RESUMO
PURPOSE: This study evaluated the effect of different loading pistons, made of various materials and with different elastic moduli acting as antagonist material, on stress distribution and fatigue behavior of a CAD/CAM silica-based ceramic. MATERIALS AND METHODS: Discs of CAD/CAM made silica-based ceramic (Nâ¯=â¯60) (VITA MARK II) were divided into six groups (nâ¯=â¯10 per group), according to the test method (M: Monotonic; F: Fatigue) and the antagonist piston material (T: Tungsten; S: Steel; G: Epoxy resin). FT, FS and FG combinations were submitted to mechanical cycling (2â¯×â¯106 cycles, 4â¯Hz, 45â¯N). The bending stress after fatigue were also valuated using Weibull analysis and the parameters η (eta), ß (beta) and the mean time to failure (MTTF) were calculated. Fractographic analysis and Finite Element Analysis (FEA) were performed. Data were analyzed using ANOVA and Tukey's tests (alpha=0.05). RESULTS: MG presented significantly less bending strength (MPa) (75.6) compared to MT (87.8) and MS (84.4) (pâ¯<â¯0.05). Six specimens from FT (MMTF: 8.3â¯×â¯106; ß:0.60; η:5.6â¯×â¯106), four from FS (MMTF: 1.9â¯×â¯106; ß:1.2; η:2.0â¯×â¯106) and one from FG (MMTF: 1.3â¯×â¯106; ß:0.48; η:0.64â¯×â¯106) survived the fatigue test. The stress peak on the tensile surface of S was similar to that of T and both were less than that of G. The failure origins were on the tensile surface. CONCLUSION: The epoxy resin pistons were able to decrease the bending stress, and life expectancy (faster failure) of a silica-based ceramic compared to tungsten and steel.
Assuntos
Cerâmica/química , Desenho Assistido por Computador , Teste de Materiais , Dióxido de Silício/química , Análise de Elementos Finitos , Propriedades de Superfície , Suporte de CargaRESUMO
Sialolithiasis is the phenomenon of blockage of the salivary glands. It frequently is associated with swelling, pain, and infection of the affected gland. Clinically, sialolithiasis manifests as an increase in the size of the affected gland and increased salivary secretion that results in pain during eating. It occurs mainly in the submandibular gland and less frequently in the parotid gland. This article presents a case involving a 23-year-old woman with Down syndrome who demonstrated sialolithiasis in the parotid duct gland. The sialolith was radiographed and removed surgically.