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Biomedical Physics & Engineering Express Aug 2021This study aimed to demonstrate the feasibility of using optical coherence tomography (OCT) for locating the sectioning site of a specimen before characterizing the...
This study aimed to demonstrate the feasibility of using optical coherence tomography (OCT) for locating the sectioning site of a specimen before characterizing the ultrastructural features of dentin surfaces as well as the inner wall of the dentinal tubules (DT) using a field emission scanning electron microscope (FESEM). Eight sound human molar teeth were extracted, examined via cross-polarization optical coherence tomography (CP-OCT), embedded, and hemisectioned using a low-speed diamond sawing machine. Next, each sectioned surface was further trimmed, polished, and examined under a confocal laser scanning microscope (CLSM) to locate the target area on the superficial dentin. Subsequently, each section was gold-coated and examined using FESEM. Backscattered reflection from the dentin layer was less than that from the enamel under CP-OCT. Distinct reflections from certain enamel and dentin microstructures were observed before sectioning the specimens. Areas with enamel cracks and dentin defects were identified and avoided during sectioning. At the micron level, the CLSM images exhibited a homogenous distribution of the DT orifices. Low magnification FESEM images showed intertubular dentin as a loosely condensed globular layer with shallow grooves in between, whereas peritubular dentin exhibited more organized condensation of apatite crystals surrounding the DT orifices. High magnification of the DT revealed a cross-linking layer of mineralized collagen network extending in the peri-intratubular lumen, with scattered globules of matrix vesicles. CP-OCT enabled the realization of rapid initial scanning and image acquisition with high contrast at the micron scale before profound insights into dentin ultrastructures at the nano scale were provided by FESEM. The variations in structural densities of the dental tissues significantly affected the image contrast and helped identify underlying structures.
Topics: Dentin; Humans; Microscopy, Confocal; Molar; Tomography, Optical Coherence
PubMed: 34340215
DOI: 10.1088/2057-1976/ac19cf -
Journal of the Mechanical Behavior of... Mar 2020The effectiveness of novel polymeric nanoparticles (NPs) application in reducing dentin permeability and facilitating dentin remineralization after endodontic treatment...
The effectiveness of novel polymeric nanoparticles (NPs) application in reducing dentin permeability and facilitating dentin remineralization after endodontic treatment was evaluated. The effect of undoped NPs, zinc, calcium and doxycycline-doped NPs (Zn-NPs, Ca-NPs and D-NPs, respectively) was tested in radicular dentin. A control group without NPs was included. Radicular dentin was assessed for fluid filtration. Dentin remineralization was analyzed by scanning and transmission electron microscopy, energy-dispersive analysis, AFM, Young's modulus (Ei), Nano DMA, Raman, and X-Ray Diffraction analysis. Ca-NPs and Zn-NPs treated dentin exhibited the lowest microleakage with hermetically sealed dentinal tubules and a zinc-based salt generation onto dentin. Zn-NPs favored crystallinity and promoted the highest Ei and functional remineralization at the apical dentin, generating differences between the values of complex modulus among groups. Ca-NPs produced closure of tubules and porosities at the expense of a relative mineral amorphization, without creating zones of stress concentration. The highest sealing efficacy was obtained in Zn-NPs-treated samples, along with the highest values of Young's modulus and dentin mineralization. These high values of Ei were obtained by closing voids, cracks, pores and tubules, and by strengthening the root dentin. When using undoped NPs or Ca-NPs, deposition of minerals occurred, but radicular dentin was not mechanically reinforced. Therefore, application of Zn-NPs in endodontically treated teeth previous to the canal filling is encouraged.
Topics: Dentin; Microscopy, Electron, Scanning; Nanoparticles; Polymers; Tooth Root; Zinc
PubMed: 32090933
DOI: 10.1016/j.jmbbm.2019.103606 -
IEEE Transactions on Ultrasonics,... Mar 2021Demineralization is a process of loss of minerals in the dental hard tissue that affects seriously the health of the patients, as it diminishes the tooth resistance,...
