ABSTRACT
Removal of bacterial biofilm from the root canal system is essential for the management of endodontic disease. Here we evaluated the antibacterial effect of N-acetylcysteine (NAC), a potent antioxidant and mucolytic agent, against mature multispecies endodontic biofilms consisting of Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans and Enterococcus faecalis on sterile human dentin blocks. The biofilms were exposed to NAC (25, 50 and 100 mg/mL), saturated calcium hydroxide or 2% chlorhexidine solution for 7 days, then examined by scanning electron microscopy. The biofilm viability was measured by viable cell counts and ATP-bioluminescence assay. NAC showed greater efficacy in biofilm cell removal and killing than the other root canal medicaments. Furthermore, 100 mg/mL NAC disrupted the mature multispecies endodontic biofilms completely. These results demonstrate the potential use of NAC in root canal treatment.
Keywords:
Antibacterial; Biofilm removal; Multispecies endodontic biofilm; N-acetylcysteine; Root canal medicament
Biofilm can be defined as a sessile, multi-cellular, microbial community characterized by cells that are firmly attached to a surface and enmeshed in a self-produced matrix of extracellular polymeric substance (EPS).11 Donlan RM, Costerton JW. Biofilms: survival mechanisms of clinically relevant microorganisms. Clin Microbiol Rev. 2002;15:167-193.,22 Siqueira JF, Rôças IN, Ricucci D. Biofilms in endodontic infection. Endod Top. 2010;22:33-49. Microbial communities in biofilms are remarkably difficult to eradicate with antimicrobial agents, and microorganisms in mature biofilms can be notoriously resistant; microorganisms grown in biofilms can be 2-1000-fold more resistant than the corresponding planktonic forms.33 Svensäter G, Bergenholtz G. Biofilms in endodontic infections. Endod Top. 2004;9:27-36. Endodontic disease is a biofilm-mediated infection, and the primary aim in the management of endodontic disease is the elimination of bacterial biofilm from the root canal system.44 Jhajharia K, Parolia A, Shetty KV, Mehta LK. Biofilm in endodontics: a review. J Int Soc Prev Community Dent. 2015;5:1-12. Although the majority of bacteria are removed by mechanical and chemical methods during endodontic treatment, it is difficult to eradicate them completely from the root canal system. Hence, the use of intracanal medicaments to disrupt biofilms and thereby eradicate residual bacterial infections within root canals has been advocated to enhance the success of root canal treatment.55 Lee JK, Chang SW, Perinpanayagam H, et al. Antibacterial efficacy of a human β-defensin-3 peptide on multispecies biofilms. J Endod. 2013;39:1625-1629.,66 Byström A, Claesson R, Sundqvist G. The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals. Endod Dent Traumatol. 1985;1:170-175. For such purposes, chlorhexidine (CHX) and calcium hydroxide (CH) have been widely used because of their excellent antimicrobial and biological activities.77 Lee JK, Park YJ, Kum KY, et al. Antimicrobial efficacy of a human β-defensin-3 peptide using an Enterococcus faecalis dentine infection model. Int Endod J. 2013;46:406-412. However, CHX is inactivated by physiological salts and has a limited ability to penetrate the deep layer of biofilms.88 Portenier I, Haapasalo H, Orstavik D, Yamauchi M, Haapasalo M. Inactivation of the antibacterial activity of iodine potassium iodide and chlorhexidine digluconate against Enterococcus faecalis by dentin, dentin matrix, type-I collagen, and heat-killed microbial whole cells. J Endod. 2002;28:634-637.,99 Chávez de Paz LE, Bergenholtz G, Svensäter G. The effect of antimicrobials on endodontic biofilm bacteria. J Endod. 2010;36:70-77. CH has low diffusibility, and its antimicrobial efficacy is compromised by the buffering effect of dentin and the resistance of Enterococcus faecalis to the hydroxyl ion.1010 Evans M, Davies JK, Sundqvist G, Figdor D. Mechanisms involved in the resistance of Enterococcus faecalis to calcium hydroxide. Int Endod J. 2002;35:221-228.
