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To assess the prevalence and incidence of dental caries in school-aged African-American children who received semi-annual fluoride varnish applications.
A cohort of six-year-old high caries-risk African-American children (n=98) was recruited in Uniontown, Alabama and followed for six years. Oral examinations were done annually by three trained/calibrated dentists. Tooth surfaces with cavitated caries, missing due to caries and with filled surfaces were recorded, using WHO criteria. Also, as part of the study, children received periodic oral health instruction, fluoride varnish applications and referral to dentists starting at baseline.
The person-level prevalence of dmfs/DMFS was: 61.2 percent at mean age 5.9 (n=98, mean dmfs/DMFS=11.6); 63.8 percent at age 6.7 (n=80, mean dmfs/DMFS=13.2); 70.6 percent at age 7.8 (n=68, mean dmfs/DMFS=14.2); 65.7 percent at age 8.8 (n=68, mean dmfs/DMFS=11.8); 55.6 percent at age 9.7 (n=63, mean dmfs/DMFS=8.8); 40.3 percent at age 10.7 (n=62, mean dmfs/DMFS=3.4); and 37.1 percent at age 11.7 (n=62, mean dmfs/DMFS=2.3). The six-year person-level incidence of dmfs/DMFS was 32.3 percent (mean dmfs/DMFS=1.6) from age 5.9 to age 11.7 (n=62).
In spite of the oral health education and fluoride varnish applications, there was substantial new dental caries in this high-risk sample. Additional studies evaluating risk factors for caries development are ongoing.
Dental caries is a chronic, infectious, transmissible, and multifactorial disease that affects a high percentage of children in both developed and developing countries. Several national surveys and other studies showed high prevalence and incidence of dental caries in both primary and permanent teeth in school-aged children, especially in disparate groups such as African American children. For example, the U.S. National Health and Nutrition Examination Survey (NHANES) from 1999-2002 showed that primary tooth dental caries prevalence was 49.1 percent in children aged six to 11 years1. In NHANES 1999-2004, among six- to 11-year-old African-American children, the prevalence of dental caries in permanent teeth was 19.03 percent, the untreated permanent tooth decay prevalence was 6.9 percent and the mean DMFS, DS and FS scores were 0.70, 0.21and 0.43, respectively1. In NHANES 1999-2004, among six- to eight-year-old African-American children, the prevalence of both primary and permanent tooth caries experience was 56.12 and the prevalence of untreated primary and permanent tooth decay experience was 37.381.
Several individual studies have assessed caries prevalence in the mixed-dentition stage. For example, Gemmel et al.2 showed that the overall mean number of carious surfaces (D+d) was 9.8 (primary dentition=8.0 and permanent dentition=1.8) in 543 children aged 6-10 years, using both clinical and radiographic examinations. Also, Willerhausen et al.3 reported that the prevalence of dental caries experience (both primary and permanent) in six-year-old children was 48 percent (n=163), 61 percent for age seven (n=356), 65 percent for age eight (n=308), 72 percent for age nine (n=274), 74 percent for age 10 (n=175) and 70 percent for age 11 (n=14). Wendari et al.4 reported that the mean dmft, dmfs, DMFT and DMFS scores were 2.6, 6.1, 0.9 and 1.4, respectively in children aged eight to12 years who were in schools receiving oral hygiene instructions (n=80), while the scores were 2.1, 5.1, 1.2 and 2.0, respectively, in the control group (n=60).
Several prospective cohort studies reported dental caries prevalence in the mixed-dentition at baseline and follow-up examinations, so it was possible to assess dental caries increments. For example, Al-Shalan et al.5 reported that the mean carious primary tooth increment (Δdmft) was 1.1 surfaces from age three to age nine years, Karjalainen et al.6 (2001) reported that the prevalence of carious lesions (only dentin lesions) and fillings combined was 8.0 percent in 148 children aged approximately three years at baseline, while it was 28.1 percent (n=135) at three-year follow-up.
