Root has endured a difficult tour of Australia - he was also left out of the final Test at the SCG - and after managing just six runs in his previous three innings the 23-year-old made way again.
Off-spinner James Tredwell took his place - meaning England went in with a bowler extra - while Stuart Broad returned from his two-game break for Boyd Rankin.
Australia made three changes, as they sought to secure the five-game series, most significantly resting Ashes hero Mitchell Johnson.
George Bailey failed to recover from a hamstring injury suffered in the one-wicket win in Brisbane on Friday while Clint McKay was omitted.
In their place James Pattinson and Dan Christian were given their first appearances of the series alongside spinner Xavier Doherty.
England captain Alastair Cook won the toss for the third straight game and again opted to bat first.
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- James Tredwell