Polishing Protocols Research Articles

Effect of lubricated polishing and repolishing on gloss, roughness and material loss of nanoparticle resin composite

Aim: The study examined how different dry and lubricated polishing protocols impact the gloss, roughness, and material loss of nanoparticle resin composites, before and after simulated toothbrushing. Methods: One hundred cylindrical resin composite specimens were prepared and divided into an unpolished group and three test groups: Dimanto (DIM), Sof-Lex Pop-On (SOF), and Astrobrush (ASTRO). These groups underwent polishing dry, with water, or with or petroleum jelly. Surface parameters including gloss (Novo-Curve – Rhopoint TM, England), roughness, and material loss (MaxSurf XT 20, MahrGoettingen, Germany) were evaluated at four stages: baseline, polishing, simulated toothbrushing, and repolishing. Data were submitted to repeated measures ANOVA (P<0.05). Results: Lubrication did not affect the studied parameters after polishing with DIM. SOF showed improved performance without lubricants, whereas ASTRO achieved higher gloss and lower roughness when lubricated. In terms of surface material loss, DIM exhibited less material loss when used with petroleum jelly, SOF had reduced material loss when used with water, and ASTRO showed the most material loss when lubricated with petroleum jelly. Conclusion: The gloss, roughness, and surface material loss of the nanoparticle resin composite are influenced by the type of polisher used and the choice of lubricant. However, none of the differences observed surpassed the established thresholds for roughness or gloss perception, suggesting that these protocols are potentially viable for clinical application. Despite detectable differences among the polishing systems and lubricant combinations, all tested options are clinically acceptable. None of them exceeded the thresholds for biofilm accumulation or perceptible differences in surface gloss.

Investigating the Impact of Pad Groove Depth Reduction on Process Variation in Oxide Chemical Mechanical Polishing

Abstract The groove depth of a polishing pad diminishes due to continuous wear from the diamond conditioner. Over the course of approximately 20 hours of use, this reduction in groove depth enhances slurry flow across both the pad grooves and surface. A fluid simulation analysis indicates that the new slurry mass fraction at 0.51 seconds increases from 72.34% for an 850 µm groove depth to 100.00% for a 250 µm depth. Consequently, polishing performance metrics including removal rate, within-wafer nonuniformity (WIWNU), and added defects exhibit variations commensurate with groove depth alterations. To explore the influence of process parameters on these polishing performance metrics, oxide film polishing experiments were conducted using pads with initial groove depths of 250, 500, 750, and 850 µm. The effects of process parameters, including pad cut rate, retainer ring pressure, and slurry flow rate on polishing were separately examined across different groove depth pads. Generally, shallow groove pads display improved removal rates but worse WIWNU. Additionally, the maximum surface temperature of the pads was recorded, serving as an indirect indicator of individual parameter effects. The findings have implications for advanced process control, guiding the optimization of polishing protocol in consideration of pad lifetime.

Comparison of Various Surface Treatment Procedures on the Roughness and Susceptibility to Staining of Provisional Prosthodontic Materials.

Esthetically pleasing temporary prostheses are often necessary for extended periods in a variety of clinical scenarios. Adjustments to the occlusion or margins are commonly needed before cementing the temporary prosthesis. Therefore, it is clinically necessary to repolish the rough surface to avoid biological and esthetic issues associated with rough surfaces. The purpose of this in vitro study was to assess and compare the impact of various polishing protocols on the surface roughness and color stability of three resin materials used for provisional crowns. A total of 150 specimens were fabricated from auto-polymerizing polymethyl methacrylate, bis-acryl composite, and Methyl methacrylate-LC resin using a stainless steel mold. Each material group was divided into five groups (n = 10) based on the applied surface treatment: positive control group (G1): no roughening or surface treatment, Negative control group (G2): acrylic bur-roughened surface without any polishing, the different surface treatment groups of silicon carbide and aluminum oxide stone polishing (G3), diamond-coated rubber twist (G4), and Surface Glaze (G5). An optical profilometer was used to assess the surface roughness of all samples. After undergoing 6000 cycles of thermocycling followed by immersion in a coffee solution for 15 days at 37 °C, color parameters were measured using a spectrophotometer both before and after a storage period to evaluate color differences. A two-way ANOVA test with α = 0.05 significance level was carried out to determine the impacts of both the materials utilized and the polishing protocol. Among the three types of resin examined, the bisacryl group exhibited superior surface quality in positive control groups, while PMMA resin demonstrated higher polishability. The diamond-coated rubber twits resulted in lower Ra values of 0.36 (0.01) µm, 0.52 (0.11) µm, and 0.28 (0.05) µm for PMMA, BAMA, and MMLC resins, respectively. The application of photo-polymerized surface glaze led to a plaque accumulation threshold of 0.2 µm across all resin groups. The greatest mean color change occurred in the negative control group, indicating a propensity for more staining on rougher surfaces. The Bisacryl resin exhibited higher ΔE values, whereas PMMA showed better color stability. The lowest ΔE values were found when the surface glaze was applied to all of the provisional crown resins. Untreated Bisacryl resin exhibited the lowest Ra values, while PMMA resins demonstrated superior surface morphology after polishing. PMMA provisional crown resins showed increased resistance to staining. The use of surface glaze enhanced both smoothness and color stability on the surfaces.

