Stress distribution in restorations with glass fiber and polyetheretherketone intraradicular posts: An in silico analysis.

This study evaluated stresses generated at maxillary central incisor (21) root restored with lithium disilicate crown (LDC), and glass fiber (GFP) or polyetheretherketone (PEEK) post. 3D models created by computed tomographic image (i-CAT Cone Beam 3D Dental Imaging System) reproduced maxillary central incisor. Each model had prosthetic LDCs (2.0 mm thick) cemented to GFP or PEEK posts with dual resin cement. Different loads were applied to each model (cervical, incisal, axial, middle). At maximum principal stress, PEEK showed higher stress than GFP in all loads, but with qualitative similarity. At minimum principal stress, PEEK and GFP showed qualitative and quantitative similarities, except axial load. Maxillary central incisor restored with GFP or PEEK and LDC presented, in general, similar stress intensity and distribution for main occlusal loads. Only two of sixteen occlusal loads tested (cervical for maximum principal; axial for minimum principal) showed significant quantitative difference.

Bond strength of self-adhesive resin cement to dentin using different adhesion protocols.

BACKGROUND: The treatment of dentin before the use of self-adhesive cements is still a crucial point to achieve the best bond strength values. The objective of this study was to evaluate the bond strength between dentin and composite resin using different adhesion strategies with self-adhesive resin cement. MATERIAL AND METHODS: Forty healthy third human molars were randomly divided into 4 groups (n = 10): CA (control); application of self-adhesive cement (Rely X U200, 3M ESPE), AD + CA: only application of conventional adhesive (Adper Single Bond 2, 3M ESPE) + self-adhesive cement, AC + AD + CA; conditioning with 37% phosphoric acid for 15 seconds + application of conventional adhesive + self-adhesive cement and AC + CA; conditioning with 37% phosphoric acid for 15s + self-adhesive cement. Blocks made of composite resin (Z250 XT, 3M ESPE) were cemented over dentin. The samples were stored for 24h in distilled water at 37ºC and then were sectioned on a metallographic cutter to obtain tooth picks with approximately 1.0 mm2 in cross section. A universal testing machine was used with a speed of 0.5 mm/min to test the microtensile bond strength,. The fracture patterns were classified as adhesive, cohesive and mixed failures. The data (MPa) were analyzed statistically by One-way ANOVA and Holm-Sidak test (α=5%). RESULTS: The AC + AD + CA and AC + CA groups had the highest averages, while the CA and AD + CA groups had the lowest bond strength values. Adhesive failure was prevalent in all groups. CONCLUSIONS: Conditioning with 37% phosphoric acid for 15s increases the adhesion of the self-adhesive resin cement to the dentin, regardless of the use of dental adhesive system. Key words:Resin cement, microtensile bond strength, acid conditioning.

Finite Element Analysis of Stress in Anterior Prosthetic Rehabilitation with Zirconia Implants with and without Cantilever.

OBJECTIVES: The aim of this study was to evaluate using finite element analysis (FEA), the stress distribution in prostheses (lithium disilicate crowns) on monotype zirconia implants with and without cantilever in the anterior region of the maxilla. MATERIALS AND METHODS: From a virtual reconstruction of bone model of the toothed maxilla from a computed tomography, three models (groups) were created: Zr (11-21)-implants placed in the area of 11 and 21 with cantilever; Zr (12-22)-implants placed in the area of 12 and 22 without cantilever; and Zr (11-22)-implants intercalated placed in the area of 11 and 22. In all models, monotype zirconia implant (4.1 × 12.0 mm) was used in single-body configuration. Lithium disilicate crowns were designed on the implants and pontics for all groups. A 150-N load was applied to the prostheses. The materials used were considered isotropic, homogeneous, and linearly elastic. FEA was performed to evaluate the maximum (tensile) and minimum (compressive) principal stresses in the implant, crowns, and bone tissue. Data were analyzed qualitatively and quantitatively. RESULTS: For all groups, the highest maximum principal stress occurred in the palatal cervical area of the implant, with the high values for the Zr (12-22) group and the low values for the Zr (11-21) group. The maximum principal stress was concentrated in the cervical palatal area of the crown, with the Zr (11-21) group presented the highest values and the Zr (12-22) group showed the lowest values. In the bone tissue all the groups presented similar values of maximum and minimal principal stress, with the palatal (maximum principal) and vestibular (minimum principal) close to the cervical of the implants the area with the highest concentration of stresses. CONCLUSIONS: The position of monotype zirconia implant did not interfere in the bone tissue stress, and the implants placed in the 11-21 present lower stress in implants and higher in the crown. The cantilever does not increase the stress in the implants, crown, and bone tissue.

Influence of the Multiple Layers Application and the Heating of Silane on the Bond Strength between Lithium Disilicate Ceramics and Resinous Cement.

OBJECTIVE: This study aimed to evaluate the bond strength between lithium disilicate ceramic and resinous cement when silane (Prosil, FGM) was applied in different amounts of layers under heating or not. MATERIALS AND METHODS: Sixty IPS E-max CAD ceramic (Ivoclar) was used. They were conditioned with 10% hydrofluoric acid for 20 seconds. The samples were distributed in six groups (n = 10): 1Sil, 1 layer of silane without heating; 1SilAq, 1 layer of silane with heating; 2Sil, 2 layers without heating; 2SilAq, 2 layers with heating; 3Sil, 3 layers without heating; and 3SilAq, 3 layers with heating. After each layer, a jet of cold air was applied for 20 seconds in groups 1Sil, 2Sil, 3Sil, and jet of hot air (50°C) in groups 1SilAq, 2SilAq, and 3SilAq. Subsequently, an adhesive layer was applied, and fourcylinders were made on the ceramic with a resin cement AllCemVeneer and photoactivated for 20 seconds. The samples were stored at 37°C for 24 hours and analyzed to the microshear test at EMIC. STATISTICAL ANALYSIS: Data were submitted to ANOVA and Tukey's test (α = 0.05). RESULTS: The results showed that there was no statistical interaction between the factors studied. The "heating" factor was not statistically significant; however, the "silane layers" factor showed differences between groups. The analysis of the results showed that the use of one (66%) or two layers (67%) of silane regardless of heating, produced higher values of bond strength, when compared with the group of three layers (62%). CONCLUSION: The use of silane with one or two layers provided a greater bond strength between lithium disilicate ceramic and resinous cement and that the heating did not influence the results.

