Restabelecimento da Dimensão Vertical de Oclusão com JIG estético modificado e Prótese Parcial Removível Overlay: relato de caso / Reestablishment of occlusal vertical dimension with a modified aesthetic JIG and an overlay removable partial denture: a case report

A reabilitação de pacientes parcialmente edêntulos com desgaste dentário severo e dimensão vertical de oclusão reduzida é desafiadora e complexa. Objetivo: Descrever o restabelecimento da dimensão vertical de oclusão e parâmetros estéticos com uma prótese parcial removível do tipo overlay (PPRO) com auxílio de um JIG estético modificado. Relato de caso: Paciente do sexo masculino, 58 anos de idade, procurou serviço odontológico queixando-se de insatisfação com a estética do sorriso e perda dos dentes posteriores. Ao exame clínico, foram observados desgaste dentário excessivo e edentulismo parcial nas arcadas superior e inferior. Então, foi proposto tratamento em 2 etapas (provisória e definitiva) com PPRO em maxila. O JIG estético foi usado como guia de referência para incrementos em resina composta fotopolimerizável e o restabelecimento da dimensão vertical de oclusão foi determinado a partir de métodos métrico, fonético e estético. Os dentes desgastados foram aumentados e os dentes ausentes substituídos por dentes artificiais a partir de uma PPRO provisória. Após 2 meses de adaptação, a reabilitação final com PPRO definitiva foi conduzida baseando-se na reabilitação com a PPRO provisória. Conclusão: O paciente relatou satisfação com a estética e desempenho funcional com o tratamento. Portanto, o JIG estético beneficia o planejamento e o tratamento para restabelecer a dimensão vertical de oclusão. Além disso, a PPRO é uma alternativa reversível, de baixo custo, para reabilitar a estética e a função de pacientes com desgaste severo e perda parcial dos dentes.

The rehabilitation of partially edentulous patients with severe tooth wear and reduced occlusal vertical dimension is challenging and complex. Objective: To describe the reestablishment of occlusal vertical dimension and aesthetic parameters with an overlay re-movable partial denture (ORPD) with the aid of a modified aesthetic JIG. Case report: A 58-year-old man sought dental service complaining of dissatisfaction with the aesthetics of his smile and a loss of posterior teeth. At clinical examination, excessive tooth wear and partially edentulism in the lower and upper arches were observed. A two-step treatment (interim and definitive) with an ORPD in the upper arch was proposed. The aesthetic JIG was used as a reference guide for the increments in light-curing resin composite, and the reestablishmentthe occlusal vertical dimension was determined using aesthetic, phonetic, and metric methods. The worn teeth were increased, and the missing natural teeth were replaced by artificial teeth using a temporary ORPD. After two months of adaptation, de-finitive rehabilitation with a definitive ORPD was performed based on the interim ORPD. Conclusion: The patient reported satisfaction with the esthetic and functional performance of this treatment. Therefore, the aesthetic JIG benefits the planning and treatment of reduced vertical dimension. Moreover, the ORPD is a reversible and lower-cost alternative to rehabilitate the aesthetics and function of patients with severe teeth wear and partial teeth loss.

Influence of acid etching and universal adhesives on the bond strength to dentin

Abstract The purpose of this study was to evaluate the influence of the application mode of three universal adhesive systems on interfacial physical properties of indirect composite restorations adhesively cemented to dentin cavities. Seventy-eight bovine lower incisors were selected and a slice of dentin (thickness: 2 mm) between the buccal surface and pulp chamber was obtained for each tooth. Conical cavities were made on this surface. The internal walls of the cavities were then coated with a hydrophilic gel, filled with composite resin and photopolymerized. The dentin/cone sets were divided into 6 groups (n=10) according to type of universal adhesive (TETRI: Tetric N Bond, FUT: Futura Bond U, SBU: Single Bond Universal) and acid etching on dentin (A: with acid etching; WA: without acid etching). The acid etching and the adhesive systems were applied to the surface of the dentin. All composite resin cones were sandblasted (Al2O3, 20 s) and silanized. After surface treatment, the cones were cemented (RelyX Ultimate) into the dentin cavity and photopolymerized. After thermocycling (10,000 cycles), samples were submitted to marginal adaptation analysis (using caries detector dye), push-out test (0.5 mm/min), and failure mode analysis. Additional samples were prepared for nanoleakage analysis (SEM). The data (MPa) were analyzed by two-way ANOVA and Tukey's post-test (5%). The groups in which the dentin was acid etched showed significantly lower bond strength values in the push-out test (p<0.01). Dentin acid etching significantly reduced the bond strength between universal adhesive systems and dentin in indirect restorative procedures.

Resumo O objetivo deste estudo foi avaliar a influência do modo de aplicação de três sistemas adesivos universais nas propriedades físicas interfaciais de restaurações indiretas de compósito adesivamente cimentadas a cavidades dentinária. Setenta e oito incisivos inferiores bovinos foram selecionados e uma fatia de dentina (espessura: 2 mm) entre a face vestibular e a câmara pulpar foi obtida para cada dente. Cavidades cônicas foram feitas nesta superfície. As paredes internas das cavidades foram então revestidas com um gel hidrofílico, preenchidas com resina composta, e fotopolimerizados. Os conjuntos dentina/cone foram divididos em 6 grupos (n=10) de acordo com o tipo de adesivo universal (TETRI: Tetric N Bond, FUT: Futura Bond U, SBU: Single Bond Universal) e ácido na dentina (A: com condicionamento ácido; WA: sem condicionamento ácido). O condicionamento ácido e os sistemas adesivos foram aplicados na superfície da dentina. Todos os cones de resina composta foram jateados (Al2O3, 20 s) e silanizados. Após o tratamento superficial, os cones foram cimentados (RelyX Ultimate) na cavidade dentinária e fotopolimerizados. Após a termociclagem (10.000 ciclos), as amostras foram submetidas a análise de adaptação marginal (usando corante detector de carie), teste push-out (0,5 mm/min) e análise do modo de falha. Amostras adicionais foram preparadas para análise de nanoinfiltração (MEV). Os dados (MPa) foram analisados por ANOVA dois fatores e pós-teste de Tukey (5%). Os grupos em que a dentina foi condicionada por ácido apresentaram valores significativamente menores de resistência de união no teste push-out (p<0,01). O condicionamento ácido da dentina reduziu significativamente a resistência de união entre sistemas adesivos universais e dentina em procedimentos restauradores indiretos.

