Growth rhythms of the cartilage of the mandibular condyle: effects of orthopaedic appliances.

The growth rate of the cartilage of the mandibular condyle in the young rat exhibits: - a circadian cycle with a maximum of the 3H-thymidine labelled cells around 13(00) and a minimum around 01(00); with a maximum in the number of mitoses around 21(00) and a minimum around 09(00). - a circannual cycle with a maximum in May and a minimum between November and January, and with a difference in rhythms between May and November. The condylar cartilage growth in response to orthopaedical appliances of the mandible is modified and exhibits: - circadian variations. - circannual variations. The responsiveness of the condylar cartilage to orthopaedic appliances is greater when the condylar cartilage growth rate is higher.