Can wheel polishers improve surface properties and color stability of monochromatic resin composites?

BACKGROUND: To overcome the color layering procedure, monochromatic resin composites have been introduced. However, little is known about their polishability, gloss and color stability. This study aimed to investigate the surface roughness, gloss, and color change of monochromatic resin composites polished with wheel systems after being immersed in coffee. MATERIALS AND METHODS: Omnichroma, Zenchroma, Essentia Universal, Charisma Diamond One and NeoSpectra ST were used to obtain 120-disc samples of 8 × 2 mm. Only one side of the sample was polished with Twist Dia (TWD) or Nova Twist (NOV). The samples were examined for surface roughness, gloss, and color (ΔE and ΔE00) before and after 7 days of immersion in coffee and subsequent repolishing. The discs were examined via SEM. Surface roughness and gloss values were analyzed using ANOVA, Tukey and Pearson correlation tests. ΔE and ΔE00 values were evaluated using T tests, multivariate ANOVA, and Dunnett's post-hoc tests. RESULTS: For TWD groups, the smoothest material was Omnichroma (p < 0.05), while for NOV groups, it was Omnichroma and Zenchroma. Omnichroma was the glossiest, while Charisma Diamond One was the least glossy. In TWD groups, Charisma Diamond One and Essentia Universal were the most discolored, while Zenchroma and Omnichroma were the least. For NOV groups, Essentia Universal and Charisma Diamond One were the most discolored, while NeoSpectra ST, Omnichroma and Zenchroma were the least. After repolishing, Charisma Diamond One did not reach the level of ΔE < 2, while the other groups showed values below. Color evaluation with the CIELab and CIEDE2000 systems revealed similar results for the TWD groups after post-staining. CONCLUSIONS: Smooth and glossy surfaces could be achieved with the wheel system regardless of the composite resin. Repolishing after discoloration ensures that the color recovery is below the acceptable limit. Color evaluations with CIELab and CIEDE2000 yielded similar results.

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

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

Evaluation of Colour Changes in Nanocomposite-Based Bulk-Fill and Universal Composite Using Different Polishing Systems.

PURPOSE: Resins composites are widely used in modern dentistry because of their aesthetic and physical properties. However, discoloration of anterior tooth restorations is a common complaint. Understanding the factors affecting the colour stability of resin composites can lead to longer-lasting repairs. This study aimed to evaluate and compare the colour changes of nanocomposite-based bulk-fill and universal resin composites after immersion in coffee using various polishing systems. MATERIALS AND METHODS: A total of 160 samples were prepared using four different composite groups, with 40 pieces for each combined group. Based on the finishing procedure, the samples were divided into four subgroups for each composite group. Three different polishing procedures were applied to the samples according to the manufacturer's instructions. The control group was not subjected to any treatment. Initial colour measurements were performed using a VITA Easyshade V spectrophotometer. After the initial measurements, the samples were immersed in a Nescafe coffee solution for seven days, followed by colour measurements. Data were analysed using the Kolmogorov-Smirnov test and two-way analysis of variance. Tukey's honest significant difference (HSD) test was used to determine differences between subgroups. RESULTS: The results indicate that bulk-fill resins exhibit more discolouration than universal composites; however, this difference was not statistically significant. The resin group with the smallest discolouration was Ceram X, and the most effective polishing method was Twist polishing. CONCLUSION: Final surface polishing significantly reduced the composites' discolouration. These findings support the selection of appropriate materials and polishing techniques to achieve aesthetic outcomes and colour stability in dental restorations.

Effect of immune-boosting beverage, energy beverage, hydrogen peroxide superior, polishing methods and fine-grained dental prophylaxis paste on color of CAD-CAM restorative materials.

