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1.
Dent Mater ; 36(5): 672-680, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32284197

RESUMO

OBJECTIVE: The present study investigated the ability of a chlorhexidine (CHX)-containing primer (0.2% aqueous solution) to inhibit dentinal enzymes, preserve the hybrid layer (HL) and remain within the HL, after 10 years of aging in artificial saliva at 37°C. METHODS: Non-carious extracted molars were assigned to two groups, cut into slabs exposing middle/deep dentin, etched and bonded with Adper Scotchbond 1XT (SB1XT) with or without 0.2% CHX aqueous solution pretreatment. Composite build-ups were made, and the specimens were cut in 1-mm thick bonded sticks. In situ zymography was performed on freshly prepared specimens (T0) and specimens aged for 10 years (T10-yr) at 37°C in artificial saliva, to investigate endogenous gelatinolytic activity within the HL. At T10-yr, specimens were also decalcified and embedded in epoxy resin for TEM analysis. Micro-Raman spectroscopy was performed at T0 and T10-yr to evaluate the chemical profiles in intertubular dentin and the HL. RESULTS: In situ zymography showed less pronounced enzymatic activity in the CHX-pretreated group (p<0.05) regardless of aging, maintaining a similar level of fluorescence at T0 and T10-yr (p>0.05). TEM results showed that 98% of the HL had been degraded in the control group, while 95% of the HL was intact in the experimental group. Moreover, all the Raman spectra peaks assigned to CHX could be identified only in the CHX-pretreated group (T0 and T10-yr). SIGNIFICANCE: In vitro, CHX remains in the HL after 10 years with its inhibitory effect preserved. This may be the underlying factor for HL preservation after this long aging period.

2.
Dent Mater ; 35(7): e153-e161, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31078308

RESUMO

OBJECTIVES: Ultra-high-speed (UHS) videography was used to visualize the fracture phenomena at the resin-dentin interface during micro-tensile bond strength (µTBS) test. We also investigated whether UHS videography is applicable for failure-mode analysis. METHODS: Ten human mid-coronal dentin surfaces were bonded using Clearfil SE Bond either in self-etching (SE) or etch-and-rinse (ER) mode. After 24-h water storage, the samples were cut into beams for µTBS test and tested at a cross-head speed of 1 mm/min. The fracture phenomena at the bonded interface were captured using a complementary metal-oxide-semiconductor digital UHS camera at 299,166 frames per second. The failure modes were classified using UHS videography, followed by scanning electron microscopy (SEM) analysis. The failure-mode distributions determined by UHS videography and SEM analysis were statistically analyzed using Fisher's exact test with Bonferroni correction. RESULTS: The crack-propagation speed exceeded 1,500 km/h. No significant difference was found between the SEM and UHS videography failure-mode distributions in the SE mode. A significant difference appeared between them in the ER mode. Significant differences in the incidence of cohesive failures within the adhesive and at the adhesive-composite interface between the SE and ER modes were identified by both SEM and UHS videography. SIGNIFICANCE: UHS videography enabled visualization of the fracture dynamics at the resin- dentin interfaces under tensile load. However, the resolution at such high frame rate was insufficient to classify the failure mode as precisely as that of SEM. Nevertheless, UHS videography can provide more detailed information about the fracture origin and propagation.


Assuntos
Colagem Dentária , Adesivos Dentinários , Resinas Compostas , Dentina , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Cimentos de Resina , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração
3.
Acta Biomater ; 90: 424-440, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30953801

RESUMO

During development of mineralized collagenous tissues, intrafibrillar mineralization is achieved by preventing mineralization precursor inhibitors that are larger than 40 kDa from entering the collagen fibrils. Such a property is incorporated in the design of a calcium chelator for dentin bonding in the etch-and-rinse technique that selectively demineralizes extrafibrillar apatite while leaving the intrafibrillar minerals intact. This strategy prevents complete demineralization of collagen fibrils, avoids collapse of collagen that blocks resin infiltration after air-drying, and protects the completely demineralized fibrils from bacteria colonization and degradation by endogenous proteases after resin bonding. In the present study, a water-soluble glycol chitosan-EDTA (GCE) conditioner was synthesized by conjugation of EDTA, an effective calcium chelator, to high molecular weight glycol chitosan, which exhibits weak chelation property. The GCE conjugate was purified, characterized by FTIR, 1H NMR, isothermal titration calorimetry and ICP-AES, and subjected to size exclusion dialysis to recover molecules that are >40 kDa. The optimal concentration and application time for etching dentin were determined by bond strength testing to ensure that the dentin bonding results were comparable to phosphoric acid etching, and maintained equivalent bond strength after air-drying of the conditioned collagen matrix. Extrafibrillar demineralization was validated with transmission electron microscopy. Inhibition of endogenous dentin proteases was confirmed using in-situ zymography. The water-soluble GCE dentin conditioner was non-cytotoxic and possessed antibacterial activities against planktonic and single-species biofilms, supporting its ongoing development as a dentin conditioner with air-drying, anti-proteolytic and antibacterial properties to enhance the durability of bonds created using the etch-and-rinse bonding technique. STATEMENT OF SIGNIFICANCE: The current state-of-the-art techniques for filling decayed teeth with plastic tooth-colored materials require conditioning the mineralized, biofilm-covered, decayed dentin with acids or acid resin monomers to create a surface layer of completely- or partially-demineralized collagen matrix for the infiltration of adhesive resin monomers. Nevertheless, fillings prepared using these strategies are not as durable as consumers have anticipated. Conjugation of polymeric glycol chitosan with EDTA produces a new conditioner for dentin bonding that demineralizes only extrafibrillar dentin, reduces endogenous protease activities and kills biofilm bacteria. The high molecular weight glycol chitosan-EDTA is non-cytotoxic to the key regenerative players within the dentin-pulp complex. This advance permits dry bonding and the use of hydrophobic resins.

