Abdullah M A
College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia.
J Prosthet Dent. 1998 Oct;80(4):490-4. doi: 10.1016/s0022-3913(98)70017-4.
Numerous factors are involved in making a void-free dental stone cast from a polyvinyl siloxane impression.
The aim of this study was to determine whether frequency and amplitude of vibration had any effect on the formation of voids on the cast surface poured from polyvinyl siloxane impression with a mechanical model vibrator.
Impressions were poured in dental stone with a mechanical model vibrator that was set at vibration frequency 3000 cycles/min (low) and 6000 cycles/min (high) by a knob. The amplitude of vibration is provided in 5 steps and remained constant for the step set on the instrument. A total of 240 casts were prepared. The vibrator was set at low frequency and 30 impressions were poured for each of the 5 steps of amplitude. The vibrator was then set at high frequency and 30 impressions were poured for each of the 5 steps of amplitude. The resultant casts were examined for the presence of surface voids under 10 x magnification.
Means for voids in all cast groups calculated for low and high vibration frequencies indicated that an increase in the amplitude of vibration caused an increase in the number of voids on the die surface.
Use of high frequency of vibration 6000 cycles/min and 0.40 mm amplitude produced significantly fewer voids (P < .0001) compared with steps 4 (0.45 mm) and 5 (0.80 mm) amplitude.
使用聚乙烯基硅氧烷印模制作无气泡牙科石膏模型涉及众多因素。
本研究的目的是通过机械模型振动器，确定振动频率和振幅对从聚乙烯基硅氧烷印模灌注的模型表面气泡形成是否有任何影响。
使用机械模型振动器将牙科石膏灌注到印模中，该振动器通过旋钮设置为振动频率3000次/分钟（低）和6000次/分钟（高）。振动幅度分5个步骤设置，且在仪器上设置的步骤中保持恒定。共制备了240个模型。将振动器设置为低频，对每个振幅的5个步骤分别灌注30个印模。然后将振动器设置为高频，对每个振幅的5个步骤分别灌注30个印模。将所得模型在10倍放大倍数下检查表面气泡的存在情况。
计算得出的低振动频率和高振动频率下所有模型组气泡的平均值表明，振动幅度的增加会导致模型表面气泡数量增加。
与振幅为4（0.45毫米）和5（0.80毫米）的步骤相比，使用6000次/分钟的高振动频率和0.40毫米的振幅产生的气泡明显更少（P < .0001）。