BACKGROUND: The effect of an immune-boosting beverage (SAM) containing Sambucus Nigra, an energy beverage (ENE), an in-office bleaching (BLE) agent with 25% hydrogen peroxide superior, glazing (GLA) or polishing (POL) methods, and professional dental prophylaxis (PDP) on the color of CAD-CAM restorative materials is unknown. METHODS: In total 210 specimens were prepared, consisting of CAD-CAM feldspathic (FC), zirconia-reinforced lithium disilicate ceramic (ZLS) and hybrid ceramic (HC). The ceramic specimens were divided according to the polishing methods of glazing (GLA) and mechanical polishing (POL). All materials were divided into two groups: with and without BLE. A 25% hydrogen peroxide superior (HPS) gel was used for BLE. After the baseline (BAS) measurement, the specimens were immersed in 3 different beverages (distilled water (DIS), SAM, ENE). After 28 days, a fine-grained (RDA 7) prophylaxis paste was applied. Statistical analysis of ∆E00 color difference values was performed by 3-way ANOVA and Bonferroni test (α = 0.05). RESULTS: The effect of all other actions except material-BLE-beverage on color for BAS-Day 28 was statistically different (p < 0.05). The effect of material, material-BLE, beverage on color for Day 28-PDP was statistically different (p < 0.05). After 28 days, the lowest color change was found in FC-GLA and HC immersed in DIS (p = 0.0001) and the highest in FC-POL immersed in ENE (p = 0.0002). PDP was efficient in color recovery in HC immersed to DIS, ENE and SAM (p = 0.0010). For FC, HC and ZLS, BLE caused a higher color change (p < 0.0001). Regardless of the material, the highest color change for BLE-beverage was found in BLE-treated specimens immersed in ENE (p = 0.0496) and the lowest color change was found in non-BLE-treated specimens immersed in SAM (p = 0.0074). CONCLUSIONS: In materials pre-exposed to 25% HPS, the effect of PDP on color recovery was lower than in unexposed materials. After 28 days, mechanical polishing produced higher color change in FC than glazing, however, in ZLS effects of glazing and mechanical polishing on color were similar. For material/polishing method, HC was the most effective. ENE caused higher color change than DIS and SAM. PDP was more effective than ENE in restoring color to DIS- and SAM-immersed specimens.

A comparison of polishing systems and thermal cycling on the surface roughness and color stability of a single-shade resin composite.

PURPOSE: To evaluate the surface roughness and color stability of a single-shade composite resin after thermal cycling with different finishing and polishing systems. METHODS: A total of 91 specimens were prepared with standard molds using a single-shade resin composite Omnichroma. The specimens were randomly separated into seven groups: Control (Mylar strip only), grit (600 grit SiC abrasive paper), OneGloss, Clearfil Twist Dia, Sof-Lex Diamond Polishing System, EVE Diacomp Plus Twist, and OptiDisc. The top surface of each specimen was polished per the manufacturers' directions. After initial measurements, 10,000 and 50,000 thermal cycles were performed. After each thermal cycling, the measurements were retaken. A generalized linear model analysis was used to compare the values, and multiple comparisons were performed with the Bonferroni correction. RESULTS: Different finishing and polishing systems and thermal cycling significantly affected the surface roughness and color change of the single-shade composite resin (P< 0.001). The smoothest surfaces were obtained with the Sof-Lex Diamond Polishing System, while the group polished with Clearfil Twist Dia showed the least color change. CLINICAL SIGNIFICANCE: The surface roughness of the single-shade resin composite exhibited acceptable values for all polishing systems tested. The color change values of the single-shade resin composite were found to be above the acceptable value for all polishing systems, but the two-step spiral polishing systems performed better in terms of color stability.

Direct Composite Restorations on Permanent Teeth in the Anterior and Posterior Region - An Evidence-Based Clinical Practice Guideline - Part 2: Recommendations for Composite Processing.

PURPOSE: Part 2 of this German S3 clinical practice guideline provides recommendations for the process of manufacturing composite restorations. It covers key aspects like caries removal, field isolation, matrix and adhesive techniques, as well as light curing and polishing. The outcomes of interest include survival rates and restoration quality. MATERIALS AND METHODS: A systematic literature search was conducted by two methodologists using MEDLINE and the Cochrane Library via the OVID platform, including studies up to December 2021. Additionally, the reference lists of relevant manuscripts were manually reviewed. Six PICO questions were developed to guide the search. Consensus-based recommendations were for- mulated by a panel of dental professionals from 20 national societies and organizations based on the collected evidence and ex- pert opinion. RESULTS: The guideline advocates for one-stage selective caries removal near the pulp and underscores the effectiveness of various isolation techniques, adhesive systems, and the crucial role of light polymerization. The use of anatomically pre- formed sectional matrices and phosphoric acid etching is recommended to enhance restoration quality. Additionally, polish- ing composite restorations is advised to improve surface finish. CONCLUSION: This guideline provides comprehensive recommendations that inform clinicians on optimizing the composite restor- ation manufacturing processes. The adoption of these best practices can improve the quality and longevity of dental restorations.

