A clinical investigation of force delivery systems for orthodontic space closure

Frictionless Mechanics for Correction of Bimaxillary Protrusion: A Case Report

The condition of bimaxillary protrusion is commonly seen by orthodontic practitioners in the course of our daily clinical work. It is characterized by both jaws being forwardly placed and increased prominence of the teeth along with lips. When there is a severe bimaxillary protrusion, it can be challenging to correct it effectively with maximum anchorage. In patients with protrusions or crowding, extraction therapy is often necessary. There are two ways to retract anteriors during extraction space closure: friction or frictionless. The present case report explains the frictionless mechanic protocol for the correction of bimaxillary protrusion using a reverse closing loop.

Implant-supported canine retraction using different reactivation intervals of elastomeric chains: A CBCT-based split-mouth randomized controlled trial

INTRODUCTION

Orthodontists attempt to maximize treatment efficiency regarding time, tooth position and adverse effects. A new approach, not yet explored, is the activation frequency.

OBJECTIVE

The aim of this split-mouth randomized controlled trial was to evaluate the effect of reactivation intervals on the efficiency of tooth movement.

METHODS

Thirty eight patients having a Class I malocclusion with bimaxillary dentoalveolar protrusion or severe crowding, Class II with mandibular deficiency or Class III, requiring first premolar extraction and canine retraction were recruited. Elastomeric chains producing 150g were replaced every two, four, six or eight weeks. There were 36, 37, 36, and 36 quadrants randomly allocated to these groups, respectively. The canine retraction rate was the primary outcome. Canine tipping, rotation, and root resorption and pain were the secondary outcomes. Only the outcome assessors were blinded to group assignment.

RESULTS

The average total movement for the 6 months was 5.14, 5.31, 2.79 and 3.85 mm for the two-week, four-week, six-week and eight-week reactivation intervals, respectively. Root resorption was significantly higher in the two-week and four-week groups. No adverse events were observed.

CONCLUSION

The canine retraction rate, tipping, rotation and pain were similar in 2, 4, 6 and 8-week activation intervals groups. Longer reactivation intervals show less root resorption. The trial protocol was not pre-registered. The study was self-funded.

Evaluation of maxillary canine and molar movement during the first phase of extraction space closure: a multilevel analysis

OBJECTIVE

This study was designed to analyze and compare the cusp and apex movements of the maxillary canines and first molars during canine retraction in the first step of extraction space closure, and to evaluate if these teeth follow a curvilinear (acceleration and/or deceleration) movement rate.

MATERIAL AND METHODS

Twenty-five patients (23.3 ± 5.1 years of age) were enrolled. The retraction of the maxillary canines was accomplished using nickel-titanium closed coil springs (100gf) on 0.020-in stainless steel archwire. Oblique cephalograms were traced and superimposed on the anatomic best fit of the maxilla (before the retraction [T0], and after one month [T1], three [T3], five [T5] and seven [T7] months). Statistics was based in a normally distributed data. Multilevel procedures were used to derive polynomials for each of the measurements. Student's t-test and one-way repeated measures ANOVA were conducted. The level of significance of 5% was adopted.

RESULTS

Canine cusps and apexes did not follow a quadratic curve regarding horizontal movement (neither accelerate nor decelerate). Canine and molar cusps showed more horizontal movement than apexes (4.80 mm vs. 2.78 mm, and 2.64 mm vs. 2.17 mm, respectively).

CONCLUSIONS

Canine did not accelerate or decelerate overtime horizontally; the cusps and apexes of the canines and molars showed more horizontal movement and larger rate at the beginning of canine retraction, followed by significantly smaller and constant movement rate after the first month.

The scientific evidence for pre-adjusted edgewise attachments and mechanics

Introduction Fixed orthodontic appliance systems continue to evolve with a wealth of evidence emerging to underpin these refinements.Aims To present the evidence from comparative prospective research informing the selection of fixed appliance design and mechanics.Design Detailed literature review.Materials and methods An electronic search to identify randomised controlled trials and clinical controlled trials was undertaken using pre-defined search terms.Results Based on high-level evidence, no one bracket system has been proven superior in terms of efficiency or outcome. Similarly, a clear advantage associated with one wire type or dimension has not been shown. The effect of lacebacks in terms of anchorage management appears to be limited, while elastomeric chain and nickel titanium closing coils are associated with similar rates of space closure.Discussion A wealth of high-quality recent evidence to support the selection of fixed appliance attachments, archwires and auxiliaries, including lacebacks and space closing mechanics, was identified.Conclusions There has been a considerable increase in the amount of high-quality evidence informing the choice of pre-adjusted edgewise mechanics in recent years. This information can be used to make evidence-based decisions in the selection and manipulation of fixed appliances during daily practice.

Methods of measuring distal canine movement and rotation- A review

This article provides an overview of the various methods for measuring distal canine movement and rotation during retraction. Various databases, including PubMed Central, Science Direct, Wiley Online Library, the Cochrane Library, Textbooks, Google Scholar, and Research Gate, and a manual search up until September 2022, were used to search for various methods of measuring distal canine movement and rotation during retraction. After excluding the duplicate articles, the papers explaining these techniques were included. Four significant techniques were identified. The digital method with 3D superimposition is the safest, most accurate, and most accessible of the methods reviewed.

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

OBJECTIVES

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Canine and molar movement, rotation and tipping by NiTi coils versus elastomeric chains in first maxillary premolar extraction orthodontic adolescents: A randomized split-mouth study

PURPOSE

The primary objective was to compare canine and molar movement between NiTi coil and elastomeric chains. The secondary objective was to compare the side effects of these techniques (rotation and tipping).

MATERIALS AND METHODS

This single-blind randomized split-mouth clinical trial was done prospectively. Healthy patients who needed extraction of the first maxillary premolars and did not require anchorage reinforcement techniques for orthodontic treatment were included. Following initial levelling and alignment a dental cast and panoramic radiographs were taken (pre-space closure documents) and canine retraction was done using elastomeric chains on one side and NiTi closed coil spring on the other side. After four months, the same documents were taken and movement (mm), as well as rotation (degree) and tipping (degree) of canines and first molars, were calculated by comparison of pre and post space closure documents by a blinded examiner. Data were analysed by independent samples t-test and Mann-Whitney U test with a significance level of 0.0125.

