|Dental Hygiene Regulation and Access to Oral Health Care:
Assessing the Variation across the U.S. States
University of Virginia
P.O. Box 400206
Charlottesville, Virginia 22904-4206
Regulations in many U.S. states prevent dental hygienists (DHs) from fulfilling their potential to improve oral health care. Wing et al. (2005) found that stringent practice regulations lower DH wages and reduce access to care. We add licensure regulations to the analysis and estimate the simultaneous effect of licensure and practice restrictions on the DH labor market and access to care. The results are consistent with licensure restrictions reducing employment, practice restrictions reducing wages, and wage and employment rates jointly influencing the prevalence of dental office visits. These results suggest that in order to significantly improve access to oral health care, states need to consider how their entry and practice regulations interact to influence outcomes.
In the United States, state legislatures and dental boards are typically responsible for promulgating dental hygiene laws and regulations. These laws and regulations create a set of restrictions on both entry into the dental hygiene profession and functions that can be performed by licensed dental hygienists (DHs). While scholars have analyzed the effect of entry and practice restrictions separately, their simultaneous effect has not been fully explored. Using a basic demand and supply framework, we model the supply of DHs as a function of entry restrictions, which influence the flow to entrants into the profession. Demand for DHs by employers is a function of scope of practice restrictions, which influence the productivity and, consequently, the wage of DHs. Entry and practice restrictions jointly affect access to care through their influence on employment and wage rates. This model is consistent with the cross-state variations in DH regulation, wage, employment, and access to care that exist across the U.S.
Access to regular dental office visits is important because if left untreated dental caries, or tooth decay, can result in pain, disability, and even death.1 Despite the importance of oral health care, many Americans lack access to care due to financial, geographic, or educational constraints. The lack of access to care is observed in the variation in use of dental services. The percentage of adults who had a dental office visit, which may have involved dental or DH services, in 2006 ranged from 58 percent in Oklahoma to 80.5 percent in Connecticut (CDC 2006). Even within low-income groups, Delaware had twice the rate of dentist visits, at 60.7 percent, than Oklahoma, at 30.6 percent (CDC 2006). Outcomes among the elderly have a similarly wide variation. In the U.S., 27 percent of elderly have lost at least five teeth, but this ranges from 13 percent in California and Hawaii to 42 percent in Kentucky and West Virginia (Gooch et al. 2003).
In order to understand how occupational regulation affects the DH labor market and access to care, we first review relevant studies on regulation of dental hygiene and other professions. We then expand the literature by developing a supply and demand model that predicts the changes in DH wage and employment rates and access to care resulting from various changes in entry and practice restrictions. We test the model using a three stage least squares (3SLS) estimation method to study the simultaneous effect of entry and practice restrictions on wages, employment rates, and access to care. Access to care is also analyzed for different population sub-groups, including for males and females and among different income and age groups. The results of this study will facilitate policymakers in better understanding the joint effect of their laws and regulations on access to oral health care. Furthermore, because entry and practice restrictions exist in many professions, this study expands the debate on health care reform by analyzing an area that is often overlooked but has the potential to significantly improve overall access to health care.
Scholars have been studying the costs and benefits of occupational regulations for more than a half of a century. Various arguments have been offered in support of licensure requirements. One potential benefit arises if licensure improves the quality of the workforce. Licensure requirements may increase the average quality of the workforce by reducing the inflow of less competent individuals (Kleiner 2006; 48-49). On the other hand, licensure may in fact reduce quality by screening out the most qualified individuals. Individuals with a high opportunity cost may opt not to enter a profession because of the high cost of obtaining a license. An example is the case of teachers, where the large upfront cost of acquiring a teaching license may discourage entry of high quality potential teachers who have many outside opportunities (Ballou and Podgursky 1998).
Empirical studies also cast doubt on whether licensure improves quality. Kleiner and Kudrle (2000) compare oral health outcomes of Air Force recruits and find no correlation between state dental licensing practices and oral health outcomes. Kleiner (2006; 56-8) also compares insurance premiums for professions that are licensed in some states but not others. He finds that insurance companies are generally indifferent to whether a state has licensure requirements. This indicates that licensure requirements do not influence the risk of a malpractice lawsuit and consequently do not influence quality. These studies suggest that the average quality of providers in states with and without licensure or with more stringent requirements does not change.
