Prevention and Treatment of Oral Complications in Hematologic Childhood Cancer Patients: An Update.

Cancers have a highly negative impact on the quality of life of paediatric patients and require an individualised oral treatment program for the phases of the disease. The aim of this study was to update existing research on oral care in children diagnosed with cancer. We carried out a literature search (in English, Spanish and Portuguese) in the Pubmed, Cochrane Library, EBSCO, WOS, SciELO, Lilacs, ProQuest, and SCOPUS databases and the websites of hospitals that treat childhood cancers. We found 114 articles and two hospital protocols. After review, we describe the interventions necessary to maintain oral health in children with cancer, divided into: phase I, before initiation of cancer treatment (review of medical record and oral history, planning of preventive strategies and dental treatments); phase II, from initiation of chemo-radiotherapy to 30-45 days post-therapy (maintenance of oral hygiene, reinforcement of parent/patient education in oral care, prevention and treatment of complications derived from cancer treatment); phase III, from 1 year to lifetime (periodic check-ups, maintenance, and reinforcement of oral hygiene, dental treatments, symptomatic care of the effects of long-term cancer treatment). The use of standardised protocols can avoid or minimise oral cancer complications and the side effects of cancer therapies.

Zn-containing Adhesives Facilitate Collagen Protection and Remineralization at the Resin-Dentin Interface: A Narrative Review.

This is a narrative review of the literature assessing the potential effectiveness of doping dentin polymeric adhesives with zinc compounds in order to improve bonding efficacy, remineralization and protection against degradation. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI and Web of Science. Through our search, we found literature demonstrating that Zn-doped dentin adhesives promote protection and remineralization of the resin-dentin interfaces. The increased bioactivity has also facilitated dentinal tubules' occlusion by crystals' precipitation contributing to improved sealing efficacy of restorations. Loading dentin adhesives with zinc gives rise to an increase of both crystallinity of mineral and crosslinking of collagen. The main role of zinc, in dentin adhesives, is to inhibit collagen proteolysis. We concluded that zinc exerts a protective effect through binding at the collagen-sensitive cleavage sites of matrix-metalloproteinases (MMPs), contributing to dentin matrix stabilization. Zinc may not only act as a MMPs inhibitor, but also influence signaling pathways and stimulate metabolic effects in dentin mineralization and remineralization processes. Zn-doped adhesives increase the longevity of dentin bonding through MMPs inhibition. Zn poses a remineralization strategy in demineralized dentin.

Effects of Fluoride and Calcium Phosphate-Based Varnishes in Children at High Risk of Tooth Decay: A Randomized Clinical Trial.

BACKGROUND: The aim of this study was to investigate the effect of the application of two varnishes-MI Varnish (5% sodium fluoride with CPP-ACP) and Clinpro White Varnish (5% sodium fluoride with fTCP)-applied every three months in children with high caries risk for 12 months on plaque indexes, salivary pH, salivary lactic acid and chemical elements concentrations. METHODS: We included 58 children aged 4-12 years, assigned to control (placebo), Clinpro and MI groups. Baseline and three-month saliva samples were taken. We assessed changes in pH, lactic acid concentrations and chemical elements in saliva. RESULTS: At 12 months, all groups showed a nonsignificant increase in pH levels and a reduction in lactic acid, which was greatest in the placebo group. There was a significant reduction in 24Mg (p = <0.001), 31P (p = 0.033) and 66Zn (p = 0.005) levels in the placebo group (p ≤ 0.05), but not in the other elements studied: 23Na, 27Al, 39K, 44Ca, 52Cr, 55Mn, 57Fe, 59Co, 63Cu, 75As, 111Cd, 137Ba, 208Pb and 19F. CONCLUSIONS: Neither pH, lactic acid concentrations or most salivary chemical elements were useful in defining patients at high risk of caries or in monitoring the effect of MI Varnish and Clinpro White Varnish after three-month application for 12 months. However, the appearance of new cavities was stopped, and the hygiene index improved, probably due to hygienic and dietary measures and the use of fluoridated toothpaste. TRIAL REGISTRATION: ISRCTN registry, ISRCTN13681286.

Influence of Fluoride Varnish Application on Enamel Adhesion of a Universal Adhesive.

Purpose: To study the effect of the varnish type, application time and surface polishing on the shear bond strength (SBS) of a universal adhesive in healthy and demineralized bovine enamel. Materials and Methods: 432 bovine primary central incisors were assigned to 18 groups according to enamel mineralization [healthy and demineralized], topical varnish [Clinpro White Varnish (CWV; 3M Oral Care) and Profluorid (PFV, Voco)], remineralization time [24 h or 21 days] and polishing or not of the enamel surface. Adhesion was tested using Futurabond M (Voco)+ and GrandioSO (Voco). Sheer bond strength (SBS) was measured and the fracture mode studied. The statistical analysis was performed using two-way ANOVA, Tukey's test, and Pearson's chi-squared test. Results: In healthy bovine enamel, CWV reduced SBS at 24 h and 21 days; polishing significantly improved SBS. PFV increased SBS in healthy enamel at 21 days and demineralized enamel at 24 h and 21 days; polishing had no effect on SBS. The application time and polishing of the enamel surface affected the behavior of varnishes with respect to SBS. There was a correlation between the type of fracture and the degree of mineralization as well as the timepoint of varnish application. Conclusions: Remineralization of demineralized enamel with fluoride varnishes permits the recovery of the bond strength obtained in healthy enamel. Of the two varnishes studied, PFV had the highest SBS and more uniform behavior, regardless of the application timepoint, degree of mineralization, and surface treatment of the enamel..

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.

Mild acids facilitate functional dentin remineralization under thermo-mechanical stimuli.

PURPOSE: To evaluate if mechanical and thermal cycling promote remineralization at the resin-dentin interface after bonding with three different adhesive approaches. METHODS: Dentin surfaces were subjected to three different treatments: demineralization (1) by 37% phosphoric acid followed by application of an etch-and-rinse dentin adhesive Single Bond (Adper Single Bond) (SB); (2) by 0.5 M ethylenediaminetetraacetic acid (EDTA) followed by SB; (3) application of a self-etch dentin adhesive: Clearfil-SEB (Clearfil SE Bond). Bonded interfaces were stored during 24 hours and then submitted for 3 months to: (1) storage at 37ºC, (2) load cycling, (3) thermocycling, and (4) thermo+load cycling. One section was extracted from each tooth, monthly. Resin-dentin interfaces were analyzed by AFM nano-indentation, Raman spectroscopy/cluster analysis and Masson's trichrome staining at 24 hours, 1, 2 and 3 months, to determine remineralization at the interface. RESULTS: Thermo+load cycling promoted the highest biomimetic remineralization at the hybrid layer formed with EDTA+SB and Clearfil-SEB, at the 1 month time point. A narrow mineral-depleted zone was observed after thermo+load cycling with EDTA+ SB, and at those specimens bonded with Clearfil-SEB. Thermo+load cycling remineralized the dentin interface treated with EDTA+SB and Clearfil-SEB, after 1 month of study period, providing bioactivity and maturity of formed minerals. CLINICAL SIGNIFICANCE: In vitro challenging (thermo+load cycling) favors dentin remineralization at the resin-dentin bonded interfaces promoted with mild conditioning acids.

In vitro mechanical stimulation facilitates stress dissipation and sealing ability at the conventional glass ionomer cement-dentin interface.

OBJECTIVE: The aim of this study was to evaluate the induced changes in the chemical and mechanical performance at the glass-ionomer cement-dentin interface after mechanical load application. METHODS: A conventional glass-ionomer cement (GIC) (Ketac Bond), and a resin-modified glass-ionomer cement (RMGIC) (Vitrebond Plus) were used. Bonded interfaces were stored in simulated body fluid, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling, 24 h cycled in sine or loaded in sustained hold waveforms. The cement-dentin interface was evaluated using a nano-dynamic mechanical analysis, estimating the complex modulus and tan δ. Atomic Force Microscopy (AFM) imaging, Raman analysis and dye assisted confocal microscopy evaluation (CLSM) were also performed. RESULTS: The complex modulus was lower and tan delta was higher at interfaces promoted with the GIC if compared to the RMGIC unloaded. The conventional GIC attained evident reduction of nanoleakage. Mechanical loading favored remineralization and promoted higher complex modulus and lower tan delta values at interfaces with RMGIC, where porosity, micropermeability and nanoleakage were more abundant. CONCLUSIONS: Mechanical stimuli diminished the resistance to deformation and increased the stored energy at the GIC-dentin interface. The conventional GIC induced less porosity and nanoleakage than RMGIC. The RMGIC increased nanoleakage at the porous interface, and dye sorption appeared within the cement. Both cements created amorphous and crystalline apatites at the interface depending on the type of mechanical loading. CLINICAL SIGNIFICANCE: Remineralization, lower stress concentration and resistance to deformation after mechanical loading improved the sealing of the GIC-dentin interface. In vitro oral function will favor high levels of accumulated energy and permits micropermeability at the RMGIC-dentin interface which will become remineralized.

A zinc chloride-doped adhesive facilitates sealing at the dentin interface: A confocal laser microscopy study.

The aim of this study was to ascertain the effect of Zn-doping of dental adhesives and mechanical load cycling on the micromorphology of the resin-dentin interdiffusion zone (of sound and caries affected dentin). The investigation considered two different Zn-doped adhesive approaches and evaluated the interface using a doubled dye fluorescent technique and a calcium chelator fluorophore under a confocal laser scanning microscopy. Sound and carious dentin-resin interfaces of unloaded specimens were deficiently resin-hybridized, in general. These samples showed a rhodamine B-labeled hybrid layer and adhesive layer completely affected by fluorescein penetration (nanoleakage) through the porous resin-dentin interface. It was thicker after phosphoric acid-etching and more extended in carious dentin. Zn-doping promoted an improved sealing of the resin-dentin interface, a decrease of the hybrid layer porosity, and an increment of dentin mineralization. Load cycling augmented the sealing of the Zn-doped resin-dentin interfaces, as porosity and nanoleakage diminished, and even disappeared in caries-affected dentin substrata conditioned with EDTA. Sound and carious dentin specimens analyzed with the xylenol orange technique produced a clearly outlined fluorescence when resins were Zn-doped, due to a consistent Ca-mineral deposition within the bonding interface and inside the dentinal tubules. It was more evident when load cycling was applied on specimens treated with self-etching adhesives that were Zn-doped. Micropermeability at the resin-dentin interface diminished after combining EDTA pretreatment, ZnCl2-doping and mechanical loading stimuli on restorations. It is clearly preferable to include the zinc compounds into the bonding constituents of the self-etching adhesives, instead of into the primer ingredients. The promoted new mineral segments contributed to reduce or avoid both porosity and nanoleakage from the load cycled Zn-doped resin dentin interfaces. EDTA+SB-ZnCl2 or SEB·Bd-Zn doping are preferred to treat caries-affected dentin surfaces. ZnO-doping encouraged for etch-and-rinse adhesives.

Oral Function Improves Interfacial Integrity and Sealing Ability Between Conventional Glass Ionomer Cements and Dentin.

