title: Moisture effect on polyether and polyvinylsiloxane dimensional accuracy and detail reproduction.
abstract: OBJECTIVE
  This investigation evaluated and compared the dimensional accuracy and surface detail reproduction of two hydrophilic polyvinylsiloxane (PVS) and two polyether (PE) impression materials when used under dry and moist conditions.
  
  
  METHODS
  Impressions were made of stainless steel dies as described in ANSI/ADA specification no. 19, with two vertical and three horizontal lines inscribed on the die superior surface. Impressions were made under dry and moist conditions (17 impressions per condition for each material). Dimensional accuracy was measured by comparing the average length of the middle horizontal line in each impression with the same line on the metal die using a measuring microscope with an accuracy of 0.001 mm. Surface detail reproduction was evaluated by using criteria similar to ADA specification no. 19: continuous replication of at least two of the three horizontal lines.
  
  
  RESULTS
  The mean percent dimensional change and SD values ranged from -0.135% (0.035) to 0.053% (0.031). A two-way analysis of variance (ANOVA) indicated that moisture did not cause significant adverse effects on the dimensional accuracy of any material (p > 0.05); however, significant differences were found between the materials (p < .05). The surface detail evaluation indicated that moisture had a significant effect on detail reproduction of PVS materials (Pearson's Chi square, p < 0.05). Under dry conditions, all materials produced satisfactory detail reproduction 100% of the time; however, under moist conditions, only 29% of Aquasil and Genie Ultra PVS impressions produced satisfactory detail reproduction, while 100% of Permadyne Garant and Impregum Penta Soft PE impressions still met the surface detail criteria.
  
  
  CONCLUSIONS
  Although moisture may not adversely affect the dimensional accuracy of either PE or hydrophilic PVS material, the evidence suggests that PE material is more likely to produce impressions with superior detail reproduction in the presence of moisture.
authors.affiliation: Department of Restorative Dentistry, University of Missouri-Kansas City School of Dentistry, MO 64108, USA. walkermp@umkc.edu
authors.forename: Mary P
authors.initials: MP
authors.lastname: Walker
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Petrie
authors.forename: Reem
authors.initials: R
authors.lastname: Haj-Ali
authors.forename: Paulette
authors.initials: P
authors.lastname: Spencer
authors.forename: Chris
authors.initials: C
authors.lastname: Dumas
authors.forename: Karen
authors.initials: K
authors.lastname: Williams
mesh_terms: D000704:Analysis of Variance; D016009:Chi-Square Distribution; D003760:Dental Impression Materials / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D015203:Reproducibility of Results; D012117:Resins, Synthetic / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D014867:Water; D017155:Wettability
chemical_list: D003760:Dental Impression Materials; D004987:Ethers; C022821:Impregum; D008768:Methylmethacrylates; C495447:Permadyne; D011145:Polyvinyls; D012117:Resins, Synthetic; D012833:Siloxanes; C480691:aquasil; C034183:vinyl polysiloxane; D014867:Water; C029919:Genie