A comparison between friction and frictionless mechanics with a new typodont simulation system

Friction versus frictionless mechanics during maxillary en-masse retraction in adult patients with Class I bimaxillary dentoalveolar protrusion: a randomized clinical trial

BACKGROUND

Extraction space closure is a challenging phase during orthodontic treatment that affects not only the total treatment duration but also the whole treatment outcome.

OBJECTIVE

To compare the efficiency of friction and frictionless mechanics during en-masse retraction of maxillary anterior teeth in adult patients with bimaxillary dentoalveolar protrusion.

TRIAL DESIGN

Two-arm parallel group, single-center randomized clinical trial.

MATERIALS AND METHODS

Thirty-two adult patients with bimaxillary protrusion were recruited and randomly allocated to two different retraction mechanics. A friction group, using NiTi coil springs and a frictionless group using closing T-loops for en-masse retraction. Randomization in a 1:1 ratio was generated by Microsoft Excel. The randomization numbers were secured in opaque sealed envelopes for allocation concealment. Retraction started in all patients following first premolars extraction using miniscrews as a source of indirect anchorage. Activation was done on a monthly basis until complete retraction of anterior segment. The rate of retraction, amount of anchorage loss, the dental, and soft tissue changes were analyzed on digital models and lateral cephalograms taken before retraction and after space closure.

BLINDING

The outcome assessor was blinded through data concealment during assessment.

RESULTS

Two patients were lost to follow up, so 30 patients completed the trial. The rate of anterior segment retraction was 0.88 ± 0.66 mm/month in the frictionless group compared to 0.72 ± 0.36 mm/month in the friction group which was statistically significant. Anchorage loss of 1.18 ± 0.72 mm in the friction group compared to 1.29 ± 0.55 mm in the frictionless group with no significant difference. Comparable dental and soft tissue changes following en-masse retraction were reported in both groups, with no statistically significant difference.

HARM

one patient complained of soft tissue swelling following miniscrew insertion, but the swelling disappeared after one week of using mouth wash.

LIMITATION

The study focused only on the maxillary arch.

CONCLUSION

Both mechanics have successfully achieved the required treatment objectives in patients with bimaxillary dentoalveolar protrusion. Frictionless group showed a faster rate of retraction than the friction group, which was statistically but not clinically significant.

TRIAL REGISTRATION

Clinicaltrials.gov with the identifier NCT03261024.

Position and root resorption of the incisors following anterior segment retraction using friction versus frictionless mechanics: A randomised controlled trial

AIM

To evaluate the three-dimensional position and root resorption of incisors after anterior segment retraction (ASR) using friction versus frictionless mechanics.

PARTICIPANTS AND METHODS

Thirty female patients (13-18 years) with bimaxillary protrusion were randomly allocated into two groups. In the intervention group, ASR was undertaken using an elastomeric chain rendering 160 g/side extending between mini-screw implant and a hook crimped on 0.017 × 0.025-inch stainless-steel wire distal to the lateral incisor. In the comparison group, ASR was undertaken using closing T-loops fabricated from 0.017 × 0.025-inch titanium molybdenum alloy (TMA) wire rendering comparable retraction force. In both groups, the canine brackets were ligated after retraction to the mini-screw implants that were inserted in both the upper and lower arches bilaterally. The primary outcome was the three-dimensional changes in the position of the incisors. The secondary outcome was root resorption. These were measured from cone-beam computed tomography scans.

RESULTS

Statistically significant decreases in the upper (UI) and lower incisors (LI) crown torque were seen in both groups; however, the difference between groups was not statistically or clinically significant (UI MD -2.04°; 95% confidence interval [CI] = -8.02-3.95; LI MD -0.49°; 95% CI = -7.06-6.08). Significant tipping of upper (MD -1.17°; 95% CI = -2.06--0.27) and lower (MD -1.13°; 95% CI = -1.66--0.60) incisors was found in the friction, but not the frictionless group after retraction; however, the changes were not clinically significant. Significant lower incisor intrusion was found in both groups after retraction; however, the difference between groups was not statistically or clinically significant (MD -0.61°; 95% CI = -1.99-0.77). Statistically significant decreases in the UI and LI root length were seen in both groups. The difference between groups for UI changes was statistically significant (MD 0.54 mm; 95% CI = -0.02-1.07) but probably not clinically significant.

CONCLUSION

Considering the limitations in the current study, there was no advantage of either mechanics over the other regarding the final position of incisors. The likelihood of root resorption should be considered when frictionless mechanics are used for retraction of incisors.

REGISTRY

Clinicaltrials.gov (NCT04878939).

Rate and anchorage loss during en-masse retraction between friction and frictionless mechanics: A randomized clinical trial

OBJECTIVE

To compare rate and anchorage loss during en-masse retraction of anterior maxillary teeth between friction mechanics (FM) and frictionless mechanics (FLM).

SETTING AND SAMPLE POPULATION

Thirty-eight patients requiring en-masse retraction of protruded anterior maxillary teeth were randomly allocated into FM and FLM groups.

METHODS

En-masse retraction with sliding mechanics (FM) using an elastomeric chain was compared with continuous mushroom loop archwire mechanics (FLM). Study models and lateral cephalograms were taken before (T1) and immediately after retraction (T2). The primary outcome was the rate of en-masse retraction. Anchorage loss was the secondary outcome. Intergroup comparison was performed using an independent t test (P < .05).

RESULTS

Baseline characteristics were similar between groups. Thirty-six patients completed the trial. Two patients were lost to follow-up in the FLM group. The rate of en-masse retraction did not differ significantly (P = .625) between FM (0.7 mm/mo) and FLM (0.8 mm/mo) groups. The intragroup comparison showed significant anchorage loss in FM (2.28 mm) and FLM (1.13 mm) groups; however, the intergroup comparison showed no statistically significant difference (P = .093). Maxillary first molar showed a statistically significant change in angulation between the two mechanic groups (P < .001). Vertical movement of the maxillary incisor and first molar showed no significant difference between FM and FLM groups (P = .143, P = .546, respectively).

CONCLUSIONS

The rate of en-masse retraction and anchorage loss was comparable between the FM and FLM groups. Significant anchorage loss was seen with both mechanics. The result suggests that both the mechanic group require external reinforcement to prevent anchorage loss.

Effect of light-emitting photobiomodulation therapy on the rate of orthodontic tooth movement : A randomized controlled clinical trial

PURPOSE

The aim of this study was to evaluate the effect of light-emitting photobiomodulation therapy (LPT) on the rate of canine distalization.

METHODS

This study was performed on 60 extraction spaces formed by extraction of the upper first premolars of 30 patients (15 in the LPT group and 15 in the control group). Paul Gjessing (PG)-segmented canine retraction springs were used for canine distalization. In the LPT group, the Biolux OrthoPulse™ (Biolux Research Ltd, Vancouver, Canada) intraoral device (wavelength 850 nm LED light and an energy density of 63 mW/cm2 [±13 mW/cm2]) was used for 5 min per day over a period of 84 days. For each patient, the diagnosis was based on standard orthodontic documentation with photographs, digital model casts, and cephalometric and panoramic radiographs. The anchorage loss, canine rotations, canine inclinations, and molar inclinations were also evaluated on plaster models obtained on days 0, 21, 42, 63, and 84. The models were measured by using 3Shape OrthoAnalyzer software (3Shape, Copenhagen, Denmark). Measurements were made by a researcher and a blinded clinician. For statistical comparison, a paired-samples t‑test and one-way analysis of variance (ANOVA) were used at the p < 0.05 level.

RESULTS

The mean canine distalization rates were 1.36 mm/21 days and 1.02 mm/21 days in the LPT and control groups, respectively, and were statistically greater in the LPT group (p < 0.001). The amount of anchorage loss, canine rotations, canine inclinations and molar inclinations were not significantly different between the LPT and control groups at any of the timepoints.

CONCLUSION

LPT has the potential to accelerate orthodontic tooth movement by 33%.

Geometrical Effects of Two Different Space Closing Loops and Its Forces and Moments—A FEM Study

Objective

To evaluate the geometrical effects of double keyhole loop (DKHL) and T-loop and its forces and moments during en mass space closure using finite element method.

Materials and Methods

A 3-dimensional finite element model of maxillary arch was created and stimulated for first premolar extraction case with 0.022 slot Roth prescription bracket. DKHL and T-loop arch wire were created using 19×25 stainless steel and was opened 1 mm for activation using 2 different methods. The study was divided into 2 groups based on the loop design, method of activation, and degree of Gable bend. The stress distribution, tooth displacement, and moment-force ratio were calculated.

Result

The overall stress distribution was more or less uniform in all the groups. However, maximum von Mises stress was observed in the second premolar region for both the groups. There was greater torque and vertical control in the anterior segment and better anchorage control in posterior segment with increase in degree of Gable bend for both the loops activated using ligature tie. Moment-force ratio of 8-10 was achieved for both the loops.

Conclusion

Therefore, DKHL was as efficient as T-loop in producing the desirable biomechanical properties during en mass space closure.

WITHDRAWN: A method to isolate forces and moments applied to teeth: An in vitro experiment

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Three-dimensional assessment of two different canine retraction techniques: a randomized split-mouth clinical trial

Introduction

The aim of this split-mouth trial was to compare power-arm sliding (PAS) and direct sliding (DS) canine retraction mechanics in terms of speed, rotation, angulation, and anchorage loss.

Methods

Thirty-six class II division 1 patients (20 females, 16 males; mean age, 16.94 ± 3.23) requiring upper first premolar extraction were included in the study. Miniscrews were used as anchorage units, and a retraction force of 150 gr was applied from the power arm on one side and from the bracket on the opposite side by using elastomeric chains. Randomization was achieved by block randomization with a 1:1 allocation ratio either to the right or the left with allocations concealed in opaque, sealed envelopes. Digital models were acquired using an intraoral scanner at the beginning of the retraction (T0), the first month (T1), the second month (T2), and the third month (T3). Before the scans, the archwire was removed, and custom metal jigs were inserted into the vertical slot of the canine brackets to evaluate the canine angulation. The digital models of each patient were separately superimposed with the local best-fit algorithm, and the retraction rate, angulation, rotation, and anchorage loss were measured. The digital measurements were performed using the Geomagic Control X software.

Results

The DS technique’s total retraction rate was higher than that of the PAS technique (2.09 and 1.57, respectively, p = .002). There was, however, no significant difference between the two techniques in terms of angulation, rotation, and anchorage loss. A negative correlation was observed between the retraction rate and age, but it was not statistically significant. No significant difference was observed between the retraction rates of female and male participants in either retraction technique.

Conclusions

For both orthodontists and patients, the DS technique is simpler and more convenient; thus, it is the preferred method for canine retraction.

Trial registration

The trial was not registered.

Protocol

The protocol was not published before the trial commencement.

Comparison of inclination and vertical changes between single-wire and double-wire retraction techniques in lingual orthodontics

Objective

The Heat Induction Typodont System (HITS), used in some recent studies, has a distinct advantage over previous tooth movement simulation methods. This study aimed to compare inclination and vertical changes between the single-wire and double-wire techniques during en masse retraction with different lengths of lever arms in lingual orthodontics using an upgraded version of the HITS.

Methods

Duet lingual brackets, which have two main slots, were used in this study. Forty samples were divided into four groups according to the length of the lever arm (3-mm or 6-mm hook) and the retraction wire (single-wire or double-wire). Four millimeters of en masse retraction was performed using lingual appliances. Thereafter, 3-dimensional-scanned images of the typodont were analyzed to measure inclination and vertical changes of the anterior teeth.

Results

Incisor inclination presented more changes in the single-wire groups than in the double-wire groups. However, canine inclination did not differ between these groups. Regarding vertical changes, only the lateral incisors in the single-wire groups presented significantly larger values than did those in the double-wire groups. Combining the effect of hook lengths, among the four groups, the single-wire group with the 3-mm hook had the highest value, while the double-wire group with the 6-mm hook showed the least decrease in crown inclination and extrusion.

Conclusions

The double-wire technique with an extended lever arm provided advantages over the single-wire technique with the same lever arm length in preventing torque loss and extrusion of the anterior teeth during en masse retraction in lingual orthodontics.

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.

Effects of bracket slot size during en-masse retraction of the six maxillary anterior teeth using an induction-heating typodont simulation system

OBJECTIVE

To investigate how bracket slot size affects the direction of maxillary anterior tooth movement when en-masse retraction is performed in sliding mechanics using an induction-heating typodont simulation system.

METHODS

An induction-heating typodont simulation system was designed based on the Calorific Machine system. The typodont included metal anterior and resin posterior teeth embedded in a sticky wax arch. Three bracket slot groups (0.018, 0.020, and 0.022 inch [in]) were tested. A retraction force of 250 g was applied in the posterior-superior direction.

RESULTS

In the anteroposterior direction, the cusp tip of the canine in the 0.020-in slot group moved more distally than in the 0.018-in slot group. In the vertical direction, all six anterior teeth were intruded in the 0.018-in slot group and extruded in the 0.020- and 0.022-in slot groups. The lateral incisor was significantly extruded in the 0.020- and 0.022-in slot groups. Significant differences in the crown linguoversion were found between the 0.018- and 0.020-in slot groups and 0.018- and 0.022-in slot groups for the central incisor and between the 0.018- and 0.022-in slot groups and 0.020- and 0.022-in slot groups for the canine. In the 0.018-in slot group, all anterior teeth showed crown mesial angulation. Significant differences were found between the 0.018- and 0.022-in slot groups for the lateral incisor and between the 0.018- and 0.020-in slot groups and 0.018- and 0.022-in slot groups for the canine.

CONCLUSIONS

Use of 0.018-in slot brackets was effective for preventing extrusion and crown linguoversion of anterior teeth in sliding mechanics.

Innovative design of closing loops producing an optimal force system applicable in the 0.022-in bracket slot system

INTRODUCTION

Most closing loops designed for producing higher moment-to-force (M/F) ratios require complex wire bending and are likely to cause hygiene problems and discomfort because of their complicated configurations. We aimed to develop a simple loop design that can produce optimal force and M/F ratio.

METHODS

A loop design that can generate a high M/F ratio and the ideal force level was investigated by varying the portion and length of the cross-sectional reduction of a teardrop loop and the loop position. The forces and moments acting on closing loops were calculated using structural analysis based on the tangent stiffness method.

RESULTS

An M/F ratio of 9.3 (high enough to achieve controlled movement of the anterior teeth) and an optimal force level of approximately 250 g of force can be generated by activation of a 10-mm-high teardrop loop whose cross-section of 0.019 × 0.025 or 0.021 × 0.025 in was reduced in thickness by 50% for a distance of 3 mm from the apex, located between a quarter and a third of the interbracket distance from the canine bracket.

CONCLUSIONS

The simple loop design that we developed delivers an optimal force and an M/F ratio for the retraction of anterior teeth, and is applicable in a 0.022-in slot system.

Velocity of Canine Retraction in Angle Class I Treated with First Premolar Extraction: Effect of Facial Pattern

Recently, new methods have been applied to increase velocity of tooth movement. A standard mean of tooth movement velocity remains to be established, however. Moreover, to our knowledge, no studies have investigated the effect of factors affecting this velocity. The aim of the present study was to investigate the effect of facial pattern on the mean velocity of canine retraction in selected cases of orthodontic treatment carried out at this hospital. A total of 112 patients with Angle Class I crowding treated with extraction of the bilateral maxillary and mandibular first premolars and a conventional edgewise bracket were selected at random. The canine retraction period was defined as that between the end of leveling and the beginning of anterior retraction, and was obtained from medical records. Calipers were used to measure how far the canine cusps moved between pre- and post-surgically on superimposed cephalometric tracings. The velocity of canine retraction was significantly slower in the maxilla of male patients with a brachyofacial pattern (p<0.01). Canine retraction is the longest stage of orthodontic treatment. Here, movement was slowest in the maxilla of male patients with a brachyofacial pattern. This indicates that treatment may take longer than average in male patients with a brachyofacial pattern, and that this should be explained prior to commencing such work.

Effects of different types of tooth movement and force magnitudes on the amount of tooth movement and root resorption in rats

OBJECTIVE

To investigate differences in the amount of tooth movement and root resorption that occurred after tipping and bodily movement of the maxillary first molar in rats.

MATERIALS AND METHODS

Ten-week-old female Wistar rats were divided into two groups according to type of tooth movement and subdivided into four subgroups according to the magnitude of applied force. Nickel-titanium closed-coil springs exerting forces of 10, 25, 50, or 100 g were applied to the maxillary left first molars to induce mesial tooth movement. We designed a novel orthodontic appliance for bodily tooth movement. Tooth movement distance and root resorption were measured using microcomputed tomography and scanning electron and scanning laser microscopy.

RESULTS

The amount of tooth movement in the bodily tooth movement group was less than half that in the tipping tooth movement group. The greatest amount of tooth movement occurred in the 10-g tipping and 50-g bodily tooth movement subgroups, and the amount of tooth movement decreased with the application of an excessive magnitude of force. Conversely, root resorption increased when the heavier orthodontic force was applied in both groups. Root resorption in the tipping tooth movement group was approximately twice that in the bodily tooth movement group.

CONCLUSIONS

Root resorption in the tipping tooth movement group was more pronounced than that in the bodily tooth movement group. Although the amount of tooth movement decreased when extremely heavy forces were applied, root resorption increased in both the tipping and bodily tooth movement groups in rats.

Are there differences on tooth movement between different sectional canine retractors?

The aim of this study was to compare the effects of two retraction springs, demonstrating differences in reactivation and constancy of force, on tooth movement during canine distalization. Upper and lower canines of 16 patients (9 females, 7 males; mean age 14.6±1.7 years) with Angle Class I or II malocclusion were included in the study. Left upper and lower canines were distalized using Poul Gjessing (PG) retractors, whereas right canines of the same patients were distalized using Hybrid retractors. Angular and linear measurements were performed on lateral cephalometric radiographs and dental models taken prior to and at the end of canine distalization. Paired Samples t-test, Repeated Measures of Analysis of Variance and Greenhouse-Geisser tests were used for statistical analysis. The mean rates of canine distalization in PG retractors were 1.03 and 0.88 mm/months and 1.13 and 0.93 mm/months for Hybrid retractors for upper and lower canines, respectively. No significant differences were detected in the rate of canine distalization, sagittal and vertical movement of canines, and first molars between retractors or arches. Despite the differences in reactivation and constancy of the forces between PG and Hybrid retractors, both revealed similar canine distalization, distal tipping, rotation, and anchorage loss of molars. As a clinical point of view, Hybrid retractors could provide more benefits due to fewer activation requirements.

Displacement pattern of the maxillary arch depending on miniscrew position in sliding mechanics

INTRODUCTION

This clinical study was performed to evaluate the anteroposterior and vertical displacement patterns of the maxillary teeth in sliding mechanics depending on the position of interradicular miniscrews after the extraction of premolars.

