Modeler liquids: Effect on the cohesive strength, color and staining resistance of stratified resin composite restorations.

PURPOSE: To evaluate the effect of filled and unfilled modeler liquids on the cohesive strength and color stability when applied in between the resin composite layers in the stratification technique and on the uppermost surface layer. METHODS: For the cohesive strength test (n= 10), 30 cylindrical samples were packed into a Teflon mold (6x2 mm) in 2 mm increments. Firstly, a dentin-shade resin composite (Empress Direct) was placed, followed by the accommodation of a body-shade resin composite (Filtek Z350 XT) and an enamel-shade resin composite (Estelite Omega). Before photoactivation of each increment, an unfilled (Signum Liquid) or filled (Modeling Resin) modeler liquid was applied between the first and second layers and on the uppermost surface layer. The control group (n= 10) did not receive modeler liquid. Cohesive strength was measured in a universal testing machine. For the color test (n= 10), the other 30 samples were fabricated for the cohesive strength test, except for the difference in the diameter (6x6 mm). Before and after the staining of the samples, color was measured using the CIEL*a*b* system with a spectrophotometer (EasyShade). Data were submitted to ANOVA, Kruskal-Wallis test, or Mann-Whitney test (α= 5%). RESULTS: Modeler liquids significantly increased cohesive strength (P= 0.008), while ΔEab (P= 0.003) and ΔE00 (P= 0.005) values presented significantly lower changes for the groups that received modeler liquids, with no significant difference between unfilled and filled modeler liquids. CLINICAL SIGNIFICANCE: Apart from increasing the interfacial strength of stratified restorations, modeler liquids minimized staining.

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.

Smoothness provided by a one-step finishing and polishing system and its maintenance after 12-month aging.

PURPOSE: To evaluate the smoothness provided by a one-step finishing and polishing system and its maintenance after hydrothermal aging and brushing of a nanofilled resin composite. METHODS: 96 samples of the nanofilled composite Filtek Z350 XT were fabricated, which, after initial average roughness (Ra) analysis, were randomly distributed into three groups, according to the selected finishing and polishing system. The multi-step systems Sof-Lex (aluminum oxide discs) and Jiffy (bullet-shaped abrasive rubbers), and the one-step system OneGloss (bullet-shaped abrasive rubber) were used. After finishing and polishing, a new Ra measurement was performed, and then half of the samples from each group were stored in artificial saliva for 12 months, while the other half underwent aging processes associating hydrothermal cycles (10,000 cycles at 5-55°C) followed by brushing (5,500 strokes), with a mid-abrasive (Crest Cavity Protection) dentifrice slurry, simulating a 12-month period in the oral cavity. Final Ra measurements were performed, and data were analyzed by generalized linear model and Tukey's test (α= 5%). RESULTS: There was interaction between finishing and polishing system and aging (P< 0.001). The one-step abrasive rubber point provided significantly higher Ra values compared to the multi-step systems, and with the discs there was higher smoothness than with the rubber point sequence. This result was maintained after 12 months in artificial saliva, but after hydrothermal cycles followed by brushing, one-step and multi-step abrasive rubber points no longer significantly differed from each other. Only for the one-step system, hydrothermal cycles followed by brushing significantly reduced Ra. CLINICAL SIGNIFICANCE: Although hydrothermal cycles followed by brushing may have increased the smoothness of nanofilled composite finished and polished with the one-step system, only the multi-step system provided a surface within the roughness threshold to avoid biofilm retention.

Effect of simplified or multi-step polishing techniques on roughness and color stability of resin composites.

PURPOSE: To evaluate the impact of simplified or multi-step polishing techniques on the roughness, color, and susceptibility to staining of different resin composites. METHODS: Discs (Ø6 mm x 2 mm) were obtained from different resin composites [nanofilled (Z350XT), suprananofilled (Estelite Omega), and nanohybrid (Forma)]. The specimens (n= 15) were submitted to a simplified protocol using abrasive discs (Sof-Lex) and spiral discs (Diacomp Plus Twist), or a multi-step protocol using abrasive discs (Sof-Lex), abrasive points (Jiffy), silicon carbide brush and felt disc with diamond pastes (Diamond Polish). The specimens were evaluated initially for roughness (Ra) and color (CIEL*a*b*, CIEDE 2000), after completing the polishing protocol, and after exposure to a coffee solution (pH= 5.01). The data were analyzed according to the variables, using generalized linear models, and the Friedman, Nemenyi, Kruskal-Wallis, Dunn, and Mann-Whitney tests (α= 0.05). RESULTS: The nanohybrid resin composite showed an increase in Ra following use of both polishing methods (P= 0.038). Both techniques promoted an increase in L* values after polishing; however, the general color changes (ΔEab and ΔE00) were greater after the multi-step polishing (P< 0.05). After immersion in coffee, the multi-step polished groups of the nanohybrid and suprananofilled resin composite showed higher L* values than the simplified polishing groups (P= 0.023), and the nanofilled resin composite showed higher ΔEab and ΔE00 values than the other resin composites, regardless of the polishing technique (P< 0.05). CLINICAL SIGNIFICANCE: The choice of the resin composite had a greater effect on roughness, color stability and susceptibility to staining than the polishing technique. However, luminosity after coffee staining was higher with the multi-step polishing technique.

Varnish with S-PRG filler reduces dentin permeability after erosive/abrasive challenge.

