Dental Materials Applied to 3D and 4D Printing Technologies: A Review

Three-Dimensional Printing Resin-Based Dental Provisional Crowns and Bridges: Recent Progress in Properties, Applications, and Perspectives

Three-dimensional (3D) printing represents a pivotal technological advancement in dental prosthetics, fundamentally transforming the fabrication of provisional crowns and bridges through innovative vat photopolymerization methodologies, specifically stereolithography (SLA) and digital light processing (DLP). This comprehensive scholarly review critically examines the technological landscape of 3D-printed resin-based dental provisional crowns and bridges, systematically analyzing their material performance, clinical applications, and prospective developmental trajectories. Empirical investigations demonstrate that these advanced restorations exhibit remarkable mechanical characteristics, including flexural strength ranging from 60 to 90 MPa and fracture resistance of 1000-1200 N, consistently matching or surpassing traditional manufacturing techniques. The digital workflow introduces substantial procedural innovations, dramatically reducing fabrication time while simultaneously achieving superior marginal adaptation and internal architectural precision. Despite these significant technological advancements, critical challenges persist, encompassing material durability limitations, interlayer bonding strength inconsistencies, and the current paucity of longitudinal clinical evidence. Contemporary research initiatives are strategically focused on optimizing resin formulations through strategic filler incorporation, enhancing post-processing protocols, and addressing fundamental limitations in color stability and water sorption characteristics. Ultimately, this scholarly review aims to provide comprehensive insights that will inform evidence-based clinical practices and delineate future research trajectories in the dynamically evolving domain of digital dentistry, with the paramount objective of advancing patient outcomes through technological innovation and precision-driven methodological approaches.

Innovating chitosan-based bioinks for dermal wound healing: Current progress and future prospects

The field of three-dimensional (3D) bio/printing, known as additive manufacturing (AM), heavily relies on bioinks possessing suitable mechanical properties and compatibility with living cells. Among the array of potential hydrogel precursor materials, chitosan (CS) has garnered significant attention due to its remarkable physicochemical and biological attributes. These attributes include biodegradability, nontoxicity, antimicrobial properties, wound healing promotion, and immune system activation, making CS a highly appealing hydrogel-based bioink candidate. This review explores the transformative potential of CS-based bioink for enhancing dermal wound healing therapies. We highlight CS's unique qualities that make it an optimal choice for bioink development. Advancements in 3D bio/printing technology for tissue engineering (TE) are discussed, followed by an examination of strategies for CS-based bioink formulation and their impacts on wound healing. To address the progress in translating advanced wound healing from lab to clinic, we highlight the current and ongoing research in CS-based bioink for 3D bio/printing in skin wound healing applications. Finally, we explore current evidence, commercialization prospects, emerging innovations like 4D printing, and the challenges and future directions in this promising field.

Influence of Material, Sterilization, and Disinfection on the Accuracy of Three-Dimensional Printed Surgical Templates: An In Vitro Study

OBJECTIVES

To evaluate the influence of the three-dimensional (3D) printing technology, material, sterilization, and disinfection on the accuracy of guided surgical templates.

MATERIAL AND METHODS

Fifty printed resin surgical templates were designed and fabricated using a digital light processing 3D printer with a photopolymerizing resin, and 50 printed metal surgical templates were designed and fabricated using a selective laser melting 3D printer with a titanium alloy. Templates from both groups were randomly divided into five subgroups involving different sterilization and disinfection procedures. The group without any sterilization or disinfection procedure served as the control group, whereas the other groups were used as the study groups (hydrogen peroxide gas plasma sterilization, 5% povidone-iodine disinfection, 75% ethyl alcohol disinfection, and steam autoclave sterilization). Implant simulations were performed on the 3D-printed resin models, and postoperative impressions were acquired with scan bodies attached to the implants. All surgical templates were digitally scanned. The root mean square was used to determine and quantify fabrication accuracy and reproducibility, and the definitive and planned implant positions were compared.

RESULTS

The printed resin templates exhibited lower fabrication accuracy and reproducibility, as well as higher 3D deviations, after steam autoclave sterilization (p < 0.001); however, the printed metal templates were not affected by the different sterilization or disinfection procedures (p > 0.05).

CONCLUSIONS

Printed metal surgical templates are viable alternatives for guided implant surgery. Preoperative steam or gas plasma sterilization is recommended, especially for metal templates, as resin templates show deformation and decreased accuracy after steam sterilization.

TRIAL REGISTRATION

chictr.org.cn number: ChiCTR2400081334.

