Tooth movement

The effect of chewing gum on the rate of en-masse space closure: A randomised controlled trial

AIM

To evaluate the effect of chewing gum on the rate of space closure, oral hygiene, pain during space closure and appliance breakage in patients undergoing fixed appliance therapy.

DESIGN

A prospective, single-centre, two-arm, parallel, double-blinded randomised controlled trial.

SETTING

Orthodontic unit of a privately funded hospital, Chennai, India.

PARTICIPANTS

In total, 28 participants were randomly allocated into a chewing gum group (CGG) (n = 14) or a control group (CG) (n = 14).

METHODS

Baseline data were collected at the start of retraction (T0), at 4 weeks (T1), 8 weeks (T2) and 12 weeks (T3) after the start of retraction. Rate of space closure, pain, oral hygiene and appliance breakage were assessed at T1, T2 and T3. Data were analysed using an independent t-test with P < 0.05 considered to be statistically significant.

RESULTS

The mean rate of space closure in the CGG was 0.9 ± 0.2 mm/month and 0.8 ± 0.2 mm/month in the CG (P = 0.07, 95% confidence intervals [CI] were 0.80-1.01 for the CGC and 0.70-0.91 for the CG). In both the groups, oral hygiene became worse between T0 and T3. At T0 and T1, participants in the CGG reported less pain at 24 h and 7 days when compared to the CG (P < 0.05). At T2 and T3, participants in the CGG reported less pain at 0 h, 24 h and 7 days when compared to the CG (P < 0.05). Appliance breakage in both groups was minimal, with an odds ratio of 0.7 (95% CI 0.1-3.8) and was similar (P = 0.66).

CONCLUSION

There was minimal increase that was clinically not significant in the rate of space closure with chewing gum. Chewing gum ensured better oral hygiene, helped alleviate pain and had no effect on appliance breakage during space closure.

Assessment of salivary tumor necrosis factor-alpha level in the initial stages of treatment with fixed appliances and clear aligners

OBJECTIVES

To assess and compare the tumor necrosis factor-alpha (TNF-α) levels in saliva samples during the initial stages of orthodontic treatment with fixed orthodontic appliances (FAs) and clear aligners (CAs).

MATERIALS AND METHODS

This longitudinal study comprised 40 patients (22 males, 18 females, mean age 22 ± 7 years) who were categorized into two equal-sized groups. Group A comprised 20 patients treated with FA, and Group B comprised 20 patients treated with CA. Unstimulated saliva was collected before the intiation of treatment and then collected again after the placement of the FA/CA at 24 hrs, 7th day, and on the 21st day in both groups. TNF-α levels were determined through ELISA.

STATISTICAL ANALYSIS

The data were subjected to statistical analysis. For intragroup comparison of TNF-α at different time points, the Wilcoxon matched-pairs signed-rank test was used, and for intergroup comparison of FAs and CAs at different time points, the Mann-Whitney U test was used.

RESULTS

TNF-α levels in the saliva increased significantly at 24 hours, followed by a decline on the 7th day and 21st day in both groups. Changes in TNF-α levels were significantly higher in the FA group than those in the CA group at different time points.

CONCLUSION

This study showed that the salivary TNF-α levels increased significantly during the initial stages of FA and CA treatment at different time points. The mean salivary TNF-α level in both FA and CA groups increased significantly at 24 hours, followed by a decline on the 7th day and then on the 21st day. There was a significant difference between the FA and CA treatment, where the CAs showed a significantly low level of TNF-α in saliva at different intervals of time when compared to the FAs.

Comparison of the Effects of Ketorolac and Acetaminophen on RANK-L Levels in the Gingival Crevicular Fluid during Orthodontic Tooth Movement: A Pilot Study

Background: Patients usually present pain due to the release of different inflammatory mediators such as prostaglandin E2 and RANK-L. Analgesics such as acetaminophen and ketorolac can inhibit RANK-L expression and this can affect orthodontic treatment by decreasing bone remodeling and slowing orthodontic dental movement. Several studies have reported a decrease in dental movement after administering some non-steroidal anti-inflammatory drugs. Proposal: The objective was to evaluate the RANK-L levels and a possible modulation by administering acetaminophen and ketorolac in patients starting orthodontic treatment. Methodology: A double-blind, randomized clinical trial was carried out with 24 subjects divided into three study groups: calcined magnesia as a placebo, acetaminophen, and ketorolac. Gingival crevicular fluid was obtained at four time points: before pharmacological intervention, at 24 h, at 48 h, and on the 5th day. RANK-L concentrations were evaluated through ELISA analysis. Also, interproximal space generated by the elastic separator at the end of the study was recorded in the different study groups using the visual analog scale. Results: An increase in RANK-L at 24 h was observed in the placebo group compared to the ketorolac and acetaminophen groups. However, no significant differences were observed in the interproximal space at day 5 in the three study groups. Conclusion: Patients who do not take analgesics at the start of orthodontic treatment have higher levels of RANK-L. Therefore, the use of ketorolac or acetaminophen could decrease bone remodeling and interfere with orthodontic dental movement.

Molecular and Biological Aspects of Orthodontic Tooth Movement: Possibilities for Bioengineering Intervention: A Narrative Review

BACKGROUND

The current review's goal is to examine, with a critical eye, the effect of various biomedical parameters on orthodontic tooth movement in an attempt to provide the reader with related mechanisms of this issue focusing on certain key points.

METHODS

This critical review was conducted using the following keywords in the search strategy: "biomedical molecules", "biomarkers", "orthodontics", "orthodontic tooth movement", "acceleration", "gene therapy", and "stem cells". Cochrane Library, Medline (PubMed), and Scopus were the databases that were used for the electronic search. Studies published until June 2023 were considered.

RESULTS

The use of biomedical approaches in orthodontic tooth movement has been investigated via different procedures and applications. Surgical approaches, biomarkers affecting orthodontic tooth movement, different biological events and mechanisms, RANK, RANK-L, OPG molecular triad, and vibration methods are the basic parameters of biomedical interventions that are examined in the present review.

CONCLUSIONS

The biomedical approach seems to offer a variety of applications to control orthodontic tooth movement. The scarcity of human studies, as well as the high cost and complexity of these methods, currently limit the available accurate data concerning this issue.

In Vitro Effect of Photobiomodulation Therapy with 980 nm Diode Laser on Gene Expression of Key Regulators of Bone Remodeling by Human Periodontal Ligament Cells under Mild Orthodontic Forces

This study investigated the effect of photobiomodulation (PBM) with 980 nm diode laser as monotherapy and in combination with compressive and tensile orthodontic forces on expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL), sclerostin (SOST) and periostin (POSTN), by human periodontal ligament cells. Isolated cells were cultured and subjected to either tensile (10% elongation) or compressive forces (25 g cm-2 ) for 24 and 48 h. Subsequently, the cells received PBM (100 mW power, 3 or 6 J cm-2 energy density) immediately after load cycle. RT-PCR was applied to assess the genes expression. Data were analyzed by one-way ANOVA, followed by post hoc Tukey test (P ≤ 0.05). We found that PBM in combination with orthodontic forces led to upregulation of bone resorption genes (RANKL and SOST) at the pressure side and their downregulation at the tension side. The expression of osteogenic genes (OPG and POSTN) increased at the tension side and decreased at the pressure side. PBM alone did not affect gene expression. In conclusion, these findings suggest that this PBM protocol may be effective in enhancement of the gene expression in favor of bone remodeling acceleration that should be confirmed in future animal and human studies.

Three-dimensional (3D) quantitative evaluation of the morphological changes of the upper anterior alveolar bone after retraction of a maxillary incisor

BACKGROUND

The purpose of this study was to assess morphological changes of the upper anterior alveolus after retraction of a maxillary incisor by applying three-dimensional (3D) superimposition of pretreatment (T1) and posttreatment (T2) cone-beam computed tomography (CBCT) data.

