The Clinical Potential of 3D-Printed Crowns Reinforced with Zirconia and Glass Silica Microfillers

Additive manufacturing trueness and internal fit of crowns in resin modified with a commercially available ceramic composite concentrate

STATEMENT OF PROBLEM

Inorganic fillers can be incorporated into additively manufactured (AM) resins to improve their properties, and a ceramic composite concentrate has been recently marketed for this purpose. However, knowledge on the printability of AM resins modified with this concentrate is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the manufacturing trueness and internal fit of AM crowns in a dental resin modified with a commercially available ceramic composite concentrate.

MATERIAL AND METHODS

A maxillary right first molar typodont tooth was prepared and digitized to design a crown in standard tessellation language (STL) format. This STL file was used to fabricate a total of 30 AM crowns, 10 with a resin with no fillers for interim restorations (AM-I), 10 AM-I resin incorporated with ceramic composite concentrate (AM-IR), and 10 with a ceramic-filled resin intended for definitive restorations (AM-D). The modification of the AM-IR resin was performed by mechanically mixing 30 wt% of a commercially available ceramic composite concentrate into AM-I. An intraoral scanner was used to digitize all crowns, which were then seated on the prepared typodont abutment and rescanned. The manufacturing trueness of each crown was measured in 4 regions (overall, external, intaglio, and marginal) and reported with root mean square (RMS) estimates. The internal gaps were calculated by using a triple scan protocol. The intaglio surface deviations were assessed with the Kruskal-Wallis and Dunn tests, while the remaining data were analyzed with the 1-way analysis of variance and Tukey honestly significant difference tests (α=.05).

RESULTS

AM-IR had the highest overall and external RMS and had higher intaglio RMS than AM-D (P≤.001). AM-I had the lowest marginal RMS (P≤.002). AM-IR had the highest average gap values (P≤.027).

CONCLUSIONS

AM-IR crowns mostly had lower trueness and high internal gaps. However, the differences among the tested materials in fabrication trueness and average gap values were small, and internal gaps were within the previously reported thresholds.

Use of Biomaterials in 3D Printing as a Solution to Microbial Infections in Arthroplasty and Osseous Reconstruction

The incidence of microbial infections in orthopedic prosthetic surgeries is a perennial problem that increases morbidity and mortality, representing one of the major complications of such medical interventions. The emergence of novel technologies, especially 3D printing, represents a promising avenue of development for reducing the risk of such eventualities. There are already a host of biomaterials, suitable for 3D printing, that are being tested for antimicrobial properties when they are coated with bioactive compounds, such as antibiotics, or combined with hydrogels with antimicrobial and antioxidant properties, such as chitosan and metal nanoparticles, among others. The materials discussed in the context of this paper comprise beta-tricalcium phosphate (β-TCP), biphasic calcium phosphate (BCP), hydroxyapatite, lithium disilicate glass, polyetheretherketone (PEEK), poly(propylene fumarate) (PPF), poly(trimethylene carbonate) (PTMC), and zirconia. While the recent research results are promising, further development is required to address the increasing antibiotic resistance exhibited by several common pathogens, the potential for fungal infections, and the potential toxicity of some metal nanoparticles. Other solutions, like the incorporation of phytochemicals, should also be explored. Incorporating artificial intelligence (AI) in the development of certain orthopedic implants and the potential use of AI against bacterial infections might represent viable solutions to these problems. Finally, there are some legal considerations associated with the use of biomaterials and the widespread use of 3D printing, which must be taken into account.

Evaluating the Translucency, Surface Roughness, and Cytotoxicity of a PMMA Acrylic Denture Base Reinforced with Bioactive Glasses

The colonisation of the surface of removable acrylic dentures by various types of microorganisms can lead to the development of various diseases. Therefore, the creation of a bioactive material is highly desirable. This study aimed to develop a denture base material designed to release bioactive ions into the oral environment during use. Four types of bioactive glasses (BAG)-S53P4, Biomin F, 45S5, and Biomin C-were incorporated into the PMMA acrylic resin, with each type constituting 20 wt.% (10 wt.% non-silanised and 10% silanised) of the mixture, while PMMA acrylic resin served as the control group. The specimens were subsequently immersed in distilled water, and pH measurements of the aqueous solutions were taken every seven days for a total of 38 days. Additionally, surface roughness and translucency measurements were recorded both after preparation and following seven days of immersion in distilled water. The cytotoxicity of these materials on human fibroblast cells was evaluated after 24 and 48 h using Direct Contact and MTT assays. Ultimately, the elemental composition of the specimens was determined through energy-dispersive X-ray (EDX) spectroscopy. In general, the pH levels of water solutions containing BAG-containing acrylics gradually increased over the storage period, reaching peak values after 10 days. Notably, S53P4 glass exhibited the most significant increase, with pH levels rising from 5.5 to 7.54. Surface roughness exhibited minimal changes upon immersion in distilled water, while a slight decrease in material translucency was observed, except for Biomin C. However, significant differences in surface roughness and translucency were observed among some of the BAG-embedded specimens under both dry and wet conditions. The composition of elements declared by the glass manufacturer was confirmed by EDX analysis. Importantly, cytotoxicity analysis revealed that specimens containing BAGs, when released into the environment, did not adversely affect the growth of human gingival fibroblast cells after 48 h of exposure. This suggests that PMMA acrylics fabricated with BAGs have the potential to release ions into the environment and can be considered biocompatible materials. Further clinical trials are warranted to explore the practical applications of these materials as denture base materials.

Biomaterials Adapted to Vat Photopolymerization in 3D Printing: Characteristics and Medical Applications

Along with the rapid and extensive advancements in the 3D printing field, a diverse range of uses for 3D printing have appeared in the spectrum of medical applications. Vat photopolymerization (VPP) stands out as one of the most extensively researched methods of 3D printing, with its main advantages being a high printing speed and the ability to produce high-resolution structures. A major challenge in using VPP 3D-printed materials in medicine is the general incompatibility of standard VPP resin mixtures with the requirements of biocompatibility and biofunctionality. Instead of developing completely new materials, an alternate approach to solving this problem involves adapting existing biomaterials. These materials are incompatible with VPP 3D printing in their pure form but can be adapted to the VPP chemistry and general process through the use of innovative mixtures and the addition of specific pre- and post-printing steps. This review's primary objective is to highlight biofunctional and biocompatible materials that have been adapted to VPP. We present and compare the suitability of these adapted materials to different medical applications and propose other biomaterials that could be further adapted to the VPP 3D printing process in order to fulfill patient-specific medical requirements.