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Recurrent caries remain a persistent concern, often linked to microleakage and a lack of bioactivity in contemporary dental composites. Our study aims to address this issue by developing a low-shrinkage-stress nanocomposite with antibiofilm and remineralization capabilities, thus countering the progression of recurrent caries. In the present study, we formulated low-shrinkage-stress nanocomposites by combining triethylene glycol divinylbenzyl ether and urethane dimethacrylate, incorporating dimethylaminododecyl methacrylate (DMADDM), along with nanoparticles of calcium fluoride (nCaF2) and nanoparticles of amorphous calcium phosphate (NACP). The biofilm viability, biofilm metabolic activity, lactic acid production, and ion release were evaluated. The novel formulations containing 3% DMADDM exhibited a potent antibiofilm activity, exhibiting a 4-log reduction in the human salivary biofilm CFUs compared to controls (p < 0.001). Additionally, significant reductions were observed in biofilm biomass and lactic acid (p < 0.05). By integrating both 10% NACP and 10% nCaF2 into one formulation, efficient ion release was achieved, yielding concentrations of 3.02 ± 0.21 mmol/L for Ca, 0.5 ± 0.05 mmol/L for P, and 0.37 ± 0.01 mmol/L for F ions. The innovative mixture of DMADDM, NACP, and nCaF2 displayed strong antibiofilm effects on salivary biofilm while concomitantly releasing a significant amount of remineralizing ions. This nanocomposite is a promising dental material with antibiofilm and remineralization capacities, with the potential to reduce polymerization-related microleakage and recurrent caries. [ABSTRACT FROM AUTHOR]

Objectives: Composites are commonly used for tooth restorations, but recurrent caries often lead to restoration failures due to polymerization shrinkage-stress-induced marginal leakage. The aims of this research were to: (1) develop novel low-shrinkage-stress (L.S.S.) nanocomposites containing dimethylaminododecyl methacrylate (DMADDM) with nanoparticles of calcium fluoride (nCaF2) or amorphous calcium phosphate (NACP) for remineralization; (2) investigate antibacterial and cytocompatibility properties. Methods: Nanocomposites were made by mixing triethylene glycol divinylbenzyl ether with urethane dimethacrylate containing 3% DMADDM, 20% nCaF2, and 20% NACP. Flexural strength, elastic modulus, antibacterial properties against Streptococcus mutans biofilms, and cytotoxicity against human gingival fibroblasts and dental pulp stem cells were tested. Results: Nanocomposites with DMADDM and nCaF2 or NACP had flexural strengths matching commercial composite control without bioactivity. The new nanocomposite provided potent antibacterial properties, reducing biofilm CFU by 6 logs, and reducing lactic acid synthesis and metabolic function of biofilms by 90%, compared to controls (p < 0.05). The new nanocomposites produced excellent cell viability matching commercial control (p > 0.05). Conclusions: Bioactive L.S.S. antibacterial nanocomposites with nCaF2 and NACP had excellent bioactivity without compromising mechanical and cytocompatible properties. The new nanocomposites are promising for a wide range of dental restorations by improving marginal integrity by reducing shrinkage stress, defending tooth structures, and minimizing cariogenic biofilms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to develop an antibacterial and calcium (Ca) and phosphate (P) rechargeable adhesive and investigate the effects of dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on dentin bonding, biofilm response, and repeated Ca and P ion recharge and re-release capability for the first time. Materials and methods: Pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol A dimethacrylate (EBPADMA), 2-hydroxyethyl methacrylate (HEMA), and bisphenol A glycidyl dimethacrylate (BisGMA) formed the adhesive (PEHB). Three groups were tested: (1) Scotchbond (SBMP, 3 M) control, (2) PEHB + 30% NACP, and (3) PEHB + 30% NACP + 5% DMAHDM. Specimens were tested for dentin shear bond strength, and Ca and P ion release, recharge, and re-release. Biofilm lactic acid production and colony-forming units (CFU) on resins were analyzed. Results: The four groups had similar dentin shear bond strengths (p > 0.1). Adhesive with DMAHDM showed significant decrease in metabolic activity, lactic acid production, and biofilm CFU (p < 0.05). The adhesives containing NACP released high levels of Ca and P ions initially and after being recharged. Conclusion: This study developed the first Ca and P ion-rechargeable and antibacterial adhesive, achieving strong antibacterial activity and Ca and P ion recharge and re-release for long-term remineralization. Clinical relevance: Considering the restoration-tooth bonded interface being the weak link and recurrent caries at the margins being the primary reason for restoration failures, this novel calcium phosphate-rechargeable and antibacterial adhesive is promising for a wide range of tooth-restoration applications to inhibit caries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The aims are: (a) To develop the first low‐shrinkage‐stress nanocomposite with antibacterial and remineralization capabilities through the incorporation of dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); (b) to investigate the effects of the new composite on biofilm inhibition, mechanical properties, shrinkage stress, and calcium (Ca) and phosphate (P) ion releases. The low‐shrinkage‐stress resin consisted of urethane dimethacrylate and triethylene glycol divinylbenzyl ether. Composite was formulated with 3% DMAHDM and 20% NACP. Mechanical properties, shrinkage stress, and degree of conversion were evaluated. Streptococcus mutans biofilm growth on composites was assessed. Ca and P ion releases were measured. The shrinkage stress of the low‐shrinkage‐stress composite containing 3% DMAHDM and 20% NACP was 36% lower than that of traditional composite control (p < 0.05), with similar degrees of conversion of 73.9%. The new composite decreased the biofilm colony‐forming unit by 4 log orders and substantially reduced biofilm lactic acid production compared to control composite (p < 0.05). Incorporating DMAHDM to the low‐shrinkage‐stress composite did not adversely affect the Ca and P ion release. A novel bioactive nanocomposite was developed with low shrinkage stress, strong antibiofilm activity, and high levels of ion release for remineralization, without undermining the mechanical properties and degree of conversion. [ABSTRACT FROM AUTHOR]

Herein, we investigated a biointeractive tooth sealing material consisted of dimethylaminohexadecyl methacrylate (DMAHDM) and amorphous calcium phosphate nanoparticles (NACPs) to address the above issues simultaneously. Of note, 5% DMAHDM was incorporated into the resin blend, and 20% NACP was added to inorganic filler content of dental formulations intended as dental sealants. The sealing materials were used to seal human extracted teeth. The sealed teeth were subjected to an early childhood caries (ECC) key pathogen (Candida albicans and Streptococcus mutans) biofilm model using a dynamic caries tooth model (CDC reactor). The biofilm growth over the sealed teeth was assessed via colony‐forming unit counting metabolic activity assays. The enamel surface hardness loss, degree of conversion, shear bond strength (SBS), and cytotoxicity were also investigated. Formulations having DMAHDM displayed antibacterial efficiency of 2.8–3.5 and 1.4–4.0 log inhibition for Streptococcus mutans and Candida albicans, respectively. Furthermore, the metabolic activity was reduced on the top of the sealed tooth with the biointeractive sealing materials (p <.05). The degree of conversion values was acceptable. The enamel surface hardness loss decreases (36 ± 9.8%) when in contact with the biointeractive tooth sealing material. The SBS of the combined formulation (5% DMAHDM + 20% NACP) was lower than commercial sealant but similar to experimental control. The investigated sealing material holds valuable dual antibacterial and antifungal activities associated with a reduced mineral loss against the cariogenic challenge promoted by ECC key pathogens. [ABSTRACT FROM AUTHOR]

Short-term studies on calcium-phosphate (CaP) ion-rechargeable composites were reported. The long-term rechargeability is important but unknown. The objectives of this study were to investigate nanocomposite with strong antibacterial and ion-recharge capabilities containing dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and evaluate long-term ion-recharge by testing for 12 cycles (taking 6 months to complete) for the first time. Three groups were tested: (1) Heliomolar control; (2) Resin+20%NACP+50%glass; (3) Resin+3%DMAHDM+20%NACP+50%glass. Biofilm acid and colony-forming units (CFU) were measured. Ion-recharge was tested for 12 cycles. NACP-DMAHDM composite reduced biofilm acid, and reduced CFU by 4 logs. High levels of ion releases were maintained throughout 12 cycles of recharge, maintaining steady-state releases without reduction in 6 months (p>0.1), representing long-term remineralization potential. Bioactive nanocomposite demonstrated long-term ion-rechargeability for the first time, showed remineralization and potent anti-biofilm functions, with promise for tooth restorations to combat caries. [ABSTRACT FROM AUTHOR]

