Friction Versus Frictionless Mechanics During Maxillary En-masse Retraction in Adult Patients With Class I Bimaxillary Dentoalveolar Protrusion: A Randomized Clinical Trial
Phase: NA
Conditions: En-masse Retraction , Class I Bimaxillary Protrusion
Sponsor: Cairo University

Friction versus Frictionless Mechanics during maxillary En-
masse Retraction in Adult Patients with Class I Bimaxillary 
dentoalveolar Protrusion: A Randomized Clinical Trial 
 
 
A Protocol Submitted To   
The Faculty of Oral and Dental Medicine,  
Cairo University   
In Partial Fulfillment of the Requirement   
For The PhD Degree in Orthodontics 
By 
Sally Magdi Riad Makram 
BDS (2008)   
MSc (2015) 
Department of Orthodontics 
Faculty of Oral and Dental Medicine  
Cairo University 
(2017) 
 
 
 

 
Administrative Information  
 
Trial registration: trial is not registered yet but is to be registered at ClinicalTrials.gov.  
Protocol version:  July 2017. Version 1  
Funding:  No sources of funding to be declared.  
Authors’ contributions:  
Sally Magdi Riad (S.M), BDS, MSc (Principal Investigator) will be responsible for 
recruitment of sample, application of different interventions, follow up of patients, writing 
the thesis, interpretation of results and drawing out conclusions.   
Fatma Abdo Abd El Said (F.A), BDS, MSc, PhD helped with developing the idea of the 
research and will help in monitoring the process of the study, reviewing the data and the 
results.  
Fady Hussein (F.H), MS, BDS, MSc, PhD initiated the study design, will help in sequence 
generation for randomization, follow up of patients, data verification and will help the 
principal investigator in interpretation of  the results. 
 
 
 
 
 
 
 

Introduction 
A] Background and Rationale: 
Protrusion of the maxillary and mandibular incisors with increased procumbency of the lips 
is considered one of the major chief complaints of adult patients seeking orthodontic 
treatment. This condition is known as bimaxillary dentoalveolar protrusion(1). 
The usual objective of  treatment in such condition is the retraction of anterior teeth with a 
resultant decrease in soft tissue convexity(2). And so, the treatment of choice for these 
patients is to extract the first premolars. In this case, maximum anchorage of the posterior 
teeth become of great importance for two reasons; to retract the anterior teeth to their greatest 
extent and to increase the chances of correcting the profile. 
With the introduction of mini-screws/implants (3) (4) as anchorage, it has become possible to 
achieve absolute anchorage (5) during anterior teeth retraction(6). 
However, there have been controversies about how to achieve maximum retraction  with 
anchorage preservation in first premolar extraction cases. Proffit and Fields(1) recommended 
separate canine retraction followed by incisors retraction for maximum anchorage, stating 
that this approach would decrease the load on the posterior teeth. However, they agreed that 
closing the space in two steps would take nearly as twice as long than closing it in a single 
step. On the other hand, Staggers and Germane (7)described anchorage as "being taxed twice 
with a two-step retraction, as opposed to once with en masse retraction". They mentioned 
that "the posterior segment is unaware of  how many teeth are being retracted and simply 
responds to the force acting on it".  So, studies were done to compare both techniques. The 
debate came to an end when no significant differences were found in the amount of retraction 
of anterior teeth and the degree of anchorage loss associated with both techniques(8)(9). This 
fact suggests that en-masse retraction  is an adequate alternative to two-step retraction during 
space closure specially that it is esthetically more acceptable(10).  
Space closure can be done either by Friction or Frictionless  mechanics. In Friction or sliding 
mechanics; the space site is closed by means of coil springs or elastics allowing the brackets 
to slide on the orthodontic archwire. On the other hand, frictionless mechanics uses loop and 

