Orthodontic tooth movement induces biological responses in periodontal tissues that can be reflected by changes in gingival crevicular fluid (GCF). This study aims to evaluate temporal changes in GCF volume during orthodontic treatment with clear aligners and conventional fixed appliances. GCF samples will be collected from the buccal site of tooth 12 and the palatal site of tooth 16 at baseline, 1 hour, 1 day, 1 week, and 1 month after appliance placement. The findings of this study will help to better understand periodontal tissue responses associated with different orthodontic treatment modalities.

Orthodontic tooth movement is a biologically mediated process that involves a complex interaction between mechanical forces and periodontal tissue responses. The application of orthodontic forces induces a cascade of cellular and molecular events within the periodontal ligament and surrounding alveolar bone, including vascular alterations, inflammatory mediator release, and bone remodeling. These biological reactions are essential for tooth movement and can be monitored through various biochemical and clinical parameters.

Gingival crevicular fluid (GCF) represents an inflammatory exudate originating from the periodontal microcirculation and contains numerous biomarkers related to periodontal tissue metabolism and inflammatory activity. Because of its non-invasive collection method and its close relationship with periodontal tissue responses, GCF has been widely used to evaluate biological processes associated with orthodontic tooth movement.

In recent years, clear aligner therapy has become an increasingly popular alternative to conventional fixed orthodontic appliances. Clear aligners deliver orthodontic forces through removable thermoplastic appliances that apply intermittent forces during tooth movement. In contrast, conventional fixed appliances provide more continuous force application through brackets and archwires. These biomechanical differences may influence the magnitude and temporal characteristics of periodontal tissue responses during orthodontic treatment.

Although several studies have investigated biochemical changes in GCF during orthodontic tooth movement, limited evidence exists regarding temporal changes in GCF volume and whether different orthodontic treatment modalities produce distinct patterns of GCF volume alteration. Understanding these biological responses may provide further insight into periodontal tissue adaptation during orthodontic therapy.

The aim of this prospective clinical study is to evaluate and compare temporal changes in gingival crevicular fluid volume during orthodontic treatment with clear aligners and conventional fixed appliances.

Participants undergoing orthodontic treatment will be assigned to either a clear aligner group or a conventional fixed appliance group. Gingival crevicular fluid samples will be collected from two standardized sampling sites: the buccal aspect of tooth 12 and the palatal aspect of tooth 16. Sampling will be performed at five time points: baseline (prior to appliance placement), 1 hour, 1 day, 1 week, and 1 month following appliance placement.

GCF volume will be measured using a Periotron device, which provides quantitative assessment of fluid volume collected from the gingival crevice. The collected data will be used to analyze temporal patterns of GCF volume changes and to compare potential differences between orthodontic treatment modalities.

The findings of this study are expected to contribute to a better understanding of periodontal tissue responses during orthodontic tooth movement and to provide additional biological insight into the effects of different orthodontic appliance systems.

Inclusion Criteria:

• Systemically healthy individuals with no history of systemic disease
• No regular pharmacological medication use within the last 6 months
• Individuals with completed mixed dentition and full permanent dentition (excluding third molars)
• No missing or impacted teeth other than third molars
• Indication for non-extraction orthodontic treatment
• Mild malocclusion with 2-4 mm crowding (Celikoglu, 2010)
• Skeletal Class I relationship (0° ≤ ANB ≤ 4°)
• Periodontally healthy individuals (gingival index <1, plaque index <1, probing depth ≤3 mm, <10% bleeding on probing, and no radiographic bone loss)
• No caries, fractures, wear, or restorations in the teeth selected for gingival crevicular fluid sampling
• Absence of parafunctional habits that could cause traumatic oral lesions

Exclusion Criteria:

• Presence of periodontal disease or radiographic bone loss
• Poor oral hygiene
• Skeletal anomalies or need for orthognathic treatment
• Temporomandibular joint disorders
• Known allergy to any medication or material
• Tobacco or alcohol use
• Personal or family history of cancer or history of chemotherapy/radiotherapy
• Participation in another clinical trial during the study period
• Presence of mixed dentition or missing teeth other than third molars

Individual participant data will not be shared because the study dataset contains identifiable clinical information and data sharing was not included in the original participant consent or ethics approval.

The investigator responsible for statistical analysis will be blinded to the treatment allocation of participants. Data will be coded prior to analysis to ensure that the outcome assessor remains unaware of group assignments.