Engineered Bio-Heterojunction with Infection-Primed H2 S Liberation for Boosted Angiogenesis and Infectious Cutaneous Regeneration.

Photodynamic therapy (PDT) acts as a powerful weapon against infectious diseases for its enormous antimicrobial activity that quickly elicits storms of reactive oxygen species (ROS). Nevertheless, redundant ROS during treatment inevitably bring detriments in revascularization. To address this dilemma, an innovative P-N bio-heterojunction (bio-HJ) material consisting of p-type copper sulfide (p-CuS), n-type bismuth sulfide (n-Bi2 S3 ), and lactate oxidase (LOx) for effective treatment of recalcitrant infectious wounds by promoting angiogenesis is devised. LOx exhausts lactic acid accumulated in infection environment and converts it to hydrogen peroxide (H2 O2 ), which subsequently yields bactericidal hydroxyl radicals (·OH) via Fenton-like reactions. Ultimately, the P-N bio-HJs exert synergistic photothermal, photodynamic, and chemodynamic effects for rapid bacterial annihilation. Moreover, in vitro and RNA-seq analyses reveal that the crafted bio-HJs dramatically expedite the proliferation of L929 cells and promote angiogenesis by up-regulating angiogenic gene expression in hypoxia-inducible factor-1 (HIF-1) signaling pathway, which may ascribe to the evolution of H2 S in response to the infection microenvironment. Critically, results of in vivo experiments have authenticated that the bio-HJs significantly boost healing rates of full-thickness wounds by slaughtering bacteria, elevating angiogenesis, and promoting cytothesis. As envisioned, this work furnishes a novel tactic for the effective treatment of bacteria-invaded wound using H2 S-liberating P-N bio-HJs.

Photo-Activated Nanofibrous Membrane with Self-Rechargeable Antibacterial Function for Stubborn Infected Cutaneous Regeneration.

For quick disinfection treatment, phototherapy, including photothermal therapy and photodynamic therapy, has emerged as a promising alternative to conventional methods. However, the bactericidal effect of phototherapy, which only works upon light, is short-lived. The remaining bacteria in situ may repopulate when the irradiation of light is withdrawn. To address this refractory concern, an antibacterial fibrous membrane consisting of electrospun poly (polycaprolactone) scaffolds and polydopamine (pDA) coated MXene/Ag3 PO4 bioheterojunctions (MX@AgP bio-HJs) is devised and developed. Upon near-infrared (NIR) illumination, the MX@AgP nanoparticle (NP) in nanofibrous electrospun membranes exert the excellent bactericidal effect of phototherapy and release Ag+ ions which stop the remaining bacteria from multiplying in the dark state. When removing NIR light, pDA in situ reduces Ag+ ions to Ag0 NPs to realize the self-rechargeability of Ag+ ions and provides enough Ag+ ions for the second phototherapy. In vivo results show that photoactivated nanofibrous membranes can re-shape an infected wound microenvironment to the regenerative microenvironment through killing bacteria, ceasing bleeding, increasing epithelialization, and collagen deposition on the wound bed, as well as promoting angiogenesis. As predicted, the proposal work offers potential prospects for nanofibrous membranes with NIR-assisted "self-rechargeable" antibacterial properties to treat bacteria-infected full-thickness wounds.

A Dentin Biomimetic Remineralization Material with an Ability to Stabilize Collagen.

The integrity of collagen matrix structure is a prerequisite for effectively inducing biomimetic remineralization. Repeated low pH stimulation activates matrix metalloproteinases (MMPs) in dental caries. Activated MMPs cause the breakdown of collagen fibrils. Collagen stabilization is a major obstacle to the clinical application of remineralization templates. Here, galardin-loaded poly(amido amine) (PAMAM)-NGV (PAMAM-NGV@galardin, PNG) is constructed to induce collagen stabilization and dentin biomimetic remineralization simultaneously, in order to combat early caries in dentin. PAMAM acts in the role of nucleation template for dentin remineralization, while galardin acts as the role of MMPs inhibitor. NGV peptides modified on the surface of dendrimer core can form small clusters with synergistic movement in short range, and those short-range clusters can form domain areas with different properties on the surface of PAMAM core and restrict the movement of collagen, favoring collagen crosslinking, which can be explained through the computational simulation analysis results. NGV peptides and galardin show a dual collagen-protective effect, laying the foundation for the dentin remineralization effect induced by PAMAM. PNG induces dentin remineralization in an environment with collagenase, meanwhile showsing anti-dentin caries efficacy in vivo. These findings indicate that PNG has great potential to combat early dentin caries for future clinical application.

