Tunable polymer-peptide hybrids for dentin tissue repair.

OBJECTIVES: This study targets to assess the remineralization capability of conditioned dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs). METHODS: Dentin conditioned surfaces were infiltrated with NPs and TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanohardness, Masson's trichrome staining microscopy, and Raman analysis. RESULTS: Dentin surfaces treated with TDg-NPs and load cycled produced higher nanohardness than the rest of the groups at the hybrid layer. At the bottom of the hybrid layer, all samples treated with TDg-NPs showed higher nanohardness than the rest of the groups. Active remineralization underneath the hybrid layer was detected in all groups after TDg application and load cycling, inducting new dentinal tubuli formation. After thermocycling, remineralization at the hybrid layer was not evidenced in the absence of NPs. Raman analysis showed increase mineralization, enriched carbonate apatite formation, and improved crosslinking and scaffolding of the collagen. CONCLUSIONS: Mechanical loading on the specimens obtained after TDg-NPs dentin infiltration inducts an increase of mineralization at the resin/dentin interface, indicating remineralization of peritubular and intertubular dentin with augmented crystallographic maturity in crystals. Enriched collagen quality was produced, generating an adequate matrix organization to promote apatite nucleation, after tideglusib infiltration. CLINICAL SIGNIFICANCE: At the present research, it has been proved the creation of reparative dentin, at the resin-dentin interface, after tideglusib dentin infiltration. Chemical stability, to favor integrity of the resin-dentin interface, is warranted in the presence of the TDg-NPs in the demineralized dentin collagen.

Effects of an MDP-based surface cleaner on dentin structure, morphology and nanomechanical properties.

OBJECTIVE: To analyze the effect of Katana™ Cleaner (KC) in nanomechanical and triboscopic properties of etched dentin. METHODS: Dentin disks from human third molars were prepared. Two main groups of study were established in function of the etching conditioning, phosphoric acid (PA) and Clearfil SE Bond primer (CSEB). Four subgroups were tested within each group: i) untreated dentin (UD), ii) etched dentin (ED) [(PAED/CSEB)], iii) etched dentin contaminated with saliva (PAED+S)/(CSEB+S), and iv) etched and contaminated dentin treated with KC (PAED+S+KC)/(CSEB+S+KC). Nano-DMA testing and imaging, atomic force microscopy (AFM) analysis and nanoroughness (SRa) measurements were obtained. Field emission scanning electron microscopy (FESEM) images were also acquired. RESULTS: Phosphoric acid etched dentin samples and those specimens contaminated with saliva (PAED+S) attained the highest SRa values, that decreased after Katana™ Cleaner application (PAED+S+KC). In the group of dentin treated with CSEB primer, all subgroups performed similar, except in CSEB+S that attained the highest SRa values. The treatment with KC restored the original values of complex modulus of the untreated dentin. KC application produced the lowest and the highest tan delta values on PAED and CSEB groups, respectively. CONCLUSION: Katana™ Cleaner provided equally mature dentin surfaces after any of the etching methods. Tan delta increased when Katana™ Cleaner was applied on the dentin surface previously etched and contaminated with saliva, regardless the kind of etchant, thus facilitating the dissipation of energy for elastic recoil during loading. CLINICAL SIGNIFICANCE: Katana™ Cleaner application after saliva contamination originated similar low roughness levels, regardless the type of etching method. Both complex and storage moduli were similar, after Katana™ Cleaner application, in any case.

Dexamethasone-doped nanoparticles improve mineralization, crystallinity and collagen structure of human dentin.

OBJECTIVES: Bioactive materials have been used for functionalization of adhesives to promote dentin remineralization. This study aims to evaluate bonding ability and both mechanical and chemical behavior of demineralized dentin infiltrated with polymeric nanoparticles doped with dexamethasone (Dex-NPs). METHODS: Dentin conditioned surfaces were infiltrated with NPs, Dex-NPs or Dex-Zn-NPs. Bonded interfaces were also created and stored for 24 h or 21d, and then submitted to microtensile bond strength testing. Dentin remineralization was analyzed by Nanohardness, Young's modulus and Raman analysis. RESULTS: At 21d of storage, dentin treated with undoped-NPs attained the lowest nanohardness and Young's modulus. Dex-NPs and Zn-Dex-NPs increased dentin nanohardness and Young's modulus after 21d Raman analysis showed high remineralization, crystallinity, crosslinking and better structure of collagen when functionalized Dex-NPs were present at the dentin interface. CONCLUSIONS: Infiltration of dentin with Dex-NPs promoted functional remineralization as proved by nanomechanical and morpho-chemical evaluation tests. Dexamethasone in dentin facilitated crystallographic maturity, crystallinity and improved maturity and secondary structure of dentin collagen. CLINICAL SIGNIFICANCE: Using dexamethasone-functionalized NPs before resin infiltration is a clear option to obtain dentin remineralization, as these NPs produce the reinforcement of the dentin structure, which will lead to the improvement of the longevity of resin restorations.

Dexamethasone and zinc loaded polymeric nanoparticles reinforce and remineralize coronal dentin. A morpho-histological and dynamic-biomechanical study.

OBJECTIVE: To investigate the effect of novel polymeric nanoparticles (NPs) doped with dexamethasone (Dex) on viscoelasticity, crystallinity and ultra-nanostructure of the formed hydroxyapatite after NPs dentin infiltration. METHODS: Undoped-NPs, Dex-doped NPs (Dex-NPs) and zinc-doped-Dex-NPs (Zn-Dex-NPs) were tested at dentin, after 24 h and 21 d. A control group without NPs was included. Coronal dentin surfaces were studied by nano-dynamic mechanical analysis measurements, atomic force microscopy, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p < 0.05). RESULTS: At 21 d of storage time, both groups doped with Dex exhibited the highest complex, storage and loss moduli among groups. Zn-Dex-NPs and Dex-NPs promoted the highest and lowest tan delta values, respectively. Dex-NPs contributed to increase the fibril diameters of dentin collagen over time. Dentin surfaces treated with Zn-Dex-NPs attained the lowest nano-roughness values, provoked the highest crystallinity, and produced the longest and shortest crystallite and grain size. These new crystals organized with randomly oriented lattices. Dex-NPs induced the highest microstrain. Crystalline and amorphous matter was present in the mineral precipitates of all groups, but Zn and Dex loaded NPs helped to increase crystallinity. SIGNIFICANCE: Dentin treated with Zn-Dex-NPs improved crystallographic and atomic order, providing structural stability, high mechanical performance and tissue maturation. Amorphous content was also present, so high hydroxyapatite solubility, bioactivity and remineralizing activity due to the high ion-rich environment took place in the infiltrated dentin.

Biomimetic Remineralization of an Extracellular Matrix Collagen Membrane for Bone Regeneration.

Natural extracellular matrix (ECM) collagen membranes are frequently used for bone regeneration procedures. Some disadvantages, such as rapid degradation and questionable mechanical properties, limit their clinical use. These membranes have a heterologous origin and may proceed from different tissues. Biomineralization is a process in which hydroxyapatite deposits mainly in collagen fibrils of the matrices. However, when this deposition occurs on the ECM, its mechanical properties are increased, facilitating bone regeneration. The objective of the present research is to ascertain if different membranes from distinct origins may undergo biomineralization. Nanomechanical properties, scanning electron (SEM) and multiphoton (MP) microscopy imaging were performed in three commercially available ECMs before and after immersion in simulated body fluid solution for 7 and 21 d. The matrices coming from porcine dermis increased their nanomechanical properties and they showed considerable mineralization after 21 d, as observed in structural changes detected through SEM and MP microscopy. It is hypothesized that the more abundant crosslinking and the presence of elastin fibers within this membrane explains the encountered favorable behavior.

Novel Pastes Containing Polymeric Nanoparticles for Dentin Hypersensitivity Treatment: An In Vitro Study.

