An overlap try from man of the match and home No 8 Tyler Ardon helped the Ospreys move into a 13-6 interval lead. After that Biggar took over and kicked three second half penalties to steer his side to a 10th league win in 13 games to lead Glasgow Warriors by a point.
The Dragons started with bang, but could only muster two Tom Prydie penalties in the first-half despite dominating at scrum time. Both teams eventually lost a front row player to a yellow card.
In the second half the introduction of former Wales scrum half Richie Rees added new impetus into the Dragons attack and he sniped his way over for a try that cut the gap to eight points. But a final penalty from Biggar made the game safe for the home side.