Effect of Grinding and Polishing Protocols on Surface Roughness, Flexural Strength, and Phase Transformation of High-Translucent 5 mol% Yttria-Partially Stabilized Zirconia

Abstract Objectives This study evaluated surface roughness, biaxial flexural strength, and phase transformation of 5Y-PSZ after grinding and polishing with different protocols. Material and Methods Two commercial 5Y-PSZ, Lava Esthetic (L) and Cercon xt (C), were used and divided into 3 groups: LC and CC represented unpolished control groups; LE and CE were polished with protocol I (EVE DIASYNT® PLUS HP following with EVE DIACERA RA); and LJ and CJ were polished with protocol II (Superfine diamond bur following with Jota ZIR Gloss polishing kit). Surface roughness was evaluated after polishing step-by-step with a contact-type profilometer. After high-gross polishing, the specimens were subjected to biaxial flexural strength test, crystallographic microstructure analysis using an X-ray diffractometer (XRD), and surface micro-topography using scanning electron microscopy (SEM). Statistical Analysis Surface roughness differences after each step and biaxial flexural strength between groups were evaluated with one-way ANOVA, followed by Bonferroni post-hoc analysis. Changes in surface roughness across four different time points within groups were assessed using one-way repeated measures ANOVA, followed by Bonferroni post-hoc analysis. Results After high-gross polishing, both polishing protocols showed significantly lower surface roughness than the grinding group (p < 0.05). The LE and CE groups exhibited the highest surface roughness values, which were significant differences from the LJ and CJ groups (p < 0.05). The LE group showed significantly lower biaxial flexural strength compared to the LC group (p < 0.05). However, there was no statistically significant difference in the CE and CJ groups compared to the control group (p > 0.05). Furthermore, all polishing protocols did not change the phase transformation of zirconia. Conclusion Polishing protocol II provided a smoother surface than the protocol I after high-gross polishing, while the biaxial flexural strength of materials remained unaffected.

Surface Roughness of Nano-Hybrid Universal Composite Restorative Materials After Different Finishing and Polishing Protocols

Surface Roughness of Nano-Hybrid Universal Composite Restorative Materials After Different Finishing and Polishing Protocols

Investigation of Polisher Head and Slurry Sweep Effect in Oxide Film Polishing

Abstract Chemical mechanical polishing (CMP) has undergone rapid advancements in global and local planarization. The synergy between the process control and the consumables is critical to overall CMP performance. In addition to optimizing consumables and equipment including a polisher, metrology, and inspection, the polishing protocol plays a crucial role in effective process management. In fabrication scenarios, protocol revision is a convenient and practical approach for problem-solving. This research focuses on the study of head sweep direction, head sweep distance, and slurry sweep effects in oxide film polishing. Sweeping toward the outside resulted in an average increase of 12.66% removal amount for ceria and 11.57% for silica compared to fixed head polishing. Moreover, a longer head sweep distance reduced non-uniformity. While the slurry sweep exhibited a non-significant effect on the removal amount, it proved valuable in optimizing the removal amount profile.