A comprehensive narrative review exploring the current landscape of digital complete denture technology and advancements

This review article comprehensively discusses the various treatment protocols and fabrication methods for complete digital dentures and focuses on systematic classification of the techniques introduced in the literature. The treatment protocols are based on conventional procedures, highlighting the areas where digital technologies can be utilized and their advantages. Particularly, it emphasizes the benefits of overcoming time and spatial limitations, along with advantages of permanent data storage. The limitations of digital technologies and potential solutions are also addressed. Current methods and alternatives for patient information acquisition, a common concern among many dentists, are presented. The fabrication methods are categorized into two main manufacturing techniques: milling and three-dimensional (3D) printing. Under the premise of advanced milling technology and limited printing capabilities, their advantages, disadvantages, and applications are compared. Novel hybrid technologies combining both methods are introduced, including challenging aspects of metal framework integration. By examining the complete digital denture fabrication and treatment process from start to finish, this article aims to discuss the present and future of digitally integrated treatment methods.

Evaluation of Internal and Marginal Accuracy (Trueness and Precision) of Laminates Using DLP Printing and Milling Methods

This study evaluated the internal and marginal accuracy (trueness and precision) of zirconia laminate veneers fabricated using the DLP printing and milling method, employing 3D analysis software program. The maxillary central incisor tooth of a typodont model was prepared by a dentist and scanned using a desktop scanner. An anatomical zirconia laminate was designed using computer-aided design (CAD) software and saved in a standard tessellation language (STL) format. Thirty zirconia laminates were manufactured using a milling machine (MLL group) and a DLP printer (PTL group). All the specimens were scanned, and their internal and marginal areas were edited accordingly. The root-mean-square value was used to assess the accuracy of the internal and marginal areas of the zirconia laminates. Statistical significance was evaluated using the Mann-Whitney U test. Statistically significant differences were found in RMS values for both groups in the internal and marginal areas (p < 0.001 and p = 0.034, respectively). The MLL and PTL groups differed significantly in terms of precision (p = 0.017), but not at the margin (p = 0.361). DLP-printed zirconia laminates demonstrated stable and consistent performance, making the technique a reliable option for producing esthetic prostheses.

Effect of Storage Conditions and Time on the Dimensional Stability of 3D Printed Surgical Guides: An In Vitro Study

PURPOSE

To evaluate the dimensional stability over time of additively manufactured surgical templates, fabricated by different resins, and stored by different methods.

MATERIALS AND METHODS

Using a 3D printer with DLS technology and two different resins (Surgical Guide (SG)-WhipMix and Key Guide (KG)-KeystoneIndustries), 96 surgical guides were additively manufactured. The guides were stored in three different environments: directly exposed to sunlight (S1), in normal interior room conditions (S2), and in darkness (S3). The guides were digitally scanned immediately after fabrication and post-processing, and after 1, 3, and 6 months of storage. For each group, the mean deviation of the root mean square (RMS) between guide's intaglio surface, as well as the axial deviation between sleeves' housings were calculated.

RESULTS

The mean axial variations of angular axis deviation of sleeves' housings ranged between 0.09° and 3.99°. The mean deviation of the RMS discrepancy in guide's intaglio ranged from 0.1 to 0.18 mm. Variations were significant (p < 0.001) only for the S1 group and only for SG material. After 3 months, an additional storage time of 3 months did not have any further effect on dimensional stability.

CONCLUSIONS

Within the limitations of the present study, storage time of a surgical guide for up to 3 months after manufacturing, as well as printing material can significantly affect surgical guide's dimensional stability, when they are exposed to direct or indirect sunlight conditions. Storage of guides in a dark environment is recommended in order to avoid an additional source of error in computer-guided surgery workflows.

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.

Synthesis and evaluation of novel urethane macromonomers for the formulation of fracture tough 3D printable dental materials

3D printing of materials which combine fracture toughness, high modulus and high strength is quite challenging. Most commercially available 3D printing resins contain a mixture of multifunctional (meth)acrylates. The resulting 3D printed materials are therefore brittle and not adapted for the preparation of denture bases. For this reason, this article focuses on toughening by incorporation of triblock copolymers in methacrylate-based materials. In a first step, three urethane dimethacrylates with various alkyl spacer length were synthesized in a one-pot two-step synthesis. Each monomer was combined with 2-phenoxyethyl methacrylate as a monofunctional monomer and a polycaprolactone-polydimethylsiloxane-polycaprolactone triblock copolymer was added as toughener. The formation of nanostructures via self-assembly was proven by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The addition of the triblock copolymer resulted in a strong increase in fracture toughness for all mixtures. The nature of the urethane dimethacrylate had a significant impact on fracture toughness and flexural strength and modulus of the cured materials. Most promising systems were also investigated via dynamic fatigue propagation da/dN measurements, confirming that the toughening also works under dynamic load. By carefully selecting the length of the urethane dimethacrylate spacer and the amount of block copolymer, materials with the desired physical properties could be efficiently formulated. Especially the formulation containing the medium alkyl spacer length (DMA2/PEMA) and 5 wt% BCP1 (block copolymer), exhibits excellent mechanical properties and high fracture toughness.

