Evaluation of Incisors' Position Following Anterior Segment Retraction Using Friction Versus Frictionless Mechanics: A Randomized Clinical Trial
Phase: NA
Conditions: Bimaxillary Protrusion
Sponsor: Future University in Egypt

1 
 
Evaluation of Incisors’ Position Following Anterior 
Segment Retraction Using Friction versus Frictionless 
Mechanics: A Randomized Clinical trial 
 
 
Thesis submitted for the partial fulfillment of Masters’ degree in 
Orthodontics  
Faculty of Oral and Dental Medicine, Future University 
  
 
Submitted by 
Name: Dorra MHD Izzat Bakhit 
B.D.S. 2015 
 
 
  (2019) 
 
 
 

2 
 
Funding: 
 no sources of funding to be declared. 
Roles and responsibilities: 
Principal investigator: 
Dorra Bakhit, BDS, will be responsible for the clinical procedures that will be 
carried out, sample recruitment, follow up of patients, writing the thesis, data 
management and results interpretation. 
Main supervisor:  
Prof. Yehya Mostafa, BDS, MSc, PhD – Chairman of the Department of Orthodontics 
and Dentofacial Orthopedics – Future University. Helped in developing the idea of the 
research, will help in interpretation of results and drawing conclusions. 
Co-supervisor:  
Dr. Fouad El Sharaby, 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, implementation of random sequence 
generation, creating analysis, interpretation of results and drawing conclusions. 
All authors contributed to refinement of the study protocol. 
Co-supervisor:  
Dr. Heba Dehis, BDS, MSc, PhD, Associate professor - Department of Orthodontics 
and Dentofacial Orthopedics – Cairo University. Will help in follow up of patients, 
creating analysis, interpretation of results and drawing conclusions. 
All authors contributed to refinement of the study protocol. 

3 
 
 
Committees: 
• Orthodontics Department Council 
• College Board Committee 
• Ethics Committee 
 
 

4 
 
Introduction 
Statement of the problem: 
Anterior segment retraction is a major step encountered in cases with upper 
incisors protrusion comprising both bimaxillary protrusion and class II Div-1. 
Extraction is the treatment of choice for these cases; space closure can be achieved 
by separately retracting the canine followed by the four incisors. It’s still debatable 
which technique used for anterior segment retraction is more superior than the other 
friction versus frictionless. 
Rationale for carrying out the trial: 
The art and science of facial aesthetics has intrigued mankind since the time 
of Egyptian culture. Upper incisors retraction is needed in cases like protrusion 
with/without skeletal discrepancy and plays a remarkable role on the appearance of 
the face as well as on the function of masticatory system[1].  
Extraction of 1st premolars is the treatment of choice for these cases with 
maximum anchorage control to retract the anterior teeth to their greatest extent and 
to increase the chances of correcting the profile. The mail goal of treatment in such 
condition is decreasing soft tissue convexity after the retraction of anterior teeth[2].  
Space closure is the main stage of orthodontic treatment when extractions are 
undertaken as part of the treatment plan. It can be achieved either by separately 
retracting the canine followed by the four incisors (two-step) or by en-masse 
retraction of the whole anterior segment simultaneously. A debate was raised 
between the two methods. It has been recommended[3] that separate canine 

5 
 
retraction followed by incisors retraction would provide less load on the posterior 
teeth, yet no significant differences were found between the two methods. 
For years, orthodontists have been looking for an efficient force system 
that can close extraction spaces quickly, aesthetically, accurately, and effectively. 
Space closure can be accomplished by adopting friction based mechanics often 
called “sliding mechanics” or without friction, also known as “Segmental 
mechanics”[4]. In Friction 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[5]. 
One of the major challenges faced by the orthodontists is to understand and 
predict the complexities involved in the response of teeth to the forces and the 
moments. Sliding mechanics is widely used due to its simplicity but it shows lack of 
force control due to friction between archwire and brackets, and a lack of vertical 
and horizontal control over anterior teeth thus making the system indeterminant[6]–
[8]. Moreover, Previous experiments have demonstrated that the sliding mechanics 
might lead to uncontrolled tipping or extrusion of the anterior segment.[9][10]. 
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[9]. 
It is well known that the amount of tip, torque, extrusion/intrusion in 
anterior teeth is very critical as it affects the final aesthetic outcome. Accordingly, 

6 
 
anterior segment vertical and horizontal control is considered a primary concern 
to all orthodontists. Despite the large number of studies dealing with mechanics 
of space closure, little evidence has been found in the orthodontic literature 
regarding the best guidelines for anterior teeth position after anterior teeth 
retraction. Therefore, a recent systematic review has recommended additional 
studies to determine the best way for anterior segment retraction.[11] 
There’s scarcity in literature concerning the issue of anterior segment 
retraction technique and its effect on anterior teeth position. Therefore, a randomized 
clinical trial has been chosen to investigate this issue, aiming to support clinicians 
with the best guidelines for anterior segment retraction. 
 
 

7 
 
Literature
of 
Review 
 
It’s widely accepted that one of the main goals seeking orthodontic treatment is 
aesthetic[12]. Aesthetics are mainly determined by controlling the position of the 
anterior teeth. Accordingly, three-dimensional control of anterior teeth during 
orthodontic treatment is important to avoid any side effects on the dentition which might 
happen due to the applied orthodontic mechanics. Several approaches have been 
implemented to control both the anteroposterior and the vertical positions of the incisors 
with multiple studies conducted to evaluate their effectiveness. 
• The review of literature will be discussed under the following titles: 
1. Friction mechanics for anterior segment retraction. 
2. Frictionless mechanics for anterior segment retraction. 
3. Friction vs. frictionless. 
4. CBCT for evaluation and its reliability. 
 
1) Friction mechanics for anterior segment retraction 
Chaudhari and Tarvade (2015)[13] compared the rate of retraction and 
anchorage loss using nickel titanium closed coil springs and elastomeric chain 
during en-masse retraction. Forty patients with first premolar extraction were 
divided into two groups for space closure. The amount of anterior retraction, 
anchor loss and rate of space closure was measured before start of retraction and 
at the end of 4 months clinically and radiographically. The results of this study 
demonstrated faster space closure with anterior retraction along with significant 
anchorage loss was achieved by using NiTi closed coil spring when compared to 
elastomeric chain. 

8 
 
Barlow and Kula (2008)[14] reviewed the literature to determine strength 
of clinical evidence concerning the influence of various factors on the efficiency 
(rate of tooth movement) of closing extraction spaces using sliding mechanics. 
Ten prospective clinical trails comparing rates of closure under different variables 
and only focusing on sliding mechanics were selected to be reviewed. They 
concluded that arch wire properties, type, size, diameter, along with bracket 
design, material, and force delivery system all affected friction and hence tooth 
movement. Then added that Elastomeric power chain produced similar rates of 
retractions as 150 and 200 g nickel-titanium springs which were equally effective 
in space closure. Moreover, arch wire size might had no effect on rate of closure 
but larger size control tipping better, and frictional differences of arch wire type 
might not be the major factor in rate of closure. 
 
2) Frictionless mechanics for anterior segment retraction 
Almeida et al. (2016)[15] compared the force system produced by 
nickel-titanium T-loop springs made with wires of different dimensions. Thirty 
compound T-loop springs were divided into three groups according to the 
dimensions of the nickel-titanium wire used for its design: 0.016" × 0.022", 0.017" 
× 0.025", and 0.018" × 0.025". The loops were tested on the Orthodontic Force 
Tester machine at an interbracket distance of 23 mm and activated 9 mm. The 
larger wires tested produced higher forces with slight increase on the moments, 
but the M/F produced by the 0.016" × 0.022" wire was the highest found. 
 
Chen et al. (2000)[16] measured the moments and forces produced by 
various orthodontic T-loop spring designs. The effects of dimension changes 
(within clinically used ranges) and the addition of gable bends with heat treatment 

9 
 
were assessed. They found that increasing the vertical or horizontal dimension 
reduced the spring's load-deflection rate and its moment-to-force ratio. Moreover, 
gable preactivation with heat treatment had the opposite effects. 
 
Kuhlberg and Burstone (1997)[17] 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 seven 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 the alpha/beta moment ratio 
was dependent only on the spring position, and independent of spring activation. 
Eccentric positioning of T-loop springs effectively produces a consistent moment 
differential through the range of spring activation. 
 
3) Friction vs. Frictionless 
Dincer et al (2000)[1] evaluated the effect of application of PG 
spring for retraction of upper incisors on the dento-alveolar structure 
compared to the effect of closed coil spring.  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. They concluded 
that mesial movement of buccal segment and distal movement of root apex of 
incisors were accompanied with the incisor retraction in both groups. 
Moreover, a significant incisors intrusion in PG group and a significant 
increase in deep bite in coil spring group. Plus, the PG spring produced three-
dimensional control in the movement of upper incisors, so that application of 

10 
 
additional intrusive mechanics after competition of the incisor retraction 
became unnecessary. 
 
Ziegler and Ingervall (1989)[18] 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 AlastiK chain was 
compared with that using the canine retraction spring designed by Gjessing. 
Results revealed that canine was retracted faster and with less distal tipping 
with the spring than with the sliding mechanics. The canine retraction spring 
was not superior to the sliding mechanics in controlling canine rotation during 
the retraction. 
 
4) CBCT for evaluation and its reliability 
Gribel et al. (2011)[19] compared the accuracy of craniometric 
measurements made on lateral cephalograms and on cone beam computed 
tomography (CBCT) images. Ten fiducial markers were placed on known 
craniometric landmarks of 25 dry skulls with stable occlusions. CBCT scans and 
conventional lateral headfilms subsequently were taken of each skull. Direct 
craniometric measurements were compared with CBCT measurements and with 
cephalometric measurements using repeated measures analysis of variance 
(ANOVA). They concluded thatCBCT craniometric measurements are accurate to 
a subvoxel size and potentially can be used as a quantitative orthodontic diagnostic 
tool. Two-dimensional cephalometric norms cannot be readily used for three-
dimensional measurements because of differences in measurement accuracy 
between the two exams.  

11 
 
 
El-Beialy et al. (2011)[20] evaluated the accuracy and reliability of 
measurements obtained from 3-dimensional (3D) cone-beam computed 
tomography (CBCT) for different head orientations. They used Stainless steel 
wires fixed to a dry skull at different places. The skull was scanned by using CBCT 
in the centered and 5 other positions. Intraobserver and interobserver reliability 
tests were performed by using 6 landmarks identified on the virtual 3D skulls by 
2 operators. They reported that CBCT measurement is a reliable technique that 
can be utilized for assessment of both linear and angular measurements. 
Database search: 
A search will be performed on electronic databases (PubMed, Cochrane library). 

12 
 
Aim of the study 
A-PICO format: 
Population: 
Female orthodontic patients requiring 1st premolars extraction followed by anterior 
segment retraction. 
Intervention: 
Anterior segment retraction using segmental mechanics (frictionless) with 
miniscrews used as anchorage. 
Comparator: 
Anterior segment retraction using sliding mechanics (friction) with miniscrews used 
as anchorage. 
Outcome measure: 
 
Outcome Name 
Measuring Tool 
Measuring Unit 
Primary 
Outcome 
Torque 
of 
anterior teeth 
CBCT 
Degrees 
 
Tip of anterior 
teeth 
CBCT 
Mm 
 
Vertical 
position 
CBCT 
Mm 

13 
 
 
Root resorption 
CBCT 
Scoring system 
of 
Levander 
and 
Malmgren[21]( 5 grades classification) 
 
B-Research question: 
In Orthodontics adolescent patients requiring 1st premolars extraction followed by 
anterior segment retraction, can frictionless mechanics offer a better control over the 
anterior segment compared to friction mechanics? 
 
 

14 
 
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 anterior teeth position during anterior segment 
retraction following 1st premolar extraction  
Primary objective (s): 
Measuring changes in extrusion/ intrusion, tip and torque of anterior teeth following 
anterior segment retraction using frictionless vs friction mechanics. 
Secondary objective: 
Measuring the root resorption during anterior segment retraction using frictionless 
vs 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 anterior segment 
retraction while the other will receive frictional mechanics during retraction to 
compare the changes in anterior teeth position. 
 
 
 

15 
 
Material and Methods 
I)participants, interventions, and outcomes 
 
A] Study Setting: 
The study will be performed in the clinic of the Orthodontic Department at the 
Faculty of Oral and Dental Medicine, Future University. The recruited sample is 
from the Egyptian urban and rural population. 
B] Eligibility criteria: 
➢ Inclusion criteria: for the participants include the following: 
 
1. Female patients, Age range (13-25) 
2. Bimaxillary protrusion requiring extraction of four first premolars and 
maximum anchorage. 
3. Patients with fully erupted permanent teeth (not necessarily including the 
3rd molar). 
4. Good general and oral health.  
5. Class I molar relation (Angle’s classification) 
 
➢ Exclusion Criteria:  for the involved subjects include: 
1. Patients suffering from any systemic diseases or syndromes or on anti-
inflammatory medication interfering with tooth movement. 
2. Patients with extracted or missing permanent teeth. (except for third 
molars). 
3. Patients with badly decayed teeth.  
4. Patients with any parafunctional habits.  
5. History of previous orthodontics treatment. 
 
 

16 
 
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 missing 
teeth.  Gingival tissues will be carefully examined for any gingivitis, 
periodontitis, recession or lesions. 
 
➢ Diagnosis 
Potential patients will be checked for fulfillment of the previously 
mentioned inclusion criteria. Every participant will be asked to sign an 
informed consent about the study. Full set of records (study models, 
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 Orthodontic Department at The Future University of 
Egypt. 
 
➢ Clinical Procedure: 
 
After taking pre-treatment records: 
• 
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 slot). 

17 
 
• 
Leveling and alignment for the bonded and banded teeth will be initiated 
following the wire sequence: 0.014 NiTi, 0.016×0.022 NiTi and  
0.017×0.025 StSt.  
• 
Then miniscrews will be placed in upper and lower arches between 2nd 
premolar and 1st molar. 
• 
The patient will be referred for extraction of 1st premolars then canine 
retraction on a 0.017×0.025 StSt arch wire. 
• 
After canine retraction, the patient will be referred for the pre-intervention 
records. 
➢ Acquisition of pre-intervention records: 
• 
The patient will be referred for CBCT which is considered to be the T0 
record. 
➢ Start of Retraction: 
 
Frictionless group:  
• 
A ligature wire will be extended between the canines and miniscrews for 
proper anchorage control. 
• 
Closing retraction T-loops will be fabricated using 0.017 x 0.025 TMA 
wire. The loop will be positioned halfway the remaining extraction space 
after canine retraction. [17], [22]. 
• 
A gable angle of 45˚ will be added. 
• 
Distal activation of 4 mm will be done which produced around 160 g of 
force per side with cinching back the wire distal to molars bilaterally.[23]. 
• 
Reactivation will be only done when the two arms of the t-loop 
approximate 2-3 mm.  
 

18 
 
Friction group:  
• 
Miniscrews will be checked for stability. In case of any dislodgment or 
instability, they will be removed and replaced. 
• 
A crimpable hook of 8mm length will be added to the archwire 
(0.017”x0.025” Stainless steel) distal to the lateral incisors passing through 
the center of resistance of the anterior segment.  
• 
A ligature tie will be tightly wounded from an undercut in the miniscrew 
head to canine bracket to stabilize the posterior segment. 
• 
Retraction will start on a 0.017”x0.025” Stainless steel archwire using 
elastomeric power chain (force applied will be 160 g per side) extending 
between the crimpable hook and the miniscrew head. 
• 
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 mini-screws stability. 
• 
Replacement of the power chain to maintain a force of 160 gm per side. 
• 
Reactivation of the T-loop by further distal activation and cinch back if 
needed. 
  
➢ Criteria for discontinuing or modifying the allocated intervention: 
  
In cases of prolonged swelling or pain related to the mini-screw the patient 
will be given strict oral hygiene measures and the beginning of retraction will 
be postponed for three weeks. 
 

19 
 
In cases of loose or broken mini-screws, the screw will be removed and 
replaced. 
➢ Retraction records 
 
Following retraction of the anterior segment, patients will be referred to the 
same radiology center to acquire the final CBCT to assess the movement and 
inclination of anterior teeth. 
 
➢ Materials 
 
• American Orthodontics Brackets, Roth prescription, 0.022 slot size. 
• American Orthodontics Elastomeric power chains. 
• American Orthodontics Elastomeric O-ties. 
• American Orthodontics Ligature wire. 
• Mini-screw (1.6- by 8-mm, bracket head design; Dual Top Anchor 
System, Jeil Medical Corporation, Seoul, Korea). 
• American Orthodontics Arch wires.  
• American Orthodontics Molar bands/tubes.  
• Crimpable hooks (Dentos Inc.) 
D] Outcomes 
 
Primary outcome: is to monitor the changes in the anterior teeth position 
(final anterior teeth tip, torque and vertical position) in association with each 
technique after retraction  
 
Secondary outcomes: are to detect the presence of any root resorption 
associated with the different methods used for anterior segment. All outcomes 

20 
 
will be assessed as the difference between T0 at the start of anterior segment 
retraction after full canine retraction and T1 after complete space closure. 
E] Participant timeline:  
1. The principle investigator will screen the potential patients through careful 
clinical examination of patients at the orthodontic department, Faculty of Oral 
and Dental Medicine at The Future University of Egypt.  
2. All recruited patients must fulfil 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. After patient's enrolment, each participant will be asked for pre-intervention 
records to ensure proper diagnosis.  
5. The co-supervisor will randomly allocate the patients to one of the 
intervention groups.  
6. Active intervention will start after proper leveling and alignment of the upper 
and lower arches and canine retraction.  
7. The principle investigator will take pre-retraction records for every participant 
(T0).  
8. In Friction mechanics group, Power chain will be used for anterior segment 
retraction while in Frictionless group, T-loop will be used for retraction.  
9. Each patient will come every 4weeks for the follow up visit, for appliance 
activation and impressions for interim records.  
10. After complete space closure, the principle investigator will take post-
retraction records for each participant (Tfinal).  
11. The principle investigator will continue the normal treatment and achieve 
proper finishing for every patient after the end of the study. 
 

21 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Screening of patients seeking 
orthodontic treatment at the 
orthodontic department outpatient
Patient enrollment 
Pre-intervention records 
Concealed Allocation 
Leveling and alignment, miniscrews, 
Extraction, canine retraction.  
Friction group 
Frictionless group 
Activation of PC and T-loop 
Acquisition of post-retraction 
Data collection and management 
Recruitment 
Preparatory 
phase 
Interventions 
Follow up 
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 

22 
 
E] Sample size calculation:  
In a previous study by Dincer et al. [1], they compared the effect of frictionless 
mechanics via PG spring (Poul Gjessing spring) (Group I) and friction mechanics 
using coil spring (Group II). The mean change in distance between central incisor 
edge and x-axis was of 0.68mm and SD of 0.73 in Group I, while Group II was -
0.32mm and SD of 0.79. 
 
Sample size calculation was done based on that study using PS software output. A 
continuous response variable from independent Group I and Group II subjects was 
planned. In the 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 needed to study 10 Group II subjects and 10 Group I 
subjects to be able to reject the null hypothesis. 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 of 15 per group was planned (Figure 1). 
 