A Different Approach to Analyzing the Surface Roughness of Prosthetic Dental Acrylic Resins

(1) Introduction: Apart from the polishing method, conventional or mechanized, the arithmetic mean roughness (Ra) is the most common metric to evaluate the surface roughness of denture base acrylic resins. An overview of the constraints related to this roughness parameter is highlighted in this study. This research introduces new parameters for accessing a functional analysis of surface roughness. (2) Materials and Methods: Five samples of CAD/CAM 3D-printed acrylic resins were prepared. Two polishing techniques, manual and mechanical, were applied. Surface roughness parameters were extracted from a profilometer reading: arithmetic mean height (Ra and Pa), skewness (Rsk and Psk), and kurtosis (Rku and Pku). (3) Results: Significant differences (p < 0.001) were found in the Ra distribution among the study samples, in contrast with the lack of significance in Pa values. Surface roughness parameters revealed an increased coefficient of variance (CV) value due to mechanized polishing across the specimens analyzed. Skewness and kurtosis indicate a more pronounced distribution with the manual polishing technique. (4) Conclusion: This preliminary study exhibits the influence of different polishing protocols on surface roughness parameters. The primary profile, skewness, and kurtosis should be assessed for the surface characterization of acrylic resins.

Analysis of Topography, Flexural Strength, and Microstructure of a Lithium Disilicate Glass- Ceramic after Surface Finishing.

To investigate the influence of finishing, polishing, and glazing on the roughness, flexural strength, and microstructure of lithium disilicate glass-ceramics. LD CAD/CAM blocks were cut into 96 discs (1.2 × 12 mm). After crystallization, a layer of glaze was applied to the discs' surfaces. The specimens were randomly divided into eight groupsn = 12) for different surface treatments (glaze [G], diamond abrasion [D], find diamond abrasion [F], and polishing [P]): G(glaze, control), GD, GDG, GDP, GF GFG, GFP, and GDFP. Mean roughness (Ra), mean square height (Rq), and maximum roughness (Rz) were measured. The biaxial flexural strength test was performed in a universal testing machine at 0.5 mm/minute. Microstructural analysis was performed using x-ray diffraction patterns (XRD). Differences on the roughness obtained in distinct groups was analyzed with Kruskal-Wallis and Bonferroni tests (α = .05). The flexural strength tests were compared with one-way ANOVA. Glazed groups (G, GDG, and GFG) presented the lowest surface roughness, lower crystallinity, and higher flexural strength than the other groups. Although polishing and glaze presented similar surface roughness, polishing protocol decreased the flexural strength compared to the control group G. Clinically adjusted LD glass-ceramic restorations should be reglazed whenever possible to improve strength.

A Novel Apparatus to Standardize the Polishing Protocol to Achieve Different Roughness of Titanium and Zirconia Disc Surfaces.

To propose and evaluate standardized polishing protocols for in vitro experiments using a custommade apparatus under controlled force to create consistent surface roughness on titanium and zirconia discs. A total of 160 discs were manufactured with a diameter of 10 mm, 80 titanium (Ti) and 80 zirconium oxide (Zr). Specimens were categorized into two groups: controlled force (CF) and without controlled force (WCF). Specimens in the CF group were polished with a custom apparatus incorporating a tension gauge on the Ti and Zr disc surfaces to achieve consistent roughness. The WCF group was polished without the use of a tension gauge. Each group had four subgroups (n = 10): control/machined with no polishing (C), rough (R), smooth (S), and very smooth (VS). The subgroups were processed using a sequence of diamond-impregnated polishing burs and polishing paste. The CF group showed consistent surface roughness and a gradual decrease in surface roughness. Control in Ti (Ra = 6.5 ± 0.03 μm) and in Zr (Ra = 5.4 ± 0.04 μm); R in Ti (Ra = 3.5 ± 0.06 μm) and in Zr (Ra = 3.2 ± 0.07 μm); S in Ti (Ra = 1.5 ± 0.04 μm) and in Zr (Ra = 1.1 ± 0.06 μm); and VS in Ti (Ra = 0.05 ± 0.002 μm) and in Zr (Ra = 0.02 ± 0.005 μm). There were significant differences for R, S, and SV under CF and WCF in Ti and Zr surfaces. The specimens polished under control force produced significantly more uniform surface roughness than those polished without controlled force and were produced with a higher degree of consistency.

