Materials and Applications of 3D Printing Technology in Dentistry: An Overview

Marginal and internal adaptation and absolute marginal discrepancy of 3D-printed, milled, and prefabricated crowns for primary molar teeth: an in vitro comparative study

BACKGROUND

The quality of marginal and internal adaptation plays a crucial role in the clinical longevity of pediatric crowns. This study aimed to evaluate the effect of restoration type (3D-printed, milled, and prefabricated) on the marginal and internal adaptation and absolute marginal discrepancy (AMD) values of crowns for primary molar teeth.

METHODS

Three restoration groups were created: 3D-printed resin, milled resin-matrix ceramic, and prefabricated zirconia crowns (n = 10 per group). A typodont tooth was prepared according to the guidelines for prefabricated zirconia crowns and scanned to design restorations. 3D-printed and milled crowns were fabricated from the same design. All crowns were cemented on standardized 3D-printed resin dies with self-adhesive resin cement. Marginal and internal adaptation and AMD values were evaluated using micro-computed tomography (micro-CT) at multiple measurement points. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey HSD tests, with statistical significance set at P < 0.05.

RESULTS

The restoration type significantly influenced the marginal and internal gap and AMD values (P < 0.05). The prefabricated crown group exhibited the highest marginal gap (233.5 ± 33.4 μm) and internal gap (538.6 ± 47.4 μm). The 3D-printed group showed the highest AMD value (299.5 ± 70.2 μm). The milled group demonstrated the lowest gap values, which remained within clinically acceptable limits.

CONCLUSIONS

Prefabricated zirconia crowns displayed the highest marginal and internal gaps, whereas milled crowns exhibited the most favorable adaptation values within clinically acceptable limits. Given their superior adaptation, CAD-CAM-produced restorations may be a recommendable alternative for pediatric patients.

Analysis of Surface Roughness and Strain Durability of Eyeglasses Frames by the 3D Printing Technology

Three-dimensional (3D) printer technology has developed rapidly in recent years and therefore has become the focus of attention in many areas. It has begun to be widely used in many areas in industry, medicine, biomedical, engineering, basic sciences, etc. Among these areas, the optician sector has also widely used 3D technology. Offering personalized eyeglass frame design, freedom of color, shape, and size in frames, 3D technology offers many advantages and conveniences for users and manufacturers. In this project, a 3D printer with high precision and consistency was developed, and eyeglass frames were designed and produced using acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG) filament types, different printing temperatures, and layer thicknesses. The surface roughness and the durability of the frames were analyzed by using an optical microscope and performing bending tests, respectively. It was observed that the lowest roughness occurred in the ABS-printed frame with 0.20 mm layer thickness at 240 °C temperature, and the highest durability of 54.7 mε obtained with the ABS-printed frames fabricated with 0.20 mm layer thickness at 235 °C temperature. Average roughness (R a), root-mean-square roughness (R q), and maximum height of profile (R z ) parameters were obtained to analyze surface roughness with respect to temperature change for fabricated frames using ABS and PETG filaments. Thus, the study proves that the production and optimization of customized eyeglass frames can be used not only for commercial and educational purposes in optical stores and optician programs at universities but also in industry, engineering, and daily life purposes.

Comparison of fit and trueness of single-unit and short-span fixed dental restorations fabricated by additive and subtractive manufacturing-A systematic review and meta-analysis

OBJECTIVES

Numerous studies have been conducted on the adaptation of dental restorations fabricated by additive (AM) and subtractive manufacturing (SM); however, the results are conflicting. This systematic review and meta-analysis aimed to evaluate the fit and trueness of fixed restorations made by AM compared to SM.

DATA

Studies investigating internal fit, marginal fit, and trueness of fixed prostheses were involved.

SOURCES

The protocol was registered in PROSPERO (registration number CRD42022323090). An electronic search was performed with a predefined search query across four medical databases on the 6th of September 2023.

STUDY SELECTION

A total of 57 eligible studies were included and sub-grouped by material type (metals, ceramics, acrylic resins, composites). The outcomes were specified as internal fit, marginal fit, and trueness expressed in micrometer (µm). Further subgrouping was based on measurement area: axial, occlusal, and marginal. When we analyzed marginal fit, there were no statistically significant differences between the two techniques in any of the subgroups. The measurement of internal fit metal and ceramic restorations provided no significant differences. However, milled acrylic resin restorations showed a significantly higher occlusal gap compared to 3D printed prostheses with 39.12 µm (95 % CI: 12.44; 65.79). In the case of trueness, a statistically significant difference was observed between ceramic AM and SM restorations with -47.76 µm (95 % CI: -95.51; -0.00). QUIN and GRADE Pro tools were used to evaluate the risk of bias and certainty of evidence.