Three-Dimensionally-Printed Polymer and Composite Materials for Dental Applications with Focus on Orthodontics

Three-dimensional printing has transformed dentistry by enabling the production of customized dental restorations, aligners, surgical guides, and implants. A variety of polymers and composites are used, each with distinct properties. This review explores materials used in 3D printing for dental applications, focusing on trends identified through a literature search in PubMed, Scopus, and the Web of Science. The most studied areas include 3D-printed crowns, bridges, removable prostheses, surgical guides, and aligners. The development of new materials is still ongoing and also holds great promise in terms of environmentally friendly technologies. Modern manufacturing technologies have a promising future in all areas of dentistry: prosthetics, periodontology, dental and oral surgery, implantology, orthodontics, and regenerative dentistry. However, further studies are needed to safely introduce the latest materials, such as nanodiamond-reinforced PMMA, PLA reinforced with nanohydroxyapatite or magnesium, PLGA composites with tricalcium phosphate and magnesium, and PEEK reinforced with hydroxyapatite or titanium into clinical practice.

Influence of various cleaning solutions on the geometry, roughness, gloss, hardness, and flexural strength of 3D-printed zirconia

This study aimed to investigate the impact of various cleaning solutions on the geometry, roughness, gloss, hardness, and flexural strength of 3D-printed zirconia. Cleaning solutions, including isopropyl alcohol (IPA, 99.9%), ethyl alcohol (EtOH, 99.9%), and tripropylene glycol monomethyl ether (TPM, ≥ 97.5%), were diluted to a concentration of 70% and categorized into six groups: IPA99, EtOH99, TPM97, IPA70, EtOH70, and TPM70. Zirconia discs, printed via digital light processing, were sintered after cleaning. The geometry, roughness, gloss, hardness, and flexural strength were analyzed. Statistical analysis was performed using one-way ANOVA with Tukey's post hoc test (p < 0.05). The thickness of TPM70 was the highest. The diameter of TPM70 was significantly larger than that of EtOH99 and IPA70 (p < 0.05). The weight of the TPM groups was significantly higher than that of IPA70 (p < 0.05). The roughness Ra of TPM70 was significantly greater than that of IPA99, EtOH99, and EtOH70 (p < 0.05). The differences in surface gloss, hardness, and flexural strength among the different groups were not statistically significant (p > 0.05). Different cleaning solutions did not affect the surface gloss, hardness, and flexural strength of 3D-printed zirconia. High and low concentrations of the same cleaning solution did not affect the surface gloss, hardness, and flexural strength. IPA70, TPM97, and EtOH can be considered viable post-printing cleaning alternatives to the traditional gold standard, IPA99.

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.

3D-printed intracoronal restorations, occlusal and laminate veneers: Clinical relevance, properties, and behavior compared to milled restorations; a systematic review and meta-analysis

OBJECTIVES

To assess the feasibility of producing 3D-printed intracoronal restorations, thin and ultrathin veneers, and to compare their mechanical behavior, accuracy, biological, and stain susceptibility to the currently applied milled restorations.

MATERIALS AND METHODS

The databases were comprehensively searched for relevant records up to January 2024 without language restrictions. All studies that assessed 3D-printed partial coverage restorations including inlays, onlays, laminate, and occlusal veneers were retrieved.

RESULTS

The web search yielded a total of 1142 records, with 8 additional records added from websites at a later stage. Only 17 records were ultimately included in the review. The included records compared 3D-printed; alumina-based- and zirconia ceramics, lithium disilicate ceramics, polymer infiltrated ceramics, polyetheretherketone (PEEK), resin composites, and acrylic resins to their CNC milled analogs. The pooled data indicated that it is possible to produce ultrathin restorations with a thickness of less than 0.2 mm. 3D-printed laminate veneers and intracoronal restorations exhibited superior trueness, as well as better marginal and internal fit compared to milled restorations (p < 0.05). However, it should be noted that the choice of materials and preparation design may influence these outcomes. In terms of cost, the initial investment and production expenses associated with 3D printing were significantly lower than those of CNC milling technology. Additionally, 3D printing was also shown to be more time-efficient.

CONCLUSIONS

Using additive manufacturing technology to produce restorations with a thickness ranging from 0.1 to 0.2 mm is indeed feasible. The high accuracy of these restorations, contributes to their ability to resist caries progression, surpassing the minimum clinical threshold load of failure by a significant margin and reliable adhesion. However, before 3D-printed resin restorations can be widely adopted for clinical applications, further improvements are needed, particularly in terms of reducing their susceptibility to stains.

