The Study of Factors Affecting Oral Health in a Sample from NHANES Survey in the United States

Aims: Oral health problems include dental caries, gum diseases, loss of natural teeth


INTRODUCTION
Oral health is greatly affected by various kinds of oral infections, such as dental caries, periodontal diseases, lesions in HIV/AIDS, mucosal and salivary gland diseases, orofacial pain and clefts, and, occasionally, oral cancer (1). Tooth loss weakens mastication and causes poor diet, nutrition, and eating behavior leading to high mortality rates (2). Also, poor oral health and periodontal diseases are predisposing factors for pneumonia, chronic obstructive pulmonary diseases, and has adverse-effects on diabetes patients (3). These oral diseases have a great impact on masticatory functions, nutritional intake, speech, swallowing, standard of living, and socialization (1). The US Surgeon General called dental caries a "silent epidemic", and it is the root cause of loss of teeth in children and can result in severe health outcomes, and even mortality (1).
The predisposing factors causing oral infections include older age, poor nutrition, tobacco and/or alcohol use, immunodeficiencies, poor dental hygiene, unfavorable social conditions, and diabetes (4).
It is found that untreated periodontal disease contributes to tooth loss among adults and is known to compromise mastication, esthetics, self-esteem, and standard of living (5). There are various complications associated with untreated tooth decay such as pain, poor appearance, dysfunction, irre-gular school attendance, and low concentration on daily life achievements (6). In the United States, untreated dental caries is observed in 53 million people in the permanent dentition, and 25% of adults aged 65 years or older have lost their natural teeth due to untreated oral conditions (7).
According to the World Health Organization (WHO), fluoride toothpaste is the most popular and accepted source of fluoride use worldwide, and it is most effective to decline the prevalence of dental caries (8). Duijster et al. (9) showed that children from families that do not practice regular tooth brushing are more prone to experience dental caries (9). In Norway, data from a cohort study has confirmed that brushing teeth of children with a fluoride toothpaste twice in a day reduces the chances of development of cavities from 2 to 5 years of age (10).
For years, the recommended age of first visit to the dentist for children was around twelve months of age, but, recently, it has changed to a time span between 6 months of age and the development of the first tooth (11). The reasons for this recommendation are to prevent Early Childhood Caries (ECC) and to discover and assess the progression of any dental pathology (11). In addition, early visits to a dentist would educate caregivers about the importance of practicing healthy oral habits, teach them about fluoride use, teething management, and the co-relation between diet and oral health (11).
The occurrence of oral diseases is more prevalent among marginalized population groups, such as people with less education, living in poor conditions, and negligent oral habits. In the United States, 35-44 years aged Hispanic Whites are twice more likely to have untreated tooth decay than non-Hispanic Whites, mainly due to lower access of minorities to dental care and low socio-economic status (12). In addition, the prevalence of dental caries is most commonly observed in individuals with poor dietary habits, high consumption of sugar, and limited access to oral healthcare (8). In 2018, oral cavity cancers rank among the top 15 most common cancers worldwide with a total of 354,864 incident cases (13).

Ethical considerations
This study was an analysis of secondary data collected from National Health and Nutrition Examination Survey (NHANES), 2017-2018. Permission to use NHANES public data was obtained from (CDC). The Human Subjects Approval Letter to proceed with secondary data analysis was obtained from the Committee of the Protection of Human Subjects at California State University, Fresno.

Study Population
In the original NHANES survey, the data were collected from the US residents selected from 30 different survey locations, aged 1 to 80 years and older, in 2017-2018. This study will focus on oral health among all age groups from 1 year and older. Of those, 9,254 participants completed the interview and 8,704 were examined. For this study, the population was examined by using the NHANES, 2017-2018. The NHANES data comprised two questionnaires: a demographic questionnaire and an oral health questionnaire. Both the questionnaires were asked at the residence of the participants using the Computer-Assisted Personal Interview (CAPI) system. A proxy was present for participants who were 16 years or under. Data were obtained on many topics regarding the individual demographics, lifestyle, and oral health status.

Variables
The dependent variable used in this study was: Rate the health of your teeth and gums. The four independent variables used in this study were: last visit to a dentist, whether you received fluoride Rx drops or tablets, Gender, and the educational level for adults 20+ years.

Data collection
This study was an analysis of secondary data collected from NHANES 2017-2018. The study examined data from individuals aged 1 and older and total participants in this age group were 9,254.
This study determined periodontal health-related factors such as last visit to the dentist, fluoride intake, rate of health of teeth and gums, gender, and educational level. Variables were analyzed using SPSS (Statistical Package for the Social Sciences).

Hypotheses
The following null hypothesis were identified to emphasize the purpose of this study: • Hypothesis 1: There is no statistically significant difference in the rate of health of teeth and gums between those who visited the dentist in the last 6 months and those who did not visit the dentist in the last 6 months.
• Hypothesis 2: There is no statistically significant difference in the rate of health of teeth and gums between those receiving fluoride drops or tablets and those not receiving fluoride drops or tablets.
• Hypothesis 3: There is no statistically significant difference in the rate of health of teeth and gums according to gender.
• Hypothesis 4: There is no statistically significant difference in the rate of health of teeth and gums according to educational level.

Data analysis
Secondary data from NHANES 2017-2018 survey was used and inputted into SPSS to test the hypothesis using the Chi-Square Test of Independence. The Chi-Square Test of Independence was used because it provides a test to determine whether there is a significant difference between two categorical variables. The significance level of 0.05%, marginal error of 5% and C.I. (Confidence Interval) of 95% was used for data analysis. The sample size calculated for this study was 369. The dependent variable was the rate of health of your teeth and gums. The independent variables were gender, educational level, last visit to a dentist, and if fluoride drops or tablets were received. The dependent and independent variables were analyzed using SPSS 25 edition statistical software.

