A 3D finite element analysis of glass fiber reinforcement designs on the stress of an implant-supported overdenture.

STATEMENT OF PROBLEM: Evidence regarding the effect of different glass fiber reinforcement designs on the biomechanical behavior of implant-supported overdentures is lacking. PURPOSE: The purpose of this finite element analysis was to analyze the stress distribution in an implant-supported overdenture reinforced with a cast metal reinforcement bar and 4 different designs of unidirectional glass fiber to minimize the risk of denture base fracture. MATERIAL AND METHODS: A 3D edentulous mandible incorporating an implant-supported overdenture model without reinforcement (control, CT) or reinforced with 1 cast metal bar reinforcement (CM) was placed over the top of the implants and 4 unidirectional glass fiber reinforcements. The glass fiber bundle was placed over the top of the implants (GF), or 2 bundled halves were placed over the top (GO) of, between (GB), or distal (GD) to implants. Three patterns of occlusal loading were simulated: L1, all artificial teeth loaded in the long axis; L2, all left-side teeth loaded in the long axis; and L3, posterior left-side teeth loaded obliquely (45 degrees). RESULTS: Under L1 and L3, the tensile stresses were higher for CT, GD, and GO and lower for GF and CM. Under L2, no differences were seen between groups. Stresses were concentrated on the periphery of the O-ring connector, on the basal area, and on the middle-lingual region of the overdenture. CONCLUSIONS: Reinforcements placed in the middle region and over the top of the implants provided better load distribution. Unidirectional glass fiber behaved as cast metal when used to reinforce the implant-supported overdenture.

Influence of different resin cements and surface treatments on microshear bond strength of zirconia-based ceramics.

AIM: This study aims to evaluate the microshear bond strength of zirconia-based ceramics with different resin cement systems and surface treatments. MATERIALS AND METHODS: Forty blocks of zirconia-based ceramic were prepared and embedded in polyvinyl chloride (PVC) tubes with acrylic resin. After polishing, the samples were washed in an ultrasonic bath and dried in an oven for 10 min. Half of the samples were subjected to sandblasting with aluminum oxide. Blocks were divided into four groups (n = 10) in which two resin cements were used as follows: (1) RelyX™ U100 with surface-polished zirconia; (2) RelyX™ U100 with surface-blasted zirconia; (3) Multilink with surface-polished zirconia; and 4) Multilink with surface-blasted zirconia. After performing these surface treatments, translucent tubes (n = 30 per group) were placed on the zirconia specimens, and resin cement was injected into them and light cured. The PVC tubes were adapted in a universal testing machine; a stiletto blade, which was bolted to the machine, was positioned on the cementation interface. The microshear test was performed at a speed of 0.5 mm/min. Failure mode was analyzed in an optical microscope and classified as adhesive, cohesive, or mixed. RESULTS: The null hypothesis of this study was rejected because there was a difference found between the resin cement and the surface treatment. There was a statistical difference (P < 0.005) in RelyX™ U100 with surface-blasted zirconia, in relation to the other three groups. For Multilink groups, there was no statistical difference between them. CONCLUSION: Self-adhesive resin cement showed a more significant tendency toward bond strength in the ceramic-based zirconium oxide grit-blasted surfaces.

Avaliação da alteração dimensional de quatro marcas comerciais de silicone por reação de adição variando o tempo de armazenagem dos moldes / Dimensional alteration assessment of four silicone brands through addition reaction varying molds storage time

O objetivo deste estudo foi mensurar e comparar a precisão dimensional de modelos de gesso confeccionados por meio de moldagem de impressão única (material pesado/fluído de uma única vez) com quatro diferentes marcas comerciais de silicone polimerizados por reação de adição (Express XT®, Futura®, Aquasil® e Virtual®). Inicialmente, foi confeccionado um modelo acrílico mestre, o qual possuía três pilares metálicos paralelos entre si e equidistantes 50 mm um do outro. Para obtenção dos moldes foram utilizadas cinco moldeiras individuais em acrílico, cujas faces externas adaptavam-se perfeitamente na base do modelo padrão, promovendo o "stop" de inserção da moldeira. Após o procedimento de moldagem e confecção dos modelos experimentais, foram medidas as distâncias entre os três cilindros e o diâmetro de cada cilindro. Essas medições foram feitas por três vezes em um mesmo ponto e, destas, criou-se uma média obtendo os resultados finais. Os valores das distâncias foram analisados estatisticamente por meio de uma análise bifatorial, e as médias comparadas pelo teste de Tukey (5%). Os dados demostraram que todas as marcas analisadas apresentaram alteração dimensional e diferiram entre si quando comparadas.

The objective of this study was to measure and compare the dimensional accuracy of plaster models made by only impression molding (heavy material/fluid at one time) of four different brands of polymerized silicone through addition reaction (Express XT®, Futura ®, Aquasil® and Virtual®). Initially, a master acrylic model was manufactured, which had three parallel metal pillars and equidistant 50 mm from each other. To obtain the impressions, we used five individual acrylic trays, whose external faces perfectly adapted to the standard model base, thus promoting the "stop" of molding insertion. Following the molding procedure and the experimental models manufacturing, distances between the three cylinders and the diameter of each cylinder were measured. These measurements were made three times at the same point, and from these average results were obtained. The distance values were statistically analyzed using a two-factor analysis and the means compared by Tukey test (5%). The data demonstrated that all the analyzed brands presented dimensional changes and differed from each other when compared.

