Peptide-assisted pre-bonding remineralization of dentin to improve bonding

Tunable polymer-peptide hybrids for dentin tissue repair

OBJECTIVES

This study targets to assess the remineralization capability of conditioned dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs).

METHODS

Dentin conditioned surfaces were infiltrated with NPs and TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanohardness, Masson's trichrome staining microscopy, and Raman analysis.

RESULTS

Dentin surfaces treated with TDg-NPs and load cycled produced higher nanohardness than the rest of the groups at the hybrid layer. At the bottom of the hybrid layer, all samples treated with TDg-NPs showed higher nanohardness than the rest of the groups. Active remineralization underneath the hybrid layer was detected in all groups after TDg application and load cycling, inducting new dentinal tubuli formation. After thermocycling, remineralization at the hybrid layer was not evidenced in the absence of NPs. Raman analysis showed increase mineralization, enriched carbonate apatite formation, and improved crosslinking and scaffolding of the collagen.

CONCLUSIONS

Mechanical loading on the specimens obtained after TDg-NPs dentin infiltration inducts an increase of mineralization at the resin/dentin interface, indicating remineralization of peritubular and intertubular dentin with augmented crystallographic maturity in crystals. Enriched collagen quality was produced, generating an adequate matrix organization to promote apatite nucleation, after tideglusib infiltration.

CLINICAL SIGNIFICANCE

At the present research, it has been proved the creation of reparative dentin, at the resin-dentin interface, after tideglusib dentin infiltration. Chemical stability, to favor integrity of the resin-dentin interface, is warranted in the presence of the TDg-NPs in the demineralized dentin collagen.

Dentin remineralization using a stimuli-responsive engineered small molecule GSK3 antagonists-functionalized adhesive

OBJECTIVES

Tideglusib has shown great performance in terms of dentin regenerative properties. This study aims to evaluate bonding ability, of demineralized dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TG) (TG-NPs).

METHODS

Dentin conditioned surfaces were infiltrated with NPs and TG-NPs. Bonded interfaces were created and stored for 24 h and then submitted to mechanical, chemical and thermal challenging. The resin-dentin interface was evaluated through a doubled dye fluorescent technique and a calcium chelator fluorophore under a confocal laser scanning microscopy, and by field emission scanning electron microscopy.

RESULTS

Dentin surfaces treated with TG-NPs and load cycled produced higher bond strength than the rest of the groups. Immersion of dentin specimens treated with undoped-NPs in collagenase solution attained the lowest microtensile bond strength (MTBS) values. Both porosity and nanoleakage decreased when dentin was infiltrated with TG-NPs, that revealed strong signals of xylenol orange stain at both hybrid layer and dentinal tubules. The presence of NPs, in general, inducted the presence of mineralized interfaces after mechanical loading and thermocycling.

CONCLUSIONS

Nanoparticles doped with tideglusib promoted the highest dentin bonding efficacy among groups, as they facilitated the maximum bond strength values with creation of mineral deposits at the hybrid layer and dentinal walls. Tideglusib enabled scarce porosity, nanoleakage and advanced sealing among dentin groups.

SIGNIFICANCE

Doping hydrophilic polymeric NPs with tideglusib, infiltrated in etched dentin represents a reproducible technique to create reparative dentin at the resin-dentin interface, by inducing therapeutic bioactivity.

Rapid Intrafibrillar Mineralization Strategy Enhances Adhesive-Dentin Interface

Biomimetic mineralization of dentin collagen appears to be a promising strategy to optimize dentin bonding durability. However, traditional postbonding mineralization strategies based on Ca/P ion release still have some drawbacks, such as being time-consuming, having a spatiotemporal mismatch, and having limited intrafibrillar minerals. To tackle these problems, a prebonding rapid intrafibrillar mineralization strategy was developed in the present study. Specifically, polyacrylic acid-stabilized amorphous calcium fluoride (PAA-ACF) was found to induce rapid intrafibrillar mineralization of the single-layer collagen model and dentin collagen at just 1 min and 10 min, as identified by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. This strategy has also been identified to strengthen the mechanical properties of demineralized dentin within a clinically acceptable timeframe. Significantly, the bonding strength of the PAA-ACF-treated groups outperformed the control group irrespective of aging modes. In addition, the endogenous matrix metalloproteinases as well as exogenous bacterial erosion were inhibited, thus reducing the degradation of dentin collagen. High-quality integration of the hybrid layer and the underlying dentin was also demonstrated. On the basis of the present results, the concept of "prebonding rapid intrafibrillar mineralization" was proposed. This user-friendly scheme introduced PAA-ACF-based intrafibrillar mineralization into dentin bonding for the first time. As multifunctional primers, PAA-ACF precursors have the potential to shed new light on prolonging the service life of adhesive restorations, with promising significance.