The aim of this study was to investigate if load cycling affects interfacial integrity of glass ionomer cements bonded to sound- or caries-affected dentin. A conventional glass ionomer, Ketac Bond, and a resin-modified glass ionomer (Vitrebond Plus), were applied to dentin. Half of the specimens were load cycled. The interfaces were submitted to dye-assisted confocal microscopy evaluation. The unloaded specimens of sound and carious dentin were deficiently hybridized when Ketac Bond was used. Ketac Bond samples showed an absorption layer and an adhesive layer that were scarcely affected by fluorescein penetration (nanoleakage), in sound dentin. Nevertheless, a higher degree of micropermeability was found in carious dentin. In Ketac Bond specimens, load cycling improves the sealing capability and remineralization at the cement-dentin interface as porosity and nanoleakage was reduced. In contrast, samples treated with Vitrebond Plus exhibited a Rhodamine B-labeled absorption layer with scarce nanoleakage in both sound and carious unloaded dentin. The adhesive layer was affected by dye sorption throughout the porous cement-dentin interface. Samples treated with Vitrebond Plus had significant increases in nanoleakage and cement-dye sorption after load cycling. Within the limitations of an in vitro study, it is expected that conventional glass ionomers will provide major clinical efficacy when applied to carious-affected or sound dentin.

Zinc-modified nanopolymers improve the quality of resin-dentin bonded interfaces.

INTRODUCTION: Demineralized collagen fibers at the hybrid layer are susceptible to degradation. Remineralization may aid to improve bond longevity. OBJECTIVES: The aim of the present study was to infiltrate zinc and calcium-loaded polymeric nanoparticles into demineralized dentin to facilitate hybrid layer remineralization. MATERIALS AND METHODS: Zinc or calcium-loaded polymeric nanoparticles were infiltrated into etched dentin, and Single Bond Adhesive was applied. Bond strength was tested after 24 h and 6 months storage. Nanomechanical properties, dye-assisted confocal laser microscopy, and Masson's trichrome staining evaluation were performed to assess for the hybrid layer morphology, permeability, and remineralization ability after 24 h and 3 months. Data were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons tests (p < 0.05). RESULTS: Immediate bond strength was not affected by nanoparticles infiltration (25 to 30 MPa), while after 6 months, bond strengths were maintained (22 to 24 MPa). After 3 months, permeability occurred only in specimens in which nanoparticles were not infiltrated. Dentin remineralization, at the bottom of the hybrid layer, was observed in all groups. After microscopy analysis, zinc-loaded nanoparticles were shown to facilitate calcium deposition throughout the entire hybrid layer. Young's modulus at the hybrid layer increased from 2.09 to 3.25 GPa after 3 months, in specimens with zinc nanoparticles; meanwhile, these values were reduced from 1.66 to 0.49 GPa, in the control group. CONCLUSION: Infiltration of polymeric nanoparticles into demineralized dentin increased long-term bond strengths. Zinc-loaded nanoparticles facilitate dentin remineralization within the complete resin-dentin interface. CLINICAL RELEVANCE: Resin-dentin bond longevity and dentin remineralization at the hybrid layer were facilitated by zinc-loaded nanoparticles.

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

The 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 demineralization 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 24h, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling (I), 24h cycled in sine (II) or square (III) waves, sustained loading held for 24h (IV) or sustained loading held for 72h (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 24h attained the highest complex and storage moduli at HL and BHL. The storage modulus was maximum in specimens load cycled in held 24h 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 72h. Areas of combined sealing and permeability were discovered at the interface of specimens load cycled in held 24h. Crack-bridging images appeared in samples load cycled with sine waveform, after FESEM examination.

Effect of zinc-doping in physicochemical properties of dental adhesives.

PURPOSE: To evaluate changes in the physicochemical properties, water sorption (WS), solubility (SO), modulus of elasticity (E), ultimate tensile strength (UTS), and microhardness (MH) tests were undertaken in zinc-doped dental adhesives. METHODS: Two bonding resins, Adper Single Bond Plus (SB) and Clearfil SE Bond (SEB), were zinc-doped by mixing them with 5, 10 or 20 wt% of ZnO powder, or with 1 or 2 wt% ZnCl2. Resin disks were made of each adhesive blend for the evaluation of WS, SO, and MH, and dumbbell-shaped specimens were prepared for E and UTS testing. RESULTS: An increase in WS and SO was observed for adhesives doped with ZnCl2. A reduction in WS was observed for the adhesive blends containing 10% or 20 wt% ZnO, while the SO was not altered in any of the ZnO-doped adhesives. An increase in E values was observed only for the SB adhesive doped with ZnCl2. For SEB-blends, the incorporation of zinc compounds did not alter the E values. UTS values decreased when SEB was doped with ZnO. SB-blends doped with 20 wt% ZnO significantly increased their MH, and the addition of zinc to the SEB-blends augmented the MH values in all cases.