Dental caries increment was also reported as part of several randomized clinical trials. For example, Kandelman and Gagnon7 examined 274 children aged eight and nine years old at baseline, one-year follow-up and two-year follow-up. At baseline, the mean DMFS+dmfs was 4.26 among those who were in the control group (n=97). One year after baseline, the average DMFS+dmfs increment was 6.06, while the mean second year increment was 3.40, respectively. Jackson et al.8 showed that the overall two-year mean DMFS+dmfs increment was 2.60 (n=517, mean age=5.63 years) in the control groups, respectively. Zimmer et al.9 reported that the mean scores of D3,4MFS (cavitated) increment were 2.61 and 2.22 in children from 9.5 to 11.5 years who were assigned to the no fluoride varnish group and fluoride varnish group, respectively. Cahen et al.10 reported that the mean three-year dmfs increments in French children aged six to eight years at baseline was 18.3 in placebo toothpaste groups (mean DMFS increments was 4.1).
There was a significant overall decrease in the U.S in the prevalence of dental caries in school-aged children since the middle of the last century. This was mainly to the widespread use of fluoride, especially community water fluoridation, which was recognized by the U.S. Centers for Disease Control and Prevention (CDC) as one of 10 public health achievements in the 20th century11. However, a high percentage of children in the world, including in the U.S., continue to suffer from dental caries and its consequences.
While the general epidemiology of dental caries in school-aged children has been well documented, there is limited information available for specific age groups. In particular, there are gaps in knowledge about the prevalence and incidence of dental caries in school-aged children among U.S minority children, including Native Americans, Hispanics and African-Americans. The purpose of this study was to assess caries prevalence and incidence among high caries-risk six-year old African-American children who lived in what is termed the “Black Belt” counties in Alabama (Black Belt counties are characterized by their fertile soil) that has not been widely studied12. These children received fluoride varnish applications and oral hygiene instructions semiannually.
This report is a secondary data analysis of a recently completed prospective study conducted at the School of Dentistry, University of Alabama at Birmingham (UAB)13,14. At baseline (fall of 2007), parents/caregivers of 98 African-American children aged approximately six years were recruited from a primary school in Perry County, Alabama. Inclusion criteria for the parent study which was about caries and bacterial acquisition were as follows: infants had to not have had all their first permanent molars erupted, be living with their biological mother, and the parents had to plan to remain in the area for at least three years. Informed consent was obtained from the children's caregivers after the study was approved by the Institutional Review Board (IRB) at University of Alabama at Birmingham.
Oral examinations were done at baseline (approximately age six) and six annual follow-up examinations from age ~seven to ~12 years by three trained examiners, using portable equipment and World Health Organization (WHO) criteria15, without radiographs. Dental explorers were used only occasionally to confirm that carious lesions were cavitated or to confirm that an esthetic composite resin or sealant was present.
Reliability assessment of dental examinations was conducted with approximately 10 children (~10 percent) annually. The overall inter-examiner reliability was estimated using a weighted average of the pairwise inter-examiner reliability estimates.
Although dental examinations were done annually by three dentists, the children were seen semi-annually for fluoride varnish application, delivery of oral hygiene instruction, and anticipatory guidance, which were conducted by the dental examiners, dental hygienists, and dental residents in the Department of Pediatric Dentistry for the first two years, and then annually. At each visit, a preventive oral health kit containing a toothbrush, fluoridated toothpaste, dental flossers, dental floss and a dental mirror were provided. Also, when cavitated dental lesions or other dental needs (i.e., need to establish dental home) were observed, referrals to dentists were made.
In this study, prevalence and net caries incidence (NCI) were assessed at the surface level and for cavitated lesions only. Prevalence of dental caries was assessed for primary teeth alone, permanent teeth alone and primary and permanent teeth combined. The severity of dental caries was defined as (mean number of decayed, missing, or filled surfaces and assessed for primary teeth alone, permanent teeth alone and primary and permanent teeth combined. In assessing the incidence of dental caries, transitional matrices were built to show the status of each surface of a particular tooth and individual at both the beginning and end of the incidence period. The following transitions were considered as cavitated caries incidence: unerupted to decayed, unerupted to filled, unerupted to missing due to caries, sound to decayed, sound to filled, sound to missing due to caries, filled to decayed and filled to missing due to caries. Decayed to sound was reported as a reversal, while the remaining transitions were reported as no change in status.
Since these children had up to seven annual dental examinations, including baseline, there were seven prevalence rates (one at each cross-sectional exam) and 21 possible incidence periods of varied length. However, after conducting some initial analyses of the available data, the following incidence periods were selected for reporting: 1) the full period (age six to 12 years) is important because it represents the entire timeframe of follow-up (n=62); 2) one-year incidence from age six to seven years had the highest sample size (n=79); 3) two-year incidence from age seven to nine years (n=67); and 4) three-year incidence, both from age six to nine years (n=76) and from age nine to 12 years (n=62).
Both prevalence and incidence were defined in two ways: as dichotomous (yes/no) and count (number of carious surfaces) variables. For incidence, person-level primary and permanent tooth NCI rates were assessed separately. Also, percentages of combined primary and permanent tooth surfaces that developed new caries experience were determined. Since all index children were African-American, race/ethnicity was not included in the analysis. All descriptive analyses were compiled using SAS 9.3 (SAS Institute Inc., Cary, NC, USA).
Dental examinations were completed annually at ages six through 12 years. Footnote in Table 1 summarizes the mean (SD) ages of the children at these examinations. Inter-examiner reliability results for the average person-level weighted kappa scores for numbers of caries-affected primary tooth surfaces (dmfs), permanent surfaces (DMFS) and combined primary and permanent tooth surfaces (dmfs+DMFS) for the three examiners were 0.98, 0.97 and 0.98, respectively. However, average person-level simple kappa scores were 0.85, 0.90 and 0.83, respectively (data not shown).
Table 1 and Figure 1 show that person-level combined primary and permanent caries experience rates (dmfs+DMFS>0) were 61.2 percent, 63.8 percent, 70.6 percent, 65.7 percent, 55.6 percent, 40.3 percent and 37.1 percent at the age six, seven, eight, nine, 10, 11 and 12 year exams, respectively. The mean dmfs+DMFS scores were 11.6, 13.2, 14.2, 11.8, 8.8, 3.4 and 2.3, respectively (mostly filled).
Table 1 and Figure 1 also show that the prevalence of primary tooth dental caries experience was 61.2 percent, 63.8 percent, 70.6 percent, 63.6 percent, 57.9 percent, 48.4 percent and 64.3 percent at ages six, seven, eight, nine, 10, 11 and 12 years, respectively. Mean dmfs scores were 11.5, 13.2, 14.0, 11.3, 8.8, 4.9 and 5.1, respectively. The respective prevalence of permanent tooth dental caries experience were 5.7 percent, 3.8 percent, 10.5 percent, 16.4 percent, 22.2 percent, 24.2 percent and 29.0 percent. Mean DMFS scores were 0.06, 0.04, 0.30, 0.64, 0.83, 0.94 and 0.89, respectively. None of the children had missing permanent tooth surfaces due to caries at any dental examination.
Table 2 shows person-level combined primary and permanent tooth surface NCI (dmfs+DMFS incidence). The six-year NCI from age six to 12 years was 32.3 percent.
Table 2 shows person-level primary tooth surface NCI (dmfs incidence). The six-year NCI rate from age 6 to 12 years was 50.0 percent. From age six to 12 years, 3.4 percent of the primary tooth surfaces had new caries experience.
Table 2 also shows person-level permanent tooth surface NCI. The one-year NCI rate from age six to seven years was 3.8 percent (n=79); the two-year NCI rate from age seven to nine years was 16.4 percent (n=67). The three-year NCI rates from ages six to nine (n=67) and nine to 12 years (n=62) were 16.4 percent and 11.3 percent, respectively. The six-year NCI rate from age six to 12 years was 22.6 percent. From ages six to seven and seven to nine years, 0.1 percent and 0.8 percent of the permanent tooth surfaces had new caries experience, respectively. For the three-year incidence periods, 0.8 percent and 0.5 percent of the permanent tooth surfaces had new caries experience from ages six to nine and nine to 12 years, respectively. From age six to 12 years, 0.7 percent of the permanent tooth surfaces had new caries experience.
