Department of Oral Special Consultation, The Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, PR China; State Key Laboratory Cultivation Base of Research, Prevention and Treatment for Oral Diseases (Nanjing Medical University), Nanjing, PR China; Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, PR China.
Department of Oral Special Consultation, The Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, PR China; State Key Laboratory Cultivation Base of Research, Prevention and Treatment for Oral Diseases (Nanjing Medical University), Nanjing, PR China; Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, PR China.
J Mech Behav Biomed Mater. 2024 Jun;154:106539. doi: 10.1016/j.jmbbm.2024.106539. Epub 2024 Apr 8.
Polyetheretherketone (PEEK) is considered as an alternative to metal material for removable partial denture (RPD). However, the retentive force is not strong as a metal RPD. This study investigated the retention and fatigue performance of PEEK clasps with different proportions of clasp arm engaging the undercut to verify a new strategy to improve their clinical performance.
Three groups (n = 10/group) of PEEK clasps with their terminal 1/3, 2/3 and the whole of retentive arms engaging the undercut were fabricated along with a group (n = 10) of conventional cobalt-chrome (CoCr) clasps as control group. Retentive forces were measured by universal testing machine initially and at an interval of 1500 cycles for a total of 15,000 fatigue cycles. The fatigue cycles were conducted by repeated insertion and removal of the clasp using fatigue testing machine. Each clasp was scanned by Trios3 scanner before and after fatigue test to obtain digital models. The deformation of the clasp was evaluated by root mean square (RMS) through aligning the two models in Geomagic wrap (2021). Scanning electron microscopy (SEM) and finite element analysis were carried out to observe the abrasion and the von Mises stress of the clasp arm. Kruskal-Wallis H test was used to compare the retentive forces and the RMSs of the studied groups followed by Bonferroni multiple comparisons.
The whole of PEEK clasp arm engaging the undercut provided higher mean retentive forces (7.99 ± 2.02 N) than other PEEK clasp groups (P < 0.001) and was closer to CoCr clasps (11.88 ± 2.05 N). The RMSs of PEEK clasps were lower than CoCr clasps (P < 0.05) while the differences among PEEK clasps were of no statistical significance (P > 0.05). SEM showed that evidences of surface abrasion were observed on the section that engaged the undercut for all groups of clasps. The stress concentration mainly occurred on the initial part of the retentive arm. The maximum von Mises stress of each group was below the compressive strength of PEEK.
Proportions of PEEK clasp arm engaging the undercut positively influenced the retentive force and the fatigue resistance of PEEK clasps was superior than CoCr clasps. It is a feasible method to improve the retention of PEEK clasps by increasing the proportion of clasp arm engaging the undercut. Clinical trials are needed to further verify this innovation.
聚醚醚酮（PEEK）被认为是可摘局部义齿（RPD）金属材料的替代品。然而，其固位力不如金属 RPD 强。本研究通过调查不同比例的卡环臂与基牙殆面下间隙（under-cut）接触的 PEEK 卡环的固位力和疲劳性能，验证一种提高其临床性能的新策略。
制作三组（每组 n=10）的 PEEK 卡环，其卡环臂的终端 1/3、2/3 和整个卡环臂与殆面下间隙接触，以及一组（n=10）传统钴铬（CoCr）卡环作为对照组。使用万能试验机测量初始和 1500 次循环（共 15000 次疲劳循环）间隔的固位力。通过疲劳试验机反复插入和取出卡环进行疲劳循环。在疲劳试验前后，使用 Trio3 扫描仪对每个卡环进行扫描，以获得数字模型。通过在 Geomagic wrap（2021）中对齐两个模型，使用均方根（RMS）评估卡环的变形。进行扫描电子显微镜（SEM）和有限元分析以观察卡环臂的磨损和 von Mises 应力。使用 Kruskal-Wallis H 检验比较研究组的固位力和 RMS，然后进行 Bonferroni 多重比较。
与其他 PEEK 卡环组相比（P<0.001），整组 PEEK 卡环臂与殆面下间隙接触提供了更高的平均固位力（7.99±2.02 N），并且更接近 CoCr 卡环（11.88±2.05 N）。PEEK 卡环的 RMS 低于 CoCr 卡环（P<0.05），而 PEEK 卡环之间的差异无统计学意义（P>0.05）。SEM 显示，所有卡环组的殆面下接触部位均出现表面磨损的迹象。应力集中主要发生在卡环臂的初始部分。每组的最大 von Mises 应力均低于 PEEK 的抗压强度。
PEEK 卡环臂与殆面下间隙的接触比例对 PEEK 卡环的固位力有积极影响，PEEK 卡环的疲劳性能优于 CoCr 卡环。通过增加卡环臂与殆面下间隙的接触比例来提高 PEEK 卡环的固位力是一种可行的方法。需要进行临床试验进一步验证这一创新。
