The Sharks trailed 2-0 but got a goal from Jason Demers in the second period and an equalizer from Joe Pavelski in the third.
After a scoreless overtime, the shootout remained scoreless until the fourth round when Thornton used a forehand shot under Lehtonen's blocker to give San Jose the advantage. Sharks goalie Alex Stalock then stopped Ray Whitney to seal the win -- San Jose's third in five games.
Stalock turned aside 42-of-44 shots.
Whitney and Antoine Roussel scored for the Stars. Lehtonen finished with 37 saves.
Boston schools pull out free condoms over wrapping complaints
Aaron Carter is still in love with Hilary Duff