Inventors use provisional applications for good reasons: they cost less, they are faster to prepare, and they give a year of "patent pending" while the full application is written. But a provisional is only worth its filing date if it describes the invention, and an August 10, 2026 Federal Circuit decision, Dental Monitoring SAS v. Align Technology, Inc., applies that rule to prior art too.
What the court decided, in one paragraph
The question was when a published patent application counts as prior art against someone else's patent. The court held that the published application gets its provisional's earlier date only if the provisional provides written description support, under 35 U.S.C. 112(a), for at least one of the published application's claims. It rejected the test the Patent Trial and Appeal Board had applied from its precedential Penumbra decision, which asked only whether the ministerial requirements for claiming priority were met and whether the provisional described the subject matter relied on. The court vacated the Board's decision and sent the case back for the Board to decide whether the provisional supports a claim of the published application.
It cuts both ways
If a competitor's published application is cited against your patent, the challenger now has to show that its provisional supports at least one of its published claims before the earlier date applies. Without that date, the application counts as prior art only as of its later filing date, which may come after your own. The same written description requirement has long applied to your own claims: under 35 U.S.C. 119(e), a claim gets a provisional's date only if the provisional discloses the claimed invention in the manner section 112(a) requires. If your provisional was a marketing one-pager with a cover sheet, the year of priority you think you have may not hold up, in litigation or at the Office. Either way, these date disputes turn on what the provisional actually discloses.
The practical rules that follow
Write the provisional as if it were the real application's technical core: describe how the invention works, the variations you actually contemplate, and the details you would need to claim later. File a new provisional as the design changes rather than trusting one early snapshot to cover everything. And when a filing service offers a same-day bargain provisional, remember what you are actually buying: a date attached to whatever disclosure is in the document, and nothing more.
For the litigation-side analysis, including what the decision means for pending patent challenges, see the full write-up at our sister site, Patent Litigator.