Review on fluoride-releasing restorative materials--fluoride release and uptake characteristics, antibacterial activity and influence on caries formation

Effect of a novel glass ionomer cement containing fluoro-zinc-silicate fillers on biofilm formation and dentin ion incorporation

OBJECTIVES

This study is aimed at evaluating the effect of a new glass ionomer cement (GIC) containing fluoro-zinc-silicate fillers on biofilm formation and ion incorporation.

MATERIALS AND METHODS

Streptococcus mutans biofilms were developed on two GIC materials: Caredyne Restore (CD) and Fuji VII (FJ); and hydroxyapatite (HA) for 24 h at 37 °C using a flow cell system. The morphological structure and bacterial viability were analyzed using a confocal laser scanning microscopy. Bacterial adhesion during the initial 2 h was also assessed by viable cell counting. To study the ion incorporation, restored cavities prepared on the root surfaces of human incisors were subjected to the elemental mapping of the zinc and fluoride ions in the GIC-dentin interface using a wavelength-dispersive X-ray spectroscopy electron probe microanalyzer.

RESULTS

Morphological observations revealed that biofilm formation in the CD group was remarkably inhibited compared with the HA and FJ groups, exhibiting sparse, thinner biofilm clusters. The microorganisms adhering to the CD group were significantly inhibited, revealing 2.9 ± 0.4 for CD, 4.9 ± 0.2 for FJ, and 5.4 ± 0.4 log colony-forming units (CFU) for HA. The CD zinc ion incorporation depth was 72.2 ± 8.0 μm. The fluoride penetration of CD was three times deeper than that of FJ; this difference was statistically significant (p < 0.05).

CONCLUSIONS

Enhanced by the incorporation of zinc and fluoride ions, the new GIC inhibited biofilm formation by interfering with bacterial adhesion.

CLINICAL RELEVANCE

A novel GIC comprised of fluoro-zinc-silicate fillers may improve clinical outcomes, such as root caries and minimally invasive dentistry.

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

OBJECTIVE

This 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.

METHODS

Standardized 4×4mm 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 48h. 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).

RESULTS

None 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.

SIGNIFICANCE

The addition of 10% QAM with a 16-carbon chain in experimental composites reduced mineral loss at the enamel-restoration margins after cariogenic challenge.

Restorative treatment of primary teeth: an evidence-based narrative review

Various methods, with a variety of materials, exist for restoring carious primary teeth. Successful restoration of primary teeth is dependent on accurate diagnosis, knowledge of the caries process, knowledge of dental materials, and treatment choice. The purpose of this evidence-based review is to present evidence that will help clinicians to make an appropriate diagnosis, from which the optimum treatment plan can be made; to explore the literature regarding restoration of carious primary teeth; and to try and draw conclusions as to which materials and methods can be recommended. This review will primarily deal with the restoration of carious cavities in primary molars. A short discussion on restoration of primary incisors is included, with presentation of what limited evidence there is relating to this.

Adsorptive Removal of Fluoride from Water Using Nanomaterials of Ferrihydrite, Apatite, and Brucite: Batch and Column Studies

This study investigated the adsorptive removal of fluoride from simulated water pollution using various (hydro)oxide nanomaterials, which have the potential to be used as sorbents for surface water and groundwater remediation. Tested nanomaterials include hematite, magnetite, ferrihydrite, goethite, hematite-alpha, hydroxyapatite (HAP), brucite, and four titanium dioxides (TiO₂-A [anatase], TiO₂-B [rutile], TiO₂-C [rutile], and TiO₂-D [anatase]). Among 11 (hydro)oxide nanomaterials tested in this study, ferrihydrite, HAP, and brucite showed two to five times higher removal of fluoride than other nanomaterials from synthetic fluoride solutions. Freundlich and Redlich-Peterson adsorption isotherms better described the adsorptive capacity and mechanism than the Langmuir isotherm based on higher R ² values, indicating better fit of the regression predictions. In addition, the adsorption kinetics were well described by the intraparticle diffusion model. Column studies in a fixed bed continuous flow through system were conducted to illustrate the adsorption and desorption behavior of fluoride on ferrihydrite, HAP, or brucite. Experimental results fitted well with the Thomas model because of the R ² values at least 0.885 or higher. By comparisons of the adsorption capacity and the rate constant, columns packed with ferrihydrite exhibited not only faster rates but also higher sorption capacity than those packed with HAP or brucite. Desorption tests in deionized water showed that the adsorbed fluoride could be desorbed at a lower efficiency, ranging from 4.0% to 8.9%. The study implicated that (hydro)oxide nanomaterials of iron calcium and magnesium could be effective sorptive materials incorporated into filtration systems for the remediation of fluoride polluted water.

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.

[Clinical efficacy of the glass ionomer cement used as pit and fissure sealant with and without acid etching in primary teeth]

OBJECTIVE

This work aimed to compare the effect of retention and preventive caries of the pit and fissure sealant on primary teeth by using glass ionomer cements (GIC) with or without acid etching technique.

METHODS

In this clinical trail, 100 children aged 3-4 years old with a split-mouth design were equally divided into two groups (the left second upper and lower mandibular primary molars were present in group A, and the right second upper and lower mandibular primary molars were present in group B; each group had 200 molars). All participants were placed in pit and fissure sealant with Ketac® Molar Easymix and seated with atraumatic restorative treatmen press-finger technique in the two groups. Group A was subjected to acid etching (40 s, 35% H₃PO₄), while group B were not subjected to acid etching. GIC preservation rate, caries rate, and decayed teeth (dt) index were observed after 12 months.

RESULTS

After a 12-month follow-up period, the completely lost, partially losing, and losing rates of GIC in 86 children (172 second primary molars) were 83.14%, 9.88%, 6.98% in group A and 62.79%, 20.35%, and 16.86% in group B, respectively. The differences between the two groups were insignificant (P<0.05). The caries rates of groups A and B were 8.14% and 16.86%, and their dt indices were 0.08±0.31 and 1.17±0.46, respectively, thereby indicating significant difference between the two groups (P<0.05).

CONCLUSIONS

Using acid etching technology, the retention rate of the pit and fissure sealant increased, while its losing rate decreased. The retention effect of the GIC was improved, and the dental caries prevention effect was enhanced. Sealant processing was a self-curing procedure that sets without the external energy. Hence, this procedure is suitable for the preventive caries of primary teeth in children.

Antimicrobial Thiol-ene-acrylate Photosensitive Resins for DLP 3D Printing

Designing digital light processing (DLP) 3D printable photosensitive resins with antibacterial properties is especially vital because of their potential applications in various biomedical fields. In this contribution, a thiol-ene-acrylate ternary system with reduced volume shrinkage and fast photopolymerization rate was chosen as the antibacterial 3D printing matrix resin. Two quaternary ammonium salt-type antibacterial agents (QAC and SH-QAC) with different molecular weight were designed and prepared, which can participate in the curing of matrix resin to achieve contact antibacterial effect. The effects of antibacterial agent content on the photopolymerization kinetics and on thermal and mechanical properties were discussed in detail. When the amount of added QAC is 4wt%, the antibacterial rate is almost 100% for Escherichia coli and Staphylococcus aureus, and when the amount of SH-QAC is 10wt%, the antibacterial rate against S. aureus is also essentially 100%. Both antibacterial photosensitive resins have been successfully applied in DLP technology to fabricate tooth model with high precision.

Effect of trifluoroethyl methacrylate comonomer on physical properties of Bis-GMA based dental composites

The purpose of this study was to investigate the effect of substituting triethyleneglycol dimethacrylate (TEGDMA) with 2,2,2-trifluoroethyl methacrylate (TFEMA) on water sorption, water solubility, degree of conversion, polymerization shrinkage, fluoride release and flexural strength of bisphenol-A-glycerolate dimethacrylate (Bis-GMA)/TEGDMA/urethane dimethacrylate (UDMA) dental composites. Flexural strength, water sorption and water solubility were measured according to ISO 4049 standard. Degree of conversion was determined by FTIR technique. Fluoride release rate in deionized water at 37°C was determined by using photometric method. One-way ANOVA and Tukey's HSD tests were used for statistical significance analysis (p<0.05). The results demonstrated that TFEMA decreased water solubility and volumetric shrinkage significantly but neither reduced water sorption, enhanced flexural strength nor improved degree of conversion. Partial substitution of TEGDMA with TFEMA in Bis-GMA/TEGDMA/UDMA dental composite had positive effect on its water solubility and volumetric shrinkage quality.

An improved dental composite with potent antibacterial function

A new BisGMA-based antibacterial dental composite has been formulated and evaluated. Compressive strength and bacterial viability were utilized to evaluate the formed composites. It was found that the new composite exhibited a significantly enhanced antibacterial function along with improved mechanical and physical properties. The bromine-containing derivative-modified composite was more potent in antibacterial activity than the chlorine-containing composite. The modified composites also exhibited an increase of 30–53% in compressive yield strength, 15–30% in compressive modulus, 15–33% in diametral tensile strength and 6–20% in flexural strength, and a decrease of 57–76% in bacterial viability, 23–37% in water sorption, 8–15% in shrinkage, 8–13% in compressive strength, and similar degree of conversion, than unmodified composite. It appears that this experimental composite may possibly be introduced to dental clinics as an attractive dental restorative due to its improved properties as well as enhanced antibacterial function.

Metallogels: Availability, Applicability, and Advanceability

Introducing metal components into gel matrices provides an effective strategy to develop soft materials with advantageous properties such as: optical activity, conductivity, magnetic response activity, self-healing activity, catalytic activity, etc. In this context, a thorough overview of application-oriented metallogels is provided. Considering that many well-established metallogels start from serendipitous discoveries, insights into the structure-gelation relationship will offer a profound impact on the development of metallogels. Initially, design strategies for discovering new metallogels are discussed, then the advanced applications of metallogels are summarized. Finally, perspectives regarding the design of metallogels, the potential applications of metallogels and their derivative materials are briefly proposed.

Evaluation of Restorative Materials Containing Preventive Additives in a Secondary Caries Model in vitro

The incorporation of antibacterial agents into dental restorative materials is a promising strategy for secondary caries prevention. Previously, Carolacton affected Streptococcus mutans biofilm formation on composite materials in vitro. The present study evaluated secondary caries formation adjacent to Carolacton-containing composites and conventional restorative materials using an artificial biofilm model. Standardized cavities were prepared in bovine dentin-enamel samples (n = 175) and restored with various dental materials (Tetric EvoCeram [T], GrandioSo composite without [G] and with Carolacton [GC], Grandio Flow without [F] and with Carolacton [FC], GrandioSo containing sodium fluoride [GNaF], and Ketac Fil [K]). After artificial aging, S. mutans was grown on the samples for 7 days. The investigation of gap sizes and secondary caries formation was performed using confocal laser scanning microscopy and transversal microradiography. Median gap size in enamel was 9.4 µm (interquartile range 7.9–12.7). Compared to all other groups significant differences in gap sizes could be observed for Ketac Fil (p < 0.001; Mann-Whitney test). Only GrandioSo composite containing 30% sodium fluoride and Ketac Fil showed significantly smaller lesion areas in enamel (p < 0.001; Mann-Whitney test) than all other groups which was confirmed by the mineral loss data (p < 0.001; Mann-Whitney test). Based on the present in vitro results, it seems that Carolacton-containing composite in the current formulation within the shown simplified monoculture biofilm model is not able to prevent caries formation compared to fluoride-releasing restorative materials.

Synthesis and characterization of Ciprofloxacin-containing divinyl oligomers and assessment of their biodegradation in simulated salivary esterase

OBJECTIVE

Two leading causes contributing to dental restoration replacement are the marginal breakdown at the composite/dentin interface and secondary caries mediated by bacteria. The objective of the present study was to synthesize oligomers which incorporated enhanced bio-stability but would also be able to generate antimicrobial function if they underwent degradation.

METHODS

Stability was incorporated into the oligomers by generating structural features that would physically hinder the availability of hydrolytically sensitive groups in the oligomers. As a proof-of concept for the antibacterial feature, antimicrobial function was achieved by covalently incorporating Ciprofloxacin (CF) into the backbone of cross-linking divinyl oligomers (referred to as EDV and HLH-CFPEG). The hydrolytic stability of the oligomers was studied in simulated human salivary esterase and compared to the commercial monomer 2,2-bis[4(2-hydroxy-3-methacryloxypropoxy)-phenyl]propane (BisGMA).

RESULTS

Both drug oligomers were found to be significantly more stable than BisGMA. Upon degradation, both drug oligomers released CF differentially in free form. Polymer synthesis from resin formulations containing 15wt% HLH-CFPEG showed a high degree of vinyl group conversion and gel content, and under hydrolytic conditions showed the release of CF during a 28-day monitoring study period.

SIGNIFICANCE

HLH-CFPEG can be used in dental resin adhesive systems for local delivery of CF to the marginal interface. Minimizing the growth of Streptococcus mutans at the marginal site can improve longevity by reducing esterase activity derived specifically from S. mutans.

A photo-crosslinked hybrid interpenetrating polymer network (IPN) for antibacterial coatings on denture base materials

An interpenetrating polymer network (IPN) structured antibacterial layer was prepared on dental base materials using a one-step photo-crosslinking method.

Polymer–antibiotic conjugates as antibacterial additives in dental resins

Dental resins containing polymer–antibiotic conjugates (PACs) demonstrate significant antibacterial properties.

Fluoride Release from Glass Ionomer with Nano Filled Coat and Varnish

OBJECTIVE

This in vitro study compares the fluoride release from microlaminated glass ionomer based on glass hybrid technology coated with two different surface coating agents.

MATERIALS AND METHODS

A total of 18 samples were divided into three groups of six samples each: (1) glass ionomer Equia Forte Fil coated with Equia Forte Coat (Equia+EC), (2) glass ionomer Equia Forte Fil coated with GC Fuji Varnish (Equia+VC) and (3) uncoated glass ionomer Equia Forte (EQUIA cont). Fluoride release was measured using an ion-selective electrode (ORION EA 940) after 24 hours, 4 days, 30 days and 64 days. Repeated measures ANOVA, multiple comparisons, Tukey's test and paired t-test were used to test the differences between the groups.

RESULTS

The differences between the groups and four time points were statistically significant (ANOVA, p<0.0001). Cumulative fluoride ion release after 64 days was 66.01 mg/l, 123.54mg/l and 203.22 mg/l for EQUIA+EC, EQUIA+VC and EQUIA cont, respectively. All the differences were statistically significant except the difference between EQUIA+VC and EQUIA cont after 24 hours.

CONCLUSIONS

The amount of released fluoride was significantly lower in the samples coated with nanofilled surface coating agent compared to the samples coated with varnish and uncoated samples.

Positive correlation between fluoride release and acid erosion of restorative glass-ionomer cements

OBJECTIVE

The aim of this study was to determine whether there is a correlation between acid erosion and fluoride release of conventional glass ionomer cements.

METHODS

Ten specimens for each material were prepared for fluoride release tests and five for acid erosion tests separately. After placed in pH cycling solution, concentration of fluoride was measured by a fluoride-ion selective electrode each day for 15 days. For the acid erosion test, specimens were immersed in a lactic acid solution and their depth measured with a spring-loaded dial gauge. The data were submitted to 3-way ANOVA, followed by Tukey's test (p<0.05) RESULTS: All materials showed ability to elute fluoride in the 15 day period of the test, with the same pattern of high fluoride release at the first 24h. Despite this, the amount of fluoride released was statistically different among the 18 groups, with the highest for Maxxion R and the lowest for Chemfil Rock (p>0.05). The highest acid erosion values were registered for Magic Glass, Ion Z, VitroFil and Maxxion R, which exceeded the maximum stipulated by the relevant ISO test (ISO 9917-1). A positive linear correlation (r²=0.4886) was found for both properties, i.e., higher fluoride release is related to higher acid erosion.

SIGNIFICANCE

Acid erosion and fluoride release are related properties of GICs, though factors such as pH and P/L ratio lead to differences between actual values for individual brands of these materials.

Fluorine-ion-releasing injectable alginate nanocomposite hydrogel for enhanced bioactivity and antibacterial property

The creation of a moist environment and promotion of cell proliferation and migration together with antibacterial property are critical to the wound-healing process. Alginate (Alg) is an excellent candidate for injectable wound dressing materials because it can form a gel in a mild environment. Taking advantage of its gelation property, an injectable nano composite hydrogel containing nano-sized (about 90 nm) calcium fluoride (CaF₂) particles was developed using in-situ precipitation process. The amount of released fluorine (F^-) ion from the nanocomposite hydrogel increased with increasing CaF₂ content inside the composite hydrogel and the ions stimulated both the proliferation and migration of fibroblast cells in vitro. The antibacterial property of the composite hydrogel against E. coli and S. aureus was confirmed through colony formation test where the number of bacterial colonies significantly decreased compared to Alg hydrogel. The in vivo results based on a full-thickness wound model showed that the nanocomposite hydrogel effectively enhanced the deposition of the extracellular matrix compared to that of the Alg hydrogel. This study demonstrates the potential of this nanocomposite hydrogel as a bioactive injectable wound-dressing material with the ability to inhibit bacterial growth and stimulate cell proliferation and migration for accelerated wound healing.

Influence of Ultrapulsed CO2 Laser, before Application of Different Types of Fluoride, on the Increase of Microhardness of Enamel In Vitro

Objective

To evaluate the influence of ultrapulsed CO₂ laser in combination with commercial fluoride products in order to verify the increase of microhardness of artificial enamel caries lesions.

Materials and Methods

Bovine enamel specimens were prepared, and artificial enamel caries lesions were created. Teeth were randomly divided into 5 groups (n=10): treated with laser (L), laser + neutral fluoride gel 2% (LNF), laser + acidulated phosphate fluoride gel 1.23% (LAFG), laser + acidulated fluoride mousse 1.23% (LAFM), and laser + fluoride varnish 5% (LFV). Microhardness was evaluated at baseline, after caries induction, after CO₂ laser irradiation + fluoride treatment in the 1st week, and after fluoride treatment at 3rd and 5th week.

Results

There was a decrease in microhardness in all groups after artificial enamel caries lesion formation; no increase in microhardness was found in the first and third weeks in all groups (p > 0.05). In the fifth week, an increase in microhardness occurred in all groups (p < 0.05).

Conclusion

Although CO2 laser irradiation in combination with different commercial fluoride products was capable of increasing microhardness on enamel caries lesions in bovine tooth enamel it is necessary to confirm these results by testing the isolated effect of fluoride on enamel surface microhardness. Also, although microhardness was higher in the fluoride varnish group than in the other groups in the fifth week it is not possible to discard the best effect of fluoride varnish treatment on absence of artifacts that may occur with the other fluoride treatments.

Clinical Relevance

In order to prove that CO2 laser may contribute to an increase in microhardness when applied to enamel lesions in combination with different commercial fluoride products it is necessary to conduct additional studies. Also, higher microhardness of fluoride varnish group should be carefully considered.

Inhibition of dentin matrix-bound cysteine cathepsins by potassium fluoride

Matrix metalloproteinases (MMPs) and cysteine cathepsins (CCs) can break down unprotected type I collagen fibrils in dentin matrix. This study investigated the use of potassium fluoride (KF) as a potential inhibitor of MMPs and CCs in dentin. Demineralized dentin beams were divided into groups (n = 10 in each group) and incubated in artificial saliva (AS, control), either alone or with one of seven concentrations of KF (6-238 mM fluoride) for 1, 7, and 21 d. After 21 d, all groups were further aged in AS for 6 months. Total MMP activity was screened using the colorimetric MMP assay. The activities of MMP-2 and MMP-9 were investigated using gelatin zymography. At the end of each incubation, changes in loss of dry mass and CC-mediated or total dissolution of collagen peptides were measured via precision weighing, C-terminal crosslinked telopeptide of type I collagen (CTX), and hydroxyproline (HYP) assays. The beams were examined using scanning electron microscopy. After 21 d, total MMP activities, dry mass loss, and CTX release for the groups exposed to 179 and 238 mM fluoride were significantly lower compared with the control group. After 6 months, all groups showed similar total MMP activity, dry mass loss, and HYP release, and CTX levels were significantly lower when the fluoride concentration was ≥24 mM. Calcium fluoride (CaF₂ )-like precipitates were observed over the beams. In summary, KF significantly inhibited the catalytic activity of dentin matrix-bound CCs but did not seem to be effective for MMP-mediated activity.

Modification of glass ionomer cements on their physical-mechanical and antimicrobial properties

OBJECTIVE

The aim of this review was to provide an insight about the factors affecting the properties of glass ionomer cements and provides a review regarding studies that are related to modification of glass ionomer cements to improve their properties, particularly on physical-mechanical and antimicrobial activity.

METHODS

PubMed and Science Direct were searched for papers published between the years 1974 and 2018. The search was restricted to articles written in English related to modification of glass ionomer cements. Only articles published in peer-reviewed journals were included. The search included literature reviews, in vitro, and in vivo studies. Articles written in other languages, without available abstracts and those related to other field were excluded. About 198 peer-review articles in the English language were reviewed.

CONCLUSION

Based on the finding, most of the modification has improved physical-mechanical properties of glass ionomer cements. Recently, researchers have attempted to improve their antimicrobial properties. However, the attempts were reported to compromise the physical-mechanical properties of modified glass ionomer cements.

CLINICAL SIGNIFICANCE

As the modification of glass ionomer cement with different material improved the physical-mechanical and antimicrobial properties, it could be used as restorative material for wider application in dentistry.

Evaluation of the efficiency of fluoride-releasing adhesives for preventing secondary caries in-vitro: a systematic review and meta-analysis

AIM

To evaluate the efficiency of fluoride-releasing adhesives for the prevention of secondary caries on in-vitro tests.

MATERIALS AND METHODS

This study was performed according to the PRISMA checklist. The bibliographic research was performed to identify in-vitro studies between January 2000 and September 2017. The selected studies were submitted to bias risk assessment and data extraction. In the meta-analysis the data were evaluated using Review Manager Software.

RESULTS

The 11 studies that met all inclusion criteria showed that the most common risks of bias were: absence of the sample size calculation description, absence of the single operator protocol and blind operation of the test machine. The meta-analysis was performed with six studies that used polarised light microscopy in order to quantify the mineral content of dentine and presented the values as means and standard deviations.

CONCLUSIONS

Most of the authors presented that the fluoride-containing adhesive systems had a significant effect to reduce in-vitro secondary caries. The meta-analysis did not present statistical difference between fluoride-free and fluoride-containing adhesive systems. The artificial caries challenge methodology may have affected the results.

Clinical wear of approximal glass ionomer restorations protected with a nanofilled self-adhesive light-cured protective coating

High viscous glass ionomer cement (GIC) has gained popularity as a restorative material; however, high wear is pointed as one of the major drawbacks of this material. Protective surface coatings were developed to protect GIC from water contamination with the additional advantage of occluding any surface cracks or porosities commonly found in this material, possibly resulting in an increased wear resistance of the restorations.

Contraction and Hydroscopic Expansion Stress of Dental Ion-Releasing Polymeric Materials

Ion-releasing polymeric restorative materials seem to be promising solutions, due to their possible anticaries effect. However, acid functional groups (monomers) and glass filler increase hydrophilicity and, supposedly, water sorption. The purpose of the study was to evaluate the influence of water sorption of polymeric materials on the stress state at the restoration-tooth interface. Beautifil Bulk Fill Flow, Beautifil Flow Plus F00, Beautifil Flow F02, Dyract eXtra, Compoglass Flow, Ionosit, Glasiosite, TwinkiStar, Ionolux and Fuji II LC were used for the study. The stress state was measured using photoelastic analysis after: 0.5, 24, 72, 96, 168, 240, 336, 504, 672, 1344 and 2016 h. Moreover, water sorption, solubility and absorption dynamic were assessed. The water sorption, solubility and absorption dynamic of ion-releasing restorative materials are material dependent properties. The overall results indicated that the tested restorative materials showed significant stress decrease. The total reduction in contraction stress and water expansion stress was not observed for materials with low value of water sorption (Beautifil Bulk Fill, Dyract eXtra, Glasionosit and Twinky Star). The photoelastic method turned out to be inadequate to evaluate stress changes of resin modified glass-ionomer cement (RMGI, Fuji II LC and Ionolux).

Mechanical loading, an important factor in the evaluation of ion release from bone augmentation materials

The controlled release of therapeutic inorganic ions from biomaterials is an emerging area of international research. One of the foci for this research is the development of materials, which spatially and temporally modulate therapeutic release, via controlled degradation in the intended physiological environment. Crucially however, our understanding of the release kinetics for such systems remains limited, particularly with respect to the influence of physiological loading. Consequently, this study was designed to investigate the effect of dynamic mechanical loading on a composite material intended to stabilize, reinforce and strengthen vertebral bodies. The composite material contains a borate glass engineered to release strontium as a therapeutic inorganic ion at clinically relevant levels over extended time periods. It was observed that both cyclic (6 MPa 2 Hz) and static (4.3 MPa) compressive loading significantly increased the release of strontium ions in comparison to the static unloaded case. The observed alterations in ion release kinetics suggest that the mechanical loading of the implantation environment should be considered when evaluating the ion release kinetics.

Effects of a bleaching agent on properties of commercial glass-ionomer cements

Objectives

This study evaluated the effects of a bleaching agent on the composition, mechanical properties, and surface topography of 6 conventional glass-ionomer cements (GICs) and one resin-modified GIC.

Materials and Methods

For 3 days, the specimens were subjected to three 20-minute applications of a 37% H₂O₂-based bleaching agent and evaluated for water uptake (WTK), weight loss (WL), compressive strength (CS), and Knoop hardness number (KHN). Changes in surface topography and chemical element distribution were also analyzed by energy-dispersive X-ray spectroscopy and scanning electron microscopy. For statistical evaluation, the Kruskal-Wallis and Wilcoxon paired tests (α = 0.05) were used to evaluate WTK and WL. CS specimens were subjected to 2-way analysis of variance (ANOVA) and the Tukey post hoc test (α = 0.05), and KH was evaluated by one-way ANOVA, the Holm-Sidak post hoc test (α = 0.05), and the t-test for independent samples (α = 0.05).

Results

The bleaching agent increased the WTK of Maxxion R, but did not affect the WL of any GICs. It had various effects on the CS, KHN, surface topography, and the chemical element distribution of the GICs.

Conclusions

The bleaching agent with 37% H₂O₂ affected the mechanical and surface properties of GICs. The extent of the changes seemed to be dependent on exposure time and cement composition.

Surface modification of polyurethane with a hydrophilic, antibacterial polymer for improved antifouling and antibacterial function

Antimicrobial surface is important for the inhibition of bacteria or biofilm formation on biomaterials. The objective of this study was to immobilize a novel hydrophilic polymer containing the antibacterial moiety onto polyurethane surface via a simple surface coating technology to make the surface not only antibacterial but also antifouling. The compound 3,4-dichloro-5-hydroxy-2(5H)-furanone was derivatized, characterized and incorporated onto polyvinylpyrrolidone containing succinimidyl functional groups, followed by coating onto the polyurethane surface. Contact angle, antibacterial function and protein adsorption of the modified surface were evaluated. The result shows that the modified surface exhibited significantly enhanced hydrophilicity with a 54-65% decrease in contact angle, increased antibacterial activity to Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa with a 24-57% decrease in viability, and reduced human serum albumin adsorption with a 64-70% decrease in adsorption, as compared to the original polyurethane.

Marine Collagen/Apatite Composite Scaffolds Envisaging Hard Tissue Applications

The high prevalence of bone defects has become a worldwide problem. Despite the significant amount of research on the subject, the available therapeutic solutions lack efficiency. Autografts, the most commonly used approaches to treat bone defects, have limitations such as donor site morbidity, pain and lack of donor site. Marine resources emerge as an attractive alternative to extract bioactive compounds for further use in bone tissue-engineering approaches. On one hand they can be isolated from by-products, at low cost, creating value from products that are considered waste for the fish transformation industry. One the other hand, religious constraints will be avoided. We isolated two marine origin materials, collagen from shark skin (Prionace glauca) and calcium phosphates from the teeth of two different shark species (Prionace glauca and Isurus oxyrinchus), and further proposed to mix them to produce 3D composite structures for hard tissue applications. Two crosslinking agents, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride/N-Hydroxysuccinimide (EDC/NHS) and hexamethylene diisocyanate (HMDI), were tested to enhance the scaffolds' properties, with EDC/NHS resulting in better properties. The characterization of the structures showed that the developed composites could support attachment and proliferation of osteoblast-like cells. A promising scaffold for the engineering of bone tissue is thus proposed, based on a strategy of marine by-products valorisation.

Fluoride-Releasing Effect of a Modified Resin Denture Containing S-PRG Fillers on Salivary Fluoride Retention: A Randomized Clinical Study

This study aimed to evaluate the clinical effect of a resin denture base containing 20wt% surface prereacted glass ionomer (S-PRG) fillers on saliva fluoride concentrations as a surrogate evaluation of caries control. The study was a double-blind randomized clinical trial with a total of 110 participants aged 35-60 years who wore a removable partial resin denture for 1.5 years. Subjects were randomly assigned to receive a partial resin denture fabricated either with or without 20wt% S-PRG fillers (n = 55 per group). After 14 days of wearing the dentures, 5,000 ppm fluoride gel was applied nightly on both sides of the denture before storing it in a denture box overnight every night for 1.5 years. The salivary fluoride concentration was measured at baseline, on days 1, 14, and 15, and at 3 months and 1.5 years of wearing the denture. A significant increase in salivary fluoride concentration in the S-PRG denture group was observed from baseline to day 1, followed by a significant decrease to an approximate baseline level. After recharge with 5,000 ppm fluoride gel, salivary fluoride increased markedly on day 15 and remained elevated at month 3 through to 1.5 years. The resin denture base containing 20wt% S-PRG fillers demonstrated an initial fluoride release that increased saliva fluoride concentrations, but the fluoride release from within the material was short lived. The long-term effect of sustained fluoride release from the denture when combined with a regular fluoride recharge regimen may be beneficial for caries prevention.

Antibacterial gluey silver-calcium phosphate composites for dentine remineralization

The development of multifunctional dental-restorative biomaterials with antibacterial activity and remineralization effect for damaged tooth repair is urgent since dental caries is still one of the most common tooth diseases in human beings. Herein, we report a facile strategy for the synthesis of gluey silver-calcium phosphate (GSCP) composites using the rapid microwave-assisted solvothermal method. The as-prepared GSCP composite is an organic-inorganic hybrid, and Ag⁺ ions display a significant influence on the formation of GSCP by interacting with adenosine triphosphate biomolecules. The as-prepared GSCP composite shows good antibacterial properties, in addition, it exhibits a great effect on sheltering dentinal canaliculi and improving the remineralization of dentine in the simulated saliva. The as-prepared GSCP composite is promising for various applications such as oral healthcare, especially, remineralization of dentine, and antibacterial applications.

Validation of a Real-Time ISE Methodology to Quantify the Influence of Inhibitors of Demineralization Kinetics in vitro Using a Hydroxyapatite Model System

The aim was to validate a novel protocol to measure the cariostatic efficacies of demineralization inhibitors by repeating previous SMR (scanning microradiography) studies investigating the dose response of Zn2+ and F- on demineralization kinetics in vitro using real-time Ca2+ ion selective electrodes (ISEs). In this study, Ca2+ release was used as a proxy for the extent of demineralization. Forty-eight hydroxyapatite (HAP) discs were allocated into 16 groups (n = 3) and adding either increasing [Zn2+], or [F-], similar to those used in the previous SMR studies. Each HAP disc was immersed in 50 mL, pH 4.0, buffered acetic acid for 1 h, and real-time ISE methodology was used to monitor the rate of increase in [Ca2+] in the demineralization solution. Next, either zinc acetate or sodium fluoride was added into each demineralization solution accordingly. Then after each [Zn2+] or [F-] addition, the HAP disc was further demineralized for 1 h, and ISE measurements were continued. The percentage reduction in the rate of calcium loss from hydroxyapatite (PRCLHAP) at each [Zn2+] or [F-] was calculated from the decrease in Ca2+ release rate, similar to that used in the previous SMR studies. A log-linear relationship between mean PRCLHAP and inhibitor concentration was found for both Zn2+ and F-, similar to that reported for each ion in the previous SMR studies. In conclusion, real-time Ca2+ ISE systems can be used to measure the cariostatic efficacies of demineralization inhibitors.

Effective Wound Healing by Antibacterial and Bioactive Calcium-Fluoride-Containing Composite Hydrogel Dressings Prepared Using in Situ Precipitation

In this study, we report the development of a hyaluronic acid (HA)-based composite hydrogel containing calcium fluoride (CaF₂) with good biocompatibility and antibacterial properties for multifunctional wound dressing applications. CaF₂ was newly selected for incorporation within HA because it can release both Ca²⁺ and F^- ions, which are well-known ions for affecting cell proliferation and inhibiting bacterial growth, respectively. In particular, an in situ precipitation process enables easy control over the released amount of F^- ions by simply adjusting the precursor solutions (calcium chloride (CaCl₂) and ammonium fluoride (NH₄F)) used for the CaF₂ precipitation. CaF₂ particles were uniformly embedded within a HA-based pure hydrogel using an in situ precipitation process. Through variation of the CaCl₂ and NH₄F concentrations used in the precipitation as well as the precipitation time, composite hydrogels with different ion-release profiles were obtained. By controlling the precipitation time, especially for 10 min and after 30 min, large differences in the ion-release profiles as a function of CaF₂ concentration were observed. A shorter precipitation time resulted in faster release of fluoride, whereas for the 30 min and 1 h samples, sustained ion release was achieved. Colony tests and live/dead assays using Escherichia coli and Staphylococcus aureus revealed a lower density of bacteria on the CaF₂ composite hydrogels than on the pure hydrogel for both strains. In addition, improved cellular responses such as cell attachment and proliferation were also observed for the CaF₂ composite hydrogels compared to those for the pure hydrogel. Furthermore, the composite hydrogels exhibited excellent wound healing efficiency, as evidenced by an in vitro cell migration assay. Finally, monitoring of the wound closure changes using a full-thickness wound in a rat model revealed the accelerated wound healing capability of the CaF₂ composite hydrogels compared with that of the pure hydrogel. Based on our findings, these CaF₂ composite hydrogels show great potential for application as advanced hydrogel wound dressings with antibacterial properties and accelerated wound-healing capabilities.

Improving the durability of resin-dentin bonds with an antibacterial monomer MDPB

The 12-methacryloxydodecylpyridium bromide (MDPB) has been reported to act as a matrix metalloprotease (MMP) inhibitor. In this study, the effects of application of MDPB on resin-dentin bonds were evaluated. The resin-dentin bonded specimens were prepared with a commercial MDPB-containing self-etching primer or a self-etching primer without MDPB, and stored 24 h or 1 year. Surfaces were pretreated with chlorhexidine or MDPB-containing cavity disinfectant. Additionally, we compared the degradation patterns between the two self-etching adhesives and etch and rinse system. Water tree formations were observed as the typical morphological phase of the two tested self-etching adhesives for both 24 h and 1 year groups. The degradation phase of collagen network depletion was observed in the adhesive interface of the etch-and-rinse system in the 1 year group. Pretreatment with chlorhexidine did not prevent bond strength reduction after 1 year. The cavity disinfectant improved the bond durability for the self-etching adhesive.

Antibacterial potency and fluoride release of a glass ionomer restorative material containing different concentrations of natural and chemical products: An in-vitro comparative study

BACKGROUND

This study investigated the antibacterial efficacy against Streptococcus mutans and fluoride release of a conventional glass ionomer (GI) contained natural and chemical agents.

MATERIAL AND METHODS

Two hundred and ten GI specimens were divided into ten groups (n=21) according to the concentrations of the additives as; Propolis extract containing GI (Groups 1, 2, 3) with concentrations of 0.25%, 0.75% and 1.25% respectively, Miswak extract containing GI (Groups 4, 5, 6) and Chlorhexidine containing GI (Groups 7, 8, 9) with the same concentrations. The prepared specimens were subjected to antimicrobial activity by well diffusion, bacterial adherence, and fluoride release (from 2 to 72 hours) assessments.

RESULTS

A higher statistically significant antibacterial activity was found in (Groups 2, 3) compared to (Groups 8, 9), while (Groups 1, 4, 5, 6, 7, 10) no antibacterial efficacy was reported. For (Groups 2, 3) had a higher statistically significant anti-adherence effect compared to the other tested groups. Enhanced ascending increase in fluoride release was observed for (Groups 3, 4) compared to (GI).

CONCLUSIONS

The increased concentration of propolis extract had a synergistic effect on the antimicrobial activity of the tested GI. Additive concentrations of 0.25% Miswak and 1.25% propolis could enhance the fluoride-releasing ability of the tested GI. Key words:Propolis, miswak, chlorhexidine, glass ionomer, fluoride.

Improvement of the mechanical, tribological and antibacterial properties of glass ionomer cements by fluorinated graphene

OBJECTIVE

The aim of this study was to improve the mechanical properties, wear resistance and antibacterial properties of conventional glass ionomer cements (GICs) by fluorinated graphene (FG), under the premise of not influencing their solubility and fluoride ion releasing property.

MATERIALS AND METHODS

FG with bright white color was prepared using graphene oxide by a hydrothermal reaction. Experimental modified GICs was prepared by adding FG to the traditional GICs powder with four different weight ratios (0.5wt%, 1wt%, 2wt% and 4wt%) using mechanical blending. Compressive and flexural strength of each experimental and control group materials were investigated using a universal testing machine. The Vickers microhardness of all the specimens was measured by a Vicker microhardness tester. For tribological properties of the composites, specimens of each group were investigated by high-speed reciprocating friction tester. Fluoride ion releasing was measured by fluoride ion selective electrode methods. The antibacterial effect of GICs/FG composites on selected bacteria (Staphylococci aureus and Streptococcus mutans) was tested with pellicle sticking method.

RESULTS

The prepared GICs/FG composites with white color were successfully fabricated. Increase of Vickers microhardness and compressive strength and decrease of friction coefficient of the GICs/FG composites were achieved compared to unreinforced materials. The colony count against S. aureus and S. mutans decreased with the increase of the content of FG. And the antibacterial rate of S. mutans can be up to 85.27% when the FG content was 4wt%. Additionally, fluoride ion releasing property and solubility did not show significant differences between unreinforced and FG reinforced GICs.

SIGNIFICANCE

Adding FG to traditional GICs could not only improve mechanical and tribological properties of the composites, but also improve their antibacterial properties. In addition, the GICs/FG composites had no negative effect on the color, solubility and fluoride ion releasing properties, which will open up new roads for the application of dental materials.

Glass Ionomer Cements can be used for Bonding Orthodontic Brackets After Cancer Radiation Treatment?

Patients undergoing radiotherapy treatment present more susceptibility to dental caries and the use of an orthodontic device increases this risk factor due to biofilm accumulation around the brackets. The objective of this study was to evaluate the shear bond strength to irradiated permanent teeth of orthodontic brackets bonded with conventional glass ionomer cement and resin-modified glass ionomer cement due to the fluoride release capacity of these materials. Ninety prepared human premolars were divided into 6 groups (n=15), according to the bonding material and use or not of radiation: CR: Transbond XT composite resin; RMGIC: Fuji Ortho LC conventional glass ionomer cement; GIC: Ketac Cem Easymix resin-modified glass ionomer cement. The groups were irradiated (I) or non-irradiated (NI) prior to bracket bonding. The specimens were subjected to a fractioned radiation dose of 2 Gy over 5 consecutive days for 6 weeks. After the radiotherapy, the brackets were bonded on the specimens with Transbond XT, Fuji Ortho LC and Ketac Cem Easymix. After 24 h, the specimens were subjected to shear bond strength test. The image of enamel surface (classified by Adhesive Remnant Index - ARI) was also evaluated and its frequency was checked among groups/subgroups. The shear bond strength variable was evaluated with ANOVA and Tukey's post-hoc test. GIC group showed the lowest adhesion values among the groups (p<0.05). There was no statistically significant difference among non-irradiated and irradiated groups (p>0.05). As for the ARI, the CR-I group showed the highest material retention on enamel surface among the irradiated groups. RMGIC group showed the highest values for shear bond strength and presented ARI acceptable for clinical practices.

Bactericidal and Bioactive Dental Composites

Aim: Antimicrobial and bioactive restorative materials are needed to develop a bacteria free environment and tight bond with the surrounding tissue, preventing the spread of secondary caries and thus extending the lifetime of dental restorations. The characteristic properties of new dental bioactive and antibacterial composites are presented in this work. The new composites have been microstructurally characterized and both long and short term properties have been studied. Methods: The Ag-doped sol-gel derived bioactive glass (Ag-BG) was incorporated into resin composite in concentrations 5, 10, and 15 wt.%, to fabricate new Ag-doped bioactive and antibacterial dental composites (Ag-BGCOMP). The microstructural properties and elemental analysis of the developed Ag-BGCOMP was observed. The total bond strength (TBS) was measured immediately and after long term of immersion in medium using microtensile testing. The capability of Ag-BGCOMPs to form apatite layer on their surface after immersion in Simulated Body Fluid (SBF) as well as the bacteria growth inhibition in a biofilm formed by Streptococcus mutans (S. mutans) were evaluated. Results: Homogeneous distribution of Ag-BG particles into the resin composite was observed microstructurally for all Ag-BGCOMPs. The TBS measurements showed non-statistically significant difference between control samples (Ag-BG 0 wt.%) and Ag-BGCOMP specimens. Moreover, the total bond strength between the surrounding tooth tissue and the material of restoration does not present any statistically significant change for all the cases even after 3 months of immersion in the medium. The bioactivity of the Ag-BGCOMPs was also shown by the formation of a calcium-phosphate layer on the surface of the specimens after immersion in SBF. Antibacterial activity was observed for all Ag-BGCOMPs, statistically significant differences were observed between control samples and Ag-BGCOMPs. Accordingly, the number of dead bacteria in the biofilm found to increase significantly with the increase of Ag-BG concentration in the Ag-BGCOMPs. Conclusions: New resin composites with antibacterial and remineralizing properties have been manufactured. Characterization of these materials provides a rationale for future clinical trials to evaluate clinical benefits and outcomes in comparison with currently used dental materials. Significance: The new developed composites could ultimately prevent restoration failure and could advance patients' wellbeing.

Fluoride release and surface roughness of a new glass ionomer cement: glass carbomer

Abstract Objective This study analyzed the fluoride release/recharge and surface roughness of glass carbomer compared to other encapsulated glass ionomer cements (GICs). Material and method The GICs tested were Glass Fill® (GC-GCP Dental), Riva Self Cure® (RS-SDI), Riva Light Cure® (RL-SDI), Equia Fil® (EF-GC Europe). The composite resin Luna® (LU-SDI) was used as control. Five samples of each material were prepared and kept in a humidifier for 24 hours (37 °C, 100% relative humidity). Fluoride release was measured in two times: before (T1: days 1, 2, 7, 14) and after topical application of fluoride (T2: days 15, 16, 21 and 28). The surface roughness was also measured in both times (T1: days 1 and 14; T2: days 15 and 28). All samples were submitted to a single topical application of acidulated fluoride phosphate (Fluor Care - FGM). Two-way ANOVA with repeated measures and Tukey's post-test (p <0.05) were used in the statistical analysis. Result Equia Fil presented the highest fluoride release in both evaluation periods, with a higher release in T1 (p <0.05). The other materials tested, including glass carbomer presented similar release in both periods (T1 and T2). Regarding surface roughness, no significant differences were observed in the interaction between the material × time factors (T1 and T2) (p=0.966). Conclusion The GICs tested presented fluoride release and recharge ability and showed no surface roughness increase by topical application of fluoride.

An end to linings under posterior composites?

BACKGROUND AND OVERVIEW

There is an uncertainty among dentists as to whether to place a lining under a direct posterior composite restoration and, if so, what material or combination of materials to use. In this article, the authors consider the evidence for the placement of a lining under posterior composites of different depths, including indications and contraindications for different lining materials.

CONCLUSIONS

The available evidence does not support the use of linings under direct, bonded posterior composites, unless being placed in deep cavities for therapeutic reasons.

PRACTICAL IMPLICATIONS

The best available evidence indicates that dentists can place posterior composites without linings, except for therapeutic purposes, with no adverse effect on postoperative complications, with possible improvements in performance in clinical service, and with efficiency savings in chairside time.

Remineralization of Natural Human Carious Dentin Lesions with an Experimental Whisker-Reinforced Atraumatic Restorative Treatment Composite

PURPOSE

To evaluate the remineralization of natural human dentin caries with an experimental whisker-reinforced Atraumatic Restorative Treatment (ART) composite.

MATERIALS AND METHODS

Teeth with moderate active dentin caries were prepared with caries-disclosing dye and hand instruments, restored with ART or resin-modified glass ionomer cement (RM-GIC), and then wet sliced into 120-µm sections with 15 sections in each group. After taking transverse microradiographs and implementing digital image analysis to determine the "mineral-loss-before," each section was incubated in artificial saliva solution (pH = 7.0) for 4 weeks and 8 weeks with 1 hour each workday in demineralization solution (pH = 4.3). Transverse microradiographs of each section were retaken, and the "mineral-loss-after" was determined. The remineralization was calculated from [1-("mineral-loss-after"/"mineral-loss-before")] × 100%. Results were statistically analyzed with a repeated-measures ANOVA with one within-subject factor (time: 4 and 8 weeks) and one between-subject factor (material: ART and RM-GIC) (α = 0.05).

RESULTS

The statistical analysis indicated that ART composite resulted in significantly higher remineralization than the RM-GIC (p ≤ 0.05). For the remineralization of each material, there was a statistical difference between 4 weeks and 8 weeks (p ≤ 0.05).

CONCLUSIONS

This experimental ART composite remineralized natural human dentin caries better than the RM-GIC.