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.

Salivary, acidic and enzymatic degradation of resin composite subjected to different finishing and polishing systems.

PURPOSE: To evaluate the effect of different finishing and polishing systems on the surface roughness of a resin composite subjected to simulated saliva-, acid-, and enzyme-induced degradation. METHODS: 160 specimens (n= 40) were fabricated with Filtek Z350 XT nanofilled composite and analyzed for average surface roughness (Ra). The specimens were finished and polished using: AD - Al2O3-impreginated rubberized discs (medium, fine, and superfine grit, Sof-Lex); SD - silicon carbide and Al2O3-impregnated rubberized discs (coarse, medium and fine grit, Jiffy,); MB - 12- and 30-multiblade burs. The control group (CT) (n= 40) comprised specimens with a Mylar-strip-created surface. Specimens from each group were immersed in 1 mL of one of the degradation methods (n= 10): artificial saliva (ArS: pH 6.75), cariogenic challenge (CaC: pH 4.3), erosive challenge (ErC: 0.05M citric acid, pH 2.3) or enzymatic challenge (EzC: artificial saliva with 700 µg/mL of albumin, pH 6.75). The immersion period simulated a time frame of 180 days. Ra measurements were also performed at the post-polishing and post-degradation time points. The data were evaluated by three-way ANOVA for repeated measures and the Tukey tests. RESULTS: There was significant interaction between the finishing/polishing system and the degradation method (P= 0.001). AD presented the greatest smoothness, followed by SD. After degradation, CT, AD and SD groups became significantly rougher, but not the MB group, which presented no difference in roughness before or after degradation. CT and AD groups showed greater roughness in CaC, ErC and EzC than in ArS. The SD group showed no difference in roughness when the specimens were polished with CaC, EzC or ArS, but those treated with ErC had greater roughness. In the MB group, the lower roughness values were found after using CaC and EzC, while the higher values were found using ErC or ArS. CLINICAL SIGNIFICANCE: As far as degradation resistance of nanofilled composite to hydrolysis, bacterial and dietary acids and enzymatic reactions is concerned, restorations that had been finished and polished with Al2O3-impregnated discs had the smoothest surfaces.

Effect of toothbrushing with conventional and whitening dentifrices on monolithic zirconia after finishing procedures.

PURPOSE: To evaluate the effect of toothbrushing with conventional and whitening dentifrices on the color difference (ΔE00), gloss (Δgloss), and surface roughness (SR) of stained stabilized zirconia with 5 mol% of yttrium oxide (5Y-TZP) after polishing or glazing. METHODS: Specimens were divided into four groups (n=20): C (control), S (staining), SG (staining and glazing) and SP (staining and polishing). 50,000 toothbrushing cycles were performed with conventional (n=10) and whitening (n= 10) dentifrice slurries. The ΔE00 and Δgloss were measured using a spectrophotometer and CIEDE2000 system while SR was measured by laser confocal microscope. The ΔE00 and Δgloss data were analyzed using 2-way ANOVA, and SR data were analyzed using the linear repeated measures model, with Bonferroni's complementary test (α= 0.05). RESULTS: The ΔE00 values were beyond the acceptability threshold and no differences were found among the groups. There was no difference among groups to Δgloss after toothbrushing with conventional dentifrice while SP presented the highest values of Δgloss after toothbrushing with whitening dentifrice. Conventional dentifrice decreased the SR of stained groups and whitening dentifrice decreased SR of S and SG. The toothbrushing with conventional and whitening dentifrices promoted color difference, but did not impair gloss and surface roughness of stained 5Y-TZP. CLINICAL SIGNIFICANCE: Monolithic zirconia has been routinely used for esthetic restorations, however the type of finishing procedures that is carried out on it must be taken into consideration, in addition to the fact that brushing can influence the color difference of the material as well as interfere with surface roughness and gloss.

In-vitro biofilm removal from TiUnite® implant surface with an air polishing and two different plasma devices.

BACKGROUND: We investigated the efficacy of two different cold atmospheric pressure jet plasma devices (CAP09 and CAPmed) and an air polishing device with glycine powder (AP) either applied as monotherapies or combined therapies (AP + CAP09; AP + CAPmed), in microbial biofilm removal from discs with anodised titanium surface. METHODS: Discs covered with 7-day-old microbial biofilm were treated either with CAP09, CAPmed, AP, AP + CAP09 or AP + CAPmed and compared with negative and positive controls. Biofilm removal was assessed with flourescence and electron microscopy immediately after treatment and after 5 days of reincubation of the treated discs. RESULTS: Treatment with CAP09 or CAPmed did not lead to an effective biofilm removal, whereas treatment with AP detached the complete biofilm, which however regrew to baseline magnitude after 5 days of reincubation. Both combination therapies (AP + CAP09 and AP + CAPmed) achieved a complete biofilm removal immediately after cleaning. However, biofilm regrew after 5 days on 50% of the discs treated with the combination therapy. CONCLUSION: AP treatment alone can remove gross biofilm immediately from anodised titanium surfaces. However, it did not impede regrowth after 5 days, because microorganisms were probably hidden in holes and troughs, from which they could regrow, and which were inaccessible to AP. The combination of AP and plasma treatment probably removed or inactivated microorganisms also from these hard to access spots. These results were independent of the choice of plasma device.

Enamel surface roughness following debonding resin clean up using high speed air-turbine and electric handpieces. In vitro study.

BACKGROUND: High speed electric handpieces have recently been growing in popularity among dental professionals. Advantages include smoother surface preparation and increased cutting efficiency. AIM: The primary objective was to compare enamel surface roughness following resin cleanup after bracket debonding using highspeed air turbine versus electric handpiece. The secondary objective was to record the time needed for resin-clean up. METHOD: Forty deidentified freshly extracted human premolars were cleaned and sectioned at the cement-enamel junction. The crowns were embedded in acrylic blocks. Enamel surface roughness parameters (Ra, Rz, Rp and Rv) were measured using a stylus profilometer. Brackets were bonded using a light-cure orthodontic adhesive and stored in distilled water for 24 h. Following bracket debonding, the specimens were randomly divided into 2 groups: First group: resin clean-up was carried out using a 12-fluted carbide bur mounted on a high-speed air turbine; and second group: where an electric handpiece was used. Surface roughness parameters were measured following resin clean up and after polishing using pumice and a rubber cup. Time needed for resin clean-up was recorded. Differences in enamel surface roughness and time between groups were compared using repeated measures ANOVA and independent samples t-test, respectively at P ≤ 0.05. RESULTS: The electric handpiece groups showed significantly higher values for Ra, Rz and Rp both following resin cleanup and polishing. Time taken for resin cleanup was significantly longer for the electric handpiece group. CONCLUSION: Considering both surface roughness and time, electric handpiece do not seem to add greater effectiveness or efficiency to resin cleanup following orthodontic bracket debonding.

Comparative effects of glazing versus polishing on mechanical, optical, and surface properties of zirconia ceramics with different translucencies.

OBJECTIVES: This study compared the effects of glazing versus polishing on mechanical, optical, and surface properties of zirconia ceramics with different translucencies. MATERIALS AND METHODS: In this in vitro study, 120 bar-shaped specimens (25 × 4 × 1.2 mm) were fabricated from three different types of zirconia with different translucencies (n = 40, DD Bio ZW, ZX2, and Cube X2). After sintering, each zirconia group was randomly divided into five subgroups of control (glazing), glazing + bur abrasion, glazing + bur abrasion + polishing with EVE Diacera® kit, glazing + bur abrasion + reglazing, and glazing + bur abrasion + polishing with EVE Diacera® kit + reglazing. The specimens underwent surface roughness, hardness, flexural strength, and translucency tests, as well as X-ray diffraction (XRD) and scanning electron microscopy (SEM) for assessment of surface topography. Data were analyzed by one-way analysis of variance, Tukey test, and Pearson test (α = .05). RESULTS: Flexural strength, surface hardness, and translucency were significantly correlated with zirconia type. ZW zirconia had significantly higher flexural strength and surface hardness and significantly lower translucency than Cube X2 and ZX2 (p < .001). Surface roughness had no significant correlation with zirconia type (p = .274). Polishing created the smoothest, and bur abrasion created the roughest surface (p < .001). Flexural strength and hardness in most experimental groups were significantly lower than in the control group (p < .001). Translucency was not significantly different in bur abrasion and polishing groups, compared with the control group; however, reglazing significantly increased the translucency (p < .001). SEM micrographs confirmed the surface roughness results. XRD showed monoclinic phase only in reglazed groups. CONCLUSION: Of different surface treatments, polishing improved the surface properties and caused the smallest change in mechanical properties of zirconia with different translucencies.