Effect of polishing process on torque loss ratio and microgap of selective laser melting abutment: an in vitro study.

BACKGROUND: The purpose of this in vitro study was to investigate the effect of polishing post-treatment process on the torque loss ratio and microgap of Selective Laser Melting (SLM) abutments before and after mechanical cycling test through improving the surface roughness of the implant-abutment interface. MATERIALS AND METHODS: Forty SLM abutments were fabricated, with 20 underwent minor back-cutting, designated as polishing, in the implant-abutment interface. The abutments were divided into three groups: SLM abutments (group A), original abutments (group B), and polished SLM abutments (group C), each containing 20 abutments. Surface roughness was evaluated using a laser microscope. Implant-abutment specimens were subjected to mechanical cycling test, and disassembly torque values were measured before and after. Scanning electron microscope (SEM) was used to measure microgap after longitudinal sectioning of specimens. Correlation between surface roughness, torque loss ratio, and microgap were evaluated. LSD's test and Tamhane's T2 comparison were used to analyze the data (α = 0.05). RESULTS: The Sz value of polished SLM abutments (6.86 ± 0.64 µm) demonstrated a significant reduction compared to SLM abutments (26.52 ± 7.12 µm). The torque loss ratio of polished SLM abutments (24.16%) was significantly lower than SLM abutments (58.26%), while no statistically significant difference that original abutments (18.23%). The implant-abutment microgap of polished SLM abutments (2.38 ± 1.39 µm) was significantly lower than SLM abutments (8.69 ± 5.30 µm), and this difference was not statistically significant with original abutments (1.87 ± 0.81 µm). A significant positive correlation was identified between Sz values and the ratio of torque loss after cycling test (r = 0.903, P < 0.01), as well as Sz values and the microgap for all specimens in SLM abutments and polished SLM abutments (r = 0.800, P < 0.01). CONCLUSION: The findings of this study indicated that the polishing step of minor back-cutting can lead to a notable improvement in the roughness of SLM abutments interface, which subsequently optimized the implant-abutment fit. It can be seen that the application of minor back-cutting method has advanced the clinical use of SLM abutments.

Comparison of polishing methods for two types of monolithic all-ceramic crowns after occlusal adjustments: Polishing paste versus glazed porcelain.

This study compared the effects of two surface preparation methods on two types of zirconia. Immediately prior to the placement of a monolithic zirconia crown, its morphology may be modified using a rotary cutting instrument for occlusal adjustments. The crown surface is scratched during the grinding process and, thus, requires polishing. Simplified zirconia crowns of 3Y and 5Y were fabricated and used as specimens. The surface roughness and gloss of the occlusal surfaces of specimens were measured and compared when a polishing compound was used after polishing points and when a silica-based coating was sintered. No significant differences were observed in surface roughness between 3Y and 5Y zirconia. The use of polishing compounds was effective because polishing points alone only resulted in a level of surface roughness that may cause wear on antagonist teeth. Although the silica-based coating improved surface properties, the polishing compound more effectively improved surface roughness.

Evaluation of direct restorations for pit-and-fissure caries using stamp combined with single-shade composite resin technique: A 12-month follow-up in vivo study.