Dentin remineralization in acidic solution without initial calcium phosphate ions via poly(amido amine) and calcium phosphate nanocomposites after fluid challenges.

OBJECTIVES: A previous study showed that the combination of poly(amido amine) (PAMAM) and rechargeable composites with nanoparticles of amorphous calcium phosphate (NACP) induced dentin remineralization in an acidic solution with no initial calcium (Ca) and phosphate (P) ions, mimicking the oral condition of individuals with dry mouths. However, the frequent fluid challenge in the oral cavity may decrease the remineralization capacity. Therefore, the objective of the present study was to investigate the remineralization efficacy on dentin in an acid solution via PAMAM + NACP after fluid challenges for the first time. METHODS: The NACP nanocomposite was stored in a pH 4 solution for 77 days to exhaust its Ca and P ions and then recharged. Demineralized dentin samples were divided into four groups: (1) control dentin, (2) dentin coated with PAMAM, (3) dentin with recharged NACP composite, and (4) dentin with PAMAM + recharged NACP. PAMAM-coated dentin was shaken in phosphate-buffered saline for 77 days to desorb PAMAM from dentin. Samples were treated in pH 4 lactic acid with no initial Ca and P ions for 42 days. RESULTS: After 77 days of fluid challenge, PAMAM failed to prevent dentin demineralization in lactic acid. The recharged NACP nanocomposite raised the pH to above 6.5 and re-released more than 6.0 and 4.0 mmol/L Ca and P ions daily, respectively, which inhibited further demineralization. In contrast, the PAMAM + NACP combined method induced great dentin remineralization and restored the dentin microhardness to 0.54 ± 0.04 GPa, which approached that of sound dentin (P = 0.426, P > 0.05). CONCLUSIONS: The PAMAM + NACP combination achieved dentin remineralization in an acid solution with no initial Ca and P ions, even after severe fluid challenges. CLINICAL RELEVANCE: The novel PAMAM + NACP has a strong and sustained remineralization capability to inhibit secondary caries, even for individuals with dry mouths.

Evaluation of the ability of adhesives with antibacterial and remineralization functions to prevent secondary caries in vivo.

OBJECTIVE: The bonding interface of dental filling therapy is the weak point in resisting secondary caries. Adhesives containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) have been demonstrated in vitro to prevent bacteria from producing acid and to promote tooth remineralization. The present study aimed to evaluate the efficacy of adhesive with NACP and DMAHDM to prevent secondary caries in vivo. MATERIALS AND METHODS: Artificial cavities were created on the first molar on both sides of the maxillary in a rat model. One side was treated with adhesive containing NACP + DMAHDM, while on the other side, a commercial adhesive served as control. After 24 days of cariogenic feeding, the degree of secondary caries was evaluated by micro-CT and a modified Keyes scoring method. Quantitative real-time PCR (qPCR) and colony-forming unit (CFU) counts were used to evaluate the antibacterial efficacy of the materials. Biocompatibility was also investigated. RESULTS: In the rat model, the adhesive with NACP + DMAHDM showed excellent biocompatibility and effectively decreased the amount of bacteria. The experimental group demonstrated excellent remineralization effectiveness, with a lower modified Keyes score and mineral loss of 34.16 ± 2.13 vol% µm, compared with 77.44 ± 7.22 vol% µm in the control group, according to micro-CT (P < 0.05), showing excellent capacity to inhibit secondary caries. CONCLUSIONS: The NACP-DMAHDM-containing adhesive exhibited good performance in preventing secondary caries in vivo. CLINICAL RELEVANCE: Adhesives containing NACP and DMAHDM have great potential for use in clinical dentistry to prevent secondary caries by inhibiting bacterial growth and promoting remineralization.

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.

Borate bioactive glass prevents zoledronate-induced osteonecrosis of the jaw by restoring osteogenesis and angiogenesis.

OBJECTIVES: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a severe complication of systemic nitrogen-containing bisphosphonate (N-BP) administration, which leads to osteonecrosis, pain, and infection. Despite much effort, effective remedies are yet to be established. This study aimed to investigate potential recovery effect of borate bioactive glass (BBG) in vitro and in vivo. METHODS: The effect of BBG on zoledronate-treated bone marrow mesenchymal cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) was explored by cell counting kit-8, EdU assay, flow cytometry, alkaline phosphatase staining, alizarin red staining, angiogenesis experiment, and real-time quantitative polymerase chain reaction. The preventive effect of BBG on zoledronate-induced osteonecrosis of the jaw in rat model was examined by micro-CT, HE staining, and immunohistochemistry. RESULTS: Exposure of BBG to BMSCs and HUVECs increased cell proliferation and restored their osteogenesis and angiogenesis potential in vitro. The BRONJ lesions were satisfactorily repaired and bone mineral density, bone volume/tissue volume, trabecula number, OCN-positive cells, and CD31-positive cells were increased in the BBG-treated groups compared with saline-treated groups. CONCLUSIONS: Exposure of BMSCs and HUVECs to BBG restores osteogenesis and angiogenesis inhibited by zoledronate. BBG successfully restores extraction socket healing of BRONJ in rat model.

Biomineralization of dentin.

A single biomineralization of demineralized dentin is significant to restore the demineralized dentin due to dental caries or erosion. In recent years, meaningful progress has been made regarding the mechanisms involved in the biomineralization of dentin collagen. Concepts changing from the classical ion-based crystallization to non-classical particle-based crystallization, inspired a different strategy to infiltrate the demineralized dentin collagen. The remarkable discovery was the report of liquid-like amorphous calcium phosphate as nanoprecursor particles to carbonated hydroxyapatite. The non-collagenous proteins and their analogues are widely investigated, for their key role in controlling mineralization during the process of crystal nucleation and growth. The in-depth studies of the gap zone provided significant improvements in our understanding of the structure of collagen and of the intrafibrillar remineralization of collagen fibrils. The collagen is not a passive substrate as previously supposed, and the active role of guiding nanoprecursor infiltration and mediating its nucleation has been demonstrated. Furthermore, recovery of mechanical properties has been evaluated to determine the effectiveness of dentin remineralization. Finally, the problems regarding the origin formation of the calcium phosphate that is deposited in the collagen, and the exact interactions between the non-collagenous proteins, amorphous calcium phosphate and collagen are still unclear. We reviewed the importance of these findings in enriching our understanding of dentin biomineralization, while addressing certain limitations that are inherent to in vitro studies.

Computer simulations of the adsorption of an N-terminal peptide of statherin, SN15, and its mutants on hydroxyapatite surfaces.

Statherin is a 43 amino acid long protein, which plays an important role in the process of biomineralization of enamel. In this work, we investigated the solvent effect on the adsorption of a peptide from the N-terminus of statherin, SN15, and its mutants SNA15 and SNS15 on the (001) face of hydroxyapatite [Ca10(PO4)6(OH)2, or HAP] with molecular dynamics simulations. The simulation results showed that the adsorption of the three peptides onto the HAP(001) surface was primarily driven by salt-bridge and electrostatic attraction in calcium phosphate (Ca/P) and sodium chloride (NaCl) solutions, respectively. SN15 adsorbs on the HAP surface with the strongest electrostatic interaction, while SNS15 is the weakest. Besides, Ca2+ around SN15 can form an equilateral triangle, which resembles the structure formed by Ca(2) ions in the HAP(001) crystal face, and this looks like the initial stage of HAP nucleation. The conformational changes of SN15 on HAP are analyzed by the root-mean-square deviation. It shows that SN15 is more stable in Ca/P solution while SNS15 is more stable in NaCl solution; the stability of SNA15 is almost the same in both solutions. This work reveals the adsorption mechanism of a series of SN peptides on the HAP surface and provides guidelines for the design of biomaterials for restoring etched enamel and regulating biomineralization.

Effect of polyvinyl siloxane impression material on the polymerization of composite resin.

STATEMENT OF PROBLEM: Polyvinyl siloxane impression material has been widely used as a lingual matrix for rebuilding missing tooth structure with composite resin. The composite resin is light polymerized in contact with the polyvinyl siloxane impression material. However, polyvinyl siloxane impression material has been shown to interact with other dental materials. PURPOSE: The purpose of this study was to assess the effect of polyvinyl siloxane impression materials on the polymerization of composite resins by assessing the Vickers microhardness and degree of conversion of polyvinyl siloxane. MATERIAL AND METHODS: The composite resins were light polymerized in contact with 3 polyvinyl siloxane impression materials (Flexitime Easy Putty; President Light Body; Xantopren L Blue) (n=8) and in contact with a matrix strip as the control group (n=8). Vickers microhardness and degree of conversion on contact surfaces were measured to evaluate the polymerization of composite resins. The depth of the effect was assessed by Vickers microhardness on section surfaces and observed with scanning electron microscopy. The results were analyzed by 1-way analysis of variance and the post hoc Tukey honest significant differences test (α=.05). RESULTS: The Vickers microhardness and degree of conversion values on the contact surfaces of the experiment groups were significantly lower than those of the control group (P<.05); the Vickers microhardness values on the section surfaces indicated that there was no significant difference at the same depth of different groups (P>.05). The scanning electron microscope observation showed that an approximately 10-µm deep unpolymerized layer was found in the experimental group. CONCLUSIONS: Polyvinyl siloxane impression materials have an inhibitory effect on the polymerization of the composite resins, but just limited to within approximately 10 µm from the surface in contact with the impression material.

