title: The effect of seating velocity on pressure within impressions.
abstract: BACKGROUND
  Oral mucosa can distort under impressions. To reduce or control mucosal distortion, modern impression techniques aim to reduce or control the impression pressure. If changing seating velocity significantly changes pressure, then this effect should be considered for clinical impressions of mucosa.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the relationship between seating velocity and pressure generation during simulated impressions.
  
  
  METHODS
  Vinyl polysiloxane impression material (Express) was placed between 2 approximating discs in a universal testing machine. The velocity at which the discs approximated was varied. The 7 selected seating velocities were 0.75 mm/s, 1 mm/s, 1.25 mm/s, 1.5 mm/s, 2 mm/s, 2.5 mm/s, and 3 mm/s. The pressure generated at the center of the disk was recorded. Five separate recordings were made for each velocity. One-way ANOVA and post hoc tests (Tukey B and Dunnett T3) (alpha=.05) were used to evaluate peak pressure data at each velocity.
  
  
  RESULTS
  The mean (SD) of the recorded pressures for each velocity were 239 (6.67) KPa, 273 (14.89) KPa, 347 (11.97) KPa, 425 (19.73) KPa, 487 (17.84) KPa, 547 (21.25) KPa, and 624 (32.60) KPa, respectively. As the velocity increased, there was a significant (P<.001) concurrent increase in peak pressure.
  
  
  CONCLUSIONS
  In this in vitro experiment, changing the velocity of seating had a significant effect on the peak pressure produced during simulated impressions.
authors.affiliation: Restorative Dentistry, Leeds Dental Institute, University of Leeds, Leeds, United Kingdom. T.P.Hyde@Leeds.ac.uk
authors.forename: T Paul
authors.initials: TP
authors.lastname: Hyde
authors.forename: Helen
authors.initials: H
authors.lastname: Craddock
authors.forename: Paul
authors.initials: P
authors.lastname: Brunton
mesh_terms: D003760:Dental Impression Materials; D003761:Dental Impression Technique; D003799:Dental Stress Analysis; D004548:Elasticity; D009061:Mouth Mucosa; D011145:Polyvinyls; D011312:Pressure; D012212:Rheology; D012833:Siloxanes; D014783:Viscosity
chemical_list: D003760:Dental Impression Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane