Research Fellow, Maxillofacial Prosthetic Service, Prosthodontic Unit, School of Dental Sciences, Health Campus, Universiti Sains Malaysia, Kota Bharu, Kelantan, Malaysia.
Senior Lecturer, Craniofacial Imaging and Additive Manufacturing Laboratory, School of Dental Sciences, Universiti Sains Malaysia, Kota Bharu, Kelantan, Malaysia.
J Prosthet Dent. 2022 Aug;128(2):219-224. doi: 10.1016/j.prosdent.2020.07.039. Epub 2021 Feb 15.
Computer-aided design (CAD) of maxillofacial prostheses is a hardware-intensive process. The greater the mesh detail is, the more processing power is required from the computer. A reduction in mesh quality has been shown to reduce workload on computers, yet no reference value of reduction is present for intraoral prostheses that can be applied during the design.
The purpose of this simulation study was to establish a reference percentage value that can be used to effectively reduce the size and polygons of the 3D mesh without drastically affecting the dimensions of the prosthesis itself.
Fifteen different maxillary palatal defects were simulated on a dental cast and scanned to create 3D casts. Digital bulbs were fabricated from the casts. Conventional bulbs for the defects were fabricated, scanned, and compared with the digital bulb to serve as a control. The polygon parameters of digital bulbs were then reduced by different percentages (75%, 50%, 25%, 10%, 5%, and 1% of the original mesh) which created a total of 105 meshes across 7 mesh groups. The reduced mesh files were compared individually with the original design in an open-source point cloud comparison software program. The parameters of comparison used in this study were Hausdorff distance (HD), Dice similarity coefficient (DSC), and volume.
The reduction in file size was directly proportional to the amount of mesh reduction. There were minute yet insignificant differences in volume (P>.05) across all mesh groups, with significant differences (P<.001) in HD. The differences were, however, only found with DB1. DSC showed a progressive dissimilarity until DB25 (0.17%), after which the increase was more prominent (0.46% to 4.02%).
A reduction of up to 75% polygons (25% of the original mesh) was effectively carried out on simulated casts without substantially affecting the amount of similarity in volume and geometry.
颌面赝复体的计算机辅助设计（CAD）是一个硬件密集型过程。网格越详细，计算机所需的处理能力就越大。已经证明，降低网格质量可以减少计算机的工作量，但对于设计过程中可以应用的口腔内赝复体，目前还没有参考的减少值。
本模拟研究的目的是建立一个参考百分比值，可以有效地减小 3D 网格的大小和多边形数量，而不会对修复体本身的尺寸产生重大影响。
在牙模上模拟了 15 种不同的上颌腭部缺损，并对其进行扫描以创建 3D 模型。从模型中制作出数字化的球根。制作出常规的缺陷球根，对其进行扫描，并与数字化球根进行比较，作为对照。然后，将数字化球根的多边形参数降低不同的百分比（原始网格的 75%、50%、25%、10%、5%和 1%），总共创建了 7 个网格组的 105 个网格。使用开源点云比较软件程序，将缩小的网格文件与原始设计逐个进行比较。本研究中使用的比较参数包括 Hausdorff 距离（HD）、Dice 相似系数（DSC）和体积。
文件大小的减少与网格减少的数量成正比。在所有网格组中，体积（P>.05）有微小但无意义的差异，HD 有显著差异（P<.001）。然而，这种差异仅在 DB1 中发现。DSC 显示出逐渐的不相似性，直到 DB25（0.17%），之后增加更为明显（0.46%至 4.02%）。
在不显著影响体积和几何相似性的情况下，模拟模型上的多边形减少了高达 75%（原始网格的 25%）。
