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.
