title: Microtomographic porosity determination in alginate mixed with various methods.
abstract: OBJECTIVE
  Mechanical spatulation of alginate impression materials reportedly produces fewer voids and superior casts than hand mixing. Two current methods of alginate mechanical preparation are a vacuum mixer Vac-U-Vestor, (Whip Mix Corp, Louisville, KY) and a semiautomated method that involves hand spatulation in a rotating bowl Alginator II (Cadco, Oxnard, CA). A new alginate-mixing machine has been introduced, TurboMax (Dentsply Raintree Essex, Sarasota, FL), with a centrifugal-spinning action that reportedly incorporates the alginate powder into the water more efficiently. The purpose of this study was to determine the number, percent, and volume distribution of porosities in alginate mixed with three mechanical-mixing methods using a nondestructive, microtomographic analysis method.
  
  
  METHODS
  Alginate was mixed by each of the three mechanical methods per respective manufacturer's guidelines, with the set alginate analyzed using a microtomography unit and proprietary software. A mean and standard deviation was determined per group and analyzed with Kruskal-Wallis ANOVA/Mann-Whitney tests.
  
  
  RESULTS
  Significant differences (p < 0.001) were found between groups per each of the three testing parameters (number, percent, volume distribution of porosities). The vacuum mixer produced significantly less percent porosity and number of porosities than the centrifugal mixer and semiautomated hand mixer. Both the vacuum mixer and centrifugal mixer produced porosities of significantly smaller volume than the semiautomated hand mixer.
  
  
  CONCLUSIONS
  Of the three mechanical mixing methods, the vacuum mixer had the best performance overall in reducing the number, percent, and volume of porosities in the mixed alginate.
authors.affiliation: United States Air Force, Advanced Education in General Dentistry Residency, Travis AFB, CA, USA.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Hamilton
authors.forename: Kraig S
authors.initials: KS
authors.lastname: Vandewalle
authors.forename: Howard W
authors.initials: HW
authors.lastname: Roberts
authors.forename: Garrett J
authors.initials: GJ
authors.lastname: Hamilton
authors.forename: Wen
authors.initials: W
authors.lastname: Lien
mesh_terms: D000464:Alginates / Q000737:chemistry*; D003760:Dental Impression Materials / Q000737:chemistry*; D003761:Dental Impression Technique / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D016062:Porosity; D011208:Powders; D012399:Rotation; D013696:Temperature; D014618:Vacuum; D014867:Water / Q000737:chemistry; D055114:X-Ray Microtomography
chemical_list: D000464:Alginates; D003760:Dental Impression Materials; D011208:Powders; D014867:Water