Comparative study of two bioactive dental materials.

OBJECTIVES: New bioactive materials were introduced to not only restore the lost dental hard tissue but also to release fluoride that inhibits demineralization and occurrence of secondary caries. The current study thus aims to assess Fluoride release as well as the mechanical and physical properties of two new commercially available bioactive restorative materials. METHODS: Two materials, Cention® Forte (CF) (Ivoclar Vivadent), Surefil one™ (SO) (Denstply Sirona), were evaluated in terms of fracture toughness (FT), flexural strength (FS), flexural modulus (FM) (ISO 4049), compressive strength (CS), and Vickers hardness (VH). In addition, thermogravimetric analysis (TGA) was performed, as well as pH measurements and quantification of Fluoride release after immersion in distilled water at times of 0, 7, 14 and 21 days. The sealing ability was evaluated using silver nitrate dye penetration on natural teeth. Finally, Energy-Dispersive X-Ray Spectroscopy (EDX) was used to investigate the surface composition of the two studied material surfaces. The data were statistically analyzed using Independent T-Tests; the chosen significance level was α = 0.05. RESULTS: CF had significantly higher FT values compared to SO (p = 0.001). Also the FS results showed that CF had significantly higher values (90.11 MPa), followed by SO (22.15 MPa). The CS values showed the same order with significantly higher values for CF (231.79 MPa). While the FM and VH showed the reverse order with SO having significantly higher values than CF. pH measurements showed that CF evolved towards significantly higher pH values after 3 weeks in distilled water, while thermal properties showed more stability and higher resistance to degradation for CF compared to SO. The silver nitrate penetration results showed significantly better sealing ability for CF compared to the self-adhesive SO. Finally, EDX surface analysis results were consistent with the release profiles and confirmed the composition of the two tested materials. SIGNIFICANCE: Both materials, demonstrated enhanced Fluoride release ability, and hence good remineralisation potential in vitro that could prevent recurrent carious lesions in vivo. The composition based on acrylic polymerization showed better mechanical resistance to bending and fracture, and higher sealing ability than those based on acid base reaction.

Is there a preferable management for root caries in middle-aged and older adults? A systematic review.

Aim This systematic review aimed to critically summarise the results of clinical studies investigating agents able to: stop the progression of carious lesions; stop the development of new root carious lesions; preserve the vitality of the infected dental tissues; and increase the surface hardness or change of surface texture, in middle-age and older adults.Methods PubMed, Scopus, and Web of Science were searched systematically, following PRISMA guidelines. Clinical trials published from 2011 to 2020 (March) were included. This systematic review is registered in the PROSPERO database (CRD42018104399). Languages were restricted to English.Results Thirteen of 312 studies were eligible for this review. Eight agents were identified in the studies and their efficacy was assessed using different methods. The agents that presented valuable results on preventing or arresting root caries were 38% silver diamine fluoride (SDF), arginine-containing toothpaste and high-fluoride toothpastes.Conclusions Based on the selected studies' findings, annual applications of 38% SDF could be the most effective treatment for root caries in older adults. In addition, the daily use of a 1.5% arginine toothpaste or a high-fluoride toothpaste could also be recommended. More research on root caries-specific diagnostic methods, especially at very early stages, is necessary.

Interface between calcium silicate cement and adhesive systems according to adhesive families and cement maturation.

OBJECTIVES: This study aimed to evaluate the interface between a calcium silicate cement (CSC), Biodentine and dental adhesives in terms of sealing ability. MATERIALS AND METHODS: Microleakage test: 160 standardized class II cavities were prepared on 80 extracted human molars. The cavities were filled with Biodentine and then divided into 2 experimental groups according to the time of restoration: composite resin obturation 15 minutes after Biodentine handling (D0); restoration after 7 days (D7). Each group was then divided into 8 subgroups (n = 5) according to the adhesive system used: etch-and-rinse adhesive (Prime & Bond); self-etch adhesive 2 steps (Optibond XTR and Clearfil SE Bond); self-etch adhesive 1 step (Xeno III, G-aenial Bond, and Clearfil Tri-S Bond); and universal used as etch-and-rinse or self-etch (ScotchBond Universal ER or SE). After thermocycling, the teeth were immersed in a silver nitrate solution, stained, longitudinally sectioned, and the Biodentine/adhesive percolation was quantified. Scanning electron microscopic observations: Biodentine/adhesive interfaces were observed. RESULTS: A tendency towards less microleakage was observed when Biodentine was etched (2.47%) and when restorations were done without delay (D0: 4.31%, D7: 6.78%), but this was not significant. The adhesives containing 10-methacryloyloxydecyl dihydrogen phosphate monomer showed the most stable results at both times studied. All Biodentine/adhesive interfaces were homogeneous and regular. CONCLUSIONS: The good sealing of the CSC/adhesive interface is not a function of the system adhesive family used or the cement maturation before restoration. Biodentine can be used as a dentine substitute.

The influence of experimental bioactive glasses on pulp cells behavior in vitro.

OBJECTIVES: To assess in vitro the effect of experimental mesoporous BAG, on human dental pulp cells (hDPCs) behavior in terms of cytocompatiblity and bioactivity via mineralization potential. METHODS: Fine (FP) and large particles (LP) of a fixed BAG composition named 0NaMBG have been elaborated by a sol-gel process. In vitro assessment was achieved on cultured primary hDPCs using indirect contact. The effect of the concentration of 800µg/mL on cell metabolic activity and cytotoxicity were examined by performing Alamar blue and crystal violet assays. Alizarin Red staining was used to detect and quantify the formation of mineralized nodules and ALP activity was colourimetrically quantified. The expression of Odontogenic markers: DMP-1 and osteopontin (OPN) expression and cell morphology was evaluated by confocal microscopy. RESULTS: According to the Alamar blue and crystal violet assay, 0NaMBG samples were non-cytotoxic. Cells treated with 0NaMBG particles expressed higher metabolic activity than control cells, especially for LP. Both FP and LP significantly increased both extra and intra cellular ALP activity. hDPCs exhibited good cell spreading and adhesion in the presence of FP and LP extracts by confocal imaging. Further, Alizarin red S assay demonstrated more mineralization nodules and significant enhancement of the extracellular calcium deposition when cells were interfaced with both FP and LP compared to the control cells. Moreover, LP extracts enhanced the production and secretion of odontogenic markers: dentin matrix protein 1 (DMP-1) and osteopontin. SIGNIFICANCE: LP have a higher surface area and pore volume, which could explain their greater bioactivity in contact with pulp cells. The clinical relevance of these findings implicate that 0NaMBG could be used as fillers in dental therapeutic materials suitable for dentin and/or pulp tissues preservation.

Bioactivity assessment of bioactive glasses for dental applications: A critical review.

OBJECTIVE: In the context of minimally invasive dentistry and tissue conservation, bioactive products are valuable. The aim of this review was to identify, clarify, and classify the methodologies used to quantify the bioactive glasses bioactivity. METHODS: Specific search strategies were performed in electronic databases: PubMed, Embase, Cochrane Library, and Scopus. Papers were selected after a review of their title, abstract, and full text. The following data were then examined for final selection: BAG investigated, objectives, criteria, methods, and outcomes. RESULTS: Sixty-one studies published from 2001 to 2019, were included. The bioactivity of BAG can be evaluated in vitro in contact with solutions, enamel, dentin, or cells. Other studies have conducted in vivo evaluation by BAG contact with dentin and dental pulp. Studies have used various analysis techniques: evaluation of apatite with or without characterization or assessment of mechanical properties. Reprecipitation mechanisms and pulp cell stimulation are treated together through the term 'bioactivity'. SIGNIFICANCE: Based on these results, we suggested a classification of methodologies for a better understanding of the bioactive properties of BAG. According to all in vitro studies, BAG appear to be bioactive materials. No consensus has been reached on the results of in vivo studies, and no comparison has been conducted between protocols to assess the bioactivity of other bioactive competitor products.

The influence of precursor addition order on the porosity of sol-gel bioactive glasses.

OBJECTIVE: The superior textural properties of sol-gel derived bioactive glasses compared to conventional melt quench glasses accounts for their accelerated bioactivity in vitro. Several studies have explored ways to improve the surface properties of sol-gel glasses in order to maximise their efficiency for bone and tooth regeneration. In this study, we investigated the effect of order of network modifying precursor addition on the textural properties of sol-gel derived bioactive glasses. METHODS: The effect of precursor addition order on the glass characteristics was assessed by switching the order of network modifying precursor (calcium acetate monohydrate and sodium acetate anhydrous) addition for a fixed composition of bioactive glass (75SiO2:5CaO:10Na2O:10P2O5). RESULTS: The results of this study showed that the order of precursor addition does influence the porosity of these glasses. For the glasses of a fixed composition and preparation conditions we achieved a doubling of surface area, a 1.5 times increase in pore volume and a 1.2 times decrease in pore size just by the mixing the network modifying precursors and adding them together in the sol-gel preparation. SIGNIFICANCE: This simple and straightforward route adaptation to the preparation of bioactive glasses would allow us to enhance the textural properties of existing and novel composition of bioactive glasses and thus accelerate their bioactivity.

Bioactive glass for dentin remineralization: A systematic review.

BACKGROUND AND OBJECTIVES: Strategies to achieve dentin remineralization is at present an important target of restorative dentistry. Remineralization of dentin by a bioactive material is complete only when the tissue regains its functionality. This is achieved when there is adequate apatite formation which most importantly translates into improved mechanical properties of dentin as a result of intrafibrillar mineralization. Bioactive glass (BAG) is a well-known implant material for bone regeneration and is proven to have excellent ability of apatite formation. Hence, recent studies have proposed BAGs as one of the most desired materials for remineralization of dentin. Therefore the aim of this systematic review was to scope the evidence of bioactive glass to remineralize dentin. METHODS: The following research question was formulated: "Is there strong evidence for bioactive glass to remineralize dentin?" Three databases (Web of science, PubMed and Science direct) were scanned independently following PRISMA guidelines. Inclusion and exclusion criteria were set to identify relevant articles based on title and abstract screening. Finally, potentially relevant articles were downloaded and the full text was scrutinized to select the articles included in this review. RESULTS: The first phase of search returned 303 articles. A total of 19 papers with full text were scrutinized for inclusion, of which 3 papers were chosen for the final synthesis. All three studies confirm that BAG treatment leads to enhanced apatite formation in dentin. Only 1 of the 3 studies has reported the mechanical properties of dentin after BAG treatment and it revealed that the Young's modulus and flexural bend strength of BAG treated dentin were much lower than natural dentin even though they had similar apatite content. CONCLUSIONS: This review highlights the importance of assessing the mechanical properties of dentin alongside to the newly formed apatite content in order to prove BAGs efficiency to remineralize this tissue. Though studies have confirmed that BAGs stimulate excellent apatite formation in dentin, it should be concluded that there isn't sufficient evidence for bioactive glass to effectively remineralize this tissue as the mechanical properties of the BAG treated dentin haven't been well explored.

Initial sliding wear kinetics of two types of glass ionomer cement: a tribological study.

The aim of this work was to characterize the initial wear kinetics of two different types of glass ionomer cement used in dentistry (the conventional glass ionomer cement and the resin-modified glass ionomer cement) under sliding friction after 28-day storing in distilled water or Ringer's solution. Sliding friction was applied through a pin-on-disk tribometer, in sphere-on-plane contact conditions, under 5 N normal load and 120 rotations per minute. The test lasted 7500 cycles and replicas were performed at 2500, 5000 and 7500 cycles. A profilometer was used to evaluate the wear volume. Data were analysed using Student's t-test at a significant level of 5%. There is no statistical significant difference between the results obtained for a given material with the maturation media (P > 0.05). However, for a given maturation medium, there are significant statistical differences between the data obtained for the two materials at each measurement (P < 0.0001). The wear rates of both materials decrease continuously during the running-in period between 0 and 2500 cycles. After 2500 cycles, the wear rate becomes constant and equal for both materials. The resin matrix contained in the resin-modified glass ionomer cement weakens the tribological behaviour of this material.

Toxicity evaluation of two dental composites: three-dimensional confocal laser scanning microscopy time-lapse imaging of cell behavior.

The purpose of this study was to investigate the in vitro biocompatibility of two dental composites (namely A and B) with similar chemical composition used for direct restoration using three-dimensional confocal laser scanning microscopy (CLSM) time-lapse imaging. Time-lapse imaging was performed on cultured human HGF-1 fibroblast-like cells after staining using Live/Dead®. Image analysis showed a higher mortality rate in the presence of composite A than composite B. The viability rate decreased in a time-dependent manner during the 5 h of exposure. Morphological alterations were associated with toxic effects; cells were enlarged and more rounded in the presence of composite A as shown by F-actin and cell nuclei staining. Resazurin assay was used to confirm the active potential of composites in cell metabolism; results showed severe cytotoxic effects in the presence of both no light-curing composites after 24 h of direct contact. However, extracts of polymerized composites induced a moderate decrease in cell metabolism after the same incubation period. Composite B was significantly better tolerated than composite A at all investigated end points and all time points. The finding confirmed that the used CLSM method was sufficiently sensitive to differentiate the biocompatibility behavior of two composites based on similar methacrylate monomers.

Impedance methodology: A new way to characterize the setting reaction of dental cements.

OBJECTIVES: Impedance spectroscopy is a non-destructive, quantitative method, commonly used nowadays for industrial research on cement and concrete. The aim of this study is to investigate the interest of impedance spectroscopy in the characterization of setting process of dental cements. METHODS: Two types of dental cements are used in this experiment: a new Calcium Silicate cement Biodentine™ (Septodont, Saint Maur-des Fossés, France) and a glass ionomer cement resin modified or not (Fuji II(®) LC Improved Capsules and Fuji IX(®) GP Fast set Capsules, GC Corp., Tokyo, Japan). The conductivity of the dental cements was determined by impedance spectroscopy measurements carried out on dental cement samples immersed in a 0.1M potassium chloride solution (KCl) in a "like-permeation" cell connected to a potentiostat and a Frequency Response Analyzer. The temperature of the solution is 37°C. From the moment of mixing of powder and liquid, the experiments lasted 2 weeks. RESULTS: The results obtained for each material are relevant of the setting process. For GIC, impedance values are stabilized after 5 days while at least 14 days are necessary for the calcium silicate based cement. SIGNIFICANCE: In accordance with the literature regarding studies of cements and concrete, impedance spectroscopy can characterize ion mobility, porosity and hardening process of dental hydrogel materials.

Quantitative evaluation of self-etching primer action on dentin permeability: a correlation between impedance measurements and acidity.

PURPOSE: To evaluate quantitatively the effect of six contemporary self-etching systems on dentin permeability by means of the electrochemical impedance technique and to correlate these results with their acidity. METHODS: 36 1.1 mm thick dentin disks were embedded in a hollow polyurethane resin cylinder. The system used was a "like" permeation cell: two electrodes immersed in a 10(-1) KCl solution were attached to a potentiostat. It was connected to a microcomputer controlled frequency response analyzer, and a 10 mV sinusoidal voltage signal over a frequency range of 1 Hz to 65 kHz was applied between the electrodes. The current passing through the dentin was measured to enable a calculation of impedance expressed in a complex number. To establish an evaluation of permeability variation, the resistance was noted for all specimens before and after the application of self-etching adhesive. A pH meter used with a combined glass-electrode measured the pH of all the systems. RESULTS: The higher decrease of the resistance of dentin samples was obtained with Experimental (EXP), which presented no significant difference with Touch and Bond (TB), Etch and Prime 3.0 (EP), and Etch Free Tenure (EF). These acidic monomers improved the dentin permeability respectively to 6.7, 5.1, 5.0 and 5.0%. The lowest values were obtained with Clearfil SE Bond (SEB) (2.0%), which showed significant difference with all the other systems. Prompt L-Pop (PLP) with 4.3% showed significant difference with EXP and SEB and no significant difference with the three other systems. The pH and permeability variation were not systematically correlated. CLINICAL SIGNIFICANCE: Significant differences, in terms of quantitative evaluation of demineralization for self-etching systems on dentin, are of interest to clinical practitioners. Dentin bonding efficiency for this sort of adhesive system is not specifically related to this parameter, but low aggressiveness could be an area of concern on enamel.

Evaluation of microleakage of composite resin restorations by an electrochemical technique: the impedance methodology.

OBJECTIVES: The aim of our in vitro study was to quantitatively evaluate dentin microleakage by means of the impedance technique. METHODS: Forty-five 2 mm thick dentin disks were embedded in a hollow polyurethane resin cylinder. The system used was a 'like' permeation cell. Standard cylindrical cavities (1.5 mm deep, 3.5 mm diameter) were prepared on the occlusal side of the disk. The current passing through the dentin was measured to calculate impedance and to establish resistance of the sample. The doses were then randomly divided into nine groups (n = 5). Each group was bounded with a different adhesive system and filled with microhybrid composite resin (Filtek P60). The initial measurement with the empty cavity and the record measurement (t = 0) were performed to evaluate initial resistance after filling. Samples were then thermocycled. RESULTS: At t = 0, the highest value was obtained with EP (550%), the lowest with PLP (115%). The values of other adhesives ranged in a group (350-450%) without statistical difference. After thermocycling, all groups exhibited no significant difference (350-230%) except PLP (50%). The lower joint degradation rate (5%) was obtained with OS with a significant difference for all systems, the higher with PLP (35%). The results for other adhesives ranged from 20 to 27% without significant difference. SIGNIFICANCE: Dentin microleakage may be quantified with the impedance technique and this has shown that, except for PLP, the differences between the two families of adhesives are slight. This methodology is able to prove the influence of thermocycling in terms of joint degradation.

Effect of a LED versus halogen light cure polymerization on the curing characteristics of three composite resins.

PURPOSE: To evaluate the effect, in vitro, of a LED (GC E Light) versus an halogen (Astralis 7) polymerization on the mechanical properties of three commercially available microhybrid composite resins. METHODS: Three commercially available composite resins (Tetric Ceram, Charisma, and Z100), and six modes of polymerization were evaluated (one mode for Astralis (AST): HIP 40 seconds and five modes for the GC E Light (GCE): standard 40 seconds, fast cure 6 seconds, fast cure 12 seconds, soft cure A 39 seconds, and turbo 10 seconds) in terms of top surface and bottom surface (2 mm-depth) microhardness, and flexural strength. Five specimens of each composite resin were made for the two mechanical properties tested. Five hardness values were recorded on each side for each sample with a Vickers diamond indenter. A three point bending test was performed at a crosshead speed of 1 mm/minute. Statistical comparisons were made using a two-way ANOVA (composite resin, polymerization mode) and a Fisher's test (P < 0.05). RESULTS: Z100 presented highest properties for both tests. Top surface microhardness: for Tetric Ceram and Charisma, the longer the exposure time, the higher the results, with no difference between AST mode and the longer GCE modes. For Z100, the highest values were obtained with AST. Whichever the material, short times (fast cure 6 seconds and turbo) exhibited poor results. Bottom surface microhardness: the samples cured with AST presented higher results but quite similar mechanical properties were achieved with the fast cure 12 GCE mode of the LED LCU. Fast cure 6 seconds and turbo obtained the lowest results. Flexural strength: the results were comparable with those obtained in bottom microhardness.

Evaluation of the long-term corrosion behavior of dental amalgams: influence of palladium addition and particle morphology.

