Initiation of secondary cartilage in the mandible of the Syrian hamster in the absence of muscle function.

The functioning lower jaw is a prerequisite of the ongoing secondary chondrogenesis in the mammalian mandibular condyle. Does the articular function also initiate secondary chondrogenesis in the mandible? The angular process of the fetal mammalian mandible possesses a large secondary cartilage without any apparent articular function. Past studies have shown that the anlage of the lower jaw of the mouse embryo grown in organ culture produces condylar and angular cartilages as in vivo. In order to clarify further the capacity of the mandibular anlage to initiate secondary chondrogenesis in a non-functional environment, mandibular arch explants taken from the prenatal hamster before any cartilage or bone formation was apparent were grown in organ culture. Both primary and secondary cartilage could be found in them within 9-10 days. The results thus indicate that initiation of the condylar and/or angular secondary cartilaginous development in the rodent mandible occurs in the absence of jaw-opening function, although the pertinent literature indicates that function maintains cartilaginous differentiation in the condyle.