bends to generate force to close the space site which allow differential moments in both 
active and reactive units(11).  
It is well known that orthodontic treatment is time consuming, and so, the speed by which 
treatment is completed is considered a primary concern to every patient and orthodontist. But 
despite the large number of studies dealing with mechanics of space closure, no enough 
evidence was found in the orthodontic literature regarding the best technique for anterior 
teeth retraction(17). And by searching the literature, no study was found to measure the patient 
satisfaction regarding the different techniques of retraction. Therefore, a recent systematic 
review(18) has  recommended additional studies to determine the best way for anterior 
segment retraction.  
From the mentioned background, we can find a gap in knowledge regarding the effectiveness 
of friction and frictionless mechanics during maxillary en-masse retraction that need further 
properly designed randomized controlled trial to achieve conclusive results.   
Accordingly, conducting a well-designed Randomized Clinical Trial, evaluating the effects 
of the two systems with respect to space closure, will provide detailed information about 
tooth movement and so; will guide the orthodontists in their choice for the suitable treatment 
mechanics to be used and will shed a light on the expected treatment outcome and duration. 
Also, this will allow more patient satisfaction and cooperation during the treatment period. 
Choice of comparator: 
Friction or Sliding mechanics is commonly(12) used due to its simplicity. However, the 
efficiency of this technique in space closure may be compromised due to binding between the 
bracket and archwire slowing the tooth movement. Theoretically, this can be overcome by 
the use of a frictionless system. The well-designed  loops and bends provide the required 
moment to force ratio with great predictability but need more wire-bending skills. In 
addition, minor errors can result in major differences in tooth movement, and some patients 
may find the loop uncomfortable(13).  
 
 

B] Aim of the Study: 
The aim of this study is to compare the effectiveness of friction and frictionless mechanics 
during maxillary en-masse retraction regarding patient satisfaction, rate and duration of 
retraction, molar anchorage loss, anterior teeth inclination and soft tissue changes.  
And so the research question of this trial is :'' In adult with Class I bimaxillary dentoalveolar 
protrusion; how does the use of friction and frictionless mechanics during maxillary en-
masse retraction affect the rate of retraction of anterior teeth and other treatment 
outcomes?'' 
PICO format: 
P- adult patients with Class I bimaxillary dentoalveolar protrusion(14). 
I-  frictionless mechanics using closing T- loops. 
C friction mechanics using NiTi coil springs. 
Ooutcome measures (1ry, 2ry): 
 
 
Outcome name 
Measuring Device 
Measuring Unit 
Primary  
(1ry) 
 
-Patient Acceptance(19) 
 
-Retraction duration 
 
-Retraction rate 
 
-Questionnaire(20) 
 
-Clinical Evaluation(16) 
 
-dental models(21) 
 
- Scoring scale from 0 to 
5 
-months 
 
-millimeter (mm) 
 

Secondary (2ry) 
- Molar Anchorage 
 
 
-Inclination of ant teeth.  
 
 
- Soft tissue changes 
- Lateral Cephalometric 
radiographs(8). 
 
-Lateral Cephalometric 
radiographs(9).  
 
- Lateral Cephalometric 
radiographs (15)(20). 
 
 
 
- Degree(°) and 
millimeter (mm). 
 
 
 
 
Research Hypothesis:  
The null hypothesis for the study is that both friction and frictionless mechanics have the 
same efficiency in retracting the anterior segment following first premolars extraction in 
adult patients with class I bimaxillary dentoalveolar protrusion. 
Objectives:  
Primary Objectives: to compare between the use of friction and frictionless mechanics during 
en-masse retraction regarding patient's satisfaction and speed of retraction. 
Secondary Objectives: to determine which technique will provide minimal anchorage loss 
with better anterior teeth inclination and better soft tissue after space closure. 
 
C] Trial Design: 
The design of this randomized controlled trial is a parallel group, two arms trial with 1:1 
allocation ratio. In one group, frictional mechanics will be applied during anterior segment 
retraction while the other will receive non-frictional mechanics during retraction to compare 
the results of space closure. 

Materials and Methods: 
I] Participants, Interventions and outcomes 
 
A] Study Setting: 
The study will take place in the clinic of the Orthodontic Department at the Faculty of Oral 
and Dental Medicine, Cairo University. The recruited sample would be from the Egyptian 
population. 
B] Eligibility criteria: 
 Inclusion criteria: 
1. Male or female adult patients with age range 18-30 yrs old(22). 
2. Class I bimaxillary dentoalveolar protrusion (23) . 
3. Full permanent dentition(24). 
4. Good oral hygiene(25). 
5. Maximum anchorage is required(26). 
6. Healthy bone between first molars and second premolars is needed(27). 
 Exclusion Criteria: 
1.  Systemic disease(28). 
2. Severe crowding(23). 
3.  Extracted or missing upper permanent tooth/teeth (except for third molars) 
(24). 
4. Any signs or symptoms or previous history of temporomandibular disorders 
(TMD) (29). 
5. Previous orthodontic treatment(30). 
 
