Osteoimmunology in orthodontic tooth movement

Breaking a dogma: orthodontic tooth movement alters systemic immunity

BACKGROUND

The prevailing paradigm posits orthodontic tooth movement (OTM) as primarily a localized inflammatory process. In this study, we endeavor to elucidate the potential ramifications of mechanical force on systemic immunity, employing a time-dependent approach.

MATERIALS AND METHODS

A previously described mouse orthodontic model was used. Ni-Ti. springs were set to move the upper 1st-molar in C57BL/6 mice and the amount of OTM was. measured by µCT. Mice were allocated randomly into four experimental groups, each. corresponding to clinical phases of OTM, relative to force application. Terminal blood. samples were collected and a comprehensive blood count test for 7 cell types as well as. proteome profiling of 111 pivotal cytokines and chemokines were conducted. Two controls. groups were included: one comprised non-treated mice and the other mice with inactivated springs.

RESULTS

Serum immuno-profiling unveiled alterations in cellular immunity, manifesting as. changes in percentages of leukocytes, monocytes, macrophages, neutrophils, and. lymphocytes, alongside key signaling factors in comparison to both control groups. The systemic cellular and molecular alterations triggered by OTM mirrored the dynamics previously described in the local immune response.

CONCLUSIONS

Although the exact interplay between local and systemic immune responses to orthodontic forces require further elucidation, our findings demonstrate a tangible link between the two. Future investigations should aim to correlate these results with human subjects, and strive to delve deeper into the specific mechanisms by which mechanical force modulates the systemic immune response.

Accelerated Orthodontics: A Descriptive Bibliometric Analysis of the Top 50 Cited Articles from 2012 to 2023

BACKGROUND AND OBJECTIVES

Accelerated orthodontics represents a significant shift in dental practice aimed at reducing treatment times while maintaining optimal patient outcomes. This bibliometric analysis evaluated the research landscape of accelerated orthodontics from 2012 to 2023, focusing on publication trends, citation patterns, influential journals, leading institutions, and key contributors.

MATERIALS AND METHODS

A comprehensive search in Scopus identified 600 relevant articles, with the top 50 most-cited papers encompassing systematic reviews, randomized controlled trials, and experimental studies. Key techniques, such as corticotomy and piezocision, have been frequently highlighted for their effectiveness in expediting tooth movement.

RESULTS

The analysis revealed fluctuating annual scientific outputs, with notable peaks driven by technological advancements and increased patient demand for quicker orthodontic solutions. However, the production of high-impact papers was hindered by delays in citation accumulation and disruptions caused by the COVID-19 pandemic. Keyword analysis identified critical themes, such as orthodontic tooth movement, malocclusion, and demographic factors, while a global collaboration map underscored extensive international research partnerships. Leading journals included the American Journal of Orthodontics and Dentofacial Orthopedics, and prominent institutions such as the University of California at Los Angeles played significant roles in advancing the field.

CONCLUSIONS

This study provides a comprehensive overview of the current state of accelerated orthodontics, emphasizing the need for continued research, particularly RCTs, to further refine and validate accelerated orthodontic techniques and improve clinical outcomes.

Contribution of diabetes mellitus to periodontal inflammation during orthodontic tooth movement

OBJECTIVE

This study aims to clarify the effects of diabetes mellitus (DM) on inflammatory profile during orthodontic tooth movement (OTM) and explore potential mechanisms.

METHODS

OTM models were established in healthy (Ctrl) and DM rats for 0, 3, 7 or 14 days. The tooth movement distance and bone structural parameters were analyzed through micro-CT. The bone resorption activity and periodontal inflammation status were evaluated through histological staining. RNA sequencing was performed to detect differentially expressed genes in force loading-treated periodontal ligament fibroblasts (PDLFs) with or without high glucose. The differential expression of inflammatory genes associated with NOD-like receptor family pyrin domain containing 3 (NLRP3) between groups was tested in vitro and in vivo.

RESULTS

DM caused remarkable reduction of alveolar bone height and density around the moved tooth, corresponding with the higher bone resorption activity and inflammatory scores of DM group. For force loading-treated PDLFs, high glucose induced the activation of inflammatory pathways, including NLRP3. Elevated expression of NLRP3 and cascade molecules (Caspase-1, GSDMD, and IL-1β) were validated by RT-qPCR, Western blot, and immunohistochemistry staining.

CONCLUSIONS

DM alters the inflammatory status of periodontium and affects tissue reconstruction during OTM. NLRP3 inflammasome may involve in diabetes-induced periodontal changes.

Ageing and Inflammation: What Happens in Periodontium?

Periodontitis is a chronic inflammatory disease with a high incidence and severity in the elderly population, making it a significant public health concern. Ageing is a primary risk factor for the development of periodontitis, exacerbating alveolar bone loss and leading to tooth loss in the geriatric population. Despite extensive research, the precise molecular mechanisms underlying the relationship between ageing and periodontitis remain elusive. Understanding the intricate mechanisms that connect ageing and inflammation may help reveal new therapeutic targets and provide valuable options to tackle the challenges encountered by the rapidly expanding global ageing population. In this review, we highlight the latest scientific breakthroughs in the pathways by which inflammaging mediates the decline in periodontal function and triggers the onset of periodontitis. We also provide a comprehensive overview of the latest findings and discuss potential avenues for future research in this critical area of investigation.

Osteoimmunology in Periodontitis and Orthodontic Tooth Movement

PURPOSE OF REVIEW

To review the role of the immune cells and their interaction with cells found in gingiva, periodontal ligament, and bone that leads to net bone loss in periodontitis or bone remodeling in orthodontic tooth movement.

RECENT FINDINGS

Periodontal disease is one of the most common oral diseases causing inflammation in the soft and hard tissues of the periodontium and is initiated by bacteria that induce a host response. Although the innate and adaptive immune response function cooperatively to prevent bacterial dissemination, they also play a major role in gingival inflammation and destruction of the connective tissue, periodontal ligament, and alveolar bone characteristic of periodontitis. The inflammatory response is triggered by bacteria or their products that bind to pattern recognition receptors that induce transcription factor activity to stimulate cytokine and chemokine expression. Epithelial, fibroblast/stromal, and resident leukocytes play a key role in initiating the host response and contribute to periodontal disease. Single-cell RNA-seq (scRNA-seq) experiments have added new insight into the roles of various cell types in the response to bacterial challenge. This response is modified by systemic conditions such as diabetes and smoking. In contrast to periodontitis, orthodontic tooth movement (OTM) is a sterile inflammatory response induced by mechanical force. Orthodontic force application stimulates acute inflammatory responses in the periodontal ligament and alveolar bone stimulated by cytokines and chemokines that produce bone resorption on the compression side. On the tension side, orthodontic forces induce the production of osteogenic factors, stimulating new bone formation. A number of different cell types, cytokines, and signaling/pathways are involved in this complex process. Inflammatory and mechanical force-induced bone remodeling involves bone resorption and bone formation. The interaction of leukocytes with host stromal cells and osteoblastic cells plays a key role in both initiating the inflammatory events as well as inducing a cellular cascade that results in remodeling in orthodontic tooth movement or in tissue destruction in periodontitis.

Cyclic pressure-induced cytokines from gingival fibroblasts stimulate osteoclast activity: Clinical implications for alveolar bone loss in denture wearers

Purpose The involvement of oral mucosa cells in mechanical stress-induced bone resorption is unclear. The aim of this study was to investigate the effects of cyclic pressure-induced cytokines from oral mucosal cells (human gingival fibroblasts: hGFs) on osteoclast activity in vitro.Methods Cyclic pressure at 50 kPa, which represents high physiologic occlusal force of dentures on the molar area, was applied to hGFs. NFAT-reporter stable RAW264.7 preosteoclasts (NFAT/Luc-RAW cells) were cultured in conditioned medium collected from hGF cultures under cyclic pressure or static conditions. NFAT activity and osteoclast formation were determined by luciferase reporter assay and TRAP staining, respectively. Cyclic pressure-induced cytokines in hGF culture were detected by ELISA, real-time RT-PCR, and cytokine array analyses.Results Conditioned media from hGFs treated with 48 hours of cyclic pressure significantly induced NFAT activity and increased multinucleated osteoclast formation. Furthermore, the cyclic pressure significantly increased the bone resorption activity of RAW264.7 cells. Cyclic pressure significantly increased the expression of major inflammatory cytokines including IL-1β/IL-1β, IL-6/IL-6, IL-8/IL-8 and MCP-1/CCL2 in hGFs compared to hGFs cultured under static conditions, and it suppressed osteoprotegerin (OPG/OPG) expression. A cytokine array detected 12 cyclic pressure-induced candidates. Among them, IL-8, decorin, MCP-1 and ferritin increased, whereas IL-28A and PDGF-BB decreased, NFAT activation of NFAT/Luc-RAW cells.Conclusions These results suggest that cyclic pressure-induced cytokines from hGFs promote osteoclastogenesis, possibly including up-regulation of IL-1β, IL-6, IL-8 and MCP-1, and down-regulation of OPG. These findings introduce the possible involvement of GFs in mechanical stress-induced alveolar ridge resorption, such as in denture wearers.

Immune System Acts on Orthodontic Tooth Movement: Cellular and Molecular Mechanisms

Orthodontic tooth movement (OTM) is a tissue remodeling process based on orthodontic force loading. Compressed periodontal tissues have a complicated aseptic inflammatory cascade, which are considered the initial factor of alveolar bone remodeling. Since skeletal and immune systems shared a wide variety of molecules, osteoimmunology has been generally accepted as an interdisciplinary field to investigate their interactions. Unsurprisingly, OTM is considered a good mirror of osteoimmunology since it involves immune reaction and bone remolding. In fact, besides bone remodeling, OTM involves cementum resorption, soft tissue remodeling, orthodontic pain, and relapse, all correlated with immune cells and/or immunologically active substance. The aim of this paper is to review the interaction of immune system with orthodontic tooth movement, which helps gain insights into mechanisms of OTM and search novel method to short treatment period and control complications.

Resolvin D1 shows osseous-protection via RANK reduction on monocytes during orthodontic tooth movement

The study aimed to investigate the role of RvD1 in acute and prolonged sterile inflammation and bone remodeling. A mouse model of sterile inflammation that involves bone resorption was used to examine endogenous RvD1 kinetics during inflammation. Application of exogenous RvD1 significantly inhibited bone remodeling via osteoclast reduction, alongside an anti-inflammatory secretome shift, increased macrophages recruitment and reduction of T-cytotoxic cells. In vitro and in vivo, RvD1 led to significant reduction in RANK expression which reduce osteoclastogenesis in a dose-dependent manner. Taken together, the data shows a dual role for RvD1, as a potent immunoresolvent agent alongside an osteoresolvent role, showing a potential therapeutic agent in bone resorption associated inflammatory conditions.

Single‐cell RNA sequencing in oral science: Current awareness and perspectives

The emergence of single‐cell RNA sequencing enables simultaneous sequencing of thousands of cells, making the analysis of cell population heterogeneity more efficient. In recent years, single‐cell RNA sequencing has been used in the investigation of heterogeneous cell populations, cellular developmental trajectories, stochastic gene transcriptional kinetics, and gene regulatory networks, providing strong support in life science research. However, the application of single‐cell RNA sequencing in the field of oral science has not been reviewed comprehensively yet. Therefore, this paper reviews the development and application of single‐cell RNA sequencing in oral science, including fields of tissue development, teeth and jaws diseases, maxillofacial tumors, infections, etc., providing reference and prospects for using single‐cell RNA sequencing in studying the oral diseases, tissue development, and regeneration.

Immunomodulatory Activities of Periodontal Ligament Stem Cells in Orthodontic Forces-Induced Inflammatory Processes: Current Views and Future Perspectives

Orthodontic tooth movement (OTM) is induced by applying active mechanical forces, causing a local non-infectious inflammatory response in the periodontal ligament (PDL). As a prerequisite for OTM, the inflammation status is associated with increased levels of various cytokines and involves the interaction between immune cells and periodontal ligament stem cells (hPDLSCs). It is well established that hPDLSCs respond to orthodontic forces in several ways, such as by secreting multiple inflammatory factors. Another essential feature of hPDLSCs is their immunomodulatory activities, which are executed through cytokine (e.g., TNF-α and IL-1β)-induced production of various soluble immunomediators (e.g., indoleamine-2,3-dioxygenase-1, tumor necrosis factor-inducible gene 6 protein, prostaglandin E₂) and direct cell-to-cell contact (e.g., programmed cell death ligand 1, programmed cell death ligand 2). It is well known that these immunomodulatory abilities are essential for local periodontal tissue homeostasis and regeneration. So far, only a handful of studies provides first hints that hPDLSCs change immunological processes during OTM via their immunomodulatory activities. These studies demonstrate the pro-inflammatory aspect of immunomodulation by hPDLSCs. However, no studies exist which investigate cytokine and cell-to-cell contact mediated immunomodulatory activities of hPDLSCs. In this perspective article, we will discuss the potential role of the immunomodulatory potential of hPDLSCs in establishing and resolving the OTM-associated non-infectious inflammation and hence its potential impact on periodontal tissue homeostasis during OTM.

The clinical management of orthodontically-induced external root resorption: A questionnaire survey

INTRODUCTION

With more dentists performing orthodontics, identifying and managing patients at risk or affected by orthodontically-induced external root resorption (OIERR) is paramount.

METHODS

This study, conducted according to STROBE (STrengthening the Reporting of OBservational studies in Epidemiology), studied Australian orthodontists. Orthodontists were asked to complete a clinical questionnaire evaluating their diagnostic and management approaches to OIERR.

