Cortellini Davide, Canale Angelo, Souza Rodrigo O A, Campos Fernanda, Lima Julia C, Özcan Mutlu
Private Practice, Riccione, Italy.
Dental Laboratory, Rimini, Italy.
J Prosthodont. 2015 Dec;24(8):615-9. doi: 10.1111/jopr.12237. Epub 2014 Oct 15.
The aim of this study was to evaluate the durability of lithium disilicate crowns bonded on abutments prepared with two types of finish lines after long-term cyclic loading.
Pressed lithium disilicate all-ceramic molar crowns were bonded (Variolink II) to epoxy abutments (height: 5.5 mm, Ø: 7.5 mm, conicity: 6°) (N = 20) with either knife-edge (KE) or large chamfer (LC) finish lines. Each assembly was submitted to cyclic loading (1,200,000×; 200 N; 1 Hz) in water and then tested until fracture in a universal testing machine (1 mm/min). Failure types were classified and further evaluated under stereomicroscope and SEM. The data (N) were analyzed using one-way ANOVA. Weibull distribution values including the Weibull modulus (m), characteristic strength (0), probability of failure at 5% (0.05), 1% (0.01), and correlation coefficient were calculated.
Type of finish line did not significantly influence the mean fracture strength of pressed ceramic crowns (KE: 1655 ± 353 N; LC: 1618 ± 263 N) (p = 0.7898). Weibull distribution presented lower shape value (m) of KE (m = 5.48; CI: 3.5 to 8.6) compared to LC (m = 7.68; CI: 5.2 to 11.3). Characteristic strengths (0) (KE: 1784.9 N; LC: 1712.1 N) were higher than probability of failure at 5% (0.05) (KE: 1038.1 N; LC: 1163.4 N) followed by 1% (0.01) (KE: 771 N; LC: 941.1 N), with a correlation coefficient of 0.966 for KE and 0.924 for LC. Type V failures (severe fracture of the crown and/or tooth) were more common in both groups. SEM findings showed that fractures occurred mainly from the cement/ceramic interface at the occlusal side of the crowns.
Lithium disilicate ceramic crowns bonded onto abutment teeth with KE preparation resulted in similar fracture strength to those bonded on abutments with LC finish line.
Pressed lithium disilicate ceramic crowns may not require invasive finish line preparations since finish line type did not impair the strength after aging conditions.
本研究旨在评估在长期循环加载后，用两种类型的肩台预备体粘结的二硅酸锂全瓷冠的耐久性。
将压制的二硅酸锂全瓷磨牙冠（Variolink II）粘结到环氧基台上（高度：5.5毫米，直径：7.5毫米，锥度：6°）（N = 20），基台肩台预备体类型为刃状（KE）或大斜面（LC）。每个组件在水中进行循环加载（1,200,000次；200牛；1赫兹），然后在万能试验机上以1毫米/分钟的速度进行测试直至断裂。对失败类型进行分类，并在体视显微镜和扫描电子显微镜下进一步评估。使用单因素方差分析对数据（N）进行分析。计算威布尔分布值，包括威布尔模量（m）、特征强度（0）、5%（0.05）、1%（0.01）的失效概率以及相关系数。
肩台预备体类型对压制陶瓷冠的平均断裂强度没有显著影响（KE：1655±353牛；LC：1618±263牛）（p = 0.7898）。与LC（m = 7.68；CI：5.2至11.3）相比，KE的威布尔分布呈现出较低的形状值（m）（m = 5.48；CI：3.5至8.6）。特征强度（0）（KE：1784.9牛；LC：1712.1牛）高于5%（0.05）的失效概率（KE：1038.1牛；LC：1163.4牛），其次是1%（0.01）的失效概率（KE：771牛；LC：941.1牛），KE的相关系数为0.966，LC的相关系数为0.924。V型失败（牙冠和/或牙齿的严重骨折）在两组中更为常见。扫描电子显微镜结果显示，骨折主要发生在牙冠咬合面的粘结剂/陶瓷界面处。
用KE预备体粘结到基牙上的二硅酸锂陶瓷冠与用LC肩台预备体粘结的陶瓷冠具有相似的断裂强度。
由于肩台预备体类型在老化条件后不会损害强度，因此压制的二硅酸锂陶瓷冠可能不需要进行侵入性的肩台预备。