OBJECTIVES: To evaluate the clinical performance of direct restorations for pit-and-fissure caries in molars using stamp combined with single-shade composite resin (S/SCR) technique, and assess the effect of the number of stamp pressing on the trueness of S/SCR technique. METHODS: Twenty molars of fifteen patients with pit-and-fissure caries but with an intact or micro-cavitated occlusal morphology were restored using S/SCR technique and were randomly divided into single pressing group (n = 10) and double pressing group (n = 10). Intraoral scans were obtained before treatment (scan 1), after filling (scan 2) and after polishing (scan 3). Deviation distribution maps of pairwise fitting were created including comparison 1 (scan1/scan 2), comparison 2 (scan1/scan 3), and comparison 3 (scan2/scan 3) using Geomagic Control X software. Root mean square (RMS) values were calculated to evaluate the trueness of restorations. Clinical performances including esthetic, functional, and biological properties of all restorations were evaluated according to FDI criteria after a 12-month follow-up. Analysis of variance, independent-samples T test and Wilcoxon rank-sum test were used for statistical analysis (α=0.05). RESULTS: RMS values for comparison 1, comparison 2, and comparison 3 were 0.1243 ± 0.0151, 0.0966 ± 0.0136, and 0.0605 ± 0.0137 mm in single pressing group, while 0.0831 ± 0.0140, 0.0741 ± 0.0107, and 0.0475 ± 0.0099 mm in double pressing group, respectively. RMS value of single pressing group was higher than that of double pressing group in the same comparison (p ≤ 0.001). No statistically significant differences were observed between the two groups regarding esthetic, functional and biological properties (p > 0.05). For all properties, all restorations scored within 3, with over 80% scoring 1. CONCLUSION: S/SCR technique presents satisfying clinical performances for pit-and-fissure caries in molars after a 12-month follow-up. Besides, double pressing can improve the trueness of restorations compared to single pressing. CLINICAL SIGNIFICANCE: S/SCR technique is efficient in direct composite resin restoration for pit-and-fissure caries, with satisfying esthetic, functional and biological properties after a 12-month follow-up. Significantly, double pressing improves the trueness of S/SCR technique, reducing the need for occlusion adjustment.

Flowable bulk-fill versus layering restorative material on Class II restorations: A randomized clinical trial.

OBJECTIVE: This study evaluated the clinical performance of Class II restorations made with flowable bulk-fill base versus conventional layering ORMOCER-based restorative material in a split-mouth randomized clinical trial. METHODS: Thirty patients received two class II restorations (n = 60) performed with different strategies. All preparations received the application of the universal self-etching adhesive system according to the manufacturer's recommendation, followed by the placement of a sectional matrix, wooden wedge, and separation ring. The first restoration was performed using 4 mm of flowable bulk-fill material covered by 2 mm of conventional viscosity restorative material (Bulk-fill technique). The second restoration was performed only with the conventional viscosity material, with a maximum of 2 mm thick increments, up to fill the cavity (Layering technique). After occlusal adjustment, the same polishing system was used for all restorations. Evaluations using the FDI criteria were conducted after 7 days, 12, and 24 months. Data were analyzed with the Fisher's Exact test (α=0.05). RESULTS: From 30 participants, 24 attended the 24-month recall, and 48 restorations were evaluated. All restorations received acceptable overall scores for esthetic and biological properties after this period, while only 6.66 % of the restorations exhibited unacceptable overall scores for the functional properties in both groups. No significant differences between the tested restorative materials and techniques were found for each FDI criterion assessed. The success rate after 2 years was 93.33 % for both groups. CONCLUSION: Both restorative materials exhibited good clinical performance for the parameters analyzed with no differences between them after 24-month follow-up. CLINICAL RELEVANCE: Flowable bulk-fill ORMOCER-based material is a suitable alternative for direct Class II restorations, providing good clinical outcomes and simplifying the restorative procedure. CLINICAL TRIAL REGISTRATION NUMBER: RBR-6mvp9w.

Influence of sandblasting and bonding on the shear bond strength between differently pigmented polyetheretherketone (PEEK) and veneering composite after artificial aging.

OBJECTIVE: Achieving a strong bond between Polyetheretherketone (PEEK) and veneering composites is challenging due to PEEKs low surface energy. This study examined the effects of sandblasting and bonding on the shear bond strength (SBS) between veneering composite and pigmented PEEK, considering artificial aging. METHODS: Of three pigmented PEEK compounds (DC4420R, DC4450R, DC4470R; Evonic Operations GmbH, Marl, Germany), 40 specimens each were milled and polished up to 2500 grit. Prior to veneering, specimens were divided into 4 subgroups: Subgroup 1: Polishing; 2: Polishing + bonding; 3: Sandblasting; 4: Sandblasting + bonding. Sandblasting was performed using Al2O3. Adhesive was an agent containing MMA (Signum Universal Bond, Kulzer GmbH, Hanau, Germany). After veneering (Composite, Kulzer GmbH) the subgroups were divided into 2 subgroups. One subgroup was immersed in 37 °C warm distilled water for 24 h. The second subgroup was artificially aged by thermocycling (TCL) with 5000 cycles in distilled water (5 °C / 55 °C; 30 s). Surface roughness, water contact angles and failure modes were recorded. SBS was measured using a universal testing machine. RESULTS: Results demonstrated that the combination of sandblasting and bonding significantly improved the SBS compared to polishing alone. PEEK color did not significantly influence the SBS. Aging by TCL had a negative effect on the SBS. SIGNIFICANCE: Sandblasting and the use of an adhesive containing MMA were found to be effective in achieving satisfactory SBS between veneering composite and pigmented PEEK surfaces. These pretreatment methods demonstrate their potential for establishing durable and reliable bonding in clinical applications.

