Revolutionizing Restorative Dentistry: The Impact of Digital Technology and 3D Printing - A Narrative Review

Introduction

Restorative dentistry has seen significant technological advancements in recent years, with three-dimensional (3D) printing emerging as a key innovation. This technology offers a multitude of applications and substantial opportunities within the dental field, with projections indicating rapid growth in the near future.¹

According to the standards established by the International Organization for Standardization (ISO) and the American Society for Testing and Materials (ASTM), 3D printing technologies construct objects by adding material layer by layer based on geometric representations.²

The 3D printing process involves building up materials such as metals, polymers, or resins in successive layers, guided by CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) digital scans. These scans are essential both for designing products and managing the manufacturing process. The technology encompases techniques such as stereolithography (SLA), digital light processing (DLP), selective laser sintering (SLS), selective laser melting (SLM), fused deposition modeling (FDM), power binder printing, photopolymer jetting, and laser bioprinting.³

The digitalization facilitated by 3D printing represents a major leap forward, allowing for the creation of highly customized treatments tailored to individual patients. This ensures a high degree of precision and quality, making it a favoured approach in contemporary restorative dentistry.¹ Along with this, its higher efficiency, passivity, flexibility, and superior material utilization make it distinct from other techniques.⁴

Although the application of 3D printing in dentistry is gaining traction, its implementation in restorative dentistry and related research remains relatively constrained.² The objective of this review was to investigate the potential uses of 3D printing in this field and to identify the factors that impact the development and effectiveness of dental materials produced through this technology.

Methods

This study aimed to comprehensively evaluate the implementation of 3D printing technology in restorative dentistry, focusing on its applications, benefits, and future research needs. The methodology involved a structured literature review to gather and analyze pertinent information from existing research and scholarly articles.

Literature Search Strategy

A systematic review was performed using scientific databases including Google Scholar, PubMed, and relevant academic journals. Keywords such as “3D printing,’’ “digital dentistry,’’ “CAD CAM,’’ “dental materials,’’ “restorative dentistry,’’ and “3D-printed dental restorations’’ were employed to identify relevant studies published up to the review date.

Inclusion Criteria

Articles were included if they discussed how 3D printing technologies are applied in restorative dentistry, explored various 3D printing methods (e.g., SLA, DLP, FDM, SLS, PolyJet, Binder Jetting), provided insights into the strengths and limitations of 3D printing technology in dental applications and reported on clinical outcomes, material properties, or processing techniques related to 3D-printed dental restorations.

Exclusion Criteria

Studies that did not specifically focus on 3D printing in restorative dentistry and were not available in English or lacked full-text accessibility were excluded from the study.

Selection Process

Initially, titles and abstracts of retrieved articles were screened to assess relevance to the study topic. Full-text articles that met the inclusion criteria were further evaluated for data extraction. A total of 58 articles were identified initially, with 36 meeting all inclusion criteria after full-text review.

Data Extraction and Synthesis

Data extracted from the selected articles included inforzation on:

• Types of different 3D printing technologies utilized in dental applications.
• Specific applications of 3D printing in restorative dentistry (e.g., crowns, veneers, prostheses).
• Comparative analyses of 3D printed vs. traditional dental restorations.
• Advantages such as precision, efficiency, and customization.
• Challenges and limitations associated with 3D printing in dental practice.

Data synthesis involved organizing and summarizing findings from the selected articles to identify trends, gaps in knowledge, and areas for future research.

Literature Review

The current advancements in restorative dentistry have been revolutionized by digital technology, particularly 3D printing, which fabricates objects layer by layer using CAD/CAM systems, ensuring exceptional accuracy and personalization. Despite its growing adoption, research and application in restorative dentistry are still developing.

Various 3D printing techniques like SLA, DLP, FDM, SLS, PolyJet, and Binder Jetting offer distinct advantages such as high precision, cost efficiency, good mechanical properties, high resolution, material versatility, and suitability for complex geometries. These technologies have significantly advanced dental training and enabled the creation of tooth dies, tooth reduction guides, provisional restorations, intracoronal restorations, veneers, and fixed prostheses.

3D printed models enhance dental training by providing accurate simulations for skill development, while tooth reduction guides ensure precise preparation for ceramic veneers, thereby enhancing restoration quality. Provisional restorations benefit from reduced production time, material conservation, and cost-effectiveness. Research indicates that 3D-printed intracoronal restorations and veneers demonstrate superior fit compared to milled alternatives, offering time and cost efficiencies in dental practice.

This literature review provides an outline of 3D print­ing technology and its current applications in restorative dentistry.

3D Printing Technology in Dentistry

In the dental segment of 3D printing, a broad range of materials are currently employed. Table 1 presents a summary of these materials, along with detailed descriptions of the most frequently used ones, specifically designed for dental purposes.⁵

Stereolithography (SLA)

SLA uses a UV laser to cure and solidify liquid photopolymer resin layer by layer.⁶ This technique is commonly used for producing dental surgical guides, models, and custom trays due to its smooth surface finish and high precision. It offers high accuracy, fine detail resolution, and good surface quality. However, the material properties can be limited, and post-processing is required to remove supports and completely cure the resin.⁷

Digital Light Processing (DLP)

Similar to SLA, it uses a digital light projector screen to flash a single image, projecting the entire layer in a single exposure, which speeds up the printing process. It is suitable for dental models, restorations, aligners, and prosthetics. This method is faster than SLA and offers good accuracy and fine detail resolution. However, it has a limited build size and potential for pixelation effects due to the digital projection.⁷

Fused Deposition Modeling (FDM)

FDM extrudes thermoplastic filament through a heated nozzle, which deposits the material layer by layer to build the object. The advantages of this technique include cost efficiency and the lack of restrictions on materials. However, it produces lower resolution and surface finish compared to SLA and DLP, with visible layer lines. At present, its applications in the dental field are limited, primarily used for foam models and individual impression trays.⁸

Selective Laser Sintering (SLS)

Selective Laser Sintering (SLS) uses a laser to sinter powdered material, typically nylon, layer by layer. This technology is often used for crowns, partial dentures and implants. It does not require support structures and offers good mechanical properties and functional prototypes. However, it is associated with high costs, requires specialized CAD software, and results in a rough surface.⁷

PolyJet Printing

PolyJet technology jets layers of curable liquid photopolymer onto a build tray, using multiple print heads to allow for different materials and colours. It is ideal for dental models, surgical guides, and intricate appliances requiring multiple materials. The technology offers high resolution, a smooth surface finish, and the ability to print multiple materials simultaneously. A higher accuracy with regard to the marginal and internal fit of the metal crowns that were made from the printed wax crowns was determined.⁹ However, it is expensive and requires support material removal and curing post processing.⁷

Binder Jetting

Binder jetting deposits a binding agent onto a powder bed layer by layer to create the object. This method is used for creating metal dental restorations and frame works. It can produce complex geometries and is suitable for mass production. However, it requires sintering and infiltration post-processing, which can add to the production time and complexity.⁷

3D Printing in Restorative Dentistry

Digital technology and 3D printing have brought significant advancements to operative dentistry, enhancing success rates and improving the quality and precision of dental procedures. This technological shift not only impacts dentists by improving the speed and efficiency of their work but also influences the marketing strategies of dental laboratories in attracting clients.¹ For patients, it influences their choice of dentist, favouring those who have adopted this new technology for more comfortable diagnosis and faster treatment outcomes over those who still rely on traditional methods.

The following are the applications of 3D printing in different aspects of restorative dentistry.