Effects of Coloring Liquid Dipping Time and Surface Finishing Procedures on the Optical Properties of Monolithic Zirconia.

BACKGROUND: Monolithic zirconia restorations can be produced from self-colored or uncolored blocks. The coloring procedure of uncolored blocks and surface treatments may affect the appearance of the restoration. AIM: The purpose of this study is to evaluate the effect of liquid coloring and surface treatments on optical properties of translucent monolithic zirconia. METHODS: All specimens were cut from zirconia blocks with a thickness of 1 mm. Specimens were dipped in the coloring liquids for 3 min, 5 min, and 7 min and then divided into groups of 10 specimens for surface treatments. Glaze and mechanical polishing were applied, and the color of the specimens was measured under the D65 lighting condition with a spectrophotometer device. Color values obtained from the CIE Lab formula and the translucency parameter (TP), opalescence parameter (OP), and contrast ratio (CR) were calculated. The normality of the data was confirmed with the Shapiro-Wilk test. A three-way analysis of variance (ANOVA) was used to assess the effect of dipping time, liquid shade, and surface treatments. RESULTS: The effect of liquid shade and dipping time on the TP, OP, and CR parameters were statistically significant, and the TP values were reduced with the application of coloring liquid. Mechanical polishing groups had higher OP values and lower TP values than glazed groups. CONCLUSION: In cases where high translucency is required, it may be advisable to use self-colored blocks and apply glaze as a surface treatment to achieve the desired optical properties.

Influence of airborne particle abrasion on dentin bonding effectiveness of a 2-step universal adhesive.

OBJECTIVE: To determine the effect of airborne particle abrasion (APA) on micro-tensile bond strength (µTBS) to dentin using different air-abrasion/polishing powders. METHODS: The bonding effectiveness of G2 Bond Universal (G2B), used in etch-and-rinse (E&R) and self-etch mode (SE), was tested on bur-cut dentin and dentin air abraded/polished using six different powders (aluminum oxide 29 µm (AO29) and 53 µm (AO53), aluminum trihydroxide (AT), sodium bicarbonate (SB), sodium bicarbonate soft (SBsoft) and bioactive glass (BG); Velopex). Adhesive-composite resin specimens were immersed in distilled water at 37 °C for one week and cut into microspecimens. Half of the specimens were subjected to 50,000 thermocycles (aged). Immediate and aged µTBS to dentin were measured. Statistical analysis was performed using linear mixed-effects (LME) modeling (p < 0.05). RESULTS: Comparing the aged bond strengths to air-abraded/polished dentin with bur-cut dentin, pretreatment with SB and SBsoft in combination with G2B used in E&R mode, and BG air polishing in combination with both application modes (E&R, SE), resulted in a significantly higher bond strength. Dentin bond strength was only significantly lower when air abraded with AO29 and using G2B in SE mode. Aging did not significantly influence bond strength for both application modes (E&R, SE), except for AO29 and AT-treated dentin, where bond strengths decrea sed significantly using G2B in SE mode. In general, G2B reached significantly higher bond strengths on air-abraded/polished dentin in E&R mode than in SE mode. CONCLUSION: Air-abrasion/polishing did not impair dentin bond strength using G2B, except when dentin was air abraded with AO29 and using G2B in SE mode. Air polishing positively influenced the bond strength to dentin in specific groups. CLINICAL SIGNIFICANCE: APA is safe concerning bonding to dentin. The E&R application mode is preferred using G2B as adhesive on air-abraded/polished dentin. Air polishing with BG positively influenced dentin bond strength for both application methods.

Treatment of peri-implant mucositis: Adjunctive effect of glycine powder air polishing to professional mechanical biofilm removal. 12 months randomized clinical study.

INTRODUCTION: To evaluate the adjunctive effect of glycine-powder air-polishing (GPAP) to full-mouth ultrasonic debridement (Fm-UD) in the treatment of peri-implant mucositis, and to determine the impact of implant and patient-level variables for disease resolution. METHODS: Individuals with a diagnosis of peri-implant mucositis were consecutively included in this randomized parallel arm clinical study. All the participants received a session of Fm-UD. Only implants allocated to the test group were additionally treated with GPAP. Clinical assessments were recorded at baseline, at 3 and at 12 months following intervention. The primary outcomes were complete disease resolution (DR1), defined as absence of bleeding sites at probing per implants, and partial disease resolution (DR2), measured as the presence of less than two bleeding sites at probing per implant. A final logistic multivariate regression model was built to evaluate the predictive role of implant and patient-level variables on DR. RESULTS: Fifty two patients and 157 implants were included. Both groups displayed significant reduction in the extent of bleeding on probing and plaque levels. At 12 months, DR1 was achieved in 16% and 27% of participants for the test and the control group respectively. IDR1 was best predicted by the number of bleeding sites (OR = 2.7, p = 0.04) and the greatest PPD value (OR = 2.7, p = 0.05), while IDR2 by the prosthetic connection (OR = 2.59, p = 0.02), the mean PPD (OR = 2.23, p = 0.04), the FMBS (OR = 4.09, p = 0.04), and number of implants (OR = 4.59, p = 0.02). CONCLUSIONS: Despite significant improvements of clinical signs of peri-implant inflammation, the use of GPAP appears to have no adjunctive effect as compared with Fm-UD alone in the achievement of DR. Elevated initial levels of bleeding and PD predicted inferior likelihood of reaching disease resolution. The present randomized parallel arm clinical study was registered on Clinicaltrials.gov and received the following registration number: NCT05801315. This clinical trial was not registered prior to participant recruitment and randomization (https://register. CLINICALTRIALS: gov/prs/app/action/SelectProtocol?sid=S0009965&selectaction=Edit&uid=U0004FXM&ts=2&cx=fje7l8).

Effect of dry and wet finishing and polishing on color change and opacity of nanofill and nanohybrid composites.

BACKGROUND: As superior esthetic is one of the main reasons for using composite resins, it is very important to be familiar with factors and techniques affecting their optical properties and appearance. AIM: The aim of this study was comparing the effect of finishing and polishing with and without water coolant, on the color change and opacity of composite resin materials. METHODS: Composites used for preparing samples were Z250 (microhybrid), Z350XT (nanofilled), and Z550 (nanohybrid). Then divided into 4 groups of 5 depending on finishing and polishing technique (dry or wet) and time (immediate and after twenty-four hours). After polishing, samples were assessed using a spectrophotometer. Color change and opacity were determined. Data was analyzed using Kolmogorov-Smirnov, ANOVA and Tukey HSD tests. RESULTS: Type of material at both time had a significant effect on ΔE and opacity. Our results in dry and wet technique immediately(T0) showed that the highest and lowest ΔE and opacity belong to Z350XT (p < 0.001). After Twenty-four hours (T24), opacity of Z250 in wet condition was higher than dry condition (p < 0.001). CONCLUSIONS: Wet or dry technique was only effective on color in immediate polishing. Regarding opacity, technique was only effective in case of delayed polishing.

Impact of air-polishing using erythritol on surface roughness and substance loss in dental hard tissue: An ex vivo study.

This ex vivo study aimed to investigate surface roughness and substance loss after treatment with different professional cleaning methods and to determine whether subsequent polishing with a rubber cup and polishing paste is necessary. Samples (flat and natural surfaces) of human enamel and dentin were prepared (baseline) and treated with either a curette, air-polishing with erythritol, a rubber cup and polishing paste, or a combination thereof (treatment). Subsequently, all samples were immersed in an ultrasonic bath (ultrasonic) to remove residues from the treatment procedures. The surface roughness values sRa and sRz as well as tissue loss were measured profilometrically. Linear regression models were used to compare group differences (roughness and loss) considering the corresponding baseline value. The significance level was set at p<0.05. sRa increased significantly after treatment with curettes or air-polishing with erythritol in both enamel (p<0.001) and dentin (p<0.001) of flat samples. The same effect was observed for sRz in dentin (p<0.001) but not for enamel compared to negative control. Polishing with a rubber cup and paste alone had no significant effect on roughness values. When combined with other treatments, the effect of curette or air-polishing with erythritol dominated the effect. In enamel, none of the tested methods led to measurable tissue loss. In dentin, air-polishing with erythritol caused ≤50% tissue loss compared to the curette. Conclusively, for enamel, treatment effects on roughness were measurable but of limited clinical relevance. For dentin, air-polishing resulted in a smaller but insignificant roughness increase and less tissue loss compared to the curette. Polishing with a rubber cup and paste did not affect surface roughness. Regarding the clinical application, the use of air-polishing seems to be a less invasive procedure than using a curette; polishing with rubber cup and paste offers no advantage in terms of reducing roughness as a final procedure.