On modeling and nanoanalysis of caries-affected dentin surfaces restored with Zn-containing amalgam and in vitro oral function.

The aim of this research was to assess the influence of mechanical loading on the ability of Zn-free versus Zn-containing amalgams to promote remineralization at the dentin interface. Sound and caries-affected dentin surfaces (CAD) were restored using Zn-free or Zn-containing dental amalgams. Midcoronal dentin surfaces were studied by (1) atomic force microscopy analysis (including plot and phase imaging, nanoindentation test [modulus of Young (Ei), nanoroughness measurements, and fibril diameter assessment], (2) Raman spectroscopy/cluster analysis, (3) x-ray diffraction, (4) field emission electron microscope and energy-dispersive analysis, for morphological, mechanical, and physicochemical characterization. Analyses were performed before amalgam placement and after amalgam removal, at 24 h and 3 weeks of load cycling. Zn-free and Zn-containing amalgams restorations promoted an increase in the modulus of Young of CAD surfaces, after 3 weeks of load cycling; at this time, Zn-containing amalgams attained higher Ei than Zn-free restorations. Zn-containing amalgams induced tubular occlusion after load cycling, in both sound and CAD. Zn free-amalgams promoted remineralization of both intertubular and peritubular dentin in CAD substrata. These minerals were identified as calcium-phosphate deposits and crystals as hydroxyl-apatite with augmented crystallographic maturity but with some components of lattice distortion. Crosslinking of collagen diminished and secondary structure of collagen increased in CAD substrate restored with Zn-containing amalgam after 3 weeks of load cycling, indicating an advanced preservation, molecular organization, and orientation of collagen fibrils after load cycling. Plot and phase images permitted to observe the topographical changes which were promoted by the mineral deposits; in general, the indexes related to higher remineralization gave rise to a decrease of nanoroughness and an augmentation of the bandwidth of the collagen fibrils. Zn-containing amalgam restorations submitted to mechanical stimuli promote remineralization of the partially mineral-depleted subjacent substrate at the caries-affected dentin.

Improved Sealing and Remineralization at the Resin-Dentin Interface After Phosphoric Acid Etching and Load Cycling.

The purpose of this study was to investigate micro-morphology of the resin-dentin inter-diffusion zone using two different single-bottle self-etching dentin adhesives with and without previous acid-etching, after in vitro mechanical loading stimuli. Extracted human third molars were sectioned to obtain dentin surfaces. Two different single-bottle self-etching dentin adhesives, Futurabond U and Experimental both from VOCO, were applied following the manufacturer's instructions or after 37% phosphoric acid application. Resin-dentin interfaces were analyzed with dye assisted confocal microscopy evaluation (CLSM), including the calcium-chelation technique, xylenol orange (CLSM-XO). CLSM revealed that resin-dentin interfaces of unloaded specimens were deficiently resin-hybridized, in general. These samples showed a Rhodamine B-labeled hybrid complex and adhesive layer completely affected by fluorescein penetration (nanoleakage) through the porous resin-dentin interface, but thicker after PA-etching. Load cycling promoted an improved sealing of the resin-dentin interface at dentin, a decrease of the hybrid complex porosity, and an increment of dentin mineralization. Load cycled specimens treated with the XO technique produced a clearly outlined fluorescence due to consistent Ca-mineral deposits within the bonding interface and inside the dentinal tubules, especially when the experimental adhesive was applied.

Functional and molecular structural analysis of dentine interfaces promoted by a Zn-doped self-etching adhesive and an in vitro load cycling model.

