Comprehensive Comparison of Canine Retraction Using Nickel-titanium Closed-coil Springs Versus Elastomeric Power Chains During Orthodontic Treatment - A Split-mouth Randomized Controlled
Phase: NA
Conditions: Root Resorption, Plaque Accumulation, Gingivitis
Sponsor: Munnal Gulzar

 
 
Comprehensive Comparison of Canine 
Retraction using Nickel-titanium Closed-coil 
Springs Versus Elastomeric Power Chains 
during Orthodontic Treatment – A Split-mouth 
Randomized Controlled 
 
 
 
Dr. Munnal Gulzar 
BDS, FCPS trainee 
Orthodontics, Section of Dentistry 
The Aga Khan University Hospital 
munnal.gulzar@aku.edu 
 
 
Dr. Mubassar Fida 
BDS, MCPS & FCPS (Orthodontics), MCPS (Periodontology),  
MCPS (Community Dentistry), PGD HIMS  
Consultant Orthodontist/ Professor, 
Section of Dentistry, Department of Surgery, 
The Aga Khan University Hospital, P.O Box 3500, Stadium Road, Karachi 74800, Pakistan 
mubassar.fida@aku.edu 
 
 
Date: 11 December 2023 
NCT no.: Not assigned 
 
 
Dental Section, Department of Surgery 
The Aga Khan University Hospital, 
Karachi

TITLE: Comprehensive Comparison of Canine Retraction using Nickel-titanium 
Closed-coil Springs Versus Elastomeric Power Chains during Orthodontic Treatment – A 
Split-mouth Randomized Controlled Trial 
 
Address and telephone number of the trial site: 
Dentistry section at Aga Khan University Hospital, Stadium Road Karachi. 
Phone number: 0334-3536106 
Email: munnal.gulzar@aku.edu  
 
Primary Investigator: 
Dr. Mubassar Fida 
BDS, MCPS & FCPS (Orthodontics), MCPS (Periodontology),  
MCPS (Community Dentistry), PGD HIMS 
 
Consultant Orthodontist/ Professor, 
Section of Dentistry, Department of Surgery, 
The Aga Khan University Hospital, P.O Box 3500, Stadium Road, Karachi 74800, Pakistan 
mubassar.fida@aku.edu 
 
Investigator:  
Dr. Munnal Gulzar 
BDS 
Resident Orthodontics, Section of Dentistry, Department of Surgery, 
The Aga Khan University Hospital, P.O Box 3500, Stadium Road, Karachi 74800, Pakistan 
 
 
 
 

TITLE: Comprehensive Comparison of Canine Retraction using Nickel-titanium Closed-
coil Springs Versus Elastomeric Power Chains during Orthodontic Treatment – A Split-
mouth Randomized Controlled Trial 
INTRODUCTION: 
Extraction versus non-extraction treatment has always been a debate in orthodontics but with the 
passage of time extraction treatment due to its greater stability has gained popularity.1,2  In patients 
with severe crowding and/or proclination of teeth, extraction of first premolars followed by 
retraction of canines has been a common and preferred practice.3  Canine retraction is a time-
consuming procedure and acceleration of this process will shorten the treatment time and also help 
in avoiding the related adverse effects.4,5 
The most common techniques used for canine retraction are sliding and loop mechanics which 
have been discussed frequently in literature.6  Both techniques possess their merits, encompassing 
advantages, such as minimal friction and precise manipulation of space closure using loops.7  
Whereas, while using sliding mechanics, one can have the benefits of reduced wire bending time, 
control of arch form and root alignment.7  However, both of these methods have their limitations.  
With loop mechanics, the additional chair side time, skills, soft tissue irritation, root resorption, 
bacterial build up and uncontrolled tipping present a challenge.8,9  Friction and binding of wire to 
the bracket slot results in slow tooth movement and anchorage loss with sliding mechanics.9 
Despite its limitations, sliding mechanics is a common technique used for canine retraction.10  The 
two widely used methods for sliding teeth include elastomeric power chains and Nickel-titanium 
(Ni-Ti) closed-coil springs.11  Elastomeric power chains are extensively used in orthodontics 
because of their ease of use, effectiveness and patient comfort by allowing periods of 
regeneration.12  Elastomeric power chains exert heavy intermittent forces when they return to their 
original length after being stretched, with decay of forces as they revert, requiring a greater number 
of appliance activation.13 
On the other hand, Ni-Ti closed-coil springs apply light continuous forces and deliver a constant 
force over a period that lead to more efficient tooth movement and steadier space closure14, with 
reduced number of appliance activation.15  An in vitro study by Barsoum et al.16 reported a 
reduction in force with Ni-Ti closed-coil springs after 18 hours and remained constant for about 

