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1.
Braz. oral res. (Online) ; 34: e004, 2020. tab, graf
Article in English | LILACS | ID: biblio-1055523

ABSTRACT

Abstract The aim of this study was to analyze the structural, morphological and mechanical properties of two different lithium disilicate glass-reinforced ceramics for CAD-CAM systems (IPS e.max CAD and Rosetta SM). Five methodologies were used for both ceramics: microstructure (n = 2) was analyzed using x-ray diffraction (XRD); morphological properties (n = 2) were analyzed by scanning electron microscopy (SEM), with and without hydrofluoric etching; porosity (n = 3) was assessed using 3D micro-computed tomography (micro-CT); flexural strength was measured (n =1 0) using the three-point bending test; and bond strength was determined with self-adhesive resin cement (n = 10), using a microshear bond test. After performing all the tests, the data were analyzed using t-Student test and two-way ANOVA. All the tests used a significance level of α = 0.05. High peak positions corresponding to standard lithium metasilicate and lithium disilicate with similar intensities were observed for both ceramics in the XRD analysis. Morphological analysis showed that the crystalline structure of the two ceramics studied showed no statistical difference after acid etching. Additionally, no significant differences were recorded in the number or size of the pores for the ceramics evaluated. Moreover, no differences in flexural strength were found for the ceramic materials tested, or in the bond strength to ceramic substrates for the resin cements. Based on the study results, no significant differences were found between the two CAD-CAM lithium disilicate glass-reinforced ceramics tested, since they presented similar crystalline structures with comparable intensities, and similar total porosity, flexural strength and bond strength.


Subject(s)
Ceramics/chemistry , Computer-Aided Design , Dental Porcelain/chemistry , Glass/chemistry , Reference Values , Surface Properties , X-Ray Diffraction , Materials Testing , Microscopy, Electron, Scanning , Reproducibility of Results , Analysis of Variance , Porosity , Dental Bonding/methods , Resin Cements/chemistry , Shear Strength , Flexural Strength
2.
Braz. oral res. (Online) ; 34: e018, 2020. tab, graf
Article in English | LILACS | ID: biblio-1089390

ABSTRACT

Abstract The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.


Subject(s)
Phosphoric Acids/chemistry , Dental Bonding/methods , Potassium Compounds/chemistry , Aluminum Silicates/chemistry , Hydrofluoric Acid/chemistry , Reference Values , Silanes/chemistry , Surface Properties , Time Factors , Materials Testing , Microscopy, Electron, Scanning , Reproducibility of Results , Analysis of Variance , Resin Cements/chemistry , Shear Strength/drug effects , Dental Porcelain/chemistry , Methacrylates/chemistry
3.
Braz. oral res. (Online) ; 33: e041, 2019. tab, graf
Article in English | LILACS | ID: biblio-1001595

ABSTRACT

Abstract: The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the "concentration" factor (p = 0.01) and the interaction "acid concentration X ceramic" (p = 0.009) had a significant effect, however, the "ceramic" (p = 0.897) and "conditioning time" (p = 0.260) factors did not influence the results. The LDHP10%60s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10%20s (6.57 MPa)bA, LCAD5%20s (6,90 ±3,5)aB and LDHP5%60s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.


Subject(s)
Ceramics/chemistry , Dental Bonding/methods , Hydrofluoric Acid/administration & dosage , Surface Properties , Time Factors , Acid Etching, Dental , Materials Testing , Microscopy, Electron, Scanning , Resin Cements/chemistry , Shear Strength , Dental Porcelain/chemistry , Dental Stress Analysis , Hydrofluoric Acid/chemistry
4.
Braz. oral res. (Online) ; 33: e012, 2019. tab, graf
Article in English | LILACS | ID: biblio-989475

ABSTRACT

Abstract The aim of this study was to investigate the mechanical performance and the fracture behavior of endocrown restorations prepared using distinct restorative materials. A total of 42 sound molars with similar crown size and shape were cut at 2 mm above the cementoenamel junction and endodontically treated. They were categorized according to the restorative material used to fabricate endocrown restorations (n=7), namely, conventional composite (Filtek™ Z350 XT), bulk fill composite (Filtek™ Bulk Fill), conventional composite modeled using resin adhesives (SBMP: Scotchbond™ Multipurpose Adhesive; or SBU: Scotchbond™ Universal Adhesive), and IPS e.max lithium disilicate (Ivoclar Vivadent; positive control). Unprepared sound teeth were used as negative control. All endocrowns were bonded using a self-adhesive cement (Rely-X™ U200). The teeth were submitted to fatigue (Byocycle) and fracture (EMIC DL500) testing. Load-to-fracture (in N) and work-of-fracture (Wf, in J/m2) values were analyzed by ANOVA (p < 0.05). The endocrowns did not fracture or de-bond upon fatigue, showing similar load-to-fracture and work-of-fracture values, regardless of the restorative material (p > 0.05). The endocrowns fabricated by combining Z350 and SBMP had the least harsh fractures, in contrast to endocrowns prepared using Z350 only, which exhibited an equilibrium between repairable and irrepairable fractures. The e.max endocrowns exhibited more aggressive failures (root fracture) than other groups, resulting in higher rates of irrepairable fractures. In conclusion, dental practitioners may satisfactorily restore severely damaged nonvital teeth using the endocrown technique. Composite endocrowns prepared using resin adhesive as modeler liquid or using bulk fill material may result in less aggressive failures, thus providing a new material perspective for endocrown restorations.


