title: Antimicrobial 2-hydroxyisocaproic acid and chlorhexidine resist inactivation by dentine.
abstract: OBJECTIVE
  To compare the antibacterial activity of 2-hydroxyisocaproic acid (HICA) with currently used root canal medicaments and to examine their interactions with potential inhibitors in nutrient-deficient and nutrient-rich conditions.
  
  
  METHODS
  First, the antibacterial activity of single concentrations of HICA, calcium hydroxide solution or slurry, chlorhexidine digluconate or acetate was tested against Enterococcus faecalis with and without potential inhibitors: dentine powder (DP), hydroxyapatite or bovine serum albumin, in a low concentration of peptone water. Relative viable counts were determined by culture at 1, 24 and 48 h. In the second set of experiments, the activity of three concentrations of HICA was evaluated against two isolates of E. faecalis with and without potential inhibitors in nutrient-rich thioglycollate broth using a modification of a standard microdilution method. The minimum bactericidal concentration was determined by culture at 1, 24 and 48 h.
  
  
  RESULTS
  Concentrations of ≥33 mg mL(-1) of HICA were found to be bactericidal against E. faecalis in both nutrient-deficient and nutrient-rich environments at 24- to 48-h incubation, whereas the initial activity of Ca(OH)2 slurry was lost at 48-h incubation. HICA tolerated well all tested potential inhibitors up to 19 mg mL(-1) . DP concentrations higher than this inhibited its activity in a dose-dependent manner in both environments. DP demonstrated moderate antibacterial activity, and it enhanced the otherwise limited activity of Ca(OH)2 slurry and solution. DP did not impact on the activity of chlorhexidine.
  
  
  CONCLUSIONS
  These results support the long-term antibacterial activity of HICA and indicate its tolerance to clinically relevant concentrations of dentine and other inhibitors commonly present in the root canal system. Therefore, HICA may have potential as an interappointment medication in the treatment of root canal infections.
authors.affiliation: Institute of Dentistry, University of Oulu, Oulu, Finland.|Department of Oral and Maxillofacial Diseases, Helsinki University and Helsinki University Hospital, Helsinki, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Sakko
authors.affiliation: Institute of Dentistry, University of Oulu, Oulu, Finland.|Department of Oral and Maxillofacial Diseases, Helsinki University and Helsinki University Hospital, Helsinki, Finland.|Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
authors.forename: L
authors.initials: L
authors.lastname: Tjäderhane
authors.affiliation: Department of Oral and Maxillofacial Diseases, Helsinki University and Helsinki University Hospital, Helsinki, Finland.|Division of Periodontology, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Sorsa
authors.affiliation: Extracta Ltd, Vantaa, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Hietala
authors.affiliation: Manchester Academic Health Science Centre, Institute of Inflammation and Repair, University Hospital of South Manchester, University of Manchester, Manchester, UK.
authors.forename: R
authors.initials: R
authors.lastname: Rautemaa
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001672:Biocompatible Materials / Q000494:pharmacology*; D002126:Calcium Hydroxide / Q000494:pharmacology; D002208:Caproates / Q000494:pharmacology*; D002417:Cattle; D002710:Chlorhexidine / Q000494:pharmacology*; D003804:Dentin / Q000187:drug effects*; D013293:Enterococcus faecalis / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D012388:Root Canal Irrigants / Q000494:pharmacology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D001672:Biocompatible Materials; D002208:Caproates; D012388:Root Canal Irrigants; D012710:Serum Albumin, Bovine; C019419:alpha-hydroxyisocaproic acid; D002126:Calcium Hydroxide; D002710:Chlorhexidine
keywords: Enterococcus faecalis; calcium hydroxide; chlorhexidine; hydroxyapatite; root canal medication; serum albumin