Licensure may also provide a social benefit if it increases the standardization of skills. Standardization reduces the asymmetric information that consumers face (Benham 1980), thereby increasing the value of seeking professional services. The increased standardization may help explain the initial rise in licensure in the U.S. (Law and Kim 2005). It is not clear, however, that asymmetric information is a genuine problem, at least in the case of dental hygiene. DHs are hired and observed by dentists, reducing the asymmetric information problem, as dentists have an incentive to ensure higher quality DHs.
What occupational regulation does appear to do is reduce the risk and increase the returns to those in the profession by allowing the occupation to reduce entry in response to market conditions (Wheelan 1999 cited in Kleiner 2006; 44). The result is to increase the cost to consumers. Numerous studies have found evidence of higher cost resulting from licensure requirements. Economic theory predicts that licensure requirements distort the labor market and allow for monopoly rents (Benham 1980; Friedman and Kuznets 1962). Friedman (1945) found that limitations on medical school positions, which are used as the primary means to restrict entry, are responsible for a large increase in physicians’ salary. Licensing exam failure rates among dentists and physicians are also used to restrict the flow of entrants, causing wages to rise (Benham et al. 1968). In fact, dental fees are estimated to be on average 8.5 to 17.9 percent higher for a variety of procedures in states without reciprocity agreements, or the automatic recognition of out-of-state licenses (Kleiner and Kudrle 2000; Shepard 1978).
Dental hygiene is unique among licensed professions, in that it is regulated by dentists rather than self-regulated in most states. Nonetheless, many of the same mechanisms for restricting entry in other professions also exist for DHs. Similar to restrictions on medical school positions (Friedman 1945), competition to enter one of the 329 dental hygiene programs that are accredited by the American Dental Association (ADA) is often intense, with many programs receiving more than twice the number of qualified applicants as positions. Licensure by credential requirements, which allows DHs to avoid retaking the clinical examination, also appear to limit the flow of entrants, much as they do in other professions. To qualify for licensure by credentials the majority of states in 2006 required the applicant to have worked previously for a specific number of years, typically between two and five years, and to pay a fee ranging from $35 to $2,000. As of 2007, no state permitted reciprocity. On the other hand, most states do not manipulate the national or regional exam pass rates to control entry, as they do with many professions such as dentistry or law. With the exception of a few states that have their own clinical exams, neither the national nor regional exam pass rates are decided at the state level (Joint Commission 2008).
The DH labor shortage in California provides an opportunity to examine the effect of educational requirements on changes in the DH labor market. Between 1997 and 2004, California experienced a period of growth in demand for oral health care due to increased prevalence in dental insurance coverage, changes in per capita income, and changes in the age structure of the population (Brown et al. 2007). During that period, DH wages rose rapidly. In contrast, the employment rate of dental assistants rose significantly, but wages did not. Dental assistants are typically unlicensed employees of dental offices who receive on-the-job training and are not permitted to perform as many functions as DHs. Brown et al. (2007) argue that California’s DH educational requirements produced a short-term bottleneck that resulted in a rapid increase in DH wages. Dental assistants faced fewer obstacles to entry, allowing the quantity of dental assistants to respond more rapidly to the increased demand. Their study did not, however, consider an alternative method of entry, licensure by credentials, which could also have helped alleviate shortages by allowing DHs in lower wage states to move to high demand areas.
Unlike entry requirements that directly influence the inflow of professionals, scope of practice restrictions prevent deploying professionals in the most cost-effective manner (Gaumer 1984). In the case of DHs, scope of practice regulations range from allowing DHs to perform only basic teeth cleaning and polishing services to conducting more complex or potentially hazardous procedures, such as administering anesthesia and conducting restorative functions. Restrictions also dictate the level of supervision required by dentists, ranging from direct supervision to complete autonomy. Direct supervision requires that the dentist is present in the office, personally diagnoses the condition, authorizes the procedure, and evaluates the performance of the DHs. General supervision requires that the dentist authorize the procedure, but does not require that the dentist be present in the treatment facility. Complete autonomy allows the DH to work without reporting to a dentist, which is currently permitted only in Colorado and in some public health settings in some states. In addition, some states limit the number of DHs that a dentist can employ.
