Evaluation of the Anchorage Loss During En-masse Retraction in Orthodontic Patients With Maxillary Protrusion Using Friction Versus Frictionless Mechanics: A Randomized Clinical Trial
Phase: NA
Conditions: Bimaxillary Protrusion
Sponsor: Future University in Egypt

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Evaluation of the Anchorage loss during En-masse  
Retraction in Orthodontic patients with Maxillary  
Protrusion Using Friction versus Frictionless  
Mechanics: A Randomized Clinical Trial 
 
 
 
Protocol submitted for the partial fulfillment of Masters’ degree in 
 Orthodontics  
Faculty of Oral and Dental Medicine, Future University in Egypt 
  
 
Submitted by 
Name: Amr Mahmoud Attia 
B.D.S. Alexandria University, 2014 
 (2019) 
 
 
 
 

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Funding: 
 no sources of funding to be declared. 
Roles and responsibilities: 
Principal investigator: 
Amr M. Attia, BDS,  will be responsible for the sample recruitment, applying      
clinical procedures of both interventions that will be carried out, follow up of           
patients, data management, results interpretation, writing the thesis and protocol  
registeration. 
Main supervisor:  
Prof. Yehya  A. Mostafa, BDS, MSc, PhD –  Chairman of the Department of          
Orthodontics and Dentofacial Orthopedics – Future University in Egypt. Helped in           
developing the idea of the research, will help in interpretation of results and drawing 
conclusions. 
Co-supervisor:  
Dr. Amr R. El-Beialy, BDS, MSc, PhD, Associate professor - Department of          
Orthodontics and Dentofacial Orthopedics – Cairo University. Helped in setting the 
study design, will help in follow up of patients, creating analysis, interpretation of 
results and drawing conclusions and help in writing thesis and supervision. 
Co-supervisor:  
Dr. Heba M. Dehis, BDS, MSc, PhD, Lecturer - Department of Orthodontics and 
Dentofacial Orthopedics – Cairo University. Will help in implementation of           
random sequence generation, allocation concealment, follow up of patients,              
interpretation of results, drawing conclusions and writing thesis & protocol             
registration. 
All authors contributed to refinement of the study protocol. 

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Committees: 
• Orthodontics and Dentofacial Orthopedics Department Council. 
• College Board Committee. 
• Ethics Committee. 
!
 

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Introduction 
Statement of the problem:  
One of the most common complaints of orthodontic patients is proclination of 
anterior teeth where there is an increase in facial convexity and as well as                     
incompetent lips. Bimaxillary dentoaleveolar protrusion and class II division I  cases 
always have this appearance. Frequently this situation requires extraction of the first 
premolars followed by fixed orthodontic appliance for space closure and retraction 
of anterior teeth. Different techniques are used including “Two-step retraction” 
where canines are retracted as a first step followed by anterior four incisors as a 
second step and “En-masse retraction” where anterior teeth are retracted as one unit. 
However, the method of “En-masse retraction” is controversial - whether to use   
frictionless or friction mechanics. 
Rationale for carrying out the trial: 
The main reasons of extraction in orthodontics is to correct severe crowding, 
achieve proper facial profile, improve lip competence and to adjust buccal                  
relationships[1-3] 
At the beginning, first premolars are extracted , initial bonding is done           
followed by leveling and alignment procedures. After this step, there are two         
general techniques to retract the six anterior teeth with less mesial drifting of the 
maxillary first permanent molar.  
The first approach is a regular procedure where the canines and incisors are 
retracted in two separate steps. Primary, the canine in the extraction quadrant is       
retracted until it comes in contact with the tooth distal to the extraction space then 
canines are anchored to the teeth distal to them where they are used as single      

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anchor units to retract the incisors. This procedure is called “Two-step retraction’’ 
technique.[4-6] 
The main advantage of this approach is that the load on the posterior teeth is 
reduced, thus minimal anchorage loss would be expected. The second step, where 
the posterior segments are anchored with the canines to retract anterior teeth         
without loosing anchorage [7].However, Closing the extraction space in two steps 
increases treatment time and also the medial displacement tendency of maxillary 
first molars is high, thus requiring further time and effort [8] 
A second technique was introduced to overcome the disadvantage of the 
“Two-step retraction” technique where the incisors and canines are retracted             
separetely. This approach is called ‘‘En-masse retraction’’. Bennett and McLaughlin 
developed the MBT system in which they used this technique [9,10].
 
“En-masse retraction” technique has become popular because of its               
simplicity, but theoretically might be expected to have more load on the posterior 
segment than the "Two-step retraction” technique. 
The use of Temporary Anchoring Devices (TADs) as anchorage is superior to 
conventional molar anchorage in maximum anchorage and hence attaining better 
treatment [11,12,13]  
Space closure is a tough process in orthodontics, as it requires a strong basis 
of biomechanics in order to close a space efficiently with minimal unwanted side 
effects. It can be done with two forms of mechanics: Friction or Frictionless            
mechanics. 
Understanding and predicting the difficulties involved in the way teeth           
respond to the forces and moments isn’t an easy challenge to many orthodontists. 
On one hand, sliding mechanics is widely used due to its simplicity, but on the other 

