Chris Dobey overcame a scare from Ross Smith to win 4-2 and book a last-16 spot at the World Darts Championship.A back-and-forth contest that saw 27 maximums posted throughout started with Dobey taking the first set with a 116 checkout before continuing his ruthless run to clinch the second with an average of 122.The world number 17 took the opening two legs in the third, but was unable to find the crucial doubles as Smith dragged himself back into the game to pull one back.Smith drew level but another tight set saw Dobey edge ahead and he hit double 16 for the match to set up a meeting with reigning world champion Michael Smith in the last 16.Another close contest saw Joe Cullen reach the next round with a 4-2 win over Ryan Searle.Cullen breezed through the opening two sets but Searle found some rhythm to take the third.'Heavy Metal' put up a fightback in the fourth, where a tight deciding leg saw him take advantage of Cullen's missed double with a 124 finish on the bullseye to level the match.A cagey set followed as 'The Rockstar' edged to victory and another tight set followed, but Cullen managed to hit double top for the win.Stephen Bunting produced a stunning performance to beat Florian Hempel 4-0.An electric opening saw Bunting set the tone with two 180s in his opening leg before winning the next one, but an excellent 164 checkout spurred Hempel on as he took the next two legs.With the first set level at 2-2, the "Bullet" took the decider with an average of 115.62 and from there the momentum was firmly with Bunting as he swept Hempel away with a whitewash, averaging 101.15 throughout.Victory means Bunting will now face Michael van Gerwen in the last 16.