Dental remineralization via poly(amido amine) and restorative materials containing calcium phosphate nanoparticles

VMT/ACP/Dextran composite nanosheets against dental caries through promoting mineralization of dentin tubules, pH buffering, and antibacterial

Dental caries is a worldwide public healthcare concern, and is closely related to the acidic environment that caused by bacterial decomposition of food. In this study, a two-step ion exchange liquid-phase stripping method was applied to strip out vermiculite (VMT) nanosheets, then amorphous calcium phosphate (ACP) and dextran were inserted between the VMT nanosheets interlayer to obtain a composite two-dimension nanosheets (VMT/ACP/Dextran). VMT/ACP/Dextran composite nanosheets exhibited excellent biocompatibility and could provide exogenous Ca2+and PO43- from ACP, provide SiO44-, Mg2+, Fe2+ and obtain buffering pH and antibacterial properties from VMT, as well as improve suspension stability and targeting Streptococcus mutans through glucan. The in vitro study showed that the composite materials could promote the mineralization and sealing of dentin tubules by releasing active ions, buffer pH 4.5 (a value close to the pH in the dental plaque environment) to pH 6.6-7.1 (values close to the pH in human saliva) through ion exchange, and exert antibacterial effects by targeting Streptococcus mutans and exerting oxidase like and peroxidase like activities to produce reactive oxygen species (ROS). The in vivo animal study showed that daily cleaning teeth using VMT/ACP/Dextran composite nanosheets could effectively reduce the incidence rate and severity of dental caries in rats. Taking together, the developed VMT/ACP/Dextran composite nanosheets, which integrated the excellent properties of VMT, ACP and dextran, can effectively prevent dental caries through a combination of factors such as buffering acids, antibacterial properties, and promoting calcification, and may be used as an active ingredient for daily oral hygiene or filling materials to prevent and treat dental caries.

Self-assembled branched polypeptides as amelogenin mimics for enamel repair

The regeneration of demineralized enamel holds great significance in the treatment of dental caries. Amelogenin (Ame), an essential protein for mediating natural enamel growth, is no longer secreted after enamel has fully matured in childhood. Although biomimetic mineralization based on peptides or proteins has made significant progress, easily accessible, low-cost, biocompatible and highly effective Ame mimics are still lacking. Herein, we construct a series of amphiphilic branched polypeptides (CAMPs) by facile coupling of the Ame's C-terminal segment and poly(γ-benzyl-L-glutamate), which serves to simulate the Ame's hydrophobic N-terminal segment. Among them, CAMP15 is the best biomimetic mineralization template with great self-assembly performance to guide the oriented crystallization of hydroxyapatite and is capable of inhibiting the adhesion of Streptococcus mutans and Staphylococcus aureus on the enamel surfaces. This work highlights the potential application of amphiphilic branched polypeptide as Ame mimics in repairing defected enamel, providing a promising strategy for prevention and treatment of dental caries.

Nanoparticles for efficient drug delivery and drug resistance in glioma: New perspectives

Gliomas are the most common primary tumors of the central nervous system, with glioblastoma multiforme (GBM) having the highest incidence, and their therapeutic efficacy depends primarily on the extent of surgical resection and the efficacy of postoperative chemotherapy. The role of the intracranial blood-brain barrier and the occurrence of the drug-resistant gene O6-methylguanine-DNA methyltransferase have greatly limited the efficacy of chemotherapeutic agents in patients with GBM and made it difficult to achieve the expected clinical response. In recent years, the rapid development of nanotechnology has brought new hope for the treatment of tumors. Nanoparticles (NPs) have shown great potential in tumor therapy due to their unique properties such as light, heat, electromagnetic effects, and passive targeting. Furthermore, NPs can effectively load chemotherapeutic drugs, significantly reduce the side effects of chemotherapeutic drugs, and improve chemotherapeutic efficacy, showing great potential in the chemotherapy of glioma. In this article, we reviewed the mechanisms of glioma drug resistance, the physicochemical properties of NPs, and recent advances in NPs in glioma chemotherapy resistance. We aimed to provide new perspectives on the clinical treatment of glioma.

Filler Mixed Into Adhesives Does Not Necessarily Improve Their Mechanical Properties

OBJECTIVES

To investigate the influence of filler type/loading on the micro-tensile fracture strength (μTFS) of adhesive resins, as measured 'immediately' upon preparation and after 1-week water storage ('water-stored').

METHODS

The morphology and particle-size distribution of three filler particles, referred to as 'Glass-S' (Esschem Europe), 'BioUnion' (GC), and 'CPC_Mont', were correlatively characterized by SEM, TEM, and particle-size analysis. These filler particles were incorporated into an unfilled adhesive resin ('BZF-29unfilled', GC) in different concentrations to measure the 'immediate' μTFS. After 1-week water storage, the 'water-stored' μTFS of the experimental particle-filled adhesive resins with the most optimum filler loading, specific for each filler type, was measured. In addition, the immediate and water-stored μTFS of the adhesive resins of three experimental two-step universal adhesives based on the same resin matrix but varying for filler type/loading, coded as 'BZF-21' (containing silica and bioglass), 'BZF-29' (containing solely silica), and 'BZF-29_hv' (highly viscous with a higher silica loading than BZF-29), and of the adhesive resins of the gold-standard adhesives OptiBond FL ('Opti-FL', Kerr) and Clearfil SE Bond 2 ('C-SE2', Kuraray Noritake) was measured along with that of BZF-29unfilled (GC) serving as control/reference. Statistics involved one-way and two-way ANOVA followed by post-hoc multiple comparisons (α<0.05).

RESULTS

Glass-S, BioUnion, and CPC_Mont represent irregular fillers with an average particle size of 8.5-9.9 μm. Adding filler to BZF-29unfilled decreased μTFS regardless of filler type/loading. One-week water storage reduced μTFS of all adhesive resins except BZF-21, with the largest reduction in μTFS recorded for BZF-29unfilled. Among the three filler types, the μTFS of the 30 wt% Glass-S and 20 wt% BioUnion filled adhesive resin was not significantly different from the μTFS of BZF-29unfilled upon water storage.

CONCLUSIONS

Adding filler particles into adhesive resin did not enhance its micro-tensile fracture strength but appeared to render it less sensitive to water storage as compared to the unfilled adhesive resin investigated.

New generation of orthodontic devices and materials with bioactive capacities to improve enamel demineralization

OBJECTIVE

The article reviewed novel orthodontic devices and materials with bioactive capacities in recent years and elaborated on their properties, aiming to provide guidance and reference for future scientific research and clinical applications.

DATA, SOURCES AND STUDY SELECTION

Researches on remineralization, protein repellent, antimicrobial activity and multifunctional novel bioactive orthodontic devices and materials were included. The search of articles was carried out in Web of Science, PubMed, Medline and Scopus.

CONCLUSIONS

The new generation of orthodontic devices and materials with bioactive capacities has broad application prospects. However, most of the current studies are limited to in vitro studies and cannot explore the true effects of various bioactive devices and materials applied in oral environments. More research, especially in vivo researches, is needed to assist in clinical application.

