RESUMO
AIM: To investigate the influence of elastic modulus mismatch between tooth and post and core restorations on mechanisms of root fracture. METHODOLOGY: Three-dimensional mathematical models of a root filled maxillary premolar tooth with supporting periodontium were constructed. The tooth was restored with a cast Ni-Cr alloy or fibre-reinforced composite post and core that was bonded or nonbonded to dentine. In the nonbonded simulation, a nonlinear contact analysis was executed to simulate a friction and a potential sliding phenomenon in the interface between tooth and post and core. Risks of root fracture and debonding at the bonded interface were estimated based on the principal stress of the root and the shear stress on the interface, respectively. RESULTS: The fracture risk of the bonded cast post and core was lower than that of the composite post and core, although the cast restoration exhibited eight times greater stress than the composite. The risk of root fracture based on the tensile stress of the tooth structures was higher with the bonded composite post and core than that with the cast post and core. These stresses doubled when the restorations were not bonded to the tooth structures. The risk of debonding of the cast post and core based on the shear stress was approximately twice that of the composite post and core. CONCLUSIONS: The elastic modulus mismatch appears to be a factor responsible for the debonding of post and cores from root canals, with the potential to increase the risk of root fracture indirectly.
Assuntos
Técnica para Retentor Intrarradicular , Fraturas dos Dentes/etiologia , Raiz Dentária/lesões , Dente não Vital/patologia , Adulto , Dente Pré-Molar/lesões , Dente Pré-Molar/patologia , Ligas de Cromo/química , Resinas Compostas/química , Simulação por Computador , Colagem Dentária/métodos , Materiais Dentários/química , Planejamento de Prótese Dentária , Cavidade Pulpar/patologia , Falha de Restauração Dentária , Dentina/patologia , Módulo de Elasticidade , Análise de Elementos Finitos , Fricção , Vidro/química , Guta-Percha/química , Humanos , Imageamento Tridimensional/métodos , Modelos Biológicos , Materiais Restauradores do Canal Radicular/química , Resistência ao Cisalhamento , Estresse Mecânico , Propriedades de Superfície , Resistência à TraçãoRESUMO
From a human fetal-brain cDNA library, we isolated and characterized a novel gene (KPNA3) encoding a protein highly homologous to certain nuclear transport proteins of Xenopus and human. The complete cDNA clone, designated karyopherin alpha 3, contained an open reading frame of 1,563 nucleotides encoding 521 amino acids. The predicted amino acid sequence showed 48%, 45% and 48% identity with Xenopus importin, yeast SRP1 and human RCH1, respectively. The similarities among these proteins suggest that karyopherin alpha 3 may be involved in the nuclear transport system. Eight repeats of the arm motif were well conserved among these proteins. The N-terminal region of the predicted karyopherin alpha 3 product was highly basic and the C-terminal region was strongly acidic. A 4.3-kb transcript was expressed in all adult human tissues examined by Northern blotting. The cDNA clone was assigned to chromosome band 13q14.3 by fluorescence in situ hybridization.
Assuntos
Proteínas de Transporte/genética , Mapeamento Cromossômico , Proteínas Fúngicas/genética , Proteínas de Choque Térmico , Proteínas Nucleares/genética , Proteínas de Saccharomyces cerevisiae , alfa Carioferinas , Sequência de Aminoácidos , Animais , Sequência de Bases , Northern Blotting , Clonagem Molecular , Humanos , Hibridização in Situ Fluorescente , Carioferinas , Dados de Sequência Molecular , Saccharomyces cerevisiae/genética , Homologia de Sequência de Aminoácidos , XenopusRESUMO
We isolated a human cDNA clone encoding a novel protein homologous to cyclophilins, specific cellular targets of cyclosporin A, which are conserved in species ranging from human to prokaryotes. This cDNA, designated hCyPX, contained an open reading frame of 498 nucleotides encoding 166 amino acids. Computer analysis indicated that its predicted amino acid sequence had 41.6%, 40.4%, and 39.2% homology to those of human, bovine, and Drosophila cyclophilins, respectively. Northern blot analysis indicated ubiquitous expression in adult human tissues, but most abundant expression in heart. Fluorescence in situ hybridization to human metaphase chromosomes localized this gene (PPIL1, peptidylprolyl isomerase [cyclophilin]-like 1) to chromosome bands 2p23.3-->p23.1.
Assuntos
Isomerases de Aminoácido/genética , Proteínas de Transporte/genética , Mapeamento Cromossômico , Clonagem Molecular , Expressão Gênica/genética , Sequência de Aminoácidos , Sequência de Bases , DNA Complementar/análise , Feto , Humanos , Dados de Sequência Molecular , Peptidilprolil IsomeraseRESUMO
From a human fetal-brain cDNA library we isolated a novel gene encoding a peptide homologous to clathrin-adaptor small chains in rat, mouse, and yeast. The cDNA, designated CLAPS3 (clathrin-associated/assembly/adaptor protein, small 3, 22 kDa), contained an open reading frame of 579 nucleotides encoding 193 amino acids. Northern-blot analysis revealed expression of a 1.35-kb transcript in all human tissues examined. This gene was mapped to chromosome bands 12p13.2 --> p13.1 by FISH.
Assuntos
Complexo 3 de Proteínas Adaptadoras , Cromossomos Humanos Par 12 , Proteínas do Tecido Nervoso/genética , Subunidades alfa do Complexo de Proteínas Adaptadoras , Subunidades sigma do Complexo de Proteínas Adaptadoras , Proteínas Adaptadoras de Transporte Vesicular , Sequência de Aminoácidos , Animais , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , DNA , Expressão Gênica , Humanos , Proteínas de Membrana/genética , Dados de Sequência Molecular , Homologia de Sequência de AminoácidosRESUMO
From a human fetal-brain cDNA library we isolated a novel gene sharing significant homology with two yeast genes, UBC9 and hus5, which encode ubiquitin-conjugating enzyme 9 (UBC9). In yeast this protein is critical for normal mitosis, and seems to be closely involved in progression of G2 to M phase of the cell cycle. The human UBC9 (h-UBC9) cDNA, (gene symbol UBE2I), contained an open reading frame of 474 nucleotides encoding 158 amino acids. Its predicted peptide showed respectively 56% and 66% identity (75% and 82% similarity) with the products of UBC9 and hus5. Northern-blot analysis revealed expression of three transcripts, 6.4 kb, 3.3 kb, and 1.35 kb, in all human tissues examined. This gene, UBE2I, was mapped to chromosome band 16p13.3 by FISH.