Search Results (336)

Pain is an unavoidable experience during orthodontic treatment. The central nucleus of the amygdala (CeA) plays a key role in regulating emotion and pain. Meanwhile, Absent in Melanoma 2 (AIM2) has been demonstrated in multiple neuroinflammatory and pain models for promoting inflammatory responses then enhancing nociceptive signaling. However, its role in pain caused by orthodontic tooth movement has not yet been clarified. In this study, C57BL/6J mice were used to establish an experimental tooth movement (ETM) model and were assigned to a control group, sham group, and experimental group. The face grooming and von Frey results showed that pain behaviors reached a peak on 1 d and returned to baseline levels by 7 d. After 14 days of continuous force application, mice developed obvious anxious behaviors and progressively worsened over time. The Western blot results revealed that tooth movement significantly increased AIM2 protein expression in the CeA. This was accompanied by a marked upregulation of NLRP3, caspase-1 and pp65. These findings suggest a potential role of NLRP3-NF-κB signaling in orthodontic tooth movement and also provide a new central target for the precise regulation of orthodontic pain. Full article

Orthodontic tooth movement (OTM) is driven by force-induced alveolar bone remodeling, yet the molecular mechanisms by which periodontal ligament stem cells (PDLSCs) sense and transduce mechanical signals remain incompletely understood. Here, we identify the epigenetic regulator HELLS as a compressive force-responsive gene and investigate its role as a mechanosensitive mediator in human PDLSCs (hPDLSCs). Compressive force downregulated HELLS expression both in vitro and in a mouse OTM model. Functionally, siRNA-mediated HELLS knockdown impaired osteogenic differentiation, as evidenced by reduced Alizarin Red S staining and alkaline phosphatase activity, and induced global transcriptomic changes indicative of altered mechanotransduction pathways. Moreover, HELLS knockdown increased YAP and RANKL expression and potentiated osteoclast differentiation of co-cultured RAW264.7 cells. Finally, we identified E2F1 as a candidate transcription factor mediating the force-induced downregulation of HELLS. Collectively, these findings establish HELLS as a potential mechano-epigenetic regulator in hPDLSCs, and suggest that its force-induced downregulation may contribute to alveolar bone remodeling during OTM by simultaneously attenuating osteogenesis and enhancing pro-osteoclastogenic signaling via transcriptional reprogramming. Full article

Background/Objectives: Photobiomodulation (PBM) is a biologically plausible adjunct for modulating orthodontic tissue response, but its role in conventional clear aligner therapy remains uncertain. This narrative review summarises the mechanistic rationale and clinical evidence on PBM used with clear aligners, focusing on treatment efficiency, predictability, patient-centred outcomes, and biological safety. Methods: Scopus was searched using PBM/low-level laser terms combined with orthodontics and clear aligners. Titles and abstracts were screened for human studies evaluating PBM as an adjunct to conventional staged clear aligner therapy and reporting treatment duration or alignment efficiency, tracking/predictability (for example, additional aligners, refinements, or fit-related outcomes), pain, or biological safety. Eight aligner-based clinical studies formed the core set. Results: The included studies comprised case reports, retrospective cohorts, pilot investigations, and one historical prospective nonrandomized comparison. Most evaluated short daily sessions of home-use near-infrared LED PBM, while some used external laser-based or combined adjunct protocols. Some studies reported shorter treatment duration, faster alignment, or fewer finishing aligners in PBM users, but these findings were difficult to attribute to PBM alone because altered tray-change intervals and close monitoring were common co-interventions. Aligner-specific pain outcomes were inconsistently reported. Limited safety data, based mainly on one retrospective pilot cohort assessing anterior teeth, found no statistically significant difference in root-volume change between PBM users and controls. Conclusions: PBM has been investigated as a potential adjunct in clear aligner orthodontics, but the available evidence remains preliminary, heterogeneous, and largely non-randomised. No high-quality randomized clinical evidence currently supports the clinical effectiveness or routine use of PBM in clear aligner orthodontics. At present, PBM should be regarded as an investigational adjunct rather than an established clinical recommendation, pending larger and better-designed trials with standardised device-specific protocols, objective adherence measures, movement-specific analyses, and longer follow-up for safety and patient benefit. Full article

