Dental Biomaterials Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt.
Int J Prosthodont. 2009 Nov-Dec;22(6):616-9.
Zirconia was recently introduced as a ceramic implant abutment due to its superior mechanical properties and white color. Nevertheless, it requires careful handling to avoid unexpected failure. The aim of this study was to examine five clinically broken zirconia implant abutments using fractography principles.
Five clinically fractured zirconia abutments were retrieved for fractographic analysis. The specimens were cleaned, sterilized, and reassembled to allow reconstruction of the broken abutments. Each fragment was gold sputter-coated and individually examined using scanning electron microscopy. The location of the crack origin was identified and the stress at failure was estimated using fracture marks observed on the broken surfaces.
For three abutments, the critical crack was located at the internal ring where the abutments met the internal metallic component. The estimated stress at failure ranged between 978 and 1,228 MPa. Friction landmarks were observed on the surface of the fixation screw, which could be responsible for the generation of high internal stresses. Two abutments broke due to overpreparation and thinning of the lateral walls.
A confirmatory radiograph is recommended before the final zirconia abutments are screwed into place to prevent improper seating and the generation of damaging internal stresses.
氧化锆最近被引入作为一种陶瓷种植体基台，因其具有优越的机械性能和白色外观。然而，它需要小心处理，以避免意外失效。本研究旨在使用断裂学原理研究五例临床断裂的氧化锆种植体基台。
从临床中取出五例断裂的氧化锆基台进行断裂分析。对样本进行清洗、消毒和重新组装，以允许对断裂的基台进行重建。每个碎片都经过金溅射涂层处理，并使用扫描电子显微镜对每个碎片进行单独检查。确定裂纹起源的位置，并根据断裂表面上观察到的断裂标记来估计失效时的应力。
对于三个基台，临界裂纹位于基台与内部金属部件接触的内部环处。失效时的估计应力在 978 至 1228 MPa 之间。在固定螺丝的表面观察到摩擦痕迹，这可能是产生高内部应力的原因。两个基台由于过度预备和侧壁变薄而断裂。
建议在最终将氧化锆基台拧入到位之前进行确认性射线照相，以防止不当的就位和产生破坏性的内部应力。