21 days.  Badran et al.17 also found that Ni-Ti closed-coil springs were less tolerated than 
elastomeric power chains by patients but produced an average of 0.5 mm more tooth movement 
than the elastomeric power chain during the 12-week study period.  Therefore, consideration of 
canine retraction with Ni-Ti closed-coil springs and elastomeric power chains is critical for 
enhancing the overall effectiveness of orthodontic treatment and to achieve desired treatment 
outcomes. 
RATIONALE: 
Premolar extraction followed by canine retraction is one of the common practices in orthodontics 
to treat malocclusion such as severe crowding and proclination of anterior teeth.18  It is essential 
to know methods and techniques that result in minimum or no adverse effects on roots of teeth and 
periodontal health.  This will help the clinicians to choose the best method that will result in a 
faster and more physiological closure of extraction spaces.  Moreover, to the best of our 
knowledge, limited studies have compared the effects of Ni-Ti closed-coil springs and elastomeric 
power chains on canine root resorption, gingival health and plaque accumulation.8,17,22  It is 
necessary to establish a comparison between these methods, as it can help clinicians to provide 
better care and enhance the overall effectiveness of orthodontic treatment.   
OBJECTIVE: 
Primary Objective: The objective of this study is to compare the canine retraction rate (in mm 
with a 100 mm marked scale) using Ni-Ti closed-coil springs versus elastomeric power chains 
during canine retraction in subjects with first premolar extractions over a period of three months. 
Secondary Objective: This study will also include an assessment of canine root resorption (in 
mm using periapical radiograph), dental plaque accumulation and gingival health (according to 
indices mentioned below with CPI-TN probe) using Ni-Ti closed-coil springs versus elastomeric 
power chains during canine retraction in subjects with first premolar extractions over a period of 
three months. 
 
 
HYPOTHESIS: 

Null Hypothesis: There is no significant difference between Ni-Ti closed-coil spring and 
elastomeric power chain on the canine root resorption, retraction rate, dental plaque accumulation 
and gingival health in subjects with first premolar extractions. 
Alternate Hypothesis: There is a significant difference between Ni-Ti closed-coil spring and 
elastomeric power chain on the canine root resorption, retraction rate, dental plaque accumulation 
and gingival health in subjects with first premolar extractions. 
OPERATIONAL DEFINITIONS: 
Ni-Ti Closed-coil Spring:19 (Annexure A) 
Ni-Ti closed-coil spring is a passive compressed spring made up of super elastic Nickel-titanium.  
Two eyelets are attached to each side of the coil to facilitate its application.  The eyelets will be 
engaged in the hooks of the second premolar and canine brackets and will apply a force of 150 
gm. 
Elastomeric Power Chain:20 (Annexure B) 
Elastomeric power chains are resilient and latex-free orthodontic materials.  They are made up of 
elastic material and consist of many connected rings.  Each ring is engaged in a bracket to apply a 
force of 175-300 gm. 
Plaque Index:17 (Annexure C) 
Plaque index is a grading system used to assess the amount of plaque present at the gingival 
margins and helps in assessing oral health.  It consists of four grades including, Grade 0, 1, 2 and 
3.  The increase in grade indicates the increased amount of plaque along the gingiva. 
Gingival Index:21 (Annexure D) 
Gingival index is a grading system that is used to assess the health of the gingiva.  It consists of 
four grades including, Grade 0, 1, 2 and 3.  The increase in grade indicates the compromised 
gingival health of the teeth. 
 