RESULTS

Orthodontists most commonly use a history of previous root resorption and the use of an orthopantomogram to screen and monitor patients. An orthopantomogram is used either 6 months for those identified as at risk of OIERR or 10-12 months for those who are not. Once detected, most orthodontists will record OIERR in terms of severity. If severe root resorption was detected, orthodontists would compromise on the treatment outcome and promptly complete treatment; if extraction sites remain closed, most orthodontists will interrupt treatment for 3-6 months. After treatment, orthodontists' retention protocol is unchanged regardless of OIERR experience. Treatment planning for patients with generalized OIERR before treatment (P = 0.002) was the only decision shown to be associated with years of clinical experience (P >0.05).

CONCLUSIONS

It is shown that no 1 method for managing OIERR exists, with most orthodontists arguing patient specificity to treatment modality. The various selected clinical approaches accurately reflect the current state of scientific literature on the topic.

Immune Changes Induced by Orthodontic Forces: A Critical Review

Orthodontic tooth movement (OTM) is generated by a mechanical force that induces an aseptic inflammatory response in the periodontal tissues and a subsequent coordinated process of bone resorption and apposition. In this review, we critically summarize the current knowledge on the immune processes involved in OTM inflammation and provide a novel insight into the relationship between classical inflammation and clinical OTM phases. We found that most studies focused on the acute inflammatory process, which ignites the initial alveolar bone resorption. However, the exact mechanisms and the immune reactions involved in the following OTM phases remain obscure. Recent studies highlight the existence of a typical innate response of resident and extravasated immune cells, including granulocytes and natural killer (NK), dendritic, and γδT cells. Based on few available studies, we shed light on an active, albeit incomplete, process of resolution in the lag phase, supported by continuously elevated ratios of M1/M2 macrophage and receptor activator of nuclear factor κB ligand/osteoprotegerin ratio. This partial resolution enables tissue formation and creates the appropriate environment for a transition between the innate and adaptive arms of the immune system, essential for the tissue's return to homeostasis. Nevertheless, as the mechanical trigger persists, the resolution turns into a low-grade chronic inflammation, which underlies the next, acceleration/linear OTM phase. In this stage, the acute inflammation dampens, and a simultaneous process of bone resorption and formation occurs, driven by B and T cells of the adaptive immune arm. Excessive orthodontic forces or tooth movement in periodontally affected inflamed tissues may hamper resolution, leading to "maladaptive homeostasis" and tissue loss due to uncoupled bone resorption and formation. The review ends with a brief description of the translational studies on OTM immunomodulation. Future studies are necessary for further uncovering cellular and molecular immune targets and developing novel strategies for controlling OTM by local and sustained tuning of the inflammatory process.

The effect of high concentration of zoledronic acid on tooth induced movement and its repercussion on root, periodontal ligament and alveolar bone tissues in rats

Zoledronic acid (ZA) is often prescribed for osteoporosis or resorptive metabolic bone disease. This study aims to evaluate the effect of ZA on orthodontic tooth movement (OTM) and root and bone resorption and its repercussion on root, periodontal ligament and alveolar bone tissues. The experimental group consisted of 72 Wistar rats divided in four subgroups: Naive, Saline and Zoledronic Acid groups at the concentration of 0.2 mg/kg [ZA (0.2)] or 1.0 mg/kg [ZA (1.0)]. The animals were subjected to i.v (dorsal penile vein) administrations of ZA or saline solution, on days 0, 7, 14 and 42. Under anesthesia, NiTi springs were installed in the first left maxillary molar with 50gf allowing the OTM, except for the negative control group (N) for mesial movement of the left first maxillary teeth. The animals were sacrificed and maxillae were removed for macroscopic and histopathological analyzes, scanning electron microscopy, computerized microtomography and confocal microscopy. Treatment with ZA decreased the OTM and the number of osteoclasts and loss of alveolar bone when compared to the naive and saline groups. Reduction of radicular resorption, increased necrotic areas and reduced vascularization in the periodontal ligament were observed in the ZA groups. ZA interferes with OTM and presents anti-resorptive effects on bone and dental tissues associated with a decreased vascularization, without osteonecrosis.

