title: Long-term dimensional stability and reproduction of surface detail of four polyvinyl siloxane duplicating materials.
abstract: OBJECTIVE
  Duplicating materials must routinely accurately reproduce the details of dental casts and thus contribute significantly to the close adaptation and success of a removable prosthesis or fixed indirect restoration. It is important to establish the long-term dimensional stability of polyvinyl siloxane materials (PVS) as they are widely used in dental technology and over the duration of a course of treatment, are stored under dental laboratory conditions. The dimensional stability of four PVS duplicating materials was investigated over a 13-week period.
  
  
  METHODS
  Forty PVS duplicate moulds of a partially dentate maxillary arch were produced from four materials (Elite double 8, Gemini transparent, C & J pourable silicone and Z Dupe). Three dimensions were measured in triplicate at baseline 1, 5, 9 and 13 weeks using computerised image analysis. Half of the specimens were measured following storage at room temperature (21+/-2 degrees C) and half at 37 degrees C to represent storage in hot climates. Specimens for scanning electron microscopy were prepared by duplicating a rugosity standard.
  
  
  RESULTS
  At room temperature two materials Elite Double 8 and Z Dupe showed no statistically significant dimensional change, the other two materials showed a slight increase of dimensions. Specimens stored at 37 degrees C showed greater differences in dimensions with Z Dupe showing statistically significant shrinkage. SEM investigation showed no surface deterioration of two materials.
  
  
  CONCLUSIONS
  None of the materials showed a change in dimension greater than 2% and the four PVS materials showed good dimensional stability over the time period of the study.
authors.affiliation: King's College, London Dental Institute, Department of Prosthodontics, London, United Kingdom.
authors.forename: Ravi
authors.initials: R
authors.lastname: Pant
authors.forename: Andrzej S
authors.initials: AS
authors.lastname: Juszczyk
authors.forename: Robert K F
authors.initials: RK
authors.lastname: Clark
authors.forename: David R
authors.initials: DR
authors.lastname: Radford
mesh_terms: D000704:Analysis of Variance; D003760:Dental Impression Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D006244:Hardness; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D003765:Models, Dental; D011145:Polyvinyls / Q000737:chemistry*; D015203:Reproducibility of Results; D012833:Siloxanes / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane