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

ObjectiveDentin 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.MethodsDentin demineralization was promoted by subjecting samples to a three-species acidic biofilm containing Streptococcus mutans, Streptococcus sanguinis, Streptococcus gordonii for 24 h. 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.ResultsThe 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.SignificanceThe 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.     

In vitro evaluation of composite containing DMAHDM and calcium phosphate nanoparticles on recurrent caries inhibition at bovine enamel-restoration margins

ObjectiveRecurrent caries is a primary reason for restoration failure caused by biofilm acids. The objectives of this study were to: (1) develop a novel multifunctional composite with antibacterial function and calcium (Ca) and phosphate (P) ion release, and (2) investigate the effects on enamel demineralization and hardness at the margins under biofilms.MethodsDimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into composite. Four groups were tested: (1) Commercial control (Heliomolar), (2) Experimental control (0% DMAHDM + 0% NACP), (3) antibacterial group (3% DMAHDM + 0% NACP), (D) antibacterial and remineralizing group (3% DMAHDM + 30% NACP). Mechanical properties and Ca and P ion release were measured. Colony-forming units (CFU), lactic acid and polysaccharide of Streptococcus mutans (S. mutans) biofilms were evaluated. Demineralization of bovine enamel with restorations was induced via S. mutans, and enamel hardness was measured. Data were analyzed via one-way and two-way analyses of variance and Tukey’s multiple comparison tests.ResultsAdding DMAHDM and NACP into composite did not compromise the mechanical properties (P > 0.05). Ca and P ion release of 3% DMAHDM + 30% NACP was increased at cariogenic low pH. Biofilm lactic acid and polysaccharides were greatly decreased via DMAHDM, and CFU was reduced by 4 logs (P < 0.05). Under biofilm acids, enamel hardness at the margins was decreased to about 0.5 GPa for control; it was about 1 GPa for antibacterial group, and 1.3 GPa for antibacterial and remineralizing group (P < 0.05).ConclusionsThe novel 3% DMAHDM + 30% NACP composite had strong antibacterial effects. It substantially reduced enamel demineralization adjacent to restorations under biofilm acid attacks, yielding enamel hardness that was 2-fold greater than that of control composites. The novel multifunctional composite is promising to inhibit recurrent caries.     

Novel bioactive adhesive containing dimethylaminohexadecyl methacrylate and calcium phosphate nanoparticles to inhibit metalloproteinases and nanoleakage with three months of aging in artificial saliva

ObjectivesThe 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.MethodsDMAHDM 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.ResultsAdding 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).SignificanceDMAHDM+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.     

Novel magnetic nanoparticle-containing adhesive with greater dentin bond strength and antibacterial and remineralizing capabilities

Objectives

A nanoparticle-doped adhesive that can be controlled with magnetic forces was recently developed to deliver drugs to the pulp and improve adhesive penetration into dentin. However, it did not have bactericidal and remineralization abilities. The objectives of this study were to: (1) develop a magnetic nanoparticle-containing adhesive with dimethylaminohexadecyl methacrylate (DMAHDM), amorphous calcium phosphate nanoparticles (NACP) and magnetic nanoparticles (MNP); and (2) investigate the effects on dentin bond strength, calcium (Ca) and phosphate (P) ion release and anti-biofilm properties.