Mechanical properties of experimental resin cements containing different photoinitiators and co-initiators.

AIM: The aim of this study was to evaluate the influence of different concentrations of two photoinitiators and one co-initiator on the flexural strength (FS) and elastic modulus (E) of experimental resin cements. MATERIALS AND METHODS: A mixture containing BisGMA, TEGDMA, and barium-aluminum-silicate (BaAlSi) and silanized colloidal silica (SiO2) filler particles was prepared with two photoinitiators, viz. camphorquinone (CQ) and bisacylphosphine oxide (BAPO). Dimethylaminoethyl methacrylate (DMAEMA) was used as co-initiator. Thirty groups (n=10) were formulated with different photoinitiator systems (CQ/DMAEMA and BAPO/DMAEMA) and concentrations (wt%) of photoinitiator and co-initiator. The photoactivation was carried out for 20 s with a light-emitting diode (LED, Bluephase, Ivoclar Vivadent) with irradiance of 1200 mW/cm2. The FS and E were obtained in a three-point bending test on a universal testing machine (0.5 mm/min). Data were subjected to the Kolmogorov-Smirnov normality test, followed by two-way ANOVA and Tukey's test (α=0.05). RESULTS: No polymerization occurred in the CQ groups without DMAEMA (0 wt%). DMAEMA 0.5 %wt and 1 %wt groups showed statistically similar FS and E results for CQ and BAPO, except for CQ 0.3 wt% (FS), CQ 0.9wt% (E) and BAPO 1.76 wt% (FS and E) for DMAEMA 0.5 %wt. No significant difference was found for FS and E values for different concentrations of photoinitiators, except for CQ 0.25 wt% (FS and E) and BAPO 0.25 wt% (E) that showed the lowest values. CONCLUSION: The wt% of the photoinitiators and co-initiator influenced the mechanical properties and the performance of CQ was dependent on the DMAEMA concentration. BAPO can be used as substitute for the conventional CQ/DMAEMA photoinitiator system.

Effect of Glass Fiber Post Adaptation on Push-Out Bond Strength to Root Dentin.

The aim of this study was to evaluate the effect of different glass fiber posts (GFPs) diameters on the push-out bond strength to dentin. Forty unirradicular human teeth were endodontically treated and used for cementation of GFPs (White Post DC, FGM) with different diameters (n=10): P1 - ø 1.6 mm coronal x 0.85 mm apical; P2 - ø 1.8 mm coronal x 1.05 mm apical; P5 - ø 1.4 mm coronal x 0.65 mm apical; and PC - customized post number 0.5 with composite resin (Tetric Ceram A2, Ivoclair Vivadent). All GFPs were cemented into the root canal using a dual-curing luting composite (Variolink II, Ivoclar Vivadent). One slice (1.7 mm) of each root third of cemented GFP (cervical, middle, and apical) was submitted to push-out testing. Failure modes of all specimens were classified as: adhesive failure between resin cement and post; adhesive failure between dentin and resin cement; cohesive failure within resin cement, post or dentin; and mixed failure. The data were analyzed with two-way ANOVA and Tukey's test (a=0.05). The highest bond strength values were presented for the P2 and PC groups. There was no statistically significant difference between the GFP thirds in each group. The groups P2, P5, and PC showed predominantly adhesive failure. For P1, the most prevalent type of failure was adhesive between resin cement and post. It may be concluded that a glass fiber post that is well adapted to the root canal presents higher bond strength values, regardless of GFP third.

Influence of Core-Veneer Thickness Ratio on the Fracture Load and Failure Mode of Zirconia Crowns.

PURPOSE: To evaluate the influence of different core-veneer thickness (CVT) ratios on fracture loads and failure modes of zirconia crowns with or without thermomechanical cycling (TC). MATERIALS AND METHODS: Forty yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) cores were veneered with a pressable ceramic and divided into four groups (n = 10): group 1 - 1:3 CVT ratio (0.5-mm core, 1.5-mm veneer); group 2 - 1:1 CVT ratio (1.0-mm core, 1.0-mm veneer); groups 3 and 4 - identical to groups 1 and 2, respectively, except that they underwent TC (1,000,000 cycles with an 84-N load applied at a 4-Hz frequency, temperature cycling at 4°C, 37°C, and 55°C - 30 seconds each). Loads were applied axially to the central fossa of the crowns with a 1 mm/min crosshead speed at 200 N until failure. RESULTS: Two-way ANOVA showed that the crowns with a 1:3 CVT ratio had a lower mean fracture load than crowns with a 1:1 CVT ratio (group 1 = 1666.4 ± 466.4 N; group 2 = 2156.6 ± 472.3 N). TC had no effect on the fracture load for crowns with the same CVT ratio. The failures observed for the crowns in groups 1, 3, and 4 were fractures within the veneering ceramic, which exposed the core. The failure severity of fractures for group 2 was less extensive, characterized by chipping within the ceramic veneer. CONCLUSION: Crowns with a 1:1 CVT ratio had higher fracture load values and more conservative failures. TC had no effect on the fracture load of the ceramic crowns.

Influence of angulation and height of tooth preparation on the distribution of tensions in prosthetic crowns for upper central incisor: in silico analysis

Aim: it was to use tridimensional finite element analysis (FEA) to analyze the effect of height and angulation of prosthetic preparations on the distribution of stresses for lithium disilicate prosthetic crowns, the underlying resin cement, and the prosthetic preparation of a superior central incisor. Methods: a CAD modeling software, SolidWorks 2013, was used to generate three-dimensional virtual models comprising the dimensions of the preparation parameters. Three angles (6, 12 and 16 degrees) were simulated on the prepared walls and two wall heights were utilized (4 and 5 mm), for a total of six model groups according to the height and angulation of the walls. A vertical line in the Y-axis was used as a reference for determining the degrees of convergence (inclination of the preparations). The chamfer finish and preparation width were standardized for all groups. Results: the 4 mm preparations behaved more appropriately when the axial wall convergence was approximately 6 degrees. The 5 mm preparations required 12 degrees of angulation. In relation to resin cement, there was better stress distribution when the angle of incisal convergence was between 6 and 12 degrees. An increase to 16 degrees led to a considerable increase in peak stress at the preparation margin. Conclusion: it was concluded that the convergence of the axial walls of coronal preparations with 4 and 5 mm heights should be 6 and 12 degrees, respectively, to avoid high tension spikes in the underlying resin cement

Resistência à compressão, flexão e tração diametral de cimentos resinosos em tempos diferentes de armazenamento / Compressive, flexural and diametral tensile strength of resin cements in different storage times

Objetivos: O objetivo desse estudo foi avaliar a resistência à compressão, tração diametral e flexão de dois cimentos resinosos de presa dual. Métodos: foi utilizado o cimento autoadesivo RelyX U200 (3M ESPE) e o cimento convencional Variolink II (Ivoclar Vivadent). Foram confeccionados corpos de prova cilíndricos com 4mm de diâmetro x 6mm de altura para o teste de compressão, 6mm de diâmetro x 2mm de altura para o teste de tração diametral (ISO 9917-1:2007) e em forma de barra com 25mm de comprimento x 2mm de altura e largura para o teste de flexão três pontos (ISO 4049:2009). As amostras foram armazenadas por 24h (n = 10) e 45 dias (n = 10) em água destilada a 37ºC. Os testes foram realizados em uma máquina universal de ensaios EMIC (DL 2000) com uma célula de carga de 2000 Kgf para o teste de compressão e 200 Kgf para os testes de tração diametral e flexão, à uma velocidade de 0,5 mm/min. Os dados foram submetidos à análise de variância dois critérios (ANOVA) e as médias comparadas pelo teste de Tukey (5%). Resultados: os resultados mostraram valores estatisticamente similares para todas as propriedades mecânicas avaliadas entre todos os cimentos e tempos de armazenamento estudados. Conclusões: A composição química dos cimentos resinosos e o armazenamento em água por 45 dias não foram suficientes para ocasionar alterações nas propriedades mecânicas avaliadas nesse estudo(AU)

Objectives: the aim of this study was to evaluate the compressive, diametral tensile and flexural strength of two dual resin cements. Materials and methods: RelyX U200 self-adhesive cement (3M ESPE) and the conventional Variolink II cement (Ivoclar Vivadent) were used. The test consisted in the preparation of cylindrical specimens measuring 4mm diameter x 6mm height for compression test, 6mm diameter x 2mm height for diametral tensile test (ISO 9917-1: 2007) and in shape of bar with 25mm length x 2mm height and width for three-point bending test (ISO 4049: 2009). The samples were stored for 24 h (n = 10) and 45 days (n = 10) in distilled water at 37°C. The tests were performed in a universal EMIC testing machine (DL 2000) with a load of 2000 Kgf for compressive test and 200 Kgf for diametral tensile and flexural strength tests at a crosshead speed of 0.5 mm/min. The data were submitted to analysis of variance (two-way ANOVA), and the means were compared by the Tukey test (5%). Results: the results showed statistically similar values of all the mechanical properties evaluated between all the resin cements and storage times. Conclusions: The chemical composition of the resin cements and storage in water for 45 days were not enough to cause changes in the mechanical properties evaluated in this study(AU)

Resistência à flexão biaxial e microdureza de cerâmicas de dissilicato de lítio sinterizadas e usinadas / Biaxial flexural strength and microhardness of sintered and hot-pressed lithium disilicate glass-ceramic

O objetivo deste estudo in vitro foi avaliar a resistência à flexão biaxial e microdureza Vickers de cerâmicas à base de dissilicato de lítio prensadas e usinadas. Foram confeccionados 34 discos (12 mm de diâmetro por 0,9 mm de espessura) de cerâmicas à base de dissilicato de lítio, sendo 17 usinadas (IPS e.max CAD, Ivoclar Vivadent) e 17 prensadas (IPS e.max Press, Ivoclar Vivadent). Os corpos-de-prova foram armazenados a 37ºC durante 24 horas. O teste de resistência à fl exão biaxial (n=12) foi realizado em uma máquina de ensaio universal (Oswaldo Filizola BME ­ São Paulo/SP, Brasil) a uma velocidade de 0,5 mm/min. Os dados de resistência à fl exão foram obtidos em N e a tensão em MPa foi calculada. O teste de microdureza Vickers (n=5) foi realizado em um durômetro (Future-Tech Corp. Model FM-700 ­ Tóquio, Japão) com cinco indentações por corpo-de-prova (50 g/15 s). Todos os dados foram avaliados quanto à normalidade pelo teste paramétrico de Kolmogorov-Smirnov, sendo posteriormente submetidos à análise de variância (Anova) um fator, e as médias comparadas pelo teste de Tukey (α=0,05). As cerâmicas testadas não apresentaram diferenças estatisticamente signifi cantes nos valores de resistência à fl exão biaxial (p=0,065), entretanto a cerâmica IPS e.max Press apresentou maiores valores de microdureza (p=0,0001). Concluiu-se que a cerâmica à base de dissilicato de lítio prensada apresenta maior valor de dureza, em comparação com a mesma cerâmica usinada. (AU)