Subject(s)
Humans , Dentin-Bonding Agents/chemistry , Composite Resins/chemistry , Resin Cements/chemistry , Crowns , Dental Restoration, Permanent/methods , Reference Values , Root Canal Filling Materials/chemistry , Tooth Fractures , Materials Testing , Reproducibility of Results , Dental Prosthesis Design , Tooth, Nonvital , Dental Restoration Failure , Dental Porcelain/chemistry , Dental Stress Analysis
5.
Braz. oral res. (Online) ; 33: e009, 2019. tab, graf
Article in English | LILACS | ID: biblio-1001606

ABSTRACT

Abstract: This study investigates the color correspondence of resin cements and try-in pastes, and the color stability of bonded lithium disilicate ceramic disks. Resin composite disks were fabricated (n = 36) to serve as the background for lithium disilicate disks prepared in two thicknesses (0.5 and 1.0 mm, n = 18 each). Two brands were used for try-in and cement procedures: Variolink Veneer and AllCem Veneer. For baseline, water was applied between the ceramic disks and their respective backgrounds to achieve the control group. This set was subjected to color measurement using an intraoral measurement device (T0). The try-in was inserted between background and ceramic, and this set was subjected to color measurement (T1). After adhesive procedures, the ceramic disk was placed under cement, and color measurement was performed with uncured cement (T2) and 24 h after light-curing (T3). Each set was immersed in distilled water and thermal-cycled, with color measurement being performed after 10,000 (T4) and 20,000 (T5) cycles. Color differences were calculated by CIELab (rEab) and CIEDE2000 (rE00). Data were analyzed by two-way ANOVA for repeated measurements and Tukey's test (α=5%). There was color correspondence of try-in and resin cement for the Variolink system, regardless of the ceramic thickness (p > 0.05). For the AllCem system, the thickness significantly influenced the color measurement (p < 0.001). The Variolink system also demonstrated color stability after 20,000 thermal cycles with rEab < 3.46 and rE00 < 2.25. It was concluded that the color correspondence between a try-in and its respective cement may vary according to resin cement composition.


Subject(s)
Color , Resin Cements/chemistry , Dental Porcelain/chemistry , Ointments/chemistry , In Vitro Techniques , Materials Testing , Ceramics/chemistry , Dental Veneers
6.
Braz. oral res. (Online) ; 33: e026, 2019. tab, graf
Article in English | LILACS | ID: biblio-1001604

ABSTRACT

Abstract: The aim of this study is to evaluate the machinability of four CAD/CAM materials (n = 13) assessed by brittleness index, Vickers hardness, and fracture toughness and interaction among such mechanical properties. The materials selected in this in vitro study are Feldspathic ceramic [FC], Lithium-disilicate glass ceramic [LD], leucite-reinforced glass ceramic [LR], and nanofilled resin material [RN]. Slices were made from the blocks following original dimensions 14 × 12 × 3 mm (L × W × H), using a precision slow-speed saw device and then surfaces were regularized through a polishing device. Brittleness index and fracture toughness were calculated by the use of specific equations for each one of the properties. The Vickers hardness was calculated automated software in the microhardness device. One-way Anova and Pearson's correlation were applied to data evaluation. LD obtained the highest values for brittleness index and was not significantly different from FC. LR presented statistically significant difference compared with RN, which had the lowest mean. Vickers hardness showed LD with the highest average, and no statistical difference was found between FC and LR. RN presented the lowest average. Fracture toughness showed FC and LR not statistically different from each other, likewise LD and RN. The brittleness index, considered also as the machinability of a material, showed within this study as positively dependent on Vickers hardness, which leads to conclusion that hardness of ceramics is related to its milling capacity. In addition, fracture toughness of pre-sintered ceramics is compared to polymer-based materials.


Subject(s)
Polymers/chemistry , Ceramics/chemistry , Computer-Aided Design , Resin Cements/chemistry , Dental Porcelain/chemistry , Aluminum Silicates/chemistry , Reference Values , Surface Properties , Materials Testing , Reproducibility of Results , Analysis of Variance , Statistics, Nonparametric , Hardness Tests
7.
Braz. oral res. (Online) ; 33: e121, 2019. tab, graf
Article in English | LILACS, BBO | ID: biblio-1132648

ABSTRACT

Abstract: The objective of the study was to analyze the surface area (SA) of the wear caused by simulated chewing on human enamel and opposing restorative material, namely: composite resin (CR), porcelain fused to metal (PFM), lithium disilicate (LD), or monolithic zirconia (MZr). Forty-eight premolars were selected as enamel specimens and divided randomly into 4 groups (n = 48; n =12) used as antagonists in chewing simulation (250,000 loading cycles) against one of the four selected test materials. Enamel and material specimens were scanned and evaluated under digital microscope, and wear SA (mm2) were recorded. Descriptive statistics, paired t-test, one-way ANOVA, and post-hoc Tukey-HSD tests were used for statistics (p < 0.05). The smallest and largest SA were exhibited by enamel against LD (0.80 mm2) and PFM (1.74 mm2), respectively. PFM (3.48 mm2) showed the largest SA and CR (2.28 mm2) showed the smallest SA. Paired t-test for SA values showed significant difference (p < 0.05) in all wear comparisons between materials and enamel antagonists. The wear of materials were greater than that of their respective enamel antagonists (p < 0.05). One-way ANOVA of the logarithmic means of wear SA revealed significant differences (P<0.05). Post-hoc Tukey test revealed significance for PFM (p < 0.05) with other materials. Wear of all test materials was greater compared to the wear of enamel antagonists. PFM and LD caused the largest and the smallest enamel wear, respectively. CR, LD, and MZr are more resistant than PFM to wear after simulated chewing against enamel.


