Department of Prosthodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey.
J Prosthodont. 2017 Oct;26(7):594-598. doi: 10.1111/jopr.12439. Epub 2016 Feb 5.
To evaluate the accuracy of the CEREC CAD/CAM system in reproducing the maximum intercuspal contacts of the casts, which include posterior teeth preparation for a fixed partial denture (FPD).
Ten pairs of gypsum casts were mounted in articulators in maximum intercuspal position (MIP) to serve as patient simulation models. Tooth #19 was removed from the cast. Occlusal contacts in MIP were identified with articulating paper, and digital impressions of the casts with unprepared teeth and buccal images in MIP were taken. Teeth #18 and #20 were prepared for an FPD, and full- and half-arch digital impressions of the casts with prepared teeth and buccal images from different sides were taken. In each situation, screenshot images of the virtual casts with occlusal contacts were saved as JPEG files. The proportions of congruence of virtual contacts with cast contacts were analyzed by superimposing screenshot images of the virtual casts onto the screenshot images of the casts with the indicated occlusal contacts in a transparent manner using an image-processing program. The data were statistically analyzed with a paired t-test.
The highest percentages of virtually indicated contacts identical to the cast contacts were observed in non-prepared full-arch digital impressions. Comparison of full-arch impressions taken before and after tooth preparation showed no difference for congruence even if the buccal image was taken from the contralateral or ipsilateral side (p > 0.05). After tooth preparation, comparing full- and half-arch digital impressions revealed that half-arch impression showed significantly lower percentages of identical contacts (p < 0.05). When comparing the buccal image side, no significant difference was detected between ipsilateral and contralateral images both for non-prepared and prepared casts (p > 0.05).
When there is no posterior antagonist contact following tooth preparation for an FPD, taking a full-arch digital impression and designing the restoration on full-arch virtual models can be advocated.
评估 CEREC CAD/CAM 系统在复制石膏模型上最大牙尖交错位（ICP）后牙牙体预备的𬌗接触点的准确性，这些模型用于固定局部义齿（FPD）的修复。
将 10 对石膏模型安装在𬌗架上，置于 ICP 位作为患者模拟模型。用𬌗蜡片标记 ICP 时的𬌗接触点，对未预备牙的模型进行数字化印模和颊面影像采集，预备牙体的𬌗面接触点及不同颊面影像也采集。预备 18 号和 20 号牙以制作 FPD，对预备后的牙体和牙弓的颊面影像进行全牙弓和半牙弓数字化印模。在每种情况下，保存带有𬌗接触点的虚拟石膏模型的截图图像作为 JPEG 文件。使用图像处理程序，以透明方式将虚拟石膏模型的截图图像与带有指示性𬌗接触点的石膏模型的截图图像叠加，分析虚拟接触点与石膏接触点的重合比例。采用配对 t 检验对数据进行统计学分析。
在未预备的全牙弓数字化印模中，虚拟指示接触点与石膏接触点完全一致的比例最高。比较牙体预备前后的全牙弓印模，即使颊面影像取自对侧或同侧，其吻合度也无差异（p＞0.05）。牙体预备后，比较全牙弓和半牙弓数字化印模发现，半牙弓印模的相同接触点比例明显较低（p＜0.05）。比较颊面影像侧，无论是否预备牙体，同侧和对侧影像之间无显著差异（p＞0.05）。
当 FPD 牙体预备后不存在后牙对抗𬌗接触点时，可以提倡采用全牙弓数字化印模和全牙弓虚拟模型设计修复体。
