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J Dent Educ. 71(2): 296-303 2007
© 2007 American Dental Education Association
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Milieu in Dental School and Practice

Educational Practices Regarding Anticoagulation and Dental Procedures in U.S. Dental Schools

Sunny A. Linnebur, Pharm.D.; Samuel L. Ellis, Pharm.D.; Jeffrey D. Astroth, D.D.S., M.S.P.H.

Key words: dentistry, dentists, education, school dentistry, dental education, dental continuing education, anticoagulants, hemorrhage

Submitted for publication 07/06/06; accepted 09/21/06


   Abstract
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 Abstract
Methods
 Results
 Discussion
 Conclusions
 References
 
Evidence suggests that stopping oral anticoagulation with warfarin is not necessary in patients requiring low-risk dental procedures and may actually increase thrombosis risk. However, widespread belief remains among dentists that stopping oral anticoagulation for dental procedures is necessary. The purpose of this study was to investigate the teaching practice of U.S. dental faculty responsible for providing education to dental students about anticoagulation. Surveys were mailed in 2003 and 2004 to fifty-five U.S. dental faculties to assess their teaching practice regarding anticoagulation and dental procedures. Twenty-eight (50.9 percent) of the schools returned surveys. Contrary to evidence indicating anticoagulation does not need to be altered, many dental faculty responded that they teach dental students to discuss with medical providers/patients about altering warfarin therapy for several routine procedures: 21.4 percent (cleaning), 14.3 percent (restorative treatment), 46.4 percent (single simple extraction), 64.3 percent (multiple simple extractions), and 17.9 percent (root canal). However, 67.9 percent stated an International Normalized Ratio (INR) of 2.0–3.0 would be acceptable prior to dental procedures. A discrepancy was also found between the number of faculty recommending altering warfarin in intermediate- to high-risk individuals compared to those recommending heparin bridging for the same patients. Overall, this study identified inconsistencies between teaching practices in U.S. dental schools and medical evidence. Dental faculty should consider comparing their teaching material with evidence regarding anticoagulation and dental procedures. Continuing education may be necessary for practicing dentists regarding this topic.

Oral anticoagulation with warfarin is widely prescribed for various medical conditions. Many patients, such as those with atrial fibrillation, multiple venous thromboembolisms, and artificial heart valves, are recommended to continue warfarin therapy indefinitely. Consequently, dental procedures in patients who are taking warfarin are common.

Some controversy regarding continuing or discontinuing anticoagulation therapy prior to dental procedures existed in the 1980s and 1990s. However, a plethora of data1–11 and expert opinions12–20 now exist to support that patients with therapeutic levels of warfarin can continue their therapy through routine dental procedures without major bleeding complications. Moreover, anticoagulation guidelines21,22 recommend that warfarin be continued through most dental procedures. Unfortunately, there is still a general belief among practicing dentists that anticoagulation must be stopped prior to dental procedures to prevent bleeding.12,23,24 This belief and practice potentially put anticoagulated patients at an unnecessary risk of thromboembolic events.16 In fact, in 1998 Wahl found that five serious thromboembolic events (including four deaths) had been reported in patients who stopped anticoagulation for dental procedures.16 At this time, it is unknown if the practice of stopping warfarin therapy prior to dental procedures is due to pressure from physicians and other providers to discontinue anticoagulation before dental procedures or due to a lack of understanding among dentists as a result of inadequate continuing education or deficiencies in dental training. Thus, the purpose of this study was to determine the characteristics of U.S. dental school teaching practices regarding anticoagulation management during dental procedures.


   Methods
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 Abstract
 Methods
Results
 Discussion
 Conclusions
 References
 
The study was approved by the Colorado Multiple Institutional Review Board in September 2003. Fifty-five U.S. dental schools were surveyed in November 2003 regarding teaching practices related to anticoagulation and dental procedures. Surveys were mailed to the faculty member(s) at each institution identified as responsible for teaching in this area. A follow-up survey was mailed in February 2004 to schools that had not yet responded.

