title: The effect of disinfecting solutions on the dimensional stability of dental alginate impression materials.
abstract: OBJECTIVE
  Dimensional changes occur in set dental alginate impression materials when immersed in disinfecting solutions. In this contribution the dimensional changes of two alginates in two disinfecting solutions, and for two specimen thicknesses, have been studied. The results were analyzed theoretically.
  
  
  METHODS
  The dimensional changes of two commercial alginates (Blueprint Cremix and Hydrogum), have been measured, in distilled water and two disinfecting solutions (Perform ID/sodium hypochlorite), using a traveling microscope, at 5 min intervals over a period of 1h. Samples of simple geometry have been studied, namely rectangular strips with thicknesses of 1.5 and 3mm, respectively.
  
  
  RESULTS
  In all cases, both alginates continuously shrank with time, in the three immersion liquids, over the hour of measurement, indicating transfer of water from the alginate into the external water or disinfecting solution. The t(1/2) shrinkage plots were generally linear, but with an intercept on the t(1/2) axis, indicating the possibility of an initial expansion at very short times. In most cases, the ratios of slopes for both thicknesses were 1.33-1.54, in contrast to the theoretical value of 2. Perform ID however gave anomalous results for the 1.5mm thick samples. At 10 min their shrinkage was 1.34-1.72%, compared with -0.42% to 0.67% in the other two media.
  
  
  CONCLUSIONS
  The effects of thickness observed were not in accord with simple Fickian theory because of the various ions diffusing into and out of the alginate. Moreover, the water content of the alginate decreased consequent on the cross-linking process.
authors.affiliation: Department of Oral Growth and Development, Dental Physical Sciences in Dentistry Unit, Queen Mary, University of London, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, London, United Kingdom.
authors.forename: Danish
authors.initials: D
authors.lastname: Muzaffar
authors.forename: Michael
authors.initials: M
authors.lastname: Braden
authors.forename: Sandra
authors.initials: S
authors.lastname: Parker
authors.forename: Mangala P
authors.initials: MP
authors.lastname: Patel
mesh_terms: D000464:Alginates / Q000737:chemistry*; D019551:Dental Disinfectants / Q000009:adverse effects / Q000737:chemistry*; D003760:Dental Impression Materials / Q000737:chemistry*; D004058:Diffusion; D007101:Immersion / Q000009:adverse effects*; D008422:Materials Testing; D014867:Water / Q000737:chemistry
chemical_list: D000464:Alginates; D019551:Dental Disinfectants; D003760:Dental Impression Materials; D014867:Water