Objective

Telescopic crowns are suitable components of partial dentures to efficiently anchor dental supra-structures to teeth or dental implants and achieve high chewing performance and wear comfort.

Usually alloy- or metal-based structures are used for the primary and the secondary crowns. The advantage is the possibility to produce precise structures with a high perfection and sufficient friction force, but the disadvantage is the corrosion instability. The recent introduction of zirconia ceramics has enabled the fabrication of ceramic primary crowns, thus reducing corrodibility.

The novel application of the high-performance polymer polyetheretherketone (PEEK) as another metal-free alternative material offers a new perspective for such applications.

Therefore, the aim of this work was to assess the performance of telescopic crowns of PEEK by comparing telescopic crowns based on the combination of PEEK (prim. crown) + PEEK (sec. crown) with the pairings ZrO₂ (prim. crown) + PEEK (sec. crown) and CoCr-alloy (prim. crown) + PEEK (sec. crown).

Methods

All specimens were CAD/CAM planned and manufactured based on a model of a tooth 26. One master dental technician performed the post-treatment. For each group of material pairing, n = 9 telescopic crown pairs were manufactured and tested. Herein not only the maximum retention force was measured but also the retention force vs. pull-off distance were analyzed. As there is no commonly accepted test protocol available, the influence of various pull off speeds were tested as well. All measurements were first made with three blocks of three crowns (3C), subsequently with three blocks of two crowns (2C) and finally with nine single crowns (1C). The long-term behavior was estimated by performing 10.000 cycles, which is related to a life-time of more than 10 years.

Results

The maximum retention force in case of PEEK + PEEK was higher in comparison to the other tested material pairings. In the range between 1 and 10 mm/ min pull off speed there was no significant influence by the pull off speed. More influence on the friction force would be expected by changes of the number of the crowns acting simultaneously. The friction force was decreasing with decreasing number of crowns but not linearly in any tested case. The long-term test has shown that the friction force remained constant.

Significance

The performance of PEEK + PEEK telescopes is comparable with the usually applied material pairings. Over long time no loss in retention force could be observed. The retention force - distance progression in the PEEK + PEEK pairing offers more security against a possible loss of retention during repair or relining. For further tests of the performance of telescopic crowns or to estimate of friction force limits, a setup with at least two, but preferably three, crowns tested in parallel is suggested.

中文翻译：

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基于 PEEK 的伸缩冠的性能比较研究

客观的

伸缩冠是局部义齿的合适组件，可有效地将牙科超结构固定到牙齿或牙种植体上，并实现高咀嚼性能和佩戴舒适度。

通常合金或金属基结构用于初级和次级牙冠。优点是可以制造出具有高完美度和足够摩擦力的精密结构，但缺点是腐蚀不稳定性。最近引入的氧化锆陶瓷使陶瓷初级冠的制造成为可能，从而降低了腐蚀性。

高性能聚合物聚醚醚酮 (PEEK) 作为另一种无金属替代材料的新应用为此类应用提供了新的视角。

因此，这项工作的目的是通过比较基于 PEEK（原始牙冠）+ PEEK（第二牙冠）与配对 ZrO ₂（原始牙冠）+的伸缩冠来评估 PEEK 伸缩冠的性能。 PEEK（第二冠）和钴铬合金（原始冠）+ PEEK（第二冠）。

方法

所有样本都是基于牙齿模型 26 的 CAD/CAM 计划和制造的。一位主要的牙科技师进行了后处理。对于每组材料配对，制造和测试了 n = 9 个伸缩式牙冠对。在此不仅测量了最大保持力，而且还分析了保持力与拉断距离的关系。由于没有普遍接受的测试协议可用，因此还测试了各种拉断速度的影响。所有测量均首先使用三组三个牙冠 (3C)，随后使用三组两个牙冠 (2C)，最后使用九个单牙冠 (1C)。长期行为是通过执行 10.000 次循环来估计的，这与超过 10 年的使用寿命有关。

结果

与其他测试材料配对相比，PEEK + PEEK 的最大保持力更高。在 1 到 10 毫米/分钟的拉脱速度范围内，拉脱速度没有显着影响。预计同时作用的冠部数量的变化会对摩擦力产生更大的影响。摩擦力随着冠部数量的减少而降低，但在任何测试情况下都不是线性的。长期测试表明摩擦力保持恒定。

意义

PEEK + PEEK 望远镜的性能与通常应用的材料配对相当。在很长一段时间内没有观察到保持力的损失。PEEK + PEEK 配对中的保持力 - 距离进展提供了更多的安全性，防止在维修或换衬期间可能出现的保持力损失。为了进一步测试伸缩式牙冠的性能或估计摩擦力极限，建议使用至少两个，但最好是三个牙冠并行测试的设置。