METHODS

Thirty-six women requiring maximum incisor retraction because of bialveolar protrusion were divided into 2 groups: group A (n = 18), miniscrew between the premolar and the molar, and group B (n = 18), miniscrew between the premolars. Cephalometric measurements for skeletal and dental changes were made before and after space closure.

RESULTS

In both groups, significant incisor retraction with intrusion of the root apex was noted, with no significant change in the first molar position. Group B displayed significantly greater intrusion at both the incisal tip (1.59 ± 1.53 mm) and the root apex (2.89 ± 1.59 mm) than did group A. In spite of the mean reduction of the vertical skeletal measurements, we failed to find significant skeletal changes.

CONCLUSIONS

Miniscrews provided firm anchorage for anterior retraction. Selection of the placement site appeared to be an important determinant for the resultant displacement pattern of the incisor segment. Discriminative intrusion or retraction might be obtained via strategic miniscrew positioning.

Experimental Investigation and Neural Network Modeling for Force System of Retraction T-Spring for Orthodontic Treatment

In this work three different cross section groups of stainless steel T-Spring, for tooth retraction, have been tested; each spring is activated for 1 mm, 2 mm, and 3 mm, and the resultant force system is evaluated by using a testing apparatus. The results showed that when the cross section and activation distances are increased, the horizontal force and moment increased, while for the moment-to-force ratio, the lowest mean value was at the first activation distance of the first group, and the highest mean values were at the third activation distance of the third group. All three groups at all activation distance are insufficient to produce bodily tooth movement. T-springs of the (0.016×0.022 in.) cross section and with frequent activation provide the best in force system production. An artificial neural network model was trained for simulation of the correlation between input parameters: spring cross section and activation distance, and the outputs spring force system. The network model has prediction ability with low mean error of force prediction (5.707%), and for the moment is (4.048%), and it can successfully reflect the results that were obtained experimentally with less costs and efforts.

Biomechanics of a modified Pendulum appliance--theoretical considerations and in vitro analysis of the force systems

The aim of this study was to analyse the acting forces and moments induced by a special orthodontic appliance, the Pendulum K, for molar distalization in the transverse and sagittal planes. The purpose-designed test set-up (artificial maxilla with anchorage unit and two electrothermodynamic molars, an electronic measuring unit, a unit with force-moment sensor, an analogue/digital converter, and a data read-out unit) allowed simulation of in vivo conditions on the one hand and precise determination of the force systems on the other. The appliances investigated were three specimens of the Pendulum K. In vitro measurement of the resulting force systems revealed that the forces and moments in the transverse and sagittal planes remained almost constant over a 3 mm measuring increment when the distal screw was continuously activated (10 activations/mm). Without reactivation of the incorporated distal screw, however, a marked decline in the force systems was recorded. The Pendulum K allows translatory distalization of the upper molars and thus dental arch expansion, dispensing with the need for permanent teeth to be extracted, subject to a corresponding indication. This is achieved by continuous adjustment of an incorporated distal screw and by specific pre-activations of the Pendulum springs.

Comparison of the finite helical axis and the rectangular coordinate system in representing orthodontic tooth movement

In orthodontics, tooth movement is typically described using the rectangular coordinate system (XYZ); however, this system has several disadvantages when performing biomechanical analyses. An alternative method is the finite helical axis (FHA) system, which describes movement as a rotation about and a translation along a single axis located in space. The purpose of this study was to examine differences between the FHA and the XYZ systems in analyzing orthodontic tooth movement. Maxillary canine retraction was done using sliding mechanics or a retraction spring with midpalatal orthodontic implants used as measuring references. Tooth movement calculated with the FHA was compared with the corresponding movement in the rectangular coordinate system weekly over a 2-month interval in eight patients. The FHA showed that sliding mechanics controlled rotation of the canine better than the retraction spring (Ricketts retractor), and that the Ricketts retractor controlled tipping better. Changes in the FHA direction and position vectors with time showed that the biomechanical forces are not uniform during the treatment period. In both mechanics, the FHA provided a simple biomechanical model for canine retraction.