Orthodontic Force Application Research Articles

Correlation of sex hormone levels with orthodontic tooth movement in the maxilla: a prospective cohort study.

Sex hormones secreted during the menstrual cycle and the application of orthodontic forces to teeth can affect the metabolism of periodontal ligaments. This study aimed to determine whether there are any differences in orthodontic tooth displacement during the menstrual cycle and when using hormonal contraceptives and whether the amount of female sex hormones influences the efficiency of tooth displacement. A total of 120 women aged between 20 and 30 years with Angle Class II requiring transpalatal arch (TPA) to derotate teeth 16 and 26 were included in this study. The participants were divided into two groups: group A, which included women with regular menstruation, and control group B, which included women taking monophasic combined oral contraceptives. Group A was divided into subgroups according to the moment of TPA activation: menstruation (A1), ovulation phase (A2), and luteal phase (A3) (examination I). On intraoral scans, measurement points were marked on the proximal mesial cusps of teeth 16 and 26, and the intermolar distance (M1) was determined. The change in the position of the measurement points 6 weeks after activation (examination II) made it possible to determine the derotating extent of teeth 16 (O16) and 26 (O26) and the widening of the intermolar distance (M2-M1). In examinations I and II, tooth mobility in the alveoli was assessed using Periotest based on the periotest values (PTV) PTV1 and PTV2, respectively. A significant difference in all parameters was observed among groups A1, A2, and A3 (P < 0.001). Group A3 showed the highest values of parameters O16, O26, and M2-M1, and group A2 showed the lowest values, which did not differ from the control group (P = 0.64). PTV2 and PTV1 were the highest in group A3 and the lowest in groups A1 and B. Intergroup differences were statistically significant (P < 0.001). With the quantification of changes in tooth mobility in the alveoli during the menstrual cycle in women undergoing orthodontic treatment, it was possible to determine that female sex hormones affect the effectiveness of orthodontic treatment, and the optimal moment for TPA activation is the luteal phase of the menstrual cycle.

To evaluate the effectiveness of biting on chewie as pain management during debonding: A cross-sectional study

: During orthodontic treatment, pain and discomfort are frequently felt by patients during procedures like separator placement, archwire placement, orthodontic force application, miniscrew placement and debonding. The purpose of this study is to look into the effects of biting on Chewie for pain management during debonding procedure. Out of sample size of 128 sites, 64 sites (right or left) was assigned as Chewie and 64 sites as control group and debonding was carried out. Pain was evaluated on VAS scale from 1 to 10. Chewie group has a mean value of 1.76, with a 95% confidence interval ranging from 1.59 (Lower) to 1.93 (Upper). Conventional group has a mean value of 2.00, with a 95% confidence interval ranging from 1.79 (Lower) to 2.20 (Upper). : Debonding performed with gently squeezing action and biting on the chewie will be sufficient to keep pain to a minimum level and no other additional pain-relief method will be required.

The effect of orthodontic Force Application and Tooth Movement on Dental Pulp

This systematic review aimed to conclusively investigate the effect of continuous intrusive force application on human pulpal blood flow (PBF). It is a well-established fact that applying a severe orthodontic force for an extended period can cause irreversible pulpitis and necrosis in the pulp by accelerating the inflammation process. In contrast, utilizing moderate and intermittent forces allows for ample tooth movement, limits pulp damage, and facilitates pulp healing. Materials and methods: A comprehensive search of published studies was conducted in several electronic databases such as MEDLINE, PubMed, EMBASE, Scopus, Web of Science, CINAHL, and the Cochrane Database of Systematic Reviews, as well as Google Scholar. The search was conducted without limitations to find published studies. The results showed that orthodontic forces can lead to a decrease in pulpal blood flow, which causes a reduction in tooth sensitivity. This reduction is indicated by an increase in response thresholds and more negative responses to tooth sensitivity tests. Conclusion: applying a severe orthodontic force over a prolonged period of time can lead to irreversible pulpitis and necrosis in the pulp due to an increase in the inflammation process. However, using moderate and intermittent forces can facilitate sufficient tooth movement while minimizing damage to the pulp. This highlights the importance of the endodontic-orthodontic interface and the need to consider dental pulp health during orthodontic treatment to avoid dental trauma.