Self-healing adhesive with antibacterial activity in water-aging for 12 months

ObjectiveSecondary caries and micro-cracks are the main limiting factors for dentin bond durability. The objectives of this study were to develop a self-healing adhesive containing dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the effects of water-aging for 12 months on self-healing, dentin bonding, and antibacterial properties for the first time.MethodsMicrocapsules were synthesized with poly (urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT). The adhesive contained 7.5% microcapsules, 10% DMAHDM, and 20% NACP (all mass). Specimens were water-aged at 37 °C for 1 day to 12 months. Dentin bond strength was measured using extracted human teeth. A single-edge-V-notched-beam (SEVNB) method was used to measure fracture toughness K_IC and self-healing efficiency. A dental plaque microcosm biofilm model was used with human saliva as inoculum.ResultsThe microcapsules + DMAHDM + NACP group showed no decline in dentin bond strength after water-aging for 12 months, which was significantly higher than that of other groups without DMAHDM (p < 0.05). A self-healing efficiency of 67% recovery in K_IC was obtained even after 12 months of water immersion, indicating that the self-healing ability was not lost in water-aging (p > 0.1). The bacteria-killing ability of this adhesive did not decline from 1 day to 12 months (p > 0.1), with biofilm CFU reduction by 3–4 orders of magnitude after the resin was water-aged for 12 months, compared to control resin.SignificanceThis novel adhesive with triple merits of self-healing, antibacterial and remineralization functions showed an excellent long-term durability in water-aging for 12 months. This multifunctional adhesive has the potential for dental applications to heal cracks, inhibit bacteria, provide ions for remineralization, and increase the restoration longevity.     

Concentration dependence of quaternary ammonium monomer on the design of high-performance bioactive composite for root caries restorations

ObjectivesDental 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.MethodsDMAHDM 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.ResultsThe 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.SignificanceA 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.     

Novel pit and fissure sealant containing nano-CaF2 and dimethylaminohexadecyl methacrylate with double benefits of fluoride release and antibacterial function

ObjectivePit and fissure sealants with antibacterial and remineralization properties have broad application prospects in caries prevention. The objectives of this study were to: (1) develop a novel pit and fissure sealant containing CaF₂ nanoparticles (nCaF₂) and dimethylaminohexadecyl methacrylate (DMAHDM); and (2) investigate the effects of nCaF₂ and DMAHDM on biofilm response and fluoride (F) ion release for the first time.MethodsHelioseal F was used as a control. Bioactive sealants were formulated with DMAHDM and nCaF₂. Flow properties, enamel shear bond strength, hardness and F ion releases were measured. Streptococcus mutans (S. mutans) biofilms were grown on sealants. Biofilm metabolic activity, lactic acid production, colony-forming units (CFU), and pH of biofilm culture medium were measured.ResultsAdding 5% DMAHDM and 20% nCaF₂ did not reduce the paste flow and enamel bond strength, compared to control (p < 0.05). Hardness of sealants with 20% nCaF₂ and DMAHDM was higher than control (p < 0.05). The F ion release from 20% nCaF₂ was much higher than that of commercial control (p < 0.05). The sealant with DMAHDM reduced the S. mutans biofilm CFU by 4 logs. The pH in biofilm medium of the new bioactive sealant was much higher (pH 6.8) than that of commercial sealant (pH 4.66) (p < 0.05).SignificanceThe new bioactive pit and fissure sealant with nCaF₂ and DMAHDM achieved high fluoride release and strong antibacterial performance. This novel fluoride-releasing and antibacterial sealant is promising to inhibit caries and promote the remineralizaton of enamel and dentin.     

Novel root canal sealer with dimethylaminohexadecyl methacrylate,nano-silver and nano-calcium phosphate to kill bacteria inside root dentin and increase dentin hardness

ObjectivesRoot 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.MethodsMethacrylate-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.ResultsIncorporating 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).SignificanceThe 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.     

Antibacterial activity and ion release of bonding agent containing amorphous calcium phosphate nanoparticles

