Significant Increase In Surface Roughness Research Articles

Effect of simulated toothbrushing on the surface roughness of LOCATOR abutments: An in vitro study

Studies evaluating the effect of toothbrushing and toothpaste abrasivity on the surface roughness of LOCATOR abutments are lacking. The purpose of this in vitro study was to compare the surface roughness of LOCATOR abutments before and after simulated toothbrushing with different toothpastes to make recommendations for the home care of patients with LOCATOR abutments. LOCATOR bone-level overdenture abutments (N=36) were analyzed with a confocal laser scanning microscope (Keyence VK-X1100) at ×5 magnification. Surface scans were made to determine the degree of surface roughness (Ra). Two toothpastes of different abrasivity (Colgate Total and Crest ProHealth) and deionized water were used as the brushing media (n=12). Each toothpaste was mixed with water in a 1:2 ratio. The abutments were brushed using soft nylon toothbrushes for 30 000 cycles in a ZM-3.12 toothbrushing simulator, which has been interpreted as 3 years of regular use. All specimens were then reanalyzed under the microscope. Changes in surface texture were compared by using a repeated measures analysis of variance (ANOVA) statistical test and a pairwise Šídák multiple comparisons test (α=.05). The mean surface roughness value of LOCATOR abutments at baseline ranged between 1.34µm and 1.35µm. After 30 000 cycles of toothbrushing simulation, the mean value increased to 1.62µm (DI water, P=.001), 1.74µm (Colgate Total, P<.001), and 2.03µm (Crest ProHealth, P<.001). All brushing media resulted in a statistically significant increase in surface roughness (P<.001). LOCATOR abutments demonstrated significant increases in surface roughness after being subjected to toothbrushing, regardless of the brushing medium. Whitening toothpaste caused significantly more surface roughness than nonabrasive toothpaste and deionized water. Deionized water resulted in the lowest increase in surface roughness.

Deterioration of direct restorative materials under erosive conditions with impact of abrasion and attrition in vitro

Objective To compare the cumulative impact of sequential wear on mechanical properties and appearance of a composite resin (CR), Filtek Z250®, a glass ionomer GI, Fuji IX GP®, and a glass hybrid (GH), Equia Forte®. Material and Methods Six equally sized specimens of each material were subjected to wear tests, i.e., simulation of brushing, chewing and acidic liquid exposure, mimicking at least 6 months of clinical exposure. Surface roughness, hardness, substance loss and degree of shade lightness were determined. Results Following wear tests, significant increase in surface roughness and decrease in hardness values were observed for all materials (p < .05). Significantly larger substance loss was found in Equia Forte® specimens compared to Filtek Z250® (p < .05), while that of Fuji IX® exceeded the measurement capacity of the instrument. Opposite to the two other materials, the shade of Filtek Z250® became darker. Conclusions Sequential wear exposure mimicking abrasion, erosion and attrition to products representing CR, GI and GH, caused weakening and change in appearance of the materials. The composite resin was the most mechanically resistant to the sequential wear.

Assessment of enamel surface roughness and hardness with metal and ceramic orthodontic brackets using different etching and adhesive systems: An in vitro study

BackgroundThis study aimed to evaluate enamel surface roughness and microhardness following the use of different bracket materials (metal or ceramic), etchants (total- and self-etchants), and adhesive systems (precoated or flash-free). MethodA total of 99 extracted human premolars were selected for the analysis. The surface roughness was first assessed (roughness control). One specimen from each subgroup was examined using a scanning electron microscope to illustrate the surface topography. Eighty-eight teeth were prepared using total- or self-etchants and bonded to precoated or flash-free adhesive metal or ceramic brackets. The remaining 11 specimens were not bonded to brackets (microhardness controls). The brackets were debonded after immersion in distilled water for 24 h. The specimens were again scanned for surface roughness and topography imaging. Finally, the microhardness was assessed using a micro-Vickers hardness test at a force of 200 g for 10 s. ResultAn overall statistically significant increase in surface roughness and reduced surface microhardness were observed in all experimental groups when compared with those in the control groups. The etchant type was the only variable found to contribute to the measured surface properties, with increased roughness and reduced microhardness introduced by total-etching compared to those by self-etching. ConclusionOrthodontic brackets introduced a significant increase in enamel surface roughness and reduce microhardness compared with untreated enamel, regardless of the bracket material, etchant type, and adhesive system. The etchant type was the only variable contributing to these changes, with total etching having a more pronounced effect.

