Investigation of Dental Implant Referral Patterns Among General Dentists and Dental Specialists: A Survey Approach

Thomas Y.H. Yoon, DDS, MS; Sable A. Muntean, BS; Richard A. Michaud, DMD; and Thanhphuong N. Dinh, DMD

The surgical placement of dental implantsis an important area of referral between a general dentist and specialist. The demand for dental implant therapy has been steadily increasing due to such factors as an expanding older population and higher predictability of implant-supported restorations.¹ In 2001, it was reported that approximately 450,000 dental implants were placed per year with an average survival rate of 95%.² In 2013, the number of implants placed dramatically increased to 1.26 million, and this number is expected to double in 7 years.³

Regardless of this demand, most general dentists do not incorporate the surgical placement of implants into their practice.⁴ According to a survey study of general dentists practicing in the state of Virginia, only 16% of respondents placed implants.⁵ A 2007 study conducted by Boston University of its dental school general dentist alumni revealed that only 10% of graduates surgically placed implants.⁶ As a result, specialists strive to gain the trust of general dentists to maintain sources of patient referrals. Specialists often speculate on the factors upon which general dentists base their specialty referral decision-making,⁷ and although the practice of dental referrals has been rendered for decades, the intricacies of this particular relationship—between general dentist and implant placement specialist—have not been well understood.

The purpose of this study was to evaluate three aspects of dental implant referrals: (1) What factors do general dentists find important when referring a patient to a specialist for the surgical placement of implants?; (2) What factors do specialists perceive as important when being referred a dental implant patient?; and (3) What factors, if any, do both specialists and general dentists mutually view as being important in dental implant referrals?

Materials and Methods

This study was approved by the Institutional Review Board of the Lake Erie College of Osteopathic Medicine (protocol number 23-115). General dentists and specialists were selected at random from the membership rosters of multiple US state and local dental societies. A randomized national sample of general dentists and specialists in the United States represents an unbiased selection and serves as a representative population of providers.⁷

To protect respondent information and to prevent inadvertent disclosure of personal data, participant responses were anonymously gathered via an online survey tool. Due to the anonymous nature of the data collection, follow-up reminders could not be conducted. From January through September 2016, a total of 6,769 surveys were emailed and 602 responses received, for a response rate of 8.9%. (Author Note: The relatively low rate of survey responses may be due to the databank that was used. Most of the email addresses the authors used were gathered from websites or Internet searches of dental practices. Thus, the authors conclude that many of the emails may not have been accessed by the dentist and/or possibly rejected through a spam filter. Additionally, email surveys needed to be sent to four different specialist groups, thus increasing the overall sample size.) Of the respondents, 356 were general dentists and 246 were specialists, including periodontists, endodontists, oral surgeons, and prosthodontists.

To indicate their number of years of experience in the field, subjects were asked to select one of five different year ranges: 0 to 5, 6 to 10, 11 to 20, 21 to 30, and 31 to 40+. Study participants were given a series of eight questions and asked to rank the importance level of each when dealing with dental implant referrals. The questions involved the following factors: distance (between the general dentist's office and the specialist's office), cost of the surgical implant (specialist's charge), insurance acceptance by the specialist, implant system used by the specialist, years in clinical practice of the specialist (experience), communication between the referring general dentist and specialist, the quality of the work by the specialist, and the ease for scheduling the patient.^8,9,10 These questions were ranked on a five-point Likert scale ranging from “Least Important” (1), to “Most Important” (5). General dentists and specialists were given similar surveys with slight wording variations (Figure 1 and Figure 2) to reflect the necessary responses for the Likert scale rating questions.

Because the study focused specifically on referral factors from general dentists to specialists for surgical placement of dental implants, the survey only included specialists who placed surgical implants and general dentists who did not place surgical implants. Questionnaires that were completed by general dentists who indicated that they had placed surgical implants were excluded from the study.

Three different data sets were used in the analysis process: one for general dentist analysis, one for specialists, and one where similar variables were combined into one data set to compare the two groups of respondents.

