Aim
To evaluate possible modifications in root canal sealers subjected to a variety of heating conditions using vibrational spectroscopy and analysis of physical and chemical properties.
Methodology
...EndoSequence BC Sealer HiFlow, Bio‐C Sealer, BioRoot RCS and AH Plus were analysed chemically using Raman spectroscopy (25–220 °C) and Fourier‐transform infrared spectroscopy (FT‐IR) (37–100 °C ). For FT‐IR, the materials were tested individually and mixed with root dentine powder. Scanning electron microscopy (SEM) and coupled energy dispersive spectroscopy (EDS) were used to evaluate surface and chemical elements. ISO 6876‐2012 and ASTM‐C266‐07 specifications were followed to evaluate flow, setting time (moist and dry), solubility and radiopacity. Also, pH analysis at 37 and 100 °C was performed. Shapiro–Wilk and Mixed ANOVA (within and between the effects of the subjects), Levene, and a post hoc analyses with Bonferroni correction were performed (P < 0.05).
Results
Vibrational spectroscopy revealed peaks of tricalcium silicate, dicalcium silicate and zirconium dioxide. Chemical changes in the Raman spectra during heating were discrete, as the inorganic content predominated the signalling for all root canal sealers. FT‐IR analysis exhibited spectral changes in water absorption for EndoSequence BC Sealer HiFlow and Bio‐C Sealer, probably related to dehydration. For BioRoot RCS and AH Plus, no significant chemical changes were observed. Bio‐C Sealer exhibited a band of polyethylene glycol only after heating to 100 °C, probably related to its thermal decomposition. SEM/EDS analysis corroborated the composition results observed in vibrational spectroscopy for all materials. Heating to 100 °C significantly changed the flowability of all calcium silicate‐based sealers with a wide variation in setting times at both temperatures, along with solubility levels above ISO standards. For all tested sealers, radiopacity fulfilled the requirements, and pH exhibited alkaline values.
Conclusions
The tested calcium silicate‐based sealers were affected by heating. Calcium silicate‐based root canal sealers had high solubility which is a concern for their clinical use. AH Plus was the only root canal sealer that was stable after heating.
Abstract Secondary caries at the margins of composite restorations has been attributed to adhesive failure and consequent accumulation of cariogenic biofilms. Objectives To develop and evaluate an ...etch-and-rinse adhesive system containing arginine for sustainable release and recharge without affecting its mechanical properties. Arginine metabolism by oral bacteria generates ammonia, which neutralizes glycolytic acids and creates a neutral environmental pH that is less favorable to the growth of caries pathogens, thus reducing the caries risk at the tooth-composite interface. Methods Experimental adhesives were formulated with methacrylate monomers and arginine at 5%, 7%, and 10% or no arginine (control). Adhesives were tested for: (i) mechanical properties of true stress (FS and UTS), modulus of elasticity (E), degree of conversion (DC), Knoop hardness number (KHN) and dentin microtensile bond strength (μ-TBS), (ii) arginine release and recharge, and (iii) antibacterial activities. Data was analyzed by t -test, one-way ANOVA and Tukey’s tests. Results FS and UTS results showed no statistically significant differences between the 7% arginine-adhesive and control, while the results for E, DC, KHN and μ-TBS showed no difference among all groups. The 7% arginine-adhesive showed a high release rate of arginine (75.0 μmol/cm2 ) at 2 h, and a more sustainable, controlled release rate (up to 0.2 μmol/cm2 ) at 30 days. Conclusions Incorporation of 7% arginine did not affect the physical and mechanical properties of the adhesive. Arginine was released from the adhesive at a rate and concentration that exhibited antibacterial effects, regardless of shifts in biofilm conditions such as sugar availability and pH. Clinical significance Secondary caries is recognized as the main reason for failure of dental restorations. The development of an arginine-based adhesive system has the potential to dramatically reduce the incidence and severity of secondary caries in adhesive restorations in a very economical fashion.
Abstract Statement of problem The efficiency of adding nanoparticles to silicone protection has proven to prevent color degradation. However, reports of other physical property changes in facial ...silicone are scarce. Purpose The purpose of this in vitro study was to evaluate the influence of adding nanoparticles on the hardness, tear strength, and permanent deformation of a facial silicone. Material and methods Specimens were made for each test, with 140 for the hardness test, 140 for the permanent deformation test, but 280 for the rupture test. This higher number was due to the fact that the first 140 specimens were ruptured and unusable after the initial reading. ZnO, BaSO4 , and TiO2 nanoparticles at concentrations of 1% and 2% of silicone were used, as well as specimens without nanoparticles that consisted of only oil paint and of only silicone. Outcomes were measured before and after 1008 hours of accelerated aging. Data were analyzed by nested analysis of variance (ANOVA) and Tukey honest significant differences test (α=.05). Results Results showed that the presence of nanoparticles influenced the properties of the assessed groups. The nanoparticles decreased hardness values. The highest values of tear strength were observed for the groups with addition of BaSO4 . The 1% ZnO group without oil paint showed the lowest values of permanent deformation. Conclusions Based on the findings of this in vitro study, the use of ZnO nanoparticles is recommended, since they did not negatively affect the properties of the materials evaluated.
SUMMARY Objectives : The aim of this present study was to investigate the effect of two surface treatments, fatigue and thermocycling, on the microtensile bond strength of a newly introduced lithium ...disilicate glass ceramic (IPS e.max Press, Ivoclar Vivadent) and a dual-cured resin cement. Methods : A total of 18 ceramic blocks (10 mm long × 7 mm wide × 3.0 mm thick) were fabricated and divided into six groups (n=3): groups 1, 2, and 3-air particle abraded for five seconds with 50-μm aluminum oxide particles; groups 4, 5, and 6-acid etched with 10% hydrofluoric acid for 20 seconds. A silane coupling agent was applied onto all specimens and allowed to dry for five seconds, and the ceramic blocks were bonded to a block of composite Tetric N-Ceram (Ivoclar Vivadent) with RelyX ARC (3M ESPE) resin cement and placed under a 500-g static load for two minutes. The cement excess was removed with a disposable microbrush, and four periods of light activation for 40 seconds each were performed at right angles using an LED curing unit (UltraLume LED 5, Ultradent) with a final 40 second light exposure from the top surface. All of the specimens were stored in distilled water at 37°C for 24 hours. Groups 2 and 5 were submitted to 3,000 thermal cycles between 5°C and 55°C, and groups 3 and 6 were submitted to a fatigue test of 100,000 cycles at 2 Hz. Specimens were sectioned perpendicular to the bonding area to obtain beams with a cross-sectional area of 1 mm(2) (30 beams per group) and submitted to a microtensile bond strength test in a testing machine (EZ Test) at a crosshead speed of 0.5 mm/min. Data were submitted to analysis of variance and Tukey post hoc test (p≤0.05). Results : The microtensile bond strength values (MPa) were 26.9 ± 6.9, 22.2 ± 7.8, and 21.2 ± 9.1 for groups 1-3 and 35.0 ± 9.6, 24.3 ± 8.9, and 23.9 ± 6.3 for groups 4-6. For the control group, fatigue testing and thermocycling produced a predominance of adhesive failures. Fatigue and thermocycling significantly decreased the microtensile bond strength for both ceramic surface treatments when compared with the control groups. Etching with 10% hydrofluoric acid significantly increased the microtensile bond strength for the control group.
Abstract Objectives The aim of this study was to investigate whether the ethanol concentration used would influence the outcomes obtained through softening tests when comparing light-activation ...modes. Methods Disc specimens ( n = 20) of Filtek Z250 and Filtek Z100 (3M ESPE) were light activated by standard (S) and pulse-delay (PD) modes. Initial Knoop hardness (KHN) measurements were performed 24 h after dry storage at 37 °C. Half of the specimens ( n = 10) of each resin-composite were stored in absolute ethanol (100%) and the other half in 75% ethanol solution, for 24 h at room temperature, and KHN was determined anew. Initial hardness data were submitted to Student's t -test ( p = 0.05). Percentages of hardness decrease were analyzed by two-way ANOVA followed by pairwise Tukey's test ( p = 0.05). The statistical analyses were performed separately for each resin-composite. Results No statistically significant differences were observed between standard and pulse-delay modes for initial Knoop hardness values. After storage in 75% ethanol solution, KHN was decreased in all cases but no significant differences were detected between light-activation modes (Filtek Z250: PD = 12.6%, S = 13.5%; Filtek Z100: PD = 13.5%, S = 11.8%) regardless of the resin-composite tested. After absolute ethanol storage, higher decrease in KHN were observed. Samples light-activated by the PD mode (Filtek Z250 = 20.4% and Filtek Z100 = 16.9%) exhibited significantly higher percentage decrease of KHN than specimens light-activated by the standard mode (Filtek Z250 = 14.1% and Filtek Z100 = 8.8%), regardless of the resin-composite tested. Conclusion The ethanol concentration affected the outcomes of the softening test.
The aim of this study was to evaluate the influence of different concentrations of hydrofluoric acid (HF) associated with varied etching times on the microshear bond strength (μSBS) of a resin cement ...to a lithium disilicate glass ceramic. Two hundred seventy-five ceramic blocks (IPS e.max Press EMX, Ivoclar Vivadent), measuring 8 mm × 3 mm thickness, were randomly distributed into five groups according to the HF concentrations (n=50): 1%, 2.5%, 5%, 7.5%, and 10%. Further random distribution into subgroups was performed according to the following etching times (n=10): 20, 40, 60, 120, and 20 + 20 seconds. After etching, all blocks were treated with a silane coupling agent followed by a thin layer of an unfilled resin. Three resin cement cylinders (∅=1 mm) were made on each EMX surface, which was then stored in deionized water at 37°C for 24 hours before testing. The μSBS was in a universal testing machine at a crosshead speed of 1 mm/min until failure. Data were submitted to two-way analysis of variance, and multiple comparisons were performed using the Tukey post hoc test (α=0.05). One representative EMX sample was etched according to the description of each subgroup and evaluated using scanning electron microscopy for surface characterization. The HF concentrations of 5%, 7.5%, and 10% provided significantly higher μSBS values than 1% and 2.5% (p<0.05), regardless of the etching times. For 1% and 2.5% HF, the etching times from 40 to 120 seconds increased the μSBS values compared with 20 seconds (p<0.05), but etching periods did not differ within the 5%, 7.5%, and 10% HF groups (p>0.05). The effect of re-etching was more evident for 1% and 2.5% HF (p<0.05). Different HF concentrations/etching times directly influenced the bond strength and surface morphology of EMX.
Abstract This study proposed smaller dimensions for samples used in solubility and dimensional change tests of root filling materials on the basis of American National Standard Institute/American ...Dental Association (ANSI/ADA) Specification No. 57. The volume, mass, and density of the test samples were determined, and 6 different samples of smaller dimensions were proposed for each test. Endofill and AH Plus sealers were used in the tests. For the solubility test, 2 samples were weighted, stored in distilled and dionized water for 24 hours, dried, and weighed again. Solubility was calculated by using samples’ weight loss (%). For dimensional change analysis, the samples’ heights were measured before and after immersion in dionized water for 30 days. For both tests, correlation between data of the different groups was observed. Kruskal-Wallis test showed that Endofill sealer presented higher solubility values than AH Plus ( P < .05). The Endofill sealer presented 0.56% of shrinkage and AH Plus 0.62% expansion. Smaller dimensions for test samples used in solubility and dimensional change tests are a viable alternative, decreasing the amount of filling material necessary for executing these tests.
We evaluated the influence of chemical disinfection and accelerated aging on the dimensional stability and detail reproduction of a silicone elastomer containing one of two opacifiers.
A total of 90 ...samples were fabricated from Silastic MDX 4-4210 silicone and divided into groups (n = 10) according to opacifier content (barium sulfate or titanium dioxide) and disinfectant solution (neutral soap, Efferdent, or 4% chlorhexidine). The specimens were disinfected 3 times per week during 60 days and then subjected to accelerated aging for 1008 hours. Dimensional stability and detail reproduction tests were performed after specimens' fabrication (baseline), chemical disinfection and periodically during accelerated aging (252, 504, and 1008 hours). The results were analyzed using 3-way repeated-measures ANOVA and the Tukey HSD test (α = 0.05).
All groups exhibited dimensional changes over time. The opacifier (p = .314), period (p < .0001) and their interactions (p = .0041) affected the dimensional stability of the silicone. Statistical significant dimensional differences occurred between groups with (0.071) and without opacifiers (0.053). Accelerated aging influenced the dimensional stability of the samples. All groups scored 2 in the detail reproduction tests, which represents the fully reproducing of three test grooves with accurate angles.
Incorporation of opacifiers alters the dimensional stability of silicones used in facial prosthetics, but seems to have no influence on detail reproduction. Accelerated aging is responsible for most of the dimensional changes in Silastic MDX4 4210, but all dimensional changes measured in this study remained within the limits of stability necessary for this application.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study evaluated the influence of etching periods on the surface/interface morphology and bond strength to glass ceramic with or without application of an unfilled resin after silane. Ceramic ...discs were divided into 12 groups, defined by etching time with 10% hydrofluoric acid: G1/G7--etching for 10 seconds, G2/G8--20 seconds; G3/G9--40 seconds; G4/G10--60 seconds; G5/G11--120 seconds and G6/G12--60 + 60 seconds. All the groups were silanated after etching and G7 - G12 received a layer of unfilled resin after silane. Microshear testing using resin cement was performed, with 12 resin cylinders tested per group. The data was submitted to two-way ANOVA and the Student-Newman-Keuls' test (p<0.05). Evaluation of the etching pattern and bonding interfaces was conducted by SEM. The bond strength means (MPa) were: 19.4 +/- 3.5, 22.3 +/- 5.1, 22.2 +/- 3.2, 17.8 +/- 2.1, 15.3 +/- 3.0 and 14.3 +/- 1.8 for G1-G6 and 17.4 +/- 4.8, 21.3 +/- 2.1, 21.1 +/- 2.3, 24.7 +/- 5.8, 20.4 +/- 2.2 and 18.5 +/- 4.6 for G7-G12. Poor etching was detected after 10 seconds of conditioning; whereas deep channels were extensively observed on surfaces etched for 120 and 60 + 60 seconds. Unfilled voids underlying the ceramic-cement interface were detected when only silane was applied. Full completion of the irregularities on G11 was detected using unfilled resin. When only silane was applied, the 60-second group and those etched for longer periods showed lower bond strengths. When both silane and unfilled resin were applied, all etching periods generally showed similar values. In conclusion, the etching period influenced the surface/interface topography and bond strength to ceramic. The application of unfilled resin was able to infiltrate all unfilled voids beneath the ceramic-cement interface, except on re-etched surfaces.
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