METHODS

The study group was comprised of 28 patients with skeletal Class II malocclusion who underwent incisor retraction. CBCT data were acquired before (T1) and after (T2) orthodontic treatment. Labial and palatal alveolar thickness were assessed at the crestal, midroot and apical levels of the retracted incisors. Following three-dimensional (3D) cranial base superimposition, we performed surface modeling and inner remodeling of the labial and palatal alveolar cortex of the maxillary incisors. Paired t-tests were used to compare T0 and T1 bone thickness and volume measurements. Comparisons between labial and palatal surface modeling, inner remodeling and outer surface modeling were performed with paired t-tests in SPSS 20.0 version.

RESULTS

We observed controlled tipping retraction of the upper incisor. After treatment, the alveolar thickness on the labial sides increased and the palatal alveolar thickness decreased. The labial cortex showed a wider range of modeling area with a larger bending height and a smaller bending angle than the palatal side. The extent of inner remodeling was more prominent than the outer surface on both the labial and palatal sides.

CONCLUSIONS

Adaptive alveolar surface modeling occurred in response to incisor tipping retraction on both the lingual and labial sides although these changes occurred in an uncoordinated manner. Tipping retraction of the maxillary incisors led to a reduction in alveolar volume.

Effect of 1% curcumin gel on myeloperoxidase activity in GCF and periodontal status in the initial phase of orthodontic tooth movement

AIM

To explore the potential effect of locally applied 1% Curcumin on myeloperoxidase (MPO) enzymatic activity in gingival crevicular fluid (GCF) and on the periodontal status during the initial phase of orthodontic tooth movement.

SETTINGS AND DESIGN

Forty patients (26 females and 14 males) aged 12-25 years who required fixed orthodontic treatment were randomly divided into two equal groups. The control and test groups were similar in the various baseline parameters, including standard oral hygiene protocol. Moreover, 1% Curcumin gel was applied around mandibular anterior teeth in the test group twice daily, from three days before to 14 days after the placement of archwires. MPO activity and periodontal status were recorded at five different time points; before placement of archwire (baseline), immediately after placement of archwire, 2 hours, 7 days, and 14 days later.

STATISTICAL ANALYSIS USED

The data were analyzed using the paired t-test for intra-group differences and the unpaired t-test for intergroup differences at five different time points. Statistical significance in the intragroup and intergroup difference of Plaque and Gingival index was calculated using the unpaired t-test.

RESULTS

Maximum MPO enzymatic activity in GCF was observed two hours after the placement of the archwire. MPO activity decreased slightly on the seventh day, but values were still elevated as compared to baseline. However, MPO activity came back to the values similar to baseline on day 14 in the control group and significantly lower than the baseline in the test group. The inter-group differences in clinical periodontal parameters were non-significant.

CONCLUSIONS

The locally applied 1% Curcumin gel appears to decrease the MPO activity in GCF on the 14^th day after placement of the archwires. However, clinical periodontal status in the initial phase of tooth movement is unaffected by curcumin if patients adhere to good plaque control.

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.

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.

In vivo investigation of gingival health and oxidative stress changes in patients undergoing orthodontic treatment with and without fluoride use

Background and Aims:

We aimed to investigate gingival index changes and oxidative stress in orthodontic patients with and without the use of fluoridated agents over a 6-month period.

Materials and Methods:

Ninety subjects divided into three groups (30 untreated controls, 30 with fixed appliances using nonfluoridated toothpaste, and 30 with fixed appliances using fluoridated toothpastes and mouthwashes ) comprised the sample. The Loe gingival index was used to rank gingival health at four specific time periods in the groups to determine differences (before, at 7 days, 30 days, and 6 months). Gingival crevicular fluid was evaluated for cytokines (interleukin [IL]-1β and tumor necrosis factor [TNF]-α) to determine differences in oxidative status between the groups.

Results:

Controls showed no changes in gingival index throughout the 6-month observation period. There was a deterioration in gingival health in both the fluoridated and nonfluoridated groups till 6 months. IL-1β levels in the fluoridated group increased from the 7^th day, reached a peak at 30 days, and remained slightly elevated at 6 months. The nonfluoridated group also showed elevated levels at all tested time periods, but levels were lower as compared to fluoridated samples. The differences in IL-1β values between the fluoridated and nonfluoridated treated groups were significant. TNF-α levels in the three groups also showed a similar pattern with elevated levels seen in both the treated groups at the 7^th, 30-day, and 6-month periods. The fluoridated group showed the highest levels at three time periods which was statistically significant.

Conclusions:

Gingival health of subjects treated with fixed orthodontic appliances deteriorated from appliance placement till a 6-month time period. Cytokines such as IL-1β and TNF-α associated with oxidative stress during orthodontic treatment increased in both the treated groups, with higher levels in fluoridated subjects. Long-term consequences of oxidative stress changes need further investigation.

Modulating OPG and TGF-β1 mRNA expression via bioelectrical stimulation

BACKGROUND

Bone remodeling is a lifelong process that ranges from orthodontic tooth movement/alignment to bone damage/healing, to overall bone health. Osteoprotegerin (OPG) and transforming growth factor β1 (TGF-β1) are secreted by osteoblasts and participate in bone remodeling. OPG promotes bone remineralization and stabilization prominent in post-mechanical repositioning of the teeth in the dental alveolus. TGF-β1 participates in regulatory processes to promote osteoblast and osteoclast equilibrium. In the context of orthodontic tooth movement, post-treatment fixation requires additional, exogenous, stabilization support. Recent research showcases supplementary solutions, in conjunction to standard tooth fixation techniques, such as OPG injections into gum and periodontal tissues to accelerate tooth anchorage; however, injections are prone to post-procedure complications and discomfort. This study utilizes noninvasive bioelectric stimulation (BES) to modulate OPG and TGF-β1 as a novel solution to regulate bone remineralization specifically in the context of post-orthodontic tooth movement.

PURPOSE

The aim of this study was to investigate a spectrum of BES parameters that would modulate OPG and TGF-β1 expression in osteoblasts.

METHODS

Osteoblasts were cultured and stimulated using frequencies from 25 Hz to 3 MHz. RT-qPCR was used to quantify changes in OPG and TGFb-1 mRNA expression.

RESULTS

OPG mRNA expression was significantly increased at frequencies above 10,000 Hz with a maximum expression increase of 332 ± 8% at 100 kHz. Conversely, OPG mRNA expression was downregulated at frequencies lower than 1000 Hz. TGF-β1 mRNA expression increased throughout all stimulation frequencies with a peak of 332 ± 72% at 250 kHz. Alizarin Red tests for calcium, indicated that mineralization of stimulated osteoblasts in vitro increased 28% after 6 weeks in culture.

DISCUSSION

Results support the working hypothesis that OPG and TGF-β1 mRNA expression can be modulated through BES. Noninvasive BES approaches have the potential to accelerate bone remineralization by providing a novel tool to supplement the anchorage process, reduce complications, and promote patient compliance and reduce post-treatment relapse. Noninvasive BES may be applicable to other clinical applications as a novel therapeutic tool to modulate bone remodeling.

Mkx regulates the orthodontic tooth movement via osteoclast induction

INTRODUCTION

The periodontal ligament (PDL) plays an important role in orthodontic tooth movement; however, the underlying molecular mechanism remains unclear. We have previously reported that the Mohawk homeobox (Mkx), a tendon-specific transcription factor, is expressed in the PDL and regulates its homeostasis.

MATERIALS AND METHODS

In the present study, we examined the role of Mkx in orthodontic tooth movement via bone remodeling induced by mechanical stimulation in Mkx-deficient rats, which are widely used as experimental animals for orthodontic force application. Orthodontic tooth movement of the maxillary first molar was performed in 7-week-old male Mkx-deficient rats (n = 4) and wild-type Wistar rats (n = 4) using coil springs for 14 days. Hematoxylin and eosin (H&E) staining and tartrate-resistant acid phosphatase (TRAP) staining were performed to evaluate morphological changes and osteoclasts. Furthermore, changes in the expression of receptor activator nuclear factor-kappa B ligand (RANKL) were demonstrated using immunostaining.

RESULTS

The amount of tooth movement was significantly lower in Mkx-deficient rats than in wild-type rats. The number of TRAP-positive cells was suppressed in Mkx-deficient rats on the compression side.

