Objectives: To determine the shear bond strength to bovine dentin of dual-cured resin cements cured in different circumstances, the contraction stress and volumetric shrinkage in both polymerization modes, and to review the failure stress distribution at the cement-tooth interface with finite element analysis.
Methods: The volumetric shrinkage of RelyX Unicem, Panavia F 2.0 and DC Core Automix was determined by mercury dilatometry.
Objectives: The aim of this study is to determine the influence of the C-factor and the mode of polymerization on the cohesive strength of various dual-cure resin cements.
Methods: Three curing conditions were tested; chemical curing with free shrinkage conditions (C=0), and constraint shrinkage conditions (C=25), and dual-curing with free shrinkage conditions (C=0). Opaque polyethylene, brass (pretreated with Clearfil SE bond), and transparent polyethylene tubes respectively, were filled with the different cements.
Unlabelled: Nickel (Ni) is a potent sensitizer and may induce innate and adaptive immune responses. Ni is an important component of orthodontic appliances (8-50 wt%). Due to chemical and mechanical factors in the oral environment, Ni is released from these appliances.
View Article and Find Full Text PDFPurpose: To determine whether two-step cementation of prefabricated fiber posts leads to higher bond strengths.
Materials And Methods: Forty-eight human canine teeth were divided into six groups and fiber posts were cemented with DC Core, RelyX Unicem and Panavia F2.0, according to a one-step or two-step procedure.
Am J Orthod Dentofacial Orthop
February 2008
Introduction: The aim of this in-vitro study was to investigate the changes in force delivery of superelastic nickel-titanium archwires used in combination with a self-ligating bracket system after dynamic fatigue-loading in a 3-bracket model under controlled temperature.
Methods: Samples of 2 superelastic nickel-titanium (active austenitic) wires, a conventional nickel-titanium wire, and a stainless steel wire, all 0.014-in round, were divided into 2 groups: static deflection and dynamic deflection.
Objective: The aim of this study was to compare three fracture toughness test methods, using four commercial dental porcelains.
Materials And Methods: The fracture toughness test techniques involved were: the single-edge-notched beam (SENB), the indentation strength method (IS), and a rather convenient ASTM standard for advanced ceramics, which is still rarely used in dental ceramic research, the Chevron-notched beam method (CN). Duceram, Duceram LFC, Sintagon Zx and Carrara Vincent were chosen for study.
Objective: This study was to investigate the influence of the bending test configurations and the crosshead displacement speeds on the fracture toughness (K(Ic)) of dental porcelains obtained with the indentation strength in bending (ISB) method.
Methods: The strength of the dental veneering porcelains Duceram and Sintagon Zx, Vickers' indented at a load of 2 kg was measured at a crosshead speed of 0.5mm/min with three test configurations, which were 3-point, 4-point, and biaxial bending.
Objectives: Besides the fixation of the restoration, an important function of dental luting cements is to seal the gap between tooth and restoration. However, as a result of adhesion, curing contraction is hindered, creating stresses. To maintain the seal these stresses neither exceed the bond nor the cohesive strength of the cement.
View Article and Find Full Text PDFIntroduction: Knowledge of factors, which influence stress and its distribution is of key importance to the successful production of durable all-ceramic restorations. The objective of this study was to evaluate, by finite element analysis (FEA), the influence of the shape of the preparation and the cement layer on the stress distribution in CAD-CAM produced all-ceramic crowns and in their cement layer.
Material And Methods: The CAD models of multi-layer all-ceramic crowns for posterior tooth 46 of three patients produced with CAD-CAM-technology were translated into a three-dimensional FEA program.
Purpose: This study evaluated the influence of fatigue loading on the performance of an adhesive and a nonadhesive cement for cast post-and-core restorations in maxillary premolars.
Materials And Methods: The adhesive cement used was Panavia 21, a resin-based composite cement, and the nonadhesive cement was PhosphaCem/C, a zinc-oxy-phosphate cement. The coronal sections of single-rooted human maxillary premolars were removed at the level of the proximal CEJ.
Objectives: The bond of adhesive luting cements to the tooth tissues and restorative materials is expected to hinder their transverse contraction for the layer thickness applied in dental restorations. It was hypothesized that the hindering of the transverse deformation will influence the relation between stress and strain (the stiffness) in the direction perpendicular to the substrate surface. The aim of this study was to investigate the relation between cement layers with different ratio between bonded and free surface (C-factor) and the stiffness of these layers, i.
View Article and Find Full Text PDFStatement Of Problem: The strength of all-ceramic restorations can be adversely affected by surface defects, leading to restoration failures. Additionally, when a 2-layer all-ceramic restoration is required for esthetic purposes, part of the stronger ceramic core material is replaced by veneering porcelain.
Purpose: This study evaluated the effect of different surface treatments on the strength of a ceramic core material and veneering porcelain, as well as the influence of veneering porcelain on the strength of a 2-layer ceramic structure.