Parametric study of the effect of phase anisotropy on the micromechanical behaviour of dentin–adhesive interfaces

Journal of the Mechanical Behavior of Biomedical Materials

et al. 2017

The aim of this study was to evaluate changes in the mechanical and chemical behavior, and bonding ability at dentin interfaces infiltrated with polymeric nanoparticles (NPs) prior to resin application. Dentin surfaces were treated with 37% phosphoric acid followed by application of an ethanol suspension of NPs, Zn-NPs or Ca-NPs followed by the application of an adhesive, Single Bond (SB). Bonded interfaces were stored for 24 h, submitted to microtensile bond strength test, and evaluated by scanning electron microscopy. After 24 h and 21 d of storage, the whole resin-dentin interface adhesive was evaluated using a Nano-DMA. Complex modulus, storage modulus and tan delta (δ) were assessed. AFM imaging and Raman analysis were performed. Bond strength was not affected by NPs infiltration. After 21 d of storage, tan δ generally decreased at Zn-NPs/resin-dentin interface, and augmented when Ca-NPs or non-doped NPs were used. When both Zn-NPs and Ca-NPs were employed, the storage modulus and complex modulus decreased, though both moduli increased at the adhesive and at peritubular dentin after Zn-NPs infiltration. The phosphate and the carbonate peaks, and carbonate substitution, augmented more at interfaces promoted with Ca-NPs than with Zn-NPs after 21 d of storage, but crystallinity did not differ at created interfaces with both ions-doped NPs. Crosslinking of collagen and the secondary structure of collagen improved with Zn-NPs resin-dentin infiltration. Ca-NPs-resin dentin infiltration produced a favorable dissipation of energy with minimal stress concentration trough the crystalline remineralized resin-dentin interface, causing minor damage at this structure.

Section: Discussionmentioning

confidence: 99%

Ions-modified nanoparticles affect functional remineralization and energy dissipation through the resin-dentin interface

Toledano

Journal of the Mechanical Behavior of Biomedical Materials

et al. 2017

“…In general, Hi and Ei were higher at intertubular sound dentin than at cariesaffected dentin, as reported by [41,42] , except when Zn-containing amalgams were employed and Ei was measured, that resulted similar in both groups (Table 2). Nevertheless, intertubular dentin is expected to have a modulus gradient from 2.7 GPa at the untreated caries-affected dentin, ramping up to 18.85 GPa after removal of Zn-containing restorations from the carious substrate, lower that at sound dentin (25.4 GPa), due to the partial demineralization [43] .This rise in nanomechanical properties correlates with an augmentation of bands at 430 (56.04) and 451 (54.82) cm -1 (v 2 mode) (~30 and 43% increase, respectively), assigned to vibration of carbonate calcium phosphate in apatite lattice [27] in carious dentin, after Zn-containing amalgam removal, in comparison with the untreated dentin (39.27 and 30.65, respectively) ( Table 3) (Fig. 2A).…”

Section: Resultsmentioning

confidence: 99%

Ex vivo detection and characterization of remineralized carious dentin, by nanoindentation and single point Raman spectroscopy, after amalgam restoration

Aguilera

Cabello

et al. 2016

J Raman Spectroscopy

The aim of this study was to assess the mechanical and chemical performance of sound and caries-affected dentin (CAD), after Zn-free vs containing amalgam restorations placement and thermocycling. Dentin surfaces were studied by Atomic Force Microscopy (AFM) analysis for surface morphological characterization (including fibril diameter assessment), nano-indentation (to measure nano-hardness-Hi and modulus of Young-Ei), and single point Raman spectroscopy for chemical analysis. Measurements were performed before amalgam placement, after amalgam removal, and after 3 months of thermocycling (100,000cy/5 ºC and 55 ºC). Restorations increased both Hi and Ei at intertubular dentin of CAD. The highest values of Hi were achieved at intertubular dentin after restoring with Zn-containing amalgams. Remineralization of dentin was attributed to the increase of both amorphous and crystalline new mineral, as lower degrees of crystal imperfections in junction with crystal disorders, and improvement in structural stability of collagen were found. Higher presence of minerals were also confirmed after the decrease of fluoridated apatite and the increase of the total water content. Proteoglycans, lipids, and proteins, augmented in both sound and CAD, providing support for the mineral growing. The increase of bands assigned to vibration of carbonate calcium phosphate contributed to a decrease of crystallinity.

“…From the stress distribution mapped by Misra et al (2004), it can be inferred that failure or fracture could probably initiate at three locations in the HL and the dentine: (i) in the adhesive tag proximal to the HL due to stress concentration, (ii), close to the BHL due to high strain; and (iii) interface between the adhesive tag and peritubular dentine of the lumen wall due to stress concentration (Misra et al, 2005). Moreover, if the bond between the adhesive tags and peritubular dentine is imperfect permitting micro-permeability (Fig 3/5A), then the stress concentration zones are probably within the HL and BHL, where stresses will concentrate and the integrity of the resin-dentine interface will be jeopardized.…”

Section: Resultsmentioning

confidence: 99%

“…This mineral growing correlates well with an increase in nano-hardness and Young's modulus (Toledano et al, 2015). The main components of dentine behave as an effective anisotropic composite material (Misra et al, 2005), whose function is additionally complicated by biological factors that can affect both the composition and the interactions between the components. As polymers, dentine components exhibit time-dependent behavior representative of viscoelastic media.…”

Section: Introductionmentioning

confidence: 99%

Nanoscopic dynamic mechanical analysis of resin–infiltrated dentine, under in vitro chewing and bruxism events

Toledano

Journal of the Mechanical Behavior of Biomedical Materials

Cabello

et al. 2016

HIGHLIGHTSSustained mechanical loading promotes failures at the resin-dentine interface.Higher viscoelastic properties of tubular dentine concentrate stress at the interface.Load cycling in sine or square wave promote healing at the resin-dentine interface. 4 ABSTRACTThe aim of this study was to evaluate the induced changes in mechanical behavior and bonding capability of resin-infiltrated dentine interfaces, after application of mechanical stimuli. Dentine surfaces were subjected to partial demineralisation through 37% phosphoric acid etching followed by the application of an etch-and-rinse dentine adhesive, Single Bond (3M/ESPE). Bonded interfaces were stored in simulated body fluid during 24 h, and then tested or submitted to the mechanical loading challenge.Different loading waveforms were applied: No cycling (I), 24 h cycled in sine (II) or square (III) waves, sustained loading held for 24 h (IV) or sustained loading held for 72 h (V). Microtensile bond strength (MTBS) was assessed for the different groups.Debonded dentine surfaces were studied by field emission scanning electron microscopy (FESEM). At the resin-dentine interface, both the hybrid layer (HL) and the bottom of the hybrid layer (BHL), and both peritubular and intertubular were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform the nano-Dynamic Mechanical analysis and to estimate the complex and storage modulus. Dye assisted Confocal Microscopy Evaluation was used to assess sealing ability. Load cycling increased the percentage of adhesive failures in all groups.Specimens load cycled in held 24 h attained the highest complex and storage moduli at HL and BHL. The storage modulus was maximum in specimens load cycled in held 24 h at peritubular dentine, and the lowest values were attained at intertubular dentine. The storage modulus increased in all mechanical tests, at peritubular dentine. An absence of micropermeability and nanoleakage after loading in sine and square waveforms were encountered. Porosity of the resin-dentine interface was observed when specimens were load cycled in held 72 h. Areas of combined sealing and permeability were discovered 5 at the interface of specimens load cycled in held 24h. Crack-bridging images appeared in samples load cycled with sine waveform, after FESEM examination.