## Facts

- Young Dental Manufacturing Co., Inc. owned U.S. Patent Nos. 5,156,547 and 5,423,679 covering an improved disposable prophy angle (DPA), a dental handpiece attachment used to polish teeth with a rotating prophy cup.
- Earlier disposable plastic DPAs existed but were criticized as rough, prone to failure, and prone to overheating.
- Young’s employee-inventor, Ronald Bailey, developed the improved DPA and assigned the patent rights to Young; the patents disclosed specific structures (including a head “aperture” limitation in asserted claims) and identified plastics such as Lexan and Celcon for components.
- After leaving Young, David G. Kraenzle designed a competing DPA, obtained U.S. Patent No. 5,224,859, and formed Q3 Special Products, Inc. to market it.
- Young sued Q3 and Kraenzle in the Eastern District of Missouri for patent infringement and asserted related state-law claims; Q3 sought declaratory judgments of noninfringement and invalidity, including best mode challenges based on alleged nondisclosure of preferred gear ratio and grades of plastic.
- The district court granted summary judgment of no literal infringement.
- A jury found no infringement under the doctrine of equivalents and found the asserted claims invalid for both failure to satisfy best mode (35 U.S.C. § 112) and obviousness (35 U.S.C. § 103); judgment entered for Q3.
- Young appealed, challenging infringement rulings, invalidity findings, and evidentiary rulings (including admission of a “Thiedemann model” as prior art evidence).

## Issues

1. Whether summary judgment of no literal infringement was proper under the asserted claims’ structural limitations.
2. Whether Young could obtain appellate reversal of the jury’s doctrine-of-equivalents noninfringement verdict, including whether Young preserved a sufficiency challenge.
3. Whether the asserted claims were invalid for failure to disclose the inventor’s best mode under 35 U.S.C. § 112.
4. Whether substantial evidence supported the jury’s verdict that the asserted claims were obvious under 35 U.S.C. § 103.
5. Whether the district court abused its discretion in admitting prior-art and related evidence, including the Thiedemann model.

## Decision

- Affirmed summary judgment of no literal infringement because the accused device did not meet a required structural limitation (including an “aperture” in the head).
- Left undisturbed the jury’s noninfringement verdict under the doctrine of equivalents, noting Young failed to preserve a sufficiency challenge by a proper Rule 50 motion and that the record supported the verdict.
- Reversed the jury’s best mode invalidity finding because the evidence did not show the inventor subjectively possessed and concealed a specific preferred mode beyond routine design choices.
- Affirmed the jury’s obviousness invalidity verdict as supported by substantial evidence in light of the prior art presented at trial.
- Affirmed evidentiary rulings, including admission of the Thiedemann model, as within the district court’s discretion.

## Legal Principles

- Literal infringement requires every claim limitation; when a claim is construed to require a specific structural element, absence of that element defeats literal infringement.
- Appellate review of the sufficiency of evidence supporting a jury verdict generally requires preservation through a timely Rule 50 motion; failure to do so limits or forecloses sufficiency challenges on appeal.
- Best mode invalidity requires proof the inventor, at filing, subjectively had a preferred mode and failed to disclose it; nondisclosure of routine optimization choices apparent to skilled artisans is insufficient absent competent evidence of concealment of a true preferred mode.
- Obviousness is a fact-driven determination; a jury’s invalidity verdict will be upheld if supported by substantial evidence based on the prior art and differences between the art and the claims.
- Evidentiary rulings on prior-art demonstrations and models are reviewed for abuse of discretion and are sustained where probative value supports admission and no reversible prejudice is shown.

## Conclusion

The Federal Circuit largely upheld judgment for the accused infringer, affirming no literal infringement, leaving the doctrine-of-equivalents verdict intact, and affirming invalidity for obviousness, while reversing best mode invalidity because the record did not show concealment of a specific preferred mode rather than ordinary engineering selection.


Young Dental Mfg. Co. v. Q3 Special Prods., Inc., 112 F.3d 1137 (Fed. Cir. 1997)