 
 
 
 

C] Interventions: 
 
S.M will fill a medical history questionnaire for every patient to exclude the presence 
of any systemic condition interfering with orthodontic treatment. (Appendix 1) 
 
 Proper examination of the oral structures is needed to identify caries, fracture or 
missing teeth. S.M will be carefully examine gingival tissues for any gingivitis, 
periodontitis, recession or lesions.  
 
 S.M will check the potential  patient to fulfill the previously mentioned inclusion 
criteria. Then will ask every participant to sign an informed consent about the study. Full 
set of records ( study models, lateral cephalometric radiographs, photos) will be taken by 
S.M for every patient as part of the routine procedure for treatment of patients in the 
outpatient clinic of the Orthodontic Department, Cairo University.  
 
 
 Clinical Procedure: 
After pre-treatment records were taken, every patient will receive: 
1. 
Banding  of  upper and lower first molars⃰. 
2. 
Bonding of upper and lower arch with MBT prescription  0.022 slot brackets⃰ . 
3. 
Leveling arch wires in sequential order starting from round NiTi flexible arch wires 
according to the need of the case then the sequence will be continued .The leveling and 
alignment stage of the upper arch will be considered completed when a 0.019×0.025 
StSt arch wire could be placed passively in all upper arch. 
4. 
Once leveling and alignment stage is completed, the principal operator S.M will refer 
the patient the uptake of pre-intervention records. 
 
 
Acquisition of pre-intervention records: 
•   S.M will take dental models before treatment as a part of the patient’s records and 
every month during the follow up period. The models will be poured in dental stone 
and trimmed according to orthodontic standards. 
 
 
 
⃰ Ormco bands, Medicime glass ionomer for bands 
 ⃰ Ormco 0.022 slot MBT brackets 

•   S.M will refer the patient for the uptake of Lateral cephalometric radiograph after the 
leveling and alignment stage before the first premolars extraction to identify the pre-
retraction position of anterior teeth and molars. 
 
 
Insertion of miniscrews: 
  
• S.M will place two miniscrews⃰; 8mm in length and 1.4 mm in diameter(23), made of 
biocompatible pure titanium between the maxillary second premolars and the first 
permanent molars bilaterally in the buccal alveolar bone using the appropriate screw 
driver. These miniscrews are used to ensure maximum anchorage during en-masse 
retraction.  
• Before implantation of miniscrews; S.M will assess the space between the roots of  
maxillary second premolar and first permanent molar by periapical radiograph. 
 
 
Implantation procedure: Under the supervision of F.H, the principal investigator  
S.M will; 
1. Give few drops of local anesthesia to the patient to ensure a pain-free procedure. 
2. Use a periodontal probe to induce a bleeding point at the predetermined area of  
miniscrews insertion to facilitate implantation. 
3. Swap the implantation area between the roots of maxillary second premolar and the first  
permanent molar by cotton soaked with Betadine solution for disinfection. 
4.Use a screw driver to drill  the miniscrews into the bone manually in a clockwise 
direction until fully engaged. This procedure will be repeated bilaterally. 
5. Give strict oral hygiene instructions to the patients including regular mouthwash for 3 
days and proper tooth brushing. 
 
 
Extraction of the first premolars 
  At this stage, S.M will refer the patient to the oral surgery department, Faculty of Oral 
and Dental medicine, Cairo University for extraction of both upper first 
 
⃰Rocky Montain Orthodontics, USA 

premolars. All dental extractions will be  done by the same dental surgeon for all the patients 
under local anesthesia and using upper premolar forceps. 
 
 
Begin of Retraction 
Friction group: The principal investigator will: 
•  Secure the upper six anterior teeth together by mean of  ligature wire to allow en-masse 
retraction during space closure. 
• Fix a crimpable hook⃰ on the main archwire (0.019×0.025 StSt) between the upper lateral 
and canine bilaterally(31). 
• Bend a small piece of 0.019’’x0.025’’stst wire and insert it  passively in the auxiliary tube 
of first molar band. The wire will be attached to the screw head to ensure proper anchorage 
control,. 
• Use light cure composite⃰  to secure the wire in the screw head properly(23) to avoid wire 
disengagement. 
• Extend NiTi coil spring from the molar band to the crimpable hooks bilaterally. 
• Apply a force of 150 g for both sides . The force is measured by a force gauge⃰ and 
activated each visit to keep it constant all over the retraction phase. 
 
Frictionless group: The principal investigator will: 
• Secure the upper six anterior teeth together by mean of  ligature wire to allow en-masse 
retraction during space closure. 
• Bend a small piece of 0.019’’x0.025’’stst wire and insert it passively in the auxiliary tube 
of first molar band. The wire will be  attached to the screw head to ensure proper anchorage 
control . 
• Use light cure composite⃰ to secure the wire in the screw head properly(23) to avoid wire 
disengagement. 
• Bend a 0.019×0.025 TMA wire to T-loops distal to upper canine   bilaterally(32). 
•  Add a gable angle of 45˚ in the canine area and anti-rotational angle of 45˚ in the retraction 
archwire(33). 
  
⃰ Ormco Crimpable arch hook 
  ⃰Grengloo (Ormco) for metal brackets   ⃰ IMD, Orthodontic force gauge 

• Cinch back the wire distal to upper first molars bilaterally. 
• Apply force of 150 g for both sides. The force is measured by a force gauge and activated 
each visit to keep it constant all over the retraction phase. 
 
 
Appliance activation 
At each visit, S.M will check the force magnitude using the same force gauge. Re-
activation of the appliance is necessary to maintain 150 g force(34) delivery throughout the 
follow up period. 
 
 
Follow up visits 
The principal investigator S.M will; 
See the patient on a monthly basis until complete anterior segment retraction is observed. 
Assess the miniscrews for mobility at every clinical appointment. 
Take alginate impression for the patient at each visit to construct the dental models  to 
assess the rate retraction. At each visit, S.M will remove the arch wires and coil springs 
before impression procedure. Alginate impression will be poured in dental stone. After 
setting, S.M will trim the dental casts and label it with the patient name, number and date. 
 
 
Criteria for discontinuing or modifying the allocated intervention:  
In case of prolonged swelling or pain related to the miniscrews, S.M will give the patient 
strict oral hygiene measures and may wait for three weeks before the beginning of 
retraction.   
In case of loose or broken any of the miniscrews, S.M will remove and replace the 
miniscrews after total resolution of the inflammation. 
 
 
Post-retraction Questionnaire: 
S.M will ask the patients of both groups to fill in questionnaires regarding their experience 
with both techniques. 
 
 
 

 Post-retraction records 
Following retraction of the anterior segment, S.M will refer the patient to the same 
radiology center to acquire the final lateral cephalometric radiograph to assess the 
movement and inclination of anterior teeth as well as the changes in soft tissue post-
retraction . (Appendix 2) 
The final dental model will assess the rate of retraction and molar anchorage loss achieved 
throughout the study.  ( Appendix 3) 
 
D] Outcomes  
Primary outcomes: is to monitor the degree of patient satisfaction with the different 
methods used for anterior segment retraction as well as the rate and speed of space closure 
following first premolars extraction to help in the choice of treatment. 
Secondary outcomes: include the molar anchorage loss associated with each technique 
during retraction as well as the final anterior teeth inclination which affect the soft tissue 
at the end of treatment. S.M will assess all the outcomes as the difference between T1 at 
the start of en-masse retraction after first premolars extraction and T2 after complete space 
closure. 
 
 
E] Participant time line: 
  
1. S.M will screen the potential patients through careful clinical examination of patients at 
the orthodontic department , Faculty of Oral and Dental Medicine, Cairo University. 
2. All recruited patients should fulfill the previously mentioned inclusion and exclusion 
criteria. 
3. S.M will ask every participant to sign an informed consent before the beginning of the 
study. 
4. After patient's enrolment, S.M will ask each participant for pre-intervention records to 
ensure proper diagnosis. 
5. S.M will randomly allocate the patients to one of the intervention group. 

6. Active intervention will begin by proper leveling and alignment of the upper and lower 
arches. 
7. S.M  will send the patients for extraction of upper first premolars. 
8. S.M will take pre- retraction records for every participant. 
9. In Friction mechanics group, NiTi coil spring is used for maxillary en-masse retraction 
while in Frictionless group, T-loop is used for retraction. 
10.Each patient will come every month for follow up visit, for appliance activation and 
uptake of impression for interim records. 
11.After complete space closure, S.M will take post-retraction  records for each participant. 
12. Every patient will fill up a questionnaire regarding his experience during treatment. 
13. S.M will continue the normal treatment and achieve proper finishing for every patient 
after the end of the study. 