Interleukin-1β Induced Matrix Metalloproteinase Expression in Human Periodontal Ligament-Derived Mesenchymal Stromal Cells under In Vitro Simulated Static Orthodontic Forces

The periodontal ligament (PDL) responds to applied orthodontic forces by extracellular matrix (ECM) remodeling, in which human periodontal ligament-derived mesenchymal stromal cells (hPDL-MSCs) are largely involved by producing matrix metalloproteinases (MMPs) and their local inhibitors (TIMPs). Apart from orthodontic forces, the synthesis of MMPs and TIMPs is influenced by the aseptic inflammation occurring during orthodontic treatment. Interleukin (IL)-1β is one of the most abundant inflammatory mediators in this process and crucially affects the expression of MMPs and TIMPs in the presence of cyclic low-magnitude orthodontic tensile forces. In this study we aimed to investigate, for the first time, how IL-1β induced expression of MMPs, TIMPs and how IL-1β in hPDL-MSCs was changed after applying in vitro low-magnitude orthodontic tensile strains in a static application mode. Hence, primary hPDL-MSCs were stimulated with IL-1β in combination with static tensile strains (STS) with 6% elongation. After 6- and 24 h, MMP-1, MMP-2, TIMP-1 and IL-1β expression levels were measured. STS alone had no influence on the basal expression of investigated target genes, whereas IL-1β caused increased expression of these genes. In combination, they increased the gene and protein expression of MMP-1 and the gene expression of MMP-2 after 24 h. After 6 h, STS reduced IL-1β-induced MMP-1 synthesis and MMP-2 gene expression. IL-1β-induced TIMP-1 gene expression was decreased by STS after 6- and 24-h. At both time points, the IL-1β-induced gene expression of IL-1β was increased. Additionally, this study showed that fetal bovine serum (FBS) caused an overall suppression of IL-1β-induced expression of MMP-1, MMP-2 and TIMP-1. Further, it caused lower or opposite effects of STS on IL-1β-induced expression. These observations suggest that low-magnitude orthodontic tensile strains may favor a more inflammatory and destructive response of hPDL-MSCs when using a static application form and that this response is highly influenced by the presence of FBS in vitro.

Dietary Salt Accelerates Orthodontic Tooth Movement by Increased Osteoclast Activity

Dietary salt uptake and inflammation promote sodium accumulation in tissues, thereby modulating cells like macrophages and fibroblasts. Previous studies showed salt effects on periodontal ligament fibroblasts and on bone metabolism by expression of nuclear factor of activated T-cells-5 (NFAT-5). Here, we investigated the impact of salt and NFAT-5 on osteoclast activity and orthodontic tooth movement (OTM). After treatment of osteoclasts without (NS) or with additional salt (HS), we analyzed gene expression and the release of tartrate-resistant acid phosphatase and calcium phosphate resorption. We kept wild-type mice and mice lacking NFAT-5 in myeloid cells either on a low, normal or high salt diet and inserted an elastic band between the first and second molar to induce OTM. We analyzed the expression of genes involved in bone metabolism, periodontal bone loss, OTM and bone density. Osteoclast activity was increased upon HS treatment. HS promoted periodontal bone loss and OTM and was associated with reduced bone density. Deletion of NFAT-5 led to increased osteoclast activity with NS, whereas we detected impaired OTM in mice. Dietary salt uptake seems to accelerate OTM and induce periodontal bone loss due to reduced bone density, which may be attributed to enhanced osteoclast activity. NFAT-5 influences this reaction to HS, as we detected impaired OTM and osteoclast activity upon deletion.

The functions of mechanosensitive ion channels in tooth and bone tissues

Tooth and bone are independent tissues with a close relationship. Both are composed of a highly calcified outer structure and soft inner tissue, and both are constantly under mechanical stress. In particular, the alveolar bone and tooth constitute an occlusion system and suffer from masticatory and occlusal force. Thus, mechanotransduction is a key process in many developmental, physiological and pathological processes in tooth and bone. Mechanosensitive ion channels such as Piezo1 and Piezo2 are important participants in mechanotransduction, but their functions in tooth and bone are poorly understood. This review summarizes our current understanding of mechanosensitive ion channels and their roles in tooth and bone tissues. Research in these areas may shed new light on the regulation of tooth and bone tissues and potential treatments for diseases affecting these tissues.

Effects of histamine on human periodontal ligament fibroblasts under simulated orthodontic pressure

As type-I-allergies show an increasing prevalence in the general populace, orthodontic patients may also be affected by histamine release during treatment. Human periodontal ligament fibroblasts (PDLF) are regulators of orthodontic tooth movement. However, the impact of histamine on PDLF in this regard is unknown. Therefore PDLF were incubated without or with an orthodontic compressive force of 2g/cm² with and without additional histamine. To assess the role of histamine-1-receptor (H1R) H1R-antagonist cetirizine was used. Expression of histamine receptors and important mediators of orthodontic tooth movement were investigated. PDLF expressed histamine receptors H1R, H2R and H4R, but not H3R. Histamine increased the expression of H1R, H2R and H4R as well as of interleukin-6, cyclooxygenase-2, and prostaglandin-E2 secretion even without pressure application and induced receptor activator of NF-kB ligand (RANKL) protein expression with unchanged osteoprotegerin secretion. These effects were not observed in presence of H1R antagonist cetirizine. By expressing histamine receptors, PDLF seem to be able to respond to fluctuating histamine levels in the periodontal tissue. Increased histamine concentration was associated with enhanced expression of proinflammatory mediators and RANKL, suggesting an inductive effect of histamine on PDLF-mediated osteoclastogenesis and orthodontic tooth movement. Since cetirizine inhibited these effects, they seem to be mainly mediated via histamine receptor H1R.