Tubule occlusion and remineralization are considered the two main goals of dentin hypersensitivity treatment. The objective is to assess the ability of dentifrices containing zinc-doped polymeric nanoparticles (NPs) to enduringly occlude the dentinal tubules, reinforcing dentin's mechanical properties. Fifteen dentin surfaces were acid-treated for dentinal tubule exposure and brushed with (1) distilled water, or with experimental pastes containing (2) 1% of zinc-doped NPs, (3) 5% of zinc-doped NPs, (4) 10% of zinc-doped NPs or (5) Sensodyne®. Topographical and nanomechanical analyses were performed on treated dentin surfaces and after a citric acid challenge. ANOVA and Student-Newman-Keuls tests were used (p < 0.05). The main results indicate that all pastes produced tubule occlusion (100%) and reinforced mechanical properties of intertubular dentin (complex modulus was above 75 GPa). After the citric acid challenge, only those pastes containing zinc-doped NPs were able to maintain tubular occlusion, as specimens treated with Sensodyne® have around 30% of tubules opened. Mechanical properties were maintained for dentin treated with Zn-doped NPs, but in the case of specimens treated with Sensodyne®, complex modulus values were reduced below 50 GPa. It may be concluded that zinc-doped NPs at the lowest tested concentration produced acid-resistant tubular occlusion and increased the mechanical properties of dentin.

Melatonin-doped polymeric nanoparticles induce high crystalline apatite formation in root dentin.

OBJECTIVE: To investigate the effect of novel polymeric nanoparticles (NPs) doped with melatonin (ML) on nano-hardness, crystallinity and ultrastructure of the formed hydroxyapatite after endodontic treatment. METHODS: Undoped-NPs and ML-doped NPs (ML-NPs) were tested at radicular dentin, after 24 h and 6 m. A control group without NPs was included. Radicular cervical and apical dentin surfaces were studied by nano-hardness measurements, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p < 0.05). RESULTS: Cervical dentin treated with undoped NPs maintained its nano-hardness values after 6 m of storage being [24 h: 0.29 (0.01); 6 m: 0.30 (0.02) GPa], but it decreased at apical dentin [24 h: 0.36 (0.01); 6 m: 0.28 (0.02) GPa]. When ML-NPs were used, nano-hardness was similar over time [24h: 0.31 (0.02); 6 m: 0.28 (0.03) GPa], at apical dentin. Root dentin treated with ML-NPs produced, in general, high crystallinity of new minerals and thicker crystals than those produced in the rest of the groups. After 6 m, crystals became organized in randomly oriented polyhedral, square polygonal block-like apatite or drop-like apatite polycrystalline lattices when ML-NPs were used. Undoped NPs generated poor crystallinity, with preferred orientation of small crystallite and increased microstrain. SIGNIFICANCE: New polycrystalline formations encountered in dentin treated with ML-NPs may produce structural dentin stability and high mechanical performance at the root. The decrease of mechanical properties over time in dentin treated without NPs indicates scarce remineralization potential, dentin demineralization and further potential degradation. The amorphous stage may provide high hydroxyapatite solubility and remineralizing activity.

Melatonin-doped polymeric nanoparticles reinforce and remineralize radicular dentin: Morpho-histological, chemical and biomechanical studies.

OBJECTIVES: To investigate the effectiveness of novel polymeric nanoparticles (NPs) doped with melatonin (ML) in reducing dentin permeability and facilitating dentin remineralization after endodontic treatment. METHODS: The effect of undoped NPs and ML-doped NPs (ML-NPs) was tested in radicular dentin, at 24 h and 6 m. A control group without NPs was included. ML liberation was measured. Radicular dentin was assessed for fluid filtration. Dentin remineralization was analyzed by scanning electron microscopy, AFM, Young's modulus (Ei), Nano DMA-tan delta, and Raman analysis. RESULTS: ML release ranged from 1.85 mg/mL at 24 h to 0.033 mg/mL at 28 d. Both undoped NPs and ML-NPs treated dentin exhibited the lowest microleakage, but samples treated with ML-NPs exhibited hermetically sealed dentinal tubules and extended mineral deposits onto dentin. ML-NPs promoted higher and durable Ei, and functional remineralization at root dentin, generating differences between the values of tan delta among groups and creating zones of stress concentration. Undoped-NPs produced closure of some tubules and porosities at the expense of a relative mineral amorphization. Chemical remineralization based on mineral and organic assessments was higher in samples treated with ML-NPs. When using undoped NPs, precipitation of minerals occurred; however, radicular dentin was not mechanically reinforced but weakened over time. SIGNIFICANCE: Application of ML-NPs in endodontically treated teeth, previous to the canal filling step, is encouraged due to occlusion of dentinal tubules and the reinforcement of the radicular dentin structure.

