Senior Researcher in Fixed Prosthodontics, Department of Conservative Dentistry, Alexandria University, Alexandria, Egypt.
Professor of Fixed Prosthodontics, Department of Conservative Dentistry, Alexandria University, Alexandria, Egypt.
J Prosthet Dent. 2024 Jan;131(1):93.e1-93.e6. doi: 10.1016/j.prosdent.2023.09.035. Epub 2023 Oct 20.
Cement spacer has a crucial influence on the adaptation of fixed restorations. Recently, digitally fabricated zirconia crowns have become more popular, but studies on the effect of occlusal cement spacer on the fit accuracy of digitally designed and milled zirconia crowns are lacking.
The purpose of this in vitro study was to investigate the effect of modifying digital occlusal spacer on the marginal and internal fit of digitally manufactured zirconia crowns.
A maxillary molar typodont tooth was prepared for a zirconia crown, scanned with the Medit i700 intraoral scanner (IOS), and the standard tessellation language (STL) file was used to produce 3-dimensionally (3D) printed definitive dies assigned to 3 groups (n=12). All dies were scanned with the IOS, and the obtained STL files were exported to a computer-aided design (CAD) software program for the designing and milling of 36 complete contour zirconia crowns. The zirconia crown design was identical in the 3 groups for all parameters (default parameters in the CAD software program) with a 80-µm radial spacer 1 mm from the finish lines. The occlusal cement spacer was adjusted to 80 µm, 40 µm, and 0 µm for group 80-80, group 40-80, and group 0-80 respectively. The internal and marginal fit of the crowns were measured on their corresponding definitive dies with the replica technique. The Kruskal-Wallis test followed by the Dunn test with the Bonferroni correction was used for statistical analysis of the results (α=.05).
The modification of occlusal cement spacer significantly affected the marginal and internal fit of digitally manufactured crowns (P<.05). Group 0-80 and group 40-80 had similar marginal gap values, which were significantly lower than those of group 80-80 (P<.017). For internal fit accuracy, group 0-80 displayed significantly lower gap values than group 40-80 and group 80-80 for all measured areas. Group 40-80 had significantly lower gap values than group 80-80 at the mid-occlusal and axio-occlusal areas (P<.017).
Modifying occlusal cement spacer significantly affected the fit of digitally fabricated zirconia crowns. Reducing or eliminating occlusal spacer resulted in significantly improved fit accuracy.
水泥间隔物对固定修复体的适应性有至关重要的影响。最近，数字化制造的氧化锆冠越来越受欢迎，但关于牙合面水泥间隔物对数字化设计和铣削氧化锆冠拟合精度影响的研究还很缺乏。
本体外研究的目的是探讨修改数字牙合面间隔物对数字化制造氧化锆冠的边缘和内部拟合的影响。
准备上颌磨牙模型，用 Medit i700 口内扫描仪（IOS）扫描，标准 tessellation language (STL) 文件用于制作三维（3D）打印的终模，终模被分配到 3 组（n=12）。所有终模均用 IOS 扫描，获得的 STL 文件被导出到计算机辅助设计（CAD）软件程序中，用于设计和铣削 36 个完整轮廓氧化锆冠。3 组的氧化锆冠设计完全相同，所有参数均相同（CAD 软件程序中的默认参数），牙合面有 80μm 厚的间隔物，距离边缘线 1mm。牙合面的水泥间隔物分别调整为 80μm、40μm 和 0μm，用于组 80-80、组 40-80 和组 0-80。用复制技术在相应的终模上测量冠的内部和边缘贴合度。采用 Kruskal-Wallis 检验，然后采用带有 Bonferroni 校正的 Dunn 检验对结果进行统计学分析（α=.05）。
牙合面水泥间隔物的修改显著影响数字化制造冠的边缘和内部贴合度（P<.05）。组 0-80 和组 40-80 的边缘间隙值相似，明显低于组 80-80（P<.017）。对于内部拟合精度，组 0-80 在所有测量区域的间隙值明显低于组 40-80 和组 80-80。组 40-80 在近中牙合和颊舌牙合区的间隙值明显低于组 80-80（P<.017）。
修改牙合面水泥间隔物显著影响数字化制造氧化锆冠的拟合度。减少或消除牙合面间隔物可显著提高拟合精度。