Results

General Dentists

A Kruskal-Wallis test was used to evaluate responses from general dentists. For practitioners with less than 5 years of experience, location of the specialist's office exhibited significance, P < .001. Quality of the work was significant among all practitioners, regardless of experience, P = .014. One variable—whether insurance is accepted—showed marginal significance among practitioners of 0 to 5 and 6 to 10 years of experience, P = .056 (Figure 3).

Regardless of number of years in practice, a vast majority of cases referred for surgical implant placement and number of implants restored remained at 10 or less per month, with 89.6% for restoration and 80.4% for cases referred (Figure 4). In regard to how many general dentists place dental implants, the results revealed that 32.8% of all general dentists are involved with the surgical placement of dental implants (Figure 5).

When general dentists were asked how many different specialists they refer to, 35.8% of respondents replied “two,” 25.8% replied “three,” 19.2% replied “one,” 5.4% replied “four,” and 13.8% replied “other” (Figure 6).

General dentists refer a greater percentage of cases to periodontists overall, 83.7%, compared to other specialties, regardless of the number of years in practice (Figure 7).

Specialists

Much like general dentists, specialists were evaluated mainly on their indicated years of experience in the profession. The eight measures provided were the same as those given to the general dentists, with a few modifications in wording to accurately assess the different sample group. A parametric one-way ANOVA test was used to analyze the data set. There were no significant results on any of the eight measures, although the travel distance to the office and the total years of clinical practice approached significance, P = .078 and P = .072, respectively. (Author Note: The authors conclude that the lack of significant results among specialists is due to the fact that multiple specialty types were surveyed. Because the specialist groups focus on different aspects of dental referrals it may have contributed to the lack of significance. Further studies that focus on each individual specialty group with a large sample size are warranted.)

Comparison Analysis

Given the differences between general dentists and specialists, a comparison across the two groups on the eight factors measured was integral to this study. A Mann-Whitney U test of differences was utilized. The results showed significant correlation between groups in communication with each other and quality of the treatment, P = .005 and P = .001, respectively. Although acceptance of insurance showed significance, it was not as strong of a correlation as the aforementioned two factors, P = .039. One measure—years of clinical practice—showed a marginally significant difference, P = .053 (Figure 8).

Discussion

The results of this research suggest there is a positive correlation among general dentists and specialists in regard to communication and quality of work. From the Likert scale used in the survey, the data was interpreted for those who scored a 4 or 5 within the appropriate categories to demonstrate the highest correlation to the given attribute.

Communication was an important aspect of referral patterns for both general dentists and specialists. This could be due to the fact that open communication builds trust, thus encouraging referrals. A study performed by Wolcott et al examined the building of trust among endodontic specialists and general dentists. Their results revealed that when a specialist submitted timely follow-up reports, the relationship strengthened significantly.¹¹ McDonald et al surveyed 212 oral and maxillofacial surgeons in New Jersey and, based on written commentary, determined that recent graduates were not well-skilled in the art of communication, particularly with regard to referrals. The authors directly attributed the development of the relationships between general dentists and specialists to communication skills.¹² Open communication appears to be critical in the general dentist and specialist referral system.

Quality of work demonstrated a positive correlation between specialists and general dentists. Although the present authors' research indicated that this was an important attribute, historical literature exhibits mixed results. Ghiabi and Matthews examined the behavioral pattern of general dentists in Nova Scotia for implant referrals. Their research indicates that quality of work was the fourth most important factor, behind such attributes as patient satisfaction and good communication.¹³ On the contrary, a study by Kothari et al evaluated the referral relationship between pediatric dentists and orthodontists. Their survey results revealed that quality of work was clearly the most important attribute that influenced pediatric dentists to refer specialty care to an orthodontist.¹⁴ The differences between findings in historical literature should be further evaluated in additional studies.

