International Dental Journal 2014; 64: 108–114
Antibiotic prophylaxis prescribing practices of dentists in Singapore Huei Jinn Tong, Shijia Hu, Betty Yuen Yue Mok, Intekhab Islam and 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 susceptible patients. The guidelines for antibiotic prophylaxis have been updated by the American Heart Association and National Institute for Health and Clinical Excellence. The antibiotic prophylaxis prescribing practices among dentists in Singapore are unknown. Aim: To determine the specific infective endocarditis antibiotic prophylaxis prescribing practices of dentists in Singapore. Methods: A questionnaire survey was sent through an email link and by postal mail. Statistical analysis was carried out using SPSS 19.0. Results: Responses were received from 458 dentists (34.3% response rate), of which 278 (65.9%) were general practitioners. The majority of respondents (39.8%) followed the American Heart Association 2007 guidelines and 30.2% followed cardiologists’ recommendations. The accuracy of prescriptions for 13 cardiac conditions and 12 dental procedures were evaluated. The median number of accurate answers for cardiac conditions was eight for the American Heart Association 1999 guidelines, and four for the American Heart Association 2007 and National Institute for Health and Clinical Excellence guidelines, respectively. The median number of accurate answers for dental procedures was generally high, both for dentists who followed the American Heart Association 1999 guidelines (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: Dentists were accurate in their prescriptions of antibiotic prophylaxis for dental procedures, but not for cardiac conditions. It may be helpful to attain a consensus among local cardiologists and dentists to unify the antibiotic prophylaxis prescription practices in Singapore. Key words: Infective endocarditis, cardiac, guidelines
INTRODUCTION Infective endocarditis (IE) is a rare condition with high morbidity and mortality in certain high risk populations1. Streptococcus viridans, Staphylococcus aureus, Enterococcus, Pseudomonas serratia and Candida are some of the microorganisms implicated in IE2, among which S. viridans is one of the major culprits thought to cause between 18 and 65% of IE cases worldwide3–5. As this large group of bacteria is found routinely and in abundance in the oral flora, it seemed reasonable that antibiotic prophylaxis should be indicated before invasive dental procedures for patients who are at risk for developing IE. Since the release of the first American Heart Association (AHA) guideline in 1955, dental health-care professionals have abided by their recommendation that antibiotics should be administered before invasive dental procedures for 108
selected patients6. Consequently, patients at risk for IE have also come to expect antibiotic prophylaxis before their dental treatment7. In recent years, the scientific community has queried whether there is a need for antibiotic prophylaxis before dental procedures. A recent Cochrane review concluded that there was no evidence that antibiotic prophylaxis was effective against bacterial endocarditis8. Furthermore, recent studies have demonstrated that poor oral hygiene and gingival bleeding after routine activities (e.g. tooth brushing), similar to dental procedures, can also result in bacteraemia with the potential to cause IE in at-risk patients9. Given that IE is more likely to be caused by frequent and chronic exposure to oral flora associated bacteraemia during routine daily activities rather than by sporadic dental procedures2, current recommendations have placed greater emphasis on the importance of regular © 2014 FDI World Dental Federation
Dentists’ antibiotics prescribing practices maintenance of oral hygiene rather than the importance of antibiotic prophylaxis before invasive dental procedures10. Other reasons cited against the routine use of antibiotic prophylaxis include the risk–benefit ratio, emergence of resistance strains, risk of adverse drug 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 to be aligned with newly available scientific evidence. The AHA 2007 guidelines tiered down their antibiotic prophylaxis recommendations to only include patients who are in the high risk category, namely those with: • Prosthetic cardiac valves • Previous history of infective endocarditis • Congenital heart disease (CHD) (i.e. unrepaired cyanotic CHD, completely