The current management of oral conditions such as dental caries and erosion mostly relies on fluoride-based formulations. Herein, we proposed the use of the remaining skeleton of
(LC) as an ...alternative to fluorides. LC is a red macroalgae of the Corallinales order, occurring in the northeast coast of Brazil, whose unique feature is the abundant presence of calcium carbonates in its cell walls. Two experimental approaches tested the general hypothesis that LC could mediate enamel de-remineralization dynamics as efficiently as fluorides. Firstly, the effect of LC on enamel de-mineralization was determined in vitro by microhardness and gravimetric measurements to test the hypothesis that LC could either prevent calcium/phosphate release from intact enamel or facilitate calcium/phosphate reprecipitation on an artificially demineralized enamel surface. Subsequently, an in situ/ex vivo co-twin control study measured the effect of LC on the remineralization of chemical-demineralized enamel using microhardness and quantitative light-induced fluorescence. With this second experiment, we wanted to test whether outcomes obtained in experiment 1 would be confirmed by an in situ/ex vivo co-twin control model. Both experiments showed that LC exhibited equivalent or superior ability to modulate enamel de-remineralization when compared to fluoride solution. LC should be explored as an alternative to manage oral conditions involving the enamel demineralization.
Abstract Objectives Contemporary adhesives lose their bond strength to dentin regardless of the bonding system used. This loss relates to the hydrolysis of collagen matrix of the hybrid layers. The ...preservation of the collagen matrix integrity is a key issue in the attempts to improve the dentin bonding durability. Methods Dentin contains collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, which are responsible for the hydrolytic degradation of collagen matrix in the bonded interface. Results The identities, roles and function of collagenolytic enzymes in mineralized dentin has been gathered only within last 15 years, but they have already been demonstrated to have an important role in dental hard tissue pathologies, including the degradation of the hybrid layer. Identifying responsible enzymes facilitates the development of new, more efficient methods to improve the stability of dentin–adhesive bond and durability of bond strength. Significance Understanding the nature and role of proteolytic degradation of dentin–adhesive interfaces has improved immensely and has practically grown to a scientific field of its own within only 10 years, holding excellent promise that stable resin–dentin bonds will be routinely available in a daily clinical setting already in a near future.
Dentin organic matrix, with type I collagen as the main component, is exposed after demineralization in dentinal caries, erosion or acidic conditioning during adhesive composite restorative ...treatment. This exposed matrix is prone to slow hydrolytic degradation by host collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins. Here we review the recent findings demonstrating that inhibition of salivary or dentin endogenous collagenolytic enzymes may provide preventive means against progression of caries or erosion, just as they have been shown to retain the integrity and improve the longevity of resin composite filling bonding to dentin. This paper also presents the case that the organic matrix in caries-affected dentin may not be preserved as intact as previously considered. In partially demineralized dentin, MMPs and cysteine cathepsins with the ability to cleave off the terminal non-helical ends of collagen molecules (telopeptides) may lead to the gradual loss of intramolecular gap areas. This would seriously compromise the matrix ability for intrafibrillar remineralization, which is considered essential in restoring the dentin's mechanical properties. More detailed data of the enzymes responsible and their detailed function in dentin-destructive conditions may not only help to find new and better preventive means, but better preservation of demineralized dentin collagenous matrix may also facilitate true biological remineralization for the better restoration of tooth structural and mechanical integrity and mechanical properties.
Gelatin-methacryloyl hydrogels (GelMA) have demonstrated their utility as scaffolds in a variety of tissue engineering applications.
In this study, a highly functionalized GelMA hydrogel was ...synthesized and assessed for degree of functionalization. As the proposed GelMA hydrogel was coupled to a visible-light photoinitiator, we hypothesized it might serve as base to formulate a model dentin primer for application in restorative dentistry.
GelMA was mixed with photoinitiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), photopolymerized for 0–40 s using a dental light-curing device and tested for extrudability, degree of photo-crosslinking (DPxlink), water sorption/solubility/swelling (WS/SL/SW) and apparent modulus of elasticity (AE). Model dentin primer was prepared by mixing GelMA+LAP with a primer of a commercial three-step etch-and-rinse adhesive. After application of GelMA-based primer to acid-etched dentin, samples were bonded with correspondent adhesive agent, photopolymerized and had their immediate bond strength compared to control samples primed and bonded with the same commercial material.
Extrudability of hydrogel was confirmed using a microsyringe to write the acronym “CDMI”. DPxlink of GelMA+LAP changed significantly as a function of photopolymerization time (20 s < 30 s ≤ 40 s). WS, SL and SW were significantly reduced in hydrogels polymerized for 30 and 40 s. AE of hydrogels varied significantly as a function of photopolymerization time (20 s < 30 s ≤ 40 s; 20 s ‡ 40 s). Bond strength of dentin primed with GelMA-based primer was lower (∼29.3 MPa) but not significantly of that of control (∼34.6 MPa).
