Donovan's twentieth and final patent, an improved multifilament dental floss bonded to a monofilament leader, was granted October 1, 1996, when she was 78.
On October 1, 1996, Marion Donovan was granted U.S. Patent 5,560,377 for an improved dental floss design, in which a multifilament yarn was bonded to a monofilament leader to improve strength, ease of threading, and durability during use. This was her twentieth and final patent, granted when she was 78 years old, a striking testament to a lifetime of sustained inventive activity spanning nearly five decades, from her first diaper patent in 1951 to this dental hygiene innovation in the mid-1990s.
The patent reflects Donovan's continued refinement of her earlier DentaLoop concept from 1985, showing her ongoing engagement with practical material science problems well into her later years. Few inventors, male or female, maintain active patent output across such a long career, and Donovan's persistence highlights both her intellectual curiosity and her rare position as a woman who built a decades-long independent inventing career entirely outside institutional or corporate research settings.
This final patent serves as a fitting capstone to a career defined by identifying overlooked, everyday inconveniences — from leaking diapers to unwieldy dental floss — and solving them with practical, patentable engineering, cementing her legacy as one of the most prolific and inventive women of twentieth-century America.