RESULTS

Overall 20 patients completed the study. The average canine movement was 3.88 and 5.45mm (distal movement) in elastomeric chains and NiTi coil groups, respectively (P=0.001). For molars, the movement was 1.20 and 1.15mm (mesial movement), respectively (P=0.529). The mean rotation of the canine in elastomeric chains and NiTi coil groups were 4.50° and 7.43° (mesiobuccal rotation), respectively (P=0.006). For the molars, the mean rotation was 0.23° and 1.90° (mesiolingual rotation), respectively (P=0.307). Average tipping of the canine in elastomeric chains and NiTi coil groups were 4.52° and 7.55° (distal tipping), respectively (P=0.011). For the molars, the numbers were 1.45° and 4.80° (mesial tipping), respectively (P=0.028).

CONCLUSION

Canine retraction by NiTi coil springs is faster compared to elastomeric powerchains with the cost of more canine tipping and rotation and more molar tipping. No significant difference was found in molar movement, rotation and tipping between the two techniques.

The effect of intraoral aging of the working stainless steel archwire on the rate of premolar extraction space closure: a randomized clinical trial

OBJECTIVES

The aims of this study were to investigate the effect of the working archwire intra-aging on the rate of upper first premolar space closure and to measure frictional resistance during space closure.

METHODS

A total of 28 subjects participated in this study. All patients were treated by upper first premolar extraction. Subjects were subdivided into 2 groups: non-replacement side: consisted of the right or left sides of the upper arch where space closure was done using the same 0.019 × 0.025-inch SS; replacement side: comprised the other side of the subjects where the working archwire was replaced with a new one each visit. The working archwire in the upper arch was split into 2 halves (new archwire on one side and old one on the other side); each one-half was connected to the other in the midline by a joining shim. Elastomeric chain was used to close extraction spaces. The amount of space closure (mm) was recorded each visit for 3 months.

RESULTS

In the non-replacement side, the rate of upper space closure was 0.80 mm/month coronally and 0.75 mm/month gingivally. In the replacement side, it was 0.69 mm/month coronally and 0.67 mm/month gingivally (p > 0.05). Mean frictional force for the non-replacement side was 3.58 ± 1.20 N, and it was 2.43 ± 1.21 N for the replacement side (p < 0.01).

CONCLUSIONS

Intraoral archwire aging has no effect on the rate of upper premolar space closure/month although frictional resistance of the aged archwire was higher than of the new one. Clinical relevance No need to replace 0.019 × 0.025-inch SS every visit during space closure to overcome corrosion and frictional resistance.

Orthodontic space closure in sliding mechanics: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

The aim of this systematic review was to compare the different force delivery systems for orthodontic space closure by sliding mechanics.

SEARCH METHODS

Multiple sources including Cochrane Central, Ovid Medline, Embase etc. were used to identify all relevant studies.

SELECTION CRITERIA

Randomized controlled trials (RCT) of parallel-group and split-mouth designs were included.

PARTICIPANTS

Orthodontic patients of any age treated with fixed orthodontic appliances and requiring space closure.

DATA COLLECTION AND ANALYSIS

Search result screening, data extraction and quality assessment were performed independently and in duplicate by 2 reviewers. The included studies were grouped into parallel-arm and split-mouth studies and subgroup analysis was then performed for the type of retraction subsets; en-masse and individual canine retraction. A traditional meta-analysis, and network meta-analysis (NMA) for direct and indirect comparisons for the rate of space closure were performed.

RESULTS

Thirteen studies, six parallel-arm and seven split-mouth were included. The traditional meta-analysis comparing Nickel-titanium (NiTi) closed coil springs and elastomeric power chain for the rate of tooth movement showed statistically significant difference favouring NiTi springs (MD: 0.24; 95% CI, 0.03-0.45; I2 0%, P = 0.02) and the comparison between NiTi springs and active ligatures also showed statistically significant result favouring NiTi springs (MD: 0.53; 95% CI, 0.44-0.63; I2 0%, P ˂ 0.00001) for the rate of tooth movement. NMA for the rate of space closure showed fairly confident evidence for NiTi coil springs when compared with elastomeric chain and active ligatures. The NiTi coil spring ranked best between all methods of space closure.

CONCLUSIONS

There is moderate quality evidence in favour of NiTi coil springs for the rate of space closure when compared with active ligature and low quality of evidence favouring NiTi springs when compared with elastomeric chain. The ranking from NMA showed NiTi coil springs to be the best method for space closure with 99% chance. An urgent need for standardization of study designs and the need for development of an agreed core outcome sets and core outcome instrument measurement sets is evident.

REGISTRATION

PROSPERO CRD42020157811.

Comparison of in vivo and in vitro force decay of elastomeric chains/modules: a systematic review and meta analysis

BACKGROUND

The study evaluated and compared the force decay of orthodontic elastomeric chains/modules in both in vivo and in vitro settings.

METHODS

A protocol in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was formulated and registered with the International Prospective Register of Systematic Reviews. A total of 53 articles (44 in vitro and 9 in vivo studies) found via search of the electronic databases of Cochrane and the National Library of Medicine (MEDLINE; PubMed), and manual search of the gray literature from institutional library resources, were selected. Data extraction, quality analysis, risk of bias assessment, and meta-analysis of the level of force decay of elastomeric chains/modules were conducted per standard protocol, and suitable statistical analyses were applied.

RESULTS

The mean force decay in the in vivo setting was 41.9% at 24 hours, 42.6% after 1 week, 46.8% after 2 weeks, and 55.0% after 3 weeks. Similarly, the force decay in the in vitro studies was 38.9% at 24 hours, 42.1% after 1 week, 44.6% after 2 weeks, and 51.1% after 3 weeks. However, at the 95% confidence interval, the force decay rates of in vivo and in vitro studies overlap, with a statistically insignificant difference in force decay observed in the in vivo and in vitro settings.

CONCLUSIONS

This systematic review and meta-analysis observed more force decay in the in vivo studies versus the in vitro studies (although this difference was statistically insignificant), with the maximum force decay occurring during the initial days, with a reduction to approximately 50% within 3 weeks. Hence, change of the elastomeric chains/module, at intervals of 3 weeks, is advised. (PROSPERO registration no. CRD42020209535).

Comprehensive comparison of canine retraction using NiTi closed coil springs vs elastomeric chains

OBJECTIVES

To compare canine retraction using NiTi closed coil springs vs elastomeric chains comprehensively in a split-mouth randomized controlled trial.

MATERIALS AND METHODS

The canines in 64 quadrants were randomly retracted into the first premolar extraction spaces using NiTi closed coil springs or elastomeric chains, in the maxilla and mandible. The retraction force was 150 g. Cone beam computed tomography scans and study models were obtained before the start of canine retraction and 6 months later. The rate and total amount of canine retraction, canine rotation, tipping, and root resorption were evaluated. A visual analogue scale was used to evaluate patients' pain experience.

RESULTS

The two methods were statistically similar for dental changes, rate of canine retraction, and root resorption. However, patients reported significantly more days of pain with the elastomeric chain compared to the NiTi closed coil springs.

CONCLUSIONS

Within the constraints of the current study, using either NiTi closed coil springs or elastomeric chains as force delivery systems for canine retraction results in no significant difference in the rate of canine retraction, tipping, rotation, or root resorption. Pain experience during retraction using elastomeric chains is more significant yet needs further investigation.

Effectiveness of vibrational forces on orthodontic treatment : A randomized, controlled clinical trial

AIM

AcceleDent® Aura (OrthoAccel® Technologies, Bellaire, TX, USA) is a class II medical device with U.S. Food and Drug Administration approval that uses SoftPulse Technology™ to increase the speed of tooth movement. The aim of this study was to evaluate the application of vibrational forces on the rate of canine distalization.

METHODS

A total of 20 patients (10 boys and 10 girls) who had class II division 1 malocclusion or severe crowding and indicated first premolar extractions for treatment were included in the study. The patients were divided into two groups: 8 in the control group and 12 in the study group. Three-dimensional digital models were taken just before canine distalization and after space closure using the 3Shape TRIOS® R700 (3Shape Inc., Copenhagen, Denmark) device. Linear measurements between molars and canines were evaluated. The results were assessed with SPSS 23.0 program (IBM, Armonk, NY, USA).

RESULTS

One subject was excluded from the study group due to insufficient oral hygiene and poor patient compliance. Tooth movement rates were 1.06 mm/month for mandibular and maxillary canine teeth in the control group. In the study group, tooth movement rates were 1.24 mm/month for maxillary canines and 1.09 mm/month for mandibular canines. These differences were not statistically significant (p > 0.05).

CONCLUSION

AcceleDent® Aura is an easy-to-use device; however, in our study its application did not have any positive effects on canine retraction rates.

Effects of transverse bodily movements of maxillary premolars on the surrounding hard tissue

INTRODUCTION

This experimental study was designed to (1) produce buccal translation of maxillary premolars and (2) evaluate the effects on the buccal alveolar bone.

METHODS

A randomized split-mouth study was designed based on 7 adult male beagle dogs. The experimental side received a custom cantilever appliance fabricated to produce a translatory force through the maxillary second premolar's center of resistance. The contralateral second premolar received no appliance and served as the control. The premolars underwent 6-7 weeks of buccal translation, followed by 3 weeks of fixed retention. Biweekly tooth movements were evaluated using intraoral and radiographic measurements. Pretreatment and posttreatment models were measured to assess tipping. Three-dimensional microscopic tomography was used to quantify the amount and density of buccal bone. Bone formation and turnover were assessed using fluorescent labeling, hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and bone sialoprotein immunostaining.

RESULTS

The applied force (100 g of force) translated (1.4 mm) and minimally tipped (4°) the experimental teeth. Lateral translation produced dehiscences at the mesial and distal roots, with 2.0 mm and 2.2 mm loss of vertical bone height, respectively. Bone thickness decreased significantly (P < 0.05) at the apical (∼0.4 mm), midroot (∼0.4 mm), and coronal (∼0.2 mm) levels. Fluorescent imaging, hematoxylin and eosin staining, and immunostaining for bone sialoprotein all showed new bone formation extending along the entire periosteal surface of the second premolar's buccal plate. Tartrate-resistant acid phosphatase staining demonstrated greater osteoclastic activity on the experimental than that of control sections.

CONCLUSIONS

New buccal bone forms on the periosteal surface during and after tooth translation, but the amount of bone that forms is less than the amount of bone loss, resulting in a net decrease in buccal bone thickness and a loss of crestal bone.

Effect of Low Intensity Pulsed Ultrasound (LIPUS) on Tooth Movement and Root Resorption: A Prospective Multi-Center Randomized Controlled Trial

The aim of this study was to evaluate the possible effect of low intensity pulsed ultrasound (LIPUS) on tooth movement and root resorption in orthodontic patients. Twenty-one patients were included in a split-mouth study design (group 1). Ten additional patients were included with no LIPUS device being used and this group was used as the negative control group (group 2). Group 1 patients were given LIPUS devices that were randomly assigned to right or left side on upper or lower arches. LIPUS was applied to the assigned side that was obtained by randomization, using transducers that produce ultrasound with a pulse frequency of 1.5 MHz, a pulse repetition rate of 1 kHz, and average output intensity of 30 mW/cm². Cone-beam computed tomography (CBCT) images were taken before and after treatment. The extraction space dimensions were measured every four weeks and root lengths of canines were measured before and after treatment. The data were analyzed using paired t-test. The study outcome showed that the mean rate of tooth movement in LIPUS side was 0.266 ± 0.092 mm/week and on the control side was 0.232 ± 0.085 mm/week and the difference was statistically significant. LIPUS increased the rate of tooth movement by an average of 29%. For orthodontic root resorption, the LIPUS side (0.0092 ± 0.022 mm/week) showed a statistically significant decrease as compared to control side (0.0223 ± 0.022 mm/week). The LIPUS application accelerated tooth movement and minimized orthodontically induced tooth root resorption at the same time.

Localizing the osseous boundaries of micro-osteoperforations

INTRODUCTION

The aim of this work was to determine how far the effects of micro-osteoperforations (MOPs) extend within bone by quantifying the damage caused and the short-term bony adaptations that occur in and around the injury site.

METHODS

With the use of a split-mouth design, 34 MOPs (Propel) were randomly placed in the mandibular furcal bone of 13 beagle dogs either 2 or 4 weeks before killing them. The control side received no treatment. Vickers hardness microindentation, microscopic computed tomography, and histologic analyses were performed to evaluate the bone surrounding the MOPs.