CONCLUSION

Orthodontic tooth movement experiments in Mkx-deficient rats suggested that Mkx is involved in osteoclast induction at the alveolar bone surface on the compression side. This study reveals the possibility that Mkx plays a mechanosensory role in orthodontic tooth movement by inducing RANKL expression and osteoclastogenesis.

Microstructural heterogeneity of the collagenous network in the loaded and unloaded periodontal ligament and its biomechanical implications

The periodontal ligament (PDL) is a highly heterogeneous fibrous connective tissue and plays a critical role in distributing occlusal forces and regulating tissue remodeling. Its mechanical properties are largely determined by the extracellular matrix, comprising a collagenous fiber network interacting with the capillary system as well as interstitial fluid containing proteoglycans. While the phase-contrast micro-CT technique has portrayed the 3D microscopic heterogeneity of PDL, the topological parameters of its network, which is crucial to understanding the multiscale constitutive behavior of this tissue, has not been characterized quantitatively. This study aimed to provide new understanding of such microscopic heterogeneity of the PDL with quantifications at both tissue and collagen network levels in a spatial manner, by combining phase-contrast micro-CT imaging and a purpose-built image processing algorithm for fiber analysis. Both variations within a PDL and among the PDL with different shapes, i.e. round-shaped and kidney-shaped PDLs, are described in terms of tissue thickness, fiber distribution, local fiber densities, and fiber orientation (namely azimuthal and elevation angles). Furthermore, the tissue and collagen fiber network responses to mechanical loading were evaluated in a similar manner. A 3D helical alignment pattern was observed in the fiber network, which appears to regulate and adapt a screw-like tooth motion under occlusion. The microstructural heterogeneity quantified here allows development of sample-specific constitutive models to characterize the PDL's functional and pathological loading responses, thereby providing a new multiscale framework for advancing our knowledge of this complex limited mobility soft-hard tissue interface.

Recombinant human insulin-like growth factor-1 promotes osteoclast formation and accelerates orthodontic tooth movement in rats

Background: IGF-1 may be an important factor in bone remodeling, but its mechanism of action on osteoclasts during orthodontic tooth movement is complex and unclear. Methodology: The closed-coil spring was placed between the left maxillary first molar and upper incisors with a force of 50 g to establish an orthodontic movement model. Eighty SD rats were randomized to receive phosphate buffer saline or 400 ng rhIGF-1 in the lateral buccal mucosa of the left maxillary first molar every two days. Tissue sections were stained for tartrate-resistant acidic phosphatase (TRAP), the number of TRAP-positive cells was estimated and tooth movement measured. Results: The rhIGF-1 group exhibited evidential bone resorption and lacuna appeared on the alveolar bone compared to the control group. Moreover, the number of osteoclasts in compression side of the periodontal ligament in the rhIGF-1 group peaked at day 4 (11.37±0.95 compared to 5.28±0.47 in the control group) after the orthodontic force was applied and was significantly higher than that of the control group (p<0.01). Furthermore, the distance of tooth movement in the rhIGF-1 group was significantly larger than that of the control group from day 4 to day 14 (p<0.01), suggesting that rhIGF-1 accelerated orthodontic tooth movement. Conclusion: Our study has showed that rhIGF-1 could stimulate the formation of osteoclasts in the periodontal ligament, and accelerate bone remodeling and orthodontic tooth movement.

Assessment of salivary pro inflammatory cytokines profile level in patients treated with labial and lingual fixed orthodontic appliances

The secretions of certain cytokines, chemokines and growth factors are triggered by orthodontic appliances, which often affect the remodelling of periodontal tissues. Critical cumulative forces are applied by various types of orthodontic appliances to the periodontium. The secretion of such molecules is probably responsible, through molecular and cellular communications, for the optimal resorption of hard tissues in the periodontal setting, which therefore enables the coordination of multiple movements of tooth. This study assessed and compared a wide range of cytokines, cellular marker analysis and defensins present in the saliva samples of human subjected to orthodontic treatment with two different treatment modalities, i.e., conventional lingual and labial fixed orthodontic appliances. A total 40 samples of saliva were obtained, of which 20 were treated with traditional lingual appliances and 20 were treated with labial fixed appliances. After 21 days of treatment, all salivary samples were collected from the subjects. In order to analyse a broad range of soluble cytokine levels in saliva by flow cytometry, a bead-based immunoassay was performed. Cell surface markers were analysed by flow cytometry. Protein levels of saliva for defensins were quantified by ELISA. Non-significant differences were observed in the cytokine levels in the saliva except for the significant effects for CCL2, IL-17A and IL-6. Cellular markers CD45 and CD326 showed high percentage in conventional lingual samples. Defensin levels were found to be lower in conventional lingual patients. Subjects with conventional lingual appliances had significantly higher salivary protein levels of IL-1β, CCL2, IL17A, and IL-6, higher CD45+ and CD326+ cells and lower defensin levels than subjects with fixed labial appliances. The current study provided a clear basis for the development of innovative methods to aid in the improvement of various procedural treatments and orthodontic equipment of next generation.

Construction of virtual intercuspal occlusion: Considering tooth displacement

Common impressions cannot accurately duplicate the dental occlusion under occlusal force due to tooth displacement and mandibular deformation. To establish new methods to construct virtual intercuspal occlusion and assess their construction accuracy. The intraoral occlusal contacts of posterior teeth of 15 subjects were recorded with 8 μm and 100 μm articulating paper, respectively, and the marked teeth and buccal bite data were scanned with an intraoral scanner. The virtual dental occlusions were separately determined by buccal bite registration (BBR) method, and 3 new methods, namely segmented tooth registration (STR), occlusal contact areas (marked by 8 μm articulating paper) registration (OCR) and mixing registration (MR) methods. With the intraoral contact areas marked by 100 μm articulating paper set as reference and contact areas of the 4 virtual occlusions as tests, sensitivity, positive predictive value (PPV) and the ratio of overlapping areas were calculated. Kruskal-Wallis test or 1-way ANOVA was used to analyse the difference among groups. The sensitivity ranged from 0.69 to 0.94 and the PPV from 0.67 to 0.90. Sensitivity of OCR group and PPV of STR and OCR groups were different from that of BBR group at overlapping threshold of 50% (P = .028, .028 and .006). There was statistical difference of the ratio of overlapping areas over reference areas, and the values of STR and OCR groups were higher than that of BBR group (P = .045 and .021). The ability of STR and OCR methods to construct virtual intercuspal occlusion was better than BBR method.

The effect of the local administration of biological substances on the rate of orthodontic tooth movement: a systematic review of human studies

BACKGROUND

The influence of different biological agents on the rate of orthodontic tooth movement (OTM) has been extensively reviewed in animal studies with conflicting results. These findings cannot be extrapolated from animals to humans. Therefore, we aimed to systematically investigate the most up-to-date available evidence of human studies regarding the effect of the administration of different biological substances on the rate of orthodontic tooth movement.

METHODS

A total of 8 databases were searched until the 16th of June 2020 without restrictions. Controlled randomized and non-randomized human clinical studies assessing the effect of biological substances on the rate of OTM were included. ROBINS-I and the Cochrane Risk of Bias tools were used. Reporting of this review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

A total of 11 studies (6 randomized clinical trials and 5 prospective clinical trials) were identified for inclusion. Local injections of prostaglandin E1 and vitamin C exerted a positive influence on the rate of OTM; vitamin D showed variable effects. The use of platelet-rich plasma and its derivatives showed inconsistent results, while the local use of human relaxin hormone showed no significant effects on the rate of OTM.

LIMITATIONS

The limited and variable observation periods after the administration of the biological substances, the high and medium risk of bias assessment for some included studies, the variable concentrations of the assessed biological agents, the different experimental designs and teeth evaluated, and the variety of measurement tools have hampered the quantitative assessment of the results as originally planned.

CONCLUSIONS AND IMPLICATIONS

Despite the methodological limitations of the included studies, this systematic review provides an important overview of the effects of a variety of biological agents on the rate of tooth movement and elucidates the deficiencies in the clinical studies that have been conducted so far to evaluate the effectiveness of these agents in humans, providing some guidelines for future robust research.

TRIAL REGISTRATION

PROSPERO ( CRD42020168481 , www.crd.york.ac.uk/prospero ).