The aim in this in vitro study was to evaluate the biaxial flexural strength and Vickers microhardness of pressable and CAD/CAM lithium-disilicate ceramics. Thirty-four samples of lithium-disilicate ceramics (12 mm diameter x 0.9 mm thick), 17 for CAD/CAM system (IPS e.max CAD, Ivoclar Vivadent) and 17 pressable (IPS e.max Press, Ivoclar Vivadent). The specimens were stored at 37ºC for 24h. The biaxial fl exural strength test (n=12) was performed in a universal testing machine (Oswaldo Filizola BME ­ São Paulo/SP, Brazil) at a crosshead speed of 0.5 mm/min. The biaxial fl exural strength data were obtained in N and converted to MPa. The Vickers microhardness test (n=5) was performed using a micro-hardness tester (Future-Tech Corp. Model FM-700 ­ Tokyo, Japan) with 5 indentations per specimen (50 g, 15 s). All data were evaluated using normality test (Kolmogorov- Smirnov) and the mean values were analyzed statistically by one-way Anova and Tukey's test (α=0.05). The ceramics evaluated did not present statistically signifi cant diff erences in the biaxial fl exural strength values (p=0.065). However, the IPS e.max Press ceramic showed the highest mean values of microhardness (p=0.0001). It is concluded that the forming technique of lithium-disilicate ceramics infl uences the Vickers microhardness values. (AU)

Efeito do tempo de armazenamento de moldes de hidrocolóide irreversível na estabilidade dimensional em diferentes localizações de modelos de gesso / Effect of the time of storage of irreversible hydrocolloid molds in dimensional stability in different locations of plaster models

O hidrocolóide irreversível por sua baixa estabilidade dimensional requer vertimento imediato do gesso. A fim de tornar sua utilização mais versátil, tem-se proposto formulações que indicam a possibilidade de vertimento do gesso no molde em até 5 dias após a moldagem. O objetivo neste estudo foi investigar o efeito do tempo de espera de armazenamento do molde na estabilidade dimensional linear do hidrocolóide irreversível (Hydrogum 5®, Zhermack). Para tal, foi confeccionado um modelo mestre em cromo-cobalto, com quatro pilares cilíndricos localizados na região de caninos e molares. Desse modelo mestre foram obtidos 40 moldes, que foram distribuídos em 4 grupos (n = 10), de acordo com os tempos de espera para vertimento do gesso tipo IV (Herostone®, Vigodent): imediatamente, 1, 3 e 5 dias após a moldagem. Os moldes foram mantidos em cuba umidificadora a 23° C. Para avaliação da estabilidade dimensional dos moldes obtidos, realizou-se a medição linear das distâncias, com paquímetro digital, entre os pilares dos modelos na região de caninos (pilares A e B) e de molares (pilares C e D), de modo que foram mensuradas as distâncias AB, AC, AD, BD, BC e CD e comparadas com as do modelo mestre. A alteração dimensional foi de -0,20 a +0,33 mm, indicando, portanto, contração e expansão, mas com excelente replicabilidade em relação ao modelo mestre. A análise de variância a dois critérios e o teste de Tukey demonstraram que o tempo de armazenamento influenciou a alteração dimensional, havendo diferença entre os dias 1 (contração) e 5 (expansão) (p = 0,039), independentemente da localização. Não houve diferença nas alterações dimensionais nas distâncias comparadas (p = 0,081), independentemente dos tempos estudados. Os resultados demonstraram que as medidas do modelo mestre foram replicadas de maneira excelente em todos os tempos decorridos da moldagem, sendo possível considerar que através de moldes de Hydrogum 5®, mesmo cinco dias após o procedimento de moldagem, podem ser obtidos modelos de gesso com estabilidade dimensional aceitável. (AU)

Irreversible hydrocolloid due to its low dimensional stability requires immediate plaster casting. In order to make its use more versatile, formulations have been proposed which indicate a possibility of casting the gypsum in the mold within 5 days after a molding. The objective of this study was to investigate the effect of mold storage time on linear dimensional stability of irreversible hydrocolloid (Hydrogum 5®, Zhermack). For this, a master model was made in chrome-cobalt, with four cylindrical pillars located in the region of canines and molars. From this master model, 40 molds were obtained, which were distributed in 4 groups (n = 10), according to waiting times for cast type IV gypsum (Herostone®, Vigodent): 1, 3 and 5 days after the molding. The molds were kept in a humidifier container at 23 ° C. To evaluate the dimensional stability of the molds obtained, perform a linear measurement of the distances, with digital caliper, between the pillars of the models in the region of canines (A and B pillars) and molars (columns C and D), so that they were measured as AB, AC, AD, BD,BC and CD distances and compared as a model. The dimensional change was from -0.20 to +0.33 mm, indicating, therefore, contraction and expansion, but with excellent replicability in relation to the master model. An analysis of variance at two criteria and Tukey's tests demonstrated the storage time influenced the dimensional change, with difference between days 1 (contraction) and 5 (expansion) (p = 0.039), regardless of location. There were no differences in size at the distances compared (p = 0.081), regardless of the times studied. The results are shown as measurements of the master model with excellent replicates at all times after molding, it being possible to assume that by means of Hydrogum 5® molds, even five days after the molding procedure, of plaster with acceptable dimensional stability. (AU)

Temporomandibular joint disorders as the only manifestation of juvenile idiopathic arthritis: a case report.

Juvenile idiopathic arthritis is a term used to include all chronic childhood arthritis of unknown etiology. It is characterized by chronic inflammation persisting for at least 6 weeks, beginning before 16 years of age. The characteristics present are chronic synovitis, arthralgia, impaired joint mobility in at least one joint, and erosion with destruction of cartilage and subchondral bone, that could be associated or not with systemic involvement, according to each subtype of the disease. During the pathologic process, the temporomandibular joint can be involved by the juvenile idiopathic arthritis, resulting in severe mandibular dysfunction, with higher frequency in female patients. Initially, these lesions can show minor alterations like flattening of the condyle, erosions, and evolve to severe lesions, like destruction of the head of the condyle. We report a case of male patient who had destruction of both condyles, as a result from juvenile idiopathic arthritis. Proposed mechanisms to explain the juvenile idiopathic arthritis was reviewed. In this report the patient did not have pain or inflammatory process, and the temporomandibular diseases was the only manifestation.

