Helicobacter pylori and Chlamydia pneumoniae in root canals 14. Nguyen AM, Engstrand L, Genta RM, Graham DY, el-Zaatari FA. Detection of Helicobacter pylori in dental plaque by re- verse transcription-polymerase chain reaction. J Clin Mi- crobiol 1993;31:783-787. 15. Mapstone NP, Lynch DA, Lewis FA, Axon AT, Tompkins DS, Dixon MF, Quirke P. Identification of Helicobacter pylori DNA in the mouths and stomachs of patients with gastritis using PCR. J Clin Pathol 1993;46:540-543. 16. Umeda M, Kobayashi H, Takeuchi Y, Hayashi J, Morotome- Hayashi Y, Yano K, Aoki A, Ohkusa T, Ishikawa I. High prev- alence of Helicobacter pylori detected by PCR in the oral cavities of periodontitis patients. J Periodontol 2003; 74: 129-134. 17. Kignel S, de Almeida Pina F, Andre EA, Alves Mayer MP, Bir- man EG. Occurrence of Helicobacter pylori in dental plaque and saliva of dyspeptic patients. Oral Dis 2005;11:17-21. 18. Ward ME, Ridgway G. Chlamydia. In: Collier L, Balows A, Sussman M, eds. Topley & Wilson´s microbiology and mi- crobial infections. Vol 2, Systematic bacteriology. 9th ed. London: Arnold, 1998: 1331-1346. 19. Miyashita N, Saito A, Kohno S, Oizumi K, Yamaguchi K, Watanabe A, Oda H, Fukano H, Yoshida K, Niki Y, Matsu- shima T. Community-acquired Chlamydia pneumoniae pneumonia in Japan: a prospective multicenter communi- ty-acquired pneumonia study. Intern Med 2002;41:943-949. 20. Grayston JT, Aldous MB, Easton A, Wang SP, Kuo CC, Campbell LA, Altman J. Evidence that Chlamydia pneu- moniae causes pneumonia and bronchitis. J Infect Dis 1993;168:1231-1235. 21. Valtonen VV. Role of infections in atherosclerosis. Am Heart J 1999;138:S431-433. 22. Tran T, Flynn MJ, Chen C, Slots J. Absence of Porphyromo- nas asaccharolytica, Bacteroides fragilis and Chlamydia pneumoniae in human subgingival plaque. Oral Microbiol Immunol 1997;12:377-378. 23. Huovinen P, Lahtonen R, Ziegler T, Meurman O, Hakkara- inen K, Miettinen A, Arstila P, Eskola J, Saikku P. Pharyn- gitis in adults: the presence and coexistence of viruses and bacterial organisms. Ann Intern Med 1989;110:612-616. 24. Mantyla P, Stenman M, Paldanius M, Saikku P, Sorsa T, Meurman JH. Chlamydia pneumoniae together with collagenase-2 (MMP-8) in periodontal lesions. Oral Dis 2004;10:32-35. 25. Nandakumar R, Whiting J, Fouad AF. Identification of se- lected respiratory pathogens in endodontic infections. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:145- 151. 162 European Journal of Dentistry 26. Ashimoto A, Chen C, Bakker I, Slots J. Polymerase chain reaction detection of 8 putative periodontal pathogens in subgingival plaque of gingivitis and advanced periodontitis lesions. Oral Microbiol Immunol 1996;11:266-273. 27. Gonzalez JM, Portillo MC, Saiz-Jimenez C. Multiple dis- placement amplification as a pre-polymerase chain reac- tion (pre-PCR) to process difficult to amplify samples and low copy number sequences from natural environments. Environ Microbiol 2005;7:1024-1028. 28. Grover A, Azmi W, Paul Khurana SM, Chakrabarti SK. Mul- tiple displacement amplification as a pre-polymerase chain reaction (pre-PCR) to detect ultra low population of Ralsto- nia solanacearum (Smith 1896) Yabuchi et al. (1996). Lett Appl Microbiol 2009;49:539-543. 29. Sathorn C, Parashos P, Messer HH. How useful is root canal culturing in predicting treatment outcome? J Endod 2007;33:220-225. 30. Siqueira JF, Jr, Rôças IN. Polymerase chain reaction-based analysis of microorganisms associated with failed end- odontic treatment. Oral Surg Oral Med Oral Pathol Oral Ra- diol Endod 2004;97:85-94. 31. Martinez-Gomis J, Diouf A, Lakhssassi N, Sixou M. Absence of Helicobacter pylori in the oral cavity of 10 non-dyspeptic subjects demonstrated by real-time polymerase chain re- action. Oral Microbiol Immunol 2006;21:407-410. 32. Asikainen S, Chen C, Slots J. Absence of Helicobacter pylori in subgingival samples determined by polymerase chain reaction. Oral Microbiol Immunol 1994;9:318-320. 33. Silva Rossi-Aguiar VP, Navarro-Rodriguez T, Mattar R, Siqueira de Melo Peres MP, Correa Barbuti R, Silva FM, Carrilho FJ, Eisig JN. Oral cavity is not a reservoir for Heli- cobacter pylori in infected patients with functional dyspep- sia. Oral Microbiol Immunol 2009;24:255-259. 34. Siqueira JF, Jr., Rôças IN. Diversity of endodontic micro- biota revisited. J Dent Res 2009;88:969-981.