Advancements in materials used for restorative and preventive treatment is being directed toward "bio-active" functionality. Incorporation of filler particles that release active components is a popular method to create bio-active materials, and many approaches are available to develop fillers with the ability to release components that provide "bio-protective" or "bio-promoting" properties; e.g. metal/calcium phosphate nanoparticles, multiple ion-releasing glass fillers, and non-biodegradable polymer particles. In this review paper, recent developments in cutting-edge filler technologies to release bio-active components are addressed and summarized according to their usefulness and functions, including control of bacterial infection, tooth strengthening, and promotion of tissue regeneration. [ABSTRACT FROM AUTHOR]

The objectives were to develop a novel rechargeable cement containing amorphous calcium-phosphate nanoparticles (nanoACP) to suppress tooth decay. Five cements were made with: (1) 60% glass particles (experimental control); (2) 40% glass+20% nanoACP; (3) 30% glass+30% nanoACP; (4) 20% glass+40% nanoACP; (5) 10% glass+50% nanoACP. Groups 1-4 had enamel bond strengths similar to Transbond XT (3M) and Vitremer (3M) (p>0.1). The nanoACP cement had calcium and phosphate ion release which increased with increasing nanoACP fillers. The recharged cement had substantial ion re-release continuously for 14 days after a single recharge. Ion re-release did not decrease with increasing recharge/re-release cycles. Groups 3-5 maintained a safe pH of medium (>5.5); however, control cements had cariogenic pH of medium (<4.5) due to biofilm acid. Therefore, nanoACP cement (1) had good bond strength to enamel, (2) possessed calcium and phosphate ion recharge/re-release capability, and (3) raised biofilm pH to a safe level to inhibit caries. [ABSTRACT FROM AUTHOR]

Literature search revealed no systematic report on iron oxide nanoparticle-incorporating calcium phosphate cement scaffolds (IONP-CPC). The objectives of this study were to: (1) use γFe2O3 nanoparticles (γIONPs) and αFe2O3 nanoparticles (αIONPs) to develop novel IONP-CPC scaffolds, and (2) investigate human dental pulp stem cells (hDPSCs) seeding on IONP-CPC for bone tissue engineering for the first time. IONP-CPC scaffolds were fabricated. Physiochemical properties of IONP-CPC scaffolds were characterized. hDPSC seeding on scaffolds, cell proliferation, osteogenic differentiation and bone matrix mineral synthesis by cells were measured. Our data demonstrated that the osteogenic differentiation of hDPSCs was markedly enhanced via IONP incorporation into CPC. Substantial increases (about three folds) in ALP activity and osteogenic gene expressions were achieved over those without IONPs. Bone matrix mineral synthesis by the cells was increased by two- to three folds over that without IONPs. The enhanced cellular osteogenesis was attributed to: (1) the surface nanotopography of IONP-CPC scaffold, and (2) the cell internalization of IONPs released from IONP-CPC scaffold. Our results demonstrate that the novel CPC functionalized with IONPs is promising to promote osteoinduction and bone regeneration. In conclusion, it is highly promising to incorporate γIONPs and αIONPs into CPC scaffold for bone tissue engineering, yielding substantially better stem cell attachment, spreading and osteogenic differentiation, and much greater bone mineral synthesis by the seeded cells. Therefore, novel CPC scaffolds containing γIONPs and αIONPs are promising for dental, craniofacial and orthopaedic applications to substantially enhance bone regeneration. [ABSTRACT FROM AUTHOR]

Metformin is an old and widely accepted first-line drug for treating type 2 diabetes. Our previous studies demonstrate that metformin can stimulate the osteo/odontogenic differentiation of human-induced pluripotent stem cell-derived mesenchymal stem cells and human dental pulp cells (DPCs). Due to the rapid dilution of metformin from the defect area, the aim of this study was to develop a drug delivery system with controlled release of metformin to promote cell viability and odontogenic differentiation of DPCs favoring dentin regeneration. Calcium phosphate cement (CPC) containing chitosan and metformin as a scaffold was synthesized. DPCs were seeded onto the scaffold, and the viability and proliferation were evaluated at several time points. For osteogenic differentiation analysis, alkaline phosphatase (ALP) activity was tested, cells were stained with Alizarin Red, and the expression of odontogenic markers was evaluated by real-time polymerase chain reaction. DPCs remained viable and attached well to the CPC-chitosan composite scaffold. Moreover, the addition of metformin to the CPC-chitosan composite did not adversely affect cell proliferation, compared to that of CPC control. Our data further revealed that the novel CPC-chitosan-metformin composite enhanced the odontogenic differentiation of DPCs, as evidenced by higher ALP activity, elevated expression of odontoblastic markers, and strong mineral deposition. These results suggest that the new CPC-chitosan-metformin composite is a highly promising scaffold with the potential for tissue engineering applications including dentin regeneration. [ABSTRACT FROM AUTHOR]