Influence of cantilever position and implant connection in a zirconia custom implant-supported fixed partial prosthesis: in silico analysis / Influência da posição do cantilever e da conexão do implante em um modelo de zirconia de uma prótese parcial fixa implanto-suportada: análise in sílico

Introduction: A better tension distribution on implants and abutments in implant-supported fixed partial prosthesis is essential in the rehabilitation of posterior mandible area. Objective: To evaluate the influence of cantilever position and implant connection in a zircônia custom implant-supported fixed partial prosthesis using the 3-D finite element method. Material and method: Four models were made based on tomographic slices of the posterior mandible with a zirconia custom three-fixed screw-retained partial prosthesis. The investigated factors of the in silico study were: cantilever position (mesial or distal) and implant connection (external hexagon or morse taper). 100 N vertical load to premolar and 300 N to molar were used to simulate the occlusal force in each model to evaluate the distribution of stresses in implants, abutments, screws and cortical and cancellous bone. Result: The external hexagon (EH) connection showed higher cortical compression stress when compared to the morse taper (MT). For both connections, the molar cantilever position had the highest cortical compression. The maximum stress peak concentration was located at the cervical bone in contact with the threads of the first implant. The prosthetic and abutment screws associated with the molar cantilevers showed the highest stress concentration, especially with the EH connection. Conclusion: Morse taper implant connetions associated with a mesial cantilever showed a more favorable treatment option for posterior mandible rehabilitation.

Introdução: Uma melhor distribuição de tensão em implantes e mini-pilares em próteses parciais fixas implanto-suportadas é essencial na reabilitação em região posterior de mandíbula. Objetivo: Avaliar a influência da posição do cantilever e conexão do implante em uma prótese fixa de três elementos confeccionada totalmente em zircônia através do método de elementos finitos tridimensionais (MEF). Material e método: Foram confeccionados quatro modelos baseados em cortes tomográficos da região posterior da mandíbula com uma prótese parcial parafusada fixada em três fixações personalizadas de zircônia. Os fatores investigados do estudo in sílico foram: posição do cantilever (mesial ou distal) e conexão do implante (hexágono externo ou cone morse). Uma carga de 100 N para a região de pré-molares e de 300 N para a região de molares foi usada para simular a força oclusal em cada modelo para avaliação da distribuição de tensões nos implantes, mini pilares, parafusos e tecido ósseo cortical e medular. Resultado: A conexão hexágono externo apresentou maior concentração de tensão no osso cortical quando comparado ao cone morse. Para ambas conexões, o cantilever distal aumentou a tensão no osso cortical. O pico máximo de tensão foi localizado no osso cervical em contato com as primeiras roscas internas do primeiro implante. Os parafusos protéticos e dos mini-pilares associados ao cantilever distal apresentaram maior concentração de tensão, especialmente na conexão hexágono externo. Conclusão: Conexão do implante cone morse associada ao cantilever mesial apresentou uma opção de tratamento mais favorável para a reabilitação na região posterior de mandíbula.

Effect of Thermocycling, Teeth, and Polymerization Methods on Bond Strength Teeth-Denture Base.

OBJECTIVE: To evaluate the shear bond strength between different artificial teeth and denture base polymerized by two polymerization methods submitted to thermocycling. MATERIALS AND METHODS: Two acrylic resins were selected according to the polymerization method (water-bath and microwave), and four different artificial teeth (Biotone, Dentsply; Trilux, Vipi Dent; Premium 8, Heraeus Kulzer; Soluut PX, Yamahachi) were also tested. The polymerization of the acrylic resin was performed by using conventional cycle (8 h at 74°C) in water-bath and using two cycles (20 min at 270 W + 5 min at 360 W) by the microwave method. The shear bond strength was evaluated after 24 h of water storage at 37°C (immediately) and after the thermocycling test (5,000 cycles, 5-55°C). The shear bond strength (n=10) was performed using a universal testing machine (Instron 4411) at a crosshead speed of 1.0 mm/min. Modes of failures were classified as cohesive and adhesive. The data (MPa) were statistically analyzed by three-way ANOVA, and the mean values were compared by the Tukey test (α = 0.05). RESULTS: In general, the polymerization by microwave showed the highest shear bond strength values, and Trilux artificial teeth had the lowest bond strength values (p < 0.05). Thermocycling did not affect the shear bond strength (p < 0.05). There was a predominance of cohesive failures for all groups. CONCLUSIONS: The chemical composition of the artificial teeth affects the bond strength, and the microwave method is preferable to perform the acrylic resin polymerization.

Resistência da união ao microcisalhamento de cimento resinoso e resina fluida à cerâmica de dissilicato de lítio / Micro-shear bond strength of resin cement and flowable resin to lithium disilicate ceramic

Objetivos: O objetivo neste estudo foi avaliar a resistência da união ao microcisalhamento de uma resina composta microhíbrida de baixa viscosidade (fluida) e de um cimento resinoso fotopolimerizável aplicados a uma cerâmica de dissilicato de lítio. Métodos: Discos de uma cerâmica de dissilicato de lítio (IPS e.max CAD, Ivoclar Vivadent) foram divididos em 2 grupos (n = 10), de acordo com material utilizado para a cimentação: cimento resinoso (Allcem Veneer, FGM) ou resina composta microhíbrida fluida (Opallis Fluida, FGM). Previamente a aplicação do material para cimentação, todas as cerâmicas receberam tratamento superficial padronizado: condicionamento com ácido fluorídrico a 10% (Condac Porcelana, FGM) por 20 s, lavagem com água por 60 s, secagem com ar por 30s e aplicação de silano (Prosil, FGM). Os materiais foram inseridos em uma matriz elastomérica (0,5 mm x 1,2 mm) sobre o bloco cerâmico. Quatro cilindros por grupo foram construídos e fotoativados por um aparelho de diodo emissor de luz (LED, Valo, Ultradent) por 40 s a uma irradiância de 1200 mW/cm2. O teste de microcisalhamento foi feito utilizando uma máquina de ensaio universal (EMIC) a uma velocidade de 0,5 mm/min. Os dados (MPa) foram submetidos ao teste de normalidade (Kolmogorov-Smirnov) e one-way ANOVA, sendo as médias comparadas pelo teste de Tukey (α=0,05). Resultados: O cimento resinoso apresentou resistência da união ao microcisalhamento estatisticamente superior à resina composta fluida (ρ=0,020). Conclusão: Melhor desempenho na união à cerâmica de dissilicato de lítio foi obtido utilizando cimento resinoso(AU)

