Significant Increase In Surface Roughness Research Articles

Effects of boron doping on the surface modification and defect evolution of silicon induced by proton implantation and annealing

Ultra-thin silicons can be obtained using SMART CUT technology, but there is a lack of systematic research on the effect of boron doping. This paper reports the effects of boron doping on surface modification and defect evolution. Monocrystalline silicon samples with different concentrations of boron doping were implanted to 3.5 × 1017H+/cm2 using a 1.52 MeV High Intensity Proton Implanter (HIPI) and annealed at 300, 400, and 550 ℃. The annealed samples were analyzed by non-contact optical profilometry, Raman spectroscopy, SEM, and TEM. The results show that appropriate boron doping can reduce the surface roughness of the exfoliated samples; excessive boron doping leads to a significant increase in surface roughness (∼525 nm) and produces a step-like morphology. Boron doping leads to changes in the type, concentration and dissociation temperature of hydrogenated defects during implantation. These changes result in the width of damage band changes vary with doping concentration. The density and diameter of the hydrogenated extended defects also changed, which results in the surface modification of samples, such as the change of the surface morphology and substrate roughness. In the end of the paper, the paper discusses the correlation between surface morphology and internal damage for different concentrations of boron doping.

Different Methods to Modify the Hydrophilicity of Titanium Implants with Biomimetic Surface Topography to Induce Variable Responses in Bone Marrow Stromal Cells.

The osteoblastic differentiation of bone marrow stromal cells (bMSCs), critical to the osseointegration of titanium implants, is enhanced on titanium surfaces with biomimetic topography, and this is further enhanced when the surfaces are hydrophilic. This is a result of changing the surface free energy to change protein adsorption, improving cell attachment and differentiation, and improving bone-to-implant contact in patients. In this study, we examined different methods of plasma treatment, a well-accepted method of increasing hydrophilicity, and evaluated changes in surface properties as well as the response of bMSCs in vitro. Commercially pure Ti and titanium-aluminum-vanadium (Ti6Al4V) disks were sand-blasted and acid-etched to impart microscale and nanoscale roughness, followed by treatment with various post-processing surface modification methods, including ultraviolet light (UV), dielectric barrier discharge (DBD)-generated plasma, and plasma treatment under an argon or oxygen atmosphere. Surface wettability was based on a sessile water drop measurement of contact angle; the elemental composition was analyzed using XPS, and changes in topography were characterized using scanning electron microscopy (SEM) and confocal imaging. The cell response was evaluated using bMSCs; outcome measures included the production of osteogenic markers, paracrine signaling factors, and immunomodulatory cytokines. All plasma treatments were effective in inducing superhydrophilic surfaces. Small but significant increases in surface roughness were observed following UV, DBD and argon plasma treatment. No other modifications to surface topography were noted. However, the relative composition of Ti, O, and C varied with the treatment method. The cell response to these hydrophilic surfaces depended on the plasma treatment method used. DBD plasma treatment significantly enhanced the osteogenic response of the bMSCs. In contrast, the bMSC response to argon plasma-treated surfaces was varied, with an increase in OPG production but a decrease in OCN production. These results indicate that post-packaging methods that increased hydrophilicity as measured by contact angle did not change the surface free energy in the same way, and accordingly, cells responded differently. Wettability and surface chemistry alone are not enough to declare whether an implant has an improved osteogenic effect and do not fully explain how surface free energy affects cell response.

Exceptional thermal stability and mechanical properties of dual-phase amorphous-nanocrystalline Al–Mo alloy films