Effect of laser bleaching, ultrasonic scaling and powered tooth brushing on surface roughness and bacterial adherence of class V composite restorations.

To evaluate and compare the effect of diode laser assisted bleaching, ultrasonic scaling and powered tooth brushing on surface roughness and bacterial adherence on class V cavities restored with composites. A total of one hundred and twenty samples (40 samples each of Brilliant Everglow, Beautifil II and Heytec-N) were prepared in standardized stainless steel molds. The samples were further subdivided into four subgroups i.e. one control group (without any intervention) and three experimental groups - diode laser assisted bleaching, ultrasonic scaling and powered tooth brushing consisting of 10 sample each. Surface roughness was measured quantitatively with the help of 3D Optical Profilometer. For bacterial adherence analysis S. mutans strain (ATCC 25175) was cultured in BHI medium and samples were evaluated for the presence of viable bacteria using the Colony Forming Unit (CFU) count. Results obtained were then tabulated and subjected to statistical analysis. Diode laser bleaching caused a significant increase in surface roughness and bacterial adherence with lowest mean change exhibited by Heytec-N followed by Beautifil II and highest by Brilliant Everglow group. Similarly, Ultrasonic scaling increased the surface roughness of all the three tested samples with significant difference between the groups. Powered tooth brushing had no effect on the surface roughness and bacterial adherence of the tested composites. Diode assisted laser bleaching and ultrasonic caused significantly higher surface roughness and bacterial adherence values for all the tested composites. It may therefore be recommended to do finishing and polishing of restorations after such procedures.

Biofunctionalization of polyetheretherketone implant material by bone-forming peptide-2 immobilization

Polyetheretherketone (PEEK) has favorable biomechanical properties to be used as an implant material. Unfortunately, it is hydrophobic and does not promote cellular adhesion, which could result in poor integration with bone tissue. Bio-functionalization of PEEK surface with osteogenic peptides derived from bone extracellular matrix proteins is an excit-ing approach to encourage bone formation around the implant. In the current study, bone-forming peptide-2 was immo-bilized on PEEK surface using two different methods, using dopamine and a diglycidyl ether as conjugate compounds, respectively. Peptide quantification test revealed that the two strategies resulted in the most amount of peptides were attached with 0.5 mM concentration and no further peptides were grafted with a higher peptide concentration. Both methods showed good peptide stability after agitation in aqueous solution. Peptide grafting was confirmed with ATR-FTIR. Surface characterizations with AFM and wettability tests resulted in a significant increase in surface roughness and surface area ratio for the peptide-grafted PEEK compared to unmodified PEEK, which led to a signifi-cant enhancement in the wettability of the modified PEEK surface

Evaluation of the effect of surface modification of Ti64 and 316 L by addition of calcium phosphate through electrical discharge machining process

In this investigation, the EDM process was applied to modify the surfaces of Ti-6Al-4 V alloy and AISI 316 L steel by the formation of hydroxyapatite coatings with the objective of providing a favorable environment for osseointegration of implants. The EDM process has the advantage of simultaneously machining and increasing surface roughness increasing surface contact area with bone tissue and implant anchorage. The hydroxyapatite coatings were formed during EDM currents of 30 A and 40 A with calcium phosphate additions. The coatings were analyzed in terms of hardness, roughness, surface profile, wear and tribological characteristics (pin on disk) and were characterized SEM/EDS and XRD. It was possible to show that on all processed surfaces the development of apatite coatings was achieved. Coating thickness and hardness were approximately 120 µm, 700HV and 12 µm, 300HV for the Ti-alloy and stainless steel, respectively. On both substrates, a significant increase in surface roughness was observed after EDM. The pin on disk tests revealed that the coefficient of friction varied from 0.54 to 0.80, and superior wear resistance of the coating formed on the AISI 316 L steel.

Influence of surface structure on friction and wear characteristics of silicone rubber for hydraulic rod seals.

This research investigates the impact of surface structure on the friction and wear characteristics of silicone rubber used as a material for hydraulic rod seals. Various silicone rubber specimens with different surface structures were prepared, and their surface morphology, water contact angle, and surface roughness were compared. Friction tests were conducted using a reciprocating sliding method to evaluate the friction coefficient and wear characteristics. The results revealed that the silicone rubber specimens coated with silicone powder exhibited a significant increase in surface roughness. However, this increase was accompanied by a decrease in surface energy, leading to the absorption and dispersion of contact pressure and frictional stress, resulting in a friction-reducing effect. Consequently, the silicone rubber specimens coated with silicone powder demonstrated a friction coefficient more than 70% lower on average compared to bare silicone rubber, and exhibited minimal wear characteristics. The irregular microstructures formed on the surface of the silicone rubber are believed to contribute to these friction and wear improvements. Alterations in stress and contact behavior of bare silicone rubber and silicone powder-coated silicone rubber with pre-curing time during indentation and sliding movements were validated through finite element analysis. These findings provide valuable insights for enhancing the performance and durability of hydraulic rod seals made from silicone rubber. This research is expected to contribute to further studies aimed at improving hydraulic seal materials.

Influence of dental prophylaxis procedures on the tooth veneer interface in resin-based composite and polymer-infiltrated ceramic veneer restorations: an in vitro study

ObjectivesThe aim of this study was to investigate the influence of dental prophylaxis cleaning procedures and artificial aging on veneers in human teeth. The external marginal and internal tooth veneer as well as the restoration surfaces were examined.Material and methodsThirty-two extracted premolars were restored with resin-based composite (RBC) and polymer-infiltrated ceramic network (PICN) veneers. Artificial aging by alternating thermocycling and subsequent prophylaxis procedure (glycine-based powder air polishing or ultrasonic scaling) was conducted for five consecutive cycles. The external marginal interface was examined by height profile measurements and the internal interface was investigated using micro X-ray computed tomography. In addition, the surface texture of the veneer surface was analyzed using confocal laser scanning microscopy.ResultsThe application of both prophylaxis procedures resulted in a deepening of the marginal interface (10 µm ± 8 µm) for materials. Furthermore, the internal interface of PICN restorations showed marginal gaps after both treatments and artificial aging (16 µm ± 3 µm). In contrast to the RBC specimens, a significant increase in surface roughness was identified for PICN veneers after ultrasonic scaling.ConclusionsThe marginal and internal interface regions in veneers fabricated from PICN and RBC were affected by prophylaxis procedures. Furthermore, it may result in increased veneer surface roughness, especially in PICN and after ultrasonic scaling, which might affect bioadhesion and longevity.Clinical relevanceAfter dental prophylaxis procedures, examination of the marginal and the internal interface as well as the veneer surface provides a precise insight into damage mechanisms and offers an assessment of longevity.

Effect of gastric acid on the surface roughness and bacterial adhesion of bulk-fill composite resins.

The purpose of this in vitro study was to evaluate the effect of gastric acid on the surface roughness and biofilm formation of bulk-fill composite resins. Twenty-seven samples of each composite resin were obtained: G1: Filtek Z250 XT (Z250), G2: Filtek Bulk Fill (FTK), G3: Tetric N-Ceram Bulk Fill (TTC), and G4: Aura Bulk Fill (AUR). The samples were quantitatively analyzed for surface roughness (Ra) using a roughness tester (n=15) and for biofilm formation (Cn) by the counting of colony-forming units (CFUs/mL) (n=9) in three different moments: after polishing (Ra0 and Cn0), after gastric acid immersion (Ra1 and Cn1), and after gastric acid and simulated tooth brushing (Ra2 and Cn2). Qualitative analysis through surface topography (n=3) was evaluated by scanning electron microscopy (SEM). Ra values were subjected to two-way repeated measures ANOVA, followed by Tukey's test. Cn values were subjected to Kruskal-Wallis analysis, followed by multiple comparisons analysis (α=0.05). Z250 and FTK showed significant increases in surface roughness at Ra1. There were fewer CFUs/mL on TTC and AUR in relation to those of Z250 and FTK for Cn0, Cn1 and Cn2. The SEM images showed that gastric acid increased the formation of cracks, exposure of fillers and micro cavities for all composite resins. After tooth brushing, the topographical changes were more evident but did not influence biofilm formation. The gastric acid promoted both degradation of the surfaces and bacterial adhesion for all composite resins.

Effects of Acidic Environments on Dental Structures after Bracket Debonding.

Brackets are metallic dental devices that are very often associated with acidic soft drinks such as cola and energy drinks. Acid erosion may affect the bonding between brackets and the enamel surface. The purpose of this study was to investigate the characteristics of brackets' adhesion, in the presence of two different commercially available drinks. Sixty human teeth were divided into six groups and bonded with either resin-modified glass ionomer (RMGIC) or resin composite (CR). A shared bond test (SBS) was evaluated by comparing two control groups with four other categories, in which teeth were immersed in either Coca-ColaTM or Red BullTM energy drink. The debonding between the bracket and enamel was evaluated by SEM. The morphological aspect correlated with SBS results showed the best results for the samples exposed to artificial saliva. The best adhesion resistance to the acid erosion environment was observed in the group of teeth immersed in Red BullTM and with brackets bonded with RMGIC. The debonded structures were also exposed to Coca-ColaTM and Red BullTM to assess, by atomic force microscopy investigation (AFM), the erosive effect on the enamel surface after debonding and after polishing restoration. The results showed a significant increase in surface roughness due to acid erosion. Polishing restoration of the enamel surface significantly reduced the surface roughness that resulted after debonding, and inhibited acid erosion. The roughness values obtained from polished samples after exposure to Coca-ColaTM and Red BullTM were significantly lower in that case than for the debonded structures. Statistical results evaluating roughness showed that Red BullTM has a more erosive effect than Coca-Cola™. This result is supported by the large contact surface that resulted after debonding. In conclusion, the prolonged exposure of the brackets to acidic drinks affected the bonding strength due to erosion propagation into both the enamel-adhesive interface and the bonding layer. The best resistance to acid erosion was obtained by RMGIC.

Room-temperature atomic layer deposition of SiO2 on microcracked ZrO2 layers

Yttria-stabilized zirconia (Y-SZ) has become a reliable material option to restore severely compromised teeth. Y-SZ materials are prone to low-temperature degradation (LTD), which generates a tetragonal-to-monoclinic (t-m) transformed, porous layer. We suggest that room-temperature atomic layer deposition (RT-ALD) could be used for the infiltration and deposition of nanoscale SiO2 film over this layer, creating a protective hybrid surface against further degradation by LTD. This study investigated the potential of developing a Y-SZ transformed layer under controlled conditions for the infiltration of silica using RT-ALD, aiming to develop a hybrid zirconia-silica interface, and to investigate the effect of silica deposition/infiltration via RT-ALD on the surface roughness and wettability of zirconia-based materials. Sintered specimens (14 mm × 4 mm x 2 mm) were prepared from four different Y-SZ materials (n = 40): low translucency 3 mol % Y-SZ (3Y-LT; Ceramill ZI, Amann Girrbach); high translucency 4 mol % Y-SZ (4Y-HT; Ceramill Zolid); and two high translucency 5 mol % Y-SZ (5Y-HT – Lava Esthetic, 3M; 5Y-SHT – Ceramill Zolid, FX white). Specimens were exposed to hydrothermal treatment (HTT) to develop similar depths of crystalline changes. RT-ALD was used to deposit a thin film of silica (SiO2). Surface roughness and wettability analyses were performed to investigate the effect of treatment (HTT and RT-ALD) and material on Y-SZ surface properties, and data was analyzed by two-way ANOVA and Tukey HSD (p < 0.05). RT-ALD and HTT-RT-ALD treated specimens of 3Y-LT and 5Y-HT materials were exposed to further hydrothermal aging (HA) and the surface was characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS). There was a significant interaction effect of material and treatment (HTT and RT-ALD) on roughness (p = 0.02), and surface wettability (p < 0.001). Silica deposition via RT-ALD resulted in a significant increase in surface roughness of all materials tested, while surface wettability was either improved or not changed based on the material type and HTT exposure. Nanofilms of SiO2 were successfully deposited on Y-SZ materials and infiltrated 3Y-LT zirconia.

