Biomineralization of dentin

Physicochemical and biological properties of dental materials and formulations with silica nanoparticles: A narrative review

OBJECTIVE

Silica nanoparticles (SNPs) have been extensively studied and used in different dental applications to promote improved physicochemical properties, high substance loading efficiency, in addition to sustained delivery of substances for therapeutic or preventive purposes. Therefore, this study aimed to review the SNPs applications in nanomaterials and nanoformulations in dentistry, discussing their effect on physicochemical properties, biocompatibility and ability to nanocarry bioactive substances.

DATA RESOURCES

Literature searches were conducted on PubMed, Web of Science, and Scopus databases to identify studies examining the physicochemical and biological properties of dental materials and formulations containing SNPs. Data extraction was performed by one reviewer and verified by another STUDY SELECTION: A total of 50 were reviewed. In vitro studies reveal that SNPs improved the general properties of dental materials and formulations, such as microhardness, fracture toughness, flexural strength, elastic modulus and surface roughness, in addition to acting as efficient nanocarriers of substances, such as antimicrobial, osteogenic and remineralizing substances, and showed biocompatibility CONCLUSIONS: SNPs are biocompatible, improve properties of dental materials and serve as effective carriers for bioactive substances CLINICAL SIGNIFICANCE: Overall, SNPs are a promising drug delivery system that can improve dental materials biological and physicochemical and aesthetic properties, increasing their longevity and clinical performance. However, more studies are needed to elucidate SNPs short- and long-term effects in the oral cavity, mainly on in vivo and clinical studies, to prove their effectiveness and safety.

Unraveling Nanomaterials in Biomimetic Mineralization of Dental Hard Tissue: Focusing on Advantages, Mechanisms, and Prospects

The demineralization of dental hard tissue imposes considerable health and economic burdens worldwide, but an optimal method that can repair both the chemical composition and complex structures has not been developed. The continuous development of nanotechnology has created new opportunities for the regeneration and repair of dental hard tissue. Increasingly studies have reported that nanomaterials (NMs) can induce and regulate the biomimetic mineralization of dental hard tissue, but few studies have examined how they are involved in the different stages, let alone the relevant mechanisms of action. Besides their nanoscale dimensions and excellent designability, NMs play a corresponding role in the function of the raw materials for mineralization, mineralized microenvironment, mineralization guidance, and the function of mineralized products. This review comprehensively summarizes the advantages of NMs and examines the specific mineralization mechanisms. Design strategies to promote regeneration and repair are summarized according to the application purpose of NMs in the oral cavity, and limitations and development directions in dental hard tissue remineralization are proposed. This review can provide a theoretical basis to understand the interaction between NMs and the remineralization of dental hard tissue, thereby optimizing design strategy, rational development, and clinical application of NMs in the field of remineralization.

The influence of neutral MDP-Na salt on dentin bond performance and remineralization potential of etch-&-rinse adhesive

OBJECTIVES

To investigate the effect of neutral 10-methacryloyloxydecyl dihydrogen phosphate salt (MDP-Na) on the dentin bond strength and remineralization potential of etch-&-rinse adhesive.

METHODS

Two experimental etch-&-rinse adhesives were formulated by incorporating 0 wt% (E0) or 20 wt% (E20) neutral MDP-Na into a basic primer. A commercial adhesive, Adper Single Bond 2 (SB, 3 M ESPE), served as the control. Sixty prepared teeth were randomly allocated into three groups (n = 20) and bonded using either one of the experimental adhesives or SB. Following 24 h of water storage, the bonded specimens were sectioned into resin-dentin sticks, with four resin-dentin sticks obtained from each tooth for microtensile bond strength (MTBS) test. Half of the sticks from each group were immediately subjected to tensile loading using a microtensile tester at a crosshead speed of 1 mm/min, while the other half underwent tensile loading after 6-month incubation in artificial saliva (AS). The degree of conversion (DC) of both the control and experimental adhesives (n = 6 in each group) and the adsorption properties of MDP-Na on the dentin organic matrix (n = 5 in each group) were determined using Fourier-transform infrared spectrometry. Furthermore, the effectiveness of neutral MDP-Na in promoting the mineralization of two-dimensional collagen fibrils and the adhesive-dentin interface was explored using transmission electron microscopy and selected-area electron diffraction. Two- and one-way ANOVA was employed to assess the impact of adhesive type and water storage on dentin bond strength and the DC (α = 0.05).

RESULTS

The addition of MDP-Na into the primer increased both the short- and long-term MTBS of the experimental adhesives (p = 0.00). No difference was noted in the DC between the control, E0 and E20 groups (p = 0.366). The MDP-Na remained absorbed on the demineralized dentin even after thorough rinsing. The intra- and extra-fibrillar mineralization of the two-dimensional collagen fibril and dentin bond hybrid layer was confirmed by transmission electron microscopy and selected-area electron diffraction when the primer was added with MDP-Na.

CONCLUSIONS

The use of neutral MDP-Na results in high-quality hybrid layer that increase the dentin bond strength of etch-&-rinse adhesive and provides the adhesive with remineralizing capability. This approach may represent a suitable bonding strategy for improving the dentin bond strength and durability of etch-&-rinse adhesive.

Advancing dentin remineralization: Exploring amorphous calcium phosphate and its stabilizers in biomimetic approaches

OBJECTIVE

This review elucidates the mechanisms underpinning intrafibrillar mineralization, examines various amorphous calcium phosphate (ACP) stabilizers employed in dentin's intrafibrillar mineralization, and addresses the challenges encountered in clinical applications of ACP-based bioactive materials.

METHODS

The literature search for this review was conducted using three electronic databases: PubMed, Web of Science, and Google Scholar, with specific keywords. Articles were selected based on inclusion and exclusion criteria, allowing for a detailed examination and summary of current research on dentin remineralization facilitated by ACP under the influence of various types of stabilizers.

RESULTS

This review underscores the latest advancements in the role of ACP in promoting dentin remineralization, particularly intrafibrillar mineralization, under the regulation of various stabilizers. These stabilizers predominantly comprise non-collagenous proteins, their analogs, and polymers. Despite the diversity of stabilizers, the mechanisms they employ to enhance intrafibrillar remineralization are found to be interrelated, indicating multiple driving forces behind this process. However, challenges remain in effectively designing clinically viable products using stabilized ACP and maximizing intrafibrillar mineralization with limited materials in practical applications.

SIGNIFICANCE

The role of ACP in remineralization has gained significant attention in dental research, with substantial progress made in the study of dentin biomimetic mineralization. Given ACP's instability without additives, the presence of ACP stabilizers is crucial for achieving in vitro intrafibrillar mineralization. However, there is a lack of comprehensive and exhaustive reviews on ACP bioactive materials under the regulation of stabilizers. A detailed summary of these stabilizers is also instrumental in better understanding the complex process of intrafibrillar mineralization. Compared to traditional remineralization methods, bioactive materials capable of regulating ACP stability and controlling release demonstrate immense potential in enhancing clinical treatment standards.

Evaluation of Physical Properties in Carboxymethyl Chitosan Modified Glass Ionomer Cements and the Effect for Dentin Remineralization: SEM/EDX, Compressive Strength, and Ca/P Ratio

OBJECTIVE

 The aim of this article was to evaluate the effects of modifying glass ionomer cement (GIC) with carboxymethyl chitosan (CMC) on surface morphology and remineralization outcomes by examining dentin morphology and calcium ion composition changes.

MATERIALS AND METHODS

 Thirty holes in a cylindrical acrylic mold were filled with three groups of restorative materials: GIC, GIC modified with CMC (GIC-CMC) 5%, and GIC-CMC10%. The surface morphology of each group's materials was observed using scanning electron microscopy (SEM). The compressive strength measurement was performed using a universal testing machine. The dentin remineralization process was performed by applying GIC, GIC-CMC5%, and GIC-CMC10% materials for 14 days on demineralized dentin cavities treated with 17% ethylenediamine tetraacetic acid (EDTA) for 7 days. A morphological evaluation was conducted using SEM. The calcium ion composition and calcium-to-phosphorous (Ca/P) ratio were examined using an energy-dispersive X-ray (EDX).

STATISTICAL ANALYSIS

 The Kruskal-Wallis and post-hoc Mann-Whitney U tests were performed to compare all four groups of calcium ions (p < 0.05).

RESULTS

 The modification of GIC with CMC affected the morphological changes in the materials in the form of reduced porosity and increased fractures. A significant difference was found in compressive strength between the GIC-CMC modification materials of GIC-CMC5% and GIC-CMC10% and the GIC control group. The dentin tubule morphology and surface changes were observed after applying GIC, GIC-CMC5%, and GIC-CMC10% materials for 14 days, as evaluated by SEM. The EDX examination showed an increase in calcium ion content and hydroxyapatite formation (Ca/P ratio) after applying the GIC-CMC10% material.

CONCLUSION

 The surface porosity of the GIC modification material with the addition of CMC tended to decrease. However, an increase in cracked surfaces that widened, along with the rise in CMC percentage, was found. This modification also reduced the compressive strength of the materials, with the lowest average yield at 10% CMC addition. Therefore, the modification of GIC with CMC affects changes in morphology, calcium ion composition, and Ca/P ratio in demineralized dentin.

A coating machine for coating filaments with bioactive nanomaterials for extrusion 3D printing

Extrusion printing based on biocompatible filaments offers a wide variety of targeted medical and dental applications in the area of personalized medicine, if combined with bioactive nanomaterials. However, this requires filament to be coated with bioactive nanomaterial. This study introduces a concept of a machine to coat filament with bioactive nanomaterials and its application. A machine was constructed with modules manufactured using additive manufacturing. A filament spool of polylactide (PLA) or glycol-modified polyethylene terephthalate (PETG) was transported through a copper tube, with the outer surface of the filament heated to the appropriate glass transition temperature to incorporate added nanomaterials such as nano-hydroxyapatite (nHA) or nano-fluorapatite(nFA). Coatings with nHA led to an increase in diameter of around 3 μm, while coatings with nFA increased the diameter by 4 μm. Printing of cubes with a standard extrusion printer platform using PLA or PETG filaments with added nHA or nFA has been successfully carried out. Scanning electron microscope (SEM) images of coated filaments and printed cubes showed an irregular distribution of nHA or nFA, which could be verified by energy dispersive X-ray analysis (EDX). Adding and adjusting bioactive nanomaterials to filament with a coating machine for filament proved to generate printable filaments. With the wide range of possible applications by different nanomaterials it is anticipated that extrusion printing can cover needs for personalized medicine and dentistry.

Promoting bond durability by a novel fabricated bioactive dentin adhesive

OBJECTIVE

To prepare a bioactive dentin adhesive and investigate its effect on promoting bonding durability of dentin.

METHODS

The mineralization of the bioactive glass with high phosphorus (10.8 mol% P2O5-54.2 mol% SiO2-35 mol% CaO, named PSC) and its ability to induce type I collagen mineralization were observed by SEM and TEM. The Control-Bond and the bioactive dentin adhesive containing 20 wt% PSC particles (PSC-Bond) were prepared, and their degree of conversion (DC), microtensile bond strength (μTBS), film thickness and mineralization performance were evaluated. To evaluate the bonding durability, dentin bonding samples were prepared by Control-Bond and PSC-Bond, and mineralizated in simulated body fluid for 24 h, 3 months, and 6 months. Then, the long-term bond strength and microleakage at the adhesive interface of dentin bonding samples were evaluated by microtensile testing and semiquantitative ELIASA respectively.

RESULTS

The PSC showed superior mineralization at 24 h and induced type I collagen mineralization to some extent under weakly alkaline conditions. For PSC-Bond, DC was 62.65 ± 1.20%, μTBS was 39.25 ± 4.24 MPa and film thickness was 17.00 ± 2.61 μm. PSC-Bond also formed hydroxyapatite and maintained good mineralization at the bonding interface. At 24 h, no significant differences in μTBS and interface microleakage were observed between the Control-Bond and PSC-Bond groups. After 6 months of aging, the μTBS was significantly higher and the interface microleakage was significantly lower of PSC-Bond group than those of Control-Bond group.

SIGNIFICANCE

PSC-Bond maintained bond strength stability and reduced interface microleakage to some extent, possibly reducing the occurrence of secondary caries, while maintaining long-term effectiveness of adhesive restorations.

Polyelectrolyte-Cation Complexes Using PAsp-Sr Complexes Induce Biomimetic Mineralization with Antibacterial Ability

Remineralized dentin with an antibacterial ability is still a significant challenge in dentistry. Previously, a polyelectrolyte-calcium complexes pre-precursor (PCCP) process is proposed for rapid collagen mineralization. In the present study, the expansion concept of the PCCP process is explored by replacing the calcium with other cations, such as strontium. The results of transmission electron microscopy (TEM), 3D stochastic optical reconstruction microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and high-resolution TEM with selected area electron diffraction demonstrate that biomimetic mineralization of collagen fibrils and demineralized dentin could be fulfilled with Sr&F-codoped hydroxyapatite (HAp) after they are treated with poly-aspartic acid-strontium (PAsp-Sr) suspension followed by a phosphate&fluoride solution. Moreover, dentin remineralized with Sr&F-codoped HAp exhibits in vitro and in vivo antibacterial ability against Streptococcus mutans. The cytotoxicity and oral mucosa irritation tests reveal excellent biocompatibility of mineralization mediums (PAsp-Sr suspension and phosphate&fluoride solution). The demineralized dentin's mechanical properties (elastic modulus and microhardness) could be restored almost to that of the intact dentin. Hence, the expansion concept of the PCCP process that replaces calcium ions with some cationic ions along with fluorine opens up new horizons for generating antibacterial remineralized dentin containing ions-doped HAp with excellent biocompatibility via biomimetic mineralization technology.

Novel biomimetic peptide-loaded chitosan nanoparticles improve dentin bonding via promoting dentin remineralization and inhibiting endogenous matrix metalloproteinases

OBJECTIVE

This study aims to synthesize novel chitosan nanoparticles loaded with an amelogenin-derived peptide QP5 (TMC-QP5/NPs), investigate their remineralization capability and inhibitory effects on endogenous matrix metalloproteinases (MMPs), and evaluate the dentin bonding properties of remineralized dentin regulated by TMC-QP5/NPs.

METHODS

TMC-QP5/NPs were prepared by ionic crosslinking method and characterized by dynamic light scattering method, scanning electron microscopy, transmission electron microscope, atomic force microscope, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The encapsulation and loading efficiency of TMC-QP5/NPs and the release of QP5 were examined. To evaluate the remineralization capability of TMC-QP5/NPs, the mechanical properties, and the changes in structure and composition of differently conditioned dentin were characterized. The MMPs inhibitory effects of TMC-QP5/NPs were explored by MMP Activity Assay and in-situ zymography. The dentin bonding performance was detected by interfacial microleakage and microshear bond strength (μSBS).

RESULTS

TMC-QP5/NPs were successfully synthesized, with uniform size, good stability and biosafety. The encapsulation and loading efficiency of TMC-QP5/NPs was respectively 69.63 ± 2.22% and 13.21 ± 0.73%, with a sustained release of QP5. TMC-QP5/NPs could induce mineral deposits on demineralized collagen fibers and partial occlusion of dentin tubules, and recover the surface microhardness of dentin, showing better remineralization effects than QP5. Besides, TMC-QP5/NPs significantly inhibited the endogenous MMPs activity. The remineralized dentin induced by TMC-QP5/NPs exhibited less interfacial microleakage and higher μSBS, greatly improved dentin bonding.

SIGNIFICANCE

This novel peptide-loaded chitosan nanoparticles improved resin-dentin bonding by promoting dentin remineralization and inactivating MMPs, suggesting a promising strategy for optimizing dentin adhesive restorations.

Reinforced dentin remineralization via a novel dual-affinity peptide

OBJECTIVES

In light of the constantly flowing saliva, anti-caries remineralization agents are inclined to be taken away. Owing to their limited residence time, the remineralization effect is not as desirable as expected. Hence, our study aimed to synthesize a novel peptide (DGP) with high affinity to both collagen fibrils and hydroxyapatite, and investigated its dentin remineralization efficacy in vitro and anti-caries capability in vivo.

METHODS

DGP was synthesized through Fmoc solid-phase reaction. The binding ability and interaction mechanism of DGP to demineralized dentin were investigated. Dentin specimens were demineralized, then treated with DGP and deionized water respectively. The specimens were incubated in artificial saliva and in-vitro remineralization effectiveness was analyzed after 14 days. The rat caries model was established to further scrutinize the in-vivo efficacy of caries prevention.

RESULTS

DGP possesses an enhanced adhesion force of 12.29 ± 1.12 nN to demineralized dentin. The favorable adsorption capacity is ascribed to the stable hydrogen bonds between S2P-101 and ASP-100 of DGP and GLY33 and PRO-16 of collagen fibers. Abundant mineral deposits and remarkable tubule occlusion were observed in the DGP group. DGP-treated dentin obtained notable microhardness recovery and higher mineral content after a 14-day remineralization regimen. DGP also demonstrated potent caries prevention in vivo, with substantially fewer carious lesions and significantly lower Keyes scoring.

SIGNIFICANCE

DGP proves to possess a high affinity to demineralized dentin regardless of saliva flowing, thus enhancing remineralization potency significantly in vitro and in vivo, potential for dental caries prevention and combatting initial dentin caries clinically.

Influence of surface pre-reacted glass-ionomer (S-PRG) filler eluate on collagen morphology, remineralization, and ultimate tensile strength of demineralized dentin

OBJECTIVE

To evaluate the effect of ions released from surface pre-reacted glass-ionomer (S-PRG) filler on collagen morphology, remineralization, and ultimate tensile strength (UTS) of demineralized dentin.