The aim of this study was to evaluate if mechanical cycling influences bioactivity and bond strength of resin-dentine interface after bonding with Zn-doped self-etching adhesives. Sound dentine surfaces were bonded with Clearfil SE Bond (SEB), 10 wt% ZnO microparticles or 2 wt% ZnCl2 were added into the SEB primer (P) or bonding (Bd) for Zn-doping. Bonded interfaces were stored in simulated body fluid (24h), and then tested or submitted to mechanical loading. Microtensile bond strength testing was performed. Debonded dentine surfaces were studied by scanning electron microscopy. Remineralisation of the bonded interfaces was assessed by nano-indentation, Raman spectroscopy, and Masson׳s trichrome staining. Load cycling (LC) increased the percentage of adhesive failures in all groups. LC increased the Young׳s modulus (Ei) at the hybrid layer (HL) when SEB, SEB·P-ZnO and SEB·P-ZnCl2 were applied, but decreased when both ZnO and ZnCl2 were incorporated into the bonding. Ei was higher when Zn compounds were incorporated into the primer (SEB·P). ZnO promoted an increase, and ZnCl2 a decrease, of both the relative presence of minerals and crystallinity, after LC. LC increased collagen crosslinking with both SEB·P-ZnO and SEB·P-ZnCl2. The ratios which reflect the nature of collagen increased, in general, at both HL and BHL after LC, confirming recovery, better organisation, improved structural differences and collagen quality. After loading, trichrome staining reflected a deeper demineralised dentine fringe when Zn-doped compounds were incorporated into SEB·Bd. Multiple Zn-rich phosphate deposits and salt formations were detected. Mineral precipitates nucleated in multilayered platforms or globular formations on peritubular and intertubular dentine.

Self-etching zinc-doped adhesives improve the potential of caries-affected dentin to be functionally remineralized.

The aim of this study was to evaluate if mechanical cycling influences bioactivity at the resin-carious dentin interface after bonding with Zn-doped self-etching adhesives. Caries-affected dentin surfaces were bonded with: Clearfil SE bond (SEB), and 10 wt. % ZnO nanoparticles or 2 wt. % ZnCl2 were added into the SEB primer or bonding components. Bonded interfaces were stored during 24 h and then tested or submitted to mechanical loading. Microtensile bond strength was assessed. Debonded dentin surfaces were studied by field emission scanning electron microscopy. Remineralization of the bonded interfaces was evaluated through nanohardness (Hi) and Young's modulus (Ei), Raman spectroscopy/cluster analysis, and Masson's trichrome staining technique. New precipitation of minerals composed of zinc-base salts and multiple Zn-rich phosphate deposits was observed in samples infiltrated with the Zn-doped adhesives. At the hybrid layer, specimens treated with ZnO incorporated in the primer (SEB·P-ZnO), after load cycling, attained the highest Ei and Hi. Load cycling increased Ei at the bottom of the hybrid layer when both, SEB undoped and SEB with ZnCl2 included in the bonding (SEB·Bd-ZnCl2), were used. ZnO incorporated in the primer promoted an increase in height of the phosphate and carbonate peaks, crystallinity, relative mineral concentration, and lower collagen crosslinking. ZnCl2 included in the bonding attained similar results, but relative mineral concentration decreased, associated to higher crosslinking and restricted collagen maturation. In general, a substantial restoration of the mechanical properties of caries-affected dentin substrata occurred when SEB-Zn doped adhesives were used and load cycled was applied, leading to functional and biochemical remineralization.

Mechanical and chemical characterisation of demineralised human dentine after amalgam restorations.