6 
hand it shows lack of force control due to friction between arch wire and brackets 
and lack of vertical and horizontal control over anterior teeth thus making the system 
indeterminant [14,15,16].  
Moreover, Previous studies have demonstrated that the sliding mechanics 
might lead to uncontrolled tipping or extrusion of the anterior segment[17,19]. On 
the other hand, theories have suggested that the drawbacks encountered with the 
sliding mechanics for incisors retraction can be overcome by the use of                    
well-designed loops providing a better control over the moment/ force ratio and thus 
the position of anterior teeth. However, minor errors in the loops design can result 
in major differences in tooth movement, and some patients may find the loops          
uncomfortable [17] 
Uncontrolled orthodontic tooth movement can have various adverse effects 
including root resorption as well as Anchorage loss if posterior segments aren’t      
stabilized and well-anchored [18]. Accordingly, vertical and horizontal control of 
posterior segments is considered a primary concern to all orthodontists. 
There is scarcity in literature regarding the effectiveness of friction and        
frictionless mechanics during ‘‘En-masse retraction’’technique on anchorage loss of 
posterior segment. Moreover there is deficiency in studies measuring the patient pain 
and satisfaction regarding the different techniques of retraction[20]. 
Accordingly, the aim of the  current randomized clincal trial (RCT) is to    
evaluate the effects of friction versus frictionless mechanics, implemented during        
“En-masse retraction”, on anchorage loss. Additionally, assessment of both           
techniques regarding  their rates, effects on root resorption as well as patient            
satisfaction and scoring will be done. 
 

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Review:
 
Literature
 
One of the primary concerns of individuals seeking orthodontic treatment is 
to improve their smile, facial esthetics and accordingly their social well being [21]. 
Many approaches have been applied to accomplish the treatment of those who have 
bimaxillary protrusion and class I division I cases without any adverse                     
consequences on the teeth that might happen due to the mechanics used.                   
“En-masse retraction” has been applied to acquire better control of posterior teeth 
and adjusting the position of buccal segment. Multiple studies have been conducted 
to evaluate the potency of different techniques in relation to the horizontal and       
vertical position of posterior teeth. 
The review of literature will be discussed under the following titles: 
 
 
1. Friction and frictionless Mechanics 
a. Friction Mechanics 
b. Frictionless Mechanics 
c. Friction vs. Frictionless Mechanics 
2. CBCT 
a. Reliability of CBCT compared to 2D x-ray. 
b. Accuracy of CBCT landmarks for assessment of anchorage loss 
c. Accuracy of CBCT for assessment of root resorption 
3. 3D digital model scanning and its reliability 
4. Anchorage control during “En-masse retraction” 
 
 

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1) Friction Vs Frictionless Mechanics 
a. Friction mechanics  
Moore and Waters (1993)[22] Examined analytically the force system 
bracket and wire in sliding mechanics spot the light on the reason of bracket 
binding. The results were checked on an enlarged model system, and             
reasonable agreement between theory and experiment was obtained. The       
results revealed that for a given bracket tip the restoring couple varies with 
the flexural rigidity of the wire, the bracket width, span length and the position 
of the bracket along the span. Moreover, as tipping happened intial intrusive 
force was brought then it turned out to be extrusive as retraction continues.  
 
Barlow and Kula (2008)[23] carried out systematic review to          
evaluate the power of clinical evidence concerning the effect of several factors 
on the efficiency of closing extraction spaces using sliding mechanics. Ten 
prospective clinical trials comparing rates of closure under different variables 
and only focusing on sliding mechanics were selected for reviewing. Of these 
ten trials, two compared arch wire variables, seven compared material          
variables used to apply force, and one examined bracket variables. Their final 
conclusion was that arch wire properties, type, size,  diameter, along with 
bracket design, material, and force delivery system all affected friction and 
hence tooth movement. Elastomeric chain produced similar rates of closure 
when compared with nickel-titanium springs where there was a little               
advantage of 200 g nickel-titanium springs over 150 g springs. Lastly, arch 
wire size has no effect on the rate of closure, although the larger wire sizes 
had better control on tipping. 
Almuzian et al. (2018)[24] conducted a systematic review and         
meta-analysis to  explore the effectiveness of nickel titanium closing springs 

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(Niti-CS) and elastomeric power chains (EPC) in orthodontic space closure 
and patient-centered outcomes between both of these methods. Only               
randomized clinical trials (RCTs) were included. Only 4 RCTs met the criteria 
out of 187 records and were included in the quantitative synthesis featuring 
290 test quadrants. The results showed   moderate quality evidence assuming 
that NiTi closing spring produces a faster rate of space closure than the        
elastomeric chain. Finally, the study couldn’t find any difference in terms of 
anchorage loss between NiTi closing spring and elastomeric chain. 
 
b. Frictionless mechanics 
Kuhlberg and Burstone (1997)[25] evaluated the effect of off-center      
positioning on the force system produced by segmented 0.017 x 0.025 inch 
TMA T-loops. The spring was tested in 7 positions, centered, 1, 2, and 3 mm 
toward the anterior attachment, and 1, 2, and 3 mm toward the posterior            
attachments. The horizontal force, vertical force, and alpha and beta moments 
were measured over 6 mm of spring activation. The results showed that       
centered T-loop produces equal and opposite moments with minimal vertical 
forces. Off-center positioning of a T-loop produces differential  moments 
where more posterior positioning produces an increased beta  moment and 
anterior positioning produces an increased alpha moment.  
 
Chen et al. (2000)[26] experimentally measured the load components 
produced by T-loop springs and the effects of design variations and the          
addition of gable bends with heat treatment. They used 0.016 inch × 0.022–
inch stainless steel wire, bent the T-loop springs on a template jig. The           
vertical (v) and horizontal (h) dimensions were 6 or 7 millimeters and 6, 7, or 

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8 millimeters, respectively. six spring geometries are identified, ten              
specimens of each design (60 total) were made-up. The same springs were 
also tested with 30° gable preactivation and stress-relieving heat treatment 
(GPH). They concluded that increasing  the vertical or horizontal dimension, 
the spring's load-deflection rate and its moment-to-force ratio was reduced. 
Additionally , gable preactivation bends with heat treatment was found to 
have the reverse result . 
 
Almeida et al. (2016)[27]  compared force systems that are produced 
by Ni-It T-Loop springs made with wires of different dimensions. Thirty        
T-Loop springs were divided into 3 groups according to their dimensions: 
0.016 X 0.022  and 0.017 X 0.025 and 0.018 X 0.025 inches respectively. It 
was concluded that the larger wires produced higher forces with slight             
increase on the moments. However, the moment to force ratio produced by 
the 0.016 X 0.022 wire was the highest.  
 
 
c. Friction vs. Frictionless 
Ziegler and Ingervall (1989)[28] conducted a clinical study of         
maxillary canine retraction with a retraction spring and with sliding                 
mechanics to assess the efficiency of maxillary canine retraction by means of 
sliding mechanics along an 0.018-inch labial arch and an elastic chain was 
compared with the canine retraction spring designed by Gjessing. Twenty-one 
subjects were included in the study where the upper first premolars were        
extracted. Results showed that rate of canine was increased and with minimal 
distal tipping with the spring group than with the sliding mechanics group. No 

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significant difference between canine retraction spring and sliding mechanics 
regarding canine rotation control in the retraction phase. However, the         
correction of rotation after the retraction is less time-consuming than the up-
righting of a tipped canine 
 
Dincer et al. (2000)[29] carried out a clinical study to evaluate the             
applicability and effects on the dentoalveolar structures of Poul Gjessing (PG) 
springs when used for retraction of the upper incisors, and to relate the results 
with the effect of a closed coil spring retraction system. 63 subjects with angle 
Class I or Class II were selected and divided into two groups, the PG group 
with 17 subjects and the closed coil spring group with 19 subjects. The results 
showed that three-dimensional controlled movement of the upper incisors can 
be obtained by application of the PG universal retraction spring as the active 
element of segmented arch mechanics. The amount of overbite reduction at 
completion of the incisor retraction makes the use of additional intrusive     
mechanics unnecessary  
  
 
2) CBCT  
a. Reliability of CBCT compared to 2D x-ray. 
Chung How Kau et al.(2009) [30] conducted a study to determine if             
measurements obtained from digital models from cone beam computed              
tomography (CBCT) images were comparable to the traditional method of 
digital study models by impressions. Digital models of 30 subjects were used. 
InVivoDental software was used to analyze CBCT scans taken by                     
a Galileos cone beam scanner. OrthoCAD software was used to analyze      

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impression scans of patients at different stages of  orthodontic treatment.      
Impressions were taken using alginate and were mailed to OrthoCAD for     
digital conversion. The results showed that digital models generated from 
CBCT  imaging are as accurate as OrthoCAD digital models in making linear 
measurements for overjet, overbite, and crowding measurements. Moreover 
CBCT digital models offer other information such as bone levels, root            
positions, and TMJ status. 
 
McNamara et al. (2011) [31] Carried out a study to evaluate the          
accuracy and reliability of craniometric measurements made on CBCT scans 
and lateral cephalograms using fiducial markers and dry skulls. Ten fiducial 
markers were placed on known craniometric landmarks of 25 dry skulls with 
stable occlusions. CBCT scans and conventional lateral headfilms                  
consequently were taken of each skull. They conlcluded that CBCT                
craniometric measurements computed by a dedicated “3D Cephalometric 
module” are more accurate than lateral cephalograms and can be used for     
craniofacial analysis. Moreover, lateral cephalograms have intrinsic              
limitations that result in distorted images, enlarged in some areas and reduced 
in others. 
 
 
 
b. Accuracy of CBCT landmarks for assessment of anchorage loss 
Chaudhary et al.(2014) [32] conducted a study to compare the rate of 
movement of canine using conventional method on one side and skeletal 

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anchorage ( micro implants )  on the other side of the same   patient.                    
17 subjects were included for extraction of all first premolars. Micro implants 
were placed between the roots of the second premolar and the first molars on 
right side, in both the arches. Retraction was done using sliding mechanics 
using stainless steel arch wire. They concluded that the movement is equal on 
the both sides although anchorage loss is seen on the conventional side using 
molar as an anchorage unit. The retraction was primarily achieved by tipping 
and partly by translation. Maxillary canine retraction was more on the  implant 
side (6.51 mm). However, Distal tipping was also more on the implant side 
(9.51°) 
 
c. Accuracy of CBCT for assessment of root resorption 
Dudic et al. (2009)[33] carried out a study to evaluate the                     
orthodontically induced apical root resorption using panoramic radiograph in 
one group and cone-beam computed tomography (CBCT) in the other group. 
They examined 275 teeth in 22 patients just before the end of their orthodontic 
treatment. Root Resorption was assessed as no, mild, moderate, severe and 
extreme. Additionally, apical root resorption was underestimated when the 
teeth were examined on a panoramic radiograph. Finally, they found out that 
CBCT would be a helpful added diagnostic tool, especially when the               
orthodontist decides to continue or modify treatment due to orthodontically 
induced root   resorption. 
 
Ren et al.(2013)[34] compared the accuracy of CBCT and periapical 
radiograph as diagnostic tool for spotting external apical root resorption. The 
study included 160 single rooted extracted premolars with predetermined 

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simulated root resorption. Two x-rays were taken for each tooth ,CBCT and 
periapical radiograph, and were blindly evaluated by two observers. The 
found out that for all external apical root resorption, the sensitivity and       
specificity values of CBCT (75.8% and 96.3%, respectfully) were greater than 
that of periapical radiographs (67.5% and 82.5%, respectfully). Therefore, 
CBCT was a reliable diagnostic for external root resorption, at the same time 
as periapical radiographs underestimated it. 
 
 
3) 3D digital model scanning and its reliability 
Alcan, Ceylanoğlu and Baysal (2009)[35] They conducted  an              
experimental study  to assess the  accuracy of digital models produced by the 
3Shape system and to test the dimensional stability of three different brands 
of alginates for durations of 1, 2, 3, and 4 days in a laboratory environment 
investigated. 105 impressions were taken from a master model with three    
different brands of alginates. 21 stone models were poured and 21 digital   
models were prepared while the remaining 84 impressions were poured after 
1, 2, 3, and 4 days, correspondingly. They found that Both the stone models 
and the digital models were highly correlated with the master model.             
Significant deformities in the alginate impressions were noted at different 
storage periods of 1 to 4 days. Therefore, Digital orthodontic models are as 
reliable as traditional stone models. Storing alginate impressions in sealed 
plastic bags for up to 4 days caused statistically significant deformation of 
alginate impressions, but the magnitude of deformation of alginate impression 
did not appear to be clinically relevant and had no adverse effect on digital 
modeling. 

15 
 
El-Beialy and Mostafa (2010)[36] compared the accuracy of dental 
measurements taken with calipers on 34 orthodontic plaster dental casts and 
those from computed tomography scans of the dentition with a dental        
measurement program (3DD, Biodent, Cairo, Egypt). The mesiodistal widths 
of teeth, arch widths, arch lengths, arch perimeters, and palatal depths were 
made with the calipers on a plaster cast. The patients were also scanned with 
computed tomography, and measurements were made digitally with 3DD, a 
3-dimensional-based dental measurements program. They found a strong 
agreement in most measurements between the conventional method and the 
3DD in the 3 planes of space. The mesiodistal measurements of the maxillary 
right and left second premolars, left central incisor, and right first molar, and 
the mandibular left and right central incisors, right canine, and left first         
premolar had fair agreement. Therefore, 3DD can be an alternative to            
conventional stone dental models. 
 
 
4) Anchorage control during ‘‘En-masse retraction’’ 
Hedayati and Shomali(2016)[37] conducted a study to detect the type 
of anterior segment movement during en masse retraction using different      
antero-posterior positions of the mini screw with different vertical heights of 
the anterior power arm. Micro implants were placed in two different positions, 
mesial and distal of the second premolar. Forces were applied to four different 
levels of anterior hook height: 0, 3, 6, and 9 mm.  Initial tooth movement in 
eight different conditions was examined and estimated with ANSYS software. 

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They concluded that placement of micro implants distal to second premolar 
had minimum adverse effect on anterior dentition. 
 
Reint Meursinge Reynders & Luisa Ladu(2017)[38] conducted a 
systematic review to compare the effectiveness of TADs as anchorage devices 
with conventional anchorage methods in patients whom treatment includes 
space closure of extracted maxillary first premolars with minimal loss of      
molar anchorage. Fourteen studies; seven RCTS and seven CCTs were in-
cluded. In total 303 patients received TISADs with 313 control patients. The 
results showed that TADs are superior to conventional methods of anchorage. 
The average difference of 2mm is both statistically and clinically significant. 
 
Database search: 
A search was performed on electronic databases (PubMed, Cochrane library). 

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Aim of the study 
A-PICO format: 
Population: 
Orthodontic patients requiring 1st premolars extraction followed by anterior segment 
retraction. 
Intervention: 
‘‘En-masse retraction’’ using frictionless mechanics with miniscrews used as          
anchorage. 
Comparator: 
‘‘En-masse retraction’’ using sliding mechanics (friction) with miniscrews used as 
anchorage. 
Outcome measure: 
 
Outcome Name 
Measuring Tool 
Measuring Unit 
Primary 
Outcome 
Anchorage loss 
CBCT 
- Linear measurement in mm 
Angular measurement in de-
grees 
Secondary 
Outcome 
Rate of space closure 
Digital scanned   
Dental Model 
 
 
 
- Scanned digital models in 
(mm) 
o Models taken every 
month 
o Analysed using 3 
Shape Software 
 
Pain 
Pain scoring sheets 
given to patients 
VAS scoring from 1-10 (Fig 1) 

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Root resorption 
CBCT 
Scoring system of Levander  
and Malmgren[39]     
(5 grades classification) 
 
Torque of anterior teeth 
CBCT 
Degrees 
 
Tip of anterior teeth 
CBCT 
Degrees 
 
Vertical position  
Digital scanned   
Dental Model 
 
Mm 
 
1st Permenant Molar 
rotation 
Digital scanned   
Dental Model 
 
Degrees 
 
B-Research question: 
In Orthodontic patients requiring 1st premolars extraction followed by ‘‘En-masse 
retraction’’, can frictionless mechanics offer a better control of anchorage loss com-
pared to friction mechanics? 
Objectives of the study 
Research hypothesis: 
The null hypothesis (H0) of this research is that there’s no difference between both 
frictionless and friction mechanics on anchorage loss during ‘‘En-masse retraction’’ 
following 1st premolar extraction  
Primary objective (s): 
Measuring anchorage loss during ‘‘En-masse retraction’’using frictionless versus   
friction mechanics. 