repaired CHD with prosthetic material or device by surgery or catheter intervention during the first 6 months after the procedure, repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device which inhibits endothelisation) • Cardiac valvulopathy after cardiac transplantation. In addition, the AHA 2007 guideline no longer specifies the types of dental procedures that require antibiotic prophylaxis but instead recommends coverage for ‘all dental procedures that involve manipulation of the gingival tissue or the periapical region of teeth or perforation of the oral mucosa’ for at-risk patients2. In the UK, the NICE guidelines took a more radical stand and recommended the cessation of antibiotic prophylaxis for all patients undergoing dental and a wide range of other 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 majority of dentists follow the AHA guidelines, this may not be true. Several factors could influence dentists’ prescribing practices such as the country where basic and advanced dental training were done, year of graduation and input from medical or cardiology colleagues. The aim of this study was to determine the antibiotic prophylaxis prescribing practices of dentists in Singapore for the prevention of IE, specifically the type of guideline followed and the accuracy of their prescriptions according to the guideline of their choice. METHODS This was a cross-sectional study that utilised a 10-item questionnaire to evaluate the antibiotic prophylaxis practices of registered dentists in Singapore. Approval to conduct the study was obtained from the National University of Singapore Institution Review Board before commencement of the study (NUS-IRB: 11-121E). The research was conducted in full accordance with the © 2014 FDI World Dental Federation
World Medical Association Declaration of Helsinki. The questionnaire was developed and piloted on a small group of generalist and specialist dentists before administration to test for readability, ease of understanding and to reduce any ambiguity of questions. A cover letter explaining the survey and the questionnaire was sent to 1,335 dentists via regular mail. Participants were asked to either complete the survey online or return their questionnaire via facsimile or regular mail. A return envelope with paid postage was enclosed with the cover letter and the questionnaire. Subsequently, two reminder email rounds were also sent to participants. Individual follow-up with non-respondents was not carried out because of the anonymity of the survey. Information collected in the questionnaire included: • Demographics – data on dentists’ type of practice (general versus specialist practice; private versus institution practice), dental school, year of graduation from basic dental degree and specialty training (if any) was collected • Antibiotic prescribing practices – dentists were surveyed on which guideline they followed in their clinical practice and the antibiotic regime (type and dosage) they prescribed. They were asked to indicate whether antibiotic prophylaxis cover was required for 13 categories of cardiac conditions and 12 dental procedures. The conditions and procedures 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 surveyed on how confident they were that their prescription was appropriate • Necessity for a local guideline – dentists were asked if they felt that developing a local guideline would be beneficial for the local dental community. Data were coded and analysed using IBM SPSS Statistics 20.0 (International Business Machines Corp, Armonk, NY, USA). Descriptive statistics was computed and comparison between groups was tested using chisquare test. Spearman’s coefficient was used to analyse the relationship between dental practitioners’ accuracy and level of confidence in their prescriptions. A value of P < 0.05 was considered to be statistically significant. RESULTS Four hundred and fifty-eight responses (34.3%) were received, of which 36 (2.7%) were invalid or incomplete. The final response rate was 31.6%. Figure 1 illustrates the response rates for the survey. Demographics The majority of the dentists surveyed (85.9%, n = 362) graduated from the Faculty of Dentistry, 109
Tong et al.
1335 invitaons to parcipate
Return to sender: 25
Web-link responses: 285
Mail quesonnaire responses: 173
Total: 458 (Response rate: 34.3%) Excluded incomplete/bad data: 36
Final: 422 (Response rate: 31.6%)
Figure 1. Response rates for the survey.