11 Gomes BP, Souza SF, Ferraz CC, et al. Effectiveness of 2% chlorhexidine gel and calcium hydroxide against Enterococcus faecalis in bovine root dentine in vitro. Int Endod J. 2003;36:267-275.-1212 Haapasalo M, Qian W, Porteiner I, Waltimo T. Effects of dentin on the antimicrobial properties of endodontic medicaments. J Endod. 2007;33:917-925.
N-acetylcysteine (NAC), a derivative of the amino acid L-cysteine, is a potent thiol-containing antioxidant that serves as a precursor of glutathione synthesis.1313 Kaplan M, Atakan IH, Aydoğdu N, et al. Influence of N-acetylcysteine on renal toxicity of cadmium in rats. Pediatr Nephrol. 2008;23:233-241. Stimulation of glutathione synthesis following administration of NAC results in greater availability of glutathione for the detoxification of oxygen-derived free radicals.1414 Ross D. Glutathione, free radicals and chemotherapeutic agents. Mechanisms of free-radical induced toxicity and glutathione-dependent protection. Pharmacol Ther. 1988;37:231-249. Several studies have shown that NAC inhibits the production and/or release of proinflammatory cytokines such as NF-κB, TNF-α, matrix metalloproteinase-9, IL-8, IL-6 and IL-1β.1515 Fox E, Brower JS, Bellezzo JM, Leingang KA. Nacetylcysteine and alpha-tocopherol reverse the inflammatory response in activated rat Kupffer cells. J Immunol. 1997;158:5418-5423.
16 Lappas M, Permezel M, Rice GE. N-Acetyl-cysteine inhibits phospholipid metabolism, proinflammatory cytokine release, protease activity, and nuclear factor-κB deoxyribonucleic acid-binding activity in human fetal membranes in vitro. J Clin Endocrinol Metab. 2003;88:1723-1729.-1717 Wuyts WA, Vanaudenaerde BM, Dupont LJ, Demedts MG, Verleden GM. N-Acetylcysteine reduces chemokine release via inhibition of p38 MAPK in human airway smooth muscle cells. Eur Respir J. 2003;22:43-49. In addition, NAC has been reported to exhibit antibacterial activity against a variety of medically important bacteria such as Staphylococcus epidermidis,1818 Pérez-Giraldo C, Rodríguez-Benito A, Morán FJ, Hurtado C, Blanco MT, Gómez-García AC. Influence of N-acetylcysteine on the formation of biofilm by Staphylococcus epidermidis. J Antimicrob Chemother. 1997;39:643-646.Escherichia coli,1919 Marchese A, Bozzolasco M, Gualco L, Debbia EA, Schito GC, Schito AM. Effect of fosfomycin alone and in combination with N-acetylcysteine on E. coli biofilms. Int J Antimicrob Agents. 2003;22:95-100.Pseudomonas aeruginosa2020 Zhao T, Liu Y. N-acetylcysteine inhibit biofilms produced by Pseudomonas aeruginosa. BMC Microbiol. 2010;10:140. and Klebsiella pneumoniae.2121 Olofsson AC, Hermansson M, Elwing H. N-acetyl-L-cysteine affects growth, extracellular polysaccharide production, and bacterial biofilm formation on solid surfaces. Appl Environ Microbiol. 2003;69:4814-4822. The antibacterial activity of NAC is likely to be achieved by inhibition of cysteine utilization in bacteria or by reaction of its thiol group (-SH) with bacterial cell proteins, thereby inducing irreversible damage to the essential proteins.1919 Marchese A, Bozzolasco M, Gualco L, Debbia EA, Schito GC, Schito AM. Effect of fosfomycin alone and in combination with N-acetylcysteine on E. coli biofilms. Int J Antimicrob Agents. 2003;22:95-100.
