Persistent oral health disparity in 12-year-old Hispanics: a cross-sectional study

Dental caries is the most prevalent chronic illness worldwide. In the United States (US) it has been referred to as a “silent epidemic” affecting 58.2 % of 12–15 year-olds, particularly in minority and immigrant groups [1]. Caries are associated with complex, yet preventable, biological and behavioral factors such as plaque and diet [2‐6], and social determinants of health [7], including structure and environment [8, 9]. Additionally, in developed countries, a higher risk of caries has been associated with populations of low socio-economic status (SES) [10] particularly in areas with large income disparities [11, 12].

Puerto Rico (PR), a non-incorporated territory of the US located in the Eastern Caribbean has a population of approximately 3,725,789 [13]. In 2011, PR had a poverty rate of 45.6 % [14] and high income inequality, measured by the Gini Index, of 0.531, compared to 0.475 in the mainland US [15]. In 1999, the poverty rate in PR was 48.2 % [16] whereas the Gini index was 0.564 [17].

The first island-wide study to estimate the dental caries prevalence in PR among school-enrolled 12-year-olds was conducted in 1997, where caries prevalence was found to be 81 % in a population of 1,435 children [18]. Further, the mean number of Decayed, Missing, and Filled Teeth (DMFT) and Surfaces (DMFS) were 3.8 and 6.5, respectively. The overall mean DMFS score reported was substantially higher than the mean DMFS reported for 12-to 17-year-olds in the United States [19] and also compared unfavorably with most of the other Caribbean countries at that time [20]. Findings from the 1997 study also identified oral health differences between children attending urban private schools (Prevalence = 75 %; mean DMFS = 4.7; mean DMFT = 3.0), rural private schools (Prevalence = 84 %; mean DMFS = 7.2; mean DMFT = 4.2) and urban public schools (Prevalence = 82 %; mean DMFS = 6.5; mean DMFT = 3.8), suggesting more localized oral health disparities.

From 1993 to 2000, the government of Puerto Rico implemented a Government Health Insurance (GHI) reform program affecting both medical and dental services [18], independent of the 1997 oral health study. The intention of the GHI was to provide third party health insurance to Medicaid and Medicare eligible [21] and the medically indigent (federal poverty level below 200 %) populations, to improve access, quality, and cost-effectiveness [22]. Prior to 1993, Puerto Ricans were entitled to health services offered in government-owned and -financed facilities; however, most patients were medically indigent [22]. Dental services were offered by centers for diagnosis and treatment (CDT) throughout the island, although they were limited to emergencies, extractions, and fillings (e.g., silver amalgam, esthetic resin, and temporary cement). Services such as dental sealants, pulpotomies, and stainless steel crowns (SSC) were not offered in CDTs at that time. After implementation of the health reform, in addition to the services provided prior to the GHI, limited preventive services (e.g., periodic dental evaluation with a complete radiographic examination every three years; bi-annual topical fluoride application for children under 19; dental sealants in temporary molars of children under eight with high risk for caries, and in permanent posterior teeth for children under 14), as well as pulpotomies and SSC are offered.

While health reforms have been implemented in various countries with the aim of improving health care and health outcomes, some that have included oral health components have had mixed and/or debatable outcomes [23, 24]. The 1997 PR study suggested that the partially initiated GHI reform may have been contributing to reducing the prevalence of dental caries, since prevention, treatment, and disease levels might be influenced by increased access to dental services [18]. However, there has been no assessment of the impact of GHI on oral health outcomes since its implementation, nor has there been a comprehensive, island-wide, dental caries survey in PR since 1997. A reassessment of the prevalence of dental caries and untreated disease after the implementation of the GHI program could provide useful information regarding dental caries trends in PR and the possible impact of the GHI on such trends.

The purpose of this study was twofold: 1) to estimate caries prevalence of 12-year-old school Puerto Ricans in 2011; and 2) compare results to data obtained in 1997 to explore any possible change in caries outcomes after a government health insurance (GHI) reform was implemented. This cross-sectional study and the study conducted in 1997 were initiatives of the University of Puerto Rico School of Dental Medicine and not conceived to serve as a surveillance activity.

Of the total 1,587 participants, 53.1 % were females, and 77.2 % were enrolled in public schools. The weighted Kappa statistics for DMFS and DMFT ranged from 0.84 to 1.0 for intra-examiner, and from 0.83 to 0.91 for inter-examiner reliability.

The purpose of this study was to estimate the prevalence of caries in 12-years-olds enrolled in school in Puerto Rico in 2011 and further explore changes in the distribution of dental caries between 1997 and 2011. The present study demonstrated a significant reduction in the prevalence of caries after the 1997 implementation of the GHI in PR, nevertheless findings also showed that dental caries remained high compared to the prevalence reported for US adolescents aged 12–15 in 2011–2012 [1]. The observed trends agree with most worldwide reports revealing a decrease in caries prevalence among children and young adults in the US, Japan, Sweden, Switzerland and Netherlands [37‐40]. The mean DMFT in the present study is higher than that reported for 12-year-olds in the US during 1999–2004 [41], and slightly higher than values for 12-year-olds in the Caribbean and the Americas [42]. Interestingly, most Caribbean nations with community fluoridation programs have lower DMFTs compared to those without fluoridation [42]. Unfortunately, most published data in the region is outdated, thereby preventing appropriate data comparisons.

A significant oral health disparity in dental caries persists between 12 year-old students enrolled in public vs. private schools, as well as between male and female students. A comparison of the caries data between 1997 and 2011 shows a larger reduction in prevalence among children enrolled in private school as compared to those in public school (both rural and urban) (Table 3). Results for mean SiC index show a reduction between 1997 and 2011; however, this value is far from the global goal of a mean SiC of <3 for 12-year-olds by 2015 [33], and more than double the value reported for children of the same age in other countries [29, 43]. Moreover, the comparison of mean SiC index data from 1997 and 2011 revealed a larger reduction in caries severity among children enrolled in private schools as compared to public schools, confirming this avoidable and unjust inequity. Our findings agree with a previous study conducted in Nevada (USA) which reported higher mean SiC index for females and 13 to 15 year olds compared to 16 to 19 year olds (both genders); however, the overall mean SiC score was higher than in our study possibly due to the inclusion of older participants (13–19 years) in their cohort [34].

Since the intent of the PR GHI reform was to improve access and quality of health services for the medically indigent population, we anticipated a decrease in the dental caries gap between public and private school children between 1997 and 2011 [18]. However, an increased gap was observed after the GHI implementation and a greater difference in mean DMFT between public rural schools and private schools was observed for 2011 compared to 1997. On the other hand, an increase was observed in the filled component of the mean DMFS along with a decrease in the decayed and missing components, suggesting an increase in dental access. While increased access to dental care provided by the GHI reform may have contributed to a decline in dental caries among 12-year-old school children in PR, a report evaluating the PR health system, indicated that 48 % of GHI beneficiaries did not use their access to dental services [44]. Other factors, such as fluoride exposure from a variety of sources [3], consumption of dietary sugar [45, 46], and social determinants of health [9, 47] among others, may similarly influence the development and control of dental caries.

Fluoride availability seems to have played a major role in the marked decline of caries prevalence in some countries [3], even without access to better dental services or improved oral hygiene habits [48]. By 1960, 70 % of PR communities received fluoridated drinking water [49] and while this service was interrupted in the late 80s due to budget constraints [50], fluoridation was then government mandated in 1988 [51]. However, as of November 2015, fluoridation has yet to be implemented. Recently, the U.S Department of Health and Human Services recommended a fluoride concentration in drinking water of 0.7 parts per million (ppm) [52]. Throughout the island, drinking water fluoride levels have ranged from 0.063 to 0.123 parts per million (ppm) from 2005 to 2011 [53].

Recent analyses suggest that limiting sugars to less than 5 % of energy intake (E) may diminish the risk of dental caries through the life-span [54], and that sugar consumption between (<3 % E - < 5 % E), or even lower (2–3 % E) [38], are ideal and should be recommended, regardless of fluoridation availability [47]. A secondary analysis of our study population revealed that children with high caries prevalence consume significantly higher amounts of total sugars, fructose and inositol, especially in beverages throughout the day (results not shown).