23 
 
1.0
0.5
0.0
-0.5
-1.0
1.0
0.8
0.6
0.4
0.2
0.0
Difference
Power
A lpha
0.05
StDev
0.76
A lternativ e
Not =
A ssumptions
11
Size
Sample
Power Curve for 2-Sample t Test
 
  
Statistical Methods  
All statistical calculations will be done using computer program IBM SPSS 
(Statistical Package for the Social Science; IBM Corp, Armonk, NY, USA) release 
22 for Microsoft Windows.  
Numerical data will be tested for the normal assumption using Kolmogorov Smirnov 
and Shapiro Wilk tests. If normal distribution was found; therefore, data will be 
statistically described in terms of mean ± standard deviation (± SD). Student t test 
will be used to compare between the study groups for independent samples in 
comparing normally distributed data. Paired t test will be used within group 
comparisons in comparing normally distributed data and Two-sided p values less 
than 0.05 will be considered statistically significant.  
 
Figure 1: Power curve for 2-sample t-test denoting the power of the study. 

24 
 
F] Recruitment strategy:  
The principal investigator will recruit the patients from the clinic of Orthodontic 
department, Faculty of Oral and Dental Medicine- Future University.  
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 (Friction) or B (Frictionless) using Microsoft 
Office Excel 2007 sheet. and 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:  
The supervisor of the study 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 will send the patient to the secretary 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 leveling and alignment stage.  

25 
 
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. 
 
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 
records. Then two assessors will carry on, blindly and independently, the 
measurements and analysis of the study. 
 
 
 

26 
 
III) Data collection, management and analysis: 
  
A] Data collection methods:  
Primary outcome:  
1. Anterior teeth torque, extrusion/intrusion: will be assessed by the principle 
investigator via CBCT taken before and after the completion of retraction. The 
principal investigator identified the landmarks, reference lines and planes, then 
interpreted the measurements in degrees and millimeters.  
 
2. Anterior teeth tip: will be assessed by the principle investigator via CBCT taken 
before and after the completion of retraction. 
 
Secondary outcomes: 
1. Root resorption: will be assessed by the principle investigator via CBCT taken 
before and after the completion of retraction. The resorption will be identified using 
scoring system of Levander and Malmgren[21] that classifies it into 5 grades: 0: no 
root resorption; 1: mild resorption, with the root of normal length and only an 
irregular contour; 2: moderate resorption, with small areas of root loss and the apex 
having 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. 
 
 
 
 

27 
 
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 and radiographs.  
 
C] Statistical Analysis:  
• The principle investigator will be responsible for the extraction of the required data 
from the CBCT taken before and after retraction 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 used 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.  
 

28 
 
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 Inter-observer and intra-observer reliability 
will be assessed using P ≤ 0.05. 
 
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.  
 

29 
 
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, 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 
department, Faculty of Oral and Dental Medicine, Future University and the Ethics 
Committee will approve such amendment before proceeding in the study .  
 

30 
 
 
 
 
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, Faculty of Oral and Dental Medicine, 
Future 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 Masters’ degree in Orthodontics, Faculty of Oral and Dental 
Medicine, Future University and it is self-funded by the principal investigator.  
 
 
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 

31 
 
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 library and will distribute additional 
copies among the main universities in Egypt. 
 
 
 
 
 
 
 

32 
 
References: 
[1] 
M. Dinçer,  a Gülşen, and T. Türk, “The retraction of upper incisors with the PG retraction 
system.,” Eur. J. Orthod., 2000. 
[2] 
D. A. Bills, C. S. Handelman, and E. A. Begole, “Bimaxillary dentoalveolar protrusion: Traits and 
orthodontic correction,” Angle Orthod., 2005. 
[3] 
W. Proffit, H. Fields, and D. Sarver, Contemporary Orthodontics. 2007. 
[4] 
M. Upadhyay, S. Yadav, and R. Nanda, “Biomechanical Basis of Extraction Space Closure,” in 
Esthetics and Biomechanics in Orthodontics: Second Edition, 2014. 
[5] 
G. L. U. Ribeiro and H. B. Jacob, “Understanding the basis of space closure in Orthodontics for a 
more efficient orthodontic treatment,” Dental Press J. Orthod., 2016. 
[6] 
M. R. Pacheco, W. C. Jansen, and D. D. Oliveira, “The role of friction in orthodontics,” Dental 
Press J. Orthod., 2012. 
[7] 
C. J. Burstone, “The segmented arch approach to space closure,” Am. J. Orthod., 1982. 
[8] 
C. J. Burstone and H. A. Koenig, “Optimizing anterior and canine retraction,” Am. J. Orthod., 1976. 
[9] 
Y. S. Chun, J. N. Rhee, and J. Row, “A comparison between friction and frictionless mechanics 
with a new typodont simulation system,” Am. J. Orthod. Dentofac. Orthop., 2001. 
[10] 
J. Y. Tominaga, M. Tanaka, Y. Koga, C. Gonzales, M. Kobayashi, and N. Yoshida, “Optimal loading 
conditions for controlled movement of anterior teeth in sliding mechanics,” Angle Orthod., 2009. 
[11] 
M. El Koussy, “Effect of Friction versus Frictionless Mechanics on the rate of anterior segment 
retraction: A systematic review. Thesis. Cairo University.2015.” 
[12] 
L. Samsonyanová and Z. Broukal, “A systematic review of individual motivational factors in 
orthodontic treatment: Facial attractiveness as the main motivational factor in orthodontic 
treatment,” International Journal of Dentistry. 2014. 
[13] 
C. Chaudhari and S. Tarvade (Daokar), “Comparison of rate of retraction and anchorage loss using 
nickel titanium closed coil springs and elastomeric chain during the en-masse retraction: A 
clinical study,” J. Orthod. Res., 2015. 
[14] 
M. Barlow and K. Kula, “Factors influencing efficiency of sliding mechanics to close extraction 
space: A systematic review,” Orthodontics and Craniofacial Research. 2008. 
[15] 
L. Almeida, A. Ribeiro, R. P. Martins, R. Viecilli, and L. P. Martins, “Nickel titanium T-loop wire 
dimensions for en masse retraction,” Angle Orthod., 2016. 
[16] 
J. Chen, D. L. Markham, and T. R. Katona, “Effects of T-Loop Geometry on Its Forces and 
Moments,” Angle Orthod., vol. 70, no. 1, pp. 48–51, 2000. 
[17] 
A. J. Kuhlberg and C. J. Burstone, “T-loop position and anchorage control.,” Am. J. Orthod. 
Dentofacial Orthop., 1997. 

33 
 
[18] 
P. Ziegler and B. Ingervall, “A clinical study of maxillary canine retraction with a retraction spring 
and with sliding mechanics,” Am. J. Orthod. Dentofac. Orthop., vol. 95, no. 2, pp. 99–106, 1989. 
[19] 
B. F. Gribel, M. N. Gribel, D. C. Frazão, J. A. McNamara, and F. R. Manzi, “Accuracy and reliability 
of craniometric measurements on lateral cephalometry and 3D measurements on CBCT scans,” 
Angle Orthod., 2011. 
[20] 
A. R. El-Beialy, M. S. Fayed, A. M. El-Bialy, and Y. A. Mostafa, “Accuracy and reliability of cone-
beam computed tomography measurements: Influence of head orientation,” Am. J. Orthod. 
Dentofac. Orthop., 2011. 
[21]      E. Levander and O. Malmgren, “Evaluation of the risk of root resorption during orthodontic 
treatment: A study of upper incisors,” Eur. J. Orthod., 1988. 
[22] 
G. Thiesen, M. V. N. N. do Rego, L. M. de Menezes, and R. H. Shimizu, “Force systems yielded by 
different designs of T-loop.,” Aust. Orthod. J., vol. 21, no. 2, pp. 103–10, 2005. 
[23] 
C. J. Burstone, “Modern Edgewise Mechanics.” 1995.