BACKGROUND

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In July 1995, Yellowitz and colleagues⁴ conducted a random mail survey of general dentists in the United States to determine their knowledge of, and opinions about, oral cancer. They found deficits in knowledge of location and appearance of cancerous and precancerous lesions, with recent dental school graduates having the highest odds of scoring high on knowledge indexes. Many dentists indicated an interest in receiving continuing education on this topic. Since this dentist survey was administered, adjunctive techniques have become available to enhance the early diagnosis of oral cancer⁵ and have been an impetus behind public educational campaigns and a renewed professional interest in the early detection of this disease.⁶

With an age-adjusted oral cancer mortality rate that is higher than the national average,⁷ North Carolina needs to improve its efforts at controlling this often disfiguring disease. High mortality rates need to be addressed in a collaborative, community-based approach that involves the general public, policy-makers, community leaders and health care providers. Our study is one component of a North Carolina needs assessment project aimed at developing a state-focused model for improved oral cancer control. It addresses dental care providers’ readiness to improve early detection efforts.

The purpose of this survey was to assess the level of knowledge and factors associated with knowledge levels (for example, a respondent’s background) among North Carolina dentists regarding oral cancer risk factors and diagnostic concepts, such as signs and symptoms and high-risk anatomical locations of oral cancer.

	SUBJECTS, MATERIALS AND METHODS

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In May 2002, we mailed a 38-item pretested survey, cover letter and business reply envelope to a random sample of 1,115 of 3,303 licensed dentists practicing in North Carolina. The North Carolina State Board of Dental Examiners supplied mailing addresses for all currently licensed dentists. Six weeks after the initial mailing, we sent a reminder postcard. Six weeks later, we sent a second complete mailing to nonrespondents. Entry of respondents into a drawing for one of five gift certificates served as an incentive to participate. After two mailings, we received 584 completed surveys, for an effective response rate of 52 percent.

The Committee on Research Involving Human Subjects of the University of North Carolina School of Dentistry, Chapel Hill, approved this voluntary confidential survey. Data were entered into a computer database (Epi Info 2002, Centers for Disease Control and Prevention, Atlanta) and analyzed with a statistical software package (SAS 8.2, SAS Institute, Cary, N.C.).

The survey asked respondents about their background, dental education, dental practice patterns, use of medical histories to assess patients’ oral cancer risk, knowledge of oral cancer risk factors and diagnostic concepts, and qualifications and training with regard to oral cancer prevention and early detection. We created three-level (low, medium, high) composite index scores for knowledge of 16 oral cancer risk factors and 14 oral cancer diagnostic concepts using previously developed scales.⁸ Respondents were asked specifically if they had ever heard of—and if they had used in the past 12 months—each of the following aids for the diagnosis of OPC:

– computer-assisted brush biopsy (OralCDx, CDx Laboratories, Suffern, N.Y.);

– toluidine blue vital dye;

– disposable light for illumination of abnormal tissue (ViziLite, Zila, Phoenix).

We conducted separate bivariate and logistic regression analyses to assess the relationship of the three-level outcome variables (risk factor knowledge index and diagnostic knowledge index) with the following independent variables:

– sex;

– type of practice (solo versus other);

– generalist versus specialist;

– year of graduation (before versus after 1982);

– biopsy/referral pattern (those who performed five or more biopsies and/or referred five or more patients with suspicious lesions versus those who referred fewer than five patients with suspicious lesions in the previous 12 months);

– having heard of or used the newer oral cancer diagnostic aids (that is, computer-assisted brush biopsy, toluidine blue vital dye or disposable illumination light).

We used Cochran-Mantel-Haenszel statistics to test the two knowledge indexes for association. The statistical significance of the coefficients in the logistic regression models was tested using the Wald statistic at the .05 level to determine which variables to include in the regression model. We calculated odds ratios and 95 percent confidence intervals from the regression coefficients and standard errors. We used P < .05 as the criterion for retaining variables in the final logistic regression models.