Advances in the Study of the Relationship Between Orthodontics and Periodontitis

This comprehensive study employed a multifaceted research methodology encompassing a systematic review of existing literature, clinical case analyses, and a series of controlled clinical trials to explore the complex relationship between orthodontic treatments and periodontal health. The study focused on evaluating the biomechanical impacts of orthodontic procedures on the periodontium, including risks such as gum recession and bone loss, particularly in patients with varying periodontal biotypes and pre-existing periodontal conditions. The research methodology involved detailed assessments of periodontal health pre- and post-orthodontic intervention, monitoring changes in gingival and bone structures using advanced imaging techniques, and recording patient-reported outcomes regarding oral health quality. The findings of this study revealed a significant correlation between orthodontic force application and changes in periodontal tissue health, highlighting the necessity of personalized treatment planning that incorporates the patient's periodontal status. Preventive measures, including the use of controlled orthodontic forces, meticulous monitoring of tooth movement, and enhanced oral hygiene practices, were shown to be effective in minimizing periodontal complications. This study contributes significantly to the dental field by providing a deeper understanding of the orthodontic-periodontal relationship and offers practical guidelines for dental professionals in managing orthodontic treatments for patients with periodontal considerations. The study's findings underscore the importance of an interdisciplinary approach in dental care, advocating for closer collaboration between orthodontists and periodontists to optimize treatment outcomes and ensure comprehensive oral health care.

Properties and Application of the Gummetal Wire for the Treatment of an Open Bite—Brief Narrative Review and Case Report

The swift integration of ‘Gummetal’ into the orthodontic armamentarium can be attributed to its distinct advantages as an entirely new Ti-Nb-based beta titanium alloy. Developed by Toyota Central R&amp;D Labs and publicly revealed in April 2003, this innovative material is rapidly reshaping orthodontic practices. Its sui generis properties allow its use as a potential substitute for the Multi-Loop Edgewise Archwire (MEAW) method. Three-dimensional orthodontic movement using this new alloy could eliminate the disadvantages of the MEAW method, such as its technical complexity and patient discomfort. In our comprehensive review of the current literature, we examined relevant publications sourced from the PUBMED database and explored one seminal work on Gummetal from the journal literature. Characteristic properties of Gummetal, such as its exceptional flexibility, superelasticity, and malleability (approximately 10 times greater than conventional metals), enable seamless formation of bends without posing challenges, thereby allowing precise control over orthodontic force application. Also worthy of mention are Gummetal’s biocompatibility and non-toxic properties, along with its low coefficient of friction. The wire seems to be a relatively easy way to achieve good occlusion. Its usage does not require extensive experience in terms of manual skill, and it is not time consuming. Diligent usage of any prescribed plastics by the patient is crucial to prevent complications and ensure successful orthodontic outcomes.

Micro-Osteoperforations Accelerate Tooth Movement without Exacerbating the Progression of Root Resorption in Rats.

A recent study reported that micro-osteoperforations (MOPs) accelerated tooth movement by activating alveolar bone remodeling. However, very little is known about the relationship between MOPs and external apical root resorption during orthodontic treatment. In this study, in order to investigate the mechanism through which MOPs accelerate tooth movement without exacerbating the progression of root resorption, we measured the volume of the resorbed root, and performed the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL) method on exposed MOPs during experimental tooth movements in rats. Male Wistar rats (11 weeks old) were divided into three groups: 10 g orthodontic force (optimal force) applied to the maxillary first molar (optimal force: OF group), 50 g orthodontic force application (heavy force: HF group), and 10 g force application plus three small perforations of the cortical plate (OF + MOPs group). On days 1, 4, 7, 10, and 14 after force application, the tooth movement and root volume were investigated by micro-computed tomography. Furthermore, the number of apoptotic cells in the pressured sides of the periodontal ligament (PDL) and surrounding hard tissues were determined by TUNEL staining. The OF + MOPs group exhibited a 1.8-fold increase in tooth movement on days 7, 10, and 14 compared with the OF group. On days 14, the HF group had a higher volume of root loss than the OF and OF + MOPs groups. On the same day, the number of TUNEL-positive cells in the HF group increased at the root (cementum) site whereas that in the OF group increased at the alveolar bone site. Furthermore, the number of TUNEL-positive cells in the OF + MOPs group increased at the alveolar bone site compared with the OF group. These results suggest that MOPs accelerate orthodontic tooth movement without exacerbating the progression of root resorption.

Early-stage periodontal ligament compression predicts orthodontically induced root resorption in rats.

To determine the effect of orthodontic pressure on periodontal ligament (PDL) compression in rats and assess correlation between PDL compression and orthodontically induced root resorption (OIRR). Eight female Wistar rats aged 10 weeks underwent surgery to place 2 mini-screws at the center of the palatal plate. 25 cN coil springs connecting the maxillary first molars and mini-screws were applied bilaterally to generate mesial force. Maxillary first molars were assigned to undergo either bodily or tipping movements. Micro-computed tomography (μCT) scans were taken on days 0, 3, 7, and 14, and histological sections were taken on day 14. OIRR was measured from histological sections, and the corresponding PDL compression ratio was quantified using μCT images. The PDL was compressed by approximately 76% in tipping movement and 55% in bodily movement after 3 days, and by approximately 47% in bodily and tipping movements after 7 days of orthodontic force application. The extent of OIRR in tipping movement was significantly greater than that in bodily movement. A strong positive correlation between OIRR and PDL compression ratio was observed on day 3; however, no correlation was observed on day 7. A strong correlation between PDL compression ratio and OIRR was observed at an early stage after the application of orthodontic force regardless of the tooth movement type (bodily or tipping), implying the importance of early stage PDL compression in the induction of OIRR.

Wilckodontics: A Multidisciplinary Approach for Orthodontic Treatment.

Wilckodontics is the periodontally accelerated orthodontic treatment, which isa clinical procedurethat combines orthodontic tooth movement with corticotomy and bone grafting. Corticotomy is the surgical procedure that involves cutting the bone, perforating the bone and mechanically altering it. This procedure makes tooth movement easy and rapid with the help of orthodontic force application. This procedure is based on the regional acceleratory phenomenon that increases the bone width, shortens the treatment time from years to months and increases the treatment stability. This procedure also reduces the need for extraction and also increases bone support for teeth and soft tissues. This review article describes the surgical procedure, advantages, disadvantages, indications, and contraindications of Wilckodontics and the current advances in this technique.

Angiotensin(1-7) attenuates tooth movement and regulates alveolar bone response during orthodontic force application in experimental animal model

BackgroundRenin–angiotensin system and its ACE2/Ang(1-7)/Mas receptor axis regulates skeletal response to multiple physiological and pathological conditions. Recent research suggested a vital role of Ang(1-7) in regulating alveolar bone metabolism and remodeling. In this context, this study evaluated the effects of the Ang(1-7)/Mas receptor axis on orthodontic tooth movement (OTM) and the alveolar bone response to mechanical load.MethodsA coil spring was placed between the right maxillary first molar and the anterior tooth of Wistar rats to apply bidirectional mechanical force. Ang(1-7) with or without a specific Mas receptor antagonist (A779) was infused using subcutaneous osmotic pumps (200 and 400 ng/kg/min: respectively). Animals were killed after 5 and 14 days from the OTM procedure after the clinical evaluation of tooth movement and mobility. Morphometric analysis of alveolar bone structure was conducted using micro-CT and the histological picture was evaluated after H&E staining. Moreover, collagen fiber distribution was assessed using Picro-Sirius red stain. In addition, bone samples were collected from the pressure and tension sites around the anterior tooth for gene expression analysis.ResultsAng(1-7) infusion suppressed the tooth movement and mobility after 14 days of the orthodontic force application. Additionally, Ang(1-7) infusion preserved the morphometric and histological structure of the alveolar bone at pressure and tension sides. These effects were abolished by adding A779 infusion. Collagen fiber distribution was dysregulated mainly by the A779 Mas receptor blockage. Ang(1-7) affected the bone formation, remodeling- and vascularity-related genes in the pressure and tension sides, suggesting a prominent suppression of osteoclastogenesis. Ang(1-7) also improved osteoblasts-related genes on the tension side, whereas the osteoclasts-related genes were augmented by A779 on the pressure side.ConclusionCollectively, the activation of Ang(1-7)/Mas receptor axis appears to hinder tooth movement and regulates alveolar bone remodeling in response to mechanical force.Graphical abstract

Mechanobiology of orthodontic tooth movement: An update.

The purpose of this review is to provide an update on the changes at the cellular and tissue level occurring during orthodontic force application. For the understanding of this process, knowledge of the mechanobiology of the periodontal ligament and the alveolar bone are essential. The periodontal ligament and alveolar bone make up a functional unit that undergoes robust changes during orthodontic tooth movement. Complex molecular signaling is responsible for converting mechanical stresses into biochemical events with a net result of bone apposition and/or bone resorption. Despite an improved understanding of mechanical and biochemical signaling mechanisms, it is largely unknown how mechanical stresses regulate the differentiation of stem/progenitor cells into osteoblast and osteoclast lineages. To advance orthodontics, it is crucial to gain a better understanding of osteoblast differentiation from mesenchymal stem/progenitor cells and osteoclastogenesis from the hematopoietic/monocyte lineage.

Micro-computed tomography evaluation of the effects of orthodontic force on immature maxillary first molars and alveolar bone mineral density of Sprague–Dawley rats

To investigate changes in the immature teeth of Sprague-Dawley rats during orthodontic treatment and to explore the changes in the peri-radicular alveolar bone through micro-computed tomography (CT). Twenty-five 26-day-old male Sprague-Dawley rats were included. The maxillary left first molar was moved mesially under a continuous force of 30 cN, and the right first molar served as the control. After orthodontic treatment for 7, 14, 21, 28, and 42 days, the root length, tooth volume, and alveolar bone mineral density (BMD) around the mesial root were measured through micro-CT. The immature teeth continued to elongate after application of orthodontic force. The root length on the force side was significantly smaller than that on the control side, whereas the differences in the volume change between both sides were not statistically significant. Alveolar bone in the coronal part of the compression and tension sides showed no difference in BMD between the experimental and control groups. The BMD of the experimental group decreased from day 14 to day 42 in the apical part of the compression side and increased from day 7 to day 42 in the apical part of the tension side. The BMD of the experimental group decreased in the root apex part on day 7. The root length and volume of immature teeth showed continued development under orthodontic forces. Alveolar bone resorption was observed on the compression side, and bone formation was observed on the tension side.

Development of a tooth movement model of root resorption during intrusive orthodontic treatment.

There is a high risk of external apical root resorption (EARR) following the application of intrusive orthodontic forces to the apical root. However, there is a lack of suitable animal models to study this phenomenon in depth. This study compared the usability of three different types of loops, namely, vertical helical loop, box loop, and L loop, for preparing a rat model of orthodontic tooth movement with invasive forces. Results showed a significant downward movement in the first molar of the rat after L loop placement for 14 days. Three-dimensional reconstructed images showed root resorption and length shortening on the apical root and decreased bone volume and trabecular thickness in the alveolar bone under compression. Histological staining revealed odontoclasts on the root resorption fossa. This study showed that orthodontic tooth movement using the L loop provides an effective experimental animal model of EARR.

Brain-derived neurotrophic factor promotes orthodontic tooth movement by alleviating periodontal ligament stem cell senescence

Orthodontic treatment in older adults is more difficult than in younger adults, partially due to delayed osteogenesis caused by senescence of human periodontal ligament stem cells (hPDLSCs). The production of brain-derived neurotrophic factor (BDNF) which regulates the differentiation and survival of stem cells decreases with age. We aimed to investigate the relationship between BDNF and hPDLSC senescence and its effects on orthodontic tooth movement (OTM). We constructed mouse OTM models using orthodontic nickel‑titanium springs and compared the responses of wild-type (WT) and BDNF+/− mice with or without addition of exogenous BDNF. In vitro, hPDLSCs subjected to the mechanical stretch were used to simulate the cell stretch environment during OTM. We extracted periodontal ligament cells from WT and BDNF+/− mice to evaluate their senescence-related indicators. The application of orthodontic force increased BDNF expression in the periodontium of WT mice, while the mechanical stretch increased BDNF expression in hPDLSCs. Osteogenesis-related indicators, including RUNX2 and ALP decreased and cellular senescence-related indicators such as p16, p53 and β-galactosidase increased in BDNF+/− mice periodontium. Furthermore, periodontal ligament cells extracted from BDNF+/− mice exhibited more senescent compared with cells from WT mice. Application of exogenous BDNF decreased the expression of senescence-related indicators in hPDLSCs by inhibiting Notch3, thereby promoting osteogenic differentiation. Periodontal injection of BDNF decreased the expression of senescence-related indicators in periodontium of aged WT mice. In conclusion, our study showed that BDNF promotes osteogenesis during OTM by alleviating hPDLSCs senescence, paving a new path for future research and clinical applications.

Quantitative Evaluation of Pentraxin-3 in Peri-Miniscrew Implant Crevicular Fluid in Patients Undergoing Orthodontic Treatment: A Prospective Study.

To assess the levels of Pentraxin-3 (PTX3) in peri-miniscrew implant crevicular fluid (PMICF) before and after orthodontic force application Material and Methods: This study included 40 miniscrew implants (MSI) sites in 11 orthodontic patients with high arch discrepancy requiring first premolar extraction using maximum anchorage mechanics for the retraction of anterior teeth. After alignment, the en-masse anterior retraction was carried out using the MSI-supported direct anchorage method. PMICF was collected from the crevice of MSI using Periopaper strips 1.2µl (OraflowInc. USA) after one hour, 24 hours, and three weeks of MSI insertion and after one hour, 24 hours, seven days, three weeks, and six weeks of the force application. Samples were quantitatively analyzed for PTX3 levels through enzyme-linked immunosorbent assay (ELISA). The trend in the change of PTX3 levels was evaluated using the Wilcoxon signed-rank test. The mean concentration of PTX3 immediately after MSI insertion was 1.19 ng/ml, significantly higher than after 3 weeks after MSI insertion (0.72 ng/ml), which may correspond to the baseline. After loading, the mean PTX3 concentration increased significantly with the peak at 24 hrs (1.28 ng/ml), followed by a gradual decline till the completion of the study (0.5 ng/ml). After MSI insertion, a rise in PTX3 levels in PMICF suggests an underlying inflammatory process. The slow decline in PTX3 level and return to the baseline after loading suggests an adaptive bone response to the stimulus.

Levels of Pro-Inflammatory and Bone-Resorptive Mediators in Periodontally Compromised Patients under Orthodontic Treatment Involving Intermittent Forces of Low Intensities.

During orthodontic treatment, diverse cytokines, enzymes, and osteolytic mediators produced within the teeth surrounding periodontal tissues determine the rate of alveolar bone remodeling and consequent teeth movement. In patients with teeth presenting reduced periodontal support, periodontal stability should be ensured during orthodontic treatment. Thus, therapies based on the application of low-intensity intermittent orthodontic forces are recommended. To determine if this kind of treatment is periodontally well tolerated, this study aimed to analyze the production of receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), interleukin (IL)-6, IL-17A, and matrix metalloproteinase (MMP)-8 in periodontal tissues of protruded anterior teeth with reduced periodontal support and undergoing orthodontic treatment. Patients with periodontitis-associated anterior teeth migration received non-surgical periodontal therapy and a specific orthodontic treatment involving controlled low-intensity intermittent orthodontic forces. Samples were collected before periodontitis treatment, after periodontitis treatment, and at 1 week to 24 months of the orthodontic treatment. During the 2 years of orthodontic treatment, no significant differences were detected in the probing depth, clinical attachment level, supragingival bacterial plaque, and bleeding on probing. In line with this, the gingival crevicular levels of RANKL, OPG, IL-6, IL-17A, and MMP-8 did not vary between the different evaluation time-points of the orthodontic treatment. When compared with the levels detected during the periodontitis, the RANKL/OPG ratio was significantly lower at all the analyzed time-points of the orthodontic treatment. In conclusion, the patient-specific orthodontic treatment based on intermittent orthodontic forces of low intensities was well tolerated by periodontally compromised teeth with pathological migration.

Osteoimmunology in Periodontitis and Orthodontic Tooth Movement.

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

Pulp fiction or pulp fact-does orthodontics damage pulpal tissue?