 
 
 
 
 
 
 
 
 
 
 
 
         
 
Screening of patients seeking orthodontic 
treatment at the orthodontic department 
outpatient  clinic 
Patient enrollement 
Acquisition of pre-intervention records 
Concealed Allocation   
Friction group 
Frictionless group 
Activation of NiTi coil spring and T-
loops 
Acquisition of post-retraction  records 
Patient questionnaire 
Missed appointments  
recorded 
After complete retraction 
4 months 
 
Eligibility criteria and 
informed consent 
Dropouts and missed 
data recorded 
Data collection and management 
Recruitment 
Preparatory phase 
Interventions 
Follow up visit 
End of study 
Pre-retraction records 
Monthly follow up 
visits for appliance 
activation and interim 
records 
 
Leveling & alignment and miniscrews 
placement followed by extraction 
 
 
2-4 months 
Average 8 months 
 
 
 
 

 
 
 
Procedures 
Study Period 
Enrolment 
Average 4months 
Allocation 
Leveling 
and 
Alignment 
2-4 months 
Retraction and follow up visits 
Average 8-9months 
Post -retraction 
3-4 months 
-t1 
-t2 
   0 
T1 
f1 
f2 
f3 
f4 
f5 
f6 
f7 
f8 
T2 
Enrolment: 
 
 
Eligibility screen 
 
Informed Consent 
 
Pre-treatment records 
 
Allocation 
 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
Interventions: 
 
Banding & Bonding 
 
Leveling &Alignment 
 
Miniscrews insertion 
 
Premolars Extraction 
 
Begin of retraction 
 
Activation 
 
Follow up visits 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
x 
x 
x 
x 
x 
x 
x 
x 
 
 
 
 
 
x 
x 
x 
x 
x 
x 
x 
x 
 
Assessments: 
 
Interim records 
 
Post- retraction records 
 
Questionnaire 
 
Anchorage loss 
 
Rate of retraction 
 
Incisors inclination 
 
Statistical Analysis  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
x 
x 
x 
x 
x 
x 
x 
x 
x 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
x 
x 
x 
x 
x 
x 
x 
x 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
 
 
 
x 
 

E] Sample size calculation: 
Our sample size calculation is based on a previous study(36) comparing the effect of 
friction and frictionless mechanics on maxillary canine retraction. The mean change in 
both groups is 1.41 ± 0.62 mm and 1.91±0.41 mm respectively. The minimum clinical 
difference is 0.5mm/month. A  t- test assuming equal variance for two independent groups 
is used. The power is set as 0.8, allocation ratio of 1:1 and the Type I error probability 
(alpha) associated with this test is set as 0.05. Results of the test showed that the group 
sample sizes of 12  is needed to reject the null hypothesis of equal means with a 
significance level of 0.05 . For consideration of drop out a sample size of 15 cases per 
group is considered. 
Computer output 
Sample  Target 
Difference    Size    Power   Actual Power 
0.5      12     0.8      0.814515 
 
The sample size is for each group. 
                       
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
1.0
0.8
0.6
0.4
0.2
0.0
Difference
Power
A lpha
0.05
StDev
0.41
A lternativ e
Not =
A ssumptions
12
Size
Sample
Power Curve for 2-Sample t Test
 
 
 

 
 
F] Recruitment strategy:    
The principal investigator will recruit the patients from the clinic of Orthodontic 
department, Faculty of Oral and Dental Medicine- Cairo University.  
Screening of patients will continue until the total number of participants for the study is 
collected. Recruitment period is expected to be 4 months.  
 
 
II] Assignment of interventions: 
 
     A] Sequence generation: 
The supervisor of the study F.H will apply Computer generated random numbers to 
randomly assign patients to group A (Friction) or B (frictionless) using Microsoft Office 
Excel 2007 sheet. F.H will write the patient numbers in the first column, and 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.  
 
B] Allocation concealment mechanism: 
F.H will write the randomization numbers of the patients in opaque white papers folded 
three times to form sealed envelopes and store it inside a box. Then will keep the Codes 
for randomization at the secretary office. 
 
