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Biomedical subjects

R van Noort

Publications and source records attributed to R van Noort.

At least 55 records · Page 3Linked to original sources
PubMed1990

The effects of recycling on the tensile bond strength of new and clinically used stainless steel orthodontic brackets: an in vitro study.

The tensile bond strength was evaluated for three different types of stainless steel orthodontic bracket/base combinations (both cast and machined integral bases, and a foil-mesh base). The cast base gave a significantly higher initial bond strength than the other two brackets. Following recycling by either chemical or thermal methods, all the bases demonstrated a significant reduction in bond strength. However, thermal recycling produced an unacceptably large reduction in the bond strength of the cast base and this method of reconditioning should be avoided with these brackets. Recycling the brackets an additional four times was found to result in a further reduction in bond strength, but this was not statistically significant. Clinically used brackets demonstrated a slightly lower, though not statistically significant, bond strength compared to unused brackets following one recycling with either the chemical or thermal method.

Acrylic Resins↗
PubMed1989

The rheology of silicone rubber impression materials.

A selection of silicone rubber impression materials were studied for their rheological properties prior to and following mixing. The techniques used were a cone and plate viscometer and a capillary viscometer. All the impression materials were found to show pseudoplastic behaviour which is readily described by a power law function. For the mixed materials the onset of molecular entanglement, whilst theoretically establishing the absolute end of the working time, gave a gross overestimate of the clinical working time. The capillary viscometer is more useful than the cone and plate viscometer in providing information on the clinical working time.

Chemical Phenomena↗
PubMed1989

Bond strengths of two integral bracket-base combinations: an in vitro comparison with foil-mesh.

The tensile/peel and shear/peel bond strengths of a cast integral bracket-base were compared with a machined integral base and a foil-mesh base. The bases were tested with both a 'no-mix' and a two-paste adhesive. The cast base performed significantly better than the other two. All the bases produced a higher bond strength when subjected to a shear mode of loading and greater bond strengths were obtained with both loading configurations when using the two-paste adhesive. These differences in bond strength between the bases cannot be explained in terms of the differences in the surface areas of the bases, so that other factors will need to be considered.

Dental Bonding↗
PubMed1986

Controlling drug release from acrylic polymers: in vitro studies with potential oral inserts.

The use of a drug modified polymer system which can release drugs such as hydrocortisone sodium succinate and chlorhexidine acetate has been explored. By partially coating the drug loaded acrylic, such that it acts as a core with an impermeable membrane covering most of the surface, the rapid releases of the drug can be prevented and near zero-order rates of release achieved. For chlorhexidine acetate the release time was extended from around 20 d to 80 d with at least 60% of the drug being released. A similar potential for the controlled release of hydrocortisone sodium succinate is described and represents an important stage in the development of an intra-oral insert for drug delivery.

Acrylates↗