Effect of parathyroid hormone on experimental tooth movement in rats

Impact of concentrated growth factor (CGF) injection on acceleration of orthodontic tooth movement in rabbits

BACKGROUND

The present study aimed to assess how a concentrated growth factor (CGF) injection affects the rate of orthodontic tooth movement in rabbits.

METHODS

This experimental investigation employed a split-mouth configuration. Before orthodontic mesialization of the maxillary first molars, CGF was prepared and administered using submucosal injections on the buccal and palatal sides of the maxillary first molars in one randomly assigned quadrant. The opposite quadrant was used as a control. The study examined four time points:1, 2, 3, and 4 weeks. The measurement of tooth movement was conducted at each follow-up point using a digital caliper. The rabbits were euthanized, and their maxillary segments, specifically the maxillary first molars, were studied histologically to identify any alterations occurring on both the tension and compression sides.

RESULTS

Significant tooth movement was observed in the experimental sides versus control sides in the second, third, and fourth week of follow-up periods (p ≤ 0.05). Histologically, on the compression side, the CGF group showed bone resorption and periodontal ligament active reactions from the first week and continued throughout the next three weeks. Also, on the tension side, the CGF group depicted cementoblastic and osteoblastic activities from the first week followed by fibroblastic activities from the second week and all activities continued till the fourth week.

CONCLUSIONS

CGF has the potential to effectively enhance orthodontic tooth movement without adverse clinical or histological effects.

Piezo1 contributes to alveolar bone remodeling by activating β-catenin under compressive stress

INTRODUCTION

The mechanosensitive ion channel, Piezo1, is responsible for transducing mechanical stimuli into intracellular biochemical signals and has been identified within periodontal ligament cells (PDLCs). Nonetheless, the precise biologic function of Piezo1 in the regulation of alveolar bone remodeling by PDLCs during compressive forces remains unclear. Therefore, this study focused on elucidating the role of the Piezo1 channel in alveolar bone remodeling and uncovering its underlying mechanisms.

METHODS

PDLCs were subjected to compressive force and Piezo1 inhibitors. Piezo1 and β-catenin expressions were quantified by quantitative reverse transcription polymerase chain reaction and Western blot. The intracellular calcium concentration was measured using Fluo-8 AM staining. The osteogenic and osteoclastic activities were assessed using alkaline phosphatase staining, enzyme-linked immunosorbent assay, quantitative reverse transcription polymerase chain reaction, and Western blot. In vivo, orthodontic tooth movement was used to determine the effects of Piezo1 on alveolar bone remodeling.

RESULTS

Piezo1 and activated β-catenin expressions were upregulated under compressive force. Piezo1 inhibition reduced β-catenin activation, osteogenic differentiation, and osteoclastic activities. β-catenin knockdown reversed the increased osteogenic differentiation but had little impact on osteoclastic activities. In vivo, Piezo1 inhibition led to decreased tooth movement distance, accompanied by reduced β-catenin activation and expression of osteogenic and osteoclastic markers on the compression side.

CONCLUSIONS

The Piezo1 channel is a key mechanotransduction component of PDLCs that senses compressive force and activates β-catenin to regulate alveolar bone remodeling.

The effect of low-frequency high-intensity ultrasound combined with aspirin on tooth movement in rats

BACKGROUND

Given the difficulties or incapacity of teeth movement in orthodontic treatment, the ways to speed tooth movement must be investigated. Besides, nonsteroidal anti-inflammatory drugs (NSAIDs) were utilized to treat pain caused by tooth movement during orthodontic treatment. The purpose of this study is to examine the impact of aspirin and low-frequency high-intensity ultrasound (LFHIU) on rat orthodontic tooth movement in rats.

METHODS

Thirty-six male Sprague-Dawley rats were divided into three groups: orthodontic (O), ultrasound-treated orthodontic (OU), and ultrasound-treated orthodontic with aspirin gavage (OUA) group. In the OU and OUA group, LFHIU (44 W/cm2, 28 kHz) was applied to the buccal side of the maxillary first molar alveolar bone for 10 s every day. In the OUA group, aspirin was given by gavage every day. The rats were sacrificed on days 1, 3, 7, and 14.

RESULTS

After ultrasonic treatment, the speed of tooth movement was increased by about 1.5 times. And the number of osteoclasts considerably increased by about 2 times. However, they decreased slightly after aspirin gavage. By Applying ultrasound therapy, Receptor Activator for Nuclear Factor-κ B Ligand (RANKL) levels in periodontal tissue were elevated. Aspirin was able to reduce these increases. Results from Micro Computed Tomography (Micro-CT) revealed that bone mineral density decreased by about 1/5 after ultrasound treatment on the compression side. The rate of bone mineral apposition indicated that bone was forming under tension, and that of the OU group increased by about 1.3 times that O group.

CONCLUSIONS

Although aspirin slowed this trend, LFHIU still enhanced overall tooth mobility in orthodontic treatment.

