Although the extent of the bond strength reduction is similar for all types of adhesives after aging, micromorphological examination is able to demonstrate the various degradation phases for each adhesive system in in vivo and in vitro. Since the bond structure of the resin–dentin bond depends on the type of adhesive, micromorphological analysis reveals various degradation patterns of bonds after aging. The objective of this article

is to provide a critical review of the degradation of resin–dentin bonds for all types of adhesive systems. Acidic solutions (i.e. 35% phosphoric acid) are used to demineralize the smear layer and the underlying intact dentin to expose the collagen network. The incomplete impregnation of the exposed collagen space by subsequent application of bonding resin INCB018424 supplier is due to imperfect resin monomer infiltration ( Fig. 3). The discrepancy between the depth of the collagen layer and resin infiltration creates an exposed demineralized dentin www.selleckchem.com/products/lee011.html zone under the hybrid layer ( Fig. 3) [26], [27], [28], [29], [30], [31], [32], [33], [34] and [35]. These zones correspond

with the sites of different modes of silver nitrate staining within the hybrid layer. Spencer and Wang reported resin monomer distribution in the demineralized dentin zone, especially evaluating the heterogeneity of the monomer–collagen interaction, using micro-Raman spectroscopy [34] and [35]. In their publications, the differentiation of resin monomer diffusion was reveal to depend on the molecular weight of the monomer at the collagen network of the hybrid layer [34] and [35]. Using atomic force microscopy (AFM), Marshall et al. observed in situ collagen morphology before and after dentin surface treatment [36], [37] and [38]. The zone of demineralized dentin and the degradation phase were found morphologically using AFM analysis [29]. The exposed collagen fibrils here underwent structural deterioration due to hydrolytic degradation, resulting Buspirone HCl in decreasing

bond strength [12], [14], [15] and [16]. In vivo morphological evidence of collagen hydrolysis was first obtained using extracted human primary teeth with resin restorations [12] and [39]. Fig. 4 shows collagen degradation within the demineralized dentin in the fractured surface of a resin–dentin bonded specimen (Scotchbond Multi-Purpose) that functioned in the human oral environment for 10 months ( Fig. 4b). Although an intact hybrid layer is visible in the control specimen at 24 h after bonding ( Fig. 4a), hydrolytic degradation of collagen fibrils ( Fig. 4b) is clearly observed after aging. There are many lateral branches of dentinal tubules at the fractured surfaces of the dentin side of a specimen in the aged specimen ( Fig. 4b), whereas there are none in the control ( Fig. 4a). The peritubular matrix of the dentinal tubules is richer in inorganic compounds than the lateral branches and the lateral branches are readily widened by collagen hydrolysis [12] and [39].