Nickel-titanium Closed-coil Springs Research Articles

Influence of ibuprofen combined with corticotomy on tooth movement and alveolar bone remodeling in rats.

To investigate the effects of corticotomy-assisted orthodontic tooth movement and administration of ibuprofen on tooth movement rate and alveolar bone response. A total of 78 adult male Wistar rats were randomly assigned to five groups: one baseline group (no treatment) and four experimental groups including orthodontic tooth movement only (OTM), orthodontic tooth movement with ibuprofen (OTMI), corticotomy-assisted orthodontic tooth movement (COTM), and corticotomy-assisted orthodontic tooth movement with ibuprofen (COTMI). Corticotomy was performed on a maxillary molar unilaterally. Nickel-titanium closed-coil springs generated a 10-gram force for maxillary first molar movement. The experimental drug groups received 15 mg/kg of ibuprofen, and the other groups received reverse osmosis water. Tooth movement and bone volume fraction were evaluated by micro-computed tomography on days 0, 7, 14, and 21. The corticotomy groups had statistically significantly higher tooth movement and lower bone volume fraction than the orthodontic groups (P < .05). The amount and rate of tooth movement were statistically significantly different between the OTM and OTMI groups, but not statistically significantly different in bone volume fraction. However, statistically significant differences were not observed in any measurements between the COTM and COTMI groups. Ibuprofen during orthodontic tooth movement inhibited tooth movement and alveolar bone remodeling but had no effect on corticotomy-assisted orthodontic treatment.

Impacts of Glucose-Dependent Insulinotropic Polypeptide on Orthodontic Tooth Movement-Induced Bone Remodeling.

Glucose-dependent insulinotropic polypeptide (GIP) exerts extra-pancreatic effects via the GIP receptor (GIPR). Herein, we investigated the effects of GIP on force-induced bone remodeling by orthodontic tooth movement using a closed-coil spring in GIPR-lacking mice (GIPRKO) and wild-type mice (WT). Orthodontic tooth movements were performed by attaching a 10-gf nickel titanium closed-coil spring between the maxillary incisors and the left first molar. Two weeks after orthodontic tooth movement, the distance of tooth movement by coil load was significantly increased in GIPRKO by 2.0-fold compared with that in the WT. The alveolar bone in the inter-root septum from the root bifurcation to the apex of M1 decreased in both the GIPRKO and WT following orthodontic tooth movement, which was significantly lower in the GIPRKO than in the WT. The GIPRKO exhibited a significantly decreased number of trabeculae and increased trabecular separation by orthodontic tooth movement compared with the corresponding changes in the WT. Histological analyses revealed a decreased number of steady-state osteoblasts in the GIPRKO. The orthodontic tooth movement induced bone remodeling, which was demonstrated by an increase in osteoblasts and osteoclasts around the forced tooth in the WT. The GIPRKO exhibited no increase in the number of osteoblasts; however, the number of osteoclasts on the coil-loaded side was significantly increased in the GIPRKO compared with in the WT. In conclusion, our results demonstrate the impacts of GIP on the dynamics of bone remodeling. We revealed that GIP exhibits the formation of osteoblasts and the suppression of osteoclasts in force-induced bone remodeling.

Analysis of Therapy by Means of Gallium Aluminum Arsenide Laser During Orthodontic Tooth Movement

Indroduction: Preliminary evidence have shown that low intensity laser therapy is able to increase the rate of tooth movement. The aim of this study was to analyze the effects of gallium aluminum arsenide (GaAlAs) laser therapy in the enhancement of speed of orthodontic tooth movement (OTM) in a clinical protocol. Materials and Methods: Thirty-six upper canines were analyzed on 18 enrolled patients. On all experimental canine, an orthodontic force of 40 g/side was applied by a nickel-titanium closed coil spring. Using a split mouth randomized design, the test side was treated using a diode laser operating at a wavelength of 780 nm in continuous wave mode with flattop handpiece (20 mW output power, dose of 5 J/cm2, and exposure time of 10 seconds) (test side) at baseline and at 7, 14, and 28 days and every 14 days until the space closure. On the control side, selected teeth were only tractionated. The primary outcome was the overall time needed to complete leveling and closing space, measured on study cast. The secondary outcome was the evaluation of pain levels related to tooth traction, evaluated using a visual analogue scale (VAS). Results: The test side showed a significant reduced overall time needed for tooth space closure (at 7 and 14 days) and less VAS score (P < 0.001) compared to control side. Conclusion: This study shows that the use of low-level laser therapy by means of GaAlAs laser was effective for accelerating tooth movement and reducing pain levels related to OTM.

Comparing patient-centered outcomes and efficiency of space closure between nickel-titanium closed-coil springs and elastomeric power chains during orthodontic treatment.

To compare patient-reported pain, discomfort, and difficulty in maintaining proper brushing between nickel-titanium closed-coil springs (CS) and elastomeric power chains (PC) when used for space closure. The secondary aims were to compare plaque control and efficiency of space closure between these two force delivery systems. A total of 48 patients who required extractions of upper first premolars and distal movement of upper canines had the CS randomly allocated to either the right or left side. Blinding was applied at data collection and analysis. Primary outcomes were pain intensity measured on visual analog scale, pain onset and duration, discomfort, and difficulty in maintaining proper brushing from the start of canine retraction at baseline and at 6 and 12 weeks thereafter. Secondary outcomes were plaque scores and the rate of space closure. No significant differences in mean pain scores, pain onset, and duration at different time intervals between CS and PC were observed. The CS side was significantly less comfortable than the PC (P < .0001) and more difficult to keep clean (P = .008). No significant differences in plaque scores were observed between CS and PC groups at any time interval. CS produced a faster rate of space closure than did PC (P = .008). CS were less tolerated than PC by patients but produced an average of 0.5 mm more movement than did the PC during the 12-week study period.

Effect of Caffeine Injection on Orthodontic Tooth Movement in Rats: An Experimental Study on Rats.

Objectives Several studies have investigated the effects of different medications on orthodontic tooth movement (OTM). This study assessed the effect of caffeine injection on OTM in rats. Materials and Methods Thirty-five male Wistar rats were randomly divided into five groups. Their first molars and central incisors were attached with a nickel-titanium closed coil spring with 50 g load. The rats in the three experimental groups received 25, 50, and 75 mg/kg caffeine intraperitoneally for 21 days. The negative control group did not receive any injection and did not undergo orthodontic treatment. The positive control group underwent orthodontic treatment and received 0.9% NaCl (saline) injection. After 21 days, all rats were sacrificed by chloroform inhalation, and the maxilla was resected. The mean number of Howship's lacunae, blood vessels, osteoclasts, and root resorption lacunae was histologically measured. The bone volume-to-total volume ratio (BV/TV) in maxillary molars was calculated by microcomputed tomography (micro-CT) to quantify bone loss. Results The amount of OTM and the number of osteoclasts, blood vessels, and Howship's lacunae significantly increased in rats under caffeine therapy, while the number of root resorption lacunae did not increase. Lower BV/TV in the caffeine groups was in accord with the increased count of osteoclasts. Conclusion Caffeine injection can significantly increase OTM in rats.

Efficacy of pulsed electromagnetic field in reducing treatment time: A clinical investigation

The long duration of orthodontic treatment is a major concern for the patient. This study aimed to evaluate the efficacy of pulsed electromagnetic field therapy (PEMF) in accelerating the orthodontic tooth movement, thus reducing treatment duration. Nineteen patients requiring extraction of first premolars were selected for this study. The study design was randomly assigned (sealed envelope randomization) split-mouth design. The rate of individual canine retraction by a nickel-titanium closed-coil spring was done. The experimental side received a PEMF generated by a circuit powered by a watch battery. The circuit was embedded in a removable appliance. Foil was used to obstruct the control side from PEMF exposure. Patients were instructed to wear the appliance for 8-10 hours. Appliance with the device was given from the commencement of canine retraction until the canine retraction of one side was complete. Tooth movement was measured on progress models. An average increase of 31% in the rate of tooth movement was observed with the PEMF. PEMF is a good option to reduce orthodontic treatment duration.

