title: Comparision of diametral tensile strength of microwave and oven-dried investment materials.
abstract: BACKGROUND
  Microwave drying technique for investment materials is believed to be timesaving by accelerating the elimination of free water content.
  
  
  OBJECTIVE
  This study compared the diametral tensile strength of 4 investment materials used in removable partial denture framework fabrication. The investment materials were subjected to microwave and conventional oven drying at different time intervals.
  
  
  METHODS
  Type III partial denture casting investments (Wirovest, Wiroplus, Biosint, PH2) were tested. A total of 160 specimens were prepared in cylindrical form at a height of 40 mm and a diameter of 20 mm, in accordance with the manufacturers' recommendations. Forty specimens were prepared from each product; 20 specimens were dried at 230 degrees C for 1 hour in an electric furnace, the other 20 were dried in a microwave oven for 10 minutes at 600 W. The dried specimens were tested at 2- and 4-hour intervals in diametral compression at a crosshead speed of 0. 5 cm/min.
  
  
  RESULTS
  The microwave drying technique resulted in greater diametral tensile strength values for all investment materials.
  
  
  CONCLUSIONS
  Within the limitations of this study, microwave drying of type III dental investment materials at 600 W for 10 minutes was, apart from strengthening the material, timesaving for the dental laboratory.
authors.affiliation: Faculty of Dentistry, Department of Prosthodontics, Hacettepe University, Ankara, Turkey.
authors.forename: S
authors.initials: S
authors.lastname: Canay
authors.forename: N
authors.initials: N
authors.lastname: Hersek
authors.forename: Y
authors.initials: Y
authors.lastname: Ciftçi
authors.forename: K
authors.initials: K
authors.lastname: Akça
mesh_terms: D000704:Analysis of Variance; D002133:Calcium Sulfate; D019245:Compressive Strength; D003734:Dental Casting Investment / Q000737:chemistry; D003779:Denture Design / Q000295:instrumentation*; D003890:Desiccation / Q000295:instrumentation*; D008422:Materials Testing; D008872:Microwaves; D013718:Tensile Strength
chemical_list: D003734:Dental Casting Investment; D002133:Calcium Sulfate