4.
J Dent ; 82: 56-62, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30690113

RESUMO

OBJECTIVES: The present in vitro study evaluated the effect of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), a cross-linking agent used as an additional therapeutic primer for luting fiber posts to radicular dentine to prevent hybrid layer degradation. METHODS: Root canal treatment was performed on 80 extracted single-rooted human teeth. A 10-mm post space was prepared and pecimens were randomly assigned to four groups (n=20) according to the bonding system: 1) All Bond 3 (Bisco); 2) All Bond 3 + 0.3M EDC; 3) Prime&Bond XP (Dentsply Sirona); 4) Prime&Bond XP + 0.3M EDC. In groups 2 and 4, EDC was applied on phosphoric acid-etched dentine for 1 min. Fiber posts (RelyX Fiber Post, 3M ESPE) were luted with a dual-cured resin cement (Core-X flow, Dentsply Sirona). Slices were prepared for micro push-out test and interfacial nanoleakage evaluation of the coronal and apical region of the canal space after 24 h and 1 year storage in artificial saliva. In-situ zymography was performed to investigate endogenous matrix metalloproteinase activities within the hybrid layer. Results were statistically analysed with three-way ANOVA test or Chi Square test. Statistical significance was set at α=0.05. RESULTS: No significant influence was identified between the two adhesives. The use of EDC significantly improved fiber post bond strength at 1 year but not at 24 h. Application of 0.3 M EDC prior to bonding significantly reduced gelatinolytic activities within the radicular hybrid layers. CONCLUSIONS: Carbodiimide was effective in preserving fibre post bond strength over time, through reducing the activities of intra-radicular endogenous proteases. CLINICAL SIGNIFICANCE: Inhibition of matrix metalloproteinases using EDC over radicular dentin could play an important role in bond strength preservation. However, the clinical relevance of these findings needs to be proven.


Assuntos
Carbodi-Imidas , Dentina , Metaloproteinases da Matriz , Carbodi-Imidas/química , Carbodi-Imidas/farmacologia , Colagem Dentária , Cavidade Pulpar , Dentina/química , Dentina/enzimologia , Adesivos Dentinários/farmacologia , Ativação Enzimática/efeitos dos fármacos , Humanos , Teste de Materiais , Metaloproteinases da Matriz/metabolismo , Cimentos de Resina , Materiais Restauradores do Canal Radicular/farmacologia
5.
J Dent ; 79: 90-95, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30367893

RESUMO

OBJECTIVES: Matrix metalloproteinases (MMPs) are dentinal endogenous enzymes claimed to have a vital role in dentin organic matrix breakdown. The aim of the study was to investigate presence, localization and distribution of MMP-7 in sound human dentin. METHODS: Dentin was powdered, demineralized and dissolved in isoelectric focusing buffer. Resolved proteins were transferred to nitrocellulose membranes for western blotting (WB) analyses. For the zymographic analysis, aliquots of dentin protein were electrophoresed in 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing fluorescently labeled gelatin. Further, the concentrations of dentinal MMPs were measured using Fluorescent Microsphere Immunoassay with a human MMP-MAP multiplex kit. Pre- and post-embedding immunolabeling technique was used to investigate the localization and distribution of MMP-7 in dentin. Dentin was cryo-fractured, the fragments partially decalcified and labeled with a primary monoclonal anti-MMP-7 and a secondary antibody conjugated with gold nanoparticles. MMP-7 labelings were identified in the demineralized dentin matrix as highly electron-dense dispersed gold particles. RESULTS: WB and zymographic analysis of extracted dentin proteins showed presence of MMP-7 (∼20-28 KDa). Further, MMP-7 was found in the supernatants of the incubated dentin beams using Fluorescent Microsphere Immunoassay. FEI-SEM and TEM analyses established MMP-7 as an intrinsic constituent of the human dentin organic matrix. CONCLUSION: This study demonstrated that MMP-7 is an endogenous component of the human dentin fibrillar network. CLINICAL SIGNIFICANCE: It is pivotal to understand the underlying processes behind dentin matrix remodeling and degradation in order to develop the most optimal clinical protocols and ensure the longevity of dental restorations.