Polymeric zinc-doped nanoparticles for high performance in restorative dentistry.

OBJECTIVES: The aim was to state the different applications and the effectiveness of polymeric zinc-doped nanoparticles to achieve dentin remineralization. DATA, SOURCES AND STUDY SELECTION: Literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken. CONCLUSIONS: Polymeric nanospheres (NPs) were efficiently loaded with zinc. NPs sequestered calcium and phosphate in the presence of silicon, and remained effectively embedded at the hybrid layer. NPs incorporation did not alter bond strength and inhibited MMP-mediated dentin collagen degradation. Zn-loaded NPs remineralized the hybrid layer inducing a generalized low-carbonate substitute apatite precipitation, chemically crystalline with some amorphous components, and an increase in mechanical properties was also promoted. Viscoelastic analysis determined that dentin infiltrated with Zn-NPs released the stress by breaking the resin-dentin interface and creating specific mineral formations in response to the energy dissipation. Bacteria were scarcely encountered at the resin-dentin interface. The combined antibacterial and remineralizing effects, when Zn-NPs were applied, reduced biofilm formation. Zn-NPs application at both cervical and radicular dentin attained the lowest microleakage and also promoted durable sealing ability. The new zinc-based salt minerals generated covered the dentin surface totally occluding cracks, porosities and dentinal tubules. CLINICAL SIGNIFICANCE: Zinc-doped NPs are proposed for effective dentin remineralization and tubular occlusion. This offers new strategies for regeneration of eroded cervical dentin, effective treatment of dentin hypersensitivity and in endodontically treated teeth previous to the canal filling. Zn-NPs also do reduce biofilm formation due to antibacterial properties.

Zn-doping of silicate and hydroxyapatite-based cements: Dentin mechanobiology and bioactivity.

The objective was to state zinc contribution in the effectiveness of novel zinc-doped dentin cements to achieve dentin remineralization, throughout a literature or narrative exploratory review. Literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. Both zinc-doping silicate and hydroxyapatite-based cements provoked an increase of both bioactivity and intrafibrillar mineralization of dentin. Zinc-doped hydroxyapatite-based cements (oxipatite) also induced an increase in values of dentin nano-hardness, Young's modulus and dentin resistance to deformation. From Raman analyses, it was stated higher intensity of phosphate peaks and crystallinity as markers of dentin calcification, in the presence of zinc. Zinc-based salt formations produced low microleakage and permeability values with hermetically sealed tubules at radicular dentin. Dentin treated with oxipatite attained preferred crystal grain orientation with polycrystalline lattices. Thereby, oxipatite mechanically reinforced dentin structure, by remineralization. Dentin treated with oxipatite produced immature crystallites formations, accounting for high hydroxyapatite solubility, instability and enhanced remineralizing activity.

Ex vivo investigations on bioinspired electrospun membranes as potential biomaterials for bone regeneration.