Analogous modulation of inflammatory responses by the endocannabinoid system in periodontal ligament cells and microglia

Background

Periodontal ligament (PDL) cells initiate local immune responses, similar to microglia regulating primary host defense mechanisms in neuroinflammatory events of the central nervous system. As these two cell types manifest similarities in their immunomodulatory behavior, this study investigated the thesis that the immunological features of PDL cells might be modulated by the endocannabinoid system, as seen for microglia.

Methods

A human PDL cell line and an Embryonic stem cell-derived microglia (ESdM) cell line were grown in n = 6 experimental groups each, incubated with cannabinoid receptor agonists arachidonoylethanolamine (AEA) (50 μM) or Palmitoylethanolamide (PEA) (50 μM) and challenged with centrifugation-induced inflammation (CII) for 6 and 10 h. Untreated samples served as controls. Quantitative real-time polymerase chain reaction was applied for gene expression analyses of inflammatory cytokines, cannabinoid receptors and ionized calcium binding adaptor molecule 1 (IBA-1). Microglia marker gene IBA-1 was additionally verified on protein level in PDL cells via immunocytochemistry. Proliferation was determined with a colorimetric assay (WST-1 based). Statistical significance was set at p < 0.05.

Results

IBA-1 was inherently expressed in PDL cells both at the transcriptional and protein level. AEA counteracted pathological changes in cell morphology of PDL cells and microglia caused by CII, and PEA contrarily enhanced them. On transcriptional level, AEA significantly downregulated inflammation in CII specimens more than 100-fold, while PEA accessorily upregulated them. CII reduced cell proliferation in a time-dependent manner, synergistically reinforced by PEA decreasing cell numbers to 0.05-fold in PDL cells and 0.025-fold in microglia compared to controls.

Conclusion

PDL cells and microglia exhibit similar features in CII with host-protective effects for AEA through dampening inflammation and preserving cellular integrity. In both cell types, PEA exacerbated proinflammatory effects. Thus, the endocannabinoid system might be a promising target in the regulation of periodontal host response.

Efficacy of Er,Cr Laser incision Corticotomy in Rapid Maxillary Canine Retraction: A Split-Mouth Randomized Clinical Trial

Introduction: This study sought to evaluate the efficacy of lasercision corticotomy for the acceleration of canine movement. Our secondary objectives were assessing the canine rotation, the rate of anchorage control, the level of pain, and the gingival index (GI). Methods: Twelve orthodontic patients (9 females and 3 males) referring to the School of Dentistry and one dental clinic from May 2019 to September 2019 participated in this split-mouth randomized clinical trial. The allocation of the test and control sides was performed by flipping a coin. The mean age of patients was 18.91±3.87 years (range 15-30 years). The treatment plan included maxillary first premolar extraction. Following the initial leveling and alignment phase, an initial impression was made. Corticotomy was carried out with the erbium, chromium-doped yttrium scandium gallium garnet (Er, Cr: YSGG) laser (3.5 W, 30 Hz, 40% air, 80% water) in one maxillary quadrant (the laser side). Canine retraction was immediately initiated following surgery using nickel-titanium closed-coil springs with 150 g force. The impression was repeated 1 month after the onset of retraction. The casts were scanned, and the distance between the canine cusp tip and the rugae line was measured to quantify the amount of anteroposterior canine movement. The molar anchorage control was also evaluated by measuring the distance between the mesial contact of the permanent first molar and the rugae line. Gingival health was evaluated using the GI. The modified McGill pain questionnaire was used to assess the level of patients' pain. Results: Lasercision corticotomy accelerated canine retraction with no adverse effect on gingival health. Anchorage loss in the posterior teeth and pain scores were not significantly different between the control and laser sides. Conclusion: Laser corticotomy can effectively accelerate canine retraction with no complications or discomfort for the patients.

Aerobic and resistance training improve alveolar bone quality and interferes with bone-remodeling during orthodontic tooth movement in mice

The direct effects of physical activity on long bones are already recognized. However, little information is available regarding distant osseous sites, such as maxillary bone. We evaluated the influence of physical training on alveolar bone quality, with and without mechanically-induced load during orthodontic tooth movement in mice. Forty-two C57BL/6 mice were divided into sedentary, resistance and aerobic training groups. Training period lasted for eight weeks and mechanical loads (orthodontic tooth movement - OTM) were applied during the last 14 days of training. Both types of training enhanced the quality of maxillary bone, increasing bone mineral density (BMD), trabecular bone volume (BV) and bone volume/total volume ratio (BV/TV). OTM significantly reduced in trained groups. Consistently, the number of osteoblasts increased whereas the number of osteoclasts decreased on the OTM side in trained groups in comparison to the sedentary group. IGF-1, RUNX2 and OPG genes expression were also increased. The RANKL/OPG ratio and IL-6 expression were reduced in the maxillary bone. Similar results were verified in the femoral bone. In line with these findings, physical training resulted in a decrease of osteoclast differentiation from femoral bone marrow; as well as the force required to fracture the tibia of trained animals increased. Physical training also caused EDL muscle hypertrophy and increased expression of IGF-1 and IGF-1/Myostatin ratio in the gastrocnemius muscle, whereas FNDC5 gene expression was similar among groups in femur, but decreased in alveolar bone submitted to OTM. In conclusion, physical training increased bone quality, not only on long bones, but also in a distant site such as the maxilla. Differences were more evident in the course of maxillary mechanical loading. Mechanisms involve systemic and local effects on bone cells and target molecules as RANKL, OPG, IL-6 and IGF-1.

The role of endothelin B receptor in bone modelling during orthodontic tooth movement: a study on ETB knockout rats

The endothelin system has an important role in bone modelling during orthodontic tooth movement (OTM); however, little is known about the involvement of endothelin B receptors (ET_B) in this process. The aim of this study was to evaluate the role of ET_B in bone modelling during OTM using ET_B knockout rats (ET_B-KO). Thirty-two male rats were divided into 4 groups (n = 8 per group): the ET_B-KO appliance group, ET_B-KO control group, wild type (ET_B-WT) appliance group, and ET_B-WT control group. The appliance consisted of a super-elastic closed-coil spring placed between the first and second left maxillary molar and the incisors. Tooth movement was measured on days 0 and 35, and maxillary alveolar bone volume, osteoblast, and osteoclast volume were determined histomorphometrically on day 35 of OTM. Next, we determined the serum endothelin 1 (ET-1) level and gene expression levels of the osteoclast activity marker cathepsin K and osteoblast activity markers osteocalcin and dentin matrix acidic phosphoprotein 1 (DMP1) on day 35. The ET_B-KO appliance group showed significantly lower osteoblast activity, diminished alveolar bone volume and less OTM than the ET_B-WT appliance group. Our results showed that ET_B is involved in bone modelling in the late stage of OTM.

Role of Oxygen Supply in Macrophages in a Model of Simulated Orthodontic Tooth Movement

Apart from periodontal ligament fibroblasts, immune cells like macrophages also play an important mediating role in orthodontic tooth movement (OTM). Upon orthodontic force application to malpositioned teeth, macrophages in the periodontal ligament get exposed to both mechanical strain and hypoxic conditions (via a compression of blood vessels). In this study, we assessed the relative impact of orthodontically induced mechanical strain and hypoxic conditions on macrophages for the mediation and regulation of OTM. Macrophages were stimulated with physiological orthodontic compressive forces of 2 g/cm² for 4 h and 24 h on gas-impermeable or gas-permeable cell culture plates under normoxic or hypoxic cell culture conditions. We quantified expression of genes involved in inflammation (Tnf, Il-6, and Cox-2), extracellular remodelling (Mmp-9), and angiogenesis (Vegf) by RT-qPCR. Furthermore, we analysed HIF-1α, prostaglandin-E2, and VEGF protein expression via immunoblotting or ELISA. Mechanical strain and oxygen supply both differentially affected expression of genes and proteins involved in inflammation and angiogenesis. In this context, we found that HIF-1α protein levels were elevated by combined mechanical strain and hypoxic conditions, whereas gas-permeable plates providing sufficient oxygen supply prevented HIF-1α stabilization at the protein level after pressure application on macrophages. Our results thus indicate that macrophages involved in the mediation of OTM are affected by and respond differently to hypoxic conditions and mechanical compressive strain, which occur concomitantly during OTM, than periodontal ligament fibroblasts (PDLF), thus indicating different roles of these cells in the regulation of OTM at the cellular-molecular level. We further observed that contrary to PDLF HIF-1α stabilization in macrophages is rather induced via the decreased oxygen supply associated with OTM than via mechanotransduction by mechanical strain.