Enamel demineralization is destructive, esthetically compromised, and costly complications for orthodontic patients. Nano-sized amorphous calcium phosphate (NACP) has been explored to address this challenge. The 20% NACP-loaded ortho-cement notably exhibited favorable behavior on reducing demineralization of enamel around brackets in a caries model designed to simulate the carious attack. The 20% NACP-loaded ortho-cement markedly promotes higher calcium and phosphate release at a low pH, and the mineral loss was almost two fold lower and carious lesion depth decreased the by 1/3. This novel approach is promising co-adjuvant route for prevention of dental caries dissemination in millions of patients under orthodontic treatment. [ABSTRACT FROM PUBLISHER]

Objectives. The objectives of this study were to: (1) develop a bioactive multifunctional composite (BMC) via nanoparticles of amorphous calcium phosphate (NACP), 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg); and (2) investigate the effects of combined BMC + poly (amido amine) (PAMAM) on remineralization of demineralized root dentin in a cyclic artificial saliva/lactic acid environment for the first time. Methods. Root dentin specimens were prepared and demineralized with 37% phosphoric acid for 15 s. Four groups were prepared: (1) root dentin control; (2) root dentin with BMC; (3) root dentin with PAMAM; (4) root dentin with BMC + PAMAM. Specimens were treated with a cyclic artificial saliva/lactic acid regimen for 21 days. Calcium (Ca) and phosphate (P) ion concentrations and acid neutralization were determined. The remineralized root dentin specimens were examined via hardness testing and scanning electron microscopy (SEM). Results. Mechanical properties of BMC were similar to commercial control composites (p = 0.913). BMC had excellent Ca and P ion release and acid-neutralization capability. BMC or PAMAM alone each achieved slight mineral regeneration in demineralized root dentin. The combined BMC + PAMAM induced the greatest root dentin remineralization, and increased the hardness of pre-demineralized root dentin to match that of healthy root dentin (p = 0.521). Significance. The excellent root dentin remineralization effects of BMC + PAMAM were demonstrated for the first time. BMC + PAMAM induced effective and complete root dentin remineralization in an acid challenge environment. The novel BMC + PAMAM method is promising for Class V and other restorations to remineralize and protect tooth structures. [ABSTRACT FROM AUTHOR]

Because of its moldability and excellent osteoconductivity, calcium phosphate cement (CPC) is highly promising for craniofacial and orthopedic applications. The objectives of this study were to investigate the response of human mesenchymal stem cells (hMSCs) to a high‐strength CPC‐chitosan scaffold and to examine cell proliferation and osteogenic differentiation. hMSCs were seeded onto CPC‐chitosan composite, CPC control, and tissue culture polystyrene (TCPS). Alkaline phosphatase activity (ALP) and mineralization of hMSCs were measured. CPC‐chitosan had a flexural strength (mean ± SD; n = 5) of (19.5 ± 1.4) MPa, higher than (8.0 ± 1.4) MPa of CPC control (p < 0.05). The percentage of live hMSCs on CPC‐chitosan was (90.5 ± 1.3)% at 8 days, matching (90.7 ± 3.8)% of CPC control (p > 0.1). The CPC‐chitosan surface area covered by the attached hMSCs increased from (51 ± 11)% at 1 day to (90 ± 4)% at 8 days (p < 0.05), matching those of CPC control (p > 0.1). Hence, the CPC strength was significantly increased via chitosan without compromising the hMSC response. At 8 days, there was a significant increase in ALP of cells in osteogenic media (10.99 ± 0.93) [(mM pNpp/min)/(μg DNA)] versus control media (3.62 ± 0.40) (p < 0.05). hMSCs in osteogenic media exhibited greater mineralization area of (47.5 ± 19.7)% compared with (6.1 ± 2.3)% in control medium on TCPS (p < 0.05). In conclusion, hMSCs showed excellent attachment and viability on the strong and tough CPC‐chitosan scaffold, matching the hMSC response on CPC control. hMSCs were successfully differentiated down the osteogenic lineage. Hence, the strong, in situ hardening CPC‐chitosan scaffold may be useful as a moderate load‐bearing vehicle to deliver hMSCs for maxillofacial and orthopedic bone tissue engineering. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [ABSTRACT FROM AUTHOR]