Photobiomodulation increases uprighting tooth movement and modulates IL-1β expression during orthodontically bone remodeling

This study investigated the effects of photobiomodulation (PBM) in acceleration of orthodontic movement of inferior molar uprighting movement. Thirty-four individuals, with indication of molar uprighting movement for oral rehabilitation, were randomly divided in two groups: verticalization + PBM (808 nm, 100 mW, 1 J per point, 10 points and 25 J/cm2 ) or verticalization + PBM simulation. Elastomeric chain ligatures were changed every 30 days for 3 months. FBM was performed immediately, 24 h, 72 h, 1 and 2 months after activation. The primary outcome was the amount of uprighting movement. Secondary outcomes were pain, amount of medication, OHIP-14 questionnaire, and cytokine IL-1β. PBM group increase uprighting movement when compared to control after 3 months and modulate IL-1β expression. For pain control, the amount of medication and OHIP-14 no difference were found. This study suggests that PBM accelerates tooth movement during molar uprighting, due to modulation of IL-1β during bone remodeling.

The role of ephrinB2-EphB4 signalling in bone remodelling during orthodontic tooth movement

OBJECTIVE

The aim of this study was to investigate the role of ephrinB2-EphB4 signalling in alveolar bone remodelling on the tension side during orthodontic tooth movement (OTM).

MATERIALS AND METHODS

An OTM model was established on sixty 8-week-old male Wistar rats. They were randomly divided into the experimental group and the control group. The animals in the experimental group were administrated with subcutaneous injection of EphB4 inhibitor NVP-BHG712 every other day, whereas the control group received only the vehicle. Samples containing the maxillary first molar and the surrounding bone were collected after 0, 3, 7, 14 and 21 days of tooth movement.

RESULTS

EphrinB2-EphB4 signalling was actively expressed on the tension side during tooth movement. Micro-CT analysis showed the distance of tooth movement in the experimental group was significantly greater than that of the control group (P < .05) with significantly increased trabecular separation (Tb. Sp) and decreased trabecular number (Tb. N) from day 14 to day 21. The number of osteoclasts significantly increased in the experimental group compared with the control group after 3 and 7 days of tooth movement (P < .05). The expressions of alkaline phosphatase (ALP) and osteopontin (OPN) were significantly reduced by inhibition of EphB4 (P < .05).

CONCLUSION

The inhibition of EphB4 suppressed bone formation and enhanced bone resorption activities on the tension side of tooth movement. The ephrinB2-EphB4 signalling might play an important role in alveolar bone remodelling during OTM.

Semaphorin 3A protects against alveolar bone loss during orthodontic tooth movement in mice with periodontitis

OBJECTIVE

This study investigated the effect of local semaphorin 3A (Sema3A) administration on alveolar bone loss during OTM in a mouse model of periodontitis.

BACKGROUND

Orthodontic tooth movement (OTM) for patients with periodontal disease is known to increase the risk of exacerbating alveolar bone loss due to inflammation of the periodontal tissue. However, its mechanism of action and prevention remains unclear.

METHODS

Mice (male 7-8 weeks old, C57BL/6J, n = 12) were divided into six groups: untreated group (control), without OTM and recovered from induced periodontitis (RP), with OTM and administered PBS or Sema3A to the gingiva after induced periodontitis (VehPO, SemaPO), with OTM and administered PBS or Sema3A to the gingiva without periodontitis induction (VehNO, SemaNO). Samples were collected on 14 days, and bone loss, histological analysis, cytokine production level, and tooth movement were assessed. Cultured human periodontal ligament (hPDL) cells were stimulated with lipopolysaccharide (LPS) and compressive force (CF), and mRNA expression levels of Sema3A and its receptors were analyzed.

RESULTS

The bone loss was significantly lower in the SemaPO group than in the VehPO group. The number of TRAP-positive cells in the SemaPO group was significantly lower than that in the VehPO group and was at the same level as that in the control group. The receptor activator of nuclear factor (NF)-kB-ligand/osteoprotegerin (RANKL/OPG) ratio and the levels of proinflammatory cytokines, including interleukin (IL)-1β, IL-6, IL-17, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ, in the gingival tissues were significantly lower in the SemaPO group than in the VehPO group. Additionally, Sema3A mRNA expression in hPDL cells was significantly decreased by co-stimulation with LPS and CF compared with that in the control group. Finally, the distance moved (dist.) and the mesial tipping angle (θ) was significantly smaller in the SemaPO group than in the VehPO group and was not significantly different from that of VehNO.

CONCLUSION

Pathological alveolar bone loss exacerbated by OTM in periodontitis might be prevented by local administration of Sema3A without inhibiting OTM.

