Background The orthodontic spring materials in use have a significant influence on the applied forces. The prerequisite to identify the in vitro < force deflection of the CAD/CAM fabricated springs is considered mandatory to identify the material characteristics. The purpose of the present investigation was to evaluate the mechanical load on 3D printed springs using different coil heights. Material and Methods The springs were digitally designed with different coil heights using Autodesk Netfabb CAD software (San Rafael, CA, USA). Test specimens were manufactured using 3D printable experimental flexible material (Code: BM2008, GC, Tokyo, Japan). The specimens were divided according to the coil height into five groups, group A (n=4mm), group B (n=6mm), group C (n=8mm), group D (n=10mm) and group E (n=12mm). All group specimens were mechanically tested using a universal testing machine. Statistical analysis was performed using K-S-Test to compare the values of each to the control group ( p < 0.001). Results The highest value in all groups was achieved by 5.43 N/mm in group A, while the lowest value was achieved by 0.11 N/mm in group E. Conclusions 3D printed springs are mechanically affected by the coil heights and there is a direct correlation to the resulting force. Furthermore, the variations within the investigated groups must be thoroughly investigated prior to clinical application. Key words: CAD/CAM, 3D printing, Orthodontics, mechanical testing, material evaluation.

Background: Three-dimensional printing is a rapidly developing technology across all industries. In medicine recent developments include 3D bioprinting, personalized medication and custom prosthetics and implants. To ensure safety and long-term usability in a clinical setting, it is essential to understand material specific properties. This study aims to analyze possible surface changes of a commercially available and approved DLP 3D printed definitive restoration material for dentistry after three-point flexure testing. Furthermore, this study explores whether Atomic Force Microscopy (AFM) is a feasible method for examination of 3D printed dental materials in general. This is a pilot study, as there are currently no studies that analyze 3D printed dental materials using an AFM. Methods: The present study consisted of a pretest followed by the main test. The resulting break force of the preliminary test was used to determine the force used in the main test. The main test consisted of atomic force microscopy (AFM) surface analysis of the test specimen followed by a three-point flexure procedure. After bending, the same specimen was analyzed with the AFM again, to observe possible surface changes. Results: The mean root mean square (RMS) roughness of the segments with the most stress was 20.27 nm (±5.16) before bending, while it was 26.48 nm (±6.67) afterward. The corresponding mean roughness (Ra) values were 16.05 nm (±4.25) and 21.19 nm (±5.71) Conclusions: Under three-point flexure testing, the surface roughness increased significantly. The p-value for RMS roughness was p = 0.003, while it was p = 0.006 for Ra. Furthermore, this study showed that AFM surface analysis is a suitable procedure to investigate surface changes in 3D printed dental materials.

Background The purpose of the presented investigation is to evaluate the resulting torque on loaded 3D printed springs using different coil thickness and length. Methods Specimens were designed and printed using the 3D printer MAX (Asiga, Sydney, Australia) with 3D printable, experimental, flexible material (Code:BM2008, GC, Tokyo, Japan). The specimens were divided into three groups according to spring coil design. Control group (n = 18), length group (n = 19) and thickness group (n = 22). Groups were tested using a Sauter Machine for torque calculation (DB, Grindelwald, Switzerland) in conjunction with a universal testing machine (Zwick Z010, Ulm, Germany) for clock-wise and anti-clockwise testing. Statistical analysis was performed using the Steel–Dwass test to compare median values of the three groups in both testing directions (p < 0.001). Results The highest torque value was determined in the thickness group for both clockwise and anti-clockwise testing directions, achieving 44.00 N/mm and 39.62 N/mm respectively. The length group ranged from 21.65 to 11.04 N/mm in clockwise direction and from 18.04 to 11.38 N/mm in counter-clockwise testing. The control group ranged from 22.72 to 17.18 N/mm in the clock-wise direction while in the anti-clock wise testing it ranged from 21.34 to 16.02 N/mm. Conclusions The amount of torque produced from the computer aided designing/computer aided manufacturing (CAD/CAM) springs is being affected by diameter more than the length design parameter in comparison to the control group. The values of the thickness group are significantly higher than those of the length group (P < 0.001).

Background: The purpose of the presented investigation is to evaluate the resulting torque on loaded 3D printed springs using different coil thickness and length. Methods: Specimens were designed and printed using the 3D printer MAX (Asiga, Sydney, Australia) with 3D printable, experimental, flexible material (Code:BM2008, GC, Tokyo, Japan). The specimens were divided into three groups according to spring coil design. Control group (n=18), length group (n=19) and thickness group (n=22). Groups were tested using a Sauter Machine for torque calculation (DB, Grindelwald, Switzerland) in conjunction with a universal testing machine (Zwick Z010, Ulm, Germany) for clock-wise and anti-clockwise testing. Statistical analysis was performed using the Steel-Dwass test to compare median values of the three groups in both testing directions (p<0.001). Results: The highest torque value was determined in the thickness group for both clockwise and anti-clockwise testing directions, achieving 44.00N/mm and 39.62N/mm respectively. For the thickness group values ranged from 21.28N/mm anti-clockwise to 44.00N/mm clockwise. The length group ranged from 21.65N/mm to 11.04N/mm in clockwise direction and from 18.04N/mm to 11.38N/mm in counter-clockwise testing. The control group ranged from 22.72N/mm to 17.18N/mm in the clock-wise direction while in the anti-clock wise testing it ranged from 21.34N/mm to 16.02N/mm. Conclusions: 3D printed springs are being affected by diameter than length as a design parameter compared to the control group. The thickness group values are statistically significant than the length group (P<0.001). Key words: CAD/CAM, 3D printing, Digital Orthodontics, Torque, Springs.

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