Silicon Carbide Abrasive Paper Research Articles

Measuring the Shear Bound Strength on Acrylic Resin Veneer to Metal Surface of Nickel (A Comparative Study)

The bound strength of metal resin interface of prosthesis is a key factor in determining the service ability of that prosthesis. The main objective of this study was to determine the effect of different surface treatment on the shear bond strength of Ni-Cr alloy (CB-Blando 72 alloy) and heat cured acrylic veneer resin (Vertex). Thirty disc shaped samples from base plate wax were prepared, the diameter of disc was (8 mm x 4.5 mm). After casting the metal, the samples were cleaned, finished and polished by silicon carbide abrasive paper with grit size (600 μm) and then the profilometer was u sed to determine the surface roughness of samples. Then the sa mples were divided in to three groups, each group contain (10) sa mples. The first group rece ived no treatment and serve as control .The Second group received micro mechanical treatment using 250 μm Al2o3 .The third group recived micro mechanical treatment using 400 μm Al2o3. The acrylic was prepared as a round shape (8 μm) in diameter and (2 μm) in thickness, which was placed on the metal surface treatment, the acrylic was fabricated in the same conventional way for construction veneer resin. Then all samples was tested the shear bond strength by using Instron universal testing machine .The result from this study showed that, the first group was give low shear bond strength while the second group showed that the air abrasion with 250 μm Al2o3 give the highest shear bond values when compared with the third group which air abrasive with 400 μm Al2o3.

Effect of chemical removal or mechanical modification of smear layer on dentin adhesion with universal resin adhesives

This study aims to investigate the effect of chemical removal or mechanical modification of the smear layer on dentin adhesion with universal adhesives. Dentin surfaces (92 teeth in total) were burnished using 320-grit silicon carbide abrasive paper, and further divided into four groups: control (Con, no treatment), phosphoric acid etching (Etc, chemical removal of smear layer), polishing with 800-grit silicon carbide abrasive paper, and ultrasonic cleaning (Pol and Ult, mechanical modification of smear layer). The scanning electron microscope was used to observe the dentin surface. Two universal resin adhesives with ‘mild’ self-etching (Clearfil universal bond quick, pH = 2.3) and ‘ultra-mild’ self-etching (All bond universal, pH = 3.2) were used. Resin-dentin bonding interface was observed by the confocal laser scanning microscope. The micro-tensile bond test (n = 20) was performed to evaluate the bond strength before and after 10,000 times thermal cycles. Failure mode was evaluated by stereomicroscope. Three-way ANOVA was used to analyze the effect of different smear layer treatments, adhesives, and thermal aging on μTBS. Smear layer treatment, adhesive, and thermal aging all had a significant effect on bond strength. Pol and Ult groups of two adhesives had no difference in bond durability, which were significantly higher than Etc and Con groups. Etc and Con groups of ‘mild’ adhesive had better bond durability than that of ‘ultra-mild’ adhesive. After 24 h storage, the μTBS of ‘mild’ adhesive in the Ult group was the highest (44.39 ± 10.71 MPa), so as after thermal cycles (41.53 ± 13.29 MPa). However, the μTBS of ‘ultra-mild’ in the Etc group was the lowest (16.70 ± 4.72 MPa) among all groups. After thermal cycles, it also showed the lowest μTBS (12.83 ± 6.75 MPa) as well. The mechanical modification of the smear layer could lead to more efficient dentin adhesion with universal resin adhesives.

Sliding wear performance of novel millet husk reinforced polypropylene composites

The current research aims to investigate the influence of novel millet husk, finger millet husk (FMH), and barnyard millet husk (BMH) as fillers on the sliding wear performance of polypropylene (PP) composites. The composites were prepared with 10 wt% loading of FMH and BMH by the extrusion injection molding (EIM) process. The sliding wear testing was performed at different combinations of sliding velocity (0.5, 1, and 1.5 m/sec), load (10, 20, and 30 N), and sliding distance (300 m) against the 1000-µm silicon carbide abrasive paper as counter surface. It was observed from the micrographs that FMH and BMH established improved adhesion with the PP matrix and lowered the specific wear rate. At higher load and velocity values, tribofilm development was observed, which lowered the rate at which composites wear out. The wear mechanism, bonding behavior, and worn-out surface have also been discussed and supported with surface analysis using a scanning electron microscope.