The survey collected both demographic information and information regarding teaching practices. Demographic information collected included dental school name, primary field of practice, practice setting, hours per week spent in direct patient care, and years of teaching the topic of anticoagulation and dentistry. The survey consisted of seven questions designed to collect information regarding teaching practices related to anticoagulation and dental procedures (Figure 1Go). Several of the survey questions were based on a previously published anticoagulation/dental survey.25 Survey responses were received by regular mail, fax, or email.


Figure 1
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  		Figure 1. Survey instrument

 
Descriptive statistics (percent) were performed for demographic information and survey responses. An analysis based on years spent teaching anticoagulation (fifteen years or less compared to greater than fifteen years) was also completed using Microsoft Excel 2003 (Redmond, WA).


   Results
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 Abstract
 Methods
 Results
Discussion
 Conclusions
 References
 
Of the fifty-five surveys mailed to U.S. dental schools, twenty-eight (50.9 percent) were returned, representing most geographic areas of the United States. Table 1Go describes the characteristics of the survey respondents. The majority of the faculty members completing the survey were associated with a Department of Oral and Maxillofacial Surgery and indicated they were full-time faculty. Slightly over 40 percent of the respondents indicated they spend greater than thirty hours per week providing direct patient care, while 18 percent indicated they provide patient care for ten or fewer hours per week. Of the faculty responding, many stated they have been teaching the topic of anticoagulation and dentistry for longer than fifteen years. Only two respondents stated they have been teaching the topic for two years or less.


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  		Table 1. Characteristics of survey respondents*
 
Table 2Go provides a summary of responses to the survey questions regarding teaching practices and anticoagulation. A few surveys did not include responses to all questions or they included text in their responses, so these responses could not be utilized. Percentage response was calculated from a total of twenty-eight responses.


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  		Table 2. Responses to survey questions*
 
In the analysis based on time spent teaching anticoagulation, no responses were statistically different between groups. However, in general, more faculty who reported teaching for greater than fifteen years responded that they do not teach students to recommend holding warfarin for low-risk dental procedures (e.g., professional cleaning, restorative treatment, simple extractions, and root canal) or with high-risk indications (e.g., artificial valve replacement, systemic emboli, history of stroke/transient ischemic attack). On the other hand, more faculty who reported teaching for fifteen years or less responded that they teach students to recommend heparin or low-molecular weight heparin (LMWH) for the same high-risk indications and also responded that they utilize Journal of the American Dental Association (JADA) or CHEST (American College of Chest Physicians) guidelines as the primary resource for teaching anticoagulation.


   Discussion
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 Abstract
 Methods
 Results
 Discussion
Conclusions
 References
 
Overall, many dental faculty responded that they teach dental students to discuss with medical providers/patients about changing warfarin for a variety of dental procedures. Some of these procedures, such as professional cleanings, restorative treatment, single simple extractions, multiple simple extractions, and conventional endodontic therapy, are considered to be low-risk procedures that should not require anticoagulation alteration prior to the procedure.12–20 Multiple studies have shown that dental extractions (both single and multiple) can be performed with International Normalized Ratios (INRs) ranging from 2.0 to 4.0 without major bleeding complications.1–11 Current anticoagulation guidelines recommend INR goals within this range: 2.0–3.0 for most patients taking warfarin and possibly higher ranges up to 3.5 or 4.0 for patients with mechanical heart valves, acute myocardial infarction, or antiphospholipid syndrome.21