Antimicrobial Activity of Glycine Air Polishing: A Clinical Split- Mouth Study on Full-Arch Implant-Supported Rehabilitations.

PURPOSE: To investigate the possible antimicrobial activity of glycine air polishing by comparing peri-implant microbiota before and after treatment. MATERIALS AND METHODS: A total of 15 patients who received implant-supported full-arch fixed rehabilitations were included. After prosthesis removal (T0), Plaque Index (PI), probing depth (PD), and bleeding on probing (BOP) were recorded. In each hemiarch, the implant with the highest PD score was selected for microbiologic sample collection from the peri-implant sulcus (T0). All patients received two different hygienic protocols (randomly administered, one per each hemiarch): glycine air-polishing (G) and cleansing with cotton pellets soaked in saline (C). At 7 days (T1) and 3 months (T2) after the intervention, PI and BOP were recorded, and new microbiologic samples were taken. Traditional polymerase chain reaction (PCR) and quantitative PCR real-time were employed for microbiologic analysis to investigate how the presence of different bacterial species varied according to the hygienic treatment performed. RESULTS: Treatment G provided a significantly higher PI score reduction around implants compared to treatment C (P = .015). No statistical difference was found in the microbial population around G and C implant sites, with Tannerella forsythia being the most commonly detected bacterial species in both G and C groups. No statistical differences were found between the antimicrobial activity of treatments C and G. CONCLUSIONS: Glycine powder air polishing is a valid method for professional hygienic care of implants and was more effective in PI reduction compared to the control treatment. However, its antimicrobial efficacy cannot be confirmed by the outcomes of the present study.

Caracterização óptica e mecânica pós desgaste de zircônias monolíticas translúcidas / Optical and mechanical post-wear characterization of translucent monolithic zirconia

