[Ultrastructural findings of the muscles around lip clefts].

Our electron microscopic observations show alterations of the muscles near the cleft margins confirming the theory resulting from light microscopic and immunohistochemical findings that the myogenic structures surrounding cleft margins are inferior tissue that is capable neither of regeneration nor of normal function. The clinical implication derived from these observations is that the tissue in the vicinity of the clefts should be generously excised when doing cheiloplasties.