Easy cleaning plus stable activation of glassy carbon electrode surface by oxygen plasma

Glassy carbon (GC) electrodes are widely used in electroanalytical applications especially in bioelectrochemistry. Their use starts with an efficient surface cleaning and activation protocol, mostly based on surface polishing steps. We studied the use of an oxygen plasma exposure of GC electrodes to replace common polishing procedures. The cyclic voltammetry (CV) responses of ferrocyanide and ferrocene-dimethanol were used to compare brand new, surface-polished and plasma-treated GC electrodes. Plasma treatment induces CV responses with improved features, close to theoretical values, as compared to other methods. The plasma effects were quasi-stable over a week when electrodes were stored in water, this being explained by increased surface energy and hydrophilicity. Furthermore, when electroreduction of diazonium was performed on GC electrodes, the surface blockade could be removed by the plasma. Thus, a short oxygen plasma treatment is prone to replace polishing protocols, that display person-dependent efficiency, in most of the experiments with GC electrodes.

Influence of coloring techniques on the surface characteristics and color stability of a monolithic zirconia ceramic

The color of monolithic zirconia restorations is obtained by presintering or postsintering coloring techniques. However, studies on the differences in surface characteristics and their influence on color stability are lacking. The purpose of this in vitro study was to evaluate the influence of shading and staining techniques for a zirconia ceramic on the surface characteristics and colorimetric parameters (color difference, translucency, and whiteness index) after exposure to coffee or red wine and then polishing. Ceramic disks (N=30; Ø10×1mm) were allocated into 3 groups: preshaded-shaded by the manufacturer (IPS e.max ZirCAD MT, shade A2); manually shaded-unshaded zirconia (IPS e.max ZirCAD MT, bleaching shade-BL) colored by the brushing technique, before sintering; stained-unshaded zirconia (IPS e.max ZirCAD MT BL) colored by the staining technique, after sintering. Spectrophotometric color assessments ensured the same initial perceived color (Vita Classical A2) for specimens included in the study (∆E00<1.77 acceptability threshold). Surface characteristics were assessed by scanning electron microscopy and atomic force microscopy. The specimens were immersed in coffee (n=5) or red wine (n=5) for 12 and 24 days and subsequently polished. The data were statistically and descriptively analyzed for color differences (∆E00), translucency parameters (TP00), and whiteness indexes for dentistry (WID), considering acceptability and perceptibility thresholds. The shaded groups found an irregular ceramic surface with uniformly sized zirconia crystals. The stained group found a glass-covered smoother surface. Significant alterations in color parameters (∆E00, TP00, WID) were observed with immersion in pigmenting beverages (P<.001) both after 12 days, and after 24 days. The shaded specimens had greater color alterations after immersion but benefited from the polishing procedure, which reduced color differences below an acceptable threshold in comparison with the baseline. Stained specimens had lower color alterations after immersion, but the polishing protocol was detrimental as it whitened the ceramic by subsurface exposure. The coloring technique influences the surface characteristics of zirconia ceramic and also the color parameters after exposure to colored beverages and polishing.

Influence of Surface Roughness on Nanocrystalline Diamond Films Deposited by Distributed Antenna Array Microwave System on TA6V Substrates

In this study, the characteristics of nanocrystalline diamond films synthesized at low surface temperature on Ti-6Al-4V (TA6V) substrates using a distributed antenna array microwave reactor aiming at biomedical applications were investigated. The surface roughness of the TA6V substrates is varied by scratching with emery paper of 1200, 2400, 4000 polishing grit. Nanocrystalline diamond (NCD) coatings with morphology, purity, and microstructure comparable to those obtained on silicon substrates usually employed in the same reactor and growth conditions are successfully achieved whatever the polishing protocol. However, the latter has a significant effect on the roughness parameters and hardness of the NCD films. The use of the finest polishing grit thus permits us to enhance the hardness value, which can be related to the work-hardening phenomenon arising from the polishing process.

Evaluation of the Effects of Different Polishing Protocols on the Surface Characterizations of 3D-Printed Acrylic Denture Base Resins: An In Vitro Study.

