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In the latter part of the 20th century, remarkable developments in new dental materials and technologies were achieved. However, regarding the impact of dental resin-based materials 3D-printed on cellular responses, there have been a limited number of published studies recently. The biocompatibility of dental restorative materials is a controversial topic, especially when discussing modern manufacturing technologies. Three-dimensional printing generates the release of residual monomers due to incomplete polymerization of materials and involves the use of potentially toxic substances in post-printing processes that cannot be completely eliminated. Considering the issue of biocompatibility, this article aims to establish an overview of this aspect, summarizing the different types of biocompatibility tests performed on materials used in 3D printing in dentistry. In order to create this comprehensive review, articles dealing with the issue of 3D printing in dentistry were analysed by accessing the main specialized search engines using specific keywords. Relevant data referring to types of materials used in 3DP to manufacture various dental devices, polymerization methods, factors affecting monomer release, cytotoxicity of unreacted products or post-curing treatments, and methods for assessing biocompatibility were analysed. Although the introduction of new restorative materials used in dental treatments is subject to national and international regulations and standards, it is necessary to investigate them regarding biocompatibility in order to support or deny the manufacturers' statements regarding this aspect. [ABSTRACT FROM AUTHOR]

Dendrimer/methyl methacrylate co-polymers were studied for use in dental composites. The aim was to determine the effects of methyl methacrylate concentration in the resin mixture and polymerization method on the degree of conversion and residual monomer content of the co-polymers. Two dendrimers were studied, D12 with 12 reactive methacrylate groups and D24 with 24 reactive groups. The concentration of methyl methacrylate varied from 20 wt% to 50 wt% of monomers. Camphorquinone (CQ) was used as the light-activation initiator and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) as the activator, both in the quantity of 3.0 wt%. Three polymerization methods were used: photo-polymerization, photo-polymerized immediately followed by post-polymerization at 120°C for 15 min, and photo-polymerization followed by post-polymerization after 7 days. The degree of conversion was determined using FT-IR. Residual monomers were extracted with tetrahydrofuran and methanol and analyzed with HPLC. The highest degrees of conversion were 65 and 62%, and the lowest residual monomer contents 1.0 and 1.5% for D12 and D24, respectively. These were measured after heat-induced post-polymerization. For D12, increasing the proportion of methyl methacrylate decreased the degree of conversion and increased the residual monomer content after photo-polymerization. Post-polymerization enhanced the polymerization of the dendrimer co-polymers in respect of degree of conversion and residual monomer content. The present study suggested that the tested dendrimer/methyl methacrylate co-polymers require heat-induced polymerization to reach the generally accepted levels of degree of conversion and residual monomers. [ABSTRACT FROM AUTHOR]

Full-evaporation head-space gas chromatography is a useful technique for the determination of free monomers and other volatile molecules contained in polymer dispersions. The method has a large working range and good repeatability. The absence of contamination in the syringe and the injection line makes it applicable in gas chromatographs equipped with autosamplers. A detailed description of the method and a comparison with the "traditional" head-space gas chromatographic technique and the liquid-injection technique described in ASTM D 4827-93 are presented. [ABSTRACT FROM AUTHOR]