Do electrical current and laser therapies improve bone remodeling during an orthodontic treatment with corticotomy?

Bone regeneration: The influence of composite HA/TCP scaffolds and electrical stimulation on TGF/BMP and RANK/RANKL/OPG pathways

The repair of critical-sized bone defects represents significant clinical challenge. An alternative approach is the use of 3D composite scaffolds to support bone regeneration. Hydroxyapatite (HA) and tri-calcium phosphate (β-TCP), combined with polycaprolactone (PCL), offer promising mechanical resistance and biocompatibility. Bioelectrical stimulation (ES) at physiological levels is proposed to reestablishes tissue bioeletrocity and modulates cell signaling communication, such as the BMP/TGF-β and the RANK/RANK-L/OPG pathways. This study aimed to evaluate the use HA/TCP scaffolds and ES therapy for bone regeneration and their impact on the TGF-β/BMP pathway, alongside their relationship with the RANK/RANKL/OPG pathway in critical bone defects. The scaffolds were implanted at the bone defect in animal model (calvarial bone) and the area was subjected to ES application twice a week at 10 µA intensity of current for 5 min each session. Samples were collected for histomorphometry, immunohistochemistry, and molecular analysis. The TGF-β/BMP pathway study showed the HA/TCP+ES group increased BMP-7 gene expression at 30 and 60 days, and also greater endothelial vascular formation. Moreover, the HA/TCP and HA/TCP+ES groups exhibited a bone remodeling profile, indicated by RANKL/OPG ratio. HA/TCP scaffolds with ES enhanced vascular formation and mineralization initially, while modulation of the BMP/TGF pathway maintained bone homeostasis, controlling resorption via ES with HA/TCP.

Dopamine promotes osteogenic differentiation of PDLSCs by activating DRD1 and DRD2 during orthodontic tooth movement via ERK1/2 signaling pathway

Introduction

Orthodontic tooth movement (OTM) involves complex interactions between mechanical forces and periodontal tissue adaptation, mainly mediated by periodontal ligament cells, including periodontal ligament stem cells (PDLSCs), osteoblasts, and osteoclasts. Dopamine (DA), a neurotransmitter known for its critical role in bone metabolism, is investigated in this study for its potential to enhance osteogenic differentiation in PDLSCs, which are pivotal in OTM. This study examined the potential of DA to facilitate OTM by binding to DA receptors (D1R and D2R) and activating the ERK1/2 signaling pathway. We propose that DA's interaction with these receptors on PDLSCs could enhance osteogenic differentiation, thereby accelerating bone remodeling and reducing the duration of orthodontic treatments, which offering a novel approach to improve clinical outcomes in orthodontic care.

Methods

This study utilized a rat OTM model, micro-CT, histological analyses, and in vitro assays to investigate dopamine's effect on osteogenesis. PDLSCs were cultured and treated with DA, and cytotoxicity, osteogenic differentiation, gene and protein expression assessed.

Results

Dopamine administration significantly increased trabecular bone density and osteogenic marker expression in an OTM rat model. In vitro, DA at 10 nM optimally promoted human PDLSCs osteogenesis without affecting proliferation. Blocking DA receptors or inhibiting the ERK1/2 pathway attenuated these effects, underscoring the importance of dopaminergic signaling in tension-induced osteogenesis during OTM.

Conclusion

Taken together, our study reveals that local dopamine administration at a concentration of 10 nM not only enhances tension-induced osteogenesis in vivo but also significantly promotes osteogenic differentiation of PDLSCs in vitro through D1 and D2 receptor-mediated ERK1/2 signaling pathway activation.

Effect of photobiomodulation and corticopuncture methods on tooth displacement and gene expression: animal study

AIM

The aim of this study was to evaluate the expression levels of vascular endothelial growth factor (VEGF), Peroxiredoxin 1 (PRX1), glucose transporter 1 (GLUT1) and type I collagen (COL1) and the rate of tooth movement comparing 3 accelerated tooth movement (ATM) methods: Corticopuncture (CP), photobiomodulation (PBM) and the combined technique (CP + PBM) on days 1, 3, 7 and 14.

METHODS

Orthodontic tooth movement was induced in 24 male Wistar rats. CP procedure included three perforations: two in the palate and one mesial to the molars. GaAlAs diode laser irradiation was performed on days 0, 2, 4 and 6, totaling 4 irradiations. 14 days (810 nm, 100 mW, 15 s). Gingival tissue was collected from the cervical area of both first molars and qPCR was performed to isolate and quantify mRNA levels.

RESULTS

All ATM groups showed increased tooth displacement compared to control after 14 days (20% for PBM; 40% for CP and 60% for CP + PBM). PBM showed higher VEGF expression on days 1,3 and 7 followed by CP and CP + PBM. PRX1 levels increased on days 1 and 3 in PBM and CP + PBM. GLUT1 increased on day 3 in all groups. No difference was found on levels of VEGF, PRX1 and GLUT1 among the groups on day 14, except for COL1 which increased significantly in PBM group.

CONCLUSION

All ATM methods showed higher expression of all of VEGF, PRX1, GLUT1, COL1 than control group. PBM and CP + PBM groups had more expression related to angiogenesis, glucose uptake, oxidative stress and collagen synthesis.

Potential Role of BMP7 in Regenerative Dentistry

In recent years, the field of regenerative dentistry has garnered considerable attention for its focus on restoring and renewing damaged dental tissue. This narrative review explores the potential of bone morphogenetic protein 7 (BMP7) and its diverse applications in the regeneration of dental tissue. Recently, significant efforts have been made to understand BMP7's role in advancing regenerative dentistry. Amongst the various signalling molecules investigated for their regenerative capabilities, BMP7 emerges as a pivotal candidate, demonstrating the ability to stimulate the regeneration of dental pulp, periodontal, craniofacial, and alveolar bone tissues for dental implant placement. Whilst BMP7 exhibits significant promise as a therapeutic agent in regenerative dentistry, further research and clinical trials are necessary to fully unlock its potential and optimise its clinical effectiveness in addressing diverse dental and craniofacial conditions. This review highlights BMP7's substantial potential and emphasises the ongoing need for continued research to effectively harness its clinical utility in diverse dental and craniofacial contexts.

Effect of estrogen depression on alveolar bone microarchitecture and periodontal ligament cells during orthodontic movement

This study aimed to evaluate the effects of the estrogen depression during orthodontic tooth movement on alveolar bone microarchitecture and periodontal ligament. Female Wistar rats were divided into two groups, one consisting of non-ovariectomized animals subjected to orthodontic tooth movement, and one comprising ovariectomized animals subjected to orthodontic tooth movement. Micro-CT assessment of bone volume to total volume (BV/TV), total porosity, trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) in the alveolar bone of the orthodontically moved tooth was performed. Histomorphometric analyses were made in the periodontal ligament, and immunoexpression of RANK, RANKL, OPG, and TUNEL were quantified. Orthodontic tooth movement in the group of ovariectomized rats was faster than in non-ovariectomized animals. The alveolar bone area showed lower values of BV/TV and trabecular thickness, and higher bone porosity and trabeculae numbers in the ovariectomized rats. Histological analyses in the ovariectomized group revealed an increase in collagen fibers in the periodontal ligament. The apoptotic cell counts in the periodontal ligament were higher in the group of ovariectomized rats than in the sham-operated rats. Ovariectomy resulted in an increase in tooth movement and alteration of the alveolar bone microstructure in the first 7 day of orthodontic tooth movement, and in the presence of apoptotic cells in the periodontal ligament.

A Biomimetic Nanogenerator to Enhance Bone Regeneration by Restoring Electric Microenvironments

Piezoelectric materials have received increasing attention in bone regeneration due to their prominent role in bioelectricity in bone homeostasis. This study aimed to develop bioactive barium titanate-chitosan-graphene oxide piezoelectric nanoparticles (BCG-NPs) to improve biocompatibility and stimulate bone repair. Butterfly loops, hysteresis loops, and in vitro microcurrent studies on BCG-NPs confirmed their good piezoelectric properties. BCG-NPs exhibited enhanced alkaline phosphatase activity, mineralized nodule formation, and expression of osteogenic-associated proteins and genes in human umbilical cord Wharton's jelly-derived mesenchymal stem cells by creating microelectric environments in response to noninvasive ultrasound stimulation. Further, BCG-NPs upregulated intracellular calcium ions via electrical stimulation. They acted synergistically with piezo-type mechanosensitive ion channel component 1 and calcium-permeable cation channel transient receptor potential vanilloid 4 to activate osteogenic differentiation. In conclusion, ultrasound-assisted BCG-NPs created a microelectric environment that putatively promoted bone repair in a noninvasive manner.

Effective Orthodontic Tooth Movement via an Occlusion-Activated Electromechanical Synergistic Dental Aligner

Malocclusion is a prevalent dental health problem plaguing over 56% worldwide. Mechanical orthodontic aligners render directional teeth movement extensively used for malocclusion treatment in the clinic, while mechanical regulation inefficiency prolongs the treatment course and induces adverse complications. As a noninvasive physiotherapy, an appropriate electric field plays a vital role in tissue metabolism engineering. Here, we propose an occlusion-activated electromechanical synergistic dental aligner that converts occlusal energy into a piezo-excited alternating electric field for accelerating orthodontic tooth movement. Within an 18-day intervention, significantly facilitated orthodontic results were obtained from young and aged Sprague-Dawley rats, increasing by 34% and 164% in orthodontic efficiency, respectively. The different efficiencies were attributed to age-distributed periodontal tissue status. Mechanistically, the electromechanical synergistic intervention modulated the microenvironment, enhanced osteoblast and osteoclast activity, promoted alveolar bone metabolism, and ultimately accelerated tooth movement. This work holds excellent potential for personalized and effective treatment for malocclusions, which would vastly reduce the suffering of the long orthodontic course.

The Effects and Mechanisms of PBM Therapy in Accelerating Orthodontic Tooth Movement

Malocclusion is one of the three major diseases, the incidence of which could reach 56% of the imperiled oral and systemic health in the world today. Orthodontics is still the primary method to solve the problem. However, it is clear that many orthodontic complications are associated with courses of long-term therapy. Photobiomodulation (PBM) therapy could be used as a popular way to shorten the course of orthodontic treatment by nearly 26% to 40%. In this review, the efficacy in cells and animals, mechanisms, relevant cytokines and signaling, clinical trials and applications, and the future developments of PBM therapy in orthodontics were evaluated to demonstrate its validity. Simultaneously, based on orthodontic mechanisms and present findings, the mechanisms of acceleration of orthodontic tooth movement (OTM) caused by PBM therapy were explored in relation to four aspects, including blood vessels, inflammatory response, collagen and fibers, and mineralized tissues. Also, the cooperative effects and clinical translation of PBM therapy in orthodontics have been explored in a growing numbers of studies. Up to now, PBM therapy has been gaining popularity for its non-invasive nature, easy operation, and painless procedures. However, the validity and exact mechanism of PBM therapy as an adjuvant treatment in orthodontics have not been fully elucidated. Therefore, this review summarizes the efficacy of PBM therapy on the acceleration of OTM comprehensively from various aspects and was designed to provide an evidence-based platform for the research and development of light-related orthodontic tooth movement acceleration devices.

Electrical stimulation therapy and rotary jet-spinning scaffold to treat bone defects

The combination of electrical stimulation (ES) and bone tissue engineering (BTE) has been successful in treatments of bone regeneration. This study evaluated the effects of ES combined with PCL + β-TCP 5% scaffolds obtained by rotary jet spinning (RJS) in the regeneration of bone defects in the calvaria of Wistar rats. We used 120 animals with induced bone defects divided into 4 groups (n = 30): (C) without treatment; (S) with PCL+ β-TCP 5% scaffold; (ES) treated with ES (10 μA/5 min); (ES + S) with PCL + β-TCP 5% scaffold. The ES occurred twice a week during the entire experimental period. Cell viability (in vitro: Days 3 and 7) and histomorphometric, histochemical, and immunohistochemical (in vivo; Days 30, 60, and 90) analysis were performed. In vitro, ES + S increased cell viability after Day 7 of incubation. In vivo, it was observed modulation of inflammatory cells in ES therapy, which also promoted blood vessels proliferation, and increase of collagen. Moreover, ES therapy played a role in osteogenesis by decreasing ligand kappa B nuclear factor-TNFSF11 (RANKL), increasing alkaline phosphatase (ALP), and decreasing the tartarate-resistant acid phosphatase. The combination of ES with RJS scaffolds may be a promising strategy for bone defects regeneration, since the therapy controlled inflammation, favored blood vessels proliferation, and osteogenesis, which are important processes in bone remodeling.

Biological mechanism of surgery-mediated acceleration of orthodontic tooth movement: A narrative review

Surgery-mediated acceleration of orthodontic tooth movement (SAOTM) has been proven effective for decades. Research has confirmed that surgical approaches play an important role in adult patients with a short orthodontic treatment time. The mechanism of SAOTM involves short-term acceleration of localized hard and soft tissue remodeling, known as the regional acceleratory phenomenon. However, no relevant review on the biological mechanism of SAOTM has been performed to date. The proposed biological mechanism of acceleration of OTM involves the participation of various cells, cytokines, and signaling pathways. We herein review the relevant literature and summarize the biological mechanism of SAOTM to provide new insights for further research on acceleration of OTM.

In Vivo Investigation of Polymer-Ceramic PCL/HA and PCL/β-TCP 3D Composite Scaffolds and Electrical Stimulation for Bone Regeneration

Critical bone defects are a major clinical challenge in reconstructive bone surgery. Polycaprolactone (PCL) mixed with bioceramics, such as hydroxyapatite (HA) and tricalcium phosphate (TCP), create composite scaffolds with improved biological recognition and bioactivity. Electrical stimulation (ES) aims to compensate the compromised endogenous electrical signals and to stimulate cell proliferation and differentiation. We investigated the effects of composite scaffolds (PCL with HA; and PCL with β-TCP) and the use of ES on critical bone defects in Wistar rats using eight experimental groups: untreated, ES, PCL, PCL/ES, HA, HA/ES, TCP, and TCP/ES. The investigation was based on histomorphometry, immunohistochemistry, and gene expression analysis. The vascular area was greater in the HA/ES group on days 30 and 60. Tissue mineralization was greater in the HA, HA/ES, and TCP groups at day 30, and TCP/ES at day 60. Bmp-2 gene expression was higher in the HA, TCP, and TCP/ES groups at day 30, and in the TCP/ES and PCL/ES groups at day 60. Runx-2, Osterix, and Osteopontin gene expression were also higher in the TCP/ES group at day 60. These results suggest that scaffolds printed with PCL and TCP, when paired with electrical therapy application, improve bone regeneration.

Electrical therapies act on the Ca2+ /CaM signaling pathway to enhance bone regeneration with bioactive glass [S53P4] and allogeneic grafts

This study aimed to investigate the application of low-intensity electrostimulation (ES) and electromagnetic stimulation (EM) associated with bioactive glass (BG) or allogeneic grafts (BB) in bone regeneration. A cell viability test on osteoblasts (UMR-106) was performed in the presence of BB and BG grafts associated with ES (10 μA/5 min) and EM (500 Hz/2 min). Critical defects (25 mm² ) in calvaria were generated in male Wistar rats, and bone regeneration was evaluated on the 30th, 60th, and 120th days after surgery. Cell proliferation increased with the application of ES in both grafts and after EM with BG. Bone remodeling was more effective using the allogeneic graft in both therapies, with increased angiogenesis, osteoblast proliferation, and OPN expression in the BB + EM group. A higher number of osteoblasts and osteoclasts, and an increase in bone sialoprotein, Runx-2, and Opn gene expression were found in the BB + ES group. The BG graft associated with EM therapy had an increased proliferation of osteoblasts and increased expression of Runx-2 and Opn. Groups that had BG and ES therapy had increased numbers of osteoblasts, osteoclasts, and increased OPN expression. The expression of voltage-gated calcium channels increased in groups with ES, while calmodulin expression increased in therapies without grafting. ES and EM therapies favored the repair of bone defects upon grafting by improving angiogenesis, osteogenic gene expression, and tissue reorganization. Despite activating different pathways, both therapies increased the intracellular concentrations of calmodulin, leading to cell proliferation and bone regeneration.

Pulpal outcomes in orthodontic tooth movement in diabetes mellitus

Diabetes mellitus impairs angiogenesis and tissue reorganization during orthodontic tooth movement (OTM). Thus, this study evaluated pulpal outcomes in orthodontic tooth movement through metabolic changes in diabetes. Male Wistar rats were used, and the in vivo study design consisted of four groups (n = 10/group): C-non-diabetic animals not subjected to orthodontic tooth movement; D-diabetic animals not subjected to orthodontic tooth movement; OTM-non-diabetic animals subjected to orthodontic tooth movement; and D + OTM-diabetic animals subjected to orthodontic tooth movement. In addition, the pulps of the distovestibular root (DV) and mesiovestibular root (MV) were assessed by histomorphometric analyses and immunoexpression of the RANKL/OPG system. Pulpal analysis of the MV root showed an increase in blood vessels in diabetic animals. Inflammatory infiltrate and fibroblastic cells were elevated in diabetic animals with tooth movement in the DV and MV roots. In the DV and MV roots, diabetic rats with OTM showed a reduction in birefringent collagen fibers. The immunostaining for RANKL was higher in the pulp tissue of OTM in diabetic and non-diabetic animals. It was concluded that the pulp tissue has less adaptive and repair capacity during OTM in diabetes. Orthodontic strength can alter the inflammatory processes in the pulp.

Influence of microcurrent on the modulation of remodelling genes in a wound healing assay

The literature has shown the beneficial effects of microcurrent (MC) therapy on tissue repair. We investigated if the application of MC at 10 μA/90 s could modulate the expression of remodeling genes transforming growth factor beta (Tgfb), connective tissue growth factor (Ctgf), insulin-like growth factor 1 (Igf1), tenascin C (Tnc), Fibronectin (Fn1), Scleraxis (Scx), Fibromodulin (Fmod) and tenomodulin in NIH/3T3 fibroblasts in a wound healing assay. The cell migration was analyzed between days 0 and 4 in both fibroblasts (F) and fibroblasts + MC (F+MC) groups. On the 4th day, cell viability and gene expression were also analyzed after daily MC application. Higher expression of Ctgf and lower expression of Tnc and Fmod, respectively, were observed in the F+MC group in relation to F group (p < 0.05), and no difference was observed between the groups for the genes Tgfb, Fn1 and Scx. In cell migration, a higher number of cells in the scratch region was observed in group F+MC (p < 0.05) compared to group F on the 4th day, and the cell viability assay showed no difference between the groups. In conclusion, MC therapy at an intensity/time of 10 μA/90 s with 4 daily applications did not affect cell viability, stimulated fibroblasts migration with the involvement of Ctgf, and reduced the Tnc and Fmod expression.

Gestational protein restriction alters the RANKL/OPG system in the dental germ of offsprings

Evaluate the dentinogenesis in the offspring of rats submitted to gestational protein restriction (GPR).

DESIGN

The offspring were evaluated at the 21st day of gestation (21 dG). Assessments were made of morphological parameters and the RANKL/OPG system - bone tissue maturation markers - in the upper incisor tooth germ. Pregnant 10-week-old female Wistar rats were divided into normal protein (NP, 17% casein, n = 5) and low protein (LP, 6% casein, n = 5) diet groups. At 21 dG, the offspring maxillae were collected for histomorphometric and immunohistochemical analyses.

RESULTS

The LP group showed decreased thickness of the dentin and odontoblast cell layers on the tooth germ. GPR led to decreased OPG expression and increased RANKL expression in the incisor germ.

CONCLUSION

The results suggested that gestational protein restriction altered odontoblast RANKL/OPG expression and decreased dentin matrix deposition and thickness in tooth development.

Microcurrent and adipose-derived stem cells modulate genes expression involved in the structural recovery of transected tendon of rats

Tendon injuries are common and have a high incidence of re-rupture that can cause loss of functionality. Therapies with adipose-derived stem cells (ASC) and the microcurrent (low-intensity electrical stimulation) application present promising effects on the tissue repair. We analyzed the expression of genes and the participation of some molecules potentially involved in the structural recovery of the Achilles tendon of rats, in response to the application of both therapies, isolated and combined. The tendons were distributed in five groups: normal (N), transected (T), transected and ASC (C) or microcurrent (M) or with ASC, and microcurrent (MC). Microcurrent therapy was beneficial for tendon repair, as it was observed a statistically significant increase in the organization of the collagen fibers, with involvement of the TNC, CTGF, FN, FMDO, and COL3A1 genes as well as PCNA, IL-10, and TNF-α. ASC therapy significantly increased the TNC and FMDO genes expression with no changes in the molecular organization of collagen. With the association of therapies, a significant greater collagen fibers organization was observed with involvement of the FMOD gene. The therapies did not affect the expression of COL1A1, SMAD2, SMAD3, MKX, and EGR1 genes, nor did they influence the amount of collagen I and III, caspase-3, tenomodulin (Tnmd), and hydroxyproline. In conclusion, the application of the microcurrent isolated or associated with ASC increased the organization of the collagen fibers, which can result in a greater biomechanical resistance in relation to the tendons treated only with ASC. Future studies will be needed to demonstrate the biological effects of these therapies on the functional recovery of injured tendons.

Diabetes mellitus and periodontitis: Inflammatory response in orthodontic tooth movement

OBJECTIVES

This study evaluated, in experimental model, the inflammatory alterations in gingival tissue and alveolar bone during the orthodontic tooth movement (OTM) in diabetes mellitus (D) and periodontitis (P).

SETTING AND SAMPLE POPULATION

Forty male Wistar rats, 90 days old and weighing 300 g.

MATERIALS AND METHODS

The sample was divided into four groups (n = 10). OTM: orthodontic movement (10 days, 0.4 N force); P + OTM: periodontitis (ligature-induced periodontitis, 3-0 silk suture thread) and orthodontic movement; D + OTM: diabetes (Alloxan-induced diabetes, 150 mg/kg) and orthodontic movement; and D + P + OTM: diabetes, periodontitis and orthodontic movement. Tooth displacement was measured; fibroblast, inflammatory cells, osteoclast and blood vessels were quantified by histomorphometric analysis. Inflammatory markers, interleukin-6 (IL-6) and tumour necrosis factor (TNF-α) were quantified by ELISA (Enzyme-Linked Immunosorbent Assay) in gingival tissue. The fibroblastic growth factor (bFGF), transforming growth factor (TGF-β1) and the vascular endothelial growth factor (VEGF) were measured via Western blotting in the alveolar bone. The results were analysed by ANOVA and Tukey's test at a 5% significance level.

RESULTS

The quantification of inflammatory cells and the expression of IL-6, TNF-α, TGF-β1 and bFGF were increased in diabetes and periodontitis. However, the number of fibroblasts and blood vessels and the percentage of birefringent collagen fibres were higher in healthy animals. There was greater tooth displacement in the OTM group.

CONCLUSION

Diabetes Mellitus modifies the inflammatory response. The increased expression of inflammatory markers IL-6, TNF-α and TGF-β1 in diabetic animals impairs neovasculogenesis and tissue reorganization during orthodontic tooth movement, which may be aggravated by periodontitis.