Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
Dent Mater. 2012 Oct;28(10):e218-28. doi: 10.1016/j.dental.2012.05.004. Epub 2012 Jun 8.
The aim of this study was to assess the effect of abutment's diameter shifting on reliability and stress distribution within the implant-abutment connection for internal and external hexagon implants. The postulated hypothesis was that platform-switched implants would result in increased stress concentration within the implant-abutment connection, leading to the systems' lower reliability.
Eighty-four implants were divided in four groups (n=21): REG-EH and SWT-EH (regular and switched-platform implants with external connection, respectively); REG-IH and SWT-IH (regular and switched-platform implants with internal connection, respectively). The corresponding abutments were screwed to the implants and standardized maxillary central incisor metal crowns were cemented and subjected to step-stress accelerated life testing. Use-level probability Weibull curves and reliability were calculated. Four finite element models reproducing the characteristics of specimens used in laboratory testing were created. The models were full constrained on the bottom and lateral surface of the cylinder of acrylic resin and one 30° off-axis load (300N) was applied on the lingual side of the crown (close to the incisal edge) in order to evaluate the stress distribution (s(vM)) within the implant-abutment complex.
The Beta values for groups SWT-EH (1.31), REG-EH (1.55), SWT-IH (1.83) and REG-IH (1.82) indicated that fatigue accelerated the failure of all groups. The higher levels of σ(vM) within the implant-abutment connection observed for platform-switched implants (groups SWT-EH and SWT-IH) were in agreement with the lower reliability observed for the external hex implants, but not for the internal hex implants. The reliability 90% confidence intervals (50,000 cycles at 300N) were 0.53(0.33-0.70), 0.93(0.80-0.97), 0.99(0.93-0.99) and 0.99(0.99-1.00), for the SWT-EH, REG-EH, SWT-IH, and REH-IH, respectively.
The postulated hypothesis was partially accepted. The higher levels of stress observed within implant-abutment connection when reducing abutment diameter (cross-sectional area) resulted in lower reliability for external hex implants, but not for internal hex implants.
本研究旨在评估基台直径变化对内六角种植体-基台连接的可靠性和应力分布的影响。假设平台转换种植体将导致种植体-基台连接内的应力集中增加，从而降低系统的可靠性。
将 84 个种植体分为四组（n=21）：REG-EH 和 SWT-EH（分别为带外连接的常规和平台转换种植体）；REG-IH 和 SWT-IH（分别为带内连接的常规和平台转换种植体）。将相应的基台拧到种植体上，并将标准化的上颌中切牙金属冠粘接到种植体上，然后进行阶跃应力加速寿命测试。计算使用水平概率威布尔曲线和可靠性。创建了四个有限元模型，以复制实验室测试中使用的样本的特征。模型在丙烯酸树脂圆柱体的底部和侧面完全受限，并在冠的舌侧（靠近切缘）施加 30°偏轴载荷（300N），以评估种植体-基台复合体内部的应力分布（s（vM））。
SWT-EH 组（1.31）、REG-EH 组（1.55）、SWT-IH 组（1.83）和 REG-IH 组（1.82）的 Beta 值表明，疲劳加速了所有组的失效。在平台转换种植体（SWT-EH 和 SWT-IH 组）中观察到的较高水平的 s（vM）在种植体-基台连接内与外部六角种植体较低的可靠性一致，但与内部六角种植体不一致。SWT-EH、REG-EH、SWT-IH 和 REG-IH 组的可靠性 90%置信区间（300N 时 50,000 次循环）分别为 0.53（0.33-0.70）、0.93（0.80-0.97）、0.99（0.93-0.99）和 0.99（0.99-1.00）。
假设的部分被接受。当减小基台直径（横截面积）时，在种植体-基台连接内观察到的较高水平的应力导致外部六角种植体的可靠性降低，但对内部六角种植体则不然。