Analysis of sliding mechanics force degradation during postextraction space closure

Introduction. Due to its simplicity, sliding mechanism is very often used in clinical practice for post-extraction space closure, however, the efficiency of this method may be reduced due to friction and changes in the properties of the materials used in this method. The most commonly used methods of sliding mechanics are nickel titanium (NiTi) closed coil spring and elastic chain. The aim of this study was to analyze force degradation in the application of nickel titanium closed coil springs and elastic chains during post-extraction space closure within treatment with fixed orthodontic appliances. Material and Methods. The total sample in this study consisted of 78 post-extraction spaces in patients who were indicated for extraction of first premolars and treatment with fixed orthodontic appliances. Nickel titanium closed coil springs and elastic chains were used to close the post-extraction spaces. Post-extraction spaces were monitored for 6 months with follow up examinations every 4 weeks. Measurements of initial force, at the beginning of mechanism activation and residual force in the observation period were performed during control examinations. Results. Results of this research showed that with both methods of sliding mechanism there was a significant decrease in the observation period. When using NiTi closed coil springs, the value of average initial force at control examination was between 189.00-210.25 g, while residual was in the range of 117.56-133.50 g that NiTi closed coil springs kept an average 61.57% of initial force. The average initial force on the control examinations for elastic chains was between 184.5-205.38 g, while residual force was in range of 100.39-113.00 g, that elastic chains retained an average 53.41% of initial force. Conclusion. There was a significant force degradation between inspections, when sliding mechanics were applied. The loss of force between activation phases of NiTi closed coil springs was smaller compared to the forces produced by elastic chains.

Space Closure Rate in Mandibular Canine Retraction by Ni-Ti Closed Coil Spring: A Clinical Trial

Introduction: In Majority of patients seeking orthodontic treatment, teeth must be extracted in order to obtain proper esthetics, occlusion, and stability as well as extraction of teeth is often a need to close residual space, after the initial decrowding and aligning. Pre adjusted fixed orthodontic appliances commonly utilize sliding mechanics for space closure with different types of force delivery systems. A variety of materials have been used as force delivery systems to close spaces between teeth as in the case of canine retraction after the extraction of premolars. Among all sliding or frictionless methods of canine retraction, super-elastic nickel titanium coil spring has a particular property in producing light continuous force at a long range of action, compared with previously available materials. Nickel-titanium closed coil spring, with a continuous action, might have some advantages in fixed appliance space closure mechanics. Materials and Methods: Over the period of one year from May 2015 to April 2016, this clinical trial was carried out and A total number of 20 patients (40 quadrants), who required canine retraction into first premolar extraction sites as part of their orthodontic treatment in the Department of Orthodontics of BSMMU selected as study population. The quadrants were affixed by nickel titanium closed coil springs (medium force, Ni-Ti extension spring, Ormco) with 200gm force measured by Correx Tension Gauge. Space closure was measured by means of direct measurement from the mesial surface of mesial wing of the 2nd premolar bracket and the distal surface of distal wing of the canine bracket with digital Vernier Calipers. Results: Mean space closer rate in mandibular canine retraction was 1.07 ± 0.12 mm/month by nickel-titanium (Ni-Ti) closed coil spring method with p value&lt;0.001. Conclusion: This study revealed that space closer rate in mandibular canine retraction by nickel-titanium (Ni-Ti) closed coil spring is 1.07 ± 0.12 mm/month. Medicine Today 2021 Vol.33(2): 90-93

Expression of circulating cell-free nucleic acids around miniscrew implant during orthodontic tooth movement\u2014a prospective study