ObjectiveRecurrent caries at the margins is a primary reason for restoration failure. The objectives of this study were to develop bonding agent with the double benefits of antibacterial and remineralizing capabilities, to investigate the effects of NACP filler level and solution pH on Ca and P ion release from adhesive, and to examine the antibacterial and dentin bond properties.MethodsNanoparticles of amorphous calcium phosphate (NACP) and a quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM) were synthesized. Scotchbond Multi-Purpose (SBMP) primer and adhesive served as control. DMADDM was incorporated into primer and adhesive at 5% by mass. NACP was incorporated into adhesive at filler mass fractions of 10%, 20%, 30% and 40%. A dental plaque microcosm biofilm model was used to test the antibacterial bonding agents. Calcium (Ca) and phosphate (P) ion releases from the cured adhesive samples were measured vs. filler level and solution pH of 7, 5.5 and 4.ResultsAdding 5% DMADDM and 10–40% NACP into bonding agent, and water-aging for 28 days, did not affect dentin bond strength, compared to SBMP control at 1 day (p > 0.1). Adding DMADDM into bonding agent substantially decreased the biofilm metabolic activity and lactic acid production. Total microorganisms, total streptococci, and mutans streptococci were greatly reduced for bonding agents containing DMADDM. Increasing NACP filler level from 10% to 40% in adhesive increased the Ca and P ion release by an order of magnitude. Decreasing solution pH from 7 to 4 increased the ion release from adhesive by 6–10 folds.SignificanceBonding agents containing antibacterial DMADDM and remineralizer NACP were formulated to have Ca and P ion release, which increased with NACP filler level from 10% to 40% in adhesive. NACP adhesive was “smart” and dramatically increased the ion release at cariogenic pH 4, when these ions would be most-needed to inhibit caries. Therefore, bonding agent containing DMADDM and NACP may be promising to inhibit biofilms and remineralize tooth lesions thereby increasing the restoration longevity.     

Caries Preventive Effects of Theobromine Containing Toothpaste on Early Childhood Caries: Preliminary Results

ObjectiveEnamel remineralizing effects of theobromine have received much attention from the clinicians. The aim of this study was to investigate the caries preventive effect of theobromine containing toothpaste on children with early childhood caries (ECC).Material and MethodsSalivary pH, buffering capacity and frequency of Streptococcus mutans (SM) levels were measured. Each child was assigned either fluoridated or theobromine containing toothpaste. The changes were analyzed using Laser Fluorescence system. Statistical analyses were performed.ResultsWe included 13 children (mean age 4.25) with 145 teeth in the fluoridated toothpaste (Colgate Kids toothpaste) group; 13 children (mean age 4.46) with 115 teeth in theobromine containing toothpaste (Theodent^TMKids toothpaste) group. Both toothpastes demonstrated enamel remineralization and were effective in increasing the buffering capacity and pH (p < 0.05). A statistically significant decrease in S. mutans levels was found in both toothpaste groups (p<0.05).ConclusionBoth toothpaste group showed a statistically significant amount of enamel remineralization. Since theobromine had the added benefits of increasing the salivary pH and decreasing the S.mutans levels, theobromine containing toothpastes can be considered effective agents in remineralizing white spot lesions and can be used in prevention of early enamel lesions.Key words: Toothpastes, Theobromine, Tooth Remineralization, Preventive Dentistry, Preschool Child     

Effects of S. mutans gene-modification and antibacterial monomer dimethylaminohexadecyl methacrylate on biofilm growth and acid production

ObjectivesAntibacterial quaternary ammonium monomers (QAMs) are used in resins. The rnc gene in Streptococcus mutans (S. mutans) plays a key role in resisting antibiotics. The objectives of this study were to investigate for the first time: (1) the effects of rnc deletion on S. mutans biofilms and acid production; (2) the combined effects of rnc deletion with dimethylaminohexadecyl methacrylate (DMAHDM) on biofilm-inhibition efficacy.MethodsParent S. mutans strain UA159 (ATCC 700610) and the rnc-deleted S. mutans were used. Bacterial growth, minimum inhibitory concentration (MIC), and minimal bactericidal concentration (MBC) were measured to analyze the bacterial susceptibility of the parent and rnc-deleted S. mutans against DMAHDM, with the gold-standard chlorhexidine (CHX) as control. Biofilm biomass, polysaccharide and lactic acid production were measured.ResultsThe drug-susceptibility of the rnc-deleted S. mutans to DMAHDM or CHX was 2-fold higher than parent S. mutans. The drug-susceptibility did not increase after 10 passages (p < 0.05). Deleting the rnc gene increased the biofilm susceptibility to DMAHDM or CHX by 2-fold. The rnc-deletion in S. mutans reduced biofilm biomass, polysaccharide and lactic acid production, even at no drugs. DMAHDM was nearly 40 % more potent than the gold-standard CHX. The combination of rnc deletion + DMAHDM treatment achieved the greatest reduction in biofilm biomass, polysaccharide synthesis, and lactic acid production.SignificanceGene modification by deleting the rnc in S. mutans reduced the biofilm growth and acid production, and the rnc deletion + DMAHDM method showed the greatest biofilm-inhibition efficacy, for the first time. The dual strategy of antibacterial monomer + bacterial gene modification shows great potential to control biofilms and inhibit caries.     

Experimental composites containing quaternary ammonium methacrylates reduce demineralization at enamel-restoration margins after cariogenic challenge

ObjectiveThis study evaluated the influence of experimental composites containing quaternary ammonium monomers (QAM) at different concentrations and alkyl chains on demineralization at enamel-composite margins after cariogenic challenge.MethodsStandardized 4 × 4 mm cavities were cut into 35 bovine enamel blocks, which were randomly divided into seven groups (n = 5) and restored with the following experimental composites and commercial materials: (G12.5) – 5% dimethylaminododecyl methacrylate (DMADDM) with a 12-carbon alkyl chain (G12.10) – 10% DMADDM, (G16.5) – 5% dimethylaminohexadecyl methacrylate (DMAHDM) with a 16-carbon alkyl chain (G16.10) – 10% DMAHDM, (CG) – control group (without QAM), (GZ250) – commercial composite (Filtek Z250^®), and (GIC) – glass ionomer cement (Maxxion R^®). After restorative procedures, initial microhardness was measured and experimental composites were subjected to Streptococcus mutans biofilm formation for 48 h. After cariogenic challenge, the samples were washed and microhardness was reassessed. A 3D non-contact profilometer was used to determine surface roughness and enamel demineralization was assessed by micro-CT. Microhardness results were analyzed by the Kruskal–Wallis and Mann-Whitney tests and micro-CT results were analyzed by Tukey’s HSD test (95% confidence interval).ResultsNone of the materials could prevent mineral loss at the enamel-restoration margins. The addition of 10% DMAHDM yielded the lowest, albeit statistically significant, mineral loss (p < 0.05). 3D non-contact profilometry showed enamel surface roughness modification after biofilm exposure. The CG had the highest roughness values. Micro-CT analysis revealed mineral loss, except for GIC.SignificanceThe addition of 10% QAM with a 16-carbon chain in experimental composites reduced mineral loss at the enamel-restoration margins after cariogenic challenge.     

Novel antibacterial low-shrinkage-stress resin-based cement

ObjectiveA low-shrinkage-stress resin-based cement with antibacterial properties could be beneficial to create a cement with lower stress at the tooth-restoration interface, which could help to enhance the longevity of the fixed dental restoration by reducing microleakage and recurrent caries. To date, there has been no report on the development of a low-shrinkage-stress and bio-interactive cement. Therefore, the objectives of this study were to develop a novel low-shrinkage-stress resin-based cement containing dimethylaminohexadecyl methacrylate (DMAHDM) and investigate the mechanical and antibacterial properties for the first time.MethodsThe monomers urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) were combined and denoted as UV resin. Three cements were fabricated: (1) UV+ 0%DMAHDM (experimental control); (2) UV+ 3%DMAHDM, (3) UV+ %5DMAHDM. RelyX Ultimate cement was used as commercial control. Mechanical properties and Streptococcus mutans (S. mutans) biofilms growth on cement were evaluated.ResultsThe novel bio-interactive cement demonstrated excellent antibacterial and mechanical properties. Compared to commercial and experimental controls, adding DMAHDM into the UV cement significantly reduced colony forming unit (CFU) counts by approximately 7 orders of magnitude, metabolic activities from 0.29 ± 0.03 A₅₄₀/cm² to 0.01 ± 0.01 A₅₄₀/cm², and lactic acid production from 22.3 ± 0.74 mmol/L to 1.2 ± 0.27 mmol/L (n = 6) (p < 0.05). The low-shrinkage-stress cement demonstrated a high degree of conversion of around 70 %, while reducing the shrinkage stress by approximately 60%, compared to a commercial control (p < 0.05).ConclusionsThe new antibacterial low-shrinkage-stress resin-based cement provides strong antibacterial action and maintains excellent mechanical properties with reduced polymerization shrinkage stress.Clinical significanceA low-shrinkage-stress resin-based cement containing DMAHDM was developed with potent antibacterial effects and promising mechanical properties. This cement may potentially enhance the longevity of fixed dental restoration such as a dental crown, inlay, onlay, and veneers through its excellent mechanical properties, low shrinkage stress, and strong antibacterial properties.     

Minimally-invasive dentistry via dual-function novel bioactive low-shrinkage-stress flowable nanocomposites

The objectives of this in vitro study were to develop a novel low-shrinkage-stress flowable nanocomposite with antibacterial properties through the incorporation of dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the mechanical and oral biofilm properties, to be used in minimally-invasive techniques.MethodsThe light-cured low-shrinkage-stress flowable resin was formulated by mixing urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) at a 1:1 mass ratio. Different mass fractions of glass, and either 5% DMAHDM or 20%NACP or both were incorporated. Paste flowability, ultimate micro tensile strength and surface roughness were evaluated. The antibacterial response of DMAHDM resin was assessed by using biofilms of human saliva-derived microcosm model. Virtuoso flowable composite was used as a control.Results(45% resin+5% DMAHDM+20% NACP+30% glass) formula yielded the needed outcomes. It had flow rate within the range of ISO requirement. The micro tensile strength was (39.1 ± 4.3) MPa, similar to (40.1 ± 4.0) MPa for commercial control (p > 0.05). The surface roughness values of the novel composite (0.079 ± 0.01) µm similar to commercial composite (0.09 ± 0.02) µm (p > 0.05). Salivary microcosm biofilm colony forming unit values were reduced by 5–6 logs (p < 0.05). Biofilm metabolic activity was also substantially reduced, compared to control composite (p < 0.05).SignificanceThe novel bioactive flowable nanocomposite achieved strong antibacterial activities without compromising the mechanical properties. It is promising to be used as pit and fissure sealants, and as fillings in conservative cavities to inhibit recurrent caries and increase restoration longevity.     

The preventive effect of grape seed extract on artificial enamel caries progression in a microbial biofilm-induced caries model

Objectives

The aim of this study was to evaluate the effect of grape seed extract (GSE) on enamel caries lesion formation in an in vitro Streptococcus mutans biofilm model.

Methods

Enamel fragments were prepared from bovine incisors and divided into six treatment groups (n = 12): inoculated Brain Heart Infusion with 1% sucrose (BHIS), 1 mg/mL GSE, 2 mg/mL GSE, 3 mg/mL GSE, 10 ppm fluoride as NaF, and uninoculated BHIS. For biofilm formation, tooth fragments were incubated anaerobically in polystyrene 6-well tissue culture plates containing BHIS, the respective agents, and S. mutans (1 × 10⁵ CFU/mL) for 24 h at 37 °C. Culture medium was replaced with fresh BHIS and respective agents daily over a 7-day period. Following caries lesion formation, lesion depth (LD) and relative optical density (ROD) were determined by polarized light microscopy (PLM) and confocal laser scanning microscopy (CLSM), respectively, to evaluate lesion progression.

Results

LDs of the 2 mg/mL GSE group (122.86 ± 13.41 μm) and the 3 mg/mL GSE group (111.92 ± 11.39 μm) were significantly smaller than those of the 1 mg/mL GSE (198.33 ± 17.70 μm) and control groups (210.86 ± 15.50 μm) (p < 0.05). Compared with the 2 mg/mL and 3 mg/mL groups, the control and 1 mg/mL GSE groups showed significantly lower ROD values when depth was less than 200 μm, indicating greater mineral loss.

Conclusions

Dose-dependent GSE inhibits in vitro enamel caries formation due to its ability to suppress growth of S. mutans and the formation of bio?lm.

Clinical signi?cance

Grape seed extract may be a novel virulence-targeted natural antimicrobial agent for caries prevention.     

Verification of antibacterial activity to enamel surfaces of new type of surface coating

ObjectivePrevention is difficult to decrease dental caries only via the partial application of fluoride. The GC Co. has developed a coating material adhesive containing fluoride and zinc. It is thought that this zinc has an effect which prevents dental caries. The aim of this study was to evaluate the influence of the Caredyne Shield® (CS) on biofilm generation by S. mutans, as compared to an acidulated phosphate fluoride (APF) gel.Materials and methodsWe performed the comparative study of the biofilm inhibitory effect which used the enamel of bovine teeth. Specimens were separated into a control group, an APF gel group, and a CS group. Biofilms were generated by adherent S. mutans. We observed the antibacterial weigh by the creation state of Biofilms.ResultsSignificant difference was observed in the number of bacterial colonies formed after 24 h, the number of bacterial colonies formed from detached S. mutans from the CS-treated experimental group were fewer in number than in the other group (p < 0.01). The biofilm formed by S. mutans 72 h after dissemination on the enamel surface was visible by fluorescence microscopy (Live/Dead staining method) and under the scanning electron microscope, in the CS-treated group, no plastic structures were observed, as the models were free of the biofilm and only scattered S. mutans cells were observed.ConclusionWe showed in this study the efficacy of CS in controlling the formation of biofilm. From such a result, we conclude that CS is a novel anticaries agent.     

Remineralization effectiveness of the PAMAM dendrimer with different terminal groups on artificial initial enamel caries in vitro

ObjectiveDisruption of the demineralization–remineralization balance could trigger the development of dental caries, making it challenging for enamel to “self-heal”. Thus, extrinsic assistance is needed to restore enamel lesions and stop undermining progression. The aim of this study was to investigate enamel remineralization in a simulated oral environment via poly (amino amine) (PAMAM) dendrimers quantitatively.MethodsBovine enamel specimens were shaken in demineralization solution (pH 4.5, 37 °C, 50 rpm/min) for 72 h to create initial enamel carious lesions. The subsurface-demineralized specimens were then divided into four groups: enamel treated with PAMAM-NH₂, enamel treated with PAMAM−COOH, enamel treated with PAMAM−OH, and enamel treated with deionized water. The treated specimens underwent subsequent 12-day pH cycling. Enamel blocks were analyzed by transverse microradiography (TMR), surface microhardness testing and scanning electron microscopy (SEM) before and after demineralization and pH cycling.ResultsGroups treated with PAMAM dendrimers showed lower lesion depth and less mineral loss, attained more vertical-section surface microhardness recovery, and adsorbed more mineral deposits (p < 0.05). The enamel lesion remineralization values of PAMAM-NH₂, PAMAM-COOH, and PAMAM-OH groups were 76.42 ± 3.32%, 60.07 ± 5.92% and 54.52 ± 7.81%, respectively.SignificanceIn conclusion, PAMAM with different terminal groups could induce enamel remineralization, among which PAMAM-NH₂ showed the most prominent competence, followed by PAMAM-COOH and PAMAM-OH, in that order.     