CLINICAL SIGNIFICANCE

3D-printed intracoronal restorations and veneers are more time and cost-efficient, more accurate, and could provide a considerable alternative to the currently applied CNC milling. Some limitations still accompany the resin materials, but this could be overcome by further development of the materials and printing technology.

Trends and future perspectives of 3D printing in prosthodontics

The three-dimensional (3D) printing technology has led to transformative shift in prosthodontics. This review summarizes the evolution, processing techniques, materials, integration of digital plan, challenges, clinical applications and future directions of 3D printing in prosthodontics. It appraises from the launch of 3D printing to its current applications in prosthodontics. The convergence of printing technology with digital dentistry has facilitated the creation of accurate, customized prostheses, redefining treatment planning, design, and manufacturing processes. The progression of this technology is from generating models to prosthesis like-fixed dental prosthesis (FDP), implants, and splints. Additionally, it exhibits more wide capabilities. The exploration of materials for 3D printing provides various options like polymers, ceramics, metals, and hybrids, each with distinctive properties that are applicable to different clinical scenarios. The combination of 3D-printing technology and digital workflow simplifies the processes of data transfer, computer-aided design (CAD) design to fabrication, decreasing errors and chairside time. The clinical benefits include enhanced accuracy, comfort, conservative lab procedures, and economics. Challenges in the technology involve significant aspects like initial investment, material availability, and skill requirements. Future trends emphasize on research for improved materials, bioprinting integration, artificial intelligence (AI) application, regularization efforts to ensure safe and common use of the technology. 3D printing offers promise in prosthodontics, addressing challenges through research. The material improvements will promote its broader adoption and revolutionize the future of dental rehabilitation.

Mechanical and Material Analysis of 3D-Printed Temporary Materials for Implant Reconstructions-A Pilot Study

In this study, the authors analyzed modern resin materials typically used for temporary reconstructions on implants and manufactured via 3D printing. Three broadly used resins: NextDent Denture 3D, NextDent C&B MFH Bleach, and Graphy TC-80DP were selected for analysis and compared to currently used acrylic materials and ABS-like resin. In order to achieve this, mechanical tests were conducted, starting with the static tensile test PN-EN. After the mechanical tests, analysis of the chemical composition was performed and images of the SEM microstructure were taken. Moreover, numerical simulations were conducted to create numerical models of materials and compare the accuracy with the tensile test. The parameters obtained in the computational environment enabled more than 98% correspondence between numerical and experimental charts, which constitutes an important step towards the further development of numeric methods in dentistry and prosthodontics.

Exploring the Horizons of Four-Dimensional Printing Technology in Dentistry

In dentistry, the integration of additive manufacturing, particularly 3D printing, has marked significant progress. However, the emergence of 4D printing, which allows materials to change shape dynamically in response to stimuli, opens up new avenues for innovation. This review sheds light on recent advancements and potential applications of 4D printing in dentistry, delving into the fundamental principles and materials involved. It emphasizes the versatility of shape-changing polymers and composites, highlighting their ability to adapt dynamically. Furthermore, the review explores the challenges and opportunities in integrating 4D printing into dental practice, including the customization of dental prosthetics, orthodontic devices, and drug delivery systems and also probing into the potential benefits of utilizing stimuli-responsive materials to improve patient comfort, treatment outcomes, and overall efficiency and the review discusses current limitations and future directions, emphasizing the importance of standardized fabrication techniques, biocompatible materials, and regulatory considerations. Owing to its diverse applications and advantages, 4D printing technology is poised to transform multiple facets of dental practice, thereby fostering the development of healthcare solutions that are more tailored, effective, and centered around patient needs.

Criteria for choosing prosthetic biomaterials according to their physicochemical properties for anterior and posterior sectors. a comprehensive review

Objective

To describe the existing knowledge about metal-free prosthetic biomaterials according to their physicochemical properties and based on this, define criteria for their placement in both the anterior and posterior sectors.

Materials and methods

A digital search was carried out in the databases: PubMed/Medline, Scopus, Web of Science and Google Scholar of the literature published in the English language without time restrictions and included original articles such as case reports, retrospective and prospective studies, narrative, comprehensive, systematic reviews and meta-analysis. Meanwhile, short communications, editorials and articles in a language other than English were excluded.

Results

40 articles were evaluated, published between 2000 and 2023. The main characteristics and physicochemical properties of ceramic biomaterials such as zirconia, feldspathic based ceramics, lithium disilicate and alumina, among others, were analyzed and summarized. In addition, certain criteria were defined based on the available scientific evidence on the use of different ceramic systems both in the anterior sector and in the posterior sector for patients who need some type of prosthetic restoration.

Conclusions

Among the different metal-free materials used for the construction of fixed dental prostheses, zirconia has been shown to have better aesthetic, biomechanical and biocompatibility properties, which makes it a candidate material for the rehabilitation of partially edentulous patients.