Localized mechanics of dentin self-etching adhesive system

The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 µm), two TAG lengths (13 or 17 µm) and two loading conditions (perpendicular and oblique-25º) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 µm) were constructed: M1 - no HL and no TAG; M2 - 3 µm of HL and 13 µm of TAG; M3 - 3 µm of HL and 17 µm of TAG; M4 - 6 µm of HL and 13 µm of TAG; and M5 - 6 µm of HL and 17 µm of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25º). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys®, Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (sigmavM) and maximum principal stress (sigmamax) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased sigmavM and sigmamax in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the sigmavM and sigmamax than TAG length. The peritubular dentin and its adjacent structures showed the highest sigmavM and sigmamax, mainly in the oblique loading

Localized mechanics of dentin self-etching adhesive system

The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 μm), two TAG lengths (13 or 17 μm) and two loading conditions (perpendicular and oblique-25o) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 μm) were constructed: Ml - no HL and no TAG; M2 - 3 μm of HL and 13 μm of TAG; M3 - 3 μm of HL and 17 μm of TAG; M4 - 6 μm of HL and 13 μm of TAG; and M5 - 6 μm of HL and 17 μm of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25°). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys®, Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (σvM) and maximum principal stress (σmax) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased σvM and σmax in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the σvM and σmax than TAG length. The peritubular dentin and its adjacent structures showed the highest σvM and σmax, mainly in the oblique loading

Laminados cerâmicos em pré-molares: análise tridimensional pelo método dos elementos finitos

Objetivo: O objetivo do presente estudo foi avaliar através do método dos elementos finitos tridimensional (3D FEA), o comportamento mecânico de uma faceta laminada de cerâmica e do cimento resionoso em um 1o pré-molar maxilar, variando a redução (parcial ou total) da cúspide vestibular. Material e método: Baseado em imagens micro-tomográficas (μCT) 2 modelos (M) tridimensionais foram construídos no programa Solidworks 2007 variando a redução da cúspide vestibular, sendo Mp o modelo composto pelo dente pré-molar restaurado com uma faceta laminada de cerâmica, com redução parcial da cúspide vestibular e Mt, o modelo semelhante ao Mp, porém com redução total da cúspide vestibular. O programa de elementos finitos ANSYS Workbench 10.0 foi utilizado para realizar as análises. O carregamento (150 N) foi aplicado próximo à ponta de cúspide vestibular, com 45º de inclinação. Foram utilizados os critérios da máxima tensão principal ( max) e da máxima tensão cisalhante ( shear) na faceta laminada e na camada de cimento resinoso. Resultados: O Mt mostrou menor shear em 9 das 12 áreas analisadas quando comparado ao Mp. O Mp mostrou menor variação da max (de -3,13 para 14,4 MPa) que o Mt para a lâmina de cerâmica (de -2,08 para 24,3 MPa) A camada de cimento apresentou variação de max semelhante entre os Mp e Mt. Os critérios de tensões utilizados não evidenciaram valores além dos limites estabelecidos para a falha estrutural do material estudado. Conclusão: O laminado cerâmico e a camada de cimento resinoso apresentaram comportamento mecânico favorável para a restauração do pré-molar frente ao carregamento adotado. O tipo de redução de cúspide não influenciou no aumento expressivo das tensões principal e cisalhante. O Mp apresentou menores valores de max em tração quando comparado ao Mt. O Mp e o Mt apresentaram comportamento favorável com relação as forças cisalhantes, sendo as maiores tensões.Objectives: Using 3-D finite element analysis (FEA) and μCT data, the aim of this study was to evaluate the behavior of the laminate veneer and the resin luting cement in a maxillary premolar with the buccal cusp partially or completed covered. Material and method: 2 3-D FEA models of a maxillary premolar were built from μCT data. All models were restored with a feldspathic laminate veneer using Solidworks. A similar tooth reduction (0.5mm) was applied for two models. The buccal cusp reduction of the premolar followed two configurations: Model (Mt) - buccal cusp completely covered by veneer; and Model (Mp) - buccal cusp partially covered by veneer. The loading (150N, in 45o) was performed on the buccal cusp of each premolar. Appropriate boundary condition was applied at the periodontal ligament surfaces and ANSYS (10.0) was used to obtain the maximum shear stress ( shear) and maximum principal stress ( max) for the laminate veneer and resin luting cement layer. Results: The Mp showed higher shear than Mt in 9 to 12 analyzed areas. The Mp showed smallest variation of max in laminate veneer (from -3,13 to 14,4 MPa) compared with Mt (from - 2,08 to 24,3 MPa). The resin luting cement showed similar variation of max between Mp and Mt (from -3.13 to 12.2 MPa) and (from -1.61 to 14.1 MPa), respectively. None of the structures exceeded the ultimate tensile strength or the shear bond strength to dentin and enamel. Conclusion: The laminate veneer and the resin luting cement layer showed an adequate behavior when veneer was applied in premolars. Cusp reduction did not affect significant increase in max and shear. In general, the Mp showed better behavior ( max) than Mt. The Mt showed better behavior ( shear) than Mp