20 Zhao T, Liu Y. N-acetylcysteine inhibit biofilms produced by Pseudomonas aeruginosa. BMC Microbiol. 2010;10:140.-2121 Olofsson AC, Hermansson M, Elwing H. N-acetyl-L-cysteine affects growth, extracellular polysaccharide production, and bacterial biofilm formation on solid surfaces. Appl Environ Microbiol. 2003;69:4814-4822. Meanwhile, depending on bacterial strains, NAC reduces the production of EPS, consequently reducing bacterial adhesion to surfaces and disrupting mature biofilms.1818 Pérez-Giraldo C, Rodríguez-Benito A, Morán FJ, Hurtado C, Blanco MT, Gómez-García AC. Influence of N-acetylcysteine on the formation of biofilm by Staphylococcus epidermidis. J Antimicrob Chemother. 1997;39:643-646.,1919 Marchese A, Bozzolasco M, Gualco L, Debbia EA, Schito GC, Schito AM. Effect of fosfomycin alone and in combination with N-acetylcysteine on E. coli biofilms. Int J Antimicrob Agents. 2003;22:95-100.,2222 Silveira LF, Baca P, Arias-Moliz MT, Rodríguez-Archilla A, Ferrer-Luque CM. Antimicrobial activity of alexidine alone and associated with N-acetylcysteine against Enterococcus faecalis biofilm. Int J Oral Surg. 2013;5:146-149. NAC has been used widely in the treatment of patients with obstructive pulmonary disease, as it breaks disulfide bonds in the mucus and inhibits bacterial biofilm formation, resulting in significant reductions in bacterial infections.2121 Olofsson AC, Hermansson M, Elwing H. N-acetyl-L-cysteine affects growth, extracellular polysaccharide production, and bacterial biofilm formation on solid surfaces. Appl Environ Microbiol. 2003;69:4814-4822.
22 Silveira LF, Baca P, Arias-Moliz MT, Rodríguez-Archilla A, Ferrer-Luque CM. Antimicrobial activity of alexidine alone and associated with N-acetylcysteine against Enterococcus faecalis biofilm. Int J Oral Surg. 2013;5:146-149.-2323 El-Feky MA, El-Rehewy MS, Hassan MA, Abolella HA, Abd El-Baky RM, Gad GF. Effect of ciprofloxacin and N-acetylcysteine on bacterial adherence and biofilm formation on ureteral stent surfaces. Pol J Microbiol. 2009;58:261-267.
In terms of oral diseases, it has been proposed that NAC exerts anti-inflammatory activity by inhibiting the expression of LPS-induced inflammatory mediators (IL-1β, -6 and -8) in phagocytic cells and gingival fibroblasts.2424 Hsu HY, Wen MH. Lipopolysaccharide-mediated reactive oxygen species and signal transduction in the regulation of interleukin-1 gene expression. J Biol Chem. 2002;277:22131-22139.
25 Kim DY, Jun JH, Lee HL, et al. N-acetylcysteine prevents LPS-induced pro-inflammatory cytokines and MMP2 production in gingival fibroblasts. Arch Pharm Res. 2007;30:1283-1292.-2626 Toker H, Ozdemir H, Eren K, Ozer H, Sahin G. N-acetylcysteine, a thiol antioxidant, decreases alveolar bone loss in experimental periodontitis in rats. J Periodontol. 2009;80:672-678. Recent investigations have demonstrated that NAC has antibacterial and antibiofilm effects against oral pathogens such as Prevotella intermedia2727 Moon JH, Jang EY, Shim KS, Lee JY. In vitro effects of N-acetyl cysteine alone and in combination with antibiotics on Prevotella intermedia. J Microbiol. 2015;53:321-329. and E. faecalis,2828 Quah SY, Wu S, Lui JN, Sum CP, Tan KS. N-acetylcysteine inhibits growth and eradicates biofilm of Enterococcus faecalis. J Endod. 2012;38:81-85. which are often found in endodontic infections. These characteristics indicate the possibility of using NAC for dental disease. Endodontic infection is the infection of the dental root canal system, and polymicrobial biofilms develop on the canal dentin walls. To evaluate the possibility of using NAC as an alternative intracanal medicament, the present study assessed the antibacterial effect of NAC against mature multispecies endodontic biofilms consisting of Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans and E. faecalis using a dentin infection model.