Evaluation of Charcoal and Sea Salt–Lemon-based Whitening Toothpastes on Color Change and Surface Roughness of Stained Teeth

To compare the efficacy of two naturally based commercially available whitening toothpastes charcoal and sea salt-lemon on stain removal of teeth in terms of color change and surface roughness. Twenty-seven intact bovine incisors were selected and randomly allocated into three main groups (n = 9) according to the tested toothpaste [I: Signal Complete 8 Charcoal; II: sea salt-lemon essence Closeup natural smile; and III: Signal Complete 8 Original (control)]. Following 4 successive days of staining protocol, each specimen in its corresponding group was brushed with the toothpaste using toothbrush simulator apparatus for three brushing cycles. Color assessment using Vita Easyshade spectrophotometer and surface roughness (Ra) measurement using contact type profilometer were performed for each specimen at baseline, after staining, and after each tooth brushing cycle. Nonparametric color data and parametric surface roughness data were analyzed. The color difference (ΔE) from after-staining protocol to different tooth brushing cycles (1,2,3) showed no significant difference on each cycle between the tested groups (p >0.05). While for color difference (ΔE) from baseline to the last tooth brushing cycle 3, the difference between groups was statistically significant where group II, sea salt-lemon-based toothpaste, had a significantly lowest (ΔE 00) value (p <0.001) indicating more whitening effect in relation to others. However, a significant increase in surface roughness was present in all tested groups (p <0.001); meanwhile, there was no significant difference between tested groups (p >0.05). After three tooth brushing cycles, none of the natural whitening toothpastes or conventional toothpastes produced had effective whitening results nor completely removed the stains back to the initial baseline tooth color. Sea salt-lemon-based whitening toothpaste had a whitening effect better than the charcoal-based toothpaste. All of the tested toothpastes increased the degree of surface roughness. Charcoal and sea salt-lemon-based whitening toothpastes do not guarantee to whiten nor completely remove the stains back to normal and their effects on enamel surface roughness should be highly clinically considered and managed.

A Comparative Evaluation of Remineralization after an Erosive Challenge by Two Different Mouthwashes on Surface Roughness

Aims: The aims of this study were to evaluate the in vitro effect of a cocoa bean husk extract (CBHE) mouthwash in comparison with that of a fluoridated mouthwash on surface roughness of the enamel surface after subjecting the teeth to two types of energy drink challenge. Materials and Methods: Eighty (80) sound maxillary first premolar were collected and randomly divided into four groups, the teeth in the first and second groups were immersed in a tiger energy drink for 14 days and then one group in a CBHE and another in a fluoride mouth rinses for 7 days. While the remaining teeth in the third and fourth groups were immersed in a red bull energy drink for 14 days and then one group in a CBHE and another in a fluoride mouth rinses for 7 days. Enamel surface was assessed by a profilometer device at a baseline, after erosive challenge and after remineralization with the different treatment materials. Results: In all groups, there was a high statistically significant increase in surface roughness after erosive challenge. Meanwhile, there was a high statistically significant decrease in surface roughness in all groups after remineralization, with no significant differences between energy drinks or remineralization materials. Conclusion: Within the limits of the current study, cocoa bean husk extract and fluoride mouth rinses had an effective remineralizing ability after erosive energy drinks which have a destructive effect on tooth enamel. CBHE mouth wash showed a similar remineralization effect to fluoride groups.

Effect of Resin Coating on Surface Roughness and Microhardness of High Viscous Glass Ionomer Cements

High viscous glass ionomer cement (HVGIC) was recently developed for atraumatic restorative treatment (ART). However, its moisture sensitivity remains a limitation thus protective coating application is recommended. This study investigated the effect of resin coating on the surface roughness and microhardness of two HVGICs (Riva Self Cure HVGIC [RV] and Equia® Forte Fil [EQ]) conditioned in food-simulating liquids (FSLs). Fifty standard disc-shaped samples were fabricated using customised stainless-steel mould (10 × 2 mm). Coating was applied on top surface of all samples and subsequently divided into five groups: air (control), distilled water, 0.02 N citric acid, heptane and 50% ethanol-water solution. The samples were conditioned in FSLs at 37°C for seven days. Subsequently, the surface roughness and microhardness of samples were measured using optical profilometry and microhardness tester, respectively. SEM analysis was done for qualitative observation of surface morphological changes. Data were analysed using one-way ANOVA, two-way ANOVA and posthoc Tukey’s test (α = 0.05). Interestingly, the results revealed that surface roughness was significantly influenced by FSLs immersion, presence of coating and the materials itself (p &lt; 0.001). The lowest surface roughness was found on control coated samples: RV (50.98±4.25) nm and EQ (62.77±3.92) nm, while the highest values seen on uncoated surfaces in citric acid: RV (505.26±31.10) nm and EQ (350.33±15.36) nm. RV samples had the lowest microhardness of 54.97±2.48 Vickers hardness number (VHN) post-immersion in citric acid. In conclusion, with the exception of RV conditioned in heptane and ethanol, the uncoated HVGICs generally had higher surface roughness than the coated HVGICs. HVGICs conditioned in citric acid showed the most significant increase in surface roughness and reduction in microhardness.

Superimposition of sequential scans to measure erosion on unpolished and curved human enamel

ObjectivesTo determine if superimposition of sequential scans can discriminate between different fluorides at step heights less than 5 μm on natural human enamel surfaces. Materials and methodsNatural, unpolished, human enamel specimens (n = 60) were randomly assigned to one of three pre-treatment toothpaste slurries with a calcium silicate/fluoride, fluoride-only and a control. Baseline and post treatment scans, from a non-contacting profilometer with a 0.01 μm z-axis and <1 μm lateral scanning resolution were imported into superimposition software to define change in mean 3D step height and surface roughness following erosion in 0.3% citric acid for 15 min. Statistical analysis conducted with two-way repeated measures ANOVA and post-hoc Tukey's multiple comparisons. ResultsConfidence and resolution of superimposition and subtraction of repeated profiles from unpolished enamel revealed accuracy within 1–2 μm. The technique was able to discriminate between the fluorides demonstrating statistical differences in mean (SD) 3D step height (μm) of 1.96 (0.40) and 2.75 (0.49) (p = 0.0024). There was a statistically significant increase in surface roughness for all groups after 15 min erosion compared to baseline. But no statistically significant difference between the interventions after 15 min erosion but there was compared to no fluoride (p = 0.006). ConclusionSuperimposition and subtraction of profiles could discriminate between fluoride interventions, which showed statistical differences in enamel loss differences less than 3 μm. Clinical significanceThis erosion model and data analysis workflow was able to distinguish differences between scans of 3 μm on unpolished enamel following the interaction with fluoride.

