Sadid-Zadeh Ramtin, Sahraoui Hadjer, Lawson Brian, Cox Robert
Department of Restorative Dentistry, University at Buffalo School of Dental Medicine, Buffalo, NY 14214, USA.
Department of Prosthodontics, University at Texas Health Science Center, San Antonio, TX 77030, USA.
Dent J (Basel). 2021 Sep 27;9(10):112. doi: 10.3390/dj9100112.
The objective of this study was to assess the quality of posterior teeth prepared for monolithic zirconia crowns.
A total of 392 STL-files of posterior preparations for monolithic zirconia crowns were evaluated in this study. Three-dimensional (3D) images were evaluated using a software (3D Viewer; 3Shape A/S, Copenhagen, Denmark) for finish line design, finish line width, occluso-cervical dimension, total occlusal convergence (TOC), intercuspal angulation, finish line quality, line angle form, and presence or absence of undercut at the axial wall and unsupported lip of enamel. The assessment was performed by two calibrated evaluators. Then, data were descriptively analyzed. Data for occluso-cervical dimension and TOC were descriptively analyzed according to their location.
Thirty-nine percent of premolars, 77% of first molars, and 91% of second molars had an average occluso-cervical dimension of less than 3 mm (premolars) and 4 mm (molars), with most of the preparations having a TOC of more than 20 degrees. More than 50% of preparations had undercut, unsupported enamel and/or unacceptable finish line quality.
The quality of tooth preparation including finish line quality, absence of unsupported enamel and undercut at the axial wall should be evaluated when preparing monolithic zirconia crowns.
本研究的目的是评估为整体式氧化锆全冠制备的后牙的质量。
本研究共评估了392个用于整体式氧化锆全冠的后牙预备的STL文件。使用一款软件（3D Viewer；3Shape A/S，丹麦哥本哈根）对三维（3D）图像进行评估，内容包括边缘线设计、边缘线宽度、咬合-颈部尺寸、总咬合聚合度（TOC）、牙尖间角度、边缘线质量、线角形态以及轴壁和釉质无支持边缘处是否存在倒凹。评估由两名经过校准的评估者进行。然后，对数据进行描述性分析。根据咬合-颈部尺寸和TOC的位置对其数据进行描述性分析。
39%的前磨牙、77%的第一磨牙和91%的第二磨牙的平均咬合-颈部尺寸小于3毫米（前磨牙）和4毫米（磨牙），大多数预备体的TOC超过20度。超过50%的预备体存在倒凹、无支持的釉质和/或不可接受的边缘线质量。
在制备整体式氧化锆全冠时，应评估包括边缘线质量、轴壁无无支持釉质和倒凹在内的牙体预备质量。