Influence of dentin pretreatment with 2.5% titanium tetrafluoride on inhibiting caries at the tooth-restoration interface in situ

ObjectiveInvestigate the effects of dentin pretreatment with 2.5% titanium tetrafluoride (TiF₄) aqueous solution followed by two-step self-etching (CLE/Clearfil SE Bond) and one-step self-etching adhesive systems (SBU/Single Bond Universal) on carious lesion inhibition at the tooth-restoration interface using an in situ model.DesignSixty-four cavities at the enamel-dentin junction of dental fragments were randomly distributed according to groups (n = 16): 1) TiF₄ + CLE; 2) TiF₄ + SBU; 3) CLE; 4) SBU. Cavities were restored using resin composite, and placed in intraoral palatal devices used by 16 volunteers for 21 days, to induce caries formation in situ. The fragments were then ground-flat to perform Knoop microhardness tests. Nine indentations were performed on each enamel and dentin substrate, subjacent to the restoration. Analysis of variance and Tukey’s test were applied.ResultsEnamel: groups receiving TiF₄ dentin pretreatment (regardless of adhesive system and tooth-restoration interface distance) presented higher hardness means at a depth of 25 μm from the outer tooth surface (p < 0.0001). Dentin: groups receiving CLE presented higher means when applying TiF₄ pretreatment, whereas groups restored with SBU presented higher means without pretreatment (p = 0.0003).ConclusionsDentin pretreatment with TiF₄ inhibited demineralization of the enamel interface in situ, regardless of the adhesive, and TiF₄ pretreatment followed by CLE application showed higher potential for inhibiting dentin demineralization at the interface.     

Antibacterial,remineralising and matrix metalloproteinase inhibiting scandium-doped phosphate glasses for treatment of dental caries

ObjectivesAntibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc³⁺ ions.MethodsSc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated.ResultsThe developed glass system showed linear Sc³⁺ ions release over time. The released Sc³⁺ shows statistically significant inhibition of S. mutans biofilm (1.2 log₁₀ CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats.SignificanceSince Sc³⁺ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.     

Use of a novel 9.3-μm carbon dioxide laser and silver diamine fluoride: Prevention of enamel demineralisation and inhibition of cariogenic bacteria

ObjectiveTo investigate the effects of a 9.3-μm carbon dioxide (CO₂) laser and silver diamine fluoride (SDF) on the prevention of enamel demineralisation and inhibition of cariogenic bacteria.MethodsEnamel blocks were applied with Laser (Group-1), SDF (Group-2), Laser + SDF (Group-3) and no treatment (Group-4), and then subjected to an 8-day pH-cycling for cariogenic challenge. Lesion depth and cross-sectional micro-hardness were assessed. Surface morphological and chemical changes were studied using scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). For the antibacterial activity, treated enamel blocks were incubated with Streptococcus mutans. The biofilm morphology, kinetics and viability were assessed by SEM, colony-forming units (CFUs) and confocal laser scanning microscope (CLSM), respectively.ResultsLesion depths (μm) for Group-1 to Group-4 were 88 ± 21, 26 ± 11, 13 ± 9 and 115 ± 25, respectively (p < 0.001; Group-2 and Group-3 < Group-1 < Group-4). Group-3 had a significantly higher cross-sectional micro-hardness than the other three groups. EDS determined that Group-4 had the lowest calcium-to-phosphorus molar ratio among the groups (p < 0.001). SEM images showed apparent bacteria accumulation on enamel surfaces in Group-4, but not in other groups. Log CFUs for Group-1 to Group-4 were 6.2 ± 0.6, 2.9 ± 0.8, 2.2 ± 1.1 and 7.3 ± 0.3, respectively (p < 0.001; Group-2 and Group-3 < Group-1 < Group-4). CLSM images revealed that live bacteria dominated in Group-4, but not in other groups.SignificanceThe irradiation with a 9.3-μm CO₂ laser alone can prevent the demineralisation of enamel and reduce the adhesion of cariogenic bacteria. Moreover, adding SDF can significantly increase the preventive effect and antibacterial ability.