Demineralization is a process of loss of minerals in the dental hard tissue that affects seriously the health of the patients, as it diminishes the tooth resistance, generating chewing problems by altering the occlusal structure, hypersensitivity, and pulpal problems. Demineralization can be produced by pathological processes as erosion or caries, or by surgical processes as etching. Due to the complexity of natural demineralization processes, it is mandatory to provide quantitative and standardized tests to allow their study in controlled laboratory conditions. Ultrasonic techniques are suitable for this purpose as they are nondestructive, quick, and provide localized mechanical information about the tissue, which is related with its degree of demineralization. In the present work, we evaluate the complete process of demineralization of the human dentin under controlled laboratory conditions using a pulse-echo ultrasonic technique. Up to 15 human dentin teeth have been demineralized with phosphoric acid at 10%. The time-of-flight measurements using the pulse-echo system allows to obtain the speed of sound in healthy (3415 m/s) and demineralized dentin tissue (1710 m/s), as well as to characterize the dynamical process of the acid penetration, which generates well-defined boundaries between two media (demineralized and mineralized dentin), showing very different mechanical properties. These boundaries advance in depth at an initial rate of [Formula: see text]/min, decelerating at -9.3 nm/min until the whole demineralization of the sample is achieved. In addition, the technique allows to measure the relevance of the demineralization produced by the acid residues inside the tooth once it has been removed from the acidic solution. Beyond the assessment of artificial demineralization lesions under laboratory conditions, as demonstrated in this article, the proposed technique opens new approaches to the assessment of demineralization caused by natural caries in vivo.
Topics: Dentin; Humans; Tooth Demineralization; Ultrasonics
PubMed: 32776879
DOI: 10.1109/TUFFC.2020.3015668 -
Journal of Dentistry Apr 2021The aim was to state the different applications and the effectiveness of polymeric zinc-doped nanoparticles to achieve dentin remineralization. (Review)
Review
OBJECTIVES
The aim was to state the different applications and the effectiveness of polymeric zinc-doped nanoparticles to achieve dentin remineralization.
DATA, SOURCES AND STUDY SELECTION
Literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken.
CONCLUSIONS
Polymeric nanospheres (NPs) were efficiently loaded with zinc. NPs sequestered calcium and phosphate in the presence of silicon, and remained effectively embedded at the hybrid layer. NPs incorporation did not alter bond strength and inhibited MMP-mediated dentin collagen degradation. Zn-loaded NPs remineralized the hybrid layer inducing a generalized low-carbonate substitute apatite precipitation, chemically crystalline with some amorphous components, and an increase in mechanical properties was also promoted. Viscoelastic analysis determined that dentin infiltrated with Zn-NPs released the stress by breaking the resin-dentin interface and creating specific mineral formations in response to the energy dissipation. Bacteria were scarcely encountered at the resin-dentin interface. The combined antibacterial and remineralizing effects, when Zn-NPs were applied, reduced biofilm formation. Zn-NPs application at both cervical and radicular dentin attained the lowest microleakage and also promoted durable sealing ability. The new zinc-based salt minerals generated covered the dentin surface totally occluding cracks, porosities and dentinal tubules.
CLINICAL SIGNIFICANCE
Zinc-doped NPs are proposed for effective dentin remineralization and tubular occlusion. This offers new strategies for regeneration of eroded cervical dentin, effective treatment of dentin hypersensitivity and in endodontically treated teeth previous to the canal filling. Zn-NPs also do reduce biofilm formation due to antibacterial properties.
Topics: Dentin; Dentistry; Nanoparticles; Polymers; Zinc
PubMed: 33636241
DOI: 10.1016/j.jdent.2021.103616 -
The Chinese Journal of Dental Research Dec 2023Dentine is a major component of teeth and is responsible for many of their functions, such as mastication and neural sensation/transduction. Over the past decades,... (Review)
Review
Dentine is a major component of teeth and is responsible for many of their functions, such as mastication and neural sensation/transduction. Over the past decades, numerous studies have focused on dentine development and regeneration using a variety of research models, including in vivo, ex vivo and in vitro models. In vivo animal models play a crucial role in the exploration of biochemical factors that are involved in dentine development, whereas ex vivo and in vitro models contribute mainly to the identification of biophysical factors in dentine regeneration, of which mechanical force is most critical. In the present review, research models involved in studies related to dentine development and regeneration were screened from publications released in recent years and summarised comprehensively, particularly in vivo animal models including prokaryotic microinjection, Cre/LoxP, CRISPR/Cas9, ZFN and TALEN, and scaffold-based in vitro and ex vivo models. The latter were further divided by the interactive forces. Summarising these research models will not only benefit the development of future dentine-related studies but also provide hints regarding the evolution of novel dentine regeneration strategies.