Objectives: The aim of this study was to evaluate the microshear bond strength of microhybrid flowable composite resin and light-curing resin cement to a lithium disilicate glass ceramic. Methods: Discs of a lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent) were divided into 2 groups (n = 10), according to the material used: resin cement (Allcem Veneer, FGM) or microhybrid flowable composite resin (Opallis Flow, FGM). Before the cementation procedure, ceramics discs received the same surface treatment: etching with 10% hydrofluoric acid gel (Condac Porcelana, FGM) for 20 s, rinsed with water for 60 s, dried with compressed air for 30 s, and silane application (Prosil, FGM). Materials were inserted into cylinder shaped orifices of an elastomeric matrix (0.5 mm x 1.2 mm) onto the ceramic surface. Four cylinders were built-up for each group and photoactivated using a light-emitting diode (LED, Valo Ultradent) for 40 s with 1200 mW/cm2 of irradiance. The microshear bond strength test was performed using a universal testing machine (EMIC) at cross-head speed of 0.5 mm/min. The data (MPa) were submitted to normality test (Kolmogorov-Smirnov) and one-way ANOVA and the means compared by Tukey test (α=0.05). Results: The resin cement showed bond strength values statistically superior to microhybrid flowable composite resin (p=0.020). Conclusion: Better bond performance to lithium disilicate glass ceramic was achieved using resin cement(AU)

Evaluation of dimensional stability and details reproduction of alginate molds storage in different times and temperature / Avaliação da estabilidade dimensional e reprodução de detalhes de moldes de alginatos armazenados por diferentes tempos e temperatura

Objective: The aim of this study was to evaluate dimensional stability and detail reproduction in alginate molds stored at different times and temperatures. Material and Methods: Three different commercially available alginates (Cavex Color Change, Jeltrate Plus and Hydrogum 5) were tested at four different times (0 - control, 1, 3 and 5 days) and two temperatures (25ºC and 37ºC) (n=5). The alginates were handled following the manufacturer's instructions. The impression procedures occurred in an environment with controlled room temperature (25ºC) and relative humidity (50±5%). A metallic model (ISO 1563:1990) was used to perform the impressions. The tray containing alginate remained on the metallic model under constant pressure (2 kgf) until the alginate gelation process. The molds were stored (different times and temperatures) and analyzed in stereomicroscope at 30x magnification and 0.5 µm accuracy (Olympus Measuring Microscope STM). The molds and the metallic model measurements were compared, and the data were statistically analyzed by Kolmogorov-Smirnov and three-way ANOVA tests, and the means were compared by Tukey test (5%). Results: The results showed no double interactions (p>0.05) and the different alginates presented statistically similar values of dimensional stability (p=0.102). However, 25ºC (temperature) and control group (time) showed the highest values of dimensional stability (p <0.05). Jeltrate Plus was the only material that presented inaccuracy in details reproduction. Conclusion: It is recommended that, for tested alginates, the stone casts should be poured immediately, even though the molds are dimensionally stable up to 5 days when stored at 25ºC.(AU)

Objetivo: O objetivo neste estudo foi avaliar a estabilidade dimensional e a reprodução de detalhes em moldes de alginatos armazenados em diferentes tempos e temperaturas. Material e Métodos: Foram testadas três diferentes marcas de alginato (Cavex ColorChange, Jeltrate Plus e Hydrogum 5), sendo que esses materiais foram armazenados por quatro diferentes tempos (0 - controle, 1, 3 e 5 dias) e duas diferentes temperaturas (25ºC e 37ºC) (n=5). Os alginatos foram manipulados seguindo as instruções do fabricante. A moldagem ocorreu em um ambiente com temperatura (25ºC) e umidade relativa (50±5%) controladas. Foi utilizado um modelo metálico (ISO 1563:1990) para a realização das moldagens. A moldeira contendo o alginato permaneceu sobre o modelo metálico sob pressão constante de 2 kgf até a geleificação do material. Em seguida, os moldes foram armazenados nos tempos e temperaturas testados, sendo posteriormente avaliados sob um microscópio comparador (Olympus Measuring Microscope STM) com precisão de 0,5 µm. As medidas dos moldes de alginato foram comparadas com as medidas do modelo metálico padrão, sendo os dados analisados estatisticamente pelos testes de Kolmogorov-Smirnov e ANOVA três fatores, sendo as médias foram comparadas pelo teste de Tukey (5%). Resultados: Os resultados mostraram nenhuma interação dupla (p>0,05), sendo que os diferentes alginatos apresentaram valores de estabilidade dimensional estatisticamente semelhantes entre si (p=0,102). Já a temperatura de 25ºC e o grupo controle (tempo) mostraram os maiores valores de estabilidade dimensional (p <0,05). O Jeltrate Plus foi o único material que apresentou imprecisão na reprodução de detalhes. Conclusão: Recomenda-se que os alginatos testados tenham os modelos de gesso vazados imediatamente, apesar dos moldes serem dimensionalmente estáveis até 5 dias desde que armazenados a 25ºC. (AU)

Temporomandibular joint disorders as the only manifestation of juvenile idiopathic arthritis: a case report / Comprometimento da articulação temporomandibular como única manifestação da artrite idiopática juvenil: um relato de caso

