Biological and anisotropy of a denture base resin obtained by 3D printing under different angulations and printing systems: DLP and LCD

• Grant number: 22/14657-0
• Support Opportunities: Regular Research Grants
• Start date: November 01, 2023
• End date: October 31, 2025
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Ana Carolina Pero
• Grantee: Ana Carolina Pero
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated researchers: Raphael Freitas de Souza

Abstract

3D printing of dental prostheses is a highly advantageous process compared to conventional techniques. By eliminating steps, reducing costs, increasing accuracy and speed, and reducing waste, additive manufacturing brings numerous improvements to the field. Recently, LCD (liquid crystal display) type printers have been introduced at much lower costs than more established technologies, such as DLP (digital light processing). LCD printers are able to operate with the same resins used for DLP, achieving good properties in some applications, such as orthodontic aligners. However, little is known about their results when used for the manufacture of complete dentures. For example, there are no studies on the interaction between buccal mucosal or microbial cells and resins for denture base obtained by LCD. Parameters such as the printing angle also deserve to be studied for LCD, since the biological interactions of resins printed in DLP, as well as their mechanical and physical properties, can vary. This project has two main objectives. Firstly, it aims to evaluate the cytotoxicity and biofilm formation of Candida albicans in a resin for denture base printed in LCD and DLP, varying the printing angles (0, 45 or 90 degrees). The second main objective will be to compare the same resin obtained by LCD and DLP, at the same angles, in terms of flexural strength, hardness, roughness, surface free energy (ELS) and resistance to staining. Specimens of a denture base resin (Cosmos Denture) will be printed under six conditions (LCD0, LCD45, LCD90, DLP0, DLP45, DLP90) and thermocycled (5,000 cycles, 5º and 55ºC). Cytotoxicity will be tested in human gingival keratinocytes (NOK-SI) using MTT and membrane integrity analysis. Biofilm formation by C. albicans will be performed for 90 min and 48 hours, and measured by counting colony forming units (CFU/mL), cell metabolism (XTT), confocal laser microscopy and scanning electron microscopy. Flexural strength of rectangular specimens will be evaluated by the three-point test, while hardness will be evaluated using a Vickers diamond. The roughness (µm) will be measured according to the Ra and Rz parameters, the ELS in a goniometer (erg cm-2), and the resistance to staining/color stability (”E00), will be evaluated before and after 12 days of immersion in coffee, simulating 1 year of consumption. On the different experimental conditions, specimens will be submitted to Fourier Transform Infrared Spectroscopy (FTIR) to analyze the degree of conversion, Electron Spectroscopy for Chemical Analysis (XPS-ESCA) for surface microstructural analysis, and differential scanning calorimetry (DSC) to determine the glass transition temperature (Tg). Statistical analysis of the data, in accordance with the assumptions of normality and homoscedasticity, will be performed with ±=.05%. Results of this research may support the use of LCD printers to obtain complete dentures, with properties comparable to DLP, or point out limitations to be overcome. This will have great relevance for the area, as LCD printers are much more accessible for use in our country. (AU)