In a subsequent multivariate analysis of ADA dental practice surveys, Wilson and colleagues⁴ suggested that sex was a statistically significant, but not substantial, variable in predicting dentist productivity. Several studies^4–6 reported that female dentists were more likely than male dentists to work part time. Price⁷ suggested that the number of hours worked by women was significantly related to the number of dependent children in their families. Brown and Lazar⁸ analyzed net income in a cohort of U.S. male and female dentists with similar demographic and practice characteristics. The authors found that female dentists had substantially smaller net incomes than their male colleagues.

The purpose of this study was to compare days worked, procedures performed, patient characteristics, income and other patterns of oral health care reported to the Washington Dental Service (WDS), Seattle, by male and female general dentists during 2001.

	METHODS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
The WDS represents more than 30 percent of all people with private dental benefits in the state of Washington. WDS maintains a comprehensive database of all benefits claims submitted by about 90 percent of the dental offices in the state. The database includes information pertaining to patients, dentists, purchasers of dental insurance plans, services rendered and dental plan design. The database is updated on a monthly basis. These data are stored on a confidential and protected computer system, and searches are conducted using a variety of software packages. Patterns of oral health care and the validity of the database for WDS dentist and patient populations have been described elsewhere.⁹

In this population, female dentists were younger and worked about 10 percent fewer days than did their male colleagues.

In this investigation, we searched for all dental services provided to WDS patients in 2001 by general dentists who worked at least 26 days per year. Variables of interest for general dentists included sex, age, days worked, procedures performed and total income from both WDS reimbursements and patient copayments. Yearly dental services reflect both those performed by the dentist as well as those performed by other members of the dental office team. We used the ADA dental procedure codes to group treatment services.¹⁰ We confirmed and amended WDS data on dentist demographics by comparing them with public information member records supplied by the Washington State Dental Association. Variables for patients who had at least one claim in 2001 included sex and age. All analyses were based on unique codes assigned to dentists and patients to protect patients’ identities and patterns of individual dental practices.

We compared practice characteristics of male and female dentists using measures of central tendency, and we assessed statistically significant differences with t tests. Multiple regression models assessed differences in dentists’ income on the basis of sex while adjusting for factors that may have confounded that association (including age, time in practice and categories of service used). To assess the impact of an increase in the relative proportion of female dentists, we estimated the expected number of patients who would be treated by a work force composed of 20 to 50 percent female dentists using the observed number of patients treated by dentists in this study.

	RESULTS

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The study population consisted of 2,212 general dentists who provided care to 760,752 WDS patients during 2001. Two hundred sixty-five (12 percent) of these dentists were female. These general dental offices reported about 4,420,000 procedures to WDS during this period; the total income from WDS and patient copayments was about $384.8 million.

Table 1 provides an overview of practice characteristics for these dentists during 2001. In this population, female dentists were younger (mean difference = 7.9 years; P < .001) and worked about 10 percent fewer days (mean difference = 17.8 days; P < .001) than did their male colleagues. In addition, female dentists treated about 10 percent fewer patients (mean difference = 40.4 patients; P = .009), performed about 10 percent fewer procedures (mean difference = 177.1 procedures; P = .06) and reported a total annual income from WDS reimbursements and patient copayments that was about 10 percent lower than that of male dentists (mean difference = $17,761; P = .03).

View this table: [in this window] [in a new window]   Table 1 PRACTICE CHARACTERISTICS OF GENERAL DENTISTS IN WASHINGTON STATE WITH CLAIMS PAID BY WDS* IN 2002 AND INCOME FROM PATIENT COPAYMENTS.

Table 2 shows practice characteristics for female and male dentists according to age cohort. In general, the number of days worked and productivity (that is, number of procedures and income) increased as dentists grew older, with the highest levels reached by dentists aged 41 to 50 years. Days worked and productivity returned to approximately the initial levels after age 50 years.

View this table: [in this window] [in a new window]   Table 2 PRACTICE CHARACTERISTICS OF GENERAL DENTISTS IN WASHINGTON STATE WITH CLAIMS PAID BY WDS* IN 2002 AND INCOME FROM PATIENT COPAYMENTS, BY AGE.

