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This study aimed to evaluate the effect of different loading conditions on the mechanical behavior and stress distribution of a leucite-reinforced glass-ceramic. Plate-shaped ceramic specimens were obtained from leucite-reinforced glass-ceramic (1.5 × 8.4 × 8.3 mm) and adhesively cemented to a dentin analog substrate. Monotonic and cyclic contact fatigue tests were performed to simulate sphere-to-flat contact, using a 6 mm diameter spherical piston; and flat-to-flat contact, using a 3 mm diameter flat piston. For the monotonic test (n=20), a gradual compressive load (0.5 mm/min) was applied to the specimen using a universal testing machine. Failure load data were analyzed with Weibull statistics. The cyclic contact fatigue test was performed using protocols (load and a number of cycles) defined by the boundary technique (n=30). Fatigue data were analyzed using an inverse power law relationship and Weibull-lifetime distribution. The stress distribution was investigated using Finite Element Analysis (FEA). The monotonic and the fatigue Weibull modulus were similar among the two contact conditions. In fatigue, the slow crack growth exponent was greater for sphere-to-flat contact, which indicates that the load level had a greater effect on the specimen’s probability of failure. In conclusion, FEA showed different stress distribution for the tested loading conditions. The stress distribution and probability of fatigue failure of specimens tested in sphere-to-flat contact showed greater dependency to load level.

To evaluate the influence of photodynamic therapy (PDT), different final irrigants, and ultrasonic activation (US) on the bond strength of glass fiber posts (GFP) to root dentin.One hundred twenty bovine roots were divided into 12 groups according to PDT application, the type of final endodontic irrigant, and US. The samples were divided into 12 groups (n = 10): G1-DW(distilled water); G2-DW+US; G3-17% EDTA; G4-17% EDTA+US; G5-17% GA (glycolic acid); G6-17% GA+US; G7-PDT+DW; G8-PDT+DW+US; G9-PDT+17% EDTA; G10-PDT+17% EDTA+US; G11-PDT+17% GA; G12-PDT+17% GA+US. After cementing the glass fiber posts with resin cement, roots were sectioned into 2-mm-thick slices. One slice from the cervical third and another from the middle third were used for the push out test (PO), and the other two for the diametral compression test (DC). Thus, 10 samples were obtained per third for each mechanical test (n = 10). Kruskal-Wallis and Student-Newman-Keuls tests were used to analyze PO and DC data, and Pearson's correlation test was used to verify the relationship between the variables. Failure patterns were analyzed with chi-square test.Significant differences were found in the PO test among the experimental groups (p 0.001; power=1.00). PDT improved bond strength when using EDTA. PDT and US increased bond strength when using GA. Favorable failure patterns occurred more frequently in Group GA+US. There was no correlation between data obtained with PO and DC tests (r = 0.112; p = 0.729).PDT provided the highest bond strength values of GFP to root dentin when associated with GA and US or when associated only with EDTA.

Objective Mechanical damages can occur from dental restoration processing and fitting, or while it is in-service. This study evaluates the damage sensitivity of translucent zirconia (5Y-PSZ) relative to conventional 3Y-PSZ following mouth-motion simulations at various loads. Methods 5Y-PSZ and 3Y-PSZ discs were adhesively bonded to a dentin-like substrate and divided into groups according to the load (50 N or 200 N) and number of cycles (up to 106) used in the chewing simulation. Specimens were mounted with 30° inclination in an electrodynamic mouth-motion simulator, and subjected to contact-slide-liftoff cyclic loading in water. Surface and sub-surface damages were analyzed using a sectioning technique. After the simulation, specimens were removed from the substrate and loaded with the damaged surface in tension for biaxial strength testing to assess their damage tolerance. Results The strength of both ceramics underwent significant degradation after mouth-motion simulations. For 5Y-PSZ, the strength degradation was greater (∼60%) and occurred at a lower number of cycles than 3Y-PSZ. Herringbone cracks emerged on 3Y-PSZ and 5Y-PSZ surfaces under a 200-N load after 50 and 10 cycles, respectively. Meanwhile at a 50-N load, cracks formed at ∼1000 cycles in both ceramics. Further increasing the number of cycles only had moderate effects on the strength of both ceramics, despite an increase in surface and sub-surface damage. More significantly, a 50-N occlusal load can debase the zirconia strengths as much as a 200-N load. Significance Surface flaws produced during the chewing simulation are capable of significant strength degradation in zirconia, even after a small number of low-load cycles.

Background: The use of zirconia-based ceramics to produce monolithic restorations has increased due to improvements in the optical properties of the materials. Traditionally, zirconiabased ceramics were veneered with porcelain or glass-ceramic and were not directly exposed to the oral environment. Therefore, there are several doubts regarding the wear of the monolithic zirconia restoration and their antagonists. Additionally, different surface treatments are recommended to promote a smooth surface, including glaze and several polishing protocols. To support the correct clinical application, it is important to understand the advantages and limitations of each surface treatment. Objective: The aim of this short literature review is to investigate the factors that may affect the wear of monolithic zirconia restorations in service and their antagonists. Methods: Pubmed/Medline database was accessed to review the literature from a 10-year period using the keywords: zirconia, monolithic, prosthesis, wear. Both clinical and in vitro studies were included in the review. Results: Studies investigated the effect of several surface treatments, including grinding with diamond- burs, polishing and glazing, on the surface roughness, phase transformation and wear capacity of monolithic zirconia. The wear behavior of monolithic zirconia was frequently compared to the wear behavior of other ceramics, such as feldspathic porcelain, lithium disilicate-based glassceramic and leucite-reinforced glass-ceramic. Human tooth, ceramics and resin composites were used as antagonist in the investigations. Only short-term clinical studies are available (up to 2 years). Conclusion: Literature findings suggest that zirconia monolithic restorations are wear resistant and unlikely to cause excessive wear to the antagonist, especially when compared to feldspathic porcelain and glass-ceramics. Monolithic zirconia should be polished rather than glazed. Yet, none of the polishing systems studied was able to completely restore the initial surface conditions of zirconia after being adjusted with burs. More clinical evidence of the antagonist tooth wear potential of monolithic zirconia is needed.

Objective To evaluate the influence of the substrate and the cement on the final color of ceramic crowns. Methods Prosthetic crowns (framework + porcelain) were fabricated using two all-ceramic systems (YZ, 3 mol% yttria-stabilized tetragonal zirconia; IZ, alumina-based zirconia-reinforced glass-infiltrated ceramic) and a metal-ceramic system (MC; n = 8). Metal (M) and resin (R) were used as substrate abutments. For R substrate, crowns were evaluated as seated (R) and after cementation (R-C). CIELAB color coordinates were obtained using a dental spectrophotometer with D65 light illumination. CIELAB, CIEDE2000 (1:1:1) and CIEDE2000 (2:1:1) color difference metrics were used. Data were analyzed using 95% confidence intervals and compared to perceptibility (PT) and acceptability (AT) thresholds. Results The ∆ E ab * , ∆E00 (1 : 1 : 1), and ∆E00 (2 : 1 : 1) values of the restorative systems evaluated using different substrates (M.R) were similar to the AT values of each metric. When non-cemented and cemented crowns were evaluated (R.R-C), MC had color difference values at PT and below AT; while YZ and IZ showed similar values to AT, for ∆ E ab * and ∆E00 (1 : 1 : 1) metrics. Conclusion The substrate and cement affected the final color of zirconia-based all-ceramic crowns, but the color differences corresponded to an acceptable match. Clinical significance As both substrate and cement influence the final color of multi-layered ceramic prosthesis, dentists and dental technicians should understand the optical properties of dental ceramics to reproduce the natural appearance of dental structures and maximize the chance for excellent color matches.

