Strong nanocomposites with Ca, PO(4), and F release for caries inhibition

Dentin remineralization induced by experimental composites containing calcium orthophosphate particles

OBJECTIVES

This study aimed to verify if composites containing dicalcium phosphate dihydrate particles (DCPD) are able to induce dentin remineralization in vitro. Additionally, the mechanical properties of the materials were tested.

METHODS

Four composites with 50 vol% inorganic content and 1 BisGMA: 1 TEGDMA (mols) were prepared, with different DCPD:glass ratios (50:0, 40:10, 30:20 and 0:50). Ca2 + release in water was monitored for 8 weeks using inductively coupled plasma optical emission spectrometry (n = 3). Composites were applied to artificial lesions (180 μm in depth) prepared in dentin discs and the specimens were kept in simulated body fluid for 8 weeks (n = 8-10). Dentin elastic modulus (EM) and hardness (H) across the lesion were determined by nanoindentation (5 mN, 5 s). Mineral density was determined by microCT. Composite degree of conversion (DC) was determined by near-FTIR spectroscopy (n = 3). Fracture strength and elastic modulus were determined using biaxial flexural test (n = 10). Data were analysed by ANOVA/Tukey test, except for mineral density (Kruskal-Wallis, alpha:0.05).

RESULTS

Ca2+ release increase linearly with DCPD fraction in the composite (p < 0.001). Lesions kept in contact with composites containing 40 % and 50 % DCPD presented significant increases in EM and H in the outer region (0-90 μm) and in EM in the inner region (90-180 μm) compared to the negative control. MicroCT was not able to differentiate among treatments. DCPD-containing composites presented DC higher than the control (p < 0.01). Flexural strength and modulus were inversely related to DCPD content (p < 0.001).

SIGNIFICANCE

The composite containing 40 vol% DCPD presented the best compromise between mechanical properties and remineralization potential.

Advancing dentin remineralization: Exploring amorphous calcium phosphate and its stabilizers in biomimetic approaches

OBJECTIVE

This review elucidates the mechanisms underpinning intrafibrillar mineralization, examines various amorphous calcium phosphate (ACP) stabilizers employed in dentin's intrafibrillar mineralization, and addresses the challenges encountered in clinical applications of ACP-based bioactive materials.

METHODS

The literature search for this review was conducted using three electronic databases: PubMed, Web of Science, and Google Scholar, with specific keywords. Articles were selected based on inclusion and exclusion criteria, allowing for a detailed examination and summary of current research on dentin remineralization facilitated by ACP under the influence of various types of stabilizers.

RESULTS

This review underscores the latest advancements in the role of ACP in promoting dentin remineralization, particularly intrafibrillar mineralization, under the regulation of various stabilizers. These stabilizers predominantly comprise non-collagenous proteins, their analogs, and polymers. Despite the diversity of stabilizers, the mechanisms they employ to enhance intrafibrillar remineralization are found to be interrelated, indicating multiple driving forces behind this process. However, challenges remain in effectively designing clinically viable products using stabilized ACP and maximizing intrafibrillar mineralization with limited materials in practical applications.

SIGNIFICANCE

The role of ACP in remineralization has gained significant attention in dental research, with substantial progress made in the study of dentin biomimetic mineralization. Given ACP's instability without additives, the presence of ACP stabilizers is crucial for achieving in vitro intrafibrillar mineralization. However, there is a lack of comprehensive and exhaustive reviews on ACP bioactive materials under the regulation of stabilizers. A detailed summary of these stabilizers is also instrumental in better understanding the complex process of intrafibrillar mineralization. Compared to traditional remineralization methods, bioactive materials capable of regulating ACP stability and controlling release demonstrate immense potential in enhancing clinical treatment standards.

Dentin erosive wear is reduced by fluoride varnishes containing nanosized sodium trimetaphosphate in vitro

This study evaluated the effect of fluoride varnishes containing micrometric or nanosized sodium trimetaphosphate (TMP) on dentin erosive wear in vitro. Bovine root dentin blocks were selected by surface hardness and randomly divided into five experimental groups/varnishes (n = 20/group): placebo, 5% sodium fluoride (NaF); 5% NaF+5% micrometric TMP; 5% NaF+2.5% nanosized TMP; and 5% NaF+5% nanosized TMP. Half of the surface of all blocks received a single application of the assigned varnish, with subsequent immersion in artificial saliva for 6 h. Varnishes were then removed and the blocks were immersed in citric acid (90 s, 4×/day, 5 days). After each erosive cycle, ten blocks of each group were immersed in a placebo dentifrice for 15 s (ERO), while the other ten blocks were subjected to abrasion by brushing (ERO+ABR). Dentin erosive wear was assessed by profilometry. Data were submitted to 2-way ANOVA and to the Holm-Sidak test (p<0.05). Dentin erosive wear was significantly higher for ERO+ABR than for ERO for all varnishes. TMP-containing varnishes promoted superior effects against dentin erosive wear compared with 5% NaF alone; and 5% nanosized TMP led to the lowest wear among all varnishes. In conclusion, the addition of TMP to conventional fluoride varnish (i.e., varnish containing only NaF) enhanced its protective effects against bovine root dentin erosion and erosion+abrasion. Additionally, the use of 5% nanosized TMP led to superior effects in comparison to 5% micrometric TMP, both for erosion and erosion+abrasion in vitro.

Antibacterial, cytotoxic and mechanical properties of a orthodontic cement with phosphate nano-sized and phosphorylated chitosan: An in vitro study

OBJECTIVES

Evaluate, in vitro, the effect of incorporating nano-sized sodium trimetaphosphate (TMPnano) and phosphorylated chitosan (Chi-Ph) into resin-modified glass ionomer cement (RMGIC) used for orthodontic bracket cementation, on mechanical, fluoride release, antimicrobial and cytotoxic properties.

METHODS

RMGIC was combined with Chi-Ph (0.25%/0.5%) and/or TMPnano (14%). The diametral compressive/tensile strength (DCS/TS), surface hardness (SH) and degree of conversion (%DC) were determined. For fluoride (F) release, samples were immersed in des/remineralizing solutions. Antimicrobial/antibiofilm activity was evaluated by the agar diffusion test and biofilm metabolism (XTT). Cytotoxicity in fibroblasts was assessed with the resazurin method.

RESULTS

After 24 h, the RMGIC-14%TMPnano group showed a lower TS value (p < 0.001); after 7 days the RMGIC-14%TMPnano-0.25%Chi-Ph group showed the highest value (p < 0.001). For DCS, the RMGIC group (24 h) showed the highest value (p < 0.001); after 7 days, the highest value was observed for the RMGIC-14%TMPnano-0.25%Chi-Ph (p < 0.001). RMGIC-14%TMPnano, RMGIC-14%TMPnano-0.25%Chi-Ph, RMGIC-14%TMPnano-0.5%Chi-Ph showed higher and similar release of F (p > 0.001). In the SH, the RMGIC-0.25%Chi-Ph; RMGIC-0.5%Chi-Ph; RMGIC-14%TMPnano-0.5%Chi-Ph groups showed similar results after 7 days (p > 0.001). The RMGIC-14%TMPnano-0.25%Chi-Ph group showed a better effect on microbial/antibiofilm growth, and the highest efficacy on cell viability (p < 0.001). After 72 h, only the RMGIC-14%TMPnano-0.25%Chi-Ph group showed cell viability (p < 0.001).

CONCLUSION

The RMGIC-14%TMPnano-0.25%Chi-Ph did not alter the physical-mechanical properties, was not toxic to fibroblasts and reduced the viability and metabolism of S. mutans.

CLINICAL RELEVANCE

The addition of phosphorylated chitosan and organic phosphate to RMGIC could provide an antibiofilm and remineralizing effect on the tooth enamel of orthodontic patients, who are prone to a high cariogenic challenge due to fluctuations in oral pH and progression of carious lesions.

Ion release mechanisms in composites containing CaP particles and hydrophilic monomers

OBJECTIVE

To investigate the effect of hydrophilic/permeable polymer matrices on water sorption/solubility (WS/SL), Ca2+ release, mechanical properties and hydrolytic degradation of composites containing dicalcium phosphate dihydrate (DCPD) particles.

METHODS

Six composites were tested, all with 10 vol% of glass particles and either 30 vol% or 40 vol% DCPD. Composites containing 1BisGMA:1TEGDMA in mols (at both inorganic levels) were considered controls. Four materials were formulated where 0.25 or 0.5 of the BisGMA/TEGDMA was replaced by pyromellitic dianhydride glycerol dimethacrylate (PMGDM)/ polyethylene glycol dimethacrylate (PEGDMA). Composites were tested for degree of conversion (FTIR spectroscopy), WS/SL (ISO 4049) and Ca2+ release (inductively coupled plasma optical emission spectroscopy). Fracture toughness (FT) and biaxial flexural strength/modulus (BFS/FM) were determined after 24 h and 60 days in water. The contributions of diffusional and relaxational mechanisms to Ca2+ release kinetics were analyzed using the semi-empirical Salim-Peppas model. Data were analysed by ANOVA/Tukey test (alpha: 0.05).

RESULTS

WS/SL was higher for composites containing PMGDM/PEGDMA compared to the controls (p < 0.001). Only at 40% DCPD the 0.5 PMGDM/PEGDMA composite showed statistically higher Ca2+ release than the control. Relaxation diffusion was the main release mechanism. Initial FT was not negatively affected by matrix composition. BFS (both DCPD fractions) and FM (30% DCPD) were lower for composites with hydrophilic/permeable networks (p < 0.01). After 60 days in water, composites with PMGDM/PEGDMA presented significant reductions in FT, while all composites had reductions in BFS/FM.

SIGNIFICANCE

Increasing matrix hydrophilicity/permeability significantly increased Ca2+ release only at a high DCPD fraction.

Composite Containing Calcium Phosphate Particles Functionalized with 10-MDP

The phosphate ester monomer 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) is capable of bonding to hydroxyapatite and, for this reason, is a key component of several self-etch adhesives. In this study, dicalcium phosphate dihydrate particles (DCPD; CaHPO4.2H2O) were functionalized with 10-MDP and used to formulate an experimental composite with 50 vol% inorganic content (3:1 DCPD:silanated barium glass ratio) dispersed in a BisGMA/TEGDMA matrix. The tested hypothesis was that DCPD functionalization would improve the composite's mechanical performance without compromising Ca2+ release. Composites containing nonfunctionalized DCPD or only reinforcing glass (in both cases, with or without 10-MDP mixed in the resin phase) were used as controls. Materials were tested for degree of conversion (DC; by Fourier transform infrared spectroscopy), water sorption (WS) and solubility (SL; according to ISO 4049), biaxial flexural strength (BFS)/modulus (FM) after 24 h and 5 mo in water, and 28-d Ca2+ release in water (by plasma-coupled optical emission spectroscopy). Data were analyzed using analysis of variance/Tukey test (alpha: 5%). DCPD functionalization did not interfere with DC. The composite containing functionalized DCPD showed significantly lower WS and SL in comparison with the material formulated with nonfunctionalized particles. The presence of 10-MDP (as a functionalizing agent or dispersed in the resin phase) reduced the composite's initial BFS and FM. After 5 mo in water, the composite with functionalized DCPD and both glass-only composites were able to maintain their mechanical properties at levels statistically similar to what was observed after 24 h. Ca2+ release was significantly reduced in both formulations containing 10-MDP. In conclusion, DCPD functionalization with 10-MDP increased the composite's resistance to hydrolytic degradation, improving its mechanical stability after prolonged water storage. However, the impaired water transit at the particle-matrix interface led to a reduction in Ca2+ release.

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL SIGNIFICANCE

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

Influence of bleaching gels formulated with nano-sized sodium trimetaphosphate and fluoride on the physicochemical, mechanical, and morphological properties of dental enamel

OBJECTIVES

To evaluate in vitro the effects of sodium fluoride (F) and nano-sized sodium trimetaphosphate (TMPnano) added to a 35% hydrogen peroxide (H2O2) bleaching gel on the color alteration, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion.