Effect of glazing application side and mechanical cycling on the biaxial flexural strength and Weibull characteristics of a Y-TZP ceramic

Abstract Glaze application on monolithic zirconia (Y-TZP) can be a practical approach to improve the mechanical properties of this material. Objective Our study evaluated the effect of glazing side and mechanical cycling on the biaxial flexure strength (BFS) of a Y-TZP. Methodology Eighty sintered Y-TZP discs (Ø:12 mm; thickness: 1.2 mm - ISO 6872) were produced and randomly assigned into eight groups (n=10), according to the factors "glazing side" (control - no glazing; GT - glaze on tensile side; GC - glaze on compression side; GTC - glaze on both sides) and "mechanical aging" (non-aged and aged, A - mechanical cycling: 1.2×106, 84 N, 3 Hz, under water at 37°C). Specimens were subjected to BFS test (1 mm/min; 1,000 Kgf load cell) and fractured surfaces were analyzed by stereomicroscopy and SEM. Hsueh's rigorous solutions were used to estimate the stress at failure of glazed specimens. Two-way ANOVA, Tukey's test (5%), and Weibull analysis were performed. Results The "glazing side", "mechanical aging" and the interaction of the factors were significant (p<0.05). Groups GC (1157.9±146.9 MPa), GT (1156.1±195.3 MPa), GTC (986.0±187.4 MPa) and GTC-A (1131.9±128.9 MPa) presented higher BFS than control groups (Tukey, 5%). Hsueh's rigorous solutions showed that the maximum tensile stress was presented in the bottom of zirconia layer, at the zirconia/glaze interface. Weibull characteristic strength (σo) of the GC was higher than all groups (p<0.05), except to GT, GTC-A and GTC, which were similar among them. The fractography showed initiation of failures from zirconia the tensile side regardless of the side of glaze application and fatigue. Conclusion Glazing zirconia applied on both tensile and compression sides improves the flexural strength of Y-TZP, regardless the mechanical aging.

Effect of different surface treatments and multimode adhesive application on the Weibull characteristics, wettability, surface topography and adhesion to CAD/CAM lithium disilicate ceramic

Abstract This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic. Methodology: For SBS test, 32 blocks (7x7x2 mm) of lithium disilicate were obtained and randomly divided into eight groups (four blocks per group) according to each surface treatment (HF 20 s, 60 s, 120 s + silanization/S or Scotch Bond Universal/ SBU) and the Monobond Etch & Prime - MEP application followed or not by SBU. On each treated surface ceramic block, up to four dual-curing resin cement cylinders were prepared and light-cured for 40s (N=120/n=15). The specimens were thermocycled (10,000 cycles, 5-55°C, 30 s) and the SBS test (50KgF, 0.5 mm/min) was performed. Furthermore, failure analysis, wettability, AFM, and SEM were carried out. SBS data (MPa) were analyzed using Student's t-test, two-way ANOVA, Tukey's test (5%) and Weibull's analysis. Results: For HF experimental groups, two-way ANOVA presented the factors "etching time" and "bonding agent" as significant (p<0.05). After silane application, the HF groups presented similar bond strength. SBU application compromised the SBS, except for 120s etching time (HF120sS: 23.39ᵃ±6.48 MPa; HF120sSBU: 18.76ᵃ±8.81MPa). For MEP groups, SBU application did not significantly affect the results (p=0.41). The MEP group presented the highest Weibull modulus (4.08A) and they were statistically different exclusively from the HF20sSBU (0.58B). Conclusion: The HF 20s, 60s, 120 s followed by silane, promoted similar resin-bond strength to ceramic and the SBU application after HF or MEP did not increase the SBS.

Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

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.

Interfacial properties and bottom/top hardness ratio produced by bulk fill composites in dentin cavities

Abstract The aim of this study was to evaluate the bond strength, bottom/top hardness ratio, marginal adaptation, and interfacial nanoleakage of regular viscosity bulk fill composites (RVBFC) and regular viscosity traditional composites (RVTC). Two RVBFC (Filtek Bulk Fill and Aura Bulk Fill) and two RVTC (Filtek Z250XT and Aura) were assessed. Forty conical cavities (4.8×2.8×4.0) were prepared in bovine dentin and restored with composites (n=10). After 24h in water, marginal adaptation was evaluated by staining with a caries detector. The top and bottom surfaces of the conical restorations were stained for five seconds and the gap percentage in the composite/dentin interface was determined using digital images on a measurement program (ImageTool). The Vickers microhardness was measured and the bottom/top microhardness ratio (B/T) was determined. Push-out bond strength test was performed in a universal testing machine (0.5mm/min) and failure modes were evaluated in a stereomicroscope (20×). Other specimens (n=3) were produced for interfacial nanoleakage evaluation. Data were analyzed using one and two-way ANOVA and Tukey's test (α=0.05). The gap percentage was higher in the bottom compared to the top. The B/T ratio of the Aura Bulk Fill was statistically lower than other composites. Push-out bond strength were similar among composites. The RVBFC presented lower nanoleakage than the RVTC in the bottom of the conical restoration and there was no difference among the materials in the top surfaces. In conclusion, Filtek Bulk Fill performed better than Aura Bulk Fill regarding the analyzed properties.

