## 3 Results  
### Tensile Test Results  
The tensile test was performed for all samples, but the last three samples were incorrectly clamped, so the results from these three specimens were unusable. Full probing dataset is available. The resulting tensile test diagrams of specimens No. 1 (red) and No. 2 (aqumarine) are shown in Figure 9. The X-axis shows the deformation (in mm), the Y-axis shows the force (in N). Other outputs of tensile tests were also text files with measured values, such as: time (s), force (N), travel (mm), elongation (mm), tensile stress (MPa), and relative elongation (%), etc. These values were processed using Microsoft Excel 2016 and subsequently, using Hooke's law, the modulus of elasticity for the first two samples was calculated. As seen in Figure 9, the curves are slightly different and are shifted in the Y axis. The values of the modulus of elasticity of sample No. 2 were trivially lower. This slight difference is not clinically relevant for medical application. However, as the clinical objective was to design a more resilient power-arm, we have conservatively chosen this second (lower) sample as representative. Figure 8: A force of the elastics gives a moment to the tooth (premolar 35) where the 3D printed biocompatible power-arm is attached (variant I. year 2018). Figure 7: **(a)** Method of creating individual base of a power-arm—first step, identification of clinical surfaces of teeth for PA, not covered with clear aligner system (Invisalign®). (b) Virtual setup in clinically driven positioning of the power-arm (variant II). (c) Aligning PA to a tooth axis on digital intraoral scan (iFero®) Intraoral Scanner). (d) PA must respect 1 mm distance from the gum to avoid swelling from mechanical irritation, as well as it must respect individual vestibular anatomy of a patient. (e) When the part of PA STL template that overlaps the tooth is removed, it forms an individual base on the PA. Individual base is effective in proper PA positioning during bonding, as well as significantly increases PA retention on the tooth [15]. The modulus of elasticity (Figure 10) was calculated as the arithmetic mean of all values of the modulus of elasticity from test sample No. 2 and its value is 2089 MPa (see Figure 9). During the testing, the transverse deformations of the sample were not recorded, so it was not possible to determine the Poisson's number, and therefore we chose the value 0.29 in the calculation. The international standard that specifies the general principles for determining the tensile properties of plastics and plastic composites under defined conditions is: ISO 527-1:2019 [27]. ISO 527 standard, belonging to the family of plastics standards, specifies the test conditions for the determination of the elastic limit, the deformation, the permissible loads, and the type of breakage of the materials of plastic composite, isotropic or orthotropic, and fiber-reinforced, when subjected to tensile stress. These results were not researched upon the test conditions defined in ISO 527. This norm, updated in 2019, is appropriate for the determination of the tensile properties of plastic composites of unknown composition and mechanical properties. Figure 10: Modulus of elasticity of the sample 1 (red) and sample 2 (aquamarine) depending on the relative elongation. Figure 9: Tensile diagram of sample No.1. (red) and No. 2 (aquamarine). The step of researching material properties in this research is shown only for information purpose for clinicians experimenting with unknown materials. This paper is intended for medical clinicians to increase their awareness about possible approaches to designing their personalized intraoral appliances. The authors of this paper want to emphasize that testing two specimens is too little for proper material design. As the material properties of Dental LT Clear Biocompatible Resin (version 1) have been confirmed by the manufacturer during the research process, there was no need to print more specimens.