Dental Training in Restorative Dentistry

3D tooth models revolutionize dental education by enabling the creation of personalized educational models that support both preoperative and operative skills development. The advent of 3D printing diminishes the divide between pre-clinical training and real-world clinical scenarios in caries management, potentially enhancing patient care quality.¹⁰ An investigation was conducted to assess a new 3D printed tooth model's efficacy in preoperative assessment and caries removal, employing the International Caries Detection and Assessment System (ICDAS). Participants unanimously agreed that these 3D printed models offer an accurate simulation of caries, making them ideal for hands on operative dentistry courses, resulting in superior learning outcomes compared to standard models.¹⁰ In a study, 3D models were generated by modifying scans from real patient files for laboratory practice, encompassing procedures like cervical abrasion and erosion restorations, direct composite veneers, aesthetic correction of rotated teeth, diastema closure, occlusal abrasion and erosion, and Maryland bridge. The findings revealed that 90.48% of the students favoured the designed 3D model as the optimal approach for laboratory practice compared to alternative methods.¹¹ Similarly, in another study, a novel 3D printed single tooth guide was fabricated for research purposes to evaluate the loss of tooth structure during coronal access preparations which resulted in tooth conservation and improved procedural efficiency.¹² The use of such 3D printed models can help students enhance their precision in conservative tooth preparations and improve overall treatment outcomes.

The advantages of incorporating 3D printed models into the training of dental students include:¹³

1) Utilizing 3D tooth models enhances hands-on training, especially for intricate procedures, potentially leading to better implementation during clinical practice.

2) Replicating individual teeth and their surrounding anatomical structures creates training conditions that closely resemble real dental procedures, easing the transition from pre-clinical to clinical settings.

3) 3D printing enables the creation of personalized tooth models with high anatomical variability, allowing consideration of specific pathological changes for more realistic training experiences.

Tooth dies

By employing an intraoral scanner, dentists can now 3D print accurate tooth dies directly, bypassing the need for conventional plaster models. Traditionally, plaster models have been considered the gold standard for crafting wax patterns or copings used in intracoronal and extracoronal restorations. This digital approach streamlines the workflow, enhancing precision and efficiency in dental restoration processes. The shift from physical plaster models to digital 3D printed dies marks a substantial improvement in the dental technology, offering improved accuracy and potentially reducing the time and costs associated with restorative dental procedures.² A research investigation compared different 3D printer technologies for chairside resin model printing, highlighting their ability to achieve precise results within 30 microns in all three dimensions (XYZ). The study determined that these printers are applicable for clinical use, as they exhibited errors well within acceptable clinical thresholds, typically below 100 microns.¹⁴ Morón Conejo et al., conducted a comparative analysis of five 3D printers used to fabricate full arch models for patients, encompassing both dental desktop and industrial printers. Results showed significant differences in accuracy, precision, and trueness, with industrial 3D printers utilizing Multijet printing technology outperforming dental desktop printers using DLP and SLA technologies.¹⁵ Use of these 3D-printed wax up models in the digital workflow for veneer preparation has also yielded high levels of patient satisfaction with esthetics outcomes.¹⁶

Tooth reduction guides

Tooth reduction guides enable clinicians to achieve the precise space necessary for ceramic veneers.¹⁷ In a recent study, researchers evaluated different veneer tooth reduction methods, including the use of 3D-printed guides. The study definitively concluded that 3D printing was superior to freehand reduction techniques.¹⁸ Reports have outlined various designs for 3D-printed guides. Some feature window preparation, horizontal, vertical, and incisal channels for precise surface reduction,while others facilitate preparation through conventional vertical access.^19,17,20 Other studies akin to the one described here have utilized a digital workflow for ceramic veneer treatment, employing stereolithographic templates for precise control of reduction depth during minimally invasive tooth preparation. This approach simplifies the procedure and represents a notable advancement compared to conventional methods.²¹ The described guided restorative dentistry technique harnesses digital CAD-CAM technology to deliver consistent and precise outcomes with minimal invasiveness and enhanced efficiency.²⁰

Provisional restorations

The use of three-dimensional (3D) printed temporary dental restorations is on the rise in clinical environments due to the extensive availability of intraoral scanning technology, user friendly dental CAD software, and the fast capabilities of 3D printing.²² Compared to traditional methods such as the lost wax technique, 3D printing offers significant advantages in material and energy conservation, reduced carbon emissions, and cost-effectiveness.²³ A meta-analysis has highlighted various printed resins utilized in different 3D printing techniques, including acrylic, composite resins, and methacrylate oligomer-based materials. The study found that polymerization plays a crucial role in the flexural strength of resins used in both 3D printing and conventional/milled techniques, resulting in significant variations. For example, SLA-3D and DLP acrylate photopolymers exhibit different strengths, and DLP bisacrylic material is often used for fabricating 3D-printed interim restorations.²⁴