Innovative Application of Diathermy in Orthodontics: A Case Report

Introduction: Several strategies have been proposed in the literature to accelerate tooth movement, many of which are invasive and have numerous side effects, such as surgical techniques (corticotomy and piezocision technique). This research investigates to what extent diathermy can accelerate the orthodontic alignment phase. Materials and Methods: A patient with lower teeth crowding index of the same magnitude was selected. The orthodontic treatment with Nickel–Titanium (NiTi) thermal arc 0.015 in the lower arch was performed, associated with a weekly application of diathermy using the intraoral handpiece. The total duration of treatment was three weeks. During each session, an intraoral transducer was employed to stimulate the hard and soft tissues of the left dental hemiarch, which was also orthodontically aligned like the right one. Results: Comparing the tooth movements of four elements of the two hemiarchies, it was found that, overall, the two teeth examined on the treated side underwent a more significant number of changes than on the untreated side, although not by a significant amount. Conclusions: The use of diathermy, according to the authors, is a non-invasive approach that may speed up the orthodontic alignment phase and reduce treatment duration, resulting in a lower risk of caries, gingival recessions, root resorptions, and patient compliance improvement, without side effects. Further studies and an adequate sample size will be needed to confirm the findings.

Mechanosensitive Piezo1 in Periodontal Ligament Cells Promotes Alveolar Bone Remodeling During Orthodontic Tooth Movement

Orthodontic tooth movement (OTM) is a process depending on the remodeling of periodontal tissues surrounding the roots. Orthodontic forces trigger the conversion of mechanical stimuli into intercellular chemical signals within periodontal ligament (PDL) cells, activating alveolar bone remodeling, and thereby, initiating OTM. Recently, the mechanosensitive ion channel Piezo1 has been found to play pivotal roles in the different types of human cells by transforming external physical stimuli into intercellular chemical signals. However, the function of Piezo1 during the mechanotransduction process of PDL cells has rarely been reported. Herein, we established a rat OTM model to study the potential role of Piezo1 during the mechanotransduction process of PDL cells and investigate its effects on the tension side of alveolar bone remodeling. A total of 60 male Sprague-Dawley rats were randomly assigned into three groups: the OTM + inhibitor (INH) group, the OTM group, and the control (CON) group. Nickel-titanium orthodontic springs were applied to trigger tooth movement. Mice were sacrificed on days 0, 3, 7, and 14 after orthodontic movement for the radiographic, histological, immunohistochemical, and molecular biological analyses. Our results revealed that the Piezo1 channel was activated by orthodontic force and mainly expressed in the PDL cells during the whole tooth movement period. The activation of the Piezo1 channel was essential for maintaining the rate of orthodontic tooth movement and facilitation of new alveolar bone formation on the tension side. Reduced osteogenesis-associated transcription factors such as Runt-related transcription factor 2 (RUNX2), Osterix (OSX), and receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG) ratio were examined when the function of Piezo1 was inhibited. In summary, Piezo1 plays a critical role in mediating both the osteogenesis and osteoclastic activities on the tension side during OTM.

lncRNA HHIP-AS1 Promotes the Osteogenic Differentiation Potential and Inhibits the Migration Ability of Periodontal Ligament Stem Cells

Alveolar bone remodeling under orthodontic force is achieved by periodontal ligament stem cells (PDLSCs), which are sensitive to mechanical loading. How to regulate functions of PDLSCs is a key issue in bone remodeling during orthodontic tooth movement. This study is aimed at investigating the roles of lncRNA Hedgehog-interacting protein antisense RNA 1 (HHIP-AS1) in the functional regulation of PDLSCs. First, HHIP-AS1 expression was downregulated in PDLSCs under continuous compressive pressure. Then, we found that the alkaline phosphatase activity, in vitro mineralization, and expression levels of bone sialoprotein, osteocalcin, and osterix were increased in PDLSCs by HHIP-AS1. The results of scratch migration and transwell chemotaxis assays revealed that HHIP-AS1 inhibited the migration and chemotaxis abilities of PDLSCs. In addition, the RNA sequencing data showed that 356 mRNAs and 14 lncRNAs were upregulated, including receptor tyrosine kinase-like orphan receptor 2 and nuclear-enriched abundant transcript 1, while 185 mRNAs and 6 lncRNAs were downregulated, including fibroblast growth factor 5 and LINC00973, in HHIP-AS1-depleted PDLSCs. Bioinformatic analysis revealed several biological processes and signaling pathways related to HHIP-AS1 functions, including the PI3K-Akt signaling pathway and JAK-STAT signaling pathway. In conclusion, our findings indicated that HHIP-AS1 was downregulated in PDLSCs under compressive pressure, and it promoted the osteogenic differentiation potential and inhibited the migration and chemotaxis abilities of PDLSCs. Thus, HHIP-AS1 may be a potential target for accelerating tooth movement during orthodontic treatment.

Combination of parathyroid hormone pretreatment and mechanical stretch promotes osteogenesis of periodontal ligament fibroblasts

INTRODUCTION

Parathyroid hormone (PTH) potentiates the mechanical loading induced bone formation in fracture healing and orthodontics. This study aimed to gain insight into the underlying mechanisms in periodontal ligament fibroblasts (PDLFs).

