-generated random number. Gingival and calculus status were not assessed around teeth with extensive dentinal caries, sub-optimal restorations or orthodontic bands/brackets since these areas are prone to plaque stagnation and inappropriate oral hygiene [32], and may produce overestimates of gingivitis prevalence and severity. Gingivitis was defined as the presence of BOP in at least one site [1]. The gingival sulcus was explored using a Hu-Friedy PCP UNC 126 periodontal probe. The probe was inserted not more than 2 mm into the gingival sulcus starting just distal to the midpoint of the buccal surface and then gently moved into the mesial interproximal area. The same procedure was completed on the palatal surface. Bleeding sites were scored after the sites of a single quadrant were probed. Each site was scored as no bleeding =0 and bleeding =1. Gingivitis extent was determined for each participant as follows: (a) limited gingivitis: 2–4 teeth or 25% to 49% of the teeth examined presented gingival bleeding; (b) extensive gingivitis: >5 teeth or >50% of the teeth examined presented gingival bleeding [33]. Children with gingivitis who did not fulfill these criteria were regarded as having localized gingival inflammation [34]. When assessing the presence of dental calculus, supragingival calculus was defined as calcified deposits located on the exposed crown and root surfaces extending up to 1 mm below the free gingival margin (FGM) and subgingival calculus was defined as mineralized deposits located more than 1 mm below the FGM. Supragingival calculus was assessed visually while using compressed air to dry teeth. A gentle tactile exam used the probe to locate subgingival calculus deposits. Each site was scored as follows: 0 = no calculus; 1 = supragingival calculus in the absence of subgingival calculus; 2 = presence of subgingival calculus only or presence of both supragingival and subgingival calculus; Y = site cannot be assessed (missing, partially erupted or deciduous tooth) [35]. The mid-buccal (buccal), mesio-buccal (buccal/mesial), mid-palatal (palatal), and mesio-palatal (palatal/mesial) surfaces were evaluated. Data were recorded on a modified NIDCR data entry form [35]. Dental plaque, probing depth, and clinical attachment level were not assessed. No radiographic examinations were performed.

After completing the oral examination, all children received an oral evaluation form to take home. This form classified the child’s oral health status from I-IV (Fig. 1) according to the severity of the oral findings and recommended the timing of their next dental visit. Those children with subgingival calculus were classified as III with the recommendation being that they “must visit a dentist as soon as possible”.

The main objective of the study, which provided the source data for this analysis, was to estimate the prevalence and distribution of caries in this population. Consequently, sample size calculations were based on the expected DMFS score values, as described earlier [26]. In order to achieve the required final sample size of 1500 students, 133 schools (102 public and 31 private) were selected across the 11 regions, assuming 75% eligibility and 75% response rate, with 2660 students being invited to participate (2660*0.75*0.75 = 1496) [26].

Only three of the 32 private schools selected in the sample were located in rural areas. Therefore, all the private schools were grouped into a single category. Since this sample was stratified by GHI regions and clustered within schools, the analysis used weights inversely proportional to the probability of selection, adjusted for non-response, and later normalized. Estimated weighted percentages (95% confidence intervals, CI) were calculated for categorical measures (gingivitis and calculus prevalence, gingivitis and calculus extent), and percent of sites bleeding on probing (BOP%) was summarized in terms of weighted means (95% CI) and standard errors around the means. Differences in gender and school type, depending on the outcome measure being assessed, employed logistic, polytomous logistic and linear regression models, while taking into account the stratified cluster sample design and adjusting for health regions. Gingivitis prevalence (yes/no) and calculus prevalence (yes/no) were studied using logistic regression; gingivitis extent (extensive, limited, none) and calculus extent (supragingival, subgingival, none) were regressed using polytomous models; percent of sites with BOP (continuous) were regressed using linear models. All models included gender, school type (private, rural-public, urban-public) and health regions. Data were recorded in Microsoft Excel, verified and imported into the SAS statistical software package version 9.3 (SAS Statistical Institute, Cary, NC) for analyses.

Gingivitis was identified in 80.41% (95% CI: 76.60, 84.21) of the schoolchildren. Geographically, prevalence across the 11 GHI regions (see Table 1) ranged from 72.36% in the East to 92.61% in the Northwest. Table 2 presents gingivitis prevalence and extent by gender and school type. Although gingival bleeding was more common in boys (81.29%) than girls (79.57%), this was not statistically significant (school type-and region-adjusted p = 0.54). The prevalence of gingivitis was highest in children attending urban-public schools (83.25%) by comparison to private (79.15%) or rural-public (77.59%) schools, but these differences were also not statistically significant after adjusting for gender and region (p = 0.16 for urban-public and p = 0.15 for rural-public). In terms of the extent of gingivitis, 19.59% (95% CI: 16.77, 22.45) of children had limited gingivitis, and 60.81% (95% CI: 56.03, 65.59) had extensive gingivitis. No statistically significant differences in gingivitis extent were observed between schoolchildren by gender (p = 0.64) or school type (rural-public p = 0.09 and urban-public p = 0.07).

The mean BOP for each child was 9.46 sites, which accounted for 17.79% (95% CI: 16.30, 19.29) of the sites probed. The mean percentage of teeth presenting BOP was 43.54% (95% CI: 40.31, 46.77) or 5.80 of the actual teeth examined. Table 2 shows that children attending urban-public and rural-public schools presented significantly higher BOP% sites compared to children attending private schools (gender and region-adjusted, urban-public p = 0.002 and for rural-public vs. private p = 0.0005).

Dental calculus was identified in 61.59% (95% CI: 56.61, 66.57) of children (Table 3), with 57.09% having supragingival and 19.78% having subgingival calculus. As shown in Table 4, boys presented a significantly higher prevalence of total calculus (66.28%, 95% CI: 60.95, 71.60; p = 0.005) and supragingival calculus (62.06%, 95% CI: 56.59, 67.65; p = 0.001) than girls (57.31%, 95% CI: 51.10, 63.51 and 52.37%, 95% CI: 46.27, 58.47, respectively). Children attending rural-public schools had a significantly higher prevalence of subgingival calculus (20.8%, 95% CI: 15.42, 26.18) compared to children in private schools (15.98%, 95% CI: 7.94–24.01; gender and region adjusted p = 0.02).