RESULTS

Microfractures produced during insertion extended ∼0.6 mm from the MOP sites. Cortical and trabecular bone were significantly less dense on the experimental than on the control side up to 4.2 mm from the edge of the MOP, but side differences were small (<5%) beyond 1.5 mm from the MOP. Experimental cortical bone was significantly softer than the control bone up to 0.8 mm from the MOP after 2 weeks of healing, and up to 0.5 mm from the MOP after 4 weeks of healing. Hematoxylin and eosin stained sections of cortical and trabecular bone showed small areas of woven bone within the MOP sites after 2 weeks, and acellular areas of bone extending ∼0.5 mm from the MOP. After 4 weeks of healing, there were greater amounts of woven bone, as well as early signs of lamellar bone, in and around the MOP sites. Markedly increased TRAP activity extending up to 2.5 mm from the MOP was evident after 2 weeks, but not after 4 weeks. Vital fluorescence staining showed diffuse bone deposition on the experimental side up to 1.5 mm from the MOP margin.

CONCLUSIONS

When MOPs are performed in beagle dogs, demineralization is transient and healing of the injured area, as well as remineralization of bone affected by MOP placement, begins during the first 2 weeks. Although the transient effects extend farther, the principal effects extend only ∼1.5 mm from the MOP site.

Effects of micro-osteoperforations on tooth movement and bone in the beagle maxilla

PURPOSE

The purpose of this study was to determine how micro-osteoperforations (MOPs) affect tooth movements, bone turnover, bone density, and bone volume.

METHODS

A split-mouth experimental design with 7 beagle dogs was used to evaluate bone surrounding maxillary second premolars that had been retracted for 7 weeks. One month after the maxillary third premolars were extracted, 8 MOPs (1.5 mm wide and 7 mm deep) were created without flaps with the use of the Propel device (6 were placed 3 mm distal to the second premolar and 2 were placed in the premolar furcation) on one randomly chosen side. The maxillary second premolars were retracted bilaterally with the use of 200 g nickel-titanium closed coil springs. Tooth movements were measured intraorally and radiographically. Microscopic computed tomography was used to evaluate the material density and volume fraction of bone distal to the premolars. Hematoxylin and eosin-stained and fluorescent sections were used to examine the bone remodeling.

RESULTS

Neither the intraoral (P = 0.866) nor radiographic (P = 0.528) measures showed statistically significant side differences in tooth movements. There also were no statistically significant differences in the density (P = 0.237) or volume fraction (P = 0.398) of bone through which the premolars were being moved. Fluorescent and histologic evaluations showed no apparent differences in osteoblasts, osteoclasts, or mineralization of bone near the teeth being moved. Bone healing was evident in and near the MOP sites, which had nearly but not completely healed after 7 weeks. Regions of acellular bone were evident extending ∼0.8 mm from the MOP sites.

CONCLUSIONS

MOPs placed 3 mm away from teeth do not increase tooth movements and have limited and transitory effect on bone.

Comparative evaluation of the maxillary canine retraction rate and anchorage loss between two types of self-ligating brackets using sliding mechanics

OBJECTIVE:

To evaluate the maxillary canine retraction rate and anchorage loss with active and passive self-ligating brackets (SLBs).

MATERIALS AND METHODS:

The study was conducted on 10 patients whose age ranged from 14–20 years. The patients had minimal to no crowding with a dental protrusion of maxillary incisor that required the extraction of maxillary first premolars and retraction of canines. The maxillary canines had to be in a good alignment and level before treatment to ensure that canine retraction had started from the same point bilaterally. A cone beam computed tomography (CBCT) had been taken for each patient's maxilla before treatment initiation and after complete canine retraction. Using nickel titanium, close-coil spring canine retraction on both sides and the rate of canine movement was measured.

RESULTS:

The patients were checked every 2 weeks to measure the retraction rate and ensure that a constant force (150 g) was being delivered to both canines. The pre- and post-canine retractions CBCT were superimposed to evaluate the pattern and rate of canine movement and anchorage loss. The result of this study showed no statistically significant difference between the two groups.

CONCLUSION:

The type of SLB, either active or passive, does not affect the rate or type of canine movement during its retraction in the orthodontic extraction cases, and the anchorage loss of the upper molars was nearly the same in both type.

The effect of orthodontic clinical use on the mechanical characteristics of nickel-titanium closed-coil springs

OBJECTIVE

To examine the effect of clinical use on both force retention and the deactivation of closed-coil nickel-titanium (NiTi) springs in a 16-week trial.

METHODS

The force-activation curves for NiTi springs were determined before and after clinical use. The rate of tooth movement and maximum force (MF), hysteresis between activation and deactivation, and mean force of the deactivation plateau (MDF) were examined and correlated as a function of 4, 8, 12 and 16 weeks of clinical use. To recover the force properties, the springs were heat treated at 100°C and the results were compared with the preceding data.

RESULTS

A total of 36 springs were analysed. The MF loss after use was 60, 74, 55, and 48 g for the 4-, 8-, 12- and 16-week springs, respectively. Heat treating had little effect on the MF. Clinical use lowered hysteresis by a mean of 180 g*mm compared with the pre-clinical use data, and heat treating increased the hysteresis by a mean of 59 g*mm above the post clinic testing data. The MDF was nominally 100 g less than the MF. Teeth moved approximately 1 mm/month, independent of the force loss.

CONCLUSIONS

The loss of MF and the lowering of the MDF was not time dependent. Heat treating can partially recover the mechanical properties of the used springs.

Effects of force magnitude on torque control in the correction of bimaxillary protrusion with mass retraction

OBJECTIVES:

This study was designed to explore whether force magnitude would influence incisor torque control and the overall outcome in patients with bimaxillary protrusion who need mass incisor retraction.

MATERIALS AND METHODS:

Forty-one female patients (aged > 15 years) with bimaxillary protrusion requiring mass incisor retraction were selected. Two sliding mechanics were utilized, with the elastic group receiving a light force of ~100 g by wearing elastics and the power chain group receiving a moderate force of ~250 g by power chain. Lateral cephalograms obtained before and after treatment were traced and measured.

RESULTS:

Patients in both groups displayed maxillary protrusion with a similar skeletal class II tendency. A longer treatment time was found in the elastic group. No difference in the distance of incisor tip movement was observed between the two groups; however, a larger inclination of upper incisors was found in the elastic group, indicating less loss of torque. In addition, larger reduction in Sella-Nasion-A and A-Nasion-B angle was observed in the elastic group, which was accompanied by a larger ratio of upper lip retraction to upper incisor retraction as well as more upper lip retraction.

CONCLUSIONS:

Sliding mechanics with elastics to generate light forces can achieve better torque control with more reduction in skeletal and soft tissue protrusion.

