Showing papers in "Dental Materials Journal in 2019"

Polymerization shrinkage, microhardness and depth of cure of bulk fill resin composites.

Abstract: The present in vitro study assessed the polymerization shrinkage/PS, Knoop microhardness/KHN and depth of cure/DC of 9 different resin composites : Filtek Bulk Fill Flowable (FBF), Surefill SDR flow (SDR), Xtra Base (XB), Filtek Z350XT Flowable (Z3F), Filtek Bulk Fill Posterior (FBP), Xtra Fill (SF), Tetric Evo Ceram Bulk Fill (TBF), Admira Fusion Xtra (ADM), and Filtek Z350XT (Z3XT). PS was assessed with a µ-CT machine, scanning 64 mm3 samples (n=8) before and after 20 s curing. KHN and DC were performed with a microhardness tester (n=8 for each group) right after 20 s light curing, with 3 readings per depth at every 0.5 mm. Low viscosity resin composites showed lower KHN values when compared with high viscosity resins. Z3XT showed the highest microhardness among the tested resin composites. Z3XT and Z3F showed lower DC when compared with bulk fill resin composites. All bulk fill resin composites presented depth of cure higher than 4.5 mm and similar or lower PS than conventional resin composites.

A review of bioceramics-based dental restorative materials.

Abstract: Currently, much has been published related to conventional resin-based composites and adhesives; however, little information is available about bioceramics-based restorative materials. The aim was to structure this topic into its component parts and to highlight the translational research that has been conducted up to the present time. A literature search was done from indexed journals up to September 2017. The main search terms used were based on dental resin-based composites, dental adhesives along with bioactive glass and the calcium phosphate family. The results showed that in 123 articles, amorphous calcium phosphate (39.83%), hydroxyapatite (23.5%), bioactive glass (16.2%), dicalcium phosphate (5.69%), monocalcium phosphate monohydrate (3.25%), and tricalcium phosphate (2.43%) have been used in restorative materials. Moreover, seven studies were found related to a newly developed commercial bioactive composite. The utilization of bioactive materials for tooth restorations can promote remineralization and a durable seal of the tooth-material interface.

Wear of dental materials: Clinical significance and laboratory wear simulation methods -A review.

Abstract: This review focusses on tribological aspects of teeth during function, the clinical significance of wear, wear of natural teeth and restorative materials and laboratory methods to simulate wear of restorative materials. Ceramic, metal alloy and amalgam show low material wear, whereas resin-based materials demonstrate substantial wear in the long term. The clinical wear shows a high variability with the patient factor accounts for about 50% of the variability. Wear as such seldomly compromises the function of the stomatognath system or individual teeth and is in most cases an esthetic problem. Particles that are ingested due to attrition and abrasion wear may pose a health risk to the patient, especially those from composite resin materials. However, systematic clinical studies on that issue are not available. For laboratory research many wear simulation devices and methods have been developed but only few are validated and have a moderate correlation with clinical wear.

Bond strength between MDP-based cement and translucent zirconia.

Abstract: The purpose was to evaluate the bond strength between adhesive cement and translucent zirconia in comparison to conventional zirconia. Four brands of translucent zirconia (BruxZir® HT, Lava™ Plus, Prettau® Anterior, and Prettau® Zirconia) and one conventional zirconia (Kavo Everest® ZS) were evaluated. Specimens were divided into groups depending on the pretreatment of the cementation surface of the zirconia: as-produced, hydrofluoric acid treatment, or sandblasted. The groups underwent three different procedures of artificial aging: water storage (24 h), 5,000 thermocycles, or long-term aging, (water storage 150 days including 37,500 thermocycles) before shear bond strength testing. Sandblasting treatment increased the bond strength significantly for all the brands of zirconia, irrespective of artificial aging procedures, in comparison to the control group. Bond strength between adhesive cement to translucent zirconia is equivalent to conventional zirconia. Sandblasting creates a cementation surface that is more durable than as-produced or hydrofluoric-acid-treated, irrespective of type of zirconia.

A comparison of the effectiveness of resin infiltration and microabrasion treatments applied to developmental enamel defects in color masking.

Abstract: This study aimed to evaluate color masking effect from treatments with resin infiltrant and two different remineralization agents applied with microabrasion to anterior teeth with developmental enamel defects. The incisors of patients aged 8-17 were evaluated. The study involved two groups including fluorosis (Group 1) and hypomineralization (Group 2) cases. These two groups were further divided based on the treatment received: Group A: Icon®, Group B: Opalustre®+Clinpro White Varnish®, and Group C: Opalustre®+Tooth Mousse®. The spectrophotometric values were recorded. Furthermore, the L* and ΔE values were evaluated by repeated measures of ANOVA. The largest increase in L* values over time after treatment was in Group 1A, followed by Group 1C and Group 1B. The largest increase in ΔE values over time after treatment was in Group 1A. Clinically observable difference was achieved as a result of all treatment groups. Especially resin infiltration treatment has been found to be more effective in teeth with fluorosis.

Evaluation of discoloration of sound/demineralized root dentin with silver diamine fluoride: In-vitro study.

Abstract: The objective was to evaluate the effect of application of silver diamine fluoride (SDF) on discoloration of demineralized dentin over time. Dentin specimens were divided into four groups according to time of dentin demineralization. A 38% SDF solution was then applied to the dentin surfaces. Half of the specimens were placed in light-proof boxes while the remainder were exposed to light. Both groups were maintained at 37˚C. Color change was determined using a spectrophotometer at different time intervals. SEM/EDS analysis were also undertaken. The 13 h EDTA demineralized group showed the highest values for color change among different time intervals, with the control being the lowest. The light exposed groups showed more color change compared to the unexposed groups. We concluded that the degree of dentin demineralization leads to a significant increase of the rate of dentin color change after application of SDF.

In vitro evaluation of visible light-activated titanium dioxide photocatalysis for in-office dental bleaching.

Abstract: The evaluation of the photocatalysis of visible light activated titanium dioxide employed in hydrogen peroxide (H2O2) was carried using seven H2O2 solutions (3.5 and 35%) and/or methylene blue (MB), with or without light irradiation (LI); the absorbance of MB was the bleaching indicator. Color analysis was performed on bovine teeth (n=12) using two different concentrations of H2O2, 6 and 35% associated with titanium dioxide (TiO2). Data were analyzed with one and two-way ANOVA, and significance level of p<0.05. Solutions containing MB, H2O2 at 3.5 or 35%, and TiO2, followed by LI, showed significant difference when compared with other groups. Greater MB reduction was found in 35% concentration. H2O2 35%+TiO2 gel showed no difference in comparison to control group. All groups for the color analysis assay showed ΔE higher than 3.3. In conclusion, TiO2 and H2O2 association is a promisor alternative for reducing the clinical time of in-office dental bleaching.

Changes in the physical properties and color stability of aesthetic restorative materials caused by various beverages.

Abstract: This study investigates the effects of various beverages on the wettability, microhardness, and color stability of aesthetic dental restorative materials. A contact angle analyzer, Vickers hardness tester, and spectrophotometer were used to characterize the properties of the materials and a total of 225 specimens were prepared: 75 each for a resin composite, compomer, and giomer. Ingestion of energy drinks and cola caused the greatest deterioration in wettability and microhardness, and coffee caused the most significant color change. In addition, the change in the resin composite was lower than that of the other restorative materials. The extent of change in the restorative materials increased with duration and frequency of contact with the beverages, so a reduction in the frequency of ingestion of these beverages is recommended.

Incorporation of a hydrophilic amide monomer into a one-step self-etch adhesive to increase dentin bond strength: Effect of application time.

Abstract: The purpose was to evaluate the effect of a hydrophilic amide monomer on μTBS of one-step adhesive to dentin at different application times. Clearfil Universal Bond Quick (UBQ), experimental adhesive (UBQexp; same compositions as UBQ but hydrophilic amide monomer was replaced with 2-hydroxyethyl methacrylate), Clearfil SE ONE and Clearfil SE Bond were applied to midcoronal dentin prepared with 600-grit SiC at different application time (0, 10, 20 and 40 s). Water sorption (Wsp) and the ultimate tensile strength (UTS) of polymerized adhesives were also measured. UBQ showed significantly lower Wsp and higher UTS than UBQexp. At each application time, UBQ exhibited significantly higher μTBSs than UBQexp. UBQ showed the highest μTBS at 0 s application time among all the adhesives. When the application time was prolonged from 0 s to 10 s, only UBQ showed no significant difference. The hydrophilic amide monomer increased μTBS with reduction in Wsp and increase in the UTS and may allow a shortened application time.

A review of the literature on the efficacy of mineral trioxide aggregate in conservative dentistry.

Abstract: The aim of this literature review was to assess the clinical performance of MTA to establish the evidence level for its effectiveness in vital pulp therapy, perforation repair, and retrograde root canal filling. A comprehensive literature survey was performed via electronic databases of PubMed/MEDLINE. A total of 58 papers were reviewed in this study, of which 2 were systematic reviews/meta-analysis, 9 were randomized controlled trials (RCTs), and the rest were fallen into other categories. Mineral trioxide aggregate (MTA) provided better pulp protection as a direct capping material when compared with calcium hydroxide. As perforation repair materials, MTA demonstrated an excellent sealing ability in vitro. For periodontal tissues around a perforation, MTA provided normal healing processes in clinical trials. It is therefore concluded that MTA has a high potential in repairing perforations. MTA is the most promising material when used for retrograde root canal filling demonstrating normal healing in short/long term clinical outcomes.

Effect of storage and aging conditions on the flexural strength and flexural modulus of CAD/CAM materials.

Abstract: Computer-aided design/computer-aided manufacturing (CAD/CAM) materials were submitted to thermocycling, to identify changes in mechanical behavior. Four CAD/CAM materials were divided in four subordinate groups (n=9): (1) dry out for 7 days, (2) distilled water at 37oC for 7 days, (3) 60,000 thermocycles, and (4) 120,000 thermocycles. Following thermocycling, samples were submitted to three-point bending test. Two-way ANOVA and post-hoc Tukey's test were performed (α=0.05). The IPS e.max CAD had a flexural strength of 396±75 MPa and flexural modulus of 84±11 GPa, followed by Vita Enamic with values of 153±17 MPa and 28±5 GPa respectively. The flexural strength recorded for Lava Ultimate was 149±28 MPa and the flexural modulus was 12±3 GPa. Vitablocs Mark II had the lowest flexural strength values (125±10 MPa) and a flexural modulus of 49±15 GPa. Although polymer-based materials have similar mechanical properties compared to ceramics, they are affected by thermo cycling conditions.

Effects of dental composite resin monomers on dental pulp cells.

Abstract: Methacrylate monomers found in many dental materials cause toxicity to dental pulp cells but the mechanism of the toxicity is poorly understood. We used cultured human dental pulp cells to test the effects of three commonly used monomers; bisphenol-A-glycidyl methacrylate (Bis-GMA), urethane dimethacrylate (UDMA), and triethyleneglycol dimethacrylate (TEGDMA). The order of toxicity was Bis-GMA>UDMA>TEGDMA. The toxicity correlated inversely with cystine uptake, with TEGDMA stimulating uptake and BisGMA and UDMA inhibiting uptake. Bis-GMA and UDMA induced oxidative stress, while TEGDMA did not. Toxicity correlated poorly with glutathione levels, as all compounds decreased cellular glutathione. TEGDMA is less toxic than Bis-GMA and UDMA likely because it stimulates cystine uptake and does not induce oxidative stress, the enhanced uptake of cystine appears to compensate for TEGDMA's direct interaction with glutathione. Bis-GMA and UDMA both deplete glutathione and inhibit cystine uptake leading to oxidative stress and cell death.

In vitro evaluation of microleakage in Class II composite restorations: High-viscosity bulk-fill vs conventional composites.

Abstract: This study compared marginal microleakage of Class II cavities restored with bulk-fill resin (Filtek™ Bulk Fill) and conventional composite resin (Filtek™ Supreme XTE). Two standardized Class II cavities were prepared in forty extracted human molars. The gingival margin was located above the cemento-enamel junction for twenty molars (groups 1 and 2) and apically for the other twenty (groups 3 and 4) (n=20). The occlusomesial cavity was filled with bulk-fill resin by insertion in bulk (groups 1 and 3) and the occlusodistal cavity was restored with conventional composite using incremental technique (groups 2 and 4). The teeth were thermocycled (500 cycles 5-55°C), stained and observed under light microscope. The microleakage was significantly lower in gingival margins located in enamel compared with dentin margins (p<0.01). There was no statistically significant difference between groups 1 and 2 (p=0.86) and groups 3 and 4 (p=0.26). Bulk-Fill resins presents gingival microleakage similar to conventional composites.

Long-term water sorption and solubility of experimental bioactive composites based on amorphous calcium phosphate and bioactive glass.

Abstract: The aim of this study was to evaluate water sorption and solubility of two series of experimental composites containing amorphous calcium phosphate (ACP) or bioactive glass (BG). Water sorption and solubility were measured for up to 287 days. The surface precipitation of calcium phosphates was evaluated by scanning electron microscopy. The ACP-series showed higher water sorption (223-568 µg/mm3) than the BG-series (40-232 µg/mm3). In contrast, the ACP-series had generally lower solubility (37-106 µg/mm3) than the BG-series (1-506 µg/mm3). The constant specimen mass for the ACP-series was attained after 14 days of water immersion, while the mass decrease due to long-term solubility in the BG-series lasted beyond 287 days. Calcium phosphates precipitated in composites with the BG filler loading of 10 wt% or more, as well as in all of the ACP-containing composites. The experimental composite series showed water sorption and solubility considerably higher than commercial materials.

Antimicrobial and antibiofilm efficacy of a copper/calcium hydroxide-based endodontic paste against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans.

Abstract: Endodontic biofilm is a microbial community, enclosed in a polymeric matrix of polysaccharide origin where are found pathogens, like bacteria and opportunistic fungi responsible for various endodontic pathologies. As clinical importance is the fact, that biofilm is extremely resistant to common intracanal irrigants, antimicrobial drugs and host immune responses. The aim of this study was to evaluate the in vitro efficacy of a Cu/CaOH2-based endodontic paste, against bacteria and fungi, such as Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. We found that such compound significantly reduced microbial replication time and cell growth. Moreover, biofilm formation and persistence were also affected; treated biofilms showed both a reduced number of cells and levels of released pyoverdine. This study provides the first evidence on effectiveness of this endodontic compound against microbial biofilms. Given its wide range of action, its use in prevention and treatment of the main oral biofilm-associated infections will be discussed.

Fracture behaviors of maxillary central incisors with flared root canals restored with CAD/CAM integrated glass fiber post-and-core.

Abstract: The objective was to evaluate the fracture resistance properties of maxillary incisors with flared canals restored with computer aided design and computer aided manufacture (CAD/CAM) integrated glass fiber post-and-core. Thirty prepared flared root canals were selected in vitro and restored with CAD/CAM integrated fiber post-and-core (Group A), prefabricated fiber posts (Group B), and cast gold alloy (Group C), respectively. After submitted to fatigue loading, each specimen was subjected to a static loading until fracture. Analysis of variance (ANOVA) tests were used to determine statistical differences. The mean fracture strengths of Groups A and C were significantly higher than those of Group B, whereas no differences were observed between Groups A and C. In addition, reparable fracture modes were mostly observed in Group A while irreparable and catastrophic fractures were mostly found in Groups B and C. These results demonstrate that, in comparison to traditional treatments, CAD/CAM integrated glass fiber post-and-core restoration significantly enhances the fracture resistance of flared root canals.

Comparison of physical properties of three commercial composite core build-up materials.

Abstract: Various materials have been used for core build-up when restoring the coronal portion of the tooth. Currently, bulk-fill resin composites have been produced to restore a large posterior cavity in single increment. This study aimed to evaluate the compressive strength, flexural strength, and microhardness of three commercial composite core build-up materials. All data were analyzed by oneway ANOVA and Tukey test methods (α=0.05). Flexural strength data were subjected to Weibull statistics analysis. All three groups presented significant differences in the compressive strength, flexural strength, and Knoop hardness. FiltekTM Z350 XT had the greatest compressive strength (MPa) and Knoop hardness while FiltekTM bulk fill had the highest flexural strength. MultiCore®Flow had the lowest properties; however, it revealed the highest Weibull modulus (m) value. With regard to the properties tested in this study, bulk-fill resin composite can be used as an alternative to conventional resin composite for core build-up material.

Ultrastructure and bonding properties of tribochemical silica-coated zirconia.

Abstract: Tribochemical silica coating (TSC) is commonly used to pretreat zirconia surfaces prior to luting. Although many studies demonstrate an adhesion-promoting effect of TSC on zirconia, its actual interaction mechanism has not been fully elucidated. We therefore characterized the ultrastructure of TSC-treated zirconia and tested shear-bond strength. STEM/EDS disclosed a micro-roughened zirconia surface partially covered with fused Al and Si, while residual unfused silica particles could also still be detected. TSC-treated zirconia having received the solely silane primer exhibited a significantly lower shear-bond strength than zirconia on which the combined 10-MDP/silane primer was applied. SEM fracture analysis revealed residual silica particles on both the zirconia and cement sides. Correlative ultrastructural and chemical surface characterization revealed that TSC deposited an inhomogeneous silica layer on the zirconia surface, which explains why the solely silane coupling agent was less effective than the combined 10-MDP/silane ceramic primer for bonding to zirconia pretreated by TSC.

Toxicity of functionalized multi-walled carbon nanotubes on bone mesenchymal stem cell in rats.

Abstract: Carbon nanotubes (CNTs) are promising biomaterials in the medical field, especially in tissue engineering of bone. However, the use of CNTs is largely confined by its unfavorable solubility and toxicity. To improve solubility and biocompatibility of CNTs, functionalization has been proven to be an effective strategy. Although various functionalized CNTs have been extensively studied, only few CNTs have the desired qualities. We compared the toxicity of several promising functionalized multi-walled carbon nanotubes (MWCNTs) on rat bone-marrow derived stem cells (BMSCs). Cell experiments showed that while acid oxidation (AO)-MWCNTs and Raw-MWCNTs exhibited significant toxicity on BMSCs, polyethylene glycols (PEG)-MWCNTs and hydroxyapatit (HA)-MWCNTs had favorable biocompatibility and a trivial effect on BMSCs. Possible mechanisms for the cytotoxicity on BMSCs included mitochondrisome and deoxyribonucleic acid damage, increased oxidative stress and damaging of cellular membranes. Our data indicated that PEG-MWCNTs and HA-MWCNTs may be promising materials for bio-related applications.

Effect of airborne particle abrasion and sintering order on the surface roughness and shear bond strength between Y-TZP ceramic and resin cement.

Abstract: This study examined the surface roughness (Ra) and shear bond strength (SBS) of Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic after airborne particle abrasion at different pressures and particle sizes, pre- and post-sintering. Ninety specimens, prepared from Y-TZP ceramic blocks (Vita In-Ceram YZ, Vita Zahnfabrik), were divided into nine subgroups: control, and 50 and 110 µm Al2O3 airborne particle abrasion at 3 and 4 bar pressure, before and after sintering, respectively. According to the sintering order, before and after surface treatments, Ra values were measured using a profilometer. SBS to Y-TZP was assessed after thermocycling, using self-adhesive resin cement (Rely X U200, 3M ESPE). Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were performed on one specimen per group. All surface-treated samples were rougher than the controls. ABS50-4 (50 µm Al2O3 airborne particle abrasion at 4 bar pressure before sintering), ABS110-3, and ABS110-4 showed the highest Ra values, among all cohorts. The controls displayed lower SBS values than the treated groups (p<0.05), which had statistically similar results to each other. Airborne particle abrasion of pre-sintered Y-TZP, followed by sintering, increased the tetragonal structure contents.

In vitro and in vivo analysis of the biodegradable behavior of a magnesium alloy for biomedical applications.

Abstract: The present study was designed to investigate the biodegradation behavior of Mg alloy plates in the maxillofacial region. For in vitro analysis, the plates were immersed in saline solution and simulated body fluid. For in vivo, the plates were implanted into the tibia, head, back, abdominal cavity, and femur and assessed at 1, 2, and 4 weeks after implantation. After implantation, the plate volumes and the formed insoluble salt were measured via micro-computed tomography. SEM/EDX analysis of the insoluble salt and histological analysis of the surrounding tissues were performed. The volume loss of plates in the in vitro groups was higher than that in the in vivo groups. The volume loss was fastest in the abdomen, followed by the head, back, tibia, and femur. There were no statistically significant differences in the insoluble salt volume of the all implanted sites. The corrosion of the Mg alloy will be affected to the surrounding tissue responses. The material for the plate should be selected based on the characteristic that Mg alloys are decomposed relatively easily in the maxillofacial region.

Effect of various polishing burs on surface roughness and bacterial adhesion in pediatric zirconia crowns.

Abstract: To evaluate the effect of various polishing points on surface roughness of pediatric zirconia crowns and to correlate findings with bacterial adhesion. Zirconia discs (n=40) were fabricated and divided into five groups according to point type used to roughen and polish: I (negative control [not roughened]); II (positive control [roughened]); and III-V, representing three commercially available point brands. Atomic force and scanning electron microscopy were used to assess surface roughness. The number of colony forming units were counted after biofilm formation. A statistically significant difference was found in surface roughness and bacterial adhesion between the positive control and the other four groups, with no difference between negative control and the three point groups. Surface roughness and bacterial adhesion were significantly and positively correlated. Surface roughness and bacterial adhesion in pediatric zirconia crowns were not significantly different from other materials regardless of polishing system.

Inhibitory effect of zinc-containing desensitizer on bacterial biofilm formation and root dentin demineralization.

Abstract: This study compared the effect of a novel zinc containing, Caredyne Shield (CS), and a fluoroaluminocalciumsilicate-based, Nanoseal (NS) desensitizers on dentin tubule occlusion, inhibition of Streptococcus mutans (S. mutans) biofilm growth, and resistance to bacterial demineralization. Desensitizers were applied to simulated hypersensitive bovine dentin, with distilled water used as a control. S. mutans biofilms were grown on the surface of each specimen in an oral biofilm simulator. CS showed the least bacterial count and water insoluble glucan amount followed by NS. Transverse micro radiography revealed that both CS and NS showed significant reduction in mineral loss and lesion depth of the associated lesion. Scanning electron micrographs showed that the two desensitizers formed obvious depositions on the dentin surfaces, occlusion of tubules and mineral tag formation.

Polytetrafluoroethylene (PTFE): A resin material for possible use in dental prostheses and devices

Abstract: Polytetrafluoroethylene (PTFE) is chemically stable, non-toxic to humans, highly resistant to heat and chemicals, and has an extremely low coefficient of friction. Therefore, PTFE is used in medical applications. We focused on the physical properties of PTFE in relation to its application as a material for use in prostheses and dental devices/instruments. PTFE exhibited low wear (approximately 1/3 that of bovine tooth, and 1/2 that of type III gold alloy), low dynamic friction (approximately 1/5 that of the other specimens), low hardness (4.8HV1.0), low coloration, and low bacterial adhesion, compared to other specimens except porcelain in wear and coloration test (p<0.01). These results suggest that PTFE could have applications in some prostheses for provisional and/or permanent use, and dental instruments/devices by providing excellent impact absorption, high wear resistance for maintenance of occlusal vertical dimension and original function, and ease of cleaning.

Mechanical properties and radiopacity of flowable fiber-reinforced composite.

Abstract: The aim was to evaluate the effect of different zirconia discontinuous fiber fractions on radiopacity and other selected properties of glass discontinuous fiber-reinforced flowable composite (Exp-SFRC). Exp-SFRC was prepared by mixing 30 wt% of resin-matrix and 45 wt% of particulate-fillers to 25 wt% of various weight-fractions of E-glass/zirconia discontinuous fiber-fillers (25:0, 20:5, 15:10, 10:15, 0:25 wt%). Flexural strength and fracture toughness were determined for each experimental material. Radiograph of each Exp-SFRC and aluminium step wedge were taken to determine the radiopacity. Degree of conversion and light-transmission were also measured. Scanning electron microscopy was used to evaluate the microstructure of the Exp-SFRC. Analysis of variance (ANOVA) revealed that fractions of E-glass/zirconia discontinuous fiber-fillers had significant effect (p<0.05) on radiopacity and other tested properties of the Exp-SFRCs. Replacing low fraction of E-glass fiber with zirconia fiber-fillers can increase the radiopacity of the fiber-reinforced composite without deteriorating the mechanical properties, although, degree of conversion was decreased.

Antibacterial and antibiofilm activity over time of GuttaFlow Bioseal and AH Plus.