Populations of low socioeconomic status (SES) are disproportionately affected by oral health diseases [9] even in countries with well-developed dental health care systems and community water fluoridation programs [48]. Additional research using a social determinants of health framework may further explain the health disparities seen between public and private school children in PR, as this disparity may be attributable to concurrent factors such as increased obesity, SES, access to care, and geographical distribution of dental services [55], in addition to effects of the GHI reform implementation. Regarding SES, the 2010 Census did not assess socio-economic data for the PR population [21], and the only available data that could be used to assess poverty trends derives from community surveys with large marginal errors due to the small sample size. It is necessary to obtain good quality data in order to make comparisons within PR and between PR and other nations. Future studies including socio-economic information, access to dental services, and the geographical distribution of such services, may be helpful to better understand the uneven reductions of dental caries and other secular changes. To address residual oral health disparities in 12-year-old Puerto Rican children, effective evidence-based public health interventions, such as water fluoridation [56], pit and fissure sealants [57], and fluoride varnish [6] programs, as well as the elaboration of a panoptic prevention policy with sugar intake reduction are recommended. In addition, research to impact care utilization targeting a comprehensive approach to preventive care [58] and follow-up studies to evaluate preventive strategies and oral health status are needed.

The study design and probabilistic stratified sampling methodology were employed to obtain nationally representative estimates of dental caries prevalence for Puerto Rico; however, the study was not designed to detect regional differences in those estimates. Since the number of school children included in some regions was small, we refrained from over-interpreting regional estimates. However, it is important to highlight that findings regarding caries trends between regions are consistent in both cohorts (1997 and 2011). The prevalence of caries was consistently higher in the Central region, whereas the lowest caries prevalence remained in the Ponce region [18]. The greatest reduction in caries prevalence between 1997 [18] and 2011 was observed in the San Juan region, whereas no reduction was observed for the Northern region. The highest mean DMFT and mean DMFS were also observed in the Central region for both cohorts (1997 and 2011). The greatest reductions in mean DMFT index, when comparing results from 1997 [18] and the present 2011 data, were observed in the San Juan, Northeast, and Central regions, whereas a modest reduction was observed in the North region. With reference to the mean DMFS, the greatest reductions were observed in the Northeast, San Juan, and Northwest while a relatively small reduction was observed in the Southeast region. As mentioned earlier, additional investigation is needed to gain insights on dental caries prevalence and severity within regions, taking into account differences in socioeconomic, social structure, environment, behavioral, and/or biological factors. The present study is the phase 1 (detecting phase) of a conceptual framework to advance our oral health disparity research agenda. Further research to understand (phase 2) and reduce (phase 3) oral health disparities in this population is essential [59]. The present publication did not address individual-level information about other risk factors, such as sugar intake, dietary patterns, knowledge, attitudes, tooth brushing, and parental educations, among others. Future publications will address the effect of these factors on dental caries.

There are several limitations to our study: the population examined was limited to 12-year-olds. The reasons for studying this age group were twofold. First, in 1997 WHO established 12 years as the global monitoring age for international comparisons [60], and secondly to allow comparisons with the 1997 cohort. Longitudinal studies in different age groups, using a broader sample size within regions, could evaluate caries trends in PR and help establish appropriate public health strategies. To allow caries data comparison, uncavitated lesions were not included in the study, as in 1997. We recognize that this is a weakness of our study since the exclusion of early caries lesions may underestimate the caries prevalence in this population. Another study limitation may be the lack of individual level economic data, and the use of a surrogate socioeconomic measure by school type, which may introduce misclassification. However, this misclassification is expected to be non-differential and most likely be introducing a small amount of bias towards the null hypothesis (no differences between high and low SES group).

At the same time, the current study has notable strengths. Probability sampling from all regions of PR allowed valid assessment of dental caries prevalence in this age group, even though it was not designed to produce region-specific prevalence estimates. The use of the SiC index allowed us to confirm disparities in dental caries. Overall, the study methods were similar to those employed in the 1997 study allowing caries data comparison. Moreover, dental examinations were conducted, in 1997 and 2011, by dentists trained by the same reference examiner. This allowed high intra- and inter-examiner reliability and will allow data comparisons with other studies locally and worldwide.

Among 12-year-old schoolchildren in Puerto Rico between 1997 and 2011, caries prevalence, extent, and severity decreased as well as the DMFT missing component, while the filled component increased. Dental caries prevalence was high and the health disparity identified in 1997 persists between children enrolled in public and private schools after more than a decade of the GHI implementation. The relationship between GHI implementation and other potentially relevant co-factors for caries warrants further research, as does the seemingly entrenched disparity across groups.