Table 3 (page 794) provides a regression analysis that assesses the effect of dentist and practice characteristics on total income from WDS reimbursements and patient copayments. The results show that dentist’s sex did not have a significant effect on total income received from WDS reimbursements and patient copayments. Total income can be explained to a large extent (R² = .8950) by dentist’s age; number of days worked, patients treated and procedures performed; and percentage of female and pediatric patients. The strongest predictors of higher income were greater numbers of days worked and procedures performed.

View this table: [in this window] [in a new window]   Table 3 REGRESSION ANALYSIS OF INDEPENDENT PREDICTORS OF INCOME FROM WDS* IN 2002 AND PATIENT COPAYMENTS.

View larger version (39K): [in this window] [in a new window]   Figure. Distribution of dental services provided by female and male general dentists in Washington state in 2001.

	DISCUSSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
This study of more than 2,000 general dentists is the first, to our knowledge, to consider dental practice characteristics and dentist’s sex using dental benefits claims rather than self-reports of dental providers, and it updates earlier studies that reported significant differences according to sex.^3–8 In this population of WDS dentists, we found no significant differences in income characteristics that were based on sex. Predictors of dentists’ income from claims reimbursements and patient copayments were principally a function of number of days worked, patients treated and procedures performed.

Days worked. Female dentists in this study worked fewer days per week than male dentists, particularly in the cohort aged 25 to 40 years. We observed this trend toward fewer days worked in all age cohorts, and our findings are consistent with a previous report.³ Women averaged about 10 percent fewer days per year than men and had a resultant income that was 10 percent lower than that of male dentists. However, the variation in the number of days worked was considerable in both groups, and the primary relationship between income and days worked—but not sex—prevailed for both men and women. For example, female dentists in the cohort aged 41 to 50 years worked more days and earned more income than did male dentists in cohorts aged 25 to 40 years and older than 50 years, and male dentists in the 25- to 40-year-old cohort worked fewer days than did men in both of the older cohorts.

Practice pattern characteristics. We also found no differences in practice pattern characteristics between male and female dentists. Indeed, the relative percentage of dental service categories was highly similar for male and female practitioners. Although the mean patient’s age was slightly lower and the proportion of female and pediatric patients was slightly higher in the general practices of women than of men, the differences were minor.

This study sample mirrored national figures^1,2 with respect to the proportion of female dentists in 2001, and it allowed us to create a simulation model to estimate the impact of different female-to-male dentist ratios. We concluded that if women made up 20 percent of this dentist population, about 2 percent (or 15,000) fewer patients would have been seen. A further decrease in patients treated (1.2 percent) would have been associated with each 5 percent increase in the proportion of female dentists in the work force.

Study limitations. We should point out that this model makes a number of assumptions, including no growth in the total dental work force and no change in practice patterns (particularly with regard to utilization of the entire dental team). Future studies should include surveys of dental office practice patterns to understand the implications of a dental work force that is increasingly female. Our simulation should be replicated in other settings across the United States. Additional information that would be beneficial is the number of patients who do not have dental insurance and were not covered in this study. Our study assumes no differences between men and women with respect to practice characteristics as they pertain to patients with and without dental insurance.

The use of claims data from one dental benefits carrier may have influenced some conclusions with respect to sex differences in practice patterns. Our data came from one insurance carrier and may not be representative of the entire population of people with dental insurance. Because WDS represents about one-third of insured patients and more than 90 percent of general dentists in Washington state, these results probably mirror those of other insurance carriers. However, all dentists represented in this study billed multiple carriers, and this analysis underestimates their total income from insured patients.

This analysis does not account for patients with social services benefits (that is, public assistance, Social Security, Medicaid, Medicare) or those without dental insurance coverage, an area that requires further study. Insurance claims–based data may underreport procedures that are not covered by insurance. Also, patients who do not have dental insurance will not be represented in this database. In observational studies such as this one, underreporting of this type likely biases the estimate toward not finding a difference between men and women where one truly exists. The fact that we found no difference supports the assumption that no systematic difference existed between men and women regarding practice patterns.

	CONCLUSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
The results of this study show that, in this WDS population, no systematic differences existed between female and male dentists with regard to income per day worked or patterns of dental care. In general, female dentists worked fewer days per year than did their male counterparts. Both groups demonstrated flexibility in work schedules on the basis of age, family responsibilities and other life choices.^3,4,6 Such flexibility is a relatively rare and positive aspect of a career in dentistry for men and women.