METHODS

Human PDLFs were cultured and subjected to uniaxial cyclic stretch at 0.5 Hz and 2000μ for 0, 6, 12, and 24 hours, respectively. 10 nM PTH was preadministered for 30 minutes before loading. The expression of PTH1R and osteogenic biomarkers Runx2, osteopontin, collagen type 1, alkaline phosphatase was assessed via immunofluorescence staining, quantitative polymerase chain reaction, or Western blot. Transfection of siPTH1R was applied, and alterations of osteogenic biomarkers were examined by Western blot. The expression of essential Wnt signal components Wnt3a, β-catenin, low-density lipoprotein receptor-related protein 5, Wnt5a, receptor tyrosine kinase-like orphan receptor 2 were examined, and the influence of dickkopf-related protein 1 on osteogenic biomarkers was evaluated.

RESULTS

The expression of PTH1R was instantaneously upregulated with PTH pretreatment and maintained a gradual increase until 24 hours. PTH synergistically enhanced the increase of Runx2, osteopontin, collagen type 1, and alkaline phosphatase under cyclic stretch, which was substantially attenuated by siPTH1R transfection. As for Wnt signal components, synergistic upregulation was detected on Wnt3a, β-catenin, and low-density lipoprotein receptor-related protein 5, whereas Wnt5a and receptor tyrosine kinase-like orphan receptor 2 increased relatively mildly. Blockage of the canonical Wnt/β-catenin pathway by dickkopf-related protein 1 impaired the boost of osteogenic biomarkers under the combined action of PTH and cyclic stretch.

CONCLUSIONS

The combination of PTH pretreatment and cyclic stretch promotes osteogenesis of PDLFs synergistically, and the canonical Wnt/β-catenin pathway is crucially involved in the underlying mechanism.

Peak loads on teeth from a generic mouthpiece of a vibration device for accelerating tooth movement

INTRODUCTION

The effect of vibrational force (VF) on accelerating orthodontic tooth movement depends on the ability to control the level of stimulation in terms of its peak load (PL) on the tooth. The objective of this study was to investigate the PL distribution on the teeth when a commercial VF device is used.

METHODS

Finite element models of a human dentition from cone-beam computed tomography images of an anonymous subject and a commonly used commercial VF device were created. The device consists of a mouthpiece and a VF source. The maxilla and mandible bites on the mouthpiece with the VF applied to it. Interface elements were used between the teeth and the mouthpiece, allowing relative motion at the interfaces. The finite element model was validated experimentally. Static load and VF with 2 frequencies were used, and the PL distributions were calculated. The effects of mouthpiece materials and orthodontic appliances on the PL distribution were also investigated.

RESULTS

The PL distribution of this kind of analyzed device is uneven under either static force or VF. Between the anterior and posterior segments, the anterior segment receives the most stimulations. The mouthpiece material affects the PL distribution. The appliance makes the PL more concentrated on the incisors. The VF frequencies tested have a negligible influence on both PL magnitude and distribution.

CONCLUSIONS

The device analyzed delivers different levels of stimulation to the teeth in both maxilla and mandible. Changing the material property of the mouthpiece alters the PL distribution.

Influence of Intermittent Parathyroid Hormone (PTH) Administration on the Outcomes of Orthodontic Tooth Movement—A Systematic Review

Objective: The aim of this review is to summarize the effects of local and systemic PTH administration on periodontal tissues during orthodontic tooth movement. Materials and methods: An electronic search was conducted on the following databases: PubMed/MEDLINE, Google Scholar, SCOPUS and Embase. On PubMed/MEDLINE, the Medical Subject Headings (MeSH) keywords used were: “orthodontic tooth movement” OR (“tooth” (All Fields) AND “tooth movement” (All Fields)) OR “tooth movement” (All Fields)) AND (“parathyroid hormone”); all studies included using CONSORT. Results: After elimination of duplicates and articles not meeting our inclusion criteria, seven animal studies were included in this review. Although the majority of the studies suggest that PTH may a have a favorable outcome on OTM, most studies were found to have several sources of bias. Conclusion: Animal studies with minimal bias and long-term clinical studies are needed to ascertain the efficacy of intermittent PTH administration in improving the rate and retention of OTM.

PTH/PTHrP in controlled release hydrogel enhances orthodontic tooth movement by regulating periodontal bone remodaling

OBJECTIVE

This study aimed to evaluate the effects of local application of parathyroid hormone (PTH) or parathyroid hormone-related protein (PTHrP) on osteogenesis and osteoclastogenesis during orthodontic tooth movement (OTM).

BACKGROUND

Periodontal bone remodeling is the crucial biological process in the OTM that involves both bone resorption and formation, with the former more important as the initiator. PTH or PTHrP both play dual roles in bone remodeling regulation, and the balance may shift to the bone resorption side when they are given continuously, suggesting them as potential candidate medicine for OTM acceleration.

