13c). This explains why both XRD and nuclear magnetic resonance (NMR) revealed that upon interaction of 10-MDP with HAp, DCPD was only very slowly deposited in the solution. This high chemical affinity of 10-MDP

to HAp along with nano-layering was first demonstrated on pure synthetic HAp using XRD and later confirmed by NMR [60]. Apatite in natural dentin is carbonated and also contains trace amounts of Na, Mg, Sr, and Al, among others [62]. Direct evidence of the formation of a nano-layered structure on natural dentin was later provided by TEM (Fig. 16), and structurally by XRD of 10-MDP-treated dentin samples (Fig. 16) [61]. Furthermore, rubbing the primer solution on the dentin surface intensified the nano-layering, which may explain why this “active” application technique increases the bond strength as observed in previous studies [61]. The way molecules interact with learn more apatite-based Doxorubicin tissues can be described

by the so-called “AD-concept” or “Adhesion-Decalcification concept” (Fig. 17) [63] and [64]. This model shows that initially all acids chemically (ionically) bond to calcium of HAp. This first bonding phase goes together with the release of phosphate (PO43−) and hydroxide (OH ) ions from HAp into their own solution, such that the surface remains electro-neutral. Whether the molecule will remain bonded or will de-bond depends on the stability of the formed bond to Ca, or in other words on the stability of the respective

calcium salt. Molecules such as 10-MDP, which is a functional monomer in self-etch adhesives, as described above, and polyalkenoic acids, which are the main components of glass-ionomers, chemically bond to Ca of HAp, forming stable calcium-phosphate and calcium-carboxylate salts, respectively, along with only a limited surface-decalcification effect. The bonding mechanism of 10-MDP-based self-etch adhesives closely resembles that of resin-modified glass-ionomers [6] and [65]. The self-etch adhesives, including 10-MDP, indeed only superficially interact with enamel and dentin, and hardly dissolve apatite crystals, but rather keep them in place within a thin submicron hybrid layer. Resin-modified glass-ionomers also typically eltoprazine present with a submicron hybrid layer that still contains substantial apatite. In this respect, glass-ionomers could even be regarded as a type of mild self-etch adhesives. Polyalkenoic acid is a polymer with a multitude of carboxyl functional groups that grab individual Ca-ions along the mineral substrate as chemical “hands.” This chemical bonding, combined with micro-mechanical interlocking through shallow hybridization, establishes the unique self-adhesiveness of glass-ionomers (even without any form of pretreatment).