Associations between utilization of dental care and oral health outcomes in the U.S. using the National Health and Nutrition Examination Survey (2017-2020) 

Abstract

Background

This analysis aims to evaluate the association between the time since and reason for a patient's last dental appointment across clinical oral health outcomes.

Methods

We used data from the 2017–2020 National Health and Nutrition Examination Survey (NHANES), a cross-sectional nationally-representative of US noninstitutionalized adults. The predictors were the time since last dental appointment and the reason for the last dental appointment (routine vs. urgent). We examined the presence and number of missing teeth and teeth with untreated coronal and root caries. Multivariable regression models were used to assess the interaction between time since last dental appointment and reason of the appointment on clinical oral health outcomes.

Results

Two-thirds of the US population had a dental appointment within a year, while 53 million individuals did not visit a dentist for the last three years. The odds of having teeth with untreated coronal or root caries increased with the length of time since the last routine appointment. Compared to those who had a dental appointment within a year, individuals who had their last dental appointment more than 3 years ago had 0.44 times the odds of having missing teeth among routine users (95%CI = 0.33, 0.59) and 0.67 times the odds among urgent users (95%CI = 0.45, 0.98).

Conclusions

Recent routine dental appointments are associated with improved oral health outcomes. Disparities exist in access to care for low-income and/or members of racial/ethnic minorities. The outcomes reiterate how social determinants of health impact access to oral health care and subsequent oral health outcomes.

Background – Oral Health and Systemic Disease

While policy makers, healthcare professionals, and health systems have been working since 2000 to “put the mouth back in the body,” patients still report challenges with receiving consistent dental care.[1, 2] Dental caries is one of the most preventable chronic diseases affecting 193.5 million U.S. adults and one out of 10 children, which is a result of a variety of environmental, behavioral, social, and biological factors.[3, 4]

Social determinants of health (SDOH) contribute significantly to an individual’s oral health status. Patients who have a low-income, are uninsured or underinsured, are underrepresented minority groups, or live in a rural area are more likely to experience poor oral health. SDOH may create barriers in an individual’s ability to find, access, and/or afford quality oral health care.[5] As a result, patients experience disparities in their oral health measured by clinical outcomes, and often this results from infrequent and inaccessible dental care use.[6, 7]

Dentists create preventive re-care plans with appointments for regular evaluation based on patient risk factors. The evaluation interval can range from 3 months for high-risk patients, to 1 year in healthy individuals. More frequent appointments allow the oral health care team to assess risk factors, detect early disease indicators, and provide prevention at the earliest signs of disease.[8, 9] However, with earlier treatment options for preventing disease, even healthy patients may benefit from frequent oral health care visits in the future to sustain population level health.

The number and consistency of dental appointments per year influence oral health outcomes, but how it influences it is not clear.[10] Previous research examined the differences in oral health outcomes between adults with routine dental appointments and adults with appointments in response to a specific problem or urgency. The results suggest conflicting ideas such that more frequent dental appointments coincide with the disadvantage of more frequent treatment, such as an increase in fillings, and thus, a greater disease experience. However, more frequent dental appointments also coincide with the advantage of more restored teeth and less active or untreated decay.[5] More recent research presents similar advantages to more frequent dental appointments including less overall tooth decay and better oral health outcomes. However, these studies examined the relationship using small, non-representative samples. In addition, none reported the magnitude of difference in oral diseases with the longer the length of time since the patient’s last dental appointment, or the difference between individuals who had a dental appointment for routine care compared to those who had an urgent appointment.[11, 12]

This study uses the nationally representative data from the National Health and Nutrition Examination Survey (NHANES) 2017-March 2020 pre-pandemic cycle to examine the elapsed time since last dental appointment to the current oral conditions and determine whether the last dental appointment was routine or urgent. Our primary aim is to assess the association between the time since the patient's last dental appointment (primary exposure) and the oral health outcomes including presence and number of coronal caries, presence of root caries, as well as presence and number of missing teeth. The secondary aim is to explore the indication for the last dental appointment (routine or urgent) and the oral health outcomes.

A priori hypothesis is that those that had recent dental appointments (< 1 year) for routine care will have better oral health outcomes (less number of teeth with coronal caries, lower probability of developing root caries, and fewer missing teeth) compared to patients who had dental appointments more than a year ago or for urgent care. Lack of oral health access is associated with increased untreated dental conditions (i.e. coronal caries, root caries and more missing teeth).

Materials and Methods

Clinical assessment of oral diseases

Trained and calibrated dental professionals conducted all the clinical examinations to assess the oral health status. We described teeth with untreated coronal caries as any dental cavity in the crown of a tooth that was both active and untreated, excluding third molars. For adults aged 18 years or older, we defined untreated root caries as any carious lesion located below the cementoenamel junction and above the gingival margin of teeth with gum recession, excluding third molars. We categorized missing teeth as teeth that had been lost due to caries or periodontal disease. Additionally, we determined the number of teeth that had coronal caries and the number of missing teeth.

Utilization of Dental Care and demographic factors

The primary predictor was the time since the last dental appointment. Based on the question, “When did you last visit a dentist?”. We categorized participants into three groups: if they had a dental appointment within a year; if more than a year, but within three years; if their last appointment to the dentist was more than 3 years ago or never.

We further categorized participants, based on the type of appointment, into routine dental care attendees or urgent appointments. Using their answers to the question “What was the main reason you last visited the dentist?”, participants were considered routine dental care attendees if they answered “Went in on own for check-up, examination, or cleaning” or “Was called in by the dentist for check-up, examination, or cleaning” or “Went for treatment of a condition that dentist discovered at earlier checkup or examination”, while urgent attendees were identified if they answered "Something was wrong, bothering or hurting me". We assigned individuals who have never been to a dentist as urgent attendees.

In our analyses, we took into account sociodemographic confounders, including age, gender, race/ethnicity, family income based on federal poverty level, and education level. The age variable was divided into seven groups (1–5, 6–11, 12–19, 20–34, 35–49, 50–64, 65+). Gender was either male or female. The race/ethnicity variable was divided into five groups, including Non-Hispanic Asian, non-Hispanic Black, non-Hispanic White, Mexican American/Hispanic, and Other, which included multi-racial groups. Family income was divided into four groups based on the ratio of family income to the federal poverty level (FPL). Finally, education level was divided into five groups: younger than 20 years old (education not reported), less than high school, completed high school/GED, some college or AA degree, and college graduate or above.

Statistical analysis plan

We described first the demographic distribution of our study population. We used a chi-square test to assess the distribution of these characteristics by the time since their last dental appointment. We reported the prevalence of having teeth with untreated coronal caries, teeth with root caries, missing any tooth, as well as the mean number of teeth with untreated coronal caries and mean number of missing teeth. National weighted estimates were reported, with the corresponding 95% confidence intervals (95%CI) and stratified by the reason of dental appointments. Taylor linearization methods were used in the survey procedures for standard error estimations, with the publicly provided masked variance pseudoprimary and masked variance pseudostratum sampling units.

Logistic regressions were used for the binary dental outcomes: presence of untreated coronal caries, presence of untreated root caries, and presence of missing teeth. Poisson regressions were used to assess the mean ratio for the count outcomes: number of teeth with untreated coronal caries and number of missing teeth. Simple logistic/Poisson regressions were run first to assess the crude estimates of the oral health outcomes by the time since last dental appointment, stratified by the reason of the appointment (routine or urgent). Then, we adjusted for demographic characteristics in the final multiple regression models with the interaction between time since the last dental appointment and reason of the appointment. Alpha was set at 0.05, and all analyses carried out using Stata 17.0 (StataCorp).

Results

Nearly two thirds of the US population had an appointment with a dental professional within a year of the survey (Table 1). It was the highest among school-age children 6–12-year-old (88.4%), Females (68.2%), non-Hispanic White individuals (67.6%). In addition, having a dental appointment within a year was higher as income and education increased. However, almost 53 million individuals did not have a dental appointment for more than three years or never had a dental appointment, and it was highest among young adults 20–34-year-old (23.8%), non-Hispanic Black individuals (21.7%) and other racial minorities (23.4%).

