The aims of this study were to: -

• Evaluate PBF in upper and lower teeth during orthodontic alignment using fixed appliances (0.014" super elastic NiTi arch wire) at different time intervals (20min, 48h, 72h and 1 month) of initial arch wire placement.
• Evaluate the PBF in upper and lower teeth during orthodontic teeth alignment using clear aligners at different time intervals (20min ,48h, 72h and 1 month) of fitting the second aligner (first active aligner).
• Compare the PBF changes between the above two different types of orthodontic appliances (fixed appliances and the clear aligners).

Aims: to evaluate the pulpal blood flow (PBF) during orthodontic teeth alignment and leveling using clear aligners (second aligner) and fixed orthodontic appliance at different time intervals of orthodontic force application.

Materials and Methods: A total of 45 subjects were subdivided in two groups: group 1: 25 subjects treated with pre-adjusted edgewise fixed appliance with 0.014 inch NiTi as the alignment arch wire and group 2: 20 subjects treated using clear aligner. In both groups, PBF was measured for the upper right and the lower left using Laser Doppler Flowmetry at different time interval (20 minutes, 48 hours, 72 hours, 1 month) after the fitting of the arch wire in group one and after the delivery of the second aligner in group two.

Inclusion Criteria:

• Both male and female subjects
• 16 or more years old
• Class I skeletal malocclusion
• mild upper and lower arches crowding. Exclusion Criteria:-
• Poor oral hygiene
• Previous orthodontic treatment
• Active periodontal disease
• Missing teeth
• Deep carious teeth
• Teeth with root resorption
• Endodontically treated teeth
• History of previous trauma
• Restoration on measured teeth
• Medical conditions affecting blood vessels
• Smoking