Effects of dentin modifiers on surface and mechanical properties of acid-etched dentin

Abstract Purpose The purpose of the present study was to evaluate dentin hardness and microtensile strength (μTS) after a simulated clinical procedure of acid etching followed by surface treatment with proposed different cross-linking agents’ protocols (1% riboflavin activated by either blue light or UVA light and Carbodiimide). Materials and method For Vickers hardness number (VHN), coronal dentinal discs were prepared and divided into five groups (n = 5) according to the cross-linking protocol. Cross-linking agents were applied after the samples were etched with 37% phosphoric acid, rinsed, and dried. The protocols included were as follows: Groups 1 and 2: surface treatment by 1% riboflavin activated by blue light (BL) for 20 s or 60 s, respectively. Groups 3 and 4: 1% riboflavin activated by UVA light for 20 s or 60 s, respectively. Group 5: 0.5 M carbodiimide surface treatment for 60 s. Microhardness of each group was tested at three stages: before treatment, after acid etching, and finally after application of the cross-linking agent. For μTS, dentin discs were sectioned into bars and divided into seven groups (n = 10): Group 1: control. Group 2: acid-etched. Groups 3–7: received the same cross-linking agent protocols as described for hardness tests. A microtensile tester was used to test the μTS. Results There was a significant reduction in VHN after acid etching, which was retained after attempted superficial cross-linking of dentin discs. However, there was no significant difference in the microtensile strength of dentin bars after acid etching and cross-linking in comparison to control untreated bars. Conclusion Under the limitations of this study, the acid etching of dentin reduced hardness, and the use of proposed cross-linking substances did not improve the hardness or μTS. An explanation for the reported improvement in resin composite bonding to etched and cross-linked dentin surfaces remains elusive.