Premolar Extraction Space Research Articles

Analysis of the Forces and Moments in Canine Bodily Movement with Different Clear Aligners’ Extraction Space Designs

This study aimed to optimize space closure efficiency by comparing the forces and moments exerted by different designs of clear aligners (CAs) during the movement of maxillary canines into the premolar extraction space. The forces and moments were measured using a multi-axis force/moment transducer on the maxillary right canine. The CAs were fabricated from thermoformed polyethylene terephthalate glycol. The following four edentulous space designs were tested: the edentulous space was left intact (Group 1); the edentulous space was replaced with a premolar pontic (Group 2); the edentulous space was replaced with a half-sized premolar pontic (Group 3); and the edentulous space was replaced with a rectangular column beam (Group 4). The maxillary right canine was moved 0.25 mm distally. All groups experienced buccodistal and intrusive forces; compared with the other groups, Group 1 showed significantly greater intrusive and smaller distal forces, and Group 4 showed significantly greater distal forces. All groups experienced distal tilting, lingual inclination, and mesial rotational moments. These findings suggest that modifying the thickness and extent of the adjacent teeth in the edentulous area of the CA can improve local stiffness, thereby reducing the tipping of the teeth into the edentulous space. This study emphasizes the importance of the CA design in controlling forces and moments for effective orthodontic treatment.

Management of anchor loss with the use of infrazygomatic implants – A case series

The mesial tipping of the first molar marks the onset of anchorage loss, and changes in the angulation of the first molar are closely related to anchorage loss. Despite the various treatment strategy, different patients show different tendencies towards anchorage loss, which influences the treatment results and must be managed. The quest for search for an ideal intraoral anchorage device has led orthodontists to micro-implants or temporary anchorage devices (TADs), which offer to solve one of the greatest dilemmas of “anchorage control. The use of miniscrews has been increased recently due to their ease of insertion and removal, reasonable cost, biocompatibility and capability to withstand orthodontic forces The introduction of the mini screw and infrazygomatic implant has provided orthodontists with a solution to the significant challenge of "anchorage control." This case series describes the successful management of anchor loss with the infrazygomatic implant(IZC) that occurred during premolar extraction space closure in a Class I and Class II malocclusion patients with severely proclined maxillary incisors.

The effects of aligner anchorage preparation on mandibular first molars during premolar-extraction space closure with clear aligners: A finite element study

This study aimed to determine the effectiveness of different aligner anchorage preparations on mandibular first molars during premolar-extraction space closure with clear aligners and to assess the effects of different modes of Class II elastics on mandibular first molars. Finite element models were constructed on the basis of cone-beam computed tomography data from an orthodontic patient. The models comprised maxilla, mandible, maxillary and mandibular teeth without first premolars, periodontal ligaments, attachments and aligners. Tooth displacement tendencies were calculated using different aligner anchorage preparations and Class II elastics on the models from the same patient. Three group sets were designed on the basis of the positions of aligner cutouts and buttons (mesiobuccal, distobuccal and lingual). Four groups were established in each of the 3 group sets. Four groups were created: (1) no elastic traction+ no anchorage preparation, (2) anchorage preparation only, (3) elastic traction only, and (4) elastic traction+ anchorage preparation. Different aligner anchorage preparations (0°, 1°, 2°, 3°) were applied on mandibular second premolars and molars. The Class II traction force was set to 100 g. With clear aligners, mandibular first molars were subject to mesial tipping, lingual tipping and intrusion. In the condition of no elastic traction, aligner anchorage preparation resulted in distal tipping, buccal tipping, and extrusion effect on mandibular first molars. Aligner anchorage preparation was more effective in the distal and lingual cutout groups than in the mesial cutout group. In the condition of Class II elastic traction, the bodily movement of mandibular first molars was achieved with a 3° anchorage preparation for the mesial cutout group and a 1.7° anchorage preparation for distal and lingual cutout groups. Absolute maximal anchorage was achieved with a 2° anchorage preparation for distal and lingual cutout groups. Clear aligner therapy caused mesial tipping, lingual tipping and intrusion of mandibular first molars during premolar-extraction space closure. Aligner anchorage preparation effectively prevented mesial and lingual tipping of mandibular molars. Distal and lingual cutout modes were more effective than mesial cutout modes in aligner anchorage preparation. For each aligner stage (0.25 mm), 1.7° aligner anchorage preparation and Class II elastics with distal or lingual cutouts led to the bodily movement of mandibular first molars, whereas 2° anchorage preparation reached absolute maximal anchorage.

Does the floor of the maxillary sinus affect tooth movement for premolar extraction space closure?

The study investigated orthodontic tooth movement by comparing various horizontal and angular measures of the teeth having different sinus-root relationship (SRR) of patients undergoing first premolar extraction treatment protocols. This retrospective cross-sectional study included 45 Taiwanese adult patients, classified as the control group (n = 15) and the sinus group (n = 30) according to SRR. The control group had type I SRR (sinus floor above the level connecting the buccal and palatal root apices), whereas the sinus group included patients with type V SRR (the buccal and palatal root displayed apical protrusion into the sinus floor). Morphology was identified using pretreatment orthopantomograms. Lateral cephalometric measurements were conducted before treatment (T1) and at debonding (T2). Post debonding, there were no statistically significant difference in the two groups. However, the incisors in the control group became marginally more upright than those of the sinus group, and the molars demonstrated tipping movement with minimal anchorage loss in the sinus group than in the control group. The total treatment time was not significantly different between the 2 groups. The study revealed that the sinus-root relationship does not affect the orthodontic tooth movement. However, a more extensive 3-D study with larger sample size is strongly recommended before coming to any conclusion. The lining of the floor of the maxillary sinus does not affect the orthodontic tooth movement.

Stability of first and second premolars extraction space closure

Premolars are the teeth most often extracted to provide space to correct crowding, excessive dental and/or labial protrusion, and to compensate for the sagittal discrepancy. After treatment, the extraction spaces have to remain closed. Nevertheless, several studies have shown a tendency for some relapse even in patients finished with an adequate occlusion. Thus, the objective of this study was to compare the stability of extraction space closure of the first and second premolars. Dental casts of 72 patients were digitized using a 3-dimensional scanner (R700; 3Shape, Copenhagen, Denmark) and divided into 2 groups. Group 1 (29 patients; mean age, 13.79 years; 4.57 years after treatment; 116 extraction spaces) was treated with first premolar extractions, and group 2 (43 patients; mean age, 15.20 years; 3.97 years after treatment; 100 extraction spaces) was treated with second premolar extractions. Chi-square tests were used to compare the numbers of open and closed extraction spaces after treatment and at the long-term posttreatment stage. tTests were used to compare the number of spaces posttreatment and at the long-term posttreatment stages. These tests were also performed in subgroups with completely closed extraction sites posttreatment. The groups showed similar numbers of extraction sites reopening. The first and second premolar extraction space closure presents a similar tendency for reopening. Considering only the patients that showed completely closed extraction spaces in the final dental models, maxillary extraction space reopening was larger in the first premolar extraction group. First and second premolar extraction space closure present similar stability.

Orthodontic space management in first molar missing or unusual extraction patients

This article aimed to describe the various clinical considerations when opening or closing first molar spaces caused by missing or extracted first molars. Orthodontic patients sometimes need unusual first molar extraction or have some missing first molars. Orthodontic treatment can manage those spaces in one of two ways: prosthetic treatment preceded by regaining orthodontic space by uprighting the adjacent teeth or orthodontic space closure without additional prostheses. To determine whether to close or open the first molar missing or extracted spaces, various factors, including adjacent periodontal status, maxillary sinus pneumatization, gingival invagination, different malocclusions, and cephalometric variables and facial treatment objectives, should be considered. The first molar missing or unusual extraction spaces should be managed with careful consideration and proper orthodontic mechanics to maximize the benefits of treatment and minimize potential risks. The chances of extraction of problematic molar vs sound premolar and molar extraction space closure with missing spaces, rather than opening spaces, increase with the development of orthodontic mechanics. Therefore, it is essential to understand the factors that determine the prognosis.