Prótese parcial removível de extremidade livre associada a um implante osseointegrado: influência do ligamento periodontal na distribuição interna das tensões

Em função da adoção de hipóteses simplificadoras nos estudos através do método dos elementos finitos (MEF), os dados sobre a menor solicitação das estruturas de suporte na associação da prótese parcial removível de extremidade livre (PPREL) com um implante osseointegrado são inconclusivos. Assim, foi objetivo do presente estudo avaliar, através do MEF bidimensional, a distribuição interna das tensões nas estruturas de suporte da PPREL associada a um implante osseointegrado, em função da reprodução homogênea e não-homogênea do ligamento periodontal (LP). Para isso, 6 modelos (M) foram criados no programa AutoCAD 2005 (Autodesk Inc.; USA), representando: MA - hemiarco contendo somente o dente 33 e o rebordo desdentado para distal; MB - semelhante ao A, com uma PPREL substituindo os dentes ausentes; MC - semelhante ao B, com um implante (Sistema Bränemark - 3,75 mm x 10,0 mm) na região retromolar suportando a base da prótese; MD, ME e MF semelhantes aos modelos A, B e C, respectivamente, com exceção do LP, que foi modelado de forma não-homogênea, com a representação de 4 conjuntos de fibras: fibras da crista, horizontais, oblíquas e apicais. Após isso, os modelos foram exportados para o programa de elementos finitos ANSYS 8.0, e carregados com forças estritamente verticais de 50N em cada ponta de cúspide, fracionadas em 5 pontos de 10N. Os mapas gerais de tensões evidenciaram máxima e mínima concentração de tensões de (em MPa): MA (58,976 e 0,0045); MB (77,863 e 0,0551); MC (207,195 e 0,0057); MD (110,33 e 0,0137); ME (191,36 e 0,0044) e MF (326,60 e 0,0076), com deslocamento máximo de (mm): MA (0,0631); MB (0,1263); MC (0,1142); MD (0,2709); ME (0,1960) e MF (0,2019).The application of many hypotheses in a finite element analysis (FEA) has been critical to obtain precise results in the removable partial denture treatment associated with an osseointegrated implant. In view of that, the purpose of the present study was to evaluated, through 2-D finite element analysis, the stress distribution in the support structures of a free-end saddle removable partial denture (RPD) associated with an osseointegrated implant, in function of the homogenous and non-homogenous condition for the periodontal ligament. For this, 6 models (M) were created in the AutoCAD software (Autodesk Inc.; USA), representing: MA - hemiarch contain only the natural tooth (33) and edentulous space in the posterior region; MB - similar to MA, with an RPD replacing the absent teeth; MC - similar to MB, with an osseointegrated implant (Branemark System - 3.75 x 10.00 mm) positioned in a posterior region in order to support the RPD base; MD, ME and MF - identical to MA, MB and MC, respectively; however, in these models, the periodontal ligament was considered an non-homogenous structure by the incorporation of four fibers groups in a sagital plane: alveolar crest fibers, horizontals, oblique, and apical fibers. After this, the models were exported to the finite element program (ANSYS 8.0) and loaded with verticals forces (50N) in each cusp. The results showed maximum and minimum stress (MPa): MA (58.976 and 0.0045); MB (77.863 and 0.0551); MC (207.195 and 0.0057); MD (110.33 and 0.0137); ME (191.36 and 0.0044) and MF (326.60 and 0.0076). The maximum displacement (mm) was: MA (0.0631); MB (0.1263); MC (0.1142); MD (0.2709); ME (0.2019) and MF (0.2019). (Complete abstract click eletronic address below

