Disc-shaped Specimens Research Articles

The impact of different surface treatments on repair bond strength of conventionally, subtractive-, and additive-manufactured denture bases.

This study aimed to examine the shear bond strength (SBS) of repair material to conventionally, subtractive-, and additive-manufactured denture bases after different surface treatments. Disk-shaped test specimens (N = 300) were prepared from denture base materials produced by one conventional (Procryla), one subtractive (Yamahachi), and one additive (Curo Denture) method. The test specimens were randomly divided into five groups (n = 10) and exposed to a variety of surface treatments-Group A: no surface treatment; Group B: grinding with silicon carbide paper; Group C: sandblasting; Group D: erbium: yttrium-aluminum-garnet laser; and Group E: plasma. Repair was performed with autopolymerizing acrylic resin (Meliodent). Surface roughness analyses were performed with a profilometer. Scanning electron microscopy was used to examine one specimen from each subgroup. SBS was evaluated on a universal testing machine. Failure types were observed under a stereomicroscope. Surface roughness values were significantly higher in all test materials in Group D than in the other groups (p < 0.001). For conventional resin, the SBS values were higher in Group C than in Groups A, D, and E (p < 0.001). For CAD/CAM material, Groups B and C had significantly greater SBS increases compared with Group E (p < 0.001). For 3D material, Group D showed higher SBS than all groups except Group C (p < 0.001). For SBS, sandblasting was most effective in the conventional group, whereas laser treatment was the most effective in the additive-manufactured group. For the subtractive group, surface treatments other than plasma exhibited similar SBS. In repairing fractured prostheses, any degree of roughening suitable for the material content may provide an SBS benefit.

Impact of the sintering parameters on the grain size, crystal phases, translucency, biaxial flexural strength, and fracture load of zirconia materials

ObjectivesTo investigate the influence of the zirconia and sintering parameters on the optical and mechanical properties. MethodsThree zirconia materials (3/4Y-TZP, 4Y-TZP, 3Y-TZP) were high-speed (HSS), speed (SS) or conventionally (CS) sintered. Disc-shaped specimens nested in 4 vertical layers of the blank were examined for grain size (GS), crystal phases (c/t’/t/m-phase), translucency (T), and biaxial flexural strength. Fracture load (FL) of three-unit fixed dental prostheses was determined initially and after thermomechanical aging. Fracture types were classified, and data statistically analyzed. Results4Y-TZP showed a higher amount of c + t’-phase and lower amount of t-phase, and higher optical and lower mechanical properties than 3Y-TZP. In all materials, T declined from Layer 1 to 4. 3/4Y-TZP showed the highest FL, followed by 3Y-TZP, while 4Y-TZP showed the lowest. In 4Y-TZP, the sintering parameters exercised a direct impact on GS and T, while mechanical properties were largely unaffected. The sintering parameters showed a varying influence on 3Y-TZP. Thermomechanical aging resulted in comparable or higher FL. Conclusion3/4Y-TZP presenting the highest FL underscores the principle of using strength-gradient multi-layer blanks to profit from high optical properties in the incisal area, while ensuring high mechanical properties in the lower areas subject to tensile forces. With all groups exceeding maximum bite forces, the examined three-unit FDPs showed promising long-term mechanical properties.

Mechanical Properties of High- and Low-Fusing Zirconia Veneering Ceramics Fired on Different Trays and Substrates.

This study aimed to evaluate the effect of ceramic type, firing tray, and firing substrate on the density, shrinkage, biaxial flexural strength, Martens' hardness, and elastic indentation modulus of zirconia veneering ceramics. Disk-shaped specimens were fabricated from a high-fusing (HFZ) and a low-fusing (STR) zirconia veneering ceramic. These specimens were then divided into 10 groups according to firing trays (round, small honeycomb-shaped, cordierite [RSC]; round, large honeycomb-shaped, aluminum oxide [RLA]; rectangular, plane, silicon nitride [RCPS]; round, plane, silicon nitride [RPS]; and rectangular, plane, calcium silicate [RCPC]) and firing substrates (firing cotton and platinum foil) used (n = 12). The density, shrinkage, biaxial flexural strength, Martens' hardness, and indentation modulus were measured, and analyzed with generalized linear model analysis (α = 0.05). The interaction between the ceramic type and firing substrate affected density (p < 0.001), and the other outcomes were affected by the interaction among all main factors (p ≤ 0.045). Higher density was observed with HFZ or platinum foil (p ≤ 0.007). RSC and RLA led to a higher density than RCPS within HFZ and led to the lowest density within STR (p ≤ 0.046). STR had a higher shrinkage (p < 0.001). RSC mostly led to a lower shrinkage of HFZ (p ≤ 0.045). The effect of ceramic type and firing substrates on the biaxial flexural strength, Martens' hardness, and indentation modulus was minimal while there was no clear trend on the effect of firing tray on these properties. Ceramic type, firing tray, and firing substrate affected the mechanical properties of the tested zirconia veneering ceramics. Firing the tested zirconia veneering ceramics over a round and small honeycomb-shaped cordierite firing tray with firing cotton mostly led to improved mechanical properties.

