Provision of specific dental procedures by general dentists in the National Dental Practice-Based Research Network: questionnaire findings

Several dentist characteristics were substantively related to provision of specific services. Dentist gender was substantively related to six of the 10 service types; males were more likely to provide each of these service types. The salience of dentist gender is an emerging finding across several treatment considerations in the network, even once gender differences in dental school graduation year and full-time/part-time status have been taken into account. We hypothesized that dentist gender would not be significantly related to service provision once graduation year and full-time status was taken into account. Consequently, it is noteworthy that four of the six gender/service associations remained substantively related to service provision in multiple regressions when graduation year and full-time status were taken into account. This does seem to be a recurring theme in most of the literature to date: although an analysis of dental claims data in Washington State revealed no gender differences in practice patterns [21], other studies have observed that male dentists are more likely to provide specific procedures. These include studies of Nova Scotia and Virginia GDs in which male dentists were more likely to perform non-surgical periodontal therapy [8, 14], endodontic services [11], and dental extractions [12, 22].

White dentists reported doing more implant procedures and less extractions. However, when adjusted in multiple regressions for their patient population’s racial distribution and insurance coverage, the association with dentist race was no longer substantively related to service provision.

Less-recent graduates in the network do substantively less extractions, but more periodontal surgery. When adjusted in multiple regressions for their patient population’s insurance coverage, the association with dentist graduation year remained substantively related to service provision. The literature is mixed in its conclusion about the effect of graduation year. Periodontal referrals have been associated with year of dental school graduation [13, 18]. Endodontic referrals were less likely among GDs with 6–10 years of experience, compared to those with more than 10 years of experience [11].

Whether or not the dentist had some type of formal training after dental school graduation was substantively related to service provision, but conclusions depended upon the type of training. When the comparison was ‘no training’ versus ‘training of any type’, those with no training were substantively less likely to provide implant, surgical periodontal, and orthodontic services. However, when the analysis took the next step to incorporate more detail about this training, those who had Fellowship in the Academy of General Dentistry (FAGD) or Mastership in the Academy of General Dentistry (MAGD) status or those who had completed some other type of training that did not include an Advanced Education in General Dentistry (AEGD) or General Practice Residency (GPR) program, were substantively more likely to provide specific service types; AEGD or GPR training was not substantively related to any service provision. The reasons for these differences were not queried in this study, but it is possible that AEGD and GPR training increases experience with many procedure types at the expense of depth with a small number of procedures, while FAGD, MAGD, or other type of training provides greater depth of experience with a small number of procedures, which is reflected in being more likely to provide these specific services. A comparable pattern was observed for dentists who are members of the American Dental Association (ADA) or Academy of General Dentistry. In a study of Virginia GDs, those with more advanced training, such as AEGD training, were more likely to refer for implant placement instead of providing these services directly [13]. In a study of AEGD and GPR training in the United States, dentists with postgraduate training were more likely to provide periodontal surgery and implants, but differences in other services were not statistically significant, except for multi-unit fixed bridges in which GDs with advanced training were actually less likely to provide these services [22].

We hypothesized that full-time dentists would be more likely to provide a wider range of service types. Whether the dentist was in employment on a full-time basis was substantively related to 9 of the 10 service types; full-time dentists were more likely to provide each of these services when compared to part-time dentists. We are not aware of other reports in the literature about this phenomenon, but this could be a salient consideration when making workforce projections.

Dentists who provide care at more than one location reported doing more dental extractions and less restorative care (including esthetically-focused restorative care). We are not aware of other reports in the literature about this phenomenon. When adjusted in multiple regressions for their patient population’s insurance coverage, the association with number of practice locations remained substantively related to service provision.

Inner city and rural practices were more likely to provide extraction and removable prosthodontic procedures, while suburban and urban practices not in the inner city were more likely to provide implants. The literature does not provide any information to which to compare, except regarding distance from a periodontist and referrals. Farther distances from a periodontist have been associated with GDs being more likely to refer periodontal care among Virginia dentists [14], but farther distances were associated with less periodontal referrals among British dentists [23], members of the Michigan Dental Association [19], and Nova Scotia dentists [8]. It is not clear if GDs’ provision of periodontal services is confounded by the GDs’ emphasis on periodontal diagnosis in the practice; that is, the extent to which periodontal diagnosis is emphasized may affect the number of patients for whom a periodontal procedure or referral is even considered.

Private practices, as compared to clinics with large public sources of funding, are more likely to provide “higher-end” services, such as restorative care and esthetically-focused restorative care, endodontics, implants, and orthodontics. This finding also parallels certain patient population characteristics listed later in Table 3 (insurance coverage and dental visitation behavior).

We hypothesized that when the GD was in a practice setting without any specialist on site, then the GD would be more likely to provide a wider range of services. We also hypothesized that if a specialist was available on site, then the GD would be less likely to provide services that could be done by that specialist. As evident in Table 3, both hypotheses were true. A limitation of this study is that we do not know if the practice employs dental hygienists. This could be a factor in how commonly certain procedures are provided, such as non-surgical periodontal care, although the directions of effect in the literature are conflicting [14, 23, 24].

We hypothesized that the shorter the wait times for new patient examinations, treatment procedures, and in the waiting room, then the more likely that the GD would be to report providing a wider range of services. As evident in Table 3, these hypotheses were true.

GDs were more likely to provide restorative care, esthetically-focused restorative care, and endodontics when their patient population had a higher percentage of private insurance coverage, and correspondingly lower-end service types when their patient population had higher percentages with public insurance or those who rely on free or reduced-fee care. Although the literature has a large amount of information about the role of insurance coverage on patients’ demand for care, little has been reported about the role of insurance coverage and visitation behaviors on whether GDs provide a full range of service types. A study of Michigan dentists did report that socioeconomic status and insurance status affected whether GDs refer their periodontal patients to a periodontist [19]. As dental insurance changes or expands to other patient populations in the future, GDs may adjust their mix of services to adapt to this changing demand. Other patient population characteristics were significantly associated with provision of specific services. It is possible that behavioral measures or disease prevalence of the patients in the practice would be a more-direct and stronger influence on referral or provision, so this would be a worthy avenue for future research in this area, if such measures could be obtained feasibly.

This study does have certain limitations that should be kept in mind when making inferences from it. We collected data via self-reports that were not validated by other means, such as observational data or dental records abstraction. As with all self-reported data, it is possible that participants’ responses may not reflect their actual behavior. Also, the study questionnaire queried how commonly specific procedures are done, but for the sake of brevity we did not query the converse: how commonly procedures are referred to specialists. It is possible that these responses would have yielded different results. Additionally, network members are not recruited randomly, so factors associated with network participation (e.g., an interest in clinical research) may make network dentists unrepresentative of dentists at large. While we cannot assert that network dentists are entirely representative, we can state that they have much in common with dentists at large, while also offering substantial diversity in these characteristics. This assertion is warranted because: 1) substantial percentages of network GDs are represented in the various response categories of the characteristics listed in Table 1[15]; 2) findings from several network studies document that network GDs report patterns of diagnosis and treatment that are similar to patterns determined from non-network GDs [25‐28]; and 3) the similarity of network GDs to non-network GDs using the best available national source, the 2010 ADA Survey of Dental Practice [29]. Regarding similarities to dentists in the ADA survey, the ADA survey samples both ADA members and non-ADA members, is based on a national probability sample, and provides the most comprehensive information on the characteristics of United States dentists. However, the ADA sample is limited to dentists in private practice, is based on a 29% response rate, and provides results from 2009. Because ADA Survey respondents cannot be practitioners in public health clinics, federal or tribal facilities, community health centers, or dental schools (provided they do not see private patients in the dental school), comparisons to network practitioners are limited in that regard. A total of 79% of ADA survey participants were general dentists, compared to 80% of network practitioners. Gender distribution in the ADA survey was 17% female [p. 6], compared to 27% female for network practitioners. The mean age in the ADA survey was 52.8 years [p. 5]; compared to 49.9 years for network practitioners. ADA Survey practices with one dentist accounted for 78% of practices [p. 8], compared to 81% for network dentists. A total of 64% of patients had private dental insurance in the ADA Survey [p. 23], compared to 59% for network practitioners.