Background: Orthodontic forces induce tissue reactions by triggering perturbations from orthodontic appliances, which lead to the modelling and remodelling of alveolar bone. Despite the growing popularity of 3D-printed aligners, no studies have compared their effects on bone metabolism in comparison with thermoformed aligners. Aim: This study aims to assess bone metabolism in patients undergoing treatment with 3D-printed aligners versus thermoformed aligners.

Inclusion Criteria:

• Minor malocclusion (2 to 4 mm of crowding) .
• Patients in need for Antero-posterior expansion and labial tipping of incisors without interproximal reduction
• No use of anti-inflammatory drugs or antibiotics in the past 6 months.
• Periodontal parameters of gingival index <1 and no pocketing with a generalized pocketing depth of <3mm.
• Radiographic parameters of no crestal bone loss.
• No history of smoking.

Exclusion Criteria:

• Signs of inflammation of the gingiva, and periodontitis.
• Systemic conditions (kidney disease, HIV, and liver disease).
• Teeth missing or poor oral hygiene.
• Bone disease e.g.; osteoporosis.

The patients will be blinded at appliance delivery, to reduce the risk of bias. Moreover, the biologist in the laboratory who will do the measurements, and the statistician will be blinded to the nature of the study.