title: Pressure generated on a simulated mandibular oral analog by impression materials in custom trays of different design.
abstract: OBJECTIVE
  The purpose was to measure the pressure exerted under a simulated mandibular edentulous impression at different locations using commonly used impression materials and four impression tray configurations.
  
  
  METHODS
  This study was performed using an oral analog that simulated an edentulous mandibular arch. Three pressure transducers were embedded in the oral analog-one pressure transducer in the anterior ridge area, and the other two in the right and left buccal shelves. Four configurations of custom trays were fabricated: trays with no relief, with and without holes; and trays with relief, with and without holes. The impression materials tested were light body polysulfide, light body vinyl polysiloxane, medium body vinyl polysiloxane, and irreversible hydrocolloid. The custom tray and the oral analog were mounted using a reline jig, and a Satec universal testing machine was used to apply a constant pressure of 1 kg/cm(2) over a period of 5 minutes on the loaded custom tray. Eighty impressions for the 16 groups (n = 5) were made, and pressures were recorded every 10 seconds. Factorial ANOVA and Tukey Multiple Comparison Test were used to analyze the results (p < 0.05).
  
  
  RESULTS
  A significant difference was found in the pressure produced using different impression materials. Irreversible hydrocolloid and medium body vinyl polysiloxane produced significantly higher pressure than light body polysulfide and light body vinyl polysiloxane impression materials. The presence of holes and/or relief significantly altered the magnitude of pressure produced by irreversible hydrocolloid and medium body vinyl polysiloxane but not light body polysulfide and light body vinyl polysiloxane.
  
  
  CONCLUSIONS
  All impression materials produced pressure during simulated mandibular edentulous impression making. For making mandibular edentulous impressions, low-viscosity impression materials-light body polysulfide and light body vinyl polysiloxane-are recommended. Tray modification was not important in changing the amount of pressure produced for the low-viscosity impression materials.
authors.affiliation: Department of Endodontics, Prosthodontics, and Operative Dentistry, Baltimore College of Dental Surgery, University of Maryland, MD 21201, USA.
authors.forename: Adel
authors.initials: A
authors.lastname: Al-Ahmad
authors.forename: Radi
authors.initials: R
authors.lastname: Masri
authors.forename: Carl F
authors.initials: CF
authors.lastname: Driscoll
authors.forename: Joseph
authors.initials: J
authors.lastname: von Fraunhofer
authors.forename: Elaine
authors.initials: E
authors.lastname: Romberg
mesh_terms: D000704:Analysis of Variance; D003760:Dental Impression Materials / Q000737:chemistry*; D003761:Dental Impression Technique; D006801:Humans; D007575:Jaw, Edentulous; D003765:Models, Dental; D011312:Pressure
chemical_list: D003760:Dental Impression Materials