The Bruins' third-round pick in last June's draft, Lauko picked up a helper - providing the screen in front - on David Kvasnicka's winner just 52 seconds into overtime, as the Czech Republic sneaked by Switzerland, 2-1.
Lauko has 26 points (12 goals, 14 assists) in 26 games for Rouyn-Noranda of the QMJHL this season, his first playing in North America.
Bukac, a defenseman and Boston's seventh round pick in 2017, played 13 minutes, 11 seconds, for the Czechs in the win.