Evaluating the Amount of Tooth Movement and Root Resorption during Canine Retraction with Friction versus Frictionless Mechanics Using Cone Beam Computed Tomography

BACKGROUND

The current study was carried out to compare the amount of tooth movement during canine retraction comparing two different retraction mechanics; friction mechanics represented by a NiTi closed coil spring versus frictionless mechanics represented by T - loop, and their effect on root resorption using Cone Beam Computed Tomography (CBCT).

METHOD

Ten patients were selected in a split-mouth study design that had a malocclusion that necessitates the extraction of maxillary first premolars and retraction of maxillary canines. The right maxillary canines were retracted using T - loops fabricated from 0.017 X 0.025 TMA wires. The left maxillary canines received NiTi coil spring with 150 gm of retraction force. Pre retraction and post retraction Cone Beam Computed Tomography were taken to evaluate the amount of tooth movement and root resorption using three-dimensional planes.

RESULTS

T - loop side showed statistically significant higher mean anteroposterior measurement than NiTi coil spring side, indicating a lower amount of canine movement pre and post a canine retraction. Concerning the root resorption, there was no statistically significant change in the mean measurements of canine root length post retraction.

CONCLUSION

The NiTi coil spring side showed more distal movement more than the T-loop side. Both retraction mechanics with controlled retraction force, do not cause root resorption.

Effectiveness of nickel-titanium springs vs elastomeric chains in orthodontic space closure: A systematic review and meta-analysis

The aim of this study is to explore the effectiveness of nickel titanium closing springs (NiTi-CS) and elastomeric power chains (EPC) in orthodontic space closure and to assess the adverse periodontal effects, cost efficiency and patient-centred outcomes between both of these methods.

METHODS

An electronic search of online databases (Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Scopus, LILACS and Web of Science), reference lists and grey literature as well as hand search were conducted without language restriction up to November/2017. Two authors blindly and in duplicate were involved in study selection, quality assessment and the extraction of data. Only randomized clinical trials (RCTs) were included. The quality of the studies was assessed using the Cochrane Collaboration's risk of bias tool. 95% confidence intervals and mean difference for continuous data were calculated. A meta-analysis that generated a random-effect model for the comparable outcomes was conducted, and heterogeneity was measured using I² statistic.

RESULTS

Of 187 records, 4 RCTs met the criteria and were included in the quantitative synthesis featuring 290 test quadrants. Faster space closure with NiTi-CS was observed with a mean difference of (0.20 mm/month, 95% CI: 0.12 to 0.28). Loss of anchorage appears to be similar within both groups when synthesized qualitatively. With exception to anchorage loss, secondary outcomes could not be investigated in the included trials.

CONCLUSIONS

There is a moderate quality of evidence suggesting a faster orthodontic space closure with the NiTi-CS when compared to EPC. A comparable amount of anchorage loss was observed regardless of the utilized method of space closure. Further high-quality RCTs with parallel-groups, reporting on the adverse effects and patient-centred values, are recommended.

Initial forces experienced by the anterior and posterior teeth during dental-anchored or skeletal-anchored en masse retraction in vitro

OBJECTIVE

To investigate initial forces acting on teeth around the arch during en masse retraction using an in vitro Orthodontic SIMulator (OSIM).

MATERIALS AND METHODS

The OSIM was used to represent the full maxillary arch in a case wherein both first premolars had been extracted. Dental and skeletal anchorage to a posted archwire and skeletal anchorage to a 10-mm power arm were all simulated. A 0.019 × 0.025-inch stainless steel archwire was used in all cases, and 15-mm light nickel-titanium springs were activated to approximately 150 g on both sides of the arch. A sample size of n = 40 springs were tested for each of the three groups. Multivariate analysis of variance (α = 0.05) was used to determine differences between treatment groups.

RESULTS

In the anterior segment, it was found that skeletal anchorage with power arms generated the largest retraction force (P < .001). The largest vertical forces on the unit were generated using skeletal anchorage, followed by skeletal anchorage with power arms, and finally dental anchorage. Power arms were found to generate larger intrusive forces on the lateral incisors and extrusive forces on the canines than on other groups. For the posterior anchorage unit, dental anchorage generated the largest protraction and palatal forces. Negligible forces were measured for both skeletal anchorage groups. Vertical forces on the posterior unit were minimal in all cases (<0.1 N).

CONCLUSIONS

All retraction methods produced sufficient forces to retract the anterior teeth during en masse retraction. Skeletal anchorage reduced forces on the posterior teeth but introduced greater vertical forces on the anterior teeth.

Comparative evaluation of pentraxin 3 levels in GCF during canine retraction with active tieback and NiTi coil spring: An in vivo study

Objectives:

To compare the levels of pentraxin 3 (PTX-3) in gingival crevicular fluid (GCF) in patients undergoing orthodontic canine retraction with active tieback and nickel titanium (NiTi) coil spring.

Materials and Methods:

Fifteen patients of the age group 15–25 years with first premolar extraction undergoing canine retraction were selected. One month after placement of 0.019” × 0.025” stainless steel wire, canine retraction was started with active tieback (150 g force) on upper right quadrant and NiTi coil spring (150 g force) on upper left quadrant. GCF samples were collected 1 h before commencement of canine retraction and thereafter at intervals of 1 h, 1 day, 1 week, and 2 weeks after application of force. The collected GCF was eluted from the microcapillary pipette in 100 μl phosphate-buffered saline (pH 5–7.2). The samples were analyzed for PTX-3 levels by the ELISA technique.

Results:

The mean levels of PTX-3 at 1 h before canine retraction (baseline) was 1.30 ± 0.22 ng/ml and at 1 h 1.66 ± 0.33 ng/ml, 1 day 2.65 ± 0.09 ng/ml, 1 week 1.96 ± 0.15 ng/ml, and 2 weeks 1.37 ± 0.18 ng/ml in active tieback group. The mean levels of PTX-3 at 1 h before canine retraction was 1.32 ± 0.30 ng/ml, and at 1 h 1.71 ± 0.39 ng/ml, 1 day 2.78 ± 0.12 ng/ml, 1 week 2.52 ± 0.18 ng/ml, and 2 weeks 2.12 ± 0.17 ng/ml in NiTi coil spring group. A significant difference of P < 0.001 was found in PTX-3 levels in GCF during canine retraction between active tieback and NiTi coil spring at 1 day, 1 week, and 2 weeks.

Conclusion:

The results showed that PTX-3 levels increased from 1 h after application of orthodontic force and reached peak at 1 day, followed by a gradual decrease at 1 week and 2 weeks in both active tie back and NiTi coil spring groups.