ObjectivesLiterature shows that the expression of various biomarkers in peri-miniscrew crevicular fluid (PMICF) is related to the stability of miniscrew implants (MSIs). The present study investigated the role and alterations in levels of circulating cell-free nucleic acids (cfNAs) in PMICF before and after orthodontic loading.Material and methodsThis prospective study consisted of forty-six MSIs placed between the second premolar and first molar in the maxillary and mandibular arches. Direct loading was done after 3 weeks of MSI insertion with nickel-titanium closed coil spring exerting a force of 200 g. The PMICF sample was collected at various time intervals, and the level of cfNA was determined. Clinical parameters, including implant mobility and gingival health, were also assessed. Pre-loading and post-loading parameters were assessed using Wilcoxon’s rank-sum test.ResultsAmong 46 MSIs, 36 were stable during the study and 10 MSIs showed peri-implant inflammation and increased mobility. There was a significant rise in the cfNA concentration 24 h after implant insertion (0.4 ± 0.86 ng/μl). The level of cfNAs significantly decreased over 3 weeks and reached the baseline level (0.2 ± 0.31 ng/μl). There was also a significant rise in the levels of cfNA (0.8 ± 0.70 ng/μl) at 24 h after loading MSIs, which gradually decreased to 0.2 ± 0.24 ng/μl after 63 days. The expression of cfNAs was on the average 0.32 units more in the cases with failed implants (P = 0.05).ConclusionscfNA levels in PMICF showed an upward trend 24 h after MSI insertion and 24 h after orthodontic loading. The expression of cfNA was more in cases with failed MSIs. Hence, the cfNAs can be considered as a prognostic biomarker of MSI stability.

Tumor necrosis factor-α enhances the expression of vascular endothelial growth factor in a mouse orthodontic tooth movement model

Background/purposeTooth movement that is achieved using orthodontic mechanical principles relies on bone resorption which takes place on the compression side via osteoclasts. Tumor necrosis factor-α (TNF-α) has been known to affect osteoclast formation in orthodontic tooth movement (OTM). Vascular endothelial growth factor (VEGF), which is one of the mediators of angiogenesis, also plays an important role in OTM by inducing vascular permeability and chemotaxis of osteoclast precursors. Therefore, the purpose of this research was to evaluate the effect of TNF-α on VEGF expression during OTM. Materials and methodsIn order to demonstrate the effect of TNF-α on VEGF expression during OTM, a nickel titanium closed coil spring was fixed to the upper left first molar and the alveolar bone beneath the upper incisors of both wild type (WT) and TNF receptors (TNFRs) deficient mice resulting in a mesial movement of the molar for 12 days. The maxilla was removed for histological analysis and real-time RCR analysis of VEGF expression. ResultsImmunohistochemical analysis revealed that there were fewer VEGF-positive cells in the periodontal membrane on the mesial side of the distobuccal root in TNFRs-deficient mice than that in WT mice during the OTM for 12 days. Furthermore, expression of VEGF mRNA is lower level in TNFRs-deficient mice than that in WT mice. ConclusionOur results indicate that TNF-α plays an important role in VEGF expression during tooth movement.

Effect of nicotine on orthodontic tooth movement and bone remodeling in rats.

ObjectiveTo quantitatively analyze the effect of nicotine on orthodontic tooth movement (OTM) and bone remodeling in rats using micro-computed tomography and tartrate-resistant acid phosphatase immunostaining.MethodsThirty-nine adult male Sprague–Dawley rats were randomized into three groups group A, 0.5 mL normal saline (n = 9, 3 per 3, 7, and 14 days); group B, 0.83 mg/kg nicotine (n = 15, 5 per 3, 7, and 14 days); and group C, 1.67 mg/kg nicotine (n = 15, 5 per 3, 7, and 14 days). Each animal received daily intraperitoneal injections of nicotine/saline from the day of insertion of identical 30-g orthodontic force delivery systems. A 5-mm nickel-titanium closed-coil spring was applied between the left maxillary first molar (M1) and the two splinted incisors. The rate of OTM and volumetric bone changes were measured using micro-computed tomography. Osteoclasts were counted on the mesial alveolar bone surface of the distobuccal root of M1. Six dependent outcome variables, including the intermolar distance, bone volume fraction, bone mineral density, trabecular thickness, trabecular volume, and osteoclast number, were summarized using simple descriptive statistics. Nonparametric Kruskal–Wallis tests were used to evaluate differences among groups at 3, 7, and 14 days of OTM.ResultsAll six dependent outcome variables showed no statistically significant among group-differences at 3, 7, and 14 days.ConclusionsThe findings of this study suggest that nicotine does not affect OTM and bone remodeling, although fluctuations during the different stages of OTM in the nicotine groups should be elucidated in further prospective studies.

Three-dimensional imaging and molecular analysis of the effects of photobiomodulation and mechanical vibration on orthodontic retention treatment in rats : Effects of photobiomodulation and mechanical vibration on orthodontic retention treatment.