Background/Objectives: The uprighting of mesially tipped mandibular second molars following first molar loss is a complex surgical and orthodontic challenge. Conventional methods often result in reciprocal anchorage loss. Mini-implants (MIs) have emerged as essential temporary anchorage devices (TADs) that provide absolute anchorage and enable more predictable tooth movements. Methods: Numerical simulations were performed to evaluate the forces required for mandibular second molar uprighting under two conditions: first, only with the second molar present, and second, with both the second and the third molars present. Although the periodontal ligament exhibits nonlinear and viscoelastic behavior in vivo, a linear elastic approximation was adopted to allow for a reliable evaluation of comparative stress distribution and initial displacement patterns within the scope of this exploratory biomechanical study. Stress distribution in the roots, periodontal ligament, and alveolar bone was assessed for each scenario. Two three-dimensional (3D) models of the left mandibular segment were created from scans of a human mandible and its teeth. The first model included the canine, the first and second premolars, and the second molar. A second model additionally incorporated the third molar. A retromolar MI was placed in both models. Molar uprighting was simulated using a spring connecting the implant to a button bonded on the mesial surface of the second molar. A force of 200 g was applied because in clinical orthodontic practice, forces that exceed approximately 2 N may cause pain or undesirable tooth mobility. Displacements along the X, Y, and Z axes, as well as regions of peak stress, were analyzed. Results: Model 1 showed maximum displacements at the furcation/mid-root, distal root apex, and distal crown, with von Mises stresses of 0.470 to 0.371 MPa. In Model 2, peak displacements occurred at the mesial root and crown, with stresses of 0.185 and 0.149 MPa, respectively. The magnitude of displacements was in the order of 10⁻⁵ mm. Such values represent initial mechanical responses rather than clinically observable tooth movements. However, the differences between models (e.g., the stress reduction) are expected to be clinically meaningful. Conclusions: Since clinical measurements regarding the stress distribution on teeth and surrounding tissues during orthodontic molar uprighting movements are impossible to perform, the finite element method (FEM) can offer insight into these aspects. The presence of the third molar significantly modulates the biomechanics of second molar uprighting via retromolar MIs. When the third molar is present, the second molar exhibits a reduced tendency for deformation during distalization, although this leads to a slower displacement. This FEM provides biomechanical insights but does not support direct clinical decision-making. The present findings should be viewed as theoretical biomechanical tendencies that require confirmation through clinical, experimental, and longitudinal studies before translation into clinical practice. Full article

Background: Closing extraction spaces with clear aligners remains a significant biomechanical challenge, frequently involving difficulties in sagittal control, torque expression, and intra-arch anchorage. Although various sequential or phased retraction strategies exist, the Caterpillar Motion protocol has not yet been formally defined. This clinical report describes the Caterpillar Motion staging protocol and illustrates its application through representative extraction cases, rather than providing a systematic review or experimental comparison. Case Presentation: Two adult patients with extraction-based malocclusions were treated using the Caterpillar Motion staging protocol. Case 1 involved bimaxillary first-premolar extractions with maximum anchorage requirements and periodontal limitations in the mandibular incisors. Case 2 presented as a full Class II malocclusion requiring maxillary first-premolar extractions with moderate anchorage for sagittal camouflage. In both cases, tooth movement was organized into alternating functional groups, with waves limited to 2 mm of sagittal closure. Discussion: The Caterpillar Motion protocol reduces the risk of aligner bowing effect, increases effective crown engagement, and redistributes anchorage demands by preventing simultaneous shortening of both arch extremities. Both cases demonstrated controlled anterior retraction, stable posterior anchorage, and favorable root parallelism. Conclusions: Caterpillar Motion offers a biomechanically coherent and clinically reproducible staging strategy for clear aligner extraction therapy. Further controlled studies are needed to validate its advantages over traditional linear and en-masse protocols. Full article

Objectives: The objective of this study is to evaluate the effect of 635 nm photobiomodulation on the rate and magnitude of maxillary canine distalization following extraction of the maxillary first premolars in adult patients. Materials and Methods: This randomized, controlled, split-mouth clinical trial included 18 adult patients undergoing extraction-based orthodontic treatment for Class II malocclusion. Maxillary first premolars were extracted, and canine distalization was performed using nickel–titanium closed-coil springs delivering a constant force of 150 g, supported by orthodontic mini-implants providing absolute anchorage. Photobiomodulation was applied on one randomized side using a 635 nm diode laser operating at 100 mW in continuous-wave mode, with an 8 mm handpiece diameter. Laser irradiation was delivered in contact mode to two application sites per session corresponding to the buccal and palatal aspects of the maxillary canine root, with an exposure time of 60 s per site. Irradiation was performed according to a predefined schedule over a 45-day observation period, while the contralateral side served as a sham-treated control. Tooth movement was assessed by repeated measurements of inter-bracket distance. A linear mixed-effects model was used to analyze the effects of treatment, time, and their interaction on tooth movement dynamics. Results: The linear mixed-effects model revealed a significant interaction between treatment and time (p < 0.001), indicating a greater rate of canine distalization on the photobiomodulation-treated side compared with the control side. Treatment and time also demonstrated significant main effects. After 45 days, the mean cumulative canine displacement was approximately 1.6 mm greater on the photobiomodulation side than on the control side. Age and sex did not significantly influence tooth movement. Conclusions: Photobiomodulation at a wavelength of 635 nm significantly increased the rate of maxillary canine distalization in adult extraction cases over a 45-day observation period. Full article