Evidence supports that alteration of warfarin therapy is not necessary for low-risk dental procedures. Zanon et al. prospectively studied dental extractions and bleeding in 250 patients stabilized on warfarin and 250 non-anticoagulated patients (control group).10 Single or multiple extractions of varying degrees of complexity were performed, with a total of 525 extractions in the anticoagulated patients and 513 extractions in the control group. After extraction, a piece of oxidized cellulose was inserted into the wound, and a silk suture was applied in all anticoagulated patients and in most of the control patients. Gauze saturated with tranexamic acid was also kept in place for thirty to sixty minutes in the anticoagulated patients. Bleeding and other complications were evaluated on the third and eighth days following the procedure. The number of bleeding complications in the anticoagulated patients (n=4) was not significantly different from the number in the control patients (n=3), p=0.7. No significant differences in bleeding were seen based on different INR values: 1.2 percent with INR 1.8–2.0; 1.3 percent with INR 2.0–3.0; and 4.8 percent with INR 3.0–4.0. No patients required alteration of anticoagulant therapy, hospitalization, or transfusion. This and other studies support that patients can continue their anticoagulation therapy during both single and multiple extractions when simple local measures are instituted. However, we found in our study that 46.4 percent and 64.3 percent of faculty stated they teach dental students to discuss with medical providers/patients altering warfarin for simple single and multiple extractions, respectively.

In another study by Blinder et al., 249 anticoagulated patients had 543 simple single and multiple dental extractions without interruption of their warfarin therapy.7 All patients received local hemostatic measures of gelatin sponges and silk sutures. INRs were measured on the day of the extraction. For results purposes, patients were divided into groups based on their INR values: 1.5–1.99, 2–2.49, 2.5–2.99, 3–3.49, and >3.5. Overall thirty (12 percent) patients presented with minor postoperative bleeding. Although slightly less bleeding (5 percent) occurred in the group with the lowest INR range compared to the other groups (range 12.8 percent to 16.6 percent), the incidence of bleeding was not significantly different between groups. In addition, the INR value did not significantly affect the incidence of bleeding. In those patients with minor postoperative bleeding, additional curettage, gelatin sponges, sutures, or gauze soaked in tranexamic acid provided hemostasis. These data indicate that the INR range prior to extraction does not significantly affect bleeding rates in anticoagulated patients when local hemostatic measures are employed. In our survey, 67.9 percent of dental faculty responded that they teach students to achieve an INR within 2.0 to 3.0, which is the therapeutic range for most anticoagulated patients. However, 17.9 percent of dental faculty responded that they teach students that INRs should be in the range of 1.5–1.9 prior to dental procedures.

Many dentists may fear that local measures are not effective at controlling bleeding in anticoagulated patients. However, numerous studies indicate that tranexamic acid-soaked gauze, tranexamic acid mouthwash, histoacryl glue, fibrin glue, gelatin sponges, and plasma gel are effective.8–10,26–32 Blinder et al. compared three local measures to stop bleeding in anticoagulated patients undergoing dental extractions.26 A total of 150 patients who had 359 extractions were treated with either 1) gelatin sponge and silk sutures; 2) gelatin sponge, silk sutures, and 500mg tranexamic acid mouthwash (repeated four times daily for four days); or 3) gelatin sponge, silk sutures, and fibrin glue. In total, thirteen (8.6 percent) of the patients presented with postoperative bleeding: three patients from group 1, four patients from group 2, and six patients from group 3. A comparison of the bleeding rates between the groups indicated no significant differences. Local measures were effective at stopping bleeding in all patients, as none required acrylic splint or systemic treatment. Thus, standard and additional local measures are effective for hemostasis in anticoagulated patients undergoing dental extractions.

In our survey we also assessed teaching practices concerning indications for warfarin and their effect on anticoagulation management around dental procedures. Interestingly, one-half of faculty indicated they teach students to consider altering warfarin around moderate- to high-risk conditions, such as in patients with an artificial heart valve, history of systemic embolism, and history of transient ischemic attack or stroke. However, only a low number of faculty (21.4 percent, artificial heart valves; 14.3 percent, history of systemic embolism; and 10.7 percent, history of transient ischemic attack or stroke) indicated they teach dental students about bridging with heparin or LMWH when changing warfarin in moderate- to high-risk patients. This disparity in teaching is concerning, as altering warfarin therapy in high-risk individuals without bridging with heparin or LMWH could place the patient at high risk of thrombosis.