Examining individuals who reported their last dental appointment for routine care (Table 2), teeth with untreated coronal caries were present in one out of four individuals who reported their last dental appointment more than three years ago, with an average of 0.70 teeth being carious (95%CI = 0.52, 0.89). In contrast, teeth with untreated coronal caries were present only among 8.4% of those who had a dental appointment within a year, with an average of 0.18 teeth affected with caries (95%CI = 0.15, 0.20). Similarly, having teeth with root caries was present among 14.3% of those who had their last dental appointment more than three years ago (95%CI = 9.7, 18.7), while only 3.8% who had a dental appointment within last year (95%CI = 2.8, 4.8). Almost a third of all individuals who reported their last dental appointment as routine care had at least one tooth missing due to dental diseases. However, the average number of missing teeth was higher the longer the time elapsed since the last dental appointment. As for those who reported their last appointment to be for urgent dental care, both the prevalence and average number of dental diseases were higher among all groups, with the highest being among those who had their last dental appointment between 1 to 3 years.

The study compared patients who reported a dental appointment within a year time frame and the longer the time since the last routine appointment was associated with higher odds of having teeth with untreated coronal or root caries, even after adjusting for socio-demographic factors (Table 3, Fig. 1, Fig. 2). In contrast, the longer the time since the last dental appointment was associated with lower odds of missing teeth. The adjusted odds of having teeth missing was 0.44 times among those who had their last dental appointment for routine care more than 3 years ago compared to those who had a routine appointment within a year (95%CI = 0.33, 0.59), and 0.67 the odds of missing teeth if the last dental appointment was more than 3 years ago or never compared to those who had an urgent dental appointment within a year (95%CI = 0.45, 0.98) (Fig. 3).

The increase in the average number of untreated coronal caries increases by 2.20 folds if the last dental appointment was 1–3 years (95%CI = 1.59, 3.04) and 2.71 folds if it was more than three years (95%CI = 2.21, 3.33) compared to individuals who had their last dental appointment within a year for routine care, after adjusting for socio-economic confounders (Table 4, Fig. 4). In addition to lower odds of having any missing teeth, those with dental appointments for routine care more than three years ago had 0.67 times the adjusted average number of missing teeth compared to those had dental appointments within a year for routine care (95%CI = 0.52, 0.86) (Fig. 5).

Discussion

Previous research suggests the frequency between dental appointments influence health outcomes, but the specific impact on oral health outcomes is yet to be determined.[15] Our study uses nationally representative data to address current gaps in the literature. This data allows us to explore the association between the self-reported frequency of dental appointments and a clinical report of oral health status. In this study, more time elapsed since last dental appointments was associated with a higher presence of untreated caries. Similarly, the longer the time since last dental appointment, the greater number of teeth with untreated coronal caries and missing teeth are observed.

The findings suggests that regular routine dental appointments support improved oral health, and the analysis further depicts how SDOH may impact the frequency between dental appointments.[16] Mexican American/Other Hispanic populations report the lowest percentage of frequency between dental appointments compared to Non-Hispanic Whites. Less high school education is associated with a lower percentage of dental appointments, with the lowest frequency for populations with less than a high school education. Lower levels of income mirror the same trend such that individuals below 100% FPL report the lowest percentage of dental appointments. In a systematic review by Northridge et al, over twenty articles were assembled to assess interventions that address oral health care disparities. The results of the review indicate the greater likelihood of poor dental health for individuals who are low-income and/or members of racial/ethnic minorities compared to populations with better access to oral health care.[6] The results from this review align closely with our findings, reiterating the impact of social determinants on the frequency of dental appointments, and subsequent oral health outcomes.

