Abstract The aim of this study was to evaluate the degree of conversion (DC) and the thermal stability of bulk-fill and conventional composite resins. Eleven composite resin samples were prepared to evaluate the DC, Vickers microhardness (VMH), mass and residue/particle loss, glass transition temperature (Tg), enthalpy, and linear coefficient of thermal expansion (CTE) using infrared spectroscopy (FTIR), microdurometer analyses, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dilatometry (DIL). The data were subjected to statistical analysis, with a significance level of 95%. DC and VMH were not influenced by the polymerized side of the sample, and statistical differences were recorded only among the materials. Decomposition temperature, melting, and mass and residue loss were dependent on the material and on the evaluation condition (polymerized and non-polymerized). Tg values were similar between the composites, without statistically significant difference, and CTE ranged from 10.5 to 37.1 (10-6/°C), with no statistical difference between the materials. There was a moderate negative correlation between CTE and the % of load particles, by weight. Most resins had a DC above that which is reported in the literature. TGA, Tg, and CTE analyses showed the thermal behavior of the evaluated composites, providing data for future research, assisting with the choice of material for direct or semidirect restorations, and helping choose the appropriate temperature for increasing the DC of such materials.

Abstract The aim of this study was to evaluate the cytotoxic effect, degree of conversion (% DC), Vickers hardness (VH), and surface morphology of composite resins. Eleven resins, nine bulk-fill resins, and two conventional resins were evaluated. Each material was sampled to evaluate DC (using FTIR), VH, cytotoxicity (using MTT and Neutral Red - NR test), surface morphology (using SEM and AFM), and organic filler (using EDS). All statistical tests were performed with SPSS and the level of significance was set at 0.05. MTT revealed that the materials presented low or no cytotoxic potential in relation to the control. Opus was the resin with the lowest cell viability at a 1:2 concentration at 72 h (32%) and at 7 days (43%), but that significantly increased when the NR test was applied at a 1:2 concentration after 7 days. Thickness and surface subjected to polymerization had no influence on DC, and differences were observed only between the materials. In the microhardness test, statistical differences were observed between the evaluated thicknesses. The bulk-fill resins analyzed in this study exhibited low and/or no cytotoxicity to L929 cells, except for Opus, which showed moderate cytotoxicity according to the MTT assay. When the NR test was used, results were not satisfactory for all composites, indicating the need for different methodologies to evaluate the properties of these materials. The assessed resins demonstrated acceptable physicomechanical properties.

RESUMO O avanço da tecnologia dos biomateriais permite desenvolver materiais que auxiliam nos processos reconstrutivos de partes do corpo e incrementam tratamentos e melhora a qualidade de vida dos seres humanos. O Polihidroxibutirato (PHB) é um polímero biocompatível, biodegradável, muito estudado para aplicações médicas e suas propriedades ainda podem ser adequadas para outras diversas aplicações com a incorporação da hidroxiapatita (HA). Esta é uma carga inorgânica biocompatível e bioativa já presente nos tecidos ósseos do organismo. Desta forma, este trabalho teve como objetivo obter membranas composta por PHB e HA para utilização como biomaterial em regeneração tecidual óssea e guiada. Para obtenção das membranas, o PHB foi processado em uma extrusora monorosca de bancada AX-Plásticos (16-mm), com Razão LD=26, a uma taxa de compressão de 1,5, específica para produção de filmes planos. Foram confeccionadas membranas de PHB puro, e os compósitos de PHB com 1%, 2% e 3% de HA. Após obtenção das membranas, as mesmas foram caracterizadas por Difração de raios X (DRX), Microscopia Eletrônica de Varredura (MEV) / Espectroscopia por Energia Dispersiva (EDS), Citotoxicidade e Molhabilidade. Nos difratogramas foi possível observar um perfil de material semicristalino e que a adição da HA diminuiu esse perfil. Nas micrografias foi visualizada uma superfície de um material denso e rugoso. Já no EDS foi evidenciado os elementos químicos presentes no PHB e na HA. O ensaio de citotoxicidade confirmou a viabilidade e consequentemente a biocompatibilidade do material obtido. Já o ensaio de Molhabilidade confirmou o caráter hidrofílico das membranas. Fundamentado nesses resultados, pode-se concluir que a metodologia para obtenção das membranas foi eficaz, sendo as mesmas biocompatíveis e que a quantidade da carga vai depender da indicação de uso do biomaterial em questão.

ABSTRACT The advancement of biomaterials technology allows the development of materials that assist in reconstructive procedures of the body parts and increase treatment and improves the humans quality of life. The polyhydroxybutyrate (PHB) is a biocompatible polymer, biodegradable, widely studied for medical applications and its properties can also be suitable for other various applications with hydroxyapatite (HA) incorporation. This is a bioactive and biocompatible inorganic filler already present in bone tissues. Thus, this study aimed to obtain membranes composed of PHB and HA for use as biomaterials in bone tissue regeneration and guided. To obtain the membranes, PHB was processed in a single screw extruder AX-Plastics bench (16 mm), with LD Ratio = 26, a compression ratio of 1.5, specific for the production of flat film. Pure PHB membranes were prepared, and composite PHB with 1%, 2% and 3% HA. After obtaining the membranes, they were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) / Energy Dispersive Spectroscopy (EDS) and Cytotoxicity. In the diffraction profile it was observed a semicrystalline material and the addition of HA decreased this profile. In the micrographs it was visualized a surface of a dense and rough material. The EDS evidenced the chemical elements present in the PHB and HA. The cytotoxicity assay confirmed the viability and thus the biocompatibility of the material. The Wettability test confirmed the hydrophilic character of the membranes. Based on these results, we can conclude that the method for obtaining the composite was effective, being biocompatible and the charge amount will depend on the biomaterial usage indication concerned.