ABSTRACT Juvenile idiopathic arthritis is a term used to include all chronic childhood arthritis of unknown etiology. It is characterized by chronic inflammation persisting for at least 6 weeks, beginning before 16 years of age. The characteristics present are chronic synovitis, arthralgia, impaired joint mobility in at least one joint, and erosion with destruction of cartilage and subchondral bone, that could be associated or not with systemic involvement, according to each subtype of the disease. During the pathologic process, the temporomandibular joint can be involved by the juvenile idiopathic arthritis, resulting in severe mandibular dysfunction, with higher frequency in female patients. Initially, these lesions can show minor alterations like flattening of the condyle, erosions, and evolve to severe lesions, like destruction of the head of the condyle. We report a case of male patient who had destruction of both condyles, as a result from juvenile idiopathic arthritis. Proposed mechanisms to explain the juvenile idiopathic arthritis was reviewed. In this report the patient did not have pain or inflammatory process, and the temporomandibular diseases was the only manifestation.

RESUMO Artrite idiopática juvenil é um termo usado para incluir toda artrite infantil crônica de etiologia desconhecida. É caracterizada por uma inflamação crônica, que persiste por pelo menos 6 semanas, com início antes dos 16 anos de idade. As características presentes são sinovite crônica, artralgia, mobilidade articular diminuída em pelo menos uma articulação, e erosão com destruição da cartilagem e do osso subcondral, podendo ser associada ou não com o envolvimento sistêmico, de acordo com cada subtipo da doença. Durante o processo patológico, a articulação temporomandibular pode ser envolvida pela artrite idiopática juvenil, resultando em disfunção mandibular severa, com maior frequência em pacientes do sexo feminino. Inicialmente, estas lesões podem mostrar pequenas alterações, como achatamento do côndilo e erosões, e evoluir para lesões graves, como a destruição da cabeça do côndilo. Relatou-se o caso de um paciente do sexo masculino, que apresentou destruição de ambos os côndilos, como resultado da artrite idiopática juvenil. Os mecanismos para explicar a artrite idiopática juvenil foram revisados na literatura. Neste relato de caso, o paciente não apresentou dor e nem processo inflamatório, sendo o comprometimento da articulação temporomandibular a única manifestação.

Resistência à tração uniaxial de copings fundidos e cimentados sobre munhões cone-morse com diferentes diâmetros e alturas / Uniaxial tensile strength of cast cemented copings for cone-morse prosthetic implant abutments with different diameters and heights

Objetivo: avaliar a resistência à tração de copings fundidos cimentados sobre pilares cone-morse com diferentes alturas e diâmetros. Material e métodos: quatro grupos (G1: 3,5 mm x 4 mm; G2: 3,5 mm x 6 mm; G3: 4,5 mm x 4 mm; e G4: 4,5 mm x 6 mm) com cinco amostras cada tiveram seus copings encerados, fundidos (liga de Ni-Cr) e cimentados (Panavia F, carga de 6 Kfg durante cinco minutos) sobre os respectivos pilares já torqueados com 25 Ncm. Depois, as amostras foram imersas em água destilada a 37oC ± 2oC durante 24 horas e submetidas ao ensaio de tração até soltura das restaurações. Os dados obtidos foram analisados estatisticamente quanto ao atendimento das pressuposições de normalidade e de homogeneidade de variância, pelos testes de Shapiro-Wilk, Levene e Anova dois critérios (α=5%). Resultados: os valores (média ± desvio-padrão) de resistência à tração (em Newtons) foram: G1: 108,9 ± 37,2; G2: 168,6 ± 43,9; G3: 143,4 ± 57,1; G4: 236,8 ± 52,2. Não houve interação estatisticamente significativa entre as variáveis diâmetro e altura (p=0,446). Ao se comparar os valores de resistência à tração, notou-se efeitos estatisticamente significativos entre o diâmetro (p=0,030) e a altura (p=0,003) dos munhões cone-morse. Munhões com 4,5 mm de diâmetro proporcionaram resistência à tração significativamente superior àquela obtida na condição em que foram empregados munhões com 3,5 mm, tanto nas condições 4 mm quanto 6 mm de altura. A resistência à tração foi aumentada (37%) com munhões 4,5 mm comparados aos munhões 3,5 mm. A resistência à tração foi aumentada (60,7%) com a altura de 6 mm, comparada à altura de 4 mm. Conclusão: pilares para implantes cone-morse com maiores dimensões proporcionam maior segurança e estabilidade às coroas cimentadas sobre implantes.

Objective: to evaluate the tensile strength of cemented copings on cone-morse abutments with different heights and diameters. Material and methods: four groups (G1: 3.5 mm x 4 mm; G2: 3.5 mm x 6 mm; G3: 4.5 mm x 4 mm; and G4: 4.5 mm x 6 mm) with five samples each had their waxed copings and cast in Ni-Cr alloy, being cemented (Panavia F, 6 Kgf-load, 5 minutes) on their respective already torqued abutments (25 Ncm). Then, samples were immersed in distilled water (37oC ± 2oC) for 24 hours and subjected to the tensile test until restorations being separated. The data obtained were analyzed statistically for normality and homogeneity of variances by the Shapiro-Wilk and Levene tests. Comparisons were made using the 2-way Anova test (α=5%). Results: the values (mean ± standard deviation) of tensile strength (in Newtons) were: G1: 108.9 ± 37.2; G2: 168.6 ± 43.9; G3: 143.4 ± 57.1; G4: 236.8 ± 52.2. There was no statistically significant interaction between the variables diameter and height (p=0.446). When comparing values of tensile strength, we observed statistically significant effects for diameter (p=0.030) and height (p=0.003). Abutments with a 4.5 mm diameter provide significantly higher tensile strength to those obtained with 3.5 mm in both 4 mm and 6 mm height conditions. The tensile strength was increased (37%) for the 4.5 mm compared to the 3.5 mm condition. The tensile strength was increased (60.7%) with a height of 6 mm, compared to height of 4 mm. Conclusion: abutments for cone-morse implants with larger dimensions provide greater safety and stability for cemented crowns.