Alternatives to amalgam: Is pretreatment necessary for effective bonding to dentin?

The aim of this study was to determine whether pretreatment of the dentin surface is beneficial or not by analysis of the bond strengths of four self-adhesive restoratives and four restoration materials where pretreatment of dentin was necessary. Bovine incisors (n=160) were ground flat on the labial surfaces to expose dentin using a grinder and silicon carbide (SiC) abrasive papers under running water. Between preparation and bonding procedures, the crowns were stored in Chloramine-T solution at 4°C. Eight different restorative materials were studied: Activa BioActive (ABA), Cention Forte (CNF), Ceram.x Spectra ST (CXS), Riva self-cure (RSC), Equia Forte (EQF), Fuji II LC (FJI), Ketac Molar (KTM), Surefil one (SFO). Four materials required pretreatment of the dental hard tissue before placement, whereas the other four were self-adhesive (no pretreatment). The specimens were mounted vertically in plaster. A preload of 5N was applied and the subsequent cross-head speed was 0.8mm/min. Shear bond strengths (MPa) were calculated as the failure load divided by the bonding area. Failure modes were recorded as adhesive, cohesive or pretest. Data were statistically analyzed via ordinal regression for inference and Tukey's method to adjust for multiple comparisons. All computations were done using R version 4.1.2 (R Core Team 2021). Smax (failure stress in MPa) of the combined groups with pretreatment were significantly higher than the self-adhesive materials. The highest frequency of pretest-failure was seen with FJI. Glass-ionomer cements without pretreatment were the only restoratives with pretest failures. Amongst materials without pretreatment, SFO had the highest bond strengths. The further reduction of the placement steps for materials used as an amalgam alternative, namely the omission of pretreatment of the dentin, results in these self-adhesive materials having lower bond strengths than materials that require pretreatment of the dentin.

In vitro release of silver ions and expression of osteogenic genes by MC3T3-E1 cell line cultured on nano-hydroxyapatite and silver/strontium-coated titanium plates.

Attempts are ongoing to improve the surface properties of dental implants by application of different coatings, aiming to enhance osseointegration, and decrease the adverse effects of titanium and its alloys used in dental implants. Coating of implant surface with hydroxyapatite (HA) is one suggested strategy for this purpose due to its high biocompatibility and similar structure to the adjacent bone. This study aimed to quantify the release of silver ions and expression of osteogenic genes by MC3T3-E1 cells cultured on nano-HA and silver/strontium (Ag/Sr)-coated titanium plates via the electrochemical deposition method. Plates measuring 10 × 10 × 0.9mm were fabricated from Ti-6Al-4V alloy, and polished with silicon carbide abrasive papers before electrochemical deposition to create a smooth, mirror-like surface. After applying homogenous nano-HA coatings with/without silver/strontium on the surface of the plates, the composition of coatings was confirmed by energy-dispersive X-ray spectroscopy (EDS), and their morphological properties were analyzed by scanning electron microscopy (SEM). The coated specimens were then immersed in simulated body fluid (SBF), and the concentration of released sliver ions was quantified by spectroscopy at 7-14days. The MC3T3-E1 osteoblastic cell line was cultured in osteogenic medium for 7-14days, and after RNA extraction and cDNA synthesis, the expression of runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osteopontin (OPN); osteogenic genes was quantified by polymerase chain reaction (PCR) using SYBR Green Master Mix kit. The expression of genes and the released amount of silver ions were compared between the two groups using the Mann-Whitney U test. The two groups were not significantly different regarding silver ion release at 14days (P > 0.05). However, silver ion release was significantly higher from nano-HA coatings with silver/strontium at 7days (P = 0.03). The difference in expression of RUNX2 (P = 0.04), OPN (P = 0.04), and OCN (P = 0.03) genes was also significant between nano-HA coating groups with and without silver/strontium at 7days, and the expressions were higher in nano-HA with silver/strontium group, but this difference was not significant at 14days. Addition of silver and strontium to specimens coated with nano-HA increased the release of silver ions within the non-toxic range, and enhanced the expression of osteogenic genes particularly after 7days.

Influence of Copper Substrate Roughness on the Growth of Intermetallic Compounds Layer in SAC305 Solder Joints

This study aimed to evaluate the effect of surface morphology of copper (Cu) substrate on the intermetallic compound (IMC) growth and interfacial reactions when soldered with SAC305 lead-free solder during a thermal aging process. The surface morphology conditions of the Cu substrate influence the growth activity of the IMC layer. This study used different grits of silicon carbide (SiC) abrasive paper (400, 800 and 1200) to grind the Cu substrate to produce different surface roughness. The resulting Cu surface morphologies were examined using an infinite focus microscope (IFM), and the parameters used in this stereometric analysis were profile roughness. Hand soldering was used to melt the SAC305 solder on the Cu substrates with different surface roughness. Subsequently, the samples were subjected to an aging temperature of 150 °C for 800 hours to grow the IMC layers. Thermal aging increased the IMC thickness at the Cu-SAC305 interfaces. After thermal aging, the IMC layer thickness and related parameters were measured and analyzed with the IFM. The growth of the IMC layer thickness depended on the different surface morphology of the substrate when the aging temperatures and Cu materials were maintained in this study. In general, the IMC morphology for the rougher Cu substrate had a scallop-shaped and uniformed layer compared to those IMC from the smooth Cu substrate. The Cu substrate ground surface roughness with 400 grit SiC abrasive paper produced an average roughness, Ra of 505.02 nm; this roughness produced the thinnest IMC layers compared to the different Cu substrates ground by SiC abrasive paper of different grits.

Influence of yttria content and surface treatment on the strength of translucent zirconia materials

Statement of problemNewly developed translucent zirconia materials have been used for anterior monolithic complete coverage restorations. Surface treatments can improve adhesion, as well as decrease or increase the strength of ceramics. However, information on the influence of surface treatments on the strength of translucent zirconias is sparse. PurposeThe purpose of this in vitro study was to measure and characterize the effects of different surface treatments, including airborne-particle abrasion, on the strength of different translucent 4 mol% and 5 mol% yttria-stabilized zirconia materials. Materials and methodsDisks (N=160) made from 4 types of translucent yttria-stabilized zirconia materials were surface-treated in 4 ways: Control groups were hand-polished with 2000-grit silicon carbide abrasive paper; as-machined; glass bead airborne-particle abraded; and alumina airborne-particle abraded. The biaxial flexural strength was measured by using a piston-on-3-ball test in a universal testing machine. The simple main effects of material type and surface treatment and their interaction on biaxial flexural strength were evaluated with 2-way ANOVA (α=.05). A priori, 1-way ANOVA and the Tukey multiple comparisons tests were used within material and treatment types (α=.05). Surface morphology was assessed by using scanning electron microscopy. Translucency, absolute transmittance, was measured by using a spectrophotometer. ResultsTwo-way ANOVA revealed that the effects of zirconia type, surface treatment, and their interaction all significantly affected biaxial flexural strength (P<.001). One-way ANOVA revealed that the 4Y material was stronger than all 5Y materials, regardless of surface treatment; all 5Y materials were ranked from strongest to weakest as polished; as-machined, or glass bead abraded; and alumina abraded. The 4Y material was stronger when alumina abraded than when glass bead abraded. Scanning electron microscopy showed that as-polished surfaces were smoother than all others; as-machined and glass bead abraded surfaces displayed little difference; alumina abraded was the roughest; and differences among materials were not discerned. The 1-way ANOVA and multiple comparisons testing showed that the 4Y material had less absolute transmittance, approximately 5% less, than all the 5Y materials. ConclusionsZirconia material type and surface treatment influenced the strength of translucent zirconia materials; a 4 mol% zirconia material was stronger than 5 mol% zirconia materials for all surface treatments tested; airborne-particle abrasion using alumina had a slight strengthening effect on a 4 mol% zirconia but had a weakening effect on 5 mol% materials; airborne-particle abrasion by using alumina produced the roughest surfaces on all materials; and the 4 mol% material was slightly less translucent than the 5 mol% materials.

Effect of Grain Refinement on Tribological Study of Low Carbon Steel

Tribological characteristics of low carbon steel (LCS) have been investigated on as-received coarse grains of 67 μm size and ultrafine-grained (UFG) microstructure of 0.2 μm size, which was prepared by equal-channel angular pressing (ECAP). Two-body abrasion tests have been carried out against silicon carbide abrasive papers at various loads. Furthermore, solid particle (silica sand) erosion tests were also conducted at normal particle impingement angles at various impact velocities. The ECAP process improved the resistance to abrasive and erosion wear of UFG LCS as compared to that of as-received coarse-grained steel. The abrasive and erosion wear resistances of UFG LCS were improved under severe conditions. The abrasive wear mechanism of as-received coarse-grained LCS was governed by micro-cutting, whereas it was microploughing in UFG LCS. The mechanism of material removal in erosive wear was brittle in as-received material in contrast to ductile in UFG steel.

On the role of capillary and viscous forces on wear and frictional performances of natural fiber composites under lubricated polishing

This paper aims to investigate the frictional and wear performances of natural flax fibers reinforced polypropylene composites subjected to lubricated mechanical polishing. Particularly, the interactions between the biocomposite surfaces and two different liquids (oil and water) are considered using a rotary tribometer where the counter-face is fed by silicon carbide (SiC) abrasive papers. Friction and wear at dry, water and oil-lubricated polishing are hence studied. The biocomposite worn surfaces are examined using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Results show a significant influence of the lubricant type on the wear and frictional performances of flax fiber composites. The lubricated friction behavior is dependent on both the hydrophilic and oleophilic properties of flax fibers. In addition to the abrasive wear, while the thermal softening of the biocomposite controls the adhesive wear mechanism at dry polishing, changing the lubricant type from water to oil leads to modify the adhesive wear sources from only capillary forces to capillary and viscous forces, which contributes to increasing the wear of flax fiber composites under oil-lubricated polishing.

In Situ Synthesized Particulates on a Zirconia Ceramic Surface and Their Effect on Bonding to Porcelain.

To explore the effect of in situ synthesized particulates on a zirconia surface on the bonding properties between zirconia and porcelain. Presintered yttrium-stabilized tetragonal zirconia (Y-TZP) was cut into slices and bars and polished with 1,200-grit silicon carbide abrasive paper. Samples were randomly divided into six groups (C, I1, I3, I5, I7, and I9) according to immersion time in hydrofluoric acid solution (0, 10, 30, 50, 70, and 90 seconds, respectively). Then, the samples were placed in calcium chloride solution for 90 seconds and dipped in sodium hydroxide solution at 80°C for 2 hours. After sintering, the surface topography and roughness were examined. After the porcelain was fired, the bonding interface was observed, and cross-sectional microhardness was measured. The shear bond strength of the zirconia to porcelain was evaluated, and failure modes were classified. A 3-point bending test was applied to confirm the effects of the treatment on the mechanical properties. The above data were statistically analyzed. Polycrystalline particulates were synthesized on the zirconia surface. The surface roughness values increased as the immersion time of the samples in hydrofluoric acid increased. The cross-sectional microhardness decreased gradually in the experimental groups. Group I7 showed an elevated bond strength (27.02 ± 2.44 MPa). Mainly mixed failure mode was obtained in the experimental groups. The Weibull characteristic strength for the experimental groups was higher than that of group C. The flexural strengths were not significantly different among the groups. In situ synthesized polycrystalline particulates on zirconia could effectively improve the bonding between zirconia ceramics and porcelain without significantly decreasing the mechanical properties.

Ultra-morphological characteristics of dentin surfaces after different preparations and treatments.

Using transmission electron microscopy (TEM), this study investigated the characteristics of smear layers after preparation of dentin surfaces using different methods. In addition, this study analyzed, using scanning electron microscopy (SEM), the interactions of smear layers with the various acidic agents used subsequently to treat the dentin surface. Mid-coronal dentin surfaces were prepared according to one of five instrumentation methods: fracture; grinding with carbide bur; grinding with regular-grit diamond bur; grinding with superfine-grit diamond bur; or grinding with 600-grit silicon carbide (SiC) abrasive paper. Then, each prepared dentin surface was further divided into control (no further treatment) or treatment with one of the following agents: phosphoric acid solution (PAS); phosphoric acid gel (PAG); Clearfil SE Bond 2 Primer (SE2); or Scotchbond Universal Adhesive (SBU). Longitudinal ultra-thin sections were made for TEM observations. Dentin discs, representing each surface preparation and treatment method described above, were created, and the morphology was examined by SEM. The TEM results revealed differences in thickness and denseness of the smear layer, according to the different methods of instrumentation used to prepare the dentin surface. The two forms of phosphoric acid completely removed the smear layer in all groups. Agglomerated silica particles were observed on the top of the collagen layer after etching with PAG. For all dentin surfaces, except for that prepared with SiC, SE2 demonstrated better etching efficacy on different smear layers, whereas SBU provided only superficial interaction.

Effect of Surface Preparation on the Isothermal Oxidation of Fe-33Ni-19Cr Alloy

The effect of surface preparation on the isothermal oxidation behavior of Fe-33Ni-19Cr alloy was study in this paper. The surface preparation of the test samples was obtained by grinding process using different grit of silicon carbide abrasive paper, namely P600, P800 and P1000. The surface area and weight of the sample were measured before the oxidation test, by using Vernier caliper and analytical balance. The ground sample of Fe-33Ni-19Cr alloys were isothermally oxidized at 1000℃ for 150 hours in laboratory air. The weight of oxidized samples was recorded after the isothermal oxidation test at every 25 hours exposure duration in order to determine the oxidation kinetic of all samples. The oxide surface morphology of Fe-33Ni-19Cr alloy was characterized by scanning electron microscope. The oxidation kinetic of all samples displayed a weight gain pattern as the exposure duration increase, followed a parabolic rate law. While the result of surface morphology shows that the lowest grit of surface finish, P600, display less oxide exfoliation occurred.

The effect of hexagonal boron nitride on wear resistance under two and three-body abrasion modes of polyetherketone composites

This investigation was performed to study the effect of hexagonal boron nitride (hBN) on abrasion wear behaviour of polyetherketone (PEK) composites. PEK composite were examined for two-body abrasive wear (2-BAW) with silicon carbide abrasive paper and three-body abrasive wear (3-BAW) test with silica sand according to ASTM standards. The Taguchi L9 design of experiment was employed to optimize the wear operating parameters. The optimized conditions with 10 N load, 320 grit size and 10 wt% of hBN resulted minimum specific wear rate (Ks). Unfilled PEK portrayed better impact strength, hardness, lower density and lower Ks under 3-BAW. However, 10 wt% of hBN was beneficial under 2-BAW condition. The SEM micrographs were analyzed to probe the wear mechanism involved in the abrasion process. Surface roughness (Ra) value measured was compared with Atomic Force Microscopy (AFM) and it was found that both the values are in good agreement. Multi-objective optimization by ratio analysis (MOORA) was implemented to rank the overall performance of PEK composites under study.

Mechanical and tribological study of short glass fiber-reinforced PA 66

Tensile, flexural, wear, and friction behaviors of polyamide 6.6 (PA 66) reinforced by different weight fractions of short glass- iber were investigated. Three-point bending flexural tests in addition to monotonic tensile tests were carried out to determine the mechanical behavior. Reciprocating friction tests were carried out without lubrication under ambient conditions. A ball-on-flat contact configuration was adopted for all tests. Reciprocating wear tests were carried out against a silicon carbide abrasive paper. Results show that the reinforcement influenced mechanical and tribological behaviors and that the orientation of glass fiber has an effect on the friction behavior. Increasing the weight fraction of glass fiber increases the ultimate strength, the flexural strength, and the elastic modulus but decreases the elongation at break. Increasing the weight fraction of glass fiber decreases the coefficient of friction and increases the wear rate. For high weight fractions, when sliding parallel to the glass fiber direction, the coefficient of friction is smaller than which is measured in the perpendicular direction. Abrasive wear mechanism of wear was illustrated via scanning electron micrographs.