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Secondary objective: 
Evaluating the rate of ‘‘En-masse retraction’’using frictionless Versus friction         
mechanics, root resorption, pain and discomfort during retraction. In addition to this, 
changes in vertical position (extrusion/ intrusion), tip and torque of anterior teeth 
will be measured following ‘‘En-masse retraction’’ using frictionless versus          
friction mechanics.  
Study design: 
This is a randomized clinical trial with two arms parallel group, and 1:1 allocation 
ratio. 
In 
one 
group, 
frictionless 
mechanics 
will 
be 
applied 
during                     
‘‘En-masse retraction’’ while the other will receive frictional mechanics during        
retraction. The anchorage loss will then be compared between both interventions. 

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Material and Methods 
I)participants, interventions, and outcomes 
 
A] Study Setting: 
The study will be performed in the clinic of the Orthodontics and Dentofacial           
Orthopedics Department at the Faculty of Oral and Dental Medicine, Future           
University in Egypt. The recruited sample would be from the Egyptian urban and 
rural population. 
 
B] Eligibility criteria: 
" Inclusion criteria:for the participants include the following: 
 
1. Orthodontic patients (both genders) 
2. Age range (14-24) 
3. Patients 
requiring 
1st 
premolars 
extraction 
followed 
by                     
‘‘En-masse retraction’’ (Bimaxillary Protrusion or Class II division 1 
cases). 
4. Patients with fully erupted permanent teeth (not necessarily including the 
3rd molar). 
5. Cases requiring maximum anchorage during anterior segment retraction.  
6. Cases with minimal crowding (2-3) mm 
 

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" Exclusion Criteria: for the involved subjects included: 
1. Patients suffering from any systemic diseases interfering with tooth move-
ment. 
2. Patients with extracted or missing permanent teeth. (except for third        
molars). 
3. Patients with badly decayed teeth.  
4. Patients with any parafunctional habits (i.e. Bruxism, tongue thrusting, 
mouth breathing, etc.…). 
5. Patients with previous orthodontic treatment  
 
C] Interventions: 
" Medical History Questionnaire: 
For every patient, to exclude the presence of any systemic condition 
interfering with orthodontic treatment.  
 
" Clinical Examination: 
Oral structures will be examined to identify caries, fracture or     miss-
ing teeth.  Gingival tissues will be carefully examined for any             
gingivitis, periodontitis, recession, or lesions. 
 
 
 

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*American Orthodontics  
**Jeil  
" Diagnosis 
Check the potential patient to fulfill the previously mentioned               
inclusion criteria. Every participant will be asked to sign an informed 
consent about the study. Full set of records (study models, panorama 
radiograph and lateral cephalometric radiographs, photos) will be 
taken for every patient as part of the routine procedure for treatment of 
patients in the clinic of the Orthodontics and Dentofacial Orthopedics 
Department, Future University in Egypt. 
 
 
" Clinical Procedure: 
After taking pre-treatment records, every patient will receive: 
• 
Bonding of all teeth except for first premolars and banding/bonding the 
first and second molars will be done using Roth prescription brackets 
(0.022 x 0.028 slot)*. 
• 
Miniscrews will then be placed in the upper arch between the second pre-
molar and first molar**. 
• 
The patient will be referred for extraction of first premolars. 
• 
Anchorage will be secured, followed by Leveling and alignment for the 
bonded and banded teeth through following the wire sequence: 0.014 
Nitti, 0.016×0.022 Nitti and  0.017×0.025 StSt.  
 
 
 

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• 
After levelling and aligning is completed (right before retraction), the pa-
tient will be referred for the uptake of pre-intervention records:  
a- CBCT 
b- Impression and models 
c- photo (Extraoral & Intraoral) 
d- pain questionnaire 
" Acquisition of pre-intervention records: 
• 
The patient will be referred for the uptake of a CBCT, which are             
considered to be the T0 records. 
• 
Impressions will be taken before retraction (without the archwire in place) 
followed by digital scanning of produced models. 
• 
Photos (Extraoral & Intraoral) 
• 
Pain questionnaire distributed with explainatory session on it  
 
" Beginning of Retraction: 
Frictionless group:  
• 
A braided ligature wire extended between the second premolars and 
miniscrews will be used for proper indirect anchorage control. 
• 
Closing retraction T-loops will be fabricated using 0.017 x 0.025 TMA 
wire. The loop will be positioned halfway the extraction space and the 
canine. [40,41]. 
• 
A gable angle of 45˚ will be added to the posterior segment. 

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• 
Distal activation of 4 mm will be applied with cinching back the wire 
to the auxillary tube distal to first molars bilaterally. [42]     
 
 
Friction group:  
• 
Crimpable hooks added to the arch wire (0.017”x0.025” Stainless steel) 
distal to the lateral incisor passing near the center of resistance of the       
anterior segment. 
• 
A ligature wire extending between the second premolar and            
miniscrews will be used for proper anchorage control. 
• 
Retraction will start on a 0.017”x0.025” Stainless steel wire using  
elastomeric chain (force applied will be 200 g per side) [43] extending    
between the crimpable hooks and the miniscrews. 
• 
The force will be measured by a force gauge and reactivated every 4 
weeks maintaining constant force of retraction all over the retraction 
phase. 
 
" Follow up visits 
Patients will be asked to attend for follow up sessions every 4 weeks for: 
• 
Evaluation miniscrews stability. 
• 
Replacement of the power chain to maintain a force of 200 gm per side. 
• 
Reactivation of the T-loop by further distal activation and cinch back. 
• 
Impression taking to determine the anchorage loss 

25 
" Criteria for discontinuing or modifying the allocated intervention: 
In cases of prolonged swelling or pain related to the miniscrews, the patient 
will be given strict oral hygiene measures and may wait for three weeks       
before the beginning of retraction. 
In cases of loose or broken miniscrews, the screw will be removed and           
replace the miniscrew after total resolution of the inflammation. 
" Criteria for Ending the retraction: 
      a-class I canines 
      b-normal overjet 
      c- closure of extraction space 
      d- reaching good profile 
Ø Post-retraction Questionnaire: 
The patients of both groups will be asked to fill in questionnaires regarding 
their experience with their allocated technique during the whole retraction 
period from day of extraction till the end of retraction. 
Ø Retraction records 
Following ‘‘En-masse retraction’’, patients will be referred to the same        
radiology center to acquire the final cone-beam CT to assess the movement 
and inclination of anterior teeth. 
The final dental model will be used to assess the rate of retraction and molar 
anchorage loss achieved throughout the study.  
 
 

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Ø Material Used 
 
• American Orthodontics Brackets, Roth prescription, 22 slot size. 
• American Orthodontics Elastomeric power chains 
• American Orthodontics Elastomeric O-ties  
• American Orthodontics Ligature wire. 
• Miniscrew, 8 mm length × 1.6 mm diameter TAD (Jeil)  
• American Orthodontics Arch wires.  
• American Orthodontics Molar bands/tubes.  
D] Outcomes 
Primary 
outcome: 
is 
to 
monitor 
the 
anchorage 
loss 
during                          
‘‘En-masse retraction’’. All outcomes will be assessed as the difference        
between T0 at the start of retraction and T1 after complete space closure. 
 
Secondary outcomes: is to monitor the changes in the anterior teeth position 
(final anterior teeth tip, torque and vertical position), rate of space closure, 
presence of any root resorption and pain associated with the  different methods 
used for retraction.  
 
 
 
 

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E] Participant timeline:  
1. The principle investigator will screen the potential patients through careful 
clinical examination of patients at the Orthodontics and Dentofacial               
Orthopedics department, Faculty of Oral and Dental Medicine, Future       
University in Egypt.  
2. All recruited patients should fulfill the previously mentioned inclusion and 
exclusion criteria.  
3. Every participant will be asked to sign an informed consent before the           
beginning of the study.  
4. Pre-intervention records will be taken for each participant after enrollment to 
ensure proper diagnosis.  
5. The principle investigator will randomly allocate the patients to one of the 
intervention groups.  
6. Anchorage will be secured by placement of miniscrew, followed by               
extraction of the first premolar. 
7. Active intervention will begin after proper levelling and alignment of teeth 
through following the wire sequence: 0.014 NiTi, 0.016×0.022 NiTi and  
0.017×0.025 StSt. 
8. The principle investigator will take pre-retraction records for every               
participant T0.  
9. In Friction mechanics group, Power chain is used for anterior segment            
retraction while in Frictionless group, T-loop is used for retraction.  
10. Each patient will come every 4 weeks for follow up visit, for appliance          
activation and uptake of impression for interim records.  
11. After complete space closure, the principle investigator will take                  
post-retraction records for each participant T1.  

28 
12. Every patient will fill up a questionnaire regarding his experience during 
treatment.  
13. The principle investigator will continue the normal treatment and achieve      
proper finishing for every patient after the end of the study. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

29 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Screening of patients seeking     or-
thodontic treatment at the         Or-
thodontics and Dentofacial     Or-
thopedics department outpatient 
clinic 
Patient enrollment 
Pre-intervention records 
Concealed Allocation 
Miniscrew placement , extraction, 
leveling and alignment.  
Friction group 
Frictionless group 
Activation of PC and T-loop 
Acquisition of post-retraction records 
Patient questionnaire 
Data collection and management 
Recruitment 
Preparatory 
phase 
Interventions 
Follow up visits 
End of study 
Eligibility criteria and 
informed consent  
Average 9 months 
After complete retraction 
Dropouts and missed 
data recorded 
Monthly follow up visits 
for activation 
Pre-retraction record 
Missed appointment 
records 