Extracellular Vesicles From Adipose Tissue-Derived Stem Cells Affect Notch-miR148a-3p Axis to Regulate Polarization of Macrophages and Alleviate Sepsis in Mice

Extracellular vesicles (EVs) from adipose tissue-derived stem cells have been reported to attenuate lipopolysaccharide (LPS) induced inflammation and sepsis while the specific mechanism is unclear. This study explored the underlying molecular mechanisms of EVs from adipose tissue-derived stem cells in reducing inflammation. LPS- induced macrophage models and mice model were established to mimic inflammation in vitro and in vivo. EVs were extracted from adipose tissue-derived stem cells and identified. It was found that proinflammatory cytokines, including IL-1β, IL-6, and TNF-α, substantially decreased after EVs were applied to LPS-stimulated macrophages and mice, and thus, LPS induced M1 polarization was inhibited and sepsis was strongly alleviated. In the LPS induced macrophages, the expression of Notch signaling molecules and the activation of the NF-κB pathway were substantially decreased after the administration of EVs. Then, RBP-J ^-/- mice and macrophages were used. It was found that the miR-148a-3p level was significantly lower in the RBP-J ^-/- macrophages than in the wildtype macrophages. In the LPS induced macrophages, the increasing of miR-148a-3p was milder in the RBP-J ^-/- macrophages than in the wild type macrophages. Then, miR-148a-3p was overexpressed in macrophages and mice, and we found that the expression of proinflammatory cytokines was increased both in vivo and in vitro. The protective effect of EVs in LPS induced sepsis was diminished by the overexpression of miR-148a-3p. In conclusion, we proved that EVs could attenuate inflammation and further protect organ function by regulating the Notch-miR148a-3p signaling axis and then decreasing macrophage polarization to M1.

Immunorthodontics: in vivo gene expression of orthodontic tooth movement

Orthodontic tooth movement (OTM) is a “sterile” inflammatory process. The present study aimed to reveal the underlying biological mechanisms, by studying the force associated-gene expression changes, in a time-dependent manner. Ni-Ti springs were set to move the upper 1^st-molar in C57BL/6 mice. OTM was measured by μCT. Total-RNA was extracted from tissue blocks at 1,3,7 and 14-days post force application, and from two control groups: naïve and inactivated spring. Gene-expression profiles were generated by next-generation-RNA-sequencing. Gene Set Enrichment Analysis, K-means algorithm and Ingenuity pathway analysis were used for data interpretation. Genes of interest were validated with qRT-PCR. A total of 3075 differentially expressed genes (DEGs) were identified, with the greatest number at day 3. Two distinct clusters patterns were recognized: those in which DEGs peaked in the first days and declined thereafter (tissue degradation, phagocytosis, leukocyte extravasation, innate and adaptive immune system responses), and those in which DEGs were initially down-regulated and increased at day 14 (cell proliferation and migration, cytoskeletal rearrangement, tissue homeostasis, angiogenesis). The uncovering of novel innate and adaptive immune processes in OTM led us to propose a new term “Immunorthodontics”. This genomic data can serve as a platform for OTM modulation future approaches.

Fucoidan inhibits tooth movement by promoting restorative macrophage polarization through the STAT3 pathway

Retention after treatment and effective anchorage control are two essential factors in orthodontics. Our study aimed to explore the effects of fucoidan on orthodontic tooth movement (OTM) and the involvement of macrophages. We established a murine OTM model to test the effect of fucoidan administration. We found that mice injected with fucoidan had a deceleration in OTM and a higher bone mineral density. Moreover, fucoidan increased the proportion of F4/80⁺ CD206⁺ macrophages and promoted the messenger RNA expression of Arg-1, CD206, and IL-10 at both in vivo and in vitro levels. In addition, macrophages showed lower expression of TNF-α, IL-1β, and IL-6 and a decrease in F4/80⁺ CD11c⁺ cells. Mechanistically, the level of phosphorylated STAT3 was elevated in unpolarized and restorative macrophages after treatment with fucoidan. Taken together, our findings suggest that fucoidan treatment inhibits OTM and enhances the stability of teeth after movement by promoting restorative macrophages through the STAT3 pathway.

