Department of Prosthodontics, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, Fujian, China.
J Prosthet Dent. 2010 Dec;104(6):389-96. doi: 10.1016/S0022-3913(10)60173-4.
Cast cobalt-chromium (Co-Cr) alloy clasps have been widely used for prosthodontic treatment, but long-term retentiveness of these clasps is not clear.
The purpose of this study was to investigate the residual retentive force of 3 types of cast Co-Cr alloy clasps in relation to their proportional limits.
Thirty half-round straight clasps and 30 circumferential clasp assemblies were made from 3 Co-Cr alloys (Hardalloy, Regalloy, and Vera PDN) (n=10). All of the straight clasps were subjected to a compression-deformation test to obtain data for displacement/load at the proportional limit. Two undercut depths (0.25 mm and 0.50 mm, n=5) were included in a cyclic fatigue test. Each circumferential clasp assembly was subjected to an insertion/removal test on a metal abutment tooth for 7200 cycles to simulate 5 years of clinical use. The residual retentive force was measured after 360 cycles; thus, the retentive force of each clasp was recorded 21 times throughout the test. The data were subjected to repeated-measures ANOVA (α=.05) to compare the retentive force of each group of clasps for different periods of fatigue testing. The ANOVA. The Student t test (α=.05) was used for analysis of clasps fabricated with the same alloy but with different undercuts. A linear correlation analysis (α=.05) was used to test the correlation between retentive forces and cycling sequences.
The mean values of displacement at the proportional limit for the 3 Co-Cr alloys varied from 0.30 mm to 0.36 mm. The mean retentive forces of each alloy group decreased dramatically after the first cycling phase (P<.05). Thereafter, the decrease was more gradual but was still significantly different compared to the original retentive forces (P<.05). Compared to clasps in the 0.25-mm undercut group, those in the 0.50-mm undercut group exhibited greater mean retentive forces before the cyclic fatigue test (P<.05), as well as a greater decrease in the retentive force at the end of the test (P<.05).
A negative correlation was found between the retentive force of cast Co-Cr alloy clasps and the logarithm of cycling sequences. After a test simulating 5 years of service, cast Co-Cr alloy clasps exhibited a residual retentive force to satisfy the requirements for clinical use.
铸造钴铬（Co-Cr）合金卡环已广泛用于修复治疗，但长期保留效果尚不清楚。
本研究旨在探讨 3 种铸造 Co-Cr 合金卡环的剩余固位力与其比例极限之间的关系。
采用 3 种 Co-Cr 合金（Hardalloy、Regalloy 和 Vera PDN）（n=10）制作 30 个半圆直卡环和 30 个环形卡环组件。所有直卡环均进行压缩变形试验，以获得比例极限下的位移/载荷数据。循环疲劳试验包括 2 种不同的（0.25mm 和 0.50mm，n=5）的倒扣深度。将每个环形卡环组件在金属基牙上进行插入/移除试验 7200 次，以模拟 5 年的临床使用。经过 360 次循环后测量剩余固位力，因此在整个试验过程中，每个卡环的固位力记录了 21 次。采用重复测量方差分析（α=.05）比较不同疲劳试验阶段每组卡环的固位力。采用学生 t 检验（α=.05）分析采用相同合金但具有不同倒扣深度的卡环。采用线性相关分析（α=.05）检验固位力与循环序列之间的相关性。
3 种 Co-Cr 合金的比例极限下的平均位移值为 0.30mm 至 0.36mm。每个合金组的平均固位力在第一次循环阶段后急剧下降（P<.05）。此后，下降趋势较为平缓，但与原始固位力仍有显著差异（P<.05）。与 0.25mm 倒扣组的卡环相比，0.50mm 倒扣组的卡环在循环疲劳试验前表现出更大的平均固位力（P<.05），试验结束时固位力的下降也更大（P<.05）。
铸造 Co-Cr 合金卡环的固位力与循环序列的对数呈负相关。经过模拟 5 年使用的测试后，铸造 Co-Cr 合金卡环仍具有残余固位力，满足临床使用要求。
