Department of Prosthodontics, Propaedeutics and Dental Materials, Dental School, Christian-Albrechts University at Kiel, Kiel, Germany.
Clin Oral Implants Res. 2012 Aug;23(8):930-7. doi: 10.1111/j.1600-0501.2011.02236.x. Epub 2011 Jul 4.
The main goals of this in vitro study were to evaluate the influence of thermocycling, ultrasonic stress and the removal force preload on the retrievability of cemented implant crowns using a clinical removal device (Coronaflex) and evaluating the tensile strength using a universal testing machine (UTM).
Thirty-six crowns were cast from a Co-Cr alloy for 36 tapered titanium abutments (5° taper, 4.3 mm diameter, 6 mm height, Camlog, Germany). The crowns were cemented with a glass-ionomer (Ketac Cem) or a polycarboxylate (Durelon) cement, followed by 3 days of storage in ionized water without thermocycling or 150 days of storage with 37,500 thermal cycles between 5°C and 55°C. Before removal, the crowns were subjected to ultrasonic stress for 0, 5 or 10 min with a contact pressure of either 50 or 500 g. The Coronaflex was used with a removal force preload of 50 or 400 cN, respectively, applied on the point of loading. Scanning electronic microscopy (SEM) was used to evaluate the impact of the removal on the abutment screws.
Crowns cemented with the glass-ionomer cement were significantly easier to remove with the Coronaflex or the UTM than crowns cemented with the polycarboxylate cement (P≤0.05). Ultrasonic stress showed no significant impact on the retrievability regardless of the contact pressure or duration applied (P>0.05). No significant differences could be found for both cements when removed with the Coronaflex or the UTM (P>0.05) after thermocycling was applied. A removal force preload of 400 cN resulted in significantly reduced removal attempts in comparison with 50 cN for both cements (P≤0.05).
Ultrasound and thermal cycling did not result in reduced cement strength, but to retrieve the crowns, the full impact of a removal instrument has to be applied. Ketac Cem can be used as a "semipermanent" solution, whereas Durelon might serve for permanent cementation. None of the abutment screws showed signs of wear caused by the removal process.
本体外研究的主要目的是评估热循环、超声应力以及去除力预载对使用临床去除器械（Coronaflex）回收粘结固位式种植体冠的影响，并使用万能试验机（UTM）评估拉伸强度。
从 Co-Cr 合金铸造 36 个锥形钛基台（5°锥度，4.3 毫米直径，6 毫米高，Camlog，德国）的冠。用玻璃离子水门汀（Ketac Cem）或聚羧酸酯水门汀（Durelon）粘结冠，然后在离子水中储存 3 天，不进行热循环，或在 5°C 和 55°C 之间储存 150 天，进行 37500 次热循环。在去除之前，将冠用接触压力为 50 或 500 克的超声应力处理 0、5 或 10 分钟。Coronaflex 分别使用 50 或 400 cN 的去除力预载，施加在加载点上。扫描电子显微镜（SEM）用于评估去除对基台螺丝的影响。
用玻璃离子水门汀粘结的冠用 Coronaflex 或 UTM 去除比用聚羧酸酯水门汀粘结的冠更容易（P≤0.05）。无论施加的接触压力或持续时间如何，超声应力对可回收性均无显著影响（P＞0.05）。在施加热循环后，用 Coronaflex 或 UTM 去除时，两种水门汀均未发现明显差异（P＞0.05）。与 50 cN 相比，去除力预载为 400 cN 时，两种水门汀的去除尝试次数明显减少（P≤0.05）。
超声和热循环并未导致粘结强度降低，但要回收冠，必须施加去除器械的全部冲击力。Ketac Cem 可作为“半永久性”解决方案，而 Durelon 可能适用于永久性粘结。没有一个基台螺丝显示出由于去除过程而导致的磨损迹象。
