Fracture Toughness of Dentin/Resin-composite Adhesive Interfaces

Abstract

The reliability and validity of tensile and shear bond strength determinations of dentin-bonded interfaces have been questioned. The fracture toughness value (KIC) reflects the ability of a material to resist crack initiation and unstable propagation. When applied to an adhesive interface, it should account for both interfacial bond strength and inherent defects at or near the interface, and should therefore be more appropriate for characterization of interface fracture resistance. This study introduced a fracture toughness test for the assessment of dentin/resin-composite bonded interfaces. The miniature short-rod specimen geometry was used for fracture toughness testing. Each specimen contained a tooth slice, sectioned from a bovine incisor, to form the bonded interface. The fracture toughness of an enamel-bonded interface was assessed in addition to the dentin-bonded interfaces. Tensile bond strength specimens were also prepared from the dentin surfaces of the cut bovine incisors. A minimum of ten specimens was fabricated for each group of materials tested. After the specimens were aged for 24 h in distilled water at 37 degrees C, the specimens were loaded to failure in an Instron universal testing machine. There were significant differences (p < 0.05) between the dental adhesives tested. Generally, both the fracture toughness and tensile bond strength measurements were highest for AllBond 2, intermediate for 3M MultiPurpose, and lowest for Scotchbond 2. Scanning electron microscopy of the fractured specimen halves confirmed that crack propagation occurred along the bond interface during the fracture toughness test. It was therefore concluded that the mini-short-rod fracture toughness test provided a valid method for characterization of the fracture resistance of the dentin-resin composite interface.

Characterizing ceramics and the interfacial adhesion to resin: II- the relationship of surface treatment, bond strength, interfacial toughness and fractography

“…Therefore, the apparent fracture toughness of the interface can be calculated from the size of the defect and the strength with the appropriate geometric factor. Thus, the apparent fracture toughness value (K A ) reflects the ability of a material to resist unstable crack propagation at the interface 52,71 . Usually, in order to maintain equal compliances of the specimen halves, i.e.…”

“…, where E 1 is the elastic modulus for the first specimen half (ceramic), d 1 is the depth of the ceramic rectangular segment, E 2 is the elastic modulus of the composite half, and d 2 is the depth of the composite rectangular segment 27,52,71 . As the microtensile test is a uniaxial tensile test, there is no need for preparing specimens with balanced compliance for the two materials to measure K A .…”

“…Another way to assess the integrity of the bond is to estimate the apparent interfacial fracture toughness of the adhesion zone by promoting crack initiation within this zone. The apparent fracture toughness value (K A ) reflects the ability of a material to resist unstable crack propagation 28,52,71 . The objective of this second part of the review is to correlate apparent interfacial toughness (K A ) with fracture surface morphological parameters of the dental ceramic-resin systems as a function of ceramic surface treatment.…”

Mapeamento da variação regional da resistência adesiva em superfícies planas de dentina.

“…Ambos o " blister test" e o teste de centrifugação não são rotineiramente empregados na avaliação da união de materiais adesivos à estrutura dentária, pois são de preparação complexa e de difícil interpretação. Além destes, na busca de melhorar a avaliação da resistência de união com o objetivo de forçar a fratura na interface sem exceder a resistência intrínseca da dentina ou da resina, outros testes mecânicos também vêm sendo desenvolvidos 13,70,86,107,110,122,123,149 . Em um teste de cisalhamento, a união é rompida por uma força aplicada paralelamente à interface adesiva 77 .…”

Avaliação Da Resistência À Fratura De Interfaces Adesivas Em Restaurações Odontológicas

“…O último requisito diz que o valor da carga máxima (P max) deve ser menor ou igual a 1,10 P Q , Os gráficos dos ensaios de tenacidade à fratura dos corpos de prova dente-restauração e dos sistemas resina-resina correspondem ao gráfico tipo Walshaw et al, 2003;Tam et al, 2001;Tam & Pilliar, 1993). Portanto, os valores determinados para esta interface no presente trabalho (de 0,279 a 0,324 MPa√m) estão dentro desta faixa.…”