Orthodontic mechanotherapies and their influence on external root resorption: A systematic review

INTRODUCTION

This systematic review assesses the literature regarding the association between orthodontic tooth movement and external root resorption. By determining the evidence level supporting the association, the results could provide clinical evidence for minimizing the deleterious effect of orthodontic tooth movement.

METHODS

Electronic databases, including MEDLINE, PubMed, Embase, Scopus, CINAHL, Cochrane Library, and LILACS, were searched up to February 2018, with hand searching of selected orthodontic journals undertaken to identify any preelectronic publications. Searches were undertaken with no restrictions on year, publication status, or language. Selection criteria included randomized controlled trials conducted with the use of fixed orthodontic appliances or sequential thermoplastic aligners on human patients. The quality of included studies was assessed with the use of the Cochrane Risk of Bias Tool and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Inter-rater agreement of the review authors was used for the inclusion of primary articles, risk of bias assessment, and evaluation of the quality of evidence (GRADE), and it was calculated with the use of the Cohen kappa statistic.

RESULTS

A total of 654 articles were retrieved in the initial search. After the review process, 25 articles describing 24 individual trials met the inclusion criteria. Sample sizes ranged from 6 to 154 patients. Most articles were classified as having unclear risks of bias and very low to low quality of evidence.

CONCLUSIONS

There is very low to low evidence for supporting positive associations between root resorption and increased force levels, force continuity, intrusive forces, and treatment duration. Moreover, by including a pause in treatment for patients experiencing root resorption, it may be possible for the clinician to reduce the severity of the condition. Of the included studies, the most common methodologic flaws include the absence of a control group, appropriate randomization strategy, and adequate examinations before and after treatment.

Assessment of tumor necrosis factor alpha (TNFα) and interleukin 6 level in gingival crevicular fluid during orthodontic tooth movement: a randomized split-mouth clinical trial

Background

Orthodontic tooth movement (OTM) is based on induction of periodontal tissue remodeling. Mechanical tooth stimulation results in the release of pro-inflammatory mediators. These mediators cause bone resorption and deposition at the pressure and tension sites and play a role in OTM. Thus, assessment of chemical biomarkers can help determine the exact amount of load and its duration of application required for each tooth and select the most efficient treatment plan with minimal complications.

Objective

This study aimed to determine the level of tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6) in gingival crevicular fluid (GCF) during OTM.

Methods

This randomized split-mouth clinical trial (parallel) was performed on 10 patients who were presenting to the Orthodontic Department of Qazvin University of Medical Sciences from November 2015 to June 2016. A canine tooth was randomly selected as the study group and subjected to distalization force while the contralateral canine tooth served as control. Using paper strip, GCF was collected from the study and control teeth prior to orthodontic force application (T0), one hour after (T1) and 28 days after force application (T2), then the level of TNFα and IL-6 was measured using ELISA. Data were analyzed using SPSS version 20 via Friedman and Wilcoxon test, and considering the significance level at p<0.05.

Results

The level of TNFα (p=0.0799) and IL-6 (p=0.678) at both sides of study teeth was higher than both side of control teeth at T1. Also, the level of IL-6 (p=0.515) and TNFα (p=0.508) were higher at the tension side compared to the pressure side; but the difference was not statistically significant.

Conclusion

Due to the free circulation of GCF in gingival sulcus, the level of mediators in the GCF collected from the mesial and distal areas alone cannot serve as a suitable index for assessment of activity at the tension and pressure sites.

Trial registration

The trial was registered at the Iranian Registry of Clinical Trials with the IRCT ID: IRCT2017030632903N2.

Funding

The present study was supported by a grant from the Research Council, Qazvin University of Medical Sciences, Qazvin, Iran (thesis no.: 40).

Experimental tooth movement temporally changes neural excitation and topographical map in rat somatosensory cortex

During orthodontic treatment, binding teeth, may change the topographically organized representation of teeth in the cerebral cortex. To test the hypothesis that experimental tooth movement (ETM) changes the somatotopy of an individual tooth arrangement in the somatosensory cortex, we examined the spatiotemporal features of cortical excitatory propagation in response to mechanical stimulation of the maxillary incisor or molar using optical imaging in late adolescent rats without or with ETM. The ETM models consisted of 1d, 3d, and 7d ETM in which a closed-coil spring was ligated between the maxillary first molar and incisors. In controls, incisor and molar mechanical stimulation evoked excitation in the rostral and dorsocaudal regions of the primary somatosensory cortex (S1), respectively. In addition, the secondary somatosensory cortex and insular oral region (S2/IOR) were also activated. Incisor stimulation-induced excitatory regions in S1 of 3d and 7d ETM shifted without changing the maximum excitatory area or peak amplitude; the incisor stimulation-responding region moved toward the dorsocaudal region, which responded to molar stimulation in the control. This shift in excitatory region was not observed in 1d ETM. One day after removal of the coil spring that was attached for 6 days, the excitatory region shift in S1 was recovered to the control region. On the other hand, 1d ETM exhibited facilitation of the excitatory area and peak amplitude upon molar stimulation, and the facilitation of excitatory propagation disappeared in 3d and 7d ETM. These results may explain the clinical finding that abnormal sensation temporally occurs during orthodontic treatment.