Although there was significance among practitioners in regard to insurance, it was a relatively weak correlation. This finding is also somewhat conflicted within dental literature. A study by Aminoshariae et al examined the role of dental insurance in treatment planning of endodontic therapy and dental implants. Their results show that insurance did not play a role in the decision-making portion of treatment planning dental implants between general dentists and specialists.¹⁵ Conversely, Reese et al reviewed 4,084 dental school patients who received endodontic therapy and/or implant placement between the years 2006 and 2011. Their results showed that the availability of insurance and the relative benefits offered significantly impacted the acceptance rate of dental implants.¹⁶ Due to the conflicting data available, further research on this topic would be beneficial.

A particularly interesting finding of the present study involves location of the specialist office to the general dentist. Few studies have found a positive correlation between distance to an office and the effect upon referrals. Linden et al found that in the United Kingdom, general dentists were not as likely to refer a patient to a periodontist who was beyond a 25-mile radius.¹⁷ Schlieve et al evaluated the relationship between orthodontists and general dentists referring to oral and maxillofacial surgeons. Their study is consistent with the present study in regard to general dentists not viewing proximity as an important factor. However, they did note that orthodontists viewed proximity as a significant finding when referring cases to oral surgeons.¹⁸ The present study confirmed that distance to the general dentist's office was a determining factor in implant referrals. However, it also noted that this factor was only significant for practitioners who had been in practice for 5 years or less. Further studies would be of interest to determine the role of this factor in the referral mechanism.

Another interesting finding within this study is in regard to the increasing number of general dentists who are placing dental implants. According to an Academy of General Dentistry survey study performed in 2003, only 4% of general dentists surgically placed dental implants. This number increased to 6% in 1999, and in 2003, 9% of general dentists surgically placed implants.¹⁹ A 2013 survey of 7,000 members of the American Academy of Facial Esthetics revealed that 20% of its membership surgically placed implants.²⁰ The present study found that 32.8% of dentists surgically place dental implants, representing a dramatic increase since 2013. A possible reason for the increase in general dentists placing implants is a greater interest in these types of continuing education courses. A survey study by Chan et al found that dental implant courses were the preferred choice of subject by those attending the 26th Asia Pacific Dental Congress in Hong Kong.²¹ Another possible reason for this increase is the integration of surgical placement within predoctoral dental school curricula. In 2005, schools such as Creighton University School of Dentistry reported that their “students place the implants.” This represented approximately 6% of all dental schools at that time with such a curriculum.²² This number steadily increased as additional schools began to incorporate surgical implant placement as a surgical elective in the predoctoral curriculum.²³

Conclusion

Using the Likert scale, data was interpreted for those who demonstrated the highest correlation to a given attribute by scoring the given categories with a 4 or 5. The results of this research suggest there is a positive correlation among general dentists and specialists in regard to communication, quality of work, and, to a lesser extent, accepted insurance.

Further consideration toward other influencing factors would be beneficial and these should be investigated as part of continuing research. Subsequent survey studies should be performed that expand on the current findings, and it would be helpful if future studies targeted specific specialty groups. Though, ultimately, the results of this research do not determine the referral decision-making process, they offer insights into the thought process of dental referral.

Acknowledgments

The authors would like to acknowledge Ms. Andona Zacks-Jordan and Mr. Sean Bogart of the Lake Erie College of Medicine Institutional Planning, Assessment, Accreditation, and Research department for their contribution in editing and statistical analysis.

About the Authors

Thomas Y.H. Yoon, DDS, MS
Director of Research
Assistant Professor of Periodontology
Lake Erie College of Osteopathic Medicine
School of Dental Medicine
Bradenton, Florida

Sable A. Muntean, BS
Student
Lake Erie College of Osteopathic Medicine
School of Dental Medicine
Bradenton, Florida

Richard A. Michaud, DMD
Assistant Professor of Endodontics
Lake Erie College of Osteopathic Medicine
School of Dental Medicine
Bradenton, Florida

Thanhphuong N. Dinh, DMD
Director of Curriculum
Assistant Professor of Restorative Dentistry
Lake Erie College of Osteopathic Medicine
School of Dental Medicine
Bradenton, Florida

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