C] Implementation: 
 
At time of intervention, the main operator S.M will send the patient to the secretary 
office. Then, the assigned employee will open the box and ask the patient to select one 
envelope. S.M 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 leveling 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 S.M is 
responsible for assigning subjects to interventions according to the concealed allocation, 
insertion of miniscrews, appliance activation at follow up visits, dental impressions and 
acquisition of dental casts.   
        Blinding of the outcome assessors: It is a single blinded study, the outcome assessors 
only will be blind. The patients name will be sealed from pre and post radiographs and 
study models. Then two assessors will carry on, blindly and independently, the 
measurements and analysis of the study. 
 
III] Data collection, management and analysis: 
 
A] Data collection methods: 
    Primary outcomes: 
1. Parent’s satisfaction: Each patient will fill a questionnaire regarding his treatment 
experience in a scale from 0-5. The questionnaire will include several questions related 
to oral hygiene, pain and discomfort experienced throughout the trial .The design of the 
questionnaire to be used in this study is following what was used in similar study by 
Baxmann et al 2010(35).  The questionnaire will be filled at the end of the retraction 
phase.  
2. Retraction duration: S.M will assess the whole duration of retraction by clinical 
observation of space closure from the distal surface of the canines to the mesial surface 
of the first molars and will  record it in months. 
3. Retraction Rate: in order to assess the antero-posterior movement of anterior teeth and 
first molar, S.M 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. 
Secondary outcomes: 
4. Molar anchorage loss, change in anterior teeth inclination and soft tissue 
changes: will be accessed by S.M via Lateral cephalometric radiograph 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 
and millimeters. 
 
B] Data management: 
A colleague outside the research team will enter the data and organize it  in excel sheets 
in the computer of the orthodontic department.  
Data will include all photographs, models, radiographs and filled questionnaire. 
 
C] Statistical Analysis: 
• S.M will be responsible for the extraction of the required data from the lateral 
cephalometric radiographs 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) values. 
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 Version 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. 

    
Assessors Reliability: 
• To achieve high reliability for measurements, the supervisors (F.A and F.H) will choose 
a well-experienced inter-examiner during the study. 
• F.A and F.H will provide a training session 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 supervisors will compare the measurements of the two assessors for disagreement 
with a difference of more than one millimeter. 
• F.H 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 (F.A and   F. H), 
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. 
C] Harm: The main operator S.M will document and report any harms or unwanted effects   
during the study intervention to the trial supervisors (F.A and F.H). Also any unpleasant 

experience will be reported by the patient in the final questionnaire at the end of the 
retraction. S.M will be responsible for the management of any adverse effects or 
unfavorable side effects resulting from the appliance. 
D] Auditing: The supervisors (F.A and F.H) will follow up and review the different 
interventions and resulting data. The supervisor (F.H)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 
(F.A) 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 CEBD [Center for Evidence Based Dentistry CU] Cairo University, Egypt will 
review the protocol and the Ethics Committee [Research Ethics Committee Cairo 
University Faculty of Oral and Dental Medicine] will 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: 
S.M 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 Council of Orthodontics department, Faculty of 
Oral and Dental Medicine, Cairo University and the Ethics Committee will approve such 
amendment before proceeding in the study . 
 
 
C] Consent: 

S.M 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:   
S.M 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 
(F.A and F.H) responsible for auditing and analysis. Also, will keep the files in the 
Department Of Orthodontics, Faculty of Oral and Dental Medicine, Cairo University 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 PhD degree in Orthodontics, faculty of oral and dental medicine, 
Cairo University and it is self-funded by the principal investigator. 
F] Access to data: 
The supervisors (F.A and F. H) and the principal investigator (S.M) 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 (S.M). Then the two group of patients will continue their regular orthodontic 
treatment according to the treatment plan described for each case. S.M will proceed in 
bonding of the lower arch, leveling and alignment, finishing and will apply proper 
retention protocol for each individual 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. S.M 
will present a copy of the thesis at the faculty of Oral and Dental Medicine, Cairo 
University library and will distribute additional copies among the main universities in 
Egypt. 
 
 
 
 
 
 
 
 
 
 
 
 

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Appendix 1 
Diagnostic chart 
 
 
  
 
 
 
 
 
 
 
 
 
 
 

         
 
 
Appendix 2 
Lateral cephalometric readings 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Appendix 3 
 
 
 
 
 
 
 
Dental cast landmarks 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
        Lines for linear and angular measurements