Chan D, Guillory V, Blackman R, Chung K H
Department of Restorative Dentistry, Dental School, University of Texas, San Antonio, USA.
J Prosthet Dent. 1997 Oct;78(4):400-4. doi: 10.1016/s0022-3913(97)70048-9.
This study measured the effects of the sprue number and position on the roughness and porosity of cast titanium crowns.
Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30-degree bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12 were double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting, according to the manufacturer's instructions, with commercially pure titanium (> 99.5%) ingots. The castings were carefully cleaned and the surface roughness was measured with a profilometer. The specimens were then embedded and sectioned. Internal porosities were quantified with photographs by computerized image analysis. Data were analyzed with an ANOVA and the Student's t test with a confidence level of 95%.
The roughness value of the occlusal third of the crowns for the single sprue group (Ra = 3.0 +/- 0.9 microns) was significantly higher than other measurements (p < 0.05). There were statistically significant differences in values of porosity areas between the single sprue group (1.5 +/- 0.7 mm2) and the double sprue group (0.2 +/- 0.2 mm2) (p < 0.01). The double sprue design resulted in a relatively smoother casting surface and less internal porosity than the single sprue design.
Improvements in the degree of roughness and porosity of titanium crown castings were the result of the double sprue design.
本研究测量了铸道数量和位置对铸造钛冠粗糙度和孔隙率的影响。
在带有30度斜面终熔线的不锈钢代型上制作24个全冠蜡型。12个蜡型用一根8号蜡铸道进行浇铸，其余12个蜡型采用双铸道浇铸。所有蜡型均用磷酸盐粘结包埋料包埋。根据制造商的说明，使用商业纯钛（>99.5%）铸锭进行钛铸造。铸件经过仔细清洁，并用轮廓仪测量表面粗糙度。然后将标本包埋并切片。通过计算机图像分析对内部孔隙率进行量化。数据采用方差分析和置信水平为95%的学生t检验进行分析。
单铸道组冠的咬合面三分之一处的粗糙度值（Ra = 3.0 +/- 0.9微米）显著高于其他测量值（p < 0.05）。单铸道组（1.5 +/- 0.7平方毫米）和双铸道组（0.2 +/- 0.2平方毫米）之间的孔隙面积值存在统计学显著差异（p < 0.01）。与单铸道设计相比，双铸道设计使铸件表面相对更光滑，内部孔隙率更低。
钛冠铸件粗糙度和孔隙率程度的改善是双铸道设计的结果。