Low-Magnitude Forces for Bone Modeling and Remodeling in Dentofacial Orthopedics

PURPOSE OF REVIEW

To examine the evidence in support of light continuous forces for enhancing bone adaptation (modeling and remodeling) in orthodontics and dentofacial orthopedics.

RECENT FINDINGS

Clinical evidence suggests that light continuous orthodontic force can achieve physiologic expansion of the maxillary arch, but the long-term stability and the biological effects of the procedure are unclear. Compared to conventional orthodontic appliances that deliver heavy interrupted forces for tooth movement, the application of low-magnitude forces in animal models leads to anabolic modeling and remodeling of the alveolar bone in the path of orthodontic tooth movement. This results in dental translation and expansion of the alveolar process. Light continuous forces are preferable to heavy forces for more physiologic dentofacial orthopedics. The interaction of low-magnitude loads with soft tissue posture achieves therapeutic adaptation of the craniofacial skeleton. The increasing emphasis on genomic medicine and personalized treatment planning should focus on low-magnitude loads in orthodontics and dentofacial orthopedics.

The influence of teriparatide in induced tooth movement: A systematic review

Background

Teriparatide is a synthetic drug similar than PTH (parathyroid hormone), which is currently used as long-term treatment option for patients with bone chronic diseases, as osteoporosis; and this drug can interfere in a positive way in orthodontic movement. Objectives: The medical literature was assessed in the present systematic review in order to determine the level of scientific evidence supporting the influence of teriparatide in induced tooth movement.

Material and Methods

The PRISMA Checklist was followed in this systematic review. Four electronic databases (PubMed; Scopus; ScienceDirect; OpenGrey) were searched without implementing restrictions of year, status, and language of publications. The inclusion criteria consisted of selecting only experimental studies comparing the influence of teriparatide in tooth movement of male Wistar rats. The exclusion criteria consisted of experiments with female rats or other experimental animals, and animals with pathologic conditions. The eligible studies were evaluated based on methodological quality. Two trained examiners performed all the research steps.

Results

The initial sample comprised 700 studies, which was reduced to 664 after the exclusion of duplicates (n=36). Three articles were selected for the final qualitative analysis. The local administration of parathyroid hormone (PTH) 1-34 or PTH 1-84 revealed major effectiveness when compared with control groups and systematic administration. Additionally, the dilution of PTH 1-34 within methyl cellulose (MC) gel increased the time range for drug release, enabling to reduce the drug concentration without decreasing the effectiveness of tooth movement.

Conclusions

Teriparatide demonstrated potential acceleration of tooth movement in Wistar rats depending on the drug concentration; drug administration; and time for drug release.

Key words:Teriparatide, tooth movement, parathyroid hormone, orthodontics.

Osteoimmunology: Major and Costimulatory Pathway Expression Associated with Chronic Inflammatory Induced Bone Loss

The field of osteoimmunology has emerged in response to the range of evidences demonstrating the close interrelationship between the immune system and bone metabolism. This is pertinent to immune-mediated diseases, such as rheumatoid arthritis and periodontal disease, where there are chronic inflammation and local bone erosion. Periprosthetic osteolysis is another example of chronic inflammation with associated osteolysis. This may also involve immune mediation when occurring in a patient with rheumatoid arthritis (RA). Similarities in the regulation and mechanisms of bone loss are likely to be related to the inflammatory cytokines expressed in these diseases. This review highlights the role of immune-related factors influencing bone loss particularly in diseases of chronic inflammation where there is associated localized bone loss. The importance of the balance of the RANKL-RANK-OPG axis is discussed as well as the more recently appreciated role that receptors and adaptor proteins involved in the immunoreceptor tyrosine-based activation motif (ITAM) signaling pathway play. Although animal models are briefly discussed, the focus of this review is on the expression of ITAM associated molecules in relation to inflammation induced localized bone loss in RA, chronic periodontitis, and periprosthetic osteolysis, with an emphasis on the soluble and membrane bound factor osteoclast-associated receptor (OSCAR).