OBJECTIVES: To identify the bile acids in the saliva of patients with and without gastroesophageal reflux disease (GERD), and evaluate their effect on tooth surface. DESIGN: A cross-sectional study involved 26 GERD patients and 40 controls without GERD. Dental erosions were identified, saliva was collected and analyzed with chromatography for bile acid identification. An in vitro study assessed the effect of enamel exposition to taurocholic acid in concentrations of 1 µM, 10 µM, and a mixture of taurocholic acid and glycocholic acid at 10 µM on enamel microhardness, calcium release, and surface topography. RESULTS: Salivary bile acids were analyzed from 22 GERD patients and 40 controls. All these participants presented taurocholic acid and glycocholic acid in the saliva. The salivary amount of taurocholic acid was greater than glycocholic acid in both GERD patients (area under the curve: 7946 vs. 1361; p

this study aimed to evaluate the adaptation and fatigue behavior of lithium disilicate glass-ceramic (LD) monolithic crowns produced by press (combined with 3D-printing) and CAD/CAM milling (control) techniques.thirty abutment preparations with a chamfer finish line were produced with a dentin analogue material and scanned with extraoral scanner. Captured images were processed using CAD software to design a premolar. Blocks of LD were milled using CAD/CAM system. For the press technique, crowns were first 3D-printed using a polymeric material and the heat-pressing protocol was performed. Crowns were adhesively cemented to the abutments and scanned using micro-CT. Files were processed and cross-sectional images were analysed in five measuring points: marginal, axial angle, axial, occlusal angle and occlusal. Fatigue test was performed in a MTS universal testing machine (2 Hz, 37°C distilled water) using an anatomic composite piston, following the step-stress method. Failures were detected with an acoustic system and confirmed by transillumination. A cumulative damage-Weibull distribution (95% CI) was used to analyze the fatigue data. Gap thickness data were analyzed using Kruskal-Wallis and Student-Newman-Keuls tests (α=0.05).CAD/CAM milling resulted in larger gap thickness in the occlusal area and smaller gap thickness in the axial angle and axial area than press (p0.05). The probability of failure was similar for crowns produced with CAD/CAM milling and press. The most frequent failure mode was radial crack.LD crowns produced using the combination of 3D-printing/press technique showed similar fatigue behavior than CAD/CAM milled control group, and resulted in smaller gap thickness at the occlusal region.A more controlled process can be achieved by replacing conventional restoration waxing with 3D printing, which in combination with the press technique produces lithium disilicate glass-ceramic monolithic crowns with good adaptation and high fatigue survival.

Statement of problem The lack of standardization regarding the loading piston material used in fatigue tests could limit the interpretation of study findings. Purpose The purpose of this in vitro study was to evaluate the effect of the piston material on the fatigue behavior of a lithium disilicate glass-ceramic. Material and methods Plate-shaped, 1.2-mm-thick, lithium disilicate glass-ceramic specimens were cemented onto a dentin analog substrate with resin cement. The specimens were divided into 4 groups according to the piston material used in the fatigue test (n=30): metal, glass fiber-reinforced epoxy resin, ceramic, and human tooth. The fatigue test was performed in a mechanical cycling machine by using the boundary technique at 2 Hz in distilled water at 37 °C. The fatigue data were analyzed by using the Weibull distribution and a lifetime-inverse power law relationship. Failures were evaluated with fractography and transillumination. Results The Weibull modulus (β) was similar among groups. The exponent of crack growth (n) was significantly greater for glass fiber-reinforced epoxy resin and tooth groups than for metal and ceramic; therefore, the probability of failure (Pf) of glass-ceramic specimens loaded by resin and tooth pistons depended more on load amplitude. Specimens tested with tooth showed the highest value of K (characteristic lifetime), which is an indication of greater survival. Radial crack was the only failure mode observed for all experimental groups. Conclusions The piston material influenced the fatigue survival of the lithium disilicate glass-ceramic. The glass fiber-reinforced epoxy resin piston closely simulated the fatigue behavior induced by the human tooth on the evaluated glass-ceramic.

The first generation of polycrystalline zirconia-based ceramic used to produce dental prosthesis showed excellent mechanical behavior; however, its low translucency limited the indication for aesthetic monolithic restorations. Thus, various strategies have been tested in order to develop a material that has high strength and good optical properties. The aim of this study was to characterize, through a literature review, the translucency of different types of zirconia-based ceramics indicated for monolithic restorations. The literature search was performed in PubMed/Medline database, from 2010 to 2019, using as keywords: zirconia, translucency, and optical properties. The 3rd (monochromatic) and 4th (multichromatic) generations of zirconia, which have high cubic phase content, showed the highest translucency among the zirconia-based ceramics investigated. Additionally, other strategies, such as the addition of lanthanum oxide and the infiltration of feldspathic glass in the zirconia surface (graded-zirconia), resulted in a good balance of optical and mechanical properties.

Statement of problem Restorative materials are cemented on different types of substrates, such as dentin, metal, and glass-fiber posts with composite resin cores. Purpose The purpose of this in vitro study was to evaluate the failure behavior after cycling fatigue of a polymer-infiltrated ceramic network material (PICN; VITA ENAMIC) cemented on different supporting substrates. Material and methods PICN plates (N=80) were obtained from computer-assisted design and computer-assisted manufacturing (CAD-CAM) blocks and cemented with a resin cement to 4 different supporting substrates (n=20): (1) human dentin (PICNDen); (2) dentin analog (PICNDenAn); (3) nickel-chromium alloy (PICNNiCr); and (4) composite resin plus fiberglass post (PICNRc). For comparison, the fracture behavior of a feldspathic ceramic (FelDenAn; VITABLOCS Mark II) and an indirect composite resin (ResDenAn; Opallis LAB Resin) cemented to the DenAn substrate was investigated (n=20). Thus, specimens were composed of the restorative material layer (1-mm thick) resin cemented (0.1-mm-thick layer) to a 2-mm-thick supporting substrate. All specimens were subjected to mechanical cycling (MC) using a pneumatic cycling machine (500 000 cycles, 2 Hz, 50 N). Specimens that did not fracture during cycling were tested under compression using a universal testing machine at a cross-head speed of 0.5 mm/min until the sound of the first crack was detected using an acoustic system. Failure data were statistically evaluated using Weibull distribution. Failures were classified as radial crack, cone crack, combined, and catastrophic fracture. Results All FelDenAn specimens were fractured during MC. Only 4 PICNRc specimens survived MC, so their fracture load data were not statistically analyzed. PICNNiCr showed the greatest characteristic load (L0) value, followed by ResDenAn. Groups PICNDenAn and PICNDen showed lower and similar L0 but statistically different Weibull modulus (m). There was a significant relationship between experimental group and failure mode (P Conclusions The supporting substrate influenced the failure behavior of PICN. When the substrate had a higher elastic modulus than the restorative material, better mechanical behavior was observed.

Monolithic zirconia crowns have become very popular; their surface finish is considered a key factor for restoration longevity. While polishing has shown excellent results in vivo, the surface glass infiltration of zirconia may offer superior damage resistance and aesthetic advantages by using tooth-colored glasses. Thus, the purpose of this study is to evaluate the efficacy of polishing and glass infiltration on the wear behavior of monolithic zirconia crowns. The wear behavior of intact natural molar teeth was investigated as a reference. Zirconia crowns were divided into 3 groups: PolZ—sintered then polished; PolGZ—polished in the presintered state and then glass infiltrated and sintered; NoPolGZ—as machined, glass infiltrated and sintered. Crowns were adhesively bonded to a dentin-like abutment. Zirconia crowns and molar teeth ( n = 15) were subjected to contact-slide-liftoff cyclic loading (200 N, 1.25 million cycles) with a steatite sphere ( r = 3 mm) as an antagonist in water. Surface and subsurface damages were investigated with optical and scanning electron microscopies. Wear depth and volume loss were determined with micro–computed tomography. PolGZ and NoPolGZ crowns exhibited shallow wear scars, where material loss remained within the glass/zirconia layer with no visible cracks. Meanwhile, PolZ crowns presented no visible wear damage. Volume loss (mm3) in the steatite antagonist was as follows (mean ± SD): PolZ = 0.022 ± 0.007, PolGZ = 0.011 ± 0.004, and NoPolGZ = 0.014 ± 0.006. Molar teeth yielded no measurable wear on the antagonist, while the wear scar on the teeth was greater than that on zirconia crowns, ranging from 0.07 to 0.35 mm3. The combination of polishing and glass infiltration on the occlusal surface of monolithic zirconia crowns yielded reduced wear on both crown and antagonist.

