The 23-year-old Root, dropped for the final Ashes Test during England's 5-0 whitewash Down Under, brought up his 200 with a dab behind square after a well-compiled innings that featured 16 boundaries from 298 balls.
Alastair Cook immediately declared the innings on 575-9, leaving Sri Lanka openers Silva and Dimuth Karunaratne to negotiate a tricky spell before tea.
Karunaratne, who successfully overturned an lbw appeal off James Anderson in the first over and offered a chance to the slips soon after, fell to Chris Jordan's third ball in Test cricket when on 38, edging to Matt Prior behind the stumps.
However, Silva (62) and Sangakkara (32) battled their way through to 140-1 at the close, although the former was lucky to survive a caught behind appeal off Stuart Broad on his way to his fourth half-century, with the third umpire ruling Prior had not claimed the catch cleanly.
Root, yet to nail a position in the line-up during his short Test career, was offered good support by Jordan, Broad and Liam Plunkett as the hosts looked to bat Sri Lanka out of the match against a bowling attack that lacked any real threat after an early three-wicket blast on the first morning of the Test.
Root's 200 beat his previous best of 180, also scored at Lord's against Australia last year, and helped rescue his side after they were struggling at 120 for four soon after lunch on the first day.
Having had little luck tossing the ball up late on the opening day, Sri Lanka's bowlers set out to bombard Root and Prior, also returning after injury and being dropped against Australia, with short balls on a pitch that appears set to become easier to bat on as the match progresses.
Prior, who passed 4,000 Test runs early in the day, never looked entirely comfortable, eventually falling for 86 when he could only fend a well-directed bouncer from Shaminda Eranga to Silva at forward short-leg, with the pair having put on 171 runs for the sixth-wicket.
Jordan, who along with Sam Robson and Moeen Ali is making his Test debut, struck a breezy 19 before becoming Eranga's third victim, while fellow fast bowlers Broad (47) and Plunkett (39) also ticked the total along to help England to their highest score against Sri Lanka, for whom Nuwan Pradeep finished with a career-best haul of four wickets.
Image: Joe Root celebrates after getting to 200
Photographs: Tom Shaw/Getty Images
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