Table 1 Demographics of respondents Year of Graduation and number of years in practice Median (Year) 1995 Mode (Year) 2010 Number of years in practice: 17.0 (11.8) Mean (SD) Type of Practice % Private practice 68 Institution practice 30 Others 2 Dental school Local (National University 85.9 of Singapore) Foreign universities 14.1 Specialisation Specialists 34.1 Generalists 65.9
Number 287 127 8 362 60 144 278
National University of Singapore. General dental practitioners 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) followed the AHA 2007 guidelines, 12.4% (n = 52) followed the AHA 1999 guidelines, and close to onethird (30.2%, n = 127) reported that their antibiotic prophylaxis prescribing practices relied solely on the recommendations of the patient’s cardiologist. In addition to their adherence to the guideline of their choice, 39.7% (n = 167) of dentists almost always or always additionally consulted the patient’s cardiologist. This practice was significantly higher in specialists compared with generalists (P < 0.001). Some of the reasons given by dentists for additionally consulting the cardiologist were: • Patients who presented with accompanying co-morbidities and are under close supervision by their cardiologists • Patients who presented with repaired or unrepaired congenital cardiac conditions and are on concurrent anticoagulant therapy 110
Requests from patients to consult their cardiologist before dental treatment • Patients were informed by cardiologists of the need for antibiotic prophylaxis even though antibiotic prophylaxis were no longer needed for their condition based on the latest guidelines • Patients who insisted on antibiotic prophylaxis (because of years of receiving antibiotic prophylaxis since they were young) even though antibiotic prophylaxis were no longer indicated for their conditions in the new guidelines. When asked the reasons for their choice of the antibiotic regime, 70.8% (n = 299) of dentists reported that they were following the regime recommended in the AHA or NICE guidelines, 15.7% (n = 66) said they followed the regime that was taught in school, 10.2% (n = 43) were following cardiologists’ advice and 3.3% (n = 14) were following their dental colleagues’ practices. Most dentists prescribed the antibiotic prophylaxis for their patients (93.7%, n = 373). The most popular choice of antibiotic was amoxicillin (92%); 1% used Augmentin, 2.5% prescribed other antibiotics and 4% said they followed whatever the cardiologists’ recommended. Accuracy of antibiotic prophylaxis prescribing practices The overall accuracy of prescriptions (with regard to correct antibiotics, cardiac conditions and dental procedures) was not significantly different between specialists and generalists (P = 0.4) across all guidelines (i.e. AHA 1999, AHA 2007 and NICE 2008). As the majority of respondents (39.8%, n = 168) subscribed to the AHA 2007 guidelines, the association between the scores of pre-2007 graduates and post-2007 graduates was examined to further assess the possible influence of undergraduate education. The differences between the number of correct responses between pre2007 graduates and post-2007 graduates was not statistically significant (P = 0.76). Accuracy of the choice of antibiotics prescribed The majority of dentists were accurately prescribing the type and dose of antibiotics for both the AHA 1999 (94%, n = 47) and AHA 2007 (90.5%, n = 143) guidelines. Accuracy of prescribing antibiotic prophylaxis for the appropriate cardiac condition Thirteen common cardiac conditions were evaluated in this section. The median number of accurate answers for cardiac conditions was higher for dentists who followed the AHA 1999 guidelines (median = 8) © 2014 FDI World Dental Federation
Dentists’ antibiotics prescribing practices Table 2 Accuracy of antibiotic prophylaxis prescriptions for cardiac conditions AHA 1999 (N = 52) Mode Median Range
8 8 4–13
Conditions MVP with regurgitation MVP without regurgitation Unrepaired ASD, PDA Unrepaired VSD Surgical repair of ASD, VSD or PDA without residual murmur > 6 months Prosthetic cardiac valve Previous infective endocarditis Complex CHD (Unrepaired, repaired ≤ 6 months or repaired with residual defects) Cardiac transplant with valvulopathy Hypertrophic cardiomyopathy CABG Surgically constructed systemic pulmonary shunts or conduits (>6 months post-surgery or total epithelisation) Pacemakers and implanted defibrillators
AHA 2007 (N = 168) 6 4 1–13
NICE 2008 (N = 33) 1 and 5 5 0–9
% of correct answers 63.0 40.7 51.9 51.9 33.3
20.7 50.6 10.3 12.6 40.2
8.8 35.3 17.6 20.6 26.5
85.2 92.6 81.5
77.0 88.5 70.1
2.9 0 5.9
66.7 38.9 59.3 24.1
60.3 25.9 44.8 20.7
5.9 20.6 29.4 23.5
MVP, Mitral Valve Prolapse; ASD, Atrial Septal Defect; PDA, Patent Ductus Arteriosus; CHD, Congenital Heart Disease; CABG, Coronary Artery Bypass Graft.
