Objectives: To evaluate the mouth movements, the neuromuscular development of the masseter and the temporomandibular joint in the human fetus at early stages of gestation. Materials and methods: Were evaluated oral movements in 12 human foetuses of 12 weeks of gestation by using two-dimensional ultrasound (Echo Imagyne, ECM). In the same way, were studied 12 fetuses spontaneously aborted for the study temporomandibular through transcranial x-rays. It was performed to the same group of fetuses, bilateral removal of masseter muscles which were stained with Bielschowsky to detect presence of neurofibrils. Results: 100% of evaluated ultrasounds, was evident the buccal opening of fetuses. An axon that came to each neuromuscular was observed in histological sections of the masseters studied. On radiographs practiced, it was possible to observe continuity of surfaces joint temporomandibular, flattened glenoid cavities and coronoid process more high than the condyle. Conclusion: The temporomandibular development and neuromuscular occur with synchronization and mouth movements in these stages of intrauterine development promote such development.
(Rev Esp Ortod. 2017;47(4):197-200)