A comparative assessment of the amount and rate of orthodontic space closure toward a healed vs recent lower premolar extraction site.

To investigate and compare the amount and rate of space closure and tooth tipping during orthodontic space closure toward a recent vs healed first premolar extraction site. The mandibular arches of 23 patients were included. Treatment plans included lower first premolar extractions. After reaching 0.019 × 0.025-inch stainless-steel archwires (SSAW), patients were subdivided into two groups (Group 1: space closure was carried out toward a healed first premolar extraction space and Group 2: space closure was carried out immediately after first premolar extraction). Elastomeric power chain from second molar to second molar was used to close lower extraction spaces. The following time points were defined: T1: just before space closure; T2-T4: 1-3 months after initial space closure. Records consisted of dental study models. The amount and rate of extraction space closure were evaluated at each time point. In Group 1 (healed socket), a total amount of 1.98 mm (coronally) and 1.75 mm (gingivally) of space closure was achieved. The rate of space closure was 0.66 mm/month coronally and 0.58 mm/month gingivally. In Group 2 (recent socket), the total amount of space closure was 3.02 mm coronally and 2.68 mm gingivally. The rate of space closure was 1.01 mm/month coronally and 0.89 mm/month gingivally. Differences between the two groups were significant (P < .01). Tipping of adjacent teeth during space closure was similar in both groups (P > .05). In the lower arch, the amount and rate of space closure toward a recent extraction site were higher than that toward a healed extraction socket with similar tipping of teeth in both groups.

Various methods of canine retraction in premolar extraction space: A case series

Following article is the review and presentation of various methodologies of canine retraction [e.g.– methods under sliding and friction less mechanics, facilitation with TADs (Temporary Anchorage Devices) and MOPs (Micro-Osteo-Perforations), and invasive procedures etc.] and comparison of these methods in terms of rate of canine retraction, and molar anchorage loss. Patient’s age ranges between 15y to 19y and only right maxillary canine was taken for comparison purpose.

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

ObjectivesThe 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.MethodsA 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.ResultsIn 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).ConclusionsIntraoral 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 relevanceNo need to replace 0.019 × 0.025-inch SS every visit during space closure to overcome corrosion and frictional resistance.

Rate of Canine Retraction and Anchorage Loss – In Smart Clip versus Conventional Brackets (An in-vivo study)

Background: To analyse the rate of maxillary canine retraction and anchorage loss in Smart Clip Self Ligating (SCSL) and Conventional (CV) brackets. Materials and Methods: Forty four subjects were selected for the study requiring sectional maxillary canine retraction in first premolar extraction space during orthodontic treatment. The self ligating bracket (Smart Clip, 3M Unitek) on maxillary canine was compared to CV bracket (APC Victory series) on the contralateral side in a random split-mouth study design. Sectional canine retraction was done with a NiTi coil spring (150 gms force, 9 mm) on 0.016 í— 0.022" slot stainless steel wire. Results: The mean rate of distal movement of maxillary canine for the conventional (CV) bracket per 28 days was 1.048 mm and 1.027 mm for smart clip self ligating bracket (SCSL). Anchorage loss in molar was 0.586 mm and 0.652 mm for CV and SCSL bracket respectively. Conclusion: The rate of canine retraction for conventional bracket was faster than self ligating bracket, but not statistically significant (p&gt;0.05). Comparatively, no major difference was found in terms of molar anchor loss between both bracket types. Therefore, this study indicates that conventional brackets are equally efficient as compared to self ligating brackets for segmental canine retraction mechanics.