Assuntos
Dentina/metabolismo , Metaloproteinases da Matriz/metabolismo , Western Blotting , Ouro , Humanos , Nanopartículas Metálicas
6.
Acta Biomater ; 75: 171-182, 2018 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-29883811

RESUMO

Secondary caries and hybrid layer degradation are two major challenges encountered in long-term resin-dentin bond stability. As a link between resin and dentin, adhesives that possess both antimicrobial and anti-proteolytic activities are in demand for eliminating bacteria-induced secondary caries and preventing hybrid layers from degradation. In the present study, a new quaternary ammonium methacryloxy silane (QAMS) prepared from sol-gel chemistry was incorporated into experimental adhesives to examine their antimicrobial effect and anti-proteolytic potential. This functional methacrylate resin monomer contains polymerizable methacryloxy functionalities as well as a positively-charged quaternary ammonium functionality with a long, lipophilic -C18H37 alkyl chain for puncturing the cell wall/membrane of surface-colonizing organisms. Antibacterial testing performed using agar diffusion test, live/dead bacterial staining and colony-forming unit counts all indicated that the QAMS-containing adhesives killed Streptococcus mutans and Actinomyces naeslundii in a dose-dependent manner via a predominant contact-killing mechanism. Gelatinolytic activity within the hybrid layers created by these adhesives was examined using in-situ zymography. Hybrid layers created with 0% QAMS-containing adhesive exhibited intense green fluorescence emitted by the hydrolyzed fluorescein-conjugated gelatin, with 4-fold increase in enzymatic activity compared with an experimental adhesive containing 5% QAMS. Taken together, incorporation of 5% QAMS in the experimental adhesive provides simultaneous antimicrobial and anti-proteolytic activities that are crucial for the maintenance of long-term resin-dentin bond integrity. STATEMENT OF SIGNIFICANCE: Durability of resin-dentin interfacial bond remains a clinically-significant challenge. Secondary caries caused by bacteria and the degradation of hybrid layers via endogenous dentin proteases are two important contributors to the poor resin-dentin bond durability. The present study developed a new 5% QAMS-containing adhesive that provides simultaneous antimicrobial and dentin protease inhibition functions to extend the longevity of resin-dentin bonds.


Assuntos
Actinomyces/crescimento & desenvolvimento , Antibacterianos , Cimentos Dentários , Dentina/enzimologia , Inibidores de Proteases , Resinas Sintéticas , Streptococcus mutans/crescimento & desenvolvimento , Antibacterianos/química , Antibacterianos/farmacologia , Cimentos Dentários/química , Cimentos Dentários/farmacologia , Humanos , Inibidores de Proteases/química , Inibidores de Proteases/farmacologia , Resinas Sintéticas/química , Resinas Sintéticas/farmacologia
7.
J Dent ; 74: 79-89, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29702152

RESUMO

OBJECTIVES: The water-associated attributes of resin-dentin interfaces created by contemporary adhesives are important determinants of bond integrity and stability. In the present work, these attributes were estimated from the perspectives of causality, to examine the behavior of the first and most-recently launched versions of universal adhesives when applied in either the etch-and-rinse mode or the self-etch mode. METHODS: The immediate cause of interfacial permeability and the time-dependent cause of water sorption were investigated in conjunction with the intermediate effect of interface degradation and the more long-term effect of loss of mechanical strength, before and after thermomechanical cycling. The results were compared with control etch-and-rinse and self-etch adhesives. RESULTS: Although the introduction of this new class of universal adhesives has brought forth significant changes to the dental adhesion arena, including more application options, reduced bonding armamentarium and increased user friendliness, the water-associated attributes that are critical for making resin-dentin bonds more durable to environmental challenges and less susceptible to degradation have remained unchanged at large, when compared with benchmarks established by former classes of adhesives. CONCLUSION: It appears that the current trend of adhesive development has brought forth significant changes but lacks the vigor that demarcates progress and technological sublimity. CLINICAL SIGNIFICANCE: The advent of the user friendly universal adhesives has brought forth significant changes to the dental adhesion arena. However, the elements that are critical for making resin-dentin bonds more durable to environmental challenges and less susceptible to degradation have remained unchanged at large.


Assuntos
Colagem Dentária/métodos , Adesivos Dentinários/química , Dentina/química , Cimentos de Resina/química , Água/química , Condicionamento Ácido do Dente/métodos , Resinas Compostas/química , Coroas , Esmalte Dentário , Materiais Dentários/química , Humanos , Teste de Materiais , Dente Serotino , Permeabilidade , Propriedades de Superfície , Resistência à Tração
8.
Pak J Pharm Sci ; 31(1(Suppl.)): 245-250, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29386150

RESUMO

MgO nanoparticles have been recently discovered as an antibacterial, however, they limited by property degradation due to agglomeration. The addition of a coating agent, such as a zein polymer, is effective in preventing agglomeration without affecting nanosized properties. The aim of this study was to assess the antimicrobial property of MgO nanoparticles when coated with a zein polymer against several oral bacteria and fungi. This was done by utilizing various assessment techniques. The ultimate aim is to use these nanoparticles in dental preparations. The antimicrobial activity of zein-coated MgO nanoparticles at different concentrations of 0.5, 1 and 2% were tested against four different microorganisms: Staphylococcus aureus, Streptococcus mutans and Enterococcus faecalis (gram positive bacteria), and Candida albicans (as oral fungus). Two different techniques were utilized: the Kirby-Bauer test, and a modified direct contact test. The results indicated that the antibacterial effect of 1% or 2% zein-coated MgO nanowires were statistically significant (p<0.05) against the four organisms studied: S. mutans, S. aureus, E. faecalis and C. albicans. Zein-coated MgO nanoparticles are a new human friendly and potent antimicrobial agent that can be incorporated in the formulation of a variety of new dental materials and products that should provide improvements in dental care and oral health.


Assuntos
Anti-Infecciosos/farmacologia , Óxido de Magnésio/farmacologia , Nanopartículas Metálicas/química , Zeína/química , Anti-Infecciosos/química , Candida albicans/efeitos dos fármacos , Relação Dose-Resposta a Droga , Enterococcus faecalis/efeitos dos fármacos , Nanopartículas Metálicas/administração & dosagem , Testes de Sensibilidade Microbiana , Nanofios/química , Staphylococcus aureus/efeitos dos fármacos , Streptococcus mutans/efeitos dos fármacos
9.
Bone ; 110: 141-149, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29408511

RESUMO

Unlike other antiresorptive medications, bisphosphonate molecules accumulate in the bone matrix. Previous studies of side-effects of anti-resorptive treatment focused mainly on systemic effects. We hypothesize that matrix-bound bisphosphonate molecules contribute to the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). In this study, we examined the effect of matrix-bound bisphosphonates on osteoclast differentiation in vitro using TRAP staining and resorption assay, with and without pretreatment with EDTA. We also tested the effect of zoledronate chelation on the healing of post-extraction defect in rats. Our results confirmed that bisphosphonates bind to, and can be chelated from, mineralized matrix in vitro in a dose-dependent manner. Matrix-bound bisphosphonates impaired the differentiation of osteoclasts, evidenced by TRAP activity and resorption assay. Zoledronate-treated rats that underwent bilateral dental extraction with unilateral EDTA treatment showed significant improvement in mucosal healing and micro-CT analysis on the chelated sides. The results suggest that matrix-bound bisphosphonates are accessible to osteoclasts and chelating agents and contribute to the pathogenesis of BRONJ. The use of topical chelating agents is a promising strategy for the prevention of BRONJ following dental procedures in bisphosphonate-treated patients.


Assuntos
Osteonecrose da Arcada Osseodentária Associada a Difosfonatos/prevenção & controle , Difosfonatos/efeitos adversos , Arcada Osseodentária/fisiopatologia , Osteoclastos/citologia , Extração Dentária/efeitos adversos , Ácido Zoledrônico/farmacologia , Aminoácidos/química , Animais , Osteonecrose da Arcada Osseodentária Associada a Difosfonatos/patologia , Osso e Ossos/fisiopatologia , Cálcio/química , Diferenciação Celular , Proliferação de Células , Quelantes/química , Difosfonatos/farmacologia , Ácido Edético/química , Humanos , Espectrometria de Massas , Camundongos , Dente Molar , Células RAW 264.7 , Ratos , Ratos Sprague-Dawley , Microtomografia por Raio-X
10.
Dent Mater ; 34(3): 452-459, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29301651

RESUMO

OBJECTIVE: The present study evaluated the influence of time, mass and surface area of demineralized dentin collagen matrices on telopeptides release. The hypotheses tested were that the rates of ICTP and CTX release by matrix bound endogenous proteases are 1) not time-dependent, 2) unrelated to specimen mass, 3) unrelated to specimen surface area. METHODS: Non-carious human molars (N=24) were collected and randomly assigned to three groups. Dentin slabs with three different thicknesses: 0.37mm, 0.75mm, and 1.50mm were completely demineralized and stored in artificial saliva for one week. Collagen degradation was evaluated by sampling storage media for ICTP and CTX telopeptidases. Activity of MMPs in the aging medium was evaluated using fluorometric activity assay kit. RESULTS: A statistically significant (p<0.05) decrease in the release of both ICTP and CTX fragments over time was observed irrespective of the specimen thickness. When data were normalized by the specimen mass, no significant differences were observed. Releases of ICTP and CTX were significantly related to the aging time as a function of surface area for the first 12h. Total MMP activity, mainly related to MMP-2 and -9, decreased with time (p<0.05). SIGNIFICANCE: Because the release of collagen fragments was influenced by specimen storage time and surface area, it is likely that cleaved collagen fragments closer to the specimen surface diffuse into the incubation medium; those further away from the exposed surface are still entrapped within the demineralized dentin matrix. Bound MMPs can only degrade the substrate within the limited zone of their molecular mobility.


