title: In vitro evaluation of pH changes induced by calcium hydroxide liners.
abstract: OBJECTIVE
  Since the highly alkaline pH of calcium hydroxide is considered by many to be responsible for its biologic activity, the possible variations of pH induced by the different calcium hydroxide liners are accepted as a major concern. The aim of the present study was to determine the pH changes of five different calcium hydroxide liners and variations of pH levels at different time intervals.
  
  
  METHODS
  The materials tested were Dycal, Life, Calic, Dycal VLC, and Calcident 450. Samples were prepared according to manufacturer instructions and by using plastic molds; five standard samples from each material were prepared. The samples were then placed in separate vials, containing 10 mL deionized water (pH 7.0), and stored at room temperature (200C). The pH measurements were taken 1 hour, 24 hours, 3 days, and 7 days after mixing. The pH variations of each material at the given time intervals were recorded, and the means were calculated.
  
  
  RESULTS
  Statistical analysis showed significantly high differences between the mean pH values induced by each material at all time intervals. The highest value for the first-hour measurement was for Dycal VLC, and the highest values for the other time intervals were for Calcident 450. The pH values of the materials exhibited statistically significant differences among all the time intervals.
  
  
  CONCLUSIONS
  All materials changed the pH of deionized water toward alkaline.
authors.affiliation: Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey.
authors.forename: Koray
authors.initials: K
authors.lastname: Gençay
authors.forename: Figen
authors.initials: F
authors.lastname: Seymen
authors.forename: Senem
authors.initials: S
authors.lastname: Selvi
authors.forename: Başak
authors.initials: B
authors.lastname: Kiziltan
mesh_terms: D002126:Calcium Hydroxide / Q000737:chemistry*; D003736:Dental Cavity Lining; D003764:Dental Materials / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008903:Minerals / Q000737:chemistry; D013997:Time Factors
chemical_list: C488982:Calcident 450; C488981:Calic; D003764:Dental Materials; D008903:Minerals; C025702:Dycal; C040408:Life (dental material); D002126:Calcium Hydroxide