title: A laboratory study evaluating the release of hydroxyl ions from various calcium hydroxide products in narrow root canal-like tubes.
abstract: OBJECTIVE
  The aim of the present study was to describe pH changes in a variety of buffering solutions within a narrow test tube containing either a gutta-percha point with incorporate calcium hydroxide, a commercial calcium hydroxide paste (Calcicur) or a freshly mixed paste of calcium hydroxide in distilled water.
  
  
  METHODS
  The test material was placed centrally in a test tube of 2 mm inner diameter. Saline (1%) was placed at one end, whilst the buffering solutions were introduced at the other. The pH of the buffering solutions was monitored using electrodes placed at each end of the test tube.
  
  
  RESULTS
  It was found that the pH 4.01 buffer strongly resisted pH changes at levels below 6.0, whilst saliva and bovine serum was buffered less and more evenly in the whole range up to pH 11.5. The calcium hydroxide containing gutta-percha points caused the pH to increase quickly in the sodium chloride solution to levels above 11.5. However, in bovine serum, in saliva and in the pH 4.01 buffer the pH remained below 8.5, 8.0 and 6.0, respectively, 1 mm from the point. In contrast, the release of hydroxyl ions from the two calcium hydroxide pastes brought pH above pH 11.5 irrespective of the buffering of the solutions 5 mm from the paste.
  
  
  CONCLUSIONS
  It is concluded that Calcicur and the calcium hydroxide-water mixture contained substantially more available calcium hydroxide than did the calcium hydroxide containing gutta-percha points, with the result that the release of hydroxyl ions from the points was limited in comparison to that from the pastes.
authors: Royal Dental College, Faculty of Health Sciences, University of Aarhus, Vennelyst Blvd., DK-8000 Aarhus C, Denmark. joost@odont.aau.dk
authors: M J
authors: MJ
authors: Larsen
authors: P
authors: P
authors: Hörsted-Bindslev
mesh_terms: D000818:Animals; D002021:Buffers; D002126:Calcium Hydroxide / Q000737:chemistry*; D002417:Cattle; D003786:Dental Pulp Cavity; D006171:Gutta-Percha / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D012388:Root Canal Irrigants / Q000737:chemistry*; D012463:Saliva / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry
chemical_list: D002021:Buffers; D012388:Root Canal Irrigants; D012710:Serum Albumin, Bovine; D017665:Hydroxyl Radical; D006171:Gutta-Percha; D002126:Calcium Hydroxide