[The mandibular symphysis of the newborn. Histologic and microradiographic study].

In this histologic and microradiographic study of the mandibular symphysis of eleven newborns, we describe each of the tissues which constitute the mandibular symphysis. To make our observations, we have investigated consecutive sections (fig. 1) of the region. At birth, the mandibular symphysis is forged by several small nodules of calcified tissue, the ossicula mentalia, and by soft tissue invisible in the microradiographs. Therefore, it is necessary to examine first the same field at an identical magnification after methylene blue staining, and then the decalcified slides after coloration according to Masson's trichromic method. Between the two hemimandibles we have observed fibrous tissue and chondriola symphysea (fig. 4 and 5). Figures 2A, 2B and 3 shows secondary cartilage bordering the mandibular symphysis and later replaced with bone by endochondral ossification. In the ossicular mentalia (fig. 6 and 7), chondroid tissue (fig. 7 and 8) is interspersed with secondary cartilage and woven bone, as it is in the extremities of the hemimandibles.