Delayed tooth movement in Runx2+/- mice associated with mTORC2 in stretch-induced bone formation

Runt-related transcription factor 2 (Runx2) is an essential transcription factor for osteoblast differentiation, and is activated by mechanical stress to promote osteoblast function. Cleidocranial dysplasia (CCD) is caused by mutations of RUNX2, and CCD patients exhibit malocclusion and often need orthodontic treatment. However, treatment is difficult because of impaired tooth movement, the reason of which has not been clarified. We examined the amount of experimental tooth movement in Runx2^+/− mice, the animal model of CCD, and investigated bone formation on the tension side of experimental tooth movement in vivo. Continuous stretch was conducted to bone marrow stromal cells (BMSCs) as an in vitro model of the tension side of tooth movement. Compared to wild-type littermates the Runx2^+/− mice exhibited delayed experimental tooth movement, and osteoid formation and osteocalcin (OSC) mRNA expression were impaired in osteoblasts on the tension side of tooth movement. Runx2 heterozygous deficiency delayed stretch-induced increase of DNA content in BMSCs, and also delayed and reduced stretch-induced alkaline phosphatase (ALP) activity, OSC mRNA expression, and calcium content of BMSCs in osteogenic medium. Furthermore Runx2^+/− mice exhibited delayed and suppressed expression of mammalian target of rapamycin (mTOR) and rapamycin-insensitive companion of mTOR (Rictor), essential factors of mTORC2, which is regulated by Runx2 to phosphorylate Akt to regulate cell proliferation and differentiation, in osteoblasts on the tension side of tooth movement in vivo and in vitro. Loss of half Runx2 gene dosage inhibited stretch-induced PI3K dependent mTORC2/Akt activity to promote BMSCs proliferation. Furthermore, Runx2^+/− BMSCs in osteogenic medium exhibited delayed and suppressed stretch-induced expression of mTOR and Rictor. mTORC2 regulated stretch-elevated Runx2 and ALP mRNA expression in BMSCs in osteogenic medium. We conclude that Runx2^+/− mice present a useful model of CCD patients for elucidation of the molecular mechanisms in bone remodeling during tooth movement, and that Runx2 plays a role in stretch-induced proliferation and osteogenesis in BMSCs via mTORC2 activation.

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Experimental tooth movement is delayed in Runx2^+/− mice compared with wild-type mice.

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Runx2 plays a role in stretch-induced proliferation and differentiation of BMSCs via mTORC2 activation.

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Runx2^+/− mice are useful model to clarify the mechanical stress-induced bone remodeling in CCD patients.

Photobiomodulation Therapy on Orthodontic Movement: Analysis of Preliminary Studies with a New Protocol

This study aimed to investigate the effectiveness of photobiomodulation therapy (PBMT) on the acceleration of orthodontic movements, deriving from its biostimulating and regenerative capacity on soft tissues, consequent to the increase in differentiation, proliferation, and activity of cells that are involved with alveolar bone remodeling. The present randomized controlled trial was conducted on six patients who required extractive orthodontic therapy because their ectopic canines had erupted. A total of eight canines were analyzed, four of which received laser irradiation (i.e., experimental group). Two weeks after the extractions, all canines of the experimental and placebo groups were distalized simultaneously and symmetrically with the laceback retraction technique. The PBMT protocol consisted of four cycles of laser applications, one each on days 0, 3, 7, and 14 of the study, with session treatment durations of 2–4 min. The results of the descriptive analysis on the distal displacement speed of the canines after 1 month of follow-up indicate an average displacement of 1.35 mm for the non-irradiated group and 1.98 mm for the irradiated group. Through inferential analysis, a statistically significant difference (p < 0.05) was found between the average speed of the irradiated canines and the control canines. The low energy density laser used in this study, with the parameters set, was found to be a tool capable of statistically significantly accelerating the distal displacement of canines.

In Vitro Evaluation of Direct and Indirect Effects of Sonic and Ultrasonic Instrumentations on the Shear Bond Strength of Orthodontic Brackets

Objective

Sonic and ultrasonic instrumentations generate vibrations that may influence debonding characteristics. The objective of this in vitro study was to assess the direct and indirect effects of sonic and ultrasonic periodontal instrumentations on the shear bond strength (SBS) and the adhesive remnant index (ARI) scores of metallic orthodontic brackets.

Methods

Metallic brackets were bonded to 75 extracted mandibular central incisors that were embedded in acrylic resin. Instrumentations around the bracket base performed with ultrasonic (UltrasonicB group, n=15) and sonic (SonicB group, n=15) scalers were used to evaluate the direct effects on the SBS of brackets. Lingual surface instrumentations with ultrasonic (UltrasonicL group, n=15) and sonic (SonicL group, n=15) scalers were performed to assess the indirect effects. The control group (n=15) did not have any treatment. Instrumentations were performed for 30 s with 0° scaler tip angulations with settings recommended by manufacturers. The SBS of the brackets tested with a universal testing machine and ARI scores were recorded. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests.

Results

The mean SBS of the control group was significantly higher than that of the UltrasonicB and SonicB groups (p=0.008). The UltrasonicL and SonicL group instrumentations also decreased the SBS, although the difference was statistically insignificant. UltrasonicB instrumentations caused significantly higher frequency of ARI scores than the control group.

Conclusion

The decrease of the SBS of metallic brackets indicates the influence of ultrasonic and sonic instrumentations on the breakage behavior at the bracket-resin interface. Instrumentations around the bracket base should be conducted with caution to decrease the bond failure risk of metallic brackets.

Evaluating the Efficacy of a Modified Piezo-Puncture Method on the Rate of Tooth Movement in Orthodontic Patients: A Clinical Study

Objective

Owing to the increasing demand from orthodontic patients for a more rapid treatment, many studies have focused on accelerated tooth movement. Currently, one of the prevalent methods to achieve accelerated tooth movement is piezo-puncture. The aim of the present study was to evaluate the effect of a modified piezo-puncture method on tooth movement rate and type during canine retraction.

Methods

A total of 17 patients who required fixed orthodontic treatment with extraction of the maxillary first premolars were included in the study. Following a split-mouth design, upper canines were retracted with Ni-Ti coil spring that applied 150 g of force on each side (piezo-puncture on one side and contralateral side served as the control). Then, the rates of tooth movement, canine angulation and rotation, and anchorage loss were evaluated at T0 (before the intervention), T1 (1 month after the intervention), and T2 (2 months after the intervention). For calculating the canine movement rate, either the distance between the canine and the lateral incisor or the space between the second premolar and the canine was measured. In addition, pain perception was documented by Visual Analog Scale. Data were analyzed using the Kolmogorov-Smirnov normality test, Spearman correlation test, paired sample t-test, and Wilcoxon signed-rank test.

Results

No significant acceleration was observed in canine movement, canine tipping, rotation, or anchorage loss of molar in different times.

Conclusion

Considering the limitations of the study, the application of piezo-puncture employing the protocol used in the present study failed to accelerate tooth movement and to decrease the unfavorable tipping, rotation, and molar anchorage loss.

Effect of statins on orthodontic tooth movement: A systematic review of animal and clinical studies

OBJECTIVE

The objective was to systematically-review the effect of statin drugs on orthodontic-tooth-movement (OTM).

DESIGN

The focused-question was "Does statin therapy affect OTM?" PubMed, Ovid Medline, Cochrane Library, Scopus, EMBASE and Web of Science databases were searched without time and language restrictions using different key words. Studies assessing the effect of adjunctive statin administration on OTM compared with orthodontic treatment alone were included. The search was performed up to and including December 2018. Data regarding the study design/grouping, subjects, age/gender, duration of follow-up, outcome variables and parameters related to OTM and statins administration were evaluated.