Statement of problem Evidence is limited for the impact of clinical adjustments and polishing on the longevity of glazed lithium disilicate restorations. Purpose The purpose of this in vitro study was to evaluate the influence of surface finishing on the survival and success rates of lithium disilicate restorations based on fatigue resistance and failure mode. Material and methods Lithium disilicate (IPS e.max CAD) maxillary premolar crowns (N=54) were cemented on a dentin analog. The restorations were divided into 3 groups: overglaze (OG), abrasion (GA), and abrasion and polishing (AP). The crowns were submitted to cyclic fatigue in 37 oC water at 100 N and 2 Hz in 2 lifetimes. The load was applied to the occlusal surface by using anatomic pistons to simulate a clinical tripod occlusal contact. After cycling, the crowns were examined for failure (cracking, chipping, or catastrophic fractures) under optical and scanning electron microscopy. Cracking was considered either a structural failure (success analysis) or a survival (clinical criteria - survival analysis). Data were analyzed by using the log rank Kaplan-Meier and Holm-Sidak tests (α=.05). Results Surface finishing had no influence on the structural integrity of lithium disilicate, with similar success rates (P=.720). The calculated survival rate was higher for AP than that for other groups (P=.028). Cracking was found for GA and AP crowns, mostly initiating from the external surface. Chipping occurred in all experimental groups, and AP crowns did not show catastrophic failures. Conclusions Although surface treatments had no influence on the success of lithium disilicate, polishing showed a positive effect on the survival rate of the crowns based on the clinical implications of cracking (no need for replacement).

Conventional flexural strength tests of restorative materials neglect the effect of essential variables that can affect their mechanical behavior. The purpose of this study was to evaluate the effect of cementation on the mechanical behavior of a nanoceramic resin. A nanoceramic resin (LU) and a leucite-reinforced glass-ceramic (IE) were evaluated. Non-cemented specimens of the materials were produced and subjected to biaxial flexural strength test ( σ f , n = 30 ). Cemented specimens were constituted of the restorative material bonded with resin cement onto a dentin analog substrate. Cemented specimens were subjected to the monotonic compressive load test ( L f , n = 20 ). Vickers microhardness (HV) and translucency parameter (TP) of the materials were characterized. Data were analyzed using t-test (σf and TP), Mann-Whitney test (Lf and HV), and Weibull analysis (σf and Lf, α = 0 . 05). Non-cemented LU showed higher σf and Weibull modulus (m) than IE. When cemented to the substrate, LU showed higher Lf than IE; however, the m-value was similar among groups. LU showed lower HV than IE and higher TP values. Cementation influenced the mechanical behavior and failure mode of the nanoceramic resin. Resumo Os testes convencionais de resistência à flexão de materiais restauradores negligenciam o efeito de variáveis essenciais que podem afetar seu comportamento mecânico. O objetivo deste estudo foi avaliar o efeito da cimentação no comportamento mecânico de uma resina nanocerâmica. Foram avaliadas uma resina nanocerâmica (LU) e uma vitrocerâmica reforçada por leucita (IE). Foram produzidos corpos de prova (CP) não cimentados dos materiais e submetidos ao teste de resistência à flexão biaxial ( σ f , n = 30 ). CPs cimentados foram constituídos pelo material restaurador cimentado adesivamente a um substrato análogo à dentina. Os CPs cimentados foram submetidos ao teste de carga compressiva monotônica ( L f , n = 20 ). A microdureza Vickers (HV) e o parâmetro de translucidez (TP) dos materiais foram caracterizados. Os dados foram analisados pelo teste t (σf e TP), teste de Mann-Whitney (Lf e HV) e análise de Weibull (σf e Lf, α = 0 . 05). A LU não cimentada apresentou σf e módulo de Weibull (m) superiores a IE. Quando cimentada ao substrato, a LU apresentou maior Lf que a IE; no entanto, o valor de m foi semelhante entre os grupos. A LU apresentou menor HV que a IE e maiores valores de TP. Concluiu-se que a cimentação influenciou o comportamento mecânico e modo de falha da resina nanocerâmica.

OBJECTIVE. To characterize the composition, microstructure and wear properties of a multilayer translucent zirconia relative to the conventional 3Y-TZP. METHODS. Two types of ceramics were evaluated: a multilayer zirconia (MULTI, IPS e.max ZirCAD Multi, Ivoclar Vivadent) and a control 3Y-TZP (IPS e.max ZirCAD LT, Ivoclar Vivadent). Pre-sintered CAD-CAM blocks were cut, ground, sintered and polished to 1 μm finish. The phase fraction and grain size were measured using XRD and FE-SEM. For wear testing (n = 12), square-shaped specimens (16x16x1 mm) were adhesively bonded to a dentin analog. Sliding wear tests were performed using a spherical zirconia antagonist (r = 3.15 mm), with 30 N load at 1.5 Hz for 500,000 cycles in water. Optical and scanning electron microscopes and 3D laser scanner were used for quantitative wear analyses. Data were analyzed using Student´s t-test (α = 0.05). RESULTS. For MULTI, the enamel layer had the highest cubic content and the largest grain size, followed by the two transition layers, and the dentin layer. 3Y-TZP showed the smallest grain size and cubic content. A significant amount of wear was observed in both materials up to 50,000 cycles until it reached a plateau. MULTI showed higher volume loss and greater wear depth than 3Y-TZP (p < 0.01). The higher volume loss was associated with extensive lateral fracture, leading to material spalling from the surface of cubic-containing zirconias. SIGNIFICANCE. The wear pattern in multi-layered zirconia was more severe than 3Y-TZP. Additionally, the different layers of the multi-layered zirconia had similar wear behavior.

Introduction The study investigated which patient and orthodontic treatment factors act as predictors for the conclusion of the ongoing treatment in a dental clinic of a specialization program in Orthodontics. Methods Data were collected from the records of patients treated from 1997 to 2015. Potential predictors for treatment conclusion were investigated: patient-related factors (PRFs) and treatment-related factors (TRFs). PRFs were sex, age, face balance, Angle malocclusion classification, open bite, denture, facial pattern, facial profile, buccal corridor, crossbite, maxillary deficiency, and sagittal mandibular behavior; and TRFs were therapeutic approaches, treatment modality, extractions, and Bolton discrepancy. The initial and final treatment dates were collected. Descriptive data analysis, univariate, and multivariate logistic regression were performed (5% significance). Results Of the 903 records, 561 patients were included in the study. It was demonstrated that starting the treatment at a young age (PRF) and the presence of crossbite (TRF) are predictive factors for the treatment conclusion. A vertical facial pattern (dolichofacial or brachyfacial) and a greater number of extractions for orthodontic reasons may contribute positively to the conclusion of the treatment. The frequency of treatment inconclusion was higher during the first 2 years of treatment (more than 50% of the patients that initiated the treatment). Conclusions Young age at the beginning of treatment and the presence of crossbite malocclusion can increase the chance of treatment conclusion.