Exploration of potential of Zylon and Aramid fibers to enhance the abrasive wear performance of polymers

Two series of composites based on two types of high performance fibers (aramid and liquid-crystalline polyoxazole) were developed by using two different base matrices viz. Polyetherimide (PEI) and Ultra-high-molecular-weight-polyethylene (UHMWPE). PEI based composites reinforced with fabrics of Zylon (liquid-crystalline polyoxazole) and Kevlar-49 (aramid) were developed by using an impregnation technique, while UHMWPE composite reinforced with fibers of Twaron (aramid) was developed by a novel co-mingling technique. These composites were evaluated for their abrasive wear performance under various loads and orientations against Silicon Carbide (SiC) abrasive paper in a single pass condition. These fabric reinforcements enhanced the abrasive wear performance up to 50% when the fabric was oriented normal to the sliding surface. However, the wear performance deteriorated when the fabric was oriented parallel to the sliding surface. Zylon fabric proved to be the most beneficial in maximizing the wear resistance of PEI matrix. These results were supported by the SEM studies done to understand the various possible wear mechanisms.

Do ozonated water and boric acid affect the bond strength to dentin in different adhesive systems?

The aim of this in vitro study was to compare the effects of the application of three different cavity disinfecting agents to dentin on the micro-shear bond strength (μ-SBS) of one self-etch and two universal adhesive systems. In total, 120 caries-free human permanent molar teeth were used in this study. Mid-coronal dentin surfaces were revealed by cutting occlusal enamel and a standard smear layer was obtained by using 600-800-1200 grid silicon carbide abrasive papers. Specimens were randomly assigned to four groups according to the disinfectant used: Group 1: Control (no disinfectant); Group 2: 2% chlorhexidine based (Consepsis); Group 3: 10 ppm ozonated water (TeknO3zone); Group 4: 5% boric acid (Handmade). Each group was divided into three subgroups according to the type of adhesive (Clearfil SE Bond, OptiBond XTR, and Tokuyama Universal). Specimens were bonded using either Clearfil SE Bond, OptiBond XTR or Tokuyama Universal, which were employed according to the manufacturer's instructions. Resin composite microcylinders were bonded using Tygon® tubes for μ-SBS testing. After specimens were stored for 24 h, at 37°C in distilled water, μ-SBS test was measured with a universal test machine (LF Plus, Lloyd, Instrument). μ-SBS results were analyzed by one-way analysis of variance (ANOVA) and Tukey's tests. When the mean microshear bond strength values of the control group were compared, the difference between the subgroups was not significant (P < 0.05). When the mean microshear bond strength values of the chx, ozonated water, and boric acid were compared, the difference between Clearfil SE Bond and Tokuyama Universal was significant (P < 0.05) and the difference between the other groups was not significant (P > 0.05). Ozonated water and boric acid may be as an alternative to other materials used as cavity disinfectants.

Effects of Polyacrylic Acid Pre-Treatment on Bonded-Dentine Interfaces Created with a Modern Bioactive Resin-Modified Glass Ionomer Cement and Subjected to Cycling Mechanical Stress.

Objectives: Resin-modified glass ionomer cements (RMGIC) are considered excellent restorative materials with unique therapeutic and anti-cariogenic activity. However, concerns exist regarding the use of polyacrylic acid as a dentine conditioner as it may influence the bonding performance of RMGIC. The aim of this study was to evaluate the effect of different protocols for cycling mechanical stress on the bond durability and interfacial ultramorphology of a modern RMGIC applied to dentine pre-treated with/without polyacrylic acid conditioner (PAA). Methods: The RMGIC was applied onto human dentine specimens prepared with silicon-carbide (SiC) abrasive paper with or without the use of a PAA conditioner. The specimens were immersed in deionised water for 24 h then divided in 3 groups. The first group was cut into matchsticks (cross-sectional area of 0.9 mm2) and tested immediately for microtensile bond strength (MTBS). The second was first subjected to load cycling (250,000 cycles; 3 Hz; 70 N) and then cut into matchsticks and tested for MTBS. The third group was subjected to load cycling (250,000 cycles; 3 Hz; 70 N), cut into matchsticks, and then immersed for 8 months storage in artificial saliva (AS); these were finally tested for MTBS. The results were analysed statistically using two-way ANOVA and the Student–Newman–Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMCGIC-bonded dentine specimens were aged as previously described and used for interfacial ultramorphology characterisation (dye nanoleakage) using confocal microscopy. Results: The RMGIC applied onto dentine that received no pre-treatment (10% PAA gel) showed no significant reduction in MTBS after load cycling followed by 8 months of storage in AS (p > 0.05). The RMGIC–dentine interface created in PAA-conditioned SiC-abraded dentine specimens showed no sign of degradation, but with porosities within the bonding interface both after load cycling and after 8 months of storage in AS. Conversely, the RMGIC–dentine interface of the specimens with no PAA pre-treatment showed no sign of porosity within the interface after any of the aging protocols, although some bonded-dentine interfaces presented cohesive cracks within the cement after prolonged AS storage. However, the specimens of this group showed no significant reduction in bond strength (p < 0.05) after 8 months of storage in AS or load cycling (p > 0.05). After prolonged AS storage, the bond strength value attained in RMGIC–dentine specimens created in PAA pre-treated dentine were significantly higher than those observed in the specimens created with no PAA pre-treatment in dentine. Conclusions: PAA conditioning of dentine prior to application of RMGIC induces no substantial effect on the bond strength after short-term storage, but its use may increase the risk of collagen degradation at the bonding interface after prolonged aging. Modern RMGIC applied without PAA dentine pre-treatment may have greater therapeutic synergy with saliva during cycle occlusal load, thereby enhancing the remineralisation and protection of the bonding interface.

The effect of dentine pre-treatment using bioglass and/or polyacrylic acid on the interfacial characteristics of resin-modified glass ionomer cements

ObjectiveTo evaluate the effect of load-cycle aging and/or 6 months artificial saliva (AS) storage on bond durability and interfacial ultramorphology of resin-modified glass ionomer cement (RMGIC) applied onto dentine air-abraded using Bioglass 45S5 (BAG) with/without polyacrylic acid (PAA) conditioning. MethodsRMGIC (Ionolux, VOCO) was applied onto human dentine specimens prepared with silicon-carbide abrasive paper or air-abraded with BAG with or without the use of PAA conditioning. Half of bonded-teeth were submitted to load cycling (150,000 cycles) and half immersed in deionised water for 24 h. They were cut into matchsticks and submitted immediately to microtensile bond strength (μTBS) testing or 6 months in AS immersion and subsequently μTBS tested. Results were analysed statistically by two-way ANOVA and Student–Newman–Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMGIC-bonded specimens were surveyed for interfacial ultramorphology characterisation (dye-assisted nanoleakage) using confocal microscopy. ResultsRMGIC applied onto dentine air-abraded with BAG regardless PAA showed no significant μTBS reduction after 6 months of AS storage and/or load cycling (p > 0.05). RMGIC–dentine interface showed no sign of degradation/nanoleakage after both aging regimens. Conversely, interfaces created in PAA-conditioned SiC-abraded specimens showed significant reduction in μTBS (p < 0.05) after 6 months of storage and/or load cycling with evident porosities within bonding interface. ConclusionsDentine pre-treatment using BAG air-abrasion might be a suitable strategy to enhance the bonding performance and durability of RMGIC applied to dentine. The use of PAA conditioner in smear layer-covered dentine may increase the risk of degradation at the bonding interface. Clinical significanceA combined dentine pre-treatment using bioglass followed by PAA may increase the bond strength and maintain it stable over time. Conversely, the use of PAA conditioning alone may offer no significant contribute to the immediate and prolonged bonding performance.

Measuring and comparing the shear bond strength of acrylic resin veneer to nickel –chromium alloy after different metal surface treatments