CLINICAL SIGNIFICANCE

Enamel demineralization (ED) is a common complication in orthodontic treatments. Prolonged ED can lead to dental caries, impacting both the aesthetics and health of teeth. It is of great significance to develop antibacterial orthodontic devices and materials that can inhibit bacterial accumulation and prevent ED. However, materials with only preventive effect may fall short of addressing actual needs. Hence, the development of novel bioactive orthodontic materials with remineralizing abilities is imperative. The article reviewed the recent advancements in bioactive orthodontic devices and materials, offering guidance and serving as a reference for future scientific research and clinical applications.

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.

Remineralization effects of enamel binding peptide, WGNYAYK, on enamel subsurface demineralization in vitro. Enamel binding peptide, WGNYAYK effect remineralization of enamel

Objectives: We investigated remineralization effects of enamel binding peptide (EBP), WGNYAYK, on enamel subsurface demineralization in vitro.Methods: Bovine lower incisor crowns were used as subsurface enamel demineralization samples, and changes of EBP binding, remineraliztion rate, hardness and microstructure were investigated. Binding of EBP, remineralization rate, hardness and structural changes were investigated. Fluorescein isothiocyatate (FITC)-labeled EBPs (0.4 mM, 4.0 mM, and 7.0 mM) were applied to the samples for 30 min at 37 °C, with sample surfaces and cross-sections observed by confocal laser scanning microscope (CLSM). Mineralization analysis samples were divided into 4 experimental groups; distilled water (DW), EBP 0.4 mM, EBP 4.0 mM, and EBP 7.0 mM. Mineral density changes were measured by micro-CT with hardness measured by nano-indentation. Samples were also observed by scanning electron microscope (SEM) for surface and longitudinal microstructure.

Results

CLSM images indicated that increased fluorescence was observed in the surface layer and up to about 20 μm below the surface layer. The remineralization rate was significantly higher for EBP 7.0 mM compared to DW (p = 0.008). Enamel surface hardness was significantly higher in all EBP groups compared to DW (p < 0.05) and was highest in the 7.0 mM group. SEM images showed obscuring of the superficial columnar structure in the 7.0 mM EBP group, indicating subsurface crystalline structure recovery.

Conclusion

The results of this study suggest that EBP binds to demineralized enamel and promotes remineralization.

Do bioactive materials show greater retention rates in restoring permanent teeth than non-bioactive materials? A systematic review and network meta-analysis of randomized controlled trials

OBJECTIVES

To answer the following research question: does the clinical evaluation of restorations on permanent teeth with bioactive materials show greater retention rates than those with non-bioactive materials?

MATERIALS AND METHODS

A search strategy was used in the following databases: MEDLINE via PubMed, Scopus, Web of Science, LILACS, BBO, Embase, The Cochrane Library, and OpenGrey. Randomized controlled trials (RCTs), with a minimum of 2-year follow-up and evaluating at least one bioactive material in permanent teeth were included. Risk of bias was detected according to the Cochrane Collaboration tool for assessing the risk of bias (RoB 2.0), and network meta-analysis was performed using a random-effects Bayesian-mixed treatment comparison model.

RESULTS

Twenty-seven studies were included. The success of the restorations was assessed using modified USPHS system in 24 studies and the FDI criteria in 3 studies. Network meta-analysis revealed three networks based on restoration preparations. Resin composites were ranked with higher SUCRA values, indicating a greater likelihood of being the preferred treatment for class I, II, and III restorations. In class V, resin-modified glass ionomer cement was ranked with the highest value.

CONCLUSION

Bioactive restorative materials showed similar good clinical performance in terms of retention similarly to conventional resin composites.

CLINICAL SIGNIFICANCE

The findings must be interpreted with caution because many RCT on restorative materials aim to verify the equivalence of new materials over the gold standard material rather than their superiority. The present systematic review also suggests that new RCT with longer follow-up periods are necessary.

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.

Evaluating the effect of poly (amidoamine) treated bioactive glass nanoparticle incorporated in universal adhesive on bonding to artificially induced caries affected dentin

BACKGROUND

The purpose of this study was to evaluate remineralisation and its effect on microtensile bond-strength of artificially induced caries affected dentin (CAD) when treated with a commercial universal adhesive modified with poly(amidoamine) dendrimer (PAMAM) loaded mesoporous bioactive glass nanoparticles (A-PMBG).

MATERIAL AND METHODS

Mesoporous bioactive glass nanoparticles (MBG) were synthesised using sol-gel process, where PAMAM was loaded (P-MBG) and added to commercial adhesive at different weight percentages (0.2, 0.5, 1 and 2 wt%). First, rheological properties of commercial and modified adhesives were evaluated. The effect of remineralization/hardness and microtensile bond-strength (MTBs) of those samples that mimicked the rheological properties of commercial adhesives were evaluated using Vickers hardness tester and universal testing machine respectively. Scanning-Electron microscope was used to visualize failed samples of MTBs and remineralization samples. Both evaluations were carried out at 1-,3 and 6-month intervals, samples being stored in stimulated salivary fluid during each time interval.

RESULTS

Addition of nanoparticles altered the rheological properties. With increase in the weight percentage of nanoparticles in commercial adhesive, there was significant increase in degree of conversion, viscosity and sedimentation rate (p < 0.05). The 0.2 and 0.5 wgt% groups closely mimicked the properties of commercial adhesive and were evaluated for remineralization and MTBs. After 6 months, 0.2wgt% group showed increased MTBs (p < 0.05) and 0.5wgt% group increased remineralization/hardness (p < 0.05).

CONCLUSION

The complex of PAMAM-MBG-Universal adhesive can remineralize the demineralised CAD thereby improving its bond-strength when evaluated for up to 6-months.

Synergistic effect of ion-releasing fillers on the remineralization and mechanical properties of resin-dentin bonding interfaces

In modern restorative dentistry, adhesive resin materials are vital for achieving minimally invasive, esthetic, and tooth-preserving restorations. However, exposed collagen fibers are found in the hybrid layer of the resin-dentin bonding interface due to incomplete resin penetration. As a result, the hybrid layer is susceptible to attack by internal and external factors such as hydrolysis and enzymatic degradation, and the durability of dentin bonding remains limited. Therefore, efforts have been made to improve the stability of the resin-dentin interface and achieve long-term clinical success. New ion-releasing adhesive resin materials are synthesized by introducing remineralizing ions such as calcium and phosphorus, which continuously release mineral ions into the bonding interface in resin-bonded restorations to achieve dentin biomimetic remineralization and improve bond durability. As an adhesive resin material capable of biomimetic mineralization, maintaining excellent bond strength and restoring the mechanical properties of demineralized dentin is the key to its function. This paper reviews whether ion-releasing dental adhesive materials can maintain the mechanical properties of the resin-dentin bonding interface by supplementing the various active ingredients required for dentin remineralization from three aspects: phosphate, silicate, and bioactive glass.

