title: Randomized controlled clinical trial on the three-dimensional accuracy of fast-set impression materials.
abstract: OBJECTIVE
  The use of fast-setting impression materials with different viscosities for the one-stage impression technique demands precise working times when mixing. We examined the effect of varying working time on impression precision in a randomized clinical trial.
  
  
  METHODS
  Focusing on tooth 46, three impressions were made from each of 96 volunteers, using either a polyether (PE: Impregum Penta H/L DuoSoft Quick, 3 M ESPE) or an addition-curing silicone (AS: Aquasil Ultra LV, Dentsply/DeTrey), one with the manufacturer's recommended working time (used as a reference) and two with altered working times. All stages of the impression-taking were subject to randomization. The three-dimensional precision of the non-standard working time impressions was digitally analyzed compared to the reference impression. Statistical analysis was performed using multivariate models.
  
  
  RESULTS
  The mean difference in the position of the lower right first molar (vs. the reference impression) ranged from ±12 μm for PE to +19 and -14 μm for AS. Significantly higher mean values (+62 to -40 μm) were found for AS compared to PE (+21 to -26 μm) in the area of the distal adjacent tooth.
  
  
  CONCLUSIONS
  Fast-set impression materials offer high precision when used for single tooth restorations as part of a one-stage impression technique, even when the working time (mixing plus application of the light- and heavy-body components) diverges significantly from the manufacturer's recommended protocol.
  
  
  CONCLUSIONS
  Best accuracy was achieved with machine-mixed heavy-body/light-body polyether. Both materials examined met the clinical requirements regarding precision when the teeth were completely syringed with light material.
authors.affiliation: Department of Prosthetic Dentistry, Center of Dentistry, Ulm University, Albert-Einstein-Allee 11, Ulm, Germany. heike.rudolph@uniklinik-ulm.de
authors.forename: Heike
authors.initials: H
authors.lastname: Rudolph
authors.forename: Sebastian
authors.initials: S
authors.lastname: Quaas
authors.forename: Manuela
authors.initials: M
authors.lastname: Haim
authors.forename: Jörg
authors.initials: J
authors.lastname: Preißler
authors.forename: Michael H
authors.initials: MH
authors.lastname: Walter
authors.forename: Rainer
authors.initials: R
authors.lastname: Koch
authors.forename: Ralph G
authors.initials: RG
authors.lastname: Luthardt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003760:Dental Impression Materials; D003761:Dental Impression Technique / Q000295:instrumentation; D061827:Dimensional Measurement Accuracy; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008334:Mandible; D008422:Materials Testing; D008875:Middle Aged; D003765:Models, Dental; D015233:Models, Statistical; D008963:Molar; D009716:Numerical Analysis, Computer-Assisted; D011145:Polyvinyls; D011446:Prospective Studies; D012117:Resins, Synthetic; D012833:Siloxanes; D018709:Statistics, Nonparametric; D013997:Time Factors; D014783:Viscosity; D055815:Young Adult
chemical_list: D003760:Dental Impression Materials; C022821:Impregum; D011145:Polyvinyls; D012117:Resins, Synthetic; D012833:Siloxanes; C480691:aquasil