Influence of Finishing Clear Aligner Marginal Termination Design on Subgingival Periodontal Microbiota During Orthodontic Treatment: A Split-Mouth Study.

The goal of this clinical trial is to learn whether the edge design of a finishing orthodontic clear aligner at the gumline affects the bacteria living in the groove between the tooth and the gum (the gingival sulcus) in patients undergoing the finishing phase of orthodontic treatment. The main question it aims to answer is: \- Does a supragingival aligner edge design - which covers approximately 2 mm of gum tissue - lead to higher levels of disease-associated bacteria in the gingival sulcus compared to a juxtagingival edge design that follows the gumline exactly, after 4 and 8 weeks of aligner wear? Researchers will compare the supragingival trimming-line design to the juxtagingival festooned design to see if covering gum tissue with the aligner edge creates conditions that favor the growth of anaerobic bacteria associated with gum disease. Participants will: * Wear finishing clear aligners with both designs simultaneously - one design on the upper jaw and one on the lower jaw - for 8 weeks * Provide fluid samples from the gum groove at 3 visits: at the start of treatment (baseline), at 4 weeks, and at 8 weeks. Two aligner edge designs are compared: a supragingival design, which has a straight horizontal edge positioned approximately 2 mm over the gumline, covering approximately 2 mm of gum tissue with direct contact but without entering the gum groove itself, and a juxtagingival design, which follows the natural scalloped shape of the gumline exactly, terminating at the free gingival margin without covering gum tissue and without entering the groove. The biological rationale for comparing these two designs is the following: the supragingival design, by covering 2 mm of gum tissue, creates a partially enclosed space at the entrance of the gum groove, potentially reducing the clearance of saliva and limiting oxygen access to that area. These conditions may favor the growth of anaerobic bacteria associated with gum disease. The juxtagingival design, by followi