Ballard G T, Leinfelder K F, Taylor D F
J Prosthet Dent. 1975 Aug;34(2):170-8. doi: 10.1016/0022-3913(75)90010-4.
Permeability of various gypsum- and phosphate-bonded investments was measured during conventional burn-out procedures. Porosity determinations were made on specimens cooled to room temperature after burn-out. As a group, the gypsum-bonded investments were found to be more permeable than the phosphate-bonded investments. Two phosphate-bonded investments were determined to be relatively impermeable to gas flow, while another exhibited permeability comparable to that of the gypsum-bonded investments. In spite of differences in permeability, the porosity of each type of investment was nearly constant. The porosity of the phosphate-bonded investment was approximately three-fourths that of the gypsum investments. These investments were modified by the addition of varying amounts of acrylic polymer for the purpose of altering permeability. The addition of acrylic polymer increased porosity and permeability of all of the materials included in this investigation. The acrylic additives, however, had no effect on the permeability of relatively impermeable investments unless used in high concentration. The results of this investigation would tend to substantiate the need for special spruing and venting procedures.
在传统的焙烧过程中，测量了各种石膏结合和磷酸盐结合包埋材料的透气性。在焙烧后冷却至室温的试样上进行孔隙率测定。总体而言，发现石膏结合包埋材料比磷酸盐结合包埋材料的透气性更强。两种磷酸盐结合包埋材料被确定为对气流相对不透气，而另一种的透气性与石膏结合包埋材料相当。尽管透气性存在差异，但每种类型包埋材料的孔隙率几乎是恒定的。磷酸盐结合包埋材料的孔隙率约为石膏包埋材料的四分之三。为了改变透气性，通过添加不同量的丙烯酸聚合物对这些包埋材料进行了改性。丙烯酸聚合物的添加增加了本研究中所有材料的孔隙率和透气性。然而，丙烯酸添加剂除非高浓度使用，否则对相对不透气的包埋材料的透气性没有影响。本研究结果倾向于证实特殊的浇铸系统和排气程序的必要性。
