Analysis of bond strength between a nylon reinforcement structure and dental resins.

BACKGROUND: Nylon is a polymer that its use to reinforce dental resins has shown positive results such as increased flexural strength. The aim of this study was to evaluate the bond strength between dental resins and a nylon reinforcement. MATERIAL AND METHODS: Forty cylindrical nylon blocks with 13 x 23 mm with 0.5% by volume of silica and 40 without were made. Half of the samples of each nylon composition were sandblasted with aluminum oxide (50µm) for 3 s (2.8 bar pressure, distance: 20 mm, incidence angle: 90o). On the nylon blocks, cylinders of chemically activated acrylic resin and indirect composite resin were made, with a bonding area of 6,28 mm2. Eight different groups were obtained according to the material used and the surface treatment (n = 10): Acrylic Resin + Nylon; GAS: Acrylic Resin + Nylon with Silica; GAT: Acrylic Resin + Nylon (Al2O3); GAST: Acrylic Resin + Nylon with Silica (Al2O3); GC: Composite Resin + Nylon; GCS: Composite Resin + Nylon with Silica; GCT: Composite Resin + Nylon (Al2O3); GCST: Composite Resin + Nylon with Silica (Al2O3). The shear test was carried out. The Student's and the Kruskal-Wallis test was adopted. RESULTS: There was no statistically difference in the bond strength for nylon with silica for the acrylic resin group. For the composite groups, nylon with silica did not present a statistically difference without surface treatment (p = 0.10) and with surface treatment the bond strength decreased (p = 0.000). The GCT showed a higher bond strength (0.89 MPa). The surface treatment improved the bond strength for the both groups. CONCLUSIONS: The presence of silica in the nylon composition did not influence the bond strength between materials evaluated. However, the surface treatment with aluminum oxide proved to be favorable for this adhesion. Key words:Nylons - Resins, Synthetic - Structures Strengthening - Dental Research.

Silica-Nylon Reinforcement Effect on the Fracture Load and Stress Distribution of a Resin-Bonded Partial Dental Prosthesis.

This study investigated the influence of silica-nylon reinforcement on the stress distribution and fracture load of a resin-bonded fixed partial dental prosthesis (RBFDP). Three-unit RBFDPs (N = 60) were inserted between the first premolar and the first molar of a maxillary model. The groups were divided according to the nylon reinforcement (n = 20/group): conventional fixed prosthesis (without reinforcement), prosthesis with silica-nylon reinforcement positioned vertically, and prosthesis with silica-nylon reinforcement positioned horizontally. Half of the specimens were tested after 24 hours in a universal testing machine until fracture (1,000 kgf; 1 mm/minute) to determine the single load to fracture. The other half was submitted to mechanical aging during 106 cycles (100 N, 2 Hz), totaling 6 groups (n = 10/group). The results were analyzed by two-way analysis of variance (ANOVA) (α = 5%). The stress distribution for non-aged groups was simulated using finite element analysis. The numeric prostheses were modeled similarly to the in vitro assay. ANOVA showed no statistical difference between groups (P < .05) for load to fracture. However, the use of the reinforcement provided stability even after the failure, as the parts did not separate. The computational analysis showed similar biomechanical behavior among the groups. The use of the nylon reinforcement does not influence the fracture load or the stress distribution, but it does enable the prosthesis to remain in position after failure.

Efeito de uma malha de nylon contendo sílica como reforço em próteses parciais fixas em resina composta indireta / Effect of a nylon mesh containing silica as reinforcement on fixed partial dentures in indirect composite resin

O presente estudo teve como objetivo avaliar as características mecânicas de próteses parciais fixas adesivas, confeccionadas em resina composta de uso indireto, reforçadas por uma malha de nylon. Para a confecção da matriz dos espécimes e estudo das tensões nas estruturas, foi realizada análise qualitativa pregressa análise de elementos finitos (FEA). A pesquisa in vitro simula uma prótese parcial fixa de três elementos com inserção entre os primeiros pré-molares e os primeiros molares superiores (n = 60; 10 por grupo). Três dos seis grupos passaram por ciclagem mecânica. Os grupos experimentais foram: G1-prótese fixa convencional; G2 - prótese convencional ciclada; G3 - prótese com reforço da malha posicionada na vertical; G4 ­ Prótese com reforço da malha posicionada na vertical ciclada; G5 ­ Prótese com reforço da malha posicionada na horizontal; G6 ­ Prótese com reforço da malha posicionada na horizontal ciclada.Todos os grupos passaram por ensaio de carga máxima a fratura (EMIC). Os resultados não apresentaram diferença estatística entre os grupos. Concluiu-se que a utilização da malha nylon proporcionou estabilidade, mesmo após a fratura da peça, pois as partes não se separam, além disso, os resultados obtidos in vitro puderam validar os dados in sílico(AU)

The present study aimed to evaluate the mechanical characteristics of adhesive fixed partial dentures, made from composite resin of indirect use, reinforced by a nylon mesh. A finite element analysis (FEA) was used to compile the specimen matrix and to study the stresses in the structures. In vitro research, simulated a fixed partial denture of three elements with insertion between the first premolars and the major maxillary molars (n = 60; 10 per group). Three of the six groups underwent mechanical cycling. The experimental groups were: G1 - conventional fixed prosthesis; G2 - conventional cyst prosthesis; G3 - prosthesis with reinforcement of the mesh positioned vertically; G4 - Prosthesis with reinforcement of the mesh positioned in the cycled vertical; G5 - Prosthetics with mesh reflux positioned horizontally; G6 - Prosthetics with mesh reinforcement positioned horizontally cycled. All groups underwent maximum fracture loading test (EMIC). The results do not present a statistic between the groups. It was concluded that the use of the nylon mesh provided stability, even after fracture of the part, as parts do not separate, besides, the results obtained in vitro could validate the data in silica(AU)