Root Resorption:22 

Root resorption is a decrease in root length and width due to an inflammatory process.  In 
orthodontics, during tooth movement, areas of necrosis develop called hyalinized areas, which 
result in root resorption.  Periapical radiographs will be taken to assess the amount of root 
resorption by determining the length of the tooth from the cusp tip to the root apex.  
Retraction Rate:16 
The retraction rate of canine will be the distance travelled divided by the time interval needed for 
closure of spaces.  It will be noted at four-time intervals i.e at the start of the canine retraction (T0), 
after first month (T1), second month (T2) and third month follow-up (T3). 
Split-mouth Study: 
A randomized controlled trial in which intervention and control are randomly allocated to the 
different quadrants in the oral cavity.  In our study, Ni-Ti closed-coil springs and elastomeric 
power chains will be randomly allocated to the right and left quadrants of maxillary and 
mandibular arches. 
MATERIAL & METHODS: 
Study Design:  A single center open labelled parallel split-mouth randomized controlled trial 
Settings:  Dental clinics, Department of Surgery, The Aga Khan University Hospital, Karachi, 
Pakistan 
Study Duration:  One year after ethical review committee (ERC) approval 
Sampling Technique:  Non-probability consecutive sampling 
SAMPLE SIZE:  
The sample size was calculated using standard estimate where n = 8(CV2) /(PC2) [1+(1-PC)2] 
where PC is the proportionate change in means (PC = (μ0 −μ1)/μ0) and CV is the coefficient of 
variation (CV = σ0/μ0 = σ1/μ1).  The study required a minimum sample size of 33 (N) patients in 
each group.  With an inflation of 40% for an estimated loss to follow up/non-response rate, we 
will be including 46 (N) participants in this study, to achieve 80% power and to detect at least a 
39% change in mean canine retraction rate values of 3.88 ± 2.66 mm and 5.45 ± 1.53 mm, with 

elastomeric power chains and Ni-Ti closed-coil springs, respectively8 and 68% or less change in 
coefficient of variation at two-sided 5% level of significance. 
SAMPLE SELECTION:  
Inclusion Criteria: 
 
Patients aged between 13 - 40 years   
 
Patients undergoing fixed orthodontic treatment  
 
Patients requiring all first premolars extraction as part of orthodontic treatment 
 
Patients with all permanent teeth present and erupted (except for second and third molars) 
 
All patients who will sign the informed consent/assent form   
Exclusion Criteria:  
 
Patients with systemic diseases that can affect tooth movements 
 
Patients with uncontrolled periodontal disease   
 
Patients with craniofacial syndromes 
 
Pregnant or lactating mothers 
 
Patients with bracket failures greater than three times per bracket during the study 
 
Patients on medications that can affect tooth movements  
 
Patients with Nickel allergy 
DATA COLLECTION PROCEDURE: 
After obtaining an approval from the Ethical Review Committee and taking informed consent and 
informed assent from the parents and child respectively, (Annexure E, F and G), these patients 
will be recruited in the study as participants.  Patients visiting the orthodontic clinic at the Aga 
Khan University Hospital Karachi will be included in this study.  Detailed information regarding 
the study will be provided to the participants and they will be given the choice to either accept or 
refuse their inclusion in the study.  After the extraction of all first premolars under local anesthesia, 
0.018” stainless steel archwires will be inserted in the maxillary and mandibular arches.  For canine 
retraction, Ni-Ti closed-coil springs and elastomeric power chains will be randomly allocated to 
the right and left quadrants of both arches.  Radiographic measurement (root resorption) and 
clinical measurements (canine retraction, plaque accumulation and gingival health) will be 

recorded at four points in time.  First, at the start of the canine retraction (T0), after first month 
(T1), second month (T2) and third month follow-up (T3).  Canine retraction rate will be recorded 
by using a 100 mm marked scale.16  Data will be collected on an organized study proforma 
(Annexure H).   
Ethical Considerations:  
This study will be carried out as per the guidelines of the World Medical Association’s Declaration 
of Helsinki.23 and the principles of Good Clinical Practice (GCP).  Any modifications in the 
protocol will be re-submitted to the ERC.  The study will be conducted in compliance with 
regulations and a copy of the final study protocol will be submitted to ERC.  All the recorded data 
of patients will remain confidential.  Access will be provided to no one except the investigators.  
Participants’ names and identities will remain undisclosed; however, data may be seen by ERC or 
any local regulatory body.  Data will be saved for 7 years as per GCP and institutional guidelines.   
Randomization: 
Randomization will be used in the study to allot one of the two treatment methods used for canine 
retraction to each side of the mouth to minimize bias and to account for individual variability.  By 
randomly assigning different retraction methods to each side of the mouth any individual-specific 
factors that may affect the treatment outcomes (oral hygiene habits, masticatory habits) are likely 
to be equally distributed across the treatment group.  Block randomization will be performed to 
code the type of retraction method in this trial and to determine the sequence of its administration 
to each participant.  This will be controlled by a research faculty member of the Section of 
Dentistry at AKUH.  
Sequence Generation: 
In this two-armed study, four-blocks, each with a block size of six-possible allocation sequences 
for treatment arms will be generated.  
(1) AABB, (2) BBAA, (3) ABAB, (4) BABA, (5) ABBA, (6) BAAB  
The blocks to be utilized and their order will be determined by the research faculty member using 
sealed envelopeTM online software.24 