This study showed that substantial additional dental caries was observed during the six years of follow-up from age six to 12 years. There was no clear trend in the person-level primary tooth surface prevalence of dental caries with age, mainly due to the natural exfoliation of primary teeth at the mixed dentition stage. In contrast, there was an overall consistent increase in the trend of permanent tooth surface prevalence of dental caries (from 5.7 percent at age six to 29.0 percent at age 12). The combined person-level prevalence rates of dmfs+DMFS were very similar to person-level prevalence of dmfs at ages six, seven, eight, nine and 10 years, since almost all children had primary teeth. However, at ages 11 and 12, the combined person-level prevalence rates of dmfs+DMFT were between the values of DMFS and dmfs (40.3 percent and 37.1 percent, respectively).
With regard to person-level primary tooth surface NCI, 48.1 percent, 54.5 percent and 58.5 percent of the children developed at least one additional surface with caries experience from ages six to seven, seven to nine and six to nine years, respectively. Although, only 14 children had primary tooth surfaces at age 12, the person-level primary tooth surface NCI remained relatively high at 42.9 percent and 50.0 percent from ages nine to 12 and six to 12 years, respectively. In contrast, since all children at age 12 had most of their permanent teeth erupted, the highest person-level permanent tooth surface NCI was from age six to 12 years, with the NCI from age six to nine higher than that from age nine to 12 (16.4 percent vs. 11.3 percent, respectively). This may be due to the report that most of the permanent tooth caries happens one to two years after the eruption, especially prior the application of sealants16.
Only limited direct comparisons of the findings of our study with published national survey results can be made. Prevalence findings in national surveys were stratified by either age, sex, race/ethnicity or SES, but not stratified by all of them together. However, the findings of our study showed a higher overall prevalence of primary and permanent tooth caries than those published in national surveys. NHANES 1999-20021 showed that person-level prevalence of dmfs was 49.1 percent in the U.S. children aged six to 11 years (all races/ethnicities), while our study showed an approximately 10-20 percent higher (absolute difference) dmfs prevalence from age six to age 12. The severity of primary tooth dental caries in our study was substantially higher than that reported from NHANES 1999-2002. Compared with the age group six to 11 years mean dmfs score in NHANES 1999-20021 (3.7), our age-specific mean dmfs scores were approximately two to nine units higher.
NHANES 1999-20021 showed that person-level prevalence of permanent tooth caries was 20.1 percent in the U.S. children aged six to 11 years (all races/ethnicities), while our study showed a lower prevalence at ages six through nine years (5.7 percent, 3.8 percent, 10.5 percent, 16.4 percent, respectively) and slightly higher prevalence at ages 10 through 12 years (22.2 percent, 24.2 percent and 29.0 percent, respectively). The severity of permanent tooth dental caries in our study was similar to that reported for NHANES 1999-20021.
Several studies have been conducted to assess dental caries prevalence and incidence in school-aged children. For example, Gemmel et al.2 showed that mean scores of d and D were 8.0 and 1.8 in children with mean age 7.9 years, respectively, while in our study mean scores of d and D were 2.4 and <0.1 at age eight, respectively. Karjalainen et al.6 showed that the dfs prevalence at age six years was 28.1 percent, compared to 61.2 percent in our study. Wendari et al.4 reported that the individual mean dmfs was 5.1 in children from eight to 12 years of age, while the age-specific mean dmfs scores were approximately three to seven units higher in our study. However, the mean DMFS score in our study was slightly lower than that reported in Wendari et al4 and this could be due to the fact that children in our cohort were younger.