Optimization of a GelMA-based dentin primers can lead to the development of promising biomimetic adhesives for dentin rehabilitation.
Abstract
Aims
Chitosan‐based biomaterials exhibit several properties of biological interest for endodontic treatment. Herein, a low molecular weight chitosan (CH) solution was tested for its ...antimicrobial activity against
Enterococcus faecalis
(
E. faecalis
) and effects on dentine structure.
Methodology
The root canal of 27 extracted uniradicular teeth were biomechanically prepared, inoculated with a suspension of
E. faecalis
and randomly assigned to be irrigated with either 5.25% sodium hypochlorite (NaClO), 0.2% CH or sterile ultrapure water (W). Bacteriologic samples were collected from root canals and quantified for of
E. faecalis
colony‐forming units (CFUs). The effectiveness of CH over
E. faecalis
biofilms was further measured using the MBEC Assay®. Additionally, dentine beams and dentine powder were obtained, respectively, from crowns and roots of 20 extracted third molars. Dentine samples were treated or not with 17% EDTA and immersed in either CH or W for 1 min. The effects of CH on dentine structure were evaluated by assessment of the modulus of elasticity, endogenous proteolytic activity and biochemical modifications.
Results
The number of
E. faecalis
CFUs was significantly lower for samples irrigated with CH and NaClO. No significant differences were found between CH and NaClO treatments. Higher modulus of elasticity and lower proteolytic activity were reported for dentine CH‐treated specimens. Chemical interaction between CH and dentine was observed for samples treated or not with EDTA.
Conclusions
Present findings suggest that CH could be used as an irrigant during root canal treatment with the triple benefit of reducing bacterial activity, mechanically reinforcing dentine and inhibiting dentine proteolytic activity.
Abstract Objectives To better comprehend the role of CHX in the preservation of resin–dentin bonds, this study investigated the substantivity of CHX to human dentin. Material and methods Dentin disks ...( n = 45) were obtained from the mid-coronal portion of human third molars. One-third of dentin disks were kept mineralized (MD), while the other two-thirds had one of the surfaces partially demineralized with 37% phosphoric acid for 15 s (PDD) or they were totally demineralized with 10% phosphoric acid (TDD). Disks of hydroxyapatite (HA) were also prepared. Specimens were treated with: (1) 10 μL of distilled water (controls), (2) 10 μL of 0.2% chlorhexidine diacetate (0.2% CHX) or (3) 10 μL of 2% chlorhexidine diacetate (2% CHX). Then, they were incubated in 1 mL of PBS (pH 7.4, 37 °C). Substantivity was evaluated as a function of the CHX-applied dose after: 0.5 h, 1 h, 3 h, 6 h, 24 h, 168 h (1 week), 672 h (4 weeks) and 1344 h (8 weeks) of incubation. CHX concentration in eluates was spectrophotometrically analyzed at 260 nm. Results Significant amounts of CHX remained retained in dentin substrates (MD, PPD or TDD), independent on the CHX-applied dose or time of incubation ( p < 0.05). High amounts of retained CHX onto HA were observed only for specimens treated with the highest concentration of CHX (2%) ( p < 0.05). Conclusion The outstanding substantivity of CHX to dentin and its reported effect on the inhibition of dentinal proteases may explain why CHX can prolong the durability of resin–dentin bonds.
Traditional bone regeneration strategies relied on supplementation of biomaterials constructs with stem or progenitor cells or growth factors. By contrast, cell homing strategies employ chemokines to ...mobilize stem or progenitor cells from host bone marrow and tissue niches to injured sites. Although silica‐based biomaterials exhibit osteogenic and angiogenic potentials, they lack cell homing capability. Stromal cell‐derived factor‐1 (SDF‐1) plays a pivotal role in mobilization and homing of stem cells to injured tissues. In this work, we demonstrated that 3‐dimensional collagen scaffolds infiltrated with intrafibrillar silica are biodegradable and highly biocompatible. They exhibit improved compressive stress‐strain responses and toughness over nonsilicified collagen scaffolds. They are osteoconductive and up‐regulate expressions of osteogenesis‐ and angiogenesis‐related genes more significantly than nonsilicified collagen scaffolds. In addition, these scaffolds reversibly bind SDF‐1α for sustained release of this chemokine, which exhibits in vitro cell homing characteristics. When implanted subcutaneously in an in vivo mouse model, SDF‐1α‐loaded silicified collagen scaffolds stimulate the formation of ectopic bone and blood capillaries within the scaffold and abrogate the need for cell seeding or supplementation of osteogenic and angiogenic growth factors. Intrafibrillar‐silicified collagen scaffolds with sustained SDF‐1α release represent a less costly and complex alternative to contemporary cell seeding approaches and provide new therapeutic options for in situ hard tissue regeneration.—Niu, L.‐N., Jiao, K., Qi, Y.‐P., Nikonov, S., Yiu, C. K. Y., Arola, D. D., Gong, S.‐Q., El‐Marakby, A., Carrilho, M. R. O., Hamrick, M. W., Hargreaves, K. M., Diogenes, A., Chen, J.‐H., Pashley, D. H., Tay, F. R. Intrafibrillar silicification of collagen scaffolds for sustained release of stem cell homing chemokine in hard tissue regeneration. FASEB J. 26, 4517–4529 (2012). www.fasebj.org
