Objectives: The effect of different etching times using four commercial phosphoric acids on calcium (Ca) content into demineralized dentin matrix, the resin-dentine microtensile bond strength (μTBS) and nanoleakage (NL) using an MDP-containing or a MDP-free universal adhesive. Methods: The phosphoric acid were used: Ultra-etch [ULE], Scotchbond Universal Etchant [SUE]; Dentsply Dental Conditioner [DDC] and Total Etch [TTE]. For Ca-content into demineralized dentin matrix, mid-coronal human dentine slices were etched for 3 s or 15 s and evaluated by energy-dispersive X-ray (EDX). Slices with no etching procedure (0 s) were used such control. The phosphoric acids (1 ml) were titrated by adding successive 1 ml drops of NaOH (0,08N). For μTBS and NL, flat dentine surfaces were etched for 3 s or 15 s. After that, an MDP-containing universal adhesive (Scotchbond Universal [SBU] and a MDP-free universal adhesive (Peak Universal Bond [PUB] were applied to flat dentine surfaces, composite resin build-ups and specimens were sectioned to obtain resin–dentine sticks. μTBS and NL were evaluated after 24h of water storage. ANOVA and Tukey’s test were applied (α = 0.05). Results: Ca content decreased significantly for all acids at times 3 and 15 s respectively when compared with the control time (0 s). Higher μTBS values were observed for ULE and SUE; the nanoleakage regarding to the acid type, lower NL values were observed for ULE and SUE mainly when compared to DDC and TTE , except for 3 s etching time for PUB adhesive, where DDC was similar to ULE and SUE. Regarding to the adhesive type, lower NL values were observed for SBU when compared to PUB. Conclusions: The ULE and SUE acids were less aggressive avoiding overreaching dentin mainly with the shortening etching time associated with MDP-containing adhesive improved bonding effectiveness.