Assuntos
Colágeno Tipo I/metabolismo , Dentina/metabolismo , Peptídeos/metabolismo , Ensaio de Imunoadsorção Enzimática , Humanos , Técnicas In Vitro , Metaloproteinases da Matriz/metabolismo , Dente Molar , Saliva Artificial , Fatores de Tempo
11.
Dent Mater ; 34(1): 78-96, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29179971

RESUMO

OBJECTIVES: Efforts towards achieving durable resin-dentin bonds have been made for decades, including the understanding of the mechanisms underlying hybrid layer (HL) degradation, manufacturing of improved adhesive systems, as well as developing strategies for the preservation of the HL. METHODS: This study critically discusses the available peer-reviewed research concerning the formation and preservation of the HL, the mechanisms that lead to the degradation of the HL as well as the strategies to prevent it. RESULTS: The degradation of the HL occurs through two main mechanisms: the enzymatic degradation of its collagen fibrils, and the leaching of the resin from the HL. They are enabled by residual unbound water between the denuded collagen fibrils, trapped at the bottom of the HL. Consequently, endogenous dentinal enzymes, such as the matrix metalloproteinases (MMPs) and cysteine cathepsins are activated and can degrade the denuded collagen matrix. Strategies for the preservation of the HL over time have been developed, and they entail the removal of the unbound water from the gaps between the collagen fibrils as well as different modes of silencing endogenous enzymatic activity. SIGNIFICANCE: Although there are many more hurdles to be crossed in the field of adhesive dentistry, impressive progress has been achieved so far, and the vast amount of available research on the topic is an indicator of the importance of this matter and of the great efforts of researchers and dental material companies to reach a new level in the quality and longevity of resin-dentin bonds.


Assuntos
Colágeno/química , Colagem Dentária/métodos , Adesivos Dentinários/química , Dentina/química , Colágeno/ultraestrutura , Reagentes para Ligações Cruzadas/química , Dentina/ultraestrutura , Metaloproteinases da Matriz/metabolismo , Propriedades de Superfície
12.
Dent Mater ; 34(2): 288-295, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29179972

RESUMO

OBJECTIVE: The objectives of the study were to evaluate the ability of a 1-ethyl-3 (3-dimethylaminopropyl) carbodiimide (EDC)-containing primer to improve immediate bond strength of either self-etch or etch-and-rinse adhesive systems and to stabilize the adhesive interfaces over time. A further objective was to investigate the effect of EDC on the dentinal MMPs activity using zymographic analysis. METHODS: Freshly extracted molars (n=80, 20 for each group) were selected to conduct microtensile bond strength tests. The following groups were tested, immediately or after 1-year aging in artificial saliva: G1: Clearfil SE (CSE) primer applied on unetched dentin, pretreated with 0.3M EDC water-solution for 1min and bonded with CSE Bond; G2: as G1 but without EDC pre-treatment; G3: acid-etched (35% phosphoric-acid for 15s) dentin pretreated with 0.3M EDC, then bonded with XP Bond (XPB); Group 4 (G4): as G3 without EDC pre-treatment. Further, gelatinase activity in dentin powder treated with CSE and XPB with and without EDC pre-treatment, was analyzed using gelatin zymography. RESULTS: The use of 0.3M EDC-containing conditioner did not affect the immediate bond strength of XPB or CSE adhesive systems (p>0.05), while it improved the bond strength after 1year of aging (p<0.05). Pre-treatment with EDC followed by the application of CSE resulted in an incomplete MMPs inactivation, while EDC pretreatment followed by the application of XPB resulted in an almost complete inactivation of dentinal gelatinases. SIGNIFICANCE: The µTBS and zymography results support the efficacy of EDC over time and reveal that changes within the dentin matrix promoted by EDC are not adhesive-system-dependent.


Assuntos
Carbodi-Imidas/química , Colagem Dentária/métodos , Adesivos Dentinários/química , Dentina/efeitos dos fármacos , Dentina/metabolismo , Metaloproteinases da Matriz/metabolismo , Cimentos de Resina/química , Condicionamento Ácido do Dente/métodos , Humanos , Técnicas In Vitro , Cura Luminosa de Adesivos Dentários , Teste de Materiais , Camada de Esfregaço , Propriedades de Superfície , Resistência à Tração
13.
Dent Mater ; 34(2): 317-330, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29179973

RESUMO

OBJECTIVES: The objective of the present study was to elucidate the mechanism of bioactive molecule extraction from mineralized dentin by calcium hydroxide (Ca(OH)2) and tricalcium silicate cements (TSC). METHODS AND RESULTS: Transmission electron microscopy was used to provide evidence for collagen degradation in dentin surfaces covered with Ca(OH)2 or a set, hydrated TSC for 1-3 months. A one micron thick collagen degradation zone was observed on the dentin surface. Fourier transform-infrared spectroscopy was used to identify increases in apatite/collagen ratio in dentin exposed to Ca(OH)2. Using three-point bending, dentin exposed to Ca(OH)2 exhibited significant reduction in flexural strength. Using size exclusion chromatography, it was found that the small size of the hydroxyl ions derived from Ca(OH)2 enabled those ions to infiltrate the intrafibrillar compartment of mineralized collagen and degrade the collagen fibrils without affecting the apatite minerals. Using ELISA, TGF-ß1 was found to be extracted from dentin covered with Ca(OH)2 for 3 months. Unlike acids that dissolve the mineral component of dentin to release bioactive molecules, alkaline materials such as Ca(OH)2 or TSC released growth factors such as TGF-ß1 via collagen degradation. SIGNIFICANCE: The bioactive molecule extraction capacities of Ca(OH)2 and TSC render these dental materials excellent for pulp capping and endodontic regeneration. These highly desirable properties, however, appear to be intertwined with the untoward effect of degradation of the collagen matrix within mineralized dentin, resulting in reduced flexural strength.


