Preliminary feasibility torque mechanical evaluation for 3D printed orthodontic springs with different parameters: in vitro study.

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).

AFM Analysis of a Three-Point Flexure Tested, 3D Printing Definitive Restoration Material for Dentistry.

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.

Fracture strength test of digitally produced ceramic-filled and unfilled dental resin restorations via 3d printing: An in vitro study.

Background: Purpose of this study was to investigate the mechanical efficiency of 3D-printed permanent and provisional implant cemented fixed bridges produced via CAD/CAM technology using an interim and a permanent ceramic filled hybrid material. Material and Methods: Two groups with twenty specimens each were designed and 3D-printed via digital light processing technology (DLP). A fracture strength test was performed. Statistical analysis was performed (p>0.05) for impression distance and force. Results: For the fracture resistance and impression distance no significant difference (p = 0.643) were detected. The specimens of interim resin showed a mean value of 365.90 ± 86.67 N. Whereas specimens of permanent ceramic filled hybrid material showed a mean value of 363.45 ± 87.57 N. Conclusions: In this in vitro study 3D-printed ceramic filled hybrid material and interim resin based on methacrylic acid esters showed an acceptable resistance to bite forces with no differences in fracture mechanism. Key words:CAD-CAM, dental resin, 3D printing.

Augmented reality in orthodontics for bracket placement using conventional mobile devices: Technical note.

BACKGROUND: Improving bracket placement accuracy through computer-aided design and a bracket navigation set supported by augmented reality (AR). METHODS: A technical workflow was developed for implementing AR-assisted orthodontic bracket positioning through a smartphone application. This innovative approach eliminates the need for three-dimensional radiation imaging or physical guides, making it a safe and convenient option for clinical use by overlapping the digitally planned bracket position over the patient clinical crown for a precise recommendation of bracket positioning. RESULTS: It was found that it is achievable and can be easily recognized from all view angles, and this proves that new techniques with new opportunities could be considered. CONCLUSIONS: AR smartphone applications can potentially be used for the accurate placement of dental brackets; thus, such applications show promise for use in the field of orthodontics.

Comparative Mechanical Testing for Digitally Produced Provisional Fixed Partial Dentures vs the Conventional Method: An In Vitro Study

PURPOSE: To examine and compare the fracture strength of implant-cemented fixed partial denture (FPD) prostheses fabricated with digital vs conventional chairside methods. MATERIALS AND METHODS: Three groups of seven specimens each were produced: group A (3D printing); group B (milling); and group C (conventional chairside manufacturing), which served as a control. All groups were cemented to standard implant abutments placed in artificial bone blocks. Fracture strength testing was performed using a universal testing machine. Statistical analysis of the resultant maximum forces was performed using SPSS version 25 software (Mann- Whitney U test, P < .05). RESULTS: The mean fracture load value of the group A FPDs was 260.14 N ± 28.88, for group B was 663.57 N ± 140.55, and for group C was 266.65 N ± 63.66. CONCLUSIONS: Milled provisional FPDs showed a higher fracture resistance compared to 3D-printed and control groups. However, no such difference could be detected between the 3D-printed and control groups.

Comparative mechanical testing for different orthodontic aligner materials over time - in vitro study.

Background: The purpose of the present study is to mechanically evaluate and compare the forces over 12 hours on different orthodontic aligners manufactured by Polyethylene terephthalate glycol (PETG). Material and Methods: Twelve orthodontic aligner specimens will be produced by a thermoforming laboratory vacuum machine. All specimens will be divided into two equal groups, group A representing Duran (Scheu Dental GmbH, Iserlohn, Germany) and group B representing Erkodur (Erkodent, Pfalzgrafenweiler, Germany). These specimens will be fabricated via CAD/CAM technology by scanning a Frasaco model (Henry Schein Dental, Gallin, Germany) using D 800 (3Shape, Copenhagen, Denmark) and printed via a Varseo S machine using Varseo ModelWax material (BEGO, Bremen, Germany). Group A specimens are manufactured by a Twinster thermoforming machine (Scheu Dental GmbH, Iserlohn, Germany) while group B is produced using Erkoform thermoforming machine (Erkodent, Pfalzgrafenweiler, Germany). Afterwards, a tooth will be removed from the printed model and replaced by an ivory tooth (Henry Schein Dental, Gallin, Germany) to apply forces at a predicted measured centre of resistance. The universal testing machine Z010 (ZwickRoell, Ulm, Germany) will be used for mechanical testing with 0.3 mm displacement over 12 hours. Statistical analysis was performed using Sigmaplot 13.0 (Systat Software GmbH, Erkrath, Germany). Behaviours over time were analysed using R2-regression analysis (SPSS 26.0, IBM SPSS Statistics, Armonk, USA). Results: There is no statistically significant difference in the maximum force between both groups (p=0.071). The mechanical testing over 12 hours showed cubic properties. Conclusions: The PETG material has no influence on the produced mechanical forces regardless of the manufacturing company. The forces over time showed no tendency towards a lower boundary of force. Key words:Mechanical testing, CAD/CAM, orthodontics, thermoplastic aligner materials.

Mechanical evaluation for three-dimensional printed orthodontic springs with different heights-in vitro study.

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.

Comparative mechanical testing for the digitally produced provisional fixed partial denture prostheses to the conventional method: in-vitro study.

PURPOSE: To examine and compare the fracture strength of digitally produced interim materials to the conventional chairside method for implant-cemented fixed partial denture prostheses. MATERIALS AND METHODS: Three groups of seven specimens each were produced: group A, 3D-printed with VarseoSmile Temp material (Bego); group B, milled using Telio CAD material (Ivoclar Vivadent), and group C, conventional chairside manufacturing method using Luxatemp material (DMG). All groups were cemented using FujiCEM 2 (GC) to Standard Abutments (SIC) placed in artificial Sawbones blocks. The fracture strength was performed using universal testing machine Z010 (ZwickRoell). Statistical analysis of the resultant maximum forces was performed using SPSS (version 25.0, IBM) software (Mann- Whitney U test, P < .05). RESULTS: The mean fracture strength of the printed provisional fixed partial dentures was 260.14 ± 28.88 N, of the milled interim fixed partial dentures was 663.57 ± 140.55 N, and for the control group reached 266.65 ± 63.66 N. Data showed a significant deviation of the normal distribution Kolmogorov-Smirnov test > .05 for all groups. CONCLUSION: Milled provisional fixed partial dentures showed a higher fracture resistance compared to 3D-printed and control chairside groups. However, for 3D-printed and control groups, no such difference could be detected.