Fatigue resistance of monolithic and multilayer zirconia crowns using veneer layering or CAD-on technique.

This study aims to evaluate the fatigue resistance of monolithic zirconia (Yz) and multilayer ceramic structures using the CAD-on technique in different thicknesses. Fifty (N=50) standardized single crowns preparations were made in fiberglass-reinforced epoxy resin (NEMA grade G10), digitalized, and restorations were machined in CAD-CAM, composing 5 groups (n= 10): Control: 1.5 mm (milled zirconia framework + manual layered porcelain); Yz monolithic 1.5 mm; Yz monolithic 1.0 mm; CAD-on 1.5 mm; and CAD-on 1.0 mm (milled zirconia framework 0.5 mm thickness bonded by a low fuse ceramic to a milled lithium disilicate layer of 1.0 mm or 0.5 mm, respectively). The G10 bases were conditioned with 10% hydrofluoric acid; the crowns were air abraded with 110 µm alumina particles; and then luted onto each other with self-adhesive resin cement. A cyclic fatigue test was performed (initial load: 400N for 10,000 cycles, frequency of 20 Hz, step size of 200N) until failure, and the data was submitted to a survival statistical analysis. No failures were observed at Yz monolithic 1.5 mm. High and similar performance was observed for Cad-On groups and Yz monolithic 1.0 mm. The control group depicted the worst behavior. The Weibull modulus of CAD-on 1.5 mm was higher than the control while being similar to the other conditions. Both the monolithic systems and the CAD-on technique showed high and similar fatigue fracture behavior and survival rates, which were also higher than the control bilayer system. Both systems reduced the occurrence of delamination failures, making them suitable for clinical use.

Effect of preheating and ultrasound application of resin-based luting agents on the failure load of a lithium disilicate glass-ceramic.

PURPOSE: To assess the effect of preheating resin-based materials and ultrasound application on the failure load of a lithium disilicate glass-ceramic. MATERIALS AND METHODS: Ninety ceramic specimens were produced (14×12×1.0 mm) and divided into 9 groups (n = 10) to be bonded to a dentin analog (Nema G10) with light-cured luting agent (LC), flowable resin composite (FL), and supra-nano filled resin composite (SN), as follows: LC/R - LC at room temperature; LC/P - preheated LC; LC/P/U - preheated LC and Ultrasound; FL/R - FL at room temperature; FL/P - preheated FL; FL/P/U - preheated FL and Ultrasound; SN/R - SN at room temperature; SN/P - preheated SN; SN/P/U - preheated SN and Ultrasound. The failure load test was performed in a universal testing machine with the aid of acoustic detection. The data was analyzed with two-way ANOVA (for failure load) and Weibull statistics (Weibull modulus - m and characteristic strength, based on 95% confidence intervals - CI). RESULTS: The analyses of failure load revealed no statistically significant difference among groups considering the type of luting agent (P = 0.075; F = 2,673), the application method (P = 0.772; F = 2,259), and the interaction between them (P = 0.297; F = 1,248). The characteristic strength did not show differences among groups (95% CI). The m, which indicates structural reliability, showed lower values for SN/P/U and SN/P, with a difference from other selected groups (95% CI). CONCLUSION: Preheating of resin-based materials and ultrasound application did not affect the failure load of lithium disilicate glass-ceramic. Lower reliability was observed with supra-nano filled resin composite.

Fatigue resistance of monolithic and multilayer zirconia crowns using veneer layering or CAD-on technique

Abstract This study aims to evaluate the fatigue resistance of monolithic zirconia (Yz) and multilayer ceramic structures using the CAD-on technique in different thicknesses. Fifty (N=50) standardized single crowns preparations were made in fiberglass-reinforced epoxy resin (NEMA grade G10), digitalized, and restorations were machined in CAD-CAM, composing 5 groups (n= 10): Control: 1.5 mm (milled zirconia framework + manual layered porcelain); Yz monolithic 1.5 mm; Yz monolithic 1.0 mm; CAD-on 1.5 mm; and CAD-on 1.0 mm (milled zirconia framework 0.5 mm thickness bonded by a low fuse ceramic to a milled lithium disilicate layer of 1.0 mm or 0.5 mm, respectively). The G10 bases were conditioned with 10% hydrofluoric acid; the crowns were air abraded with 110 μm alumina particles; and then luted onto each other with self-adhesive resin cement. A cyclic fatigue test was performed (initial load: 400N for 10,000 cycles, frequency of 20 Hz, step size of 200N) until failure, and the data was submitted to a survival statistical analysis. No failures were observed at Yz monolithic 1.5 mm. High and similar performance was observed for Cad-On groups and Yz monolithic 1.0 mm. The control group depicted the worst behavior. The Weibull modulus of CAD-on 1.5 mm was higher than the control while being similar to the other conditions. Both the monolithic systems and the CAD-on technique showed high and similar fatigue fracture behavior and survival rates, which were also higher than the control bilayer system. Both systems reduced the occurrence of delamination failures, making them suitable for clinical use.

Resumo Este estudo teve como objetivo avaliar o comportamento à fadiga de estruturas cerâmicas monolíticas de zircônia (Yz) e multicamadas utilizando a técnica CAD-on em diferentes espessuras. Cinquenta (N=50) preparos unitários padronizados foram confeccionados em resina epóxi reforçada com fibra de vidro (NEMA grau G10), digitalizados e as restaurações usinadas em CAD-CAM, compondo 5 grupos (n= 10): Controle: 1,5 mm (estrutura de zircônia fresada + porcelana estratificada manualmente); Yz monolítica 1,5 mm; Yz monolítica 1,0 mm; CAD-on em 1,5 mm; e CAD-on 1,0 mm (estrutura de zircônia fresada com 0,5 mm de espessura ligada por uma cerâmica de baixa fusão a uma camada de dissilicato de lítio fresado de 1,0 mm ou 0,5 mm, respectivamente). As bases do G10 foram condicionadas com ácido fluorídrico a 10%; as coroas foram jateadas com partículas de alumina de 110 μm; e então cimentadas uma sobre a outra com cimento resinoso autoadesivo. Foi realizado um teste de fadiga cíclica (carga inicial: 400N para 10.000 ciclos, frequência de 20 Hz, step de 200N) até a falha, e os dados foram submetidos a uma análise estatística de sobrevivência. Nenhuma falha foi observada para Yz monolítica de 1,5 mm. Desempenho alto e semelhante foi observado para os grupos Cad-On e Yz monolítica 1,0 mm. O grupo controle apresentou o pior comportamento. O módulo de Weibull do CAD-on 1,5 mm foi maior que o grupo controle, sendo semelhante às outras condições. Tanto os sistemas monolíticos quanto a técnica CAD-on apresentaram alto e semelhante desempenho mecânico e taxas de sobrevivência, que também foram superiores ao sistema bicamada de controle. Ambos os sistemas reduziram a ocorrência de falhas de delaminação, tornando-os adequados para uso clínico.

Fatigue performance of adhesively luted glass or polycrystalline CAD-CAM monolithic crowns.

STATEMENT OF PROBLEM: Data comparing the fatigue performance of adhesively luted glass or polycrystalline ceramic systems for computer-aided design and computer-aided manufacturing (CAD-CAM) are scarce. PURPOSE: The purpose of this in vitro study was to evaluate and compare the fatigue performance of monolithic crowns manufactured from glass or polycrystalline CAD-CAM ceramic systems adhesively luted to a dentin analog. MATERIALS AND METHODS: Fifty-four pairs of standardized preparations of dentin analog (NEMA Grade G10) and simplified ceramic crowns of 1.5-mm thickness were obtained with 3 ceramic materials: lithium disilicate (LD) glass-ceramic (IPS e.max CAD); zirconia-reinforced lithium silicate (ZLS) glass-ceramic (Vita Suprinity); and translucent yttrium fully stabilized polycrystalline zirconia (Trans YZ) (Prettau Anterior). The simplified crowns (n=15) were adhesively cemented onto the preparations and subjected to step-stress fatigue test (initial load of 400 N, 20 Hz, 10 000 cycles, followed by 100-N increment steps until failure). Collected data (fatigue failure load [FFL] and cycles for failure [CFF]) were submitted to survival analysis with the Kaplan-Meier and Mantel-Cox post hoc tests (α=.05) and to Weibull analysis (Weibull modulus and its respective 95% confidence interval). Failed crowns were submitted to fractography analysis. The surface characteristics of the internal surface (roughness, fractal dimension) of additional crowns were accessed, and the occlusal cement thickness obtained in each luted system was measured. RESULTS: Trans YZ crowns presented the highest values of FFL, CFF, and survival rates, followed by ZLS and LD (mean FFL: 1740 N>1187 N>987 N; mean CFF: 149 000>92 613>73 667). Weibull modulus and cement thickness were similar for all tested materials. LD presented the roughest internal surface, followed by ZLS (mean Ra: 226 nm>169 nm>93 nm). The LD and ZLS internal surfaces also showed higher fractal dimension, pointing to a more complex surface topography (mean fractal dimension: 2.242=2.238>2.147). CONCLUSIONS: CAD-CAM monolithic crowns of Trans YZ show the best fatigue performance. In addition, ZLS crowns also showed better performance than LD crowns.

Influência de diferentes silanos na resistência de união entre cerâmica de dissilicato de lítio e cimento resinoso / Influence of different silanes on the bond strength between lithium disilicate and resin cement

Objetivo: O objetivo do estudo foi avaliar o uso de diferentes marcas de silano na resistência de união entre a cerâmica de dissilicato de lítio e o cimento resinoso. A hipótese nula avaliada foi que as diferentes marcas de silanos apresentariam similar resistência de união. Métodos: Foram confeccionados 80 discos de dissilicato de lítio (IPS E.max CAD) com (12 mm x 1 mm). Após a cristalização, foram incluídos em tubos de PVC com resina acrílica e polidos com lixas de carbeto de silício, sob irrigação com água. Após aplicação de ácido hidrofluorídrico 10%, foram lavados e secos e divididos aleatoriamente em 4 grupos para aplicação do silano (n=20). S-Y: Yller; S-M: Monobond N; S-U: Ultradent; S-DS: Dentsply Sirona. Uma matriz de silicone com 4 orifícios foi confecionada e preenchida posteriormente com o cimento resinoso (Multilink N) para realização do teste de microcilhamento (EMIC) e os dados foram avaliados pelo teste one-way ANOVA. Resultados: Análise de variância mostrou que não houveram diferenças estatísticas nos valores médios entre os grupos de tratamento (p=0,404). A média e desvio padrão (DP) da resistência de união (MPa) nos grupos foram: S-Y: 26,9 (6,3); S-M: 28,3 (5,8); S-U: 29,0 (8,0); S-DS: 31,8 (11,0). Conclusões: As diferentes marcas de silano avaliadas apresentaram resistência de união similar entre si. Porém, a aplicação de silano é fundamental para obter melhorias na resistência de união(AU)

Objective: To evaluate the use of different brands of silane in the bond strength between lithium disilicate and resin cement. The null hypothesis evaluated was that the different brands of silanes would present similar bond strength. Methods: 80 lithium disilicate discs (IPS E.max CAD) were made with 12 mm in diameter x 1 mm in thickness. After crystallization, they were included in PVC tubes with acrylic resin and polished with silicon carbide sandpaper, under irrigation with water, creating a smooth and flat surface and randomly divided into 4 groups (n = 20). G1: Yller; G2: Monobond N; G3: Ultradent; G4: Dentsply Sirona. The samples were stored for 24h in distilled water for subsequent microcutting testing. One-way analysis of variance was used to obtain the results. Results: Analysis of variance showed that there were no statistical differences in the mean values between the treatment groups (p = 0.404). The mean and standard deviation (SD) of the bond strength (MPa) in the groups were: G1: 26.9 (6.3); G2: 28.3 (5.8); G3: 29.0 (8.0); G4: 31.8 (11.0). Conclusions: The different brands of silane evaluated showed similar bond strength. However, application of silane is essential to obtain improvements in bond strength(AU)

Novas perspectivas para reabilitação de dentes tratados endodonticamente / Novel perspectives for the rehabilitation of endodontically treated teeth

Vários fatores podem influenciar o desempenho clínico de dentes com tratamento endodôntico (DTE). Além disso diversas são as opções restauradoras indicadas em respeito a este cenário, em especial com o notório avanço de novas técnicas e tecnologias para uso clínico. Dentre estas corriqueiramente envolvem-se o uso de restaurações diretas (confeccionadas com resina composta), pinos metálicos ou de fibra de vidro, pinos pré-fabricados ou fresados, assim como restaurações indiretas compostas de coroas cerâmicas, inlays, onlays ou endocrowns; sempre com o foco na reabilitação funcional e estética do caso em tela. Neste trabalho, através de uma revisão narrativa, foram expostos conceitos relativos às modalidades restauradores que se advêm do uso de novas tecnologias na reabilitação de dentes tratados endodonticamente(AU)

Several factors may influence the clinical performance of endodontically treated teeth (ETT). In addition, there are several restorative options indicated regarding this scenario, especially with the notable advance of new techniques and technologies for clinical use. These routinely involve the use of direct restorations (made of composite resin), metal or fiberglass posts, prefabricated or milled posts, as also indirect restorations composed of ceramic crowns, inlays, onlays or endocrown; always focusing on functional and aesthetic rehabilitation of the case in hand. In this study, through a narrative review, concepts related to the restorative modalities that were introduced with the use of new technologies in the rehabilitation of endodontically treated teeth were discussed(AU)

Correlation between patient complaint, temporomandibular disorder diagnosis and mandible head morphology

The aim of this study was to evaluate the correlation between patient complaints, clinical diagnosis of temporomandibular disorder (TMD) based on the diagnostic criteria for TMD, and morphology of the mandibular condyle obtained by cone-beam computed tomography (CB-CT). Data were collected from 40 patients. The anatomy of the mandibular condyle was assessed using CB-CT, the diagnosis of TMD according to diagnostic criteria for TMD, and patients' complaints was registered at the appointment. Data were explored and all statistical references were completed in bicaudal tests, with 95% confidence level (α=0.05). The Chisquared test was used with Bonferroni correction (z-tests). Main complaints found were grouped as muscular, articular, muscular and articular, or headache and articular symptoms. Clinical diagnosis of TMD involved myalgia, local myalgia, myofascial pain, myofascial pain with reference, myofascial pain with arthralgia, arthralgia, or disc displacement with reduction. At least one joint showed condylar flattening, erosion, sclerosis, or osteophytes. No correlation was observed between main complaints, clinical diagnosis, and morphology of the mandibular condyle in all comparisons. The findings suggest that due to the absence of clinical and morphological correlation, CB-CTs should be requested only in specific cases, when doubt remain after careful TMD diagnosis, to avoid their over-indication(AU)

Avaliação da rugosidade superficial de uma resina composta com uso de diferentes polidores / Evaluation of the surface roughness of a composite resin using different polishers

Introdução: A rugosidade superficial é definida pela superfície de um material restaurador após as etapas de acabamento e polimento, e é afetada pelas propriedades do compósito resinoso, bem como pelos instrumentos utilizados para a realização do polimento. Objetivos: Avaliar a rugosidade superficial de uma resina composta nano-híbrida polida com diferentes sistemas de polimento por Microscopia de Força Atômica (MFA) e análise dos polidores por Microscopia Eletrônica de Varredura (MEV). Materiais e métodos: Os fatores em estudo são os sistemas de polimento em três níveis: Enhance (Dentsply), Ultra-Gloss (American Burrs) e Dura-Gloss (American Burrs). As unidades experimentais são formadas por 30 corpos de prova em resina composta convencional nano-híbrida, divididos aleatoriamente em 3 grupos (n=10). O Grupo G1 recebeu tratamento com o sistema de polimento de uma única etapa: Dura-Gloss; o Grupo G2, sistema de polimento de múltiplas etapas: Ultra-Gloss; e o Grupo G3 recebeu o tratamento com o sistema de polimento de uma única etapa: Enhance. A variável de resposta quantitativa se dá pela rugosidade superficial avaliada pela Microscopia de Força Atômica (MFA). Resultados: Os resultados obtidos demonstram que os sistemas de polidores Dura-Gloss e Ultra-Gloss apresentaram rugosidade superficial similar entre si (p=0,201) e diferiram estatisticamente do sistema Enhance (p=0,023, Ultra-Gloss e p=0,000, DuraGloss), o qual apresentou maior rugosidade superficial para a resina composta nano-híbrida. Conclusão: Os polidores Dura-Gloss e Ultra-Gloss tem maior capacidade de polimento da resina composta nano-hibrida(AU)

Introduction: The surface roughness is defined by the surface of a restorative material after the finishing and polishing steps, and is affected by the properties of the resinous composite as well as by the instruments used to perform the polishing. Objectives: To evaluate the surface roughness of a polished nano-hybrid composite resin with different polishing systems by atomic force microscopy (MFA) and polishing analysis by scanning electron microscopy (SEM). Materials and Methods: the factors under study are polishing systems at three levels: Enhance (Dentsply), Ultra-Gloss (American Burrs) and Dura-Gloss (American Burrs). The experimental units are composed of 30 specimens in conventional nano-hybrid composite resin, divided randomly into 3 groups (n = 10). The G1 Group received treatment with the single-stage polishing system: Dura-Gloss, Group G2, multi-step polishing system: UltraGloss and Group G3 was treated with the single-stage polishing system: Enhance. The quantitative response variable is given by the surface roughness evaluated by atomic force microscopy (MFA). Results: the results showed that the systems of Dura-Gloss and UltraGloss polishers presented similar surface roughness (p = 0.201) and differed statistically from the Enhance system (p = 0.023, Ultra-Gloss and p = 0.000, Dura- Gloss), which presented higher surface roughness for the nano-hybrid composite resin. Conclusion: Dura-Gloss and Ultra-Gloss polishers have a higher polishing capacity of nano-hybrid composite resin(AU)

Assessment of stress/strain in dental implants and abutments of alternative materials compared to conventional titanium alloy-3D non-linear finite element analysis.

The aim of this study was to assess the stress/strain in dental implant/abutments with alternative materials, in implants with different microgeometry, through finite element analysis (FEA). Three-dimensional models were created to simulate the clinical situation of replacement of a maxillary central incisor with implants, in a type III bone, with a provisional single crown, loaded with 100 N in a perpendicular direction. The FEA parameters studied were: implant materials-titanium, porous titanium, titanium-zirconia, zirconia, reinforced fiberglass composite (RFC), and polyetheretherketone (PEEK); and abutment materials-titanium, zirconia, RFC, and PEEK; implant macrogeometry-tapered of trapezoidal threads (TTT) and cylindrical of triangular threads (CTT) (ø4.3 mm × 11 mm). Microstrain, von Mises, shear, and maximum and minimum principal stresses in the structures and in peri-implant bone were compared. There was increased stress and strain in peri-implant bone tissue caused by implants of materials with lower elastic modulus (mainly for PEEK and RFC). They also presented higher concentration of stresses in the implant itself (especially RFC). Zirconia implants led to lower stress and strains in peri-implant bone tissue. Less rigid abutments (RFC and PEEK) associated with titanium implants led to higher stress in the implant and in peri-implant bone tissue. The TTT macrogeometry showed a higher stress concentration in the implant and peri-implant bone tissue. The stress/strain in peri-implant bone tissue and implant structures were affected by the material used, where reduced values were caused by stiffer materials. Lower stress/strain values were obtained with cylindrical implants of triangular treads.

Microstructure, topography, surface roughness, fractal dimension, internal and marginal adaptation of pressed and milled lithium-disilicate monolithic restorations.

PURPOSE: To characterize the effect of two processing techniques (pressing and CAD/CAM - Computer Aided Design/Computer Aided Machining) of lithium-disilicate (LD) based crowns on the microstructure, topography, roughness, fractal dimension, internal and marginal adaptation. METHODS: One-hundred identical preparations for monolithic crowns were made with dentin analogue material (G10 epoxy resin). One of the preparations was scanned and a monolithic crown in lithium-disilicate was planned in the CAD system. Fifty crowns were milled in a wax pattern and subjected to pressing (IPS e.max Press), while 50 crowns were machined at CAD/CAM (IPS e.max CAD) and posteriorly crystallized. Internal and marginal adaptation were assessed via replica technique at four manufacturing moments (Milled wax pattern; LDPRESS; Milled LDCAD; Crystallized LDCAD) and considering 5 regions (margin, cervico-axial angle, axial wall, axial-occlusal angle and occlusal wall). Complementary analysis considering microstructure and topography, roughness and fractal dimension were performed in Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). RESULTS: The processing technique resulted in different ceramic microstructure, topography, roughness and fractal dimension, whereas CAD/CAM lead to smoother, more homogeneous but more complex topography features (higher fractal dimension) in comparison to the pressing technique (P<0.05). Regarding marginal and internal fit, LDPRESS crowns showed to be more adapted at the margin, while LDCAD were more adapted at the occluso-axial angle; other regions were not statistically different (α=0.05). CONCLUSIONS: CAD/CAM and the pressing techniques for manufacturing LD crowns lead to completely different ceramic surface characteristics and affect crown adaptation at the margin and at occluso-axial angle.

Influence of inorganic filler content of resin luting agents and use of adhesive on the performance of bonded ceramic.

STATEMENT OF PROBLEM: The inorganic filler of resin-based luting agents and the use of an adhesive layer could influence the bonding ability, mechanical performance, and interface morphology of bonded feldspathic ceramic. PURPOSE: The purpose of this in vitro study was to investigate the influence of resin-based luting agents loaded with different inorganic filler content, with or without an adhesive, on microtensile bond strength, biaxial flexural strength, and the adhesive interface morphology of bonded ceramic specimens. MATERIAL AND METHODS: Experimental resin-based luting agents with low (55wt%), intermediate (65wt%), and high (75wt%) filler contents were bonded to ceramic specimens, with or without a layer of adhesive. The resin-based luting agents were characterized by measuring viscosity, elastic modulus, Poisson ratio, and degree of conversion (n=3 for each test). The response variables for the bonded ceramic specimens were ceramic-resin microtensile bond strength (n=30), biaxial flexural strength (n=30) and characteristic strength, and Weibull modulus. Scanning electron microscopy was used for fractographic and interface analyses of the specimens fractured in the microtensile test (n=3). Data were subjected to ANOVA with the post hoc Tukey test (α=.05). Weibull moduli were also calculated. RESULTS: Increased inorganic filler content yielded significantly higher viscosity, stiffness, and film thickness. However, the Poisson ratio and degree of conversion were not affected. The lowest bond strength values were observed for the resin-based luting agents with high inorganic filler content when no adhesive was used and for the resin-based luting agent with low filler content when the adhesive was used. The increase in filler content of the resin-based luting agent appeared to be associated with a higher frequency of mixed failures. Increased filler content resulted in higher biaxial flexural and characteristic strength and decreased structural reliability. The adhesive helped fill irregularities on ceramic and slightly increased film thickness but had only a minor effect on mechanical strength. CONCLUSIONS: Experimental resin-based luting agent loaded with high inorganic filler content strengthened the bonded feldspathic ceramic and yielded significantly higher viscosity and film thickness. In contrast, the bond strength was lower if no adhesive was used.

Restorative Possibilities Using Zirconia Ceramics for Single Crowns.

Two clinical cases are presented to explore technical differences and discusses the advantages and disadvantages of using veneered or monolithic zirconia to manufacture posterior single crowns. The first case describes the clinical steps in manufacturing a monolithic crown on a mandibular left second premolar using high translucency zirconia. It shows the use of a conservative tooth preparation based on the superior mechanical properties that this material presents as well as the final optical characteristics achieved by shading and staining. In the second case, a conventional bilayer restorative treatment was made using zirconia framework followed by veneering with feldspar ceramic on a mandibular left first molar. Recent literature indicates that each of these restorative alternatives presents specific advantages and disadvantages. Factors such as mechanical performance, fracture, esthetic characteristics, clinical success, complication rates, adhesion and antagonist wear performance are discussed comparing the two restorative assemblies. The data highlight that monolithic crowns prevent a major problem reported on bilayer restorations: the chipping of veneering ceramic. Monolithic crowns also allow minimally invasive tooth preparations, thus increasing tooth remnant preservation. However, data that support esthetic performance similarity between monolithic and bilayer assemblies are lacking, thus the predictability of use is restricted for the posterior region, as cases demanding high esthetic appeal continue to fundamentally use bilayer restorations. Failures were not found, and patient satisfaction was reported in both techniques after the 12-month follow up.