compared with the AHA 2007 (median = 4) and NICE guidelines (median = 4). Dentists who subscribed to the NICE 2008 guidelines indicated that they would prescribe antibiotics for certain cardiac conditions, which was not in congruence with the 2008 NICE guidelines (Table 2). Accuracy of prescribing antibiotic prophylaxis for the appropriate dental procedure Dentists were asked the question ‘if the patient requires antibiotic cover, would you prescribe it only for procedures that involve the manipulation of gingival tissues or periapical region of teeth or perforation of oral mucosa?’ The majority of dentists subscribing to 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 followed the NICE 2008 guidelines. Following this, 12 dental procedures were also evaluated. The median number of accurate answers for various dental procedures was generally high, both for dentists who followed the AHA 1999 guidelines (median = 10) as well as AHA 2007 (median = 9). Dentists who followed either the AHA 1999 or 2007 guidelines were able to correctly indicate antibiotic prophylaxis for clearly invasive procedures (e.g. periodontal procedures and tooth extractions, etc.; range of accuracy 81.8–100%). Conversely, they did not prescribe antibiotics for clearly non-invasive procedures (e.g. routine injections through non-infected sites) and bonding of orthodontic brackets and appliance adjustments (range of accuracy 77.3–100%). © 2014 FDI World Dental Federation
However, the accuracy was found to be variable for certain procedures where the invasiveness of the procedure may be debatable. Dentists who followed the AHA 1999 guidelines were inaccurately prescribing antibiotic prophylaxis for the following procedures: endodontic instrumentation not beyond apex (accuracy 54.4%), intra-ligamental injections: (accuracy 26.1%) and initial placement of orthodontic bands (45.4%). For the AHA 2007 guidelines, postoperative suture removal (accuracy 7.5%), intraligamental injections (accuracy 52.3%) and placement of orthodontic bands (accuracy 24.6%) were the procedures for which antibiotics were most frequently incorrectly prescribed. Conﬁdence of prescription In total, 67.4% of dentists reported that they were very confident (23.4%, n = 99) or confident (44%, n = 186) that their prescriptions were accurate. More specialists (73.3%) were very confident or confident that their prescriptions were accurate compared with generalists (64.1%); however, this difference was not statistically significant (P = 0.096). The overall correlation between the level of confidence displayed by dentists and accuracy of prescriptions was not statistically 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 a standardised local guideline was necessary. 111
Tong et al. DISCUSSION The results of this study showed that the majority of respondents (54.6%) followed either the AHA 1999 or 2007 guideline. The tendency for more dentists to follow the AHA guidelines is likely reflective of the fact that these guidelines are being taught in the local undergraduate dental curriculum. As the majority of respondents (39.8%, n = 168) followed the AHA 2007 guidelines, a comparison of the accuracy levels of pre- and post-2007 graduates was carried out. Overall, accuracy levels with regard to both cardiac conditions and dental procedures were found to be independent of whether they graduated before or after 2007. Despite being taught the 2007 guidelines in dental school, dentists who graduated post-2007 did not demonstrate better knowledge of the AHA 2007 guidelines compared with those who graduated before 2007. This result is similar to the study by Zadik et al.13, and suggests that continuing education remains a viable means to keep dentists updated on new changes in IE prophylaxis guidelines. Accuracy of regimes and cardiac conditions to prescribe antibiotics (based on guidelines chosen) One of the major changes to the AHA 2007 guideline, with the exception of valvulopathy following cardiac transplant, was that the majority of valvular diseases regardless of the presence or absence of regurgitation is no longer a condition for which prophylaxis is recommended. In addition, the detailed list of dental procedures where prophylactic antibiotics were needed in the AHA 1999 guideline has since been removed in the AHA 2007 guideline. The administration of antibiotic prophylaxis is now recommended for at-risk patients in ‘all dental procedures that involve manipulation of the gingival tissue or the periapical region of teeth or perforation of the oral mucosa’2,13. Unlike its predecessor, the AHA 2007 guideline allows dentists greater autonomy