Despite putting in a below-par performance for much of the encounter, Juve took the lead when Dybala – whose long-term future in Turin is rumoured to be in doubt – slotted home from close range eight minutes after coming on.
Dybala's effort came against the run of play, with Juve sparred by wasteful finishing and a superb block from Alex Sandro, who prevented Ibrahima Mbaye from putting Bologna ahead.
However, Juve's strength in depth proved the difference as they became the first side in Serie A history to win at least 22 of their first 25 games of a season, with the result also a timely boost for boss Massimiliano Allegri after the Champions League defeat to Atletico Madrid in midweek.
Bologna were unfortunate not to capitalise on their opponents' sluggish start – Federico Santander clipping over from close range before Nicola Sansone and Simone Edera shot wide.
Santander should have done better with a strike that flashed wide just before the half-hour mark, and Federico Bernardeschi's curling effort almost made Bologna pay for their profligacy.
Juve barely improved in attack after the interval and needed a fantastic last-ditch intervention from Alex Sandro to deny Mbaye from point-blank range.
Allergi turned to Dybala for inspiration and was swiftly rewarded for the positive change when the Argentine forward latched on to a loose ball and made no mistake with a composed first-time finish in the 67th minute.
Bologna rallied late on and Mattia Perin came to Juve's rescue in in the closing minutes, tipping Sansone's dipping strike onto the woodwork to make sure his side kept a 14th clean sheet in Serie A this term.
Juve bounce back
Juve were disappointing against Atletico in European action and while Bologna deserved more for a battling display, Dybala's moment of quality now has the leaders further clear of second-placed Napoli.
Bologna, meanwhile, remain in the relegation zone after failing to secure anything against the reigning champions
Dybala gives Allegri a boost
The future for Dybala and Allegri at Juve has been the subject of media interest of late. But, despite being benched, the former made his mark when called upon, suggesting he still has a point to prove with the Serie A giants.
Ronaldo cuts a frustrated figure
It has been a superb maiden season in Serie A for Ronaldo, but the league's leading scorer – who lined up on the left wing – put in an unusually sloppy display.
