Within this context, the Wisconsin Dental Association, or WDA, has received inquiries from its members, state legislators and concerned citizens about the adequacy of the long-term supply of dental services in the state. The WDA had difficulty responding to these inquiries in the absence of hard data on the supply of and demand for dental services in Wisconsin. Realizing the need for a formal study of these issues, the WDA contracted with a research organization to do the following:

– develop baseline data on the current supply of and demand for dental services at the state and county levels;

– determine the demand for dental services, taking into account expected changes in the population and other relevant factors;

– estimate the number of dentists needed in 10 years (2010);

– in the event of a supply-and-demand imbalance, assess the potential impact of several practical strategies for increasing the supply of dental services within a 10-year time frame.

This article presents the results of this analysis at the state level. The results at the county level are available from the WDA.

Several national organizations monitor the adequacy of the dental work force: the ADA, the American Dental Education Association and the Bureau of Health Manpower, an agency of the federal government. Two reviews of previous work force studies by these organizations identified several important limitations, including failure to take into account changes in treatment technologies, dentist productivity and improvements in oral health.^2,3

	METHODS

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The primary data used in this study come from the state of Wisconsin, ^4,5 the ADA^6–8 (ADA Survey Center, unpublished data, March 29, 2000) and the federal government.^9–12 Information was available on the number, age, sex and specialty distribution of dentists by county; the number of dentists retiring and starting practices; the number and types of auxiliaries employed; and the number of hours dentists worked per week and per year. We used state and national census and economic data to describe Wisconsin’s population in terms of numbers of people and their age, sex, per capita income and other sociodemographic characteristics.

We applied a multivariate model of the dental care system to these data sets to project the supply and demand for dental services during the next 10 years.¹³ On the supply side, these analyses included yearly estimates of the number of dentists retiring from and entering practice and growth in dentists’ productivity. We based estimates of retiring dentists on an aging of all dentists who graduated each year since 1955, as well as on the assumption that 20, 50, 20 and 10 percent of dentists retire after 40, 35, 30 and 25 years in practice, respectively, and that the average retirement age is 62 years.¹⁴ We based estimates of dentists entering practice on a regression analysis of practice entry activity in the past 10 years. To estimate the annual rates of growth in dentist productivity during the past 40 years, we used a broad measure of dental output (expenditures for dental care divided by the price index of dental services) and ADA measures of the dental work force.^6,7

We estimated the demand for dental care during this same period (2001–2010) from the growth of the Wisconsin population and projected changes in per capita utilization (dental output divided by the population). Our projections of trends in both productivity and utilization were based on national data because of the lack of state-level information. On the basis of these analyses, we identified imbalances between the supply and demand for dental care, and we determined the number of dentists needed to correct these imbalances.

	RESULTS

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Where data are available, we provide comparisons with national data.

Baseline. As of 2000, Wisconsin had 2,979 dentists in active practice for a dentist-to-population ratio of one dentist per 1,775 people. The average age of dentists is 49.78 years, 9.85 percent of Wisconsin dentists are female and 16.52 percent are specialists. The dental work force in Wisconsin and the nation are generally similar, but Wisconsin has fewer female dentists and specialists. This is expected in a state with a large rural population. Marquette University School of Dentistry, Milwaukee, was the alma mater of 71.32 percent of Wisconsin dentists.

Table 1 compares the demographic characteristics of the Wisconsin population and the nation. Wisconsin, as of 2000, had 5,287,825 residents and covered an area of 54,320 square miles.^11,12 Approximately 34 percent of the population lives in rural communities. Average per capita income is $28,955¹⁵; 11.2 percent of the population is eligible for the Medicaid program,⁴ and 91.8 percent of the population lives in an area in which the water supply contains preventive levels of fluoride.^5,16 Compared with the U.S. population, Wisconsin is a little less affluent and more rural.

View larger version (21K): [in this window] [in a new window]   Figure 1. Estimated average annual dental output per dentist, United States, 1960–1998. Sources: Center for Medicare and Medicaid Services,9 U.S. Bureau of Labor Statistics10 and American Dental Association.6,7

View larger version (25K): [in this window] [in a new window]   Figure 2. Estimated average annual utilization of dental services per capita, United States, 1960–1998. Sources: Center for Medicare and Medicaid Services,9 U.S. Bureau of Labor Statistics10 and U.S. Bureau of the Census.11

View larger version (30K): [in this window] [in a new window]   Figure 3. Needed and expected numbers of dentists in Wisconsin, 2000–2010. A: Needed number of dentists considering constant dentist-to-population ratio. B: Needed number of dentists considering growth in productivity and utilization. E. Expected number of dentists.

	INCREASING THE SUPPLY OF SERVICES

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– increase the number of dentists entering practice;

– improve the productivity of dentists in practice.

