Siqueira JF, Rôças IN, Ricucci D, Hülsmann M. Causes and management of post-treatment apical periodontitis. Br Dent J. 2014;216:305–12.
Gomes BPFA, Pinheiro ET, Gadê-Neto CR, Sousa ELR, Ferraz CR, Zaia A, et al. Microbiological examination of infected dental root canals. Oral Microbiol Immunol. 2004;19:71–6.
Barbosa-Ribeiro M, Arruda-Vasconcelos R, Louzada LM, Dos Santos DG, Andreote FD, Gomes BPFA. Microbiological analysis of endodontically treated teeth with apical periodontitis before and after endodontic retreatment. Clin Oral Investig. 2021;25:2017–27.
Ran SJ, Jiang W, Zhu CL, Liang JP. Exploration of the mechanisms of biofilm formation by enterococcus faecalis in glucose starvation environments. Aust Dent J. 2015;60:143–53.
McHugh CP, Zhang P, Michalek S, Eleazer PD. pH required to kill enterococcus faecalis in vitro. J Endod. 2004;30:218–9.
Al-Ahmad A, Ameen H, Pelz K, Karygianni L, Wittmer A, Anderson AC, et al. Antibiotic resistance and capacity for biofilm formation of different bacteria isolated from endodontic infections associated with root-filled teeth. J Endod. 2014;40:223–30.
Arya S, Duhan J, Tewari S, Sangwan P, Ghalaut V, Aggarwal S. Healing of apical periodontitis after nonsurgical treatment in patients with type 2 diabetes. J Endod. 2017;43:1623–7.
Bender IB, Bender AB. Diabetes mellitus and the dental pulp. J Endod. 2003;29:383–9.
Fouad AF, Zerella J, Barry J, Spångberg LS. Molecular detection of enterococcus species in root canals of therapy-resistant endodontic infections. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005;99:112–8.
Pérez-Losada FL, Estrugo-Devesa A, Castellanos-Cosano L, Segura-Egea JJ, López-López J, Velasco-Ortega E. Apical periodontitis and diabetes mellitus type 2: a systematic review and meta-analysis. J Clin Med. 2020;9:540.
Mesgarani A, Haghanifar S, Eshkevari N, Ehsani M, Khafri S, Nafarzade S, et al. Frequency of odontogenic periradicular lesions in diabetic patients. Caspian J Intern Med. 2014;5:22–5.
Segura-Egea JJ, Cabanillas-Balsera D, Jiménez-Sánchez MC, Martín-González J. Endodontics and diabetes: association versus causation. Int Endod J. 2019;52:790–802.
Yip N, Liu C, Wu D, Fouad AF. The association of apical periodontitis and type 2 diabetes mellitus: a large hospital network cross-sectional case-controlled study. J Am Dent Assoc. 2021;152:434–43.
Wang HW, Lai EH, Yang CN, Lin SK, Hong CY, Yang H, et al. Intracanal metformin promotes healing of apical periodontitis via suppressing inducible nitric oxide synthase expression and monocyte recruitment. J Endod. 2020;46:65–73.
Cameron AR, Morrison VL, Levin D, Mohan M, Forteath C, Beall C, et al. Anti-inflammatory effects of metformin irrespective of diabetes status. Circ Res. 2016;119:652–65.
Soukas AA, Hao H, Wu L. Metformin as anti-aging therapy: is it for everyone? Trends Endocrinol Metab. 2019;30:745–55.
Chen GG, Woo P, Ng S, Wong G, Chan D, van Hasselt CA, et al. Impact of metformin on immunological markers: implication in its anti-tumor mechanism. Pharmacol Ther. 2020;213:107585.
Patkee WR, Carr G, Baker EH, Baines DL, Garnett JP. Metformin prevents the effects of Pseudomonas aeruginosa on airway epithelial tight junctions and restricts hyperglycaemia-induced bacterial growth. J Cell Mol Med. 2016;20:758–64.
Malik F, Mehdi SF, Ali H, Patel P, Basharat A, Kumar A, et al. Is metformin poised for a second career as an antimicrobial? Diabetes Metab Res Rev. 2018;34:e2975.
Liu Y, Jia Y, Yang K, Li R, Xiao X, Zhu K, et al. Metformin restores tetracyclines susceptibility against multidrug resistant bacteria. Adv Sci (Weinh). 2020;7:1902227.
Hadrup N, Sharma AK, Loeschner K. Toxicity of silver ions, metallic silver, and silver nanoparticle materials after in vivo dermal and mucosal surface exposure: a review. Regul Toxicol Pharmacol. 2018;98:257–67.
Cui J, Sun Q, Duan M, Liu D, Fan W. Establishment and characterization of silver-resistant enterococcus faecalis. Folia Microbiol. 2020;65:721–33.
Montelongo-Peralta LZ, Leon-Buitimea A, Palma-Nicolas JP, Gonzalez-Christen J, Morones-Ramirez JR. Antibacterial activity of combinatorial treatments composed of transition-metal/antibiotics against mycobacterium tuberculosis. Sci Rep. 2019;9:5471.
Katva S, Das S, Moti HS, Jyoti A, Kaushik S. Antibacterial synergy of silver nanoparticles with gentamicin and chloramphenicol against enterococcus faecalis. Pharmacogn Mag. 2018;13:S828–33.