Abstract: The sealers' antibacterial and antibiofilm activities against Enterococcus faecalis were evaluated by direct contact test (DCT) and confocal laser scanning microscopy (CLSM), respectively, after 1 day, and 1 and 4 weeks of aging. Cell viability was determined by adenosin triphosphate (ATP) assay after DCT. The parameters evaluated for the antibiofilm property were total biovolume and percentage of green cells in E.faecalis biofilms. The data from the bioluminescence ATP assay as well as the total biovolume and green percentage were analyzed by non-parametric tests, Kruskal-Wallis for global comparison and Kolmogorov-Smirnov for each two variables. Results of the DCT and CLSM for all parameters evaluated show that the antimicrobial activity of AH Plus decreased over time, whereas GuttaFlow Bioseal had an opposite property, increasing its antibacterial activity as the material aged.

Transmission of light through fiber-reinforced composite posts.

Abstract: The aim of this in vitro study was to explore light transmission through an individually formed fiber-reinforced composite (FRC) post compared with two prefabricated FRC posts. Three different glass FRC posts from different manufacturers were used: two groups included prefabricated glass FRC posts (RelyX and GC Fiber Posts) and one group consisted of individually formed E-glass FRC posts with semi-interpenetrating polymer network (semi-IPN) polymer matrix (everStick Post). Various lengths of posts and lightprotected cylinders were made. The specimens were light-polymerized on the test tray of a light radiance testing device (MARC Resin Calibrator). Light transmission in the direction of fibers was registered. Light transmission decreased with increasing post length (p≤0.001; ANOVA) up to 12 mm in all post groups. The individually formed FRC post showed highest light transmission in all cylinder lengths (p<0.001) compared to prefabricated FRC posts, which could benefit polymerization of post material and luting cement.

Early bond strengths of 4-META/MMA-TBB resin cements to CAD/CAM resin composite.

Abstract: The purpose of this study was to evaluate the early tensile bond strengths of three different resin cements; Super Bond C&B (conventional and quick type) and ResiCem to a CAD/CAM composite block. A CAD/CAM composite block (Shofu Block HC) was ground and silanized according to the manufacturers' instructions before cementation. A conventional tensile bond strength test (O: 4 mm) was performed 10 min, 1 h and 24 h after bonding. Super Bond C&B (quick type) showed the highest bond strength at 24 h. However, results of a three-point bend test showed the mechanical properties were weaker for the Super Bond C&B cements compared with composite cement, Resicem. The 4-META/MMA-TBB resin is a suitable resin cement to bond to a CAD/CAM composite block.

Application of hydroxyapatite nanoparticle-assembled powder using basic fibroblast growth factor as a pulp-capping agent.

Abstract: We have previously fabricated hydroxyapatite (HAP) nanoparticle-assembled powder (nano-HAP) plates and granules by assembling low-crystallinity HAP nanoparticles without template/binder molecules or high-temperature/pressure treatments. In this study, we combined the nano-HAP with fibroblast growth factor (FGF) 2, which promotes odontoblast differentiation, and used this as a pulpcapping agent for dentin defects created in rat molars. The tissue response was then radiologically and histologically assessed at 1 and 2 weeks after capping, to assess the biocompatibility and ability of this material to promote hard tissue formation. The application of nano-HAP/FGF2 induced the invasion of dental pulp cells and vessels, and was consistently found to stimulate formation of a dentinal bridge containing numerous dentinal tubules. We thus succeeded in treating the pulp exposure by using a physiological approach to promote tissue regeneration. Further investigations should be performed to explain exactly how the nano-HAP/FGF2 combination contributes to calcified tissue formation.

Assessment of mechanical properties of WaveOne Gold Primary reciprocating instruments.

Abstract: This study aimed to evaluate cyclic fatigue resistance and bending properties and torque/force generation of WaveOne Gold (WOG) Primary in comparison with WaveOne (WO) Primary and Reciproc (RE) R25. A cyclic fatigue test revealed that the WOG Primary took significantly longer time to fracture compared with the WO Primary (p<0.05). The WOG Primary had the smallest load values at a deflection of 0.5 and 2 mm (p<0.05), as measured with a cantilever bending test. Torque/force measurement demonstrated that maximum upward force and maximum counterclockwise torque values in the WOG Primary were significantly lower than those in the RE R25 (p<0.05). Under the present experimental condition, the WOG Primary showed a higher cyclic fatigue resistance compared with the WO Primary, a higher flexibility compared with the WO Primary and RE R25, and generated a significantly lower maximum torque compared with the RE R25.