Efeito da distribuição de tensões em laminados cerâmicos de dissilicato de lítio e feldspática utilizando análise de elementos finitos tridimensionais / Effect of stress distribution on lithium disilicate and feldspathic ceramics laminates using three-dimensional finite element analysis

Atualmente, a estética dental tornou-se de grande importância na aparência pessoal, exigindo avanços tecnológicos na área odontológica e, consequentemente, materiais com características ópticas semelhantes aos dentes naturais e que preservam os remanescentes. Os sistemas adesivos tornaram possível a reparação de dentes com alterações na cor, forma ou posições que prejudicavam o equilíbrio estético e funcional. O objetivo deste estudo foi verificar a distribuição de tensões em facetas de cerâmica feldspática e dissilicato de lítio minimamente invasivas, pelo método de elemento finito. foi construído um modelo representativo de um incisivo central superior, com dimensões médias encontradas na literatura. Sobre esse dente, foi simulado um preparo conservador para laminado cerâmico. Sobre o preparo, foi simulado um laminado cerâmico de 0,5mm de espessura, o qual foi discretizado em cerâmica feldspática ou dissilicato de lítio por meio do módulo de elasticidade característico de cada material. Os modelos foram submetidos a cargas de 50 N, sob angulação de 30º em relação ao longo eixo do dente. Os resultados foram apresentados em gráficos de tensão com seus respectivos valores numéricos representados em escala de cores. Por meio da análise de elemento finito foi possível observar que o fragmento cerâmico de dissilicato de lítio apresentou valores numéricos de tensão semelhantes aos de cerâmica feldspática para todos os critérios avaliados, tensão de tração, compressão e cisalhamento. Conclui-se que as cerâmicas de dissilicato de lítio e feldspática foram caracterizadas por um comportamento mecânico semelhante em relação à distribuição das tensões.

Dental aesthetic has currently become of great importance in the appearance, requiring technological advances in the dental area and consequently, materials with optical characteristics similar to the natural teeth and that preserve the remnants. Adhesive systems made possible to repair teeth with changes in color, shape or positions that undermined the aesthetic and functional balance. The aim of this study was to verify the stress distribution in feldspathic ceramics and lithium disilicate minimally invasive through the finite element method. A representative model of a central upper incisor was constructed, with average dimensions found in the literature. On this tooth, a conservative preparation for ceramic laminate was simulated. On the preparations, a 0.5 mm thick ceramic laminate was simulated, which was discretized in feldspathic ceramics or lithium disilicate by means of the elasticity modulus characteristic of each material. The models were submitted to loads of 50 N under an angle of 30º in relation to the tooth long axis. The results were presented in tensile graphs with their respective numerical values represented in color scale. Through the finite element analysis, it was possible to observe that the lithium disilicate ceramic fragment presented tensile numerical values similar to those of feldspathic ceramics for all criteria evaluated, tensile stress, compression and shear. It is concluded that the lithium feldspathic and disilicate ceramics were characterized by a similar mechanical behavior in relation to the stress distribution.

Distorção de modelos de gesso obtidos a partir de duas técnicas de moldagem preliminar / Distortion of stone casts obtained from two preliminary impression techniques

O objetivo deste trabalho foi comparar, por meio de medições tridimensionais, modelos de gesso obtidos a partir de duas técnicas de moldagem preliminar: godiva (GG) e dupla moldagem com alginato (GA). Para isso, foi utilizado um modelo padrão metálico com três cilindros posicionados na região de molares esquerdo (A) e direito (B) e na região de papila incisiva (C). Para GG foi realizada a moldagem convencional com material plastificado entre 60-65°C. Para GA foi utilizada a técnica da mínima pressão equalizada, com a primeira moldagem realizada seguindo a proporção indicada pelo fabricante e a segunda com aumento de 25% na quantidade de água. Para avaliação da distorção, os modelos de gesso de cada grupo foram submetidos às medições tridimensionais em equipamento por coordenadas (n=10/grupo). O plano de nivelamento foi considerado no topo dos três cilindros e o centro de origem pela simetria dos cilindros A e B, permitindo a aferição da distância entre os cilindros (AB e BC), o diâmetro de cada cilindro (A, B e C) e a altura do palato. Os dados foram analisados por ANOVA 2 fatores e teste de Tukey (α=0.05). houve influência da interação do material de moldagem e localização das medidas (p0.05) entre os grupos, GG resultou em maior alteração dimensional nas mensurações dos diâmetros A, B e C. GG e GA não diferiram na estabilidade dimensional, portanto sendo consideradas técnicas clinicamente viáveis.

The aim of this study was to compare, through three-dimensional measurements, stone casts obtained by two preliminary impression techniques: compound (CG) and double-alginate (AG) impression. for this purpose, a metal pattern model with three cylinders positioned in the left (A) and right (B) molars and incisal papilla (C) regions was used. for CG, conventional impression with plasticized material between 60-65°C was carried out. for AG, the equalized minimum pressure technique was used with the first impression taken according to the proportion indicated by the manufacturer, and the second with 25% increase in the water quantity. To evaluate the distortion, the stone casts of each group were submitted to three-dimensional measurements in equipment by coordinates (n=10/group). The leveling plane was considered at the top of the three cylinders, and the center of origin by A and B cylinders symmetry, which allowed measurement of the distance between the cylinders (AB and BC), diameter of each cylinder (A, B and C) and palate height. The data were evaluated by two-way ANOVA and Tukey tests (α=0.05). There was influence on the interaction of impression material and location of the measurements (p0.05) between the groups, CG resulted in greater dimensional change in the measurements of A, B and C diameters. CG and AG did not differ in dimensional stability, thus being considered clinically feasible techniques.