MATERIALS AND METHODS

Bovine incisor root dentins were demineralized with EDTA and divided into three treatment groups: 1) water (control); 2) S-PRG filler eluate; 3) 125 ppm sodium fluoride (NaF). After a 3-min treatment, the specimens were stored in simulated body fluid (SBF) for 3 months. Collagen morphology and remineralization were assessed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). Additionally, ultimate tensile strength (UTS) was measured.

RESULTS

TEM and SEM demonstrated that S-PRG induced more effective remineralization compared to NaF, while the control group exhibited faint mineral deposition with collagen degradation. S-PRG displayed the most homogenous mineral deposition in collagen fibrils, along with closure of interfibrillar spaces. Extensive mineral precipitation was observed within dentinal tubules in the S-PRG group. In addition, S-PRG filler eluate demonstrated significantly higher phosphate-to-amide ratio and UTS compared to NaF and control groups (p < 0.05).

CONCLUSIONS

Ion released from S-PRG filler positively influenced collagen morphology, remineralization, and ultimate tensile strength of demineralized dentin.

CLINICAL SIGNIFICANCE

S-PRG filler enhances remineralization and improve the biomechanics of demineralized dentin.

Analysis of color stability and degree of conversion of different types of resin composites

Resin composites containing surface pre-reacted glass (S-PRG) have been introduced to reduce demineralization and improve remineralization of the tooth structure. However, water diffusion within the material is necessary for its action, which can impair its overall physicomechanical properties over time, including color stability. This study aimed to evaluate the color stability and related degree of conversion (DC) of four resin composites. Discs (6 x 4 mm, n = 5/group) of microhybrid (MH), nanofilled (NF), nanohybrid (NH), and S-PRG-based nanohybrid (S-PRG-NH) composites with two opacities (A2/A2E and A2O/A2D) were prepared. Color (CIELab and CIEDE2000) was evaluated with a spectrophotometer after aging in grape juice (2 x 10 min/10mL/7days). The DC was analyzed by using Fourier transform infrared spectroscopy before and after light-curing. Data were statistically analyzed by using two-way analysis of variance and post-hoc least significant difference tests (p<0.05). In the color stability analysis, the interaction between filler type and opacity was significant (CIELab, p = 0.0015; CIEDE2000, p = 0.0026). NH presented the highest color stability, which did not differ from that of MH. The greatest color alteration was observed for S-PRG-NH. S-PRG fillers also influenced DC (p < 0.05). The nanohybrid resin composite presented favorable overall performance, which is likely related to its more stable organic content. Notwithstanding the benefits of using S-PRG-based nanohybrid resins, mostly in aesthetic procedures, professionals should consider the susceptibility of such resins to color alteration, probably due to the water-based bioactive mechanism of action.

Triple Function of Amelogenin Peptide-Chitosan Hydrogel for Dentin Repair

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.

Application of 20% silver nanoclusters in polymethacrylic acid on simulated dentin caries; its penetration depth and effect on surface hardness

The aims of this study were: To evaluate the surface hardness of simulated dentin caries lesions treated with either silver nanoclusters (AgNCls) synthesized in polymethacrylic acid (PMAA) or 38% silver diammine fluoride (SDF), as well as observe the penetration of the treatment solutions into the simulated caries lesions. Dentin blocks 4 mm thick obtained from caries-free third molars were sectioned and then simulated caries lesions on the occlusal dentin surfaces were created. Each specimen (n = 8) was divided into four sections: (A) treated with 20% AgNCls/PMAA; (B) treated with SDF 38% (FAgamin, Tedequim, Cordoba, Argentina); (C) sound tooth protected by nail-varnish during artificial caries generation (positive control); and (D) artificial caries lesion without surface treatment (negative control). AgNCls/PMAA or SDF were applied on the simulated lesions with a microbrush for 10 s, then excess removed. The surface hardness was measured by means of Vickers indentation test. To trace the depth of penetration, up to 400 μm, of silver ions, elemental composition of the samples was observed using EDX, coupled with SEM, and measured every 50 μm from the surface towards the pulp chamber. Laser Induced Breakdown Spectroscopy (LIBS) was also employed to trace silver ion penetration; the atomic silver line 328.06 nm was used with a 60 μm laser spot size to a depth of 240 μm. Student's-t test identified significant differences between treatment groups for each depth and the Bonferroni test was used for statistical analysis of all groups (p < 0.05). Mean surface hardness values obtained were 111.2 MPa, 72.3 MPa, 103.3 MPa and 50.5 MPa for groups A, B, C and D respectively. There was a significant difference between groups A and C compared with groups B and D, the group treated with AgNCls/PMAA achieved the highest surface hardness, similar or higher than the sound dentin control. A constant presence of silver was observed throughout the depth of the sample for group A, while group B showed a peak concentration of silver at the surface with a significant drop beyond 50 μm. The 20% AgNCls/PMAA solution applied to simulated dentin caries lesions achieved the recovery of surface hardness equivalent to sound dentin with the penetration of silver ions throughout the depth of the lesion.

Engineered Biomaterials Trigger Remineralization and Antimicrobial Effects for Dental Caries Restoration

Dental caries is the most prevalent chronic disease globally, significantly impacting individuals' quality of life. A key reason behind the failure of implanted restorations is their biological inactivity, meaning they are unable to form crosslinks with the surrounding tooth structures, thus making patients susceptible to implant loss and recurrent tooth decay. For the treatment of caries, antibacterial medicine and remineralization are effective means of treating the recurrence of caries. Owing to the rapid progression in the biomaterials field, several biomaterials have been reported to display antimicrobial properties and aid in dentin remineralization. Bioactive materials hold considerable potential in diminishing biofilm accumulation, inhibiting the process of demineralization, enabling dentin remineralization, and combating bacteria related to caries. Bioactive materials, such as fluoride, amorphous calcium phosphate, bioactive glass, collagen, and resin-based materials, have demonstrated their effectiveness in promoting dentin remineralization and exerting antibacterial effects on dental caries. However, the concentration of fluoride needs to be strictly controlled. Although amorphous calcium phosphate can provide the necessary calcium and phosphorus ions for remineralization, it falls short in delivering the mechanical strength required for oral mastication. Resin-based materials also offer different advantages due to the complexity of their design. In this review, we delve into the application of advanced bioactive materials for enhancing dentin remineralization and antibacterial properties. We eagerly anticipate future developments in bioactive materials for the treatment of dental caries.

Remineralizing Ability of Resin Modified Glass Ionomers (RMGICs): A Systematic Review

The selective caries removal approach leads to the need to use materials with the ability to remineralize remaining partially demineralized dentin. Among the materials proposed are resin-modified glass ionomer cements (RMGICs). The aim of this systematic review was to evaluate, based on in vitro experimental studies, whether RMGICs are suitable for remineralizing affected dentin. A systematic literature search was performed in four databases, followed by article selection, data extraction, and quality assessment. Studies assessing the remineralizing potential of RMGICs on dentin were included in our review. Studies which compared such properties between different RMGICs or with other materials were also eligible. The studies report the remineralizing ability of RMGICs, albeit with differences between different commercial products. RMGICs show a similar ability to conventional GICs to remineralize affected dentin, fulfilling the function for which they are designed. Moreover, the incorporation of additives, such as bioactive glass (BAG) or CCP-ACP, improves their remineralizing potential. The results of this review support the use of RMGICs as restorative materials after selective caries removal.

EDTA-functionalized silica nanoparticles as a conditioning agent for dentin bonding using etch-and-rinse technique

OBJECTIVE

This study investigated the possibility of using ethylenediaminetetraacetic acid functionalized silica nanoparticles (EDTA-SiO₂) as a dentin-conditioning agent using etch-and-rinse technique to promote the durability of dentin bonding.

METHODS

The SiO₂-EDTA were synthesized by N- [(3- trimethoxysilyl) propyl] ethylenediamine triacetic acid (EDTA-TMS) and SiO₂ (50 nm), then characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The capacity of SiO₂-EDTA to chelate calcium ions from dentin was examined by inductively coupled plasma-optic emission spectrometry (ICP-OES). The dentin surfaces conditioned with SiO₂-EDTA were detected by field emission scanning electron microscopy (SEM), TEM and microhardness testing. For dentin bonding, dentin surfaces were adopted wet- or dry-bonding technique and bonded with adhesive (Adper^TM Single Bond2) and applied composite resin (Filtek Z350) on them. The durability of dentin bonding was evaluated by mircotensile bond strength test, in-situ zymography and nanoleakage testing.

RESULTS

FTIR, TGA and XPS results showed that SiO₂-EDTA contained N element and carboxyl groups. SEM, TEM and microhardness results indicated that SiO₂-EDTA group created extrafibrillar demineralization and retained more intrafibrillar minerals within dentin surface. In the dentin bonding experiment, SiO₂-EDTA group achieved acceptable bond strength, and reduced the activity of matrix metalloproteinase and nanoleakage along bonding interface.