Scope of practice regulations are often analyzed in the context of jurisdictional battles between professions. In the case of dental hygiene, when DHs are unable to independently perform tasks, the demand for dentists increases. The result is in an underutilization of DHs and an increase in dental wages (DeVany et al. 1982). The potentially anti-competitive effect of dental hygiene regulation came under scrutiny by the Federal Trade Commission (FTC) in the late 1980s and again in 2003. A FTC study estimated that the price effects of states-imposed restrictions on the number of dental auxiliaries that dentists are permitted to employ or the functions DH can perform resulted in a seven to eleven percent increase in the average price of a dental visit (Liang and Ogur 1987). In 2003, the FTC issued a complaint against the South Carolina Dental Board for prohibiting dental hygienists from providing teeth cleaning services to Medicaid children. The case was eventually settled.
One consequence of the higher price of services is that it encourages providers to focus on the higher-cost, higher-quality market segment, while eliminating the low-cost market segment. The elimination of the low-cost market segment is particularly troubling when it serves to prevent lower income individuals from purchasing important health care services. Seeking to draw a link from practice restrictions to access to oral health care, Wing et al. (2005) constructed an index of practice restrictions, the dental hygiene professional practice index (DHPPI), covering all fifty states in 2001. They found that restrictive regulations not only reduce DH salaries, but also decreased the percent of the population that visited a dental office or clinic. The results are consistent with practice restrictions reducing the services available to the lower income segment of the oral health care market.
This study makes three contributions to the literature. First, we quantify the distinction between entry and practice regulations. Occupational regulation literature has generally looked at entry and practice regulations separately. But the fact that both entry and practice restrictions are expected to influence the DH labor market suggests that both types of restrictions need to be considered. Second, the DH labor market is determined by both wage and employment rates, which are endogenous to each other. Unlike previous studies of DHs, we use simultaneous equations to solve the endogeneity between wage and employment rates. Finally, we quantify the effects of entry and practice restrictions on access to care among different sub-populations. Together, these contributions improve our understanding of the importance of occupational regulations on health outcomes among DHs specifically and among licensed professions generally.
A basic supply and demand model captures the relationship between entry and practice restrictions, wages, employment, and access to care. In this model, supply of DHs is a function of entry restrictions, while demand for DHs is a function of practice restrictions. Access to care depends on availability and price of providers, where the per capita number of DHs, dentists, dental assistants, and their mean wage serve as proxy variables. The basic model can be written as a system of interdependent equations:
(1) DH = f(Wdh, ER) (Supply)
(2) Wdh = f(DH, PR, Wd, Wda) (Demand)
, , ,
(3) Visits = f(DH, D, DA, Wdh, Wd, Wda) (Outcome)
DH = per capita DHs
Wdh = wage of DHs
ER = entry restrictions
PR = practice restrictions
Wd = wage of dentists
Wda = wage of dental assistants
D = per capita dentists
DA = per capita dental assistants
The first two equations represent a labor market demand and supply relationship. The supply of DHs to the labor market is a function of wages (Wdh) and entry restrictions (ER). As in a typical supply relationship, DH wage is positively correlated with DH employment, resulting in an upward supply curve. Other things equal, higher DH wages encourage more DHs to enter the labor market, thereby increasing employment. Entry requirements, which affect the flow into the profession at all wage levels, shift the supply curve.
In the demand equation, DH wage is the dependent variable. When DHs are relatively scarce, employers, typically dental offices, must bid up wages to attract DHs. However, as more DH are in the labor market, the wage dental offices are willing to pay decreases, resulting in a downward sloping demand curve. Variables that shift the demand curve include practice restrictions (PR) and the price of substitutes or compliments (Wdh, Wd, Wda). Practice restrictions shift the supply curve by changing the productivity, and consequently value, of DHs. The wage that dentists and dental assistants receive represents the price of substitutes or complements to DHs. It is unclear whether dentists and dental assistants are complements, because they work as a team, or whether they are substitutes, because there is overlap in the functions that they perform. As the cost of a complement increases, demand for DHs decreases, implying a negative correlation. As the cost of a substitute increases, then demand for DHs increases, implying a positive correlation.
Two key assumptions of the model are that entry restrictions do not directly influence wages and that practice restrictions do not directly influence DH employment rates. These assumptions are central to identifying the system of equations and are consistent with the literature. Studies on entry restrictions, such as licensure passage rates and slots at educational institutions, focus on the flow of entrants into the profession (Friedman 1962; Kleiner 2006). Alternatively, practice restrictions change the distribution of work, which influences wages (DeVany et al. 1982). In theory, practice restrictions could influence the desirability and job satisfaction of a profession, thereby, directly influencing entry. However, there is little empirical evidence of this in practice. Therefore, this analysis assumes that practice restrictions directly influence the labor market through wages and that entry restrictions directly influence employment rates.