MATERIALS AND METHODS

Bovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 35% H2O2 (HP); 35% H2O2 + 0.1% F (HP/F); 35% H2O2 + 1% TMPnano (HP/TMPnano); 35% H2O2 + 0.1% F + 1% TMPnano (HP/F/TMPnano) and 35% H2O2 + 2% calcium gluconate (HP/Ca). The gels were applied 3 times by 40 min; once each 7-day. The Commission Internationale de l'Eclairage (CIE) L*a*b* total color alteration (ΔE), color alteration by CIEDE2000 (ΔE00), whitening index (ΔWID), surface (SH) and cross-sectional hardness (ΔKHN), surface roughness (Ra), and transamelodentinal diffusion were determined. Enamel surfaces were evaluated by Scanning Electron Microscopy (SEM) and X-ray Dispersive Energy (EDX). Data were submitted to ANOVA, followed by the Student-Newman-Keuls test (p <0.05).

RESULTS

ΔE, ΔE00, and ΔWID were similar among the gels that promoted a bleaching effect after treatment (p <0.001). Mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion were lower for HP/F/TMPnano; the HP and HP/Ca groups presented the highest values (p <0.001). For SEM/EDX, surface changes were observed in all bleached groups, but less intense with TMPnano.

CONCLUSIONS

Gels containing F/TMPnano do not interfere with the bleaching effect and reduce enamel demineralization, roughness, H2O2 diffusion, and morphological changes.

CLINICAL RELEVANCE

Whitening gels containing F/TMPnano can be used as a new strategy to increase safety and maintain clinical performance.

Efficacy of bioactive materials in preventing Streptococcus mutans-induced caries on enamel and dentine

The study investigated the ability of bioactive materials used to restore enamel and dentine specimens to prevent caries. Enamel (n = 50) and dentine (n = 50) specimens were obtained from bovine incisors, prepared, and randomly allocated to one of five groups according to the restorative treatment: alkasite without adhesive system; alkasite with adhesive system; high viscosity glass ionomer cement; resin composite; no restoration; negative control group. Specimens were restored, exposed to a thermal cycling aging protocol, sterilized, and exposed to a cariogenic challenge induced by Streptococcus mutans and then submitted to surface and subsurface microhardness tests and polarized light microscopy to verify the caries lesion development in enamel or dentine surrounding the restorative materials. Data were analyzed using one-way ANOVA. In enamel and dentine, glass ionomer cement, alkasite without and with adhesive system presented a lower percentage surface microhardness loss than resin composite and negative control. Enamel subsurface microhardness presented no statistically significant differences between glass ionomer cement, alkasite without and with adhesive system. Glass ionomer cement also did not present statistically significant differences from resin composite and the negative control. In dentine, glass ionomer cement showed the highest subsurface microhardness values. In conclusion, bioactive restorative materials provide greater protection to enamel and dentine against surface caries development than resin composite.

Evaluation of Antibacterial Activity of a Bioactive Restorative Material Versus a Glass-Ionomer Cement on Streptococcus Mutans: In-Vitro Study

BACKGROUND

Dental caries management consists of both preventive and restorative approaches. Pediatric dentists can rely on many techniques and materials to restore decayed teeth, but a high failure rate is still observed, mainly due to secondary caries. New restorative bioactive materials combine the mechanical and aesthetic characteristics of resinous materials with the capability to remineralize and the antimicrobial properties of glass ionomers, thus counteracting the occurrence of secondary caries. The aim of this study was to assess the antimicrobial activity against Streptococcus mutans of a bioactive restorative material (ACTIVA™ BioActive-Restorative™-Pulpdent©) and a glass ionomer cement with silver particles added (Ketac™ Silver-3M©), using agar diffusion assay.

METHODS

Each material was formed into disks of 4 mm in diameter, and four discs of each material were placed on nine agar plates. The analysis was repeated seven times.

RESULTS

Both materials showed statistically significant growth inhibition properties against S. mutans (p < 0.05). The difference in the effectiveness of the two materials was not statistically significant.

CONCLUSION

Both ACTIVA™ and Ketac™ Silver can be recommended since both are similarly effective against S. mutans. However ACTIVA™, given its bioactivity and better aesthetics and mechanical properties compared to GICs, may provide better clinical performance.

Activity of Sodium Trimetaphosphate Nanoparticles on Cariogenic-Related Biofilms In Vitro

In light of the promising effect of sodium trimetaphosphate nanoparticles (TMPn) on dental enamel, in addition to the scarce evidence of the effects of these nanoparticles on biofilms, this study evaluated the activity of TMPn with/without fluoride (F) on the pH, inorganic composition and extracellular matrix (ECM) components of dual-species biofilms of Streptococcus mutans and Candida albicans. The biofilms were cultivated in artificial saliva in microtiter plates and treated with solutions containing 1% or 3% conventional/microparticulate TMP (TMPm) or TMPn, with or without F. After the last treatment, the protein and carbohydrate content of the ECM was analyzed, and the pH and F, calcium (Ca), phosphorus (P), and TMP concentrations of the biofilms were determined. In another set of experiments, after the last treatment, the biofilms were exposed to a 20% sucrose solution, and their matrix composition, pH, and inorganic component contents were evaluated. 3% TMPn/F significantly reduced ECM carbohydrate and increased biofilm pH (after sucrose exposure) than other treatments. Also, it significantly increased P and F levels before sucrose exposure in comparison to 3% TMPm/F. In conclusion, 3% TMPn/F affected the biofilm ECM and pH, besides influencing inorganic biofilm composition by increasing P and F levels in the biofilm fluid.

Buffering Capacity and Effects of Sodium Hexametaphosphate Nanoparticles and Fluoride on the Inorganic Components of Cariogenic-Related Biofilms In Vitro

Despite the remarkable effects of sodium hexametaphosphate nanoparticles (HMPnano) on dental enamel de-/re-mineralization processes, information on the effects of these nanoparticles on biofilms is scarce. This study assessed the effects of HMPnano, with or without fluoride (F), on the inorganic components and pH of Streptococcus mutans and Candida albicans dual-species biofilms. Solutions containing conventional/micro-sized HMP (HMPmicro) or HMPnano were prepared at 0.5% and 1%, with or without 1100 ppm F. A 1100 ppm F solution and pure artificial saliva were tested as positive and negative controls, respectively. The biofilms were treated three times and had their pH analyzed, and the concentrations of F, calcium, phosphorus, and HMP in the biofilm biomass and fluid were determined. In another set of experiments, after the last treatment, the biofilms were exposed to a 20% sucrose solution, and the biofilm pH and inorganic components were evaluated. The 1% HMPnano solution with F led to the highest biofilm pH, even after exposure to sucrose. The 1% HMPnano solution without F led to significantly higher phosphorus concentrations in comparison to all other groups. It can be concluded that 1% HMPnano and F influenced the biofilm pH, besides affecting most of the inorganic components of the dual-species biofilms.

Effects of sodium hexametaphosphate microparticles or nanoparticles on the growth of saliva-derived microcosm biofilms

OBJECTIVES

This study evaluated the effects of sodium hexametaphosphate microparticles (HMPmicro) or nanoparticles (HMPnano) on the growth of saliva-derived microcosm biofilms MATERIALS AND METHODS: Saliva-derived biofilms were formed on glass coverslips for 24 h. Thereafter, Streptococcus mutans (C180-2) was incorporated or not into the biofilms. From that time point onwards, solutions containing 0.2% HMPmicro or HMPnano, combined or not with 220 ppm F, were constantly present in the culture medium. In addition, 220 ppm F alone (220F) and McBain medium without any compound were also tested as positive and negative controls (CTL), respectively. After 96 h, the biofilms were plated on anaerobic blood agar or sucrose agar bacitracin for total and S. mutans CFU-counting, respectively. Biofilms' lactic acid production was analysed spectrophotometrically. Data were submitted to ANOVA or Kruskal-Wallis' tests, followed by Student-Newman-Keuls' test (p<0.05; n=12).

RESULTS

HMPmicro or HMPnano led to significantly lower lactic acid production, and significant reductions in total CFU-counting in microcosm biofilms, supplemented or not with S. mutans, in comparison to both controls, with significant differences between 220F and CTL. No significant differences were observed among the groups treated with HMPmicro or HMPnano (with or without F). The same trend was seen for S. mutans CFU-counting, in biofilms supplemented with S. mutans.

CONCLUSIONS

HMP significantly reduced total and S. mutans CFU counts, as well as lactic acid production by saliva-derived microcosm biofilms.

CLINICAL RELEVANCE

These findings in saliva-derived microcosm biofilms suggest that HMP stands as a promising alternative for the control of cariogenic biofilms.

Developments in resin-based composites

With the phasing down of dental amalgam use in response to the Minamata Convention, it is likely that resin-based composite restoratives will be the dental material of choice for the direct restoration of compromised dentition in the UK, at least for the foreseeable future. The current materials have a finite lifespan, with failures predominately due to either secondary caries or fracture. Consequently, there is considerable in vitro research reported each year with the intention of producing improved materials. This review describes the recent research in materials designed to have low polymerisation shrinkage and increased mechanical properties. Also described is research into materials that are either antimicrobial or are designed to release ions into the surrounding oral environment, with the aim of stimulating remineralisation of the surrounding dental tissues. It is hoped that by describing this recent research, clinicians will be able to gain some understanding of the current research that will potentially lead to new products that they can use to improve patient treatment in the future.

Provides an overview of recent research developments aimed at improving the performance of resin-based composites.

Details the recent developments in monomers and fillers to produce resin-based composites that either have lower polymerisation shrinkage or better mechanical properties compared to current commercially available products.

Describes recent research on developing resin-based composites that can act as potential sources of antimicrobial or remineralising agents.

Effects of nano-sized sodium hexametaphosphate on the viability, metabolism, matrix composition, and structure of dual-species biofilms of Streptococcus mutans and Candida albicans

This study evaluated the effects of micrometric or nano-sized sodium hexametaphosphate (HMPnano), combined or not with fluoride (NaF, 1100 ppm), on dual-species biofilms of Streptococcus mutans and Candida albicans. Biofilms were treated with solutions containing the polyphosphates at 0.5% or 1.0%, with/without fluoride (F), in addition to positive and negative controls. Biofilms were analysed by colony-forming units (CFU) counting, metabolic activity, production of biomass, composition of extracellular matrix, and structure. 1% HMPnano + F led to the lowest S. mutans CFU, while C. albicans CFU counts were not affected by any solution. 1% HMPnano led to the lowest metabolic activity, except for 1% HMPnano + F. All solutions promoted reductions in biofilm biomass compared to controls. Also, 1% HMPnano + F promoted the lowest concentrations of carbohydrates in the biofilm matrix, besides substantially affecting biofilms' structure. In conclusion, HMPnano and F promoted higher antibiofilm effects compared with its micrometric counterpart for most of the parameters assessed.

Effect of Fluoride-based Varnishes with Added Calcium and Phosphate on Microhardness of Esthetic Restorative Materials: An In Vitro Study

Background and objectives

Fluoride varnishes are being used to prevent caries in children. The high concentration of fluoride in varnishes apart from caries prevention may cause changes in surface properties of esthetic restorations. The study aims to evaluate and compare the effect of four commercially available fluoride varnishes with added calcium and phosphate on microhardness of three esthetic materials namely conventional GIC (Fuji II), high viscosity GIC (Fuji IX), and nanocomposite (Filtek Z350).

Materials and methods

A total of 28 pellets were made of each material and stored in distilled water at 37 °C for 48 hours. The microhardness of the pellets was tested which served as a baseline. These were then randomly divided into four subgroups. In one subgroup Profluorid varnish was applied, second subgroup MI varnish was applied, third subgroup Embrace varnish was applied, and in the fourth subgroup Enamel Pro varnish was applied as per protocol. Thereafter, all the pellets were subjected to microhardness testing (load = 100 g for 15 seconds).

Results

The fluoride varnishes increased the microhardness of conventional GIC (Fuji II) whereas in case of high viscosity GIC (Fuji IX) the application of varnishes reduced the microhardness. In case of nanocomposite restorative material (Filtek Z350) only Profluorid varnish increased its microhardness.

Conclusion

Fluoride varnish and calcium-phosphate containing fluoride varnish effect on the microhardness of restorative material is material dependent. So, the choice of fluoride varnish with or without proprietary additives depends on the nature and composition of the restorative material.

How to cite this article

Shetty RS, Bhat SS, HK Sundeep, et al. Effect of Fluoride-based Varnishes with Added Calcium and Phosphate on Microhardness of Esthetic Restorative Materials: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(2):187-193.

Current and Advanced Nanomaterials in Dentistry as Regeneration Agents: An Update

In modern dentistry, nanomaterials have strengthened their foothold among tissue engineering strategies for treating bone and dental defects due to a variety of reasons, including trauma and tumors. Besides their finest physiochemical features, the biomimetic characteristics of nanomaterials promote cell growth and stimulate tissue regeneration. The single units of these chemical substances are small-sized particles, usually between 1 to 100 nm, in an unbound state. This unbound state allows particles to constitute aggregates with one or more external dimensions and provide a high surface area. Nanomaterials have brought advances in regenerative dentistry from the laboratory to clinical practice. They are particularly used for creating novel biomimetic nanostructures for cell regeneration, targeted treatment, diagnostics, imaging, and the production of dental materials. In regenerative dentistry, nanostructured matrices and scaffolds help control cell differentiation better. Nanomaterials recapitulate the natural dental architecture and structure and form functional tissues better compared to the conventional autologous and allogenic tissues or alloplastic materials. The reason is that novel nanostructures provide an improved platform for supporting and regulating cell proliferation, differentiation, and migration. In restorative dentistry, nanomaterials are widely used in constructing nanocomposite resins, bonding agents, endodontic sealants, coating materials, and bioceramics. They are also used for making daily dental hygiene products such as mouth rinses. The present article classifies nanostructures and nanocarriers in addition to reviewing their design and applications for bone and dental regeneration.

Functional fillers for dental resin composites

Dental resin composites (DRCs) are popular materials to repair caries. Although various types of DRCs with different characteristics have been developed, restoration failures still exist. Bulk fracture and secondary caries have been considered as main causes for the failure of composites restoration. To address these problems, various fillers with specific functions have been introduced and studied. Some fillers with specific morphologies such as whisker, fiber, and nanotube, have been used to increase the mechanical properties of DRCs, and other fillers releasing ions such as Ag⁺, Ca²⁺, and F^-, have been used to inhibit the secondary caries. These functional fillers are helpful to improve the performances and lifespan of DRCs. In this article, we firstly introduce the composition and development of DRCs, then review and discuss the functional fillers classified according to their roles in the DRCs, finally give a summary on the current research and predict the trend of future development.

Review of nano-technology applications in resin-based restorative materials

OBJECTIVE

Nanotechnology has progressed significantly and particles as small as 3 nm are being employed in resin-based restorative materials to improve clinical performance. The goal of this review is to report the progress of nanotechnology in Restorative Dentistry by reviewing the advantages, limitations, and applications of resin-based restorative materials with nanoparticles.

MATERIALS AND METHODS

A literature review was conducted using PubMed/Medline, Scopus and Embase databases. In vitro, in vivo and in situ research studies published in English between 1999 and 2020, and which focused on the analysis of resin-based restorative materials containing nanoparticles were included.

RESULTS

A total of 140 studies were included in this review. Studies reported the effect of incorporating different types of nanoparticles on adhesive systems or resin composites. Mechanical, physical, and anti-bacterial properties were described. The clinical performance of resin-based restorative materials with nanoparticles was also reported.

CONCLUSIONS

The high surface area of nanoparticles exponentially increases the bioactivity of materials using bioactive nanofillers. However, the tendency of nanoparticles to agglomerate, the chemical instability of the developed materials and the decline of rheological properties when high ratios of nanoparticles are employed are some of the obstacles to overcome in the near future.

CLINICAL SIGNIFICANCE

In spite of the recent advancements of nanotechnology in resin-based restorative materials, some challenges need to be overcome before new nano-based restorative materials are considered permanent solutions to clinical problems.

Ion release and recharge from a fissure sealant containing amorphous calcium phosphate

To assess- the release of calcium and phosphate ions from a fissure sealant containing amorphous calcium phosphate (ACP), and to determine the re-release capacity of these ions when charged with a solution containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). Nine blocks of ACP resin-based sealant were prepared and immersed in three solutions at different pH (4.0, 5.5, 7.0), and calcium and phosphate ion release was measured with ion chromatography at 1, 3, 5, 7, 14, 21 and 28 days after immersion. Sixty days after immersion, each block was charged with CPP-ACP solution in three 7-day cycles to investigate the re-release of these ions, which was measured on days 1, 3, and 7. No difference was observed in initial calcium ion release at pH 4.0 and pH 5.5. At both values, ion release was significantly higher than at pH 7.0 (p<0.001). Initial phosphate release was significantly different among the three pH values (p<0.001). After re-charging the specimens, calcium ion re-release was greater than phosphate ion release. Initial ion release from ACP resin-based sealant was greatest at the lowest pH. Ion release decreased with time. As the number of recharge cycles increased, ion re-release also improved. Phosphate ion re-release required more recharge cycles than calcium ion re-release.

Cutting-edge filler technologies to release bio-active components for restorative and preventive dentistry

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.

Novel Protein-Repellent and Antibacterial Resins and Cements to Inhibit Lesions and Protect Teeth

Orthodontic treatment is increasingly popular as people worldwide seek esthetics and better quality of life. In orthodontic treatment, complex appliances and retainers are placed in the patients’ mouths for at least one year, which often lead to biofilm plaque accumulation. This in turn increases the caries-inducing bacteria, decreases the pH of the retained plaque on an enamel surface, and causes white spot lesions (WSLs) in enamel. This article reviews the cutting-edge research on a new class of bioactive and therapeutic dental resins, cements, and adhesives that can inhibit biofilms and protect tooth structures. The novel approaches include the use of protein-repellent and anticaries polymeric dental cements containing 2-methacryloyloxyethyl phosphorylcholine (MPC) and dimethylaminododecyl methacrylate (DMAHDM); multifunctional resins that can inhibit enamel demineralization; protein-repellent and self-etching adhesives to greatly reduce oral biofilm growth; and novel polymethyl methacrylate resins to suppress oral biofilms and acid production. These new materials could reduce biofilm attachment, raise local biofilm pH, and facilitate the remineralization to protect the teeth. This novel class of dental resin with dual benefits of antibacterial and protein-repellent capabilities has the potential for a wide range of dental and biomedical applications to inhibit bacterial infection and protect the tissues.

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

Tooth decay is prevalent, and secondary caries causes restoration failures, both of which are related to demineralization. There is an urgent need to develop new therapeutic materials with remineralization functions. This article represents the first review on the cutting edge research of poly(amido amine) (PAMAM) in combination with nanoparticles of amorphous calcium phosphate (NACP). PAMAM was excellent nucleation template, and could absorb calcium (Ca) and phosphate (P) ions via its functional groups to activate remineralization. NACP composite and adhesive showed acid-neutralization and Ca and P ion release capabilities. PAMAM+NACP together showed synergistic effects and produced triple benefits: excellent nucleation templates, superior acid-neutralization, and ions release. Therefore, the PAMAM+NACP strategy possessed much greater remineralization capacity than using PAMAM or NACP alone. PAMAM+NACP achieved dentin remineralization even in an acidic solution without any initial Ca and P ions. Besides, the long-term remineralization capability of PAMAM+NACP was established. After prolonged fluid challenge, the immersed PAMAM with the recharged NACP still induced effective dentin mineral regeneration. Furthermore, the hardness of pre-demineralized dentin was increased back to that of healthy dentin, indicating a complete remineralization. Therefore, the novel PAMAM+NACP approach is promising to provide long-term therapeutic effects including tooth remineralization, hardness increase, and caries-inhibition capabilities.

Toward dental caries: Exploring nanoparticle-based platforms and calcium phosphate compounds for dental restorative materials

Millions of people worldwide suffer from a toothache due to tooth cavity, and often permanent tooth loss. Dental caries, also known as tooth decay, is a biofilm-dependent infectious disease that damages teeth by minerals loss and presents a high incidence of clinical restorative polymeric fillings (tooth colored fillings). Until now, restorative polymeric fillings present no bioactivity. The complexity of oral biofilms contributes to the difficulty in developing effective novel dental materials. Nanotechnology has been explored in the development of bioactive dental materials to reduce or modulate the activities of caries-related bacteria. Nano-structured platforms based on calcium phosphate and metallic particles have advanced to impart an anti-caries potential to restorative materials. The bioactivity of these platforms induces prevention of mineral loss of the hard tooth structure and antibacterial activities against caries-related pathogens. It has been suggested that this bioactivity could minimize the incidence of caries around restorations (CARS) and increase the longevity of such filling materials. The last few years witnessed growing numbers of studies on the preparation evaluations of these novel materials. Herein, the caries disease process and the role of pathogenic caries-related biofilm, the increasing incidence of CARS, and the recent efforts employed for incorporation of bioactive nanoparticles in restorative polymer materials as useful strategies for prevention and management of caries-related-bacteria are discussed. We highlight the status of the most advanced and widely explored interaction of nanoparticle-based platforms and calcium phosphate compounds with an eye toward translating the potential of these approaches to the dental clinical reality.

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Current progress and future applications of functional nanoparticles and remineralizing compounds incorporated in dental direct restorative materials.

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Overview of the antibacterial and remineralizing mechanisms presenting direct and indirect implications on the tooth mineral loss.

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These investigations, although in the initial phase of evidence are necessary and their results are encouraging and open the doors to future clinical studies that will allow the therapeutic value of nanotechnology-based restorative materials to be established.

Ion release, antimicrobial and physio-mechanical properties of glass ionomer cement containing micro or nanosized hexametaphosphate, and their effect on enamel demineralization

OBJECTIVES

To evaluate the effects of hexametaphosphate microparticles (mHMP) or nanoparticles (nHMP) incorporated in glass ionomer cement (GIC) on antimicrobial and physico-mechanical properties, fluoride (F) release, and enamel demineralization.

MATERIAL AND METHODS

HMP solutions were obtained at concentrations of 1, 3, 6, 9, and 12%, for screening of antimicrobial activity. Next, mHMP or nHMP at 6, 9, and 12% were incorporated into a resin-modified GIC and the antibacterial activity was evaluated. The resistance to diametral tensile and compressive strength, surface hardness, and degree of monomer conversion as well as F and HMP releases of GICs were determined. Furthermore, specimens were attached to enamel blocks and submitted to pH-cycling, and mineral loss was determined. Parametric and non-parametric tests were performed, after checking data homoscedasticity (p < 0.05).

RESULTS

HMP solutions at 6, 9, and 12% demonstrated the best antibacterial activity. GIC containing HMP showed better antibacterial effects at 9 and 12% for nHMP. Regarding F and HMP releases, the highest levels of release occurred for groups containing 9 and 12% nHMP. With the increase in HMP concentration, there was lower mineral loss. However, the incorporation of mHMP or nHMP in GIC reduced values of physico-mechanical properties when compared to the control GIC.

CONCLUSIONS

nHMP improves antimicrobial activity and fluoride release, and decreases enamel demineralization, but reduces the physico-mechanical properties of GIC.

CLINICAL RELEVANCE

The association of GIC/HMP could be an alternative material for patients at high risk for dental caries and could be indicated for low-stress regions or provisional restorations.

Protein-repelling adhesive resin containing calcium phosphate nanoparticles with repeated ion-recharge and re-releases

OBJECTIVES

The objectives were to develop a calcium (Ca) and phosphate (P) ion-rechargeable and protein-repellent adhesive containing nanoparticles of amorphous calcium phosphate (NACP) and 2-methacryloyloxyethyl phosphorylcholine (MPC), and investigate the MPC effects on ion recharge and re-releases for the first time.

METHODS

Pyromellitic glycerol dimethacrylate and ethoxylated bisphenol-A dimethacrylate were used to fabricate adhesive PEHB. Six adhesives were tested: (1) Scotchbond (SBMP); (2) PEHB, (3) PEHB + 20%NACP; (4) PEHB + 30%NACP; (5) PEHB + 20%NACP+3%MPC; (6) PEHB + 30%NACP+3%MPC. Dentin shear bond strength, Ca/P ion release, recharge and re-release, and protein adsorption were measured. A microcosm biofilm model was tested for lactic-acid production and colony-forming units (CFU).

RESULTS

Adding NACP + MPC did not negatively affect dentin bond strength (p > 0.1). With increasing the number of recharge/re-release cycles, the Ca/P ion re-release reached similarly higher levels (p > 0.1), indicating long-term remineralization capability. One recharge enabled the adhesives to have continued re-releases for 21 days. Incorporation of 3% MPC yielded 10-fold decrease in protein adsorption, and 1-2 log decrease in biofilm CFU.

CONCLUSIONS

The new rechargeable adhesive with MPC + 30%NACP greatly reduced protein adsorption, biofilm growth and lactic acid. Incorporation of MPC did not compromise the excellent Ca/P ion release, rechargeability, and dentin bond strength.

CLINICAL SIGNIFICANCE

Novel bioactive adhesive containing MPC + NACP is promising to repel proteins and bacteria, and inhibit secondary caries at the restoration margins. The method of NACP + MPC to combine CaP-recharge and protein-repellency is applicable to the development of a new generation of materials including composites and cements to suppress oral biofilms and plaque formation and protect tooth structures.

Bioactive Dental Composites and Bonding Agents Having Remineralizing and Antibacterial Characteristics

Current dental restorative materials are typically inert and replace missing tooth structures. This article reviews efforts in the development of a new generation of bioactive materials designed to not only replace the missing tooth volume but also possess therapeutic functions. Composites and bonding agents with remineralizing and antibacterial characteristics have shown promise in replacing lost minerals, inhibiting recurrent caries, neutralizing acids, repelling proteins, and suppressing biofilms and acid production. Furthermore, they have demonstrated a low cytotoxicity similar to current resins, with additional benefits to protect the dental pulp and promote tertiary dentin formation. This new class of bioactive materials shows promise in reversing lesions and inhibiting caries.

Polymerization kinetics of experimental bioactive composites containing bioactive glass

OBJECTIVES

To investigate the polymerization kinetics and the degree of conversion (DC) of experimental resin composites with varying amount of bioactive glass 45S5 (BG).

METHODS

Experimental resin composites based on a photo-curable Bis-GMA/TEGDMA resin system were prepared. The composite series contained 0, 5, 10, 20, and 40 wt% of BG and reinforcing fillers up to the total filler amount of 70 wt%. Composite specimens were light cured with 1219 mW/cm² for 20 or 40 s and their DC was monitored during 5 min at the data collection rate of 2 s^-1 using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).

RESULTS

The 5-min DC values for experimental composites were in the range of 42.4-55.9% and 47.3-57.9% for curing times of 20 and 40 s, respectively. The differences in the 5-min DC between curing times of 20 s or 40 s became more pronounced in materials with higher BG amount. Within both curing times, a decreasing trend of the 5-min DC values was observed with the increasing percentage of BG fillers. The maximum polymerization rate also decreased consistently with the increasing BG amount.

CONCLUSIONS

Unsilanized BG fillers showed a dose-dependent inhibitory effect on polymerization rate and the DC. Extending the curing time from 20 to 40 s showed a limited potential to improve the DC of composites with higher BG amount.

SIGNIFICANCE

The observed inhibitory effect of BG fillers on the polymerization of resin composites may have a negative influence on mechanical properties and biocompatibility.

Curing potential of experimental resin composites with systematically varying amount of bioactive glass: Degree of conversion, light transmittance and depth of cure

OBJECTIVES

The aim of this work was to investigate the curing potential of an experimental resin composite series with the systematically varying amount of bioactive glass 45S5 by evaluating the degree of conversion, light transmittance and depth of cure.

METHODS

Resin composites based on a Bis-GMA/TEGDMA resin with a total filler load of 70 wt% and a variable amount of bioactive glass (0-40 wt%) were prepared. The photoinitiator system was camphorquinone and ethyl-4-(dimethylamino) benzoate. The degree of conversion and light transmittance were measured by Raman spectroscopy and UV-vis spectroscopy, respectively. The depth of cure was evaluated according to the classical ISO 4049 test.

RESULTS

The initial introduction of bioactive glass into the experimental series diminished the light transmittance while the further increase in the bioactive glass amount up to 40 wt% caused minor variations with no clear trend. The curing potential of the experimental composites was similar to or better than that of commercial resin composites. However, unsilanized bioactive glass fillers demonstrated the tendency to diminish both the maximum attainable conversion and the curing efficiency at depth.

CONCLUSIONS

Experimental composite materials containing bioactive glass showed a clinically acceptable degree of conversion and depth of cure. The degree of conversion and depth of cure were diminished by bioactive glass fillers in a dose-dependent manner, although light transmittance was similar among all of the experimental composites containing 5-40 wt% of bioactive glass.

CLINICAL SIGNIFICANCE

Reduced curing potential caused by the bioactive glass has possible consequences on mechanical properties and biocompatibility.

Trends in restorative composites research: what is in the future?

Clinical trials have identified secondary caries and bulk fracture as the main causes for composite restoration failure. As a measure to avoid frequent reinterventions for restoration replacement, composites with some sort of defense mechanism against biofilm formation and demineralization, as well as materials with lower susceptibility to crack propagation are necessary. Also, the restorative procedure with composites are very time-consuming and technically demanding, particularly concerning the application of the adhesive system. Therefore, together with bulk-fill composites, self-adhesive restorative composites could reduce operator error and chairside time. This literature review describes the current stage of development of remineralizing, antibacterial and self-healing composites. Also, an overview of the research on fiber-reinforced composites and self-adhesive composites, both introduced for clinical use in recent years, is presented.

Effect of calcium phosphate nanocomposite on in vitro remineralization of human dentin lesions

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, 1h per day) and remineralization (pH 7, 23h 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.

Novel multifunctional dental cement to prevent enamel demineralization near orthodontic brackets

OBJECTIVES

White spot lesions due to biofilm acid-induced enamel demineralization are prevalent in orthodontic treatments. The aim of this study was to develop a novel bioactive multifunctional cement with protein-repellent, antibacterial and remineralizing capabilities, and investigate the effects on enamel hardness and lesion depth in vitro for the first time.

