Antibiotic prophylaxis prescribing practices of dentists in Singapore

ORIG INAL ART ICLE

Antibiotic prophylaxis prescribing practices of dentistsin Singapore

Huei Jinn Tong, Shijia Hu, Betty Yuen Yue Mok, Intekhab Islamand Catherine Hsu Ling Hong

Faculty of Dentistry, National University of Singapore, Singapore.

Background: Infective endocarditis is a serious complication that results in significant morbidity and mortality in suscep-tible patients. The guidelines for antibiotic prophylaxis have been updated by the American Heart Association andNational Institute for Health and Clinical Excellence. The antibiotic prophylaxis prescribing practices among dentists inSingapore are unknown. Aim: To determine the specific infective endocarditis antibiotic prophylaxis prescribing practicesof dentists in Singapore. Methods: A questionnaire survey was sent through an email link and by postal mail. Statisticalanalysis was carried out using SPSS 19.0. Results: Responses were received from 458 dentists (34.3% response rate), ofwhich 278 (65.9%) were general practitioners. The majority of respondents (39.8%) followed the American Heart Asso-ciation 2007 guidelines and 30.2% followed cardiologists’ recommendations. The accuracy of prescriptions for 13 car-diac conditions and 12 dental procedures were evaluated. The median number of accurate answers for cardiacconditions was eight for the American Heart Association 1999 guidelines, and four for the American Heart Association2007 and National Institute for Health and Clinical Excellence guidelines, respectively. The median number of accurateanswers for dental procedures was generally high, both for dentists who followed the American Heart Association 1999guidelines (median = 10) and American Heart Association 2007 (median = 9) guidelines. Majority of respondents(82.8%) felt that developing a local guideline would be beneficial to the local dental community. Conclusion: Dentistswere accurate in their prescriptions of antibiotic prophylaxis for dental procedures, but not for cardiac conditions. Itmay be helpful to attain a consensus among local cardiologists and dentists to unify the antibiotic prophylaxis prescrip-tion practices in Singapore.

Key words: Infective endocarditis, cardiac, guidelines

INTRODUCTION

Infective endocarditis (IE) is a rare condition withhigh morbidity and mortality in certain high risk pop-ulations1. Streptococcus viridans, Staphylococcus aur-eus, Enterococcus, Pseudomonas serratia and Candidaare some of the microorganisms implicated in IE2,among which S. viridans is one of the major culpritsthought to cause between 18 and 65% of IE casesworldwide3–5. As this large group of bacteria is foundroutinely and in abundance in the oral flora, it seemedreasonable that antibiotic prophylaxis should be indi-cated before invasive dental procedures for patientswho are at risk for developing IE. Since the release ofthe first American Heart Association (AHA) guidelinein 1955, dental health-care professionals have abidedby their recommendation that antibiotics should beadministered before invasive dental procedures for

selected patients6. Consequently, patients at risk forIE have also come to expect antibiotic prophylaxisbefore their dental treatment7.In recent years, the scientific community has que-

ried whether there is a need for antibiotic prophylaxisbefore dental procedures. A recent Cochrane reviewconcluded that there was no evidence that antibioticprophylaxis was effective against bacterial endocardi-tis8. Furthermore, recent studies have demonstratedthat poor oral hygiene and gingival bleeding afterroutine activities (e.g. tooth brushing), similar to den-tal procedures, can also result in bacteraemia withthe potential to cause IE in at-risk patients9. Giventhat IE is more likely to be caused by frequent andchronic exposure to oral flora associated bacteraemiaduring routine daily activities rather than by sporadicdental procedures2, current recommendations haveplaced greater emphasis on the importance of regular

108 © 2014 FDI World Dental Federation

International Dental Journal 2014; 64: 108–114

doi: 10.1111/idj.12088

maintenance of oral hygiene rather than the impor-tance of antibiotic prophylaxis before invasive dentalprocedures10. Other reasons cited against the routineuse of antibiotic prophylaxis include the risk–benefitratio, emergence of resistance strains, risk of adversedrug reactions2 and drug cost implications11.For the above reasons, both the AHA2 and the

