Assessment of Hydroxyapatite Nanospheres Incorporated Dentin Adhesive. A SEM/EDX, Micro-Raman, Microtensile and Micro-Indentation Study

Abstract

Hydroxyapatite (HA) delivery with resin adhesives has potential for re-mineralization of resin–dentin interface. The study prepared an adhesive containing HA and confirmed its presence in adhesive and interaction with the dentin using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Micro-Raman spectroscopy. The aim was to assess the influence of HA incorporation in dentin adhesive on its microtensile bond strength (μ-tbs) and Knoop microhardness (KHN). Thirty teeth each were bonded with CA and HA adhesive using a 10-s smear and photo-polymerized. The specimens in each adhesive group (CA and HA) were divided into sub-groups of 24 h, 8 weeks, and 16 weeks (n = 10) aging durations. μ-tbs was assessed at a crosshead speed of 0.5 mm/minute and bonded interface was analyzed using SEM (n = 20) and Raman spectroscopy (n = 10). Softening of HA adhesive and CA was assessed using KHN. HA adhesive presented higher μ-tbs compared to CA. With an increase in storage time, HA adhesive presented with 100% adhesive failure. Softening was less and KHN was higher for HA adhesive compared to CA (p < 0.05). KHN reduction was higher in CA [19.6 (5.1)%] compared to the HA adhesives [9.7 (4.5)%]. HA adhesive showed superior μTBS and microhardness compared to CA. In the absence of nanoleakage, HA modified adhesive exhibited enhanced bond integrity and better durability of resin dentin bond compared to control adhesive.