Evaluating flexure properties, hardness, roughness and microleakage of high-strength injectable dental composite: an in vitro study

BackgroundRecently, a new generation of high-strength flowable dental composites has been introduced by manufacturers. The manufacturers claim that these materials have enhanced mechanical and physical properties and are suitable for use in a wide range of direct anterior and posterior restorations, even in high-stress bearing areas.AimThe objective of this study was to assess certain physical and mechanical properties of these recently introduced high-strength flowable composites in comparison to conventional multipurpose dental composites.MethodsFour types of high-strength flowable composites (Genial Universal FLO, Gaenial Universal Injectable, Beautifil Injectable, and Beautifil Flow Plus) were tested in experimental groups, while a nanohybrid conventional composite (Filtek Z350 XT) was used as the control. For flexure properties, ten rectangular samples (2 × 2 × 25 mm) were prepared from each composite material and subjected to 5000 cycles of thermocycling. Samples were then subjected to flexural strength testing using the universal testing machine. Another twenty disc-shaped specimens of dimensions (5 mm diameter × 2 mm thickness) were fabricated from each composite material for surface roughness (Ra) (n = 10) and hardness (VHN) test (n = 10). All samples underwent 5000 cycles of thermocycling before testing. Additionally, microleakage testing was conducted on 60 standardized class V cavities prepared on molar teeth and divided randomly into five groups (n = 12). Cavities were then filled with composite according to the manufacturer’s instructions and subjected to thermocycling for 1000 cycles before testing using methylene blue solution and a stereomicroscope.ResultsAll tested materials were comparable to the control group in terms of flexural strength and surface roughness (p > 0.05), with Gaenial Universal FLO exhibiting significantly higher flexural strength compared to the other flowable composite materials tested. However, all tested materials demonstrated significantly lower elastic modulus and surface hardness than the control group (p < 0.05). The control group exhibited higher microleakage scores, while the lowest scores were observed in the Gaenial Universal FLO material (p < 0.05)ConclusionThe physical and mechanical behaviors of the different high-strength flowable composites investigated in this study varied. Some of these materials may serve as suitable alternatives to conventional composites in specific applications, emphasizing the importance of dentists being familiar with material properties before making material selections.

Color Differences of Polimerized Resin-Based Composites and Corresponding Shade Guides

Objective: The purpose of this study is to analyze and compare the colors (A2, A3 and A3.5) of polymerized resin-based composites (RBCs) with respect to the shade numbers within each product line and the VITAPAN Classical® shade guide they purported to represent. Methods: Three A-shades (A2, A3 and A3.5) from four RBC products (Harmonize®, Empress® Direct®, Grandio® and Filtek® 500) were compared within the VITAPAN Classical® shade guide and within their own commercial shade guide. Nine disk-shaped specimens, 6 mm in diameter and 2 mm thick, were prepared for each RBC color (three of each color). The color measurements were made according to the CIE L*a*b* color scale (quantifying L*c*h*a*b* values) using a Vita Easyshade Compact IV® digital spectrophotometer. We calculated the CIEDE2000 color differences between polymerized composites and shade guides, as well as between composites. The values obtained from composites and samples of the color guides in the CIE L*a*b* space were represented by ICC3D software (Version 1.2.9) Results: The ANOVA test verified the existence of statistically significant differences between composites for the same shades (p &lt; 0.05) except for shade A2. CIEDE2000 color differences between composites and the VITAPAN Classical® shade guide ranged from 3.5 to 13.1 depending on the composite and the shade. Conclusions: There were color differences among the polymerized resin-based composites, between these and their own shade guides/manufacturer’s commercial guides, and between the former and the corresponding samples of the VITAPAN Classical® shade guide. Clinical significance: Color selection when performing an aesthetic dental restoration is essential for the clinician and the patient to obtain an optimal result. Taking into account the color difference (∆E00) for each composite with the VITAPAN Classical® shade guide or with the manufacturers’ commercial guide allows for more precision with shade selection in aesthetic dentistry.