National Institute for Health and Clinical Excellence(NICE)12 have revised and updated their guidelines tobe aligned with newly available scientific evidence.The AHA 2007 guidelines tiered down their antibioticprophylaxis recommendations to only include patientswho are in the high risk category, namely those with:

• Prosthetic cardiac valves

• Previous history of infective endocarditis

• Congenital heart disease (CHD) (i.e. unrepairedcyanotic CHD, completely repaired CHD withprosthetic material or device by surgery or catheterintervention during the first 6 months after the pro-cedure, repaired CHD with residual defects at thesite or adjacent to the site of a prosthetic patch orprosthetic device which inhibits endothelisation)

• Cardiac valvulopathy after cardiac transplantation.In addition, the AHA 2007 guideline no longer speci-

fies the types of dental procedures that require antibi-otic prophylaxis but instead recommends coverage for‘all dental procedures that involve manipulation of thegingival tissue or the periapical region of teeth or perfo-ration of the oral mucosa’ for at-risk patients2. In theUK, the NICE guidelines took a more radical stand andrecommended the cessation of antibiotic prophylaxisfor all patients undergoing dental and a wide range ofother invasive procedures in their 2008 guideline12.At present, the medical and dental authorities in

Singapore have not officially endorsed any guidelines.While it is the authors’ postulation that the majorityof dentists follow the AHA guidelines, this may notbe true. Several factors could influence dentists’ pre-scribing practices such as the country where basic andadvanced dental training were done, year of gradua-tion and input from medical or cardiology colleagues.The aim of this study was to determine the antibioticprophylaxis prescribing practices of dentists in Singa-pore for the prevention of IE, specifically the type ofguideline followed and the accuracy of their prescrip-tions according to the guideline of their choice.

METHODS

This was a cross-sectional study that utilised a 10-itemquestionnaire to evaluate the antibiotic prophylaxispractices of registered dentists in Singapore. Approval toconduct the study was obtained from the National Uni-versity of Singapore Institution Review Board beforecommencement of the study (NUS-IRB: 11-121E). Theresearch was conducted in full accordance with the

World Medical Association Declaration of Helsinki.The questionnaire was developed and piloted on a smallgroup of generalist and specialist dentists before admin-istration to test for readability, ease of understandingand to reduce any ambiguity of questions. A cover letterexplaining the survey and the questionnaire was sent to1,335 dentists via regular mail. Participants were askedto either complete the survey online or return theirquestionnaire via facsimile or regular mail. A returnenvelope with paid postage was enclosed with the coverletter and the questionnaire. Subsequently, two reminderemail rounds were also sent to participants. Individualfollow-up with non-respondents was not carried outbecause of the anonymity of the survey.Information collected in the questionnaire included:

• Demographics – data on dentists’ type of practice(general versus specialist practice; private versusinstitution practice), dental school, year of gradua-tion from basic dental degree and specialty training(if any) was collected

• Antibiotic prescribing practices – dentists were sur-veyed on which guideline they followed in theirclinical practice and the antibiotic regime (type anddosage) they prescribed. They were asked to indi-cate whether antibiotic prophylaxis cover wasrequired for 13 categories of cardiac conditions and12 dental procedures. The conditions and proce-dures were selected based on the guidelines.(Answers given: Yes/Yes if bleeding is anticipated/No/Unsure/Will consult with cardiologist)

• Confidence in prescription – dentists were surveyedon how confident they were that their prescriptionwas appropriate

• Necessity for a local guideline – dentists were askedif they felt that developing a local guideline wouldbe beneficial for the local dental community.Data were coded and analysed using IBM SPSS Statis-

tics 20.0 (International Business Machines Corp,Armonk, NY, USA). Descriptive statistics was computedand comparison between groups was tested using chi-square test. Spearman’s coefficient was used to analysethe relationship between dental practitioners’ accuracyand level of confidence in their prescriptions. A value ofP < 0.05 was considered to be statistically significant.

RESULTS

Four hundred and fifty-eight responses (34.3%) werereceived, of which 36 (2.7%) were invalid or incom-plete. The final response rate was 31.6%. Figure 1illustrates the response rates for the survey.