The ability of entry and practice restrictions to vary simultaneously is a central contribution of this model to the literature and provides a realistic picture of occupational regulations in the states. The stringency of entry and practice restrictions in states does not follow a uniform pattern. Practice restrictions, measured by DHPPI, have less than a 0.1 correlation with any entry restriction (where 0 is no correlation and 1 is perfect correlation). The highest correlation is between two entry restrictions, practice years for credentials and cost of credentials, which have a correlation coefficient of 0.33. Therefore, we need to consider how varying the level of entry and practice restrictions affects DH wage and employment rates.
Under one scenario, the stringency of entry and practice restrictions moves in the same direction. The result is an unambiguous change in the equilibrium quantity of DHs and an ambiguous change in wages. For example, when both entry and practice restrictions are stringent, then we expect to observe lower DH employment rates but we cannot predict the effect on wages (Graph 1). Stringent entry requirements reduce the flow into the profession, while stringent practice restrictions reduce wages, which discourages individuals from choosing to enter the profession. The result is that both restrictions discourage entry. The restrictions, however, work against each other in the wage dimension. Stringent entry requirements result in scarcity of DHs, which increases wages. Stringent practice restrictions lower productivity, which reduces wages. Thus, the observed wage will depend on the relative movement and elasticity of demand and supply. In the reverse situation, liberal entry and practice regulations increase the DH employment rate, but wages remains ambiguous. Liberal entry requirements encourage entry, which reduces wages. Liberal practice restrictions increase productivity and wages, which encourages entry.
Under the alternative scenario, states choose a mix of occupational regulations. When the stringency of entry and practice restrictions move in opposite directions, then the effect on wage can be predicted, while the effect on employment rates cannot. For example, if a state imposes stringent practice restrictions and liberal entry restrictions, then we can expect to observe lower wages and an ambiguous quantity of DHs (Graph 2). Stringent practice restrictions reduce DH productivity, which decreases wages. Liberal entry requirements increase the flow into the profession, which reduces scarcity and produces lower wage rates. At the same time, however, employment rates are ambiguous. Liberal entry requirements encourage entry, while stringent practice restrictions discourage entry due to the lower wage rates. On the other hand, when a state imposes liberal practice restrictions and stringent entry restrictions, we expect to observe higher wage rates and ambiguous employment rates. Liberal practice restrictions increase productivity and wages. Stringent entry restrictions reduce entry into the profession, which creates scarcity that can drive up wages. Employment is ambiguous because the higher wages from liberal practice restrictions encourage entry, while stringent entry restrictions limit entry into the profession.
Insert Graphs 1 and 2
The final component of the model is access to care (Visits), which is a function of the availability of health care providers and prices. Higher DH, dental (D), and dental assistant (DA) employment rates, which are proxies for availability of oral health care services, are expected to improve access to care. Alternatively, higher wages of oral health providers (Wdh, Wd, Wda) are expected to increase price and, consequently, reduce access to care. The reduction in access to care is expected to have the strongest effect on lower-income individuals who are less likely to have insurance or for whom the cost of oral health services are a larger share of income, as well as for younger individuals who may have a lower perceived need for care.
Comparing entry and practice restrictions with access to care reveals some general patterns among the states. In general, states that have liberal entry and practice restrictions tend to have higher rates of dental visits, states with stringent restrictions tend to have lower rates, and states with mixed regulations tend to be closer to the average in access to care. Graph 3 show states that have above or below average DHPPI scores and DH graduates per 100,000. The DHPPI represents practice restriction and DH graduates per capita represents one component of entry restrictions. Graph 4 shows the number of dental office visits for each state in 2006, using the CDC (2006) Behavioral . Connecticut and Minnesota, for example, have liberal entry and practice restrictions and have among the highest percentage of adults visiting a dental office. At the other end of the spectrum, Oklahoma and Arkansas have less than the mean DHPPI index and number of DH graduates and have the lowest level of access to care in the U.S. In the middle range, states like California or Colorado tend to have liberal practice restrictions but stringent entry restrictions and are close to the average in dental office visits. Similarly, North Dakota and Wyoming have a high number of graduates and below average DHPPI and are in the mid-range of dental office visits. There are exceptions to the general trend. For example, Rhode Island and Massachusetts have very high rates of dental office visits even though they have below average DHPPI index. These exceptions demonstrate the need to control for other factors, such as income level and population density, in a more systematic way.
Insert Graphs 3 and 4