Anticoagulation guidelines suggest that, in patients at intermediate to high risk of thrombosis, heparin or LMWH should be utilized when holding warfarin therapy for procedures.21 This practice minimizes the time the patient is not adequately anticoagulated from approximately one week (when holding warfarin) to less than one day (when bridging with heparin or LMWH). Although heparin bridging is primarily the responsibility of the primary care provider, many patients may not let their physicians know about the procedure and may proceed through the dental work without adequate protection for thrombosis. Thus, practicing dentists should be aware that stopping warfarin prior to dental procedures in some patients necessitates additional anticoagulation coverage with a heparin product. In addition, weighing the risk of bleeding versus thrombosis is extremely important as heparin and LMWH can be costly, time-consuming, and difficult for some patients to manage. Thus, avoiding the need for heparin products by continuing warfarin therapy through dental procedures is less complicated in general than stopping warfarin.

Since many studies and review articles are available on the topic of anticoagulation and dental procedures, it is not surprising that we found 64.3 percent of dental faculty utilize medical literature, recommendations from JADA, or recommendations from CHEST as the primary resource for their lectures on the topic. However, 28.6 percent of faculty stated they rely on clinical experience rather than evidence-based medicine to teach on this topic. It is possible that those unfamiliar with anticoagulation data and guidelines are the faculty teaching students that holding warfarin for low-risk dental procedures is appropriate. In our analysis based on years spent teaching anticoagulation, those with a shorter teaching history indicated they utilize recommendations from JADA and CHEST in their teaching more so than those with a longer teaching history. This is a positive finding; however, it did not translate into the junior faculty teaching to alter warfarin less often for low-risk dental procedures. Our survey results also indicate that the majority of dental faculty stated the physician is the primary clinician responsible for managing warfarin therapy. Thus, physicians also need to be educated with data and guidelines pertaining to dental procedures in anticoagulated patients.

This study has several limitations. First, the results relied upon survey responses, which were only received by approximately one-half of dental schools in the United States. In addition, some surveys were only partially completed or had text instead of a marked reply, so the replies could not be counted. Next, the survey was mailed in late 2003 and early 2004, so the faculty may have already updated their teaching practices in subsequent years to reflect more current guidelines and data. Finally, the survey was limited to questions regarding warfarin and did not include questions about other antiplatelet agents like aspirin or clopidogrel. It is possible that some respondents may have responded differently to the survey if they were asked about both warfarin and antiplatelet agents. However, evidence also supports that antiplatelet agents do not need to be stopped prior to dental procedures.12,33


   Conclusions
Top
 Abstract
 Methods
 Results
 Discussion
 Conclusions
References
 
Inconsistencies were found between teaching practices in U.S. dental schools and medical evidence regarding 1) changing warfarin therapy prior to low-risk dental procedures and 2) heparin bridging for intermediate- to high-risk patients. Dentists should be aware that changing warfarin therapy prior to routine, low-risk dental procedures, including simple single and multiple extractions, is not necessary and that local measures are effective at controlling bleeding. Dental faculty should consider comparing their teaching material with available evidence on this topic and updating their material if necessary. Continuing education in the area of anticoagulation may also be warranted for practicing dentists.


   Acknowledgments
 
The authors would like to acknowledge the assistance of Michele Ensign, dental hygienist, for her help with data collection and analysis.


   Footnotes
 
Dr. Linnebur is Assistant Professor, Department of Clinical Pharmacy; Dr. Ellis is Assistant Professor, Department of Clinical Pharmacy; and Dr. Astroth is Associate Professor, Department of Applied Dentistry—all at the University of Colorado at Denver and Health Sciences Center. Direct correspondence and requests for reprints to Dr. Sunny A. Linnebur, Department of Clinical Pharmacy, University of Colorado at Denver and Health Sciences Center, 4200 E. Ninth Ave., Campus Box C238, Denver, CO 80262; 303-315-1561 phone; 303-315-4630 fax; sunny.linnebur{at}uchsc.edu.

This research was supported by an investigator-initiated clinical research grant from Bristol-Myers Squibb.


   REFERENCES
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 References
 

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