## 2 Materials and Methods  
### 3D-FEA Design of Model Geometry  
A CBCT scan of a 28-year old clinically female with normal occlusion from an already available database, which was taken with [PERSON] (Cefla, Imola, Italy) for other clinical purposes, was used for the reconstruction of a 3D finite model simulating the cross-section of a maxillary right central incisor. This scan was defined as the model for this analysis, as data from CBCT can be used to reconstruct 3D tooth geometry with high linear, volumetric, and geometric accuracy [22]. A total of 185 layered slice images with a voxel dimension of 68 mm, a field of view of \(11\times 8\) cm, and a slice thickness of 0.3 mm were saved in DICOM format and then imported into Mimics software (version 21.0, Materialise, Leuven, Belgium) for the construction of the surface and segmenting of the scanned objects into separate elements. Global image thresholding was applied to reduce the size of the 3D geometry by selecting and sectioning the maxilla in the area related to the central incisor. To mimic the actual clinical conditions, all tooth parts, including the enamel, dentine, and pulp with the surrounding cement and periodontal ligament, which plays a major role in distributing and transferring the heat and forces produced during thermal and masticatory function into the alveolar process through the bones [23], and the cortical and trabecular bone of the maxilla, which is important to prevent impractical stress distributions [24], were included in the 3D model, which were then saved in stereolithography (STL) format. The produced STL files were examined and assembled on Autodesk Meshmixer software version 3.0 (Autodesk, San Rafael, California), where mesh improvement and refinement were carried out. The average geometrical dimensions of the solid tooth and its supporting structures were modified based on the anatomical measurements suggested by Wheeler's Dental Anatomy. The morphology of the enamel, dentin, and pulp was adjusted according to previous studies [25]. The thickness of cement is considered to be 50 \(\upmu\)m in the cervical area and increased gradually to 200 \(\upmu\)m in the apical area, while the periodontal ligament covered 12.5 mm of the root surface with a thickness of 0.18 mm [26; 27]. The supporting bone was divided into lamina dura, cancellous bone, and cortical bone, which were redesigned to standardize the geometry of each component [28], as shown in Figure 1.  
After the basic model of the central incisor was set up, a second modeling step was performed to obtain the veneer-restored incisors, based on the clinical presentation protocol specifying that the cervical margin is to be located 1.0 mm coronal to the cement-enamel junction. A distinct set of  
Figure 1: Exploded model and constructed geometry models of the maxillary central incisor with veneer restoration. procedures was followed to create the tooth pattern with three different veneer preparation designs as follows:  
* Model A: Non-preparation design  
Here, the laminate veneer was bonded directly on the unprepared tooth surface without any preparation of the underlying tooth structure or reduction of the incisal edge [1; 5] (Figure 2A). * Model B: Conventional preparation design  
The preparation was carried out according to the standard guidelines for tooth preparation required for veneers by making a chamfer finish line with a width of 0.5 mm at the cervical region on the labial surface and half of the proximal surfaces [7; 16], and a 0.5-mm reduction on the labial surface in the middle and the incisal third continuing into the proximal area without breaking the interproximal contact area [6; 29]. Moreover, preparations were made to the incisal edge (butt-joint design) in which the incisal edge was prepared bucco-palatally and reduced by 0.5 mm without involving the palatal area [29] (Figure 2B). * Model C: Proposed preparation design  
The proposed preparation design was modeled with a modification by combining the conventional preparation and non-preparation designs.