Demographics

The majority of the dentists surveyed (85.9%,n = 362) graduated from the Faculty of Dentistry,

© 2014 FDI World Dental Federation 109

Dentists’ antibiotics prescribing practices

National University of Singapore. General dentalpractitioners made up 65.9% (n = 278) of the sample.Table 1 shows the demographics of the respondents.

Antibiotic prophylaxis guidelines

The majority of the dentists (39.8%, n = 168) fol-lowed the AHA 2007 guidelines, 12.4% (n = 52) fol-lowed the AHA 1999 guidelines, and close to one-third (30.2%, n = 127) reported that their antibioticprophylaxis prescribing practices relied solely on therecommendations of the patient’s cardiologist. Inaddition to their adherence to the guideline of theirchoice, 39.7% (n = 167) of dentists almost always oralways additionally consulted the patient’s cardiolo-gist. This practice was significantly higher in special-ists compared with generalists (P < 0.001). Some ofthe reasons given by dentists for additionally consult-ing the cardiologist were:

• Patients who presented with accompanying co-mor-bidities and are under close supervision by theircardiologists

• Patients who presented with repaired or unrepairedcongenital cardiac conditions and are on concurrentanticoagulant therapy

• Requests from patients to consult their cardiologistbefore dental treatment

• Patients were informed by cardiologists of the needfor antibiotic prophylaxis even though antibioticprophylaxis were no longer needed for their condi-tion based on the latest guidelines

• Patients who insisted on antibiotic prophylaxis(because of years of receiving antibiotic prophylaxissince they were young) even though antibiotic pro-phylaxis were no longer indicated for their condi-tions in the new guidelines.When asked the reasons for their choice of the anti-

biotic regime, 70.8% (n = 299) of dentists reportedthat they were following the regime recommended inthe AHA or NICE guidelines, 15.7% (n = 66) saidthey followed the regime that was taught in school,10.2% (n = 43) were following cardiologists’ adviceand 3.3% (n = 14) were following their dental col-leagues’ practices. Most dentists prescribed the antibi-otic prophylaxis for their patients (93.7%, n = 373).The most popular choice of antibiotic was amoxicillin(92%); 1% used Augmentin, 2.5% prescribed otherantibiotics and 4% said they followed whatever thecardiologists’ recommended.

Accuracy of antibiotic prophylaxis prescribingpractices

The overall accuracy of prescriptions (with regard tocorrect antibiotics, cardiac conditions and dental pro-cedures) was not significantly different between spe-cialists and generalists (P = 0.4) across all guidelines(i.e. AHA 1999, AHA 2007 and NICE 2008). As themajority of respondents (39.8%, n = 168) subscribedto the AHA 2007 guidelines, the association betweenthe scores of pre-2007 graduates and post-2007 grad-uates was examined to further assess the possibleinfluence of undergraduate education. The differencesbetween the number of correct responses between pre-2007 graduates and post-2007 graduates was not sta-tistically significant (P = 0.76).

Accuracy of the choice of antibiotics prescribed

The majority of dentists were accurately prescribingthe type and dose of antibiotics for both the AHA1999 (94%, n = 47) and AHA 2007 (90.5%,n = 143) guidelines.

Accuracy of prescribing antibiotic prophylaxisfor the appropriate cardiac condition

Thirteen common cardiac conditions were evaluatedin this section. The median number of accurateanswers for cardiac conditions was higher for dentistswho followed the AHA 1999 guidelines (median = 8)

1335 invita�ons topar�cipate

Web-linkresponses: 285

Total: 458(Response rate: 34.3%)

Final: 422(Response rate:

31.6%)

Excludedincomplete/baddata: 36

Return tosender: 25

Emails-Notprac�cing:6

Mail ques�onnaireresponses: 173

Figure 1. Response rates for the survey.

Table 1 Demographics of respondents

Year of Graduation and number of years in practiceMedian (Year) 1995Mode (Year) 2010Number of years in practice:Mean (�SD)

17.0 (�11.8)

Type of Practice % NumberPrivate practice 68 287Institution practice 30 127Others 2 8

Dental schoolLocal (National Universityof Singapore)

85.9 362

Foreign universities 14.1 60SpecialisationSpecialists 34.1 144Generalists 65.9 278


Tong et al.

compared with the AHA 2007 (median = 4) andNICE guidelines (median = 4). Dentists who subscribedto the NICE 2008 guidelines indicated that theywould prescribe antibiotics for certain cardiac condi-tions, which was not in congruence with the 2008NICE guidelines (Table 2).

