Ordered that the order is affirmed insofar as appealed from, with costs.
To avoid dismissal for failure to timely serve a complaint after a demand therefor has been served pursuant to CPLR 3012 (b), a plaintiff must demonstrate both a reasonable excuse for the delay in serving the complaint and a meritorious cause of action ( see Maldonado v Suffolk County, 23 AD3d 353; Giordano v Vanchieri Perrier, 16 AD3d 621; Tutora v Schirripa, 1 AD3d 349). The determination of what constitutes a reasonable excuse for a default lies within the sound discretion of the Supreme Court ( see Low Surgical Med. Supply, Inc. v McAfee, 15 AD3d 547; Carnazza v Shoprite of Staten Is., 12 AD3d 393; Adams v Alexander, 291 AD2d 467). Contrary to the appellants `contention, the Supreme Court providently exercised its discretion in finding that the plaintiff offered a reasonable excuse for her delay in serving the complaint ( see Low Surgical Med. Supply, Inc. v McAfee, supra; Carnazza v Shoprite of Staten Is., supra; Fine v Fine, 12 AD3d 399; Du Jour v DeJean, 247 AD2d 370). Furthermore, the plaintiff adequately demonstrated the potential merit of those of her causes of action which are predicated upon ordinary negligence rather than dental malpractice, and there is no indication that the appellants were prejudiced by her relatively short delay in serving a complaint ( see Lewis v St. Francis Hosp., 10 AD3d 678; Klosterman v Federal Express Co., 271 AD2d 492; Kramer v Rosenthal, 204 AD2d 406).