The Effect of Diode Laser Irradiation on Surface Roughness of Bleached Enamel: An in Vitro Study

Aims: To evaluate the influence of post bleaching diode laser irradiation on the surface roughness of bleached enamel. Materials and methods: Forty bovine teeth were prepared and then randomly divided into two equal groups (n=20) according to the in–office bleaching technique as follows: CB: Conventional in–office bleaching technique LB: Laser–assisted in–office bleaching technique. Each group was then subdivided into two subgroups (n=10) according to laser irradiation setting as follows: C2: Conventionally bleached followed by 2-Watt laser irradiation, C4: Conventionally bleached followed by 4-Watt laser irradiation, L2: Laser–assisted bleached followed by 2Watt laser irradiation and L4: Laser–assisted bleached followed by 4Watt laser irradiation. Surface roughness was assessed three times for all the specimens: before bleaching, 24 hours after bleaching and finally 24 hours after post bleaching diode laser irradiation by utilizing profilometer. Paired samples t–test and independent samples t– test was utilized for statistical analysis at p≤0.05. Results: Both bleached groups exhibited a significant increase in the surface roughness of enamel with no statistically significant difference between them. Post bleaching diode laser irradiation at 4Watt resulted in a significant increase in surface roughness of enamel, while 2Watt diode laser irradiation resulted in non–significant increase in surface roughness of enamel. Conclusions: In–office bleaching techniques had a negative impact on enamel in terms of surface roughness. Post bleaching diode laser irradiation at 2Watt power parameter is more preferred than 4Watt power parameter.

Direct Radiotherapy-Induced Effects on Dental Hard Tissue in Combination With Bleaching Procedure

Introduction: The aim of this study was to evaluate the effects of radiation and tooth bleaching on the physical and morphological properties of enamel and dentin on permanent teeth.Materials and Methods: Eighty fresh, non-carious third molars were used in this study. Before cutting the crown in half, the teeth samples were randomly allocated to treatment and control groups by using a lottery method. The first group (n = 20) underwent standard radiation protocol (2 Gy/fraction/day, 5 days/week) with bleaching treatment afterward using 16% carbamide peroxide gel, the second group (n = 20) underwent standard radiation protocol with afterward bleaching treatment using 38% hydrogen peroxide, the third group (n = 20) underwent a short, one strong, experimental dose of 70 Gy with afterward bleaching treatment using 16% carbamide peroxide gel, and the fourth group (n = 20) underwent one strong, experimental dose of 70 Gy with afterward bleaching treatment using 38% hydrogen peroxide gel. Groups 5–8 (n = 20) served as control as they underwent only bleaching treatment. Vickers microhardness and surface roughness were performed before (initial) and after irradiation and before bleaching or after only bleaching. The effects of irradiation and bleaching on microhardness (or roughness) of enamel and dentin were analyzed in the repeated-measures ANOVA model.Results: Enamel microhardness after experimental single 70-Gy irradiation or after standard radiation protocol and bleaching with 16 or 38% gel was not statistically significant from microhardness in the control group (p &amp;gt; 0.05). There was a statistically significantly greater reduction in the average microhardness of enamel and dentin during bleaching with 38% gel compared to 16% for both radiation protocols (p &amp;lt; 0.001). After experimental 70-Gy irradiation and bleaching, a 16% statistically significant increase in surface roughness was found for enamel (p = 0.006) and dentin (p = 0.018), while this was not recorded for 38% gel. There was a statistically significantly greater increase in the average roughness of enamel and dentin during bleaching with 38% gel compared to 16% (p &amp;lt; 0.001) for both radiation protocols.Conclusions: Directly induced radiation leads to potential damage of hard dental tissues, which can be further damaged by additional bleaching. If teeth whitening is necessary after irradiation, it is suggested to use lower concentrations of whitening gels.

