Alkaline phosphatase activity in gingival crevicular fluid in response to different magnitudes of continuous orthodontic forces

The current study was undertaken to evaluate the effect of continuous force of different magnitudes (150, 50g) on alkaline phosphatase activity (ALP), with a focus on the amount of tooth movement after application of these forces. Eight female subjects (age range 13 to 15 years) participated in the 6 weeks study. A continuous retraction force of 150g was applied to 1 of the maxillary canines (group I) whereas a continuous force of 50g was applied to the other (group II) with a nickel-titanium closed coil spring. Gingival crevicular fluid (GCF) was collected from the mesial and distal sides of each experimental canine immediately before appliance activation and weekly over the following 6 weeks. The clinical gingival condition was evaluated at the baseline and at the end of the experiment. GCF ALP activity was determined spectrophotometrically at 37 C by kinetic method. The results showed insignificant changes in the clinical condition. GCF ALP activity was significantly greater in tension sites of group I and II as compared with the baseline. Moreover the enzymatic activity in tension sites of group I was significantly greater than that of group II. In both groups, a significant greater ALP activity was observed in tension sites compared with compression sites. The results showed insignificant difference in the amount of distal movement of the canines produced by the 2 forces. It was concluded that effective tooth movement can be produced with lower forces and ALP activity in GCF can be considered a suitable indicator of the biologic activity in the periodontium during orthodontic tooth movement.