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Journal of Dental Research Feb 2015Dentin can be described as a biological composite with collagen matrix embedded with nanosized hydroxyapatite mineral crystallites. Matrix metalloproteinases (MMPs) and... (Review)
Review
Dentin can be described as a biological composite with collagen matrix embedded with nanosized hydroxyapatite mineral crystallites. Matrix metalloproteinases (MMPs) and cysteine cathepsins are families of endopeptidases. Enzymes of both families are present in dentin and collectively capable of degrading virtually all extracellular matrix components. This review describes these enzymes and their presence in dentin, mainly focusing on their role in dentin caries pathogenesis and loss of collagen in the adhesive hybrid layer under composite restorations. MMPs and cysteine cathepsins present in saliva, mineralized dentin, and/or dentinal fluid may affect the dentin caries process at the early phases of demineralization. Changes in collagen and noncollagenous protein structure may participate in observed decreases in mechanical properties of caries-affected dentin and reduce the ability of caries-affected dentin to remineralize. These endogenous enzymes also remain entrapped within the hybrid layer during the resin infiltration process, and the acidic bonding agents themselves (irrespective of whether they are etch-and-rinse or self-etch) can activate these endogenous protease proforms. Since resin impregnation is frequently incomplete, denuded collagen matrices associated with free water (which serves as a collagen cleavage reagent for these endogenous hydrolase enzymes) can be enzymatically disrupted, finally contributing to the degradation of the hybrid layer. There are multiple in vitro and in vivo reports showing that the longevity of the adhesive interface is increased when nonspecific enzyme-inhibiting strategies are used. Different chemicals (i.e., chlorhexidine, galardin, and benzalkonium chloride) or collagen cross-linker agents have been successfully employed as therapeutic primers in the bonding procedure. In addition, the incorporation of enzyme inhibitors (i.e., quaternary ammonium methacrylates) into the resin blends has been recently promoted. This review will describe MMP functions in caries and hybrid layer degradation and explore the potential therapeutic role of MMP inhibitors for the development of improved intervention strategies for MMP-related oral diseases.
Topics: Cathepsins; Collagen; Dental Bonding; Dental Caries; Dental Materials; Dentin; Disease Progression; Humans; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases
PubMed: 25535202
DOI: 10.1177/0022034514562833 -
Brazilian Dental Journal 2022Thisstudy aimed to evaluate the effect of the electric current direction application on the resin composite-dentin bond strength using three adhesive systems. Human...
Thisstudy aimed to evaluate the effect of the electric current direction application on the resin composite-dentin bond strength using three adhesive systems. Human molar teeth were distributed according to the adhesive system (two-step self-etch - Clearfil SE Bond, Kuraray [CSE]; one-step self-etch - Single Bond Universal, 3M ESPE [SBU]; and two-step etch-and-rinse - Adper Single Bond 2, 3M ESPE [SB2]), electric current direction (without electric current - control, direct and reverse electric currents - 35µA), and storage time (24h - immediate and 6 months). Resin composite blocks (Filtek Z350XT, 3M ESPE) were bonded to dentin. The teeth/resin composites specimens were stored in distilled water at 37ºC for 24 hours and 6 months for the microtensile bond strength (µTBS) test (n = 10; ~12 sticks for each tooth). Failure patterns were analyzed on a stereomicroscope and classified as cohesive-dentin, cohesive-resin, adhesive or mixed. Adhesive penetration into dentin and hybrid layer formation were evaluated in a scanning electron microscope (n = 6). Data were submitted to a three-way ANOVA followed by Tukey's post hoc test (α = 0.05). There are no differences in µTBS when the adhesive systems were applied under direct and reverse electric currents, but both electric currents increased the µTBS for all adhesive systems. SBU showed the lowest µTBS values for control groups in both storage times and direct electric current in 6 months of storage. The adhesive failure pattern was more frequently observed in all groups. The electric current formed long resin tags for all adhesive systems. Storage for 6 months did not significantly decrease µTBS values. Both directions of electric current (positive and negative charges) at 35µA can increase the µTBS of the adhesive systems tested to dentin.
Topics: Humans; Dental Cements; Dentin
PubMed: 36477969
DOI: 10.1590/0103-6440202204870 -
Journal of Biomechanics Aug 2022Investigations into teeth mechanical properties provide insight into physiological functions and pathological changes. This study sought to 1) quantify the spatial...
Investigations into teeth mechanical properties provide insight into physiological functions and pathological changes. This study sought to 1) quantify the spatial distribution of elastic modulus, hardness and the microstructural features of dog dentin and to 2) investigate quantitative relationships between the mechanical properties and the complex microstructure of dog dentin. Maxillary canine teeth of 10 mature dogs were sectioned in the transverse and vertical planes, then tested using nanoindentation and scanning electron microscopy (SEM). Microstructural features (dentin area fraction and dentinal tubule density) and mechanical properties (elastic modulus and hardness) were quantified. Results demonstrated significant anisotropy and spatial variation in elastic modulus, hardness, dentin area fraction and tubule density. These spatial variations adhered to a consistent distribution pattern; hardness, elastic modulus and dentin area fraction generally decreased from superficial to deep dentin and from crown tip to base; tubule density generally increased from superficial to deep dentin. Poor to moderate correlations between microstructural features and mechanical properties (R = 0.032-0.466) were determined. The results of this study suggest that the other constituents may contribute to the mechanical behavior of mammalian dentin. Our results also present several remaining opportunities for further investigation into the roles of organic components (e.g., collagen) and mineral content on dentin mechanical behavior.
Topics: Animals; Dentin; Dogs; Elastic Modulus; Hardness; Mammals; Microscopy, Electron, Scanning; Structure-Activity Relationship; Tooth
PubMed: 35834939
DOI: 10.1016/j.jbiomech.2022.111218 -
Brazilian Dental Journal 2021The aim of this study was to evaluate the effect of 2% chlorhexidine digluconate (CHX) on microtensile bond strength (µTBS) between an adhesive system and under 3...
The aim of this study was to evaluate the effect of 2% chlorhexidine digluconate (CHX) on microtensile bond strength (µTBS) between an adhesive system and under 3 dentin conditions. For that, this study evaluated the adhesive interface at initial, after 6 months and 1 year of storage. Forty-eight human third molars were prepared and randomly divided into 3 groups, according to dentin substrates: sound dentin (Sd), caries-infected dentin (Ci) and caries-affected dentin (Ca). The groups were subdivided into two according to the dentin pre-treatment: application of 2% CHX or without pre-treatment (control). The dentin surfaces were etched with 35% phosphoric acid gel and bonded with Adper Single Bond 2 (3M ESPE) adhesive system according to manufacturer's instructions. Subsequently, the specimens were stored in deionized water at 37°C for 24h, 6 months and 1 year. Two additional teeth were used to analyze the bonding interfaces by SEM. Data was submitted to three-way ANOVA in a split plot design and Tukey's test (α = 0.05). The results showed that Ci decreased µTBS values when compared to Ca and Sd, regardless storages time or treatment. Stored samples for 6 months and 1 year decreased the µTBS for the control group, but no difference was found between storages time for the CHX group. As a conclusion, the 2% CHX application after etching showed improved dentin bond strength in the storage time, regardless of the substrates evaluated.
Topics: Composite Resins; Dental Bonding; Dentin; Dentin-Bonding Agents; Humans; Materials Testing; Resin Cements; Tensile Strength
PubMed: 34787246
DOI: 10.1590/0103-6440202104463 -
FASEB Journal : Official Publication of... Feb 2021The objectives of our study were to investigate the roles of mTORC1 in odontoblast proliferation and mineralization and to determine the mechanism by which mTORC1...
The objectives of our study were to investigate the roles of mTORC1 in odontoblast proliferation and mineralization and to determine the mechanism by which mTORC1 regulates odontoblast mineralization. In vitro, MDPC23 cells were treated with rapamycin (10 nmol/L) and transfected with a lentivirus for short hairpin (shRNA)-mediated silencing of the tuberous sclerosis complex (shTSC1) to inhibit and activate mTORC1, respectively. CCK8 assays, flow cytometry, Alizarin red S staining, ALP staining, qRT-PCR, and western blot analysis were performed. TSC1-conditional knockout (DMP1-Cre ; TSC1 , hereafter CKO) mice and littermate control (DMP1-Cre ; TSC1 , hereafter WT) mice were generated. H&E staining, immunofluorescence, and micro-CT analysis were performed. Transcriptome sequencing analysis was used to screen the mechanism of this process. mTORC1 inactivation decreased the cell proliferation. The qRT-PCR and western blot results showed that mineralization-related genes and proteins were downregulated in mTORC1-inactivated cells. Moreover, mTORC1 overactivation promoted cell proliferation and mineralization-related gene and protein expression. In vivo, the micro-CT results showed that DV/TV and dentin thickness were higher in CKO mice than in controls and H&E staining showed the same results. Mineralization-related proteins expression was upregulated. Transcriptome sequencing analysis revealed that p53 pathway-associated genes were differentially expressed in TSC1-deficient cells. By inhibiting p53 alone or both mTORC1 and p53 with rapamycin and a p53 inhibitor, we elucidated that p53 acts downstream of mTORC1 and that mTORC1 thereby promotes odontoblast mineralization. Taken together, our findings demonstrate that the role of mTORC1 in odontoblast proliferation and mineralization, and confirm that mTORC1 upregulates odontoblast mineralization via the p53 pathway.
Topics: Animals; Cell Line; Cell Proliferation; Dentin; Mechanistic Target of Rapamycin Complex 1; Mice; Odontoblasts; Tooth Calcification; Transcriptome; Tuberous Sclerosis Complex 1 Protein; Tumor Suppressor Protein p53
PubMed: 33508145
DOI: 10.1096/fj.202002016R -
Journal of Prosthodontic Research Oct 2016The aim of this article is to review available literature on the clinical procedure of immediate dentine sealing for indirect bonded restorations. (Meta-Analysis)
Meta-Analysis Review
PURPOSE
The aim of this article is to review available literature on the clinical procedure of immediate dentine sealing for indirect bonded restorations.
STUDY SELECTION
More than 40 articles reporting the technique, studies, outcomes, etc. were reviewed after PUBMED/MEDLINE search, most of them addressing the specific situation of dentin bonding for indirect restorations.
RESULTS
It is known that tooth preparation for indirect bonded restorations can result in significant dentin exposures. Immediate application and polymerization of the dentin bonding agent to the freshly cut dentin, prior to impression making is therefore recommended by some authors. Literature indicates that this procedure, immediate dentine sealing (IDS), appears to achieve improved bond strength, fewer gap formations, decreased bacterial leakage, and reduces post-cementation sensitivity. This rational approach to adhesion is also reported to have a positive influence on tooth structure preservation, patient comfort, and long term survival of indirect bonded restorations.
CONCLUSION
In the extensive literature regarding advantages of using IDS technique significant differences have been shown when compared to Delayed Dentine Sealing. Although more research is required in this field, presently there are NO scientific reasons not to recommend IDS in routine practice.
Topics: Dental Bonding; Dental Restoration, Permanent; Dentin; Dentin-Bonding Agents; Humans; PubMed; Resins, Synthetic; Tooth Preparation, Prosthodontic
PubMed: 27131858
DOI: 10.1016/j.jpor.2016.04.001 -
Journal of Oral Biosciences Mar 2020The Bone Morphogenetic Proteins (BMPs) direct tooth development and still express in the adult tooth. We hypothesized that inhibition of BMP function would therefore...
OBJECTIVES
The Bone Morphogenetic Proteins (BMPs) direct tooth development and still express in the adult tooth. We hypothesized that inhibition of BMP function would therefore disrupt dentinogenesis by differentiated odontoblasts.
