Objective: Orthodontic treatments with custom-made active elements may lead to more efficient treatment with fewer side effects. The objective of this in vitro study was to determine whether individually constructed, mathematically simulated and 3D printed power chains can generate adequate forces for orthodontic tooth movement. Methods: An individual measurement device was developed using a high precision load cell, amplifier and microcontroller for signal processing. Elastic chains were designed and subsequently printed from two different thermoplastic Polyurethan (TPU) filaments and thermoplastic elastomer (TPE) filament. With the CAD-data a finite elemente analysis (FEA) was performed to calculate the reactive forces to be expected at different activation levels. The measured force development of the test objects was compared with the results from the FEA. Results: The results showed a high precision of the measurement device with ICC of 0.999 and a Dahlberg error of 0.05 N. The measured forces ranged from 168 g to 680 g. There was a significant correlation between measured and calculated forces (R 0.91 to 0.98). Discussion: In this study, the fully digital workflow of producing an individualized active orthodontic treatment element, which developed almost exactly the force values calculated in the FEA, was shown. Future clinical use seems promising in combination with fully individualized and digitally planned treatment approaches. This offers the possibility to integrate these insights from examplary applications into patient-specific digital planning in orthodontics. The combination of CBCT root reconstruction, intraoral scans with customized brackets, and wires is the perfect starting point to add mechanical and numerical simulations. This would be the next step from shape driven planning to force driven planning. The goal is to reduce treatment time and negative side effects, e.g., root resorption. Conclusion: This in vitro study is the first to show the possible individualized construction and 3D printing of elastic chains exhibiting reproducible, predefined forces. Keywords: force measurement, 3D printing, digital workflow, finite elemente, orthodontics

Bei erwachsenen Patienten ist eine kombiniert kieferorthopädisch-kieferchirurgische Kombinationstherapie oft die einzige Möglichkeit, ausgeprägte Kieferfehlstellungen zu korrigieren. Ein zentraler Teil ist dabei die Planung der operativen Verlagerung und deren Verschlüsselung durch Operationssplinte. Durch die Kombination von 3-D-Röntgenbildgebung (DVT/CT), Intraoralscan und 3-D-Druck ist es möglich, dieses Verfahren vollständig virtuell durchzuführen. Im Beitrag werden Voraussetzungen in der Diagnostik, der Verarbeitung der Intraoralscans und DVT/CT-Daten, der virtuellen OP-Planung, der Konstruktion der Splinte einschließlich deren 3-D-Druck anhand eines Patientenbeispiels dargestellt. Keywords: Dysgnathie, Operation, OP-Splinte, Kieferorthopädie, Modelloperation

Since the advent of aligner orthodontics, many aspects of the planning and production processes have evolved. One constant is the fabrication of aligners from thermoforming sheets. The present in vitro study investigates the possibilities of direct 3D printing of aligners with fused filament fabrication. Based on a virtual model, aligners of different thicknesses were created digitally. Activation was planned for 0.4 mm movement of the maxillary left first molar. Aligners were printed using a fused filament fabrication printer with different filaments: three elastic (thermoplastic polyurethane, thermoplastic elastomer and polypropylene) and two stiffer ones (thermoplastic copolymer and polypropylene). Using a special force measurement apparatus with three-axis force and moment sensors, the forces delivered were measured and the aligners were inspected visually. Aligners with a wall thickness greater than 0.9 mm were printed successfully. The surface showed the typical layer structure, and the surface quality was found to differ depending on the material. The forces measured ranged from 0.63 to 1.57 N and moments from 29 to 78 Nmm. Polyethylene terephthalate glycol aligners were too stiff for further investigation. The in vitro measurements indicate that it may be possible to generate biologically effective forces for tooth movement with fused filament fabrication 3D printed aligners. The results may be a starting point for further research on the application of printing elastomers in orthodontics. Keywords: 3D printing, aligners, forces, moments, thermoplastic copolymers, thermoplastic elastomers, thermoplastic polyurethane