We aimed to evaluate and compare effects of photobiomodulation (PBM) and low-magnitude high-frequency mechanical vibration (HFMV) on orthodontic retention. Sixty-four female Wistar albino rats were divided into 9groups (2negative and positive controls each, 3PBM and 2HFMV groups) and studied for 25days. In the experimental groups, closed nickel-titanium closed coil springs with a50 cN force were placed for 10days between the maxillary incisor and molar. PBM and HFMV were applied daily over long- (15days) and short-term (7days) retention periods. The PBM groups received PBM with asingle wavelength (650 nm) or higher wavelengths (532, 650, 940 nm) for 9 min per day. HFMV groups received HFMV of 10, 20, and 30 Hz for 10 min per day. Right and left maxilla were assessed using micro-computed tomography imaging and real-time polymerase chain reaction. The amount of tooth movement during the retention period, expression levels of cyclooxygenase‑2 (COX-2), osteoprotegerin (OPG), and receptor activator of nuclear factor-kappaB ligand (RANKL) mRNA gene expression levels, OPG/RANKL ratios, alveolar bone trabecular thickness (Tb.Th), trabecular number (Tb.N), and structure model index were analyzed. Kruskal-Wallis and Mann-WhitneyU tests were used for multiple comparisons of the nonparametric distributed data and binary comparisons, respectively. When using the long-term retention protocol, PBM and HFMV treatment increased Tb.N (p < 0.05) and decreased COX‑2 mRNA gene expression levels (p < 0.05) and Tb.Th (p < 0.05) compared to controls. For short-term retention, PBM and HFMV decreased the amount of relapse tooth movement compared to controls. In addition, Tb.Th (p < 0.05) and the mRNA gene expression levels of COX‑2 and RANKL (p < 0.05) were decreased. PBM and HFMV might be able to support retention after orthodontic tooth movement by reducing bone resorption and increasing bone quality.

Effect of TNF-α on osteocyte RANKL expression during orthodontic tooth movement

Background/purposeOrthodontic tooth movement (OTM) is facilitated by two events; bone resorption on the compression side and bone formation on the tension side simultaneously termed bone remodeling. Osteocytes play a critical role in bone remodeling during OTM, as they have been described as the critical source of nuclear factor-κB ligand (RANKL) necessary for bone remodeling during OTM. Tumor necrosis factor (TNF)-α is a cytokine that acts by amplifying RANKL expression in osteocytes. In this study, we evaluated the effects of TNF-α on RANKL expression in osteocyte during OTM. Materials and methodsWe assessed whether TNF-α influenced RANKL expression in osteocyte during orthodontic tooth movement by using wild-type (WT) and TNF receptor I and II deficient (TNFRsKO) mice. A Nickel-titanium closed coil spring was attached to the maxillary alveolar bone near the incisors and the upper left first molar, and the first molars were moved mesially in WT and TNFRsKO mice. After OTM, the number of RANKL-positive osteocytes in the alveolar bone was evaluated by immunohistochemistry. ResultsThe number of RANKL-positive osteocyte in the alveolar bone significantly increased in WT mice than in TNFRsKO mice after OTM. ConclusionThe results indicate that TNF-α induces the expression of RANKL in osteocyte during OTM.

Changes in alveolar bone morphology after traction of buccally vs palatally unilateral maxillary impacted canines: A cone-beam computed tomography study

The objective of this study was to evaluate the 3-dimensional changes in alveolar bone morphology after traction of buccally vs palatally unilateral maxillary impacted canines (MIC). Following a split-mouth model, 27 cone-beam computed tomography images of unilaterally MIC (14 palatally and 13 buccally) and 27 contralateral unimpacted controls were obtained before and after traction using nickel-titanium closed-coil springs and a rigid anchorage appliance. Alveolar bone height and width were measured in the axial, coronal, and sagittal slides by 3 calibrated orthodontists, taking into account the impaction characteristics. A t test was used to compare the 2 groups, and a paired t test was applied for intragroup comparisons (both sides). A multiple linear regression model was used to evaluate the influence of the predictor variables on alveolar bone dimensional changes. The alveolar height showed a significantly greater decrease in palatally MIC (2.09 to 2.79mm) than buccally MIC (0.28 to 0.57mm)(P<0.05) for all surfaces. However, the alveolar width increased similarly in both groups up to 1.36mm. In general, the affected side had a more significant height loss and greater increases in alveolar width than the nonaffected side. Regression analysis indicated that buccally MIC and age decreased alveolar changes, whereas female sex increased alveolar changes (P<0.05). MIC traction with nickel-titanium closed-coil springs and heavy anchorage induces significant 3-dimensional changes in alveolar bone characterized by alveolar bone height decreases and cervical alveolar bone width increases. The height decrease is greater in palatally than in buccally MIC.

Chemokine C-C motif ligand 8 in periodontal ligament during orthodontic tooth movement

ObjectivesTo investigate the roles of chemokine (C-C motif) ligand 8 (CCL8) in periodontal ligament during orthodontic tooth movement (OTM). MethodsBioinformatics analyzed 100 genes in human periodontal ligament cells that were most upregulated after 48 hours of mechanical stress, and these genes were classified through GO and KEGG databases. Nickel-titanium closed-coil springs were placed between right first molar and incisors to produce 20 cN of orthodontic force in eight-week-old male SD rats for 1 and 2 days, followed by immunohistochemical staining of CCL8. Human periodontal ligament fibroblasts (hPDLFs) were stimulated by 14% cyclic tension force (Flexcell FX-5000 T Tension System) or hypoxia conditions to mimic OTM for 1 and 2 days, then the resulting CCL8 were examined through ELISA. Scratching assay was performed by treating hPDLFs with different concentrations of CCL8 (1 ng/ml, 10 ng/ml, 100 ng/ml). The migration, proliferation, and adhesion abilities of 100 ng/ml CCL8-treated hPDLFs were also examined. qRT-PCR and western blot detected matrix metalloproteinase 3, periostin, and osteoprotegrin expressions of hPDLFs under 100 ng/ml CCL8. ResultsBioinformatic analysis demonstrated that CCL8 was upregulated after applying mechanical stress for 48 hours. CCL8 secretion showed upregulation after 24 hours of OTM applicationsin vivo and in vitro. CCL8-treated hPDLFs showed significant positive effects on cell proliferation and matrix metalloproteinase 3. It also inhibited periostin and osteoprotegrin expressions. ConclusionsCCL8 was upregulated in periodontal ligament during initial stage of OTM. Although CCL8 in human periodontal ligaments showed no significant effects on cell migration ability, it did enhance cell proliferation and osteoclastogenesis.

Analytical methodology to measure periodontal bone morphometry following orthodontic tooth movement in mice.

Basic research in orthodontics is commonly conducted in rodents. However, experimental studies on orthodontic tooth movement (OTM) lack a standard method to examine OTM and periodontal changes. This study describes a unifying protocol for the analysis of OTM and associated bone microarchitectural changes in mice using microcomputed tomography (µCT). Mice (10 animals/group) were divided into control and OTM groups. OTM was generated by anchoring a nickel-titanium closed-coil spring to the upper incisors to pull the upper left first molar. A third group of TNFα -/- mice was added since these are known to have slower OTM. Using µCT, we implemented and tested a number of methods to measure OTM distance and examine 3D bone morphometric parameters associated with OTM in mice. In total, we tested five methods to measure the OTM distance in mice. The results indicated that measuring the intermolar diastema, and assessing tooth movement relative to the anterior root of the zygomatic arch, displayed the lowest standard deviation and enabled optimal detection of intergroup differences. We also developed two protocols for µCT analysis of the periradicular bone that yielded no false-positive results. Our results revealed that including the width of the periodontal ligament rather than excluding it from the region of interest in mice detected more statistically significant differences in the morphometric parameters between the OTM and control sides and between WT and TNFα -/- mice despite more subtle differences. We, therefore, propose new guidelines for a standardized μCT-based method to analyse OTM and the extent of the periradicular bone structural changes in mice.