Análise das tensões sobre os dentes e núcleos intrarradiculares variando o material e a quantidade de remanescente coronário pelo método 3D de elementos finitos / Intraradicular core and teeth tensions analysis with variation of material and quantity of coronary remanescent by the 3d finite element method

Um fator de insucesso bastante frequente na terapia com núcleos metálicos fundidos é a fratura radicular dos dentes suportes. Essa situação é afetada pela quantidade de estrutura coronária remanescente, bem como o tipo de liga metálica utilizado. O objetivo deste estudo é comparar as tensões e sua distribuição em um dente incisivo central superior. Para isto, este dente foi reconstruído virtualmente a partir de uma tomografia computadorizada e, por fim, exportado para um software de edição de modelos visuais Ansys Design Modeler v10 (Ansys Inc., Canonsburg, PA, EUA). Foram analisados ainda, neste trabalho, a variação de três fatores de projeções dentinárias, bem como suas interações. Houve a criação de grupos: um modelo controle sem projeção e outros catorze modelos variando a projeção dentinária e o material utilizado na confecção do núcleo metálico fundido. A disponibilidade de 1,5 mm de estrutura dentária cervical remanescente, que proporciona o efeito férula, aumenta a resistência à fratura da raiz, fratura do núcleo e deslocamento do núcleo. A presença da férula resulta, também, em uma menor tensão na dentina do que a sua ausência. Dessa forma, a presença da férula, a altura do remanescente e o material utilizado para a confecção do núcleo metálico fundido são variáveis que afetam diretamente as tensões que atuam sobre o dente tratado endodonticamente (AU).

A frequent failure factor in the therapy with molten metal cores is the root fracture of tooth holders. This situation can be affected by the quantity of coronary remanescent structure as well as the type of alloy used. The aim of this study is to compare the tensions and their distribution in a maxillary central incisor tooth. Therefore, this tooth was virtually reconstructed from a computed tomography and finally exported to a visual models editing software Ansys Design Modeler v10 (Ansys Inc., Canonsburg, PA, USA). In this work were also analyzed the variation of three factors of dentin projections, as well as their interactions. There was the creation of groups: a model control without projection and fourteen other models varying the dentin projection and the material used in the manufacturing of the molten metal core. The availability of 1.5 mm remanescent cervical tooth structure, which provides the ferrule effect, increases resistance of root fracture, of core fracture, and core displacement. The ferrule presence also results in less tension on dentin than in its absence. Thus, the presence of ferrule, the remanescent height and the material used to manufacture the molten metallic core are variables that directly affect the tensions actuating on the endodontically treated tooth (AU).

Avaliação da estabilidade dimensional de diferentes marcas de silicone por reação de condensação ­ estudo in vitro / Assessment of the dimensional stability of distinct condensation silicone trademarks ­ an in vitro study

Na prática odontológica, o vazamento de gesso nos moldes é muitas vezes tardio, e a maioria é enviada ao laboratório para verter o gesso em até 72 horas. Portanto, os profissionais devem ficar cientes do tempo de atraso tolerável para o qual o material de moldagem permanecerá dimensionalmente preciso. O objetivo deste estudo foi avaliar a alteração dimensional de quatro marcas comerciais de silicone por reação de condensação: Speedex (Vigodent)®, Coltex/Coltoflax (Vigodent)®, Clonage (Nova DFL)® e Zetaplus/Oranwash (Zhermack)®, em função de seis diferentes tempos de vazamento de gesso, e sugerir o tempo máximo de armazenagem dos moldes. Para isso, foi confeccionado um modelo mestre com três cilindros metálicos, fixados em região de rebordo alveolar de uma maxila em acrílico, e 12 moldeiras individuais. A técnica de moldagem utilizada foi a do material em consistência densa e fluida em dois estágios. foram obtidos 72 modelos em gesso GC fujirock® EP melhorado tipo IV, os quais foram mensurados com paquímetro digital Mytutoyo®. Os resultados foram comparados ao modelo controle e aplicados ao teste de hipóteses "t de student". Concluiu-se que as marcas comerciais de silicone por reação de condensação Zetaplus® e Clonage® apresentaram modelos experimentais que não diferiram estatisticamente do modelo mestre para todos os tempos estudados. Já as marcas comerciais Coltex Coltoflax® e Speedex® apresentaram-se estatisticamente diferentes ao modelo mestre nos maiores tempos de armazenamento.

In dental practice, plaster casting is often late, and most are sent to the laboratory to pour the plaster in up to 72 hours. Therefore professionals should be aware of the tolerable delay time for which the molding material will remain dimensionally accurate. The objective of this study was to evaluate the dimensional alteration of four commercial brands of silicone by condensation reaction, Speedex (Vigodent)®, Coltex / Coltoflax (Vigodent)®,Clonage (Nova DFL)®, Zetaplus / Oranwash (Zhermack)®, in function of six different casting times, and suggest the maximum storage time of the molds. Therefore, a master model with three metal cylinders was made, fixed in the alveolar ridge region of an acrylic jaw, and 12 individual trays. The technique of molding used was that of the material in dense consistency and fluid in two stages. A total of 72 GC fujirock® EP improved plaster models were obtained, which were measured using a Mytutoyo® digital caliper. The results were compared to the control model and the "t student" hypothesis test was applied. It was concluded that the trademarks of silicone by condensation reaction Zetaplus® and Clonage® presented experimental models that did not differ statistically from the master model for all the studied times. Coltex Coltoflax® and Speedex® trademarks were statistically different from the master model in the longest storage times.