to decide which procedures they feel could cause bleeding and, consequently, the need for antibiotic prophylaxis. Although some have argued that this change in the guideline would result in confusion, this study demonstrates that regardless of the version of the AHA guideline, dentists were able to accurately prescribe the correct type and dose of antibiotics for the appropriate types of dental procedure. However, this accuracy did not translate to prescribing practices with regard to cardiac conditions. This is indicative that dentists were more confident when making decisions for situations within their area of expertise. Even though there were more cardiac conditions requiring antibiotic prophylaxis in the AHA 1999 guideline, dentists were able to accurately prescribe 112
antibiotic prophylaxis for the conditions listed in the former guideline compared to the more recent AHA 2007 guideline. Confusion between the guidelines or not being up-to-date with the changes in the new AHA guideline could explain this observation. Another reason may be that many dentists rely on rote learning or memory to guide their decision for the need for antibiotic prophylaxis for the various cardiac conditions. Sadowsky and Kunzel14 found that general dental practitioners who had a better understanding of patient risk factors and the principles underlying the AHA recommendations were more likely to follow guidelines accurately. Consequently, this could have accounted for the confusion and hence inaccuracies when prescribing antibiotic prophylaxis for cardiac conditions. It was also noted that dentists who followed the NICE 2008 guideline consistently fared worse in terms of accuracy than those who followed the AHA 1999 or 2007 guidelines, with many still prescribing antibiotic prophylaxis for their patients. The only logical explanation for the inaccurate prescribing decisions would be that practitioners were confused between the AHA and NICE guidelines. Our findings are not unique to Singapore. The applicability of the revised recommendations for antibiotic prophylaxis has previously been evaluated and reported in Canada, Europe, the USA and the UK15–17. Surveys on antibiotic prophylaxis administrations in the UK prior to the NICE 2008 guidelines demonstrated that there were wide variations in administration strategies of antibiotic prophylaxis among general dental practitioners, even when recommendations were clearly defined18. Several studies carried out on the AHA guidelines also revealed that dentists had inadequate knowledge and compliance with previous versions of AHA guidelines15,16; many practitioners often relied on prescribing practices of their fellow practitioners rather than prescribing based on their own understanding of the guidelines. In addition, a common belief amongst dental practitioners was that the decision to prescribe antibiotics when in doubt was a wise and conservative one16,18. This study also evaluated the confidence level of dentists and accuracy of their prescriptions. While dentists exhibited high levels of confidence in their decisions, this was not correlated with the accuracy of their prescribing practices. This observation is comparable with that of other reported studies15,18–20. In addition, our study did not find that dental specialists had a higher level of accuracy of prescriptions compared with generalists. This is contrary to popular belief and evidence in the literature which suggests that specialists are more knowledgeable about specific medical conditions, use more resources, and may achieve better clinical outcomes21, which could have potentially translated to more accurate antibiotic prophylaxis prescriptions. © 2014 FDI World Dental Federation
Dentists’ antibiotics prescribing practices Need for additional consultation Our study found that a significant number of dentists routinely consulted cardiologists for advice on the need of antibiotic prophylaxis for their patients, in addition to referencing the guidelines. A possible explanation may be that, unlike other countries such as Australia22, Canada23, the UK12 and the USA2, Singapore does not have any official guideline endorsed by the local health authorities. As such, local dentists may feel the need for affirmation from cardiologists regarding antibiotic prophylaxis regimes, rather than relying on a guideline that may or may not be supported by the patient’s cardiologist. Consequently, dentists could also be seen as being less willing to shoulder patient’s risks of developing IE and choose to err on the side of caution and involve their medical counterpart in the decision-making process. Perhaps