Study Design and any Changes after Trial Commencement
This single-center study was a 2-arm parallel randomized clinical trial with a 1:1 allocation. The methods were not changed after the initiation of the trial.
Participants, Eligibility Criteria, and Settings
The study was reviewed and approved by the Institutional Review Board Committee (IRB) at King Abdallah Hospital/ Jordan University of Science and Technology (JUST) with approval number 2016/124/89. Participants were recruited from new patients attending postgraduate orthodontic clinic at JUST during the period between February/2017to July/2017. Patients who agreed to participate in the study and fulfilled the following criteria were included in this study:
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Caucasian patient requiring complete upper and lower orthodontic treatment with fixed appliance without any additional appliances (e.g. Quad-helix, trans-palatal arch or headgear).
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Class I malocclusion.
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Medically-fit patients with no medical condition associated with RR risk.
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Adequate oral hygiene and no periodontal diseases; before the start of orthodontic treatment, the subjects were referred to the periodontal department to check periodontal conditions and for regular oral car
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No prior orthodontic treatment.
Patients were excluded if they had cleft lip/palate or any other syndromes, hypodontia, spacing in the anterior region or well aligned teeth, had a periapical infection in any tooth, endodontic treatment for mandibular or maxillary anterior teeth10 or had blocked-out tooth that did not allow for placement of the bracket and full AW engagement at the initial bonding appointment. Patients with parafunctional habits or history of dental trauma or pre-existing RR were excluded as well11–12. Informed consent was signed by the patient or by the parent of the patient if under 18 years of age after we clarified the purpose of the intervention and the associated risks and benefits.
Interventions
All patients were treated using pre-adjusted edgewise fixed appliance from 3M®Unitek Company (Victory Series, 3M Unitek, Monrovia, California, USA; slot 0.022”; Roth prescription). Treatment started with bonding all teeth in the upper and lower arches. In group A the AW sequence used was 0.014 NiTi AW followed by 0.019x0.025 NiTi AW then 0.019x0.025 stainless-steel AW. The AW sequence used for group B was 0.014 NiTi AW followed by 0.018 NiTi AW, 0.016x0.022 NiTi AW, 0.019x0.025 NiTi AW then 0.019x0.025 SS AW. All archwires used for both groups were from 3M Unitek® Company (3M Unitek, Monrovia, California, USA) and all NiTi wires were of superelastic type. Archwires were tied and fully engaged to all bracket slots in both groups using elastic ligatures (Ormco, California, USA) in figure of eight configuration. Patients were recalled every 45 days and they were reminded of their appointments either by phone calling or by text messages one to two days earlier.
In group A, the 0.014 NiTi AW was retied in the same way to the brackets in the 45 days’ interval appointments until this AW was passively engaged in the brackets slots after which the 0.019x0.025NiTi AW was inserted and tied until it is passively engaged in all brackets, after that the 0.019x0.025SS AW was placed.
For group B, all archwires used in the sequence 0.014NiTi AW, 0.018NiTi AW, 0.016x0.022NiTi AW, 0.019x0.025NiTi, AW were left fully engaged in all bracket slots for 45 days before retying or proceeding to the next AW in the sequence until reaching the working AW. All patients were treated by the same investigator (M.A.).
Outcomes (Primary and Secondary) and any Changes after Trial Commencement
Age, gender and incisor relationship (according to British Standard Classification of Malocclusion, 1983) were recorded in the examination session.
Primary Outcomes
Good quality alginate (Hydrogum from Zhermack Company, Badia Polesine – Italy) impressions to fabricate study models were taken before treatment (T1) for the upper and lower arches. Three-dimensional digital casts were generated from plaster models using Ceramill Map 400 scanner (Amann Girrbach, Koblach, Austria), which is accurate to 0.02 mm. Pretreatment crowding was measured in millimeters from the digital casts using Ceramill Mind design software (Amann Girrbach). The degree of crowding in the lower and upper arches was measured by calculating the difference between the summation of the mesio-distal widths of the incisors, canines and premolars and the arch space available between the mesial contact points of the first molars. Available space was measured by summing the distance between the mesial contact point of the first molar to the distal contact point of the canine and the distance from the distal contact point of the canine to the mesial contact point of the central incisor on both sides of the arch13. Lower labial segment irregularity was recorded according to the irregularity index described by Little (1975)14. Upper labial segment irregularity was measured by the same way8,15. The degree of maximum displacement was measured from the most severely displaced tooth to the line of the arch.
Speed of Alignment
Alignment speed was assessed by calculating the number of visits and time in days between the first day of treatment (T1) and the day working AW was reached (T2) for each patient.
Secondary Outcomes
Root Resorption
To assess RR, digital periapical radiographs were taken for the upper and lower incisors for each patient using intraoral sensors from KAVO Company. Those sensors were scanned using DIGORA® Optime scanner and a digital version of the radiograph was imported from the scanner to personal computer (PC) using Digora for Windows 2.5 software which has an accuracy up to 0.01 mm.
Two radiographs were taken for each incisors, the initial radiographs were taken before bond-up and the final radiographs were taken when the working AWs were placed. Crown length from the cemento-enamel junction to the incisal-tip was measured from the initial radiograph (C1) and the final radiograph (C2), root length was measured from the cemento-enamel junction to the tip of the root in both initial (R1) and final (R2) radiographs. A correction factor for magnification between the start and end-point radiographs was calculated as C1/C2. Apical RR was measured using the formula8:
Apical RR = R1 − R2 × (C1/C2 ).
There were no outcome changes after the initiation of the trial.
Sample Size Calculation
Sample size calculation was performed using G*power 3.1.9.4.(1) assuming a large effect size (0.85). The calculation revealed that 46 patients are required (23 patients per group) to achieve a power (1-β error) of 80% at alpha level of (0.05). Eight patients were added to compensate for attrition rate of 15% to compensate for nonresponsive and/or incomplete data.
Interim Analyses and Stopping Guidelines
Not applicable.
Randomization (Random Number Generation, Allocation Concealment, Implementation)
Participants were randomly allocated to either group A or group B. Randomization sequence was created using Excel 2010 (Microsoft, Redmond, WA, USA) with a 1:1 allocation using random block size 2. The allocation sequence was concealed in sequentially numbered, opaque and sealed envelopes from the investigator (K.A.) responsible for assigning participants into the intervention groups until the time of allocation implementation. Randomization sequence creation and allocation concealment were applied by another operator (S.A.).
Blinding
Blinding of the investigator (M.A.) was not possible during clinical intervention and only participants were blinded to the type of AW sequence used. Blinding of the investigator was implemented at data measurement stage as the investigator (M.A.) was blinded to which AW sequence was used for each participant by coding all 3D models. The investigator (K.A.) who did the statistical analysis was blinded to the type of AW sequence used in each group.
Statistical Analysis (Primary and Secondary Outcomes, Subgroup Analyses)
Data analysis included descriptive and analytic statistics obtained with Statistical Package for the Social Sciences (SPSS) software, version 23.0 (Chicago, Ill). Data were checked for normality. Descriptive statistics were calculated and both study groups were compared for pretreatment characteristics. Comparisons were conducted using t-test or chi-square test; depending on the examined variable (numerical or categorical). Statistical significance was predetermined at the P ≤ 0.05 level for all tests.
Independent t-test was used to compare the average time and number of visits required to reach the working AW and the mean magnitude of root resorption for each incisor in the two groups.
Measurement Error
Intra-examiner reliability for RR and study models measurements was determined by having 15 models and 30 radiographs re-measured six weeks after the original measurements.