Nickel titanium springs versus stainless steel springs: A randomized clinical trial of two methods of space closure

OBJECTIVE

To compare the clinical performance of nickel titanium (NiTi) versus stainless steel (SS) springs during orthodontic space closure.

DESIGN

Two-centre parallel group randomized clinical trial.

SETTING

Orthodontic Department University of Manchester Dental Hospital and Orthodontic Department Countess of Chester Hospital, United Kingdom.

SUBJECTS AND METHODS

Forty orthodontic patients requiring fixed appliance treatment were enrolled, each being randomly allocated into either NiTi (n = 19) or SS groups (n = 21). Study models were constructed at the start of the space closure phase (T0) and following the completion of space closure (T1). The rate of space closure achieved for each patient was calculated by taking an average measurement from the tip of the canine to the mesiobuccal groove on the first permanent molar of each quadrant.

RESULTS

The study was terminated early due to time constraints. Only 30 patients completed, 15 in each study group. There was no statistically significant difference between the amounts of space closed (mean difference 0.17 mm (95%CI -0.99 to 1.34; P = 0.76)). The mean rate of space closure for NiTi coil springs was 0.58 mm/4 weeks (SD 0.24) and 0.85 mm/4 weeks (SD 0.36) for the stainless steel springs. There was a statistically significant difference between the two groups (P = 0.024), in favour of the stainless steel springs, when the mean values per patient were compared.

CONCLUSIONS

Our study shows that stainless steel springs are clinically effective; these springs produce as much space closure as their more expensive rivals, the NiTi springs.

Accelerated tooth movement with piezocision and its periodontal-transversal effects in patients with Class II malocclusion

OBJECTIVE

To compare the extent of canine distalization and the transversal changes, postdistalization gingival indices, and mobility scores between patients who were undergoing orthodontic treatment involving upper premolar extraction with (experimental group) or without piezocision.

MATERIALS AND METHODS

Twenty maxillary canines of 10 patients were evaluated with split mouth design. Pre- and postdistalization dental casts were prepared and scanned with an orthodontic scanner to compare the extent of distalization and transversal changes between the two groups. The pre- and postdistalization gingival indices and mobility scores were also calculated.

RESULTS

Three-dimensional analysis of the models revealed significant differences in tooth movement (lesser anchorage loss and greater canine distalization) between the experimental and control groups. Furthermore, the distalization time was shortened in the experimental group. There were no differences in the transversal changes, pre- and postdistalization gingival indices, or mobility scores between groups.

CONCLUSION

Piezocision-assisted distalization accelerates tooth movement, decreases the anchorage loss for posterior teeth, and does not induce any maxillary transversal change. Moreover, piezocision does not have any adverse effects on periodontal health.

Can posterior teeth of patients be translated buccally, and does bone form on the buccal surface in response?

OBJECTIVE

To produce buccal translation and determine whether buccal bone forms on the cortical surfaces.

MATERIALS AND METHODS

Eleven patients requiring maxillary first premolar extractions participated in this prospective, randomized, split-mouth study. Pre- and posttreatment records included models, photographs, and small field of view CBCT images. One randomly chosen maxillary first premolar was moved buccally with 50 g of force applied approximately at the tooth's center of resistance. The other premolar served as the control. Forces were re-activated every 3 weeks for approximately 9 weeks, after which the teeth were held in place for 3 weeks. Pre- and posttreatment records were analyzed and superimposed to evaluate changes in the dental-alveolar complex.

RESULTS

There was significant (P < .05) movement of the experimental premolar with minimal buccal tipping (2.2°). Changes in maximum bone height were bimodal, with 6 patients showing 0.42 mm and 5 patients showing 8.3 mm of vertical bone loss. Buccal bone thickness 3 mm apical to the CEJ decreased 0.63 mm. Direct measurements and CBCT superimpositions showed that buccal bone over the roots grew 0.46 mm and 0.51 mm, respectively.

CONCLUSIONS

It is possible to produce buccal bodily tooth movement with only limited amounts of tipping. Such movements are capable of producing buccal bone apposition, but there are potential limitations.

The effect of different environmental factors on force degradation of three common systems of orthodontic space closure

Background:

Different environmental conditions, such as high temperature or exposure to some chemical agents, may affect the force decay of different methods of space closure during orthodontic treatment. The aim of this in vitro study was to evaluate the force decay pattern in the presence of tea as a popular drink in some parts of the world and two mouthwashes that are usually prescribed by the orthodontist once the treatment is in progress.

Materials and Methods:

Elastic chain (EC), nickel-titanium (Ni-Ti) closed coil spring and tie-back (TB) method were used as the means of space closure. The specimens were placed in five different media: Hot tea, hot water (65°), chlorhexidine mouthwash, fluoride mouthwash and the control group (water at 37°). The specimens were stretched 25 mm and the elastic force of three systems was measured at the beginning of the study, after 24 h, after 1 week and after 3 weeks. One-way ANOVA was used to compare the results between the groups and Duncan test was carried out to compare the sets of means in different groups (P ≤ 0.05).

Results:

Tea increases the force decay in the EC and TB groups. Oral mouthwashes also resulted in more rapid force decay than the control group. EC and Ni-Ti groups were not much affected in the presence of oral mouthwashes.

Conclusion:

Regarding the immersion media, TB method showed the biggest variation in different media and Ni-Ti coil spring was least affected by the type of media.

Canine retraction: A systematic review of different methods used

Canine retraction is a very important step in treatment of patients with crowding, or first premolar extraction cases. In severe crowding cases until, the canines have been distilized to relive the crowding, space to correctly align the incisors will not be available. Correct positioning of the canines after retraction is of great importance for the function, stability, and esthetics. The aim of this systematic review was to examine, in an evidence-based way, which kinds of canine retraction methods/techniques are most effective and which have the least side effects. A literature survey was performed by applying the Medline Database (Entrez PubMed) and Science Direct database covering the period from 1985 to 2014, to find out efficient ways to accomplish canine retraction. Randomized controlled trials (RCTs), prospective and retrospective controlled studies, and clinical trials were included. Two reviewers selected and extracted the data independently and assessed the quality of the retrieved studies. The search strategy resulted in 324 articles, of which 22 met the inclusion criteria. Due to the vast heterogeneity in study methods, the scientific evidence was too weak to evaluate retraction efficiency during space closure. The data so far reviewed proved that elastomeric power chains, elastic threads, magnets, NiTi coil springs, corticotomies, distraction osteogenesis, and laser therapy, all are able to provide optimum rate of tooth movements. All the methods were nearly similar to each other for retraction of canines Most of the techniques lead to anchorage loss in various amounts depending on the methods used. Most of the studies had serious problems with small sample size, confounding factors, lack of method error analysis, and no blinding in measurements. To obtain reliable scientific evidence, controlled RCT's with sufficient sample sizes are needed to determine which method/technique is the most effective in the respective retraction situation. Further studies should also consider patient acceptance and cost analysis as well as implants and minor surgeries for canine retraction.