Assuntos
Compostos de Cálcio/química , Hidróxido de Cálcio/química , Colágeno/efeitos dos fármacos , Colágeno/metabolismo , Cimentos Dentários/química , Dentina/efeitos dos fármacos , Silicatos/química , Fator de Crescimento Transformador beta1/metabolismo , Apatitas/química , Capeamento da Polpa Dentária , Dentina/química , Humanos , Técnicas In Vitro , Teste de Materiais , Microscopia Eletrônica de Transmissão , Espectroscopia de Infravermelho com Transformada de Fourier
14.
Dent Mater ; 33(12): 1340-1350, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28942948

RESUMO

The application of a cross-linker to demineralized dentin is reportedly effective at extending the durability of dentin bonds. OBJECTIVE: To compare the effect of a cross-linker pretreatment on the fatigue crack growth resistance of resin-dentin bonds prepared with a two- vs. three-step adhesive system. METHODS: Bonded interface Compact Tension (CT) specimens were prepared using commercial two- and three-step etch-and-rinse adhesives and compatible hybrid resin-composite. For the treated groups, adhesive bonding was preceded by a 1min application of an experimental carbodiimide (EDC) conditioner to the acid-etched dentin. The control groups received no such treatment. The fatigue crack growth resistance was examined after storage in artificial saliva at 37°C for 0, 3 and 6 months. RESULTS: There was no significant difference in the immediate fatigue crack growth resistance the control and EDC-treated groups at 0 months for either adhesive system. After 3 and 6 months of storage, the EDC-treated groups exhibited significantly greater (p≤0.05) fatigue crack growth resistance than the controls. Although the EDC treatment was equally effective in deterring degradation for both adhesives, bonds prepared with the three-step system exhibited the lowest resistance to fatigue crack growth overall. SIGNIFICANCE: An EDC treatment applied during dentin bonding could help maintain the durability of bonds prepared with two or three-step adhesive bonding systems.


Assuntos
Carbodi-Imidas/química , Resinas Compostas/química , Reagentes para Ligações Cruzadas/química , Colagem Dentária , Falha de Restauração Dentária , Adesivos Dentinários/química , Condicionamento Ácido do Dente , Análise do Estresse Dentário , Teste de Materiais , Microscopia Eletrônica de Varredura , Saliva Artificial , Propriedades de Superfície , Resistência à Tração
15.
J Adhes Dent ; 19(4): 341-348, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28849803

RESUMO

PURPOSE: To examine the effect of CHX pre-treatment on long-term bond strength of fiber posts luted with self-adhesive resin cements. MATERIALS AND METHODS: Seventy-two single-rooted teeth were selected for root canal treatment and post space preparation. The tested self-adhesive cement/post combinations were (N = 36): 1. RelyX Fiber-Posts luted with RelyX Unicem; 2. Rebilda Posts luted with Bifix SE Cement. For both self-adhesive cements, half of the specimens (experimental groups) were luted after the application of a solution of 2% CHX, while no CHX application was performed for the remaining specimens (control groups). Luted specimens were cut and used for push-out bond strength evaluation immediately, and after storage in artificial saliva for 6 months or 1 year. Additional specimens were processed for quantitative interfacial nanoleakage analysis. RESULTS: ANOVA showed that the variable times of storage had a significant influence on the results (p < 0.05), while no influence of the luting procedure (cements with or without CHX) on the final outcome (p > 0.05) was found. Tukey's pairwise post-hoc test showed that the radicular bond strength decreased with time of storage. In particular, a significant difference was found between T0 and T1y, but not between T0 and T6m. In contrast, in terms of pretreatment, no significant reduction in push-out bond strength was observed, irrespective of the aging time. CONCLUSION: CHX pretreatment did not prevent bond strength degradation of fiber posts luted with self-adhesive cements.


Assuntos
Clorexidina , Cimentos Dentários , Cimentos de Resina , Resinas Compostas , Colagem Dentária , Análise do Estresse Dentário , Dentina , Teste de Materiais , Técnica para Retentor Intrarradicular
16.
Acta Biomater ; 61: 144-156, 2017 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-28801267

RESUMO

The medical literature is replete with the maxim 'primum non nocere', cautioning health care providers to avoid doing any harm to human subjects in their delivery of medical care. Sodium hypochlorite (NaOCl) is a well-established irrigant for root canal treatment because of its antimicrobial and organic tissue remnant dissolution capability. However, little is known about the deleterious effect of this strong oxidizing agent on the integrity of human mineralized dentin. Iatrogenically-induced loss of dentin integrity may precipitate post-treatment root fracture and has potential medico-legal complications. In the present work, transmission electron microscopy provided evidence for collagen destruction in the surface/subsurface of dentin treated with high NaOCl concentrations and long contact times. Size exclusion chromatography showed that the hypochlorite anion, because of its small size, penetrated the water compartments of apatite-encapsulated collagen fibrils, degraded the collagen molecules and produced a 25-35µm thick, non-uniform "ghost mineral layer" with enlarged, coalesced dentinal tubules and their lateral branches. Fourier transform-infrared spectroscopy identified increases in apatite/collagen ratio in NaOCl-treated dentin. The apatite-rich, collagen-sparse dentin matrix that remained after NaOCl treatment is more brittle, as shown by the reductions in flexural strength. Understanding the deleterious effects of NaOCl on mineralized dentin enables one to balance the risks and benefits in using high NaOCl concentrations for lengthy periods in root canal debridement. Delineating the mechanism responsible for such a phenomenon enables high molecular weight, polymeric antimicrobial and tissue dissolution irrigants to be designed that abides by the maxim of 'primum non nocere' in contemporary medical practices. STATEMENT OF SIGNIFICANCE: The antimicrobial and tissue-dissolution capacities of NaOCl render it a well-accepted agent for root canal debridement. These highly desirable properties, however, appear to be intertwined with the untoward effect of collagen matrix degradation within mineralized dentin. Because of its small size, the hypochlorite anion is capable of infiltrating mineralized collagen and destroying the collagen fibrils, producing a mineral-rich, collagen sparse ghost mineral matrix with reduced flexural strength. Findings from the present work challenge the biosafety of NaOCl when it is used in high concentrations and for lengthy time periods during root canal treatment, and laid the background work for future biomaterials design in debridement of the canal space.