OBJECTIVES: To assess the surface characteristics and composition that may enhance osteoblasts viability on novel electrospun composite membranes (organic polymer/silicon dioxide nanoparticles). METHODS: Membranes are composed by a novel polymer blend, the mixture of two hydrophilic copolymers 2-hydroxyethylmethacrylate-co-methylmethacrylate and 2-hydroxyethylacrylate-co-methylacrylate, and they are doped with silicon dioxide nanoparticles. Then the membranes were functionalized with zinc or doxycycline. The membranes were morphologically characterized by atomic force and scanning electron microscopy (FESEM), and mechanically probed using a nanoindenter. Biomimetic calcium phosphate precipitation on polymeric tissues was assessed. Cell viability tests were performed using human osteosarcoma cells. Cells morphology was also studied by FESEM. Data were analyzed by ANOVA, Student-Newman-Keuls and Student t tests (p < 0.05). RESULTS: Silica doping of membranes enhanced bioactivity and increased mechanical properties. Membranes morphology and mechanical properties were similar to those of trabecular bone. Zinc and doxycycline doping did not exert changes but it increased novel membranes bioactivity. Membranes were found to permit osteoblasts proliferation. Silica-doping favored cells proliferation and spreading. As soon as 24 h after the seeding, cells in silica-doped membranes were firmly attached to experimental tissues trough filopodia, connected to each other. The cells produced collagen and minerals onto the surfaces. CONCLUSIONS: Silica nanoparticles enhanced surface properties and osteoblasts viability on electrospun membranes. CLINICAL SIGNIFICANCE: The ability of silica-doped matrices to promote precipitation of calcium phosphate, together with their mechanical properties, observed non-toxicity, stimulating effect on osteoblasts and its surface chemistry allowing covalent binding of proteins, offer a potential strategy for bone regeneration applications.

Polymeric nanoparticles protect the resin-dentin bonded interface from cariogenic biofilm degradation.

The objective was to assess doxycycline (Dox) and zinc (Zn) doped nanoparticles' (NPs) potential to protect the resin-dentin interface from cariogenic biofilm. Three groups of polymeric NPs were tested: unloaded, loaded with zinc and with doxycycline. NPs were applied after dentin etching. The disks were exposed to a cariogenic biofilm challenge in a Drip-Flow Reactor during 72 h and 7 d. Half of the specimens were not subjected to biofilm formation but stored 72 h and 7 d. LIVE/DEAD® viability assay, nano-dynamic mechanical assessment, Raman spectroscopy and field emission electron microscopy (FESEM) analysis were performed. The measured bacterial death rates, at 7 d were 46% for the control group, 51% for the undoped-NPs, 32% for Dox-NPs, and 87% for Zn-NPs; being total detected bacteria reduced five times in the Dox-NPs group. Zn-NPs treated samples reached, in general, the highest complex modulus values at the resin-dentin interface over time. Regarding the mineral content, Zn-NPs-treated dentin interfaces showed the highest mineralization degree associated to the phosphate peak and the relative mineral concentration. FESEM images after Zn-NPs application permitted to observe remineralization of the etched and non-resin infiltrated collagen layer, and bacteria were scarcely encountered. The combined antibacterial and remineralizing effects, when Zn-NPs were applied, reduced biofilm formation. Dox-NPs exerted an antibacterial role but did not remineralize the bonded interface. Undoped-NPs did not improve the properties of the interfaces. Application of Zn-doped NPs during the bonding procedure is encouraged. STATEMENT OF SIGNIFICANCE: Application of Zn-doped nanoparticles on acid etched dentin reduced biofilm formation and viability at the resin-dentin interface due to both remineralization and antibacterial properties. Doxycycline-doped nanoparticles also diminished oral biofilm viability, but did not remineralize the resin-dentin interface.

Polymeric nanoparticles for endodontic therapy.

The effectiveness of novel polymeric nanoparticles (NPs) application in reducing dentin permeability and facilitating dentin remineralization after endodontic treatment was evaluated. The effect of undoped NPs, zinc, calcium and doxycycline-doped NPs (Zn-NPs, Ca-NPs and D-NPs, respectively) was tested in radicular dentin. A control group without NPs was included. Radicular dentin was assessed for fluid filtration. Dentin remineralization was analyzed by scanning and transmission electron microscopy, energy-dispersive analysis, AFM, Young's modulus (Ei), Nano DMA, Raman, and X-Ray Diffraction analysis. Ca-NPs and Zn-NPs treated dentin exhibited the lowest microleakage with hermetically sealed dentinal tubules and a zinc-based salt generation onto dentin. Zn-NPs favored crystallinity and promoted the highest Ei and functional remineralization at the apical dentin, generating differences between the values of complex modulus among groups. Ca-NPs produced closure of tubules and porosities at the expense of a relative mineral amorphization, without creating zones of stress concentration. The highest sealing efficacy was obtained in Zn-NPs-treated samples, along with the highest values of Young's modulus and dentin mineralization. These high values of Ei were obtained by closing voids, cracks, pores and tubules, and by strengthening the root dentin. When using undoped NPs or Ca-NPs, deposition of minerals occurred, but radicular dentin was not mechanically reinforced. Therefore, application of Zn-NPs in endodontically treated teeth previous to the canal filling is encouraged.