Accuracy of prescribing antibiotic prophylaxisfor the appropriate dental procedure

Dentists were asked the question ‘if the patientrequires antibiotic cover, would you prescribe it onlyfor procedures that involve the manipulation of gingi-val tissues or periapical region of teeth or perforationof oral mucosa?’ The majority of dentists subscribingto the AHA 1999 (96%, n = 48) and AHA 2007(98.1%, n = 155) guidelines answered this accurately,compared with only 10.5% (n = 2) of those who fol-lowed the NICE 2008 guidelines.Following this, 12 dental procedures were also eval-

uated. The median number of accurate answers forvarious dental procedures was generally high, both fordentists who followed the AHA 1999 guidelines(median = 10) as well as AHA 2007 (median = 9).Dentists who followed either the AHA 1999 or 2007guidelines were able to correctly indicate antibioticprophylaxis for clearly invasive procedures (e.g. peri-odontal procedures and tooth extractions, etc.; rangeof accuracy 81.8–100%). Conversely, they did notprescribe antibiotics for clearly non-invasive proce-dures (e.g. routine injections through non-infectedsites) and bonding of orthodontic brackets and appli-ance adjustments (range of accuracy 77.3–100%).

However, the accuracy was found to be variable forcertain procedures where the invasiveness of the pro-cedure may be debatable. Dentists who followed theAHA 1999 guidelines were inaccurately prescribingantibiotic prophylaxis for the following procedures:endodontic instrumentation not beyond apex (accu-racy 54.4%), intra-ligamental injections: (accuracy26.1%) and initial placement of orthodontic bands(45.4%). For the AHA 2007 guidelines, postoperativesuture removal (accuracy 7.5%), intraligamental injec-tions (accuracy 52.3%) and placement of orthodonticbands (accuracy 24.6%) were the procedures forwhich antibiotics were most frequently incorrectlyprescribed.

Confidence of prescription

In total, 67.4% of dentists reported that they werevery confident (23.4%, n = 99) or confident (44%,n = 186) that their prescriptions were accurate. Morespecialists (73.3%) were very confident or confidentthat their prescriptions were accurate compared withgeneralists (64.1%); however, this difference was notstatistically significant (P = 0.096). The overall corre-lation between the level of confidence displayed bydentists and accuracy of prescriptions was not statisti-cally significant (P > 0.05 for all guidelines).

Necessity for local guideline

An overwhelming majority of generalists (90.2%,n = 251) and specialists (77.7%, n = 112) felt that astandardised local guideline was necessary.

Table 2 Accuracy of antibiotic prophylaxis prescriptions for cardiac conditions

AHA 1999 (N = 52) AHA 2007 (N = 168) NICE 2008 (N = 33)

Mode 8 6 1 and 5Median 8 4 5Range 4–13 1–13 0–9

Conditions % of correct answers

MVP with regurgitation 63.0 20.7 8.8MVP without regurgitation 40.7 50.6 35.3Unrepaired ASD, PDA 51.9 10.3 17.6Unrepaired VSD 51.9 12.6 20.6Surgical repair of ASD, VSD or PDA without residualmurmur > 6 months

33.3 40.2 26.5

Prosthetic cardiac valve 85.2 77.0 2.9Previous infective endocarditis 92.6 88.5 0Complex CHD (Unrepaired, repaired ≤ 6 months orrepaired with residual defects)

81.5 70.1 5.9

Cardiac transplant with valvulopathy 66.7 60.3 5.9Hypertrophic cardiomyopathy 38.9 25.9 20.6CABG 59.3 44.8 29.4Surgically constructed systemic pulmonary shunts or conduits(>6 months post-surgery or total epithelisation)

24.1 20.7 23.5

Pacemakers and implanted defibrillators 63.0 48.3 38.2

MVP, Mitral Valve Prolapse; ASD, Atrial Septal Defect; PDA, Patent Ductus Arteriosus; CHD, Congenital Heart Disease; CABG, CoronaryArtery Bypass Graft.



