Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, SP, Brazil.
J Appl Oral Sci. 2010 Sep-Oct;18(5):487-92. doi: 10.1590/s1678-77572010000500010.
The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior.
This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure.
72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05).
Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted.
Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.
使用钛制造可摘局部义齿（RPD）支架的兴趣日益增加，但评估铸造方法对卡环行为影响的研究较少。
本研究比较了感应/离心铸造和等离子/真空压力铸造法对商用纯钛（CP Ti）和钴铬（Co-Cr）可摘局部义齿环形卡环的孔隙率和固位力的影响。
从 CP Ti（n=36）和 Co-Cr 合金（n=36；对照组）中铸造 72 个支架。对于每种材料，18 个支架由电磁感应铸造，离心注射，而另外 18 个支架由等离子体和真空压力铸造。对于每种铸造方法，形成三个亚组（n=6）：0.25mm、0.50mm 和 0.75mm 下切。对试件进行射线照相，并进行模拟 5 年支架使用的插入/取出试验。采用方差分析和 Tukey 检验对材料和铸造方法进行比较（α=0.05）。
感应/离心铸造组的 18 个试件中有 3 个和等离子/真空压力铸造组的 18 个试件中有 9 个出现孔隙，但只有 1 个和 7 个试件分别因模拟试验而被拒绝。对于 Co-Cr 合金，未发现缺陷。比较铸造方法，仅在 Co-Cr 合金 0.25mm 和 0.50mm 下切时观察到统计学差异（p<0.05）。对于 0.25mm 和 0.75mm 下切，取决于所用材料，观察到显著差异。对于 0.50mm 下切，当材料感应铸造时，观察到显著差异。
虽然两种铸造方法都能生产出令人满意的 CP Ti RPD 支架，但等离子/真空压力铸造法的孔隙发生率高于感应/离心铸造法，后者使卡环刚性更高，产生更高的固位力值。
