Toothbrush maker Ultreo Inc. has filed a countersuit against P&G, claiming the maker of Oral-B products has “falsely” disparaged the company, according to the Business Journal.

In September, P&G filed suit in U.S. District Court for the Southern District of New York, saying that Ultreo used false advertising related to its ultrasound toothbrushes. Ultreo, based in Redmond, Wash., had over the summer raised $11.3 million in venture capital toward development of the brush, which could threaten the market position of both Oral-B and Sonicare in the roughly $800 million power toothbrush market.

P&G’s suit sought to stop Ultreo from making what P&G called false marketing claims regarding the plaque removal effects of ultrasound.

In a statement, Ultreo denied P&G’s claims and said it used strong scientific evidence for its marketing and that P&G’s claims were “without merit.”

“It’s obvious that this is the real source of concern for P&G. The fact that a $76 billion market leader is attacking and disparaging a $3 million startup offering a technological innovation simply validates Ultreo’s acceptance by the marketplace,” Ultreo CEO Jack Gallagher said in a statement.

The Ultreo toothbrush sells for $149 and replacement brushes cost $20. As of midsummer, the company had shipped 12,000 units. Procter’s newest Oral-B power brush model, the Triumph, retails for about $150, as does Sonicare’s newest Elite model.