RESULTS

Nine studies (1 clinical and 8 studies performed in animal-models) were included. Six studies used Simvastatin, whereas three studies used Atorvastatin. Six experimental studies and one clinical study reported reduction in OTM upon statin administration. Two experimental studies reported no effect of statin administration on OTM. In 90 % of the studies, the risk-of-bias was high.

CONCLUSION

Based upon the high risk-of-bias and methodological inconsistencies among the included studies, the influence of statin delivery on OTM remains debatable.

Low-intensity pulsed ultrasound enhances the rate of lateral tooth movement and compensatory bone formation in rats

INTRODUCTION

Because mechanical stimulation of the periodontal ligament by low-intensity pulsed ultrasound (LIPUS) has been shown to increase the speed of bone remodeling, this study aimed to examine the effects of LIPUS stimulation on the rate of tooth movement and bone remodeling during lateral tooth movement.

METHODS

Twelve-week-old Wistar rats were divided into 2 groups. The LIPUS group received experimental tooth movement with LIPUS stimulation, and the tooth movement (TM) group were provided experimental tooth movement without LIPUS. For each group, the upper right first molars were moved buccally with fixed appliances. LIPUS exposure was placed in the region corresponding to the right maxillary first molar. Three days after tooth movement, tartrate-resistant acid phosphatase was examined. Fourteen days after tooth movement, the intermolar width, bone mineral content, and bone volume fraction were analyzed by micro-computed tomography, and newly formed bone was measured histomorphometrically.

RESULTS

The number of TRAP-positive cells in the compressed region was higher in the LIPUS group. The intermolar width was significantly higher in the LIPUS group than in the TM group. The alveolar bone around the maxillary first molar showed no differences in bone mineral content and bone volume fraction between the LIPUS and TM groups. The LIPUS group exhibited a more significant amount of newly formed alveolar bone than the TM group.

CONCLUSIONS

The present study provides evidence of the beneficial effects of LIPUS on the lateral tooth movement.

Elastic fiber system evaluated in the digestive organ of rats

According to our previous reports, the intraperiodontal elastic fiber system comprises oxytalan fibers, whereas all types of elastic system fibers are present in the gingiva. Much remains to be elucidated regarding the topographic development of the elastic fiber system that constitutes the walls of the digestive organs. This study aimed to examine the topographic development of the elastic fiber system in the periodontal tissue, oral cavity and digestive tract of rats at light- and electron microscopic levels. At embryonic day 20, in situ hybridization revealed the mRNA expression of tropoelastin in the putative gingival lamina propria but not in the dental follicle. At the postnatal stage, the masticatory mucous membrane of the gingiva and hard palate comprised three different types of elastic system fibers (oxytalan, elaunin and elastic fibers). Conversely, the elastic fiber system comprised elaunin and elastic fibers in other oral mucosae and the lining mucosae of digestive tract organs (the esophagus, stomach and small intestine). The findings of our study suggest that the elastic fiber system is mainly related to tissue resistance in the periodontal ligament and tissue elasticity in the oral mucosae without masticatory mucosae and the overlying mucosa of digestive tracts and both functions in the gingiva and hard palate, respectively. The appearance of elaunin fibers in the periodontium of rats aged 14 weeks suggests the expression of tropoelastin induced by mechanical stressors such as mastication. The intraperiodontal difference in the distribution of elaunin fibers suggests heterogeneity among fibroblasts constituting the periodontium.

Effect of static compressive force on in vitro cultured PDL fibroblasts: monitoring of viability and gene expression over 6 days

OBJECTIVES

The aim was to investigate the impact of static compressive force (CF) application on human PDL-derived fibroblasts (HPDF) in vitro for up to 6 days on the expression of specific genes and to monitor cell growth and cell viability.

MATERIALS AND METHODS

CF of 2 g/cm² was applied on HPDFs for 1-6 days. On each day, gene expression (cFOS, HB-GAM, COX2, IL6, TNFα, RUNX2, and P2RX2) and secretion (TNFα, PGE₂) were determined by RT-qPCR and ELISA, respectively. Cell growth and cell viability were monitored daily.

RESULTS

In comparison with controls, significant upregulation of cFOS in compressed HPDFs was observed. HB-GAM showed no changes in expression, except on day 5 (P < 0.001). IL6 expression was significantly upregulated from day 2-5, reaching the maximum on day 3 (P < 0.001). TNFα expression was upregulated on all but day 2. COX2 showed upregulation, reaching the plateau from day 3 (P < 0.001) until day 4 (P < 0.001), and returning to the initial state till day 6. P2RX7 was downregulated on days 2 and 4 to 6 (P < 0.001). RUNX2 was downregulated on days 2 and 5 (both P < 0.001). Cells in both groups were proliferating, and no negative effect on cell viability was observed.

CONCLUSION

Results suggest high molecular activity up to 6 days, therefore introducing further need for in vitro studies with a longer duration that would explain other genes and metabolites involved in orthodontic tooth movement (OTM).

CLINICAL RELEVANCE

Extension of an established in vitro force application system for prolonged force application (6 days) simulating the initial phase of OTM.

Vesicular nucleotide transporter mediates adenosine triphosphate release in compressed human periodontal ligament fibroblast cells and participates in tooth movement-induced nociception in rats

OBJECTIVE

Pain control is imperative in orthodontic treatment. Adenosine triphosphate (ATP) is a key mediator released from periodontal ligament cells that excites nociceptive nerve endings. Vesicular nucleotide transporter (VNUT), encoded by the Solute carrier family 17 member 9 (SLC17A9) gene, participates in ATP uptake into secretory vesicles; thus, it may mediate tooth movement-induced pain. In the present study, we examined whether VNUT in periodontal ligament cells participates in tooth movement-induced nociception.

DESIGN

Expression levels of SLC17A9, connexin 43, and pannexin 1 in human periodontal ligament fibroblasts (HPDLFs) were examined by quantitative reverse transcription-polymerase chain reaction. Mechanical force via centrifugation-induced ATP release was measured using an ATP bioluminescence assay. Inhibitors were used to evaluate the role of ATP transporters. Face-grooming behaviors were assessed as indicators of nociceptive responses after experimental tooth movement in rats, as well as the effects of drugs for the pain-like behavior.

RESULTS

After HPDLFs underwent mechanical stimulation by centrifugation, SLC17A9 mRNA expression in the cells was significantly upregulated. Increased ATP release from HPDLFs after mechanical stimulation was suppressed by treatment with clodronic acid, a VNUT inhibitor, at concentrations of 0.1 and 1.0 μM. In rats, face-grooming behaviors (indicators of nociception) were significantly increased on day 1 after experimental tooth movement. Increased face-grooming behaviors were suppressed by systemic administration of clodronic acid (0.1 mg/kg).

CONCLUSIONS

These results indicate that release of ATP from periodontal ligament cells via VNUT is important for nociceptive transduction during orthodontic treatment. Thus, VNUT may provide a novel drug target for tooth movement-induced pain.

Cytokine levels in gingival crevicular fluid during orthodontic treatment with aligners compared to conventional labial fixed appliances: a 3-week clinical study

Objective: To test the hypothesis that the levels of IL-1ß and TNF-α increased more and IL-1α, IL-2, IL-6, IL-8 increased less, after 3 weeks of treatment with conventional labial fixed appliance and with aligners. Material and methods: Forty patients who were treated either with labial brackets (n = 20) or aligners (n = 20). Gingival crevicular fluid (GCF) samples were collected at baseline and after 21 days. Cytokine levels were evaluated by enzyme-linked immune sorbent assay (ELISA). Plaque index (PI), gingival index (GI), and bleeding on probing (POB) were also examined. Results: The levels of IL-1α, IL-1ß, IL-2, IL-6, IL-8 and TNF-α in the GCF were significantly increased in both groups. The levels of IL-2, IL-6, IL-8 increased more in patients treated with aligners compared to those treated by labial fixed appliances. There was a statistically significant difference in change of the mean cytokine levels of IL-1α, IL-2, IL-6, IL-8 and TNF-α compared to labial fixed appliances and aligners. Conclusions: The levels of the six studied cytokines in GCF (IL-1α, IL-1ß, IL-2, IL-6, IL-8 and TNF-α) increased after 3 weeks both after treatment with conventional labial fixed appliance and with aligners. IL-1ß and TNF-α showed a prominent increase compared to the other cytokines in the GCF of teeth by both the labial fixed appliance and aligners. However, there were only minor differences in the changes of the cytokine levels from baseline to 3 weeks between the two groups. There were no differences between the groups regarding PI, GI or POB.