Biomimetic remineralization of human enamel in the presence of polyamidoamine dendrimers in vitro.

Poly(amidoamine) (PAMAM) dendrimers, known as artificial proteins, have unique and well-defined molecular size and structure. It has previously been used to mimic protein-crystal interaction during biomineralization. In this study, generation 4.5 (4.5G) PAMAM with carboxylic acid (PAMAM-COOH) was synthesized and utilized to remineralize the surface of etched enamel in vitro. Using confocal laser scanning microscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy we observed that 4.5G PAMAM-COOH can be absorbed on the etched enamel surface and that it can induce the formation of hydroxyapatite crystals with the same orientation as that of the enamel prisms on longitudinal and transversal enamel surfaces. The self-assembly behavior of PAMAM in the mineralization solution was also investigated and the result showed that 4.5G PAMAM can assemble to microribbon structure similar to the behavior of amelogenins. Therefore, we concluded that 4.5G PAMAM-COOH assemblies can act as the organic template on enamel surface and in mineralization solution to control the nucleation site and morphology of new-grown crystals to form the biomimetic structure of human enamel, which may open a new way for repairing damaged enamel.

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.

Metronidazole and Ketoprofen-Loaded Mesoporous Magnesium Carbonate for Rapid Treatment of Acute Periodontitis In Vitro.

In the clinical pharmacological treatment of acute periodontitis, local periodontal administration is expected to be preferable to systemic administration. However, the action of the active medicine component is hindered and diminished by the limitation of drug solubility, which does not provide timely relief of the enormous pain being suffered by patients. This study aimed to develop a mesoporous magnesium carbonate (MMC) medicine loading system consisting of MMC, metronidazole (MET), and ketoprofen (KET), which was noted as MET-KET@MMC. A solvent evaporation process was utilized to load MET and KET in MMC. Scanning electron microscopy, nitrogen sorption, thermogravimetric analysis, and X-ray diffraction were performed on the MET-KET@MMC. The rapid drug release properties were also investigated through the drug release curve. The rapid antiseptic property against Porphyromonas gingivalis (P. gingivalis) and the rapid anti-inflammatory property (within 1 min) were analyzed in vitro. The cytotoxicity of MET-KET@MMC was tested in direct contact with human gingival cells and human oral keratinocytes. Crystallizations of MET and KET were completely suppressed in MMC. As compared to crystalline MET and KET, MMC induced higher apparent solubility and rapid drug release, resulting in 8.76 times and 3.43 times higher release percentages of the drugs, respectively. Over 70.11% of MET and 85.97% of KET were released from MMC within 1 min, resisting bacteria and reducing inflammation. MET-KET@MMC nanoparticles enhanced the solubility of drugs and possess rapid antimicrobial and anti-inflammatory properties. The MET-KET@MMC is a promising candidate for the pharmacotherapy of acute periodontitis with drugs, highlighting a significant clinical potential of MMC-based immediate drug release systems.

An engineered dual-functional peptide with high affinity to demineralized dentin enhanced remineralization efficacy in vitro and in vivo.

Dental caries continues to be a major global public health problem. Remineralization of demineralized dentin is regarded as one of the hotspots in the current study in the treatment of dental caries. However, traditional remineralization agents, which usually lack the ability to bind to demineralized dentin collagen, are easily removed by the fluids in the oral cavity, thus decreasing the remineralization efficacy. Non-collagenous proteins (NCPs) have significant effects on the biomineralization of dentin due to their dual high binding capacity to the collagen fibers and minerals. But NCPs are hard to extract, store and use directly. Inspired by the biological behavior of NCPs, in this study, we selected two functional sequences of NCPs to develop a novel and engineered dual-functional peptide (which is referred to as CYP) with collagen-binding and mineral-absorbing capability. The binding ability of CYP to collagen fibers and demineralized dentin was investigated, and the results suggested that CYP was endowed with good binding capacity to demineralized dentin, which could resist the washing of the fluid. In addition, we confirmed that CYP exerted formidable remineralization effects in collagen fibers and demineralized dentin following an in vitro remineralization regimen. Furthermore, the dual functions of CYP with good biocompatibility can simultaneously bind collagen and induce nanocrystal precipitation, thereby significantly absorbing calcium and phosphorus ions to form regenerated minerals for reversing the tooth decay process in the rat caries model. Overall, the dual functional peptide CYP fabricated in this study provides an ideal and smart strategy for dentin remineralization and the treatment of caries.