Natural rubber latex allergy: implications for the orthodontist

Natural rubber latex (NRL) allergy can have potentially serious consequences, and reports of orthodontic patients reacting to NRL have increased significantly over recent years. It is therefore important for the orthodontist to know how to manage patients with an NRL allergy and how to deal with possible reactions to NRL. Safe and effective practice depends on recognizing patients who are at risk of NRL allergy, and an awareness of materials and equipment that contain NRL and the availability of suitable NRL-free alternatives.

Comparison of canine retraction by in vivo method using four brands of elastomeric power chain

OBJECTIVE

To investigate the amount of space closure by movement of canines into the extraction spaces using four brands of elastomeric power chains (EPCs) by intraoral application with pre-adjusted appliance for 6 weeks.

MATERIALS AND METHODS

The sample size calculation was based on the studies of Boester and Johnston and also with repeated measures analysis of variance (ANOVA) continuous data for force degradation, standard deviation of 24.9 g, and also from a pilot study, which totaled to around 17 patients with a mean age of 20 ± 2 years and receiving fixed orthodontic treatment that required retraction of canines into the premolar extraction spaces in all four dental arch quadrants. Four brands of EPCs, namely the Ormco, 3M Unitek, Rocky Mountain, and Highland, which were closed-link with five loops delivering less than or equal to 250 g were used. The rates of canine retraction were measured between the attachment points on the canine bracket hook and first molar hook using a Mitutoyo Digital Vernier Caliper at the time of first application, after 3 weeks of use, and at the end of 6 weeks of use, and were subjected to statistical calculations.

RESULTS

The distances recorded from canine retraction were similar with slight differences noticed in the four brands of EPCs. However, no statistically significant difference was observed in relation to the EPCs.

CONCLUSION

Although all brands of the EPCs produced space closure of canines, it was observed that not much of a significant difference existed among the products tested.

In-vivo force decay of nickel-titanium closed-coil springs

INTRODUCTION

Nickel-titanium closed-coil springs are purported to deliver constant forces over extended ranges of activation and working times. In-vivo studies supporting this claim are limited. The objective of this study was to evaluate changes in force-decay properties of nickel-titanium closed-coil springs after clinical use.

METHODS

Pseudoelastic force-deflection curves for 30 nickel-titanium coil springs (used intraorally) and 15 matched laboratory control springs (simulated intraoral conditions: artificial saliva, 37°C) were tested before and after retrieval via dynamic mechanical analysis and a testing machine, respectively, to evaluate the amounts of force-loss and hysteresis change after 4, 8, or 12 weeks of working time (n = 10 per group). The effects of the oral environment and clinical use on force properties were evaluated by comparing in-vivo and in-vitro data.

RESULTS

The springs studied showed a statistically significant decrease in force (approximately 12%) after 4 weeks of clinical use (P <0.01), with a further significant decrease (approximately 7%) from 4 to 8 weeks (P = 0.03), and force levels appearing to remain steady thereafter. Clinical space closure at an average rate of 0.91 mm per month was still observed despite this decrease in force. In-vivo and in-vitro force-loss data were not statistically different.

CONCLUSIONS

Nickel-titanium closed-coil springs do not deliver constant forces when used intraorally, but they still allow for space-closure rates of approximately 1 mm per month.

Does the bracket-ligature combination affect the amount of orthodontic space closure over three months? A randomized controlled trial

Objective: To investigate the effect of bracket–ligature combination on the amount of orthodontic space closure over three months.

Design: Randomized clinical trial with three parallel groups.

Setting: A hospital orthodontic department (Chesterfield Royal Hospital, UK).

Participants: Forty-five patients requiring upper first premolar extractions.

Methods: Informed consent was obtained and participants were randomly allocated into one of three groups: (1) conventional pre-adjusted edgewise brackets and elastomeric ligatures; (2) conventional pre-adjusted edgewise brackets and Super Slick® low friction elastomeric ligatures; (3) Damon 3MX® passive self-ligating brackets. Space closure was undertaken on 0·019×0·025-inch stainless steel archwires with nickel–titanium coil springs. Participants were recalled at four weekly intervals. Upper alginate impressions were taken at each visit (maximum three). The primary outcome measure was the mean amount of space closure in a 3-month period.

Results: A one-way ANOVA was undertaken [dependent variable: mean space closure (mm); independent variable: group allocation]. The amount of space closure was very similar between the three groups (1 mm per 28 days); however, there was a wide variation in the rate of space closure between individuals. The differences in the amount of space closure over three months between the three groups was very small and non-significant (P = 0·718).

Conclusion: The hypothesis that reducing friction by modifying the bracket/ligature interface increases the rate of space closure was not supported. The major determinant of orthodontic tooth movement is probably the individual patient response.

In situ evaluation of orthodontic elastomeric chains

The hypothesis tested in this study was that intraoral exposure of elastomeric chains alters their tensile strength. For such purpose, it was evaluated the in situ behavior of different elastomeric chains stretched for 3 weeks. Three kinds of elastomeric chains, Plastic chain (PC), Memory chain (MC) and Super slick chain (SSC), were randomly placed in 3 quadrants of 13 patient in a fixed distance of 16 mm and mean initial force of 180 g. Tensile testing was performed in an universal testing machine at different intervals: initial, 1 h, 24 h, 1 week, 2 weeks and 3 weeks. A two-way ANOVA test was performed to identify the influence of both material and time on the force decrease. A subsequent one-way ANOVAtest with the Tukey's post hoc test was used to identify statistically significant intragroup and intergroup remaining force (g and %) differences at 5% significance level. The effect of both the material and the time factors were significant. All groups showed significant force decrease after the 1-h period (23% for PC and 14% for MC and SSC). At the end of the 3-week period, the remaining force was 57% (96 g), 67% (129 g) and 71% (125 g) for PC, MC and SSC, respectively. In conclusion, intraoral exposure of elastomeric chains altered their tensile strength. In general, the greater force decrease occurred within the first hour. The remaining force of the enhanced chains measured at each time interval was greater than the conventional one (PC). After 3 weeks, only the enhanced chains maintained the force applied over 100 g.

