饰瓷厚度和冷却速度对磨牙锆瓷冠残余应力的影响

Effects of veneering porcelain thickness and cooling rate on the residual stress in zirconia molar crowns

目的:观察饰瓷厚度和不同冷却速度对磨牙锆瓷冠残余应力的影响。方法:将6个下颌磨牙氧化锆单冠按牙尖饰瓷厚度分为1 mm组、2 mm组和3 mm组各2个,每组分别取1个采用快速冷却法,另1个采用慢速冷却法烧结上釉;然后用维氏压痕技术对每个牙冠的4个牙尖(每个尖取5个点)进行测试,并根据压痕裂缝长度计算出表面的残余应力。结果:快速冷却法试件表面的残余应力主要是压力,慢速冷却法试件表面的残余主要是张力;快速冷却法1 mm组的残余应力明显高于2 mm和3 mm组(P<0.05),但2 mm组与3 mm组残余应力无统计学差异(P>0.05);慢速冷却法不同瓷厚度各组间两两相比均无统计学差异(P>0.05);快速与慢速冷却法相比,不同瓷厚度各组间均有统计学差异(P<0.05)。结论:冷却速度、饰瓷厚度对锆瓷冠的残余应力均有明显影响。

AIM： To investigate the effects of veneering porcelain thickness and cooling rate on the residual stress in zirconia molar crowns. METHODS： 6 veneered zirconia copings were divided into 3 groups based on veneering porcelain thickness （ 1 mm, 2 mm and 3 mm, n = 2） of flattened cusp heights . Half of the samples were fast cooled during final glazing, the other half were slowly cooled. Vickers indentation technique was used to determine surface residual stress. Data were statistically analysed. RESULTS： Compressive stress was recorded in fast cooling groups, while tensile stress was recorded in slow cooling groups. The highest residual compressive stress was recorded on the fast cooled 1 mm cusps, which was significantly higher than that on the 2 and 3 mm crowns （P 〈 0.05）. There was a linear trend for residual stress to decrease with veneering porcelain thickness increase in the fast cooled group （P 〈 0.05 ）. No significant difference was found between the various cusp heights after slow cooling （ P 〉 0.05 ）. CONCLUSION： Cooling rate, decorative porcelain thickness have important influence on residual stress.