	RESULTS

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Of the 584 respondents, 479 (82 percent) were male, 365 (63 percent) were in solo practice and 469 (80 percent) were general dentists. Of the 469 general dentists, 90 (19 percent) also had completed either a general practice residency (GPR) or an advanced education in general dentistry (AEGD) program. Specialists included 27 oral and maxillofacial surgeons (5 percent), 21 periodontists (4 percent), 19 orthodontists (3 percent), 17 pediatric dentists (3 percent), 12 endodontists (2 percent), 10 public health dentists (2 percent) and nine prosthodontists (1 percent), but no oral pathologists or oral radiologists. Year of graduation from dental school ranged from 1944 to 2001, with a median year of 1982.

Of the 584 respondents, 339 (58 percent) reported having performed biopsies and/or referred five or more patients with suspicious lesions in the previous year, 456 (78 percent) had heard of one or more oral cancer diagnostic aids and 123 (21 percent) had used one or more oral cancer diagnostic aids. Respondents reported the following in regard to having specific knowledge of and using the diagnostic aids within the previous 12 months:

– sixty-nine percent had heard of the computer-assisted brush biopsy and 20 percent had used it;

– forty-six percent had heard of toluidine blue vital dye and 2 percent had used it;

– thirty-six percent had heard of the disposable light for illumination of abnormal tissue and 1 percent had used it.

As shown in Figure 1, the percentage distribution of correct responses to the 16 risk factor knowledge items ranged from 8 percent to 100 percent. As Figure 2 shows, the percentage distribution of correct responses to the 14 diagnostic knowledge items ranged from 45 to 99 percent. The mean correct risk factor knowledge score was 8.7 (range, 0 to 15), and the mean correct diagnostic knowledge score was 8.6 (range, 0 to 12). Knowledge levels were significantly associated with each other (Mantel-Haenszel ², P < .0001).

View larger version (33K): [in this window] [in a new window]   Figure 1. Dentists responding correctly to the 16 risk factor knowledge items.

View larger version (41K): [in this window] [in a new window]   Figure 2. Dentists responding correctly to the 14 diagnostic knowledge items. OC: Oral cancer.

The strongest independent variable in each model was having heard of diagnostic aids.

	DISCUSSION

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Being able to routinely detect oral cancer at an early stage and counsel patients in prevention is a continuous challenge for the dental profession. Dentists must be familiar with the risk factors and clinical signs and symptoms of oral cancer if they are to be effective in identifying, referring and counseling high-risk patients. Several opportunities exist to educate dental professionals: the first is in dental school (compulsory), the second is postgraduate education (self-selective) and the third occurs later, in continuing education (self-selective). The association between higher knowledge scores and recency of dental school graduation is important.

Of the 379 general dentists without GPR or AEGD training, 102 (27 percent) scored high on the risk factor knowledge index and 30 (8 percent) scored high on the diagnostic knowledge index. This compares with 32 (36 percent) and 10 (11 percent), respectively, of the 90 general dentists with GPR or AEGD training. In addition, 13 (48 percent) of the 27 oral and maxillofacial surgeons scored high on the risk factor knowledge index, while four (15 percent) scored high on the diagnostic knowledge index. Twenty (23 percent) of the 88 other specialists combined scored high on the risk factor knowledge index and 2 percent scored high on the diagnostic knowledge index.