Subject(s)
Humans , Adolescent , Adult , Young Adult , Zirconium/chemistry , Metal Ceramic Alloys/chemistry , Composite Resins/chemistry , Dental Enamel/chemistry , Dental Porcelain/chemistry , Tooth Wear/etiology , Mastication , Reference Values , Surface Properties , Image Processing, Computer-Assisted , Materials Testing , Analysis of Variance , Statistics, Nonparametric , Dental Polishing/methods , Microscopy/instrumentation
8.
J. appl. oral sci ; 27: e20180297, 2019. graf
Article in English | LILACS, BBO | ID: biblio-1012517

ABSTRACT

Abstract Polymer-based composite materials have been proposed as an alternative for single unit restorations, due to their resilient and shock absorbing behavior, in contrast to the brittleness of ceramic materials that could result in failure by fracture. Objective: To evaluate the fatigue strength and damage modes of monolithic posterior resin nanoceramic and lithium disilicate glass ceramic crowns. Methodology: Twenty-six resin nanoceramic (RNC) and lithium disilicate glass ceramic (LD) 2 mm monolithic crowns (n=13) were cemented on composite resin replicas of a prepared tooth and subjected to cyclic load with lithium disilicate indenters for 2 million cycles. Specimens and indenters were inspected every 500,000 cycles and suspended when presenting fractures or debonding. Surviving specimens were embedded in epoxy resin, polished and subsurface damage was analyzed. Specimens presenting fractures or severe subsurface damage were considered as failures. Survival data was subjected to Fisher's exact test; damage modes were subjected to Mann-Whitney test (p<0.05). Results: There were no debonding, cohesive or catastrophic failures. Considering subsurface damage, 53.8% of RNC and 46.2% of LD crowns survived the fatigue test, presenting no statistical difference. Chief damage modes were radial cracks for RNC and inner cone cracks for LD, presenting no statistical difference. Conclusions: The results suggest that if debonding issues can be resolved, resin nanoceramic figures can be an alternative to posterior crowns. Although distinct, damage modes revealed potential to cause bulk fracture in both glass ceramic and resin nanoceramic crowns.


Subject(s)
Humans , Ceramics/chemistry , Resin Cements/chemistry , Crowns , Dental Porcelain/chemistry , Surface Properties , Time Factors , Materials Testing , Reproducibility of Results , Dental Prosthesis Design , Computer-Aided Design , Statistics, Nonparametric , Dental Restoration Failure , Dental Restoration Wear , Dental Restoration, Permanent/methods , Dental Stress Analysis
9.
J. appl. oral sci ; 27: e20180351, 2019. graf
Article in English | LILACS, BBO | ID: biblio-1012511

ABSTRACT

Abstract Objective Since the transmittance of ceramics can influence the degree of conversion (DC) of resin cements, ceramics composition and shade should be considered in the selection of resin cement. This in vitro study aimed to evaluate the effect of the transmittance of different composition, opacities and shades of ceramics on the degree of conversion of two dual-cured resin cements. Methodology Sixty discs were prepared from low translucency (LT) and medium opacity (MO) lithium disilicate ceramic, and zirconia ceramic (Z). Each group was subdivided into 5 subgroups (n=4) in shades A2, A3.5, B2, C2 and D3. The transmittance measurement was performed in a spectrophotometer. The Variolink II and Rely X U200 resin cements were photoactivated by LED (1400 mW/cm2) for 40 s through the ceramic discs and without the discs (control group). The DC was measured with infrared FTIR spectroscopy, immediately after light activation. Data were analyzed with Kruskall-Wallis and one-way ANOVA, following post-hoc comparisons by Tukey test and Pearson's correlation test (P<0.05). Results LT ceramic exhibited higher transmittance values compared to MO and Z ceramics. LTA2 and LTB2 showed statistically higher transmittance values compared to MOA2, MOA3.5 and ZA3.5. For Variolink II, the ceramic interposition did not influence the DC, since there were no statistical differences between groups with ceramic interposition and the control group. For Rely X U200 cement, the interposition of some ceramics types/shades (LTA3.5, MOA2, MOA3.5 and ZA3.5) significantly decreased the DC values compared to control group. A positive correlation was found between the ceramic transmittance and DC values of both tested cements. Conclusions. The transmittance and DC values of the cements were influenced by composition and shades of the ceramics. The higher the transmittance of ceramics, the higher the DC values for both cements.


Subject(s)
Zirconium/chemistry , Resin Cements/chemistry , Dental Porcelain/chemistry , Reference Values , Spectrophotometry/methods , Materials Testing , Reproducibility of Results , Analysis of Variance , Statistics, Nonparametric , Phase Transition , Light-Curing of Dental Adhesives , Curing Lights, Dental , Polymerization
10.
Braz. dent. j ; 29(5): 492-499, Sept.-Oct. 2018. tab, graf
Article in English | LILACS | ID: biblio-974174

ABSTRACT

Abstract This study evaluated the effect of different hydrofluoric acid (HF) concentrations on the bond strength between a lithium disilicate-based glass ceramic and a resin cement. Eighty ceramic-blocks (12×7×2 mm) of IPS e.Max CAD (Ivoclar Vivadent) were produced and randomly assigned to 8 groups, considering 2 study factors: HF concentration in 4 levels, i.e., 1% (HF1), 3% (HF3), 5% (HF5), and 10% (HF10), and storage in 2 levels, i.e., baseline (tests were performed 24 h after cementation), and aged (storage for 150 days + 12,000 thermal-cycles at 5°C and 55°C). Acid etching (20 s) was performed, followed by washing, drying, and silanization. Four resin cement cylinders (ϕ= 0.96 mm) were built-up from starch matrices on each ceramic sample (n= 40). Additional ceramic samples were etched and analyzed for contact angle, micro-morphology, and roughness. In baseline condition (without aging), the HF3, HF5, and HF10 groups showed similar bond strength values (13.9 - 15.9 MPa), and HF1 (11.2 MPa) presented lower values than HF5, being that statistically different (p= 0.012). After aging, all the mean bond strengths statistically decreased, being that HF3, HF5, and HF10 (7.8 - 11 MPa) were similar and higher than HF1 (1.8 MPa) (p= 0.0001). For contact angle, HF3, HF5, and HF10 presented similar values (7.8 - 10.4°), lower than HF1 and CTRL groups. HF5 and HF10 presented rougher surfaces than other conditions. For better bond strength results, the tested ceramic may be etched by HF acid in concentrations of 3%, 5%, and 10%.