Objective: To evaluate in vitro forces and moments generated by clear aligners in relation to attachment geometry and 3D printing technology. Materials and methods: Five different movements of a premolar were simulated in a virtual model. Combined with four attachment geometries, horseshoe models were printed using fused filament fabrication and digital light processing 3D printing. On these models, 120 aligners (100 active and 20 passive) were produced with 0.6- and 0.8-mm foils (Erkodur, Erkodent Erich Kopp, Pfalzgrafenweiler, Germany). Using a modular 3D printable orthodontic measurement apparatus, forces and moments were measured for all active aligners. Statistical analysis, including the intraclass correlation coefficient and a generalised linear model, was conducted to obtain information about the influence of model fabrication technology, attachments, movement and aligner foil thickness on force, which was calculated as a vector. Results: Error measurement showed an excellent intraclass correlation coefficient, greater than 0.93 for all directions. The printing technology had no significant influence on force development of the thermoformed aligners (P = 0.7123), and the aligner material showed borderline significance (P = 0.0531). The presence or absence of attachments was also not significant (P = 0.5153). In the generalised linear model, type of movement, aligner material and vertical rectangular attachments 1 mm in size were identified as predictors of the amount of force generated. Conclusion: Printing technology does not influence the amount of force generated by aligners. The presence or absence and variation in shape of attachments may be influential but do not show consistent behaviour. Keywords: 3D printing, aligner orthodontics, attachments, forces

Artificial intelligence is now involved in many aspects of our everyday life. In digital orthodontic practice in particular, practitioners are constantly and mostly unknowingly confronted with different levels of implementations of artificial intelligence. The present article, the third in a three-part series, will seek to shed light on some of these algorithms using common examples from a standard orthodontic digital workflow. Keywords: aligner orthodontics, artificial intelligence, digital orthodontics, machine learning

Objective: To illustrate the production and clinical application of a positioner made entirely from thermoplastic polyurethane using CAD/CAM technology and fused filament fabrication 3D printing for finishing after multibracket treatment. Materials and methods: Directly after removal of the multibracket appliance, both arches were scanned (T0), including a construction bite to record the desired relationship. After mesh repair, optimisation and segmentation, a visual treatment objective was generated for finishing (maximum range of movement 0.25 to 0.40 mm) using OnyxCeph³ 3D Lab (Image Instruments, Chemnitz, Germany) (T1). Virtual aligners with a thickness of 2.0 mm were constructed over the visual treatment objective, followed by edge smoothing and structural control. Support construction and slicing were done using Simplify3D (Simplify3D, Cincinnati, OH, USA). The positioner was made from medical thermoplastic polyurethane (layer height 0.2 mm) through fused filament fabrication 3D printing and was inserted 1 day after debonding. The patient was instructed to wear the appliance for 24 hours a day except when eating and exercising. A second scan was taken after 14 days (T2). The tooth movements were measured, visualised and compared with the visual treatment objective by superimposing the scans. Results: Tooth movements in the maxilla ranged between 0.10 and 0.26 mm in translation and 0.1 to 1.2 degrees in rotation; the respective values for the mandible were 0.10 to 0.34 mm and 0.9 degrees. The extent of the tooth movement differed depending on the type of tooth and the direction of movement. Conclusion: For the first time, a custom-made, clinically applicable CAD/CAM generated positioner made from thermoplastic polyurethane was produced through fused filament fabrication 3D printing. Keywords: 3D printing, CAD/CAM, fused filament fabrication, positioner

Artificial intelligence is now involved in many aspects of our daily life. In digital orthodontic practice in particular, practitioners are constantly and mostly unknowingly confronted with different levels of implementations of artificial intelligence. The present article, the second in a three-part series, will seek to shed light on some of these algorithms using common examples from a standard orthodontic digital workflow. Keywords: aligner orthodontics, artificial intelligence, digital orthodontics, machine learning