DISCUSSION

The results of this study showed that the majority ofrespondents (54.6%) followed either the AHA 1999or 2007 guideline. The tendency for more dentists tofollow the AHA guidelines is likely reflective of thefact that these guidelines are being taught in the localundergraduate dental curriculum.As the majority of respondents (39.8%, n = 168)

followed the AHA 2007 guidelines, a comparison ofthe accuracy levels of pre- and post-2007 graduateswas carried out. Overall, accuracy levels with regardto both cardiac conditions and dental procedures werefound to be independent of whether they graduatedbefore or after 2007. Despite being taught the 2007guidelines in dental school, dentists who graduatedpost-2007 did not demonstrate better knowledge ofthe AHA 2007 guidelines compared with those whograduated before 2007. This result is similar to thestudy by Zadik et al.13, and suggests that continuingeducation remains a viable means to keep dentistsupdated on new changes in IE prophylaxis guidelines.

Accuracy of regimes and cardiac conditionsto prescribe antibiotics (based on guidelines chosen)

One of the major changes to the AHA 2007 guideline,with the exception of valvulopathy following cardiactransplant, was that the majority of valvular diseasesregardless of the presence or absence of regurgitationis no longer a condition for which prophylaxis is rec-ommended. In addition, the detailed list of dental pro-cedures where prophylactic antibiotics were needed inthe AHA 1999 guideline has since been removed inthe AHA 2007 guideline. The administration of anti-biotic prophylaxis is now recommended for at-riskpatients in ‘all dental procedures that involve manipu-lation of the gingival tissue or the periapical region ofteeth or perforation of the oral mucosa’2,13. Unlike itspredecessor, the AHA 2007 guideline allows dentistsgreater autonomy to decide which procedures theyfeel could cause bleeding and, consequently, the needfor antibiotic prophylaxis. Although some haveargued that this change in the guideline would resultin confusion, this study demonstrates that regardlessof the version of the AHA guideline, dentists wereable to accurately prescribe the correct type and doseof antibiotics for the appropriate types of dental pro-cedure. However, this accuracy did not translate toprescribing practices with regard to cardiac condi-tions. This is indicative that dentists were more confi-dent when making decisions for situations withintheir area of expertise.Even though there were more cardiac conditions

requiring antibiotic prophylaxis in the AHA 1999guideline, dentists were able to accurately prescribe

antibiotic prophylaxis for the conditions listed in theformer guideline compared to the more recent AHA2007 guideline. Confusion between the guidelines ornot being up-to-date with the changes in the new AHAguideline could explain this observation. Another rea-son may be that many dentists rely on rote learning ormemory to guide their decision for the need for antibi-otic prophylaxis for the various cardiac conditions.Sadowsky and Kunzel14 found that general dental prac-titioners who had a better understanding of patient riskfactors and the principles underlying the AHA recom-mendations were more likely to follow guidelines accu-rately. Consequently, this could have accounted for theconfusion and hence inaccuracies when prescribingantibiotic prophylaxis for cardiac conditions. It wasalso noted that dentists who followed the NICE 2008guideline consistently fared worse in terms of accuracythan those who followed the AHA 1999 or 2007 guide-lines, with many still prescribing antibiotic prophylaxisfor their patients. The only logical explanation for theinaccurate prescribing decisions would be that practi-tioners were confused between the AHA and NICEguidelines.Our findings are not unique to Singapore. The

applicability of the revised recommendations for anti-biotic prophylaxis has previously been evaluated andreported in Canada, Europe, the USA and the UK15–17.Surveys on antibiotic prophylaxis administrations inthe UK prior to the NICE 2008 guidelines demon-strated that there were wide variations in administra-tion strategies of antibiotic prophylaxis amonggeneral dental practitioners, even when recommenda-tions were clearly defined18. Several studies carriedout on the AHA guidelines also revealed that dentistshad inadequate knowledge and compliance with pre-vious versions of AHA guidelines15,16; many practitio-ners often relied on prescribing practices of theirfellow practitioners rather than prescribing based ontheir own understanding of the guidelines. In addition,a common belief amongst dental practitioners wasthat the decision to prescribe antibiotics when indoubt was a wise and conservative one16,18.This study also evaluated the confidence level of den-