Fan W, Duan M, Sun Q, Fan B. Simvastatin enhanced antimicrobial effect of Ag+ against E. Faecalis infection of dentine through PLGA co-delivery submicron particles. J Biomater Sci Polym Ed. 2020;31:2331–46.
Fan W, Sun Q, Li Y, Tay FR, Fan B. Synergistic mechanism of Ag+–Zn2+ in anti-bacterial activity against enterococcus faecalis and its application against dentin infection. J Nanobiotechnology. 2018;16:10.
Bowler P, Murphy C, Wolcott R. Biofilm exacerbates antibiotic resistance: is this a current oversight in antimicrobial stewardship? Antimicrob Resist Infect Control. 2020;9:162.
Pillai SK, Sakoulas G, Eliopoulos GM, Moellering RC, Murray BE, Inouye RT. Effects of glucose on fsr-mediated biofilm formation in enterococcus faecalis. J Infect Dis. 2004;190:967–70.
Seneviratne CJ, Yip JWY, Chang JWW, Zhang CF, Samaranayake LP. Effect of culture media and nutrients on biofilm growth kinetics of laboratory and clinical strains of enterococcus faecalis. Arch Oral Biol. 2013;58:1327–34.
George S, Kishen A, Song KP. The role of environmental changes on monospecies biofilm formation on root canal wall by enterococcus faecalis. J Endod. 2005;31:867–72.
Love RM. Enterococcus faecalis–a mechanism for its role in endodontic failure. Int Endod J. 2001;34:399–405.
Mohammadi Z, Abbott PV. The properties and applications of chlorhexidine in endodontics. Int Endod J. 2009;42:288–302.
Basrani B, Tjäderhane L, Santos JM, Pascon E, Grad H, Lawrence HP, et al. Efficacy of chlorhexidine- and calcium hydroxide–containing medicaments against enterococcus faecalis in vitro. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003;96:618–24.
Tanzer JM, Slee AM, Kamay BA. Structural requirements of guanide, biguanide, and bisbiguanide agents for antiplaque activity. Antimicrob Agents Chemother. 1977;12:721–9.
Mijnendonckx K, Leys N, Mahillon J, Silver S, Van Houdt R. Antimicrobial silver: uses, toxicity and potential for resistance. Biometals. 2013;26:609–21.
Kędziora A, Speruda M, Krzyżewska E, Rybka J, Łukowiak A, Bugla-Płoskońska G. Similarities and differences between silver ions and silver in nanoforms as antibacterial agents. Int J Mol Sci. 2018;19:444.
Spengler G, Martins A, Schelz Z, Rodrigues L, Aagaard L, Martins M, et al. Characterization of intrinsic efflux activity of enterococcus faecalis ATCC29212 by a semi-automated ethidium bromide method. In Vivo. 2009;23:81–7.
Li XZ, Nikaido H, Williams KE. Silver-resistant mutants of Escherichia coli display active efflux of Ag+ and are deficient in porins. J Bacteriol. 1997;179:6127–32.
Kayaoglu G, Ørstavik D. Virulence factors of enterococcus faecalis: relationship to endodontic disease. Crit Rev Oral Biol Med. 2004;15:308–20.
Graunaite I, Lodiene G, Maciulskiene V. Pathogenesis of apical periodontitis: a literature review. J Oral Maxillofac Res. 2012;2:e1.
Wang L, Jin H, Ye D, Wang J, Ao X, Dong M, et al. Enterococcus faecalis lipoteichoic acid–induced NLRP3 inflammasome via the activation of the nuclear factor kappa B pathway. J Endod. 2016;42:1093–100.
Segura-Egea JJ, Martín-González J, Castellanos-Cosano L. Endodontic medicine: connections between apical periodontitis and systemic diseases. Int Endod J. 2015;48:933–51.
Tan Y, Chen J, Jiang Y, Chen X, Li J, Chen B, et al. The anti-periodontitis action of metformin via targeting NLRP3 inflammasome. Arch Oral Biol. 2020;114:104692.
Lai EH, Yang CN, Lin SK, Wang HW, Kok SH, Hong CY, et al. Metformin ameliorates periapical lesions through suppression of hypoxia-induced apoptosis of osteoblasts. J Endod. 2018;44:1817–25.
Sun M, Dong J, Xia Y, Shu R. Antibacterial activities of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) against planktonic and biofilm growing Streptococcus mutans. Microb Pathog. 2017;107:212–8.
Yuan L, Lyu P, Huang YY, Du N, Qi W, Hamblin MR, et al. Potassium iodide enhances the photobactericidal effect of methylene blue on enterococcus faecalis as planktonic cells and as biofilm infection in teeth. J Photochem Photobiol B. 2020;203:111730.
Swimberghe R, Coenye T, De Moor R, Meire MA. Biofilm model systems for root canal disinfection: a literature review. Int Endod J. 2019;52:604–28.
Wu D, Fan W, Kishen A, Gutmann JL, Fan B. Evaluation of the antibacterial efficacy of silver nanoparticles against enterococcus faecalis biofilm. J Endod. 2014;40:285–90.
Murakami Y, Kawata A, Suzuki S, Fujisawa S. Cytotoxicity and pro−/anti-inflammatory properties of cinnamates, acrylates and methacrylates against raw264.7 cells. In Vivo. 2018;32:1309–22.
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