Topics: Animals; Dentin; Tooth; Regeneration
PubMed: 38126366
DOI: 10.3290/j.cjdr.b4784033 -
European Cells & Materials Nov 2021Since the discovery of bioactive molecules sequestered in dentine, researchers have been exploring ways to harness their activities for dental regeneration. One specific... (Review)
Review
Since the discovery of bioactive molecules sequestered in dentine, researchers have been exploring ways to harness their activities for dental regeneration. One specific area, discussed in this review, is that of dental-pulp capping. Dental-pulp caps are placed when the dental pulp is exposed due to decay or trauma in an attempt to enhance tertiary dentine deposition. Several materials are used for dental-pulp capping; however, natural biomimetic scaffolds may offer advantages over manufactured materials such as improved aesthetic, biocompatibility and success rate. The present review discusses and appraises the current evidence surrounding biomimetic dental-pulp capping, with a focus on bioactive molecules sequestered in dentine. Molecules covered most extensively in the literature include transforming growth factors (TGF-βs, specifically TGF-β1) and bone morphogenetic proteins (BMPs, specifically BMP-2 and BMP-7). Further studies would need to explore the synergistic use of multiple peptides together with the development of a tailored scaffold carrier. The roles of some of the molecules identified in dentine need to be explored before they can be considered as potential bioactive molecules in a biomimetic scaffold for dental-pulp capping. Future in vivo work needs to consider the inflammatory environment of the dental pulp in pulpal exposures and compare pulp-capping materials.
Topics: Bone Morphogenetic Proteins; Dental Pulp; Dental Pulp Capping; Dentin, Secondary; Humans
PubMed: 34842279
DOI: 10.22203/eCM.v042a26 -
Journal of the Mechanical Behavior of... Dec 2022Human dentin is a hierarchical material with multi-level micro-/nano-structures, consisting of tubule, perti-tubular dentin (PTD) and intertubular dentin (ITD) as the...
Human dentin is a hierarchical material with multi-level micro-/nano-structures, consisting of tubule, perti-tubular dentin (PTD) and intertubular dentin (ITD) as the major constituents at microscale; and the PTD and ITD are further composed of collagen and hydroxyapatite (HAp) crystals with different volume fractions at nanoscale. In most cases, the HAp is considered as elastic while the collagen as viscoelastic material. It is of great significance to study the hierarchical structure and viscoelasticity of human dentin to understand the mechanical properties of dentin for further development of restorative materials. Based on this, this paper focuses on multiscale modeling of the elastic properties and dynamic viscoelastic response of dentin and establishes a bottom-up micromechanics model from nano-to macro-scale. In order to study the nanostructural effect on the viscoelastic behavior of hierarchical structures, the homogenization theories of random platelets composites (HTRPC) and the locally-exact homogenization theory (LEHT) are introduced for the homogenization of heterogeneous materials of microstructures at different levels. The HTRPC, based on Eshelby Inclusion theory, is used to predict the effective modulus of PTD and ITD. The LEHT is a method for homogenizing multiphase dentin characterized by repeated unit cells (RUCs). The resulting predictions are in very good agreement with several experimental data from the literature. In addition, the results of nanostructrual effect on dentin show that the viscoelasticity of dentin is majorly contributed by collagen and the HAp greatly provide the strength and hardness of dentin. Furthermore, the ageing effect on dentin's viscoelasticity is considered from the proposed multiscale micromechanics model. It is demonstrated that the ageing effect is much more influential in affecting the loss moduli of dentin than the storage.
Topics: Humans; Dentin; Hardness; Collagen
PubMed: 36302275
DOI: 10.1016/j.jmbbm.2022.105525 -
Journal of Dental Research Dec 2023Biomimetic strategies like peptide-guided collagen mineralization promise to enhance the effectiveness of dentin remineralization. We recently reported that rationally...
Biomimetic strategies like peptide-guided collagen mineralization promise to enhance the effectiveness of dentin remineralization. We recently reported that rationally designed amelogenin-derived peptides P26 and P32 promoted apatite nucleation, mineralized collagen, and showed potential in enamel regrowth and dentin remineralization. To facilitate the clinical application of amelogenin-derived peptides and to uncover their effectiveness in repairing dentin, we have now implemented a chitosan (CS) hydrogel for peptide delivery and have investigated the effects of P26-CS and P32-CS hydrogels on dentin remineralization using 2 in situ experimental models that exhibited different levels of demineralization. The efficacy of the peptide-CS hydrogels in dentin repair was evaluated by characterizing the microstructure, mineral density, mineral phase, and nanomechanical properties of the remineralized samples. The new strategy of atomic force microscopy PeakForce quantitative nanomechanical mapping was used for direct visualization and nanomechanical analysis of repaired dentin lesions across the lesion depth. Results from the 2 models indicated the potential triple functions of peptide-CS hydrogels for dentin repair: building a highly organized protective mineralized layer on dentin, occluding dentinal tubules by peptide-guided in situ mineralization, and promoting biomimetic dentinal collagen remineralization. Importantly, peptides released from the CS hydrogel could diffuse into the dentinal matrix and penetrate the dentinal tubules, leading to both surface and subsurface remineralization and tubule occlusion. Given our previous findings on peptide-CS hydrogels' potential for remineralizing enamel, we see further promise for hydrogels to treat tooth defects involving multiple hard tissues, as in the case of noncarious cervical lesions.