tists and accuracy of their prescriptions. While dentistsexhibited high levels of confidence in their decisions,this was not correlated with the accuracy of their pre-scribing practices. This observation is comparable withthat of other reported studies15,18–20. In addition, ourstudy did not find that dental specialists had a higherlevel of accuracy of prescriptions compared with gener-alists. This is contrary to popular belief and evidencein the literature which suggests that specialists aremore knowledgeable about specific medical conditions,use more resources, and may achieve better clinicaloutcomes21, which could have potentially translated tomore accurate antibiotic prophylaxis prescriptions.


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Need for additional consultation

Our study found that a significant number of dentistsroutinely consulted cardiologists for advice on the needof antibiotic prophylaxis for their patients, in additionto referencing the guidelines. A possible explanationmay be that, unlike other countries such as Australia22,Canada23, the UK12 and the USA2, Singapore does nothave any official guideline endorsed by the local healthauthorities. As such, local dentists may feel the need foraffirmation from cardiologists regarding antibiotic pro-phylaxis regimes, rather than relying on a guideline thatmay or may not be supported by the patient’s cardiolo-gist. Consequently, dentists could also be seen as beingless willing to shoulder patient’s risks of developing IEand choose to err on the side of caution and involvetheir medical counterpart in the decision-making pro-cess. Perhaps the development of an official set ofguidelines may resolve these issues.One of the shortcomings of this survey is the low

response rate. It is possible that the dentists whoresponded to this survey were practitioners who areinherently more concerned about controversial dentalmanagement issues, thus introducing a source of self-selection bias. This could also account for the slightlyhigher number of respondents who have undergonespecialty training. Nonetheless, this study still pro-vides an interesting insight into the antibiotic prophy-laxis practices among these dentists.

CONCLUSION

This study is unique in that it strives to dissect the cruxof the problem and identify which aspect of antibioticprophylaxis prescription is confusing to dentists. Theresults of this study demonstrate that there is a definitelack of uniformity and accuracy in the antibiotic pro-phylaxis prescribing practices of dentists in Singapore.The majority of the dentists, though knowledgeableand accurate on the type of dental procedures thatrequired antibiotic cover, were less accurate when itcame to prescribing antibiotic prophylaxis for the cor-rect group of cardiac patients. The discrepancies inantibiotic prophylaxis practices as identified throughthis study suggest the need for educational efforts toassimilate dentists to the guideline of choice. This isparamount as inadequate knowledge can cause overuseof antibiotics, with the attendant risks of toxicity andemergence of resistant strains. Educating patients aboutthe new guidelines may also be required as patient fac-tors are an important influence against change24.While the majority of dentists surveyed felt that

establishing local antibiotic prophylaxis guidelineswould be helpful, it was not clear whether a new localguideline should be drafted or whether professionalbodies should take a stand on which of the existing

guidelines to follow. The authors are unsure if there isa need for a new guideline to be drafted, given thatmuch work has already been performed by the NICEand AHA committees. Instead of reinventing thewheel, perhaps it would be more productive and pru-dent to attain a consensus among the local cardiology,infectious disease and dental professionals to deter-mine which guideline should be adopted nationwide.

Acknowledgements

This study was funded by the Singapore Dental Asso-ciation Endowment Fund. The authors thank the fol-lowing people for their help: Dr Lim Shy Min forhelp in data entry; and Dr Shen Liang, Senior Biostat-istician at the Yong Loo Lin School of Medicine forher input on the statistics for the project. The authorsdeclare no competing financial interests.

Conflicts of interest

None declared.

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Correspondence to:Huei Jinn Tong,

Faculty of Dentistry,National University of Singapore,

11 Lower Kent Ridge Road,Singapore 119083, Singapore

Email: [email protected]


Tong et al.

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Antibiotic prophylaxis prescribing practices of dentists in Singapore