Resumo O objetivo deste estudo foi avaliar a resistência de união, razão base/topo de microdureza, adaptação marginal e nanoinfiltração interfacial de resinas compostas bulk fill (BF) e tradicional (RT) de viscosidade regular.: Duas BF (Filtek Bulk Fill e Aura Bulk Fill) e duas RT (Filtek Z250XT e Aura) foram testados. Quarenta cavidades cônicas (4,8×2,8×4,0) foram preparadas em dentina bovina e restauradas com os compósitos (n=10). Depois de 24 h em água, a adaptação marginal foi avaliada por meio do corante com detector de cárie. As faces de topo e base das restaurações cônicas foram coradas por cinco segundos e a porcentagem de fendas na interface compósito/dentina foi determinada utilizando-se imagens analisadas num programa (ImageTool). A microdureza Vickers foi mensurada e a razção base/topo de microdureza (B/T) foi determinada. A resistência de união por push-out foi executada numa máquina de ensaios universal (0,5mm/min) e o padrão de fratura avaliado num estereomicroscópio (20x). Espécimes adicionais (n=3) foram confeccionados para avaliação da nanoinfiltração interfacial. Os dados foram analisados por meio de ANOVA a dois fatores e teste de Tukey (a=0,05). A porcentagem de fendas foi maior na base que no topo. A B/T da Aura Bulk Fill foi estatisticamente menor que os demais compósitos. A resistência de união por push-out foi similar entre os compósitos. As BF apresentaram menos nanoinfiltração que as RT na base das restaurações cônicas e não houve diferenças entre os materiais no topo. Conclui-se que a Filtek Bulk Fill comportou-se melhor que a Aura Bulk Fill considerando-se as propriedades analisadas.

Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics

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.

Bond and topography evaluation of a Y-TZP ceramic with a superficial low-fusing porcelain glass layer after different hydrofluoric acid etching protocols / Avaliação da adesão e topografia de uma zircônia Y-TZP com uma camada de glaze após diferentes protocolos de condicionamento com ácido fluorídrico

Introduction: Despite being one of the most studied ceramics today, zirconia still does not have a well-defined adhesion protocol. Objective: Evaluate the influence of different etching times and hydrofluoric acid (HF) concentrations on the zirconia surface and bond strength between a vitrified Y-TZP ceramic and a resin cement. Materials and method: The zirconia surface treatments were: sandblasting with silica-coated alumina (Co); glaze application + 5% HF etching for 5s (G5-5s), 10s (G5-10s) or 20s (G5-20s); glaze application + 10% HF etching for 5s (G10-5s), 10 (G10-10s) or 20s (G10-20s) . Then, cement cylinders (3.3 × 3.3 mm) were built up for shear bond test on all specimens. The specimens were subjected to 6000 thermal cycling before the test. Fractures were analyzed by stereomicroscope. Data were statistically analyzed by Kruskal-Wallis and Dunn statistical tests (5%). Extra samples of each group were made to obtain profilometry and scanning electron microscopy (SEM). Result: Zirconia-cement bond strength was affected by the ceramic surface treatments (p = 0.001). G10-5s (2.71 MPa) recorded the highest bond strength values, followed by the Co (2.05 MPa) while G5 groups had the lowest bond value. Adhesive failure of the samples predominated. The image analysis revealed G5 groups seem to have a lower roughness when compared to groups treated by 10% HF. The creation of pores in the low-fusing porcelain glass layer surface occurred only when 10% HF was used. Conclusion: The low-fusing porcelain glass layer application was able to overcome the sandblasting and obtain a greater adhesive bond to the resinous cement, however, only when 10% HF was used for an interval of 5 seconds.

Introdução: Apesar de ser uma das cerâmicas mais estudadas atualmente, a zircônia ainda não possui um protocolo bem definido para uma cimentação adesiva. Objetivo: Avaliar a influência de diferentes tempos de condicionamento e concentrações do ácido fluorídrico (AF) na superfície da zirconia e na resistência de união entre uma cerâmica Y-TZP vitrificada e um cimento resinoso. Material e método: Os tratamentos de superfície foram: jateamento com óxido de alumínio revestido com sílica (Co); aplicação de glaze + condicionamento com AF 5% por 5s (G5-5s), 10s (G5-10s) ou 20s (G5-20s); aplicação de glaze + condicionamento com AF 10% por 5s (G10-5s), 10 (G10-10s) ou 20s (G10-20s). Em seguida, cilindros de cimento (3,3 × 3,3mm) para teste de cisalhamento foram feitos em todos os espécimes. Os espécimes foram submetidos a 6000 ciclos térmicos antes do teste de adesão. As fraturas foram analisadas por estereomicroscópio. Os dados foram analisados ​​estatisticamente por Kruskal-Wallis e Dunn (5%). Amostras extra de cada grupo foram feitas para realização de perfilometria e microscopia eletrônica de varredura (MEV). Resultado: A resistência de união zircônia-cimento foi afetada pelos tratamentos de superfície (p = 0,001). Os grupos G10-5s (2,71 MPa) registraram os maiores valores de resistência de união, seguidos pelos Co (2,05 MPa), enquanto os grupos G5 apresentaram o menor valor de união. Falhas adesivas foram predominantes. As análises por imagem revelaram que os grupos G5 parecem ser menos rugosos quando comparados aos grupos tratados com AF 10%. A criação de poros na superfície vítrea (glaze) ocorreu apenas quando foi utilizado AF 10%. Conclusão: A aplicação de camada de vidro de porcelana de baixa fusão foi capaz de superar o jateamento e obter uma maior adesão adesiva ao cimento resinoso, no entanto, somente quando foi utilizado 10% de HF por um intervalo de 5 segundos.

Effect of different bonding protocols on degree of monomer conversion and bond strength between orthodontic brackets and enamel