Chitosan (CS) and phloroglucinol (PhG), two extracts abundantly found in marine life, were investigated for their ability to biomodify demineralized dentin by enhancing collagen crosslinks and ...improving dentin extracellular matrix (ECM) mechanical and biochemical stability. Dentin obtained from non-carious extracted human molars were demineralized with phosphoric acid. Baseline Fourier-transform infrared (FTIR) spectra, apparent flexural elastic modulus (AE) and dry mass (DM) of each specimen were independently acquired. Specimens were randomly incubated for 5 min into either ultrapure water (no-treatment), 1% glutaraldehyde (GA), 1% CS or 1% PhG. Water and GA were used, respectively, as a negative and positive control for collagen crosslinks. Specimens’ post-treatment FTIR spectra, AE, and DM were obtained and compared with correspondent baseline measurements. Additionally, the host-derived proteolytic activity of dentin ECM was assessed using hydroxyproline assay (HYP) and spectrofluorometric analysis of a fluorescent-quenched substrate specific for matrix metalloproteinases (MMPs). Finally, the bond strength of an etch-and-rinse adhesive was evaluated after application of marine compounds as non-rinsing dentin primers. Dentin specimens FTIR spectral profile changed remarkably, and their AE increased significantly after treatment with marine compounds. DM variation, HYP assay and fluorogenic substrate analysis concurrently indicated the biodegradation of CS- and PhG-treated specimens was significantly lesser in comparison with untreated specimens. CS and PhG treatments enhanced biomechanical/biochemical stability of demineralized dentin. These novel results show that PhG is a primer with the capacity to biomodify demineralized dentin, hence rendering it less susceptible to biodegradation by host-proteases.
Display omitted
•Phloroglucinol is an extract of brown seaweed with biological functions unexplored in dentistry.•Marine compounds, chitosan and phloroglucinol were capable of biomodifying dentin ECM.•Chitosan and phloroglucinol enhanced dentin ECM flexural elastic modulus.•Chitosan and phloroglucinol reduced biodegradation of dentin ECM.•Chitosan and phloroglucinol modulated the MMP-related activity of dentin ECM.
This study evaluated the water sorption, solubility and kinetics of water diffusion in commercial and experimental resins that are formulated to be used as dentin and enamel bonding agents.
Four ...commercial adhesives were selected along with their solvent–monomer combination: the bonding resins were of Adper Scotchbond Multi-Purpose (MP) and Clearfil SE Bond (SE) systems, and the “one-bottle” systems, Adper Single Bond (SB) and Excite (EX). Five experimental methacrylate-based resins of known hydrophilicities (R1, R2, R3, R4 and R5) were used as reference materials. Specimen disks were prepared by dispensing the uncured resin into a mould (5.8
mm
×
0.8
mm). After desiccation, the cured specimens were weighed and then stored in distilled water for evaluation of the water diffusion kinetics over a 28-day period.
Resin composition and hydrophilicity (ranked by their Hoy's solubility parameters) influenced water sorption, solubility and water diffusion in both commercial and experimental dental resins. The most hydrophilic experimental resin, R5, showed the highest water sorption, solubility and water diffusion coefficient. Among the commercial adhesives, the solvated systems, SB and EX, showed water sorption, solubility and water diffusion coefficients significantly greater than those observed for the non-solvated systems, MP and SE (
p
<
0.05). In general, the extent and rate of water sorption increased with the hydrophilicity of the resin blends.
The extensive amount of water sorption in the current hydrophilic dental resins is a cause of concern. This may affect the mechanical stability of these resins and favor the rapid and catastrophic degradation of resin–dentin bonds.
Abstract Introduction Collagen-degrading matrix metalloproteinases (MMPs) are expressed by odontoblasts and present in dentin. We hypothesized that odontoblasts express other collagen-degrading ...enzymes such as cysteine cathepsins, and their activity would be present in dentin, because odontoblasts are known to express at least cathepsin D. Effect of transforming growth factor beta (TGF-β) on cathepsin expression was also analyzed. Methods Human odontoblasts and pulp tissue were cultured with and without TGF-β, and cathepsin gene expression was analyzed with DNA microarrays. Dentin cathepsin and MMP activities were analyzed by degradation of respective specific fluorogenic substrates. Results Both odontoblasts and pulp tissue demonstrated a wide range of cysteine cathepsin expression that gave minor responses to TGF-β. Cathepsin and MMP activities were observed in all dentin samples, with significant negative correlations in their activities with tooth age. Conclusions These results demonstrate for the first time the presence of cysteine cathepsins in dentin and suggest their role, along with MMPs, in dentin modification with aging.
PDF
