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A common reason for dental composite restoration failure is recurrent caries at the margins. Our objectives were to: (1) develop a novel low-shrinkage-stress, antibacterial and remineralizing resin composite; (2) evaluate the effects of dimethylaminohexadecyl methacrylate (DMAHDM) on mechanical properties, biofilm inhibition, calcium (Ca) and phosphate (P) ion release, degree of conversion, and shrinkage stress on the new low-shrinkage-stress resin composite for the first time. The resin consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) with high resistance to salivary hydrolytic degradation. Composites were made with 0%–8% of DMAHDM for antibacterial activity, and 20% of nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Mechanical properties and Streptococcus mutans biofilm growth on composites were assessed. Ca and P ion releases, degree of conversion and shrinkage stress were evaluated. Adding 2–5% DMAHDM and 20% NACP into the low-shrinkage-stress composite did not compromise the mechanical properties (p > 0.05). The incorporation of DMAHDM greatly reduced S. mutans biofilm colony-forming units by 2–5 log and lactic acid production by 7 folds, compared to a commercial composite (p < 0.05). Adding 5% DMAHDM did not compromise the Ca and P ion release. The low-shrinkage-stress composite maintained a high degree of conversion of approximately 70%, while reducing the shrinkage stress by 37%, compared to a commercial control (p < 0.05). The bioactive low-shrinkage-stress composite reduced the polymerization shrinkage stress, without compromising other properties. Increasing the DMAHDM content increased the antibacterial effect in a dose-dependent manner. [ABSTRACT FROM AUTHOR]

Recurrent dental caries is one of the main reasons for resin composite restoration failures. This study aimed to: (1) develop a bioactive, low-shrinkage-stress, antibacterial and remineralizing composite and evaluate the sustainability of its antibacterial effect against Streptococcus mutans (S. mutans) biofilms; and (2) evaluate the remineralization and cariostatic potential of the composite containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM), using dentin hardness measurement and a biofilm-induced recurrent caries model. The antibacterial and remineralizing low-shrinkage-stress composite consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE), 3% DMAHDM and 20% NACP. S. mutans biofilm was used to evaluate antibiofilm activity, before and after 3 months of composite aging in acidic solution. Human dentin was used to develop a recurrent caries biofilm-model. Adding DMAHDM and NACP into low shrinkage-stress composite did not compromise the flexural strength. The low-shrinkage-stress composite with DMAHDM achieved substantial reductions in biofilm colony-forming units (CFU), lactic acid production, and biofilm biomass (p < 0.05). The low-shrinkage-stress DMAHDM+NACP composite exhibited no significant difference in antibacterial performance before and after 3 months of aging, demonstrating long-term antibacterial activity. Under S. mutans biofilm acidic attack, dentin hardness (GPa) was 0.24 ± 0.04 for commercial control, and 0.23 ± 0.03 for experimental control, but significantly higher at 0.34 ± 0.03 for DMAHDM+NACP group (p < 0.05). At an instrumental compliance of 0.33 μm/N, the polymerization shrinkage stress of the new composite was 36% lower than that of a traditional composite (p < 0.05). The triple strategy of antibacterial, remineralization and lower shrinkage-stress has great potential to inhibit recurrent caries and increase restoration longevity. Statement of Significance Polymerization shrinkage stress, masticatory load over time as well as biochemical degradation can lead to marginal failure and secondary caries. The present study developed a new low-shrinkage-stress, antibacterial and remineralizing dental nanocomposite. Polymerization shrinkage stress was greatly reduced, biofilm acid production was inhibited, and tooth dentin mineral and hardness were preserved. The antibacterial composite possessed a long-lasting antibiofilm effect against cariogenic bacteria S. mutans. The new bioactive nanocomposite has the potential to suppress recurrent caries at the restoration margins, protects tooth structures, and increases restoration longevity. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Objective There has been no report on the effect of incorporating protein repellent 2-methacryloyloxyethyl phosphorylcholine (MPC) into a composite containing nanoparticles of amorphous calcium phosphate (NACP) on calcium (Ca) and phosphate (P) ion rechargeability. The objectives of this study were to develop a Ca and P ion-rechargeable and protein-repellent composite for the first time, and investigate the effects of MPC and NACP on mechanical properties, protein-repellency, anti-biofilm effects, and Ca and P ion recharge and re-release. Methods NACP were synthesized using a spray-drying technique. The resin contained ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). Three NACP composites were made with 0 (control), 1.5%, and 3% of MPC. NACP (20%) and glass particles (50%) were also added into the resin. Protein adsorption was measured using a micro-bicinchoninic acid (BCA) method. A human saliva microcosm biofilm model was used to determine biofilm metabolic activity, lactic acid, and colony-forming units (CFU). Ca and P ion recharge and re-release were measured using a spectrophotometric method. Results Flexural strengths and moduli of CaP-rechargeable composites matched those of a commercial composite without CaP rechargeability (p > 0.1). Adding 1.5% and 3% MPC reduced protein adsorption to 1/3 and 1/5, respectively, that of commercial composite (p < 0.05). Adding 3% MPC suppressed biofilm metabolic activity and lactic acid production, and reduced biofilm CFU by nearly 2 logs. All three NACP composites had excellent ion rechargeability and higher levels of ion re-releases. One recharge yielded continuous ion release for 21 days. The release was maintained at the same level with increasing number of recharge cycles, indicating long-term ion release. Incorporation of MPC did not compromise the CaP ion rechargeability. Significance Incorporating 3% MPC into NACP nanocomposite greatly reduced protein adsorption, biofilm growth and lactic acid, decreasing biofilm CFU by nearly 2 logs, without compromising Ca and P recharge. This protein-repellent NACP-MPC rechargeable composite with long-term remineralization is promising for tooth restorations to inhibit secondary caries. [ABSTRACT FROM AUTHOR]

Objective Secondary caries is a primary reason for dental restoration failures. The objective of this study was to investigate the remineralization of human dentin lesions in vitro via restorations using nanocomposites containing nanoparticles of amorphous calcium phosphate (NACP) or NACP and tetracalcium phosphate (TTCP) for the first time. Methods NACP was synthesized by a spray-drying technique and incorporated into a resin consisting of ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). After restoring the dentin lesions with nanocomposites as well as a non-releasing commercial composite control, the specimens were treated with cyclic demineralization (pH 4, 1 h per day) and remineralization (pH 7, 23 h per day) for 4 or 8 weeks. Calcium (Ca) and phosphate (P) ion releases from composites were measured. Dentin lesion remineralization was measured at 4 and 8 weeks by transverse microradiography (TMR). Results Lowering the pH increased ion release of NACP and NACP-TTCP composites. At 56 days, the released Ca concentration in mmol/L (mean ± SD; n = 3) was (13.39 ± 0.72) at pH 4, much higher than (1.19 ± 0.06) at pH 7 (p < 0.05). At 56 days, P ion concentration was (5.59 ± 0.28) at pH 4, much higher than (0.26 ± 0.01) at pH 7 (p < 0.05). Quantitative microradiography showed typical subsurface dentin lesions prior to the cyclic demineralization/remineralization treatment, and dentin remineralization via NACP and NACP-TTCP composites after 4 and 8 weeks of treatment. At 8 weeks, NACP nanocomposite achieved dentin lesion remineralization (mean ± SD; n = 15) of (48.2 ± 11.0)%, much higher than (5.0 ± 7.2)% for dentin in commercial composite group after the same cyclic demineralization/remineralization regimen (p < 0.05). Significance Novel NACP-based nanocomposites were demonstrated to achieve dentin lesion remineralization for the first time. These results, coupled with acid-neutralization and good mechanical properties shown previously, indicate that the NACP-based nanocomposites are promising for restorations to inhibit caries and protect tooth structures. [ABSTRACT FROM AUTHOR]

The objectives of this study were to develop a novel method to remineralize dentin lesions, and investigate the remineralization effects of poly (amido amine) (PAMAM) dendrimer plus a bonding agent with nanoparticles of amorphous calcium phosphate (NACP) in a cyclic artificial saliva/lactic acid environment for the first time. Dentin lesions were produced via phosphoric acid. Four groups were tested: (1) dentin control, (2) dentin with PAMAM, (3) dentin with NACP bonding agent, and (4) dentin with PAMAM plus NACP bonding agent. Specimens were treated with cyclic artificial saliva/lactic acid. The remineralized dentin was examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). NACP bonding agent yielded a dentin shear bond strength similar to commercial controls (Prime & Bond NT, Dentsply; Scotchbond Multi-purpose, 3M) ( p > 0.1). Increasing NACP in bonding agent from 0 to 40% did not affect bond strength. NACP bonding agent neutralized the acid and released Ca ions with concentrations of 4 to 20 mmol/L, and P ions of 2 to 9 mmol/L. PAMAM or NACP bonding agent alone achieved slight remineralization. The PAMAM + NACP group achieved the greatest dentin remineralization p < 0.05). At 20 days, PAMAM + NACP increased the hardness of pre-demineralized dentin to reach the normal dentin hardness ( p > 0.1). In conclusion, superior remineralization of PAMAM + NACP bonding agent was demonstrated for the first time. PAMAM + NACP bonding agent induced dentin remineralization under acid challenge, when conventional remineralization methods such as PAMAM alone did not work well. The novel PAMAM + NACP bonding agent method is promising to improve the longevity of resin-dentin bonds, inhibit caries, and protect teeth. [ABSTRACT FROM AUTHOR]

Objectives The objective of this study was to investigate the effects of poly (amido amine) (PAMAM), composite with nanoparticles of amorphous calcium phosphate (NACP), and the combined PAMAM + NACP nanocomposite treatment, on remineralization of demineralized dentin in a cyclic artificial saliva/lactic acid environment for the first time. Methods Dentin specimens were prepared and demineralized with 37% phosphoric acid for 15 s. Four groups were prepared: (1) dentin control, (2) dentin coated with PAMAM, (3) dentin with NACP composite, (4) dentin with PAMAM + NACP. Specimens were treated with a cyclic artificial saliva/lactic acid regimen for 21 days. Acid neutralization and calcium (Ca) and phosphate (P) ion concentrations were measured. The remineralized dentin specimens were examined by scanning electron microscopy (SEM) and hardness testing. Results NACP nanocomposite had mechanical properties similar to commercial control composites (p > 0.1). NACP composite had acid-neutralization and Ca and P ion release capability. PAMAM or NACP composite each alone achieved remineralization and increased the hardness of demineralized dentin (p < 0.05). PAMAM + NACP nanocomposite achieved the greatest mineral regeneration in demineralized dentin and the greatest hardness increase in demineralized dentin, which approached the hardness of healthy dentin (p > 0.1). Significance The superior remineralization efficacy of PAMAM + NACP was demonstrated for the first time. PAMAM + NACP induced remineralization in demineralized dentin in an acid challenge environment, when conventional remineralization methods such as PAMAM did not work well. The novel PAMAM + NACP composite approach is promising for a wide range of dental applications to inhibit caries and protect tooth structures. [ABSTRACT FROM AUTHOR]

Objectives Calcium phosphate (CaP) composites with Ca and P ion release can remineralize tooth lesions and inhibit caries. But the ion release lasts only a few months. The objectives of this study were to develop rechargeable CaP dental composite for the first time, and investigate the Ca and P recharge and re-release of composites with nanoparticles of amorphous calcium phosphate (NACP) to achieve long-term inhibition of caries. Methods Three NACP nanocomposites were fabricated with resin matrix of: (1) bisphenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) at 1:1 mass ratio (referred to as BT group); (2) pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA) at 1:1 ratio (PE group); (3) BisGMA, TEGDMA, and Bis[2-(methacryloyloxy)ethyl] phosphate (BisMEP) at 2:1:1 ratio (BTM group). Each resin was filled with 20% NACP and 50% glass particles, and the composite was photo-cured. Specimens were tested for flexural strength and elastic modulus, Ca and P ion release, and Ca and P ion recharge and re-release. Results NACP nanocomposites had strengths 3-fold of, and elastic moduli similar to, commercial resin-modified glass ionomer controls. CaP ion recharge capability was the greatest for PE group, followed by BTM group, with BT group being the lowest ( p < 0.05). For each recharge cycle, CaP re-release reached similarly high levels, showing that CaP re-release did not decrease with more recharge cycles. After six recharge/re-release cycles, NACP nanocomposites without further recharge had continuous CaP ion release for 42 d. Significance Novel rechargeable CaP composites achieved long-term and sustained Ca and P ion release. Rechargeable NACP nanocomposite is promising for caries-inhibiting restorations, and the Ca and P ion recharge and re-release method has wide applicability to dental composites, adhesives, cements and sealants to achieve long-term caries-inhibition. [ABSTRACT FROM AUTHOR]

Objectives: The tooth-resin bond is the weak link of restoration, with secondary caries as a main reason for failure. Calcium phosphate-containing resins are promising for remineralization; however, calcium (Ca) and phosphate (P) ion releases last only a couple of months. The objectives of this study were to develop the first rechargeable CaP bonding agent and investigate the key factors that determine CaP ion recharge and re-release.Methods: Nanoparticles of amorphous calcium phosphate (NACP) were synthesized. Pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol-A dimethacrylate (EBPADMA), 2-hydroxyethyl methacrylate (HEMA), and bisphenol-A glycidyl dimethacrylate (BisGMA) were used to synthesize three adhesives (denoted PE, PEH and PEHB). NACP were mixed into adhesive at 0-30% by mass. Dentin shear bond strengths were measured. Adhesive specimens were tested for Ca and P initial ion release. Then the ion-exhausted specimens were immersed in Ca and P solution to recharge the specimens, and the recharged specimens were then used to measure ion re-release for 7 days as one cycle. Then these specimens were again recharged and the re-release was measured for 7 days as the second cycle. Three recharge/re-release cycles were tested.Results: PEHB had the highest dentin bond strength (p<0.05). Increasing NACP content from 0 to 30% did not affect dentin bond strength (p>0.1), but increased CaP release and re-release (p<0.05). PEHB-NACP had the greatest recharge/re-release, and PE-NACP had the least (p<0.05). Ion release remained high and did not decrease with increasing the number of recharge/re-release cycles (p>0.1). After the third cycle, specimens without further recharge had continuous CaP ion release for 2-3 weeks.Significance: Rechargeable CaP bonding agents were developed for the first time to provide long-term Ca and P ions to promote remineralization and reduce caries. Incorporation of NACP into adhesive had no negative effect on dentin bond strength. Increasing NACP filler level increased the ion recharge and re-release capability. The new CaP recharge method and PMGDM-EBPADMA-NACP composition may have wide application in adhesives, composites and cements, to combat caries and remineralize lesions. [ABSTRACT FROM AUTHOR]

Abstract: Antibacterial and remineralizing dental composites and adhesives were recently developed to inhibit biofilm acids and combat secondary caries. It is not clear what effect these materials will have on dental pulps in vivo. The objectives of this study were to investigate the antibacterial and remineralizing restorations in a rat tooth cavity model, and determine pulpal inflammatory response and tertiary dentin formation. Nanoparticles of amorphous calcium phosphate (NACP) and antibacterial dimethylaminododecyl methacrylate (DMADDM) were synthesized and incorporated into a composite and an adhesive. Occlusal cavities were prepared in the first molars of rats and restored with four types of restoration: control composite and adhesive; control plus DMADDM; control plus NACP; and control plus both DMADDM and NACP. At 8 or 30days, rat molars were harvested for histological analysis. For inflammatory cell response, regardless of time periods, the NACP group and the DMADDM+NACP group showed lower scores (better biocompatibility) than the control group (p =0.014 for 8days, p =0.018 for 30days). For tissue disorganization, NACP and DMADDM+NACP had better scores than the control (p =0.027) at 30days. At 8days, restorations containing NACP had a tertiary dentin thickness (TDT) that was five- to six-fold that of the control. At 30days, restorations containing NACP had a TDT that was four- to six-fold that of the control. In conclusion, novel antibacterial and remineralizing restorations were tested in rat teeth in vivo for the first time. Composite and adhesive containing NACP and DMADDM exhibited milder pulpal inflammation and much greater tertiary dentin formation than the control adhesive and composite. Therefore, the novel composite and adhesive containing NACP and DMADDM are promising as a new therapeutic restorative system to not only combat oral pathogens and biofilm acids as shown previously, but also facilitate the healing of the dentin–pulp complex. [Copyright &y& Elsevier]

Abstract: Objectives: Composites are the principal material for tooth cavity restorations due to their esthetics and direct-filling capabilities. However, composites accumulate biofilms in vivo, and secondary caries due to biofilm acids is the main cause of restoration failure. The objectives of this study were to: (1) synthesize new antibacterial monomers and (2) develop nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and antibacterial monomer. Methods: Two new antibacterial monomers were synthesized: dimethylaminohexane methacrylate (DMAHM) with a carbon chain length of 6, and dimethylaminododecyl methacrylate (DMADDM) with a chain length of 12. A spray-drying technique was used to make NACP. DMADDM was incorporated into NACP nanocomposite at mass fractions of 0%, 0.75%, 1.5%, 2.25% and 3%. A flexural test was used to measure composite strength and elastic modulus. A dental plaque microcosm biofilm model with human saliva as inoculum was used to measure viability, metabolic activity, and lactic acid production of biofilms on composites. Results: The new DMAHM was more potent than a previous quaternary ammonium dimethacrylate (QADM). DMADDM was much more strongly antibacterial than DMAHM. The new DMADDM–NACP nanocomposite had strength similar to that of composite control (p >0.1). At 3% DMADDM in the composite, the metabolic activity of adherent biofilms was reduced to 5% of that on composite control. Lactic acid production by biofilms on composite containing 3% DMADDM was reduced to only 1% of that on composite control. Biofilm colony-forming unit (CFU) counts on composite with 3% DMADDM were reduced by 2–3 orders of magnitude. Significance: New antibacterial monomers were synthesized, and the carbon chain length had a strong effect on antibacterial efficacy. The new DMADDM–NACP nanocomposite possessed potent anti-biofilm activity without compromising load-bearing properties, and is promising for antibacterial and remineralizing dental restorations to inhibit secondary caries. [Copyright &y& Elsevier]

Abstract: Objectives: Secondary caries at the restoration margins remains the main reason for failure. Although calcium phosphate (CaP) composites are promising for caries inhibition, there has been no report of CaP composite to inhibit caries in situ. The objectives of this study were to investigate the caries-inhibition effect of nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) in a human in situ model for the first time, and to determine colony-forming units (CFU) and Ca and P ion concentrations of biofilms on the composite restorations. Methods: NACP with a mean particle size of 116nm were synthesized via a spray-drying technique. Two composites were fabricated: NACP nanocomposite, and control composite filled with glass particles. Twenty-five volunteers wore palatal devices containing bovine enamel slabs with cavities restored with NACP or control composite. After 14 days, the adherent biofilms were collected for analyses. Transverse microradiography determined the enamel mineral profiles at the margins, and the enamel mineral loss ΔZ was measured. Results: NACP nanocomposite released Ca and P ions and the release significantly increased at cariogenic low pH (p <0.05). Biofilms on NACP nanocomposite contained higher Ca (p =0.007) and P ions (p =0.005) than those of control (n =25). There was no significant difference in biofilm CFU between the two composites (p >0.1). Microradiographs showed typical subsurface lesions in enamel next to control composite, but much less lesion around NACP nanocomposite. Enamel mineral loss ΔZ (mean±sd; n =25) around NACP nanocomposite was 13.8±9.3μm, much less than 33.5±19.0μm of the control (p =0.001). Significance: Novel NACP nanocomposite substantially reduced caries formation in a human in situ model for the first time. Enamel mineral loss at the margins around NACP nanocomposite was less than half of the mineral loss around control composite. Therefore, the Ca and P ion-releasing NACP nanocomposite is promising for caries-inhibiting restorations. [Copyright &y& Elsevier]

Dental plaque build-up on the cervical area adjacent to gingival margins is a trigger factor for secondary caries around restored root caries lesions. Dimethylaminohexadecyl methacrylate (DMAHDM) and amorphous calcium phosphate nanoparticles (NACP) impart anti-caries effect by reducing the bacterial growth and releasing high concentrations of calcium and phosphate ions, respectively. The present study explored the optimization and formulation of dental composite with increased concentration of DMAHDM combined with NACP and its effect on mechanical behavior and antibacterial response. DMAHDM was incorporated into dental composite formulation at 3% and 5% with 20% NACP fillers. Mechanical properties were assessed by flexural strength and elastic modulus. The cationic charge density of the samples was determined using fluorescein staining assay. A human saliva-derived microcosm biofilm model was used to assess antibacterial response via colony-forming units, metabolic activities, lactic acid production, and live/dead assay. Surface roughness was measured after 48 h-biofilm formation. The viability of human saliva microcosm biofilms was DMAHDM concentration-dependent, where all the microbiological assays were substantially reduced in the presence of 5%DMAHDM. The increased DMAHDM concentration mirrors an increased surface charge density of composites by 8–12 folds and reduced the growth of cariogenic species by 2–5 log (p ≤ 0.05). Metabolic activity and lactic acid were reduced by 70–90% and 48–99%, respectively. Increasing DMAHDM concentration up to 5% and its association with NACP fillers did not adversely affect the mechanical properties. A highly potent antibiofilm bioactive composite for root caries restorations having DMAHDM-NACP could be flexibly tailored during formulation without detrimental outcome for mechanical function. The enhanced antibacterial performance of the novel bioactive composite has great potential to suppress the dental plaque build-up that triggers secondary caries around the restored root caries lesions. [ABSTRACT FROM AUTHOR]

The objectives of this study were to: (1) develop a multifunctional adhesive via dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); and (2) investigate its ability to provide metalloproteinases (MMPs) deactivation and remineralization for long-term dentin bonding durability. DMAHDM and NACP were incorporated into Adper™ Single Bond 2 Adhesive (SB2) at mass fractions of 5% and 20%, respectively. Degree of conversion and contact angle were measured. Endogenous MMP activity of the demineralized dentin beams, Masson's trichrome staining, nano-indentation, microtensile bond strength and interfacial nanoleakage analyses were investigated after 24 h and 3 months of storage aging in artificial saliva. Adding DMAHDM and NACP did not compromise the degree of conversion and contact angle of SB2 (p > 0.05). DMAHDM and NACP incorporation reduced the endogenous MMP activity by 53 %, facilitated remineralization, and increased the Young's modulus of hybrid layer by 49 % after 3 months of aging in artificial saliva, compared to control. For SB2 Control, the dentin bond strength decreased by 38 %, with greater nanoleakage expression, after 3 months of aging (p < 0.05). However, DMAHDM+NACP group showed no loss in bond strength, with much less nanoleakage, after 3 months of aging (p > 0.05). DMAHDM+NACP adhesive greatly reduced MMP-degradation activity in demineralized dentin, induced remineralization at adhesive-dentin interface, and maintained the dentin bond strength after aging, without adversely affecting polymerization and dentin wettability. This new adhesive has great potential to help eliminate secondary caries, prevent hybrid layer degradation, and increase the resin-dentin bond longevity. [ABSTRACT FROM AUTHOR]

Root canal re-infection and weakening of roots are two main challenges in endodontics. The objectives of the study were: (1) to develop a novel root canal sealer containing dimethylaminohexadecyl methacrylate (DMAHDM), nanoparticles of silver (NAg), and nanoparticles of amorphous calcium phosphate (NACP), and (2) to investigate the effects on the physical, anti-biofilm, remineralizing ions, and hardness of human dentin for the first time. Methacrylate-resin dual-cured root canal sealer contained 5% DMAHDM, 0.15% NAg, and NACP at 10%, 20% and 30% mass fractions. The flow, film thickness, and Ca and P ions release were investigated. The effects of NACP on radicular dentin hardness after treatment with sodium hypochlorite (NaOCL) and ethylenediaminetetraacetic acid (EDTA) were assessed. Antibacterial properties were measured against Enterococcus faecalis (E. faecalis) -impregnated dentin blocks; colony-forming units (CFU) and live/dead assays were measured. Incorporating DMAHDM, NAg and NACP did not adversely influence the flow and film thickness properties. Sealer with 30% NACP neutralized the acid and increased the solution pH (p < 0.05). Sealer containing 30% NACP regenerated dentin minerals lost due to NaOCL and EDTA treatment, and increased the dentin hardness to match that of sound dentin (p > 0.1). Incorporating 5% DMAHDM and 0.15% NAg reduced biofilm CFU of E. faecalis -impregnated dentin blocks by nearly 3 logs when compared control group (p < 0.05). The novel therapeutic root canal sealer with triple bioactive agents of DMAHDM, NAg and NACP neutralized acid, raised the pH, regenerated dentin minerals, increased root dentin hardness, and reduced dentin-block-impregnated biofilm CFU by 3 logs. This new sealer with highly desirable antibacterial and remineralization properties are promising to increase the success rate of endodontic therapy and strengthen the tooth root structures. [ABSTRACT FROM AUTHOR]

Objectives The occurrence of tooth root caries is increasing as the world population ages and tooth retention in seniors increases. Class V restorations with subgingival margins are difficult to clean and often lead to periodontitis. The objectives of this study were to develop a Class V composite containing dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate mechanical properties and the inhibition of six species of periodontitis-related biofilms for the first time. Methods Ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM) were mixed at 1:1 mass ratio to form the resin matrix. DMAHDM, NACP, and glass particles were incorporated at 3%, 20% and 50% by mass, respectively. Six species were tested: Porphyromonas gingivalis , Prevotella intermedia , Prevotella nigrescens , Aggregatibacter actinomycetemcomitans , Fusobacterium nucleatum and Enterococcus faecalis . Colony-forming units (CFU), live/dead assay, biomass via crystal violet staining, and polysaccharide production by biofilms were determined on composites. Result Adding 3% DMAHDM to composite did not affect the flexure strength and elastic modulus (p > 0.1). For all six species of periodontal pathogens, the DMAHDM composite had biofilm CFU nearly three orders of magnitude less than that without DMAHDM. The killing efficacy of DMAHDM composite against the six species was: E. faecalis < F. nucleatum < P. nigrescens = P. intermedia < A. actinomycetemcomitans < P. gingivalis . Biofilm biomass and polysaccharide were also greatly reduced via DMAHDM (p < 0.05). Significance The novel nanocomposite containing DMAHDM and NACP showed strong inhibiting effect against all six species of periodontitis-related pathogens. This composite is promising for Class V restorations to restore root caries and combat periodontitis. [ABSTRACT FROM AUTHOR]

Objective A new adhesive containing nanoparticles of amorphous calcium phosphate (NACP) with calcium (Ca) and phosphate (P) ion rechargeability was recently developed; however, it was not antibacterial. The objectives of this study were to: (1) develop a novel adhesive with triple benefits of Ca and P ion recharge, protein-repellent and antibacterial functions via dimethylaminohexadecyl methacrylate (DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine (MPC); and (2) investigate dentin bond strength, protein adsorption, Ca and P ion concentration, microcosm biofilm response and pH properties. Methods MPC, DMAHDM and NACP were mixed into a resin consisting of ethoxylated bisphenol A dimethacrylate (EBPADMA), pyromellitic glycerol dimethacrylate (PMGDM), 2-hydroxyethyl methacrylate (HEMA) and bisphenol A glycidyl dimethacrylate (BisGMA). Protein adsorption was measured using a micro bicinchoninic acid method. A human saliva microcosm biofilm model was tested on resins. Colony-forming units (CFU), live/dead assay, metabolic activity, Ca and P ion concentration and biofilm culture medium pH were determined. Results The adhesive with 5% MPC + 5% DMAHDM + 30% NACP inhibited biofilm growth, reducing biofilm CFU by 4 log, compared to control (p < 0.05). Dentin shear bond strengths were similar (p > 0.1). Biofilm medium became a Ca and P ion reservoir having ion concentration increasing with NACP filler level. The adhesive with 5% MPC + 5% DMAHDM + 30% NACP maintained a safe pH > 6, while commercial adhesive had a cariogenic pH of 4. Significance The new adhesive with triple benefits of Ca and P ion recharge, protein-repellent and antibacterial functions substantially reduced biofilm growth, reducing biofilm CFU by 4 orders of magnitude, and yielding a much higher pH than commercial adhesive. This novel adhesive is promising to protect tooth structures from biofilm acids. The method of using NACP, MPC and DMAHDM is promising for application to other dental materials to combat caries. [ABSTRACT FROM AUTHOR]

Objectives The objectives of this study were to: (1) develop a novel adhesive for prevention of tooth root caries and secondary caries by possessing a combination of protein-repellent, antibacterial, and remineralization capabilities for the first time; and (2) investigate the effects of 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM), and nanoparticles of amorphous calcium phosphate (NACP) on dentin bond strength, protein-repellent properties, and dental plaque microcosm biofilm response. Methods MPC, DMAHDM and NACP were added into Scotchbond Multi-Purpose primer and adhesive. Dentin shear bond strengths were measured. Adhesive coating thickness, surface texture and dentin–adhesive interfacial structure were examined. Protein adsorption onto adhesive resin surface was determined by the micro bicinchoninic acid method. A human saliva microcosm biofilm model was used to investigate biofilm metabolic activity, colony-forming unit (CFU) counts, and lactic acid production. Results The resin with 7.5% MPC + 5% DMAHDM + 30% NACP did not adversely affect dentin shear bond strength ( p > 0.1). The resin with 7.5% MPC + 5% DMAHDM + 30% NACP produced a coating on root dentin with a thickness of approximately 70 μm and completely sealed all the dentinal tubules. The resin with 7.5% MPC + 5% DMAHDM + 30% NACP had 95% reduction in protein adsorption, compared to SBMP control ( p < 0.05). The resin with 7.5% MPC + 5% DMAHDM + 30% NACP was strongly antibacterial, with biofilm CFU being four orders of magnitude lower than that of SBMP control. Significance The novel multifunctional adhesive with strong protein-repellent, antibacterial and remineralization properties is promising to coat tooth roots to prevent root caries and secondary caries. The combined use of MPC, DMAHDM and NACP may have wide applicability to bonding agents, cements, sealants and composites to inhibit caries. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Secondary caries is the main reason for restoration failure, and replacement of the failed restorations accounts for 50–70% of all restorations. Antibacterial adhesives could inhibit residual bacteria in tooth cavity and invading bacteria along the margins. Calcium (Ca) and phosphate (P) ion release could remineralize the lesions. The objectives of this study were to incorporate nanoparticles of silver (NAg) and nanoparticles of amorphous calcium phosphate (NACP) into adhesive for the first time, and to investigate the effects on dentin bond strength and plaque microcosm biofilms. Methods: Scotchbond multi-purpose adhesive was used as control. NAg were added into primer and adhesive at 0.1% by mass. NACP were mixed into adhesive at 10%, 20%, 30% and 40%. Microcosm biofilms were grown on disks with primer covering the adhesive on a composite. Biofilm metabolic activity, colony-forming units (CFU) and lactic acid were measured. Results: Human dentin shear bond strengths (n =10) ranged from 26 to 34MPa; adding NAg and NACP into adhesive did not decrease the bond strength (p >0.1). SEM examination revealed resin tags from well-filled dentinal tubules. Numerous NACP infiltrated into the dentinal tubules. While NACP had little antibacterial effect, NAg in bonding agents greatly reduced the biofilm viability and metabolic activity, compared to the control (p <0.05). CFU for total microorganisms, total streptococci, and mutans streptococci on bonding agents with NAg were an order of magnitude less than those of the control. Lactic acid production by biofilms for groups containing NAg was 1/4 of that of the control. Significance: Dental plaque microcosm biofilm viability and acid production were greatly reduced on bonding agents containing NAg and NACP, without compromising dentin bond strength. The novel method of incorporating dual agents (remineralizing agent NACP and antibacterial agent NAg) may have wide applicability to other dental bonding systems. [Copyright &y& Elsevier]