Molecular Analysis of Gingival Crevicular Fluid in Response to the Magnitude of Orthodontic Force: a Longitudinal Randomized Split-mouth Study

Patient selection:

Fifteen orthodontic patients with class II division I malocclusion, who required the extractions of maxillary first premolars bilaterally, distal canine movement, and maximum anchorage control as a part of fixed orthodontic treatment plan were invited to participate in the study. All subjects were in good general health with clinically and radiological healthy periodontal tissues (the probing depths ≤3 mm, full-mouth plaque and bleeding score ≤15%, and no bone loss radiographically). Patients were excluded if they were smokers, had had previous orthodontic treatment, had taken a course of anti-inflammatory drugs within 1 month and antimicrobial agents in the previous 3 months prior to the start of the study.

Experimental Design:

The first premolars were extracted at least 20 days prior to the distalization of the canines. Ten days prior to the application of orthodontic force all subjects underwent full-mouth scaling and oral hygiene instructions to ensure optimal plaque control and oral hygiene instruction was reinforced throughout the whole study period. In each patient, two mini-screw implants (1.5 mm in diameter and 8.0 mm in length) were placed bilaterally into the inter-radicular bone between the maxillary second premolar and first molar in the attached gingiva.The upper right and left canines of the same patient were randomly distalized using a continuous force of 75 or 150 g with nickel-titanium closed coil springs. Simple randomization by flipping a coin was used to determine the assignment of each site for two different forces.

GCF sampling: