Objective: To evaluate microtensile bond strength (μTBS) of four types of adhesives including the "modified-bioactive" and their effect on micromorphological patterns of resin/dentin interface, immediately after 24hours and after 6months storage, followed by thermocycling. Material and Methods: Eighty extracted sound permanent molars were collected from patients seeking extraction in the outpatient clinic oral surgery department, Faculty of Dentistry at Mansoura University, according to the

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... lation of our institutional ethical committee under # (A03160321). The selected molars were assigned into four groups according to adhesive types: non-modified self-etch adhesive modified self-etch adhesive with hydroxyapatite nanorods, universal adhesive, resin-modified glass ionomer adhesive. The groups according to time of testing were subdivided into two subgroups: (a) was immediately evaluated, (b) was subjected to the 6months storage in artificial saliva followed by thermocycling (2000cycles). Results: The Two-way ANOVA test showed that the "adhesive type" and "time" partially affected the µTBS results. There was no significant difference in μTBS between non-modified and modified groups (p>0.05). However, there was a significant difference in μTBS between the universal group (Delayed) (D) and the non-modified group (Immediate) (I). There is a high significance of all tested groups with the resin-modified glass ionomer adhesive delayed group (p<0.05). Conclusion: The incorporation of hydroxyapatite -nanorod to self-etch adhesive improve bond strength with no significant difference. Aging did not affect negatively the bond strength between groups except Riva group. There is a considerable significant difference between the Universal adhesive aged group and the non-modified adhesive immediate group.