The mineralizing effect of zinc oxide-modified hydroxyapatite-based sealer on radicular dentin.

OBJECTIVE: The aim of this study was to evaluate the remineralization ability of three endodontic sealer materials at different root dentin regions. MATERIAL AND METHODS: Cervical, medial, and apical root dentin surfaces were treated with two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite); an epoxy resin-based canal sealer, AH Plus; and gutta-percha. Remineralization, at the inner and outer zones of dentin disk surfaces, was studied by nanohardness (Hi) and Raman analysis. Nanoroughness and collagen fibrils width measurements were performed. Numerical data, at 24 h or 12 m, were analyzed by ANOVA and Student-Newman-Keuls (p < 0.05). RESULTS: At the outer and inner zones of the cervical dentin treated with oxipatite, the highest Hi after 12 m of immersion was achieved. The same group showed the highest intensity of phosphate peak, markers for calcification and crystallinity. Nanoroughness was lower and fibril diameter was higher at the inner zone of the dentin treated with oxipatite. Dentin mineralization occurred in every region of the root dentin treated with oxipatite and calcypatite, especially at the inner zone of the dentin after 12 m. CONCLUSIONS: Oxipatite reinforced the inner root zone at any third of the radicular dentin, by increasing both nanohardness and remineralization. When using calcypatite, the highest nanohardness was found at the apical third of the inner root dentin, but the lowest mechanical performance was obtained at the cervical and the medial thirds of the roots. Therefore, application of oxipatite as sealing cement of root canals is recommended. CLINICAL RELEVANCE: Oxipatite, when used as an endodontic sealing material, strengthens radicular dentin.

A zinc oxide-modified hydroxyapatite-based cement favored sealing ability in endodontically treated teeth.

OBJECTIVES: To evaluate the effectiveness of different endodontic canal sealers for dentin permeability reduction and to determine the viscoelastic performance of root dentin after their application. METHODS: Cervical, medial and apical root dentin surfaces were treated with two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite); an epoxy resin- based canal sealer, AH Plus; and gutta-percha. Root dentin was evaluated for fluid filtration. Field emission scanning electron microscopy, energy dispersive analysis, AFM, Young's modulus and Nano-DMA analysis were also performed, at the inner and outer zones of dentin. RESULTS: Dentin treated with oxipatite showed the lowest microleakage among groups with hermetically sealed tubules and zinc-based salt formations. Samples treated with oxipatite showed the highest Ei at the cervical dentin third among groups, at 6 m of storage. Oxipatite promoted the highest complex modulus and tan delta values at the inner zone of both cervical and medial root dentin. Calcypatite favored the lowest tan delta outcomes at the inner zone of apical dentin at 6 m. CONCLUSIONS: Specimens treated with oxipatite showed the highest sealing ability, based on the highest Young's modulus and dentin mineralization, achieved by closing dentinal tubules, voids and pores that reinforced the inner zone of root dentin. The homogeneity of viscoelastic properties among the different root dentin thirds favored the energy dissipation without creating zones of stress concentration and micro-cracking which would have challenge micropermeability. Thereby, among the tested materials oxipatite is proposed as canal filling material and sealer in endodontics. CLINICAL SIGNIFICANCE: Oxipatite could be considered a good candidate for root canal filling material and sealer due to its improved long-term sealing ability and to the advanced remineralization, and so to the enhanced energy dissipation achieved at the inner zone of the radicular dentin.