the development of an official set of guidelines may resolve these issues. One of the shortcomings of this survey is the low response rate. It is possible that the dentists who responded to this survey were practitioners who are inherently more concerned about controversial dental management issues, thus introducing a source of selfselection bias. This could also account for the slightly higher number of respondents who have undergone specialty training. Nonetheless, this study still provides an interesting insight into the antibiotic prophylaxis practices among these dentists. CONCLUSION This study is unique in that it strives to dissect the crux of the problem and identify which aspect of antibiotic prophylaxis prescription is confusing to dentists. The results of this study demonstrate that there is a definite lack of uniformity and accuracy in the antibiotic prophylaxis prescribing practices of dentists in Singapore. The majority of the dentists, though knowledgeable and accurate on the type of dental procedures that required antibiotic cover, were less accurate when it came to prescribing antibiotic prophylaxis for the correct group of cardiac patients. The discrepancies in antibiotic prophylaxis practices as identified through this study suggest the need for educational efforts to assimilate dentists to the guideline of choice. This is paramount as inadequate knowledge can cause overuse of antibiotics, with the attendant risks of toxicity and emergence of resistant strains. Educating patients about the new guidelines may also be required as patient factors are an important influence against change24. While the majority of dentists surveyed felt that establishing local antibiotic prophylaxis guidelines would be helpful, it was not clear whether a new local guideline should be drafted or whether professional bodies should take a stand on which of the existing © 2014 FDI World Dental Federation
guidelines to follow. The authors are unsure if there is a need for a new guideline to be drafted, given that much work has already been performed by the NICE and AHA committees. Instead of reinventing the wheel, perhaps it would be more productive and prudent to attain a consensus among the local cardiology, infectious disease and dental professionals to determine which guideline should be adopted nationwide. Acknowledgements This study was funded by the Singapore Dental Association Endowment Fund. The authors thank the following people for their help: Dr Lim Shy Min for help in data entry; and Dr Shen Liang, Senior Biostatistician at the Yong Loo Lin School of Medicine for her input on the statistics for the project. The authors declare no competing financial interests. Conﬂicts of interest None declared. REFERENCES 1. Habib G, Hoen B, Tornos P et al. Guidelines on the prevention, diagnosis, and treatment of infective endocarditis (new version 2009): the task force on the prevention, diagnosis, and treatment of infective endocarditis of the European Society of Cardiology (ESC). Endorsed by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC) for infection and cancer. Eur Heart J 2009 30: 2369–2413. 2. Wilson W, Taubert KA, Gewitz M et al. Prevention of infective endocarditis: guidelines from the American heart association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation 2007 116: 1736–1754. 3. Mylonakis E, Calderwood S. Infective endocarditis in adults. N Engl J Med 2001 345: 1318–1330. 4. Tleyjeh I, Steckelberg J, Murad H et al. Temporal trends in infective endocarditis: a population-based study in Olmsted county, Minnesota. JAMA 2005 293: 3022–3028. 5. Strom B, Abrutyn E, Berlin J et al. Dental and cardiac risk factors for infective endocarditis: a population-based case–control study. Ann Intern Med 1998 129: 761–769. 6. Soheilipour S, Scambler S, Dickinson C et al. Antibiotic prophylaxis in dentistry: part I. A qualitative study of professionals’ views on the NICE guideline. Br Dent J 2011 211: E1. 7. Soheilipour S, Scambler S, Dickinson C et al. Antibiotic prophylaxis in dentistry: part II. A qualitative study of patient perspectives and understanding of the NICE guideline. Br Dent J 2011 211: E2. 8. Glenny AM, Oliver R, Roberts GJ et al. Antibiotics for the prophylaxis of bacterial endocarditis in dentistry. Cochrane Database Syst Rev 2013 10: CD003813. 9. Lockhart P, Brennan M, Thornhill M et al. Poor oral hygiene as a risk factor for infective endocarditis-related bacteremia. J Am Dent Assoc 2009 140: 1238–1244.
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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]
© 2014 FDI World Dental Federation