The two main challenges facing dental composite restorations are secondary caries and bulk fracture. Previous studies developed whisker‐reinforced Ca‐PO4 composites that were relatively opaque. The objective of this study was to develop an esthetic glass particle‐reinforced, photo‐cured calcium phosphate composite. Tetracalcium phosphate (TTCP) particles were incorporated into a resin for Ca and PO4 release, while glass particles provided reinforcement. Ion release and mechanical properties were measured after immersion in solutions with pH of 7, 5.5, and 4. For the composite containing 40% mass fraction of TTCP, incorporating glass fillers increased the strength (p < 0.05). Flexural strength (Mean ± SD; n = 6) at 30% glass was 99 ± 18 MPa, higher than 54 ± 20 MPa at 0% glass (p < 0.05). Elastic modulus was 11 GPa at 30% glass, compared to 2 GPa without glass. At 28 days, the released Ca ion concentration was 4.61 ± 0.18 mmol/L at pH of 4, much higher than 1.14 ± 0.07 at pH of 5.5, and 0.27 ± 0.01 at pH of 7 (p < 0.05). PO4 release was also dramatically increased at cariogenic, acidic pH. The TTCP‐glass composite had strength 2–3 fold that of a resin‐modified glass ionomer control. In conclusion, the photo‐cured TTCP‐glass composite was "smart" and substantially increased the Ca and PO4 release when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit tooth caries. Its mechanical properties were significantly higher than previous Ca, PO4, and fluoride releasing restoratives. Hence, the photo‐cured TTCP‐glass composite may have potential to provide the necessary combination of load‐bearing and caries‐inhibiting capabilities. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [ABSTRACT FROM AUTHOR]

(1) Background: Vascularization remains a critical challenge in bone tissue engineering. The objective of this study was to prevascularize calcium phosphate cement (CPC) scaffold by co-culturing human periodontal ligament stem cells (hPDLSCs) and human umbilical vein endothelial cells (hUVECs) for the first time; (2) Methods: hPDLSCs and/or hUVECs were seeded on CPC scaffolds. Three groups were tested: (i) hUVEC group (hUVECs on CPC); (ii) hPDLSC group (hPDLSCs on CPC); (iii) co-culture group (hPDLSCs + hUVECs on CPC). Osteogenic differentiation, bone mineral synthesis, and microcapillary-like structures were evaluated; (3) Results: Angiogenic gene expressions of co-culture group were 6–9 fold those of monoculture. vWF expression of co-culture group was 3 times lower than hUVEC-monoculture group. Osteogenic expressions of co-culture group were 2–3 folds those of the hPDLSC-monoculture group. ALP activity and bone mineral synthesis of co-culture were much higher than hPDLSC-monoculture group. Co-culture group formed capillary-like structures at 14–21 days. Vessel length and junction numbers increased with time; (4) Conclusions: The hUVECs + hPDLSCs co-culture on CPC scaffold achieved excellent osteogenic and angiogenic capability in vitro for the first time, generating prevascularized networks. The hPDLSCs + hUVECs co-culture had much better osteogenesis and angiogenesis than monoculture. CPC scaffolds prevacularized via hPDLSCs + hUVECs are promising for dental, craniofacial, and orthopedic applications. [ABSTRACT FROM AUTHOR]