Evaluation of wear resistance and surface properties of additively manufactured restorative dental materials.

OBJECTIVES: To evaluate the wear resistance of three additively manufactured dental crown materials (NextDent C&B MFH, Saremco print CROWNTEC and Bego VarseoSmile Crown) under two environmental conditions (dry and artificial saliva), two loads (49 N and 70 N) and two surface treatments (polished and glazed). METHODS: A total of 120 specimens were divided into 24 groups and tested for wear under two loads (49 N and 70 N), surface treatment (polished or glazed), and environment (dry or submerged in artificial saliva). All samples underwent reciprocating wear testing at 1 Hz using a wear simulator, replicating 48 months of In Vivo conditions with a stainless-steel ball as the antagonist. The coefficient of friction (CoF), surface roughness, volumetric and vertical wear loss were measured and statistically analysed. Confocal microscopy assessed the surface properties of crown materials and the antagonists. RESULTS: The NextDent material demonstrated the most homogenous wear, with relatively low vertical and volumetric loss across all groups (p < 0.004). NextDent and Bego materials performed similarly in artificial saliva regardless of the load type (p > 1.000). The CoF remained below 0.3 for all groups. All groups exhibited significant increases in surface roughness after testing, however, this did not correlate with an increase in the CoF. Confocal analysis revealed material deformities due to load and notable scratch marks on the stainless-steel antagonists. CONCLUSION: It was found that all investigated addtively manufactured materials can be suggested for provisional use. Both vertical loss and volumetric loss results should be included for material evaluation. CoF and surface roughness should be implemented into wear evaluation. CLINICAL SIGNIFICANCE: This study highlights the practical value of additively manufactured dental crown materials, particularly for provisional restorations. However, their extended use requires careful consideration of individual patient needs, emphasising the need for judicious clinical application evaluation.

Does dental material type influence bacterial adhesion under the same polishing conditions? Direct observation using a fluorescent staining technique: An in vitro study.

Highly polished 3, 4, and 5 mol% yttria-stabilized zirconia and CAD/CAM composite resin samples were prepared, and the influence of surface roughness (Ra and Sa, 21 areas/group), wettability (contact angle and surface energy, 3 samples/group), and surface chemical composition (2 samples/group) on single-strain bacterial adhesion models (Porphyromonas gingivalis, Streptococcus oralis, Streptococcus sanguinis, Streptococcus gordonii, and Streptococcus mutans) were compared via fluorescent staining with graphical analysis (21 areas/group). Statistical analysis was performed using the Shapiro-Wilk test followed by one-way analysis of variance with Tukey's test or the Kruskal-Wallis test with Dunn's test (α=0.05) and linear regression. For dental zirconia with the same surface roughness, the yttria content did not significantly influence the initial bacterial adhesion. However, higher bacterial adhesion was detected for the composite resin owing to its high C, O, and Si contents. There was no correlation between surface energy and bacterial adhesion for any bacterial strain (p<0.005).

Effect of different polishing methods on roughness and color stability of air-abraded restorative materials after artificial accelerated aging.