OBJECTIVES: The purpose of this study was to evaluate the ability of Zn-free vs Zn-containing amalgams to induce remineralisation at the dentine interface. METHODOLOGY: Sound and caries-affected dentine surfaces (CAD) were subjected to both Zn-free and Zn-containing dental amalgam restorations. Dentine surfaces were studied by nano-indentation, Raman spectroscopy/cluster analysis, X-ray diffraction (XRD), field emission electron microscope (FESEM) and energy-dispersive analysis (EDX), for mechanical, morphological and chemical characterisation. Analyses were performed before and after placement amalgam restorations. RESULTS: Zn-containing amalgams restorations promoted an increase in the nano-mechanical properties of sound and CAD surfaces. In samples from sound or CAD restored with Zn-containing amalgams, it was evidenced: (a) new mineral calcium-phosphate deposits (intratubular and intertubular) with augmented crystallographic maturity; these crystals were identified as hydroxyl-apatite, and (b) a generalised crosslinking reduction plus an increase in those values testing nature and secondary structure of collagen. It indicates an optimal preservation, molecular organisation and orientation of collagen fibrils. SIGNIFICANCE: Zn-containing amalgams promote remineralisation of subjacent dentine, which is more evident in caries affected dentine surfaces.

Effect of in vitro chewing and bruxism events on remineralization, at the resin-dentin interface.

The purpose of this study was to evaluate if different in vitro functional and parafunctional habits promote mineralization at the resin-dentin interface after bonding with three different adhesive approaches. Dentin surfaces were subjected to distinct treatments: demineralization by (1) 37% phosphoric acid (PA) followed by application of an etch-and-rinse dentin adhesive, Single Bond (SB) (PA+SB); (2) 0.5 M ethylenediaminetetraacetic acid (EDTA) followed by SB (EDTA+SB); (3) application of a self-etch dentin adhesive, Clearfil SE Bond (SEB). Different loading waveforms were applied: No cycling (I), cycled in sine (II) or square (III) waves, sustained loading hold for 24 h (IV) or sustained loading hold for 72 h (V). Remineralization at the bonded interfaces was assessed by AFM imaging/nano-indentation, Raman spectroscopy and Masson's trichrome staining. In general, in vitro chewing and parafunctional habits, promoted an increase of nano-mechanical properties at the resin-dentin interface. Raman spectroscopy through cluster analysis demonstrated an augmentation of the mineral-matrix ratio in loaded specimens. Trichrome staining reflected a narrow demineralized dentin matrix after loading in all groups except in PA+SB and EDTA+SB samples after sustained loading hold for 72 h, which exhibited a strong degree of mineralization. In vitro mechanical loading, produced during chewing and bruxism (square or hold 24 and 72 h waveforms), induced remineralization at the resin-dentin bonded interface.

Bond strength and bioactivity of Zn-doped dental adhesives promoted by load cycling.

The purpose of this study was to evaluate if mechanical loading influences bioactivity and bond strength at the resin-dentin interface after bonding with Zn-doped etch-and-rinse adhesives. Dentin surfaces were subjected to demineralization by 37% phosphoric acid (PA) or 0.5 M ethylenediaminetetraacetic acid (EDTA). Single bond (SB) adhesive­3M ESPE­SB+ZnO particles 20 wt% and SB+ZnCl2 2 wt% were applied on treated dentin to create the groups PA+SB, SB+ZnO, SB+ZnCl2, EDTA+SB, EDTA+ZnO, and EDTA+ZnCl2. Bonded interfaces were stored in simulated body fluid for 24 h and tested or submitted to mechanical loading. Microtensile bond strength (MTBS) was assessed. Debonded dentin surfaces were studied by high-resolution scanning electron microscopy. Remineralization of the bonded interfaces was assessed by atomic force microscope imaging/nanoindentation, Raman spectroscopy/cluster analysis, and Masson's trichrome staining. Load cycling (LC) produced reduction in MTBS in all PA+SB, and no change was encountered in EDTA+SB specimens, regardless of zinc doping. LC increased the mineralization and crystallographic maturity at the interface; a higher effect was noticed when using ZnO. Trichrome staining reflected a narrow demineralized dentin matrix after loading of dentin surfaces that were treated with SB-doped adhesives. This correlates with an increase in mineral platforms or plate-like multilayered crystals in PA or EDTA-treated dentin surfaces, respectively.