This study was carried out under the approved guidelines of the Review Board of Kyung Hee University, Seoul, Korea (KHD IRB-1106-02). We collected 27 single-rooted human premolar teeth with fully formed apices and caries-free crowns from patients undergoing tooth extraction for orthodontic reasons. Dentin blocks were prepared as described previously.2929 Cheng L, Zhang K, Weir MD, Liu H, Zhou X, Xu HH. Effects of antibacterial primers with quaternary ammonium and nano-silver on Streptococcus mutans impregnated in human dentin blocks. Dent Mater. 2013;29:462-472. Briefly, the dentin blocks were cut from the middle one-third of each root and the thickness was adjusted to approximately 4 mm × 4 mm × 1 mm. The smear layer was removed by immersing the specimens in an ultrasonic bath of 17% EDTA (pH 7.2), followed by 2.5% sodium hypochlorite, for 5 min each. After neutralization with a 5% sodium thiosulfate solution, the dentin blocks were thoroughly rinsed with distilled water and then sterilized by autoclaving for 15 min at 121 °C. The sterile dentin blocks were incubated in brain heart infusion broth (Difco Laboratories, Detroit, MI, USA) at 37 °C for 24 h to ensure no bacterial contamination.
It has been shown that 3-week-old mature biofilms are more resistant to disinfecting agents than planktonic bacteria and young biofilms.3030 Shen Y, Stojicic S, Haapasalo M. Antimicrobial efficacy of chlorhexidine against bacteria in biofilms at different stages of development. J Endod. 2011;37:657-661. To examine the effect of NAC on 3-week-old biofilms, preformed mature multispecies endodontic biofilms were established on the dentin blocks as described previously,55 Lee JK, Chang SW, Perinpanayagam H, et al. Antibacterial efficacy of a human β-defensin-3 peptide on multispecies biofilms. J Endod. 2013;39:1625-1629. with some modifications. Briefly, peptone-yeast extract-glucose (PYG) was dissolved in 10 mM potassium phosphate buffer, pH 7.5, and each bacterial species was grown in this medium at 37 °C anaerobically (80% N2, 10% H2, 10% CO2). The bacterial culture was grown to exponential phase, then diluted to an optical density at 600 nm (OD600) of approximately 0.1 in fresh medium. To prepare the multispecies suspension, four OD-adjusted bacterial cultures were mixed in equal proportions. Sterile dentin blocks were immersed in the multispecies suspension and then incubated at 37 °C for 3 weeks, with PYG medium being changed every 2 or 3 days. Biofilm formation and bacterial penetration into the dentinal tubules were confirmed using scanning electron microscopy (SEM).
After the 3-week incubation, the dentin blocks were gently washed with saline to remove unattached bacteria, then treated with 100 µL of one of the following medicaments: sterile saline (control), NAC (25, 50 and 100 mg/mL, Sigma Chemical Co., St. Louis, MO, USA), saturated CH solution (Sigma), or 2% CHX (Sigma). Adenosine triphosphate (ATP) bioluminescence measurements in relative light units (RLU) has been utilized as a quantitative assay to evaluate viable bacteria in different biological samples, including mixed biofilm populations such as dental plaque.3131 Sánchez MC, Llama-Palacios A, Marín MJ, et al. Validation of ATP bioluminescence as a tool to assess antimicrobial effects of mouthrinses in an in vitro subgingival-biofilm model. Med Oral Patol Oral Cir Bucal. 2013;18:e86-e92. At 7 days after exposure to the medicaments, the viability of the bacterial cells in the biofilms was evaluated by quantifying ATP-bioluminescence using BacTiter-Glo™ Microbial Cell Viability Assay Kit (Promega, Madison, WI, USA) according to the manufacturer's instructions. Results were expressed as the percentage of RLU and calculated as shown below. Percentage of RLU in the saline treated biofilm was assumed as 100. Relative viability (% RLU) = (RLU of medicament treated biofilm - background RLU)/(RLU of saline treated biofilm - background RLU) × 100%. Colony forming unit (CFU) counting, the most commonly used conventional viable bacterial quantification, was also performed. Briefly, biofilm bacterial cells were harvested from the dentin blocks by sonication as described previously,3030 Shen Y, Stojicic S, Haapasalo M. Antimicrobial efficacy of chlorhexidine against bacteria in biofilms at different stages of development. J Endod. 2011;37:657-661. then diluted serially in PYG medium and subsequently enumerated by plating them on agar plates which were incubated for 48 h at 37 °C. The biofilm morphology was assessed using SEM.