Assuntos
Dentina/efeitos dos fármacos , Endodontia , Hipoclorito de Sódio/farmacologia , Aminoácidos/análise , Calcificação Fisiológica/efeitos dos fármacos , Cromatografia por Troca Iônica , Colágeno/metabolismo , Dentina/ultraestrutura , Ensaio de Imunoadsorção Enzimática , Humanos , Espectroscopia de Infravermelho com Transformada de Fourier
17.
Dent Mater ; 33(8): 904-914, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28577892

RESUMO

Application of collagen cross-linkers to demineralized dentin improves bond durability. While the benefits of cross-linking treatments to bond strength and fatigue resistance have been explored, changes in hybrid layer stiffness with aging have not been examined. OBJECTIVE: To examine the influence of a cross-linking treatment using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) on hybrid layer stiffness of resin-dentin adhesive bonds, using spatially-resolved nanoscopic Dynamic Mechanical Analysis (nanoDMA). METHODS: Bonded interface specimens were prepared using a two-step (SB) or three-step (SBMP) etch-and-rinse adhesive. Adhesive bonding of the treated groups was preceded by a 1min application of an experimental EDC conditioner to the acid-etched dentin. Control specimens did not receive EDC treatment. The bonded interfaces were evaluated using nanoDMA to determine the dynamic mechanical properties after storage in artificial saliva at 37°C for 0, 3 and 6 months. RESULTS: The EDC treatment had no influence on the dynamic mechanical properties of the hybrid layer immediately after bonding. There was also no reduction in the hybrid layer stiffness after 3 and 6 months aging as defined by the complex modulus and storage modulus. However, there was a significant reduction in the loss modulus and tanδ components (i.e. viscous behavior) of the hybrid layers with aging. Degradation occurred to both adhesive systems with storage, but was greatest for SB. Without EDC treatment, the reduction in tanδ of the hybrid layer prepared with SB exceeded 80% in 6 months. SIGNIFICANCE: The application of EDC to acid-etched dentin helps maintain the viscoelasticity of hybrid layers.


Assuntos
Adesivos Dentinários , Dentina , Saliva Artificial , Colágeno , Colagem Dentária , Cimentos Dentários , Humanos , Teste de Materiais , Cimentos de Resina , Resistência à Tração , Fatores de Tempo
18.
Eur J Oral Sci ; 125(4): 288-293, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28643463

RESUMO

A water-soluble crosslinking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), has been used as a pretreatment of acid-etched dentin to inactivate matrix-bound endogenous dentin proteases. The aim of this study was to evaluate the effect of pH on the inactivation capacity of EDC. Demineralized dentin beams (1 × 2 × 6 mm) were divided into six groups (n = 8 per group). Then, EDC (0.3 M) was solubilized in distilled water with pH of 2, 4, 6, 7, 9, or 11. Control EDC was solubilized in 0.1 M 2-(N-morpholino) ethanesulfonic acid (MES) buffer and its pH was adjusted to 6. The dentin beams were pretreated for 1 min with EDC at each pH or with EDC in MES buffer at pH 6.0 and then incubated in 1 ml of simulated body fluid (pH 7.2) for 1, 3, 7, or 14 d. Untreated beams served as controls. At each study time-point, the dry mass of dentin beams was assessed and the incubation media were analyzed for carboxyterminal telopeptide of type-I collagen (ICTP) and C-terminal telopeptide of type I collagen (CTX) using specific ELISAs. Data were subjected to repeat-measures anova. The results of the study indicated that specimens pretreated with EDC in MES buffer showed the lowest collagen degradation in terms of mass loss and release of telopeptides, while specimens pretreated in alkaline media showed the highest collagen degradation. This study indicates that the pH of the EDC solution plays an important role in the stability of dentin protease inactivation.