Silver-loaded nanoparticles affect ex-vivo mechanical behavior and mineralization of dentin

Background: The aim was to evaluate the effect of silver loaded nanoparticles (NPs) application on the triboscopic, crystallographic and viscoelastic properties of demineralized dentin. Polymethylmetacrylate-based NPs and Ag loaded NPs were applied on demineralized dentin. Material and Methods: Treated and untreated surfaces were probed by a nanoindenter to test viscoelasticity, and by atomic force microscopy to test nanoroughness and collagen fibril diameter. X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging were also used. Results: Dentin treated with Ag-NPs attained the lowest complex modulus, and the highest tan delta values after 7 days of storage. Dentin treated with undoped-NPs achieved the lowest nanoroughness and the greatest collagen bandwidths among groups. Crystals were identified as hydroxyapatite with the highest crystallographic maturity and crystallite size in dentin treated with undoped-NPs. Texture increased in all samples from 24 h to 7 d, except in dentin surfaces treated with Ag-NPs at 310 plane. Polyhedral, block-like, hexagonal or plate-like shaped apatite crystals constituted the bulk of minerals in dentin treated with Ag-NPs, after 7 d. Polyhedral or rounded/drop-like, and polymorphic in strata crystal apatite characterized the minerals when undoped-NPs were used, with more crystalline characteristics after 7 d than that found when Ag-NPs were applied. Ag-NPs application did not improve the mechanical performance of dentin and did not produce dentin remineralization. However, energy was dissipated through the dentin without showing stress concentration; contrary was occurring at dentin treated with undoped- NPs, that provoked bridge-like mineral deposits at the dentin surface. Conclusions: Ag-NPs application did not enhance the mechanical properties of cervical dentin, though the energy dissipation did not damage the dentin structure. Remineralization at dentin was not produced after Ag-NPs appli-cation, though improved crystallinity may lead to increase stability of the apatite that was generated at the dentin surface

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Zn-containing polymer nanogels promote cervical dentin remineralization.

OBJECTIVE: Nanogels designing for effective treatment of eroded cervical dentin lesions. MATERIALS AND METHODS: Polymethylmetacrylate-based nanoparticles (NPs) were doxycycline (D), calcium, or zinc loaded. They were applied on eroded cervical dentin. Treated surfaces were characterized morphologically by atomic force and scanning electron microscopy, mechanically probed by a nanoindenter to test nanohardness and Young's modulus, and chemically analyzed by Raman spectroscopy at 24 h and 7 days of storage. Data were submitted to ANOVA and Student-Newman-Keuls multiple comparisons tests. RESULTS: Dentin treated with Zn-NPs attained the highest nanomechanical properties, mineralization, and crystallinity among groups. Nanoroughness was lower in Zn-treated surfaces in comparison to dentin treated with undoped gels. Dentin treated with Ca-NPs created the minimal calcification at the surface and showed the lowest Young's modulus at peritubular dentin. Intertubular dentin appeared remineralized. Dentinal tubules were empty in samples treated with D-NPs, partially occluded in cervical dentin treated with undoped NPs and Ca-NPs, and mineral covered when specimens were treated with Zn-NPs. CONCLUSIONS: Zn-loaded NPs permit functional remineralization of eroded cervical dentin. Based on the tested nanomechanical and chemical properties, Zn-based nanogels are suitable for dentin remineralization. CLINICAL RELEVANCE: The ability of zinc-loaded nanogels to promote dentin mineralization may offer new strategies for regeneration of eroded cervical dentin and effective treatment of dentin hypersensitivity.

Stored potential energy increases and elastic properties alterations are produced after restoring dentin with Zn-containing amalgams.

The aim of this research was to ascertain the mechanical and chemical behavior of sound and caries-affected dentin (CAD), after the placement of Zn-free vs containing amalgam restorations. Peritubular and intertubular dentin 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 (E * ) and storage modulus (E'); b) Raman spectroscopy was used to describe the hierarchical cluster analysis (HCA). Assessments were performed before restoration placement and after restoring, and after 3 months of storage with thermocycling (100,000cy/5 °C and 55 °C). When CAD was treated with Zn-containing restorations, differences between E * and E' at both peritubular and intertubular dentin augmented, with energy concentration and production of implications in the mechanical performance of the restored teeth. E * and E' were very low at intratubular dentin of CAD restored with Zn-containing restorations. The relative presence of minerals, the phosphate crystallinity and the crosslinking of collagen increased their values at both types of dentin (peritubular and intertubular) when CAD was treated with Zn-containing restorations. The nature and secondary structure of collagen improved in CAD treated with Zn-containing amalgams. Different levels of dentin remineralization were revealed by hierarchical cluster analysis.

