Publication: Changes in human pulp blood flow during canine retraction
Aim: To evaluate the effects of maxillary canine retraction on pulpal blood flow (PBF) in humans as recorded by laser Doppler flowmetry (LDF).Methods: Maxillary canines of 24 participants were divided into two groups (n=12 each). Teeth in the study group underwent maxillary canine retraction using mini-implants as anchorage for approximately 4 months, with 100g of force applied via coil springs. Subjects in the control group received no orthodontic treatment. LDF measurements were recorded at baseline (T0); during retraction, at 24hours (T1), 3 days (T2), 7 days (T3) and 1 month (T4); and at the end of retraction (T5) in the study group and at similar time-points in control subjects. Data were analyzed using the Friedman, Wilcoxon signed rank and Mann-Whitney U tests, with the significance level set at 0.05.Results: No significant changes in PBF perfusion units (PU) were observed in the control group over the course of the study. However, PBF in the study group increased significantly from T0 (3.60.2 PU) to T1 (3.7 +/- 0.2 PU, p<0.001) and decreased severely from T1 to T2 (3.3 +/- 0.1, p<0.001). PBF in the study group was still significantly lower at T3 (3.4 +/- 0.1 PU, p<0.001) in comparison to T0; however, at T4 and T5, PBF was found to have returned to pre-retraction levels.Conclusion: The fact that PBF values returned to initial levels within one month of the initiation of retraction despite short-term, hyperaemic, regressive changes demonstrates that the changes observed in PBF during canine retraction are reversible.