Research progress of biomimetic materials in oral medicine

Biomimetic materials are able to mimic the structure and functional properties of native tissues especially natural oral tissues. They have attracted growing attention for their potential to achieve configurable and functional reconstruction in oral medicine. Though tremendous progress has been made regarding biomimetic materials, significant challenges still remain in terms of controversy on the mechanism of tooth tissue regeneration, lack of options for manufacturing such materials and insufficiency of in vivo experimental tests in related fields. In this review, the biomimetic materials used in oral medicine are summarized systematically, including tooth defect, tooth loss, periodontal diseases and maxillofacial bone defect. Various theoretical foundations of biomimetic materials research are reviewed, introducing the current and pertinent results. The benefits and limitations of these materials are summed up at the same time. Finally, challenges and potential of this field are discussed. This review provides the framework and support for further research in addition to giving a generally novel and fundamental basis for the utilization of biomimetic materials in the future.

Engineered Peptides Enable Biomimetic Route for Collagen Intrafibrillar Mineralization

Overcoming the short lifespan of current dental adhesives remains a significant clinical need. Adhesives rely on formation of the hybrid layer to adhere to dentin and penetrate within collagen fibrils. However, the ability of adhesives to achieve complete enclosure of demineralized collagen fibrils is recognized as currently unattainable. We developed a peptide-based approach enabling collagen intrafibrillar mineralization and tested our hypothesis on a type-I collagen-based platform. Peptide design incorporated collagen-binding and remineralization-mediating properties using the domain structure conservation approach. The structural changes from representative members of different peptide clusters were generated for each functional domain. Common signatures associated with secondary structure features and the related changes in the functional domain were investigated by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) and circular dichroism (CD) spectroscopy, respectively. Assembly and remineralization properties of the peptides on the collagen platforms were studied using atomic force microscopy (AFM). Mechanical properties of the collagen fibrils remineralized by the peptide assemblies was studied using PeakForce-Quantitative Nanomechanics (PF-QNM)-AFM. The engineered peptide was demonstrated to offer a promising route for collagen intrafibrillar remineralization. This approach offers a collagen platform to develop multifunctional strategies that combine different bioactive peptides, polymerizable peptide monomers, and adhesive formulations as steps towards improving the long-term prospects of composite resins.

Peptides in Dentistry: A Scoping Review

Currently, it remains unclear which specific peptides could be appropriate for applications in different fields of dentistry. The aim of this scoping review was to scan the contemporary scientific papers related to the types, uses and applications of peptides in dentistry at the moment. Literature database searches were performed in the following databases: PubMed/MEDLINE, Scopus, Web of Science, Embase, and Scielo. A total of 133 articles involving the use of peptides in dentistry-related applications were included. The studies involved experimental designs in animals, microorganisms, or cells; clinical trials were also identified within this review. Most of the applications of peptides included caries management, implant osseointegration, guided tissue regeneration, vital pulp therapy, antimicrobial activity, enamel remineralization, periodontal therapy, the surface modification of tooth implants, and the modification of other restorative materials such as dental adhesives and denture base resins. The in vitro and in vivo studies included in this review suggested that peptides may have beneficial effects for treating early carious lesions, promoting cell adhesion, enhancing the adhesion strength of dental implants, and in tissue engineering as healthy promotors of the periodontium and antimicrobial agents. The lack of clinical trials should be highlighted, leaving a wide space available for the investigation of peptides in dentistry.

Polyphenols Can Improve Resin-Dentin Bond Durability by Promoting Amorphous Calcium Phosphate Nanoparticles to Backfill the Dentin Matrix

Objective

To investigate the effects of proanthocyanidins (PA), myricetin, resveratrol, and kaempferol on the modification of dentin collagen and the inhibition of matrix metalloproteinase (MMP) activity, and to evaluate their contributions to the biomimetic remineralization and resin-dentin bonding performance.