Dual-functional adhesive containing amorphous calcium phosphate nanoparticles and dimethylaminohexadecyl methacrylate promoted enamel remineralization in a biofilm-challenged environment.

OBJECTIVE: The cariogenic biofilm on enamel, restoration, and bonding interface is closely related to dental caries and composite restoration failure. Enamel remineralization at adhesive interface is conducive to protecting bonding interface and inhibiting secondary caries. This study intended to assess the remineralization efficiency of adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on initial caries lesion of biofilm-coated enamel. METHODS: Artificial initial carious lesion was created via 72-hour immersion in demineralization solution and cariogenic biofilm was formed after 24-hour culture of Streptococcus mutans (S. mutans). Specimens were then divided into 4 groups: enamel control, enamel treated with NACP, DMAHDM and NACP+DMAHDM respectively. Samples next underwent 7-day cycling, 4 h in BHIS (brain heart infusion broth containing 1 % sucrose) and 20 h in AS (artificial saliva) per day. The pH of BHIS was tested daily. So did the concentration of calcium and phosphate in BHIS and AS. Live/dead staining, colony-forming unit (CFU) count, and lactic acid production of biofilms were measured 7 days later. The enamel remineralization efficiency was evaluated by microhardness testing and transverse microradiography (TMR) quantitatively. RESULTS: Enamel of NACP+DMAHDM group demonstrated excellent remineralization effectiveness. And the NACP+DMAHDM adhesive released a great number of Ca2+ and PO43- ions, increased pH to 5.81 via acid neutralization, decreased production of lactic acid, and reduced CFU count of S. mutans (P < 0.05). SIGNIFICANCE: The NACP+DMAHDM adhesive would be applicable to preventing secondary caries, strengthening enamel-adhesive interface, and extending the lifespan of composite restoration.

Adhesion of Streptococcus mutans on remineralized enamel surface induced by poly(amido amine) dendrimers.

The aim of this study was to investigate the surface topography of remineralized enamel induced by poly(amido amine) (PAMAM) dendrimers and evaluate Streptococcus mutans (S. mutans) adhesion on regenerated enamel for the first time. PAMAM-COOH and PAMAM-NH2 were used as organic templates to induce enamel surface remineralization. The mineral deposits after remineralization were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The surface topography of the remineralized enamel was analyzed by atomic force microscopy (AFM). An AFM tipless cantilever was functionalized with S. mutans and acted as a force probe to measure the adhesion force between bacteria and the remineralized enamel surface. Colony-forming unit (CFU) counts of biofilm on remineralized enamel surface were performed after 24 h incubation in S. mutans suspension. Both PAMAM-COOH and PAMAM-NH2 achieved effective remineralization on demineralized enamel surfaces, which smoothed the enamel surface and reduced S. mutans adhesion. PAMAM dendrimers are promising materials for early caries treatment because of their excellent remineralization ability. The remineralization induced by PAMAM dendrimers smoothed the surface and reduced S. mutans adhesion, which could prevent secondary caries.

A novel anticaries agent, honokiol-loaded poly(amido amine) dendrimer, for simultaneous long-term antibacterial treatment and remineralization of demineralized enamel.