Electronic databases PubMed, Scopus and Embase were systematically searched and restricted to articles published between February 2009 and 2022. Studies were categorized using the modified method by the Swedish Council of Technology Assessment in Health Care. 20 studies were included, one of which was categorized as high quality (Grade A) and 19 of which were of moderate quality (Grade B). Exclusion criteria included articles with insufficient descriptions of reliability and reproducibility testing, review articles and case reports, and studies including traumatised teeth. Three independent authors examined titles, abstracts and full texts of relevant articles against the inclusion criteria. Disagreements were resolved by discussion. Retrieved studies were assessed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data extracted included tooth movement performed, the appliance and force used, follow-up of subjects, changes in pulpal blood flow (PBF), tooth sensibility, expression of inflammation-related proteins, along with pulpal histology and morphology changes during tooth movement (intrusion, extrusion and tipping). Overall risk of bias was unclear. A reduction in pulpal blood flow and tooth sensibility due to the application of orthodontic forces was reported by studies included in the review. Increases in the activity of proteins and enzymes related to inflammation of the pulp was reported. Two studies reported histological changes of the pulpal tissues related to orthodontic treatment. Orthodontic forces cause multiple temporary detectable changes in the dental pulp. The authors conclude there are no clear signs of permanent pulpal damage to healthy teeth due to the application of orthodontic forces.

Cellular and Structural Changes of the Pulp in Rats after Continuous Orthodontic Force Application: A Pilot Study

Cellular and Structural Changes of the Pulp in Rats after Continuous Orthodontic Force Application: A Pilot Study

Effects of short-term orthodontic force application on the root at different developmental stages in rat maxillary molars

The suitable timing and duration of orthodontic force to be applied to teeth with developing roots are unclear. We investigated the effects of short-term orthodontic force application on the roots at different root developmental stages in rats to predict the optimal timing for orthodontic treatment of teeth with developing roots. Light orthodontic force was applied on the maxillary first molars of rats from postnatal day (PN) 21 or PN28 for 3 days. After that, the force was released, and the roots were evaluated on PN35 to determine the root length, apical morphology, and cell proliferation of the maxillary first mesial roots using microcomputed tomography and histologic evaluation. When a light orthodontic force was applied from PN21, the root length did not differ from that in age-matched controls. In addition, after the force was released, the roots attained the normal root-completing length and had a well-formed root apical morphology at PN35. Conversely, when the force was applied from PN28, the roots showed apical abnormalities characterized by deformed dentin and disorganized arrangement of odontoblasts, reduced apical cell proliferation, and significantly shorter length than those in the age-matched controls at PN31. The shortened root and disturbed apical integrity could not be rescued by releasing the orthodontic force at PN35. Short-term orthodontic force at the late and slow root developmental stage results in a shortened root and a defect in the root apex with reduced cell proliferation. Our findings support that orthodontic force for a limited duration during the active and rapid root developmental stage is more favorable than during the late and slow stage.

Changes in the Pulp Tissue Complex Induced by Orthodontic Forces: Is There a Need for Concern? A Systematic Review and Meta-Analysis of RCTs and Prospective Clinical Trials.

To identify and assess any changes in the pulp tissue complex following orthodontic force application. Published and unpublished literature was searched in seven databases until 9 August 2022 for randomised controlled trials (RCTs) and prospective trials (nR-PCT). Representative key words included 'pulp response', 'pulp tissue', 'orthodontic force', and 'tooth movement'. Study selection, data extraction, risk of bias and certainty of evidence assessment were conducted independently by two reviewers. Random effects meta-analyses with respective confidence intervals (95%CIs) were conducted where applicable. A total of 363 records were screened, a final number of 24 articles were eligible for qualitative synthesis, while 8 of those contributed to meta-analyses. There was evidence that pulpal blood flow (PBF) decreased after 3 weeks of tooth movement compared to no force application (4 studies, mean difference: -1.68; 95% CI: -3.21, -0.15; p = 0.03). However, this was not the case after 6 months of treatment (p = 0.68). A rise in the activity of aspartate aminotransferase (AST) was detected after 7 days of treatment, but combining 2 studies, this was not statistically significant (p = 0.25). Other outcomes were assessed through single studies. Risk of bias was within the range of 'some concerns/moderate to high/critical overall', while certainty of evidence was low to very low according to GRADE. As a short-term effect, PBF decreased upon initiation of orthodontic force application, while enzymatic and peptide activity within the pulp was transiently affected. Further long-term evidence of improved quality and certainty is needed.