Microbicidal efficacy of thiocyanate hydrogen peroxide after adding lactoperoxidase under saliva loading in the quantitative suspension test A. Welk a, *, P. Rudolph b , J. Kreth c , Ch. Schwahn d , A. Kramer b , H. Below b a Department of Restorative Dentistry, Periodontology and Endodontology, Dental School, University of Greifswald, Rotgerber-Street 8, 17475 Greifswald, Germany b Institute of Hygiene and Environmental Medicine, University of Greifswald, Walther-Rathenau-Street 49a, 17475 Greifswald, Germany c Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 907, Oklahoma City, OK 73104, USA d Institute of Epidemiology and Social Medicine, University of Greifswald, Walther-Rathenau-Street 48, 17475 Greifswald, Germany 1. Introduction The lactoperoxidase–thiocyanate–hydrogen peroxide system, one of saliva’s defence systems, has been shown to inhibit bacterial 1–5 and fungal viability. 6 In addition, antiviral activity was found. 7–9 Therefore, stimulating or supporting this innate host defence system by adding parts of the lactoperoxidase– thiocyanate–hydrogen peroxide system or the complete system to dental hygiene products could be interesting as an adjuvant to mechanical plaque control. However, the antimicrobial effects of the lactoperoxidase–thiocyanate– archives of oral biology 56 (2011) 1576–1582 article info Article history: Accepted 28 April 2011 Keywords: Lactoperoxidase-thiocyanate- hydrogen peroxide system Quantitative suspension test Effectiveness Saliva Streptococcus mutans Streptococcus sanguinis Candida albicans abstract Objective: As shown in the quantitative suspension test adding lactoperoxidase to a thiocy- anate (SCN  ) hydrogen peroxide (H 2 O 2 ) combination over the physiological saliva level has significant positive antimicrobial effects to a level of totally killing Streptococcus mutans, Streptococcus sanguinis, and Candida albicans. The aim of this study was to evaluate this positive effect under human saliva loading. Methods: The bactericidal and fungicidal effect of lactoperoxidase was evaluated in a quanti- tative suspension test by using two test mixtures of a 2.0% thiocyanate and1.2% hydrogen peroxide solution, one without (Group A) and one with (Group B) lactoperoxidase under saliva loading. Following the quantitative suspension tests (EN-13727/EN-13624), the growth of surviving bacteria and fungi in a nutrient broth was measured. The exposure times were restricted to 1, 3, 5, and 15min. All statistical analyses were carried out with SPSS 11.5. Results: In the quantitative suspension test, the combination of thiocyanate and hydrogen peroxide showed relatively low antimicrobial effectiveness on S. mutans, S. sanguinis, and C. albicans in the presence of human saliva at measured time points in comparison to the mixture with lactoperoxidase, which showed a high bactericidal activity within 15 min (S. mutans and S. sanguinis) and fungicidal activity within 3 min (C. albicans). Conclusion: The antimicrobial effectiveness of the tested thiocyanate hydrogen peroxide combination was increased significantly by adding lactoperoxidase in the quantitative suspension test under human saliva loading. # 2011 Elsevier LtdElsevier Ltd. All rights reserved. * Corresponding author at: Department of Restorative Dentistry, Periodontology and Endodontology, Dental School of the University of Greifswald, Rathenau Straße 42a, 17475 Greifswald, Germany. Tel.: +49 3834 86 7169; fax: +49 03834 86 7171. E-mail address: welk@uni-greifswald.de (A. Welk). available at www.sciencedirect.com journal homepage: http://www.elsevier.com/locate/aob 0003–9969/$ – see front matter # 2011 Elsevier LtdElsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2011.04.016