Abstract Objectives This study evaluated the role of endogenous dentin MMPs in auto-degradation of collagen fibrils within adhesive-bonded interfaces. The null hypotheses tested were that adhesive ...blends or chlorhexidine digluconate (CHX) application does not modify dentin MMPs activity and that CHX used as therapeutic primer does not improve the stability of adhesive interfaces over time. Methods Zymograms of protein extracts from human dentin powder incubated with Adper Scotchbond 1XT (SB1XT) on untreated or 0.2–2% CHX-treated dentin were obtained to assay dentin MMPs activity. Microtensile bond strength and interfacial nanoleakage expression of SB1XT bonded interfaces (with or without CHX pre-treatment for 30 s on the etched surface) were analyzed immediately and after 2 years of storage in artificial saliva at 37 °C. Results Zymograms showed that application of SB1XT to human dentin powder increases MMP-2 activity, while CHX pre-treatment inhibited all dentin gelatinolytic activity, irrespective from the tested concentration. CHX significantly lowered the loss of bond strength and nanoleakage seen in acid-etched resin-bonded dentin artificially aged for 2 years. Significance The study demonstrates the active role of SB1XT in dentin MMP-2 activation and the efficacy of CHX inhibition of MMPs even if used at low concentration (0.2%).
Abstract Objective The function of endogenous MMP-3 and its distribution within the human dentine is unclear. Thus, the aim of the present study was to assay the presence and distribution of MMP-3 ...within human sound dentine by means of biochemical and immunohistochemical assays. Methods Powdered dentine from extracted human teeth was prepared and (1) partially demineralised with 1% H3 PO4 for 10 min or (2) untreated (control). The presence of MMP-3 was measured using a colorimetric assay system (QuantiSir™, Epigentek, USA). Additional cryo-fractured dentine fragments were processed for immunohistochemical identification of MMP-3 under FEI-SEM. Casein-zymography was used to investigate MMP-3 activity. Results MMP-3 detected level was 2.732 ng/μL in partially demineralised dentine powder, whilst it increased to 3.280 ng/μL in mineralised dentine. The FEI-SEM analysis revealed positive immunolabelling patterns for MMP-3, predominantly localized on the intertubular collagen fibrillar network showing MMP-3 directly or indirectly bound to the collagen fibrils. Casein-zymograms showed positive proteolytic activity for MMP-3 in demineralised dentine powder. Conclusion The results of the study clearly revealed the presence and distribution of MMP3 in human sound dentine. Whilst the presence was verified, its role is still unclear. Future studies are needed to investigate the possible involvement of MMP-3 in physiological and pathological condition of the dentine–pulp complex.
Abstract Objectives This study investigated the effects of an electric field produced by a new device for the application of etch-and-rinse adhesives on demineralized dentin surfaces. Methods Three ...simplified etch-and-rinse adhesives (Single Bond, Prime&Bond NT and One-Step) were applied with the electric device and compared with controls prepared with disposable sponges. Specimens were processed for microtensile bond strength test and nanoleakage investigation using high resolution SEM. Results Microtensile testing revealed higher bond strengths ( p < 0.05) for all adhesives tested when electricity was used. Adhesive interfaces prepared with electric impulses exhibited very homogenous hybrid layers with minimal nanoleakage compared with the controls. Significance The use of electricity produced by a new electronic device during the application of dentin adhesives may increase adhesive adaptation to the dentin substrate and improve dentin hybridization due to the substrate modifications induced by an electric field on the demineralized dentin organic matrix.
Abstract Objective Preservation of structural and biochemical properties of the root dentin matrix is crucial to favor healing and regenerative periodontal processes. Aim of this study was to ...evaluate the biochemical characteristics of collagen and chondroitin sulphate of root dentin surfaces exposed by periodontal disease after acid conditioning by means of an immunohistochemical technique. Design Human teeth scheduled for extraction due to periodontal reason were submitted to: (A) scaling and root planning; (B) ultrasonic instrumentation; (C) no instrumentation. Teeth were then exposed to: (1) 10% citric acid; (2) 17% EDTA; (3) no etching. A double immunolabeling technique was performed to identify type-I collagen and proteoglycans and analyzed under FEI-SEM. Results Use of 10% citric acid revealed intense labeling for collagen fibrils and proteoglycans; lower labeling was found after EDTA conditioning. Unetched specimens showed residual smear layer on the dentin surface resulting in no evident surface labeling. Conclusions This study supports the hypothesis that manual or ultrasonic instrumentation alone is not able to expose the sound dentin matrix, whereas a subsequent acidic conditioning exposes collagen fibrils and associated proteoglycans. The immunohistochemical technique revealed that despite their acidity, both citric acid and EDTA were able to preserve the structural and biochemical properties of the exposed dentin matrix.