Background/Objectives: This finite element analysis (FEA) assessed stress distribution in the tooth and dentin within an intact periodontium under 4 N of force and five orthodontic movements (intrusion, extrusion, rotation, tipping, and translation), using four failure criteria commonly used in numerical dental studies. Secondly, differences between brittle- and ductile-like failure criteria were found, and the most accurate criterion was determined. Additionally, movements more prone to inducing external orthodontic root resorption were assessed. Methods: Using nine 3D models of the second lower premolar, 180 numerical simulations were performed. The models were anatomically accurate based on CBCT scans. FEA employed the brittle-like Maximum Principal (MaxP), Minimum Principal (MinP), and ductile-like Von Mises (VM) and Tresca (T). Results: The results showed that tipping was less prone to external orthodontic root resorption than translation, extrusion, intrusion, and rotation, which showed areas of high stress concentration in the cervical third of the root. High-stress areas were visible only when the dentin-pulp-NVB components were separately analyzed, and not when the entire tooth structure was assessed. Only by correlating the qualitative with the quantitative results could the difference between brittle-like and ductile-like failure criteria be seen. Conclusions: In total, 4 N of applied orthodontic force can induce limited islands of external orthodontic root resorption (intrusion–extrusion on the vestibular side, rotation–translation on the lingual and distal–lingual sides). The ductile-like failure criteria maintained the accuracy of the results across all FEA simulations, while the brittle-like criteria showed various quantitative and qualitative inconsistencies. Full article

Objectives: This study aimed to analyze the three-dimensional displacement of maxillary first molars using a finite element model with two headgear configurations, namely cervical and horizontal pull headgears, as well as pendulum, infrazygomatic miniscrews, Bollard miniplates, Advanced Molar Distalization Appliance (AMDA), and Beneslider. The goal was to clarify how variations in anchorage design and force direction influence molar movement across the sagittal, vertical, and transverse planes. Methods: A three-dimensional finite element model of the maxillary dentition and supporting structures was constructed using reference anatomical data and standardized material properties. Each appliance was virtually simulated under its clinically recommended force magnitude and direction to ensure realistic biomechanical conditions. The orientation of each force vector relative to the molar’s center of resistance (CR) was analyzed, and resulting tooth displacements were quantified along the sagittal (Z), vertical (Y), and transverse (X) axes using 49-node reference paths connecting key anatomical landmarks. Results: Appliances applying forces through or above the molar CR, such as the AMDA, infrazygomatic miniscrews, and Bollard miniplates, produced nearly bodily distalization with minimal tipping (<0.6° (range 0.3–0.6°)) and slight intrusion (−0.12 to −0.18 mm). Conversely, systems delivering forces below the CR, such as the cervical headgear and pendulum, resulted in greater crown tipping and extrusion. The Beneslider exhibited an intermediate displacement pattern with moderate vertical control. Conclusions: Force vector height and direction relative to the molar CR critically determine 3D displacement behavior. Skeletal anchorage and adjustable systems, particularly the AMDA, demonstrated the most controlled distalization pattern with minimal tipping, whereas conventional tooth-borne designs induced more tipping and extrusion. Full article

