OBJECTIVETo investigate the exerted force in different phases of the female menstrual cycle, as well as the changes in estrogen (E2), osteocalcin (OCN), receptor activator of nuclear factor-kappa B ligand (RANKL), and osteoprotegerin (OPG) levels in the gingival crevicular fluid (GCF) during orthodontic tooth movement, to provide a theoretical basis for the selection of the best opportunity for efficient tooth movement.

METHODSTwelve women (aged 18 years to 28 years) with extracted first premolars had been selected. Six women in the group were randomly selected as the menstrual period group, whereas the remaining six were assigned to the ovulation period group. Right canines were retracted with 1.5 N NiTi close coil spring. GCF samples were collected prior to the force exertion experiments at 0 (T0), 15 (T1), 30 (T2), and 45 d (T3). The levels of E2, OCN, OPG and RANKL in GCF were measured by chemiluminescence and enzymelinked immunosorbent assay.

RESULTSThe E2 and OCN levels were significantly higher in the ovulation period group than in the menstrual period group (P < 0.05). No significant differences were found in RANKL and OPG levels between the two groups (P > 0.05). Finally, no significant difference was found in RANKL/OPG ratio between the two groups (P > 0.05).

CONCLUSIONExerted force on teeth during the menstrual period may promote rapid tooth movement.