OBJECTIVES: The purpose of this investigation was to evaluate the long-term corrosion behavior of experimental amalgams as a function of particle morphology and palladium content. METHODS: Samples of four experimental high copper amalgams were prepared according to ADA specifications. Two of them had the same chemical composition but one had lathe cut particles (LCP) and the other had spherical particles (SP). The two others had spherical powders with an addition of 0.5 wt% of palladium (SP 0.5) and 1 wt% of palladium(SP 1) for the other. Corrosion resistance was evaluated by electrochemical techniques in Ringer's solution in a thermostated cell at 37 degrees C for samples aged 5, 8, 12, 16 months and 10 years. Potentiokinetic curves were drawn and the potential and the current density corresponding to the first anodic peak were registered. RESULTS: For all the amalgam samples the corrosion behavior improves over the 10-year period. SP samples exhibit a better behavior than LCP. Palladium addition improves corrosion behavior as compared to samples without palladium. No real difference is found regarding the amount of palladium between 0.5 and 1%. The potentials progress from a range between 0 and 20 mV/SCE to a range of 60-80 after 10 years. The stabilization of the potential begins after only 16 months. Except for the LCP, all the values converge to the same level of 80 mV/SCE. SIGNIFICANCE: The addition of no more than 0.5 wt% Palladium in a high copper amalgam powder improves the corrosion behavior of the amalgam up to a period of 10 years. The potential of the first anodic peak increases for each amalgam, probably in relation to the evolution of the structure of the material. Clinically, it is of interest to consider the good electrochemical behavior of older restorations when contemplating the repair or replacement of such fillings. At the same time, galvanic current can occur when a new amalgam restoration is placed in contact with an old one even if the same amalgam is used. In this situation, the new filling will be anodic and its degradation will be accelerated. The evaluation of the corrosion behavior of dental amalgams has to take into account the age of the samples.

Influence of new light curing units and bonding agents on the microleakage of Class V composite resin restorations.

PURPOSE: To evaluate the influence of four light curing units on the stress induced by polymerization of two dentin bonding systems and a composite resin. METHODS: Standardized kidney-shaped Class V cavities were prepared on the buccal and lingual surfaces at approximately 1 mm below the cemento-enamel junction (2 mm deep, 6-7 mm wide and 2 mm high). Two dentin bonding systems (DBS), Single Bond (SB), Optibond Solo Plus (OS+), and four light curing units (LCU): Astralis 7 (mode HIP 40 seconds), Elipar Highlight (soft start polymerization 40 seconds), GC e Light (8 mm tip) (fast cure of 12 seconds), and Optilux 501 (turbo tip) (fast cure of 10 seconds) were tested. The preparations were restored using the same microfilled composite (Filtek A110, shade A3). The teeth were thermocycled, immersed in a dye solution and sectioned. The enamel failures and the occlusal and cervical dentin microleakages were measured. RESULTS: No enamel and occlusal dentin microleakage was found. Concerning cervical dentin microleakage, with Single Bond, no significant difference was noted for all the light curing units (P< 0.05). With OptiBond Solo Plus, the filled adhesive, only two, the LCU Elipar and GC e Light, presented no statistical difference when all of the others exhibited statistical differences among themselves. The light intensity, the exposure duration, and the light source of the LCU are important parameters. When comparing the influence of the dentin adhesive, OS+ presented results significantly greater than SB, depending upon which lights were used. The Optilux 501 showed no significant difference. To act as a shock absorber, the adhesive needs to have time to compensate for the polymerization shrinkage.

Effect of conditioners on dentin permeability using an impedance method.

OBJECTIVES: The aim of our in vitro study was to contribute to an elaboration of a protocol to evaluate the permeability of dentin and the effect of different acid conditioners by means of the electrochemical impedance technique. MATERIALS AND METHODS: Twenty-four 1.1mm thick dentin disks were embedded in a hollow polyurethane resin cylinder. The system used was a 'like' permeation cell: two electrodes immersed in a 10(-1) KCl solution were attached to a potentiostat. It was connected to a microcomputer controlled frequency response analyzer and a 10 mV sinusoidal voltage signal over a frequency range of 1 Hz to 65 kHz was applied between the electrodes. The current passing through the dentin was measured to enable a calculation of impedance expressed in a complex number. To establish an evaluation of permeability variation, the resistance was noted for all specimens before and after the application of dentin conditioners. RESULTS: The highest resistance decrease was obtained with 32% phosphoric acid and 10-3 solution which improved the permeability, respectively, 9.0 and 6.9% with no significant difference. The acidic monomer can be considered as intermediate (4.3%) between 10-3 solution and the polyacrylic acid (2.8%) with no significant difference. CONCLUSIONS: By measuring electrical resistance of dentin disks with the impedance method, we can evaluate the ionic conduction through the sample and achieve quantitative values about permeability. The action of dentin conditioners can be significantly evaluated regarding their action in terms of resistance of the etched zone (REZ) and increasing dentin permeability.