Twiggs S Warren, Mackert J Rodway, Oxford Amalia L, Ergle Janet W, Lockwood Petra E
Oral Rehabilitation/Dental Materials, Medical College of Georgia, School of Dentistry, Augusta, GA 30912-1260, USA.
Dent Mater. 2005 Jun;21(6):580-5. doi: 10.1016/j.dental.2005.01.001. Epub 2005 Apr 18.
The purpose of this investigation was to determine if the change in the leucite weight fraction during an isothermal heat treatment could be estimated by observing the deformation of PFM strips in a high-heating-rate, computer-controlled bending beam viscometer (BBV).
Specimens of a commercial body porcelain were fired according to the manufacturer's instructions-50 disk specimens for quantitative X-ray diffraction (XRD) and 100 bimaterial strip specimens for BBV. The XRD specimens were annealed at temperatures between 650 and 1000 degrees C, and leucite weight fraction was measured using an alumina internal standard. The BBV specimens were annealed in the BBV using time-temperature schedules designed to elucidate the leucite crystallization behavior between 700 and 1000 degrees C. Timoshenko's equation for a bimaterial thermostat was used to estimate the change in the thermal expansion of the porcelain near room temperature. Changes in leucite weight fraction were determined from these thermal expansion changes.
The means and SDs were compared to values obtained by quantitative XRD. Good agreement was obtained between values of leucite weight fraction derived from beam deformation and those determined by quantitative XRD (p> or =0.45). The anneal sequence showed that the increase in leucite weight fraction at 800 or 900 degrees C is reversible by an anneal at 1000 degrees C.
The BBV technique yields comparable results to quantitative XRD and provides the opportunity to efficiently monitor porcelain leucite changes nondestructively over multiple heat treatments. This technique could prove useful for testing firing schedules designed to stabilize the leucite content in dental porcelain.
本研究旨在确定通过在高加热速率、计算机控制的弯曲梁粘度计（BBV）中观察烤瓷熔附金属（PFM）条带的变形，是否能够估算等温热处理过程中白榴石重量分数的变化。
按照制造商的说明烧制一种商用体瓷标本——50个用于定量X射线衍射（XRD）的圆盘标本和100个用于BBV的双材料条带标本。XRD标本在650至1000摄氏度之间的温度下退火，并使用氧化铝内标测量白榴石重量分数。BBV标本在BBV中使用设计用于阐明700至1000摄氏度之间白榴石结晶行为的时间 - 温度时间表进行退火。使用双材料恒温器的铁木辛柯方程来估算接近室温时瓷的热膨胀变化。从这些热膨胀变化中确定白榴石重量分数的变化。
将平均值和标准差与通过定量XRD获得的值进行比较。由梁变形得出的白榴石重量分数值与通过定量XRD确定的值之间取得了良好的一致性（p≥0.45）。退火序列表明，在800或900摄氏度时白榴石重量分数的增加在1000摄氏度退火时是可逆的。
BBV技术产生的结果与定量XRD相当，并提供了在多次热处理过程中无损地有效监测瓷中白榴石变化的机会。该技术可能被证明对测试旨在稳定牙科瓷中白榴石含量的烧制时间表有用。