Last Visit to a Dentist and Health of Teeth and Gums
The NHANES survey asked the residents about their last visit to the dentist. The responses were recorded to include: 6 months or less, more than 6 months ago, more than 1 year ago, more than 2 years ago, more than 3 years ago, more than 5 years ago, never, don't know (see Table 2). The first hypothesis stated that there is no statistically significant difference in the rate of health of teeth and gums between those who visited the dentist in the last 6 months and those who did not visit the dentist in the last 6 months. The Pearson Chi-Square value was 1121.787, df= 21, and p-value was < 0.001. Since the p-value was less than 0.05, it can be concluded that there was a significant difference between the health of teeth and gums between those who visited the dentist in the last 6 months and those who did not visit the dentist in the last 6 months.  The second hypothesis stated that there is no statistical difference in the rate of health of teeth and gums between those receiving fluoride drops or tablets and those not receiving fluoride drops or tablets. The Pearson Chi-Square value was 8.784, df= 6, and the p-value was 0.185. Since the p-value was greater than 0.05, it can be concluded that there was no significant difference in the rate of health of teeth and gums between those receiving fluoride drops or tablets and those not receiving fluoride drops or tablets. The results of this test fail to reject the null hypothesis.

Gender and Health of Teeth and Gums
The survey asked the participants about their gender. The answers were recorded as Male and Female (see Table 4). The third hypothesis stated that there is no statistically significant difference in the rate of health of teeth and gums according to gender. The Pearson Chi-Square value was 5.391, df= 3, and the p-value was .145. Since the p-value was greater than 0.05, it can be concluded that there was no significant difference in the rate of health of teeth and gums according to gender. The results of this test fail to reject the null hypothesis.

Educational Level and Health of Teeth and Gums
The survey asked the residents about their educational level for 20 years and above adults. The answers were recorded as Less than 9th grade, 9-11th grade, High school graduate, some College or AA graduate, College graduate or above, Refused, and Don't know (see Table 5). The fourth hypothesis stated that there is no statistically significant difference in the rate of health of teeth and gums according to the educational level. The Pearson Chi-Square was 17.133, df= 18, and p-value was .514. Since the p-value was greater than 0.05, it can be concluded that there was no significant difference in the rate of health of teeth and gums according to the educational level. The results of this test fail to reject the null hypothesis.

DISCUSSION
Periodontal health is defined as a state of being free from inflammation associated with gingivitis or periodontitis clinically (14). This study was an analysis of secondary data collected from NHANES 2017-2018. This study found a significant difference in the rate of health of teeth and gums between those who visited the dentist in the last 6 months and those who did not visit the dentist in the last 6 months. The findings of this study showed that 1,006 residents rated their health of teeth and gums as excellent, having last seen a dentist in 6 months or less. According to the findings of this study, the health of teeth and gums significantly deteriorated for those who did not visit the dentist in more than 2 years. The findings of this research question were similar to studies discussed in the literature review. The literature shows that dental caries in children can be prevented if they visit a dentist before or soon after the eruption of their first tooth (11).
At the same time, literature also suggests that children with high family income and lower mean of caries experience were more likely to visit the dentist (15).
This study did not find a significant difference in the rate of health of teeth and gums between those receiving drops or tablets and those not receiving drops or tablets among children aged 3-15 years in the US. The findings of this study suggest that 71 children who received fluoride drops or tablets rated the health of their teeth and gums as excellent, and 651 children who did not receive fluoride drops or tablets also rated the health of their teeth and gums as excellent.
The findings of this research question were different from the reviewed literature. The literature suggests that higher fluoride concentration in drinking water in the US is associated with lower dental caries (16). Also, the literature highlights that children who do not consume tap water that contains fluoride were more likely to experience dental caries in their lifetime (16).
This study found no significant difference in the rate of health of teeth and gums according to gender among participants aged 1 and older. The results of this study showed that 869 females rated the health of teeth and gums as excellent, and 818 males rated the health of teeth and gums as excellent. Also, 1,114 females rated the health of their teeth as very good as compared to 1,020 males. In this study, the number of participating females tended to rate the health of their teeth and gums higher than males. However, there was no significant difference between gender and the rate of health of their teeth and gums. The literature shows mixed results, some literature suggests that females having lower levels of protective IgA as compared to males, pregnancies, and being more prone to harbor S. mutants can lead them to develop dental caries (17). The growing literature suggests that both men and women are equally aware of oral hygiene, and both have equal chances of developing dental caries (18).
This study found no significant difference in the rate of health of teeth and gums according to educational level among participants aged 20 years and above. The findings suggest that participants who have some college or AA degree have reported better health of their teeth and gums as compared to participants who are less educated than them. But the numbers are not very significant to conclude an association between educational level and health of teeth and gums.
The findings of this research question are different from the reviewed literature. The literature suggests that in a study conducted by Kuter & Uzel in 2020, the results showed that a mother's educational level is directly related to children's tooth brushing but not related to the number of cavities in a child's mouth (19).
In conclusion, this study demonstrated that there were significant differences among one of four hypotheses. There was a significant difference in the rate of health of teeth and gums between those who visited the dentist in the last 6 months and those who did not visit the dentist in the last 6 months. This study concludes that individuals who have visited the dentist in 6 months or less have rated their health of teeth and gums as excellent as compared to those who did not visit the dentist in the last 6 months. Overall, the results of the study suggest further and advanced research regarding factors affecting oral health in the US residents.
Although the results of the secondary data analysis presented in this manuscript found no statistically significant differences in the health of teeth and gums in association with intake of fluoride drops or tablets, gender, and educational level, it is important to test these differences across diverse groups, as significant differences may be present by ethnicity.