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Biomedical subjects

A J Feilzer

Publications and source records attributed to A J Feilzer.

42 records · Page 3Linked to original sources
PubMed1991

Destructive stresses in adhesive luting cements.

In this study, curing shrinkage stress development was monitored in a glass-ionomer and a BisGMA composite luting cement adhesively placed at film thicknesses ranging from 30 to 200 microns. The nature and magnitude of the stress development depended greatly on the formulation and film thicknesses of the lute. The thicker the layer, the faster the stress development in the glass ionomer and the slower in the composite. The contraction stress had a detrimental effect on the cohesive strength of the glass ionomer and on the adhesive strength of the composite cement.

Adhesiveness↗
PubMed1990

Quantitative determination of stress reduction by flow in composite restorations.

In this study, the reduction of the polymerization shrinkage stress by flow of four chemically-initiated composites was investigated in relation to the cavity configuration. In an experimental set-up simulating restorations bonded to cavity walls, the developing shrinkage stress accompanied by flow was recorded as a function of time for several configurations. For each configuration, theoretical shrinkage stress curves were also drawn, excluding stress reduction by flow. These data were obtained from Young's modulus determinations at the early setting stage and the corresponding polymerization shrinkage. By comparison of the theoretical stress with the experimentally determined stress, a measure for the ability to flow in the bonded situation could be obtained. It was found that the flow strongly depended on the type of composite and on the configuration of the cavity.

Composite Resins↗
PubMed1990

Relaxation of polymerization contraction shear stress by hygroscopic expansion.

We studied relaxation by hygroscopic expansion of the interfacial polymerization shear stress of bonded resin composites. In the experimental set-up, resin composite-cured-to-glass strips bent due to the polymerization shrinkage. The strips were stored wet or dry. The curvatures of the bent strips were recorded, by the scanning of the glass surfaces with a contact profilometer, periodically over a period of two months. From the measured deflections, we calculated the maximum tangential bending stress in the resins near the adhesive interface, which provided an estimation for the maximum shear stress values occurring at both ends of the strips. In the particular experimental set-up, the shear stresses in Bis-GMA/TEGDMA and urethane dimethacrylate-based resins were either fully relieved or converted into an "expansion stress" by hygroscopic expansion. The hydrophobic tricyclodecane dimethacrylate-based resins showed very little stress relaxation.

Absorption↗
PubMed1989

Increased wall-to-wall curing contraction in thin bonded resin layers.

Wall-to-wall (WTW) polymerization contraction of filled and unfilled chemically and photo-initiated resins was studied in relation to the WTW distance. In an experimental set-up, the resins were bonded to two opposing disks, and the axial (WTW) displacement resulting from the polymerization shrinkage was measured continuously. It was found that the WTW contraction increased with decreasing WTW distance and ultimately reached a value of almost three times the linear polymerization shrinkage.

Chemical Phenomena↗
PubMed1987

Setting stress in composite resin in relation to configuration of the restoration.

The setting stress in composite resins was studied as a function of restoration shape. The shape is described by the configuration factor, C, the ratio of the restoration's bonded to unbonded (free) surfaces. In an experimental set-up, the shape of the restoration was simulated by cylindrical forms of various dimensions. The shrinkage stress was measured continuously. It was shown that in most of the clinically relevant cavity configurations, the stress-relieving flow is not sufficient to preserve adhesion to dentin by dentin-bonding agents.

Bisphenol A-Glycidyl Methacrylate↗