Resumo Este estudo avaliou o efeito de diferentes concentrações de ácido fluorídrico (HF) na resistência de união entre uma cerâmica vítrea à base de dissilicato de lítio e um cimento resinoso. Oitenta blocos cerâmicos (12×7×2 mm) de IPS e.Max CAD (Ivoclar Vivadent) foram produzidos e distribuídos aleatoriamente em 8 grupos, considerando 2 fatores de estudo: concentração de HF em 4 níveis, isto é, 1% (HF1), 3% (HF3), 5% (HF5), e 10% (HF10), e armazenamento em 2 níveis, isto é, condição inicial (testes foram realizados 24 h após a cimentação), e envelhecidos (150 dias de armazenamento + 12.000 ciclos térmicos a 5°C e 55°C). Condicionamento ácido (20 s) foi realizado, seguido por lavagem, secagem e silanização. Quatro cilindros de cimento resinoso (ϕ= 0.96 mm) foram construídos a partir de matrizes de amido em cada amostra cerâmica (n= 40). Amostras cerâmicas adicionais foram condicionadas e analisadas quanto ao ângulo de contato, micro-morfologia e rugosidade. Na condição inicial (sem envelhecimento), os grupos HF3, HF5, e HF10 mostraram valores de resistência de união similares (13.9 - 15.9 MPa), e HF1 apresentou valores menores que HF5, sendo estatisticamente diferente (p= 0.012). Após o envelhecimento, todas as médias de resistência de união diminuíram estatisticamente, sendo que HF3, HF5 e HF10 foram similares e maiores que HF1 (p= 0.0001). Para o ângulo de contato, HF3, HF5 e HF10 apresentaram valores similares (7.8 - 10.4°), menores que os grupos HF1 e CTRL. HF5 e HF10 apresentaram superfícies mais rugosas que as outras condições. Para melhores resultados de resistência de união, a cerâmica testada pode ser condicionada com ácido fluorídrico nas concentrações de 3%, 5% e 10%.


Subject(s)
Acid Etching, Dental/methods , Ceramics/chemistry , Dental Bonding/methods , Resin Cements/chemistry , Dental Porcelain/chemistry , Hydrofluoric Acid/chemistry , Stress, Mechanical , Surface Properties , Materials Testing , Microscopy, Atomic Force , Shear Strength
11.
Braz. dent. j ; 29(2): 202-207, Mar.-Apr. 2018. tab, graf
Article in English | LILACS | ID: biblio-951528

ABSTRACT

Abstract This study evaluated the effect of the accelerated artificial aging (AAA) on feldspar ceramic strength and the reinforcing effect promoted by adhesive cementation with resin luting agent. One hundred twenty feldspar ceramic disks were obtained. Sixty disks were acid-etched, silanized, and coated with an experimental resin luting agent simulating the adhesive luting procedures. Four groups were created (n=30): uncoated ceramic (control group), uncoated ceramic submitted to AAA, ceramic coated with resin luting agent, and coated ceramic submitted to AAA. Biaxial flexural testing with ball-on-ring setup was carried out. Biaxial flexural strength (s bf , MPa), characteristic strength (s 0 , MPa), and Weibull modulus (m) were calculated for axial positions z=0 (ceramic surface) and z=−t2 (luting agent surface). Data of s bf at positions z=0 and z=-t2 were separately submitted to statistical analyses (a=0.05). The uncoated ceramic submitted to AAA had no significant difference in s bf and s 0 compared with the control group. Resin coating of the ceramic increased s bf and s 0 at z=0. The AAA increased the s bf and s 0 for the resin-coated ceramic specimens at z=0 and also the s 0 at axial position z=-t2. The structural reliability at z=0 and z=-t2 was not influenced by the variables tested. In conclusion, resin coating improved the mechanical strength of the feldspar ceramic. The AAA procedure was not effective in aging the uncoated or resin-coated feldspar ceramic specimens.


Resumo Este estudo avaliou o efeito do envelhecimento artificial acelerado (EAA) na resistência da cerâmica feldspática e o reforço promovido pela cimentação adesiva com cimento resinoso. Cento e vinte discos de cerâmica feldspática foram obtidos. Sessenta discos foram condicionados com ácido, silanizados, e recobertos com um cimento resinoso experimental simulando os procedimentos de cimentação adesiva. Quatro grupos foram criados (n=30): cerâmica sem recobrimento (grupo controle), cerâmica sem recobrimento submetida ao EAA, cerâmica recoberta com cimento resinoso, cerâmica recoberta com cimento resinoso submetida ao EAA. O teste de resistência à flexão biaxial foi realizado utilizando o dispositivo pistão-anel. Resistência à flexão biaxial (s fb , MPa), resistência característica (s 0 , MPa), e módulo de Weibull (m) foram calculados para as posições axiais z=0 (superfície da cerâmica) e z=−t2 (superfície do cimento). Os dados de s fb em z=0 e z=−t2 foram submetidos a análises estatísticas separadamente (a=0,05). A cerâmica não recoberta submetida ao EAA não teve diferença significante na s fb e s 0 comparada com o grupo controle. O recobrimento com cimento resinoso da cerâmica aumentou a s fb e s 0 em z=0. O EAA aumentou a s fb e s 0 para os espécimes de cerâmica recobertos com cimento resinoso em z=0 e também a s 0 em z=−t2. A confiabilidade em z=0 e z=−t2 não foi influenciada pelas variáveis testadas. Concluindo, o recobrimento com cimento resinoso melhorou a resistência mecânica da cerâmica feldspática. O procedimento de EAA não foi efetivo em envelhecer os espécimes de cerâmica feldspática recobertos ou não com cimento resinoso.


Subject(s)
Materials Testing , Potassium Compounds/chemistry , Resin Cements/chemistry , Dental Cements/chemistry , Dental Porcelain/chemistry , Aluminum Silicates/chemistry , Dental Bonding , Composite Resins/chemistry , Dental Stress Analysis
12.
J. oral res. (Impresa) ; 7(1): 30-36, ene. 22, 2018. ilus, tab, graf
Article in English | LILACS | ID: biblio-1119250

ABSTRACT

This study evaluated the shear stress distribution on the adhesive interface and the bond strength between resin cement and two ceramics. For finite element analysis (FEA), a tridimensional model was made using computer-aided design software. This model consisted of a ceramic slice (10x10x2mm) partially embedded on acrylic resin with a resin cement cylinder (Ø=3.4 mm and h=3mm) cemented on the external surface. Results of maximum principal stress and maximum principal shear were obtained to evaluate the stress generated on the ceramic and the cylinder surfaces. In order to reproduce the in vitro test, similar samples to the computational model were manufactured according to ceramic material (Zirconia reinforced lithium silicate - ZLS and high translucency Zirconia - YZHT), (N=48, n=12). Half of the specimens were submitted to shear bond test after 24h using a universal testing machine (0.5 mm/min, 50kgf) until fracture. The other half was stored (a) (180 days, water, 37ºC) prior to the test. Bond strength was calculated in MPa and submitted to analysis of variance. The results showed that ceramic material influenced bond strength mean values (p=0.002), while aging did not: YZHT (19.80±6.44)a, YZHTa (17.95±7.21)a, ZLS (11.88±5.40)b, ZLSa (11.76±3.32)b. FEA results showed tensile and shear stress on ceramic and cylinder surfaces with more intensity on their periphery. Although the stress distribution was similar for both conditions, YZHT showed higher bond strength values; however, both materials seemed to promote durable bond strength.


Subject(s)
Humans , Dental Bonding , Dentin-Bonding Agents/chemistry , Composite Resins/chemistry , Resin Cements , Dental Alloys/chemistry , Dental Porcelain/chemistry , Materials Testing , Adhesiveness , Dental Stress Analysis/methods
13.
Braz. oral res. (Online) ; 32: e001, 2018. tab, graf
Article in English | LILACS | ID: biblio-889461

ABSTRACT

Abstract: This study aimed to compare the vertical marginal gap of teeth restored with lithium disilicate crowns fabricated using CAD/CAM or by pressed ceramic approach. Twenty mandibular third molar teeth were collected after surgical extractions and prepared to receive full veneer crowns. Teeth were optically scanned and lithium disilicate blocks were used to fabricate crowns using CAD/CAM technique. Polyvinyl siloxane impressions of the prepared teeth were made and monolithic pressed lithium disilicate crowns were fabricated. The marginal gap was measured using optical microscope at 200× magnification (Keyence VHX-5000, Japan). Statistical analysis was performed using Wilcoxon test. The lithium disilicate pressed crowns had significantly smaller (p = 0.006) marginal gaps (38 ± 12 μm) than the lithium disilicate CAD/CAM crowns (45 ± 12 μm). This research indicates that lithium disilicate crowns fabricated with the press technique have measurably smaller marginal gaps compared with those fabricated with CAD/CAM technique within in vitro environments. The marginal gaps achieved by the crowns across all groups were within a clinically acceptable range.


Subject(s)
Humans , Dental Impression Technique , Computer-Aided Design , Dental Marginal Adaptation/standards , Crowns/standards , Dental Porcelain/chemistry , Reference Standards , Reference Values , Materials Testing , Reproducibility of Results , Dental Prosthesis Design , Statistics, Nonparametric , Dental Impression Materials
14.
Braz. oral res. (Online) ; 32: e43, 2018. tab, graf
Article in English | LILACS | ID: biblio-889490

ABSTRACT

Abstract To investigate how the hydrofluoric acid (HF) concentrations applied to a lithium disilicate glass-ceramic (EMX) affects the surface morphology and microtensile bond strength (μTBS) of ceramics to dentin, using light-cured resin cements with or without UDMA. Sixty-three EMX square ceramic blocks were etched for 20 seconds using different HF concentrations (1%, 5% and 10%) and luted to dentin using two types of resin cement combinations: BisGMA/TEGDMA and BisGMA/TEGDMA/UDMA (n = 10). Each bonded EMX-dentin block was sectioned to obtain 1 mm2 sticks for μTBS evaluation. Half of the sticks were tested after 24 hours and the other half was assessed after 6 months of water storage. Data were statistically assessed using split-plot three-way ANOVA and multiple comparisons were performed using the Tukey's post hoc test (α = 0.05). One EMX sample from each HF concentration was analyzed using field-emission scanning electron microscope (FE-SEM) to characterize the etching pattern. According to the FE-SEM images, increasing the concentration of HF from 1 to 5 and then to 10% led to increased removal of glassy matrix and greater exposure of lithium disilicate crystals. The 10% HF concentration yielded higher μTBS when compared to 1% for BisGMA/TEGDMA formulation (p < 0.05); whereas HF 1% and 5% showed similar μTBS values when compared to 10% HF for BisGMA/TEGDMA/UDMA resin matrix (p > 0.05) at both storage times. Water aging decreased the μTBS values (p < 0.05), except when 10% HF was associated with BisGMA/TEGDMA resin cement. Resin cement formulation and hydrofluoric acid concentrations can interfere with the immediate and long-term glass-ceramic bond strength to dentin.


Subject(s)
Ceramics/chemistry , Dental Bonding/methods , Resin Cements/chemistry , Dental Porcelain/chemistry , Hydrofluoric Acid/chemistry , Surface Properties , Tensile Strength , Materials Testing , Microscopy, Electron, Scanning , Dental Stress Analysis
15.
Braz. oral res. (Online) ; 32: e118, 2018. tab, graf
Article in English | LILACS | ID: biblio-974438

ABSTRACT

Abstract The aim of this study was to evaluate stress distribution in an occlusal veneer according to the restorative material, restoration thickness, and cement layer thickness. A tridimensional model of a human maxillary first molar with an occlusal veneer preparation was constructed using a modeling software of finite element analysis. The model was replicated 9 times to evaluate the factors: restoration thickness (0.6, 1.2, and 1.8 mm) and cement layer thickness (100, 200, and 300 μm). Then, each model received different restorative materials (High Translucency Zirconia - [YZHT], Lithium Disilicate - [LD], Zirconia Reinforced Lithium Silicate - [ZLS], Feldspathic - [F], and Hybrid Ceramic - [HC]), totaling forty-five groups. An axial load (600 N) was applied on the occlusal face for static structural analysis. Solids were considered isotropic, homogeneous, and linearly elastic. Contacts were considered perfectly bonded. Fixation occurred in the dental root and a mechanical static structural analysis was performed. Descriptive statistical analysis and one-way ANOVA (α =10%) were performed for tensile stress peak values in the restoration and cement layer. The difference between groups was compared using the Tukey's test with 10% significance to match the percentage of the mesh convergence test. According to the results, the cement layer thickness did not influence stress distribution in the restoration (p ≥ 0.10). The thicker the restoration, the higher the tensile stress concentration in the restoration. The graphs showed higher stress concentration in the YZHT, followed by LD, F, ZLS, and HC. Also, the restorative material influenced stress concentration on the cement layer, which decreased according to the sequence HC>YZHT>ZLS>LD>F. HC stood out for causing the least stress concentration in the restoration. Cement layer thickness did not interfere in the mechanical performance of the restorations.


Subject(s)
Humans , Ceramics/chemistry , Dental Cements/chemistry , Dental Restoration, Permanent/methods , Dental Veneers , Reference Values , Silicate Cement/chemistry , Tensile Strength , Zirconium/chemistry , Materials Testing , Reproducibility of Results , Analysis of Variance , Dental Prosthesis Design , Resin Cements/chemistry , Dental Restoration Failure , Finite Element Analysis , Dental Porcelain/chemistry , Dental Stress Analysis , Elastic Modulus , Lithium/chemistry
16.
Braz. oral res. (Online) ; 32: e53, 2018. tab, graf
Article in English | LILACS | ID: biblio-952144

ABSTRACT

Abstract This in vitro study evaluated the fatigue strength of different ceramic materials indicated for monolithic restorations. Disc-shaped specimens were made according to ISO 6872 from five different ceramic materials: feldspathic ceramic (FC), polymer-infiltrated ceramic network (PIC), lithium disilicate glass-ceramic (LD), zirconia-reinforced lithium silicate glass-ceramic (ZLS), and high translucent tetragonal zirconia polycrystals doped by yttrium (YZ-HT). After obtaining the mean of each material (n = 5) from monotonic load-to-failure tests, specimens (n = 20) were subjected to fatigue tests (staircase method) using a biaxial flexural setup (piston-on-three-balls), to determine the fatigue strength. The parameters used for fatigue tests were: 100,000 cycles at 10 Hz, initial load of ~ 60% of mean load-to-failure, and step size of 5% of the initial load (specific for each ceramic material). Kruskal-Wallis and Bonferroni's test (α = 0.05) were used to analyze the fatigue strength data. Fatigue strength (MPa) of the materials was statistically different among each other as follows: YZ-HT (370.2 ± 38.7) > LD (175.2 ± 7.5) > ZLS (152.1 ± 7.5) > PIC (81.8 ± 3.9) > FC (50.8 ± 1.9). Thus, it can be concluded that, in terms of fatigue, high translucent polycrystalline zirconia is the best choice for monolithic restorations as it bears the highest load before cracking/fracturing.


Subject(s)
Stress, Mechanical , Ceramics/chemistry , Computer-Aided Design , Dental Restoration Failure , Reference Values , Surface Properties , Tensile Strength , Zirconium/chemistry , Materials Testing , Microscopy, Electron, Scanning , Reproducibility of Results , Pliability , Dental Porcelain/chemistry , Dental Stress Analysis
17.
J. appl. oral sci ; 26: e20180004, 2018. tab, graf
Article in English | LILACS, BBO | ID: biblio-954510

ABSTRACT

Abstract Objective This study aimed to evaluate the effect of the cavity preparation and ceramic type on the stress distribution, tooth strain, fracture resistance and fracture mode of human molar teeth restored with onlays. Material and Methods Forty-eight molars were divided into four groups (n=12) with assorted combinations of two study factors: BL- conventional onlay preparation with boxes made from leucite ceramic (IPS-Empress CAD, Ivoclar Vivadent); NBL- conservative onlay preparation without boxes made from leucite ceramic; BD- conventional onlay preparation with boxes made from lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent); NBL- conservative onlay preparation with boxes made from lithium disilicate glass ceramic cuspal deformation (µS) was measured at 100 N and at maximum fracture load using strain gauge. Fracture resistance (N) was measured using a compression test, and the fracture mode was recorded. Finite element analysis was used to evaluate the stress distribution by modified von Mises stress criteria. The tooth strain and fracture resistance data were analyzed using the Tukey test and two-way ANOVA, and the fracture mode was analyzed by the chi-square test (α=0.05). Results The leucite ceramic resulted in higher tooth deformation at 100 N and lower tooth deformation at the maximum fracture load than the lithium disilicate ceramic (P<0.001). The lithium disilicate ceramic exhibited higher fracture resistance than the leucite ceramic (P<0.001). The conservative onlay resulted in higher fracture strength for lithium disilicate ceramic. Finite element analysis results showed the conventional cavity preparation resulted in higher stress concentration in the ceramic restoration and remaining tooth than the conservative onlay preparation. The conservative onlays exhibited increased fracture resistance, reduced stress concentration and more favorable fracture modes. Conclusion Molars restored with lithium disilicate CAD-CAM ceramic onlays exhibited higher fracture resistance than molars restored with leucite CAD-CAM ceramic onlays.


Subject(s)
Humans , Ceramics/chemistry , Computer-Aided Design , Dental Cavity Preparation/methods , Dental Porcelain/chemistry , Aluminum Silicates/chemistry , Inlays/methods , Polyurethanes/chemistry , Reference Values , Tooth Fractures , Acrylic Resins/chemistry , Materials Testing , Reproducibility of Results , Analysis of Variance , Statistics, Nonparametric , Composite Resins/chemistry , Dental Restoration Failure , Finite Element Analysis , Dental Stress Analysis , Elastic Modulus , Molar
18.
J. appl. oral sci ; 25(6): 700-707, Nov.-Dec. 2017. tab, graf
Article in English | LILACS, BBO | ID: biblio-893664

ABSTRACT

Abstract Due to increasing of aesthetic demand, ceramic crowns are widely used in different situations. However, to obtain long-term prognosis of restorations, a good conversion of resin cement is necessary. Objective: To evaluate the degree of conversion (DC) of one light-cure and two dual-cure resin cements under a simulated clinical cementation of ceramic crowns. Material and Methods: Prepared teeth were randomly split according to the ceramic's material, resin cement and curing protocol. The crowns were cemented as per manufacturer's directions and photoactivated either from occlusal suface only for 60 s; or from the buccal, occlusal and lingual surfaces, with an exposure time of 20 s on each aspect. After cementation, the specimens were stored in deionized water at 37°C for 7 days. Specimens were transversally sectioned from occlusal to cervical surfaces and the DC was determined along the cement line with three measurements taken and averaged from the buccal, lingual and approximal aspects using micro-Raman spectroscopy (Alpha 300R/WITec®). Data were analyzed by 3-way ANOVA and Tukey test at =5%. Results: Statistical analysis showed significant differences among cements, curing protocols and ceramic type (p<0.001). The curing protocol 3x20 resulted in higher DC for all tested conditions; lower DC was observed for Zr ceramic crowns; Duolink resin cement culminated in higher DC regardless ceramic composition and curing protocol. Conclusion: The DC of resin cement layers was dependent on the curing protocol and type of ceramic.


Subject(s)
Humans , Resin Cements/chemistry , Dental Cements/chemistry , Dental Porcelain/chemistry , Esthetics, Dental , Curing Lights, Dental , Surface Properties , Materials Testing
19.
J. appl. oral sci ; 25(5): 566-574, Sept.-Oct. 2017. tab, graf
Article in English | LILACS, BBO | ID: biblio-893657

ABSTRACT

Abstract Objective: This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany) thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany). Material and Methods: Thirty zirconia bars (20.0x4.0x1.0 mm) and six zirconia blocks (12.0x7.5x1.2 mm) were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10) were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. Results: The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor "thickness of the porcelain" was statistically significant (p=0.001) and the l-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. Conclusion: The smallest (1 mm) thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different.


Subject(s)
Zirconium/chemistry , Ceramics/chemistry , Dental Porcelain/chemistry , Reference Values , Surface Properties , Tensile Strength , Time Factors , Materials Testing , Reproducibility of Results , Analysis of Variance , Pliability , Microscopy, Confocal , Dental Restoration Failure , Dental Stress Analysis , Hardness Tests , Hot Temperature
20.
Bauru; s.n; 2017. 84 p. ilus, tab.
Thesis in Portuguese | LILACS, BBO | ID: biblio-883241

ABSTRACT

O propósito deste trabalho foi avaliar, in-vitro, a alteração de cor da cerâmica de dissilicato de lítio, após o envelhecimento artificial acelerado (EAA), variando-se os seguintes aspectos: processo de confecção (cerâmica monolítica e com infraestrutura coberta por cerâmica de revestimento), espessuras de 1,5 e 2,0mm e substratos de resina e liga metálica, com e sem cimento. Para isso foram confeccionadas 40 pastilhas de cerâmica IPS e.max Press, que foram divididas em 2 grupos (n=20): LT (cerâmica de baixa translucidez na cor A2) e HO (cerâmica de alta opacidade). Neste grupo as pastilhas foram confeccionadas com 0,5mm de espessura e, posteriormente, revestidas com a cerâmica IPS e.max Ceram na cor A2 e com espessuras de 1,0 e 1,5mm. Foram utilizados substratos em resina composta (n=20) e em liga metálica (cobre-alumínio) (n=20). Para a cimentação foi utilizado o cimento de polimerização dual Variolink II, na cor translúcida. A leitura da cor foi realizada em um espectrofotômetro (Minolta CM2600d), equipado com fonte de luz padrão D65 (luz do dia). A cor determinada no aparelho é expressa em coordenadas CIE L* a* b* e os valores correspondentes foram utilizados para calcular o E. Foram feitas as seguintes comparações: discos de cerâmica antes do EAA vs discos de cerâmica cimentadas sobre os substratos antes do EAA; discos de cerâmica cimentadas sobre os substratos antes do EAA vs discos de cerâmica cimentadas sobre os substratos após o EAA; discos de cerâmica antes do EAA vs discos de cerâmica cimentadas sobre os substratos após o EAA; discos de cerâmica antes do EAA vs discos de cerâmica após o EAA. Os dados foram submetidos a análise estatística (ANOVA) a 3 critérios e (ANOVA) a 2 critérios e testes de Tukey, p<0,05). Os resultados mostraram que: 1. os grupos somente de discos de cerâmica vs discos de cerâmica com 1,5 e 2,0mm de espessuras, cimentadas em substratos de resina e liga metálica, antes do EAA. O menor valor encontrado de E (E=3,6) foi com o grupo de discos da cerâmica HOA2 com 2mm de espessura cimentados em substrato de metal, seguido pelo grupo da mesma cerâmica com 1,5mm de espessura cimentada em substrato de resina. O maior valor encontrado (E=10,0) foi com os discos de cerâmica LTA2 com 1,5 e 2mm de espessuras e cimentados em substrato de metal; 2. os grupos com discos de cerâmicas com 1,5 e 2,0mm de espessuras e cimentados em substratos de resina e liga metálica antes do EAA vs o mesmo grupo após EAA. Os grupos de discos com a cerâmica HOA2 com 2mm de espessura cimentados em substrato de metal teve menor alteração de cor (E=1,1) e a maior alteração de cor ocorreu com o grupo da cerâmica LTA2 com 2mm de espessura cimentada em substrato de metal (E=2,1); 3. os grupos somente com discos de cerâmica antes do EAA vs grupos de cerâmicas com discos de 1,5 e 2,0mm de espessuras e cimentados em substratos de resina e liga metálica após o EAA. O menor valor encontrado (E=3,7) foi com a cerâmica HOA2 com revestimento e 2mm de espessura cimentada em substrato de metal. O maior valor encontrado (E=10,0) foi o da cerâmica LTA2 com 1,5 e 2mm de espessuras cimentadas em substrato de metal; 4. os grupos discos de cerâmica, antes e após o processo de EAA O grupo que teve menor alteração de cor foi o da cerâmica HOA2 com 1,5mm (E=0,6). O grupo que teve maior alteração de cor foi o da cerâmica LTA2 com 2mm (E=2,2). Concluiu-se que o EAA causou alteração na cor final das cerâmicas de dissilicato de lítio, levando-se em conta as variáveis pesquisadas.(AU)


The purpose of this in vitro study was to evaluate the color changing of the lithium disilicate ceramic discs after accelerated artificial aging (AAA) varying the following aspects: manufacturing process (monolithic ceramic and infrastructure with ceramic covering), thickness of the ceramic (1.5 and 2.0 mm) and abutment substrate (composite resin and alloy), with and without cement. Forty ceramic discs were fabricated with ceramic IPS e.max Press and divided into two groups (n = 20): LT (low translucency, shade A2) and HO (high opacity). In the HO group, the discs were fabricated with a thickness of 0.5 mm of the IPS e.max Ceram combined with a thickness of 1 or 1.5mm of veneering ceramic, shade A2. The abutments substrates were fabricated with composite resin (n = 20) and metallic alloy (n = 20). The resin cement used was Variolink II translucent color. Color was measured with a spectrophotometer and expressed in CIE L * a * b * coordinates. Color differences (E) were calculated. The data were analyzed with ANOVA and the Tukey HSD test (p <0.05).The results showed that 1.in the groups of ceramic discs vs. ceramic discs with 1.5 and 2.0mm thickness, cemented on resin substrates and metal alloy, before AAA, the lowest value of E (E = 3,6) was obtained for HOA2 ceramic discs with 2mm thickness cemented in metal substrate, followed by ceramic discs with 1.5mm thickness cemented in substrate of resin. The highest value (E = 10.0) was observed for ceramic discs LTA2 with 1.5 and 2mm thickness and cemented in metal substrate; 2. In the groups with ceramic discs with 1.5 and 2.0mm thickness and cemented on resin and metal substrates prior to AAA vs the same group after AAA, the HOA2 ceramic discs with 2mm thickness cemented on a metal substrate had the smallest color change (E = 1,1) and the largest occurred for LTA2 with 2mm thickness and cemented in metallic substrate (E = 2.1); 3. In the groups of ceramic discs before AAA vs groups of ceramic with discs of 1.5 and 2.0mm of thickness and cemented on resin substrates and metal alloy after AAA, the lowest value (E = 3,7) was obtained for HOA2 veneering ceramic 2mm thickness cemented on a metal substrate. The highest value found (E = 10.0) was for LTA2 ceramic with 1.5 and 2mm thickness cemented on a metal substrate; 4. comparing the groups of ceramic discs before and after the AAA process, the lowest color change was obtained for HOA2 ceramic with 1.5mm (E = 0.6) and the greatest color change was fore LTA2 ceramic with 2mm (E = 2.2). It was concluded that the AAA caused alteration in the final color of the lithium disilicate ceramics, taking into account the variables studied.(AU)


Subject(s)
Ceramics/chemistry , Dental Porcelain/chemistry , Dental Prosthesis Design , Prosthesis Coloring , Resin Cements/chemistry , Analysis of Variance , Color , Colorimetry , Materials Testing , Metal Ceramic Alloys , Reproducibility of Results , Spectrophotometry , Time Factors
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