Allocation Sequence Concealment: 
After fulfilling the inclusion criteria and obtaining consent, the patient will be recruited in the 
study.  During the recruitment of the participants in the trial, the sealed envelope for a participant 
will be opened by the enrolling team member and will be allotted an intervention according to the 
ascending order sequence already generated by the principal investigator who is also a 
biostatistician. 
Enrollment: 
After obtaining approval from the ERC (AKUH), each participant fulfilling the inclusion criteria 
for the study and consenting to participate in the trial will be assigned a participant ID. 
Blinding: 
The study investigators, patients recruited, and assessors will not be blinded during the trial.  All 
the measurements will be recorded by the co-investigator on the study proforma (Annexure H). 
POSSIBLE RISKS OR BENEFITS: 
Nickel is a known allergen, though people with nickel allergy tolerate stainless steel brackets and 
wires quite satisfactorily.25  However, in case of any adverse events such as  allergic reaction to 
Ni-Ti closed-coil spring such as contact dermatitis, rash, bumps, redness or irritation of the skin 
or mucosa, its use will be stopped, and patient will be excluded from the study. 
Adverse events will be reported to ERC within a week and any serious adverse event will be 
reported to the Department of surgery, sponsors, CTU, DRC, and ERC within 24 hours.  All 
emergency side effects will be managed in the emergency department and the Department of 
Surgery will bear the charges.   
 
 
STUDY GROUPS:  

The patients will be screened using the inclusion and exclusion criteria by the co-investigator.  
Measurements for the canine root resorption, retraction rate, plaque accumulation and gingival 
health will be taken at T0, T1, T2 and T3.   
Intervention: Ni-Ti closed-coil springs 
Control: Elastomeric power chains 
The participants will receive routine instructions for oral hygiene maintenance and care of the 
appliance verbally. 
MATERIAL STORAGE: 
Ni-ti closed-coil springs and Elastomeric power chains will be stored at room temperature at the 
Department of Surgery, Dental inventory.   
DATA ANALYSIS:  
Data will be entered and analyzed in SPSS for Windows (version 23.0, SPSS Inc. Chicago).  
Frequencies and proportions will be reported for categorical variables, such as gender.  Shapiro-
Wilk test will be used to check the normality of the data.  Descriptive statistics, such as means and 
standard deviations for normally distributed or median and interquartile range (IQR) for non-
normally distributed data will be reported for all baseline clinical factors.  Paired t-test will be used 
for the pairwise comparison.  For the two groups the mean/median scores for retraction rate, root 
resorption, gingival health and plague accumulation between the two groups will be assessed using 
Independent t-test for normally distributed data and Man-Whitney U test for non-normally 
distributed data.  A p-value < 0.05 at 95% confidence interval will be considered as statistically 
significant. 
On achieving 50% of the sample size, an interim analysis will be run, if the results show that the 
given intervention is successful in significantly improving the rate of canine retraction in patients 
then further trial will be stopped and all the participants will be given the intervention. 
FINANCE: 
Departmental funds from the Department of Surgery and intramural grants will be applied for.   

PUBLISHING POLICY/PLAN: 
For publication the data will be utilized, and it could be presented in either national or worldwide 
forums.   
DATA CONFIDENTIALITY: 
All the recorded data of patients will remain confidential.  Access will be provided to no one except 
the investigators.  Participants’ names and identities will remain undisclosed; however, data may 
be seen by ERC or any local regulatory body.  Data will be saved for 7 years as per GCP and 
institutional guidelines. 
 
 

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Annexure A: Ni-Ti Closed-coil Spring19 
 
 
 
 
 

Annexure B: Elastomeric Power Chain20 
 
 
 
 
 

Annexure C: Plaque Index17 
0 
No plaque 
1 
Thin plaque layer at the gingival margin, only detectable by scraping 
with a probe 
2 
Moderate layer of plaque along the gingival margin; inter-dental 
spaces. Plaque is visible to the naked eye 
3 
Abundant plaque along the gingival margin; interdental spaces filled 
with plaque 
 
 
 

Annexure D: Gingival Index21 
0 
Normal gingiva; no inflammation; no discoloration (erythema); no 
bleeding 
1 
Mild inflammation; slight erythema; minimal superficial alterations; no 
bleeding 
2 
Moderate inflammation; erythema; bleeding on probing 
3 
Severe inflammation; severe erythema and swelling; tendency to 
spontaneous bleeding; possible ulceration