Comparação estética entre sistemas cerâmicos sobre substrato escurecido / Esthetic comparison between ceramic systems on darkened substrate

Objetivo: O objetivo deste trabalho foi avaliar visualmente a possível influência de um substrato escurecido no resultado estético de coroas com infraestruturas de dissilicato de lítio ou zircônia. Metodologia: O delineamento foi observacional, transversal e descritivo. Para o experimento, foi selecionado um paciente com necessidade de coroas totais no 11 e 21, onde um dos dois elementos deveria ser escurecido. Uma coroa de dissilicato de lítio foi confeccionada sobre o substrato sem alteração de cor. Para o elemento escurecido foram confeccionadas uma coroa de dissilicato de lítio e uma de zircônia, criando-se duas situações clínicas. Sem conhecimento de qual material foi usado, os avaliadores responderam a um questionário que comparava o resultado estético das coroas de dissilicato de lítio ou zircônia com a coroa de dissilicato de lítio sobre o substrato normal, assim como as duas situações clínicas entre si. No total, 20 cirurgiões-dentistas participaram como avaliadores. Os avaliadores julgaram as restaurações como excelentes, aceitáveis ou inaceitáveis e, após, foi realizada uma análise descritiva das avaliações. Resultados: Os resultados demonstraram que houve diferença estética entre as restaurações de dissilicato de lítio e de zircônia, sendo que o dissilicato de lítio não conseguiu bloquear a cor do substrato, mesmo sendo utilizada uma pastilha opaca (MO). Conclusão: Concluiu-se que em casos de substrato escurecido está indicada a utilização de uma infraestrutura com opacidade suficiente, como a zircônia, podendo ocorrer diferenças visualmente perceptíveis e inaceitáveis caso seja utilizado um material translúcido como o dissilicato de lítio(AU)

Purpose: The objective of this work was to evaluate visually the possible influence of a darkened substrate on the aesthetic result of crowns with infiltrations of lithium disilicate or zirconia. Methodology: The design was observational, transversal and descriptive. For the experiment, a patient with total crowns at 11 and 21 was selected, where one of the two elements should be darkened. A crown of lithium disilicate was made on the substrate without color change. For the darkened element, a crown of lithium disilicate and one of zirconia were created, creating two clinical situations. Without knowing which material was used, the evaluators answered a questionnaire that compared the aesthetic result of the lithium disilicate or zirconia crowns with the lithium disilicate crown on the normal substrate, as well as the two clinical situations. A total of 20 dental surgeons participated as evaluators. The evaluators judged the restorations to be excellent, acceptable or unacceptable, and afterwards a descriptive analysis of the evaluations was performed. Results: The results showed that there was aesthetic difference between the restorations of lithium disilicate and zirconia, and the lithium disilicate could not block the color of the substrate, even though an opaque ingot (MO) was used. Conclusion: It was concluded that in cases of darkened substrate, an infrastructure with sufficient opacity, such as zirconia, with visually perceptible and unacceptable differences, if a translucent material such as lithium disilicate is used(AU)

Do endodontic retreatment techniques influence the fracture strength of endodontically treated teeth? A systematic review and meta-analysis.

One of the major concerns about endodontically retreated teeth (ERT) is undoubtedly its loss of remnant structure, which could lead to consequently greater fracture risk. Therefore, the objective of this systematic review is to assess the influence of endodontic retreatment on the fracture strength of the dental tooth remnant. In vitro studies assessing the influence of mechanical retreatment on the mechanical properties (static or under fatigue) of restored teeth were searched in PubMed and SCOPUS databases. Three independent reviewers screened titles/abstracts of articles and the full-text of potentially eligible studies. The risk of bias was independently assessed by one researcher and verified by another two. Comparison between the mean load to fracture of teeth after endodontic treatment and after endodontic retreatment were estimated using pairwise random effects meta-analysis to calculate pooled mean differences. Three studies were included for the systematic review and 2 for the meta-analysis. The pooled effect indicated a statistical difference (Mean difference: -121.03 95%CI: -183.02, -59.05) between conditions favoring the endodontically treated teeth. However, the low number of studies combined with their heterogeneity made it difficult to prove such phenomenon. ERT might present lower fracture strength than endodontically treated teeth. However, more coherent laboratory tests may provide better evidence and quantitative parameters on how much reliability can be attributed to an endodontic retreatment, in addition to which technique can provide more predictable results in this conservative approach.

Different fabrication techniques of implant-supported prostheses: microhardness and fracture strength

Aim: This study evaluated the mechanical behavior of implant-supported crowns obtained by different fabrication technique after thermomechanical cycling. Methods: Thirty-two external hexagon dental implants were divided into four groups (n=10): CC ­ conventional casting with torch; EI ­ electromagnetic induction casting; PL ­ plasma casting; and CAD-CAM ­ milling through computer-aided design and computer-aided manufacturing. Vickers microhardness of the specimens were made before and after the thermomechanical cycling, and then subjected to fracture load. Fracture pattern was evaluated. Results: No significant difference was observed comparing the microhardness before and after thermomechanical cycling. CAD-CAM group presented significant lower microhardness than the other groups. No significant statistical difference was showed on fracture load between the groups. The CAD-CAM and PL presented lower number of failure by plastic deformation. Conclusion: The manufacturing techniques affected the mechanical behavior and the failure pattern of implant-supported crowns tested

Inorganic filler content of resin-based luting agents and the color of ceramic veneers.

The influence of inorganic filler content of resin-based luting agents (RBLAs) on color change (ΔE00), CIEL*a*b* (individual color coordinates), and translucency parameters (TP) of simulated ceramic laminate veneer (CLV) was investigated. RBLAs with low, intermediate, and high inorganic filler content (55%, 65%, and 75% mass fractions, respectively) were prepared. Feldspar ceramic (Vitablocs Mark II) specimens (1.2 mm × 0.8 mm, A1C shade) were bonded to simulated composite resin substrates (1.6 mm × 1.2 mm, A2D shade) using three experimental and a commercial (RelyX Veneer) RBLA (translucent shade). The ΔE00 was calculated by CIEDE2000 color difference metric under three conditions (before, immediately after, and 24 h after luting). The TP was calculated using CIEL*a*b* color coordinates measured over white and black backgrounds. Surface morphology of the RBLAs was analyzed. One-way and two-way analyses of variance with a post-hoc Tukey's test were used respectively to calculate TP, CIEL*a*b* coordinates, and ΔE00 (α= 0.05). Overall, the tested RBLAs presented clinically visible ∆E00 values under the three conditions evaluated. For all RBLAs, higher ∆E00 values were observed between measurements obtained before and immediately after luting. Different inorganic filler content did not significantly increase the opacity of the ceramic-luting agents-resin composite set. The variation in inorganic filler content did not influence significantly the TP of simulated CLV; although all of the experimental RBLAs tested yielded ∆E00 above the perceptibility threshold. The L*, a*, and b* individual color coordinates were cementation-dependent.

Feldspar Ceramic Strength and The Reinforcing Effect by Adhesive Cementation Under Accelerated Aging.

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.

Lesões cervicais não-cariosas de abfração: prevalência e relação com bruxismo do sono / Non-carious abfraction cervical lesions: prevalence and relationship with sleep bruxism

As lesões cervicais não cariosas (LCNCs) são caracterizadas pela perda da estrutura dentária localizada na região próxima a junção cemento-esmalte. Considerando que uma das possíveis etiologias das LCNCs é a sobrecarga oclusal, torna-se importante a compreensão da relação entre a prevalência destas lesões e os fatores associados com o bruxismo do sono. Objetivo: Avaliar a prevalência de LCNCs do tipo abfração e sua relação com o diagnóstico positivo de bruxismo do sono em uma amostra de pacientes da IMED e CEOM. Metodologia: Este foi um estudo clínico do tipo transversal, onde foi realizada avaliação observacional em uma amostra de 25 pacientes de ambos os sexos, com idade entre 20 e 62 anos. O diagnóstico de bruxismo do sono foi realizado através de um questionário e exame clínico intra-oral. Enquanto o diagnóstico de abfração foi realizado por meio de exame clínico intra-bucal com auxílio de sonda exploradora e milimetrada. Foram utilizados o teste exato de Fisher e Mann-Whitney para análise estatística (α=0,05). Resultados: A prevalência de lesões de abfração na amostra total de dentes foi de 5,64%, sendo significativamente maior em pacientes bruxômanos (8,83%) do que em pacientes sem bruxismo (1,38%) (p=0,017). A presença de bruxismo foi associada à presença de abfrações (p=0,012). Conclusão: O diagnóstico positivo do bruxismo do sono é um fator de risco, aumentando consideravelmente a chance de o paciente apresentar LCNCs do tipo abfração(AU)

Non-carious cervical lesions (NCCL) are characterized by tooth structure loss located near the cement-enamel junction. Considering one of the possible etiologies of NCCL and occlusal overload, it becomes important to understand the relationship between the prevalence of these lesions and overhead factors in the oral environment. Objective: Evaluate the prevalence of the abfraction type of NCCL and its relationship with the positive diagnosis of sleep bruxism in a sample of patients of IMED and CEOM. Methodology: This was a clinical cross-sectional study, which was conducted an observational evaluation of a 25 patients sample of both genders, aged between 20 and 62 years. The diagnosis of sleep bruxism was conducted through a questionnaire and intra-oral clinical examination. The diagnosis of abfraction was performed through intra-oral clinical examination with the help of exploitative and millimetric probe. It was used Fisher's exact test and Mann-Whitney test for statistical analysis (α=0.05). Results: The prevalence of abrasion damage to the total sample of teeth was 5.64%, being significantly higher in patients whose have bruxism (8.83%) than in patients without bruxism (1.38%) (p=0.017). The presence of bruxism was associated with the presence of abfraction (p=0.012). Conclusion: It was concluded that the positive diagnosis of sleep bruxism is a risk factor, increasing considerable the possibility of the patient presenting the abfraction type of NCCL(AU)

Pino de fibra de vidro anatômico: relato de caso / Anatomic glass fiber post: case report

Introdução: Pinos pré-fabricados de fibra de vidro possuem boas propriedades mecânicas e estéticas. Porém, estes podem não se adaptar bem em canais amplos ou excessivamente cônicos prejudicando sua retenção ao canal radicular. Uma alternativa para esta desvantagem, é a utilização da técnica de pino anatômico. Objetivo: O objetivo do relato de caso foi apresentar a técnica de confecção de um pino fibra de vidro anatômico em dente anterior com reduzido remanescente coronário e ampla embocadura do canal radicular. Relato de Caso: Paciente masculino, 49 anos, procurou atendimento odontológico com queixa da aparência estética de seus dentes anteriores superiores. Após remoção de uma coroa metalocerâmica e um pino-núcleo metálico fundido do elemento 12, foram confeccionados um pino de fibra de vidro anatômico, núcleo de preenchimento e coroa provisória. Foram realizadas as facetas em resina composta nos elementos 13, 11, 21, 22 e 23. Uma coroa de cerâmica reforçada por dissilicato de lítio (IPS e.max CAD, Ivoclar Vivadent) foi cimentada no elemento 12. Conclusões: Através da técnica pino de fibra de vidro anatômico, é possível reabilitar dentes anteriores tratados endodonticamente sem a utilização de pinos metálicos, apresentando bons resultados estéticos. Entretanto, uma condição oclusal dentro dos princípios de uma oclusão mutuamente protegida deve ser almejada para garantir longevidade da restauração(AU)

Introduction: Prefabricated glass fiber posts present good mechanical and esthetic proprieties. However, these may not fully fit in large canal or excessively conical damaging your retention in the root canal. An alternative to this disadvantage, it is the use of post anatomic technique. Aim: the aim of the case report was to present the technique to obtain an anatomic glass fiber post in anterior teeth with reduced coronal remaining and large access of the root canal. Case Report: Man patient 49 year-old searched dental care with complaint of the esthetic appearance of your anterior maxillary teeth. After the removal of a metalceramic crown and a cast core and post of the tooth 12, an anatomic glass fiber post, resin core and interim crown were performed. Direct composite resin veneers were performed in the teeth 13, 11, 21, 22 and 23. A crown of reinforced lithium disilicate ceramic (IPS e.max CAD, Ivoclar Vivadent) was luted at tooth 12. Conclusions: It is possible to restore endodontically treated teeth without to use metal posts presenting improved esthetic results using the technique of anatomic glass fiber post. However, an occlusal condition concerning the principles of protected occlusion must be founded to guarantee a long-term restoration(AU)

Parafunctional loading and occlusal device on stress distribution around implants: A 3D finite element analysis.

STATEMENT OF PROBLEM: An occlusal device is frequently recommended for patients with bruxism to protect implant-supported restorations and prevent marginal bone loss. Scientific evidence to support this treatment is lacking. PURPOSE: The purpose of this 3-dimensional (3D) finite element study was to evaluate the influence of an acrylic resin occlusal device, implant length, and insertion depth on stress distribution with functional and parafunctional loadings. MATERIAL AND METHODS: Computer-aided design software was used to construct 8 models. The models were composed of a mandibular bone section including the second premolar and first and second molars. Insertion depths (bone level and 2 mm subcrestal) were simulated at the first molar. Three natural antagonist maxillary teeth and the placement or not of an occlusal device were simulated. Functional (200-N axial and 10-N oblique) and parafunctional (1000-N axial and 25-N oblique) forces were applied. Finite element analysis (FEA) was used to determine the maximum principal stress for the cortical and trabecular bone and von Mises for implant and prosthetic abutment. RESULTS: Stress concentration was observed at the abutment-implant and the implant-bone interfaces. Occlusal device placement changed the pattern of stress distribution and reduced stress levels from parafunctional loading in all structures, except in the trabecular bone. Implants with subcrestal insertion depths had reduced stress at the implant-abutment interface and cortical bone around the implant abutment, while the stress increased in the bone in contact with the implant. CONCLUSIONS: Parafunctional loading increased the stress levels in all structures when compared with functional loading. An occlusal device resulted in the lowest stress levels at the abutment and implant and the most favorable stress distribution between the cortical and trabecular bone. Under parafunctional loading, an occlusal device was more effective in reducing stress distribution for longer implants inserted at bone level. Subcrestally, implant insertion yielded the most favorable biomechanical conditions at the abutment-implant interface and at the coronal surface of the cortical bone, mainly when there was no occlusal device.