Abstract
The wide application of additive manufacturing in dentistry implies the further investigation into oral micro-organism adhesion and biofilm formation on vat-photopolymerization (VP) dental resins. The surface characteristics and microbiological analysis of a VP dental resin, printed at resolutions of 50 μm (EG-50) and 100 μm (EG-100), were evaluated against an auto-polymerizing acrylic resin (CG). Samples were evaluated using a scanning electron microscope, a scanning white-light interferometer, and analyzed for Candida albicans (CA) and Streptococcus mutans (SM) biofilm, as well as antifungal and antimicrobial activity. EG-50 and EG-100 exhibited more irregular surfaces and statistically higher mean (Ra) and root-mean-square (rms) roughness (EG-50-Ra: 2.96 ± 0.32 µm; rms: 4.05 ± 0.43 µm/EG-100-Ra: 3.76 ± 0.58 µm; rms: 4.79 ± 0.74 µm) compared to the CG (Ra: 0.52 ± 0.36 µm; rms: 0.84 ± 0.54 µm) (p < 0.05). The biomass and extracellular matrix production by CA and SM and the metabolic activity of SM were significantly decreased in EG-50 and EG-100 compared to CG (p < 0.05). CA and SM growth was inhibited by the pure unpolymerized VP resin (48 h). EG-50 and EG-100 recorded a greater irregularity, higher surface roughness, and decreased CA and SM biofilm formation over the CG.
Highlights
The oral cavity is constituted of a complex and diverse microbiota that influences oral and systemic health [1], such as Streptococcus mutans, a major cariogenic bacterial species [2], and Candida albicans, a fungal species able to act as an opportunistic pathogen leading to mucosal and disseminated infections [3] under conditions that trigger the imbalance of the oral and immune system homeostasis [4,5,6]
Products manufactured with threedimensional (3D) printing have become popular in dentistry, being increasingly used due to the ease of acquisition, processing, and manipulation of the images obtained through intraoral scanning [8,9]
Digital-light-processing (DLP) technology is one of the first 3D-printing processes, which is categorized according to ISO/ASTM 52900/15(E) as a vat-photopolymerization (VP) process, wherein the photopolymerizable liquid is selectively cured by light projection of the object to be printed through a small projector or mirrors that display a single image at one time [13]
Summary
The oral cavity is constituted of a complex and diverse microbiota that influences oral and systemic health [1], such as Streptococcus mutans, a major cariogenic bacterial species [2], and Candida albicans, a fungal species able to act as an opportunistic pathogen leading to mucosal and disseminated infections [3] under conditions that trigger the imbalance of the oral and immune system homeostasis [4,5,6]. The additive-manufacturing technologies: vat-photopolymerization, power bed fusion, binder jetting, material extrusion, direct energy deposition, material jetting and sheet lamination enable the application to substrates such as polymers, metals and ceramics, yielding different results regarding accuracy, precision and trueness, providing diverse and wide applications [10,11,12]. Digital-light-processing (DLP) technology is one of the first 3D-printing processes, which is categorized according to ISO/ASTM 52900/15(E) as a vat-photopolymerization (VP) process, wherein the photopolymerizable liquid is selectively cured by light projection of the object to be printed through a small projector or mirrors that display a single image at one time [13]. Each layer is photoactivated so that the resolution of the item to be printed is directly related to the number of projectors and mirrors used in the technique. At each activation, solid layers of small cubic blocks, referred to as voxels, originate from the interaction of the light with the resin of origin, until the object is completely formed [10,14,15,16,17]
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