Does the retention system influence the stability of implant-supported maxillary overdentures? A comparison with fixed and conventional dentures.

PURPOSE: The purpose of this in vitro study was to compare the stability of removable implant-supported maxillary overdentures with fixed complete dentures and conventional dentures. METHODS: Four types of complete dentures were tested: conventional complete dentures; overdentures retained by a male resilient attachment system; overdentures retained by a combination of clip bar and attachment system; and fixed complete dentures. Each group was placed in the posterior and anterior region and the stability was recorded by measuring the vertical displacement of the prosthesis. RESULTS: There was a difference in the vertical movement of the prosthesis according to the type of system. The results showed that the behavior of the overdenture retained by a combination of a clip bar and attachment system is comparable with the stabilization of an implant-retained fixed complete denture. CONCLUSIONS: Overdentures retained by a combination of a clip bar and attachment presented better stability and retention capacity under our experimental conditions, close to that of the positive control (fixed complete denture), with the advantages of removable overdentures.

Changes in protein fractions, trypsin inhibitor and proteolytic activity in the cotyledons of germinating chickpea.

The chickpea seed germination was carried out in 6 days. During the period it was observed a little variation on total nitrogen contents, however the non protein nitrogen was double. A decrease of 19.1 and 20.6% in relation to total nitrogen was observed to the total globulin and albumin fractions, respectively. The gel filtration chromatography on Sepharose CL-6B and SDS-PAGE demonstrated alterations on the distribution patterns of the albumin and total globulin fractions between the initial and the sixth day of germination suggesting the occurrence of protein degradation in the germination process. The assay for acid protease only appeared in the albumin fraction with casein and chickpea total globulin as substrates, whereas the former was more degraded than the latter, however the transformations detected in the protein fractions appear indicated that others enzymes could be acting during the process. The trypsin inhibitor activity had a little drop after six day of germination indicating a possible increase on the digestibility of the proteins.

Peroxidase from peach fruit: thermal stability

Peroxidase from peach fruit was purified 28.9 fold by DEAE-cellulose, Sephadex G-100 and hydroxylapatite chromatography. The purified enzyme showed only one peak of activity with an optimum pH of 5.0 and temperature of 40§C. The calculated activation energy (Ea) for the reaction was 7.97 kcal/mol. The enzyme was heat-labile in the temperature range of 60 to 80§C with a fast inactivation at 80§C. PAGE of the inactivation course at 70§C showed only one band of activity. Different sugars increased the heat stability of the activity in the following order: sucrose>glucose>fructose. Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar concentrations (10 to 40 per cent, w/w) with the Ea for inactivation with sucrose concentration from 0 to 20 per cent (w/w). After inactivation at 70§C the enzyme was able to be reactivated by up to 40 per cent of the initial activity when stored at 30§C

Effect of pH and temperature on the immunogenicity of glycinin (Glycine max L.).

Sensitive immunologic techniques for the detection of alterations that occur in protein antigens were used to evaluate the immunogenicity of soybean glycinin after isolation, heat denaturation and pH alteration. The objective was to determine the effect of these agents on the immunogenic ability of this protein fraction. Immunologic assays performed on heat-denatured glycinin up to 80 degrees C in the presence of antinative glycinin serum demonstrated that glycinin retains its immunogenic properties. Above 90 degrees C this biological property begins to disappear, with protein insolubilization and epitope modification due to the conformational changes imposed by temperature. A reduction in immunogenicity also occurred when glycinin was taken to pH 2.0 (below its pl) and pH 11.00 (above its pl) and exposed to high temperatures in the presence of native antiglycinin serum. From these data one can conclude that, at extreme pH values, intramolecular reactions may occur which, in combination with the structural disorganization caused by high temperatures, may contribute to the reduction of immunogenicity.

Isolation and in vitro hydrolysis of lentil protein fractions by trypsin.

The albumin and globulin fractions from lentil seeds were isolated and characterised by gel filtration. The latter was shown to be homogeneous and the former heterogeneous on PAGE. The amino acid analysis revealed high values of amidic amino acids for both fractions with great differences in the sulphur-containing amino acids. Native albumin, globulin and salt-soluble proteins were markedly resistant to trypsin hydrolysis compared to casein. The SDS-PAGE of native salt-soluble proteins indicated that the globulin fragments (20 to 30 kD) were slowly digested in the presence of albumin. The heating increased the hydrolysis of the proteins in the order: salt-soluble, albumin and globulin. The facilitated hydrolysis of the heated salt-soluble fraction seemed to be due to protein-protein interactions induced by heat.