After incubation for 1 day, the multispecies bacteria had become successfully impregnated into the interior of the dentin blocks, and bacterial biofilm-like structures consisting mostly of cocci were observed on the surface of the dentin blocks (Fig. 1). The mature 3-week-old biofilms were composed of rods and coccal cells, forming a layered structure of bacterial aggregates covering the dentin surface. No obvious structural disruption was observed in the biofilms treated with saline for 7 days. Treatment of the biofilms with either CH or CHX for 7 days resulted in partial disruption of the layered structure, whereas 25 and 50 mg/mL NAC resulted in obvious disruption of the biofilms with clearly exposed dentin surface. Compared with the saline treated biofilm, significant reduction (over 99%) in CFUs counts and % RLU was observed in the biofilms treated with 25 and 50 mg/mL NAC. Furthermore, NAC (≥25 mg/mL) showed statistically higher bactericidal effect than CH and CHX. In the 100 mg/mL NAC treatment group, biofilm structure completely disappeared (Fig. 1) and viable cells were not detected (Table 1). These results clearly indicate that 100 mg/mL NAC completely disrupted the mature multispecies endodontic biofilms consisting of A. naeslundii, L. salivarius, S. mutans and E. faecalis, probably via affecting EPS produced by the bacterial cells. Small pieces of cell debris and a very limited number of dead cells observed on the dentin surface without biofilm structure may be related to physicochemical linkages between cells and dentin surface because cell viability has limited influence on attachment, as suggested by previous studies.2727 Moon JH, Jang EY, Shim KS, Lee JY. In vitro effects of N-acetyl cysteine alone and in combination with antibiotics on Prevotella intermedia. J Microbiol. 2015;53:321-329.,3232 Parkar SG, Flint SH, Palmer JS, Brooks JD. Factors influencing attachment of thermophilic bacilli to stainless steel. J Appl Microbiol. 2001;90:901-908. It seems that NAC at the concentrations from 25 to 50 mg/mL can remove the mature multispecies biofilm partially, but was still able to effectively kill the bacteria located in the remaining biofilm that was at most a few cell layers thick.
Scanning electron microscope (SEM) images of multispecies endodontic biofilms. Multispecies bacteria were successfully impregnated into the interior of the sterile dentin blocks after incubation for 1 day. After the 3-week incubation, the mature biofilm exhibited a layered structure of bacterial aggregates covering the dentin surface. The mature multispecies biofilms were treated with saline, saturated calcium hydroxide solution (CH), 2% chlorhexidine solution (CHX) or NAC at the indicated concentrations for 7 days and then observed using SEM at a magnification of 20,000× and 100,000× (inset) operating at 10 kV.
Collectively, NAC exhibited strong biofilm removal and killing activities against the mature multispecies endodontic biofilms formed on the dentin surfaces. It is noteworthy that NAC has also been proposed as a substitute for ibuprofen for post-endodontic pain,3333 Ehsani M, Moghadamnia A, Zahedpasha S, et al. The role of prophylactic ibuprofen and N-acetylcysteine on the level of cytokines in periapical exudates and the post-treatment pain. Daru. 2012;20:30. and exerts anti-inflammatory activity through its ability to inhibit the expression and release of a variety of proinflammatory cytokines.3434 Sadowska AM, Manuel-Y-Keenoy B, De Backer WA. Antioxidant and anti-inflammatory efficacy of NAC in the treatment of COPD: discordant in vitro and in vivo dose-effects: a review. Pulm Pharmacol Ther. 2007;20:9-22.,3535 Lappas M, Permezel M, Rice GE. N-Acetyl-cysteine inhibits phospholipid metabolism, proinflammatory cytokine release, protease activity, and nuclear factor-κB deoxyribonucleic acid-binding activity in human fetal membranes in vitro. J Clin Endocrinol Metab. 2003;88:1723-1729. All these observations demonstrate that NAC has the potential to be developed as an alternative intracanal medicament.