Abstract The objective of the present study was to evaluate the effect of different surface treatments and polymerization protocols on the bond strength of brackets to enamel, and the degree of conversion of the bonding agents. 120 bovine crowns were embedded in acrylic resin blocks and sanded. Next, the blocks were randomly assigned into 12 groups. Metal brackets were bonded to enamel according to the "surface treatment" factor (A: Phosphoric Acid; ATxt: Phosphoric Acid + Transbond XT Primer®; Tse: Transbond Plus Self Etching Primer®; and SBU: Scotchbond Universal®) and "polymerization" factor (R20: Radii-Cal®/20 seconds; V20: Valo Cordless®/20 seconds; and V3: Valo Cordless®/3 seconds). All samples were stored for 6 months (water, 37ºC) and then subjected to a shear bond strength test (SBS). Bond failures were classified according to the Adhesive Remnant Index (ARI) and analyzed with the Kruskal-Wallis and Mann-Whitney tests (5%). Using the same factors, 120 resin discs were made to assess the degree of conversion (DC) of the monomer. Data from the SBS (MPa) and DC (%) were analyzed by analysis of variance (2 factors) and Tukey's test (5%). For the SBS, the factors "polymerization" (R20 = 8.1B; V20 = 13.2A; V3 = 5.2C, p = 0.0001) and "surface treatment" (A = 3.1C; ATxt = 13.6A; Tse = 12.3A; SBU = 6.3B, p = 0.0001) were statistically significant among groups. The highest adhesion value were found for the ATxt/V20 group (22.2A) and the lowest value for the A/R20 group (1.2E). Regarding ARI, score 2 was the most prevalent in groups A, ATxt, V20 and V3, while score 4 was the most prevalent in the Tse, SBU and R20 groups, with no significant difference between them (p = 1.0). Regarding DC, the factors "polymerization" (R20 = 66.6A; V20 = 58.4B; V3 = 45.1C, p = 0.0001) and "surface treatment" (A = 52B, ATxt = 59.7A, Tse = 51.4B, SBU = 63.8A, p = 0.0001) were statistically significant. Tse was more sensitive to the variations in polymerization protocols than the other surface treatments. Treatment A did not present suitable bond strength or degree of conversion.

Can heat-pressed feldspathic ceramic be submitted to multiple heat-pressing?

Abstract The aim of this study was to determine if multiple processing (heat-pressing) of a dental ceramic influences flexural strength, hardness, and microstructure. Ninety bar-shaped specimens (15 mm × 4 mm × 2 mm) of a pressed ceramic (Vita PM9) were fabricated and randomly divided into 6 groups (n = 15) according to the factors "number of pressings" (C1, C2, and C3, fired 1, 2, and 3 times, respectively) and "mechanical cycling" (M). Half of the specimens were mechanically cycled (106 cycles, 45 N, 3.4 Hz, in water) and all specimens were tested for 3-point bending (0.5 mm/min, load 1000 kgf) and Vickers hardness (19.6 N for 20 s). X-ray diffraction was used to characterize the phases and scanning electron microscopy to characterize the microstructure. The flexural strength data was statistically analyzed with Weibull analysis, ANOVA, and Tukey test. Hardness data was evaluated by 2-way ANOVA and Fisher test. All tests were performed with a significance level of 0.05. Two-way ANOVA revealed that neither "number of pressings" (p=0.085) or "mechanical cycling" (0.055) significantly affected flexural strength. But Weibull analysis showed significant difference for Weibull moduli and characteristic strength between groups. For hardness, a statistical difference was seen for the interaction "Number of pressings * Mechanical cycling", (p = 0.016). Hardness decreased in the following order: C1 (775±17.2), CM3 (751±101), CM2 (735±45), C3 (701±82), CM1 (671±82), and C2 (663±92). Fewer defects were observed with an increased number of firings. Therefore, the possibility of recycling PM9 ceramic does not interfere in the evaluated mechanical properties and improves microstructure.

Influência da Concentração e do Tempo de Condicionamento com Ácido Hidrofluorídrico na Rugosidade e Morfologia Superficial de uma Zircônia Glazeada / Influence of Hydrofluoric Acid Concentration and Etching Time on the Surface Roughness and Morphology of a Glazed Zirconia

Objetivo: Avaliar o efeito da concentração e do tempo de condicionamento com ácido fluorídrico na rugosidade e morfologia superficial de uma zircônia glazeada. Materiais e Métodos: Blocos de cerâmica à base de zircônia (5×5×3 mm) (Vita YZ-2000-Cubes, Vita- Zahnfabrik, Alemanha) foram confeccionados e divididos em 6 grupos, de acordo com os fatores "concentração do ácido fluorídrico (HF)" (5% e 10%) e "tempo de condicionamento" (20 s, 60 s e 90 s) (n=2): HF10/20 = HF 10% + 20 s; HF10/60 = HF 10% + 60 s; HF10/90 = HF 10% + 90 s; HF5/20 = HF 5% + 20 s; HF5/60 = HF 5% + 60 s; HF5/ 90 = HF 5% + 90 s. O glaze (Vita Akzent, Vita-Zahnfabrik, Alemanha) foi aplicado com o auxílio de um pincel e sinterizado de acordo com as recomendações do fabricante. Após os diferentes protocolos de condicionamento, foram aferidas cinco medições de rugosidade (Ra) para cada espécime em Perfilômetro Digital (Wyko®, Modelo NT- 1100, Veeco, EUA). Os dados (µm) obtidos foram analisados estatisticamente com análise de variância (ANOVA 2-fatores) e Teste de Tukey (95%). Resultados: O fator "concentração do ácido fluorídrico" (p=0,149) não foi significante estatísticamente. No entanto, o fator "tempo de condicionamento" (p=0,009) foi significante. A interação entre os fatores também apresentou significância estatística (p=0,00). As médias de rugosidade (±desvio-padrão) obtidas foram (µm): GHF10/20=1,94(±0,72)A, GHF5/90=1,92(±0,19)A, GHF5/ 20=1,38(±0.48)AB, GHF5/60=1,18(±0,63)B, GHF10/60=1,17(±0,30)B, GHF10/90=0,82(±0,27)B (Tukey). Conclusão: Conclui-se que o ácido fluorídrico (10%) em maior concentração, associado a um menor tempo de condicionamento (20 s), promoveu maior rugosidade superficial da zircônia glazeada. (AU)

Objective: The aim of this study was to evaluate the effect of different etching protocols on the surface roughness of a glazed zirconia. Material and Methods: Zirconia ceramic-blocks (5 × 5 × 3 mm) (Vita YZ-2000-Cubes, Vita-Zahnfabrik, Germany) were prepared and divided into 6 groups according to the variables "concentration of hydrofluoric acid (HF)" (5 % and 10 %) and " etching time " (20 s, 60 s and 90 s) (n = 2), as follows: HF10/20 = HF 10% + 20 s; HF10/60 = HF 10% + 60 s; HF10/90 = HF 10% + 90 s; HF5/20 = HF 5% + 20 s; HF5/60 = HF 5% + 60 s; HF5/90 = HF 5% + 90 s. The glaze (Vita Akzent, Vita- Zahnfabrik, Germany) was applied with a brush and sintered according to the manufacturer's recommendations. After different etching protocols, five roughness (Ra) measurements were taken for each specimen in a digital profilometer (Wyko ®, Model NT-1100, Veeco, USA). The data were statistically analyzed using analysis of variance (ANOVA 2­way) and Tukey's test (95%). Results: The variable "concentration of hydrofluoric acid" (p=0.149) was not statistically significant, while the variable "etching time" (p=0.009) was significant. The interaction between variables was statistically significant (p = 0.00). The roughness averages (± standard deviation) obtained were (µm): GHF10/20=1.94(±0.72)A, GHF5/90=1.92(±0.19)A, GHF5/ 20=1.38(±0.48)AB, GHF5/60=1.18(±0.63)B, GHF10/60=1.17(±0.30)B, GHF10/90=0.82(±0.27)B (Tukey). Conclusion: It can be concluded that hydrofluoric acid (10%) at a higher concentration associated with a lower etching time (20 s) promoted higher superficial roughness on glazed zirconia. (AU)

Bonding of the Polymer Polyetheretherketone (PEEK) to Human Dentin: Effect of Surface Treatments

Abstract Polyetheretherketone (PEEK) is a material suitable for frameworks of fixed dental prostheses. The effect of different surface treatments on the bond strength of PEEK bonded to human dentin was evaluated. One hundred PEEK cylinders (3 mm×3 mm) were divided into five groups according to surface treatment: silica coating, sandblasting with 45 μm Al2O3 particles, etching with 98% sulfuric acid for 5, 30 and for 60 s. These cylinders were luted with resin cement onto 50 human molars. First, each tooth was embedded in epoxy resin and the buccal dentin surface was exposed. Then, two delimited dentin areas (Æ:3 mm) per tooth were etched with 35% phosphoric acid and bonded with a two-step self-priming adhesive system. After the luting procedure the specimens were stored in water (24 h/37 °C). Shear bond strength (SBS) was tested using a universal testing machine (crosshead speed 0.5 mm/min; load cell 50 kgf) and failure types were assessed. Stress data (MPa) were analyzed using the Kruskal-Wallis test. Comparison of the proportions of different failure types was performed using the Bonferroni method (p<0.05). Kruskal-Wallis demonstrated that differences among groups were not significant (p=0.187). Mean SBS were as follows: silica coating, 2.12±1.12 MPa; sandblasting, 2.37±0.86 MPa; sulfuric acid 5 s, 2.28±1.75 MPa; sulfuric acid 30 s, 1.80±0.85 MPa; sulfuric acid 60 s, 1.67±0.94 MPa. Adhesive and mixed failures were predominant in all groups. Both physical and chemical surface treatments produced adhesion between PEEK, resin cement and dentin.

Resumo O poli-éter-éter-cetona (PEEK) é um material indicado para as estruturas de próteses parciais fixas. O efeito de diferentes tratamentos de superfície na resistência de união entre PEEK e dentina humana foi avaliado. Cem cilindros de PEEK (3 mm×3 mm) foram divididos em cinco grupos de acordo com tratamento de superfície: silicatização, jateamento com partículas de Al2O3 45 µm, condicionamento com ácido sulfúrico 98% por 5, 30 e 60 s. Esses cilindros foram cimentados com cimento resinoso em cinquenta molares humanos. Primeiro, cada dente foi incluído em resina epóxica e a superfície dentinária vestibular foi exposta. Depois, duas áreas (Æ:3 mm) em dentina/por dente foram delimitadas, condicionadas com ácido fosfórico a 35% e receberam aplicação de um sistema adesivo de dois passos. Após o procedimento de cimentação, as amostras foram armazenadas em água (24 h/37 °C). A resistência da união ao cisalhamento (SBS) foi testada em uma máquina universal de ensaios (velocidade 0,5 mm/min; célula de carga 50 kgf), e foram avaliados os tipos de falha. Os dados de tensão (MPa) foram analisados pelo teste de Kruskal-Wallis. A comparação das percentagens de diferentes tipos de falha foi realizada utilizando o método de Bonferroni (p<0,05). O teste de Kruskal-Wallis demonstrou que as diferenças entre os grupos não foram significantes (p=0,187). As médias de SBS foram: silicatização, 2,12±1,12 MPa; jateamento, 2,37±0,86 MPa; ácido sulfúrico por 5 s, de 2,28±1,75 MPa; ácido sulfúrico por 30 s, 1,80±0,85 MPa, ácido sulfúrico por 60 s, 1,67±0,94 MPa. Falhas adesivas e mistas foram predominantes em todos os grupos. Ambos tratamentos de superfície, físicos e químicos, promoveram adesão entre PEEK, cimento resinoso e dentina.

Efeito da aplicação tópica de um verniz de TiF4 quimicamente estável na desmineralização do esmalte dentário bovino: estudo in vitro / Effect of topical application of a chemically stable TiF4 varnish on the demineralization of bovine enamel: an in vitro study

Objetivo: Avaliar, in vitro, o efeito preventivo da aplicação tópica de um verniz à base de tetrafluoreto de titânio quimicamente estável e de um verniz à base de fluoreto de sódio sobre o esmalte bovino, mediante ciclagem de pH. Metodologia: A amostra foi constituída por 75 blocos de esmalte bovino 3×3 mm, sendo 15 aleatoriamente alocados em cada um dos cinco grupos: G1: Dentifrício Fluoretado + Verniz sem princípio ativo; G2: Dentifrício Fluoretado + Verniz à base de TiF4 (4 minutos); G3: Dentifrício Fluoretado + Verniz à base de TiF4 (24 horas); G4: Dentifrício Fluoretado + Verniz à base de NaF (24 horas); G5: Dentifrício Fluoretado. A ciclagem de pH foi realizada por um período de 14 dias, constando de oito ciclos, a 37 °C. Os blocos tratados foram mantidos em solução desmineralizante por oito horas e, por 16 horas, em solução remineralizante, sendo submetidos à análise da superfície em microscopia eletrônica de varredura e espectroscopia de energia dispersiva. Resultado: O verniz à base de TiF4 promoveu uma maior proteção ao esmalte quando comparado com os demais grupos. Mesmo após o período de ciclagem, foram encontrados fósforo, cálcio, sódio, magnésio, titânio, cloro, silício, alumínio, enxofre, potássio, oxigênio e flúor na superfície do esmalte. Conclusão: O aspecto da estrutura adamantina submetida à ação do tetrafluoreto de titânio revelou a presença de uma película protetora. O cálcio e o fósforo foram os principais compostos inorgânicos encontrados no esmalte, sendo observadas alterações na constituição química da camada superficial adamantina em função do tratamento com fluoreto instituído.

Objective: To evaluate the in vitro preventive effect of topical application of achemically stable titanium-tetrafluoride (TiF4) varnish and a sodium fluoride (NaF) varnish on bovine enamel by pH cycling test. Methodology: The sample consisted of 75 blocks of bovine enamel measuring 3x3mm, which were randomly assigned to 5 groups of 15, as follows: G1: Fluoridated dentifrice + varnish without active principle; G2: fluoridated dentifrice + TiF4 varnish (4 minutes); G3: fluoridated dentifrice + TiF4 varnish (24 hours); G4:fluoridated dentifrice + NaF varnish (24 hours); G5: fluoridated dentifrice.A pH cycling was carried out for a period of 14 days, consisting of 8 cycles at 37 °C. The treated blocks were kept in demineralizing and remineralizing solutions for 8 and 16 hours, respectively, being then subjected to surface analysis under scanning electron microscopy and dispersive energy spectroscopy. Result: The TiF4 varnishshowed a greater protection to enamel when compared with the other groups.Even after the cycling period, the following elements were found on the enamel surface: phosphorus, calcium, sodium, magnesium, titanium, chlorine, silicon, aluminum, sulfur, potassium, oxygen and fluorine. Conclusion: The adamantine structure subjected to the action of titanium tetrafluoride revealed the presence of a protective pellicle.Calcium and phosphorus were the major inorganic compounds found in enamel. Furthermore, there were changes in the chemical composition of the adamantine surface layer as a result of the treatment with fluoride.

Desempenho Clínico de Restaurações Cerâmicas Livres de Metal: Revisão da Literatura / Clinical Service of Metal Free Restorations: Literature Review

O objetivo desse estudo foi avaliar, por meio deuma revisão de literatura, o desempenho clínico derestaurações livres de metal do tipo inlay/onlay, faceta, coroaunitária e prótese parcial fixa, destacando suas principaisfalhas, bem como a longevidade de cada tipo de restauração.Material e Métodos: A revisão sobre o tema, “Restauraçõescerâmicas livres de metal”, foi realizada utilizando asseguintes bases de dados: Medline, Portal Capes-Periódicos,Scielo, Bireme e BBO. Livros específicos sobre a temáticada pesquisa também foram consultados. Apenas artigospublicados entre 1990 e 2012 foram selecionados. Foramencontrados 400 artigos, dos quais, após criteriosa filtragem,selecionaram-se 70. Revisão da literatura: Verificou-se quea longevidade clínica das restaurações cerâmicas após 5anos de acompanhamento variou de acordo com o tipo derestauração: inlay/onlay (93 a 100%), faceta laminada (83 a100%), coroa unitária (91 a 100%) e prótese fixa (70 a 100%).Diversas falhas foram relatadas durante o uso clínico dessasrestaurações, entretanto, a principal foi a fratura da cerâmica,seguida de descolamento da cerâmica e cáries secundárias.Considerações finais: Pôde-se concluir que todos os tiposde restaurações apresentaram uma longevidade clínicaaceitável...

The objective of this study was to evaluate, througha literature review, the clinical performance of different metalfree ceramic restorations as inlay/onlay, veneer, crown andfixed partial denture, highlighting their major flaws and thelongevity of each type of restoration. Methodology: Thereview about the subject, “metal-free ceramic restorations,was performed using the following databases: Medline,Portal, Capes Periodicals, Scielo, Bireme and BBO. Books onspecific topics of research were also consulted. Only articlespublished between 1990 and 2009 were selected. It werefound 400 articles, of which selected after careful screeningis 83. Literature review: It was found that the clinical longevityof ceramic restorations after 5 years of follow up variedaccording to the type of restoration: inlay / onlay (93 to 100%),veneer ceramic (83 to 100%), single crown (91 to 100%)and fixed partial denture (70 to 100%). Several failures werereported during the clinical use of these restorations;however, the failure reported was the fracture of the ceramic,followed by the debonding of the ceramic and secondarycaries. Final considerations: It was observed that all kindsof restorations showed acceptable clinic longevity...

Influência de Protocolos de Jateamento na Rugosidade da Superfície de uma Cerâmica de Zircônia Tetragonal Parcialmente Estabilizada por Ítria / Influence of Air Abrasion Protocols on the Surface Roughness of an Yttria Partially Stabilized Tetragonal Zirconia Ceramic

Objetivo: Avaliar a influência de diferentes protocolos de jateamento na rugosidade superficial de uma cerâmica policristalina de zircônia tetragonal estabilizada com ítria(Y-TZP), assim como a topografia superficial da cerâmica após o tratamento.Método: A partir de dois blocos cerâmicos (LAVA, 3M ESPE), obtiveramse 54 espécimes (7,5x4x7,5mm), sendo estes regularizados com lixas dÆágua em granulação fina e sinterizados em forno específico do sistema cerâmico. Em seguida, os corpos de prova foram incluídos em resina acrílica e as superfícies a serem tratadas foram lixadas em politriz com lixas dÆágua em granulação decrescente (600 a 1.200), associadas a pastas de polimento de 10µm, 3µm e sílica coloidal em disco de feltro, sendo distribuídas aleatoriamente em 9 grupos, de acordo com os fatores ôpartículaõ e ôpressãoõ(n=6): Gr1- controle; Gr2-Al2O3(50µm)/2,5bar; Gr3- Al2O3(110µm)/2,5 bar; Gr4-SiO2(30µm)/2,5bar; Gr5- SiO2(30µm)/2,5bar; Gr6- Al2O3(50µm)/3,5bar; Gr7- Al2O3(110µm)/3,5bar; Gr8- SiO2(30µm)/3,5bar; Gr9-SiO2(30µm)/3,5bar. Após os tratamentos, a rugosidade das superfícies foi analisada por meio de um perfilômetro óptico digital e a morfologia, por meio de Microscopia Eletrônica de Varredura (MEV). Os dados (µm) obtidos foram submetidos à análise estatística por meio do teste de Dunnett (5%), ANOVA (2 fatores) e teste de Tukey (5%).Resultados: O tipo de partícula (p=0,0001) e a pressão (p=0,0001) utilizada no jateamento influenciaram os valores de rugosidade entre os grupos experimentais (ANOVA).

Os valores médios de rugosidade (µm) obtidos para os grupos experimentais (Gr2 a Gr9) foram, respectivamente: 0,37D; 0,56BC; 0,46BC; 0,48CD; 0,59BC; 0,82A; 0,53BCD; 0,67AB. A análise em MEV revelou que o Al2O3, independente do tamanho das partículas e da pressão utilizada, danificou a superfície dos espécimes, uma vez que foram observados danos superficiais na cerâmica, na forma de ranhuras e de lascamentos.Conclusão: O jateamento com Al2O3(110µm)/3,5bar foi o tratamento que promoveu a maior rugosidade nas superfícies cerâmicas, embora não signifique que este protocolo promova melhor união cerâmicacimento em relação aos demais tipos de jateamento

Objective: To evaluate the influence of different air abrasion protocols on the surface roughness of an yttria-stabilized polycrystalline tetragonal zirconia) (Y-TZP) ceramic, as well as the surface topography of the ceramic after the treatment. Method: Fifty-four specimens (7.5x4x7.5mm) obtained from two ceramic blocks (LAVA, 3M ESPE) were flattened with fine-grit sandpaper and subjected to sintering in the ceramic systemÆs specific firing oven. Next, the specimens were embedded in acrylic resin and the surfaces to be treated were polished in a polishing machine using sandpapers of decreasing abrasion (600- to 1,200-grit) followed by felt discs with 10µm and 3µm polishing pastes and colloidal silica. The specimens were then randomly assigned to 9 groups, according to factors ôparticleõ and ôpressureõ(n=6): Gr1- control; Gr2-Al2O3(50µm)/2.5 bar; Gr3- Al2O3(110µm)/2.5 bar; Gr4- SiO2(30µm)/2.5 bar; Gr5- SiO2(30µm)/2.5 bar; Gr6- Al2O3(50µm)/3.5 bar; Gr7-Al2O3(110µm)/3.5 bar; Gr8- SiO2(30µm)/3.5 bar; Gr9- SiO2(30µm)/3.5 bar. After treatments, surface roughness was analyzed by a digital optical profilometer and the morphology was examined by scanning electron microscopy (SEM). Data (µm) were subjected to statistical analysis by DunnettÆs test (5%), two-way ANOVA and TukeyÆs test (5%).Results: The type of particle (p=0.0001) and the pressure (p=0.0001) used in the air abrasion protocols influenced the surface roughness values among the experimental groups (ANOVA).

The mean surface roughness values (µm) obtained for the experimental groups (Gr2 to Gr9) were, respectively: 0.37D; 0.56BC; 0.46BC; 0.48CD; 0.59BC; 0.82A; 0.53BCD; 0.67AB. The SEM analysis revealed that Al2O3, regardless of the particle size and pressure used, caused damage to the surface of the specimens, as it produced superficial damages on the ceramic, in the form of grooves and cracks. Conclusion: Al2O3 (110 µm/3.5 bar) air abrasion promoted the highest surface roughness on the ceramics, but it does not mean that this protocol promotes better ceramic-cement union compared to the other air abrasion protocols

Influência de Diferentes Sistemas Adesivos na Resistência de União de Pinos de Fibra à Dentina Intrarradicular / Influence of Different Adhesive Systems on the Bond Strength of Fiber Post to Root Dentin

Objetivo: Avaliar a influência de três sistemas adesivos na resistência de união ao push-out de pinos de fibra cimentados adesivamente à dentina radicular. A hipótese foi de que a resistência de união varia em função do tipo de sistema adesivo. Método: Os canais de 30 dentes bovinos unirradiculares (16mm de comprimento) foram preparados com brocas específicas (FGM) até 12mm. 14 mm de cada raiz foi incluída em resina acrílica e divididas em 3 grupos (n=10), de acordo com o fator ôadesivoõ (3 níveis): Gr1-Scotchbond Multipurpose Plus (3M ESPE), Gr2- One Step (Bisco) and Gr3- Excite DSC (Ivoclar). Os sistemas adesivos foram aplicados com um microbrush, seguindo as recomendações do fabricante. Os pinos de fibra (White Post DC, FGM) foram cimentados com cimento resinoso dual (All-Cem, FGM). Após, os núcleos de resina composta (Llis, FGM) foram confeccionados e cada conjunto raiz/pino/núcleo foi submetido à ciclagem mecânica (Erios, Brazil) (106ciclos, 84N, 4 Hz, inclinação de 45º, 37ºC, sob refrigeração constante). Cada espécime foi seccionado em quatro fatias (1.8mm), as quais foram submetidas ao teste push-out em máquina de ensaio universal (ServoPulser û Shimadzu) (50Kgf, 1mm/min). Os dados (MPa) foram analisados utilizando ANOVA (1-way) e Tukey test (5%). Resultados: O fator ôadesivoõ (p= 0,0352) influenciou significantemente a força de união (ANOVA). O Gr1 (6,8±3,8 MPa)aapresentou valores de resistência de união superior ao Gr2 (3,1±1,5 MPa)be semelhantes ao Gr3 (4,4±3,3)a,b. Além disso, Gr3 e Gr2 foram semelhantes entre si (Tukey). A hipótese foi aceita. Conclusão: Baseado nos resultados concluiu-se que os sistemas adesivos com polimerização química e dual devem ser os selecionados para procedimentos de cimentação adesiva de pinos de fibra

Objective: To evaluate the influence of three adhesive systems on the bond strength of fiber post luted to root dentine. The hypothesis was that the bond strength is influenced by the adhesive system. Method: The canals of thirty single-root bovine roots (16mm in length) were prepared using the preparation drill (FGM) until 12mm. 14 mm of each root was embedded with acrylic resin and the specimens were allocated into three groups (n=10), considering the factor ôadhesiveõ (3 levels): Gr1- Scotchbond Multipurpose Plus (3M ESPE), Gr2- One Step (Bisco) and Gr3- Excite DSC (Ivoclar Vivadent). The adhesive systems were applied using a microbrush, according to the manufactureÆs recommendations. The fiber posts (White Post DC, FGM) were luted with dual resin cement (All-Cem,FGM). After, the cores with composite resin (Llis, FGM) were made and each set of root/post/core was submitted to the mechanical cycling (Erios, Brazil) (106cycles, 84N, 4 Hz, inclination of 45º, 37ºC, water). Each specimen was cut in 4 samples (1.8mm in thickness), which were submitted to the push-out test in a universal testing machine (ServoPulser û Shimadzu) (50Kgf, 1mm/min). The data (MPa) were analyzed using ANOVA (1-way) and Tukey test (5%). Results: The factor ôadhesiveõ (P=0.00352) influenced the bond strength significantly (ANOVA). Gr1 (6.8±3.8 MPa)apresented higher bond strength values than Gr2 (3.1±1.5 MPa)band similar to Gr3 (4.4±3.3)a,b. Moreover, Gr3 and Gr2 were similar between them (Tukey). The hypothesis was accepted. Conclusion: Based on the results it was concluded that chemical and dual polymerization adhesive system should be used for the adhesive luting fiber post procedures

Shear bond strength of orthodontic brackets bonded using halogen light and light-emitting diode at different debond times

The aim of this in vitro study was to compare the photoactivation effects of QTH (Quartz-Tungsten-Halogen) and LED (Light-Emitting Diode) on the SBS (Shear Bond Strength) of orthodontic brackets at different debond times. Seventy-two bovine lower incisors were randomly divided into two groups according to the photoactivation system used (QTH or LED). The enamel surfaces were conditioned with Transbond self-etching primer, and APC (Adhesive Pre-Coated) brackets were used in all specimens. Group I was cured with QTH for 20 s and Group II with LED for 10 s. Both groups were subdivided according to the different experimental times after bonding (immediately, 24 h and 7 days). The specimens were tested for SBS and the enamel surfaces were analyzed according to the Adhesive Remnant Index (ARI). The statistical analysis included the Tukey's test to evaluate the main effects of photoactivation and debond time on SBS. The Chi-square test was used to compare the ARI values found for each group, and no statistically significant difference was observed. The debond time of 7 days for QTH photoactivation showed statistically greater values of SBS when compared to the immediate and 24 h periods. There was no statistically significant difference between the QTH and LED groups immediately and after the 24 h period. In conclusion, bonding orthodontic brackets with LED photoactivation for 10 s is suggested because it requires a reduced clinical chair time.

O efeito da temperatura de queima da camada de opaco na resistência flexural de uma cerâmica vítrea submetida à cocção sobre uma liga decobalto-cromo / Opaque layer firing temperature effect on the flexural strength of glass ceramic fused to cobalt-chromium alloy

Este estudo avaliou a influência da temperatura de queima da camada de opaco na resistência de união entre uma liga de cobalto-cromo e uma cerâmica, após serem submetidos ao ensaio de flexão de três pontos. Considera-se a hipótese: o aumento da temperatura de queima do opaco melhora a resistência flexural da cerâmica aplicada sobre o metal. Barras metálicas (25x3x0,5mm) (n=30) foram fundidas em Co-Cr e as áreas centrais das barras (8x3mm) foram jateadas com partículas de óxido de alumínio de 150μm e divididas em 3 grupos de acordo com a temperatura de queima da camada de opaco (n=10): G1 (grupo controle) – 900°C; G2 – 950°C e G3 – 1000°C. As cerâmicas opaca e de corpo (Vita Omega 900) foram queimadas sobre a área central. Os espécimes foram mantidos em água destilada à 37° C durante 24 horas e a seguir foram submetidos ao teste de flexão de três pontos. Após o teste, os tipos de falhas foram classificados. Os dados obtidos foram analisados estatisticamente (Kruskal-Wallis 1 e teste de Dunn , μ=0,05). A diferença dos valores médios de resistência flexural foi estatisticamente significante (p=0,004), sendo que os grupos G2- 19,84±4,24N e G3- 22,43±5,94N exibiram valores de resistência flexural maiores que o grupo G1-12,525±1,08N. Concluiu-se que o aumento da temperatura de queima da camada de opaco melhorou significantemente os valores de resistência flexural. O modo de falha predominante foi adesiva na interface metal/cerâmica para o grupo G1 e exclusivamente coesiva na zona interfacial camada de opaco/Co-Cr com presença de cerâmica na superfície dos grupos G2 e G3.

This study evaluated the opaque layer firing temperature on the flexural strength of a ceramic fused to commercial cobaltchromiumalloy (Co-Cr). The hypotheses were that opaque layer temperature increasing get higher the metal/ceramicbond strength. Metallic frameworks (25x3x0.5 mm) (n=30) were cast in Co-Cr and airborne particle abraded with 150μm aluminum oxide at the central area of the frameworks (8x3 mm) and after divided into three groups, according toopaque layer firing temperature (n=10): G1 (control) – 900°C; G2- 950°C and G3- 1000°C. Opaque ceramic were appliedand the glass ceramic (Vita Omega 900, Vita Zahnfabrick, Bad Sãckingen, Germany) was fired onto them (thickness:1 mm). The specimens were kept in distilled water at 37ºC for 24 hours, after that it were submitted to three pointsflexural strenght test. After the test, failure types were noted. The data were analyzed using 1 way Kruskal-Wallis andDunn test (5%). The difference in mean flexure strength values were statistically significant (p=0,004). The groups G2-19,84±4,24N and G3- 22,43±5,94N presented higher flexure strength values than G1- 12,525±1,08N. It was concludedthat the opaque layer temperature increasing improved the flexure bond strength values significantly. The failure typepredominant was adhesive at metal/ceramic interface for group G1 sample and exclusively cohesive at the opaqueceramic/Co-Cr interfacial zone with presence of ceramic on the metal surface for groups G2 and G3.