PURPOSE: To evaluate the effect of air abrasion and polishing procedures on roughness and color stability of ceramic and composite materials after artificial accelerated aging. METHODS: In this study, six restorative materials were tested: feldspathic ceramic (CEREC Blocks), glass ceramic (IPS e.max CAD), resin-based hybrid ceramic (Cerasmart), microhybrid composite (Charisma Classic), nanohybrid composite (Charisma Diamond) and nanoceramic composite (CeramXOne). Forty square-shaped composite specimens were fabricated from each composite and CAD-CAM ceramic material. Initial surface roughness measurements were performed using a profilometer and color measurements of each specimen with a spectrophotometer. Ten control specimens for each group did not receive air abrasion. The other specimens were treated by an air abrasion device and then were randomly divided into three subgroups of 10 specimens (n= 10). After air abrasion, 10 specimens of each group did not receive polishing (Air abrasion group) and others were repolished with Sof-Lex kit (Sof-Lex group) or a rubber kit (Rubber group). Surface roughness and color measurements were repeated before and after 300 hours of artificial accelerated aging (AAA). The univariate test and then three-way ANOVA and two-way ANOVA were performed for comparison of groups (α= 0.05). RESULTS: The univariate statistical analysis revealed that the restorative materials were differently affected after air abrasion, polishing methods and AAA (P< 0.001). Three-way ANOVA showed that the surface roughness of the restorative materials increased after air abrasion and AAA (P< 0.001). Two-way ANOVA showed statistically significant differences between color changes of ceramic (CEREC and IPS e.max CAD) and composite based restorative materials (P< 0.001). CLINICAL SIGNIFICANCE: Clinicians should be aware that air abrasion at a specified power and time significantly changes the surface roughness of the materials except for CEREC. Additionally, polishing procedures (Sof-Lex, Rubber) did not significantly reduce the surface roughness of the ceramic groups. After air abrasion, depending on the material type used clinically, restorations should be repolished to reduce roughness and ensure color stability.

Comparison of surface properties of universal shade and conventional resin-based composites after degradation and repolishing.

PURPOSE: To investigate the discoloration, line roughness and gloss of conventional and universal shade resin-based composites. METHODS: Clearfil AP-X (AP-X) and Estelite Sigma Quick (EQ) samples were prepared. Discoloration, roughness, and gloss were measured on mirror-polished, alkaline-degraded, and repolished surfaces. The superficial layer degraded by alkaline immersion (degraded layer) was ground off from the sample surface. After removing the degraded layer, the surface was polished with aluminum oxide powder (1.0 µm and 0.3 µm), to create a repolished specimen. Scanning electron microscopy observations were made of the specimens. RESULTS: The results were compared with those for Omnichroma (OC) from a previous study. All the materials showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials. CLINICAL SIGNIFICANCE: The materials tested showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials.

Effects of different polishing procedures on the color stability of recent resin composites.

PURPOSE: To evaluate different polishing methods' effects on the color stability of recent resin composites. METHODS: 160 samples for color stability evaluation and 40 samples for the degree of conversion evaluation were prepared with four different resin composites [Harmonize (H), Filtek Universal (F), Omnichroma (O), Essentia Universal (E)] and light cured. For color stability evaluation, samples prepared from each resin composite were divided into four groups: three polishing procedures and a control group. The ΔE00 was calculated between initial, and after immersion in coffee solution for 12 days. The degree of conversion was evaluated with Fourier Transform Infrared Spectroscopy. The statistical analysis of ΔE00 values was made with the two-way ANOVA, Tukey HSD, and Tamhane's T2 tests. One-way ANOVA and Tukey HSD tests were used to compare the degree of conversion values (P< 0.05). RESULTS: In all composite groups, mylar (control) groups had the highest ΔE00, and no differences between other polishing procedures. According to the polishing procedures, Omnichroma showed the highest ΔE00 values (on mylar groups O vs F, P< 0.001; O vs H, P< 0.001; O vs E, P< 0.001). There was a significant difference between the composite groups in terms of the degree of monomer conversion (P< 0.05). Omnichroma showed, significantly, the highest discoloration. CLINICAL SIGNIFICANCE: Different polishing procedures showed effective performance on current composite surfaces. Omnichroma resin composite showed higher color change than composites with similar properties.

In vitro study on the impact of various polishing systems and coffee staining on the color stability of bleach-shaded resin composite.

OBJECTIVE: To evaluate the effects of different polishing techniques and coffee staining on the color stability of four commercially available bleach-shade composite resins, namely microhybrid, nanohybrid, nanofilled, and injectable nanohybrids. MATERIAL AND METHODS: A total of 224 discs (8 mm diameter and 2 mm thickness) were fabricated from four different bleach-shade composite resins, namely microhybrid (Gradia Direct Anterior), nanohybrid (Palfique LX5), nanofilled (Filtek Universal), and injectable nanohybrid (flowable G-aenial universal injectable). The composite resin groups were polished via four techniques: no polishing, 4-step polishing using aluminum oxide discs, 3-step polishing using silicon rubber diamond discs, and one-step polishing. Half of each group was immersed in water, while the other half was immersed in coffee for 12 days (n = 7). Colors were measured using a clinical spectrophotometer, and color differences were calculated (ΔE). The results were analyzed statistically. RESULTS: The alterations in color were significantly influenced by the techniques employed for finishing and polishing techniques, composite resin type, and degree of coffee staining. Regardless of the polishing technique and storage medium, different material types showed a significant color change (ΔE) at P < 0.001. Filtek exhibited the most significant color change, followed by Gradia and Palfique, with no significant differences between them. In addition, Different polishing techniques resulted in significant color changes (P < 0.001). The highest degree of color change was seen in the no-polishing group, followed by the 4-step and 1-step polishing groups, with negligible differences between each other. Also, Storage media had a significant effect on ΔE values. CONCLUSION: Appropriate finishing and polishing procedures can improve the color stability of bleach-shaded composite resins. Coffee has a deleterious effect on color; however, injectable flowable nanohybrid composites are more resistant to staining.