Developing Bioactive Dental Resins for Restorative Dentistry

Despite its reputation as the most widely used restorative dental material currently, resin-based materials have acknowledged shortcomings. As most systematic survival studies of resin composites and dental adhesives indicate, secondary caries is the foremost reason for resin-based restoration failure and life span reduction. In subjects with high caries risk, the microbial community dominated by acidogenic and acid-tolerant bacteria triggers acid-induced deterioration of the bonding interface and/or bulk material and mineral loss around the restorations. In addition, resin-based materials undergo biodegradation in the oral cavity. As a result, the past decades have seen exponential growth in developing restorative dental materials for antimicrobial applications addressing secondary caries prevention and progression. Currently, the main challenge of bioactive resin development is the identification of efficient and safe anticaries agents that are detrimental free to final material properties and show satisfactory long-term performance and favorable clinical translation. This review centers on the continuous efforts to formulate novel bioactive resins employing 1 or multiple agents to enhance the antibiofilm efficacy or achieve multiple functionalities, such as remineralization and antimicrobial activity antidegradation. We present a comprehensive synthesis of the constraints and challenges encountered in the formulation process, the clinical performance-related prerequisites, the materials' intended applicability, and the current advancements in clinical implementation. Moreover, we identify crucial vulnerabilities that arise during the development of dental materials, including particle aggregation, alterations in color, susceptibility to hydrolysis, and loss of physicomechanical core properties of the targeted materials.

Investigating salivary concentration of calcium ion in hypothyroidism

Background and Aims

Hypothyroidism is the most common disease of the thyroid gland. Thyroid hormone plays a crucial role in regulating tissue growth and metabolism. Additionally, patients with thyroid dysfunction have a higher incidence of caries and periodontal problems. The presence of calcium and phosphate ions seems to be effective in remineralizing teeth and reducing caries. The aim of this study was to evaluate the salivary level of calcium in patients with hypothyroidism.

Results

The results of this study showed that saliva calcium concentration in patients with hypothyroidism is significantly lower than healthy subjects. Also, no significant association was found between salivary calcium levels and TSH and T4 hormones level of blood.

Conclusion

The increased prevalence of dental caries in patients with hypothyroidism may be related to a decrease in their calcium levels.

Nanomaterials Modulating the Fate of Dental-Derived Mesenchymal Stem Cells Involved in Oral Tissue Reconstruction: A Systematic Review

The critical challenges in repairing oral soft and hard tissue defects are infection control and the recovery of functions. Compared to conventional tissue regeneration methods, nano-bioactive materials have become the optimal materials with excellent physicochemical properties and biocompatibility. Dental-derived mesenchymal stem cells (DMSCs) are a particular type of mesenchymal stromal cells (MSCs) with great potential in tissue regeneration and differentiation. This paper presents a review of the application of various nano-bioactive materials for the induction of differentiation of DMSCs in oral and maxillofacial restorations in recent years, outlining the characteristics of DMSCs, detailing the biological regulatory effects of various nano-materials on stem cells and summarizing the material-induced differentiation of DMSCs into multiple types of tissue-induced regeneration strategies. Nanomaterials are different and complementary to each other. These studies are helpful for the development of new nanoscientific research technology and the clinical transformation of tissue reconstruction technology and provide a theoretical basis for the application of nanomaterial-modified dental implants. We extensively searched for papers related to tissue engineering bioactive constructs based on MSCs and nanomaterials in the databases of PubMed, Medline, and Google Scholar, using keywords such as "mesenchymal stem cells", "nanotechnology", "biomaterials", "dentistry" and "tissue regeneration". From 2013 to 2023, we selected approximately 150 articles that align with our philosophy.

Biomineralization-Inspired Anti-Caries Strategy Based on Multifunctional Nanogels as Mineral Feedstock Carriers

Background

Dentin caries remains a significant public concern, with no clinically viable material that effectively combines remineralization and antimicrobial properties. To address this issue, this study focused on the development of a bio-inspired multifunctional nanogel with both antibacterial and biomineralization properties.

Methods

First, p(NIPAm-co-DMC) (PNPDC) copolymers were synthesized from N-isopropylacrylamide (NIPAm) and 2-methacryloyloxyethyl-trimethyl ammonium chloride (DMC). Subsequently, PNPDC was combined with γ-polyglutamic acid (γ-PGA) through physical cross-linking to form nanogels. These nanogels served as templates for the mineralization of calcium phosphate (Cap), resulting in Cap-loaded PNPDC/PGA nanogels. The nanogels were characterized using various techniques, including TEM, particle tracking analysis, XRD, and FTIR. The release properties of ions were also assessed. In addition, the antibacterial properties of the Cap-loaded PNPDC/PGA nanogels were evaluated using the broth microdilution method and a biofilm formation assay. The remineralization effects were examined on both demineralized dentin and type I collagen in vitro.

Results

PNPDC/PGA nanogels were successfully synthesized and loaded with Cap. The diameter of the Cap-loaded PNPDC/PGA nanogels was measured as 196.5 nm at 25°C and 162.3 nm at 37°C. These Cap-loaded nanogels released Ca2+ and PO43- ions quickly, effectively blocking dental tubules with a depth of 10 μm and promoting the remineralization of demineralized dentin within 7 days. Additionally, they facilitated the heavy intrafibrillar mineralization of type I collagen within 3 days. Moreover, the Cap-loaded nanogels exhibited MIC50 and MIC90 values of 12.5 and 50 mg/mL against Streptococcus mutans, respectively, with an MBC value of 100 mg/mL. At a concentration of 50 mg/mL, the Cap-loaded nanogels also demonstrated potent inhibitory effects on biofilm formation by Streptococcus mutans while maintaining good biocompatibility.

Conclusion

Cap-loaded PNPDC/PGA nanogels are a multifunctional biomimetic system with antibacterial and dentin remineralization effects. This strategy of using antibacterial nanogels as mineral feedstock carriers offered fresh insight into the clinical management of caries.

An epigallocatechin gallate-amorphous calcium phosphate nanocomposite for caries prevention and demineralized enamel restoration

Biomineralization with amorphous calcium phosphate (ACP) is a highly effective strategy for caries prevention and defect restoration. The identification and interruption of cariogenic biofilm formation during remineralization remains a challenge in current practice. In this study, an epigallocatechin gallate (EGCG)-ACP functional nanocomposite was developed to prevent and restore demineralization by integrating the antibacterial property of EGCG and the remineralization effect of ACP. The synthesized EGCG-ACP showed good biocompatibility with L-929 ​cells and human gingival fibroblasts. Under neutral conditions, the sustained release of ACP from EGCG-ACP restored the microstructure and mechanical properties of demineralized enamel. Under acidic conditions, protonated EGCG released from EGCG-ACP exerted a strong antibacterial effect, and the ACP release rate doubled within 4 ​h, resulting in the prevention of demineralization in the presence of cariogenic bacteria. The pH-responsive features of EGCG-ACP to promote the protonation of EGCG and ACP release facilitated its performance in remineralization effect to overcome the difficulty of restoring demineralized enamel in a cariogenic acidic environment, which was evidenced by the in vivo experiment carried out in a rat oral cariogenic environment. The results of this study indicate the potential of EGCG-ACP for the prevention of enamel demineralization and provide a theoretical basis its application in populations with high caries risk.

Smart Dental Materials Intelligently Responding to Oral pH to Combat Caries: A Literature Review

Smart dental materials are designed to intelligently respond to physiological changes and local environmental stimuli to protect the teeth and promote oral health. Dental plaque, or biofilms, can substantially reduce the local pH, causing demineralization that can then progress to tooth caries. Progress has been made recently in developing smart dental materials that possess antibacterial and remineralizing capabilities in response to local oral pH in order to suppress caries, promote mineralization, and protect tooth structures. This article reviews cutting-edge research on smart dental materials, their novel microstructural and chemical designs, physical and biological properties, antibiofilm and remineralizing capabilities, and mechanisms of being smart to respond to pH. In addition, this article discusses exciting and new developments, methods to further improve the smart materials, and potential clinical applications.

Inorganic Compounds as Remineralizing Fillers in Dental Restorative Materials: Narrative Review

Secondary caries is one of the leading causes of resin-based dental restoration failure. It is initiated at the interface of an existing restoration and the restored tooth surface. It is mainly caused by an imbalance between two processes of mineral loss (demineralization) and mineral gain (remineralization). A plethora of evidence has explored incorporating several bioactive compounds into resin-based materials to prevent bacterial biofilm attachment and the onset of the disease. In this review, the most recent advances in the design of remineralizing compounds and their functionalization to different resin-based materials' formulations were overviewed. Inorganic compounds, such as nano-sized amorphous calcium phosphate (NACP), calcium fluoride (CaF₂), bioactive glass (BAG), hydroxyapatite (HA), fluorapatite (FA), and boron nitride (BN), displayed promising results concerning remineralization, and direct and indirect impact on biofilm growth. The effects of these compounds varied based on these compounds' structure, the incorporated amount or percentage, and the intended clinical application. The remineralizing effects were presented as direct effects, such as an increase in the mineral content of the dental tissue, or indirect effects, such as an increase in the pH around the material. In some of the reported investigations, inorganic remineralizing compounds were combined with other bioactive agents, such as quaternary ammonium compounds (QACs), to maximize the remineralization outcomes and the antibacterial action against the cariogenic biofilms. The reviewed literature was mainly based on laboratory studies, highlighting the need to shift more toward testing the performance of these remineralizing compounds in clinical settings.

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.

Biomimetic approaches and materials in restorative and regenerative dentistry: review article

Biomimetics is a branch of science that explores the technical beauty of nature. The concept of biomimetics has been brilliantly applied in famous applications such as the design of the Eiffel Tower that has been inspired from the trabecular structure of bone. In dentistry, the purpose of using biomimetic concepts and protocols is to conserve tooth structure and vitality, increase the longevity of restorative dental treatments, and eliminate future retreatment cycles. Biomimetic dental materials are inherently biocompatible with excellent physico-chemical properties. They have been successfully applied in different dental fields with the advantages of enhanced strength, sealing, regenerative and antibacterial abilities. Moreover, many biomimetic materials were proven to overcome significant limitations of earlier available generation counterpart. Therefore, this review aims to spot the light on some recent developments in the emerging field of biomimetics especially in restorative and regenerative dentistry. Different approaches of restoration, remineralisation and regeneration of teeth are also discussed in this review. In addition, various biomimetic dental restorative materials and tissue engineering materials are discussed.

Dendritic Polymers in Tissue Engineering: Contributions of PAMAM, PPI PEG and PEI to Injury Restoration and Bioactive Scaffold Evolution

The capability of radially polymerized bio-dendrimers and hyperbranched polymers for medical applications is well established. Perhaps the most important implementations are those that involve interactions with the regenerative mechanisms of cells. In general, they are non-toxic or exhibit very low toxicity. Thus, they allow unhindered and, in many cases, faster cell proliferation, a property that renders them ideal materials for tissue engineering scaffolds. Their resemblance to proteins permits the synthesis of derivatives that mimic collagen and elastin or are capable of biomimetic hydroxy apatite production. Due to their distinctive architecture (core, internal branches, terminal groups), dendritic polymers may play many roles. The internal cavities may host cell differentiation genes and antimicrobial protection drugs. Suitable terminal groups may modify the surface chemistry of cells and modulate the external membrane charge promoting cell adhesion and tissue assembly. They may also induce polymer cross-linking for healing implementation in the eyes, skin, and internal organ wounds. The review highlights all the different categories of hard and soft tissues that may be remediated with their contribution. The reader will also be exposed to the incorporation of methods for establishment of biomaterials, functionalization strategies, and the synthetic paths for organizing assemblies from biocompatible building blocks and natural metabolites.

Novel dental resin infiltrant containing smart monomer dodecylmethylaminoethyl methacrylate

Objectives

White spot lesions (WSLs) are prevalent and often lead to aesthetic problems and progressive caries. The objectives of this study were to: (1) develop a novel resin infiltrant containing smart monomer dodecylmethylaminoethyl methacrylate (DMAEM) to inhibit WSLs, and (2) investigate the effects of DMAEM incorporation on cytotoxicity, mechanical properties, biofilm-inhibition and protection of enamel hardness for the first time.

Methods

DMAEM was synthesized using 1-bromododecane, 2-methylamino ethanol and methylmethacrylate. DMAEM with mass fractions of 0%, 1.25%, 2.5% and 5% were incorporated into a resin infiltant containing BisGMA and TEGDMA. Cytotoxicity, mechanical properties and antibacterial effects were tested. After resin infiltration, bovine enamel was demineralized with saliva biofilm acids, and enamel hardness was measured.

Result

DMAEM infiltration did not increase the cytotoxicity or compromise the physical properties when DMAEM mass fraction was below 5% (p > 0.05). Biofilm metabolic activity was reduced by 90%, and biofilm lactic acid production was reduced by 92%, via DMAEM (p < 0.05). Mutans streptococci biofilm CFU was reduced by 3 logs (p < 0.05). When demineralized in acid and then under biofilms, the infiltrant + 5% DMAEM group produced an enamel hardness (mean ± sd; n = 6) of 2.90 ± 0.06 GPa, much higher than 0.85 ± 0.12 GPa of the infiltrant + 0% DMAEM group (p < 0.05).

Significance

A novel resin infiltrant with excellent mechanical properties, biocompability, strong antibacterial activity and anti-demineralization effect was developed using DMAEM for the first time. The DMAEM resin infiltrant is promising for inhibiting WSLs, arresting early caries, and protecting enamel hardness.

Comparative evaluation of incorporation calcium silicate and calcium phosphate nanoparticles on biomimetic dentin remineralization and bioactivity in an etch-and-rinse adhesive system

BACKGROUND

This study aimed to evaluate the remineralization potential and bioactivity of adhesives, containing amorphous calcium phosphate (ACP) and calcium silicate (CS) nanoparticles (NPs).

MATERIAL AND METHODS

In this study, dentin slices (n=60) were prepared and etched with phosphoric acid. Next, they were divided into two groups: pre- and post-immersion in a simulated body fluid (SBF) for three weeks. The two groups were also divided into five subgroups (n=6 per subgroup), including the control (0 wt.% NPs); adhesives containing 1 wt.% and 2.5 wt.% (CS) nanoparticles; and adhesives containing 1 wt.% and 2.5 wt.% ACP nanoparticles. The remineralization potential and bioactivity of the adhesives were evaluated. The shear bond strength of the samples (n=18) was also assessed using a universal testing machine.

RESULTS

The present results revealed that the adhesive containing ACP and CS nanoparticles showed bioactivity and remineralization potential without any reduction in the bond strength.

CONCLUSIONS

The outcomes revealed that Cs and ACP nanoparticles induced mineralization in the dentin and incorporation of these nanoparticles to dentin bonding agents could improve the bio-functionalization of dentin bond. Key words:Calcium phosphate, calcium silicate, fourier transform infrared spectroscopy, scanning electron microscopy, tooth remineralization.

Advanced Drug Delivery Platforms for the Treatment of Oral Pathogens

The oral cavity is a complex ecosystem accommodating various microorganisms (e.g., bacteria and fungi). Various factors, such as diet change and poor oral hygiene, can change the composition of oral microbiota, resulting in the dysbiosis of the oral micro-environment and the emergence of pathogenic microorganisms, and consequently, oral infectious diseases. Systemic administration is frequently used for drug delivery in the treatment of diseases and is associated with the problems, such as drug resistance and dysbiosis. To overcome these challenges, oral drug delivery systems (DDS) have received considerable attention. In this literature review, the related articles are identified, and their findings, in terms of current therapeutic challenges and the applications of DDSs, especially nanoscopic DDSs, for the treatment of oral infectious diseases are highlighted. DDSs are also discussed in terms of structures and therapeutic agents (e.g., antibiotics, antifungals, antiviral, and ions) that they deliver. In addition, strategies (e.g., theranostics, hydrogel, microparticle, strips/fibers, and pH-sensitive nanoparticles), which can improve the treatment outcome of these diseases, are highlighted.

Mussel-Inspired Hydrogels for Fluoride Delivery and Caries Prevention

Fluoride agents hold promise for the repair and prevention of caries lesions, but their interaction with enamel is often hampered and diminished because of the dynamic wet environment in the oral cavity, which affects the efficacy of fluoride delivery and limits treatment success. We herein developed a mussel-inspired wet adhesive fluoride system (denoted TS@NaF) fabricated by the self-assembly of tannic acid (TA), silk fibroin (SF), and sodium fluoride (NaF). TS@NaF demonstrated remarkable biological stability and biocompatibility, showed reliable wet adhesion, released fluoride ions (F−) topically, and induced significant deposition of calcium fluoride (CaF2) onto enamel in vitro. Furthermore, TS@NaF provided an anticaries effect in vitro and induced a detectable increase in enamel mineral density. Advanced fluoride-releasing bioadhesives are therefore promising candidates for caries prevention and highlight the great potential of mussel-inspired dental materials in clinical applications.

Nanomaterials in Dentistry: Current Applications and Future Scope

Nanotechnology utilizes the mechanics to control the size and morphology of the particles in the required nano range for accomplishing the intended purposes. There was a time when it was predominantly applied only to the fields of matter physics or chemical engineering, but with time, biological scientists recognized its vast benefits and explored the advantages in their respective fields. This extension of nanotechnology in the field of dentistry is termed ‘Nanodentistry.’ It is revolutionizing every aspect of dentistry. It consists of therapeutic and diagnostic tools and supportive aids to maintain oral hygiene with the help of nanomaterials. Research in nanodentistry is evolving holistically but slowly with the advanced finding of symbiotic use of novel polymers, natural polymers, metals, minerals, and drugs. These materials, in association with nanotechnology, further assist in exploring the usage of nano dental adducts in prosthodontic, regeneration, orthodontic, etc. Moreover, drug release cargo abilities of the nano dental adduct provide an extra edge to dentistry over their conventional counterparts. Nano dentistry has expanded to every single branch of dentistry. In the present review, we will present a holistic view of the recent advances in the field of nanodentistry. The later part of the review compiled the ethical and regulatory challenges in the commercialization of the nanodentistry. This review tracks the advancement in nano dentistry in different but important domains of dentistry.

Remineralization of human dentin type I collagen fibrils induced by carboxylated polyamidoamine dendrimer/amorphous calcium phosphate nanocomposite: an in vitro study

Intrafibrillar mineralization of type I collagen fibrils is of great significance in dental remineralization, which is the key of caries prevention and treatment. Herein, two substances that have the remineralization ability, carboxylated polyamidoamine dendrimer (PAMAM-COOH) and nano-sized amorphous calcium phosphate (n-ACP) were combined to synthesize a novel nanomaterial, carboxylated polyamidoamine dendrimer/amorphous calcium phosphate nanocomposite (PAMAM-COOH/ACP). This article aims to evaluate the remineralization effect of PAMAM-COOH/ACP of dentin type I collagen fibrils in vitro. Fluorescence labeling technique was innovatively used to observe and evaluate the remineralization effect. PAMAM-COOH/ACP showed superior remineralization ability of human dentin type I collagen fibrils, especially the intrafibrillar remineralization. Therefore, the novel nanomaterial PAMAM-COOH/ACP is promising to prevent and treat various diseases caused by dentin demineralization and to improve various dental materials.

Evaluation of the Antibacterial Activity and the Remineralizing Potentiality of Two Natural Extracts and Their Mixture (In Vitro Study)

AIM: This study aimed to assess the antibacterial activity against the cariogenic Streptococcus mutans (ATCC 25175) and the commensal Actinomyces viscous (1300 EMCCN) oral bacteria and to determine the remineralizing effect of the previously demineralized bovine enamel lesion of ginger extract, eggshell extract as well as their mixture. METHODS: The two different extracts; eggshell extract and ginger extract were prepared as well as their mixture in an equal volume. Their antibacterial activity against S. mutans and A. viscous was assessed by well diffusion test and clear zones diameters measurement (mm). Chlorhexidine and Dimethyl sulfoxide solution were utilized as positive and negative control, respectively. Thirty-six anterior bovine teeth were subjected to artificial caries pH cycling regimen including alternate demineralization and remineralization for 5 days. Then they were randomly divided into three groups (G) (n = 12): G1: Ginger, G2: Eggshell, and G3: Mixture. Specimens of each group were separately immersed in 50 ml of the tested extract for 12 h seven successive days. Vickers Microhardness and Energy Dispersive X-ray (EDX) Analysis were assessed at baseline, after demineralization and remineralization. RESULTS: Both extracts had antibacterial effect against the profile growth of S. mutants. However, the mixture showed the highest statistically significant mean inhibition zone diameters (mm), followed by ginger and eggshell extracts with no statistically significant difference between them. Regarding the remineralizing efficacy; G1:(Ginger) group showed the highest statistically significant mean microhardness followed by G3:(Mixture) group, then eggshell treated specimens; which showed the least statistically significant mean microhardness values. Regarding EDIX analysis results, a statistically significant increase in F (wt%) after remineralization in both eggshell and ginger treated specimens. CONCLUSION: Ginger as well as mixture extracts not only have antibacterial effect against cariogenic bacteria but also have a strong remineralizing ability of demineralized enamel.

Comparative evaluation of remineralizing effect of fluoride and nonfluoride agents on artificially induced caries using different advanced imaging techniques

Aim:

The aim of the study is to evaluate and compare the in-vitro remineralization efficacy of remineralizing agents, i.e., fluoride-free toothpaste, fluoride toothpaste, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), CPP-amorphous calcium fluoride phosphate (CPP ACFP), and silver diamine fluoride (SDF) paste on dentine over time.

Methodology:

Seventy-five extracted human permanent molars were selected. The buccal section of these samples was shaped into a slab. Artificial caries was induced by dipping the samples into the demineralizing solution (pH 4.5) for 21 days. They were then divided into five groups (n = 15). Each experimental group underwent one of the following treatments: Group 1 – Fluoride-free toothpaste (negative control), Group 2 – Fluoride toothpaste (positive control), Group 3 – CPP-ACP, Group 4 – CPP-Amorphous Calcium fluoride Phosphate and Group 5 – SDF. Postremineralizing treatment, Scanning electron microscope, Energy dispersive X-ray and Quantitative light induced fluorescence imaging were carried out to analyze the remineralizing efficacy. The data obtained was then subjected to statistical analysis using ANOVA and Paired t-tests.

Results:

It was seen that SDF showed highest remineralization efficacy followed by CPP-amorphous calcium fluoride phosphate, CPP-ACP, fluoride toothpaste and fluoride-free toothpaste. The difference in mean value among the groups was statistically significant (P < 0.001).

Conclusion:

SDF showed the highest remineralizing potential in scanning electron microscopy and energy dispersive X-ray, followed by CPP-ACFP, CPP-ACP, Fluoride toothpaste, and Fluoride-free toothpaste. Quantitative light fluorescence analysis showed more fluorescence changes in the CPP-ACFP followed by CPP-ACP, Fluoride toothpaste, and Fluoride-free toothpaste.

Advances in biomineralization-inspired materials for hard tissue repair

Biomineralization is the process by which organisms form mineralized tissues with hierarchical structures and excellent properties, including the bones and teeth in vertebrates. The underlying mechanisms and pathways of biomineralization provide inspiration for designing and constructing materials to repair hard tissues. In particular, the formation processes of minerals can be partly replicated by utilizing bioinspired artificial materials to mimic the functions of biomolecules or stabilize intermediate mineral phases involved in biomineralization. Here, we review recent advances in biomineralization-inspired materials developed for hard tissue repair. Biomineralization-inspired materials are categorized into different types based on their specific applications, which include bone repair, dentin remineralization, and enamel remineralization. Finally, the advantages and limitations of these materials are summarized, and several perspectives on future directions are discussed.

Hydroxypropylmethylcellulose as a film and hydrogel carrier for ACP nanoprecursors to deliver biomimetic mineralization

Demineralization of hard tooth tissues leads to dental caries, which cause health problems and economic burdens throughout the world. A biomimetic mineralization strategy is expected to reverse early dental caries. Commercially available anti-carious mineralizing products lead to inconclusive clinical results because they cannot continuously replenish the required calcium and phosphate resources. Herein, we prepared a mineralizing film consisting of hydroxypropylmethylcellulose (HPMC) and polyaspartic acid-stabilized amorphous calcium phosphate (PAsp-ACP) nanoparticles. HPMC which contains multiple hydroxyl groups is a film-forming material that can be desiccated to form a dry film. In a moist environment, this film gradually changes into a gel. HPMC was used as the carrier of PAsp-ACP nanoparticles to deliver biomimetic mineralization. Our results indicated that the hydroxyl and methoxyl groups of HPMC could assist the stability of PAsp-ACP nanoparticles and maintain their biomimetic mineralization activity. The results further demonstrated that the bioinspired mineralizing film induced the early mineralization of demineralized dentin after 24 h with increasing mineralization of the whole demineralized dentin (3-4 µm) after 72-96 h. Furthermore, these results were achieved without any cytotoxicity or mucosa irritation. Therefore, this mineralizing film shows promise for use in preventive dentistry due to its efficient mineralization capability.

Demineralization Inhibition by Two Calcium-releasing Restorative Materials

OBJECTIVE

To compare the ability of two calcium-releasing restorative materials to inhibit root dentin demineralization in an artificial caries model.

METHODS AND MATERIALS

Preparations were made at the cementum-enamel junction of extracted human molars (40, n=10/material) and restored with two calcium-releasing materials (Experimental composite, Pulpdent Corporation and Cention N, Ivoclar Vivadent), a resin composite (Filtek Supreme Ultra, 3M Oral Care), and a resin-modified glass ionomer (RMGI) (Fuji II LC, GC). All materials (other than the RMGI) were used with an adhesive (Scotchbond Universal Adhesive, 3M Oral Care) in the self-etch mode, which was light cured for 10 seconds. All restorative materials were light cured in 2-mm increments for 20 seconds and then finished with a polishing disc. Teeth were incubated (37°C) for 24 hours in water. An acid-resistant varnish was painted onto the teeth around the restoration, leaving a 2-mm border of uncovered tooth. A demineralization solution composed of 0.1 M lactic acid, 3 mM Ca3(PO4)2, 0.1% thymol, and NaOH (to adjust pH=4.5), and a remineralization solution composed of 1.5 mM Ca, 0.9 mM P, and 20 mM Tris(hydroxymethyl)-aminomethane (pH=7.0) were prepared. Specimens were placed in the demineralization solution for 4 hours, followed by the remineralization solution for 20 hours and cycled daily for 30 days. The specimens were embedded, sectioned into 100-μm sections, and the interface between the restorative material and root dentin was viewed with polarized light microscopy. A line was drawn parallel with the zone of demineralization for each tooth. The area of "inhibition" (defined as the area external to the line) or "wall lesion" (defined as the area internal to the line) was measured with image evaluation software. Areas of inhibition were measured as positive values, and areas of wall lesions were measured as negative areas.

RESULTS

A one-way analysis of variance (ANOVA) found significant differences between materials for "inhibition/wall lesion" areas in root dentin (p<0.001). Tukey post hoc analysis ranked materials (μm2, mean ±SD): Fuji II LC (5412±2754) > Cention N (2768±1576) and experimental composite (1484±1585) > Filtek Supreme Ultra (-1119±1029).

CONCLUSION

The experimental composite and Cention N materials (used with an adhesive) showed net areas of inhibition greater than a reference resin composite, albeit at a lower level than a reference RMGI material (used with no adhesive).

Mussel-inspired self-assembly engineered implant coatings for synergistic anti-infection and osteogenesis acceleration

Implant associated infections (IAI) and poor osseointegration are the two major causes for titanium implant failure, leading to subsequent financial burden and physical sufferings. Therefore, advanced implants with excellent anti-infection and osseointegration performance are needed. In this work, mussel-inspired tannic acid (TA) mediated layer-by-layer (LbL) self-assembly was used for fabricating bonded polyethylene glycol (PEG) and 8DSS (8 repeating units of aspartate-serine-serine) coatings (Ti/8DSS/PEG) on the surface of titanium implants. The coating is designed to simultaneously reduce bacterial adhesion through the super-hydrophilic effect of PEG and promote osseointegration through the effective biomineralization of 8DSS. The obtained Ti/8DSS/PEG implant exhibits superior anti-biofouling capabilities (anti-protein adhesion and anti-bacterial adhesion against S. aureus and E. coli) and excellent biocompatibility. Meanwhile, the Ti/8DSS/PEG implant accelerates osteoblast differentiation and presents significantly better osteogenic ability than bare titanium implants in vivo. This mussel-inspired TA mediated LbL self-assembly method is expected to provide a multifunctional and robust platform for surface engineering in bone repair.

Role of bioglass in enamel remineralization: Existing strategies and future prospects-A narrative review

Enamel, once formed, loses the ability to regenerate due to the loss of the formative ameloblasts. It is subjected to constant damaging events due to exposure to external agents and oral microbiomes. An enamel remineralization process targets to replenish the lost ionic component of the enamel through a multitude of methods. Enamel remineralization is highly challenging as it has a complex organized hierarchical microstructure. Hydroxyapatite nanocrystals of the enamel vary in size and orientation along alignment planes inside the enamel rod. The inability of the enamel to remodel unlike other mineralized tissues is another substantial deterrent. One of the well-known biomaterials, bioglass (BG) induces apatite formation on the external surface of the enamel in the presence of saliva or other physiological fluids. Calcium, sodium, phosphate, and silicate ions in BG become responsive in the presence of body fluids, leading to the precipitation of calcium phosphate. Studies have also demonstrated the bactericidal potential of BG against Streptococcus mutans biofilms. The anticariogenicity and antibacterial activity were found to be enhanced when BG was doped with inorganic ions such as F, Ag, Mg, Sr, and Zn. Due to the versatility of BG, it has been combined with a variety of agents such as chitosan, triclosan, and amelogenin to biomimic remineralization process. Key strategies that can aid in the development of contemporary enamel remineralization agents are also included in this review.

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.

Effect of chlorhexidine-loaded poly(amido amine) dendrimer on matrix metalloproteinase activities and remineralization in etched human dentin in vitro

To investigate the effect of chlorhexidine (CHX)-loaded carboxyl-terminated poly (amido amine) dendrimer (CHX-PAMAM-COOH) on matrix metalloproteinase (MMP) activities and remineralization in human dentin, CHX-PAMAM-COOH was prepared and characterized by Fourier-transform infrared spectroscopy. The inhibitory effects of CHX, PAMAM-COOH, and CHX-PAMAM-COOH on soluble recombinant human matrix metalloproteinase (rhMMP-2) and dentin-bound endogenous MMP activity were measured using an MMP Activity Assay Kit. In situ zymography was performed to evaluate the gelatinase activity in dentin pretreated with CHX, PAMAM-COOH, and CHX-PAMAM-COOH. The remineralization of etched dentin pretreated with CHX, PAMAM-COOH, and CHX-PAMAM-COOH was evaluated by field emission-scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) after incubation in artificial saliva for 14 days. The results of the rhMMP-2 activity assay showed that the MMP-2 activity in the CHX-PAMAM-COOH group and the CHX group decreased significantly to 5.58 ± 0.85% (P < 0.05) and 4.86 ± 1.12% (P < 0.05), respectively, but that in the PAMAM-COOH group increased significantly to 213.38 ± 0.11% (P < 0.05). The results of total MMP activity and in situ zymography showed a significant reduction in endogenous gelatinase activity in dentin in the CHX-PAMAM-COOH group and the CHX group. The SEM and EDS results showed that rod-like crystals were formed on the etched dentin surface in the PAMAM-COOH group and the CHX-PAMAM-COOH group, and their Ca/P ratios were 1.73 and 1.71, respectively. In conclusion, CHX-PAMAM-COOH can inhibit dentin-bound endogenous MMPs and induce remineralization in etched dentin simultaneously. However, it is important to note that the catalytic role of PAMAM dendrimers may have an undesired excitatory effect on MMP activity, which cannot be ignored if PAMAM dendrimers were used alone in the oral environment.

Remineralization effectiveness of adhesive containing amorphous calcium phosphate nanoparticles on artificial initial enamel caries in a biofilm-challenged environment

OBJECTIVES

Dental caries is closely associated with acid-producing bacteria, and Streptococcus mutans is one of the primary etiological agents. Bacterial accumulation and dental demineralization lead to destruction of bonding interface, thus limiting the longevity of composite. The present study investigated remineralization effectiveness of adhesive containing nanoparticles of amorphous calcium phosphate (NACP) in a stimulated oral biofilm environment.

METHODS

The enamel blocks were immersed in demineralization solution for 72 h to imitate artificial initial carious lesion and then subjected to a Streptococcus mutans biofilm for 24 h. All the samples then underwent 4-h demineralization in brain heart infusion broth with sucrose (BHIS) and 20-h remineralization in artificial saliva (AS) for 7 days. The daily pH of BHIS after 4-h incubation, lactic acid production, colony-forming unit (CFU) count, and content of calcium (Ca) and phosphate (P) in biofilm were evaluated. Meanwhile, the remineralization effectiveness of enamel was analyzed by X-ray diffraction (XRD), surface microhardness testing, transverse microradiography (TMR) and scanning electron microscopy (SEM).

RESULTS

The NACP adhesive released abundant Ca and P, achieved acid neutralization, reduced lactic acid production, and lowered CFU count (P < 0.05). Enamel treated with NACP adhesive demonstrated the best remineralization effectiveness with remineralization value of 52.29 ± 4.79% according to TMR. Better microhardness recovery of cross sections and ample mineral deposits were also observed in NACP group.

CONCLUSIONS

The NACP adhesive exhibited good performance in remineralizing initial enamel lesion with cariogenic biofilm.

SIGNIFICANCE

The NACP adhesive is promising to be applied for the protection of bonding interface, prevention of secondary caries, and longevity prolonging of the restoration.

Drug Delivery (Nano)Platforms for Oral and Dental Applications: Tissue Regeneration, Infection Control, and Cancer Management

The oral cavity and oropharynx are complex environments that are susceptible to physical, chemical, and microbiological insults. They are also common sites for pathological and cancerous changes. The effectiveness of conventional locally-administered medications against diseases affecting these oral milieus may be compromised by constant salivary flow. For systemically-administered medications, drug resistance and adverse side-effects are issues that need to be resolved. New strategies for drug delivery have been investigated over the last decade to overcome these obstacles. Synthesis of nanoparticle-containing agents that promote healing represents a quantum leap in ensuring safe, efficient drug delivery to the affected tissues. Micro/nanoencapsulants with unique structures and properties function as more favorable drug-release platforms than conventional treatment approaches. The present review provides an overview of newly-developed nanocarriers and discusses their potential applications and limitations in various fields of dentistry and oral medicine.

The Antibacterial and Remineralizing Effects of Biomaterials Combined with DMAHDM Nanocomposite: A Systematic Review

Researchers have developed novel nanocomposites that incorporate additional biomaterials with dimethylaminohexadecyl methacrylate (DMAHDM) in order to reduce secondary caries. The aim of this review was to summarize the current literature and assess the synergistic antibacterial and remineralizing effects that may contribute to the prevention of secondary caries. An electronic search was undertaken in MEDLINE using PubMed, Embase, Scopus, Web of Science and Cochrane databases. The initial search identified 954 papers. After the removal of duplicates and screening the titles and abstracts, 15 articles were eligible for this review. The amalgamation of 2-methacryloyloxyethyl phosphorylcholine (MPC) and silver nanoparticles (AgNPs) with DMAHDM resulted in increased antibacterial potency. The addition of nanoparticles of amorphous calcium phosphate (NACP) and polyamidoamine dendrimers (PAMAM) resulted in improved remineralization potential. Further clinical studies need to be planned to explore the antibacterial and remineralizing properties of these novel composites for clinical success.

Dental Restorative Materials for Elderly Populations

The incidence of dental caries, especially root caries, has risen in elderly populations in recent years. Specialized restorative materials are needed due to the specific site of root caries and the age-related changes in general and oral health in the elderly. Unfortunately, the restorative materials commonly used clinically cannot fully meet the requirements in this population. Specifically, the antibacterial, adhesive, remineralization, mechanical, and anti-aging properties of the materials need to be significantly improved for dental caries in the elderly. This review mainly discusses the strengths and weaknesses of currently available materials, including amalgam, glass ionomer cement, and light-cured composite resin, for root caries. It also reviews the studies on novel anti-caries materials divided into three groups, antimicrobial, remineralization, and self-healing materials, and explores their potential in the clinical use for caries in the elderly. Therefore, specific restorative materials for caries in the elderly, especially for root caries, need to be further developed and applied in clinical practice.

The use of bioactive glass (BAG) in dental composites: A critical review

OBJECTIVE

In recent years, numerous studies have analyzed the role of bioactive glass (BAG) as remineralizing additives in dental restorative composites. This current review provides a critical analysis of the existing literature, particularly focusing on BAGs prepared via the melt-quench route that form an "apatite-like" phase when immersed in physiological-like solutions.

METHODS

Online databases (Science Direct, PubMed and Google Scholar) were used to collect data published from 1962 to 2020. The research papers were analyzed and the relevant papers were selected for this review. Sol-gel BAGs were not included in this review since it is not a cost-effective manufacturing technique that can be upscaled and is difficult to incorporate fluoride.

RESULTS

BAGs release Ca²⁺, PO₄^3- and F^- ions, raise the pH and form apatite. There are numerous published papers on the bioactivity of BAGs, but the different glass compositions, volume fractions, particle sizes, immersion media, time points, and the characterization techniques used, make comparison difficult. Several papers only use certain characterization techniques that do not provide a full picture of the behavior of the glass. It was noted that in most studies, mechanical properties were measured on dry samples, which does not replicate the conditions in the oral environment. Therefore, it is recommended that samples should be immersed for longer time periods in physiological solutions to mimic clinical environments.

SIGNIFICANCE

BAGs present major benefits in dentistry, especially their capacity to form apatite, which could potentially fill any marginal gaps produced due to polymerization shrinkage.

Influence of Hydroxyapatite Nanospheres in Dentin Adhesive on the Dentin Bond Integrity and Degree of Conversion: A Scanning Electron Microscopy (SEM), Raman, Fourier Transform-Infrared (FTIR), and Microtensile Study

An experimental adhesive incorporated with different nano-hydroxyapatite (n-HA) particle concentrations was synthesized and analyzed for dentin interaction, micro-tensile bond strength (μTBS), and degree of conversion (DC). n-HA powder (5 wt % and 10 wt %) were added in adhesive to yield three groups; gp-1: control experimental adhesive (CEA, 0 wt % HA), gp-2: 5 wt % n-HA (HAA-5%), and gp-3: 10 wt % n-HA (HAA-10%). The morphology of n-HA spheres was evaluated using Scanning Electron Microscopy (SEM). Their interaction in the adhesives was identified with SEM, Energy-Dispersive X-ray (EDX), and Micro-Raman spectroscopy. Teeth were sectioned, divided in study groups, and assessed for μTBS and failure mode. Employing Fourier Transform-Infrared (FTIR) spectroscopy, the DC of the adhesives was assessed. EDX mapping revealed the occurrence of oxygen, calcium, and phosphorus in the HAA-5% and HAA-10% groups. HAA-5% had the greatest μTBS values followed by HAA-10%. The presence of apatite was shown by FTIR spectra and Micro-Raman demonstrated phosphate and carbonate groups for n-HA spheres. The highest DC was observed for the CEA group followed by HAA-5%. n-HA spheres exhibited dentin interaction and formed a hybrid layer with resin tags. HAA-5% demonstrated superior μTBS compared with HAA-10% and control adhesive. The DC for HAA-5% was comparable to control adhesive.

Bibliometric Analysis of Literature Published on Antibacterial Dental Adhesive from 1996-2020

This study aimed to investigate the current state of research on antibacterial dental adhesives. The interest in this field can be drawn from an increasing number of scholarly works in this area. However, there is still a lack of quantitative measurement of this topic. The main aim of this study was to consolidate the research published on the antibacterial adhesive from 1996 to 2020 in Web of Science indexed journals. The bibliometric method, a quantitative study of investigating publishing trends and patterns, was used for this study. The result has shown that a gradual increase in research was found, whereby a substantial increase was observed from 2013. A total of 248 documents were published in 84 journals with total citations of 5107. The highly cited articles were published mainly in Q1 category journals. Most of the published articles were from the USA, China, and other developed countries; however, some developing countries contributed as well. The authorship pattern showed an interdisciplinary and collaborative approach among researchers. The thematic evaluation of keywords along with a three-factor analysis showed that 'antibacterial adhesives' and 'quaternary ammonium' have been used commonly. This bibliometric analysis can provide direction not only to researchers but also to funding organizations and policymakers.

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.

Molecular insight into the interfacial chemical functionalities regulating heterogeneous calcium-arsenate nucleation

Heterogeneous nucleation induced by natural organic matter (NOM) can lower the energy barrier for calcium arsenate (Ca-As) precipitation, which aids in immobilizing arsenate (As^Ⅴ). However, it remains unclear how certain chemical functionalities of NOM affect Ca-As nucleation at the molecular scale. By analyzing changes in the local supersaturation and/or interfacial energy, the present work investigates the Ca-As heterogeneous nucleation kinetics and mechanisms on functional-group-modified model surfaces. Mica surfaces modified by functional groups of amine (NH₂), hydroxyl (OH), or carboxyl (COOH) through self-assembled monolayers were used to investigate how chemical functionalities affect the Ca-As heterogeneous nucleation, in which the distributions of formation kinetics and size (as measured by the change in particle height) of nucleated Ca-As particles were measured by using in situ atomic force microscopy. In a parallel analysis, a quartz-crystal microbalance with dissipation was used to detect the buildup of Ca²⁺ and/or HAsO₄^2- ions at the solid-fluid interface. PeakForce quantitative nanomechanical mapping and dynamic force spectroscopy using functional-group-modified tips made it possible to calculate the binding energies holding functional groups to Ca-As particles. Nucleated Ca-As particles were characterized by using Raman spectroscopy and high-resolution transmission electron microscopy. The results indicate that the height of amorphous Ca-As particles formed on a modified mica surface may be ranked in descending order as NH₂ > OH > bare mica > COOH, as determined by the buildup of Ca²⁺ and HAsO₄^2- ions at the solid-fluid interface and the decrease of interfacial energy due to the functional groups. These nanoscale observations and molecular-scale determinations improve our understanding of the roles played by chemical functionalities on NOM in immobilizing dissolved As through heterogeneous nucleation in soil and water.