title: Effect of frequency and amplitude of vibration and role of a surfactant on void formation in models poured from polyvinyl siloxane impressions.
abstract: OBJECTIVE
  To determine whether the frequency and amplitude of vibration and the use of surfactant has any effect on the formation of voids on the cast surface, poured from a polyvinyl siloxane impression material, using a mechanical model vibrator.
  
  
  METHODS
  A total of 100 impressions of a master die were made using Reprosil, Type 1, Medium Viscosity, Regular body, and Dentsply Caulk. The test group was subdivided into a surfactant and non-surfactant group, 50 impressions each. The impressions were poured in a dental stone with a mechanical model vibrator that was set at a vibration frequency of 3000 cycles / minute (low) and 6000 cycles / minute (high) with the help of a knob. The resultant casts were examined with a Stereomicroscope (LABOMED CZM4) under ×10 magnifications.
  
  
  RESULTS
  For the low and high frequencies, when surfactant and non-surfactant groups were compared, for all the amplitudes and for both the material groups, the surfactant groups resulted in fewer void formations and showed very high statistical significance (P-value = 0.001).
  
  
  CONCLUSIONS
  The lowest mean voids were obtained for high frequency surfactant groups. Reprosil: High frequency amplitude 2 being the most prominent, produced the least mean voids (mean = 23.2000, P = 0.001, very highly significant). In comparison, the surfactant groups produced the least voids for both frequencies.
authors.affiliation: Department of Prosthodontics, Mcods, Manipal, India.
authors.forename: N Kulashekar
authors.initials: NK
authors.lastname: Reddy
authors.forename: In
authors.initials: I
authors.lastname: Aparna