Additional dentists. On average, 56 dentists are expected to enter practice each year in Wisconsin for the next 10 years. An additional 19 dentists per year are needed to reach the objective of 194 more dentists by 2010. Three options for achieving this goal are to encourage more graduates of Marquette University dental school to practice in Wisconsin; to increase the number of students graduating from Marquette; and to recruit more graduates from dental schools outside Wisconsin.

With respect to Marquette graduates, in past years, about 40 percent of the 75 students in each graduating class eventually entered practice in Wisconsin. Almost all graduates who stayed in Wisconsin were state residents when they entered dental school. Graduates from other states tend not to stay in Wisconsin. Therefore, one option is for Marquette to increase the number of students accepted from Wisconsin, keeping the total class size at 75. For example, accepting 20 more students from Wisconsin (starting in 2001) and 20 fewer students from elsewhere would be expected to result in 100 more Marquette graduates practicing in the state by 2010. This strategy assumes that additional qualified candidates from Wisconsin are available.

Another option is to increase the size of the Marquette graduating class by 20 percent (15 students), assuming that the current ratio of instate to out-of-state students remains the same. This would result in 30 more dentists entering practice in Wisconsin by 2010. This strategy has little effect by itself, because most of the additional students are from other states and are likely to leave Wisconsin to open practices. Furthermore, the addition of more students to each class will require more resources (such as faculty, space and equipment) and may be difficult to finance without additional public or private subsidies.

The third option is to recruit dentists graduating from schools in other states. This strategy is unlikely to work, because other states that are facing the same problems as Wisconsin are likely to match any financial incentives offered by Wisconsin to attract new out-of-state graduates.

Dentists’ productivity: auxiliaries. The addition of more dental hygienists and assistants will increase the productivity of dentists, allowing them to increase their number of patients. For example, a 10 percent increase in the number of auxiliaries employed by Wisconsin dentists is the equivalent of adding 160 dentists to the work force. This strategy assumes that Wisconsin dentists want to employ more auxiliaries and that trained hygienists and assistants are available.

A recent survey conducted for the WDA (Innovative Resource Group, unpublished data, December 2000) indicated that dentists’ demand for dental hygienists is greater than the current supply. Thus, it appears that dentists do want to employ more hygienists, and efforts are already under way to train more dental hygienists in community college programs throughout the state.

Dentists’ productivity: patient management. Based on national data, the average general practitioner has about 1,900 active patients. On average, these patients visit the practice 3.2 times per year. With the large improvements in oral health taking place both nationally and in Wisconsin, a significant, but unknown, number of patients in the average practice receive primarily maintenance care. Some experts suggest that dentists could accept more new patients if they adjusted the time interval between maintenance visits for healthy patients.^17,18 For example, a 5 percent reduction in the number of patients visiting Wisconsin dentists twice per year and a concomitant increase in new patients is the equivalent of adding 150 dentists to the work force.

The feasibility of this strategy depends on patient and dentist acceptance of fewer maintenance visits for healthy patients. Because of the lifelong habits of patients and dentists, this approach may require a substantial educational effort for both groups.

	DISCUSSION

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This article takes a market-oriented, or purchasing-power, approach to measuring demand and not a public health approach (which would involve professionally determined oral health status and need for treatment). It is assumed that the current availability of dental services reflects actual market demand and is socially acceptable. Thus, we have assessed the adequacy of the estimated supply of dental services (relative to the estimated demand) in the year 2010 with respect to the current level of access to care.

This analysis estimated the supply and demand for dental care in Wisconsin during the next 10 years. The data show that more dentists will retire from than enter practice. This is the result of a 37 percent decline nationally in the number of dental school graduates from 1978 to 1990. A recent study indicated that the imbalance between the numbers of dentists leaving and entering practice would continue to increase until about the year 2015.¹⁹ Thus, the decline in the Wisconsin dental work force is likely to continue for another five years beyond 2010.

In addition to population size, the other important factor increasing demand for dental services is the population’s level of affluence.

The decline in the number of dentists is partially offset by the substantial increase in dentists’ productivity in the past 10 years. At an annual increase of 1.8 percent, dentists are able to provide more services and see more patients because of the better use of resources. Many factors influence dentists’ productivity, but the key factors are the use of more auxiliaries, space and equipment. Other factors that may contribute to better productivity are healthier patients who require less chair time, better dental materials and other treatment technologies, and electronic information systems.

This analysis assumes that the past rate of productivity improvement will continue for the next 10 years. This is a reasonable assumption, because the main drivers of increased productivity can continue to expand. For example, the average practice in Wisconsin still does not employ a full-time dental hygienist.

On the demand side, the Wisconsin population is growing, but rather slowly. The annual rate of increase is only half the national average (0.92 percent) and is much less than that of Sun Belt states such as Florida and Arizona. If Wisconsin had Florida’s rate of population growth, it would be more difficult to correct the projected imbalance between the supply and demand for dental services.