Methods

Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and in situ zymography were applied to verify the collagen modification and MMP activity inhibition induced by these four polyphenols. Scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis, X-ray diffraction (XRD), ATR-FTIR, Vickers hardness numbers (VHN), and micro-computed tomography (micro-CT) were performed to characterize the remineralized dentin. Microtensile bond strength (μTBS) and nanoleakage were investigated to evaluate the effects of the four polyphenols on resin-dentin bonding durability.

Results

ATR-FTIR and in situ zymography confirmed that these four polyphenols could modify dentin collagen and inhibit MMP activity, respectively. Chemoanalytic characterization exhibited the efficacies of the four polyphenols in promoting dentin biomimetic remineralization. The surface hardness of PA-pretreated dentin was the greatest. Micro-CT results demonstrated that the PAs group possessed the highest amount of dentin surface minerals and the lowest amount of deep-layer minerals. The surface and deep-layer mineral contents of the Myr group were higher than Res and Kae groups. Treatment with these four polyphenols significantly increased the initial μTBS compared with the control group without primer conditioning. μTBS decreased significantly during aging, and the decrease was more severe in the PAs and Kae groups than in the Myr and Res groups. With or without aging, the polyphenol groups exhibited relatively less fluorescence. However, the Myr and Res groups showed less serious nanoleakage after aging.

Conclusion

PA, myricetin, resveratrol, and kaempferol can modify dentin collagen, inhibit MMP activity, promote biomimetic remineralization, and improve resin-dentin bond durability. Compared with PA and kaempferol, myricetin and resveratrol are more effective in improving resin-dentin bonding.

Biomineralization of Collagen-Based Materials for Hard Tissue Repair

Hydroxyapatite (HA) reinforced collagen fibrils serve as the basic building blocks of natural bone and dentin. Mineralization of collagen fibrils play an essential role in ensuring the structural and mechanical functionalities of hard tissues such as bone and dentin. Biomineralization of collagen can be divided into intrafibrillar and extrafibrillar mineralization in terms of HA distribution relative to collagen fibrils. Intrafibrillar mineralization is termed when HA minerals are incorporated within the gap zone of collagen fibrils, while extrafibrillar mineralization refers to the minerals that are formed on the surface of collagen fibrils. However, the mechanisms resulting in these two types of mineralization still remain debatable. In this review, the evolution of both classical and non-classical biomineralization theories is summarized. Different intrafibrillar mineralization mechanisms, including polymer induced liquid precursor (PILP), capillary action, electrostatic attraction, size exclusion, Gibbs-Donnan equilibrium, and interfacial energy guided theories, are discussed. Exemplary strategies to induce biomimetic intrafibrillar mineralization using non-collagenous proteins (NCPs), polymer analogs, small molecules, and fluidic shear stress are discussed, and recent applications of mineralized collagen fibers for bone regeneration and dentin repair are included. Finally, conclusions are drawn on these proposed mechanisms, and the future trend of collagen-based materials for bone regeneration and tooth repair is speculated.

Effect of aspartic acid on the crystallization kinetics of ACP and dentin remineralization

Type I collagen and non-collagen proteins are the main organic components of dentin. This study aimed to investigate the biomimetic remineralization of demineralized dentin by aspartic acid (Asp), which is abundant in non-collagenous proteins (NCPs). Asp was added to a mineralizing solution containing polyacrylic acid (PAA) to explore the mechanism of Asp regulating the pure amorphous calcium phosphate (ACP) phase transition process. The remineralization process and superstructure of the remineralized layer of demineralized dentin were evaluated and analyzed by transmission electron microscope (TEM) and scanning electron microscope (SEM), and the biological stability of the remineralized layer was investigated by collagenase degradation experiment. It demonstrated that Asp promoted the crystallization kinetics of PAA-stabilized amorphous calcium phosphate to hydroxyapatite (HAP), and shortened the remineralization time of demineralized dentin from 7 days to 2 days. The newly formed remineralized dentin had similar morphology and biological stability to the natural dentin layer. The presence of a large number of Asp residues in NCPs promoted the phase transformation of ACP, and further revealed the mechanism of action of NCPs in dentin biomineralization. This experiment also showed that Asp promoted the biomimetic remineralization of dentin; the morphology and hierarchical structure of remineralized layer was similar to that of natural teeth, and had good biological properties.