CONCLUSION

Fixed restorations manufactured with additive manufacturing are valid alternatives to subtractive manufacturing in the digital workflow.

CLINICAL SIGNIFICANCE

Additive manufacturing is an accurate and cost-effective manufacturing method of digital workflow, especially for metal and resin fixed restorations. Once the challenges in ceramics manufacturing are addressed, AM will show more significant promise in the field.

A Novel Approach of Administering Cranberry Extract Into 3D-Printed Denture Bases for the Prevention of Denture-Induced Stomatitis: An Observational Study

BACKGROUND

Complete dentures play an important role in restoring oral function and aesthetics, yet they may contribute to denture stomatitis, necessitating improved materials and hygiene practices. Cranberry extract, known for its antifungal properties, presents a promising avenue for preventing stomatitis when incorporated into novel denture materials.

AIMS AND OBJECTIVES

This research aimed to assess the efficiency of cranberry extract-infused stereolithography (SLA) 3D-printable resins in preventing denture-induced stomatitis and compare their mechanical properties with conventional heat-cured denture base polymers.

MATERIALS AND METHODS

Fifteen patients aged 45 to 60 with completely edentulous maxillary and mandibular arches received two sets of dentures: control dentures made from heat-activated polymethyl methacrylate (PMMA) and treatment dentures made from cranberry-infused 3D-printed resin. Candidal colony-forming units (CFUs) and confocal microscopy were used to assess biofilm formation on 30 samples. For the evaluation of mechanical properties, 30 samples were made in each group, and the flexural strength and fracture toughness were examined for both the control and test groups.

RESULTS

Significantly fewer CFUs were observed in 3D-printed dentures compared to PMMA dentures at 104 concentrations (p=0.03). Biofilm thickness was significantly lower in 3D-printed dentures (p=0.039), but volume fraction biofilm exhibited no discernible change (p>0.05). Surface coverage was significantly reduced in 3D-printed dentures (p=0.028). Flexural strength was higher in 3D-printed samples (124.25±2.67 MPa) compared to PMMA (109.76±9.35 MPa), with a statistically significant difference. Fracture toughness was also significantly higher in 3D-printed dentures (1.60±0.12) compared to PMMA (1.38±0.95) (p=0.028).

CONCLUSION

Cranberry-infused 3D-printable resins demonstrate promise in dropping Candida adhesion and biofilm formation, potentially lowering the risk of denture stomatitis. Moreover, these resins exhibit superior mechanical properties compared to conventional denture base polymers, suggesting a potential alternative for prosthodontic applications.

Recent Progress in PDMS-Based Microfluidics Toward Integrated Organ-on-a-Chip Biosensors and Personalized Medicine

The organ-on-a-chip (OoC) technology holds significant promise for biosensors and personalized medicine by enabling the creation of miniature, patient-specific models of human organs. This review studies the recent advancements in the application of polydimethylsiloxane (PDMS) microfluidics for OoC purposes. It underscores the main fabrication technologies of PDMS microfluidic systems, such as photolithography, injection molding, hot embossing, and 3D printing. The review also highlights the crucial role of integrated biosensors within OoC platforms. These electrochemical, electrical, and optical sensors, integrated within the microfluidic environment, provide valuable insights into cellular behavior and drug response. Furthermore, the review explores the exciting potential of PDMS-based OoC technology for personalized medicine. OoC devices can forecast drug effectiveness and tailor therapeutic strategies for patients by incorporating patient-derived cells and replicating individual physiological variations, helping the healing process and accelerating recovery. This personalized approach can revolutionize healthcare by offering more precise and efficient treatment options. Understanding OoC fabrication and its applications in biosensors and personalized medicine can play a pivotal role in future implementations of multifunctional OoC biosensors.

Three-Dimensional-Printed Photopolymer Resin Materials: A Narrative Review on Their Production Techniques and Applications in Dentistry

Additive manufacturing (3D printing) has transformed dentistry by providing solutions with high precision and accuracy achieved through digital workflows, which facilitate the creation of intricate and personalized structures. Additionally, 3D printing promotes cost efficiency by reducing material waste and errors while enabling on-demand production, minimizing the need for extensive inventories. Recent advancements in 3D-printed resin materials have enhanced their clinical applications by improving mechanical strength, biocompatibility, esthetics, and durability. These innovations have facilitated the fabrication of complex and patient-specific structures, such as dental prostheses, surgical guides, and orthodontic appliances, while significantly reducing production time and material waste. Ongoing research and innovation are expected to strengthen resin properties, including strength, translucency, and durability, broadening their clinical applications. The ongoing evolution of 3D printing technology is poised to play a critical role in driving personalized treatments, streamlining clinical workflows, and shaping the future of dental care. This narrative review comprehensively examines the production techniques and clinical applications of 3D-printed photopolymer resins across various dental specialties, including prosthodontics, orthodontics, pediatric dentistry, maxillofacial surgery, periodontology, endodontics, and conservative dentistry. Additionally, the review provides insight into the transformative impact of these technologies on patient care, highlights existing challenges, and suggests future directions for advancing resin properties and their integration into routine dental practice.

Polycarbonate-Acrylonitrile Butadiene Styrene Three Dimensional Printing Material Exhibits Biocompatibility and Enhances Osteogenesis and Gingival Tissue Formation with Human Cells

Three dimensional (3D) printing materials are widely used in dental applications, but their biocompatibility and interactions with human cells require evaluation. This study aimed to identify materials meeting biocompatibility, mechanical strength, and tissue-forming requirements for safe dental applications. We assessed the cytotoxicity of resins and thermoplastic filaments in human HaCaT keratinocytes, gingival fibroblasts (hGFs), and stem cells from human exfoliated deciduous teeth (SHED) using PrestoBlue assays. Three resins, including two types of surgical guide resins, exhibited strong cytotoxicity after 4-72 h, while 2 h exposure to an FDA-approved surgical guide resin did not affect SHED cell viability. In contrast, six thermoplastic filaments showed no significant cytotoxicity even after 72 h. Among these, polycarbonate-acrylonitrile butadiene styrene (PC-ABS) demonstrated excellent toughness, heat resistance, and surface quality at a low cost. SHED cells cultured on PC-ABS dishes and micro bone structures showed strong proliferation and osteogenic potential. Culture inserts made of PC-ABS also supported the growth of HaCaT keratinocytes and the hGFs formed gingival tissue, which was superior to that formed on commercially available PET inserts. In conclusion, PC-ABS is a promising 3D printing material for dental applications due to its biocompatibility, ability to promote osteogenesis, and support for gingival tissue formation, with no observed cytotoxicity.

An update on CAD-CAM usage for removable partial denture fabrication: A systematic review

The accuracy of Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) systems in the fabrication of removable partial denture (RPD) frameworks compared to conventional manufacturing methods is of interest to dentists. Known data show that CAD-CAM systems produce RPD frameworks with superior fit and adaptation, potentially reducing post-insertion adjustments and enhancing patient satisfaction. The importance of digital impressions, advanced CAD software and the capabilities of milling or 3D printing equipment in determining the success of CAD-CAM fabricated frameworks is highlighted. Despite promising results, further research is needed to evaluate the long-term clinical performance of CAD-CAM systems in RPD fabrication and to address the existing limitations.

Polymeric Materials Used in 3DP in Dentistry-Biocompatibility Testing Challenges

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.

Biomechanical research using advanced micro-nano devices: In-Vitro cell Characterization focus

BACKGROUND

Cells in the body reside in a dynamic microenvironment subjected to various physical stimuli, where mechanical stimulation plays a crucial role in regulating cellular physiological behaviors and functions.

AIM OF REVIEW

Investigating the mechanisms and interactions of mechanical transmission is essential for understanding the physiological and functional interplay between cells and physical stimuli. Therefore, establishing an in vitro biomechanical stimulation cell culture system holds significant importance for research related to cellular biomechanics.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we primarily focused on various biomechanically relevant cell culture systems and highlighted the advancements and prospects in their preparation processes. Firstly, we discussed the types and characteristics of biomechanics present in the microenvironment within the human body. Subsequently, we introduced the research progress, working principles, preparation processes, potential advantages, applications, and challenges of various biomechanically relevant in vitro cell culture systems. Additionally, we summarized and categorized currently commercialized biomechanically relevant cell culture systems, offering a comprehensive reference for researchers in related fields.

