Ireland scored four first-half tries at the Stade de la Beaujoire and four after the break to see off the Pacific islanders, who were playing their first game of the tournament in France but, despite the inclusion of several former All Blacks in their lineup, proved no match for the top-ranked team.
Sexton only played the first half but scored a try, a penalty and four conversions for a 16-point tally that took him to 1,090, going past Ronan O’Gara’s record of 1,083.
Ireland’s first three tries came from Tadhg Beirne, Caelan Doris and Mack Hansen before an obviously delighted Sexton went past the record by dotting down between the posts to open up a 31-13 lead at the break.
Bundee Aki scored twice in the second half and James Lowe and Rob Herring also crossed to extend Ireland's lead.
Tonga scored their try on the stroke of half-time through Vaea Fifita and fly-half William Havili, whose elder brother is in the New Zealand squad, did not miss any of his kicks to notch up 11 points.
Ireland attacked spaces left by Tonga’s propensity to over-concentrate their defensive line and broke through the middle to set up the tries for Beirne and Sexton.
Doris’ 26th-minute effort came off a driving maul and Hansen jinxed his way off the touchline on the right wing for a sparkling try.
Ireland made multiple changes early in the second half before again breaching Tonga’s line with Lowe looping around to finish off another strong driving maul.
Aki hit the line at speed to burst through a gap and sprint away for their sixth try and he grabbed another soon afterwards.
Herring added Ireland’s eighth try just before the final whistle to allow Sexton’s replacement Ross Byrne to put over his fourth conversion.