Surface roughness and optical characteristics evaluations after chairside adjustment of different zirconia types.

Limited evidence is available for the effect of chairside adjustment using rotary cutting instruments on the surface roughness and optical properties of different zirconia types. To evaluate the effect of simulated adjustments on surface roughness and optical properties of different zirconia types. Three Partially Stabilized Zirconia (PSZ) types based on mole percent yttria (Y) concentration from the same manufacturer (Katana; Kuraray) were used: 3Y-PSZ, 4Y-PSZ, and 5Y-PSZ. Thirty disk-shaped specimens (Ø14 × 1.2 mm) from different zirconia types (N = 90) were prepared. Specimens were either left without adjustment (NA), adjusted with Dialite ZR finishing and polishing system (Brasseler) (APol), or adjusted with course diamond instruments only (ADia). The specimens were distributed into 9 groups (n = 10): Group 3Y-PSZ/NA, Group 3Y-PSZ/APol, Group 3Y-PSZ/ADia, Group 4Y-PSZ/NA, Group 4Y-PSZ/APol, Group 4Y-PSZ/ADia, Group 5Y-PSZ/NA, Group 5Y-PSZ/APol, and Group 5Y-PSZ/ADia. The surface roughness of specimen was analyzed using an Atomic Force Microscope (AFM) (Bruker's Dimension Icon, Bruker) and Root Means Square (RMS) were recorded (nm). Surface Gloss (SG), Translucency Parameter (TP), and Contrast Ratio (CR) values of all groups were recorded using an integrating sphere spectrophotometer. Statistical analysis was performed using analysis of variance (ANOVA) and Tukey's multiple comparison tests for pairwise comparisons at p < 0.05 and 95% confidence interval. APol had no effect on the surface roughness (p = 0.88) while ADia had a significant negative effect (p < 0.05) despite the type of zirconia. Out of the three testes optical properties, only SG was negatively affected by ADia for all types of zirconia (p < 0.05). The two adjustment types did not affect the TP of all the tested zirconia (p = 0.91). The CR was not affected by the tested adjustments for all zirconia types (p = 0.726). Proper zirconia adjustment following a sequence of burs and polishers can maintain acceptable roughness and optical properties. Adjustment of zirconia with rough diamond can lead to deleterious effects and should be avoided. Chairside adjustment of zirconia could lead to rougher surface and unpredictable changes of surface gloss. Therefore, zirconia adjustment should be minimized to the greatest extent possible and a proper protocol should be followed if had to be done.

Biaxial flexural strength of hydrothermally aged resin-based materials

PurposeThe strength of temporary restorations plays a vital role in full-mouth reconstruction, and it can be impacted by the aging process. The aim of this in vitro study was to evaluate the biaxial flexural strength and fractographic features of different resin-based materials submitted to thermal aging. Material and methodsOne hundred and ninety-two resin disc-shaped specimens (6.5 mm in diameter and 0.5 mm in thickness) were fabricated and divided into six experimental groups according to the resin-based materials (Filtek Bulk-Fill flowable resin; J-Temp temporary resin; and Fuji Lining glass ionomer cement) and aging process (before and after thermal cycling). Biaxial flexural strength test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min before and after thermal cycling (5 °C and 55 °C, 5760 cycles, 30 s). The mechanical properties were assessed using Weibull parameters (characteristic strength and Weibull modulus) (n = 30). Fractured specimens were examined under a polarized light stereomicroscope to identify crack origin and propagation direction. The surface microstructure of the resin-based materials was assessed by scanning electron microscopy (n = 2). The Weibull modulus (m), characteristic strength, and reliability properties were calculated, and a contour plot was used to detect differences among groups (95% confidence interval). ResultsThe Weibull modulus (m), characteristic strength, and reliability of the resin-based compounds were influenced by material type and thermal aging (p < 0.05). Weibull modulus (m) revealed no differences when comparing the materials and aging process (p > 0.05), except for the preceding aging period where Filtek Bulk-Fill exhibited higher values compared to J-Temp (p < 0.05). Filtek Bulk-Fill demonstrated superior characteristic strength and reliability compared to J-Temp and Fuji Lining before and after thermal cycling (p < 0.05). Fractography of the resin-based materials showed fractures originating from surface defects exposed to tensile side and their propagation toward the compressive side. Generally, no differences in surface microstructure were observed on micrographs before and after thermal aging for Filtek Bulk-Fill and Fuji Lining. However, the aging process developed flaws in J-Temp. ConclusionResin-based material composition resulted in different flexural strength performance, impacting the Weibull modulus (m), characteristic strength, and reliability of the resin-based restorations.