Physicochemical Properties and Bacterial Adhesion of Conventional and 3D Printed Complete Denture PMMA Materials: An In Vitro Study - Part I

AIM

To evaluate and compare the surface morphology, wettability, roughness, and bacterial adhesion properties of polymethyl methacrylate (PMMA) materials fabricated by conventional methods and 3D printing for complete denture applications.

MATERIALS AND METHODS

Two PMMA materials were investigated: Conventionally processed (ProBase Hot) and 3D-printed (3DP) (V-Print Dentbase). Surface morphology (n = 3) was analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Surface roughness (n = 10) was measured using an optical profilometer. Wettability was assessed through contact angle measurements (n = 6) at 10, 30, and 60 seconds. Bacterial adhesion (n = 9) and biofilm formation (n = 3) were evaluated using Escherichia coli (E. coli) as a model organism, with quantitative bacterial counts and SEM analysis of bacterial morphology. Data were statistically analyzed.

RESULTS

Scanning electron microscopy analysis revealed nanoparticles on the surface of 3DP samples, while EDX detected silicon in these samples, absent in conventional PMMA. 3D-printed surfaces exhibited significantly lower roughness (1.05 ± 0.32 µm) compared to conventional surfaces (20.46 ± 6.71 µm) (p < 0.001). Contact angle measurements showed that 3DP surfaces were more hydrophilic (64-68°) than conventional surfaces (100°) (p < 0.05). Bacterial adhesion studies demonstrated more adherent bacteria on 3DP surfaces (92.5 ± 30.8) compared to the conventional surfaces (57.6 ± 12.5), but biofilm formation was observed only on conventional surfaces.

CONCLUSION

3D-printed PMMA exhibited distinct surface characteristics compared to conventionally processed PMMA, including the presence of silicon nanoparticles, lower surface roughness, and higher hydrophilicity. While 3DP surfaces showed higher initial bacterial adherence, in contrast, they appeared to inhibit biofilm formation, which highlights the complex nature of bacterial interactions with these materials.

CLINICAL SIGNIFICANCE

Further clinical studies are needed to validate the results of this investigation and generate clinical translational data. How to cite this article: Khoury P, Kharouf N, Etienne O, et al. Physicochemical Properties and Bacterial Adhesion of Conventional and 3D Printed Complete Denture PMMA Materials: An In Vitro Study - Part I. J Contemp Dent Pract 2024;25(11):1001-1008.

Impact of printing layer thickness on the flexural strength of nanocomposite 3D printed resins: An in vitro comparative study

Background

This study evaluated the influence of various printing layer thicknesses with silicon dioxide nanoparticles (SiO2NPs) incorporated as a reinforcement material on the flexural strength of 3D-printed denture base resins.

Material and Methods

Asiga (DentaBASE, Asiga, Erfurt, Germany) and NextDent (Denture 3D+, NextDent B.V., Soesterberg, The Netherlands) 3D-printed resins were modified with different concentrations of SiO2NPs (0.25 % and 0.5 wt%). A total of 180 specimens (bar-shaped, 64 × 10 × 3.3 mm) were fabricated (N = 90/resin). Each resin was subdivided into three groups (n = 30) according to the SiO2NP concentration (0 %, 0.25 %, and 0.5 wt%) Each concentration was divided into three groups (n = 10) according to the printing layer thickness (50 µm, 75 µm, and 100 µm). Specimens were printed according to the manufacturer's instructions and then subjected to 10,000 thermal cycles. A three-point bending test was used to measure the flexural strength (MPa). One-way analysis of variance (ANOVA) and Tukey's post hoc tests were used to analyze the data (α = 0.05).

Results

For both resins, printing layer thicknesses of 50 µm and 75 µm exhibited significantly higher flexural strength than 100 µm (P < 0.001). The 50 µm thickness showed the greatest flexural strength values (81.65 ± 4.77 MPa and 84.59 ± 6.21 MPa for Asiga and NextDent, respectively). The 100 µm thickness showed the lowest flexural strength values (74.35 ± 5.37 and 73.66 ± 5.55 MPa) for Asiga and NextDent, respectively. The flexural strength significantly increased with the addition of SiO2NPs with printing layer thicknesses of 50 µm and 75 µm (P < 0.001), whereas the modified and unmodified groups printed with a 100 µm layer thickness did not differ significantly. Asiga 0.25 %/50 µm and NextDent 0.5 %/50 µm showed the highest flexural strength values (97.32 ± 6.82 MPa and 97.54 ± 7.04 MPa, respectively). Scanning electron microscopy fractured surfaces analysis revealed more lamellae and irregularities with lower printing layer thicknesses and SiO2NP concentrations.

