The objectives if this study was to evaluate the efficacy of 3 different rectangular archwires in the correction of the curve of Spee (COS), to record the time needed to level excessive COS in the mandibular arch using the 3 archwire sizes, to investigate the changes in intercanine and intermolar widths and arch length during leveling, to measure the arterio-posterior and vertical movement for the lower incisors and lower molars, to record pulpal blood flow and to detect the root resorption in the lower anterior teeth associated with leveling excessive COS using the 3 different archwires.

Fifty one subjects with an excessive COS were included in this study. The subjects will be randomly divided into three groups; Group one (17 patients): leveling of COS using 0.017X0.025-inch stainless steel archwire. Group two (17 patients): leveling of COS using 0.019X0.025-inch stainless steel archwire. Group three (17 patients): leveling of COS using 0.021X0.025-inch Titanium molybdenum archwire.

In the three groups, a 5mm depth reverse COS will be inserted. Records consisted of lateral cephalograms (pre-treatment, at T0 and post-treatment), peri-apical radiographs (at T0 and at T5), study casts (pre-treatment and at each time point during the tudy). Patients will be followed up on monthly visits without removing leveling archwires where alginate impressions were taken for the lower arch. Pain scores during the first week of leveling will be recorded using visual analogue scale (VAS).The amount of COS correction in mm, changes in intercanine in mm, intermolar and arch length in mm, pain scores and lower incisors root resorptions in mm will be measured.

Inclusion Criteria:

• Age ≥ 16 years and ≤ 30 years
• Overbite covering more than half of the lower incisor height
• Curve of Spee ≥ 4 millimeters
• Mild crowding in lower arch where non-extraction treatment is indicated.
• Normally inclined or retroclined lower incisors
• Averaged or reduced lower vertical height
• Good oral hygiene and healthy periodontium
• All permanent teeth are present except for the third molars

Exclusion Criteria:

• Severe crowding in lower arch where extraction treatment is indicated.
• Missing permanent molars or Premolars
• Poor oral hygiene and Periodontal disease
• Systemic health problems and medications were taken
• History of previous orthodontic treatment
• Smoking

The patient was blinded to the intervention used. However, it was not possible to blind the clinician during treatment.