Calcium phosphate cement (CPC) sets in situ and forms apatite with excellent osteoconductivity and bone‐replacement capability. The objectives of this study were to formulate an injectable tetracalcium phosphate‐dicalcium phosphate cement (CPCD), and investigate the powder/liquid ratio and needle‐size effects. The injection force (mean ± SD; n = 4) to extrude the paste increased from (8 ± 2) N using a 10‐gauge needle to (144 ± 17) N using a 21‐gauge needle (p < 0.05). With the 10‐gauge needle, the mass percentage of extruded paste was (95 ± 4)% at a powder/liquid ratio of 3; it decreased to (70 ± 12)% at powder/liquid = 3.5 (p < 0.05). A relationship was established between injection force, F, and needle lumen cross‐sectional area, A: F = 5.0 + 38.7/A0.8. Flexural strength, S, (mean ± SD; n = 5) increased from (5.3 ± 0.8) MPa at powder/liquid= 2 to (11.0 ± 0.8) MPa at powder/liquid = 3.5 (p < 0.05). Pore volume fraction, P, ranged from 62.4% to 47.9%. A relationship was established: S = 47.7 × (1 – P)2.3. The strength of the injectable CPCD matched/exceeded the reported strengths of sintered porous hydroxyapatite implants that required machining. The novel injectable CPCD with a relatively high strength may be useful in filling defects with limited accessibility such as periodontal repair and tooth root‐canal fillings, and in minimally‐invasive techniques such as percutaneous vertebroplasty to fill the lesions and to strengthen the osteoporotic bone. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [ABSTRACT FROM AUTHOR]

Calcium phosphate cement (CPC) sets in situ to form resorbable hydroxyapatite and is promising for orthopaedic applications. However, it requires on-site powder-liquid mixing during surgery, which prolongs surgical time and raises concerns of inhomogeneous mixing. The objective of this study was to develop a premixed CPC scaffold with macropores suitable for tissue ingrowth. To avoid the on-site powder-liquid mixing, the CPC paste was mixed in advance and did not set in storage; it set only after placement in a physiological solution. Using 30% and 40% mass fractions of mannitol porogen, the premixed CPC scaffold with fibers had flexural strength (mean ± sd; n = 5) of (3.9 ± 1.4) MPa and (1.8 ± 0.8) MPa, respectively. The scaffold porosity reached (68.6 ± 0.7)% and (74.7 ± 1.2)%, respectively. Osteoblast cells colonized in the surface macropores of the scaffold and attached to the hydroxyapatite crystals. Cell viability values for the premixed CPC scaffold was not significantly different from that of a conventional non-premixed CPC known to be biocompatible ( P > 0.1). In conclusion, using fast-dissolving porogen and slow-dissolving fibers, a premixed macroporous CPC scaffold was developed with strength approaching the reported strengths of sintered porous hydroxyapatite implants and cancellous bone, and non-cytotoxicity similar to a biocompatible non-premixed CPC. [ABSTRACT FROM AUTHOR]

Clinical data indicate that secondary caries and restoration fracture are the most common problems facing tooth restorations. Our ultimate goal was to develop mechanically‐strong and caries‐inhibiting dental composites. The specific goal of this pilot study was to understand the relationships between composite properties and the ratio of reinforcement filler/releasing filler. Nanoparticles of monocalcium phosphate monohydrate (MCPM) were synthesized and incorporated into a dental resin for the first time. Silicon carbide whiskers were fused with silica nanoparticles and mixed with the MCPM particles at MCPM/whisker mass ratios of 1:0, 2:1, 1:1, 1:2, and 0:1. The composites were immersed for 1–56 days to measure Ca and PO4 release. When the MCPM/whisker ratio was changed from 0:1 to 1:2, the composite flexural strength (mean ± SD; n = 5) decreased from 174 ± 26 MPa to 138 ± 9 MPa (p < 0.05). A commercial nonreleasing composite had a strength of 112 ± 14 MPa. When the MCPM/whisker ratio was changed from 1:2 to 1:1, the Ca concentration at 56 days increased from 0.77 ± 0.04 mmol/L to 1.74 ± 0.06 mmol/L (p < 0.05). The corresponding PO4 concentration increased from 3.88 ± 0.21 mmol/L to 9.95 ± 0.69 mmol/L (p < 0.05). Relationships were established between the amount of release and the MCPM volume fraction vMCPM in the resin: [Ca]= 42.9 v MCPM2.7, and [PO4] = 48.7 v MCPM1.4. In summary, the method of combining nanosized releasing fillers with reinforcing fillers yielded Ca‐ and PO4‐releasing composites with mechanical properties matching or exceeding a commercial stress‐bearing, nonreleasing composite. This method may be applicable to the use of other Ca–PO4 fillers in developing composites with high stress‐bearing and caries‐preventing capabilities, a combination not yet available in any dental materials. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [ABSTRACT FROM AUTHOR]

