—Judgment, Supreme Court, Nassau County (Beatrice Burstein, J.), entered August 30, 1991, which, upon defendant’s motion for a directed verdict, dismissed the complaint, unanimously affirmed, without costs.
In this action for dental malpractice, plaintiif failed to establish a prima facie case of liability through her expert witness. The witness said nothing of the applicable standard of care for treatment, did not know how the procedure was performed, did not set forth the manner in which defendant deviated from any standard, and did not explain how the injury was caused (see, Gibson v D’Amico, 97 AD2d 905, lv denied 61 NY2d 603). Nor was the alleged negligence obvious and within the competence of lay persons (see, supra, at 906). The burden of proving causation remained with plaintiif, and it is of no moment that defendant did not offer an explanation as to other possible causes of plaintiff’s injury (see, Mortensen v Memorial Hosp., 105 AD2d 151, 158). Concur — Murphy, P. J., Sullivan, Carro, Wallach and Tom, JJ.