Etch and rinse versus self-etching adhesives systems: Tridimensional micromechanical analysis of dentin/adhesive interface

The purpose of this study was to evaluate stress distribution in the hybrid layer produced by two adhesive systems using three-dimensional finite element analysis (FEA). Four FEA models (M) were developed: Mc, a representation of a dentin specimen (41 x 41 x 82 mu m) restored with composite resin, exhibiting the adhesive layer, hybrid layer (HL), resin tags, peritubular dentin, and intertubular dentin to simulate the etch-and-rinse adhesive system; Mr, similar to Mc, with lateral branches of the adhesive; Ma, similar to Mc, however without resin tags and obliterated tubule orifice, to simulate the environment for the self-etching adhesive system; Mat, similar to Ma, with tags. A numerical simulation was performed to obtain the maximum principal stress (sigma(max)). The highest sigma(max) in the HL was observed for the etch-and-rinse adhesive system. The lateral branches increased the sigma(max) in the HL. The resin tags had a little influence on stress distribution with the self-etching system. (C) 2012 Elsevier Ltd. All rights reserved

Laminate veneers - a review and clinical case

The laminate veneers are great choice for rehabilitation for anterior segment of the mouth. Actually, due the employment of dental cements and bonding to dentin, the uses of laminate veneers is an effective and conservative treatment, showing a high rate success rate. This paper presents a clinical case of 50 years old male, J.C.H, who have a chief complaint of an unattractive smile. After the diagnosis and planning, 10 laminate veneers were placed from the second bicuspid (15) to the second bicuspid (25). The correct indication of laminate veneers allows restorations with appropriate esthetic and patient's satisfaction with immediate effect on quality of life. © 2011 Nova Science Publishers, Inc

Influence of buccal cusp reduction when using porcelain laminate veneers in premolars. A comparative study using 3-D finite element analysis

Objectives: Based on a maxillary premolar restored with laminate veneer and using the 3-D finite element analysis (FEA) and mCT data, the aim of this study was to evaluate the influence of different types of buccal cusp reduction on the stress distribution in the porcelain laminate veneer and in the resin luting cement layer. Methods: Two 3-D FEA models (M) of a maxillary premolar were built from mCT data. The buccal cusp reduction followed two configurations: Mt-buccal cusp completely covered by porcelain laminate veneer; and Mp-buccal cusp partially covered by porcelain laminate veneer. The loading (150 N in 458) was performed on the top of the buccal cusp. The finite element software (Ansys Workbench 10.0) was used to obtain the maximum shear stress (σmax) and maximum principal stress (σmax). Results: The Mp showed reduced the stress (σmax) in porcelain laminate veneer (from-2.3 to 24.5 MPa) in comparison with Mt (from-5.3 to 27.4 MPa). The difference between the peak and lower stress values of σmax in Mp (-6.8 to 26.7 MPa) and Mt (-5.3 to 27.4 MPa) was similar for the resin luting cement layer. The structures not exceeded the ultimate tensile strength or the shear bond strength. Conclusions: Cusp reduction did not affect significant increase in σmax and τmax. The Mt showed better stress distribution (τmax) than Mp. © 2011 Published by Elsevier Ireland on behalf of Japan Prosthodontic Society

Localized mechanics of dentin self-etching adhesive system

The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 mu m), two TAG lengths (13 or 17 mu m) and two loading conditions (perpendicular and oblique-25 degrees) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 mu m) were constructed: M1 - no HL and no TAG; M2 - 3 mu m of HL and 13 mu m of TAG; M3 - 3 mu m of HL and 17 mu m of TAG; M4 - 6 mu m of HL and 13 mu m of TAG; and M5 - 6 mu m of HL and 17 mu m of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25 degrees). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys (R), Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (sigma(vM)) and maximum principal stress (sigma(max)) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased sigma(vM) and sigma(max) in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the sigma(vM) and sigma(max) than TAG length. The peritubular dentin and its adjacent structures showed the highest sigma(vM) and sigma(max), mainly in the oblique loading