Tooth movement and cytokines in gingival crevicular fluid and whole blood in growing and adult subjects

Introduction: Tooth movement has been studied largely with respect to the force required for tipping when pressure distribution varies along the length of the periodontal ligament. But important factors for effective canine translation include the nature and magnitude of applied stress and the patient's cell biology. The purpose of this research was to test 3 hypotheses: (1) the velocity of tooth translation (vt) is related to applied stress and growth status, (2) a threshold of stress accounts for the lag phase, and (3) vt is correlated with the ratio (AI) of 2 cytokines (IL-1β, IL-1RA) measured in gingival crevicular fluid (GCF) and stimulated whole blood (SWB). Methods: Continuous maxillary canine retraction stresses of 13 kPa and 4, 26, or 52 kPa were applied bilaterally in 6 growing and 4 adult subjects for 84 days. Dental models and GCF samples were collected at 1- to 14-day intervals. Cytokines were measured in GCF and SWB cell cultures. Results:Vt was positively related to stress and was higher in growing subjects (P = .001). It was also related to AIGCF in growers (R2 = 0.56) and nongrowers (R2 = 0.72). Canines moved with 52 kPa showed a lag phase, and postlag phase AIGCF was twice that of lag phase AIGCF. Mean vt and associated AIGCF during the postlag phase were nearly double the values for canines moved with 13 and 26 kPa. SWB production of cytokines was dose-dependent. For growing subjects, SWB IL-1RA was correlated with vt (R = 0.70-0.72), and AISWB and IL-1β concentrations were correlated with AIGCF (R = 0.73-0.78). Conclusions:Vt varied with growth status and stresses ≤ 52 kPa; stresses of < 52 kPa showed no lag phase; and equivalent stresses yielded subject-dependent differences in vt, which correlated with cytokines in GCF and SWB.