Bond Strength Characteristics Research Articles

A Comparison of the Shear Bond Strength between a Luting Composite Resin and Both Machinable and Printable Ceramic–Glass Polymer Materials

This study aims to compare the shear bond strength (SBS) and Weibull characteristics between a luting composite resin and both printable and two different machinable ceramic–glass polymer materials. A total of 36 substrates were prepared, with 12 in each group. Printable substrates (12 mm × 12 mm × 2 mm) were printed by using permanent crown resin (3D-PR). Machinable substrates were obtained from Cerasmart 270 (CS) and Vita Enamic (VE) blocks (2 mm in thickness). The bonding surfaces of substrates were polished and airborne abraded (50 µm Al2O3). A self-adhesive luting composite resin (RelyX U200, 3M ESPE, St. Paul, MN, USA, SLC) was applied on substrates with the help of a cylindrical (Ø3 × 3 mm) mold. The SBS test was conducted using a universal test machine. The SBSs of three materials were compared using a one-way analysis of variance (ANOVA) (α = 0.05). The Weibull modulus was calculated for each material. The Kruskal–Wallis and chi-square tests were carried out for the failure mode analysis. There was no significant difference between the SBSs of the three materials (p = 0.129). The Weibull modulus was 3.76 for the 3D-PR, 4.22 for the CS, and 6.52 for the VE group. Statistical analysis showed no significant difference between the failure modes of the groups (p = 0.986). Mixed-failure fractures were predominantly observed in all three groups. The results show that the SBS of the SLC to printable 3D-PR is comparable to that of CS and VE material. Failure modes of printable 3D-PR show similar results with two different machinable ceramic–glass polymers.

Investigation on Interfacial Bond Strength Characteristics of Concrete Filled in Galvanized Steel Tubes Utilizing Statistical Analysis and Advanced Prediction Techniques

Investigation on Interfacial Bond Strength Characteristics of Concrete Filled in Galvanized Steel Tubes Utilizing Statistical Analysis and Advanced Prediction Techniques

Antimicrobial properties and bonding durability of pH-responsive dentin adhesives with chlorhexidine-load mesoporous silica nanoparticles

In this study, we synthesized pH-sensitive CHX@SBA-PDA nanoparticles and characterized their structure. These nanoparticles were then incorporated into Single Bond 2 commercial dentin adhesive. Subsequently, timely and long-term antibacterial evaluation, cytotoxicity evaluation and bonding properties were conducted. The results demonstrated the successful synthesis of CHX@SBA-PDA nanoparticles. Moreover, CHX@SBA-PDA exhibited excellent pH sensitivity and maintained a high release rate of chlorhexidine (CHX) under cariogenic low pH conditions. At pH 5.0, the release rate could reach up to 71.1% after 24 h of incubation with CHX@SBA-PDA nanoparticles. Among the different adhesive formulations tested, the 2% wt adhesive displayed the strongest immediate and 30 days bacterial inhibition ability (p < 0.05). No significant difference was observed in immediate shear strength among the four groups (p > 0.05). After undergoing pH cycling, all functional adhesive groups exhibited higher shear strength compared to the control group (p < 0.05). Furthermore, there was no significant difference in cell proliferation activity between the experimental group and control group (p > 0.05). In conclusion, our functional dentin adhesive containing CHX@SBA-PDA nanoparticles demonstrated long-term antibacterial properties as well as improved bond strength characteristics, thus, offering a promising approach to enhance durability of bonded restorations.

Evaluation of the Mechanical and Adhesion Characteristics of Indirect Restorations Manufactured with Three-Dimensional Printing.

The aim of this study was to investigate the marginal fit and bond strength characteristics of onlay restorations manufactured by three-dimensional printing (Varseo XS, Bego GmbH, Bremen, Germany) and CAD/CAM (CAMcube, Montreal, QC, Canada) systems. Class II onlay cavities on sixty mandibular molars were prepared in cavities and restored in three separate groups using different fabrication methods. Digital and conventional impressions were taken to design the restorations in the CAD system (DWOS, Straumann GmbH, Freiburg, Germany). To evaluate the marginal fit and void volumes, all specimens were scanned with microcomputed tomography. A microshear test was performed to compare the bond strength of the restorations to the tooth surface. The marginal fit values measured for the 3D-printed and CAD/CAM onlay restorations were found to be at clinically acceptable levels (<120 µm), and no significant difference could be observed between the three different fabrication methods (p > 0.05). According to the microshear test results, the CAD/CAM group had the highest bond strength values before (34.82 MPa) and after (26.87 MPa) thermal cycling (p < 0.05), while the 3D-printed and conventionally produced onlays had similar results (p < 0.05). 3D printing technology is a promising option for indirect restorations; however, the post-production phase is as crucial as the printing and cementation phases.

Bond strength and interface characteristics between magnesium phosphate cement mortar and ordinary Portland cement concrete in a frigid environment

ABSTRACT The rapid repair of airport runways and concrete pavements using magnesium phosphate cement mortar (MPCM) in frigid environments requires the MPCM to have high bond strength with ordinary Portland cement (OPC). In this study, the effects of the pouring temperature of MPCM, surface roughness, water content, and strength grade of concrete on the interfacial bond strength and characteristics between MPCM and OPC were investigated in a frigid environment (−20°C ± 2°C). The results indicated that the 3-h compressive strength of MPCM reached 30 MPa, whereas the 3-h flexural bond strength between MPCM and OPC (BS MPCM-OPC) exceeded 2.5 MPa when the pouring temperature for the MPCM mixture is 0-5°C in a frigid environment. The moisture content of concrete before freezing had a more significant impact on BS MPCM-OPC than the influence of concrete roughness in a frigid environment; however, the influence of the concrete strength grade can be disregarded. The hydration heat of MPCM can quickly release with an increase in the pouring temperature, which accelerates phosphate dissolution and promotes the generation of struvite and the development of the BS MPCM-OPC. Furthermore, the interface bonding between MPCM and OPC involves physical bonding, mechanical anchoring, and weak chemical bonding in a frigid environment.

Shear bond strength characteristics on surface treatment modalities of CAD-CAM resin polymers.

The purpose of this in vitro study was to analyze the shear bond strength of composite resin to a commercially available high-performance polymer material for fixed, screw-retained full arch restorations. A total of 135 computer-aided design and computer-aided manufacturing, high-performance polymer (HPP) blocks were cut and obtained from discs (Trilor 95, Harvest Dental, Brea, CA). The samples were 10mm × 10mm × 10mm. The specimen surfaces were grouped as untreated (Group A), 50 μm Al2O3 (Group B), 110 μm Al2O3 (Group C), Rocatec (3M, St. Paul, MN) activated with silica-modified alumina oxide treatment (Group D); and trimmed coarsely with a carbide bur (Group E). Group A samples were used as controls. After surface treatments, the specimens were gently cleansed with oil-free steam and alcohol wipes. Surface conditioning was performed on all physically treated samples. The manufacturer's recommendations were followed for bonding composite resin to the samples with light-cured Visio.link (Bredent, Chesterfield, UK). Cylinders were veneered with composite resins (diameter 5mm, height 4mm) and polymerized on the specimen surfaces through plastic tubes. Twenty-seven specimens were used for each testing group and aging tests were performed. The experimental samples were thermocycled. Shear bond strength and scanning electron microscopic tests were performed. Means and standard deviations were calculated. Statistical analysis was performed with post-hoc Tukey tests. Statistical analysis revealed that there was a significant difference between the groups (p<0.001). The highest shear bond strengths were achieved for the specimens bonded with Visio.link without physical surface treatments (270.47MPa). The lowest bond strengths were found for specimen surfaces abraded with 110 μm Al2O3 (117.03 Mpa) CONCLUSIONS: The results of this laboratory study indicated that the specimens used with Visio.link as provided by the manufacturer had the highest shear bond strengths between the composite resin and high-performance polymer test specimens. Modifications of the high-performance polymer surfaces with carbide burs did not change bonding strengths with the composite materials.