Chairside polishing kits are an alternative to laboratory polishing techniques. The effects of using a chairside polishing kit on a three-dimensional (3D)-printed acrylic denture base (ADB) have not been reported previously. Thus, this study aimed to evaluate the effects of different chairside polishing techniques on the surface characterizations of ABD, including surface roughness average (Ra), average maximum profile height (Rz), and scanning electron microscopy (SEM) representations. One hundred and twenty disc-shaped specimens were fabricated from one conventional heat-polymerized (HP) ADB resin and two 3D-printed (Asiga (AS) and NextDent (ND)) ADB resins (n = 40 per material). Each group was further divided based on the polishing protocol (n = 10) as follows: conventional polishing protocol (C), microdont chairside polishing kit (M), shofu chairside polishing kit (S), and an unpolished group (U). The Ra and Rz values were measured using an optical profilometer. Two-way ANOVA and post hoc tests were used for data analysis (α = 0.05) at significant levels. In unpolished groups, there was a statistically significant difference between HP-U vs. AS-U and ND-U groups (p < 0.0001). For Ra, the lowest values were observed in HP-C, AS-S, and ND-C. While the highest values were shown in all unpolished groups. Within the material, there were statistically significant differences between the three polishing protocols (C, M, and S) vs. unpolished (p < 0.0001), while there was no significant between C, M, and S groups (p = 0.05). The Rz values had the same pattern as the Ra values. The two chairside polishing kits were comparable to conventional polishing techniques, and they can be recommended for clinical application.

Biofilm Formation on the Surfaces of CAD/CAM Dental Polymers.

Dental polymers are now available as monolithic materials which can be readily used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems. Despite possessing numerous advantages over conventionally produced polymers, the polymers produced by either of these systems fail to exhibit immunity to surface microbial adhesion when introduced into the oral environment, leading to the development of oral diseases. The aim of this study was to analyze the biofilm formation of six microorganisms from the oral cavity and its correlation to the surface characteristics of CAD/CAM dental polymers. A total of ninety specimens were divided into three groups: resin-based composite, polymethyl methacrylate, and polyether ether ketone. The experimental procedure included surface roughness and water contact angle measurements, colony forming unit counting, and scanning electron microscopy analysis of biofilm formed on the surface of the tested materials. The data were analyzed using the Kruskal-Wallis test, with a Dunn's post hoc analysis, and one way analysis of variance, with a Tukey's post hoc test; the correlation between the measurements was tested using Spearman's correlation coefficient, and descriptive statistics were used to present the data. Despite using the same manufacturing procedure, as well as the identical manufacturer's finishing and polishing protocols, CAD/CAM dental polymers revealed significant differences in surface roughness and water contact angle, and the increased values of both parameters led to an increase in biofilm formation on the surface of the materials. The CAD/CAM resin-based composite showed the lowest number of adhered microorganisms compared to CAD/CAM polymethyl methacrylate and CAD/CAM polyether ether ketone.

Effects of polishing protocols on the surface roughness and color stability of polyetheretherketone (PEEK).

This study aimed to evaluate the effects of different polishing protocols on the surface properties and color stability of the polyetheretherketone (PEEK). A total of 96 disc-shaped specimens were fabricated from PEEK material and divided into 6 different groups: control (CN), ''Abraso-Starglanz'' polishing paste (A), ''Yildiz'' polishing paste (Y), ''Enhance'' polishing system (EN), ''Super snap'' polishing kit (SS), and silicone polisher (SP). Surface roughness (Ra) were measured with a profilometer and the surface topography was examined under scanning electron microscope. Color differences were measured with a spectrophotometer according to the CIEDE2000 (∆E00) formulation before and after coffee immersion. Data were statistically analyzed with Kruskall-Wallis and Spearman's correlation analysis (p<0.05, p<0.001). A statistically significant difference was observed between the Ra measurements of the polishing protocols (p<0.001). Ra measurements except A, Y, and SS groups were found to be higher than the clinical acceptable threshold of surface roughness (0.20 μm). In ΔE00 measurements, statistically significant differences were observed between the CN and SP (p=0.041), EN (p=0.001), and A (p=0.002) polishing protocols. No correlation was found between Ra and color stability. Only in the A, Y and SS polishing protocols, Ra measurements were not found to be risky in terms of acceptable threshold of surface roughness. Polishing protocols have also generally failed to maintain the color stability. Considering the surface roughness and color stability, the ''Abraso-Starglanz'' paste may be suitable method for PEEK material.