The prevalence of dental caries in our study was not consistently greater than that reported in other studies. For example, Willerhausen et al.3 reported lower prevalence rates of combined dmfs+DMFS in German children aged six, seven and eight years of 48.0 percent, 61.0 percent and 65.0 percent, respectively, compared to 61.2 percent, 63.8 percent and 70.6 percent in our study, respectively. However, Willerhausen et al.3 reported higher prevalence rates at ages nine, 10 and 11 years of 72.0 percent, 74.0 percent and 70.0 percent, respectively, compared to 65.7 percent, 55.6 percent and 40.3 percent in our study, respectively. In contrast, Shalan et al.5 showed that the prevalence rates of dmfs and DMFS among Minnesota children with mean age of nine years were 68.7 percent and 45.2 percent, respectively, while our study showed lower prevalence at age nine (63.6 percent and 16.4 percent, respectively).
There are no published studies that assessed children's mixed dentition dental caries incidence as the primary focus. Nevertheless, there are some prospective cohort studies and randomized controlled trials that reported results which enabled us to indirectly assess dental caries increments and incidence and compare them to the results of our study. For example, Kandelman and Gagnon7 reported a slightly higher score for mean combined dmfs+DMFS increment from age eight to nine (6.1) in a control group of Canadian school-aged children than that reported in our study from age seven to nine years (5.2). Also, Jackson et al.8 reported that the overall mean 21-month dmfs+DMFS increment was 2.9 in the control group. Zimmer et al.9 showed that mean cavitated DMFS increments in children from age 9.5 to 11.5 were 2.6 and 2.2 in the control and fluoride varnish groups, respectively, while in our study the mean DMFS increment from age nine to age 12 was 0.9.
Our study addressed both prevalence and incidence of dental caries in a cohort of children whom families live in persistent poverty, with a low rate of employment, limited education, poor health, and high rates of single motherhood and dependence on public assistance programs. These children lack some, if not all, health services, including dental care12.
Generally, the prevalence and severity (dmfs/DMFS) of dental caries in school-aged children reported in our study were higher than those reported in most of the published studies and national surveys at ages six through 12 years. However, the findings of our study were that the incidence of dental caries in school-aged children and dmfs/DMFS increments were similar to those reported in most of the published studies. This was because our study showed a high disease prevalence at baseline (age six), resulting in similar incidence of tooth caries in spite of the high age-specific prevalence.
The most important limitation with our study was the reliance on a small convenience sample; thus, caution is needed when interpreting the findings of this study, which are not generalizable to other African-American children.
Furthermore, this study could have underestimated the prevalence and the incidence of dental caries among the index children, because caries was reported at the cavitated level only and radiographs were unavailable.
In spite of the limitations mentioned above, our study is unique. There are very few studies that have reported the prevalence, incidence, and dmfs and DMFS increments among school-aged, high caries-risk, African-American children at the surface level and by tooth type.
Assessment of incidence of dental caries in school-aged children is difficult because it must be done longitudinally and is, therefore, costly, time-consuming and subject to attrition17. Also, ethical standards when studying high caries risk populations requires that treatment (at least preventive treatment) be offered for children.
Although all of the children in our study received fluoride varnish treatments when they came for the study visits, at six-month intervals for two years and annually thereafter, additional dental caries was observed. Many factors could be associated with the high prevalence and incidence of dental caries among our cohort of African-American children, such as living in a non-fluoridated town, low socioeconomic status and poor dietary behaviors. Thus, additional studies evaluating risk factors for caries development and dietary behaviors are necessary to better understand the disease process and determine foci for prevention of caries. Since the main preventive approach for occlusal caries (sealants) is different from that for proximal caries (topical fluoride), knowing the incidence patterns (occlusal vs. proximal) will help identify tooth surfaces at highest risk of developing dental caries, which is important for the determination of the best preventive intervention modality or combined modalities to decrease the prevalence and incidence of dental caries in school-aged children.
In the future, time-to-event analysis can be conducted to assess the age at which the children develop their first decayed tooth (or other outcomes) and risk factors associated with time to developing dental caries.
The authors would like to thank the Pediatric Dentistry residents and coordinators who helped selflessly in Uniontown, Alabama. Also, the authors wish to thank the National Institutes of Health for supporting the project through the NIDCR grant: R01-DE016684.