Objective The aim of this study was to investigate the circadian rhythm of the proliferative index of mandibular osteoblasts of goats in a normal situation.Methods Twenty four healthy goats were selected and randomly divided into six groups. They were killed, and a piece of bone tissue with 2 cm×2 cm×0.5 cmwas obtained from rightmandibularmental foramen region at 0∶00, 4∶00, 8∶00, 12∶00, 16∶00 and 20∶00 time points, after they had been fed for one week. The primary cell culture method was used to cultivate osteoblasts from the bone. The method of anti-5-bromodeoxyuridine monoclonal antibody and the flow cytometric analysis were used to detect the proliferative index of the mandibular osteoblasts at different time. The data were analyzed using the method of single cosine rhythmometry.Results The proliferative indexes of the mandibular osteoblasts of goats were higher at the nighttime and lower in the daytime. The undulation of the proliferative indexes displayed a significant circadian rhythm (P