PERUBAHAN FORCE NIKEL TITANIUM CLOSED COIL SPRING DAN ELASTIC CHAIN TERHADAP PERUBAHAN TEMPERATUR

Introduction: Fixed orthodontic appliances which made of nickel titanium closed coil spring dan elastic chain is the most commonly used in dentistry. There are various factors that able to change the force of orthodontic appliances such as temperature, pH, and time. The purpose of this research is to find out the influence of temperature toward the force changes in nickel titanium closed coil spring and elastic chain. Method: The method that used in this study was an experimental research with 36 research samples. The samples were attached on an acrylic board and soaked with different temperatures. The force was measured with force gauge NK-500 and noted within 0 hour, 24 hours, 72 hours, 168 hours and 240 hours. Result: The result of this research was statistically done by using Kruskal Wallis (α= 0,05). The temperature changes in each treatment that set based on different length of time showed that there was a reduction of force both in elastic chain and nickel titanium closed coil spring. In line with the research result, the reduction force in nickel titanium closed coil spring was higher than in elastic chain. Conclusion: Temperature changes can alter the force in nickel titanium closed coil spring and elastic chain.

Analysis of stress distribution in lingual orthodontics system for effective en-masse retraction using various combinations of lever arm and mini-implants: A finite element method study

The aims and objectives of this study were to evaluate the von Mises stress and principal stress distribution and displacement of anterior teeth in a lingual orthodontics system along the periodontal ligament and alveolar bone by various combinations of mini-implants and lever arm during en-masse retraction. Four 3-dimensional finite element (FE) models of the bilateral maxillary first premolar extraction cases were constructed. Lingual brackets were (0.018-in slots) positioned over the center of the clinical crown. In all 4 models, 150g of retraction force was applied with the help of a nickel-titanium closed coil spring with different combinations of mini-implants and lever arm on each side. FE analysis was then performed to evaluate stress distribution, principal stress, von Mises stress, and displacement of the anterior teeth using ANSYS software (version 12.1; Ansys, Canonsburg, Pa). The FE study was enough to validate the analysis results obtained by software tools with FE simulation instead of experimental readings. Thus, statistical analysis was not required. In this study, maximum tensile stresses were observed in the periodontal ligament at the mesial cervical region of the canine with values of 1.84MPa, 2.02MPa, 1.88MPa, and 2.08MPa for models 1-4, respectively. Maximum von Mises stress in alveolar bone was 8.05MPa, 8.23MPa, 8.19MPa, and 8.37MPa for models 1-4, respectively, which was within the optimum limit (135MPa). Variable amounts of displacements like lingual crown tipping, lingual root tipping, and extrusion were observed in all the models. The 15-mm long lever arm models (models 2 and 4) showed a more controlled crown (0.015mm) and root movement (0.004mm) compared with 12-mm long lever arm models (models 1 and 3). In lingual orthodontics, controlled root movement increased as we increased the length of the lever arm. It was also concluded that the amount of increased controlled tipping found with the placement of the mini-implant was toward the palatal slope.

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.

Assessment of Root Changes and Bone Density Accompanying Different Methods of Accelerated Orthodontic Tooth Movement

Purpose: This study was carried out to evaluate root surface changes and bone density accompanying two different methods of accelerated orthodontic tooth movement by Cone beam computed tomography (CBCT). Patients and methods: The present study was applied to twenty patients. With bimaxillary dento-alveolar protrusion or Angle Class II Division 1 malocclusion. The line of treatment was the extraction of the upper first bicuspids and then cuspid distalization. The patient’s sample was divided into two equal groups. In the group I, one side of the maxillary arch was chosen for treatment with peizocision, and in the group II, injectable platelet-rich fibrin (i-PRF) injection was used. The opposite sides in two groups acted as controls. Canine distalization was performed in both sides by 150 gm. of force applied from nickel titanium closed coil spring. The following parameters were measured from cone-beam tomography: volumetric root length and bone density.Besides this, the canine retraction rate was measured from casts Results: The canine retraction rates were greater in experiential sides than in the control sides in the two groups. Decrease volumetric root length and bone density were recorded in both groups after canine retraction Conclusions: Piezocision technique and i-PRF injection are efficient procedures that reduce the time needed for canine distalization. No significant differences regarding volumetric root resorption were observed in both groups between the experiential side and the control one after canine retraction.