CONCLUSION

It was possible to generate a feasible dentin conditioning agent (SiO₂-EDTA), which could create dentin extrafibrillar demineralization and improve dentin bond durability.

CLINICAL SIGNIFICANCE

This study introduces a new dentin conditioning scheme based on SiO₂-EDTA to create extrafibrillar demineralization for dentin bonding. This strategy has the potential to be used in clinic to promote the life of restoration bonding.

Mineralization promotion and protection effect of carboxymethyl chitosan biomodification in biomimetic mineralization

Biomimetic mineralization emphasizes reversing the process of dental caries through bio-inspired strategies, in which mineralization promotion and collagen protection are equally important. In this study, carboxymethyl chitosan (CMC) was deemed as an analog of glycosaminoglycan for biomimetic modification of collagen, both of the mineralization facilitation and collagen protection effect were evaluated. Experiments were carried out simultaneously on two-dimensional monolayer reconstituted collagen model, three-dimensional reconstituted collagen model and demineralized dentin model. In three models, CMC was successfully cross-linked onto collagen utilizing biocompatible 1-Ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxy sulfosuccinimide sodium salt to achieve biomodification. Results showed that CMC biomodification increased collagen's hydrophilicity, calcium absorption capacity and thermal degradation resistance. In demineralized dentin model, the activity of endogenous matrix metalloproteinases was significantly inhibited by CMC biomodification. Furthermore, CMC biomodification significantly improved cross-linking and intrafibrillar mineralization of collagen, especially in the two-dimensional monolayer reconstituted collagen model. This study provided a biomimetic mineralization strategy with comprehensive consideration of collagen protection, and enriched the application of chitosan-based materials in dentistry.

Novel bioactive dental restorations to inhibit secondary caries in enamel and dentin under oral biofilms

OBJECTIVE

To provide the first review on cutting-edge research on the development of new bioactive restorations to inhibit secondary caries in enamel and dentin under biofilms. State-of-the-art bioactive and therapeutic materials design, structure-property relationships, performance and efficacies in oral biofilm models.

DATA, SOURCES AND STUDY SELECTION

Researches on development and assessment new secondary caries inhibition restorations via in vitro and in vivo biofilm-based secondary caries models were included. The search of articles was carried out in Web of Science, PubMed, Medline and Scopus.

CONCLUSIONS

Based on the found articles, novel bioactive materials are divided into different categories according to their remineralization and antibacterial biofunctions. In vitro and in vivo biofilm-based secondary caries models are effective way of evaluating the materials efficacies. However, new intelligent and pH-responsive materials were still urgent need. And the materials evaluation should be performed via more clinical relevant biofilm-based secondary caries models.

CLINICAL SIGNIFICANCE

Secondary caries is a primary reason for dental restoration failures. Biofilms produce acids, causing demineralization and secondary caries. To inhibit dental caries and improve the health and quality of life for millions of people, it is necessary to summarize the present state of technologies and new advances in dental biomaterials for preventing secondary caries and protecting tooth structures against oral biofilm attacks. In addition, suggestions for future studies are provided.

The development of a dental light curable PRFe-loaded hydrogel as a potential scaffold for pulp-dentine complex regeneration: An in vitro study

AIM

The study aimed to develop a bicomponent bioactive hydrogel formed in situ and enriched with an extract of platelet-rich fibrin (PRFe) and to assess its potential for use in pulp-dentine complex tissue engineering via cell homing.

METHODOLOGY

A bicomponent hydrogel based on photo-activated naturally derived polymers, methacrylated chitosan (ChitMA) and methacrylated collagen (ColMA), plus PRFe was fabricated. The optimized formulation of PRFe-loaded bicomponent hydrogel was determined by analysing the mechanical strength, swelling ratio and cell viability simultaneously. The physical, mechanical, rheological and morphological properties of the optimal hydrogel with and without PRFe were determined. Additionally, MTT, phalloidin/DAPI and live/dead assays were carried out to compare the viability, cytoskeletal morphology and migration ability of stem cells from the apical papilla (SCAP) within the developed hydrogels with and without PRFe, respectively. To further investigate the effect of PRFe on the differentiation of encapsulated SCAP, alizarin red S staining, RT-PCR analysis and immunohistochemical detection were performed. Statistical significance was established at p <  .05.

RESULTS

The optimized formulation of PRFe-loaded bicomponent hydrogel can be rapidly photocrosslinked using available dental light curing units. Compared to bicomponent hydrogels without PRFe, the PRFe-loaded hydrogel exhibited greater viscoelasticity and higher cytocompatibility to SCAP. Moreover, it promoted cell proliferation and migration in vitro. It also supported the odontogenic differentiation of SCAP as evidenced by its promotion of biomineralization and upregulating the gene expression for ALP, COL I, DSPP and DMP1 as well as facilitated angiogenesis by enhancing VEGFA gene expression.

CONCLUSIONS

The new PRFe-loaded ChitMA/ColMA hydrogel developed within this study fulfils the criteria of injectability, cytocompatibility, chemoattractivity and bioactivity to promote odontogenic differentiation, which are fundamental requirements for scaffolds used in pulp-dentine complex regeneration via cell-homing approaches.

Effects of Arginine-calcium carbonate pretreatment on the remineralizing and bonding performance of phosphorylated dentin

OBJECTIVES

To evaluate the effects of Arginine-calcium carbonate (Arg-CaCO₃) paste treatment of phosphorylated dentin on remineralizing and bonding performance during direct and indirect restorations under pulpal pressure.

METHODS

Under simulated pulpal pressure, dentin of healthy third molars were abraded and acid etched for 15s, then randomly divided into 4 groups: negative control group; Arg-CaCO₃ group (1min); 2.5% Sodium trimetaphosphate (STMP) group (3min); S-A group, 2.5% STMP + Arg-CaCO₃. After 24h, remineralization and dentin tubular occlusion were assessed by Attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR), Micro-Raman spectroscopy, Vickers hardness, Field-emission scanning electron microscope (FESEM) and Energy X-ray dispersive spectrometer (EDS). The liquid environment was the simulated body fluid (SBF) permeated from dentin tubules due to pulpal pressure. Stick specimens prepared with self-etch dentin adhesive were tested for microtensile bond strength (μTBS) and interfacial silver nanoleakage on both immediate direct restoration and indirect restoration with a 7-day temporary period. Data were analyzed by the Kruskal-Wallis test, Mann-Whitney test, Welch ANOVA or one-way ANOVA and Tukey post hoc test (p < 0.05).

RESULTS

The pretreatment of 2.5% STMP with Arg-CaCO₃ significantly increased relative mineral content by ATR-FTIR, Raman and FESEM-EDS, simultaneously enhancing dentin tubular occlusion (%) and mechanical property to the most considerable extent. Furthermore, the pretreatment significantly promoted the μTBS of indirect restoration and reduced nanoleakage after 7 days.

CONCLUSIONS

The application of Arg-CaCO₃ paste on phosphorylated dentin could improve intra- and extra-tubular mineralization and the stability of adhesion interface.

CLINICAL RELEVANCE

Without exceeding the amount of conventional tooth preparation, combining 2.5% STMP with Arg-CaCO₃ paste before the self-etch bonding system might be a promising clinical strategy to relieve dentin hypersensitivity and strengthen bonding performance efficiently and conveniently.

Remineralization Potential of Three Restorative Glass Ionomer Cements: An In Vitro Study

The aim of this in vitro study was to evaluate the remineralizing ability of three glass ionomers on demineralized dentin with different thicknesses and time periods. Fifty third molars were obtained and were sectioned into 1-, 2-, and 3-mm thick slices (n = 36 for each thickness). The specimens were demineralized with 18% EDTA for 2 h. From the glass ionomer cements (GICs) under study (Ketac Molar Aplicap, Equia Forte, or Riva Light Cure), 1 mm was placed over each slice, set, and preserved in PBS until observation after 1, 7, 14, and 28 days after placement. For each material, thickness, and time, three samples were prepared. Using Fourier Transform Infrared Spectrometry (FTIR), apatite formation was determined on the side opposite to that on which the material had been placed. By means of Energy Dispersive Spectroscopy (EDX), the changes in the Calcium/Phosphate (Ca/P) ratio were evaluated. These changes were compared between the different materials by means of a two-way ANOVA test, considering time and dentin thickness, for a significance level of p < 0.05. Results: FTIR showed a peak at 1420 cm^-1, evidencing the presence of carbonated hydroxyapatite in all the materials after 14 days, which indicates that a remineralization process occurred. Riva Light Cure showed the most homogeneous results at all depths at 28 days. The Ca/P ratio was maximum at 7 days in 2 mm of dentin for Riva Light Cure and Equia Forte HT (3.16 and 3.07; respectively) and for Ketac Molar at 14 days in 1 mm (3.67). All materials induced remineralization. Equia Forte achieved the greatest effect at 2 mm and Ketac Molar at 1 mm, whereas Riva Light Cure showed similar results at all depths. In terms of Ca/P ratio, Equia Forte and Riva Light Cure remineralized best at 2 mm, whereas for Ketac Molar, it was 1 mm. Carbonate apatite formation was higher at 24 h and 7 days for Ketac Molar, whereas it decreased at 14 days for Ketac Molar and peaked in Riva Light Cure and Equia Forte.

Biomineralization-inspired mineralized hydrogel promotes the repair and regeneration of dentin/bone hard tissue

Maxillofacial hard tissue defects caused by trauma or infection often affect craniofacial function. Taking the natural hard tissue structure as a template, constructing an engineered tissue repair module is an important scheme to realize the functional regeneration and repair of maxillofacial hard tissue. Here, inspired by the biomineralization process, we constructed a composite mineral matrix hydrogel PAA-CMC-TDM containing amorphous calcium phosphates (ACPs), polyacrylic acid (PAA), carboxymethyl chitosan (CMC) and dentin matrix (TDM). The dynamic network composed of Ca²⁺·COO^- coordination and ACPs made the hydrogel loaded with TDM, and exhibited self-repairing ability and injectability. The mechanical properties of PAA-CMC-TDM can be regulated, but the functional activity of TDM remains unaffected. Cytological studies and animal models of hard tissue defects show that the hydrogel can promote the odontogenesis or osteogenic differentiation of mesenchymal stem cells, adapt to irregular hard tissue defects, and promote in situ regeneration of defective tooth and bone tissues. In summary, this paper shows that the injectable TDM hydrogel based on biomimetic mineralization theory can induce hard tissue formation and promote dentin/bone regeneration.

Important roles of odontoblast membrane phospholipids in early dentin mineralization

The objective of this study was to first identify the timing and location of early mineralization of mouse first molar, and subsequently, to characterize the nucleation site for mineral formation in dentin from a materials science viewpoint and evaluate the effect of environmental cues (pH) affecting early dentin formation. Early dentin mineralization in mouse first molars began in the buccal central cusp on post-natal day 0 (P0), and was first hypothesized to involve collagen fibers. However, elemental mapping indicated the co-localization of phospholipids with collagen fibers in the early mineralization area. Co-localization of phosphatidylserine and annexin V, a functional protein that binds to plasma membrane phospholipids, indicated that phospholipids in the pre-dentin matrix were derived from the plasma membrane. A 3-dimensional in vitro biomimetic mineralization assay confirmed that phospholipids from the plasma membrane are critical factors initiating mineralization. Additionally, the direct measurement of the tooth germ pH, indicated it to be alkaline. The alkaline environment markedly enhanced the mineralization of cell membrane phospholipids. These results indicate that cell membrane phospholipids are nucleation sites for mineral formation, and could be important materials for bottom-up approaches aiming for rapid and more complex fabrication of dentin-like structures.

Evaluation of different remineralization agents in the treatment of natural caries-affected dentin in permanent teeth

BACKGROUND

In the preventive treatment protocol, providing remineralization of the tissue in demineralized dentin caries is an important step.

OBJECTIVE

In this in vitro study, the effectiveness of remineralization agents in natural caries-affected dentin (NCAD) were investigated.

METHODS

Forty caries slices were prepared from permanent molar dentin with International Caries Detection and Assessment System (ICDAS 2) (Code 3). The interventions with 8 days pH cycling were as follows: Deionized water (DW); 5% Sodium Fluoride (5% NaF) Varnish; Casein Phosphopeptide-Amorphous Calcium Fluoride Phosphate (CPP-ACFP); Calcium Glyserophosphate (CaGP) + Magnesium (Mg) + Xylitol. DIAGNOdent (Laser Fluorescence, LF), Surface Microhardness (SMH), and X-ray Fluorescence (XRF) Spectroscopy measurements were calculated before and after pH cycling.

RESULTS

LF values decreased between 5% NaF, CCP-ACFP and CaGP. NCAD treated with 5% NaF, CaGP and CCP-ACFP exhibited statistically higher hardness compared to the control group. After 5% NaF application, SMH values were significantly higher than the others. There was no statistically significant difference between baseline and after pH cycling hardness of the control group. After cycling, XRF showed that Ca and P concentrations were increased in all groups.

CONCLUSION

The application of agents used in the study could be recommended and promoted as a treatment option of caries dentin for conventional management of caries.

Proline-rich protein from S. mutans can perform a competitive mineralization function to enhance bacterial adhesion to teeth

A proline-rich region was found in Streptococcus mutans (S. mutans) surface antigen I/II (Ag I/II). The functions of this region were explored to determine its role in the cariogenic abilities of S. mutans; specifically, the proline-rich region was compared with human amelogenin. The full-length amelogenin genes were cloned from human (AmH) and surface antigen I/II genes from S. mutans. Then, the genes expressed and purified. We analyzed the structure and self-assembly ability of AmH and Ag I/II, compared their capacities to induce mineralization, and assessed the adhesion ability of S. mutans to AmH- and Ag I/II-coated tooth slices. AmH formed ordered chains and net frames in the early stage of protein self-assembly, while Ag I/II formed irregular and overlapping structures. AmH induced mineralization possessed a parallel rosary structure, while Ag I/II-induced mineralization is rougher and more irregular. The S. mutans adhesion assay indicated that the adhesion ability S. mutans on the Ag I/II-induced crystal layer was significantly higher than that on the AmH-induced crystal layer. S. mutans' Ag I/II may have evolved to resemble human amelogenin and form a rougher crystal layer on teeth, which play a competitive mineralization role and promotes better bacterial adhesion and colonization. Thus, the cariogenic ability of S. mutans Ag I/II is increased.

Efficacy of Rice Husk Nanosilica as A Caries Treatment (Dentin Hydroxyapatite and Antimicrobial Analysis)

OBJECTIVE

 Rice husk nanosilica has a porous, amorphous structure with a silica (SiO2) surface. Silica interacts with calcium ions to form hydroxyapatite and can induce the formation of reactive oxygen species (ROS), which harm microorganisms. This research determines the effect of rice husk nanosilica on the increase in dentin hydroxyapatite and its antimicrobial effects against Streptococcus mutans.

MATERIALS AND METHODS

 We divided 27 dental cavity samples into three groups (n = 9). Group 1: normal dentin, Group 2: demineralized dentin, Group 3: demineralized dentin treated with rice husk nanosilica. The samples were analyzed using X-ray diffraction (XRD) to evaluate the formation of dentin hydroxyapatite. To analyze the viability of S. mutans after exposure to 2% nanosilica rice husk, we conducted an antimicrobial MTT assay.

STATISTICAL ANALYSIS

 The Kruskal-Wallis test evaluates the formation of dentin hydroxyapatite, and the t-test evaluates the viability of S. mutans.

RESULTS

 There was an increase in the amount of dentin hydroxyapatite after the application of rice husk nanosilica compared with the control group (normal dentin), and 2% rice husk nanosilica had an antimicrobial effect (p < 0.005) in the group exposed to it.

CONCLUSION

 Rice husk nanosilica can induce the formation of dentin hydroxyapatite and has antimicrobial effects.

A potential role of p75NTR in the regulation of circadian rhythm and incremental growth lines during tooth development

Objective: Tooth morphogenesis and the formation of hard tissues have been reported to be closely related to circadian rhythms. This study investigates the spatiotemporal expression and relationship of p75NTR with core clock genes, mineralization-related or odontogenesis-related genes, and aims to derive the potential role of p75NTR in regulating circadian rhythm and incrementality growth line formation during tooth development.

Materials and methods: The dynamic morphology of the rat dental germ was observed at seven stages (E14.5 d, E16.5 d, E18.5 d, P.N. 4 d, P.N. 7 d, P.N. 10 d, and P.N. 15 d). Next, the expressions of p75NTR and other target factors were traced. The ectomesenchymal stem cells (EMSCs) were isolated from the E18.5d rat dental germs and synchronized using 50% of fetal bovine serum. Then, they were cultured in light/light (L.L.), dark/dark (D.D.), and light/dark (L.D.) conditions for 48 h. The total RNA was collected every 4 h, and the circadian rhythm dynamics of target factors were observed. To reveal the mechanism further, p75NTR was down-regulated in p75NTR^ExIII−/− mice and up-regulated in immortalized mouse dental apical papilla progenitor cells. The change tendencies of other target factors were also detected.

Results: The clock genes Bmal1, Clock, Per1, and Per2 were all expressed in tooth germs before the formation of dental hard tissues and demonstrated a regular oscillating expression pattern in EMSCs from dental germs. Their expression was affected by the L.D. stimulus, and most of them were promoted by D.D. conditions. p75NTR presented a similar expression pattern and a positive or negative relationship with most clock genes, mineralization-related and odontogenesis-related factors, such as brain and muscle ARNT-like protein-1 (Bmal1), runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), MSH-like 1 (MSX1), dentin matrix acidic phosphoprotein 1 (Dmp1), and dentin sialophosphoprotein (Dspp). Moreover, the arrangement, morphology, and even boundary in pre-odontoblast/pre-ameloblast layers were disordered in the p75NTR^ExIII−/− mice.

Conclusion: Circadian rhythm was found to affect tooth development. p75NTR might play a crucial role in regulating clock genes in the mineralization and formation of the dental hard tissues. p75NTR is actively involved in the odontoblast-ameloblast junction and cell polarity establishment during tooth morphogenesis.

Promoting effect of a calcium-responsive self-assembly β-sheet peptide on collagen intrafibrillar mineralization

Recently, a de novo synthetic calcium-responsive self-assembly β-sheet peptide ID8 (Ile-Asp-Ile-Asp-Ile-Asp-Ile-Asp) has been developed to serve as the template inducing hydroxyapatite nucleation. The aim of this study was to evaluate the effect of ID8 on intrafibrillar mineralization of collagen making full use of its self-assembly ability. The mineralization experiments were carried out in vitro on both bare Type I collagen and fully demineralized dentin samples. The calcium-responsive self-assembly of ID8 was revealed by circular dichroism spectrum, 8-anilino-1-naphthalenesulfonic acid ammonium salt hydrate assay, attenuated total reflection Fourier transform infrared spectrum (ATR-FTIR) and transmission electron microscope (TEM). Polyacrylic acid (450 kDa) with a concentration of 100 μg ml⁻¹ was selected as the nucleation inhibitor based on the determination of turbidimetry and TEM with selected area electron diffraction (TEM-SAED). The results showed that collagen intrafibrillar mineralization was significantly promoted with the pretreatment of self-assembly ID8 detected by TEM-SAED, SEM, X-ray diffraction and ATR-FTIR. The pretreatment of collagen utilizing self-assembly ID8 not only enhanced intermolecular hydrogen bonding but also contributed to calcium retention inside collagen and significantly increased the hydrophilicity of collagen. These results indicated that peptides with self-assembly properties like ID8 are expected to be potential tools for biomimetic mineralization of collagen.

Advances in Scaffolds Used for Pulp-Dentine Complex Tissue Engineering - A Narrative Review

Pulp necrosis in immature teeth disrupts root development and predisposes roots to fracture as a consequence of their thin walls and open apices. Regenerative endodontics is a developing treatment modality whereby necrotic pulps are replaced with newly formed healthy tissue inside the root canal. Many clinical studies have demonstrated the potential of this strategy to stimulate root maturation and apical root-end closure. However, clinical outcomes are patient-dependent and unpredictable. The development of predictable clinical protocols is achieved through the interplay of the three classical elements of tissue engineering, namely, stem cells, signaling molecules, and scaffolds. Scaffolds provide structural support for cells to adhere and proliferate and also regulate cell differentiation and metabolism. Hence, designing and fabricating an appropriate scaffold is a crucial step in tissue engineering. In this review, four main classes of scaffolds used to engineer pulp-dentine complexes, including bioceramic-based scaffolds, synthetic polymer-based scaffolds, natural polymer-based scaffolds, and composite scaffolds, are covered. Additionally, recent advances in the design, fabrication, and application of such scaffolds are analysed along with their advantages and limitations. Finally, the importance of vascular network establishment in the success of pulp-dentine complex regeneration and strategies used to create scaffolds to address this challenge are discussed.

Development and characterization of ion-releasing fiber-reinforced flowable composite

OBJECTIVE

This study aimed to develop and characterize an ion-releasing experimental fiber-reinforced flowable composite (Bio-SFRC) and dentin treatment solution made of poly(acrylic acid) (PAA) with a high molecular weight. In addition we also evaluated the interface structure and mineralization potential between the Bio-SFRC and dentin.

METHODS

Some mechanical properties (flexural properties and fracture toughness) of Bio-SFRC in comparison with commercial inert (G-aenial Flo X) and ion-releasing materials (ACTIVA-BioActive Base/Liner and Fuji II LC) were assessed (n = 8/group). Calcium-release at different time-points was measured during the first six weeks by using a calcium-ion selective electrode. Surface analysis of composites after being stored in simulated body fluid (SBF) was investigated by using SEM/EDS. Dentin disks (n = 50) were prepared from extracted sound teeth and demineralization was simulated by acid etching. SEM/EDS was used to evaluate the microstructure of dentin on the top surface and at interface with composites after being stored in SBF.

RESULTS

Bio-SFRC showed higher fracture toughness (1.6 MPa m^1/2) (p < 0.05) compared to Flo X (1.2 MPa m^1/2), ACTIVA (1 MPa m^1/2) and Fuji II LC (0.8 MPa m^1/2). Accumulative calcium release after six weeks from Bio-SFRC (15 mg/l) was higher than other tested ion-releasing materials (≈ 6 mg/l). Mineralization was clearly seen at the interface between treated dentin and Bio-SFRC. None of the commercial tested materials showed signs of mineralization at the interface and dentinal tubules remained open.

SIGNIFICANCE

Developing such reinforced ion-releasing flowable composite and PAA solution might offer the potential for mineralization at the interface and inside the organic matrix of demineralized dentin.

Degradation and Stabilization of Resin-Dentine Interfaces in Polymeric Dental Adhesives: An Updated Review

Instability of the dentine-resin interface is owed to the partial/incomplete penetration of the resin adhesives in the collagen fibrils. However, interfacial hydrolysis of the resin-matrix hybrid layer complex activates the collagenolytic and esterase enzymes that cause the degradation of the hybrid layer. Adequate hybridization is often prevented due to the water trapped between the interfibrillar spaces of the collagen network. Cyclic fatigue rupture and denaturation of the exposed collagen fibrils have been observed on repeated application of masticatory forces. To prevent interfacial microstructure, various approaches have been explored. Techniques that stabilize the resin–dentine bond have utilized endogenous proteases inhibitors, cross linking agents’ incorporation in the exposed collagen fibrils, an adhesive system free of water, and methods to increase the monomer penetration into the adhesives interface. Therefore, it is important to discover and analyze the causes of interfacial degradation and discover methods to stabilize the hybrid layer to execute new technique and materials. To achieve a predictable and durable adhesive resin, restoration is a solution to the many clinical problems arising due to microleakage, loss of integrity of the restoration, secondary caries, and postoperative sensitivity. To enhance the longevity of the resin-dentine bond strength, several experimental strategies have been carried out to improve the resistance to enzymatic degradation by inhibiting intrinsic collagenolytic activity. In addition, biomimetic remineralization research has advanced considerably to contemporary approaches of both intrafibrillar and extrafibrillar remineralization of dental hard tissues. Thus, in the presence of biomimetic analog complete remineralization of collagen, fibers are identified.

Correlation between Two Evaluation Methods for the Effect of Two Desensitizing Materials: An In Vitro Study

AIM: This study was conducted to assess the efficiency of enamel matrix derivative (EMD) on dentin remineralization at two different application times. MATERIALS AND METHODS: Thirty-two human dentin specimens of 1 mm thickness were prepared and randomly divided into two groups according to the treatment material (M) used: fluoride varnish with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (M1) and Enamel matrix derivative (EMD) (M2). Following treatment, each group was subdivided into two subgroups (n = 8) based on the storage time in artificial saliva into: (S); subgroup (S1); storage for 15 days and subgroup (S2); storage for 30 days. Dentin permeability was measured for all specimens at baseline and after applying the treatment protocol. All specimens were photomicrographed using ESEM before and after the treatment protocol. RESULTS: The highest permeability reduction percent mean value was recorded for M1S2 specimens (90% ± 20), with a statistically significant difference with other subgroups, followed by subgroup M2S2 (56% ± 8) and subgroup M1S1 (51% ± 11), respectively. Meanwhile, the subgroup M2S1 had the lowest mean value (36% ± 9). In addition, the dentin permeability test was confirmed by the ESEM results. CONCLUSION: EMD could be used as a promising remineralizing agent for dentin remineralization.

Tannic acid induces dentin biomineralization by crosslinking and surface modification

It is currently known that crosslinking agents can effectively improve the mechanical properties of dentin by crosslinking type I collagen. However, few scholars have focused on the influence of crosslinking agents on the collagen-mineral interface after crosslinking. Analysis of the Fourier transform infrared spectroscopy (FTIR) results showed that hydrogen bonding occurs between the tannic acid (TA) molecule and the collagen. The crosslinking degree of TA to collagen reached a maximum 41.28 ± 1.52. This study used TA crosslinked collagen fibers to successfully induce dentin biomineralization, and the complete remineralization was achieved within 4 days. The crosslinking effect of TA can improve the mechanical properties and anti-enzyme properties of dentin. The elastic modulus (mean and standard deviation) and hardness values of the remineralized dentin pretreated with TA reached 19.1 ± 1.12 GPa and 0.68 ± 0.06 GPa, respectively, which were close to those of healthy dentin measurements, but significantly higher than those of dentin without crosslinking (8.91 ± 1.82 GPa and 0.16 ± 0.01 GPa). The interface energy between the surface of collagen fibers and minerals decreased from 10.59 mJ m^-2 to 4.19 mJ m^-2 with the influence of TA. The current work reveals the importance of tannic acid crosslinking for dentin remineralization while providing profound insights into the interfacial control of biomolecules in collagen mineralization.

Deep and compact dentinal tubule occlusion via biomimetic mineralization and mineral overgrowth

Dentinal tubule (DT) occlusion by desensitizing agents has been widely applied to inhibit the transmission of external stimuli that cause dentin hypersensitivity (DH). However, most desensitizing agents merely accomplish porous blocking or the formation of a superficial tubular occlusion layer, resulting in a lack of mechanical and acid resistance and long-term stability. Herein, combining biomimetic mineralization and mineral overgrowth of the dentinal matrix was shown to effectively occlude DTs, resulting in the formation of a compact and deep occluding mineral layer that is strongly bound to the organic matrix on tubule walls. This DT occlusion method could achieve both mechanical resistance and acid resistance, demonstrating the potential of an inexpensive, long-term, and efficient therapy for treating DH.

Bioactive remineralization of dentin surface with calcium phosphate-based agents: An in vitro analysis

Background:

With the increasing prevalence of erosive tooth wear affecting both adults and children; designing optimum protocols of management in a noninvasive manner is gaining precedence.

Aim:

Comparative evaluation of topically applied calcium phosphate-based agents casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and beta tricalcium phosphate (β-TCP) on the surface of eroded dentin.

Materials and Methods:

Dentin blocks from human third molars in four groups were subjected to the surface treatment: (G1) sound dentin (G2) demineralized dentin (G3) CPP-ACP (G4) β-TCP. All the samples except control (G1) were immersed in an acidic solution incubated at 37°C for 96 h. The samples in G3 and G4 were topically treated with CPP-ACP and β-TCP for 4 min twice daily for 14 days; followed by pH-cycling for 21 days. Surface hardness testing and surface morphology were observed using the scanning electron microscopy. Data were analyzed using the Statistical Package for the Social Sciences (SPSS) software with Kruskal-Wallis test and post hoc test.

Results:

Dentin treated with both CPP-ACP (37.25) and β-TCP (32.05) recorded significantly higher VHN than demineralized (G2-23.51) but lower compared to sound control (G1-57.06).

Conclusion:

The topical application of CPP-ACP and β-TCP agents shows definite potential in promoting the hardening of demineralized dentin surface.

Cross-Linking of Apatite-Gelatin Nanocomposites as the Basis for Dentine Replacement Materials

A novel approach for the production of a bioinspired dentine replacement material is introduced. An apatite-gelatin nanocomposite material was cross-linked with various cross-linkers. These nanocomposites have a high resemblance to mammalian dentine regarding its composition and properties. A precipitation reaction was used to produce apatite-gelatin nanocomposites as starting materials. Cross-linking of the gelatin has to be performed to produce dentine-like and thus tough and robust apatite-gelatin nanocomposites. Therefore, the efficacy of various protein cross-linkers was tested, and the resulting materials were characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, and EXAFS as well as CHNS analysis and tested for their mechanical performance using Vickers hardness measurements as well as for their dissolution stability in EDTA. Especially glutaraldehyde, proanthocyanidins, and transglutaminase gave promising results with hardness values of up to 63 HV0.2. To further improve the material properties, we combined the effective cross-linker transglutaminase with casein, which led to an improved interconnection between the single nanocomposite platelets. By doing so, a cross-linked composite was obtained, which shows even higher hardness values than does human dentine, at 76 HV_0.2. The combination of apatite-gelatin nanocomposites with an effective cross-linker resulted in a bioinspired material with composition and properties close to those of human dentine.

Manifestation and Mechanisms of Abnormal Mineralization in Teeth

Tooth biomineralization is a dynamic and complicated process influenced by local and systemic factors. Abnormal mineralization in teeth occurs when factors related to physiologic mineralization are altered during tooth formation and after tooth maturation, resulting in microscopic and macroscopic manifestations. The present Review provides timely information on the mechanisms and structural alterations of different forms of pathological tooth mineralization. A comprehensive study of these alterations benefits diagnosis and biomimetic treatment of abnormal mineralization in patients.

Forced Biomineralization: A Review

Biologically induced and controlled mineralization of metals promotes the development of protective structures to shield cells from thermal, chemical, and ultraviolet stresses. Metal biomineralization is widely considered to have been relevant for the survival of life in the environmental conditions of ancient terrestrial oceans. Similar behavior is seen among extremophilic biomineralizers today, which have evolved to inhabit a variety of industrial aqueous environments with elevated metal concentrations. As an example of extreme biomineralization, we introduce the category of "forced biomineralization", which we use to refer to the biologically mediated sequestration of dissolved metals and metalloids into minerals. We discuss forced mineralization as it is known to be carried out by a variety of organisms, including polyextremophiles in a range of psychrophilic, thermophilic, anaerobic, alkaliphilic, acidophilic, and halophilic conditions, as well as in environments with very high or toxic metal ion concentrations. While much additional work lies ahead to characterize the various pathways by which these biominerals form, forced biomineralization has been shown to provide insights for the progression of extreme biomimetics, allowing for promising new forays into creating the next generation of composites using organic-templating approaches under biologically extreme laboratory conditions relevant to a wide range of industrial conditions.

Experimental Dental Composites Containing a Novel Methacrylate-Functionalized Calcium Phosphate Component: Evaluation of Bioactivity and Physical Properties

The aim of this study was to synthesize and characterize a novel methacrylate-functionalized calcium phosphate (MCP) to be used as a bioactive compound for innovative dental composites. The characterization was accomplished by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The incorporation of MCP as a bioactive filler in esthetic dental composite formulations and the ability of MCP containing dental composites to promote the precipitation of hydroxyapatite (HAp) on the surfaces of those dental composites was explored. The translucency parameter, depth of cure, degree of conversion, ion release profile, and other physical properties of the composites were studied with respect to the amount of MCP added to the composites. Composite with 3 wt.% MCP showed the highest flexural strength and translucency compared to the control composite and composites with 6 wt.% and 20 wt.% MCP. The progress of the surface precipitation of hydroxyapatite on the MCP containing dental composites was studied by systematically increasing the MCP content in the composite and the time of specimen storage in Dulbecco's phosphate-buffered solution with calcium and magnesium. The results suggested that good bioactivity properties are exhibited by MCP containing composites. A direct correlation between the percentage of MCP in a composite formulation, the amount of time the specimen was stored in PBS, and the deposition of hydroxyapatite on the composite's surface was observed.

Use of phosphorylated PAMAM and carboxyled PAMAM to induce dentin biomimetic remineralization and dentinal tubule occlusion

It is crucial to emphasize the biomineralization therapeutic method to repair etched dentin in clinic. Non-collagenous proteins (NCPs) play critical role in the biomineralization of dentine. In this paper, we synthesized the phosphate-terminated polyamidoamine dendrimer (PAMAM-PO₃H₂) by one-step modification successfully and examined by Fourier-transform infrared spectroscopy (FTIR) and ¹H-nuclear Magnetic Resonance (¹H-NMR) to characterize the structure of PAMAM-PO₃H₂. PAMAM-PO₃H₂ and carboxylterminated dendrimers (PAMAM-COOH) were applied as the dual biomimetic analogs of NCPs. Through the characterization of FT-IR, field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), the surfaces of human dentin were covered with regenerated crystals and the dentinal tubules were occluded by PAMAM-PO₃H₂ and PAMAM-COOH. In summary, the combination of PAMAM-PO₃H₂ and PAMAM-COOH may be another feasible therapeutic method for the treatment of dentin caries and dentin hypersensitivity.

Simulation Insight into the Synergic Role of Citrate and Polyaspartic Peptide in Biomineralization

Hydroxyapatite (HAP) is one of the most important inorganic components in biological minerals such as bones and teeth. More than 90% of the total citrate is accumulated in human bones and other biomineralized tissues. In addition, mineralizing proteins are enriched in glutamate and aspartate residues, which are important for their mineral-regulating properties. However, how citrate ions (CITs) and/or acidic amino acids regulate the formation of HAP is still unclear. In this work, molecular dynamics simulations were performed to study how CIT regulates the adsorption behavior of polyaspartic acid (PASP) on the HAP surface in the calcium phosphate solution. The simulation results indicate that PASP can be used as an ion chelator to complex Ca²⁺ and can serve as templates for HAP mineralization by templating the distribution of Ca²⁺ on its surface, which are attributed to the -COO^- and α-helix structure. Most importantly, the orientation distributions of PASP in all systems are narrower with the help of CIT, thereby PASP can be adsorbed on the HAP surface stably with a "lying-down" orientation. This indicates that CIT can be used as a bridging agent to bond the acidic peptide to the HAP surface in biomineralization. Thus, the synergic role of CIT and the acidic peptide on the HAP surface were revealed in this work, which can provide new insights into the interfacial phenomena during the biomineralization.

A novel dentin bonding scheme based on extrafibrillar demineralization combined with covalent adhesion using a dry-bonding technique

Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations.

Pourbaix-Guided Mineralization and Site-Selective Photoluminescence Properties of Rare Earth Substituted B-Type Carbonated Hydroxyapatite Nanocrystals

Rare-earth labeling in biological apatite could provide critical information for the pathologic transition (osteoclastic) and physiologic regeneration (osteogenesis) of bone and teeth because of their characteristic site-sensitive fluorescence in different coordinative conditions of various tissues in many biological processes. However, the rare-earth labeling method for biological apatites, i.e., carbonated-hydroxyapatite, has been rarely found in the literature. In this paper, we report a Pourbaix-diagram guided mineralizing strategy to controllable carbonation and doping of rare-earth ions in the hydroxyapatite (HA) lattice. The carbonation process of hydroxyapatite was achieved by controllable mineralization in hydrothermal condition with K₂CO₃ as the carbonate source, which results into the pure B-type carbonated hydroxyapatite (CHA) with tunable carbonate substitution degree. All of the as-synthesized materials crystalized into P63/m (No. 176) space group with the lattice parameter of a decreases and c increases with the increasing of carbonate content in the reactants. Structural refinement results revealed that the substitution of planar CO₃²⁻ is superimposed on one of the faces of PO₄³⁻ tetrahedral sub-units with a rotation angle of 30° in reference to c-axis. All of the hydrothermally synthesized CHA nanocrystals show hexagonal rod-like morphology with the length of 70–110 nm and diameter of 21–35 nm, and the decreasing length/diameter ratio from 3.61 to 2.96 from low to high carbonated level of the samples. Five rare-earth cations, of Pr³⁺, Sm³⁺, Eu³⁺, Tb³⁺, and Ho³⁺, were used as possible probe ions that can be doped into either HA or CHA lattice. The site-preference of Tb³⁺ doping is the same in the crystallographic site of HA and CHA according to characteristic emission peaks of ⁵D₄–⁷F_j (j = 3–6) transitions in their photoluminescent spectroscopy. Our work provides a controllable carbonation method for rare-earth labeling hydroxyapatite nanomaterials with potential biologically active implant powders for bone repair and tissue regeneration.

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.

Rechargeable adhesive with calcium phosphate nanoparticles inhibited long-term dentin demineralization in a biofilm-challenged environment

OBJECTIVES

This study aims to investigate the long-term demineralization-inhibition capability of a rechargeable adhesive with nanoparticles of amorphous calcium phosphate (NACP) on dentin in a biofilm-challenged environment.

METHODS

The NACP adhesive was immersed in a pH 4 solution to exhaust calcium (Ca) and phosphate (P) ions and then recharged with Ca and P ions. Dentin samples were demineralized underStreptococcus mutans biofilms for 24 h and randomly divided into two groups: (1) dentin control, (2) dentin with recharged NACP adhesives. Each day, all the samples were immersed in brain heart infusion broth with 1% sucrose (BHIS) for 4 h, and then in artificial saliva (AS) for 20 h. This cycle was repeated for 10 days. The pH of BHIS, the Ca and P ions content of the BHIS and AS were measured daily. After 10 days, the lactic acid production and colony-forming units of the biofilms were tested. The changes of remineralization/demineralization were also analyzed.

RESULTS

Dentin in the control group showed further demineralization. The recharged NACP adhesive neutralized acids, increasing the pH to above 5, and released large amounts of Ca and P ions each day. The recharged NACP adhesive decreased the production of lactic acid (P < 0.05), inhibited dentin demineralization and sustained the dentin hardness in the biofilm-challenged environment, showing an excellent long-term demineralization-inhibition capability.

CONCLUSIONS

The NACP adhesive could continuously inhibit dentin demineralization in a biofilm-challenged environment by recharging with Ca and P ions.

SIGNIFICANCE

The rechargeable NACP adhesive could provide long-term dentin bond protection.

Effects of a biomimetic analog-based experimental bonding system on caries-affected and sound dentin

This study compared the ultrastructure, chemical composition, and proteases activity (PA) of sound (SD) and caries-affected dentin (CAD) in the dentin hybrid layer after using an experimental bonding system containing pyromellitic dianhydride glycerol methacrylate and biomimetic analogs. The bonding system used a three step and a total-etch procedure. Polyacrylic acid (5%) and sodium trimetaphosphate (5%) were added to the primer and monocalcium phosphate monohydrate (9%), beta-tricalcium phosphate (10.5%), and calcium hydroxide (0.5%) were added to the adhesive. Transmission electron microscopy (TEM) was used to evaluate the resultant structure, particularly the adhesive-dentin and the demineralized-SD interfaces. The chemical composition was evaluated through energy-dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). The PA was measured with the Coomassie Blue-G250 coloring test, and the PA data were analyzed by ANOVA. EDS identified the presence of isolated calcium phosphate nanoparticles in the demineralized region; however, the SAED analysis did not show any evidences of hydroxyapatite (HA) neoformation in SD and CAD. The biomimetic analog-based adhesive system inhibited the activities of dentin proteases immediately after treatment. Additionally, the proteolytic activity on the affected dentin resembled that of the SD. In conclusion, no HA formed in the demineralized SD and CAD although there were calcium and phosphate deposits. The experimental adhesive system inhibited dentin proteases. The present study uses a new approach to investigate the hybrid layer behavior in dentin. The experimental adhesive system was synthesized and used on sound and affected-caries dentin as the substrate to reproduce real clinical conditions.

Effect of poly (γ-glutamic acid)/tricalcium phosphate (γ-PGA/TCP) composite for dentin remineralization in vitro

The poly (γ-glutamic acid)/tricalcium phosphate (γ-PGA/TCP) composite was fabricated as a novel biomineralization material function in preventing caries. Demineralized bovine dentin specimens were prepared and randomly divided into 5 groups (i. α-TCP, ⅱ. γ-PGA, ⅲ. γ-PGA/TCP, ⅳ. CPP-ACP, and ⅴ. deionized water) and subjected to 14 days of pH cycling. Remineralization ability was evaluated by lesion depth, mineral loss and microhardness. The morphology of dentin depositions was observed with scanning electron microscope (SEM), the crystal structure was determined by X-ray diffraction (XRD), and the wettability was tested by contact angle measurements. ANOVA revealed specimens treated by γ-PGA/TCP presented the statistically least lesion depth (p<0.01) and mineral loss (p<0.001), and the highest hardness (p<0.001). SEM revealed prominent intra- and inter-tubular precipitates in both γ-PGA and γ-PGA/TCP groups. The XRD patterns of the deposition structures in all groups were similar to those of sound dentin, and the contact angle of water decreased after γ-PGA/TCP treatment.

A Novel 3D Osteoblast and Osteocyte Model Revealing Changes in Mineralization and Pro-osteoclastogenic Paracrine Signaling During Estrogen Deficiency

Recent in vitro studies have revealed that the mechanobiological responses of osteoblasts and osteocytes are fundamentally impaired during estrogen deficiency. However, these two-dimensional (2D) cell culture studies do not account for in vivo biophysical cues. Thus, the objectives of this study are to (1) develop a three-dimensional (3D) osteoblast and osteocyte model integrated into a bioreactor and (2) apply this model to investigate whether estrogen deficiency leads to changes in osteoblast to osteocyte transition, mechanosensation, mineralization, and paracrine signaling associated with bone resorption by osteoclasts. MC3T3-E1s were expanded in media supplemented with estrogen (17β-estradiol). These cells were encapsulated in gelatin-mtgase before culture in (1) continued estrogen (E) or (2) no further estrogen supplementation. Constructs were placed in gas permeable and water impermeable cell culture bags and maintained at 5% CO2 and 37°C. These bags were either mechanically stimulated in a custom hydrostatic pressure (HP) bioreactor or maintained under static conditions (control). We report that osteocyte differentiation, characterized by the presence of dendrites and staining for osteocyte marker dentin matrix acidic phosphoprotein 1 (DMP1), was significantly greater under estrogen withdrawal (EW) compared to under continuous estrogen treatment (day 21). Mineralization [bone sialoprotein (BSP), osteopontin (OPN), alkaline phosphatase (ALP), calcium] and gene expression associated with paracrine signaling for osteoclastogenesis [receptor activator of nuclear factor kappa-β ligand (RANKL)/osteoprotegerin OPG ratio] were significantly increased in estrogen deficient and mechanically stimulated cells. Interestingly, BSP and DMP-1 were also increased at day 1 and day 21, respectively, which play a role in regulation of biomineralization. Furthermore, the increase in pro-osteoclastogenic signaling may be explained by altered mechanoresponsiveness of osteoblasts or osteocytes during EW. These findings highlight the impact of estrogen deficiency on bone cell function and provide a novel in vitro model to investigate the mechanisms underpinning changes in bone cells after estrogen deficiency.