United States: Statements Made during Prosecution May Be Used to Interpret Claim Language Not Found in Specification

The U.S. Court of Appeals for the Federal Circuit has held that statements made during prosecution may be used to interpret an ambiguous term not defined in the specification. All Dental Prodx, LLC v. Advantage Dental Prods., Inc., Case No. 02-1107 (Fed. Cir. Oct. 25, 2002).

Advantage owns a patent directed to a method for making a custom dental impression tray. Advantage's patent has two independent claims containing limitations to "an original unidentified mass of thermosetting material." The term "original unidentified mass" is not defined in the specification.

All Dental sought a declaratory judgment that the Advantage patent was invalid and not infringed by its product. The district court granted summary judgment of non-infringement because All Dental's products have a specific pre-formed shape and size and are, thus, not an "unidentified mass." Additionally, the court held independent claims invalid for indefiniteness and lack of written description.

On appeal, the Federal Circuit reversed, holding "the failure of the specification to specifically mention a limitation that later appears in the claims is not a fatal one when one skilled in the art would recognize upon reading the specification that the new language reflects what the specification shows has been invented." With respect to indefiniteness, the Court held that statements made during prosecution concerning what the prior art "did not teach or disclose" and concerning what the claimed invention "teaches away from" could be used to clarify the meaning of the disputed term. Because these statements disclaimed the use of a specific shape and did not embrace any specific form, the Court held, "the meaning of the phrase 'original unidentified mass,' … is indeed definite and clear."