Background and aim

Long-term edentulism associated with vertical loss of alveolar bone might lead to increased suprastructure height. This study aimed to evaluate the effect of suprastructure height on the stability of the implant-abutment connection by investigating the stability of two different two-piece titanium implants with internal hexagonal or conical connections under simulated oral loading conditions.

Materials and methods

A total of 48 specimens were used. The specimens were divided into 2 groups according to their implant-abutment connection (group H: internal hex connection, group C: conical connection). Each group was further divided into 3 groups according to the applied suprastructure height (H1; C1: 10 mm, H2; C2: 14 mm and H3; C3: 18 mm) (n = 8). All specimens were subjected to a cyclic loading force of 98 N for 5 million simulated chewing cycles. Then, all implants that survived the chewing simulation were quasi-statically loaded until failure. The monotonic-failure load and monotonic-bending moment at failure were evaluated.

Results

After the dynamic chewing loading, the implants showed the following survival rates: group H: 95.8%; group C: 100%. The implant suprastructures revealed survival rates of 100% and 91.5% for groups H and C, respectively. After the artificial chewing simulation of 5 million cycles, some implants in the groups with higher crowns (14 mm and 18 mm) showed crack formation and plastic deformations under the light microscope. Regarding monotonic-failure load, implants with shorter suprastructures (10 mm) revealed higher resistance to failure (C1: 1496 and H1: 1201 N) than longer suprastructures (18 mm) (C3: 465 and H3: 585 N) which was expected. The mean monotonic-bending moment values at failure ranged from 400.7 Ncm to 673.3 Ncm.

Conclusion

Implant-supported restorations with increased crown height are considered stable for an extended time period (5 million cycles which equals approximately 20 years clinical service) and a reliable treatment option in case of increased inter-arch distance. There was no difference in stability of the two internal connections. Nevertheless, the integrity of implant components might be impaired when crowns with increased heights are applied.

中文翻译：

---

假体冠高和种植体-基台连接设计选择对种植体-基台长期稳定性的影响：一项室内研究

背景和目标

与牙槽骨垂直缺失相关的长期牙龈松动可能导致超结构高度增加。这项研究的目的是通过研究两种不同的两件式钛制植入物的内部六边形或圆锥形连接在模拟的口腔负荷条件下的稳定性，从而评估超结构高度对种植体-基台连接稳定性的影响。

材料和方法

总共使用了48个标本。根据它们的种植体-基台连接将样品分为两组（H组：内六角连接，C组：圆锥形连接）。根据应用的超结构高度将每组进一步分为三组（H1； C1：10 mm； H2； C2：14 mm； H3； C3：18 mm）（n = 8）。所有样本均经受98 N的循环加载力，进行了500万次模拟咀嚼循环。然后，将所有在咀嚼模拟中幸存下来的植入物准静态加载直至失效。评估了单调破坏载荷和破坏时的单调弯曲力矩。

结果

动态咀嚼负荷后，植入物的存活率如下：H组：95.8％； H组：95.8％C组：100％。植入物的超结构显示H组和C组的存活率分别为100％和91.5％。在对500万个周期进行人工咀嚼模拟之后，在较高的冠冠（14毫米和18毫米）组中，一些植入物在光学显微镜下显示出裂纹形成和塑性变形。关于单调破坏载荷，与预期的较长的上部结构（18 mm）（C3：465和H3：585 N）相比，具有较短的上部结构（10 mm）的植入物显示出更高的抗破坏能力（C1：1496和H1：1201 N）。破坏时的平均单调弯矩值在400.7 Ncm至673.3 Ncm之间。

结论

牙冠高度增加的植入物支持的修复体被认为在较长的时间内是稳定的（5百万个周期，相当于大约20年的临床服务），并且在牙弓间距离增加的情况下是可靠的治疗选择。两个内部连接的稳定性没有差异。然而，当应用高度增加的牙冠时，植入物组件的完整性可能会受到损害。