METHODS
We generated mice overexpressing the BMP-inhibitory protein Noggin in differentiated odontoblasts and osteocytes under control of a Dmp1 promoter-driven cre transgene. We compared the dentin phenotype in these mice with that in WT littermates and in mice with a Smad4 odontoblast/osteocyte knockout mediated by the same cre and therefore lacking all BMP and Tgfβ signaling in the same tissues.
RESULTS
Three-month-old first molars from both Noggin-expressing and Smad4-deleted mice showed decreased dentin volume with enlarged pulp cavities, and both displayed less organized and mineralized dentinal tubules compared to WT. The Smad4-ablated phenotype was more severe. While dentin sialophosphoprotein (DSPP) and bone sialoprotein (BSP) were decreased in the dentin of both lines, dentin matrix protein 1 (DMP1) was sharply increased in Noggin-expressing teeth.
CONCLUSIONS
The phenotypes we observed in Noggin-overexpressing and Smad4-conditional knockout teeth resemble the phenotype of Dentinogenesis Imperfecta (DGI) type III. Our results show that BMPs regulate post-natal dentinogenesis and that BMP-inhibitory proteins like Noggin play a role in that regulation. The increased severity of the Smad4 phenotype indicates that Tgfβ ligands, in addition to BMPs, play a crucial role in post-developmental dentinogenesis.
Topics: Animals; Carrier Proteins; Dentin; Dentinogenesis; Extracellular Matrix Proteins; Mice; Phosphoproteins; Sialoglycoproteins
PubMed: 31862386
DOI: 10.1016/j.job.2019.11.001 -
Dental Materials : Official Publication... Nov 2021This study tested the effects of small leucine-rich proteoglycan (SLRP) proteins on phosphoric acid (PA)-treated dentin bonding overtime and the role of such SLRPs in...
OBJECTIVE
This study tested the effects of small leucine-rich proteoglycan (SLRP) proteins on phosphoric acid (PA)-treated dentin bonding overtime and the role of such SLRPs in the remineralization potential of demineralized dentin collagen.
METHODS
Coronal dentin sections of human molars were used. SLRPs were either decorin (DCN) or biglycan (BGN) in core or proteoglycan form (with glycosaminoglycans, GAGs). Groups were: No treatment (control), DCN core, DCN + GAGs, BGN core, BGN + GAGs. Samples were etched with PA for 15 s and prior to application of Adper Single Bond Plus and composite buildup an aliquot of the specific SLRPs was applied over dentin. Twenty-four hours or 6 months after the bonding procedure, samples were tested for microtensile bond strength (MTBS). Debonded beams were analyzed by scanning electron microscopy (SEM). For remineralization studies, dentin blocks were fully demineralized, infused with the SLRPs, placed in artificial saliva for 2 weeks, and evaluated by transmission electron microscopy (TEM).
RESULTS
MTBS test presented a mean of 51.4 ± 9.1 MPa in control with no statistically significant difference to DCN core (47.6 ± 8.3) and BGN core (48.3 ± 6.5). The full proteoglycan groups DCN + GAGs (27.4 ± 4.5) and BGN + GAGs (36.4 ± 13.6) showed decreased MTBS compared to control (p < 0.001). At 6 months, control or core-treated samples did not have a statistically significant difference in MTBS. However, SLRPs with GAGs showed statistically significant improvement of bonding (62.5 ± 6.0 for DCN and 52.8 ± 8.1 for BGN, p < 0.001) compared to their baseline values. SEM showed that GAGs seem to favor water retention but overtime help remineralization. TEM of demineralized dentin indicated a larger collagen fibril diameter pattern of samples treated with core proteins compared to control and a smaller diameter with DCN + GAGs in water with evidence of mineralization with DCN + GAGS, BGN core and BGN + GAGs.
SIGNIFICANCE
In conclusion, core proteins seem not to affect dentin adhesion significantly but the presence of GAGs can be detrimental to immediate bonding. However, after ageing of samples, full proteoglycans, particularly DCN, can significantly improve bonding overtime while promoting remineralization which can prove to be clinically beneficial.
Topics: Collagen; Dentin; Extracellular Matrix; Humans
PubMed: 34538503
DOI: 10.1016/j.dental.2021.09.003 -
Gerodontology Jun 2018This study aimed to identify the changes in the time-dependent deformation response of coronal dentin with ageing and its relationship with changes in chemical...
OBJECTIVE
This study aimed to identify the changes in the time-dependent deformation response of coronal dentin with ageing and its relationship with changes in chemical composition.
BACKGROUND
The structural behaviour of dentin with ageing is affected by changes in the density and diameter of its dentinal tubules (ie porosity), as well as changes in chemical composition throughout the tooth. However, little is known about the time-dependent deformation behaviour of aged dentin and the importance of its hierarchical structure and variations in chemical composition.
MATERIALS AND METHODS
The spherical indentation response of aged coronal dentin was analysed in the outer, middle and inner regions, and its time-dependent deformation response was modelled in terms of its microstructure and chemical composition using a model recently proposed for young dentin.
RESULTS
The viscous deformation behaviour of aged dentin followed a power-law response with a decrease in the stress exponent when compared to young dentin. These results can be explained by cross-linking of the collagen present in the tissue.
CONCLUSION
A decrease in the deformation ability of aged dentin was found. This behaviour could be a result of a dissolution process and reprecipitation of the minerals present in intertubular dentin into the dentinal tubules.
Topics: Age Factors; Aged; Aged, 80 and over; Aging; Collagen; Dental Stress Analysis; Dentin; Female; Humans; Male; Middle Aged; Spectrum Analysis, Raman; Tooth Crown
PubMed: 29368792
DOI: 10.1111/ger.12321 -
Operative Dentistry Mar 2023This study evaluated the etching pattern, surface microhardness, and bond strength for enamel and dentin submitted to treatment with phosphoric, glycolic, and ferulic...
This study evaluated the etching pattern, surface microhardness, and bond strength for enamel and dentin submitted to treatment with phosphoric, glycolic, and ferulic acids. Enamel and dentin blocks were treated with phosphoric, glycolic, and ferulic acid to evaluate the surface and adhesive interface by scanning electron microscopy (2000×). Surface microhardness (Knoop) was evaluated before and after etching, and microtensile bond strength was evaluated after application of a two-step adhesive system (Adper Single Bond 2, 3M ESPE) at 24 hours and 12 months storage time points. Analysis of variance (ANOVA) and Tukey's test showed a decrease in the microhardness values for both substrates after application of each acid (p<0.0001). The reduction percentage was significantly higher for enamel treated with phosphoric acid (59.9%) and glycolic acid (65.1%) than for ferulic acid (16.5%) (p<0.0001), and higher for dentin that received phosphoric acid (38.3%) versus glycolic acid (27.8%) and ferulic acid (21.9%) (p<0.0001). Phosphoric and glycolic acids led to homogeneous enamel demineralization, and promoted the opening of dentinal tubules, whereas ferulic acid led to enamel surface demineralization and partially removed the smear layer. The adhesive-enamel interface showed micromechanical embedding of the adhesive in the interprismatic spaces when phosphoric and glycolic acids were applied. Ferulic acid showed no tag formation. Microtensile bond strength at both time points, and for both substrates, was lower with ferulic acid (p=0.0003/E; p=0.0011/D; Kruskal Wallis and Dunn). The bond strength for enamel and dentin decreased when using phosphoric and glycolic acids at the 12-month time evaluation (p<0.05). Glycolic acid showed an etching pattern and microhardness similar to that of phosphoric acid. Ferulic acid was not effective in etching the enamel or dentin, and it did not provide satisfactory bond strength to dental substrates.
Topics: Humans; Dental Bonding; Glycols; Surface Properties; Phosphoric Acids; Dental Enamel; Dentin; Tooth Demineralization; Tensile Strength; Dentin-Bonding Agents; Resin Cements
PubMed: 36656318
DOI: 10.2341/21-143-L