The findings expand on previous studies that examine how the type of dental appointments – routine versus urgent – impact oral health outcomes. Patients that had dental appointments more than three years ago or have never been had less presence of missing teeth than those that had dental appointments less than three years ago. Similarly, those that had dental appointments more than one year ago or have never been had less presence of missing teeth than those that had dental appointments less than one year ago. This lower presence of missing teeth among patients with more time since last dental appointment, could be explained by a greater disease experience among patients that have more frequent dental appointments.[15] This possible explanation is supported by our finding that, regardless of reason of the dental appointment, those who had dental appointments more than a year ago or never had more presence of untreated coronal and root caries. In this sense, less time between dental appointments likely results in less untreated caries due to more frequent treatment and/or use of more prevention-based care.[10, 11, 15]

Previous research provides conflicting results regarding the relationship between the frequency of dental appointments and the impact this has on oral health outcomes. Sheiham et al., 1985 reports more frequent dental appointments resulted in a lower rate of tooth loss, fewer teeth with active decay, yet a higher average number of fillings. This article demonstrated the advantages of frequent dental appointments such that patients had more functioning and/or restored teeth. However, Sheiham et al., 1985 also reported increased appointments came at a disadvantage of a higher disease experience, maybe due to over treatment, indicating frequent dental appointments maintain oral function but do not prevent future disease.[15] Our results are similar to Sheiham et al., 1985 as more frequent dental appointments resulted in less teeth with untreated caries. However, our results differed in the potential association between the recency of dental appointments and the number of missing teeth.

NHANES data provides a relatively large sample size and a rigorous study design. Therefore, the data analyzed in our study are nationally representative and can be generalized to non-institutionalized US civilians. The oral health outcomes are also assessed clinically, which furthers the strength and validity of this study. However, it is important to note, that as a cross-sectional study, NHANES is restricted to association evaluations, rather than causality. Dental care utilization examined in our analysis was only the last dental appointment, rather than the number of appointments within a specific period of time. There are also potential limitations with reporting bias, as the timing and reason for the last of dental appointment was self-reported by participants. Finally, there might be unknown variables affecting the frequency of dental appointments, factors like their risk of dental caries, salivary markers, and oral hygiene practice.[11, 17, 18] However, the analysis controlled for potential confounding factors including age, gender, race, education, and income to strengthen the internal validity of our estimates.

Conclusion

There is a significant need for more accessible dental services, particularly for populations more likely to face additional barriers to care.[5, 19] While no direct relationship was concluded in this study between the frequency of dental appointments and oral health outcomes, our results indicate the positive impacts consistent and frequent routine dental appointments can have on oral health outcomes. Through our findings, we recommend that individuals should visit the dentist for frequent, routine care to reduce urgent visits and/or negative oral health outcomes. However, one potential hurdle to obtaining consistent and frequent dental care is the cost associated with such care.[19] As such, our findings support the implementation of an insurance policy that covers annual dental preventive appointments, which would save costs and reduce dental-related emergency appointments. Our results also indicate a call to action for clinicians and insurance providers alike to ensure that dental appointments consist primarily of prevention-focused care. Populations that face greater obstacles to access dental care, in particular, can benefit from more frequent and prevention-focused dental care.[6, 20]

Abbreviations

Declarations

Ethics Approval and Consent to Participate

Informed consent was obtained during the NHANES survey. Survey participants are assured that no information can be linked back to them or any other individual, during the informed consent process. Since our study is a secondary analysis of publicly available data, no additional ethical approval is necessary.

Consent for Publication

Not applicable.

Availability of Data and Materials

The datasets generated and analyzed during the current study are available in the Centers for Disease Control and Prevention, National Health and Nutrition Examination Survey (NHANES) repository, https://www.cdc.gov/nchs/nhanes/index.htm.

Competing Interests

Not applicable.

Funding 

The present study was supported and funded by King Saud University, College of Dentistry.

Author Contributions

HRA participated in the writing of the article and interpretation of data. NL participated in the collection, analysis, and interpretation of data. EK participated in the writing of the article and interpretation of data. MAA participated in the collection, analysis, and interpretation of data, and writing of the article. All authors read and approved the final manuscript.

Acknowledgments

The authors appreciate the use of the publicly available data set provided by the Centers for Disease Control and Prevention.

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