Farshad Bajoghli, Ehsan Ghasemi, Mahmoud Sabouhi, Reza Khodadadi, Mozhdeh Behdarvand
Department of Fixed Prosthodontics, Faculty of Dentistry, Esfahan University of Medical Sciences, Iran.
Indian J Dent Res. 2013 Mar-Apr;24(2):216-9. doi: 10.4103/0970-9290.116686.
Resistance form of full metal-ceramic crown is an important feature that determines longevity of these restorations. This study evaluated the resistance form of full metal-ceramic prepared with four different design features.
An acrylic tooth was prepared with 20° total occlusal convergence (TOC) angle, 2.5 mm of occlusocervical dimension and a shoulder finishing line. This design lacked resistance form. The crown preparation was subsequently modified by preparing Mesial Occlusal Distal isthmus, placing occlusal inclined plane, and reducing TOC. Four metal dies from these designs were constructed by lathe machine and then 10 metal copings were fabricated for each preparation. Metal coping were cemented on metal dies with temp-bond cement. Force was applied at 45° from lingual to buccal direction with universal testing machine.
The data were evaluated by Kruskal-Wallis and non-parametric Mann-Whitney test.
All features increased resistance form when compare to control group. However, reduce TOC group showed greatest value of resistance.
Within the limitation of this study, reducing the tapering of occlusocervival dimension is the most effective way in increasing resistance form, although, other features were also effective.
全金属烤瓷冠的抗力形是决定这些修复体使用寿命的一个重要特征。本研究评估了具有四种不同设计特征的全金属烤瓷冠的抗力形。
制备一个丙烯酸树脂牙，其总咬合聚合角（TOC）为20°，咬合颈向尺寸为2.5mm，有肩台边缘线。该设计缺乏抗力形。随后通过制备近中咬合远中峡部、设置咬合斜面和减小TOC对冠预备体进行修改。用车床加工制作这些设计的四个金属代型，然后为每个预备体制作10个金属基底冠。用临时粘结水门汀将金属基底冠粘结在金属代型上。用万能试验机从舌侧至颊侧方向呈45°施加力。
采用Kruskal-Wallis检验和非参数Mann-Whitney检验对数据进行评估。
与对照组相比，所有特征均增加了抗力形。然而，减小TOC组的抗力值最大。
在本研究的局限性内，减小咬合颈向尺寸的锥度是增加抗力形的最有效方法，尽管其他特征也有效。