Objetivos: O estudo avaliou, para quatro diferentes zircônias monolíticas translúcidas, o efeito da microestrutura e do estado da superfície (glazeada versus polida após simulação de ajuste oclusal) nas seguintes respostas: (1) propriedades mecânicas (resistência a flexão biaxial, tenacidade à fratura e dureza Vickers; (2) molhamento de superfície a partir da verificação do ângulo de contato; (3) perda de volume e rugosidade superficial após ensaio de desgaste e (4) parâmetros de translucidez. Materiais e métodos: quatro diferentes blocos de zircônias translúcidas foram utilizadas nesse estudo; Prettau anterior, Lava Plus, Cercon hT e Cercon xT. Foram confeccionados 112 espécimes em formato de disco para cada material, tendo sido todos eles glazeados e parte dos espécimes foram ajustados superficialmente com o uso de pontas diamantadas (simulação de ajuste oclusal) e posteriormente polidos com o uso de ponta de borrachas (simulação de polimento clínico). Os espécimes utilizados nos ensaios de dureza Vickers e tenacidade à fratura foram polidos com o uso de lixas e soluções diamantadas em politriz semiautomática. Parte dos espécimes confeccionados sofreram o ensaio de desgaste. Anteriormente, foram levados a um perfilômetro óptico para determinação de seu perfil topográfico para a determinação da rugosidade e posterior avaliação da perda de volume. Em seguida, os discos foram submetidos ao ensaio de desgaste em uma simuladora da mastigação por meio milhão de ciclos com carga de 30 N e frequência de 2 Hz. Após o ensaio de desgaste, os espécimes foram submetidos novamente à análise topográfica através de perfilometria óptica para determinação da perda de volume e rugosidade superficial. Foram avaliadas também as propriedades mecânicas por meio dos ensaios de resistência a flexão biaxial, tenacidade a fratura e dureza Vickers, e a análise de molhamento de superfície por meio da mensuração do ângulo de contato e caracterização das propriedades de ópticas sobre os parâmetros de translucidez. Resultados: na resistência á flexão foi verificado o efeito do estado da superfície, na condição ajuste Cercon hT apresentou o maior valor e o Lava Plus o menor, para a condição glaze não foi encontrada diferença entre os valores de resistência os materiais testados; os valores médios de dureza foram semelhantes para os materiais testados; as médias de tenacidade à fratura foram significativamente diferentes Lava Plus apresentou o maior valor e o Cercon hT e Prettau o menor que foram semelhantes entre si; para os valores de ângulo de contato foram estatisticamente superiores na condição ajuste para todos os materiais; para os valores médios de rugosidade média foi verificado o efeito do ajuste e posterior polimento para o Cercon hT, após ensaio de desgaste foi verificado o aumento da rugosidade para todos os materiais independente da condição, os valores de Ra para a condição ajuste foi numericamente maior se comparada a condição glaze para todos os materiais, os valores médios de perda de volume após ensaio de desgaste foi significativamente maior para o Lava Plus na condição ajuste, para os demais materiais o estado as superfície não afetou significativamente a perda de volume, para os valores do parâmetro de translucidez os materiais Lava Plus e Prettau tiveram valores menores semelhantes e significativos aos valores de Cercon hT e xT que foram superiores e semelhante entre si, na condição ajuste os materiais Cercon hT e Cercon xT continuaram apresentando valores semelhantes e superiores a Prettau, o Lava Plus após ajuste apresentou valores semelhantes estatisticamente aos valores de PT dos materiais Cercon xT e hT o material Cercon hT apresentou maior valor de resistência após ajuste Conclusão: Houve efeito da microestrutura e do estado de superfície para a resistência à flexão, rugosidade média e para o parâmetro de translucidez; o efeito da microestrutura na tenacidade à fratura, e foi observado o efeito do estado de superfície para os valores do ângulo de contato e na perda de volume.

Effect of different finishing and polishing systems on surface properties of universal single shade resin-based composites.

BACKGROUND: Recently, universal single-shade resin composites have become increasingly available in the dental market. The modification of their composition can have an inadvertent effect on their physical and surface properties, and subsequently determinantal effect on their clinical function and longevity. Therefore, this study aimed to evaluate the effect of different finishing and polishing (F/P) systems on surface roughness (Ra), surface gloss (GU), and Vickers microhardness (VMH) of universal single-shade RBCs. MATERIALS AND METHODS: Four commercial RBCs were used; the universal single-shade RBCs were Omnichroma, Charisma® Diamond ONE, and Vittra APS Unique, and a conventional nanocomposite Filtek™ Z250 XT was used as a control. The 3 F/P systems were Sof-Lex™ XT, Enhance®/PoGo®, and Diacomp® Plus Twist. A total of 160 discs were used for the 3 F/P system groups for all RBCs (n = 10). After F/P, the Ra, GU, and VMH were assessed. The data were analyzed using 2-way ANOVA at p-value < 0.05. RESULTS: Significant differences were found among the four RBCs and the 3 F/P systems (p < .000). Omnichroma showed the lowest Ra and acceptable GU, but the lowest VMH. Charisma showed the highest Ra, acceptable GU, and VMH. Vittra showed acceptable Ra, GU, and VMH and Filtek showed the highest GU, VMH, and acceptable Ra. CONCLUSION: Although conventional nanohybrid RBC (Filtek Z250 XT) showed better GU and VMH values, the universal single-shade RBCs demonstrated comparable surface properties. The highest GU & VMH and lowest Ra were achieved by Diacomp followed by Enhance and Soflex.

In vitro pilot study comparing a novel implantoplasty sonic instrumentation protocol with a conventional protocol using burs.

BACKGROUND AND OBJECTIVES: The aim of implantoplasty (IP) is to remove titanium implant layers that have been contaminated and to smoothen the implant surfaces so they retain less plaque. However, existing IP methods are very invasive and reduce implant wall thickness. AIM: To investigate the suitability of novel sonic tips in IP and to compare this novel protocol with conventional abrasive procedures. MATERIALS AND METHODS: Thirty dental implants (Ø 4.1 mm, 10 mm length) were distributed in three groups and investigated according to the protocol of Sivolella et al., with modifications to the instrument's feed rate, the applied contact force, and the speed of implant rotations per minute. The upper third of the implant was processed with a diamond-coated bur (BUR) or novel non-diamond-coated sonic tips (AIRSCALER). After standardized IP, the surfaces were analyzed by tactile profilometry and scanning electron microscopy (SEM). Changes in implant weight, implant material loss, and implant fracture strength were assessed. RESULTS: The mean roughness (Ra , Sa ), implant material loss, and change in implant weight were significantly lower in the AIRSCALER group than in the BUR group, whereas the mean compression resistance values were significantly higher in the AIRSCALER group than in the BUR group. CONCLUSIONS: IP with uncoated sonic tips smoothes the surfaces and reduces structural loss of the implant in the area of microthreads. This new IP method could be of great clinical importance, especially for implants with microthreads and reduced diameter or wall thickness.

Comparison of surface roughness parameters Ra/Sa and Rz/Sz with different measuring devices.

OBJECTIVES: The aim of this in-vitro study was to investigate the influence of the measuring devices (mechanical and optical) on the surface values Ra/Sa and Rz/Sz of different materials and machined surfaces. MATERIAL AND METHODS: Mechanical (contact profilometry (CP): Perthometer S6P, Perthen Mahr, G) and optical (scanning electron microscope (SEM): Phenom, FEI, NL; confocal 3D laser scanning microscope (CLSM): VK-100, Keyence, J) measuring devices were used to determine the surface roughness Ra/Sa and Rz/Sz. Glass-ceramic (Empress, Ivoclar-Vivadent, FL), zirconia (Cercon HT, Dentsply, D), composite (Grandio, Voco, D), denture base material (Palapress, Kulzer, D) and titanium (grade 4) were investigated (n = 10 measurements) after surface finishing: sandblasting (Al2O3; 250 µm), diamond treatment (80 µm; wet), sandblasting (Al2O3; 50 µm), and polishing (grit of 4000; wet; Tegramin-25, Struers, D). STATISTICS: Shapiro-Wilk, ANOVA, Bonferroni post-hoc tests (α = 0.05). RESULTS: Surface characteristics Ra/Sa and Rz/Sz, which were detected with mechanical and optical measuring devices on different materials and surface finishing, showed significant (p ≤ 0.001, ANOVA) differences. Significant (p ≤ 0.045, Bonferroni) differences between CP, SEM and CLSM (line; area) were found, mainly for Ra/Sa. DISCUSSION: The surface roughness on different dental materials and differently machined surfaces were influenced by the individual mechanical and optical measuring devices. Optical methods measure a significantly higher roughness value for all materials and surface finishes.

Effect of coffee thermocycling on the surface roughness and stainability of denture base materials with different chemical compositions manufactured with additive and subtractive technologies.

OBJECTIVE: To evaluate the effect of coffee thermocycling (CTC) on the surface roughness (Ra ) and stainability of denture base materials with different chemical compositions fabricated by using additive and subtractive manufacturing. MATERIALS AND METHODS: Disk-shaped specimens were additively (FREEPRINT denture, AM) or subtractively (G-CAM, GSM and M-PM, SM) fabricated from three pink denture base materials in different chemical compositions (n = 10). Ra was measured before and after polishing, while color coordinates were measured after polishing. Specimens were subjected to CTC (5000 cycles) and measurements were repeated. Color differences (ΔE00 ) after CTC were calculated. Ra among different time intervals within materials was evaluated by using repeated measures analysis of variance (ANOVA), while 1-way ANOVA was used to evaluate the Ra of different materials within each time interval and the ΔE00 values. Color coordinates within each material were compared by using paired samples t-tests (α = 0.05). RESULTS: Ra before polishing was the highest for all materials (p < 0.001), while SM had its lowest Ra after CTC and AM had its lowest Ra after polishing (p ≤ 0.008). Before polishing, AM had the highest Ra among the materials (p < 0.001). After polishing, SM had higher Ra than AM (p < 0.001). After CTC, GSM had the lowest Ra (p ≤ 0.048). SM had the lowest (p ≤ 0.031) and AM had the highest (p < 0.001) ΔE00 . CTC decreased the a* and b* values of SM and AM (p ≤ 0.017), and increased the L* values of AM (p < 0.001). CONCLUSIONS: Polishing significantly reduced the surface roughness of all materials. CTC did not increase the surface roughness of materials above the clinically acceptable threshold. Only AM had perceptible color change when previously reported threshold values for denture base materials were considered. CLINICAL SIGNIFICANCE: Tested denture base materials may have similar surface stability after coffee thermocycling. However, subtractively manufactured denture base materials may have improved color stability when subjected to long-term coffee consumption.

Effect of printing layer orientation and polishing on the fatigue strength of 3D-printed dental zirconia.

OBJECTIVE: The aim of the study was to evaluate the influence of surface polishing and printing layer orientation on the fatigue behaviour of 3 mol% yttria-stabilized zirconia (3Y-TZP) by stereolithography (SLA) in comparison with subtractive manufacturing. MATERIALS AND METHODS: 60 experimental zirconia bar-shaped specimens were 3D-printed (P) via SLA, and 30 specimens were milled (M) from commercial zirconia block (Lava™ Frame, 3 M ESPE AG). All specimens had the same dimensions (1 mm × 1 mm x 12 mm) after sintering. The 3D-printed specimens were randomly divided according to printing orientations: parallel or perpendicular to the tensile surface in the fatigue test. The specimens were subsequently submitted to two surface finishing protocols (n = 15/gr): unpolished or polished. Their phase compositions were analysed by X-ray diffraction. The fatigue behaviour was evaluated by a stepwise approach. RESULTS: The milled and both 3D-printed groups showed similar phase compositions for the as-sintered condition. Considerable amounts of rhombohedral phase were detected after polishing. Milled unpolished samples presented significantly higher fatigue strength than 3D-printed unpolished samples. Polishing did not improve the fatigue strength for milled zirconia but was advantageous for the 3D-printed specimens. 3D-printed specimens with parallel printing-layer orientation were significantly stronger than specimens with perpendicular layers regardless of surface finishing. CONCLUSION: The manufacturing techniques had a significant influence on the fatigue strength of 3Y-TZP, but not on the phase compositions of the surface. The polishing protocol showed different effects on 3Y-TZP fatigue strength and induced phase transition of the 3Y-TZP from Tetragonal to Rhombohedral. The best fatigue strength was achieved through milling using an unpolished surface and SLA-printed layers that were parallel to the tensile surface, followed by polishing.

Influence of different surface finishing procedures of strength-gradient multilayered zirconia crowns on two-body wear and fracture load: Lithium silicate or leucite glazing versus polishing?

OBJECTIVES: To examine the influence of different finishing procedures on the surface roughness, wear resistance and fracture load of strength-gradient multilayered zirconia. MATERIALS AND METHODS: Zirconia crowns (Multilayer 3D pro; n = 96) were manufactured and treated with a lithium-silicate- (LISI_S), leucite-based glaze spray (LEU_S), leucite-based glaze mass (LEU_M) or polished (POL). Natural molars (CG; n = 24) acted as a control. Roughness was determined on flat glazed specimens (n = 28). Two-body wear was examined by digitalizing and matching the occlusal surface before and after thermo-mechanical aging (6,000 thermal and 1,200,000 chewing cycles). The groups were split to measure fracture load initially and after aging. Kolmogorov-Smirnov, Spearman correlation, Kruskal-Wallis-H, Levene's test, one-way ANOVA with Scheffé post-hoc and Weibull modulus were computed. RESULTS: POL presented the lowest and LEU_S the highest roughness. Following POL, no ceramic loss was observed. LISI_S, LEU_S and LEU_M showed lower ceramic wear than the CG. The lowest wear of the antagonist was observed for the CG. LISI_S showed a lower antagonistic wear than LEU_S, LEU_M and POL. LISI_S, LEU_S, LEU_M and POL showed higher fracture load values and Weibull moduli than the CG. Artificial aging did not impact the fracture load or Weibull moduli. SIGNIFICANCE: With glazed groups showing height losses closer to the CG, glazing should be preferred to polishing when approximating the wear behavior of a natural dentition. Finishing of monolithic zirconia by glazing with a lithium silicate-based spray is recommended to preserve the antagonists. All examined zirconia crowns presented sufficient mechanical properties to withstand masticatory forces, even after prolonged aging.