For the groupteated with Clear Aligners (CA), the treatment provided the application of Invisalign clear aligner system and the absence of any other auxiliaries apart from Invisalign optimized attachments. Each subject was instructed to wear aligners for 22 hours per day, except during meals and oral hygiene procedures and to replace aligners once a week, always the same day of the week. Every six stages the clinician personally checked the good aligner fitting, the position of the attachments and the patient collaboration.

For the group treated with Fixed Appliance (FA), the straight wire treatment included an aligning and leveling phase, achieved by using Nickel-Titanium arches (0.016/0.019 × 0.025 arc sequence) and a phase with heavier stainless steel rectangular arches (0.019 × 0.025); during this last treatment phase patients were instructed to use Class II elastics for at least 16 h/day.

Pre- (T0) and post-treatment (T1) lateral cephalogram were collected from all selected patients. Treatment time was an average of 18 months (T1-T0=18 months).

For the Fixed Appliance group, the straight wire treatment included an aligning and leveling phase, achieved by using Nickel-Titanium arches (0.016/0.019 × 0.025 arc sequence) and a phase with heavier stainless steel rectangular arches (0.019 × 0.025); during this last treatment phase patients were instructed to use Class II elastics for at least 16 h/day.

Pre- (T0) and post-treatment (T1) lateral cephalogram were collected from all selected patients. Treatment time was an average of 18 months (T1-T0=18 months).

A sample of 40 patients (19M and 21F), mean age 15.4±1.8 years was collected from the Department of Orthodontics at Policlinico "Tor Vergata" of Rome, from September 2023 to June 2024. The sample was randomly divided in two groups: FA group (Fixed Appliance), consisted of 20 patients (9 M, 11F) treated by straight-wire fixed appliance and Class II elastics: CA group (Clear Aligners), consisted of 20 patients (9M, 11F) treated by Comprehensive Package Invisalign® system and Class II elastics. For both FA and CA groups, the inclusion criteria were the following: full permanent dentition (excluding third molars), Class II molar relationship (2,5-4 mm), no or moderate crowding (0- 3 mm) no history of orthodontic treatment.

Pre- (T0) and post-treatment (T1) lateral cephalogram were collected from all selected patients. Treatment time was an average of 18 months (T1-T0=18 months).