Monitoring the polymerization process of acrylic resins.

Four groups of autopolymerizing acrylic resins used for various purposes in current dental practice were investigated by monitoring their temperature changes during the polymerization process. Resins were compared in terms of characteristic parameters (such as the time interval needed to reach mechanical stability and the maximum temperature generated during the polymerization process) and interpretations were made of such temporal temperature profiles.     

A study of acrylic resin denture base material distortion using computer-aided holographic interferometry.

A holographic interferometer for investigating deformations of dental prostheses is described. Residual stress relaxation resulting from the polymerization of acrylic resin dentures is qualitatively studied during the first 48 hours following fabrication. The resulting fringe patterns show a symmetry that is correlated to the shape of the denture. A quantitative analysis of the interferograms was performed with the aid of a computer program. The computer-aided holographic interferometer was tested using disk-shaped acrylic resin materials. Dimensional deformations resulting from temperature changes were measured with an accuracy better than 0.2 microns. Because of the aging of the resin material, the reaction to temperature changes may differ as a function of time and may be studied using quantitative comparison of deformation plots. For convenience, the original object shape can be added to or subtracted from the graphical deformation data.     

Optimization of pyrrolo[3,4-f]indole-5,7-dione and indole-5,6-dicarbonitrile derivatives as inhibitors of monoamine oxidase

In recent studies, we have investigated the monoamine oxidase (MAO) inhibition properties of pyrrolo[3,4-f]indole-5,7-dione and indole-5,6-dicarbonitrile derivatives. Since numerous high potency MAO inhibitors are present among these chemical classes, the present study synthesizes 44 additional derivatives in an attempt to further derive structure-activity relationships (SARs) and to establish optimal substitution patterns for MAO inhibition. The results show that, with the exception of one compound, all indole-5,6-dicarbonitrile derivatives (10) exhibit submicromolar IC₅₀ values for the inhibition of MAO, with the most potent MAO-A inhibitor exhibiting an IC₅₀ value of 0.006 μM while the most potent MAO-B inhibitor exhibits an IC₅₀ value of 0.058 μM. Interestingly, an N-oxide derivative ( 4c ) also proved to be a potent and nonspecific MAO inhibitor. With the exception of one compound, all of the pyrrolo[3,4-f]indole-5,7-diones (28) also exhibit submicromolar IC₅₀ values for the inhibition of an MAO isoform. The most potent inhibitor exhibit an IC₅₀ value of 0.011 μM for MAO-A. This study proposes that high potency MAO inhibitors such as those investigated here, may act as lead compounds for the development of treatments for neurodegenerative and neuropsychiatric disorders such as Parkinson's disease and depression.     

Influence of border moulding on the dimensional stability of complete denture impression trays

In the process of making a final impression for complete dentures, the dimensional stability of the impression tray is an important factor. The aim of this study was to measure the dimensional stability of trays of different materials, namely shellac (SH), clear thermoplastic acrylic (TP) and self-curing acrylic (SC), during the process of border moulding. Changes were measured in upper and lower trays immediately after manufacture, following storage for 24 h, directly following border moulding and 1, 2 and 14 days after moulding.

The trays were manufactured on a metal master model on which nine reference points for the upper tray and eight for the lower were measured by means of a measuring microscope. The dimensional changes relative to the master model were calculated. Self-curing acrylic and thermoplastic trays proved to be stable during the process of border moulding. The lower impression trays of shellac suffered appreciable shrinkage and were considered unreliable.