Calcium phosphate cement (CPC) can self-harden in vivo to form hydroxyapatite (HA) with excellent osteoconductivity. In recent studies, CPC-chitosan composites are developed with high mechanical strength and washout resistance. The objectives of the present study are to optimize the setting time and mechanical properties of a CPC-chitosan composite by tailoring the chitosan content, and to evaluate the bioresorbability by using an in vitro dissolution model. Six chitosan mass fractions are tested: 0, 10, 15, 20, 25, and 30%. Specimens are immersed in solutions with pH ranging from 3.5 to 5 to simulate the acidic environments produced by osteoclasts in vivo. Dissolution is measured as the fraction of mass loss versus immersion time from 7 d to 28 d. The CPC-chitosan composite with 20% by mass chitosan has a setting time (mean±SD; n=4) of 13±1 min, significantly less than 87±7 min for CPC control without chitosan (p<0.05). The composite flexural strength (mean ± SD; n=6) was 14±2MPa, significantly higher than 4±1MPa of CPC control (p<0.05). At an intermediate pH of 4.5, the fraction of mass loss for CPC with 20% chitosan and CPC control without chitosan are not significantly different (p > 0.1). The dissolution rates (fraction of mass loss per day, %/d) were 1.05 for CPC control and 1.08 for CPC-chitosan. In summary, a CPC-chitosan composite is developed with fast-setting and a flexural strength three-fold of that of CPC control without chitosan. Both materials are soluble in acidic environments, indicating that adding chitosan did not compromise the bioresorbability of CPC. The strong and resorbable CPC-chitosan composite may be useful in moderate stress-bearing craniofacial and orthopedic repairs. [ABSTRACT FROM AUTHOR]

Calcium phosphate cement (CPC) hardens in situ to form solid hydroxyapatite, can conform to complex cavity shapes without machining, has excellent osteoconductivity, and is able to be resorbed and replaced by new bone. Therefore, CPC is promising for use in craniofacial and orthopaedic repairs. However, the low strength and lack of macroporosity of CPC limit its use. The aim of the present study was to increase the strength and toughness of CPC while creating macropores suitable for cell infiltration and bone ingrowth, and to investigate the effects of chitosan and mesh reinforcement on the composite properties. Specimens were self-hardened in 3 mm×4 mm×25 mm molds, immersed in a physiological solution for 1–84 d, and tested in three-point flexure. After 1 d, the unreinforced CPC control had a flexural strength (mean±s.d.; n=6) of (3.3±0.4) MPa. The incorporation of chitosan or mesh into CPC increased the strength to (11.9±0.8) and (21.3±2.7) MPa, respectively. The incorporation of both chitosan and mesh synergistically into CPC dramatically increased the strength to (43.2±4.1) MPa. The work-of-fracture (WOF) (toughness) was also increased by two orders of magnitude. After 84 d immersion in a simulated physiological solution, the meshes in CPC dissolved and formed interconnected cylindrical macropores. The novel CPC scaffold had a flexural strength 39% higher, and WOF 256% higher than the conventional CPC without macropores. The new composite had an elastic modulus within the range for cortical bone and cancellous bone, and a flexural strength higher than those for cancellous bone and sintered porous hydroxyapatite implants. In conclusion, combining two different reinforcing agents together in self-hardening CPC resulted in superior synergistic strengthening compared to the traditional use of a single reinforcing agent. The strong and macroprous CPC scaffold may be useful in stress-bearing craniofacial and orthopaedic repairs. [Copyright &y& Elsevier]