Investigation on residual bond strength and microstructure characteristics of fiber-reinforced geopolymer concrete at elevated temperature

Fiber-reinforced geopolymer concrete has been attracting attention and interest worldwide due to its sustainable properties. However, few studies have reported the pull-out behaviour of fiber-reinforced geopolymer concrete (GPC) at elevated temperatures. In order to bridge this knowledge gap, a series of detailed investigations aimed to investigate the effect of elevated temperatures on the mechanical and microstructure properties of fiber-reinforced geopolymer concrete. In the present investigation, crimped steel fibers (SF), polypropylene fibers (PF), basalt (BF), and hybrid fibers such as SF:PF and PF:BF is employed to develop the GPC. Alkaline activators such as sodium hydroxide (NaOH) of 8 M and 10 M and Na2SiO3/NaOH ratios of 2.5 are used in the production of M35 and M40 grade GPC. Compressive strength, weight loss, crack pattern, bond strength, and microstructure of fiber-reinforced GPC specimens have been evaluated, after exposing to higher temperature following ISO 834 standard fire curve. Results from the conducted tests show that adding various types of fibers improves the compressive strength and bond strength of the GPC specimens. More specifically, amongst all tested specimens, the exposed GPC-BF shows lesser weight loss and higher residual compressive strength with fewer cracks on the surface of the specimens. on the other hand, GPC with SF shows higher residual bond strength than other fiber-reinforced GPC specimens. Microstructure analysis (SEM/EDAX) confirms the extent of damage and contribution of fiber in the temperature-exposed GPC. A statistical relationship and correlation has been obtained between compressive and bond strength.

Repair Bond Strength and Surface Characteristics of Two Ceramic Materials Subjected to Different Laser Surface Treatment Combinations.-An in vitro study

Repair Bond Strength and Surface Characteristics of Two Ceramic Materials Subjected to Different Laser Surface Treatment Combinations.-An in vitro study

Bond strength characteristics of high strength alkali activated slag concrete mixes

Bond characteristics are influenced by several factors such as concrete compressive strength, type, diameter, and embedment length of the bar and confinement of concrete. Herein, an attempt has been made to evaluate the bond strength characteristics of a new class of high-strength, flowable, alkali activated slag concrete mixes made using the industrial by-products from iron and steel industries. Such evaluations are made using the results of direct pull out tests where again, the bond stress – slip behaviour of the trial mixes at different ages are also studied. GGBFS was used as the principal binder along with fine amorphous quartz powder in the development of the present class of high strength, flowable AASC mixes. While mixtures of steel slag sand and quartz sand were used as the fine aggregates, 12.5 mm down electric-arc furnace slag aggregates constituted the coarse aggregate fractions in all these mixes. The alkaline solutions used consisted of mixtures of specified amounts of sodium hydroxide flakes dissolved in the calculated quantity of water pre-mixed with the liquid sodium silicate solution. The experimental study was planned based on Taguchi’s design of experiments methodology. A set of AASC mixes were developed and evaluated for their workability characteristics along with compressive strengths at the ages of 3, 28, 56 and 90 days. Bond strength characteristics of a set of nine of such mixes were evaluated in an initial calibration phase. Strength prediction equations were then derived based on those initial results, the predictive capability of which were then assessed and ascertained with actual results of experiments on a set of six new mixes, in the prediction phase. Further better bond stress-slip behavior, with higher bond strength values, varying in the range of 12–14 MPa as compared to control OPC based reference concrete mix were obtained for the AASC mixes.

Experimental Study on the Bonding Performance of HIRA-Type Material Anchor Solids Considering Time Variation

In order to reveal the evolution of bonding performance of HIRA (High Intensity and Rapid Agent) anchor solids with maintenance time, the evolution characteristics of bond strength and stress distribution at the interface between HIRA-based anchor solids and a geotechnical body under different maintenance times and the fine damage pattern of anchor solids were studied by an indoor pull-out test of anchor solids. The comparative analysis was performed with 42.5 grade ordinary Portland cement (hereinafter referred to as P.O 42.5). The results show that the early strength and rapid setting characteristics of HIRA type material are obvious, and the difference between its average peak bond strength and that of cement is 10.45 times. The shear stress distribution has obvious stress concentration characteristics, and the peak value will appear and shift with the increase in load, and the peak shift of the HIRA anchor solid occurs earlier than that of cement. Due to different stress levels, the damage of the HIRA anchor solid after being pulled out increases with the increase in maintenance time, while that of cement gradually becomes more severe. The overall damage of the HIRA material is generally lower than that of cement in the same period.

Bond strength characteristics of masonry using hemp fibre and chicken mesh reinforced mortar

The bonding between the masonry unit and mortar plays very important role in strength of masonry. To improve the bond strength, we need to concentrate on the mortar properties. The present study focusses on the bond strength of masonry by adding reinforcement for the mortar. The hemp fibre and chicken mesh are used as a reinforcement for the mortar. For the test masonry triplets are used with mortar of proportion 1:4. The optimum dosage for hemp fibre is found to be 2% and chicken mesh is added along with mortar joints. The bond strength was tested in universal testing machine and the results have compared each other. From the study it was found that, the bond strength of hemp fibre reinforced triplets is found to be 27% higher than the chicken mesh reinforcement and 73% higher than the unreinforced mortar masonry.

Influence of Post-Deposition Thermal Treatments on the Morpho-Structural, and Bonding Strength Characteristics of Lithium-Doped Biological-Derived Hydroxyapatite Coatings

We report on hydroxyapatite (HA) of biological-origin doped with lithium carbonate (LiC) and lithium phosphate (LiP) coatings synthesized by Pulsed laser deposition onto Ti6Al4V substrates fabricated by the Additive manufacturing technique. A detailed comparison from the structural, morphological, chemical composition, wetting behavior and bonding strength standpoints of as-deposited (NTT) and post-deposition thermal-treated (TT) coatings at temperatures ranging from 400 to 700 °C (i.e., TT400–TT700), was performed. Structural investigations indicated a complete crystallization of the initially amorphous HA-based layers at temperatures in excess of 500 °C. The morphological analyses emphasized the rough appearance of the film surfaces, consisting of particulates whose dimensions increased at higher temperatures, with an emphasis on LiC coatings. AFM investigations evidenced rough surfaces, with a clear tendency to increase in corrugation with the applied temperature, in the case of LiC coatings. A hydrophobic behavior was observed for control, NTT and TT400 samples, whilst a radical shift towards hydrophilicity was demonstrated for both types of structures at higher temperatures. In the case of TT500–TT700 coatings, the pull-out adherence values increased considerably compared to control ones. Taking into consideration the obtained results, the positive influence of post-deposition thermal treatments (performed at higher temperatures) on the physical–chemical and mechanical properties of LiC and LiP coatings was indicated. Alongside these improved characteristics observed at elevated temperatures, the sustainable nature of the used BioHA materials should recommend them as viable alternatives to synthetic HA ones for bone implant applications.

Mechanical behavior of bonded interface between steam-cured concrete and SCC under direct shear test: Experimental and numerical studies

The interlayer damage of slab ballastless track for high-speed railway has become a weak link that affects the safe operation of track structure. Under the combined action of the train self-weight load and wheel-rail friction, the track plate presents complex stress state. Meanwhile, the interlayer defects and bond state have a great influence on the damage mechanism of track plate. The failure mechanism of concrete-concrete interface under combined stress has been focused on, but it is still not well quantitatively investigated at the grain scale. In this paper, the discrete element method (DEM) combined with digital speckle and acoustic emission monitoring technology is used to conduct the direct shear tests on bonded samples composed of steam-cured concrete and self-compacting concrete (SCC) with different bond interface characteristics. On this basis, it is quantitatively analyzed the effects of interfacial bond strength and interfacial morphological characteristics on the compressive-shear mechanical properties and damage patterns of bonded samples, and the deterioration mechanism of the interface is explained from a mesoscopic perspective. The results show that the compression-shear mechanical response and damage features of the bonded samples are the result of the combined effect of bond strength and morphological characteristics of the interface. The increase of bond strength makes the samples change from shear cracking damage along the interface to tensile cracking damage inside the concrete. The bonded area ratio (BAR) of the interface maintains a good positive linear correlation with the shear strength, and the increase of BAR makes the brittle failure more obvious in the post-peak stage. The increase of interface roughness coefficient (IRC) makes more compressive stress concentration areas form in the interface, which enhances the shear strength of the bonded sample to a certain extent.

Microshear Bond Strength, Ultramorphological, and Elemental Assessment of Gold–Silver Nanoparticle-treated Dentin Bonded to Resin Composite with Different Adhesive Modes

The aim of the present study is to evaluate the effect of Ag-Au NPs formulation as surface pretreatment by assessing the microshear bond strength, ultra-morphological, and elemental characteristics of gold-silver nanoparticle-treated dentin to resin composite with different adhesive modes. A total of 60 extracted sound human permanent molars were selected to test the microshear bond strength of composite resin to dentin (40 teeth) and 20 molars were used to assess the ultramorphological and elemental characteristics of silver-gold nanoparticles using environmental scanning electron microscope (ESEM) with energy-dispersive X-ray (EDX) analyzer. The specimens were randomly divided into two main groups according to measured tests either microshear bond strength or elemental analysis. For the bond-strength testing group, 40 teeth were equally distributed into two main groups (20 each) according to dentin-surface pretreatment with or without the use of silver-gold nanoparticles. Then, each group was further divided into two subgroups (10 specimens for each) according to adhesive mode. For ultramorphological and elemental analysis, 20 teeth were equally divided into similar previously mentioned groups according to treatment modalities (5 teeth per group). The multimode bonding agent used in this study was single-bond universal, 3M. The data were collected and statistically analyzed. The significance level was set at p ≤0.05. The results showed that different etching modes had no statistically significant effect. Also, pretreatment had no statistically significant effect. The interaction between the two variables also had no statistically significant effect. Majority of samples in all groups had mixed failure mode. Ultramorphological examination of the tested samples treated with silver-gold nanoparticles revealed proper dispersion of nanoparticles in dentin. The new formulation of silver-gold nanoparticles did not interfere with the bond strength and sealing ability of resin composite restoration in different adhesion modes. The cavity disinfection with silver-gold nanoparticles did not affect the marginal integrity of resin composite restoration. Further studies should be done to evaluate the impact of application of silver-gold nanoparticles in long duration with other adhesive systems in the clinical scenario.

Adhesive system properties and its behavior under simulated pulpal pressure in sound and caries-affected dentin and aging

This study aimed to evaluate the bond strength (BS) and adhesive interface characteristics of sound (SD) and caries-affected dentin (CAD) in the presence of simulated pulpal pressure (SPP) and after aging in solvents. The study also evaluated the physical and mechanical properties of the adhesive system under solvent challenge. Seventy-two SD and 36 natural CAD human molars were used. Thirty-six sound molars were submitted to artificial formation of caries by pH cycling (artificial CAD). Chemical analysis was performed in FTIR, and the surface microhardness (KHN) was measured. All specimens had SPP (20 cm H 2 0) and were etched with 37% phosphoric acid, and an adhesive system (Scotchbond Universal, 3 M ESPE) and composite resin block was applied. Tooth-resin sticks were randomly divided into groups according to storage time (24 h and 30 days) and solvents: deionized water (W), 99% ethanol (E) and methyl ethyl ketone (MEK). The specimens were submitted to BS testing (0.5 mm/min; 10 kgf), and the adhesive interface was evaluated by SEM. After aging in solvents, the adhesive samples were evaluated using flexural strength (FS), modulus of elasticity (ME), sorption (SR), and solubility (SL). Chemical differences in dentin were observed through mineral content loss in N-CAD and A-CAD were observed in FTIR analysis. N-CAD showed the lowest mean KHN. Dentin, time, interaction dentin-time, and interaction dentin-time-solvent ( p = 0.003 < 0.05) had a statistically significant effect on BS values. The characteristics of the adhesive interface differ among substrates and aging solvents on SEM. Ethanol differed significantly after 30 days with the lowest means values in the analysis of FS, ME, SR, SL. Natural caries-affected dentin, ethanol aging solvent and 30 days of storage time showed to be the most aggressive factors in terms of reducing bond strength, negatively interfering with the quality of the adhesive interface under simulated pulpal pressure. The properties of the adhesive system were more compromised with aging in ethanol.

Effect of Different Surface Treatments on the Micro-Shear Bond Strength and Surface Characteristics of Zirconia: An In Vitro Study.

Purpose To study the effect of different surface treatments on the micro-shear bond strength and surface characteristics of zirconia. Methods Two types of zirconia ceramics were tested: opaque (O) and translucent (T). Each type of zirconia was further allotted into four groups based on the type of surface treatment method. The four groups were: control (C), air abrasion with 110 µm Al2O3 particles (A), etching with Zircos–E Etching solution for 2 hours (E), and a combination of air abrasion and etching (AE). After the surface treatment, all specimens were ultrasonically cleaned and 10 resin cement cylinders were attached to the zirconia discs in each group. A micro-shear bond strength test was performed in a universal testing machine at a crosshead speed of 0.5 mm/min. The fracture surfaces were assessed under a compound microscope. SEM, EDAX, and AFM analyses were done for the zirconia specimens after being subjected to surface treatment. Statistical analysis for the bond strength test was done using the Shapiro–Wilk test, one-way analysis of variance (ANOVA), and Post hoc Tukey test. Results The micro-shear bond strength values for the groups were as follows in megapascals (MPa): OC 18.96 (5.54), OA 22.66 (2.51), OE 28.48 (4.50), OAE 28.63 (4.53), TC 22.82 (5.46), TA 25.36 (5.17), TE 28.12 (4.76), and TAE 32.00 (3.47). The one-way analysis of variance (ANOVA) and post hoc Tukey HSD tests were done which showed significant results in the groups. In opaque zirconia, significant differences were seen in the etching and air abrasion with etching groups when compared with the control and air abrasion groups. There was no difference between the etching and air abrasion with etching groups. For translucent zirconia, the only significant difference was seen in the air abrasion with etching group in comparison with the control and air abrasion groups. The mode of failure was majorly adhesive. The surface topography and surface roughness showed significant differences between the groups. The EDAX results showed material loss that occurred due to sandblasting in the air abrasion groups. Conclusions Etching with Zircos–E Etching solution significantly increased the bond strength of zirconia to resin cement when compared with other surface treatment methods. In translucent zirconia, the best results can be achieved by combining etching with air abrasion.

Effect of combining different surface treatments on the surface characteristics of polyetheretherketone-based core materials and shear bond strength to a veneering composite resin

Statement of problemHigh-performance polyetheretherketone (PEEK) has been used in dentistry because of its excellent physical and chemical properties. However, its lack of translucency requires the use of a veneering composite resin for esthetic applications. Data on bonding a veneering composite resin to PEEK are still scarce. PurposeThe purpose of this in vitro study was to assess the effect of using and combining different surface treatments on the surface roughness and wettability of PEEK core materials and the shear bond strength (SBS) to a veneering composite resin. Material and methodsSixty square PEEK specimens were divided according to surface treatments into 6 groups: group N, no surface treatment; group A, airborne-particle abrasion; group L, ER:YAG laser treatment; group LA, laser treatment and airborne-particle abrasion; group P, plasma treatment; and group PA, plasma treatment and airborne-particle abrasion. Surface roughness (Ra) and wettability (contact angle θ) were measured followed by evaluation of the surface topography. After veneering, the SBS was measured. A 1-way analysis of variance (ANOVA) was used to assess all interactions with multiple pairwise comparisons (α=.05). ResultsThe highest mean Ra values were obtained for the combination treatment groups (LA 2.94 ±0.1 and PA 2.7 ±0.1 μm) (P<.001). While the laser (1.3 ±0.1 μm) and plasma treatment (1.4 ±0.1 μm) groups had the lowest Ra values, LA and PA had the highest wetting of PEEK surfaces (LA 6.9 ±0.7 and PA 4.9 ±0.2 degrees) (P<.001). The highest mean SBS values were demonstrated on PEEK surfaces with combination treatments (LA 22 ±1.3 and PA 21.2 ±0.8 MPa) (P<.001). ConclusionsCombining airborne-particle abrasion with laser or plasma treatments increased the surface roughness and wettability of PEEK surfaces favorably compared with applying each of the 3 treatments individually. The combinations enhanced the bond strength of PEEK to the veneering composite resin.

Testing methods and design specifications for CFRP-prestressed concrete members: A review of current practices and case studies

This paper presents a synthesis of test methods and design specifications in regard to concrete members prestressed with carbon fiber reinforced polymer (CFRP) composite tendons. Unlike other state-of-the-art articles handling laboratory experiments and numerical modeling, practical contents are collated and appraised for the benefit of structural and materials engineers who are interested in adopting this nonconventional technology. Various experimental approaches are synopsized, including sampling requirements, property measurement, load-bearing capacity, bond strength, and time-dependent characteristics. As far as implementation is concerned, specific design provisions are reviewed and their applicability is evaluated against recent research findings. Emphasis is placed on prestressing limits, flexural and shear behavior, serviceability, and embedment length. To assist practitioners’ understanding of manufacturing procedures, representative applications are described with sequential pictures. Research needs are identified to address current challenges facing the prestressed concrete community.

Re-mineralization potential, shear bond strength and hydration characteristics of experimentally prepared tri-calcium aluminate phase-modified glass ionomer cement on sound and caries-affected dentin (An in vitro/in vivo study)

BackgroundThis study aimed to in vivo and in vitro evaluate the remineralization potential and shear bond strength (SBS) of experimentally prepared tri-calcium aluminate (C3A)-modified glass ionomer cements on sound and artificial caries-affected dentin (CAD). A pure tricalcium aluminate (C3A) phase prepared via solid state reaction at elevated temperature from chemically pure calcium carbonate and alumina, to formulate ceramic composite of composition: 75% C3A, 15% CaSO4·2H2O and 10% Bi2O3. The influence of artificial saliva solution on the hydration characteristics and microstructure of the synthesized composite was investigated by X-ray diffraction (XRD) analysis, FTIR spectral analysis, pH determination and scanning electron microscope (SEM) in comparison with distilled water curing medium. Modified cements of C3A glass ionomers (C3A-CGIC) were prepared by addition of the experimentally prepared C3A to the powder component of the conventical glass ionomer cement (CGIC). Five and 10 wt% of C3A- CGICs powder were prepared and compared to CGIC. Cements were applied in prepared class V cavities in rabbits’ teeth either to sound or artificial CAD. All rabbits were killed after 15 days, and then, Ca and P wt% were evaluated at the cement–dentin interface using Energy-Dispersive X-ray Analysis. Specimens for SBS evaluation were prepared for the tested cements bonded either to sound or artificial CAD, then tested using universal testing machine.ResultsThe XRD results indicate that there is an acceleration effect on the hydration reactions and decrease in the rate of conversion process of C3A phase composite due to the presence of free ions in saliva solution which was emphasized by the results of the IR spectral bands of the hydrated paste samples. The SEM micrographs showed a more-dense microstructure with large accumulations of aluminate hydrate crystals of samples cured under saliva solution. Results of the prepared C3A-CGICs showed that 10wt% C3A-GIC group had the highest statistically significant mean Ca, P wt% and SBS values on CAD compared to 5wt% C3A-GIC and CGIC.Conclusions10 wt% C3A-GIC has a remineralizing effect on artificial CAD under in vivo conditions, plus its improved bonding to dentin compared to CGIC. Thus, it might be promising restorative/base with advanced remineralization potential and adequate bond strength to both sound dentin and CAD.

An in-vitro study investigating the effect of air-abrasion bioactive glasses on dental adhesion, cytotoxicity and odontogenic gene expression

ObjectiveTo assess the microtensile bond strength (MTBS) and interfacial characteristics of universal adhesives applied on dentine air-abraded using different powders. The analysis includes the cytotoxicity of the powders and their effect on odontogenic gene expression. MethodsSound human dentine specimens were air-abraded using bioglass 45S5 (BAG), polycarboxylated zinc-doped bioglass (SEL), alumina (AL) and submitted to SEM analysis. Resin composite was bonded to air-abraded or smear layer-covered dentine (SML) using an experimental (EXP) or a commercial adhesive (ABU) in etch&rinse (ER) or self-etch (SE) modes. Specimens were stored in artificial saliva (AS) and subjected to MTBS testing after 24 h and 10 months. Interfacial nanoleakage assessment was accomplished using confocal microscopy. The cytotoxicity of the powders was assessed, also the total RNA was extracted and the expression of odontogenic genes was evaluated through RT-PCR. ResultsAfter prolonged AS storage, specimens in the control (SML) and AL groups showed a significant drop in MTBS (p > 0.05), with degradation evident within the bonding interface. Specimens in BAG or SEL air-abraded dentine groups showed no significant difference, with resin-dentine interfaces devoid of important degradation. The metabolic activity of pulp stem cells was not affected by the tested powders. SEL and BAG had no effect on the expression of odontoblast differentiation markers. However, AL particles interfered with the expression of the odontogenic markers. SignificanceThe use of bioactive glass air-abrasion may prevent severe degradation at the resin-dentine interface. Unlike alumina, bioactive glasses do not interfere with the normal metabolic activity of pulp stem cells and their differentiation to odontoblasts.