Resumo Próteses fixas com infraestrutura de metal ou cerâmica apresentam muitas falhas devido ao lascamento da cerâmica vítrea de cobertura. Assim, próteses monolíticas produzidas com apenas um material foram desenvolvidas no intuito de diminuir estas falhas. Cerâmicas à base de zircônia tiveram suas propriedades ópticas modificadas para permitir a confecção de próteses monolíticas. Portanto, o objetivo deste estudo foi verificar através de uma revisão da literatura o comportamento mecânico e clínico das próteses monolíticas à base de zircônia. Foi feita uma busca na base de dados PubMed/Medline (2010 a 2017) utilizando as palavras-chave: zircônia (zirconia), monolítica (monolithic) e prótese (prosthesis). Foram selecionados 13 estudos laboratoriais e 5 estudos clínicos. Os estudos laboratoriais mostraram que próteses monolíticas à base de zircônia apresentam alta resistência à fratura, à fadiga e ao lascamento. Próteses com espessura mínima de 0,7 mm devem ser confeccionadas para que sejam suficientemente resistentes às cargas impostas pela mastigação, tendo carga de fratura semelhante a coroas metalocerâmicas. Os estudos clínicos relatam baixas taxas de falha para esse tratamento protético. Próteses monolíticas à base de zircônia apresentam comportamento mecânico e clínico favorável para a reabilitação da região posterior. Abstract Dental prosthesis produced with metal or ceramic infrastructure show high rates of chipping of the glass-ceramic veneer. Thus, monolithic prosthetic restorations produced with only one material were developed in order to reduce these failures. Zirconia-based ceramics had their optical properties modified to produce monolithic restorations. Therefore, the objective of this study was to verify, through a literature review, the mechanical and clinical behavior of zirconia-based monolithic dental prostheses. PubMed/Medline database was used to search for manuscripts (2010 to 2017) using the following keywords: zirconia, monolithic and prosthesis. Thirteen in vitro studies and five clinical studies were selected. Studies have shown that zirconia-based monolithic prostheses exhibit high resistance to fracture, fatigue and chipping. To support the chewing load and achieve similar mechanical behavior as the metal-ceramic system, restorations should be produced with a minimum thickness of 0.7 mm. Clinical studies report low failure rates for this prosthetic treatment. Zirconia-based monolithic dental prostheses present mechanical and clinical behavior favorable for the rehabilitation of the posterior region.

PURPOSE To evaluate the fatigue behavior of two crystalline-reinforced ceramics: leucite-reinforced (VL) and lithium disilicate-based (VD) glass-ceramics. MATERIALS AND METHODS Bar-shaped specimens (16 × 4 × 1.2 mm) were produced for each ceramic using prefabricated CAD/CAM blocks. For each group, 30 specimens were subjected to a three-point flexural strength test in a universal testing machine. For VL and VD, 36 and 41 specimens were subjected to a cyclic fatigue test, respectively. The cyclic fatigue test was performed with a pneumatic mechanical cycling machine (1 Hz; 37°C distilled water). Specimens were tested at two stress levels for each preset lifetime (103 and 104 cycles for VL; 104 and 105 cycles for VD) following the boundary technique. Fractography was performed with a scanning electron microscope. Data were analyzed with Weibull analysis. RESULTS There were significant differences among groups for characteristic strength (σ0 ) and Weibull modulus (m), as the confidence intervals did not overlap. The VD group presented the highest values of σ0 , but the lowest Weibull modulus. Both groups showed a reduction of approximately 60% of the initial flexural strength (σf ) after cycling for 104 cycles. For VD tested in fatigue, there was no degradation of σf when the number of cycles was increased from 104 to 105 . The VL group showed an 18% decrease in σf when the number of cycles increased from 103 to 104 . Flexural strength values estimated for a 5% probability of failure were 36 MPa for VL and 55 MPa for VD, after 104 cycles. CONCLUSION Both glass-ceramics showed similar strength degradation (60%) after a lifetime of 104 cycles, despite their distinct mechanical properties. Mechanical cycling in humid conditions proved to be an important factor for the degradation of the mechanical properties of crystalline-reinforced glass-ceramics.

Resumo A substituição do metal utilizado como infraestrutura de restaurações protéticas pela cerâmica policristalina à base de zircônia tetragonal estabilizada por ítria (Y-TZP) resultou em dúvidas sobre a qualidade de união entre as cerâmicas de infraestrutura e de recobrimento. Assim, surgiram alguns tratamentos de superfície com o intuito de melhorar a união porcelana-Y-TZP. O objetivo deste estudo foi avaliar o efeito de um tratamento de superfície na resistência de união entre a porcelana e a Y-TZP, bem como comparar os resultados com um grupo controle metal-cerâmica. Três grupos experimentais foram avaliados (n=10): YC - infraestrutura de Y-TZP recoberta com porcelana VM9; YB - infraestrutura de Y-TZP recoberta com um agente de união e porcelana VM9; MC - infraestrutura de níquel-cromo recoberta com opaco e porcelana VM13. Os corpos de prova foram confeccionados usando lâminas do material de infraestrutura, e sobre elas foi construído um cilindro de porcelana (3 mm de diâmetro, 6 mm de altura), sinterizado de acordo com as instruções do fabricante. Os grupos foram submetidos ao teste de cisalhamento em uma máquina de ensaio universal com velocidade de 0,5 mm/min. Após os testes, as falhas foram classificadas como adesiva, mista ou coesiva. Os dados de resistência de união (σf) foram analisados estatisticamente com Anova de um fator (α=0,05). As médias (desvio-padrão) de σf (MPa) foram: YC - 19,7 (7,8); YB - 22,5 (6,4); MC - 24,2 (6,6). Não foi encontrada diferença estatística entre os grupos (p=0,377). Houve relação entre o grupo experimental e o modo de falha. Apenas os grupos YC e YB apresentaram falha coesiva na porcelana. Concluiu-se que a infraestrutura à base de Y-TZP tem resistência de união à porcelana semelhante ao “padrão ouro” metal-cerâmica. A aplicação de um agente de união não teve influência na resistência de união entre porcelana e Y-TZP.

The objective of this study was to evaluate the effects of glycolic acid (GA) (with pH 1.2 and 5) and ethylenediaminetetraacetic acid (EDTA) on the chemical and mechanical properties of dentin to investigate the potential use of GA as final irrigant in the root canal therapy. Specifically, changes in microhardness, smear layer removal, erosion, mineral content distribution, apatite/collagen ratio and flexural strength of mineralized dentin treated with GA were assessed. Saline solution was used as a negative control. Knoop microhardness (KHN) was measured on the root canal lumen of root segments. Dentin beams were used for 3-point flexural strength (σ) test. Scanning electron microscopy (SEM) images of root sections were obtained for evaluation of smear layer removal and dentin erosion on root segments and energy dispersive X-ray spectroscopy (EDS) was used for mineral content distribution. The apatite/collagen ratio (A/C) in dentin powder were examined by Fourier transform infrared (FTIR) spectroscopy. KHN, σ and A/C results were statistically analyzed with ANOVA and Tukey tests (α = 0.05). Smear layer and dentin erosion scores were analyzed with Kruskal-Wallis and Dunn tests (α = 0.05). Root dentin treated with EDTA and GA presented similar KHN regardless of the pH (p > 0.05). However, KHN was significantly reduced in EDTA and GA groups when compared to control group (p

Objective To evaluate the cyclic contact fatigue resistance and failure mode of ceramics for monolithic and multilayer restorations. Methods Ceramic structures (10 mm × 1.8 mm) were fabricated as follows (n = 28): (1) CAD-on- trilayer structure composed of Y-TZP (yttria stabilized tetragonal zirconia polycrystal- IPS e.max ZirCAD) infrastructure, fusion glass–ceramic (IPS e.max CAD Crystall/Connect) and lithium disilicate-based glass–ceramic (IPS e.max CAD); (2) ZFC- bilayer structure composed of Y-TZP infrastructure veneered by a fluorapatite glass–ceramic (IPS e.max Ceram); (3) LDC- monolithic lithium-disilicate glass–ceramic (IPS e.max CAD); and (4) YZW- monolithic Y-TZP (Zenostar Zr Translucent). All ceramics structures were bonded to a dentin analog substrate (G10). Specimens were submitted to cyclic contact fatigue test in a pneumatic cycling machine with 80 N load and 2 Hz frequency in distilled water at 37 °C. Test was interrupted after 104, 105, 5 × 105 and 106 cycles and the presence or absence of failure was recorded. Fatigue data were analyzed using Kaplan–Meier (log rank) and Holm–Sidak tests (α = 0.05). The relationship between the type of crack leading to failure and the experimental group was analyzed using chi-square test (α = 0.05). Results There was no statistical difference between CAD-on and YZW groups (p = 0.516), which presented the highest survival rates after cyclic loading, followed by ZFC and LDC groups (p Significance Monolithic Y-TZP (YZW) showed similar fatigue resistance to CAD-on multilayer specimens, but different failure mode. Monolithic lithium disilicate glass–ceramic (LDC) and Y-TZP conventionally veneered by glass–ceramic (ZFC) showed lower survival time under fatigue.