Secondary caries often occurs at the tooth-composite margins. This study developed a novel bioactive composite containing DMAHDM (dimethylaminohexadecyl methacrylate) and NACP (nanoparticles of amorphous calcium phosphate), inhibiting caries at the enamel restoration margins in an in vitro saliva-derived biofilm secondary caries model for the first time. Four composites were tested: (1) Heliomolar nanocomposite, (2) 0% DMAHDM + 0% NACP, (3) 3% DMAHDM + 0% NACP, (D) 3% DMAHDM + 30% NACP. Saliva-derived biofilms were tested for antibacterial effects of the composites. Bovine enamel restorations were cultured with biofilms, Ca and P ion release of nanocomposite and enamel hardness at the enamel restoration margins was measured. Incorporation of DMAHDM and NACP into composite did not affect the mechanical properties (p > 0.05). The biofilms' CFU (colony-forming units) were reduced by 2 logs via DMAHDM (p < 0.05). Ca and P ion release of the nanocomposite was increased at cariogenic low pH. Enamel hardness at the margins for DMAHDM group was 25% higher than control (p < 0.05). With DMAHDM + NACP, the enamel hardness was the greatest and about 50% higher than control (p < 0.05). Therefore, the novel composite containing DMAHDM and NACP was strongly antibacterial and inhibited enamel demineralization, resulting in enamel hardness at the margins under biofilms that approached the hardness of healthy enamel. [ABSTRACT FROM AUTHOR]

Dental sealants with antibacterial and remineralizing properties are promising for caries prevention among children and adolescents. The application of nanotechnology and polymer development have enabled nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) to emerge as anti-caries strategies via resin-based dental materials. Our objectives in this study were to (1) incorporate different mass fractions of NACP into a parental rechargeable and antibacterial sealant; (2) investigate the effects on mechanical performance, and (3) assess how the variations in NACP concentration would affect the calcium (Ca) and phosphate (PO4) ion release and re-chargeability over time. NACP were synthesized using a spray-drying technique and incorporated at mass fractions of 0, 10, 20 and 30%. Flexural strength, flexural modulus, and flowability were assessed for mechanical and physical performance. Ca and PO4 ion release were measured over 70 days, and three ion recharging cycles were performed for re-chargeability. The impact of the loading percentage of NACP upon the sealant's performance was evaluated, and the optimized formulation was eventually selected. The experimental sealant at 20% NACP had flexural strength and flexural modulus of 79.5 ± 8.4 MPa and 4.2 ± 0.4 GPa, respectively, while the flexural strength and flexural modulus of a commercial sealant control were 70.7 ± 5.5 MPa (p > 0.05) and 3.3 ± 0.5 GPa (p < 0.05), respectively. A significant reduction in flow was observed in the experimental sealant at 30% NACP (p < 0.05). Increasing the NACP mass fraction increased the ion release. The sealant formulation with NACP at 20% displayed desirable mechanical performance and ideal flow and handling properties, and also showed high levels of long-term Ca and PO4 ion release and excellent recharge capabilities. The findings provide fundamental data for the development of a new generation of antibacterial and rechargeable Ca and PO4 dental sealants to promote remineralization and inhibit caries. [ABSTRACT FROM AUTHOR]

Objectives: Fracture and secondary caries are the primary reasons for dental restoration failure. The objective of this study was to develop a self-healing composite to heal cracks, while containing dimethylaminohexadecyl methacrylate (DMAHDM) for antibacterial function and nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Methods: Microcapsules were synthesized with poly(urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid. Composite contained 20 mass% of NACP and 35% glass fillers. In addition, composite contained 0%, 2.5%, 5%, 7.5%, or 10% of microcapsules. A single edge Vnotched beam method measured fracture toughness (KIC) and self-healing efficiency. A dental plaque microcosm biofilm model was used to test the antibacterial properties. Results: Incorporation of microcapsules up to 7.5% into the composite did not adversely affect the mechanical properties (p > 0.1). Successful self-healing was achieved, with KIC recovery of 65-81% (mean ± sd; n = 6) to regain the load-bearing capability after composite fracture. The self-healing DMAHDM-NACP composite displayed a strong antibacterial potency, inhibiting biofilm viability and lactic acid production, and reducing colony-forming units by 3-4 orders of magnitude, compared to control composite without DMAHDM. Conclusions: A dental composite was developed with triple benefits of self-healing after fracture, antibacterial activity, and remineralization capability for the first time. Clinical significance: The self-healing, antibacterial and remineralizing composite may be promising for tooth cavity restorations to combat bulk fracture and secondary caries. The method of using triple agents (self-healing microcapsules, DMAHDM, and NACP) may have wide applicability to other dental composites, adhesives, sealants and cements. [ABSTRACT FROM AUTHOR]