Dual-phase amorphous-nanocrystalline Al-x at.% Mo (x = 20, 26, 30) alloy films prepared in the way of dual-phase co-growth directly through magnetron sputtering were studied in terms of thermally induced microstructural evolution and mechanical properties via annealing at 550 °C. It was observed that, the annealed Al-26 and 30 at.% Mo alloy films maintained stable dual-phase amorphous-nanocrysatlline structure and precipitated Al8Mo3 nano-grains dispersed in amorphous matrix uniformly. After annealing, the surface roughness of Al-26 and 30 at.% Mo alloy films remained unchanged of 7.5 nm and the hardness and elastic modulus of them were as high as 13 and 210 GPa which enhanced about 50 % and 24 % than before, respectively. In contrast, the Al-20 at.% Mo alloy film crystallized completely and mainly contained intermetallic Al12Mo phase along with apparent grain coarsening after annealing, which resulted in significant increase of surface roughness and deterioration of hardness. The excellent thermal stability of dual-phase amorphous-nanocrystalline Al-26 and 30 at.% Mo alloy films stem from the small driving force for precipitated Al8Mo3 nano-grain growth, as well as benefit from effect of diffusion field impingement.

Effect of Beverage Solutions on Surface Roughness of PEEK CAD –CAM, 3D Printing Denture Base and Heat Cure Acrylic Resin Denture Base Materials

The Aim: The aim of this research was to investigate how distilled water, tea, coffee, and cola affected the surface roughness of poly ether ether ketone CAD-CAM, 3D printing, and heat cure acrylic resin denture bases at specific intervals (6 ,12days). Materials and Methods: Disk shape 10 mm (diameter) ×2 m m (thickness), manufactured from materials used which were PEEK, 3D printing and heat cure acrylic resin. Total number of samples are n= (75) samples, control samples not immersed in beverage media n= 15, experimental samples immersed in beverage solutions (distilled water, tea, coffee and cola) n=60 for evaluating the surface roughness at (6, 12 and 24 days) .Then all collecting data were statically analyzed by spss v ersion 25, by means of descriptive statistics, analysis of variance (ANOVA) and duncan multiple range tests at p ≤ 0.05. The Results: The results revealed a significant increase in surface roughness in all beverage solutions at p ≤ 0.0 5. Conclusions: All beverage solutions had a negative effect on surface roughness of all experimental materials, the surface roughness increased. cola had the most aggressive effect followed by coffee then tea and distilled water have the least ef fect.

GO-tagged PEI sizing agent imparts self-healing and excellent mechanical properties to carbon fiber reinforced epoxy laminates.

Carbon fiber-reinforced epoxy (CFRE) laminates have attracted significant attention as a structural material specifically in the aerospace industry. In recent times, various strategies have been developed to modify the carbon fiber (CF) surface as the interface between the epoxy matrix and CFs plays a pivotal role in determining the overall performance of CFRE laminates. In the present work, graphene oxide (GO) was used to tag a polyetherimide (PEI, termed BA) containing exchangeable bonds and was employed as a sizing agent to improve the interfacial adhesion between CFs and epoxy. This unique GO-tagged-BA sizing agent termed BAGO significantly enhanced the mechanical properties of CFRE laminates by promoting stronger interactions between CFs and the epoxy matrix. The successful synthesis of BAGO was verified by Fourier-transform infrared spectroscopy. Additionally, the partial reduction of GO owing to this tagging with BA was further confirmed by X-ray diffraction and Raman spectroscopy, and the thermal stability of this unique sizing agent was evaluated using thermogravimetric analysis. The amount of GO in BAGO was optimized as 0.25 wt% of BA termed 0.25-BAGO. The 0.25-BAGO sizing agent resulted in a significant increase in surface roughness, from 15 nm to 140 nm, and surface energy, from 13.2 to 34.7 mN m-1 of CF. The laminates prepared from 0.25-BAGO exhibited a remarkable 40% increase in flexural strength (FS) and a 35% increase in interlaminar shear strength (ILSS) due to interfacial strengthening between epoxy and CFs. In addition, these laminates exhibited a self-healing efficiency of 51% in ILSS due to the presence of dynamic disulfide bonds in BAGO. Interestingly, the laminates with 0.25-BAGO exhibited enhanced Joule heating and enhanced deicing, though the EMI shielding efficiency slightly declined.