Assuntos
Reagentes para Ligações Cruzadas/farmacologia , Dentina/enzimologia , Etildimetilaminopropil Carbodi-Imida/análogos & derivados , Peptídeo Hidrolases/efeitos dos fármacos , Ensaio de Imunoadsorção Enzimática , Etildimetilaminopropil Carbodi-Imida/farmacologia , Humanos , Concentração de Íons de Hidrogênio , Técnicas In Vitro , Dente Molar
19.
Acta Biomater ; 57: 435-448, 2017 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-28499631

RESUMO

Limitations associated with wet-bonding led to the recent development of a selective demineralization strategy in which dentin was etched with a reduced concentration of phosphoric acid to create exclusive extrafibrillar demineralization of the collagen matrix. However, the use of acidic conditioners removes calcium via diffusion of very small hydronium ions into the intrafibrillar collagen water compartments. This defeats the purpose of limiting the conditioner to the extrafibrillar space to create a collagen matrix containing only intrafibrillar minerals to prevent collapse of the collagen matrix. The present work examined the use of polymeric chelators (the sodium salt of polyacrylic acid) of different molecular weights to selectively demineralize extrafibrillar dentin. These polymeric chelators exhibit different affinities for calcium ions (isothermal titration calorimetry), penetrated intrafibrillar dentin collagen to different extents based on their molecular sizes (modified size-exclusion chromatography), and preserve the dynamic mechanical properties of mineralized dentin more favorably compared with completely demineralized phosphoric acid-etched dentin (nanoscopical dynamic mechanical analysis). Scanning and transmission electron microscopy provided evidence for retention of intrafibrillar minerals in dentin surfaces conditioned with polymeric chelators. Microtensile bond strengths to wet-bonded and dry-bonded dentin conditioned with these polymeric chelators showed that the use of sodium salts of polyacrylic acid for chelating dentin prior to bonding did not result in significant decline in resin-dentin bond strength. Taken together, the findings led to the conclusion that a chelate-and-rinse conditioning technique based on extrafibrillar collagen demineralization bridges the gap between wet and dry dentin bonding. STATEMENT OF SIGNIFICANCE: The chelate-and-rinse dental adhesive bonding concept differentiates from previous research in that it is based on the size-exclusion characteristics of fibrillar collagen; molecules larger than 40kDa are prevented from accessing the intrafibrillar water compartments of the collagen fibrils. Using this chelate-and-rinse extrafibrillar calcium chelation concept, collagen fibrils with retained intrafibrillar minerals will not collapse upon air-drying. This enables adhesive infiltration into the mineral-depleted extrafibrillar spaces without relying on wet-bonding. By bridging the gap between wet and dry dentine bonding, the chelate-and-rinse concept introduces additional insight to the field by preventing exposure of endogenous proteases via preservation of the intrafibrillar minerals within a collagen matrix. If successfully validated, this should help prevent degradation of resin-dentine bonds by collagenolytic enzymes.


Assuntos
Colágeno/química , Dentina/química , Dente Molar/química , Desmineralização do Dente , Humanos
20.
J Dent ; 62: 54-63, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28506642

RESUMO

OBJECTIVE: A recently-launched universal adhesive, G-Premio Bond, provides clinicians with the alternative to use the self-etch technique for bonding to dentine without waiting for the adhesive to interact with the bonding substrate (no-waiting self-etch; Japanese brochure), or after leaving the adhesive undisturbed for 10s (10-s self-etch; international brochure). The present study was performed to examine in vitro performance of this new universal adhesive bonded to human coronal dentine using the two alternative self-etch modes. METHODS: One hundred and ten specimens were bonded using two self-etch application modes and examined with or without thermomechanical cycling (10,000 thermal cycles and 240,000 mechanical cycles) to simulate one year of intraoral functioning. The bonded specimens were sectioned for microtensile bond testing, ultrastructural and nanoleakage examination using transmission electron microscopy. Changes in the composition of mineralised dentine after adhesive application were examined using Fourier transform infrared spectroscopy. RESULTS: Both reduced application time and thermomechanical cycling resulted in significantly lower bond strengths, thinner hybrid layers, and significantly more extensive nanoleakage after thermomechanical cycling. Using the conventional 10-s application time improved bonding performance when compared with the no-waiting self-etch technique. Nevertheless, nanoleakage was generally extensive under all testing parameters employed for examining the adhesive. CONCLUSION: Although sufficient bond strength to dentine may be achieved using the present universal adhesive in the no-waiting self-etch mode that does not require clinicians to wait prior to polymerisation of the adhesive, this self-etch concept requires further technological refinement before it can be recommended as a clinical technique. CLINICAL SIGNIFICANCE: Although the surge for cutting application time to increase user friendliness remains the most frequently sought conduit for advancement of dentine bonding technology, the use of the present universal adhesive in the no-waiting self-etch mode may not represent the best use of the adhesive.


Assuntos
Condicionamento Ácido do Dente/métodos , Colagem Dentária/métodos , Adesivos Dentinários/química , Dentina/patologia , Dentina/ultraestrutura , Teste de Materiais , Resinas Compostas/química , Luzes de Cura Dentária , Cimentos Dentários/química , Infiltração Dentária , Materiais Dentários/química , Humanos , Concentração de Íons de Hidrogênio , Metacrilatos , Microscopia Eletrônica de Transmissão , Dente Serotino , Estresse Mecânico , Propriedades de Superfície , Temperatura , Resistência à Tração , Fatores de Tempo , Desmineralização do Dente
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