METHODS

A total of 40 rats underwent orthodontic mesialization of the maxillary first molars and received no micro-perforation (MOP), or MOP followed by injection of temperature-sensitive hydrogel containing PTH, PTHrP, or normal saline. The rats were sacrificed after 2-week OTM, except for the relapse groups, which had one more week of observation after removal of the force appliances. The amount of tooth movement, rate of relapse after OTM, and effects on the bone remodeling were assessed through micro-computed tomography (μCT) analysis, alkaline phosphatase (ALP) assay, alizarin red staining, tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemistry (IHC) analysis, Western blot (WB), and quantitative real-time polymerase chain reaction (qRT-PCR). The effects of PTHrP on the osteogenic differentiation of human periodontal ligament cells (hPDLCs) were explored in vitro.

RESULTS

The cumulative release of PTH or PTHrP from PECE hydrogels was beyond 75% at 14 days in a sustained manner. After the intervention in vivo, the distance of OTM in the PTH (0.78 ± 0.06 mm) or PTHrP (0.81 ± 0.04 mm) group was significantly larger than that of the MOP only (0.51 ± 0.04 mm) or the no MOP (0.46 ± 0.05 mm) group. Moreover, PTH injection significantly reduced the rate of relapse after OTM (25.7 ± 4.3%) compared to the control (69.6 ± 6.1%). μCT analysis showed decreased BV/TV, BS/BV, and Tb.N, while increased Tb.Sp of alveolar bone in the PTH or PTHrP group. There were also more TRAP-positive osteoclasts in the PTH or PTHrP group with a significantly enhanced ratio of receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG). The protein expressions of PTH/PTHrP type 1 receptor (PTHR1), alkaline phosphatase (ALP), osteocalcin (OCN), runt-related transcription factor 2 (RUNX2), and β-catenin were significantly increased in the PTH or PTHrP group, as well as the gene expressions of Pth1r, Bglap, and Alpl. There was no significant difference between the effects of PTH and PTHrP. Nevertheless, inhibition of PTHrP on the osteogenic differentiation of hPDLCs was detected in vitro with decreased expression of OCN, RUNX2, COL-1, and ALP.

CONCLUSION

Local injection of either PTH or PTHrP carried by controlled release PECE hydrogel similarly enhances OTM in rats through regulating periodontal bone remodeling, which deserves further study for potential clinical application.

Lithium chloride promotes osteogenesis and suppresses apoptosis during orthodontic tooth movement in osteoporotic model via regulating autophagy

Osteoporosis is a widely distributed disease that may cause complications such as accelerated tooth movement, bone resorption, and tooth loss during orthodontic treatment. Promoting bone formation and reducing bone resorption are strategies for controlling these complications. For several decades, the autophagy inducer lithium chloride (LiCl) has been explored for bipolar . In this study, we investigated the autophagy-promoting effect of LiCl on bone remodeling under osteoporotic conditions during tooth movement. Ovariectomy was used to induce osteoporosis status in vivo. The results showed that LiCl rejuvenated autophagy, decreased apoptosis, and promoted bone formation, thus protecting tooth movement in osteoporotic mice. Furthermore, in vitro experiments showed that LiCl reversed the effects of ovariectomy on bone marrow-derived mesenchymal stem cells (BMSCs) extracted from ovariectomized mice, promoting osteogenesis and suppressing apoptosis by positively regulating autophagy. These findings suggest that LiCl can significantly decrease adverse effects of osteoporosis on bone remodeling, and that it has great potential significance in the field of bone formation during tooth movement in osteoporosis patients.

Intermittent parathyroid hormone promotes cementogenesis via ephrinB2-EPHB4 forward signaling

Intermittent parathyroid hormone (PTH) promotes periodontal repair, but the underlying mechanisms remained unclear. Recent studies found that ephrinB2-EPHB4 forward signaling mediated the anabolic effect of PTH in bone homeostasis. Considering the similarities between cementum and bone, we aimed to examine the therapeutic effect of PTH on resorbed roots and explore the role of forward signaling in this process. In vivo experiments showed that intermittent PTH significantly accelerated the regeneration of root resorption and promoted expression of EPHB4 and ephrinB2. When the signaling was blocked, the resorption repair was also delayed. In vitro studies showed that intermittent PTH promoted the expression of EPHB4 and ephrinB2 in OCCM-30 cells. The effects of PTH on the mineralization capacity of OCCM-30 cells was mediated through the ephrinB2-EPHB4 forward signaling. These results support the premise that the anabolic effects of intermittent PTH on the regeneration of root resorption is via the ephrinB2-EPHB4 forward signaling pathway.

Inhibitory Effects of 4-Hexylresorcinol on Root Resorption Induced by Orthodontic Tooth Movement

Root resorption during orthodontic tooth movement (OTM) is caused by an imbalance between the bone turnover rate and applied mechanical stress. The administration of 4-hexylresorcinol (4HR) increases the bone turnover rate and factors associated with bone formation. Thus, 4HR may show protective activity against root resorption during orthodontic tooth movement (OTM). A total of 40 rats (male: 20; female: 20) were included in this study, and the mandibular first molar was subjected to excessive orthodontic force. The experimental group (n = 20) received 12.8 mg/kg of 4HR every 2 weeks. The controls (n = 20) received a solvent without 4HR. Both groups had the same sex distribution. On Day 28 after the initiation of OTM, all the animals were sacrificed for micro-computed tomography analysis, Western blot analysis, and immunohistochemistry. The ratios of the root length and root volume to the total volume were significantly higher in the experimental group compared to those in the control group (p < 0.05). The expression levels of OPG, RANKL, alkaline phosphatase, and Runx2 in the experimental group according to Western blotting were significantly higher in the experimental group compared to those in the control group (p < 0.05). Their expression was mainly found in the periodontal ligament area. In conclusion, the administration of 4HR decreased the root resorption caused by OTM and increased the expression levels of OPG, RANKL, alkaline phosphatase, and Runx2.

Intermittent parathyroid hormone improves orthodontic retention via insulin-like growth factor-1

OBJECTIVES

This study aimed to investigate the effects of intermittent parathyroid hormone (iPTH) on the stability of orthodontic retention and to explore the possible regulatory role of insulin-like growth factor-1 (IGF-1) in this process.

METHODS

Forty-eight 6-week-old male Wistar rats were adopted in this study. An orthodontic relapsing model was established to investigate the effects of iPTH on orthodontic retention. In vitro, an immortalized mouse cementoblast cell line OCCM-30 was detected by flow cytometry to study the effects of iPTH on cell proliferation and apoptosis. By application of a specific IGF-1 receptor inhibitor, the role of IGF-1 was also explored.

RESULTS

In vivo study found that daily injection of PTH significantly reduced the relapsing distance. Histological staining and ELISA assay showed faster periodontal regeneration during retention period in PTH group with increased RANKL/OPG ratio and greater amount of OCN, ALP, and IGF-1 in gingival cervical fluid (GCF). Cell experiment revealed that iPTH promoted proliferation and suppressed apoptosis of cementoblast. IGF-1 receptor inhibitor significantly restrained the anabolic effect of iPTH on OCCM-30 cells.

CONCLUSIONS

These findings suggest that iPTH could improve the stability of tooth movement by promoting periodontal regeneration. IGF-1 is essential in mediating the anabolic effects of iPTH.

Effects of estrogen on root repair after orthodontically induced root resorption in ovariectomized rats

INTRODUCTION

This study aimed to investigate the effects of estrogen on root repair after orthodontically induced root resorption.

METHODS

Seventy-two 6-week-old female Wistar rats were randomly divided into 3 groups: ovariectomy only (OVX), ovariectomy plus estradiol injection (OVX + E2), and sham operation (control). E2 was administrated to all the experimental animals after the establishment of the root repair model. One-way analysis of variance with the Tukey post-hoc test was used to analyze the experimental results.

RESULTS

Micro-computed tomography and hematoxylin and eosin staining showed that the total volumes of resorption lacunae were significantly smaller in the control and OVX + E2 groups than those in the OVX group. Alkaline phosphatase and tartrate-resistant acid phosphatase stainings suggested that the cementoblastic activities and the amount of new cementum formation were inhibited while the activities of osteoclasts were obvious in the OVX group. The immunohistochemistry stainings revealed that the osteoprotegerin to receptor activator of nuclear factor-кB ligand ratio and the phosphorylated extracellular signal-regulated kinases to extracellular signal-regulated kinases ratio of the control and OVX + E2 groups were significantly greater than those of the OVX group.

CONCLUSIONS

These findings demonstrated that estrogen administration might be a solution to reduce orthodontically induced root resorption through the activation of extracellular signal-regulated kinase-1/2 pathway and enhancement of cementogenesis.

Effects Of Triptolide On Tooth Movement And Root Resorption In Rats

Purpose

The aim of this study was to investigate the effects of triptolide on the tooth movement and root resorption in rats during orthodontic treatment.

Material and methods

A total of 48 male Wistar rats were divided into three groups of 16 each. The right maxillary first molars of rats were drawn mesially by closed coil nickel-titanium spring with a force of 50 g. The two experimental groups received intraperitoneal injections of triptolide for 14 days at a dose of 15 µg/kg/day and 30 µg/kg/day, respectively. The control group received vehicle injections. After 14 days, the rats were humanely killed. The amount of tooth movement was measured. Eight rats from each group were randomly chosen for analysis of the percentage of root resorption area by scanning electron microscopy. For the remaining eight rats in each group, the H&E staining, tartrate-resistant acid phosphatase (TRAP) staining and immunohistochemistry analysis were performed.