Periodontally accelerated osteogenic orthodontics combined with recombinant human bone morphogenetic protein-2: An outcome assessment

Context:

Periodontally accelerated osteogenic orthodontics (PAOO) combines alveolar corticotomy, bone graft materials, and the application of orthodontic forces for rapid correction of malocclusions.

Aims:

The present study aims to primarily assess differences in orthodontic treatment duration, bone quality around corticotomy sites, postoperative healing, and subjective pain when corticotomy was done conventionally and with the placement of recombinant human bone morphogenetic protein-2 (rhBMP-2).

Settings and Design:

Thirty individuals participated in this study. Individuals were randomly assigned into each of the following experimental groups; C + BMP: Corticotomy with 0.5 μg/mL rhBMP-2 and C: Corticotomy only.

Materials and Methods:

Clinical parameters included recording the duration of the treatment period, visual analog scale scores and early wound healing index scores. The evaluation of bone density was performed at baseline, 3 months, and 6 months by using RVG.

Statistical Analysis Used:

Two-way analysis of variance and post hoc multiple comparison tests were used to compare data between test and control groups at different time points.

Results:

rhBMP-2 application was effective in reducing the overall treatment time and resulted in an increase in bone density around corticotomy sites at the end of the treatment period when compared to conventional corticotomy procedure. Placement of rhBMP-2 neither delayed wound healing nor affected participant pain scores.

Conclusions:

From this trial conducted over a period of 6 months, rhBMP-2 has the potential to function as a regenerative material in PAOO.

The effect of cyclic tensile force on the actin cytoskeleton organization and morphology of human periodontal ligament cells

To explore Girdin/Akt pathway protein expression and morphology change by cyclic tension in the periodontal ligament cells. Human periodontal ligament cells were exposed to cyclic tension force at 4000 μstrain and 0.5 Hz for 6 h though a four-point bending system. Cyclic tension force upregulated F-actin, Girdin and Akt expression in hPDL. In transmission electron microscope assay showed that there are more and bigger mitochondria, more and longer cynapses, more cellular organisms after tension force stimulation than control. The actin filament was changed to be regular lines and pointed to poles of cells. However, we found that the Girdin-depleted cells are small and there are more micro-organisms including more lysosomes and matrix vesicles than control. These finding suggest that the STAT3/Girdin/Akt pathway in PDL to response to mechanical stimulation as well, and Girdin may play a significant role in triggering cell proliferation and migration during orthodontic treatment. It provided an insight into the molecular basis for development of a vitro cell model in studying orthodontic treatment.

The effect of orthodontic separator and short-term fixed orthodontic appliance on inflammatory mediators and somatosensory function

BACKGROUND

Although inflammation can alter cytokines release and nerve function, it is not yet fully established if orthodontic-induced inflammation can cause significant extraoral trigeminal somatosensory alterations and release of inflammatory chemical mediators.

OBJECTIVE

The primary aim of this study was to investigate the impact of orthodontic separator and short-term fixed orthodontic appliance on the extraoral trigeminal somatosensory function and concentrations of cytokines in the gingival crevicular fluid (GCF).

METHODS

Twenty-two female patients were evaluated as follow: baseline, 24 hour-after elastomeric separator (-aES), 24 hour- and 1 month-after bonding brackets (-aBB) at both arches. The outcome variables were as follows: self-reported pain (Visual Analog Scale), QSTs (current perception threshold-CPT, cold detection threshold-CDT, warm detection threshold-WDT, mechanical detection threshold-MDT, mechanical suprathreshold-MST and wind-up ratio-WUR. All QSTs were performed at infra-orbital and mental nerve entry zone at patient`s dominant side. In addition, GCF samples in order to assess cytokines profile (IL-1β,IL-8,IL-6 and TNF-α) were collected. ANOVA and Tukey's post hoc analyses were performed (a = 5%).

RESULTS

Patients reported higher pain intensity 24 hour-aBB compared to baseline and 24 hour-aES (P < 0.050). Patients were less sensitive to pin-prick pain (MST) at 24 hour-aBB and 1 month-aBB compared to baseline (P < 0.006). Significant increases in IL-6 levels were observed 24 hour-aBB (P < 0.001). Multiple comparison analysis showed significant increase in IL-1β levels (P < 0.001) and TNF-α (P < 0.001) 1 month-aBB compared to baseline.

CONCLUSION

Elastomeric separators only induced mild pain and were not able to significantly increase proinflammatory cytokines level in the GCF. In addition, orthodontic fixed appliance may induce only minor somatosensory changes at extraoral trigeminal locations.

Cyclic tensile force stimulates BMP9 synthesis and in vitro mineralization by human periodontal ligament cells

Periodontal ligament (PDL) cells are mechanosensitive and have the potential to differentiate into osteoblast-like cells under the influence of cyclic tensile force (CTF). CTF modulates the expression of regulatory proteins including bone morphogenetic proteins (BMPs), which are essential for the homeostasis of the periodontium. Among the BMPs, BMP9 is one of the most potent osteogenic BMPs. It is yet unknown whether CTF affects the expression of BMP9 and mineralization. Here, we demonstrated that continuously applied CTF for only the first 6 hr stimulated the synthesis of BMP9 and induced mineral deposition within 14 days by human PDL cells. Stimulation of BMP9 expression depended on ATP and P2Y ₁ receptors. Apyrase, an ecto-ATPase, inhibited CTF-mediated ATP-induced BMP9 expression. The addition of ATP increased the expression of BMP9. Loss of function experiments using suramin (a broad-spectrum P2Y antagonist), MRS2179 (a specific P2Y ₁ receptor antagonist), MRS 2365 (a specific P2Y ₁ agonist), U-73122 (a phospholipase C [PLC] inhibitor), and thapsigargin (enhancer of intracytosolic calcium) revealed the participation of P2Y ₁ in regulating the expression of BMP9. This was mediated by an increased level of intracellular Ca ²⁺ through the PLC pathway. A neutralizing anti-BMP9 antibody decreased mineral deposition, which was stimulated by CTF for almost 45% indicating a role of BMP9 in an in vitro mineralization. Collectively, our findings suggest an essential modulatory role of CTF in the homeostasis and regeneration of the periodontium.

In Vitro Weight-Loaded Cell Models for Understanding Mechanodependent Molecular Pathways Involved in Orthodontic Tooth Movement: A Systematic Review

Cells from the mesenchymal lineage in the dental area, including but not limited to PDL fibroblasts, osteoblasts, and dental stem cells, are exposed to mechanical stress in physiological (e.g., chewing) and nonphysiological/therapeutic (e.g., orthodontic tooth movement) situations. Close and complex interaction of these different cell types results in the physiological and nonphysiological adaptation of these tissues to mechanical stress. Currently, different in vitro loading models are used to investigate the effect of different types of mechanical loading on the stress adaptation of these cell types. We performed a systematic review according to the PRISMA guidelines to identify all studies in the field of dentistry with focus on mechanobiology using in vitro loading models applying uniaxial static compressive force. Only studies reporting on cells from the mesenchymal lineage were considered for inclusion. The results are summarized regarding gene expression in relation to force duration and magnitude, and the most significant signaling pathways they take part in are identified using protein-protein interaction networks.

