Purpose: To investigate the bracket transfer accuracy of the indirect bonding technique (IDB). Methods: Systematic search of the literature was conducted in PubMed MEDLINE, Web of Science, Embase, and Scopus through November 2021. Selection Criteria: In vivo and ex vivo studies investigating bracket transfer accuracy by comparing the planned and achieved bracket positions using the IDB technique were considered. Information concerning patients, samples, and applied methodology was collected. Measured mean transfer errors (MTE) for angular and linear directions were extracted. Risk of bias (RoB) in the studies was assessed using a tailored RoB tool. Meta-analysis of ex vivo studies was performed for overall linear and angular bracket transfer accuracy and for subgroup analyses by type of tray, tooth groups, jaw-related, side-related, and by assessment method. Results: A total of 16 studies met the eligibility criteria for this systematic review. The overall linear mean transfer errors (MTE) in mesiodistal, vertical and buccolingual direction were 0.08 mm (95% CI 0.05; 0.10), 0.09 mm (0.06; 0.11), 0.14 mm (0.10; 0.17), respectively. The overall angular mean transfer errors (MTE) regarding angulation, rotation, torque were 1.13° (0.75; 1.52), 0.93° (0.49; 1.37), and 1.11° (0.68; 1.53), respectively. Silicone trays showed the highest accuracy, followed by vacuum-formed trays and 3D printed trays. Subgroup analyses between tooth groups, right and left sides, and upper and lower jaw showed minor differences. Conclusions and implications: The overall accuracy of the indirect bonding technique can be considered clinically acceptable. Future studies should address the validation of the accuracy assessment methods used.

This scoping review aims to provide a comprehensive summary of the current literature on 3D-printed orthodontic aligners. It was conducted following the Preferred Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. An electronic literature search was conducted across the PubMed, Embase, and Web of Science databases. After applying the inclusion criteria, a total of 46 eligible studies published until September 2024 were selected for qualitative synthesis. To date, scientific evidence is primarily available for Tera Harz TC (Graphy, Seoul, Republic of Korea), which is the only studied material approved for orthodontic tooth movements. Although additional materials were identified during the literature search, there is a lack of scientific studies regarding their characteristics and clinical use. This review highlights that while material properties and biocompatibility are of critical importance, the clinical efficacy and long-term safety of 3D-printed aligners require further investigation. Many studies exhibit significant variability in testing methodologies, making substantiated comparisons challenging. Moreover, the existing literature primarily comprises in vitro studies, with limited clinical trials assessing the effectiveness of 3D-printed aligners. Given the current gaps in knowledge and the evolving nature of this field, further well-designed controlled clinical studies are necessary to evaluate the clinical performance and safety of 3D-printed aligners. The findings underscore the need for standardized protocols and comprehensive reporting to enhance the reliability of future research in this area.

Oxidative stress (OS) is a common feature of many inflammatory diseases, oral pathologies, and aging processes. The impact of OS on periodontal ligament cells (PDLCs) in relation to oral pathologies, including periodontal diseases, has been investigated in different studies. However, its impact on orthodontic tooth movement (OTM) remains poorly understood. This study used an in vitro model with human PDLCs previously exposed to H₂O₂ to investigate the effects of OS under a static compressive force which simulated the conditions of OTM. Human PDLCs were treated with varying concentrations of H₂O₂ to identify sub-lethal doses that affected viability minimally. To mimic compromised conditions resembling OTM under OS, the cells were pretreated with the selected H₂O₂ concentrations for 24 h. Using an in vitro loading model, a static compressive force (2 g/cm²) was applied for an additional 24 h. The cell viability, proliferation, and cytotoxicity were evaluated using live/dead and resazurin assays. Apoptosis induction was assessed based on caspase-3/7 activity. The gene expression related to bone remodeling (RUNX2, TNFRSF11B/OPG, BGLAP), inflammation (IL6, CXCL8/IL8, PTGS2/COX2), apoptosis (CASP3, CASP8), and autophagy (MAP1LC3A/LC3, BECN1) was analyzed using RT-qPCR. This study suggests an altering effect of previous OS exposure on static-compression-related mechanosensing. Further research is needed to fully elucidate these mechanisms.