Bacterial Adhesion on Dental Polymers as a Function of Manufacturing Techniques.

The microbiological behavior of dental polymer materials is crucial to secure the clinical success of dental restorations. Here, the manufacturing process and the machining can play a decisive role. This study investigated the bacterial adhesion on dental polymers as a function of manufacturing techniques (additive/subtractive) and different polishing protocols. Specimens were made from polyaryletherketone (PEEK, PEKK, and AKP), resin-based CAD/CAM materials (composite and PMMA), and printed methacrylate (MA)-based materials. Surface roughness (Rz; Ra) was determined using a laser scanning microscope, and SFE/contact angles were measured using the sessile drop method. After salivary pellicle formation, in vitro biofilm formation was initiated by exposing the specimens to suspensions of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Adherent bacteria were quantified using a fluorometric assay. One-way ANOVA analysis found significant influences (p < 0.001) for the individual parameters (treatment and material) and their combinations for both types of bacteria. Stronger polishing led to significantly (p < 0.001) less adhesion of S. sanguinis (Pearson correlation PC = -0.240) and S. mutans (PC = -0.206). A highly significant (p = 0.010, PC = 0.135) correlation between S. sanguinis adhesion and Rz was identified. Post hoc analysis revealed significant higher bacterial adhesion for vertically printed MA specimens compared to horizontally printed specimens. Furthermore, significant higher adhesion of S. sanguinis on pressed PEEK was revealed comparing to the other manufacturing methods (milling, injection molding, and 3D printing). The milled PAEK samples showed similar bacterial adhesion. In general, the resin-based materials, composites, and PAEKs showed different bacterial adhesion. Fabrication methods were shown to play a critical role; the pressed PEEK showed the highest initial accumulations. Horizontal DLP fabrication reduced bacterial adhesion. Roughness < 10 µm or polishing appear to be essential for reducing bacterial adhesion.

The Influence of Polishing on the Mechanical Properties of Zirconia—A Systematic Review

Purpose: To systematically review studies that investigated the consequences of various polishing protocols on the mechanical properties of zirconia. The effects on the roughness and crystalline phase transformation were also evaluated. Materials and methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) was followed. The electronic searches were conducted via OVID MEDLINE (R) and Scopus for publications between 1996 and August 2022. The search strategy was limited to full texts in the English language and in vitro studies. The influences on flexural strength, hardness, fracture strength, fracture toughness, wear resistance, roughness and phase transformation were collected. Various methodologies to measure these properties were also outlined and compared. The risk of bias for included studies was evaluated according to a modified Consolidated Standards of Reporting Trials (CONSORT) checklist. Results: After removing duplicates, the systematic search identified a total of 419 studies. Nineteen studies satisfied the inclusion criteria and were selected for final analysis. Fifteen of the included studies observed the changes in surface roughness along with the mechanical properties and ten studies detected the tetragonal (T) to monoclinic (M) phase transformation. Eight studies also investigated the change in properties after polishing the ground surface. Testing parameters were not consistent among studies due to the varying methods. Conclusions: To a certain extent, polishing influences the strength, hardness, toughness and wear resistance. The damage in some mechanical properties, as well as the roughened surface, from grinding can be restored via an appropriate polishing treatment. The polishing process itself barely induces the transition from the tetragonal to monoclinic phase of zirconia, while this commonly occurs after grinding. If the subsequent polishing is adequate, the transformed monoclinic phase can be eliminated with the removal of the outermost surface layer. In dentistry, polishing is an imperative step to maintain the superior functions and service life of zirconia for patients.

Effect of Wet and Dry Finishing and Polishing Technique on Microhardness and Flexural Strength of Nanocomposite Resins.