Background: Orthodontic tooth movement is traditionally explained through mechanical deformation of the periodontal ligament (PDL); however, increasing evidence indicates that immune mechanisms critically shape bone remodeling outcomes. Mechanical stimuli influence immune cell recruitment, cytokine release, and phenotypic polarization, but these components are rarely integrated into a unified framework. Conceptual framework: We propose the Osteoimmune Axis Model, a conceptual framework describing how mechanical loading may bias immune polarity and thereby gate periodontal remodeling. Compressive loading appears to favor an M1 macrophage/Th17-dominant program associated with pro-inflammatory cytokines and enhanced RANKL-mediated osteoclastogenesis. In contrast, tensile or physiological strains may favor M2 macrophages and regulatory T cells (Treg), supporting IL-10, TGF-β, angiogenesis, extracellular-matrix repair, and osteoblastic activity. Stromal cells are proposed to act as mechanosensors and immune amplifiers that shape cytokine gradients and feedback loops. Predictions: The model predicts that identical forces may produce divergent outcomes depending on immune baseline; load duration may be more destructive than peak magnitude; tensile strain may stabilize M2/Treg pathways; thin periodontal phenotypes may shift toward the catabolic pole at lower mechanical loads; ROS may amplify immune-mediated bone loss; and immunomodulation may raise the threshold for pathological remodeling. Conclusion: The Osteoimmune Axis integrates mechanobiology and immunology into a testable framework for explaining variability in orthodontic periodontal remodeling and for generating hypothesis-driven, immune-aware risk assessment. Full article

Background/Objectives: Clinical and scientific professionalization in orthodontics requires a comprehensive understanding of the biomechanical principles governing force generation and distribution produced by orthodontic appliances, beyond purely esthetic considerations. In this context, finite element analysis (FEA) has emerged as a fundamental computational tool for the detailed evaluation of the biomechanical behavior of the dentoalveolar system. The aim of this study was to map and synthesize the available scientific evidence on the application of FEA in the assessment of force distribution, tooth movement, and the mechanical response of periodontal tissues during orthodontic treatment. Methods: Original studies published between 2020 and 2025 that relied exclusively on computational simulations using FEA were included. Eligible studies addressed orthodontic biomechanics, including tooth movement, appliance–tooth–periodontium interactions, or the mechanical evaluation of orthodontic attachments. Clinical studies, narrative reviews, and articles without finite element modeling were excluded. A systematic literature search was conducted in the PubMed and ScienceDirect databases to answer the following question: Which FEA methodologies have been used to evaluate the biomechanical behavior of orthodontic appliances? Results: Data were categorized according to key biomechanical variables. The findings indicate an increasing use of FEA as a supportive tool in orthodontic research. However, significant limitations were identified, including lack of methodological standardization, limited model validation, and insufficient correlation between computational outcomes and clinical evidence. Conclusions: Currently, FEA in orthodontics is used predominantly for descriptive purposes, particularly for visualizing stress and strain distributions. Greater standardization and validation are required to enhance its translational applicability in clinical relevance. Full article

Background/Objectives: Orthodontic mini-implants have become indispensable in modern orthodontics due to their ability to provide absolute anchorage, independent of patient compliance. Our research aims to illustrate the versatility of mini-implants in addressing diverse biomechanical challenges across different planes of tooth movement (sagittal, transverse, and vertical) based on a retrospective clinical analysis. Methods: A retrospective analysis of orthodontic treatments performed with mini-implants (Dual Top and JS systems) was conducted, focusing on predefined biomechanical objectives and outcomes. The analysis encompassed distinct biomechanical applications, including incisor retraction and space closure using sequential direct and indirect anchorage; transverse and vertical correction of adult open bite through mini-implant–assisted rapid palatal expansion (MARPE) and molar intrusion; deep bite correction via simultaneous upper and lower incisor intrusion; and unilateral molar distalization using palatal skeletal anchorage. Results: Mini-implants provided stable, reproducible anchorage in all cases, enabling complex three-dimensional tooth movements with minimal side effects. Sequential reuse of the same mini-implants for both indirect and direct anchorage reduced treatment invasiveness and enhanced anchorage efficiency. Combined skeletal expansion and posterior intrusion allowed improved transverse and vertical control in adult open-bite presentations. Pure incisor intrusion was achieved without molar extrusion or incisor proclination, while unilateral molar distalization was effectively managed using palatal skeletal anchorage. Across all cases, mini-implants enhanced treatment efficiency, reduced the need for auxiliary appliances, and ensured predictable outcomes. Conclusions: Orthodontic mini-implants represent a highly versatile and minimally invasive anchorage system adaptable to a broad range of biomechanical situations. Their ability to provide stable, reusable, and site-specific anchorage supports efficient correction of complex malocclusions and reinforces their pivotal role in contemporary orthodontic practice. Full article