Bone cutting performance and mechanical properties of piezo-surgical tips: a nano-indentation study

Purpose: The aims of this study were to compare the mechanical properties of piezo-surgical tips such as nano-hardness, elastic modulus, surface roughness, and wear level, and to measure their cutting performance. 
 Materials and Methods: In this study, 31 piezo-surgical tips were used, three for control and 28 for testing. The testing tips were equally divided into four groups with different numbers of osteotomies: the four-, 8-, 16-, and 32-osteotomy groups. The mean osteotomy duration was recorded during osteotomy. Scanning electron microscopy images of the tips in the test groups were obtained before and after osteotomy, and the wear level of the tips was measured. 
 Results: A statistically significant increase was observed in the nano-hardness of the piezo-surgical tips depending on the number of osteotomy (for 4-use; 22.47±1.67H and for 32-use; 28.49±3.42H). The elasticity value of the testing tips was in the range of 218.55±15.74E to 241.26±10.46E, and all of the values were significantly higher than those in the control group (174.39±13.53E). As the frequency of use increased, a significant increase in surface roughness was observed (from 16.67±1.50 to 56.12±2.60). A positive correlation was found between the frequency of use and the wear level of the tips, and between the surface roughness and wear level of the tips. 
 Conclusion: With the increase in the number of osteotomies, significant changes in the mechanical and physical properties of the piezo-surgical tips that affected their bone-cutting performance were observed.

Changes in Gloss Alteration, Surface Roughness, and Color of Direct Dental Restorative Materials after Professional Dental Prophylaxis.

In the context of optimizing dental care for patients who are elderly, the purpose of this in vitro study was to evaluate the surface gloss (with a micro-area gloss meter) of, surface roughness (with a compact surface roughness measuring instrument) of, and color change (with a dental colorimeter) in two commercially available injectable resin-based composites (Estelite Universal Flow (EUF) and Beautifil Flow Plus F00 (BFP)) as well as two glass-ionomer cements (GC Fuji II LC CAPSULE (FLC) and GC Fuji IX GP EXTRA CAPSULE (FGP)), before and after dental prophylaxis. After 24 h, the surfaces of each specimen were polished at 2500 rpm with a prophy brush (Mersage Brush, Shofu) and one-step prophylaxis paste (Prophy Paste Pro, Directa): under 100 or 300 gf load, and for 10 or 30 s, 4× cycles of cleaning. After mechanical cleaning, conditions were found for a significant reduction in the gloss level (EUF, BFP, or FLC; p < 0.05) and a significant increase in surface roughness (BFP; 300 gf load, 10 s × four cycles of cleaning). Overall, the longer time or higher prophylaxis load tended to decrease the surface gloss. However, the observed change in surface roughness varied between the restorative materials. There was no color change post-prophylaxis.

Solid dust induced roughening and overheating of TBC-coated superalloy

Thermal barrier coatings (TBC) on superalloy blade/vane enable an increase in turbine inlet temperature (TIT) and aero-engine efficiency. However, the deposition of dust on TBC significantly ablates superalloys and becomes a bottleneck for advanced engine development. This paper presents a comprehensive modeling approach, based on an experiment involving dust deposition on a TBC-coated substrate, aimed at understanding the fundamental cause of substrate ablation. The results show that a significant increase in surface roughness is obtained experimentally with dust accumulation. The temperature field within the TBC-substrate system is disturbed by surface roughening. Consequently, the film cooling is seriously destroyed. While the dust accumulated on the TBC surface also contributes to heat insulation by increasing the effective TBC thickness, localized overheating of the substrate occurs and then leads to ablation and premature failure of the substrate. This elucidation of the overheating mechanism could inform the development of strategies to resist dust accumulation in advanced aero engines.

Degradation mechanism analysis of substrate and microporous layer of gas diffusion layer in proton exchange membrane fuel cell

Robust electrochemical corrosion of gas diffusion layers (GDL) in proton exchange membrane fuel cell (PEMFC) could cause significant decline of cell performance. However, the detailed mechanism still remains elusive. Herein, the structural characteristics of GDL after electrochemical accelerated stress test (AST) and sequent impacts on the mass-transfer performance of membrane electrode assemblies were explored. With the electrochemical corrosion duration increasing, polytetrafluoroethylene (PTFE) peeling and carbon fibers exposure were observed on substrate layer surface, while corrosion pores were detected on microporous layer (MPL). Both substrate layer and MPL experienced significant increase in surface roughness, which was reflected in the surface and bulk resistance. Surface contact angle and water permeability threshold tests showed that surface and internal hydrophobicity of GDL degraded comprehensively. More significant carbon corrosion in MPL and PTFE loss in substrate layer were revealed by X-ray photoelectron spectroscopy and thermogravimetric analysis. Collectively, worse power density and severe ohmic and mass-transfer polarization after AST were confirmed and the oxygen mass-transfer performance was analyzed in single-cell tests. This work clearly explains the distinctive degradation mechanisms of the substrate layer and MPL and provides guidance for the design and application of GDL.

Mechanical and tribological properties of basalt fiber fabric reinforced polyamide 6 composite laminates with interfacial enhancement by electrostatic self-assembly of graphene oxide

Exploring simple, efficient and applicable interfacial optimisation methods is important to enhance the overall performance of basalt fibre (BF) fabric-reinforced thermoplastic composite laminates. Graphene oxide (GO) was introduced on the surface of BF fabric through electrostatic self-assembly to improve the interfacial bonding of BF fabric-reinforced polyamide 6 (PA6) composites laminates (BF/PA6) for enhancing the mechanical and frictional wear properties of the composites. It was concluded that surface electrostatic assembly of GO resulted in a significant increase in surface roughness, wettability, surface energy and surface chemical activity of BF fabrics without damaging the fibre backbone structure. With the GO concentration of 0.8 g/L, the interlaminar shear strength, impact strength, flexural strength and flexural modulus of the BF/PA6 composites were increased by 85.1 %, 43.2 %, 53.2 % and 63.4 %, and the average friction coefficient and wear rate was reduced by 15.2 % and 40.5 %, respectively. The introduced homogeneous GO strengthens the interfacial bonding of such fibre-fabric reinforced thermoplastic composites by creating mechanical engagement, similar compatibility and chemical cross-linking between the BF fabrics and the PA6 matrix. With enhanced interfacial bonding, the BF fabric reinforced thermoplastic composites possess enhanced stress damage resistance. Under frictional reciprocating stress, the introduced GO inhibited the generation and expansion of microcracks, formed frictional transfer film to play solid lubrication and anti-wear role, and enhanced the thermal stability of the composites to mitigate the frictional thermal damage. The interfacial enhancement method of BF fabric-reinforced thermoplastic composites provided in this study is simple, green, efficient and has good potential for application.

Air-polishing technology is an effective alternative chairside method for cleaning dentures.

To investigate the efficiency and abrasiveness of air-polishing on different types of denture base acrylic resins and whether air-polishing can be an effective technique to clean dentures chairside. A total of 60 specimens were prepared (n = 20/group); heat-polymerized polymethyl methacrylate (PMMA) (G1), subtractive manufacturing (SM) (G2) and additive manufacturing (AM) denture base resins (G3). Equal number of specimens in each group were stained with permanent marker or nail polish and pumice mixture to mimic calcified biofilm. All specimens were treated using EMS Airflow® Prophylaxis Master with two different powders; erythritol or sodium bicarbonate powder, following manufacturer instructions. Efficacy of the powders and surface roughness of the specimens were measured. Scanning electron microscopy imaging was captured for qualitative observation. The highest efficacy for stain removal was found in erythritol powder on G1 (98.06% ± 1.304%). The lowest was found in the erythritol powder on G3 (91.83% ± 3.611%). The highest efficacy for biofilm removal was found in sodium bicarbonate powder on G3 (71.49% ± 8.607%), and the lowest was found in erythritol powder on G2 (11.64% ± 4.68%). Only AM resins had statistically significant increases in surface roughness with the use of erythritol powder (p < 0.001). The use of sodium bicarbonate powder significantly increases surface roughness of heat-polymerized (p < 0.025) and AM resins (p < 0.724). Air-polishing technology has shown to be effective and suitable for cleaning dentures. The sodium bicarbonate powder showed superior efficacy in cleaning dentures compared to the erythritol powder. Both powders show varyingly increase roughness depending on denture resin.

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.