Conclusion

The flexural strength increased with printing layer thicknesses of 50 µm or 75 µm combined with SiO2NP reinforcement.

3D printed full-arch versus digital reference dental models: A systematic review

The present systematic review and meta-analysis aimed to evaluate and compare the accuracy of different 3D printing techniques used for fabricating full-arch dental models against digital reference models. The review included studies that assessed the accuracy of stereolithography (SLA), digital light processing (DLP), PolyJet and fused filament fabrication (FFF) technologies. A total of seven studies were analyzed, providing insights into the trueness and precision of 3D-printed models. The findings reveal that while all examined 3D printing technologies produced models with clinically acceptable accuracy, DLP and PolyJet techniques consistently demonstrated superior precision and trueness compared to SLA and FFF. The results indicate that DLP and PolyJet technologies are particularly suitable for applications requiring high dimensional fidelity, such as in Prosthodontics. However, the studies also highlighted some limitations, including small sample sizes and variations in study design, which may impact the generalizability of the results. Future research should focus on large-scale clinical trials and explore the impact of post-processing on model accuracy. This review underscores the importance of selecting appropriate 3D printing technologies based on clinical requirements to ensure optimal outcomes in dental prosthetics.

The Applications of 3D-Printing Technology in Prosthodontics: A Review of the Current Literature

Prosthodontics has become increasingly popular because of its cosmetic attractiveness. 3D printing has revolutionized prosthodontics, enabling the creation of high-quality dental prostheses. It creates detailed restorations, such as crowns, bridges, implant-supported frameworks, surgical templates, dentures, and orthodontic models. In addition, it saves production time but faces challenges such as elevated expenses and the requirement for innovative materials and technologies. This review gives insights into the uses of 3D printing in prosthodontics, presenting how it has significantly changed clinical practices. This article discusses different materials and techniques. Additionally, it showcases the capacity of 3D printing to improve prosthodontic practice and proposes prospects for future investigation.

Step-by-Step Implementation of Three-Dimensional Print Technology in Preoperative Neurosurgery Planning

This study presents a detailed methodology for integrating three-dimensional (3D) printing technology into preoperative planning in neurosurgery. The increasing capabilities of 3D printing over the last decade have made it a valuable tool in medical fields such as orthopedics and dental practices. Neurosurgery can similarly benefit from these advancements, though the creation of accurate 3D models poses a significant challenge due to the technical expertise required and the cost of specialized software. This paper demonstrates a step-by-step process for developing a 3D physical model for preoperative planning using free, open-source software. A case involving a 62-year-old male with a large infiltrating tumor in the sacrum, originating from renal cell carcinoma, is used to illustrate the method. The process begins with the acquisition of a CT scan, followed by image reconstruction using InVesalius 3, an open-source software. The resulting 3D model is then processed in Autodesk Meshmixer (Autodesk, Inc., San Francisco, CA), where individual anatomical structures are segmented and prepared for printing. The model is printed using the Bambu Lab X1 Carbon 3D printer (Bambu Lab, Austin, TX), allowing for multicolor differentiation of structures such as bones, tumors, and blood vessels. The study highlights the practical aspects of model creation, including artifact removal, surface separation, and optimization for print volume. It discusses the advantages of multicolor printing for visual clarity in surgical planning and compares it with monochromatic and segmented printing approaches. The findings underscore the potential of 3D printing to enhance surgical precision and planning, providing a replicable protocol that leverages accessible technology. This work supports the broader adoption of 3D printing in neurosurgery, emphasizing the importance of collaboration between medical and engineering professionals to maximize the utility of these models in clinical practice.

Special Issue "Recent Process Design and Development Strategies for Dental Materials"

The field of dental materials is rapidly evolving, and this Special Issue of the International Journal of Molecular Sciences offers a comprehensive examination of the latest advancements in process design and development strategies [...].

Advancements in Dental Care: The Evolving Landscape of Prosthetic Dentistry

In the dental field, the specialty of prosthodontics stands out as the frontline of innovation, continually pushing the boundaries to enhance both function and aesthetics for optimal oral rehabilitation [...].