In addition to population size, the other important factor increasing demand for dental services is the population’s level of affluence. The average Wisconsin citizen will see a 62 percent increase in his or her income by 2010. It is well-known that as income increases, so does the demand for medical and dental care.

Taking into account the net effect of these different supply and demand trends, Wisconsin will need 194 more dentists in the year 2010 to provide year 2000 levels of access. This is much less than the 424 dentists estimated if one simply looks at the unadjusted dentist-to-population ratio for this period.

Because the analyses showed a decline in the number of dentists—both absolutely and relative to population size—we considered several options for increasing the supply of services within a 10-year time frame. These options are not mutually exclusive. Indeed, there is much to be said for a multifaceted approach that involves including more students from Wisconsin in the class entering Marquette University School of Dentistry, using more auxiliaries and other practice staff, and scheduling recall visits on the basis of patients’ risk of disease. In fact, the latter two strategies already may be under way, as natural market forces provide Wisconsin dentists with incentives to use more staff and to schedule patients according to their risk levels.

This article does not offer any recommendations or make any value judgments on the adequacy of the current or future supply of dental services. These decisions are the responsibility of the WDA and the people of Wisconsin. Also, this report does not consider the possible impact of changes in the general economy on the demand for dental care. Demand is sensitive to changes in the economy, and a major downturn could reduce the need for additional dentists; however, it is beyond the scope of this article to speculate on these larger economic conditions.

This study should not be generalized to the nation overall or to other states. Although the dentist-to-population ratio is expected to decline nationally during the next 15 years, as more dentists leave than enter practice and the population grows at about 0.90 percent a year, the supply and demand for dental services varies greatly among states and probably among regions within states. Thus, the supply and demand for dental services should be studied carefully before any sweeping changes in the size of dental school classes, the number of auxiliaries trained or the scope of auxiliary duties are made, or other interventions to increase the supply of services are tried.

We used a market-based framework to assess the demand for care in the analysis presented here. In this model, the financial ability to purchase services is the critical factor in translating clinical need for care into demand for care. Clearly, significant segments of the population—poor, near-poor and medically disabled people—have substantial need for additional dental care, but they do not have the resources to purchase these services. It makes little sense to increase the supply of services to meet this unmet need when these underserved populations are unable to purchase the services. Of course, if federal and state governments were to decide to allocate additional public revenues to subsidize the purchasing power of low-income populations, this would increase the effective demand for dental care. Based on the long history of inadequate Medicaid funding in most states, a substantial increase in public support for dental care is unlikely to occur in the near future.

A major limitation of this study is the amount and quality of data available on the Wisconsin dental care system. Most data on dental practice characteristics and dentists’ productivity came from national surveys of dental practices sponsored by the ADA. These surveys do not sample enough dentists in each state to permit statistically valid estimates of practice activities in a given state. The findings from this study likely would have been more precise if more Wisconsin-specific data were available. To address this problem, states can undertake their own practice surveys; however, this is an expensive and time-consuming activity that may be beyond the capacity of all but the largest states. Another option is for states to contract with the ADA to increase the number of dentists sampled in a given state during the ADA’s annual practice survey. (To accomplish this, the state would have to cover the additional expense the ADA would incur in providing larger state samples.) This approach should provide an adequate sample of practices to obtain meaningful state-specific data and, at the same time, would be less expensive and provide comparative national data.

This study did not assess the potential impact of several other important factors on the future supply of dental services. One omitted factor is the expected number of hours worked per week and per year by dentists. Dentists are now working 37 hours per week and 48 weeks per year. Fifteen years ago, they were working 42 hours per week for 48 weeks per year.²⁰ The reasons for the decline in hours worked per week are not clear, but they may include higher dentist incomes, an older work force and other factors. If further reductions in the average workweek occur, the projected imbalance between the supply and demand for care will increase.

Another factor that was not considered is the growing number of female dentists in the work force. The evidence is incomplete, but one report has suggested that the average length of time spent in professional careers varies by sex (that is, women spend less time in careers).²¹

These two issues cannot be resolved with currently available data, but they should be monitored closely over the next five years. They have the potential to significantly affect the supply of dental services in the country.

	CONCLUSIONS

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Based on the number of dentists entering and leaving practice in Wisconsin for the next 10 years, we estimate that there will be 297 fewer dentists in 2010 than in 2000. However, taking into account increases in dentists’ productivity, in the Wisconsin population and in utilization, the state will need 194 additional dentists to maintain current access levels. This shortfall in dentists appears relatively easy to correct by a combination of recruiting more students from Wisconsin by the Marquette University School of Dentistry, employing more dental auxiliaries and implementing risk-based scheduling of recall appointments. The results of this study cannot be generalized to other areas of the country because of the considerable variation among states in the supply of and demand for dental care.