Abstract Objectives The application of an electric field has been shown to positively influence the bonding of dentin bonding systems (DBS) by improving adhesive impregnation into dentin. However, ...the mechanism responsible for this phenomenon has not been completely elucidated. The aim of this study was to clarify the effects of pH, matrix ionic strength, and applied voltage on the migration of commonly used DBS monomers in a model matrix (agarose gel). Methods Some common monomers examined were bis-GMA (2,2-bis4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl propane); HEMA (2-hydroxyethyl methacrylate); 2-MP (bis2-(methacryloyloxy) ethyl phosphate); TCDM di(hydroxyethyl methacrylate) ester of 5-(2,5,-dioxo tetrahydrofurfuryl)-3-methyl-3-cyclohexenyl-1,2-dicarboxylic acid; and TEGDMA (triethylene glycol dimethacrylate). Agarose gels poured into a horizontal 10-well electrophoretic cell were used to mimic the collagen fibrils of the dentin organic matrix. The role of pH, matrix ionic strength, and voltage on monomer migration was assayed by modifying the experimental conditions. Results Results of experiments performed at pH 3.1, 6.3, 8.5, and 12.3; at low, medium, and high ionic strength; and at 50 and 100 V clearly showed that DBA monomer migration toward both the anode and the cathode can be affected by each of these parameters. Significance Migration of acrylic monomers toward the anode or cathode can be achieved as desired by selective choice of pH, ionic strength, and applied voltage. Additional studies are needed to evaluate the synergistic effects of DBS monomer blends on migration in an electric field.
The aim of this study was to investigate whether an electrical device for dental adhesive application (ElectroBond) influences bonding of two-step etch-and-rinse adhesives.
Human teeth were selected ...and cut perpendicularly to their long axis to expose middle/ deep dentin. Specimens were then longitudinally sectioned into halves (experimental and control halves) to create two similar bonding substrates. Experimental halves were bonded using an ElectroBond-assisted application, while control halves were bonded with disposable sponges. The adhesives tested were Adper Scotchbond 1XT and XP-BOND. Bonded specimens were submitted to the microtensile bond strength test. Additional adhesive interfaces were prepared and processed for nanoleakage investigation involving TEM examination.
The microtensile bond test revealed higher values (p < 0.05) for both adhesives if ElectroBond was used during layering (55.5 +/- 7.9 MPa for Adper Scotchbond 1XT and 54.7 +/- 7.1 MPa for XP-BOND) compared to the conventional mechanical adhesive application technique (41.1 +/- 6.1 MPa for Adper Scotchbond 1XT and 38.0 +/- 7.8 MPa for XP-BOND). No difference between the two adhesives was found under the same application conditions. With electricity-assisted application, TEM micrographs revealed a significant decrease in nanoleakage expression compared to the controls.
The use of an electric current produced by ElectroBond during the application of two-step etch-and-rinse adhesives may enhance resin impregnation, thus improving dentin hybridization. Further studies should be done to confirm that this device can similarly improve adhesive application in vivo.
The beta1 isoform of phospholipase-C is exclusively present in the nucleus of several hematopoietic and non-hematopoietic cell lines and primary cells of different species. When present, it ...represents the key enzyme for initiating the nuclear phospholipid breakdown that is involved in the cellular response to proliferating and differentiating stimuli. We have studied the expression of this enzyme isoform in the rat cerebellar cortex. We demonstrate that phospholipase-C beta1 (PLCbeta1) is predominantly expressed in the neurons of the granular layer, while it is virtually absent in the molecular and Purkinje cell layers of rat cerebellar cortex. This pattern of expression is partially different from that of the mouse cerebellar cortex, where not only granular cells, but also Purkinje cells express PLCbeta1. The high level of synaptic inputs that converge on granular cells may imply a constantly active nuclear phospholipid metabolism that may not be strictly required for the appropriate cellular responses of the other cell types of rat cerebellar cortex.
Part I was an overview of the role and function of proteoglycans and glycoproteins in the pulpo–dentin complex; part II will focus on enzymes, serum proteins, and growth factors. This review will ...discuss current knowledge regarding matrix metalloproteinases (MMPs), cathepsins, serum proteins, and growth factors in dentin and the related dentin–pulp complex in an attempt to better understand their nature, role, and function in the dentin extracellular matrix (ECM) environment. Dentin formation in physiological and pathological conditions has been widely studied. However, the regulation and involvement of non‐collageneous enzymes, serum proteins, and growth factors are still not completely elucidated. MMPs, a family of 23 endopeptidases in humans, are collectively capable of degrading virtually all ECM components, and their specific tissue inhibitors (TIMPs: tissue inhibitors of matrix metalloproteinases) participate in organo‐ and morphogenesis, physiological tissue turnover, and pathological tissue destruction. Similarly, the lysosomal cysteine proteinases (cathepsins) are capable of degrading ECM proteins such as collagen, laminin, fibronectin, and proteoglycans. These enzymes are implicated in a variety of pathological conditions, especially in diseases involving tissue re‐modeling states. Dentin also contains serum‐derived proteins (such as albumin, immunoglobulins, and transferrin), and a variety of growth factors in the mineralized ECM are available for release during demineralization or other injury. A detailed description of the components of the above‐mentioned dentin non‐collageneous proteins will be summarized in this literature review.
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