Continuing education. Once in practice, dentists should obtain the best continuing education in early detection of oral cancer to meet their needs. Hands-on diagnostic evaluation of oral lesions and palpation of lymphadenopathy in patients, as well as hands-on activity in simulated clinical situations (including demonstration of, and practice in, biopsy techniques), may have the highest educational value and the most immediate applicability to clinical practice. However, continuing education via video (digital video disk and video home system videotapes) and seminar/lecture formats may be more accessible.⁹

Because of the asymptomatic nature of premalignant and early malignant oral lesions, a primary strategy of early detection lies in the health care provider’s review of the patient’s medical and dental history, as well as the extraoral and intraoral visual inspection of the head and neck (including manual palpation of related sites).¹⁰ Practice patterns including routine, systematic oral cancer examinations and biopsy (or referral for biopsy) of suspicious lesions must follow from improved knowledge and a heightened index of suspicion. Stahl and colleagues⁶ reported that 62.2 percent of a random sample of U.S. dentists surveyed about the impact of the ADA oral cancer campaign said that having a better understanding of what to look for would motivate them to test small, benign-appearing lesions routinely for early signs of oral cancer. The box provides a simple, seven-step guide for improving the chances of detecting oral cancer at an early stage.

Dentists must be vigilant about oral mucosal alterations.¹² If suspicious erythroleukoplakic or ulcerative lesions persist after possible traumatic or infectious etiology has been ruled out, the clinician should sample the tissue in a full-thickness surgical or punch biopsy procedure and send the tissue to a laboratory for histologic evaluation. Alternatively, the clinician can refer the patient to another practitioner for the surgical sampling procedure. As mentioned above, several new early detection technologies, including the brush biopsy, toluidine blue vital dye and the chemiluminescent light, are available to assist dentists by alerting them to the need for further analysis of possibly diseased tissue.²

Toluidine blue. Use of toluidine blue has improved the sensitivity and specificity of visual examinations when used in selected cases in which suspicious mucosal characteristics are present.^13–15 After years of research into its application as an oral rinse or a topical agent, tolonium chloride (toluidine blue) has been shown to be effective in detecting oral precancerous and malignant lesions.¹⁶ This metachromatic dye is a nuclear stain that binds to DNA, thus showing increased dye uptake in areas of tissue with high nucleic acid content, such as those undergoing dysplastic or malignant change. The product is marketed in Europe, Asia and the Middle East as OraTest rinse (Zila Europe, Salisbury, England), and the parent company is testing a version of the kit in Phase 3 clinical trials in the United States. Toluidine blue and acetic acid can be obtained for clinical use in the United States, but the sequence of rinses with vital dye has not been used widely owing to the dye’s staining properties. However, a study in the United Kingdom did demonstrate high levels of acceptance by patients and dentists.¹⁷

Brush biopsy. The brush biopsy may have utility in evaluating oral mucosal lesions of unknown significance. Using a "cytobrush," the dentist samples the altered oral mucosal surface, places a full-thickness sample of mucosal cells on a slide with fixative and mails the sample to a central laboratory facility. At the laboratory, the sample is analyzed by computer—along with standard microscopic evaluation by a pathologist—for abnormal cell characteristics indicating dysplasia or malignancy. ^2,5,18 Despite its high sensitivity, specificity and positive predictive values in the original U.S. clinical trial⁵ and in additional studies,^19,20 considerable controversy has arisen regarding the efficacy of the brush biopsy technique in clinical practice. Because not all potentially malignant disease is detected with this noninvasive procedure,^21–23 complete reliance on this cytologic screening test probably should be avoided.

Disposable light for illumination of abnormal tissue. The newest marketed technique is modeled after a chemiluminescent light that, when combined with Papanicolaous tests of cervical mucosa, has been shown in a multicenter trial to improve the detection of cervical premalignant lesions compared with Pap tests alone.²⁴ In a darkened room, the clinician holds the chemiluminescent light wand over oral mucosal tissue that has been prerinsed with 1 percent acetic acid; abnormal mucosa appear as an opaque acetowhite alteration, alerting the clinician to the need for a scalpel biopsy.² One pilot study of 150 patients²⁵ demonstrated the feasibility of its use intraorally; however, large-scale studies are required to elucidate issues related to the sensitivity, specificity and predictive value of this technology in the detection of oral premalignant and malignant changes.

Dentists with greater knowledge of both risk factors and diagnostic concepts were significantly more likely to have identified suspicious lesions and to have performed biopsies or referred patients for biopsies.