PURPOSE To assess the influence of a screw access hole (SAH) and mechanical cycling on the fracture load of implant-supported crowns (ISCs) manufactured with screw-retained (s) or cement-retained (c) abutments with either metal (M) or zirconia (Z) infrastructure. MATERIALS AND METHODS Six groups of restorations were made based on type of infrastructure (M or Z), fixation (s or c), and whether they underwent aging (a) with mechanical cycling: Zc, Zs, Zsa, Mc, Ms, and Msa. All ISCs were porcelain veneered and tested for compression to failure in distilled water (37°C) using a universal testing machine. ISCs from groups Zsa and Msa were mechanically cycled (106 cycles; 2 Hz, 100 N) in distilled water before compressive testing. Fractographic principles were followed to assess the fracture surfaces. The fracture load data were statistically analyzed using one-way analysis of variance and Tukey test (α = .05). The relationships between experimental group and failure mode were analyzed using chi-square test (α = .05). RESULTS Regardless of the infrastructure material, cement-retained ISCs (Zc and Mc) showed higher fracture load values than screw-retained ISCs (Zs, Zsa, Ms, and Msa) (P .05). Aging had no effect on the fracture load of ISCs. There was a significant relationship between failure mode and experimental group (P < .001). Catastrophic fractures were found only in Zc and Zs. All metal-based ISCs failed from chipping reaching the metal infrastructure. CONCLUSION Cement-retained ISCs showed higher fracture resistance than screw-retained prostheses. No catastrophic failures were found for metal-based ISCs. Aging did not affect the fracture load, but did affect the failure mode of ISCs.

This study evaluated the fracture load (Lf) and the failure mode of CAD-on (Ivoclar Vivadent) ceramic structures, testing the hypotheses that Lf of multilayer structures is governed by the veneering ceramic strength and that chipping is more frequent in multilayer than monolithic structures. Disc-shaped specimens were fabricated as follows: CAD-on- trilayer structure composed of Y-TZP (yttria stabilized tetragonal zirconia polycrystal- IPS e.max ZirCAD) infrastructure, fusion glass-ceramic (IPS e.max CAD Crystall/Connect) and lithium disilicate-based glass-ceramic (IPS e.max CAD); YLD- bilayer structure composed of Y-TZP infrastructure and fluorapatite layering ceramic (IPS e.max Ceram); LDC- monolithic lithium-disilicate glass-ceramic (IPS e.max CAD); and YZW- monolithic Y-TZP (Zenostar Zr Translucent). The specimens were loaded in compression until failure and fracture surfaces were evaluated using fractographic principles. Lf values were statistically analyzed using the Weibull statistics, Kruskal-Wallis and Dunn tests (a= 0.05). YZW (1329 N) and CAD-on (1085 N) showed the greatest Lf median values, followed by YLD (832 N) and LDC (421 N). All monolithic structures (LDC and YZW) fractured catastrophically and all YLD structures failed by chipping. The CAD-on technique seems to be a very promising fabrication process because it showed high Lf, similar to monolithic zirconia, and small chipping rate. Resumo Este estudo avaliou a carga de fratura (Cf) e o modo de falha de estruturas cerâmicas fabricadas pela técnica CAD-on (Ivoclar Vivadent), testando as hipóteses de que a Cf das estruturas multicamadas é governada pela resistência da cerâmica de cobertura e o lascamento é mais frequente nas estruturas em multicamadas do que em monolíticas. Corpos de prova no formato de disco formam fabricados da seguinte forma: CAD-on- estrutura de 3 camadas composta por infraestrutura de Y-TZP (zircônia tetragonal parcialmente estabilizada por ítria - IPS e.max ZirCAD), vidro de fusão (IPS e.max CAD Crystall/Connect) e cobertura de cerâmica vítrea a base de dissilicato de lítio (IPS e.max CAD); YLD- estrutura de 2 camadas composta por infraestrutura de Y-TZP e cobertura de cerâmica (IPS e.max Ceram); LDC- monolítico em cerâmica vítrea a base de dissilicato de lítio (IPS e.max CAD); e YZW- monolítico em Y-TZP (Zenostar Zr Translucent). Os corpos de prova foram testados sob carga de compressão até a falha e as fraturas avaliadas seguindo os princípios da fractografia. Os valores de Lf foram analisados estatisticamente usando as estatísticas de Weibull, Kruskal-Wallis e Dunn (a = 0,05). YZW (1329 N) e CAD-on (1085 N) apresentaram os maiores valores medianos de Cf, seguidos por YLD (832 N) e LDC (421 N). Todas as estruturas monolíticas (LDC e YZW) fraturaram catastroficamente e todas as estruturas YLD falharam por lascamento. A técnica CAD-on parece ser um processo de fabricação bastante promissor pois mostrou alta Cf, similar a zircônia monolítica, e baixa taxa de lascamento.

To evaluate the effect of two aging methods (mechanical cycling and autoclave) on the mechanical behavior of veneer and framework ceramic specimens with different configurations (monolithic, two and three-layers).Three ceramics used as framework for fixed dental prostheses (YZ-Vita In-Ceram YZ; IZ-Vita In-Ceram Zirconia; AL-Vita In-Ceram AL) and two veneering porcelains (VM7 and VM9) were studied. Bar-shaped specimens were produced in three different designs: monolithic, two layers (porcelain-framework) and three layers (porcelain-framework-porcelain). Specimens were tested for three-point flexural strength at 1MPa/s in 37°C artificial saliva. Three different experimental conditions were evaluated (n=10): control; mechanical cycling (2Hz, 37°C artificial saliva); and autoclave aging (134°C, 2 bars, 5h). Bi-layered specimens were tested in both conditions: with porcelain or framework ceramic under tension. Fracture surfaces were analyzed using stereomicroscope and scanning electron microscopy. Results were statistically analyzed using Kruskal-Wallis and Student-Newman-Keuls tests.Only for AL group, mechanical cycling and autoclave aging significantly decreased the flexural strength values in comparison to the control (p0.01). YZ, AL, VM7 and VM9 monolithic groups showed no strength degradation. For multi-layered specimens, when the porcelain layer was tested in tension (bi and tri-layers), the aging methods evaluated also had no effect on strength (p≥0.05). Total and partial failure modes were identified.Mechanical cycling and autoclave aging protocols had no effect on the flexural strength values and failure behavior of YZ and IZ ceramic structures. Yet, AL monolithic structures showed a significant decrease in flexural strength with any of the aging methods.

This study aimed to characterize the fatigue behavior using two fatigue methods, boundary and staircase, and to predict the probability of failure (Pf) of zirconia-reinforced lithium silicate glass-ceramic (ZLS). Bar-shaped specimens of ZLS (18 ×4 ×1.2 mm) were fabricated. Thirty specimens were subjected to a three-point flexural strength test using a universal testing machine with 0.5 mm/min crosshead speed, in 37 °C distilled water. Flexural strength data were analyzed with Weibull statistics. Eighty-six bars were subjected to cyclic fatigue using boundary and staircase methods. Fatigue tests were performed in a pneumatic cycling machine (2 Hz, 37 °C distilled water) for 10 ³ and 104 cycles. Fatigue data were analyzed using an inverse power law relationship and log normal-lifetime distribution. Fracture toughness (KIc) was determined using V-notched specimens (18 ×4 ×3 mm) and the short beam toughness method (n = 7). Vickers hardness (VH) was evaluated (4.9 N, 20 s). Fractographic and EDS analyses were also performed. ZLS showed a characteristic strength of 197 MPa, Weibull modulus of 4, VH of 6.67 GPa and KIc of 1.93 MPa m1/2. After 103 cycles, for both methods, there was a degradation of 78% of the initial strength. There was no significant degradation when the number of cycles increased from 103 to 104. Both methods resulted in similar Pf and precision at 40 MPa (~50% Pf). Yet, staircase shows good accuracy and precision in predicting the stress amplitude for a P f near 50%; while boundary is also effective for P f lower than 50%. The fatigue methods evaluated show similar accuracy and precision for predicting the Pf of a glass-ceramic when simulations were made in the range of stress levels and lifetimes used in the fatigue tests.

Objetivo: avaliar a influência do uso de agentes clareadores com cálcio na microdureza do esmalte dental. Materiais e método: o estudo é experimental, laboratorial e realizado com dentes bovinos. Oito coroas de incisivos bovinos foram seccionadas em quatro partes e divididas em quatro grupos, de acordo com o tipo de agente clareador (n=8): (Con) protocolo de consultório (peróxido de hidrogênio 35% – HP 35%); (Com+Ca) protocolo de consultório com cálcio (HP 35%); (Cas) protocolo caseiro (peróxido de carbamida 10%); (Cas+Ca) protocolo caseiro com cálcio (HP 6%). As amostras foram tratadas de acordo com as recomendações do fabricante para cada agente clareador. A microdureza do esmalte foi avaliada antes, imediatamente após e 7 dias após os tratamentos clareadores. Foi utilizado um microdurômetro e ponta Vickers, com uma carga de 200 g por 15 segundos. As amostras permaneceram em água destilada a 37°C durante todo o experimento. Os dados foram avaliados com ANOVA e teste de Tukey (p=0,05). Resultados: para os tratamentos de consultório, não houve diferença na microdureza entre os tempos de avaliação e entre os agentes clareadores (p≥0,05). Já para os tratamentos caseiros, não houve diferença entre os grupos com e sem cálcio, mas, para ambos, ocorreu uma significativa redução na microdureza imediatamente após a conclusão do tratamento, que se manteve após os sete dias de armazenamento em água destilada (p

Different methods are available to produce all-ceramic dental prosthesis. Each processing step may introduce flaws to the material, which compromises its properties and reliability. The objective of this study was to evaluate the effect of fabrication method on the fracture behavior of prosthetic crowns produced with an alumina-based glass-infiltrated zirconia-reinforced ceramic. Two groups of all-ceramic crowns were produced according to the fabrication method of the infrastructure (IS) (n=30): IZC - IS produced by CAD-CAM; IZS - IS produced by slip-casting. The IS were veneered with porcelain and cemented to fiber-reinforced composite dies with resin cement. Crowns were loaded in compression to failure using a universal testing machine, at 1 mm/min crosshead speed and 37 ºC distilled water. Fractography was performed using stereomicroscope and SEM. Data were statistically analyzed with Student’s t test (α=0.05) and Weibull analysis. There were no significant differences among the experimental groups for fracture load (p=0.481) and Weibull modulus. For both groups, the failure mode was catastrophic failure involving IS and porcelain. It was concluded that the fabrication methods evaluated resulted in all-ceramic crowns with similar fracture behavior and reliability. Resumo Diferentes métodos estão disponíveis para produzir próteses totalmente cerâmicas. Cada etapa do processamento pode introduzir falhas no material, comprometendo suas propriedades e confiabilidade. O objetivo desse estudo foi avaliar o efeito do método de fabricação no comportamento de fratura de coroas produzidas com uma cerâmica à base de alumina, infiltrada com vidro e reforçada com zircônia. Dois grupos de coroas totalmente cerâmicas foram produzidos de acordo com o método de fabricação da infraestrutura (IS) (n=30): IZC - IS produzida com a tecnologia CAD-CAM, e IZS - IS produzida com a técnica slip-casting. As IS foram recobertas com porcelana e cimentadas sobre um pilar utilizando cimento resinoso. As coroas foram submetidas a uma carga de compressão até a fratura utilizando uma máquina de ensaios universal, com velocidade de 1 mm/min, em água a 37 ºC. Análise fractográfica foi realizada em estereomicroscópio e MEV. Os dados foram analisados estatisticamente com teste t de Student (α=0,05) e análise de Weibull. Não houve diferença estatística entre os grupos experimentais para a carga de fratura (p=0,481) e módulo de Weibull. Para ambos os grupos, o modo de falha foi fratura catastrófica envolvendo IS e porcelana de recobrimento. Concluiu-se que os métodos de fabricação avaliados resultaram em coroas com comportamento de fratura e confiabilidade semelhantes.

Objectives Ceramics and composites are the most used materials for dental application. Recently, the characteristics of both were combined on the called "polymer-infiltrated ceramic-network" (PICN). The aim of this review is to report the behavior of PICN, comparing the findings that may support the correct clinical application. Overview The PICN material is a structure with a sintered ceramic matrix infiltrated with a polymer matrix. Studies evaluated this material microstructure and composition, mechanical properties and adhesive behavior. The most cited mechanical properties are flexural strength, compressive strength, elastic modulus, Weibull modulus, hardness, fracture toughness and fatigue resistance. Most studies compared PICN with feldspathic porcelain, lithium disilicate glass-ceramic, lithium silicate, zirconia-reinforced glass-ceramic, leucite reinforced glass-ceramic, polycrystalline alumina and zirconia. Other studies evaluated a similar material (a nanoceramic resin). Clinical significance The mechanical properties of the PICN are equivalent to the properties of nanoceramic resins, lower to lithium disilicate glass ceramic and superior to feldspathic porcelain. Yet, the findings suggest a highly resistant material to degradation at low loads (close to physiological situation) when cemented on a substrate.

Statement of problem Variables involving the indication, manufacturing, and clinical use of ceramic restorations make the standardization of in vitro studies a challenge and raise questions as to the clinical validity of the resulting data. Purpose The purpose of this in vitro study was to assess the effect of piston material on the fracture behavior of ceramics tested under compressive load. Material and methods Two ceramics were evaluated: a lithium disilicate–based glass-ceramic (D) and a feldspathic porcelain (P). Plate-shaped ceramic specimens (1.5-mm thick) were adhesively cemented onto a dentin analog substrate. The specimens from each ceramic were divided into 4 groups according to the piston material (n=20): metal (M) (stainless steel), composite resin (R) (NEMA-G10, fiber-reinforced epoxy resin), ceramic (C) (lithium disilicate–based glass-ceramic), and human tooth (T) (canine). A gradual compressive load (0.5 mm/min) was applied to the center of the specimen with a universal testing machine. The test was performed in 37°C distilled water, and the initial crack was detected by using an acoustic system. The fracture load values (N) were statistically analyzed with the Kruskal-Wallis and Dunn tests (α=.05). A finite element analysis (FEA) was also performed. Results Piston material had no influence on fracture load and failure mode of ceramic D. Ceramic P showed higher fracture load values when loaded with the composite resin piston. Ceramic P showed more combined failures (cone crack and radial crack) than D. The FEA showed a distinct stress distribution for R piston on P. Pistons C and T resulted in similar stress distribution, fracture load, and failure mode for both ceramics. Conclusions The effect of piston material on the ceramic fracture behavior depends on the ceramic being evaluated.

To evaluate the fatigue behavior of two crystalline-reinforced ceramics: leucite-reinforced (VL) and lithium disilicate-based (VD) glass-ceramics.Bar-shaped specimens (16 × 4 × 1.2 mm) were produced for each ceramic using prefabricated CAD/CAM blocks. For each group, 30 specimens were subjected to a three-point flexural strength test in a universal testing machine. For VL and VD, 36 and 41 specimens were subjected to a cyclic fatigue test, respectively. The cyclic fatigue test was performed with a pneumatic mechanical cycling machine (1 Hz; 37°C distilled water). Specimens were tested at two stress levels for each preset lifetime (10There were significant differences among groups for characteristic strength (σBoth glass-ceramics showed similar strength degradation (60%) after a lifetime of 10

All-ceramic restorations are attractive because of their long lasting esthetics and the ability to with- stand the oral conditions. However, bonding to ceramics has challenged the dental community for the last few decades. The clinical success of a ceramic restoration is strongly dependent on the quality and durability of the bond between the resin cement and the restoration. This study presents the bonding mechanisms and the me- chanical tests to evaluate the adhesive interfaces of resin-bonded ceramic restorations, mainly the zirconia- based restorations, which are the most popular. An adequate bond involves ceramic surface changes for mechanical retention, which can be achieved using primers, such as acids and airborne particle abrasion. Selective etching of high crystalline content ceramics mostly occurs within grain boundaries that offer little micromechanical retention and an insufficient bond to resin. The most popular surface treatment to improve adhesion to high crystalline content ceramics involves the treatment of surfaces with airborne particle abrasion and chemical bonding. Yet, there are reports on new methods to enhance the resin bond to zirconia that need further investigation. This study provides scientific evi- dences to guide the clinical procedures on bonding ceramic restorations.

A zircônia tetragonal policristalina estabilizada por ítria (Y-TZP) vem sendo amplamente empregada na Odontologia como material de infraestrutura (IE) de coroas e próteses parciais fixas devido às suas características mecânicas como alta resistência e tenacidade à fratura. O objetivo desta revisão de literatura é buscar evidências em estudos in vitro e in vivo a respeito do comportamento mecânico, adesão e longevidade clínica de próteses fixas confeccionadas com IE de Y-TZP. Foram obtidos artigos, na base de dados online Medline/Pubmed, seguindo a seguinte combinação de palavras-chaves: zircônia tetragonal estabilizada por ítria ("Y-TZP"), adesão ("adhesion"; "bonding"), propriedades mecânicas ("mechanical properties"), estudos clínicos ("long-term clinical trials"), longevidade ("longevity"). A busca abrangeu os anos de 1990 a 2012. De acordo com a literatura, a Y-TZP apresenta propriedades mecânicas superiores às demais cerâmicas odontológicas devido a um mecanismo de tenacificação associado à transformação de fase cristalina (transformation toughening). Ainda, a silicatização associada a silanização tem sido indicada como o tratamento de superfície mais adequado para cimentação adesiva de IE em Y-TZP, além do uso de um cimento resinoso contendo monômeros fosfatados (MDP). Nos estudos clínicos, a Y-TZP tem mostrado altas taxas de sucesso como IE de coroas unitárias e PPFs. Apesar do comportamento mecânico e de união da Y-TZP não estarem completamente esclarecidos, estudos apontam resultados promissores em relação à aplicação clínica deste material. Yttrium stabilized tetragonal zirconia polycrystal (Y-TZP) has been widely used in Dentistry as framework material for dental crowns and fixed partial dentures (FPDs) due to its mechanical characteristics, such as high fracture strength and toughness. The objective of this literature review is to search for scientific evidence concerning the mechanical behavior, adhesion and clinical longevity of Y-TZP-based restorations. Literature was obtained from online Medline/Pubmed database using the following key-words combination: Y-TZP; adhesion; bonding; mechanical properties; long-term clinical trials; longevity. Articles from 1990 to 2012 were searched. According to the literature, Y-TZP-based ceramic shows superior mechanical properties when compared to other dental ceramics due to a crystal phase transformation toughening mechanism. In addition, silica coating associated with silanization is recommended as the most successful surface treatment for Y-TZP adhesive cementation, and the use of a MDP-containing resinous cement system. According to the clinical studies, Y-TZP has high success rates when used as framework material for single crowns and FPDs. Although the mechanical and adhesive behavior of Y-TZP is not completely understood, studies show Y-TZP as a promising ceramic for clinical application.

The objective of this study was to evaluate in vitro the time-dependent fluoride (F) release from three adhesive systems: Clearfil Protect Bond (CPB - Kuraray), FL Bond II (FLB- Shofu) and Adper Single Bond 2 (SB2 - 3M ESPE) (negative control). CPB and FLB are fluoride containing adhesives that use different F releasing mechanisms. The tested hypothesis was that the F releasing mechanism influences the amount of released F in water. Disc-shaped specimens (5 mm × 3 mm) were fabricated using a plastic matrix (Demetron Research Corp). Three specimens were produced for each material and each period of evaluation (1, 7, 14, 21 and 28 days) (n=3). Subsequently, the specimens were stored in 10 mL distilled water at 37° C until the analyses were done using a liquid membrane for selective F ion electrode (Orion 710). Four readings were performed on the first day and the remaining evaluation times had one reading/day. Results were statistically analyzed by two-way ANOVA and Tukey's test (α=0.05). CPB released the greatest amount of fluoride in all evaluated periods with the greatest value at 6th h (0.183 ppm) thereafter decreasing gradually up to the 7th day when it significantly increased again until the 21st day. In most measurements, FLB showed similar mean fluoride release values as SB2. Therefore, the fluoride release mechanism influenced the amount of fluoride released in water, confirming the study hypothesis.

To test the hypothesis that step-stress analysis is effective to predict the reliability of an alumina-based dental ceramic (VITA In-Ceram AL blocks) subjected to a mechanical aging test.Bar-shaped ceramic specimens were fabricated, polished to 1μm finish and divided into 3 groups (n=10): (1) step-stress accelerating test; (2) flexural strength-control; (3) flexural strength-mechanical aging. Specimens from group 1 were tested in an electromagnetic actuator (MTS Evolution) using a three-point flexure fixture (frequency: 2Hz; R=0.1) in 37°C water bath. Each specimen was subjected to an individual stress profile, and the number of cycles to failure was recorded. A cumulative damage model with an inverse power law lifetime-stress relation and Weibull lifetime distribution were used to fit the fatigue data. The data were used to predict the stress level and number of cycles for mechanical aging (group 3). Groups 2 and 3 were tested for three-point flexural strength (σ) in a universal testing machine with 1.0MPa/s stress rate, in 37°C water. Data were statistically analyzed using Mann-Whitney Rank Sum test.Step-stress data analysis showed that the profile most likely to weaken the specimens without causing fracture during aging (95% CI: 0-14% failures) was: 80MPa stress amplitude and 10(5) cycles. The median σ values (MPa) for groups 2 (493±54) and 3 (423±103) were statistically different (p=0.009).The aging profile determined by step-stress analysis was effective to reduce alumina ceramic strength as predicted by the reliability estimate, confirming the study hypothesis.

Objectives To describe and apply a method of modelling dental crowns and three-unit fixed partial dentures (FPD) for finite element analyses (FEA) from 3D images obtained using a micro-CT scanner. Methods A crown and a three-unit fixed partial denture (FPD) made of a ceramic framework (Y-TZP) and veneered with porcelain (VM9) were scanned using an X-ray micro-CT scanner with a pixel size of 6.97 μm. Slice images from both structures were generated at each 0.034 mm and processed by an interactive image control system (Mimics). Different masks of abutments, framework and veneer were extracted using thresholding and region growing tools based on X-ray image brightness and contrast. 3D objects of each model were incorporated into non-manifold assembly and meshed simultaneously. Volume meshes were exported to the FEA software (ABAQUS), and the load-generated stress distribution was analyzed. Results FEA models showed great shape resemblance with the structures. The use of non-manifold assembly ensured matching surfaces and coinciding nodes between different structural parts. For the crown model, tensile stresses were concentrated in the internal surface of the core, near to the applied load. For the FPD model, the highest tensile stresses were located in the framework, on the cervical area of connectors and pontic. Conclusions Valid 3D models of dental crown and FPD can be generated by combining micro-CT scanning and Mimics software, emphasizing its importance as design tool in dental research. Clinical significance The 3D FEA method described in this work is an important tool to predict the stress distribution, assisting on structural design of dental restorations.

Objectives (1) To measure the marginal and internal adaptation of different prosthetic crowns infrastructures (IS); (2) to analyze two types of methodologies (replica and weight technique) used to evaluate the adaptation of indirect restorations. Methods Ceramic IS were fabricated using CAD/CAM technology and slip-casting technique, and metal IS were produced by casting ( n = 10). For each experimental group, the adaptation was evaluated with the replica (RT) and the weight technique (WT), using an impression material (low viscosity silicon) to simulate the luting agent. Cross-sectional images of the silicon replica were obtained and analyzed with Image J software to measure the low viscosity silicon layer thickness at pre-determined points. The silicon layer was also weighted. Results were statistically analyzed with ANOVA and Tukey's test ( α = 0.05). Pearson correlation was used to analyze the relation between the two types of evaluation methods. Results All IS evaluated showed clinically acceptable internal and marginal adaptation. Metal IS showed the best adaptation, irrespective of the measuring technique (RT and WT). The IS produced by CAD–CAM showed greater gap values at the occlusal area than at other evaluated regions. The IS produced by the dental laboratory technician showed similar gap values at all evaluated regions. There is no correlation between RT and WT ( p > 0.05). Significance Different levels of adaptation were found for the different experimental groups and for the different evaluation methods. However, all IS evaluated showed clinically acceptable values of marginal and internal adaptation.

Statement of problem Investigating the mechanical behavior of ceramics in a clinically simulated scenario contributes to the development of new and tougher materials, improving the clinical performance of restorations. The optimal in vitro environment for testing is unclear. Purpose The purpose of this in vitro study was to investigate the failure behavior of a leucite-reinforced glass-ceramic under compression loading and fatigue in different simulated oral environment conditions. Material and methods Fifty-three plate-shaped ceramic specimens were produced from computer-aided design and computer-aided manufactured (CAD-CAM) blocks and adhesively cemented onto a dentin analog substrate. For the monotonic test (n=23), a gradual compressive load (0.5 mm/min) was applied to the center of the specimens, immersed in 37oC water, using a universal testing machine. The initial crack was detected with an acoustic system. The fatigue test was performed in a mechanical cycling machine (37oC water, 2 Hz) using the boundary technique (n=30). Two lifetimes were evaluated (1×10 6 and 2×10 6 cycles). Failure analysis was performed using transillumination . Weibull distribution was used to evaluate compressive load data. A cumulative damage model with an inverse power law (IPL) lifetime-stress relationship was used to fit the fatigue data. Results A characteristic failure load of 1615 N and a Weibull modulus of 5 were obtained with the monotonic test. The estimated probability of failure (P f ) for 1×10 6 cycles at 100 N was 31%, at 150 N it was 55%, and at 200 N it was 75%. For 2×10 6 cycles, the P f increased approximately 20% in comparison with the values predicted for 1×10 6 cycles, which was not significant. The most frequent failure mode was a radial crack from the intaglio surface. For fatigue, combined failure modes were also found (radial crack combined with cone crack or chipping). Conclusions Fatigue affects the fracture load and failure mode of leucite-reinforced glass-ceramic.

Resumo Os pilares protéticos, usados como intermediários entre a prótese e o implante, são feitos de titânio e outros metais, que possuem estrutura confiável. A cor acinzentada desses metais, acrescidos a recessão gengival e a camadas finas de tecidos adjacentes, acaba exposta, o que compromete a estética. Com isso, foram introduzidos os pilares cerâmicos (zircônia, alumina ou zircônia/alumina) que fornecem boas propriedades ópticas, assim como biocompatibilidade e estética duradoura. O objetivo desse estudo foi avaliar, através de uma revisão sistemática da literatura, as taxas de sobrevivência dos pilares metálicos e cerâmicos, bem como seus principais tipos de falha. Foi realizada uma pesquisa nas bases de dados Pubmed de 1999 a 2015 utilizando as palavras-chave: cerâmicas (ceramics), pilar (abutment), implantes dentários (dental implants) e prótese parcial fixa (partial fixed denture). Foram selecionados 16 artigos de pesquisa clínica e estudos de coorte. Segundo os estudos, não houve diferença significativa nos índices biológicos e radiográficos entre os pilares cerâmicos e metálicos, quando comparados uns com os outros e com os dentes naturais, em estudos de até 11 anos. Também não foi observada perda significativa de osso marginal entre a avaliação inicial e a última avaliação para ambos tipos de pilares (titânio e cerâmicos). Pilares de alumina têm taxa de sobrevivência de 94,7% a 100% em estudo de acompanhamento clínico de até 7 anos. Pilares de zircônia têm taxa de sobrevivência semelhante aos pilares de titânio (100%) em estudos de acompanhamento clínico de até 11 anos. Apenas em um estudo de 7 anos, a taxa de sobrevivência caiu para 97,6%, para os pilares de zircônia. Os modos de falha encontrados para os pilares foram fratura e afrouxamento do parafuso. A semelhança no comportamento mecânico e biológico entre os materiais torna os pilares cerâmicos uma boa alternativa na Implantodontia.

Statement of problem The effect of screw-access holes and mechanical cycling on fracture resistance of 3-unit screw-retained zirconia-based implant-supported fixed dental prostheses (ISFDPs) is unknown. Purpose The purpose of this in vitro study was to evaluate the effect of screw-access holes on the maximum fracture load (L f ) of 3-unit ISFDPs fabricated with the same abutment design for screw (s)-retained and cement (c)-retained with either a metal- or zirconia-based framework, testing the hypotheses that ISFDPs with screw-access holes have the lowest L f and that mechanical cycling decreases the L f of screw-retained ISFDPs. Material and methods Models with fiberglass bases with 2 implants were fabricated. Special abutments were designed to allow for both s- and c-retained ISFDPs. The study considered the type of framework (s-retained metal-based and s-retained zirconia-based), fixation (s and c), and aging (a) with mechanical cycling, resulting in the following experimental groups (n=12): c-retained metal-based ISFDP; s-retained metal-based ISFDP (Ms); s-retained zirconia-based ISFDP aged by mechanical cycling (Zsa); and s-retained metal-based ISFDP aged by mechanical cycling (Msa). All ISFDPs were porcelain veneered and subjected to compressive load to failure. Fracture load data were statistically analyzed using 1-way ANOVA and Tukey range tests (α=.05). Fractography was used to evaluate the fracture surfaces. Results Cement-retained ISFDP (Zc and Mc) showed the greatest L f values ( P f values than those for Ms. Aging significantly decreased the L f of Zsa but had no effect on Msa. Chipping was the failure mode most frequently found. Only Zs and Zsa ISFDPs showed catastrophic failures. Conclusions ISFDPs with screw-access holes showed lower L f values, regardless of the framework type. Mechanical cycling affected the L f of screw-retained zirconia-based ISFDPs.

Statement of problem Ceramic restorations often require adjustments using diamond rotary instruments, which damage the glazed surface. The effect of these adjustments on the fracture behavior of these restorations is unclear. Purpose The purpose of this in vitro study was to evaluate the influence of induced surface defects on the fracture load and mode of failure of lithium disilicate–based (LDS) glass ceramic restorations. Material and methods Premolar crowns were obtained from LDS computer-aided design and computer-aided manufacturing blocks (n=60) and glazed. The crowns were bonded to dentin analog dies and divided into 5 groups (n=12), as follows: glaze; abrasion (diamond rotary instrument 2135); abrasion and reglaze; abrasion and polishing (diamond rotary instrument 2135F, 2135 FF, and polishing devices); and polishing. The topography of the crowns was examined by scanning electron microscopy, and roughness was measured. A compressive load (0.5 mm/min) was applied by a piston to the center of the lingual cusp until fracture. The fracture load was recorded and data were statistically analyzed by ANOVA and the Tukey HSD test (α=.05). Fractured crowns were examined to determine the fracture origin. Results Polishing and/or reglazing resulted in lower roughness than for the abraded group ( P P =.696). Catastrophic fracture with origin at the intaglio surface was the mode of failure for all the crowns. Conclusions The experiment design successfully submitted the crowns to a clinical stress state, resulting in a clinically relevant failure. Reglazing or polishing were effective in reducing surface defects. Surface treatments had no effect on the immediate catastrophic failure of LDS crowns.

Objectives To evaluate the reliability of monolithic and multilayer ceramic structures used in the CAD-on technique (Ivoclar), and the mode of failure produced in ceramic structures bonded to a dentin analog material (NEMA-G10). Methods Ceramic specimens were fabricated as follows (n = 30): CAD-on- trilayer structure (IPS e.max ZirCAD/IPS e.max Crystall./Connect/IPS e.max CAD); YLD- bilayer structure (IPS e.max ZirCAD/IPS e.max Ceram); LDC- monolithic structure (IPS e.max CAD); and YZW- monolithic structure (Zenostar Zr Translucent). All ceramic specimens were bonded to G10 and subjected to compressive load in 37 °C distilled water until the sound of the first crack, monitored acoustically. Failure load (Lf) values were recorded (N) and statistically analyzed using Weibull distribution, Kruskal–Wallis test, and Student-Newman–Keuls test (α = 0.05). Results Lf values of CAD-on and YZW structures were statistically similar (p = 0.917), but higher than YLD and LDC (p Significance Monolithic zirconia (YZW) and CAD-on structures showed similar failure resistance and reliability, but a different fracture behavior.