Polishing methods for composites restoration: the influence on human gingival fibroblasts behaviour.

BACKGROUND: Carious/Non-carious cervical lesions with gingival recessions may require both dental and periodontal reconstructive therapy, where flaps/grafts may be placed in contact with a dental filling material. Human Gingival Fibroblasts (HGF-1) response during the early phase of healing could vary according to the procedures employed to cure the dental composite. Moreover, oxygen diffusion into dental composite inhibits the polymerization reaction, creating an oxygen-inhibited layer (OIL) that presents residual unreacted monomers. The aim of this study was to assess the effect of different polishing techniques and OIL on HGF-1. METHODS: Composite discs polished with different techniques (diamond rubber, abrasive discs and tungsten carbide burr) were used. An additional not polished smooth group obtained with and without OIL was used as control. Samples were physically characterized through the analysis of their hydrophilicity and surface topography through contact angle measurement and SEM, respectively; afterwards the biologic response of HGF-1 when cultured on the different substrates was analyzed in terms of cytotoxicity and gene expression. RESULTS: The finishing systems caused alterations to the wettability, even if without a proportional relation towards the results of the proliferation essay, from which emerges a greater proliferation on surfaces polished with one-step diamond rubber and with abrasive discs as well as a direct effect of the glycerin layer, confirming that surface roughness can heavily influence the biological response of HGF-1. CONCLUSIONS: Surfaces wettability as well as cellular behavior seem to be affected by the selection of the finishing system used to lastly shape the restoration. Especially, the presence of OIL act as a negative factor in the regards of human gingival fibroblasts. The present study may provide the first clinical instruction regarding the best polishing system of composite material when the restoration is placed directly in contact with soft tissue cells. Understanding HGF-1 behavior can help identifying the polishing treatment for direct restoration of carious/non-carious cervical lesions associated with gingival recessions.

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

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

Effect of rotation frequency of polishing discs on the surface roughness of resin composite material.

The aim of this study was to evaluate the effect of rotation frequency (rpm) of different polishing discs on the surface roughness of a nanohybrid resin composite material. 126 specimens were prepared in metal molds of 10 mm diameter and 2 mm depth using a nanohybrid resin composite material. The prepared specimens were kept in distilled water for 24 hours. Polishing treatments at 5k, 10k, 15k, and 20k rpm were applied to the nanohybrid resin composite material by grouping different brand polishing discs: Sof-Lex Contouring and Polishing Discs (3M Espe, USA) (3M Group), Optidisc (Kerr Corporation, USA) (Kerr Group), Super-Snap Rainbow Technique Kit (Shofu Dental, Japan) (Shofu Group), Finishing Disc (Bisco Dental, USA) (Bisco Group). The surface roughness was evaluated at three different points by atomic force microscopy for all specimens and scanning electron microscopy was used for visual assessment. Data were evaluated by Two Way ANOVA and Tukey's HSD Test. The mean surface roughness (Ra, µm) of all prepared samples showed significant differences (α = 0.05). According to Two-Way ANOVA, there is a statistically significant relationship between the rpm values and the discs. The 3M group showed the highest roughness value at all rpm speeds. Shofu group at 15k, 20k rpm, Bisco group at 10k, 15k, 20k rpm, the Kerr group at 15k, 20k rpm showed the lowest roughness value and had roughness close to the surfaces finished with a mylar strip. The smoothest surfaces were obtained at 15k rpm, even though polishing discs from different brands were used. It was also observed that 5k and 20k rpm polishing speeds can increase the surface roughness of the nanohybrid resin composite material.