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  • Title: Effect of frequency and amplitude of vibration and role of a surfactant on void formation in models poured from polyvinyl siloxane impressions.
    Author: Reddy NK, Aparna I.
    Journal: J Conserv Dent; 2011 Apr; 14(2):151-5. PubMed ID: 21814356.
    Abstract:
    AIMS: 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. MATERIALS AND 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.
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