The biological basis of treating jaw discrepancies: An interplay of mechanical forces and skeletal configuration

Jaw discrepancies and malrelations affect a large proportion of the general population and their treatment is of utmost significance for individuals' health and quality of life. The aim of their therapy is the modification of aberrant jaw development mainly by targeting the growth potential of the mandibular condyle through its cartilage, and the architectural shape of alveolar bone through a suture type of structure, the periodontal ligament. This targeted treatment is achieved via external mechanical force application by using a wide variety of intraoral and extraoral appliances. Condylar cartilage and sutures exhibit a remarkable plasticity due to the mechano-responsiveness of the chondrocytes and the multipotent mesenchymal cells of the sutures. The tissues respond biologically and adapt to mechanical force application by a variety of signaling pathways and a final interplay between the proliferative activity and the differentiation status of the cells involved. These targeted therapeutic functional alterations within temporo-mandibular joint ultimately result in the enhancement or restriction of mandibular growth, while within the periodontal ligament lead to bone remodeling and change of its architectural structure. Depending on the form of the malrelation presented, the above treatment approaches, in conjunction or separately, lead to the total correction of jaw discrepancies and the achievement of facial harmony and function. Overall, the treatment of craniofacial and jaw anomalies can be seen as an interplay of mechanical forces and adaptations occurring within temporo-mandibular joint and alveolar bone. The aim of the present review is to present up-to-date knowledge on the mechano-biology behind jaw growth modification and alveolar bone remodeling. Furthermore, future molecular targeted therapeutic strategies are discussed aiming at the improvement of mechanically-driven chondrogenesis and osteogenesis.

The intricate anatomy of the periodontal ligament and its development: Lessons for periodontal regeneration

The periodontal ligament (PDL) connects the tooth root and alveolar bone. It is an aligned fibrous network that is interposed between, and anchored to, both mineralized surfaces. Periodontal disease is common and reduces the ability of the PDL to act as a shock absorber, a barrier for pathogens and a sensor of mastication. Although disease progression can be stopped, current therapies do not primarily focus on tissue regeneration. Functional regeneration of PDL may be achieved using innovative techniques, such as tissue engineering. However, the complex fibrillar architecture of the PDL, essential to withstand high forces, makes PDL tissue engineering very challenging. This challenge may be met by studying PDL anatomy and development. Understanding PDL anatomy, development and maintenance provides clues regarding the specific events that need to be mimicked for the formation of this intricate tissue. Owing to the specific composition of the PDL, which develops by self-organization, a different approach than the typical combination of biomaterials, growth factors and regenerative cells is necessary for functional PDL engineering. Most specifically, the architecture of the new PDL to be formed does not need to be dictated by textured biomaterials but can emerge from the local mechanical loading conditions. Elastic hydrogels are optimal to fill the space properly between tooth and bone, may house cells and growth factors to enhance regeneration and allow self-optimization by the alignment to local stresses. We suggest that cells and materials should be placed in a proper mechanical environment to initiate a process of self-organization resulting in a functional architecture of the PDL.

Force-induced IL-8 from Periodontal Ligament Cells Requires IL-1β

During orthodontic tooth movement, mechanical stresses induce inflammatory reactions in the periodontal ligament (PDL). We hypothesized that chemokines released from PDL cells under mechanical stress regulate osteoclastogenesis, and investigated the profiles and mechanisms of chemokine expression by human PDL cells in response to mechanical stress. In vitro, shear stress and pressure force rapidly increased the gene and protein expressions of IL-8/CXCL8 by PDL cells. Consistently, amounts of IL-8 in the gingival crevicular fluid of healthy individuals increased within 2 to 4 days of orthodontic force application. The PDL cells constitutively expressed low levels of IL-1β, which were not further increased by mechanical stress. Interestingly, neutralization of IL-1β abolished IL-8 induction by mechanical stresses, indicating that IL-1β is essential for IL-8 induction, presumably though autocrine or paracrine mechanisms. Finally, experiments with signal-specific inhibitors indicated that MAP kinase activation is essential for IL-8 induction.

Osteoprotective Effects of IL-33/ST2 Link to Osteoclast Apoptosis

The relevance of IL-33 and its receptor ST2 for bone remodeling is not well-defined. Our aim was to assess the role and underlying mechanisms of IL-33/ST2 in mechanically induced bone remodeling. BALB/c (wild type) and ST2 deficient (St2(-/-)) mice were subjected to mechanical loading in alveolar bone. Microtomography, histology, and real-time quantitative PCR were performed to analyze bone parameters, apoptosis and bone cell counts, and expression of bone remodeling markers, respectively. MC3T3-E1 osteoblastic cells and bone marrow cells were used to verify if mechanical force triggered IL-33 and ST2 expression as well as the effects of IL-33 on osteoclast differentiation and activity. Mechanical loading increased the expression of IL-33 and ST2 in alveolar bone in vivo and in osteoblastic cells in vitro. St2(-/-) mice had increased mechanical loading-induced bone resorption, number of osteoclasts, and expression of proresorptive markers. In contrast, St2(-/-) mice exhibited reduced numbers of osteoblasts and apoptotic cells in periodontium and diminished expression of osteoblast signaling molecules. In vitro, IL-33 treatment inhibited osteoclast differentiation and activity even in the presence of receptor activator of NF-κB ligand. IL-33 also increased the expression of pro-apoptotic molecules, including Bcl-2-associated X protein (BAX), cell-surface Fas receptor (FAS), FASL, FAS-associated death domain, tumor necrosis factor-related apoptosis-inducing ligand, and BH3 interacting-domain death (BID). Overall, these findings suggest that IL-33/ST2 have anti-osteoclastogenic effects and reduce osteoclast formation and activity by inducing their apoptosis.

Expression of SOST/sclerostin in compressed periodontal ligament cells

Background/purpose

Bone resorption and inhibition of bone formation occur on the compressed side during orthodontic tooth movement. Bone formation inhibitory factors such as sclerostin (encoded by SOST) are secreted on the compressed side by periodontal ligament (PDL) cells. PDL cells control bone metabolism, and compressed PDL cells inhibit bone formation during orthodontic tooth movement. The aim of this study was to identify the inhibitory factors of bone formation in PDL cells.

Materials and methods

Changes in SOST expression and subsequent protein release from human PDL (hPDL) cells were assessed using the real-time polymerase chain reaction (PCR), semiquantitative PCR, and immunofluorescence in hPDL cells subjected to centrifugal force (40g and 90g). To confirm the effects on bone formation, human alveolar bone-derived osteoblasts (hOBs) were grown with the addition of sclerostin peptide. In vivo, a compressive force was applied using the Waldo method in rats, and the distribution of sclerostin in PDL tissues was examined by immunohistochemistry.

Results

SOST expression was downregulated in vitro by centrifugation at 90g for 24 hours but upregulated by centrifugation at 40g based on real-time PCR, as was confirmed by immunofluorescence staining. The addition of sclerostin peptide significantly decreased the mineralized area in hOBs. However, slightly weakly sclerostin-positive PDL cells were observed on the compressed side in vivo.

Conclusion

These results indicate that PDL cells subjected to light compressive force exhibit increased expression of SOST/sclerostin, which inhibits bone formation on the compressed side during orthodontic tooth movement.

The effect of calcitriol on high mobility group box 1 expression in periodontal ligament cells during orthodontic tooth movement in rats

High mobility group box 1 (HMGB1) is a late inflammatory cytokine that plays an important role in periodontal tissue remodeling during orthodontic tooth movement. Calcitriol (1,25-dihydroxyvitamin D3 [1α,25 (OH)2D3]) is a systemic calcium-regulating hormone shown to downregulate expression of multiple proinflammatory cytokines in human periodontal ligament cells in response to orthodontic force. The purpose of this study was to investigate the effect of 1α,25(OH)2D3 on the expression of HMGB1 in periodontal ligament (PDL) cells during orthodontic tooth movement. Seven-week-old male Wistar rats were used for experimentation. Tooth movement was assessed using a nickel-titanium coil spring to apply mechanical loading to the tooth for 5 days. This was followed by administration of either 1α,25(OH)2D3 or normal saline by gavage every other day for up to 28 days. Immunohistochemistry was used to analyze the expression of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and HMGB1. After discontinuation of orthodontic force, expression of the early inflammatory cytokines IL-6 and TNF-α were time-dependently reduced in the 1α,25(OH)2D3 group compared with the control group at each time point. Similarly, expression of HMGB1 was decreased over time in both the 1α,25(OH)2D3 and normal saline groups, and 1α,25(OH)2D3 administration enhanced this decline. These findings indicate that administration of 1α,25(OH)2D3 might provide a favorable microenvironment for orthodontic tooth movement by downregulating expression of HMGB1 in PDL cells.