This in vitro study was aimed to assess the effect of wet and dry finishing and polishing techniques on the flexural strength and microhardness of different commercial nanoparticle contained composite resins. The samples were made of Z250 (microhybrid), Z350 XT (nanofilled), and Z550 (nanohybrid) resin composites. Each group was subdivided into 2 subgroups according to polishing protocols. Subgroup 1 for each composite underwent wet polishing, and subgroup 2 was subject to dry polishing technique. Flexural strength and microhardness of the samples were measured at two different times of polishing (T 0 and T 24). The flexural strength test and microhardness test were measured by a 3-point bending test using a universal testing machine, and a Vickers machine, respectively. Data were analyzed by Kolmogorov-Smirnov, two-way ANOVA, and Tukey HSD tests. ANOVA showed that the type of composite has a significant effect on flexural strength. Two-way ANOVA showed that, at T 0, flexural strength of all composites in the dry technique was higher than in the wet technique (p = 0.019). At T 24, Z350 XT had the lowest, and Z250 had the highest flexural strength in both techniques. The time and technique of polishing were also significantly effective on hardness. At T 0, hardness was higher in the wet compared to the dry method (p = 0.008). Tukey test showed that, at T 24, the hardness of Z350 XT was significantly higher than the other materials in both techniques. Immediate wet finishing and polishing presented lower flexural strength. Delayed dry/wet finishing and polishing significantly enhanced the hardness of the samples.

Surface smoothness of resin composites after polishing-A systematic review and network meta-analysis of in vitro studies.

A systematic review and network meta-analysis was performed to provide evidence for the best polishing protocol for different types of resin composites to minimize surface roughness. A search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, EMBASE, and Cochrane Library on July 2, 2019 (updated in December, 2020). In vitro studies that included at least two systems for polishing resin composites and analyzed surface roughness were included. The risk of bias was evaluated. A random-effects Bayesian-mixed treatment comparison model was used to compare surface roughness in resin composites with the different types of polishers. Surface under the cumulative ranking curve (SUCRA) analysis was performed to rank the probability for the best polishing system. After removal of duplicates, title and abstract screening yielded 34 studies. Network meta-analysis was not possible for hybrid and microhybrid composites. SUCRA analysis showed that abrasive paper discs allowed greater surface smoothness for nanohybrid and nanofill composites to a probability of between 83% and 91.6%. Silicon carbide brush had a 78.2% probability of being the best system for microfill composites. The use of abrasive paper disc polishers showed a favorable result in nanofill and nanohybrid resin composites. Silicon carbide brush has a greater chance of promoting a smoother surface for microfill resin composites.

Randomized in situ evaluation of surface polishing protocols on the caries-protective effect of resin Infiltrant

The aim of this placebo-controlled randomized in situ study was to evaluate the effect of different surface polishing protocols on enamel roughness, bacterial adhesion and caries-protective effect of a resin infiltrant. Seventy-five bovine enamel samples having artificial caries lesions were treated with a resinous infiltrant and afterwards randomly dividided into five polishing protocols: aluminum oxide flexible disks (Al2O3-Disks), silicon carbide tips (SIC-Tips), silicon carbide brush (SIC-Brush), silicon carbide polyester strips (SIC-Strips) or no polishing [negative control (NC)]. Average surface roughness (Ra) was assessed by profilometry. Samples were mounted in palatal appliances under a mesh for biofilm accumulation. Fifteen volunteers wore the intraoral appliances (14-days) and cariogenic challenge was triggered by sucrose solutions. Biofilm formed was collected for microbiological analysis of caries-related bacteria (Streptococcus mutans, Lactobacillus acidophilus) and demineralization was assessed by cross-sectional microhardness. Mean Knoop hardness numbers (Kg/mm2) were plotted over lesion depth (µm) and area under the lesion curve was subtracted from sound enamel to determine demineralization (ΔS, Kg/mm2xµm). Data were analyzed by ANOVA and post-hoc comparisons (α = 0.05). NC resulted in significantly higher Ra means than Al2O3-Disks and SIC-Strips. Bacterial counts were not significantly different between the groups (p > 0.05). Regards ΔS means, however none of the groups were significantly different to NC (6983.3 kg/mm2xµm /CI 4246.1–9720.5, p > 0.05). Conclusions: Polishing protocols (Al2O3-Disks, SIC-Strips) significantly decreseased roughness of infiltrated-enamel, however none of the polishing protocols could signicantly decrease bacterial counts nor resulted in significant less demineralization.