Background
Diro, Inc. owned U.S. Patent No. 5,749,731 covering an emergence cuff — a plastic device used in dental implantology that is temporarily placed around the abutment portion of a dental implant to preserve the space between the implant and the surrounding gum tissue while the permanent crown is being fabricated. Properly managing this gingival tissue space allows the final crown to achieve a natural appearance emerging from beneath the gum line. Bicon, Inc. was the exclusive licensee of the ‘731 patent.
Straumann Company sold two products that Bicon alleged infringed: an “impression cap” — a plastic device that attaches to the implant shoulder while a dental mold is taken, then is removed immediately after mold completion — and a “burnout coping” — a cone-shaped plastic structure used in the dental laboratory to help fabricate the permanent crown but never placed in the patient’s mouth at all. Straumann moved for summary judgment of non-infringement, arguing that neither product fit within the ‘731 patent claims properly construed. The district court agreed and granted summary judgment. Bicon appealed.
The Court’s Holding
The Federal Circuit affirmed. Writing for the court, Judge Bryson addressed a fundamental question in claim interpretation: when is a claim’s preamble a limiting part of the claim? The court held that a preamble is limiting when it recites essential structural elements of the claimed invention — elements that are necessary for the claim body to make sense or that define what is being claimed in a substantive way, rather than merely providing background context or describing the intended purpose.
The preamble of the ‘731 patent’s claims described the device as an “emergence cuff” for use “with an abutment.” The court found that the abutment was an essential structural element of the claimed invention, not merely a statement of intended use: the entire function and structure of the emergence cuff, as described in the patent, required it to be used in conjunction with a specific type of abutment. Without the abutment, the emergence cuff was not the claimed invention. The claim’s preamble thus limited the claim to a combination of the emergence cuff and the abutment, not just the cuff alone.
Under this construction, Straumann’s impression cap and burnout coping did not infringe: the impression cap was not used with the required type of abutment in the claimed combination, and the burnout coping was never placed in the patient’s mouth at all and thus could not perform the tissue-preservation function that defined the patent’s claimed combination.
Key Takeaways
- A claim’s preamble is limiting when it recites essential structural elements of the claimed invention — elements that define what is being claimed, rather than merely providing background context or naming the intended use.
- Conversely, a preamble is not limiting when it merely states the purpose for which the claimed structure is designed, without adding structural elements that otherwise aren’t captured in the claim body.
- Patent drafters should be aware that preamble language describing structural combinations or required components may limit claim scope even if the body of the claim does not expressly require those components.
- To avoid having preamble language treated as limiting, practitioners should ensure that the claim body is complete and self-sufficient — all essential claim elements should appear in the body, and the preamble should provide only context and naming.
- This case is frequently cited for the proposition that preamble language describing the combination or relationship between claimed components and other structures can limit claims when that combination is the invention.
Why It Matters
Bicon v. Straumann provides a useful and concrete example of when a claim preamble is treated as a limiting claim element. The preamble-limiting question arises frequently in patent litigation, particularly in medical device and mechanical cases where claimed devices are designed to be used in combination with other components. Whether the preamble limits the claim can be dispositive on infringement: a competitor’s product that lacks the required combination may avoid infringement simply because it does not satisfy the preamble limitation.
For dental implant manufacturers and their patent counsel, the case illustrates the importance of understanding how preamble language will be interpreted before asserting a patent. If a patent’s claims require a specific combination — emergence cuff plus abutment — then standalone components or temporary single-use items may not infringe, even if they broadly fall within the described technology. Defendants facing preamble-limited claims can use this precedent to argue that their products lack the essential combination described in the preamble.