Chemical and photo-initiated aging enhances transport risk of microplastics in saturated soils: Key factors, mechanisms, and modeling

Microplastics (MPs) inevitably undergo aging transformation and transport process in environmental compartments. In this study, the polystyrene MPs were aged via three different oxidation methods including persulfate oxidation (PS), UV irradiation (UV), and UV irradiated persulfate oxidation (UVPS). All three treatments induced the great transformation of MPs, with the significant increase in surface roughness and in oxygen-containing functional groups, i.e., COOH or COOC. The UVPS aging showed synergetic effect due to the strengthened photo-initiated chemical oxidation, compared to UV and PS alone. All aged MPs exhibited the enhanced transport (34.9%-89.2%) in sandy and clay loam soils than pristine MPs (30.5%), and the synergetic effect was also observed in the transport behaviors of the UVPS MPs. Higher transport of MPs and aged MPs occurred in sandy soil than that in clay loam soil since the latter one contained high Fe minerals that tend to retain MPs, which was confirmed by the model quartz sand column experiment. Modeling on the migration of MPs retained in soil under a rainstorm scenario showed that the aged MPs had the stronger remobility and greater proportion of cumulative flux than pristine ones in the soil profile. These findings provided new insights on the fate and transport of MPs in natural soil and their potential risk to groundwater contamination.

Evaluation of Wear and Surface Roughness of Different CAD/CAM Monolithic Ceramic Materials

ABSTRACT Purpose: To evaluate the wear and surface roughness of different CAD/CAM monolithic ceramic materials opposing monolithic zirconia. Material and Methods: Twenty-seven rectangular-shaped specimens were milled from different ceramic materials by using a precision saw and divided (n=9) into 3 groups: group ZLS, zirconia-reinforced lithium silicate; group LD, lithium disilicate glass ceramic; and group ZR, 4-mol yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP). Antagonist material were milled from a partially sintered 4Y-TZP blank with a CAD/CAM system. Two-body wear test was performed in a mastication simulator. The wear of the specimens and antagonists was determined by calculating the weight loss. The surface roughness of the specimens and antagonists before and after wear testing was analyzed by using a digital image analysis software program. The surfaces of ceramic specimens and antagonists were inspected by using scanning electron microscopy. Data were statistically analyzed by using 1-way ANOVA and the Tukey post hoc test (p = 0.05). Results: One-way ANOVA revealed significant amount of weight loss for all ceramic types (p < 0.05). No statistically significant differences were found between the different ceramic types when comparing their percentage change of weight (p = 0.544). As for the surface roughness, one-way ANOVA revealed significant increase in surface roughness for all ceramic types after chewing simulation (p < 0.05). No statistically significant differences were found between the different ceramic types when comparing their percentage change roughness (p = 0.251). Conclusions: The different types of tested ceramics showed similar wear resistance when opposed to monolithic zirconia.

Modification of an anion exchange membrane based on rapid mussel-inspired deposition for improved antifouling performance

In this study, an anion exchange membrane (AEM) was modified by rapid deposition of polydopamine (PDA) and 2,5-diaminobenzenesulfonic acid (DSA), where DSA was further immobilized by mussel-inspired PDA on the membrane surface. The surface properties of the AEM were characterized by a series of analysis techniques such as ATR-FTIR, XPS, AFM and SEM analysis, contact angle and zeta potential measurements. The results indicated that a uniform membrane surface was obtained by the rapid deposition of PDA/DSA complexes, which endowed the membrane with negative charge and higher hydrophilicity without significant increase of surface roughness. The rapid deposition of PDA/DSA complexes on the membrane surface improved significantly the antifouling performance of AEM to an organic foulant, i.e., sodium dodecyl sulfate (SDS) in electrodialysis. According to the change of the area electrical resistance after the fouling experiment, the antifouling performance of the modified AEM could be improved by 50.6 % under optimal modification parameter compared with the pristine AEM. The surface negative charge and higher hydrophilicity reduced the adsorption of organic foulants on the membrane and restricted the formation of a fouling layer on the membrane surface, hence contributed to the improvement of antifouling performance of the modified AEM.