Dentists with greater knowledge of both risk factors and diagnostic concepts were significantly more likely to have identified five or more suspicious lesions and to have performed biopsies or referred patients for biopsies in the previous 12 months than were less knowledgeable respondents. We did not ask respondents specifically how many lesions had positive biopsy results. However, these findings indicate that increased referral and biopsy practices are associated with greater provider knowledge levels.

Because this study showed that having actually used a diagnostic aid was not significantly associated with knowledge levels, we cannot conclude that use of aids reinforced the dentist’s practice of referring patients or performing biopsies. It is likely, however, that exposure to additional diagnostic techniques improves the dentist’s confidence in regard to his or her decision to perform a more thorough examination. This possibility is supported by the finding that nearly two-thirds of dentists responding to a national survey evaluating the impact of the ADA’s oral cancer campaign reported that they evaluated small lesions more frequently because of the availability of the brush biopsy test.⁶

Study limitations. Given the 52 percent response rate, we did not calculate population-based estimates, and nonresponse bias may have limited our study findings. Similar response rates have been reported for mail surveys of practicing dentists about oral cancer conducted nationally^6,26 and in Maryland.²⁷ We believe that survey nonrespondents were more likely to have had lower knowledge levels and less interest in the topic than were those who completed and returned the survey. If nonresponse bias affected our results, it would most likely have resulted in higher knowledge levels than truly exist among practitioners in North Carolina.

We conducted this survey shortly after the ADA initiated a nationwide effort to increase the public’s and providers’ knowledge about early detection of oral cancer. In late 2001, the ADA’s national oral cancer awareness campaign was launched to increase public awareness of oral cancer.⁶ Cities in North Carolina were not among the 11 cities targeted for this media intervention, which included advertisements in a variety of outdoor venues (such as billboards, bus-shelter signs and taxi tops). Thus, we do not suggest that this public-focused media event had a direct impact on dentists’ knowledge levels, use of adjunctive diagnostic aids or practice patterns in North Carolina. However, the educational campaign targeting dentists, which included advertisements in ADA publications, may have had an impact on dentists’ awareness in North Carolina at the time that our survey was conducted.

The lessons learned from promoting early detection of breast, cervical and colorectal cancer (for which effective screening tests exist) suggest that a diverse set of strategies targeted to each group involved (public policy–makers, clinicians, patients and organizational systems/practice settings) is most effective at improving cancer screening rates when used synergistically.²⁸ An example of this is the concurrent public and provider educational approach taken in the 2001 ADA campaign.

More public education (such as training provided by health care professionals or lay health care workers) in conducting oral self-examinations may enhance awareness and empower patients. Physicians would benefit from training in early detection of oral cancer provided by dental educators. To enhance the effectiveness of this important dental public health effort, we need public policy and professional organizational/insurance industry changes that facilitate patient access to providers, result in consensus recommendations regarding preventive care, provide appropriate insurance coverage and reimbursement, and result in consensus regarding the efficacy and validity of the existing and emerging adjunctive diagnostic technologies.

	CONCLUSIONS

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The results of our survey of dentists in North Carolina show that higher levels of knowledge regarding oral cancer risk factors and diagnostic concepts were associated with more recent dental school training, having heard of oral cancer diagnostic aids, and having performed more biopsies or referred more patients for biopsies of suspicious lesions. Educational strategies to enhance clinicians’ knowledge of oral cancer risk factors and diagnostic concepts, as well as to promote early detection, are needed in North Carolina.

These programs should include information about the availability and use of adjunctive diagnostic techniques. Along with these programs, we need enhanced public awareness; professional organizational support; and implementation of policies that facilitate continued patient and provider participation in routine oral cancer examinations, as well as dentist education and training to ensure proficiency in conducting these examinations. Combined, these efforts have the potential to increase early detection, diagnosis and referral of patients with suspicious oral lesions and improve the health of the public.