Mechanical property measurement at high temperature based on a new disc-shaped specimen

Three-dimensional digital image correlation (3D-DIC) is frequently used to measure mechanical properties of materials. However, the traditional dumbbell-shapedspecimen has some limitations for measurment of mechanical properties of materials by use of 3D-DIC at high temperature due to two reasons: (1) its transverse dimension is very small and only a small number of valid speckles can be used in 3D-DIC; and (2) only a small amount of valid information, such as the average deformation of the gauge length, can be used to obtain mechanical properties in one direction. In this work, a new test method based on a disc-shaped standard specimen is first proposed. By use of analytical solutions of a disc under a uniform radial load, and measured results of the full-field displacement of the disc-shaped specimen by 3D-DIC in an effective test region at different high temperatures, mechanical properties at different high temperatures are identified.

Effect of curing mode of resin composite cements on water sorption, color stability, and biaxial flexural strength

ObjectivesTo determine whether water sorption and solubility of a recently introduced self-adhesive cement is comparable to two clinically tested resin composite cements after thermal aging, and if this is affected by the curing mode. Whether water sorption is correlated with color difference and biaxial flexural strength was also investigated. MethodsWater sorption and solubility of three resin composite cements {RelyX Universal (RUV), (Panavia V5 (PV5), Panavia SA plus (PSA)} were measured after thermal aging. Disk-shaped specimens were either light-cured or autopolymerized (n = 15 per group). Color difference ΔE00 and biaxial flexural strength were also obtained. ResultsSorption was highest for RUV (auto: 54.9 ± 9.0 µg/mm3, light: 49.7 ± 4.9 µg/mm3), followed by PSA (auto: 37.7 ± 1.4 µg/mm3, light: 34.5 ± 1.1 µg/mm3) and PV5 (auto: 21.7 ± 0.7 µg/mm3, light: 22.1 ± 0.4 µg/mm3). Light-curing reduced solubility values, particularly for RUV (from 60.7 ± 20.8 µg/mm3 to 6.4 ± 0.8 µg/mm3). Color differences of ΔE00 > 1.8 (considered clinically not acceptable) were noted after aging for RUV and PSA. Sorption and ΔE00 values after aging were correlated linearly (R2 = 0.970). Biaxial flexural strength values were highest for PV5 (light: 153.4 ± 15.9 MPa; auto: 133.2 ± 18.0 MPa) and lowest for RUV (light: 99.3 ± 12.8 MPa; auto: 35.1 ± 8.3 MPa). SignificanceLight-curing has beneficial effects on sorption, color stability, and biaxial flexural strength of resin composite cements. Cements containing 2-hydroxymethacrylate such as RUV and PSA are more prone to water sorption and color changes.

How does artificial aging affect the mechanical properties of occlusal splint materials processed via various technologies?

The mechanical reliability of occlusal splints and their long-term behavior are significant factors determining the clinical outcome of temporomandibular disorder (TMD) therapy. However, improvements are still needed in this area. This in vitro study aimed to (1) compare the hardness and flexural properties of materials manufactured using 3 techniques for occlusal splint fabrication (conventional heat curing, thermoforming followed by light curing, and three-dimensional (3D) printing) and (2) analyze the effect of artificial aging on the properties of the materials. A total of 120 disc-shaped specimens were manufactured for the Shore D hardness evaluation, and 120 bar-shaped specimens were fabricated for the flexural properties evaluation (n = 15 for each group). Each material was tested in 2 groups of specimens, non-aged and artificially aged (stored for 90 days in water at 37°C). Statistical differences were assessed using one-way or two-way parametric analysis of variance (ANOVA) with Tukey's or Šídák's post-hoc test, or the non-parametric KruskalWallis test with Dunn's post-hoc test. A p-value of less than 0.05 was considered statistically significant. The mechanical properties of the materials varied significantly. Among the non-aged materials, the 3D-printed resin exhibited the highest Shore D hardness (85.3D), but it decreased significantly after 90 days of water storage (80.4D, p < 0.0001). The unpolished heat curing acrylic showed the highest resistance to artificial aging (p = 0.0436). However, its hardness decreased significantly after polishing (81.0D vs. 83.4D, p = 0.0015). The conventional heat curing material also exhibited superior flexural properties (σ = 89.63 MPa, E = 2616 MPa). All tested materials were susceptible to deterioration due to aging. The conventional method of occlusal splint fabrication remains the optimal choice, particularly for long-term use. However, it is still necessary to develop materials that are resistant to aging in order to ensure successful clinical performance.