30 
F] Sample size calculation:  
Our sample size calculation is based on a previous study comparing the effect of 
friction and frictionless mechanics29. Using PS software output, we are planning a 
study of a continuous response variable from independent Group I and Group II sub-
jects with 1 Group I(s) per Group II subject. In a previous study the response within 
each subject group was normally distributed with standard deviation 0.76. If the true 
difference in the Group II and Group I means is 1.0, we will need to study 10 Group 
II subjects and 10 Group I subjects to be able to reject the null hypothesis that the 
population means of the Group II and Group I are equal with probability (power) 
0.8. The Type I error probability associated with this test of this null hypothesis is 
0.05. Considering drop out a sample size 15 per group is appropriate. 
G] Recruitment strategy:  
The principal investigator will recruit the patients from the clinic of Orthodontics 
and Dentofacial Orthopedics department, Faculty of Oral and Dental Medicine -    
Future University in Egypt.  
Screening of patients will continue until the total number of participants for the study 
is collected.  
II) Assignment of interventions:  
A] Sequence generation:  
The supervisor of the study will apply Computer generated random numbers to     
randomly assign patients to group A (Frictionless) or B (friction) using Microsoft 
Office Excel 2007 sheet. The patient numbers will be written in the first column, and 
the supervisor will select function RAND()to generate the randomization number in 
the second column. These numbers will be sorted according to the randomization 
number so the first column numbers will be randomly distributed.  
 

31 
B] Allocation concealment mechanism:  
The supervisor of the study (Dr. Heba M. Dehis) will write the randomization      
numbers of the patients on opaque white papers folded three times to form sealed 
envelopes and store it inside a box. The codes for randomization will be securely 
held at the secretary’s office.  
 
C] Implementation:  
At the time of intervention, the main operator will send the patient to the secretary’s 
office. Then, the assigned employee will open the box and ask the patient to select 
one envelope. The main operator will assign each participant for the corresponding 
intervention either (friction or frictionless group) according to the list of codes of 
randomization.  
Assignment to either intervention will occur before levelling and alignment stage.  
 
D] Blinding:  
Blinding of the operators: Blinding will not be possible for the operators during 
the application interventions and during the follow up visits. The principal operator 
is responsible for assigning subjects to interventions according to the concealed       
allocation, appliance activation at follow up visits, dental impressions and                  
acquisition of dental casts.  
 
Blinding of the outcome assessors: It is a single blinded study, therefore, only the 
outcome assessors will be blind. The patients name will be sealed from pre and post 
radiographs and study models. Then two assessors will carry out, blindly and            
Independently, the measurements and analysis of the study. 
 
 

32 
III) Data collection, management and analysis: 
  
A] Data collection methods:  
 
Primary outcomes: 
1. Anchorage loss: will be accessed by the principal investigator via CBCT taken 
before and after the completion of retraction by identifying the landmarks,           
reference lines and planes, then will interpret the measurements in degrees and 
millimeters. 
 
Secondary outcomes: 
1. Retraction rate: to assess the antero-posterior movement of anterior teeth and first 
molars, the principle investigator will take study models for every participant 
monthly during the follow up visits. Then will digitize the models and identify the 
landmarks, reference lines and planes on the pre, interim and post-retraction digital 
dental models for measurements reading. Also, by identifying the landmarks,         
reference lines and planes using CBCT taken before and after the completion of     
retraction. 
 
2. Pain: each patient will fill a questionnaire regarding his treatment experience in a 
Visual Analog Scale (VAS) scoring from 1-10 by making a handwritten mark on a 
10-cm line that represents a continuum between “no pain” on the left end (0 cm) of 
the scale and the “worst pain” on the right end of the scale (10 cm). The questionnaire 
will include several questions related to oral hygiene, pain and discomfort experi-
enced throughout the trial. 
 
3. Root resorption: will be accessed by the principle investigator via CBCT taken 
before and after the completion of retraction. The resorption will be identified   using 

33 
scoring system of Levander and Malmgren34 that classifies it into 5 grades: 0, no 
root resorption; 1, mild resorption, with the root of normal length and only an irreg-
ular contour; 2, moderate resorption, with small areas of root loss and the apex hav-
ing an almost straight contour; 3, severe resorption, with loss of almost one third of 
root length; and 4, extreme resorption, with loss of more than one third of the root 
length. 
 
4. Anterior teeth torque: will be accessed by the principle investigator via CBCT 
taken before and after the completion of retraction. The principal investigator will 
identify the landmarks, reference lines and planes, then will interpret the               
measurements in degrees.  
 
5. Anterior teeth extrusion/intrusion: will be accessed by the principle investigator 
via CBCT taken before and after the completion of retraction. The principal               
investigator will identify the landmarks, reference lines and planes, then will             
interpret the measurements in millimeters.  
 
6. Anterior teeth tip: will be accessed by the principle investigator via scanned      
digital models taken before and after the completion of retraction. 
 
7. Molar Rotation: will be accessed by the principal investigator via digitalized    
dental models. These records will be taken before and after the completion of            
retraction by identifying the landmarks, reference lines and planes, then will              
interpret the measurements of the angles in degrees. 
 
 
 

34 
 
B] Data management:  
A colleague outside the research team will enter the data and organize it in excel 
sheets in the computer of the Orthodontics and Dentofacial Orthopedics department.  
Data will include all photographs, models, radiographs and filled questionnaire.  
 
 
 
C] Statistical Analysis:  
• The principle investigator will be responsible for the extraction of the required data 
from the CBCT taken before and after retraction as well as the study models taken 
at every follow up visit. The data will be sent to a specialized statistician.  
 