Invisalign eighth-generation features for deep-bite correction and posterior arch expansion

Invisalign eighth-generation features for deep-bite correction and posterior arch expansion

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

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

Quality of finishing occlusion and long-term stability of orthodontic treatments with premolar extractions: A systematic review

Studies about orthodontic relapse have always confirmed the occurrence of some occlusal changes after orthodontic treatment. The reopening of premolar extraction spaces is one of the most frequently observed movements and would have several origins: gingival folds, root proximities, muscular imbalance... and particularly unstable end of treatment occlusion. The aim of this systematic review was to study the correlation between quality of the occlusal finishing after orthodontic treatment with premolars extraction and reopening of extraction spaces. The review was undertaken according to PRISMA recommendations from the Cochrane Handbook through an electronic consultation of the PubMed database to identify clinical trials that responded to the PICO research question. Five studies met all the inclusion criteria. Three studies used the Peer Assessment Rating (PAR) in assessing the quality of the occlusal finishing. For two of these studies, there is a correlation between poor occlusal finishing and reopening of extraction space. For the other three studies, no cause-and-effect relationship between these two factors has been proven. The divergence of the published results was explained by the fact that the stability of an orthodontic treatment depends on multiple parameters. Further controlled clinical studies should be conducted to objectively evaluate, without interfering with other parameters, the role of occlusal finishing in the long-term stability of orthodontic treatment.

Mechanical environment for lower canine T-loop retraction compared to en-masse space closure with a power-arm attached to either the canine bracket or the archwire.

To assess the mechanical environment for three fixed appliances designed to retract the lower anterior segment. A cone-beam computed tomography scan provided three-dimensional morphology to construct finite element models for three common methods of lower anterior retraction into first premolar extraction spaces: (1) canine retraction with a T-loop, (2) en-masse space closure with the power-arm on the canine bracket (PAB), and (3) power-arm directly attached to the archwire mesial to the canine (PAW). Half of the symmetric mandibular arch was modeled as a linear, isotropic composite material containing five teeth: central incisors (L1), lateral incisor (L2), canine (L3), second premolar (L4), and first molar (L5). Bonded brackets had 0.022-in slots. Archwire and power-arm components were 0.016 × 0.022 in. An initial retraction force of 125 cN was used for all three appliances. Displacements were calculated. Periodontal ligament (PDL) stresses and distributions were calculated for four invariants: maximum principal, minimum principal, von Mises, and dilatational stresses. The PDL stress distributions for the four invariants corresponded to the displacement patterns for each appliance. T-loop tipped the canine(s) and incisors distally. PAB rotated L3 distal in, intruded L2, and extruded L1. PAW distorted the archwire resulting in L3 extrusion as well as lingual tipping of L1 and L2. Maximum stress levels in the PDL were up to 5× greater for the PAW than the T-loop and PAB methods. T-loop of this type is more predictable because power-arms can have rotational and archwire distortion effects that result in undesirable paths of tooth movement.

Bimaxillary protrusion and gummy smile treated with clear aligners: Closing premolar extraction spaces with bone screw anchorage

Inadequate posterior anchorage is a serious limitation for aligner treatment involving extraction of four first premolars. Inappropriate axial inclinations may compromise intermaxillary occlusion and stability. OrthoBoneScrew® (OBS) anchorage is designed to augment the Invisalign® clear aligner G6 solution to produce more predictable outcomes as illustrated by the current case report. An 18-year-old female presented with two chief complains: (1) Protrusive, incompetent lips, and (2) excessive gingival exposure when smiling (“gummy smile”). Clinical evaluation revealed bimaxillary protrusion, hypermentalis activity, anterior crowding, and excessive anterior axial inclinations, particularly of the lower incisors (116°). The American Board of Orthodontic (ABO) discrepancy index (DI) was 21. The treatment plan was extraction of all four first premolars, and clear aligner (Invisalign®) therapy anchored with four OBSs: Infra-zygomatic crest (IZC), and between the roots of the upper central and lateral incisors (Incisal) bilaterally. Eighteen months of initial treatment with 45 aligners retracted and intruded the anterior segments in both arches by closing the extraction spaces with supplemental anchorage provided by IZC and Incisal OBSs. The final series of 20 refinement aligners achieved an excellent outcome as evidenced by an ABO cast-radiograph evaluation (CRE) score of 10, and a pink and white (P&amp;W) dental esthetic score of 3. Post-treatment analysis revealed multiple opportunities for improvement. The patient was well satisfied with the final outcome.