The Impact of Repeated Steam Sterilization Cycles on the Efficacy of Chairside Adjustment Kits for Polishing Monolithic Multi-Layered Zirconia Dental Restoration Material.

BACKGROUND Before insertion, chairside adjustment kits are heat sterilized for positioning and polishing dental restorations. This study aimed to evaluate the effects of 2 steam sterilization cycles on the efficacy of polishing highly translucent monolithic zirconia (HTMLZ) dental restoration material. MATERIAL AND METHODS 100 HTMLZ disc-shaped specimens were adjusted (grinding, finishing, polishing) with EVE Diacera kit. Two steam sterilization techniques [standard (Gp S), immediate/flash (Gp (F)] of CAK were further subgrouped based on number of sterilization cycles [cycle 1 (control), cycle 5, 10, 15, and 20 (experimental)] (n=10 each). Each subgroup accordingly was evaluated for average surface roughness (Ra) and root mean square roughness (Rq) using a profilometer. Mean and standard deviation of 5 subgroups were statistically analyzed using one-way ANOVA/post hoc Tukey's test. Scanning electron microscopy complemented Ra, Rq measurements. Statistical differences of P≤0.05 were considered significant. RESULTS HTMLZ specimens in both groups showed increased (Ra/Rq) values after repeated sterilization of EVE Diacera kit, with Gp F showing lesser increase than Gp S (20 cycles). Gp F at 10 cycles and Gp S at 15 cycles showed clinically unacceptable roughness threshold (0.25 μm). Differences between subgroups for Ra and Rq values were significant (P≤0.05) with less differences within groups observed in early cycles (1, 10). Results validate the manufacturer's recommendations of using flash sterilization/10 cycles for EVE Diacera kit. CONCLUSIONS Repeated sterilization reduces efficacy of chairside adjustment kit to produce smooth surfaces on HTMLZ. This study recommends flash sterilization to a maximum of 10 times to get the clinically acceptable results of Ra and Rq.

Influence of additives and binder on the physical properties of dental silicate glass-ceramic feedstock for additive manufacturing

ObjectivesThe aim of the study was to investigate the impact of organic additives (binder, plasticizer, and the cross-linking ink) in the formulation of water-based feedstocks on the properties of a dental feldspathic glass-ceramic material developed for the slurry-based additive manufacturing technology “LSD-print.” Material and methodsThree water-based feldspathic feedstocks were produced to study the effects of polyvinyl alcohol (AC1) and poly (sodium 4-styrenesulfonate) (AC2) as binder systems. A feedstock without organic additives was tested as the control group (CG). Disc-shaped (n = 15) and bar (n = 7) specimens were slip-cast and characterized in the green and fired states. In the green state, density and flexural strength were measured. In the fired state, density, shrinkage, flexural strength (FS), Weibull modulus, fracture toughness (KIC), Martens parameters, and microstructure were analyzed. Disc-shaped and bar specimens were also cut from commercially available CAD/CAM blocks and used as a target reference (TR) for the fired state. ResultsIn the green state, CG showed the highest bulk density but the lowest FS, while the highest FS in the green state was achieved with the addition of a cross-linking ink. After firing, no significant differences in density and a similar microstructure were observed for all slip-cast groups, indicating that almost complete densification could be achieved. The CAD/CAM specimens showed the highest mean FS, Weibull modulus, and KIC, with significant differences between some of the slip-cast groups. SignificanceThese results suggest that the investigated feedstocks are promising candidates for the slurry-based additive manufacturing of restorations meeting the class 1a requirements according to DIN EN ISO 6871:2019–01.

Color Stability of Bioactive Restorative Material vs Nanohybrid Resin Composite: An In Vitro Study.

