Introduction

Selective caries removal is a common method in restorative dentistry to maintain pulpal health, but bonding to caries-affected dentin (CAD) remains challenging due to its altered structure and reduced mineral content.

Objectives

The current research compared the shear bond strength (SBS) of a two-step total-etch (Single Bond 2;
SB2) and one-step self-etch (Scotchbond Universal; SU) adhesive systems applied to sound and CAD.

Material and methods

A total of 100 molars were allotted into two main groups (n = 50) based on dentin condition, i.e., sound dentin and CAD, with CAD induced by a 14-day pH cycling model. Then, every dentin group was divided into two subgroups (n = 25) based on type of adhesive, either SB2 or SU, forming four experimental groups: Subgroups 1 and 2: SB2 applied to sound and CAD; Subgroups 3 and 4: SU applied to sound and CAD. According to the supplier’s instructions, adhesives were used and then composite build-up using nanofilled composite (Filtek Z350 XT). Following a 24-hour water storage period, specimens were examined for SBS using a universal testing device.

Results

Sound dentin exhibited significantly higher SBS than CAD, irrespective of the adhesive type. SB2 showed higher bond strengths than SU across both sound and CAD conditions, and the type of adhesive and dentin condition interacted significantly.

Conclusions

Bonding to CAD has a negative impact on SBS compared to SD in both adhesive systems. The two-step total-etch adhesive generally provide superior SBS on both sound and CAD conditions compared to the one-step self-etch adhesive.