A zinc-doped endodontic cement facilitates functional mineralization and stress dissipation at the dentin surface

BACKGROUND: The purpose of this study was to evaluate nanohardness and viscoelastic behavior of dentin surfaces treated with two canal sealer cements for dentin remineralization. MATERIAL AND METHODS: Dentin surfaces were subjected to: I) 37% phosphoric acid (PA) or II) 0.5 M ethylenediaminetetraacetic acid (EDTA) conditioning prior to the application of two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite), respectively. Samples were stored in simulated body fluid during 24 h or 21 d. The intertubular and peritubular dentin were evaluated using a nanoindenter to assess nanohardness (Hi). The load/displacement responses were used for the nano-dynamic mechanical analysis to estimate complex modulus (E*) and tan delta (δ). The modulus mapping was obtained by imposing a quasistatic force setpoint to which a sinusoidal force was superimposed. AFM imaging and FESEM analysis were performed. RESULTS: After 21 d of storage, dentin surfaces treated with EDTA+calcypatite, PA+calcypatite and EDTA+oxipatite showed viscoelastic discrepancies between peritubular and intertubular dentin, meaning a risk for cracking and breakdown of the surface. At both 24 h and 21 d, tan δ values at intertubular dentin treated with the four treatments performed similar. At 21 d time point, intertubular dentin treated with PA+oxipatite achieved the highest complex modulus and nanohardness, i.e., highest resistance to deformation and functional mineralization, among groups. CONCLUSIONS: Intertubular and peritubular dentin treated with PA+oxipatite showed similar values of tan δ after 21 d of storage. This produced a favorable dissipation of energy with minimal energy concentration, preserving the structural integrity at the dentin surface

Silver improves collagen structure and stability at demineralized dentin: A dynamic-mechanical and Raman analysis.

OBJECTIVE: This study aimed to evaluate the effect of silver loaded nanoparticles (NPs) application on dentin remineralization. METHODS: Polymethylmetacrylate-based NPs and silver loaded NPs (Ag-NPs) were applied on demineralized dentin surfaces. Dentin was characterized morphologically by scanning electron microscopy, mechanically probed by a nanoindenter to test nanohardness and Young modulus, and chemically analyzed by Raman spectroscopy after 24 h and 7 d of storage. Untreated surfaces were used as control. Data were submitted to ANOVA and Student-Newman-Keuls multiple comparisons tests (P < 0.05). RESULTS: After Raman analysis, dentin treated with Ag-NPs obtained the lowest mineralization and intensity of stoichiometric hydroxyapatite when compared with specimens treated with undoped-NPs. The lowest relative mineral concentration, expressed as the ratio phosphate or carbonate/phenyl group, and crystallinity was attained by dentin treated with Ag-NPs, after 7 d. Ag-NPs application generated the highest values of collagen crosslinking (intensity at 1032 cm-1 band). The molecular conformation of the collagen's polypeptide chains, amide-I and CH2 also attained the highest peaks in dentin treated with Ag-NPs. Staggered and demineralized collagen fibrils were observed covering the dentin surfaces treated with Ag-NPs, at both 24 h and 7 d. Samples treated with Ag-NPs attained the lowest values of nanohardness and Young's modulus at 7 d of storage. CONCLUSIONS: Peritubular and intertubular dentin were remineralized when using undoped-NPs. After 7 d, collagen treated with NPs was remineralized but dentin treated with Ag-NPs attained an improved collagen matrix structure and stability but the lowest mineralization and crystallinity. CLINICAL SIGNIFICANCE: Preservation of the demineralized organic matrix is fundamental in operative dentistry. Silver contributed to improve crosslinking, nature and secondary structure of demineralized dentin collagen, for further long-term intrafibrillar mineralization.