This study is intended primarily to compare the alignment efficiency and rate of two different types of archwires that are used in the first stage of orthodontic treatment , also addressing pain and root resorption that may be associated during treatment, with the hypothesis being a consideration of no deference between the two archwires.

This will be a multicenter non-stratified prospective randomized clinical trial with parallel groups trial with equal randomization (1:1 allocation ratio), two public orthodontic center will allocate patients for this trial. The patients will be initially assessed for eligibility to be included in the study by the investigator. Those who will meet the inclusion criteria will be informed about the nature of the study verbally to take the initial approval for participation. Then they will be provided by the patient information sheet and consent form, which explains the nature of the study, to read carefully at home and provide their decision about participation at the subsequent appointment. If the patient age below 18 years, parent assent should be taken. Any further enquiries regarding the study by the patient should be resolved by the investigator on the second visit.

The patients will be treated with straight wire appliance using MBT prescription brackets with 0.022-inch slot (Pinnacle®, Ortho Technology, USA). Bracket placement will be standardized using a height gauge. Initially, teeth polishing will be performed with pumice and rubber cup for 10 seconds using a low-speed handpiece, followed by water rinsing and air drying (oil-free air spray for 30 seconds). Bonding technique will be standardized as follows:

• Teeth etching with 37% phosphoric acid gel for 30 seconds.
• Rinsing thoroughly (5 seconds per tooth for liquid etchant and 10 seconds per tooth for gel etchant) to stop the etching process and to remove demineralized particles then air drying until the white frosty appearance of the etched surface is observed.
• Application of a thin layer of Light Bond™ Sealant (Reliance®, Itasca, USA) for one minute and air application for 5 seconds.
• Bonding of brackets and tubes using Light Bond™ light cure orthodontic adhesive (Reliance®, Itasca, USA) applied on their bases and light-cured above interproximal contacts at a distance of 2-3 mm (5 seconds mesially and 5 seconds distally for brackets and 10 seconds mesially and 10 seconds occlusally for molar tubes).

All the participants will receive a standardized treatment protocol. At the day of bonding, 0.016-inch archwire will be placed for the Smartarch group. It will be re-ligated every four weeks. While, for the super elastic NiTi group, 0.014-inch archwire will be placed at the day of bonding and eight weeks later it will be replaced by the 0.018-inch archwire for another eight weeks. Archwires will be tied to the bracket by elastomeric modules, with laceback of canines to first molars. If there is any debonding during treatment, this should be dealt with as an emergency case and re-bonded within 24 hours, otherwise the case will be considered as dropout. Since this study will be performed during the initial phase of treatment, no deviation in the protocol of treatment will be accepted (such as adding additional archwire in the sequence or using power chain). A good-quality alginate impression for the lower arch should be taken pre-treatment and after 4, 8, 12 and 16 weeks and a stone study model is obtained. Periapical X-ray for the mandibular central incisors will be taken pre-treatment and after 16 weeks. The participants will be provided by a visual analog scale (0-10) to record their pain perception during the first week after each wire placement.

Inclusion Criteria:

• Patients indicated for fixed appliance orthodontic treatment with 5-9 mm crowding of mandibular anterior teeth according to Little's irregularity index (LII).
• Presence of all mandibular permanent teeth, except the third molars.
• Overbite and overjet that do not interfere with bracket placement on mandibular anterior teeth.
• No history of trauma or root resorption in the mandibular incisors.

Exclusion Criteria:

• Previous orthodontic treatment.
• Less than 5mm of mandibular incisor crowding (LII).
• Blocked-out teeth that cannot be engaged with the aligning archwire.
• Prior experience of periodontal disease and loss of attachment.

It will be available on request.