It was a fair achievement given his side slipped to 76-4 on day two, then 209-7 early on day three at the Gabba, threatening to collapse into ignominy yet again.
Pat Cummins impressed in a knock of 42, while England bowlers Moeen Ali and Jimmy Anderson both appeared to be restricted by niggles.
Smith was summoned to the middle on Friday after only 10.3 overs and didn't offer a single chance, even though he adopted a more aggressive approach in the final stages of Australia's innings that spanned 130.3 overs.
The gifted batsman, who reacted with typical fervent to every wide, wicket, boundary and blunder, has attracted comparisons to Allan Border in the past because of his negative body language.
The ongoing match has offered more-positive parallels. Smith carried the run- scoring burden without blinking, blunting an on-song attack to reach three figures after 261 deliveries.
The milestone, every bit as resolute as Border's 273-ball ton in 1987, was celebrated with a flurry of emotions. Smith roared as he beat the coat of arms on his chest, demanding his teammates in the stands to step up.
Root often asked his quicks to bowl short to Smith. He tinkered with fields like a crazed professor but couldn't come up with the formula to conjure the elusive and all-important wicket.
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