This study aimed to assess the color stability of bioactive restorative materials vs nanohybrid resin composites after 3 months of immersion in three frequently consumed beverages. Thirty disk-shaped specimens of Giomer dental restorative material (Shofu, Japan) and nanohybrid resin composite (Tokuyama, Japan) were performed using a Teflon mold. Super-Snap system (Shofu, Japan) was utilized to finish and polish the specimens to be preserved for 24 hours in distilled water at 37°C. The samples had been divided into three subgroups (Coffee, tea, Pepsi) (n = 5). The initially displayed color measurements of the samples were performed using a spectrophotometer (VITA Easyshade® V). After 7 days, 30 days, and 90 days, color measurements were repeated, and the E of each sample was estimated. E of each sample was calculated. The Giomer group showed statistically significant higher E values than the nanohybrid resin composite where the p-value was ≤0.0001. Tea subgroup showed the highest statistically significant E values in both groups where the p-value was ≤ 0.0001. The highest statistically significant color change was recorded at 3 months. The color of bioactive restorative material is less stable if compared with nanohybrid resin composite. As tea and coffee are popular beverages, particularly in Middle Eastern nations, dentists must advise patients about the color change of resin restorations. Patients are advised to brush their teeth immediately after consuming these beverages. How to cite this article: Saber EH, Abielhassan MH, Abed YA, et al. Color Stability of Bioactive Restorative Material vs Nanohybrid Resin Composite: An In Vitro Study. J Contemp Dent Pract 2024;25(3):221-225.

In Vitro Comparison of Optical Properties Between Single-Shade and Conventional Composite Resin Restorations.

The recently developed single-shade composite resin (using the concept of structural coloring) is a promising option to eliminate the process and subjectivity of shade selection. However, current evidence of its performance is still insufficient. This study aimed to evaluate the color matching, color stability, and refractive index (RI) of single-shade restorations compared with conventional composite resin. This in vitro study was conducted on 48 extracted maxillary premolars. The teeth were sorted into three tooth shade groups (B2, A3, and A3.5). Each group included two subgroups based on the materials used: Omnichroma (OM;Tokuyama Dental, Tokyo, Japan) and Filtek Z350 (FT; 3M ESPE, St. Paul, MN, USA). Buccal and lingual Class V round cavities were prepared and restored according to the randomly assigned subgroups, with the test single-shade material (OM) on one surface and the matching conventional control material (FT) of the proper shade on the other surface of each tooth. Color matching was evaluated by visual assessment and a spectrophotometer. All specimens were distributed into four staining groups and immersed in various staining beverages (black coffee, Arabic coffee, Coca-Cola, and distilled water) for four weeks. Color changes were assessed using a spectrophotometer. Four groups of disc-shaped specimens (single-shade, B2, A3, and A3.5) were fabricated to evaluate the RI using a refractometer. Statistical analyses were performed to compare the materials. The mean value of the color difference (ΔE) of single-shade restorations was significantly higher than that of paired conventional restorations in all shade groups. The highest mean ΔE was in subgroup A3.5-OM (8.84 ± 2.39) and showed significantly less color matching than other OM subgroups (p=0.009). The visual assessment showed comparable and acceptable color matching in all subgroups except A3.5-OM (p=0.006). There was a significant color change after the staining test within and across staining groups, but the color change was comparable between the OM and FT subgroups. The RI of single-shade material was significantly higher than conventional material (p<0.05). The color matching of single-shade restorations was affected by tooth shade. Its color stability was influenced by various staining substances but was similar to conventional restorations.

Osteoblast cell behavior on polyetheretherketone dental implant surfaces treated with different grit size aluminum oxide particles: An in vitro analysis

The hydrophobic and bioinert nature of polyetheretherketone (PEEK) implants needs to be addressed for successful osseointegration. The purpose of this in vitro study was to evaluate the osteoblast cell behavior on PEEK implant surfaces treated with airborne-particle abrasion using different grit size aluminum oxide (Al2O3) particles. Disk-shaped specimens (n=96) were prepared from medical grade PEEK rods and were distributed into 4 groups (n=24) of untreated PEEK (PEEK 0), airborne-particle abrasion using 50-μm Al2O3 particles (PEEK 50), airborne-particle abrasion using 110-μm Al2O3 particles (PEEK 110), and airborne-particle abrasion using 150-μm Al2O3 particles (PEEK 150). The surface characteristics were assessed using water contact angle (WCA) measurements and scanning electron microscopy (SEM). MG-63 osteoblast cells were cultured, and the biocompatibility of PEEK was assessed using a CellTiter-blue cell viability assay and florescence staining at day 1, 3, and 7. The specimens were stained with Alizarin red to assess the osteoblast cell differentiation on day 10 and 14. The Levene test was used to test the homogeneity of variances. One-way and Welch ANOVA with post hoc corrections were used to assess the overall statistical significance of differences among the groups (α=.05). The lowest mean WCA was demonstrated in PEEK 150 (49.25 ±5.51) and the highest in PEEK 0 (89.14 ±4.24) (P<.001). SEM images of PEEK 150 illustrated a more complex structure with a large area of globular outcroppings throughout the surface. PEEK 150 showed the highest cell metabolic activity at each time point with florescence staining showing a substantial cell confluence at day 3 and 7. Although PEEK 150 did not show a significant increase in cell proliferation, the number of cells attached was significantly higher than other groups (P<.05). PEEK 110 and 150 also showed a substantial increase in the extent of mineralization. Airborne-particle abrasion using moderate Al2O3 grit size (110- or 150-μm) improved the hydrophilicity and osteoblast cell behavior on PEEK implants.

Açaí juice stains a glazed resin-modified glass-ionomer cement.

The aim of this study was to assess whether açaí compromises the surface colour and roughness of RMGIC in vitro. Disc-shaped specimens (2 mm thick, 8 mm in diameter) of Vitremer™ (3M ESPE, St Paul, MN, USA) were prepared according to the manufacturer 's instructions. The mixture was inserted into a silicone mouldplaced between two mylar strips, and light cured. Specimens were randomly divided into three groups (n=25) according to the solutions to be used for chemical degradation: artificial saliva (control), açaí sorbet and açaí juice. A spectrophotometer CM-2600d/2500d (Konica Minolta, Tokyo, Japan) was used to analyse the colour (CIELa*b* scale). Surface roughness (Ra, mm) was measuredusing theprofilometer Surfcorder SE 1700 (Kosaka Corp, Tokyo, Japan). The specimens were subjected to three daily soaks (6 ml, 15 minutes) for 14 days at 37°C. They were washed in distilled water and placed in fresh saliva (30 minutes in the interval). After the third soak in a day, they were stored in fresh saliva overnight. Outcomes were analysed at baseline (L*, a*, b*, Ra) and after degradation (L'*, a'*, b'*, Ra'). The pH values of saliva, sorbet, and juice were 7.0, 3.8, and 4.9, respectively. ΔE* values were 6.6 for saliva, 6.9 for sorbet and 7.8 for juice. There was a significant ΔE* difference between saliva (p=0.005) and juice (p=0.002), and between juice and sorbet (p=0.019), but none between saliva and sorbet (p=0.401). There was no significant Δb* difference between the solutions. No difference between juice and sorbet was observed for Δa*, but they were significantly different from saliva (p<0.001). Brightness (L*) changed significantly. Juice showed the highest ΔE* (7.8) and ΔL* (7.7). No significant change was observed for roughness and there was no difference between the solutions for ARa. Açaí and saliva led to unacceptable staining, but no significant roughness changes in the resin-modified glass-ionomer cement.

Development of ZTA (80% Al2O3/20% ZrO2) pre-sintered blocks for milling in CAD/CAM systems

The present work aims to develop a production method of pre-sintered zirconia-toughened-alumina (ZTA) composite blocks for machining in a computer-aided design and computer-aided manufacturing (CAD-CAM) system. The ZTA composite comprised of 80% Al2O3 and 20% ZrO2 was synthesized, uniaxially and isostatically pressed to generate machinable CAD-CAM blocks. Fourteen green-body blocks were prepared and pre-sintered at 1000 °C. After cooling and holder gluing, a stereolithography (STL) file was designed and uploaded to manufacture disk-shaped specimens projected to comply with ISO 6872:2015. Seventy specimens were produced through machining of the blocks, samples were sintered at 1600 °C and two-sided polished. Half of the samples were subjected to accelerated autoclave hydrothermal aging (20h at 134 °C and 2.2 bar). Immediate and aged samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Optical and mechanical properties were assessed by reflectance tests and by biaxial flexural strength test, Vickers indentation and fracture toughness, respectively. Samples produced by machining presented high density and smooth surfaces at SEM evaluation with few microstructural defects. XRD evaluation depicted characteristic peaks of alpha alumina and tetragonal zirconia and autoclave aging had no effect on the crystalline spectra of the composite. Optical and mechanical evaluations demonstrated a high masking ability for the composite and a characteristic strength of 464 MPa and Weibull modulus of 17, with no significant alterations after aging. The milled composite exhibited a hardness of 17.61 GPa and fracture toughness of 5.63 MPa m1/2, which remained unaltered after aging. The synthesis of ZTA blocks for CAD-CAM was successful and allowed for the milling of disk-shaped specimens using the grinding method of the CAD-CAM system. ZTA composite properties were unaffected by hydrothermal autoclave aging and present a promising alternative for the manufacture of infrastructures of fixed dental prostheses.

