Effect of sequential Injectable Platelet Rich Fibrin (i-PRF) following Leukocyte-Platelet Rich Fibrin (L-PRF) on maxillary canine retraction: split-mouth randomized controlled trial.

OBJECTIVE: To evaluate the efficacy of injectable platelet-rich fibrin (i-PRF) following autologous leukocyte platelet-rich fibrin (L-PRF) placement on retraction of maxillary canine, and RANKL and OPG expression in gingival crevicular fluid (GCF) during comprehensive orthodontic treatment. MATERIALS AND METHODS: Sixteen subjects (age range, 18-25 years) requiring all 1st premolar extractions were enrolled. L-PRF plugs were placed in both maxillary 1st premolar extraction sockets. The i-PRF was injected submucosally after 4-weeks of L-PRF placement on the experimental sides. Canine retraction was initiated immediately after 1st premolars extraction and L-PRF placement using NiTi closed coil springs. Amount of canine retraction was evaluated from the study models prepared immediately before the 1st premolars extraction and 4-weeks, 8-weeks and 12-weeks after the start of canine retraction. The RANKL and OPG levels in GCF were measured immediately before the 1st premolars extraction and at 4-weeks, 6-weeks, 8-weeks, 10-weeks and 12-weeks after the beginning of canine retraction. RESULTS: Over 12-weeks period, significantly greater amount of canine retraction was observed on experimental (4.77 ± 0.35 mm) sides compared to control (3.6 ± 0.48 mm) (P < 0.001). On experimental sides, a significant increase in the RANKL (P < 0.001) and decrease in the OPG levels (P < 0.001) were observed. In control sides, there was a negative, and in experimental sides, a positive correlation between the amount of canine retraction and RANKL and OPG levels in the GCF. CONCLUSION: Injection of i-PRF after 4-weeks of L-PRF application significantly enhanced the amount of canine movement and modulated bone metabolism by increasing RANKL and decreasing OPG levels in GCF.