Velocity of orthodontic active space closure with and without photobiomodulation therapy: a single-center, cluster randomized clinical trial

The objective of this two-arm, parallel randomized clinical trial was to assess the effectiveness of low-level light therapy (photobiomodulation) using an intraoral light-emitting diode (LED) device with respect to accelerating premolar extraction space closure during en masse retraction. This trial was conducted between January 2013 and February 2014 at the European Univeristy College Department of Orthodontics. The study included 60 orthodontic patients (age range, 11.3–47.1 years; mean age, 20.4 years) with premolar extractions. Patients (n = 60) were randomized into the photobiomodulation (PBM) group (n = 30) or the control group (n = 30). Eligibility criteria included no active caries, good oral hygiene, and an extraction orthodontic treatment plan. Extraction spaces were closed using NiTi closed springs utilizing 150 g of force. Extraction spaces were measured on study models at the beginning of en masse retraction (T1) and at space closure completion (T2). All measurements were obtained by a single investigator who was blinded to the group allocation of study models. The primary outcome was the velocity of extraction space closure (mm/month) during the period of en masse retraction. Treatment allocation was implemented using randomization with 2 major blocks of 30 patients, by asking each patient to draw a sealed envelope (n = 60) indicating allocation to the PBM or control group. The allocation ratio was 1:1. The PBM group of patients (n = 30) was treated with intraoral infrared LED light therapy for 3 min per arch per day using OrthoPulse™ (Biolux Research®, Vancouver, Canada) producing a continuous 850-nm wavelength and a power density of 33 mW/cm2 per arch per day to achieve a total energy density of approximately 6 J/cm2 at the surface of the device during the en masse retraction phase; patients were required to maintain over 80% compliance with daily device use. Compliance was monitored by the device controller’s onboard computer. Sixty patients were randomized between the two groups. Fifteen patients dropped out during the study period, but were accounted for in the primary analysis as an intention to treat (ITT) analysis through multiple imputations. Mean age for the PBM and control groups were 20.7 and 22 years, respectively. Patients treated with PBM exhibited a statistically significant higher velocity of space closure by 0.22 mm/month (95% confidence interval [CI], 0.09–0.49; p < 0.01). The mean velocity of space closure in the PBM group was 1.08 mm/month (SD 0.54) compared with the control group’s 0.86 mm/month (SD 0.42). A secondary analysis was conducted on the 45 patients that reached the primary outcome and did not deviate from the study protocol (15 dropout patients removed), providing 123 extraction spaces for the analysis—23 patients from the PBM group and 22 patients from the control group. No serious harms due to treatments were encountered during the study period. The results of this study suggest that PBM therapy accelerated the rate of orthodontic space closure during en masse retraction. This trial and its protocol were not registered on a publicly accessible registry.

Assessment of stability of orthodontic mini-implants under orthodontic loading: A computed tomography study.

Miniscrews have been used in recent years for anchorage in orthodontic treatment. However, it is not clear whether the miniscrews are absolutely stationary or move when force is applied. This prospective clinical study was undertaken to evaluate the mobility of orthodontic miniscrews under orthodontic loading using computed tomography. Ten adult patients (7 females and 3 males with mean age of 19 years, 7 mm overjet) who required en masse retraction of upper and lower anterior teeth infirst premolar extraction spaces were included in this study. After initial alignment of anterior teeth, the 0.019" ×0.025" stainless steel archwire were placed in preadjusted edgewise appliance. The miniscrews (diameter - 1.3 mm, length - 7 mm) were inserted in between second premolar and thefirst molar in the maxilla (zygomatic buttress) and in mandible on the buccal side as direct anchorage. Immediately after placement of miniscrews without waiting period, NiTi coil springs (force of 150 g in the maxilla and 100 g in the mandible) were placed for the retraction. Denta Scans were taken immediately before force application (T1) and 6 months later (T2). The mean changes obtained at T1 and T2 in Denta Scans (axial plane, coronal plane, paraxial plane) were evaluated to determine any movement of different parts of miniscrews using one-way ANOVA test and Student's unpaired t-test. On average, miniscrews were extruded and tipped forward significantly, by 1 mm at the screw head in the axial plane (Group III) and 0.728 mm in the coronal plane (Group IV). Tail of miniscrews showed average tipping of 0.567 mm in the axial plane (Group I) and 0.486 mm in the paraxial plane (Group V). Least average mobility was shown by screw body of 0.349 mm in the axial plane (Group II). Clinically, no significant mobility was observed. Miniscrews are a stable anchorage for orthodontic tooth movement but do not remain absolutely stationary like an endosseous implant throughout orthodontic loading although miniscrews might move according to placement site, orthodontic loading, and inflammation of peri-implant tissue. Waiting period between miniscrews placement and orthodontic loading does not significantly affect the miniscrew mobility so immediate loading can be recommended. To prevent hitting any vital organs because of miniscrew mobility, it is recommended that they can be placed in a nontooth-bearing area that has no foramen, major nerves, or blood vessel pathway, or in a tooth-bearing area allowing a 1.5 mm safety clearance between the miniscrew and dental root.

Rapid maxillary canine retraction by dental distraction: A clinical study.

Aim:The aim of this clinical study was to perform rapid maxillary canine retraction through distraction of the periodontal ligament and investigate the rate and amount of canine retraction, amount of anchor loss, the nature of tooth movement achieved, and radiographic changes in the periodontal ligament region during and after canine distraction.Materials and Methods:This study was conducted on 10 distractions ranging in age from 14 years to 25 years who needed canine retraction and first premolar extraction in the maxillary arch. Ten canine distractions were carried out with custom-made, tooth-borne intra-oral distraction device.Results:The results indicate that the periodontal ligament can be distracted just like the mid-palatal suture in rapid palatal expansion and the maxillary canines are retracted rapidly into the first premolar extraction space at the rate of about 2.53 mm/week.Conclusion:Though this study indicates that the periodontal ligament can be distracted to elicit rapid tooth movement, the long-term effects of canine distraction are not well known and need close monitoring.

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.

Clinical efficiency of nonconventional elastomeric ligatures in the canine retraction phase of preadjusted edgewise appliance therapy: An in-vivo study

Various ligation techniques and materials have been shown to affect the frictional resistance and the rate of tooth movement with sliding mechanics for space closure. The aim of this study was to evaluate the clinical efficiency of nonconventional elastomeric ligatures and conventional elastomeric ligatures during the canine retraction phase by comparing the rates of canine retraction. The 20 patients (12 female, 8 male) in our sample had individual canine retraction (in the first premolar extraction space) in each quadrant (2 maxillary, 2 mandibular) with nonconventional elastomeric ligatures and conventional elastomeric ligatures on either side of the arch. The amount of canine retraction in each interval of 1 month was determined. The rate of canine retraction was calculated and subjected to statistical calculations. The rates of canine retraction were higher with the nonconventional elastomeric ligatures. However, no statistically significant difference was observed in relation to the maxillary arch. Clinically, in most instances, canine retraction was completed in the same interval in both groups. No significant difference in the rate of canine retraction was observed between the nonconventional elastomeric ligature and conventional elastomeric ligature groups in the maxillary arch. Clinically, the nonconventional elastomeric ligature group showed no reduction in time required for complete canine retraction in the maxillary and mandibular arches.