title: Contact angle of unset elastomeric impression materials.
abstract: BACKGROUND
  Some elastomeric impression materials are hydrophobic, and it is often necessary to take definitive impressions of teeth coated with some saliva. New hydrophilic materials have been developed.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to compare contact angles of water and saliva on 7 unset elastomeric impression materials at 5 time points from the start of mixing.
  
  
  METHODS
  Two traditional polyvinyl siloxane (PVS) (Aquasil, Take 1), 2 modified PVS (Imprint 4, Panasil), a polyether (Impregum), and 2 hybrid (Identium, EXA'lence) materials were compared. Each material was flattened to 2 mm and a 5 μL drop of distilled water or saliva was dropped on the surface at 25 seconds (t0) after the start of mix. Contact angle measurements were made with a digital microscope at initial contact (t0), t1=2 seconds, t2=5 seconds, t3=50% working time, and t4=95% working time. Data were analyzed with a generalized linear mixed model analysis, and individual 1-way ANOVA and Tukey HSD post hoc tests (α=.05).
  
  
  RESULTS
  For water, materials grouped into 3 categories at all time-points: the modified PVS and one hybrid material (Identium) produced the lowest contact angles, the polyether material was intermediate, and the traditional PVS materials and the other hybrid (EXA'lence) produced the highest contact angles. For saliva, Identium, Impregum, and Imprint 4 were in the group with the lowest contact angle at most time points.
  
  
  CONCLUSIONS
  Modified PVS materials and one of the hybrid materials are more hydrophilic than traditional PVS materials when measured with water. Saliva behaves differently than water in contact angle measurement on unset impression material and produces a lower contact angle on polyether based materials.
authors.affiliation: Student, Department of Chemistry, University of Alabama at Birmingham, Birmingham, Ala.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Menees
authors.affiliation: Resident, Department of Biomaterials, University of Alabama at Birmingham School of Dentistry, Clinical and Community Sciences, Birmingham, Ala.
authors.forename: Rashmi
authors.initials: R
authors.lastname: Radhakrishnan
authors.affiliation: Associate Professor, Department of Prosthodontics, University of Alabama at Birmingham School of Dentistry, Restorative Sciences, Birmingham, Ala.
authors.forename: Lance C
authors.initials: LC
authors.lastname: Ramp
authors.affiliation: Professor and Assistant Dean, Clinical Research, Department of Biomaterials, University of Alabama at Birmingham School of Dentistry, Clinical and Community Sciences, Birmingham, Ala.
authors.forename: John O
authors.initials: JO
authors.lastname: Burgess
authors.affiliation: Assistant Professor, Department of Biomaterials, University of Alabama at Birmingham School of Dentistry, Clinical and Community Sciences, Birmingham, Ala. Electronic address: nlawson@uab.edu.
authors.forename: Nathaniel C
authors.initials: NC
authors.lastname: Lawson
mesh_terms: D003760:Dental Impression Materials / Q000737:chemistry*; D003761:Dental Impression Technique; D020724:Elastomers / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D012117:Resins, Synthetic / Q000737:chemistry*; D012463:Saliva / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: D003760:Dental Impression Materials; D020724:Elastomers; D012117:Resins, Synthetic; D014867:Water