Date of Degree
PhD (Doctor of Philosophy)
Levy, Steven M.
First Committee Member
Childers, Noel K.
Second Committee Member
Caplan, Daniel J.
Third Committee Member
Carter, Knute D.
Fourth Committee Member
Warren, John J.
Fifth Committee Member
Cavanaugh, Joseph E.
Sixth Committee Member
Kolker, Justine L.
My PhD projects were secondary analyses of data from a prospective study conducted at the University of Alabama at Birmingham. Two cohorts of low socioeconomic status, African-American children from Perry County, Alabama, were invited to participate. Children in the 1st Cohort (Cohort 1, n=98) were approximately six years old at baseline and followed for 6 years, while children in the 2nd Cohort (Cohort 2, n=95) were approximately one-year-old at baseline and followed for five years.
For the first dissertation project, the prevalence and incidence of dental decay were assessed for children in Cohort 1. The findings of this report showed that 60-70% of the children had dental decay experience at each of the six annual exams. Approximately a third of the children had additional new tooth decay from age 6 to age 12.
For the second project, risk factors for time to dental decay occurrence were assessed using a relatively new analytic approach which allowed the use of time-dependent risk factors for children in Cohort 1. This was the first time for this analytic approach to be used in the dental literature, although it is widely used in medical research. The merit of using this technique was that, since dental decay risk factors can change with time, the value of the risk factor was allowed to change over time. The second project showed that about 29% of the children had their first permanent tooth decay event during the six-year follow-up. Final results showed that greater consumption of water, milk and 100% juice were associated with lower dental decay hazards, while greater consumption of added-sugar juice was associated with greater hazard of having an event.
The third PhD project was designed to assess the patterns of and the relationship between initial Mutans Streptococci detection and dental caries experience occurrence in African-American pre-school children with mean age of 1 year at baseline. The third project dealt with the MS variable as a “time-dependent variable”, using a statistical analysis called “Extended Cox hazards modeling”. To the knowledge of the author, this is the first published study which has used this relatively new analytic approach to assess the complex relationship between MS detection and dental caries experience.
In addition, in the third project, the behavioral risk factors for having a positive salivary MS test were assessed. This study found that median MS acquisition survival (when 50% of the children had positive salivary MS test) was 2 years and mean survival time was 2.09±0.09 among African-American children who had valid MS acquisition tests (n=99). Approximately 23% of the children did not have any positive salivary MS test by age 4 years. Multivariable analysis showed that not having a positive salivary MS test at any of the study exams was associated with having acute illness in the previous 6 months and being recruited into the study before 10 months of age. Results of extended Cox proportional hazards modeling showed a significant relationship between having a caries experience event at any given time during the follow-up period and having a positive salivary MS test at any point in time (HR=2.25, 95% CI 1.06-4.75).
In this dissertation work, I studied the burden of dental decay in two cohorts of low socioeconomic status, African-American children from Perry County, Alabama. Children in Cohort 1 (n=98) were six years old at baseline and followed for 6 years, while children in Cohort 2 (n=95) were approximately one-year-old at baseline and followed for five years.
Most of the children were from single parent families 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 studied. These counties are desperately poor. Persistent poverty, a low rate of employment, limited education, poor health, and high rates of single motherhood and dependence on public assistance programs are important characteristics of the Black Belt Counties. Also, many rural communities in Alabama’s Black Belt lack some, if not all, health services, including dental care.
The findings of this report showed that 60-70% of the children in Cohort 1 had dental decay experience at each of the six annual exams. Approximately a third of the children had additional new tooth decay from age 6 to age 12 and that water and 100% juice consumption were associated with longer time to experiencing dental decay. Also, this work showed that more than 90% of the children in Cohort 2 acquired decay-causing oral bacteria by age 4 years, which was found to be significantly associated with experiencing permanent dental decay.
African American Children, Biostatistics, Dental Caries, Public Health
xiv, 178 pages
Includes bibliographical references (pages 166-178).
Copyright © 2017 Tariq Ghazal
Ghazal, Tariq. "Prevalence, incidence and risk factors for dental caries in preschool and school-aged African American children: a prospective cohort study." PhD (Doctor of Philosophy) thesis, University of Iowa, 2017.