Effect of Force Magnitude on Canine Retraction and Gingival Crevicular Fluid Proteome

Patients' participation in the study at the first visit (T0) Timepoint 0, will be started at the stage of canine retraction. At this appointment, 0.019 x 0.025-inch stainless steel archwire will be placed; power arms will be fabricated from 17x25-inch stainless steel on the maxillary first molars and canines. The height of the power arm will be matched with the center of resistance of both canines and molars based on the root length measured on the periapical radiographs. The archwire will be engaged in the canine bracket using stainless steel ligature wire.

At the T0 appointment, before applying the retraction force, periapical radiographs of canines (with coronal and apical reference wires for calibration and magnification correction) and GCF (gingival crevicular fluid) samples of each canine will be collected. Gingival sulcus of mesial and distal to canine (bilaterally) will be chosen as sites for GCF sample collection. The study coordinator will take a digital scan using iTero® Element™ in the clinic as the baseline (T0). As the split-mouth design will be applied in this study, right and left sides will be assigned randomly for either 150gm (light force) or 400gm force (heavy force) for each subject. NiTi coil spring calibrated for force magnitude at oral temperature will be used to deliver the assigned force will be engaged from the first molars to the canine power arms. IRB-approved written instructions will also be provided to all the participants. Follow-up visits will be scheduled. After applying the force, follow-up visits will be scheduled at (T1) 1-2 weeks, (T2) 4-5 weeks, (T3) 8-9 weeks, (T4)12-13 weeks, and (T5)16-17 weeks. A new digital scan will be taken at each study appointment (T0 - T5). These digital scans will be used for tooth movement measurements. GCF samples (mesial and distal to canines bilaterally) will be collected only for the first 3 appointments (T0 - T2) for the first 10 participants only in this study.

Periapical radiographs for canines on both sides will be obtained on (T0) Timepoint 0, and (T3) 8-9 weeks and (T5) 16-17 weeks of the study for each participant and analyzed to measure the EARR (external apical root resorption). Following the last study visit, all subjects' treatment will continue as recommended by the primary orthodontic care provider. No new data will be reviewed or collected after (T5).

Inclusion criteria

• Healthy patient, non-smoker
• Age: 11 - 16 years of age, inclusive.
• A full complement of dentition (central incisor to 1st molar) in the four quadrants, except second molars
• Patients requiring at least upper bilaterally maxillary 1st premolar extraction as a treatment plan (Class I bimaxillary protrusion/ crowding or Class II maxillary dentoalveolar protrusion/ crowding)
• At least 5 mm of space left between canine and 2nd premolar to be closed at the time of canine retraction
• At least six months after the extraction of first premolars and in a 0.019 x 0.025-inch stainless steel archwire in the maxilla
• The ability to read and understand English and to provide informed consent

Exclusion criteria

• Patients under 11 years of age and over the age of 16.
• Non-extraction treatment plan
• Extraction of maxillary tooth other than first premolars bilaterally.
• Evidence of poor oral hygiene
• Evidence of previous root resorption
• Missing or impacted tooth in any of the quadrant except 3rd molars.
• Medical issues that affect tooth movement
• Inability to provide oral and written consent to participate.
• Patient on medications that may alter bone metabolisms like bisphosphonates, oral contraceptives, or PTH (parathyroid hormone)
• Chronic illness or syndromic patients.
• Pregnant women, prisoners, and decisional impaired