Effect of Reduced-Step Polishing Systems on Color Stability of Nanocomposites Submitted to Thermocycling Staining with Common Beverages - An In Vitro Study.

Long-term color stability of composite resins is one of the most important factors influencing the clinical longevity of aesthetic restorations. This study evaluated the effect of novel reduced steps and gold standard multiple steps polishing systems of two composite resins; a nano-filled (Filtek Z350XT) versus a supra-nanofill (Palfique LX5) on their color stability after submitting to thermocycling with common beverages. Sixty disc-shaped specimens were fabricated from both composite resins ( n = 30). From each material, ten specimens acted as the control group (Mylar strip), ten specimens were polished with Sof-Lex Diamond spirals, and ten were polished with Super-Snap X-Treme discs. All the specimens were thermocycled with staining solutions. Color was measured by a spectrophotometer before and after thermocycling and color difference (ΔE*) was calculated. One-way analysis of variance followed by Tukey's post-hoc test and independent t -test ( α = 0.05) were used. A significantly highest color change was recorded for both control subgroups ( P < 0.05), and the Sof-Lex Diamond spiral showed significantly the lowest color change ( P < 0.05). Both the control and Sof-Lex Diamond spiral subgroups of Palfique LX5 produced significantly lower color change compared with subgroups of Filtek Z350 ( P < 0.05). Sof-Lex Diamond spiral polishing system provided the least color difference for both composites, while there was no significant difference between the materials when the Super-Snap X-Treme polishing system was used.

Effect of Child Health Drinks on Color Stability of Various Aesthetic Restorative Materials - An In Vitro Study.

In pediatric dentistry, the esthetically pleasing materials have tremendously changed the concept of restorative practice. 1. The aim of the study is to evaluate the effect of child health drinks on color stability of various esthetic restorative materials via spectrophotometric analysis and to identify the esthetic restorative material that is color-stable against child health drinks. A total of 120 disk-shaped specimens with a diameter of 12 mm and a thickness of 2 mm were made from a composite (Dyract), giomer (Shofu), and composite (GC). Each group of 40 specimens of each material was divided into four sub-groups. Each sub-group was stored in different solutions, distilled water, Bournvita, Horlicks, and Pediasure, for 60 days. The color change measurement was done using a spectrophotometer both before and after staining. One-way analysis of variance depicted that when the ΔE values of the restorative material were tested against each of the child health drink, there was a statistically significant difference between all child health drinks (P < 0.00001). When restorative materials were compared with the staining agent on 60 days duration, except Pediasure and Control, others (i.e. Horlicks and Bournvita) showed a statistically high significance (P < 0.05). Bournvita caused the highest color changes in 60 days time interval, followed by Horlicks and Pediasure. When the discoloration of several materials is studied, the highest level of discoloration was observed in the compomer, followed by the giomer, and the lowest level in the composite.

Thermal oxidation description methodology of thermal barrier coatings on gas turbine blades considering service characteristics

Predicting the thickness of Thermally Grown Oxide (TGO) and the residual stresses induced by TGO growth in the Thermal Barrier Coatings (TBCs) is significant work in analyzing the failure of TBCs. In practical applications, the operating temperature, oxygen partial pressure, aluminium content in TBCs, and porosity of the topcoat affect the oxidation rate. Therefore, a novel oxidation rate model is proposed to describe the effect of such factors. The parameters in the proposed model were fitted with isothermal degradation test data from prior literature. Then, a method for calculating the residual stress in a disk-shaped specimen was developed based on the oxidized growth strain model and the oxidized model. Finally, a variable-temperature oxidation experiment was performed to validate the new oxidation model. The average error between the predicted and experimental thicknesses is approximately 10%, and the average error between the residual stresses is 30%. Under the variable-temperature condition, the error between the predicted thickness and the average experimental thickness is 3.9%.