MATERIALS AND METHODS

2-Methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM), and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into a resin-modified glass ionomer (RMGI). Extracted human premolars had brackets bonded via four groups: (1) Transbond XT (TB), (2) RMGI (GC Ortho LC), (3) RMGI+MPC+DMAHDM, (4) RMGI+MPC+DMAHDM+NACP. Demineralization was induced via a dental plaque microcosm biofilm model. Samples were tested using polarized light microscopy (PLM) for lesion depth. Enamel hardness was tested for different groups.

RESULTS

Incorporating MPC, DMAHDM and NACP did not affect enamel bond strength. "RMGI+MPC+DMAHDM+NACP" group had the least lesion depth in enamel (p<0.05). Groups with NACP had the highest enamel hardness (p<0.05). Mineral loss (ΔS) in enamel for NACP group was about one third that for RMGI control. "RMGI+MPC+DMAHDM" had greater effect on demineralization-inhibition, compared to RMGI and TB controls. "RMGI+MPC+DMAHDM+NACP" was more effective in protecting enamel prisms from dissolution by biofilm acids, compared to RMGI and TB control groups.

CONCLUSION

The Novel "RMGI+MPC+DMAHDM+NACP" cement substantially reduced enamel demineralization adjacent to orthodontic brackets, yielding much less lesion depth and greater enamel hardness under biofilm acid attacks than commercial controls. The clinical significance is that the novel multi-agent (RMGI+MPC+DMAHDM+NACP) method is promising for a wide range of preventive and restorative applications to combat caries.

Poly(amido amine) and calcium phosphate nanocomposite remineralization of dentin in acidic solution without calcium phosphate ions

OBJECTIVE

Patients with dry mouth often have an acidic oral environment lacking saliva that provides calcium (Ca) and phosphate (P) ions. However, there has been no study on dentin remineralization by placing samples in an acidic solution without Ca and P ions. Previous studies used saliva-like solutions with neutral pH and Ca and P ions. Therefore, the objective of this study was to investigate a novel method of combining poly(amido amine) (PAMAM) with a composite of nanoparticles of amorphous calcium phosphate (NACP) on dentin remineralization in an acidic solution without Ca and P ions for the first time.

METHODS

Demineralized dentin specimens were tested into four groups: (1) dentin control, (2) dentin coated with PAMAM, (3) dentin with NACP nanocomposite, (4) dentin with PAMAM plus NACP composite. Specimens were treated with lactic acid at pH 4 without initial Ca and P ions for 21 days. Acid neutralization and Ca and P ion concentrations were measured. Dentin specimens were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and hardness testing vs. remineralization efficacy.

RESULTS

NACP composite had mechanical properties similar to commercial control composites (p>0.1). NACP composite neutralized acid and released Ca and P ions. PAMAM alone failed to induce dentin remineralization. NACP alone achieved mild remineralization and slightly increased dentin hardness at 21days (p>0.1). In contrast, the PAMAM+NACP nanocomposite method in acid solution without initial Ca and P ions greatly remineralized the pre-demineralized dentin, restoring its hardness to approach that of healthy dentin (p>0.1).

SIGNIFICANCE

Dentin remineralization via PAMAM+NACP in pH 4 acid without initial Ca and P ions was demonstrated for the first time, when conventional methods such as PAMAM did not work. The novel PAMAM+NACP nanocomposite method is promising to protect tooth structures, especially for patients with reduced saliva to inhibit caries.

Antibacterial Activity and Bonding Ability of an Orthodontic Adhesive Containing the Antibacterial Monomer 2-Methacryloxylethyl Hexadecyl Methyl Ammonium Bromide

Irreversible white spot lesion (WSL) occurs in up to 50% of patients during orthodontic treatment. Therefore, orthodontic adhesives need to be able to inhibit or reduce bacterial growth in order to prevent or minimize WSL. This study evaluated the antibacterial effect and shear bond strength (SBS) of a resin-based orthodontic adhesive containing the antibacterial monomer 2-methacryloxylethyl hexadecyl methyl ammonium bromide (MAE-HB). MAE-HB was added at three concentrations (1, 3, and 5 wt%) to a commercial orthodontic adhesive Transbond XT, while the blank control comprised unmodified Transbond XT. Their antibacterial effects on Streptococcus mutans were investigated after 0 and 180 days of aging. The SBS of metal brackets bonded to the buccal enamel surface of human premolars was assessed. Compared with the blank control, the MAE-HB-incorporated adhesive exhibited a significant contact inhibitory effect on the growth of S. mutans (P < 0.05), even after 180 days of aging. SBS and adhesive remnant index values revealed that the bonding ability of the experimental adhesive was not significantly adversely affected by the incorporation of MAE-HB at any of the three concentrations. Therefore, orthodontic adhesives with strong and long-lasting bacteriostatic properties can be created through the incorporation of MAE-HB without negatively influencing bonding ability.

Antibacterial Properties of Calcium Fluoride-Based Composite Materials: In Vitro Study

The aim of the study was to evaluate antibacterial activity of composite materials modified with calcium fluoride against cariogenic bacteria S. mutans and L. acidophilus. One commercially available conventional light-curing composite material containing fluoride ions (F2) and two commercially available flowable light-curing composite materials (Flow Art and X-Flow) modified with 1.5, 2.5, and 5.0 wt% anhydrous calcium fluoride addition were used in the study. Composite material samples were incubated in 0.95% NaCl at 35°C for 3 days; then dilution series of S. mutans and L. acidophilus strains were made from the eluates. Bacteria dilutions were cultivated on media afterwards. Colony-forming unit per 1 mL of solution (CFU/mL) was calculated. Composite materials modified with calcium fluoride highly reduced (p < 0.001) bacteria growth compared to commercially available composite materials containing fluoride compounds. The greatest reduction in bacteria growth was observed for composite materials modified with 1.5% wt. CaF₂. All three tested composite materials showed statistically greater antibacterial activity against L. acidophilus than against S. mutans.