Sheehan's first was sandwiched by tries from Jack Crowley and Jack Conan in the opening 40 minutes as Ireland took a 19-0 lead into the break.
The hooker sealed the bonus point early in the second period before the home side's wingers got in on the act, James Lowe and Calvin Nash crossing late on.
Italy were limited to few chances by a stubborn green wall in defence, making just two visits to the opposing 22, as Ireland stopped an opposition team scoring a point in a Five or Six Nations match for the first time since 1987.
CONFIDENT CROWLEY TAKES CONTROL
Much of the pre-Championship talk, around Ireland in particular, naturally centred around Crowley as the heir apparent in the No.10 jersey.
The Munster man is very much his own player, one determined not to live in Johnny Sexton’s shadow, and he is already looking at home with the sizable responsibility entrusted to him.
Fresh from an assured display in Marseille, the fly-half was straight into the action in Dublin. After his opposite number Paolo Garbisi missed a penalty which would have put Italy in front, Crowley made him pay by crossing for his first international try in the eighth minute.
Hugo Keenan and Robbie Henshaw made the hard yards in the build-up and Crowley, who had taken contact himself seconds beforehand, was quickly up on his feet to accept Craig Casey’s pass and go over on the right.
He missed the conversion and the Azzurri then enjoyed a spell of possession inside the Irish half as they sought a response. But a killer instinct was lacking, Ange Capuozzo’s crossfield kick going out on the full proving an example of costly inaccuracies in attack.
Ireland, by contrast, have built a reputation for ruthlessness under Andy Farrell and were not in the mood to pass up opportunities.
Sheehan, fresh from a chargedown on Stephen Varney which got the crowd off their feet, went over for his side’s second try with Crowley again at the heart of the foundations.
A clever no-look pass to Keenan got Ireland motoring and Crowley then sent the ball through the hands via both centres to Sheehan, who bulldozed into Capuozzo and dotted down.
There was time for another score before the break as Ireland’s pack again asserted their authority, with Conan the man to benefit on this occasion as he powered over from a couple of metres out.
SHEEHAN STRETCHES ADVANTAGE
Ireland set out in search of securing the bonus point as soon as possible in the second half and Sheehan ensured they did just that.
When Italy were penalised for collapsing the scrum, Crowley located the corner and the forwards did the rest, with the prolific hooker on hand to provide the finishing touch.
He was inches away from his hat-trick shortly afterwards when set free on the left, only to be held up just short as the home side kept their foot on the pedal.
When the ball was recycled, it eventually found its way to Robbie Henshaw, who stretched out a right hand to dot down what he thought was Ireland’s fifth try only for his effort to be disallowed for double movement following a review.
Italy’s task became steeper when Tommaso Menoncello was sent to the sin-bin for a trip on James Lowe just before the hour mark and the wing was quick to made the numerical advantage count.
Lowe shrugged off the attentions of three Italian defenders with a show of serious power on the left-hand side to extend the lead to 29-0, though Crowley’s conversion was unsuccessful for a third time.
Italy introduced Ross Vintcent for his international bow late on but handling errors continued to frustrate the visitors, who were unable to build phases when given opportunities to lay a platform inside the Ireland half.
The hosts’ handling, on the other hand, came to the fore late on when they added a sixth try. Stuart McCloskey’s excellent offload soon found its way to Jamison Gibson-Park, who set Nash free to score in the corner.
Gibson-Park enjoyed an influential cameo and came close to adding his own name to the scoresheet with the clock in the red but the ball slipped from his grasp just short of the line, the knock-on bringing an end to another professional job well done by Farrell's side.
Wales are next up in Round 3 as Ireland look to keep their bid for back-to-back Grand Slams on course and in this mood, you would not bet against them.