Results

The amount of tooth movement and the ratio of root resorption area were significantly decreased in the triptolide-treated rats. The number of TRAP-positive cells was significantly lower in triptolide-treated groups. Moreover, the expression of nuclear factor kappa B ligand (RANKL) was reduced. In contrast, the expression of osteoprotegerin was significantly up-regulated. In the tension side, the expressions of runt-related transcription factor 2 and osteocalcin were significantly enhanced by triptolide injection.

Conclusion

Triptolide injection could arrest orthodontic tooth movement and reduce root resorption in rats via inhibition of osteoclastogenesis. In addition, triptolide may exert a positive effect on osteoblastogenesis.

[Adjunctive interventions to accelerate orthodontic tooth movement]

Orthodontic treatment is a time-consuming process whose duration usually takes 2-3 years. In general, long-term treatment duration possesses higher risks of complications, which may have adverse impact on patients. Therefore, exploring safe and effective adjunctive interventions to accelerate orthodontic tooth movement and shortening the treatment duration are of profound clinical significance. Currently, numerous adjunctive interventions have been generated and developed to accelerate orthodontic tooth movement, which can be divided into two main categories: surgical and non-surgical. However, an intervention that is widely accepted as a routine practice in orthodontic clinic is lacking. This article aims to review com-mon adjunctive interventions used to accelerate orthodontic tooth movement. This review can be used as a basis to guide clinical practice, shorten treatment duration, and improve patients' prognosis.

Systematic review of biological therapy to accelerate orthodontic tooth movement in animals: Translational approach

OBJECTIVES

To systematically review and evaluate what is known regarding contemporary biological therapy capable of accelerating orthodontic tooth movement (OTM) in animal model.

MATERIALS AND METHODS

MedLine, Scopus, Web of Science and OpenGrey were searched without restrictions until June 2019. Following study retrieval and selection, relevant data was extracted using a standardized table. Risk of bias (RoB) assessment was performed using the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool.

RESULTS

Fifty-one animal studies were included. Two biological therapies were identified as capable of accelerating the OTM: chemical methods (49 studies) and gene therapy (2 studies). The main substances that increased the OTM rate were cytokines (13 studies), followed by growth factors (6 studies) and hormones (5 studies). Most studies were assessed to be at unclear or high RoB. The application protocols, measurement and reporting of outcomes varied widely and methodologies were not adequately reported.

CONCLUSIONS

Although biological therapies to accelerate OTM have been widely tested and effective in preclinical studies, the validity of the evidence is flawed to support translational of these results. There is a need for well-designed experimental studies to translate these methods for clinical field.

Innovative evaluation of local injective gel of curcumin on the orthodontic tooth movement in rats

Background

Curcumin is the most active compound in turmeric. It can suppress the nuclear factor kappa-light-chain-enhancer of activated B cells pathway and prevent the osteoclastogenesis procedure. This study aimed to be the first to evaluate the effect of curcumin on the rate of orthodontic tooth movement (OTM).

Materials and Methods

Forty rats were used as follows in each group: (1) negative control: Did not receive any appliance or injection; (2) positive control: received 0.03 cc normal saline and appliance; (3) gelatin plus curcumin (G): Received 0.03 cc hydrogel and appliance; and (4) chitosan plus curcumin (Ch): Received 0.03 cc hydrogel and appliance. They were anesthetized and closed nickel-titanium coil springs were installed between the first molars and central incisors unilaterally as the orthodontic appliance. After 21 days, the rats were decapitated, and the distance between the first and second molars was measured by a leaf gauge. Howship's lacunae, blood vessels, osteoclast-like cells, and root resorption lacunae were evaluated in the histological analysis. Data were analyzed by one-way ANOVA, Tukey's test, and t-test (P < 0.05 consider significant).

Results

No significant difference was found in OTM between groups delivered orthodontic forces. Curcumin inhibited root and bone resorption, osteoclastic recruitment, and angiogenesis significantly.

Conclusion

Curcumin had no significant inhibitory effect on OTM. While it had a significant role on decreasing bone or root resorption (P > 0.05).

Orthodontic tooth movement: The biology and clinical implications

Orthodontic tooth movement relies on coordinated tissue resorption and formation in the surrounding bone and periodontal ligament. Tooth loading causes local hypoxia and fluid flow, initiating an aseptic inflammatory cascade culminating in osteoclast resorption in areas of compression and osteoblast deposition in areas of tension. Compression and tension are associated with particular signaling factors, establishing local gradients to regulate remodeling of the bone and periodontal ligament for tooth displacement. Key regulators of inflammation and tissue turnover include secreted factors like RANK ligand and osteoprotegerin, transcription factors such as RUNX2 and hypoxia-inducible factor, cytokines, prostaglandins, tissue necrosis factors, and proteases, among others. Inflammation occurred during tooth movement needs to be well controlled, as dysregulated inflammation leads to tissue destruction manifested in orthodontic-induced root resorption and periodontal disease. Understanding the biology has profound clinical implications especially in the area of accelerating orthodontic tooth movement. Surgical, pharmacological, and physical interventions are being tested to move teeth faster to reduce treatment times and time-dependent adverse outcomes. Future developments in acceleratory technology and custom appliances will allow orthodontic tooth movement to occur more efficiently and safely.

Preventive effects of tonsil-derived mesenchymal stem cells on osteoradionecrosis in a rat model

BACKGROUND

The purpose of this study was to investigate the effects of tonsil-derived mesenchymal stem cells (MSCs) on osteoradionecrosis (ORN).

METHOD

We generated a mandibular ORN rat model using a combination of 20-Gy single-dose irradiation and tooth extraction. Study groups were negative control (tooth extraction only), ORN group (irradiation, tooth extraction), Matrigel-1 group (Matrigel; BD Biosciences, San Jose, CA; irradiation, Matrigel application immediately after tooth extraction), tonsil-derived MSC-1 group (irradiation, tonsil-derived MSC application immediately after tooth extraction), Matrigel-4 group (irradiation, Matrigel application 4 weeks after tooth extraction), and tonsil-derived MSC-4 group (irradiation, tonsil-derived MSC application 4 weeks after tooth extraction).

RESULT

Bone mineral density was significantly lower in the ORN group than in the negative control group. The tonsil-derived MSC-1 group showed significantly higher bone mineral density than did the ORN and tonsil-derived MSC-4 groups.

CONCLUSION

A single 20-Gy dose of irradiation combined with tooth extraction successfully generated ORN in the rat model. The tonsil-derived MSCs can be effective for bone regeneration in ORN, particularly when applied immediately after dentoalveolar trauma or surgery.

The effect of caffeine on orthodontic tooth movement in rats

Objective(s):

to determine the effect of different doses of caffeine on orthodontic tooth movement (OTM) in rats.

Materials and Methods:

Forty male 250-300 g Sprague-Dawley rats were randomly divided into four groups of ten animals each and received 0 (control), 1 g/l, 2 g/l and 3 g/l caffeine in tap water for 3 days. Orthodontic appliances were ligated between the maxillary first molars and incisors on the 4th day of the study period. All rats were sacrificed after 2 weeks of treatment after which OTM was measured. Hematoxylin/eosin-stained sections of the molars were prepared and the mesial roots were examined for resorption-lacunae depth and osteoclast number. ANOVA was used for statistical analysis (P<0.05).

Results:

A significant decrease in OTM was observed only in the 2 g/l (P=0.043) and 3 g/l (P<0.01) caffeine-receiving rats compared to the control animals. Osteoclast counts and resorption-lacunae depths demonstrated significant differences between each of the caffeine groups and control rats (P<0.05). None of the variables showed significant differences between the caffeine groups (P>0.05).

Conclusion:

According to our findings, one of the effects of caffeine consumption during orthodontic treatment in rats was decreased root resorption. Additionally, concentrations of 2 g/l and 3 g/l inhibited OTM which seems to be due to its influence on osteoclast numbers.

The Potential Use of Pharmacological Agents to Modulate Orthodontic Tooth Movement (OTM)

The biological processes that come into play during orthodontic tooth movement (OTM) have been shown to be influenced by a variety of pharmacological agents. The effects of such agents are of particular relevance to the clinician as the rate of tooth movement can be accelerated or reduced as a result. This review aims to provide an overview of recent insights into drug-mediated effects and the potential use of drugs to influence the rate of tooth movement during orthodontic treatment. The limitations of current experimental models and the need for well-designed clinical and pre-clinical studies are also discussed.

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.

Expression analysis of α-smooth muscle actin and tenascin-C in the periodontal ligament under orthodontic loading or in vitro culture

α-smooth muscle actin (α-SMA) and tenascin-C are stress-induced phenotypic features of myofibroblasts. The expression levels of these two proteins closely correlate with the extracellular mechanical microenvironment. We investigated how the expression of α-SMA and tenascin-C was altered in the periodontal ligament (PDL) under orthodontic loading to indirectly reveal the intrinsic mechanical microenvironment in the PDL. In this study, we demonstrated the synergistic effects of transforming growth factor-β1 (TGF-β1) and mechanical tensile or compressive stress on myofibroblast differentiation from human periodontal ligament cells (hPDLCs). The hPDLCs under higher tensile or compressive stress significantly increased their levels of α-SMA and tenascin-C compared with those under lower tensile or compressive stress. A similar trend was observed in the tension and compression areas of the PDL under continuous light or heavy orthodontic load in rats. During the time-course analysis of expression, we observed that an increase in α-SMA levels was matched by an increase in tenascin-C levels in the PDL under orthodontic load in vivo. The time-dependent variation of α-SMA and tenascin-C expression in the PDL may indicate the time-dependent variation of intrinsic stress under constant extrinsic loading.