title: A comparative evaluation of tray spacer thickness and repeat pour on the accuracy of monophasic polyvinyl siloxane impression material: in vitro study.
abstract: OBJECTIVE
  This study was aimed to determine the effect of various tray spacer thickness and subsequent repeated pours on the accuracy and dimensional stability of the impression made from monophasic polyvinyl siloxane material.
  
  
  METHODS
  Custom trays with different spacer thickness (2, 4 and 6 mm) were used for making an impression of a master model simulating 3 unit fixed partial denture with monophasic polyvinyl siloxane material. These impressions were poured with die stone and repoured. Distance between the reference points were measured and subjected to statistical analysis.
  
  
  RESULTS
  Casts obtained from 1 st , 2 nd and 3 rd pour of the impression in 2, 4 and 6 mm spacer thickness tray have similar dimensional accuracy amongst each other and with the master model except in molar diameter and inter-abutment distances of cast obtained from 6 mm spacer thickness tray.
  
  
  CONCLUSIONS
  The vertical distance of stone dies were decreased, whereas horizontal distance increased as the thickness of impression material is increased. There were statistically non-significant changes occurring among the repeated pours in 2, 4 and 6 mm spacer thickness.
  
  
  CONCLUSIONS
  2 and 4 mm spacer thickness are acceptable for making an impression for three unit fixed partial denture with monophasic polyvinyl siloxane material and it was not affected by two subsequent (1 st and 2 nd) repeated pours.
authors.affiliation: Department of Prosthodontics, Jan Nayak Ch. Devi Lal Dental College, Sirsa, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kumar
authors.forename: Deepti
authors.initials: D
authors.lastname: Yadav
authors.forename: Reena
authors.initials: R
authors.lastname: Yadav
authors.forename: Aman
authors.initials: A
authors.lastname: Arora
mesh_terms: D003760:Dental Impression Materials; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D011145:Polyvinyls; D012833:Siloxanes
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane