Oral Implantology Research Group, Sir John Walsh Research Institute, School of Dentistry, University of Otago, Dunedin, New Zealand.
Clin Implant Dent Relat Res. 2010 Mar;12(1):26-38. doi: 10.1111/j.1708-8208.2008.00127.x.
Soldered or cast bars are used as a standard of care in attachment systems supporting maxillary and mandibular implant overdentures. When failures of these bars occur, currently there is a lack of evidence in relation to their specific etiology, location, or nature.
To investigate the failure process of a case series of six failed soldered bars, four intact soldered bars, and one intact cast milled bar, which had been supporting implant overdentures.
A total of 11 different overdenture bars were removed from patients with different configuration of opposing arches. A failed bar (FB) group (n = 6) had failed soldered overdenture bars, which were recovered from patients following up to 2 years of wear before requiring prosthodontic maintenance and repair. An intact bar (IB) group (n = 5) had both soldered bars and a single cast milled bar, which had been worn by patients for 2 to 5 years prior to receiving other aspects of prosthodontic maintenance. All bars were examined using scanning electron microscopy to establish the possible mode of failure (FB) or to identify evidence of potential failure in the future (IB).
Evidence of a progressive failure mode of corrosion fatigue and creep were observed on all the FB and IB usually around the solder areas and nonoxidizing gold cylinder. Fatigue and creep were also observed in all the IB. Where the level of corrosion was substantial, there was no evidence of wear from the matrices of the attachment system. Evidence of an instantaneous failure mode, ductile and brittle overload, was observed on the fracture surfaces of all the FB, within the solder and the nonoxidizing gold cylinders, at the solder/cylinder interface.
Corrosion, followed by corrosion fatigue, appears to be a key factor in the onset of the failure process for overdenture bars in this case series of both maxillary and mandibular overdentures. Limited sample size and lack of standardization identify trends only but prevent broad interpretation of the findings.
在支持上颌和下颌种植覆盖义齿的附着体系统中，使用焊接或铸造杆作为标准。当这些杆发生故障时，目前缺乏与它们的特定病因、位置或性质相关的证据。
调查一系列 6 个焊接失败的、4 个完整焊接的和 1 个完整铸造铣削的杆的失效过程，这些杆曾经支撑着种植覆盖义齿。
总共从具有不同对颌弓配置的患者中取出 11 个不同的覆盖义齿杆。一个失效杆（FB）组（n=6）有失效的焊接覆盖义齿杆，这些杆是从患者身上取下的，他们在需要修复之前已经佩戴了 2 年。一个完整杆（IB）组（n=5）有焊接杆和单个铸造铣削杆，这些杆在接受其他方面的修复之前，已经被患者佩戴了 2 到 5 年。所有的杆都用扫描电子显微镜进行了检查，以确定可能的失效模式（FB）或识别未来潜在失效的证据（IB）。
在所有的 FB 和 IB 上，通常在焊接区域和非氧化金圆柱体周围，观察到腐蚀疲劳和蠕变的渐进失效模式的证据。在所有的 IB 中也观察到了疲劳和蠕变。在腐蚀程度较高的地方，没有发现附着系统的矩阵有磨损的迹象。在所有的 FB 的断裂表面上，观察到了瞬时失效模式，即韧性和脆性过载，在焊接和非氧化金圆柱体内部，以及在焊接/圆柱体界面。
在这个上颌和下颌覆盖义齿的病例系列中，腐蚀，接着是腐蚀疲劳，似乎是覆盖义齿杆失效过程的一个关键因素。样本量有限且缺乏标准化，只能识别趋势，但不能广泛解释这些发现。