Background: Pharmacological agents may interfere with the biological processes underlying orthodontic tooth movement (OTM), potentially affecting treatment duration, pain control, and periodontal outcomes. Methods: A systematic review was conducted according to PRISMA 2020 guidelines and registered in PROSPERO. Human studies were prioritized to assess clinically relevant effects on OTM and pain, while animal and in vitro studies were included to support biological interpretation. Results: Sixty-four studies were included. Human evidence indicates that NSAIDs effectively reduce orthodontic pain but may decrease the rate of tooth movement in a dose-dependent manner. Antiresorptive drugs, particularly bisphosphonates, were consistently associated with reduced OTM. Topical antimicrobials, fluoride agents, and probiotics improved periodontal and enamel outcomes without significantly affecting tooth movement. Most evidence derived from preclinical models showed mechanistic consistency but limited clinical applicability. Overall certainty of evidence ranged from low to very low. Conclusions: Pharmacological agents can influence orthodontic outcomes, particularly pain perception and tooth movement rate. A thorough medication history is essential during orthodontic treatment planning. Current evidence remains limited, highlighting the need for well-designed clinical trials to support personalized orthodontic care. Full article

Orthodontic tooth movement (OTM), a complex biological process driven by orchestrated bone remodeling, involves osteoclastic bone resorption and osteoblastic bone formation in response to mechanical force. Traditionally, OTM-related cell death has been discussed in terms of apoptosis and necrosis. However, recent advances in cell death research have revealed various forms of regulated cell death (RCD) beyond these conventional categories. This review summarizes the current understanding of the diverse RCD pathways and their roles in various cell populations during OTM. It delineates the involvement of distinct RCD mechanisms, including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis. On the compression side, these RCD pathways in periodontal ligament (PDL) cells, cementoblasts, cementocytes, and bone-related cells actively drive inflammatory responses, promote bone resorption, and contribute to root resorption. Conversely, on the tension side, specific RCD pathways, notably autophagy in the PDL and osteocytes, play crucial roles in promoting osteogenesis and tissue repair. Collectively, cell death is not merely a passive elimination of cells but actively functions as a critical switch for alveolar bone remodeling during OTM. Understanding these multifaceted RCD mechanisms provides novel insights into the biological regulation of tooth movement and identifies potential therapeutic targets for enhancing tooth movement efficiency and mitigating adverse effects. Full article

Mechanical loading is a central cue in periodontal tissues, where compression of the periodontal ligament guides remodeling and orthodontic tooth movement (OTM). However, most mechanobiology studies have used two-dimensional cultures with poorly defined loading, and the role of autophagy under realistic three-dimensional compression remains unclear. In this study, we constructed a three-dimensional static compression model by encapsulating human periodontal ligament cells in collagen–alginate–CaSO₄ hydrogels, whose swelling, degradation, and viscoelasticity approximate those of native matrix. When exposed to a controlled static compressive stress, the cells exhibited an early autophagic response with increased ATG7, Beclin1, and LC3-II/LC3-I; accumulation of LC3-positive puncta; and reduced p62 expression between 4 and 8 h. Pharmacological modulation showed that activation of AKT-mTOR signaling suppressed this response, whereas its inhibition further augmented autophagy, identifying AKT-mTOR as a negative regulator of compression-induced autophagy. Together, these findings demonstrate that moderate static compression drives AKT-mTOR-dependent autophagy in periodontal ligament cells and establish a simple hydrogel platform for quantitative studies of periodontal remodeling. Full article

Orthodontic force magnitude influences angiogenesis during orthodontic tooth movement (OTM); however, the role of senescent cells remains largely unclear. This study investigated the localization of senescent cells and their expression of vascular endothelial growth factor (VEGF) during angiogenesis using a rat horizontal OTM model with different force magnitudes. Nickel–titanium coil springs exerting 60 g or 180 g of orthodontic force were applied to the maxillary first molar of 15-week-old male Sprague–Dawley rats; untreated rats served as controls. Tooth movement was evaluated by stereomicroscopy and micro-computed tomography. Senescent cells (p21, p16) and angiogenesis (CD31 and VEGF) were evaluated by multiplex immunofluorescence. Tooth movement was observed under both the 60 g and 180 g conditions. The 60 g group showed increased cellularity, vascular density, and VEGF expression, suggesting an optimal mechanical force. In contrast, the 180 g group reduced cellularity and angiogenesis, consistent with excessive force. Senescent cells were more abundant in the 60 g group, with over 40% expressing VEGF. These findings suggest that force magnitude influences the presence of VEGF⁺ senescent cells, which may be associated with the angiogenic process in OTM. This work provides insights into the mechanisms underlying optimal force in orthodontic treatment. Full article