The periodontal ligament (PDL) is crucial for maintaining the integrity and functionality of tooth-supporting structures. Mechanical forces applied to the tooth during orthodontic tooth movement generate pore pressure gradients, leading to interstitial fluid movement within the PDL. The generated fluid shear stress (FSS) stimulates the remodeling of PDL and alveolar bone. Herein, we present the construction of a parallel fluid-flow apparatus to determine the effect of FSS on PDL cells. The chamber was designed and optimized using computer-aided and computational fluid dynamics software. The chamber was formed by PDMS using a negative molding technique. hPDLCs from two donors were seeded on microscopic slides and exposed to FSS of 6 dyn/cm² for 1 h. The effect of FSS on gene and protein expression was determined using RT-qPCR and Western blot. FSS upregulated genes responsible for mechanosensing (FOS), tissue formation (RUNX2, VEGFA), and inflammation (PTGS2/COX2, CXCL8/IL8, IL6) in both donors, with donor 2 showing higher gene upregulation. Protein expression of PTGS2/COX2 was higher in donor 2 but not in donor 1. RUNX2 protein was not expressed in either donor after FSS. In summary, FSS is crucial in regulating gene expression linked to PDL remodeling and inflammation, with donor variability potentially affecting outcomes.

The aim of this study was to investigate the load deflection characteristics of Gummetal^® wires in comparison to nickel–titanium (NiTi) wires. Four different NiTi wires and one Gummetal^® archwire were analyzed in two dimensions (0.014″ (0.36 mm) and 0.016″ × 0.022″ (0.41 mm × 0.56 mm)) and in two different orientations (edgewise and ribbonwise) using three-point bending tests at T = 37 °C. Force–displacement curves were recorded and analyzed. The Gummetal^® 0.014″ wires exhibited higher forces compared to the NiTi wires at 2.0 mm deflection. At 1.0 mm deflection, the opposite pattern was observed. For the 0.016″ × 0.022″ Gummetal^® wires, the forces were within the force interval of the NiTi wires at 2.0 mm deflection. At a deflection of 1.0 mm, no residual force was measurable for the Gummetal^® wires. All the NiTi wires investigated showed hysteresis and a superelastic plateau. However, the Gummetal^® did not form a plateau, but hysteresis was present. An easier plastic deformability compared to the NiTi wires was observed for all the tested geometries.

In recent years, there has been a growing number of adult orthodontic patients with periodontal disease. The progression of periodontal disease is well-linked to oxidative stress (OS). Nevertheless, the impact of OS on orthodontic tooth movement (OTM) is not fully clarified. Therefore, we applied an OS in vitro-model utilizing H₂O₂ to study its effect on tension-induced mechanotransduction in human osteoblasts (hOBs). Experimental parameters were established based on cell viability and proliferation. Apoptosis detection was based on caspase-3/7 activity. Gene expression related to bone-remodeling (RUNX2, P2RX7, TNFRSF11B/OPG), inflammation (CXCL8/IL8, IL6, PTRGS2/COX2), autophagy (MAP1LC3A/LC3, BECN1), and apoptosis (CASP3, CASP8) was analyzed by RT-qPCR. IL6 and PGE2 secretion were determined by ELISA. Tension increased the expression of PTRGS2/COX2 in all groups, especially after stimulation with higher H₂O₂ concentration. This corresponds also to the measured PGE2 concentrations. CXCL8/IL8 was upregulated in all groups. Cells subjected to tension alone showed a general upregulation of osteogenic differentiation-related genes; however, pre-stimulation with OS did not induce significant changes especially towards downregulation. MAP1LC3A/LC3, BECN1 and CASP8 were generally upregulated in cells without OS pre-stimulation. Our results suggest that OS might have considerable impacts on cellular behavior during OTM.