Effects of systematically varied thiourethane-functionalized filler concentration on polymerization behavior and relevant clinical properties of dental composites

Effect of thiourethane on the polymerization and mechanical properties of composite resin: A systematic review

STATEMENT OF PROBLEM

Thiourethane has high chemical affinity with polymeric materials and its addition has been suggested for improving adhesives and composite resin. However, a systematic review of thiourethane addition is lacking.

PURPOSE

The purpose of this systematic review was to analyze the articles in the dental literature that studied the effect of thiourethane added to the resin matrix of dental materials related to polymerization shrinkage and mechanical properties.

MATERIAL AND METHODS

The systematic review was prepared in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines and was registered in the Open Science Framework (osf.io/sb9my). The population, intervention, comparison, outcome, and study design (PICOS) were the following: composite resin, thiourethane addition, composite resin without addition, evaluation of polymerization and mechanical properties, and in vitro experimental studies. Initially, 204 articles were found, 150 of which were excluded because of duplication. After reading the titles and abstracts based on the application of eligibility criteria, 21 articles were selected for reading in full, and all were included in the systematic review. Three reviewers evaluated the articles independently in 2 phases based on the eligibility criteria (selection of the title and reading of the article in full), with the reviewers' doubts and discrepancies being analyzed and resolved in a meeting with the authors.

RESULTS

Most of the articles reported a significant improvement in the polymerization shrinkage and mechanical properties of experimental polymeric materials with the addition of oligomers.

CONCLUSIONS

Thiourethane added to resin dental materials improved their polymerization shrinkage values and mechanical properties.

The Effect of Ash Silanization on the Selected Properties of Rigid Polyurethane Foam/Coal Fly Ash Composites

According to the assumptions of the European Union, by 2050 it is planned to achieve climate neutrality. For this purpose, a document called the “European Green Deal” was established, which is a set of policies of the European Commission. One of the assumptions is a circular economy that takes into account the use of waste in subsequent production cycles. In order to meet the latest trends in environmentally friendly materials and use of waste in the production of building materials, composites of rigid polyurethane foam with 10 wt.% of waste were produced. Fly ash from coal combustion after modification was used as a filler. Three types of modifications were used: silanization, sieving, and both processes together. The silanization process was carried out for 1 and 2% silane ([3-(2-aminoethylamino)propyl]trimethoxysilane) concentration in relation to the fly ash mass. The sieving was aimed at reaching a fraction with a particle diameter below 75 µm. Six composites with modified fillers were compared and one material containing unchanged fly ash was used as a reference. A comparative analysis was carried out on the basis of surface analysis, thermal stability and physical properties. It turned out that the polyurethane materials modified fly ash silanized with 1% and 2% silane solution proved the best results in performed tests. On the other hand, the polyurethane foam containing sieved ash was characterized by the lowest flammability and the lowest emission of smoke and CO. The use of modified fly ash in technology of polyurethane foams can be a good method of its disposal and can increase the applicability of the composites.