OBJECTIVE: Existing agents to induce enamel self-repair and inhibit the progression of dental caries in the early stage have been proven to be inadequate and far from satisfactory. In this study, a honokiol-loaded poly(amido amine) (PAMAM) dendrimer (PAMH) was constructed to combat early caries lesions in enamel. METHODS: PAMH was prepared via a codissolution method. Computational simulation analysis was used to explore the mechanism of honokiol release. The cytotoxicity of PAMH was tested. The antibacterial effects of PAMH were tested by planktonic growth assays and biofilm formation inhibition assays. The remineralization effect of PAMH was examined via transverse microradiography and scanning electron microscopy after a pH cycling model. The in vivo anti-caries effect of PAMH was carried out in a rat model. RESULTS: Honokiol released from PAMH was slower but more durable in a cariogenic pH environment than in a neutral pH environment, which could be explained through the computational simulation analysis results. Under electrostatic action, P3 beads with the same charge repelled each other and extended outwards, resulting in the rapid expansion of the PAMAM dendrimer and accelerating the release of the drug. At a low pH of 5.5, the protonated P3 beads were not charged and the protonated P1 beads were positively charged. However, the electrostatic repulsive interaction between protonated P1 beads was restricted by the P3 beads in the outermost layer of the PAMAM dendrimer, so the swelling rate was relatively slow, resulting in the slow release of drug molecules in the acidic environment. The cytotoxicity demonstration and the biocompatibility experiment in animal study showed that PAMH is biologically safe. PAMH showed excellent enamel remineralizing ability after pH cycling and showed a long-term antibacterial effect in vitro. Meanwhile, PAMH showed long-term anticaries efficacy in vivo. SIGNIFICANCE: Our findings indicated that PAMH had great potential to combat early caries lesions in enamel for future clinical application.

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.

Two-in-one strategy: a remineralizing and anti-adhesive coating against demineralized enamel.

Tooth enamel is prone to be attacked by injurious factors, leading to a de/remineralization imbalance. To repair demineralized enamel and prevent pulp inflammation caused by biofilm accumulation, measures are needed to promote remineralization and inhibit bacterial adhesion on the tooth surface. An innovative material, poly (aspartic acid)-polyethylene glycol (PASP-PEG), was designed and synthesized to construct a mineralizing and anti-adhesive surface that could be applied to repair demineralized enamel. A cytotoxicity assay revealed the low cytotoxicity of synthesized PASP-PEG. Adsorption results demonstrated that PASP-PEG possesses a high binding affinity to the hydroxyapatite (HA)/tooth surface. In vitro experiments and scanning electron microscopy (SEM) demonstrated a strong capacity of PASP-PEG to induce in situ remineralization and direct the oriented growth of apatite nanocrystals. Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD) and Vickers hardness tests demonstrated that minerals induced by PASP-PEG were consistent with healthy enamel in Ca/P ratio, crystal form and surface micro-hardness. Contact angle tests and bacterial adhesion experiments demonstrated that PASP-PEG yielded a strong anti-adhesive effect. In summary, PASP-PEG could achieve dual effects for enamel repair and anti-adhesion of bacteria, thereby widening its application in enamel repair.

Nano-calcium phosphate and dimethylaminohexadecyl methacrylate adhesive for dentin remineralization in a biofilm-challenged environment.

OBJECTIVE: Dentin remineralization at the bonded interface would protect it from external risk factors, therefore, would enhance the longevity of restoration and combat secondary caries. Dental biofilm, as one of the critical biological factors in caries formation, should not be neglected in the assessment of caries preventive agents. In this work, the remineralization effectiveness of demineralized human dentin in a multi-species dental biofilm environment via an adhesive containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) was investigated. METHODS: Dentin demineralization was promoted by subjecting samples to a three-species acidic biofilm containing Streptococcus mutans, Streptococcus sanguinis, Streptococcus gordonii for 24h. Samples were divided into a control group, a DMAHDM adhesive group, an NACP group, and an NACP+DMAHDM adhesive group. A bonded model containing a control-bonded group, a DMAHDM-bonded group, an NACP-bonded group, and an NACP+DMAHDM-bonded group was also included in this study. All samples were subjected to a remineralization protocol consisting of 4-h exposure per 24-h period in brain heart infusion broth plus 1% sucrose (BHIS) followed by immersion in artificial saliva for the remaining period. The pH of BHIS after 4-h immersion was measured every other day. After 14 days, the biofilm was assessed for colony-forming unit (CFU) count, lactic acid production, live/dead staining, and calcium and phosphate content. The mineral changes in the demineralized dentin samples were analyzed by transverse microradiography. RESULTS: The in vitro experiment results showed that the NACP+DMAHDM adhesive effectively achieved acid neutralization, decreased biofilm colony-forming unit (CFU) count, decreased biofilm lactic acid production, and increased biofilm calcium and phosphate content. The NACP+DMAHDM adhesive group had higher remineralization value than the NACP or DMAHDM alone adhesive group. SIGNIFICANCE: The NACP+DMAHDM adhesive was effective in remineralizing dentin lesion in a biofilm model. It is promising to use NACP+DMAHDM adhesive to protect bonded interface, inhibit secondary caries, and prolong the longevity of restoration.