A systematic review of force decay in orthodontic elastomeric power chains

INTRODUCTION

Elastomeric chains are one of several devices used to provide force for orthodontic tooth movement, but the force they exert diminishes over time and can thus be difficult to control. The objective of this investigation was to provide a systematic review of publications pertinent to force decay in orthodontic elastomeric chains.

MATERIALS AND METHODS

A systematic review was performed via electronic querying of multiple databases for the period 1970-2011. Queries were limited to a set of specific keywords in two languages (English and French). Five main reviews were consulted manually to identify relevant publications. Two investigators sorted out those studies that complied with selection criteria.

RESULTS AND DISCUSSION

A total of 53 studies were found to be relevant to force decay in elastomeric chains, including 22 on force decay over time, seven on the force consequences of pre-stretching, 12 on the impact of the environment on the force delivered, and 11 on clinical efficacy.

CONCLUSION

The force delivered by elastomeric chains decays rapidly over time, affecting their mechanical properties and clinical efficacy when studied in either human saliva or laboratory test media.

A comparison of resistance to sliding of self-ligating brackets under an increasing applied moment

OBJECTIVE

To test the null hypotheses that at clinically relevant amounts of applied moment, there are no differences in the amount of resistance to sliding (RS) between self-ligating (SL) and conventionally ligated (CL) brackets on both stainless steel (SS) and nickel-titanium (NT) archwire.

MATERIALS AND METHODS

Three different SL brackets and one CL bracket, all 0.022″ slot, were tested on a custom-built device to simulate canine retraction mechanics in the second-order dimension. The setup allowed for simultaneous and continuous measurement of RS and applied moment at the bracket-archwire interface. The brackets tested were Damon3, In-Ovation R, Smartclip, and Victory, all of which were tested with 0.019″ × 0.025″ SS and NT archwires. The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets and both archwire types. Descriptive measures, analysis of variance, and Tukey-Kramer post-test comparisons were used to calculate results.

RESULTS

All brackets displayed a greater amount of RS with NT than with SS archwires. At the higher moment levels (4000 g-mm), no significant reduction in RS was found between CL and SL brackets on both SS and NT archwires. At lower levels of applied moment (2000 g-mm), reductions in RS of 18% (42.7 g) and 18% (38.5 g) were found between the CL bracket and the best performing SL bracket on NT and SS, respectively.

CONCLUSION

At low values of applied moment, some statistical differences were found; however, in general, the differences in RS amongst the various SL and CL brackets tested may not be clinically relevant.

Open-Coil Retraction Spring

Sliding mechanic has become a popular method for space closure with developments in preadjusted edgewise appliance. Furthermore, various space closing auxiliaries have been developed and evaluated extensively for their clinical efficiency. Their effectiveness enhanced with optimum force magnitude and low-load deflection rate (LDR)/force decay. With the advent of NiTi springs in orthodontics, LDRs have been markedly reduced. For use of NiTi, clinician has to depend upon prefabricated closed coil springs. “Open Coil Retraction Spring (OCRS)” is developed utilizing NiTi open-coil spring for orthodontic space closure. This paper describes fabrication and clinical application of OCRS which have number of advantages. It sustains low LDR with optimum force magnitude. Its design is adjustable for desired length and force level. It is fail-safe for both activation and deactivation (i.e., it cannot be over activated, and decompression limit of open coil is also controlled by the operator, resp.). A possibility to offset the OCRS away from mucosa helps to reduce its soft-tissue impingement.

Self-ligating vs conventional twin brackets during en-masse space closure with sliding mechanics

INTRODUCTION

The aim of this study was to compare the rate of en-masse space closure with sliding mechanics between passive self-ligating SmartClip brackets (3M Unitek, Monrovia, Calif) and conventional twin brackets ligated with stainless steel ligatures.

METHODS

Nineteen patients including 20 arches participated in this prospective trial with 0.018-in slot brackets. All patients had first premolar extractions in at least 1 arch, with the second premolar and the first molar distal to the extraction site bonded with SmartClip brackets on 1 side and conventional twin brackets on the other. The sides were alternated with each consecutive patient. Space closure was achieved on 0.016 x 0.022-in stainless steel wires with nickel-titanium coil springs activated 6 to 9 mm. The patients were recalled every 5 weeks until 1 side had closed. The distances from the mesial aspect of the canine bracket to the distal aspect of the first molar bracket were recorded before and after space closure, and an average rate of space closure per month was calculated.

RESULTS

Thirteen patients completed the trial (14 arches); the median rates of tooth movement for the SmartClip bracket side (1.1 mm per month) and the conventional twin bracket side (1.2 mm per month) were not significantly different (P = .86).

CONCLUSIONS

There was no significant difference in the rate of en-masse space closure between passive SmartClip brackets and conventional twin brackets tied with stainless steel ligatures.

An in vitro comparison of the force decay generated by different commercially available elastomeric chains and NiTi closed coil springs

This in vitro study was designed to compare the forces generated by commercially available elastomeric chains and NiTi closed coil springs, and to determine their force decay pattern. Forty elastomeric chains and forty NiTi closed coil springs were divided into 4 groups according to the following manufacturers: (1) Morelli®, (2) Abzil®, (3) TP Orthodontics® and (4) American Orthodontics®. The specimens were extended to twice their original length and stored in artificial saliva at 37°C. Initial force was measured by means of an Instron universal testing machine and then at 1, 4, 7, 14, 21, and 28 days. The results revealed that the elastomeric chains delivered a mean initial force of 347 g for Morelli®, 351 g for American Orthodontics®, 402 g for Abzil®, and 404 g for TP Orthodontics®. The NiTi closed coil springs generated a mean initial force of 196 g for American Orthodontics®, 208 g for TP Orthodontics®, 216 g for Abzil®, and 223 g for Morelli®. The mean percentage of force decay observed after 28 days for the elastomeric chains was 37.4% for TP Orthodontics®, 48.1% for American Orthodontics®, 65.4% for Morelli®, and 71.6% for Abzil®. After 28 days, the NiTi closed coil springs presented a mean percentage of force decay of 22.6% for American Orthodontics®, 29.8% for Abzil®, 30.6% for Morelli®, and 45.8% for TP Orthodontics®. At the end of the study, significant differences were observed between the elastomeric chains and the NiTi closed coil springs. The results indicated that the studied NiTi closed coil springs are more adequate for dental movement than the elastomeric chains.