The bond strength of metal-resin interface of prosthesis is a key factor indetermining the serviceability of that prosthesis. The main objective of this study wasto determine the effect of different surface treatment on the shear bond strength of Ni-Cr alloy (CB-Blando 72 alloy) and heat cured acrylic veneer resin (Ivoclar Co.).Onehundred twenty eight disc shaped samples from base plate wax were prepared, thediameter of disc was (8mm×4.5mm).After casting the metal, the samples werecleaned, finished, and polished by silicon carbide abrasive paper with a grit size(600μm), and then the profilometer was used to determine the surface roughness ofthe samples (Ra) which ranged between (0.09-0.13μm). Then the samples weredivided into 2 categories ,each category contain (64)samples which also weresubdivided into 8 group ,the first category include (A, B, C, D, E, F, G, H) and thesecond category include (At, Bt, Ct, Dt, Et, Ft, Gt, Ht), according to the metal surfacetreatment which include :Group A, At: Received no treatment and serve as control.Group B, Bt: Received chemical treatment using chemical bonding agent (Metalprimer II).Group C, Ct: Received micromechanical treatment using air abrasion with 50μmAl2O3.Group D, Dt: Received micromechanical treatment using air abrasion with 50μmAl2O3 +metal primer IIGroup E, Et : Received micromechanical treatment using air abrasion with110μmAl2O3.Group F, Ft: Received micromechanical / chemical treatment using (airAbrasion110μm Al2O3 + metal primer II application).Group G ,Gt: Received micromechanical treatment using air abrasion 250μm Al2O3.Group H, Ht: Received micromechanical /chemical treatment using (air abrasion250μm Al2O3 +metal primer II).The acrylic was then prepared as round shape (8mm in diameter and 2mm inthickness) that was placed on the metal surface treatment; the acrylic was fabricated inthe same conventional way for construction veneer resin.For the specimens in the first category, the specimens were tested under drycondition, while in the second category; the specimens were tested after (24) hoursstorage in water room temperature (37˚C) and (1000 time) thermocycling. The shearbond strength was tested in instron universal testing machine.The results before and after thermocycling showed that the air abrasion with50μm Al2O3 plus metal primer II group gave the highest shear bond values, followedby air abrasion with 110μm Al2O3 plus metal primer II, followed by air abrasion with50μm Al2O3, followed by air abrasion with 250μm Al2O3 plus metal primer II,followed by air abrasion with 110μm Al2O3, followed by air abrasion with 250μm,followed by metal primer II group, and followed by untreated group.Also after thermocycling showead that the micromechanical/chemical treatment(air abrasion with Al2O3+metal primer II) gave the highest and more durable shearbond strength values than other groups

The Effects of Tricalcium Phosphate and Novamin Remineralizing Agents on Microhardness of Bleached Enamel with 35% Hydrogen Peroxide-An In vitro Study

Objectives: The aim of the present study was to evaluated the effects of remineralizing agents (Tricalcium phosphate and Novamin) on microhardness of bleached enamel surface with 35% hydrogen peroxide (in office).Materials and Methods: Forty human permanent maxillary premolars free from caries or enamel malformation were used. The teeth were sectioned transversally across the cemento-enamel junction, and specimens were embedded in self-cure acrylic. The labial enamel surface faced upward and then they were ground flat and polished with silicon carbide abrasive papers. A total specimen were prepared and kept in deionized water. Then the specimens were drying subjecting them for baseline microhardness testing (control). The dental bleaching treatment was performed just on the labial enamel surface of the specimens using a commercial 35% hydrogen peroxide Whitness HP bleaching gel (in-office ).It was used according to the manufacture instruction. Microhardness was tested for all specimens after bleaching. Specimens were divided into two groups according to remineralizing agent n=20, Group I: Treated by NUPRO Sensodyne with NovaMin, Group II: Treated by Clinpro™ White Varnish Tri-Calcium Phosphate. The remineralizing agent was applied for three minutes per day. Two remineralizing agents were applied for fourteen consecutive days. After each application procedure, the specimens were washed with deionized water and then kept in artificial saliva. At the end of the fourteen days the remineralized specimens were subjected to microhardness testing and values were recorded. All the data were analyzed by ANOVA and Tukey’s post hoc test. Results: Results revealed that a statistically significant decrease on mean microhardness values after enamel bleaching compared to control, followed by a significant increase on mean microhardness after the application of the both remineralizing agents. One way-ANOVA showed a statistically insignificant difference between NUPRO Sensodyne with NovaMin and Clinpro™ White Varnish at p≥0.05.Conclusions: Based on the results of this in vitro study both Tricalcium phosphate and Novamin are effective in remineralization of bleached enamel surface and no significant difference was detected in their efficacy.