The aim of this study is to compare the effectiveness of using heat-activated NiTi with superelastic NiTi archwires during the initial phase of orthodontic treatment.

Primary Objective:

To compare the difference in the amount of crowding in the lower incisors after 4 and 8 weeks from the start of treatment.

Secondary Objectives:

1. To compare the amount of orthodontically-induced inflammatory root resorption (OIIRR) in the apical region of mandibular central incisors between the two groups of archwires
2. To compare the amount of pain perception between the two groups of archwires during the 1st week after each wire placement.

Objectives: To compare the heat-activated nickel titanium (HANT) with superelastic nickel titanium (SENT) archwires in terms of their effectiveness in aligning teeth, possibility of inducing root resorption, and patient perception of pain during the initial phase of treatment.

Subjects and Methods: Orthodontic patient aged 12 years or over with lower anterior crowding of 3-6 mm. who need treatment without extraction, were randomly allocated to the HANT and SENT archwires groups with a 1:1 allocation ratio. Archwire sequence in both groups was 0.014-inch and 0.016-inch, respectively. Each archwire was placed for 4 weeks. Outcome measures included the amount of crowding using Little's irregularity index (LII), apical root resorption, and pain perception. The effectiveness of alignment was tested using 2X2 mixed factorial ANOVA, while root resorption and pain perception were tested by the Mann-Whitney U test, and Wilcoxon signed-rank test (P<0.05).

Inclusion Criteria:

1. Patients indicated for fixed appliance orthodontic treatment who have a moderate crowding (3-6mm) according to the Little's irregularity index (LII).
2. Full set of lower permanent dentition excluding the third molars.
3. No history of trauma or root resorption in the lower incisors.

Exclusion Criteria:

1. Previous orthodontic treatment.
2. Less than 3mm of lower incisor crowding (LII) or with spaced incisors.
3. Severe crowding in the lower arch (greater than 7mm) which requires extraction.
4. Blocked-out teeth that cannot be engaged with the aligning archwire.
5. Patients with periodontally compromised teeth.

Materials, Methods, Results

Blinding to treatment allocation was possible only for the investigator and data analyst because the clinicians could know the type of archwiers from their flexibility. All the trial documents were labeled with the study ID number, which was used for participant identification and data collection without unmasking the allocation group. This allowed the investigator to complete data collection and measurements blindly.