PURPOSE: To evaluate the effect of different varnishes on dentin permeability to erosive/abrasive challenges. METHODS: 60 superficial dentin discs were randomly allocated to six groups (n=10): Duraphat, PRG Barrier Coat, Clinpro XT, Profluorid, Fluor Protector S and untreated (control). Permeability tests were carried out: after acid conditioning, after treatment, and after abrasive/erosive challenges. The abrasive-erosive challenges were performed for 5 days (citric acid and in remineralizing saliva), as well as abrasion with toothpaste slurry (Colgate Total 12). Scanning electron microscopy (SEM) images were obtained of the dentin surfaces (5,000x) after the treatments, and after the erosive/abrasive challenges. RESULTS: Kruskal-Wallis and Dunn tests showed that all the varnishes promoted a decrease in dentin permeability directly after application, with Clinpro XT showing the highest percentage (69.52%) of dentin sealing (P= 0.0188). After the erosive/abrasive challenge, only PRG Barrier Coat varnish showed dentin sealing ability with reduced dentin permeability (42.16%) (P= 0.0014). However, none of the applied varnishes promoted a statistically significant difference in the percentage of dentin sealing, compared with the control group (P> 0.05). Clinpro XT showed a higher percentage of dentin sealing, while only PRG Barrier Coat showed reduced dentin permeability after the erosive/abrasive challenge. CLINICAL SIGNIFICANCE: Varnish containing S-PRG filler has the efficacy needed to be used as a coating material to reduce dentin permeability in situations of erosive/abrasive challenges.

Long-term bond strength of ormocer-based resin composites using a universal adhesive used in different adhesive strategies.

PURPOSE: To evaluate over time the bond strength to dentin of different resin composites (RBCs) associated with the universal adhesive system applied with self-etching or total-etching strategies. METHODS: 60 human third molars were obtained, randomly divided into experimental groups (n= 10) according to RBCs: methacrylate-based nanofilled (Z350 XT); low-viscosity Ormocer-based bulk-fill (Admira Fusion X-base Universal); or high-viscosity Ormocer-based bulk-fill composite (Admira Fusion X-tra). The adhesion procedure was performed using a universal adhesive (Futurabond U) applied in self-etching or total-etching mode. Occlusal preparations (Class I) were made, measuring 4 mm in mesiodistal length, 4 mm in depth, and 3 mm in buccolingual height. The cavities were restored considering the RBCs and adhesive strategies, and the light curing was performed using a LED unit (BluePhase) as recommended by the manufacturers. For this, the nanofilled RBCs were inserted by the oblique incremental technique while the bulk-fill RBCs were inserted in single increments. The samples were stored in water for 24 hours in an oven; to be sectioned, the sticks were randomly separated, stored in distilled water for 24 hours (immediate) or 12 months (long-term), and taken to the universal machine for a microtensile test (MPa). The fractured sticks were examined to classify the type of fracture. The results were analyzed by ANOVA and Tukey's test (α= 0.05). RESULTS: The MPa values of methacrylate-based nanofilled or high-viscosity Ormocer-based RBC were not affected by the strategy used to apply the universal adhesive system (P> 0.05). However, for the low-viscosity Ormocer-based RBC, higher values were obtained when the total-etching strategy was used compared to the self-etching mode (P< 0.05). After 12 months, when using the total-etching strategy low-viscosity Ormocer-based RBC, higher MPa values were obtained compared to the other materials (P< 0.05). CLINICAL SIGNIFICANCE: Regardless of the adhesive strategy used, the high-viscosity RBCs, whether based on methacrylate or Ormocer, showed similar adhesive behavior. Low-viscosity Ormocer-based RBC showed greater long-term bond strength associated with the universal adhesive applied in the total-etching strategy.

Influence of calcium lactate and fluoride solution mouthrinses on tooth sensitivity and effectiveness of color change during in-office bleaching: A randomized clinical trial.

PURPOSE: To conduct a clinical evaluation of calcium lactate and sodium fluoride mouthrinses in reducing sensitivity and efficacy of color change during in-office bleaching. METHODS: 75 participants were selected and divided into three groups (n= 25), according to the type of desensitizing treatment tested: calcium lactate mouthrinse prior to sodium fluoride mouthrinse before each bleaching session; daily mouthrinse with sodium fluoride; control (absence of mouthrinse). Each mouthrinse was used for 1 minute. Bleaching was performed following the same protocol in all groups, with 40% hydrogen peroxide (Opalescence Boost), in three 40-minute sessions, with a 48-hour interval between sessions. Clinical parameters such as sensitivity, gingival irritation and mouthrinse acceptability were assessed using Visual Analogue Scale (VAS) and clinical examination at two timepoints: baseline (before any treatment) and 48 hours after the end of treatment. The color was evaluated with a spectrophotometer (VITA Classical scale guide, 3D Master guide and CIEL*a*b*). The data were analyzed by generalized linear models and by one-way ANOVA. RESULTS: There was significant color change in all groups according to the VITA Classical scale guide (P< 0.001). There was no significant difference among the groups for ΔL*, Δa*, Δb* and ΔE over time (P> 0.05). The control group presented a significant increase in sensitivity (P= 0.008). The other groups showed no significant difference between initial and final timepoints (P> 0.05). No symptoms of gingival irritation were observed in any of the groups evaluated. All desensitizing treatments presented high acceptability. Bleaching treatment was effective, regardless of association with desensitizing treatments. No treatment prevented bleaching sensitivity, but the absence of a combined desensitizing treatment led to increased sensitivity. CLINICAL SIGNIFICANCE: Although bleaching sensitivity during in-office bleaching treatment cannot be avoided, daily fluoridated mouthrinse or calcium lactate used prior to fluoridated mouthrinse prevented its increase.

Clinical and radiographic evaluation of high viscosity bulk-fill resin composite restorations.

PURPOSE: To perform a clinical and radiographic evaluation comparing Filtek Bulk Fill high viscosity bulk-fill resins with Filtek Z350 XT nanoparticulate for 1 year. METHODS: 58 restorations were performed for each material (bulk-fill and nanoparticulate), for a total of 116 restorations. Among these, 42 Class I and 16 Class II restorations were performed for each group, in molars and premolars. Clinical evaluation was performed 7 days (baseline), 6 months and 1 year after restorations, using the World Dental Federation (FDI) criteria. Radiographs were obtained at 7 days and 1 year after the restoration was placed and the radiopacity was measured using Image J software at the same time interval. RESULTS: Of the 70 restorations available for evaluation at 1 year, the Mann-Whitney and Friedman tests showed no statistically significant difference for the FDI criteria analyzed. Greater radiopacity was observed for bulk-fill resin compared to nanoparticulate (two-way ANOVA, P= 0.022). This same test showed no difference in radiopacity between the groups in the two evaluation periods (P= 0.062). The high viscosity bulk-fill resin composite presented similar clinical performance to nanoparticulate resin in this evaluation period and higher radiopacity was observed for this material when compared to nanoparticulate resin, in both time periods. CLINICAL SIGNIFICANCE: The high viscosity bulk-fill resin composite showed similar performance to the nanoparticulate resin during the evaluation period of 1 year. Radiopacity showed high values for the bulk-fill resin when compared to nanoparticulate resin. The bulk-fill resin has potential to be used in posterior teeth.

Effect of sucralfate against hydrochloric acid-induced dental erosion.

OBJECTIVE: Devising effective measures for the prevention of hydrochloric acid (HCl)-induced erosion is of great significance. This is even more important in dentine, in which products have limited diffusion. Therefore, agents that can bind to proteins forming an acid-resistant gel-like coat, such as sucralfate, may stand out as a promising alternative. This study investigated the protective effect of sucralfate suspensions against HCl-induced dental erosion. MATERIALS AND METHODS: In the first experiment, hydroxyapatite (HAp) crystals were pre-treated with a commercial sucralfate suspension (CoSS, pH 5.9), a stannous-containing sodium fluoride solution (NaF/SnCl2 pH 4.5), two prepared sucralfate suspensions (PrSS, pH 5.9 and 4.5), or deionized water (DI, control). HAp dissolution was measured using a pH-stat system. In a subsequent experiment, embedded/polished enamel and root dentine slabs were allocated into five groups to be treated with one of the tested substances prior to and during erosion-remineralization cycles (HCl-2 min + artificial saliva 60 min, two times per day, 5 days). Surface loss was assessed profilometrically. Data were analyzed by ANOVA and Tukey's tests. RESULTS: HAp dissolution was as follows: NaF/SnCl2 < CoSS < PrSS/pH 4.5, while PrSS/pH 5.9 = DI and both did not differ from CoSS and PrSS/pH 4.5. In enamel, surface loss did not differ between CoSS and PrSS/pH 4.5, with both having lower surface loss than PrSS/pH 5.9 and DI and NaF/SnCl2 differing only from DI. In root dentine, surface loss was as follows: CoSS < PrSS/pH 5.9 < (NaF/SnCl2 = DI), while PrSS/pH 4.5 = CoSS = PrSS/pH 5.9. CONCLUSION: Sucralfate suspension provided anti-erosive protection to HCl-induced erosion. CLINICAL RELEVANCE: Sucralfate may protect teeth against erosion caused by gastric acid.

Influence of ceramic laminate on water sorption, solubility, color stability, and microhardness of resin cements.

PURPOSE: To evaluate the influence of ceramic laminate on color stability, surface microhardness, water sorption, and solubility of resin luting agents. METHODS: Disk-shaped specimens (10 × 2 mm) of dual-cured resin cements (RelyX ARC or RelyX Ultimate) were obtained, and a light-cured luting agent (RelyX Veneer) was used. In Experiment 1, disk-shaped resin cements (n = 10) were submitted to: I) polymerization with or without ceramic laminate (0.7 mm), and II) immersion in distilled water or coffee, 3 hours daily for 20 days. The surface microhardness loss (%SML) was determined, and the color variables were assessed by the CIE L*a*b* system (ΔE, ΔL*) and the shade guide units (ΔSGU). In Experiment 2, other disk-shaped specimens (n = 5) were submitted to polymerization with or without ceramic laminate to assess their water sorption (WS) and solubility (S). Statistical analysis was performed using 3-way ANOVA and Tukey's test for ΔE, ΔL* and %SML; Mann-Whitney, Kruskal-Wallis, and Dunn's tests for ΔSGU; and 2-way ANOVA and Tukey's test for WS and S. The significance level was set at 5%. RESULTS: No statistically significant differences among the resin cements was observed for %SML, WS, or S, regardless of stain exposure or presence of ceramic laminate during light activation. Coffee caused a significant decrease in ΔL* values. All the resin cements presented visually detectable color alteration for ΔE; however, RelyX Ultimate showed less color change after coffee exposure. RelyX ARC showed the greatest color change in water. RelyX Veneer presented the highest values of ΔSGU, compared with the other resin cements. The WS, S, and %SML of resin cements were not influenced by the staining solution or the presence of ceramic laminate during light activation; however, RelyX Ultimate resin cement presented the best color stability. CLINICAL SIGNIFICANCE: Resin cements can present color changes over time, affecting the long-term esthetic success of laminate ceramic restorations. RelyX Ultimate resin cement presented the best color stability, thus making it a suitable indication for cementing ceramic laminates.

Incorporation of ZnCl2 into an etch-and-rinse adhesive system on flexural strength, degree of conversion and bond durability to caries-affected dentin.

PURPOSE: To evaluate the effect of a zinc chloride (ZnCl2) solution (2% wt), incorporated into a two-step etch-and-rinse adhesive system (AS), on microtensile bond strength (µTBS) to caries-affected dentin (CAD). METHODS: First, the degree of conversion (DC) of the AS with and without the ZnCl2 solution was evaluated by Fourier transform infrared spectroscopy (FTIR). Second, beam-shaped samples (7 mm × 2 mm × 1 mm) were prepared with the AS containing the ZnCl2 solution to perform flexural strength (FS) tests. For µTBS testing purposes, CAD surfaces were etched with phosphoric acid and randomly divided into three groups (n=10) : ZnCl2- AS with ZnCl2; NT (no treatment)- AS without ZnCl2; and CHX - pretreatment with 2% chlorhexidine solution. AS (Adper Single Bond 2) was applied according to the manufacturer's instructions, and resin composite restorations were built up. After 24 hours, the resin-dentin blocks were sectioned into specimens (0.8 mm2), and then subjected to micro;TBS testing immediately following, or after 6 or 12 months of water storage (WS). The adhesive interface was evaluated by scanning electron microscope. Both µTBS and FS tests were performed using a universal testing machine ( 0.5 mm/minute). FS and DC data were submitted to the Student t-test, and µTBS data were subjected to two-way ANOVA and Tukey's test (α= 0.05). RESULTS: DC was not affected by ZnCl2 incorporation into AS (P= 0.2527). Higher FS values were obtained in the group with ZnCl2 added to AS. Regarding µTBS, the mean of the NT group was statistically higher than that of the ZnCl2 or the CHX groups (P< 0.001(, regardless of WS, but the latter groups did not differ from each other. µTBS at 24 hours was statistically superior to that of 6 and 12 months of WS (P< 0.001).

In situ evaluation of surface roughness and micromorphology of temporary soft denture liner materials at different time intervals.

OBJECTIVE: To perform an in situ evaluation of surface roughness and micromorphology of two soft liner materials for dentures at different time intervals. BACKGROUND: The surface roughness of materials may influence the adhesion of micro-organisms and inflammation of the mucosal tissues. The in situ evaluation of surface roughness and the micromorphology of soft liner materials over the course of time may present results different from those of in vitro studies, considering the constant presence of saliva and food, the changes in temperature and the pH level in the oral cavity. MATERIALS AND METHODS: Forty-eight rectangular specimens of each of the two soft liner materials were fabricated: a silicone-based material (Mucopren Soft) and an acrylic resin-based material (Trusoft). The specimens were placed in the dentures of 12 participants (n = 12), and the materials were evaluated for surface roughness and micromorphology at different time intervals: 0, 7, 30 and 60 days. Roughness (Ra) was evaluated by means of a roughness tester. Surface micromorphology was evaluated by scanning electron microscopy. RESULTS: Analysis of variance for randomised block design and Tukey's test showed that surface roughness values were lower in the groups using the silicone-based material at all the time intervals (P < .0001). The average surface roughness was higher at time interval 0 than at the other intervals, for both materials (P < .0001). The surface micromorphology showed that the silicone material presented a more regular and smoother surface than the acrylic resin-based material. CONCLUSION: The surface roughness of acrylic resin-based and silicone-based denture soft liner materials decreased after 7 days of evaluation, leading to a smoother surface over time. The silicone-based material showed lower roughness values and a smoother surface than the acrylic resin-based material, thereby making it preferred when selecting more appropriate material, due its tendency to promote less biofilm build-up.

Kinetics of salivary pH after acidic beverage intake by patients undergoing orthodontic treatment.

The saliva of patients undergoing orthodontic treatment with fixed appliances can potentially present a delay in the diluting, clearing, and buffering of dietary acids due to an increased number of retention areas. The aim of this clinical trial was to compare salivary pH kinetics of patients with and without orthodontic treatment, following the intake of an acidic beverage. Twenty participants undergoing orthodontic treatment and 20 control counterparts had their saliva assessed for flow rate, pH, and buffering capacity. There was no significant difference between salivary parameters in participants with or without an orthodontic appliance. Salivary pH recovery following acidic beverage intake was slower in the orthodontic subjects compared to controls. Patients with fixed orthodontic appliances, therefore, seem to be at higher risk of dental erosion, suggesting that dietary advice and preventive care need to be implemented during orthodontic treatment.

Evaluation of bond strength between leucite-based and lithium disilicate-based ceramics to dentin after cementation with conventional and self-adhesive resin agents.

The aim of this study was to compare the microtensile bond strength of two heat-pressed ceramics (leucite-based--IPS Empress Esthetic/Ivoclar Vivadent, and lithium disilicate-based --IPS e.max Press/Ivoclar Vivadent) to dentin with the use of conventional and self-adhesive resin cements. The occlusal surface of 60 intact human molars was removed and the dentin was exposed. Ceramic blocks were cemented randomly with regard to the cementation systems (n = 10): conventional dual resin cement (Variolink II/Ivoclar Vivadent), conventional self-polymerizing resin cement (Multilink/Ivoclar Vivadent), and dual self-adhesive resin cement (RelyX U100/3M ESPE). The dual cementation systems were photoactivated with a LED light device (Radii Cal, SDI) for 40 seconds. The specimens were sectioned to obtain sticks of approximately 1 mm2 for microtensile tests on a universal testing machine (EMIC). The type of fracture was analyzed under a scanning electron microscope. The Analysis of Variance (ANOVA) and the Tukey test (alpha = 0.05) showed that there was no difference between types of ceramic. Average microtensile bond strength was higher for the conventional dual resin cement (Variolink II) and the self-adhesive dual resin cement (RelyX U100), despite greater prevalence of premature loss of the sticks with the latter. Average bond strength was lower when the conventional self-polymerizing resin cement (Multilink) was used. Leucite-based and lithium disilicate-based cements present similar bond strength to the dentin with conventional dual resin cement (Variolink II) and a dual self-adhesive cement (RelyX U100).

Effect of different design and surface treatment on the load-to-failure of ceramic repaired with composite.

Glass ceramics are widely used to manufacture esthetic veneers, inlays, onlays, and crowns. Although the clinical survival rates ofglass-ceramic restorations arefavorable,fractures or chips are common. Certain cases can be repaired with direct composite. AIM: The aim of this study was to investigate the interaction effect of different designs and surface treatments on the load-to-failure of lithium disilicate glass-ceramic repaired with nanofilled composite. MATERIALS AND METHOD: Lithium-disilicate glass-ceramic slabs (IPS e.max Press, Ivoclar Vivadent) with three different designs of the top surface (flat, single plateau, or doubleplateau) (n=U) received 'no treatment', '5% HF etching', or "AI2O3 sandblasting". HF-etched and sandblasted slabs also received silane and universal one-step adhesive application. All slabs were incrementally repaired with nanofilled composite (Filtek Z350, 3M ESPE) up to6 mm above the highest ceramic top plateau. Specimens were stored in artificial saliva at 37 °C for 21 days and then subjected to 1,000 thermocycles between 5 and 55 °C. The interface composite-ceramic of each specimen was tensile tested until failure in a universal testing machine and the mode of failure was determined under a stereomicroscope. The ceramic surface morphology of one representative tested specimen from each subgroup (design/surface treatment) was observed through scanning electron microscopy (SEM). RESULTS: Regardless of ceramic design, the absence of surface treatment resulted in significantly lower load-to-failure values. No significant differences in load-to-failure values were observed between HF-etched and sandblasted specimens for the flat design; however, HF etching resulted in significantly higher load-to-failure values than sandblasting for both single plateau and double plateau designs. The majority (60%) of HF-etched specimens with single plateau or double plateau presented mixed failures. SEM photomicrographs showed that HF-etched specimens had smoother surfaces than sandblasted specimens. CONCLUSION: The surface treatment of a defective lithium disilicate glass-ceramic restoration has more influence than its macroscopic design on the retention of the composite repair. HF etching seems to provide higher bond strength to the composite repair.

Embora fraturas e lascamento de restauragoes vitrocerámicas sejam comuns, alguns casos podem ser reparados com compósito direto. OBJETIVO: investigar o efeito da interagao de diferentes formas e tratamentos de superficie na carga de ruptura de uma vitrocerámica reforgada com dissilicato de litio reparada com compósito nanoparticulado. MATERIAIS E MÉTODOS: A superficie superior de espécimes de vitroceramica (IPS e.max Press, Ivoclar Vivadent) foi preparada com tres formas (plana, plato único, ou duplo) e recebeu (n=11): 'nenhum tratamento', 'condicionamento com ácido hidrofluoridrico 5%', ou 'jateamento com AfOf. Ambos espécimes condicionados e jateados receberam silano e adesivo universal. Todos os espécimes foram reparados incrementalmente com compósito (Filtek Z350, 3M ESPE) até6 mm acima do plato cerámico mais alto, armazenados em saliva artificial á 37 °C por 21 dias, e submetidos á 1.000 termociclos (5 e 55 °C). A interface compósito-cerámica de cada amostra foi testada á tragao até sua falha em máquina universal e o modo de falha foi determinado com estereomicroscópio. A morfologia da superficie de uma amostra representativa de forma/tratamento de superficie foi observada através de microscopia eletronica de varredura (MEV). RESULTADOS: Independentemente da forma ceramica, a ausencia de tratamento superficial resultou em valores de carga de ruptura significativamente menores. Nao foi observada differenga significativa entre os espécimes planos condicionados ou jateados; no entanto, o condicionamento resultou em valores significativamente maiores que o jateamento para espécimes com plato único e duplo. A maioria (60%) dos espécimes condicionados e com plato único ou duplo apresentou falhas mistas. Imagens SEM demonstraram rugosidade superficial mais regular dos espécimes condicionados que os jateados. CONCLUSÕES: O tratamento superficial de uma restauragao defeituosa de vitrocerámica reforgada por dissilicato de litio tem maior influencia na retengao do reparo de compósito do que sua forma macroscópica; ainda, o condicionamento com ácido hidrofluoridrico parece proporcionar maior resistencia de uniao ao reparo com compósito.