Topics: Amelogenin; Chitosan; Collagen; Dentin; Hydrogels; Minerals; Peptides; Tooth Remineralization
PubMed: 37880947
DOI: 10.1177/00220345231198228 -
Journal of Dental Research Sep 2019The evolution of bonded restorations has undergone great progress over several decades. Nonetheless, life spans of bonded restorations are limited mainly because of the...
The evolution of bonded restorations has undergone great progress over several decades. Nonetheless, life spans of bonded restorations are limited mainly because of the eventual incidence of recurrent caries. Over time, water and waterborne agents (acids, enzymes) degrade the components of the dentin/restoration interface, allowing bacterial colonization and dentin reinfection at the margins of the restoration. We developed a 2-tier protective technology consisting of priming/coating dentin with amphipathic and antimicrobial peptides (AAMPs) to obtain hydrophobic/water-repellent and antibiofilm dentin-resisting recurrent caries around bonded restorations. We tested a series of AAMPs to assess their structure-function relationships as well as the effects of different dentin-conditioning methods on the structural features of AAMP-coated dentin. We found relation between the secondary structure of AAMPs (high portion of β-sheet), the antimicrobial potency of AAMPs, and the AAMPs' ability to form hydrophobic coatings on dentin. We also determined that AAMPs had preferential adsorption on the mineral phase of dentin, which suggested that peptides arrange their cationic and hydrophilic motifs in direct contact with the negatively charged minerals in the hydrophilic dentin. These results led us to explore different dentin-conditioning methods that would increase the mineral/collagen ratio and their effect on AAMP immobilization. We innovatively imaged the spatial distribution of the AAMPs in relation to the dentinal tubules and collagen network using a minimally invasive multimodal imaging technique: multiphoton-second harmonic generation. Using multiphoton-second harmonic generation imaging, we determined that partial deproteinization of dentin increased the amount of immobilized AAMPs as compared with the total etched dentin at the dentin surface and extended deeply around dentinal tubules. Last, we analyzed the release rate of AAMPs from dentin coatings in artificial saliva to predict their stability in the clinical setting. In conclusion, priming dentin with AAMPs is a versatile new approach with potential to fortify the otherwise vulnerable adhesive-based interfaces.
Topics: Animals; Antimicrobial Cationic Peptides; Cattle; Dental Bonding; Dental Caries; Dental Restoration, Permanent; Dentin; Dentin-Bonding Agents; Mice; NIH 3T3 Cells
PubMed: 31313946
DOI: 10.1177/0022034519863772 -
Journal of Dentistry Mar 2023The present review discussed the biomechanical properties of cracks and fractures in crown and root dentine and attempted to explain why cracked teeth and vertical root... (Review)
Review
OBJECTIVES
The present review discussed the biomechanical properties of cracks and fractures in crown and root dentine and attempted to explain why cracked teeth and vertical root fractures are so frequent despite the existence of multiple crack toughening mechanisms in dentine. The implications of this knowledge were used to justify how these defects are managed clinically.
DATA, SOURCES AND STUDY SELECTION
Literature search was conducted on PubMed, Web of Science, and Scopus for a narrative review on fracture mechanics of crown and root dentine as well as the clinical management of cracked teeth and teeth with vertical root fracture.
CONCLUSIONS
Although dentine is tougher and less brittle than enamel, it's facture toughness is considerably lower than most ductile metals. Because the initiation toughness of dentine is very low, cracks initiate from incipient damage under low stress While crack toughening mechanisms exist that enable dentine to resist crack extension, these mechanisms are often inadequate for protecting dentine from crack propagation that ultimately leads to catastrophic failure. Additional factors such as ageing also reduces the resistance of dentine to crack growth. Because dentine cracks are eventually filled with bacteria biofilms upon exposure to oral fluids, they enable rapid bacteria ingress into the dental pulp via open dentinal tubules. To date, treatment options for cracked teeth are limited. While most teeth with vertical root fracture are recommended for extraction, new strategies have been reported that appeared to achieve short-term success in preserving these teeth.
CLINICAL SIGNIFICANCE
Current strategies for the management for dentine cracks and fractures are limited and their long-term effectiveness remain uncertain. Understanding the characteristics, toughening mechanism and weakening factors of tooth cracks is helpful in designing better treatment.
Topics: Humans; Tooth; Dental Enamel; Tooth Fractures; Cracked Tooth Syndrome; Dentin
PubMed: 36657703
DOI: 10.1016/j.jdent.2023.104424