Evaluation and Comparison of Alkaline Phosphatase Specific Activity in Gingival Cervicular Fluid during Orthodontic Canine Retraction using Sliding and Friction Less Techniques

The aim of this study was to compare the specific activity of alkaline- phosphatase (ALP) in GCF during two techniques of canine retraction (sliding and frictionless) to find whether this parameter has the potential as a diagnostic biomarker of tissue response in orthodontic tooth movement.
Subjects and In a clinical trial 5 subjects (aged 12-20 yr) with bimaxillary dentoalveolar protrusion were selected. After the extraction of four first premolars, the sliding and frictionless techniques were used cross-sectionally to retract canines in each subject. GCF samples were collected from mesial aspect of each canine by using strile paper points (#15) at four time intervals (immediately after the appliances were fitted, at the time of initial activation, 15 and 30 days afterwards). ALP and microprotein levels were assayed by means of quantitative colorimetric technique and tooth movement at each sampling interval was measured by using a digital caliper.
After the activation of the appliances, average specific activity of ALP in GCF at tension sites was significantly increased using either techniques (P= 0.014). In addition, the specific activity of ALP at sampling intervals in both techniques, showed significant differences. Change in specific activity of APL in sampling intervals, in frictionless technique was significantly higher than sliding technique only in 15-day sampling interval, but not in others.
This study shows that alveolar bone formation can be measured via ALP activity in GCF samples. Therefore this will be a reliable diagnostic tool for monitoring orthodontic tooth movement in clinical practice.