Precision of polyether ether ketone (PEEK) or cobalt-chrome implant bar fit to implants after mechanical cycling.

Based on its mechanical properties, PEEK (polyether-ether-ketone) might be useful in restorative procedures. In oral rehabilitation, its viability has been studied mainly for prostheses and dental implants. AIM: The aim of this study was to evaluate the fit accuracy of dental implant bars made of either PEEK or cobalt-chrome submitted to cycling mechanics. MATERIALS AND METHOD: This was an experimental in vitro study, where units were treated with two implants and mini-abutments, joined by cobalt-chrome or polyether-ether-ketone PEEK bars. A total 20 bars were prepared (n=10 per group) and subjected to mechanical cycling tests (1 million cycles on the distal cantilever of the bar in the vertical direction, 120N and sinusoidal loading, at a frequency of 2Hz). The fit at the abutment/implant interface was measured before and after cycling, and the counter-torque of the vertical screw of the mini abutments was measured after cycling, using a digital torquemeter. Data were analyzed by three-way ANOVA and Tukey's test at 5% significance level. RESULTS: No statistically significant interaction was found among the three factors considered (bar material, implant positioning and mechanical cycling) (p = 0.592). No significant difference was identified in the interaction between bar material and implant positioning (p = 0.321), or between implant positioning and mechanical cycling (p = 0.503). The association between bar material and mechanical cycling was statistically significant (p = 0.007), with the cobalt-chrome bar resulting in greater misfit with mechanical cycling. There was no difference in counter-torque values between groups. CONCLUSIONS: The PEEK bar provided better fit of the mini abutments to the implants, even after mechanical cycling. The counter-torque of the screws was similar in all scenarios considered.

O PEEK (Poli-éter-éter-cetona) é um material considerado para uso em procedimentos restauradores devido às suas propriedades mecânicas. Na reabilitação oral, sua viabilidade tem sido estudada principalmente para uso em próteses e implantes dentários. Objetivos: O objetivo deste estudo foi avaliar a precisão da adaptação de duas barras diferentes do tipo protocolo confeccionadas em PEEK ou Cobalto-Cromo, após serem submetidas à mecânica ciclística. Materiais e Método: As unidades experimentais foram constituídas por barras confeccionadas em Poli-ether-ether-Ketone (PEEK) e em Cobalto-Cromo (Co-Cr). Trata-se de um estudo experimental, in vitro, onde verificou-se unidades constituídas por dois implantes e mini pilares unidos com barras de Cobalto-Cromo ou PEEK. Foram confeccionados um total de 20 barras (n=10 em cada grupo) e as barras foram submetidas a ensaios de ciclagem mecânica (1 milhão de ciclos no cantilever distal da barra no sentido vertical, 120N e carregamento senoidal, a uma frequência de 2Hz). Antes e após a ciclagem realizou-se a mensuração da desadaptação na interface pilar/implante e após a ciclagem foi medido o contra-torque do parafuso vertical dos mini-pilares através de torquímetro digital TQ 8800 (LT Lutron, Taiwan). Os dados foram submetidos a ANOVA a três critérios e teste de Tukey ao nível de significância a 5%. Resultados: Constatou-se que não houve interação estatisticamente significativa entre os três fatores estudados, ou seja, entre o material da barra, o posicionamento do implante e a ciclagem mecânica (p = 0,592). Também não se identificou diferença estatística significativa da interação entre o material da barra e o posicionamento do implante (p = 0,321), nem entre o posicionamento do implante e a ciclagem mecânica (p = 0,503). Já a associação entre o material da barra e a ciclagem mecânica foi estatisticamente significativa (p = 0,007), onde a barra de Cobalto-Cromo resultou em maior desadaptação com a ciclagem mecânica. Não houve diferença nos valores dos contra-torques entre os grupos. Conclusões: Conclui-se que a barra de protocolo fabricada em PEEK proporcionou melhor adaptação dos mini pilares aos implantes mesmo após a ciclagem mecânica. Por fim, o contra-torque dos parafusos foi semelhante em todos os cenários avaliados.

Ozone gas therapy for tooth bleaching preserves enamel microhardness, roughness and surface micromor.

After ozone therapy for bleaching, it is important to evaluate enamel surface properties, to ensure that bleaching provides adequate conditions for sound dental substrate. Aim: The aim of this in vitro study was to evaluate the effects of a bleaching treatment with 10% carbamide peroxide (CP), with or without ozone (O), on the microhardness, roughness and micromorphology of the enamel surface. Materials and Method: Bovine enamel blocks were planed and distributed among the following three bleaching treatment groups (n=10): CP - 1 hour per day/14 days (Opalescence PF 10%/ Ultradent); O - 1 hour per day every 3 days/3 sessions (Medplus V Philozon, 60 mcg/mL and oxygen flow rate of 1 L/min); and OCP - CP with O, 1 hour per day every 3 days/3 sessions. Enamel surface microhardness (Knoop), roughness (Ra), and micromorphology by scanning electron microscopy (5,000x magnification) were determined before and after the treatments. Results: ANOVA and Tukey-Kramer's test showed that enamel microhardness remained unchanged by treatment with O and OCP (p=0.0087), but decreased by treatment with CP. Treatment with O promoted higher enamel microhardness than the other groups (p=0.0169). Generalized linear mixed models for repeated measures over time indicated treatment with CP increased enamel roughness more than OCP or O (p=0.0003). CP produced slight irregularities in enamel micromorphology after the whitening treatment. O, with or without CP, maintained the mechanical and physical properties of microhardness and enamel surface micromorphology, and either maintained or reduced surface roughness, compared to the conventional tray-delivered CP bleaching treatment. Conclusions: Treatment with 10% carbamide peroxide in trays promoted greater changes in enamel surface properties than treatments with ozone and with 10% ozonized carbamide peroxide in the office.

É importante avaliar as propriedades da superfície do esmalte após a aplicação da ozonioterapia para clareamento, para garantir que o efeito clareador proporcione condições adequadas para um substrato dentário hígido. ultório. Objetivo: O objetivo deste estudo in vitro foi avaliar os efeitos de um tratamento clareador com peróxido de carbamida (PC) a 10%, associado ou não ao ozônio (O), na microdureza, rugosidade e micromorfologia da superfície do esmalte. Materiais e Método: Blocos de esmalte bovino foram aplainados e distribuídos entre três grupos de tratamento clareador (n=10): PC - 1 hora por dia/14 dias (Opalescence PF 10%/ Ultradent); O - 1 hora por dia a cada 3 dias/3 sessões (Medplus V Philozon, 60 mcg/mL e fluxo de oxigênio de 1 L/min); e PCO - CP com O, 1 hora por dia a cada 3 dias/3 sessões. A microdureza (Knoop), a rugosidade (Ra) e a micromorfologia da superfície do esmalte avaliada por microscopia eletrônica de varredura (aumento de 5.000x) foram analisadas antes e após os tratamentos. Resultados: ANOVA e teste de Tukey-Kramer mostraram que O e PCO mantiveram os valores de microdureza do esmalte ao final do tratamento (p=0,0087), enquanto PC promoveu diminuição da microdureza. O promoveu maiores valores de microdureza do esmalte do que os outros grupos ao final do tratamento (p=0,0169). Modelos lineares generalizados mistos para medidas repetidas no tempo indicaram um aumento na rugosidade da superfície para PC, levando a maior rugosidade do esmalte ao final do tratamento, em comparação com PCO ou O (p=0,0003). PC apresentou pequenas irregularidades na micromorfologia do esmalte após o tratamento clareador. O, com ou sem PC, manteve as propriedades mecânicas e físicas de microdureza e micromorfologia da superfície do esmalte, e manteve ou reduziu a rugosidade da superfície, em comparação com o tratamento clareador a base de PC aplicado em moldeira convencional. Conclusões: O tratamento com peróxido de carbamida a 10% para uso em moldeiras promoveu maiores alterações nas propriedades de superfície do esmalte do que aquelas observadas nos tratamentos com ozônio e com peróxido de carbamida ozonizado a 10% para uso em consultório.

The potential of salivary albumin to degrade composite resin.

Albumin is a salivary enzyme capable of cleaving ester linkages and catalyzing degradation of resin-based dental materials. However, the effect of concentration-dependent esterolytic action on composite resins as yet remains unexplored. Aim: The purpose of this study was to evaluate whether artificial saliva formulations with different concentrations of albumin affected the surface roughness, flexural strength and microhardness of a composite resin. Materials and Method: Specimens (25x2x2mm) of a nanofilled composite (Filtek Z350XT, 3M/ESPE) were prepared and analyzed for average surface roughness (Ra/pm). The specimens were then allocated to 6 groups (n=30), to be treated with different salivary albumin concentrations: 0, 10, 50, 100, 200, 400 pg/mL. The specimens were stored in their respective artificial saliva groups, half of them for 24 h and the remainder for 180 days (artificial saliva renewed weekly), after which they were submitted to a new Ra reading, and tested for three-point flexural strength (FS, MPa). The specimens stored for 180 days were analyzed for Knoop microhardness (KH, Kg/mm2). Data were submitted to two-way ANOVA (Ra and FS) and one-way ANOVA (KH). Results: Although Ra increased (p < 0.001) and FS decreased (p < 0.001) from 24 hours to 180 days of storage, the albumin concentration did not significantly affectRa (p = 0.168), FS (p = 0.477) or KH (p = 0.378). Conclusion: The esterolytic action of albumin did not increase the artificial-saliva-induced hydrolytic degradation of the composite resin.

Albumina, uma enzima encontrada na saliva, é capaz de clivar ligagoes éster e catalisar a degradando de materiais dentários á base resina. Apesar da agao esterolítica ser potencialmente concentragao-dependente, a investigando desse efeito sobre resinas compostas ainda permanence inexplorado. Objetivo: O objetivo deste estudo foi avaliar se formulagoes de saliva artificial contendo diferentes concentragoes de albumina afetariam a rugosidade superficial, a resistencia flexural e a microdureza de uma resina composta. Materials e Método: Corpos de pro-va em barra (25x2x2mm) foram confeccionados a partir de uma resina composta nanoparticulada (Filtek Z350XT, 3M/ESPE) e foram submetidos á leitura de rugosidade superficial média inicial (Ra, pm), em rugosímetro. Entao, as amostras foram divididas em 6 grupos (n=30) de acordo com a concentrando de albumina na saliva: 0, 10, 50, 100, 200, 400 pg/mL. As amostras foram armazenadas nas formulagoes de saliva artificial correspondente ao seu grupo, metade por 24 h e as demais por 180 dias (com trocas de saliva semanais). As amostras foram submetidas a no-vas leituras de rugosidade (Rafinal) e avaliadas quanto á resistencia flexural de tres pontos (RF, MPa). As amostras armazenadas por 180 dias foram avaliadas quanto á microdureza Knoop (KH, Kg/mm2). Os dados foram submetidos a análises de variáncia a dois critérios (Ra e RF) e a um critério (KH). Resultados: Apesar de haver aumento na Ra (p < 0,001) e uma diminuigao da RF (p < 0,001) de 24 h para 180 dias, a concentragao de albumina nao afetou significativamente a Ra (p = 0,168), a RF (p = 0,477) ou a KH (p = 0,378). Conclusoes: A agdo esterolítica da albumina nao aumentou a degradagao hidrolítica da resina composta induzida pela saliva artificial.

Counteractive effect of antacid suspensions on intrinsic dental erosion.

This in vitro study aimed to investigate the anti-erosive effect of antacid suspensions applied to enamel after exposure to hydrochloric acid (HCl). Ninety bovine enamel slabs were embedded, flattened, and polished. Reference areas were created and specimens were divided into six groups. They were exposed to 0.01 M HCl (pH 2) for 2 min, followed by immersion for 1 min in one of the following test suspensions: magnesium hydroxide, aluminum hydroxide, magnesium hydroxide/aluminum hydroxide, sodium alginate/sodium bicarbonate/calcium carbonate, or hydrated magnesium aluminate. Artificial saliva was used as a negative control. Specimens were subjected to a total of five cycles of erosion/antacid treatment. Enamel surface loss was measured (in micrometers) by optical profilometry. In addition, baseline and final surface microhardness (SMH) values of enamel were obtained. It was found that antacid suspensions significantly reduced enamel loss, and that similar protection was afforded by all formulations. No differences were observed between the final enamel SMH values among groups. Antacid suspensions counteracted HCl-induced enamel loss, although they were not effective in reducing enamel softening. Mouth rinsing with antacid suspensions after vomiting can potentially represent a promising strategy to counteract enamel loss caused by erosion.

Bonding strategy of a universal adhesive system containing chitosan: influence on dentin permeability, and effect on adhesive layer micromorphology.

AIM: This study evaluated the influence of chitosan added to a universal adhesive system used in totaletch (TE) or self-etch (SE) mode on dentin permeability, and on the micromorphology of the adhesive layer. MATERIALS AND METHOD: Dentin discs were obtained from human third molars and randomly distributed according to bonding strategy (TE or SE), and to whether or not 1% chitosan (C) was added to a universal adhesive system (Single Bond Universal/3M ESPE), to create the following groups (n=10): TE, TEC, SE, and SEC. Dentin permeability was measured at baseline and after application of dentin treatments. The surface of the adhesive layer (AL) and the dentin adjacent to the AL were examined under a scanning electron microscope. RESULTS: There were no significant differences in permeability percentage between the groups with and without C (TE and SE versus TEC and SEC) (p>0.05; Mann Whitney test). Dentin permeability was lower when the adhesive system was applied in the SE mode, regardless of the addition of C. The micromorphology of the AL surface showed irregularities, and a greater degree of porosity, when the adhesive system was applied in the SE mode, regardless of chitosan addition. There was a greater depth of penetration of the adhesives into the dentin adjacent to the AL in both the TE and TEC groups. Chitosan added to the adhesive system did not influence dentin permeability. CONCLUSIONS: The self-etch strategy led to lower dentin permeability, and to more irregularities on the surface of the adhesive layer.

OBJETIVO: Este estudo avaliou a influência da quitosana adicionada a um sistema adesivo universal usado no modo total-etch (TE) ou self-etch (SE) na permeabilidade dentinária e na micromorfologia da camada adesiva. Materiais e método: Discos de dentina foram obtidos de terceiros molares humanos e distribuídos aleatoriamente de acordo com a estratégia de união (TE ou SE), e para incorporação ou não de quitosana a 1% (Q) em um sistema adesivo universal (Single Bond Universal/3M ESPE), para obter os seguintes grupos (n=10): TE, TEQ, SE e SEQ. A permeabilidade da dentina foi medida no início e após a aplicação dos tratamentos de dentina. A superfície da camada adesiva (CA) e a dentina adjacente à CA foram examinadas em microscópio eletrônico de varredura. RESULTADOS: Não houve diferenças significativas no percentual de permeabilidade entre os grupos com e sem Q (TE e SE versus TEQ e SEQ) (p>0,05; teste de Mann Whitney). Houve um menor percentual de permeabilidade dentinária quando o sistema adesivo foi aplicado no modo SE, independentemente da incorporação de Q. A micromorfologia da superfície da CA apresentou irregularidades e maior grau de porosidade quando o sistema adesivo foi aplicado no modo SE, independentemente da adição de Q. Houve maior profundidade de penetração dos adesivos na dentina adjacente à CA nos grupos TE e TEQ. A quitosana adicionada ao sistema adesivo não influenciou a permeabilidade dentinária. Conclusões: A estratégia autocondicionante levou a uma menor permeabilidade dentinária e a mais irregularidades na superfície da camada adesiva.