• The specialized statistician will be responsible for the statistical analysis of the 
study by:  
1. Presenting the data as mean, standard deviation (SD) and Standard error (SE) val-
ues.  
2. Using Paired t-test to compare between the friction and the frictionless group of 
retraction as well as to compare between the pre-and post -treatment data for each 
group.  
3. Using Anova test to determine the rate of anterior segment retraction.  
4. Statistically evaluate the patient acceptance for both techniques.  
• For this study, the specialized statistician will use IBM11 SPSS12 Statistics   Ver-
sion 20 for Windows to perform the required statistics.  
• The significance level will be P ≤ 0.05. Highly significant variables are detected 
when P value is less than 0.01. 

35 
Assessors Reliability: 
• To achieve high reliability for measurements, the supervisor will choose a          
well-experienced inter-examiner during the study.  
• A training session will be provided for the examiners to ensure standard             
measurements techniques.  
• Each examiner will complete the measurements on a model and will repeat the 
procedure after one week to assess the intra- and inter-examiner reliability.  
• The supervisor will compare the measurements of the two assessors for                   
disagreement with a difference of more than one millimeter.  
• the supervisor will evaluate the amount of variation in measurements among and 
between examiners to test the performance of each assessor.  
• The examiner with less reliability will receive additional training but will be           
replaced during the study.  
• The specialized statistician will calibrate the intra and inter-examiner reliability for 
the measurements of the study by the Intra-class correlation coefficient (ICC). The 
closer the ICC to 1.0, the higher reliability between assessors. According to     
Fleiss:" ICC values between 0.7 and 0.9 represent good reliability.". The kappa 
scores between study examiners will be calculated, a range of 0.60-0.80 will           
represent acceptable reliability.  
 
IV) Method Monitoring:  
A] Data Monitoring: An independent Data Monitoring Committee (DMC) will 
monitor the results of the study. The Committee will include the trial’s supervisors, 
who will periodically review the trial data and identify the need for any adjustments 
or modifications during the study.  
 
B] Interim Analysis: no interim analysis will be performed during the study.  

36 
 
C] Harm: The main operator will document and report any harms or unwanted       
effects during the study intervention to the trial supervisors. Also any unpleasant 
experience will be reported by the patient in the final questionnaire at the end of the 
retraction. The main operator will be responsible for the management of any adverse 
effects or unfavorable side effects resulting from the appliance. 
  
D] Auditing: The supervisor will follow up and review the different interventions 
and resulting data. And he will periodically follow up the trial progress including 
recruitment of patients, allocation of participants to study groups; adherence to        
interventions and reporting of harms. A meeting with the senior supervisor will be 
set every 3 months to monitor the progress of the study and the need for any              
adjustments. 
 
V) Ethics and dissemination:  
A] Research Ethics Approval:  
The Ethical committee in Future University in Egypt will review the protocol before 
they approve it. The research Ethics committee will evaluate the different                   
interventions of the study to ensure its ethical validity and the potential benefits to 
the participants. 
  
B] Protocol amendments:  
The main investigator will be responsible to complete a formal amendment in case 
of any modifications or adjustments to protocol that may affect the conduct of the 
study, as changes in the study design or intervention procedures. The Orthodontics 
and Dentofacial Orthopedics department, Faculty of Oral and Dental Medicine,   

37 
Future University in Egypt and the Ethics Committee will approve such amendment 
before proceeding in the study. 
 
C] Consent:  
The main investigator will be in charge for detailed explanation and elaboration of 
the different steps of the study interventions for each patient. Then will ask every 
participant to sign a written consent before they begin treatment. The consent will 
be written in Arabic.  
 
D] Confidentiality:  
The main investigator will store any personal information about the participants     
collected during the study separately from study records in locked files in areas with 
only access to the supervisors responsible for auditing and analysis. Also, will keep 
the files in the Department Of Orthodontics and Dentofacial Orthopedics, Faculty of 
Oral and Dental Medicine, Future University in Egypt and will identify all the          
reports, data and administrative forms by a coded ID number to maintain participant 
confidentiality. Participant information won't be used outside the study except with 
written permission of the participant.  
 
E] Declaration of interests:  
No financial interests are to be declared by the supervisors and the principle operator. 
This study is a part of a Masters’ degree in Orthodontics and Dentofacial                     
Orthopedics department, Faculty of Oral and Dental Medicine, Future University in 
Egypt and it is self-funded by the principal investigator.  
 
 
 
 

38 
F] Access to data:  
The supervisors and the principal investigator will only have access to the data of 
the study. All the data will be secured by a password to maintain confidentiality. No 
other parties are allowed to assess the results until the study is terminated and the 
conclusions are revealed.  
 
G] Ancillary and post-trial care:  
Any complication associated with the intervention will be managed by the principal 
operator. Then the two group of patients will continue their regular orthodontic   
treatment according to the treatment plan described for each case. 
 
H] Dissemination Policy:  
The trial results will be available to the participants, health care professionals and 
the public by publication of the study in high quality national and international    
journals. The principal investigator will present a copy of the thesis at the Faculty of 
Oral and Dental Medicine, Future University in Egypt library and will distribute           
additional copies among the main universities in Egypt. 
 
 
 
 
 
 
 

39 
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Appendix 
 
Fig 1: