Yoshizawa Mizuma, Takaba Masayuki, Osawa Takahito, Iwasa Fuminori, Baba Kazuyoshi
Department of Prosthodontics, Graduate School of Dentistry, Showa University, Tokyo, JPN.
Division of Fixed Prosthodontics, Department of Restorative and Biomaterials Sciences, Meikai University School of Dentistry, Saitama, JPN.
Cureus. 2024 Dec 14;16(12):e75705. doi: 10.7759/cureus.75705. eCollection 2024 Dec.
This study aims to evaluate the effects of taper angle and the number of insertion-removal cycles on the retention force of 4 mol% yttria partially stabilized zirconia (4Y-PSZ) double crowns over time.
Primary and secondary crowns were fabricated using 4Y-PSZ with taper angles of 2°, 4°, and 6° (n=15). Retention force during crown removal was measured after applying 50-N and 100-N loads. Insertion-removal cycles were performed at 0, 2500, 5000, 7500, and 10,000 cycles, and retention force was assessed at each stage. Contact conditions between the inner and outer crowns were evaluated via color mapping at 0 and 10,000 cycles. Two-way ANOVA was used for statistical analysis, followed by Tukey's test for multiple comparisons.
Retention force significantly decreased with smaller taper angles and higher cycle numbers (p<0.01). For a taper angle of 4°, the initial retention force of 10.36 N decreased significantly to 5.98 N after 10,000 cycles (p<0.01). For a taper angle of 6°, the initial retention force of 1.64 N dropped to 0.03 N after 10,000 cycles. Color mapping revealed continuous contact along the axial surface, with strong point contacts, particularly in the central axial region. Smaller taper angles exhibited stronger contact points, which decreased with repeated cycles, indicating changes in contact conditions.
Higher retentive forces were achieved with increased loading pressures and smaller taper angles, while repeated insertion-removal cycles led to a progressive reduction in retention. These findings provide foundational data supporting the clinical application of 4Y-PSZ double crowns.
本研究旨在评估锥角和插入-取出循环次数对4 mol%氧化钇部分稳定氧化锆（4Y-PSZ）双冠随时间变化的固位力的影响。
使用锥角为2°、4°和6°的4Y-PSZ制作初冠和次冠（n = 15）。在施加50 N和100 N载荷后测量冠取出过程中的固位力。在0、2500、5000、7500和10000次循环时进行插入-取出循环，并在每个阶段评估固位力。通过在0和10000次循环时的颜色映射评估内冠和外冠之间的接触情况。采用双向方差分析进行统计分析，随后进行Tukey多重比较检验。
固位力随着锥角减小和循环次数增加而显著降低（p<0.01）。对于4°的锥角，初始固位力为10.36 N，在10000次循环后显著降至5.98 N（p<0.01）。对于6°的锥角，初始固位力为1.64 N，在10000次循环后降至0.03 N。颜色映射显示沿轴向表面连续接触，有强烈的点接触，特别是在中央轴向区域。较小的锥角表现出更强的接触点，随着循环次数的增加而减少，表明接触情况发生了变化。
增加加载压力和减小锥角可获得更高的固位力，而反复的插入-取出循环导致固位力逐渐降低。这些发现为4Y-PSZ双冠的临床应用提供了基础数据。
