Head hits back for Australia after Root's majestic 160
Root's superb innings, his 41st ton to match Ricky Ponting, was only ended courtesy of a brilliant caught-and-bowled by Michael Neser, who finished with 4-60.
Australia were left to negotiate the final session of day two at a sold-out Sydney Cricket Ground, which they did for the loss of Jake Weatherald (21) and Marnus Labuschagne (48).
By stumps the hosts -- who have already won the series -- had raced to 166-2 with nightwatchman Neser on one alongside Head.
"I think it's set interestingly," Root told TNT Sports.