Acknowledgements
This study was supported by a grant of the Korean Health Technology R&D Project, Ministry of Health and Welfare (HI13C1945) and by the Ministry of Science, ICT and Future Planning (NRF-2015R1C1A2A01054588).
References
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1Donlan RM, Costerton JW. Biofilms: survival mechanisms of clinically relevant microorganisms. Clin Microbiol Rev. 2002;15:167-193.
-
2Siqueira JF, Rôças IN, Ricucci D. Biofilms in endodontic infection. Endod Top. 2010;22:33-49.
-
3Svensäter G, Bergenholtz G. Biofilms in endodontic infections. Endod Top. 2004;9:27-36.
-
4Jhajharia K, Parolia A, Shetty KV, Mehta LK. Biofilm in endodontics: a review. J Int Soc Prev Community Dent 2015;5:1-12.
-
5Lee JK, Chang SW, Perinpanayagam H, et al. Antibacterial efficacy of a human β-defensin-3 peptide on multispecies biofilms. J Endod. 2013;39:1625-1629.
-
6Byström A, Claesson R, Sundqvist G. The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals. Endod Dent Traumatol. 1985;1:170-175.
-
7Lee JK, Park YJ, Kum KY, et al. Antimicrobial efficacy of a human β-defensin-3 peptide using an Enterococcus faecalis dentine infection model. Int Endod J. 2013;46:406-412.
-
8Portenier I, Haapasalo H, Orstavik D, Yamauchi M, Haapasalo M. Inactivation of the antibacterial activity of iodine potassium iodide and chlorhexidine digluconate against Enterococcus faecalis by dentin, dentin matrix, type-I collagen, and heat-killed microbial whole cells. J Endod. 2002;28:634-637.
-
9Chávez de Paz LE, Bergenholtz G, Svensäter G. The effect of antimicrobials on endodontic biofilm bacteria. J Endod. 2010;36:70-77.
-
10Evans M, Davies JK, Sundqvist G, Figdor D. Mechanisms involved in the resistance of Enterococcus faecalis to calcium hydroxide. Int Endod J. 2002;35:221-228.
-
11Gomes BP, Souza SF, Ferraz CC, et al. Effectiveness of 2% chlorhexidine gel and calcium hydroxide against Enterococcus faecalis in bovine root dentine in vitro. Int Endod J. 2003;36:267-275.
-
12Haapasalo M, Qian W, Porteiner I, Waltimo T. Effects of dentin on the antimicrobial properties of endodontic medicaments. J Endod. 2007;33:917-925.
-
13Kaplan M, Atakan IH, Aydoğdu N, et al. Influence of N-acetylcysteine on renal toxicity of cadmium in rats. Pediatr Nephrol. 2008;23:233-241.
-
14Ross D. Glutathione, free radicals and chemotherapeutic agents. Mechanisms of free-radical induced toxicity and glutathione-dependent protection. Pharmacol Ther. 1988;37:231-249.
-
15Fox E, Brower JS, Bellezzo JM, Leingang KA. Nacetylcysteine and alpha-tocopherol reverse the inflammatory response in activated rat Kupffer cells. J Immunol 1997;158:5418-5423.
-
16Lappas M, Permezel M, Rice GE. N-Acetyl-cysteine inhibits phospholipid metabolism, proinflammatory cytokine release, protease activity, and nuclear factor-κB deoxyribonucleic acid-binding activity in human fetal membranes in vitro. J Clin Endocrinol Metab 2003;88:1723-1729.
-
17Wuyts WA, Vanaudenaerde BM, Dupont LJ, Demedts MG, Verleden GM. N-Acetylcysteine reduces chemokine release via inhibition of p38 MAPK in human airway smooth muscle cells. Eur Respir J. 2003;22:43-49.
-
18Pérez-Giraldo C, Rodríguez-Benito A, Morán FJ, Hurtado C, Blanco MT, Gómez-García AC. Influence of N-acetylcysteine on the formation of biofilm by Staphylococcus epidermidis. J Antimicrob Chemother 1997;39:643-646.
-
19Marchese A, Bozzolasco M, Gualco L, Debbia EA, Schito GC, Schito AM. Effect of fosfomycin alone and in combination with N-acetylcysteine on E. coli biofilms. Int J Antimicrob Agents 2003;22:95-100.
-
20Zhao T, Liu Y. N-acetylcysteine inhibit biofilms produced by Pseudomonas aeruginosa. BMC Microbiol 2010;10:140.
-
21Olofsson AC, Hermansson M, Elwing H. N-acetyl-L-cysteine affects growth, extracellular polysaccharide production, and bacterial biofilm formation on solid surfaces. Appl Environ Microbiol 2003;69:4814-4822.
-
22Silveira LF, Baca P, Arias-Moliz MT, Rodríguez-Archilla A, Ferrer-Luque CM. Antimicrobial activity of alexidine alone and associated with N-acetylcysteine against Enterococcus faecalis biofilm. Int J Oral Surg. 2013;5:146-149.
-
23El-Feky MA, El-Rehewy MS, Hassan MA, Abolella HA, Abd El-Baky RM, Gad GF. Effect of ciprofloxacin and N-acetylcysteine on bacterial adherence and biofilm formation on ureteral stent surfaces. Pol J Microbiol. 2009;58:261-267.
-
24Hsu HY, Wen MH. Lipopolysaccharide-mediated reactive oxygen species and signal transduction in the regulation of interleukin-1 gene expression. J Biol Chem. 2002;277:22131-22139.
-
25Kim DY, Jun JH, Lee HL, et al. N-acetylcysteine prevents LPS-induced pro-inflammatory cytokines and MMP2 production in gingival fibroblasts. Arch Pharm Res. 2007;30:1283-1292.
-
26Toker H, Ozdemir H, Eren K, Ozer H, Sahin G. N-acetylcysteine, a thiol antioxidant, decreases alveolar bone loss in experimental periodontitis in rats. J Periodontol. 2009;80:672-678.
-
27Moon JH, Jang EY, Shim KS, Lee JY. In vitro effects of N-acetyl cysteine alone and in combination with antibiotics on Prevotella intermedia. J Microbiol 2015;53:321-329.
-
28Quah SY, Wu S, Lui JN, Sum CP, Tan KS. N-acetylcysteine inhibits growth and eradicates biofilm of Enterococcus faecalis. J Endod. 2012;38:81-85.
-
29Cheng L, Zhang K, Weir MD, Liu H, Zhou X, Xu HH. Effects of antibacterial primers with quaternary ammonium and nano-silver on Streptococcus mutans impregnated in human dentin blocks. Dent Mater 2013;29:462-472.
-
30Shen Y, Stojicic S, Haapasalo M. Antimicrobial efficacy of chlorhexidine against bacteria in biofilms at different stages of development. J Endod. 2011;37:657-661.
-
31Sánchez MC, Llama-Palacios A, Marín MJ, et al. Validation of ATP bioluminescence as a tool to assess antimicrobial effects of mouthrinses in an in vitro subgingival-biofilm model. Med Oral Patol Oral Cir Bucal. 2013;18:e86-e92.
-
32Parkar SG, Flint SH, Palmer JS, Brooks JD. Factors influencing attachment of thermophilic bacilli to stainless steel. J Appl Microbiol. 2001;90:901-908.
-
33Ehsani M, Moghadamnia A, Zahedpasha S, et al. The role of prophylactic ibuprofen and N-acetylcysteine on the level of cytokines in periapical exudates and the post-treatment pain. Daru 2012;20:30.
-
34Sadowska AM, Manuel-Y-Keenoy B, De Backer WA. Antioxidant and anti-inflammatory efficacy of NAC in the treatment of COPD: discordant in vitro and in vivo dose-effects: a review. Pulm Pharmacol Ther. 2007;20:9-22.
-
35Lappas M, Permezel M, Rice GE. N-Acetyl-cysteine inhibits phospholipid metabolism, proinflammatory cytokine release, protease activity, and nuclear factor-κB deoxyribonucleic acid-binding activity in human fetal membranes in vitro. J Clin Endocrinol Metab. 2003;88:1723-1729.
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Publication Dates
-
Publication in this collection
Jan-Mar 2018
History
-
Received
29 Apr 2016 -
Accepted
21 Apr 2017