Intracoronal restorations

3D-printed intracoronal restorations have demonstrated greater time and cost efficiency, superior accuracy, and potential as a viable alternative to CNC (computer numerical control) milling. A meta-analysis comparing 3D-printed intracoronal restorations and veneers made from materials like alumina-based and zirconia ceramics, lithium disilicate ceramics, polymer-infiltrated ceramics, polyetheretherketone (PEEK), resin composites, and acrylic resins found that 3D-printed restorations exhibited superior trueness and better marginal and internal fit compared to their CNC-milled counterparts.²⁵ However, it is important to consider that outcomes can be influenced by material choice and preparation design.²⁵

Regarding cost, the initial investment and production expenses associated with 3D printing were significantly lower than those for CNC milling technology. Additionally, 3D printing was found to be more time-efficient.²⁵ Bae et al., assessed the accuracy of inlay restorations made by additive manufacturing (AM) using polymer VisiJet FTX Green (3D Systems) and ProJet 1200 (3D Systems) and found that AM-produced inlays were more accurate than those produced by subtractive methods.²⁶

In a similar study, Yoen Ah Lim evaluated the marginal and internal fitness and three-dimensional (3D) accuracy of class II inlays fabricated using the conventional Tescera (TS) resin method, milling of hybrid and zirconia blocks, and 3D printing with NextDent C&B. The study concluded that the 3D-printed inlays had better marginal and internal fitness and accuracy than those produced by conventional and milling methods commonly used in dentistry.²⁷Another study by Oriol Cantó-Navés et al., found that printed onlays adapted significantly better to the prepared tooth than milled onlays, with printed onlays also exhibiting better gap reproducibility.²⁸

The high accuracy of these restorations enhances their ability to resist caries progression, surpassing the minimum clinical threshold for load failure, and ensures reliable adhesion. However, for 3D-printed resin restorations to be widely adopted in clinical practice, improvements are needed to reduce their susceptibility to staining.²⁵

Veneer

3D printing facilitates the production of high-resolution veneers with an adequate surface finish, reducing both manufacturing time and material waste, making it a cost effective method for fabricating both provisional and definitive restorations.^29,30 Materials commonly used for 3D printing veneers include resins and zirconia.^29,31 These zirconia cores for veneers have the advantages of superior esthetics, high mechanical strength, and biocompatible properties.³²

In Alghauli et al., study, it was discovered that 3D printing may achieve more precise production of laminate veneers compared to milling. Specifically, 3D-printed axial surfaces demonstrated superior trueness compared to milled axial surfaces.³¹ Ioannidis et al., evaluated the marginal and internal fit of 3D-printed zirconia occlusal veneers and compared them with CAD-CAM zirconia or heat-pressed lithium disilicate ceramic (LS2) restorations on molars. The study found that 3D-printed zirconia veneers produced using lithography-based ceramic manufacturing, had production accuracy (26 μm) and marginal adaptation (95 μm) comparable to convention-al methods.³³

Although 3D-printed veneers offer minimally invasive indirect restorative solutions for anterior teeth, they also provide on-demand chairside treatment options with higher accuracy tailored to preparation dimensions. Notably, 3D printing technology allows for the simultaneous processing of multiple prostheses, ensuring efficient use of materials in dental prosthesis manufacturing.³⁴

Fixed prosthesis

The progress in 3D-printed crown resin materials, with enhanced mechanical and physical properties, is increasingly intriguing for dentistry.³⁵ Various additive manufacturing methods, including inkjet printing, SLS, and DLP 3D printing technology, have been employed for crown fabrication, utilizing materials such as metals, ceramics, and hybrid resins.²

In their meta-analysis, Jain et al., identified that 3D-printed provisional crown and fixed dental prosthesis (FDP) resins demonstrate superior mechanical properties compared to conventional and CAD/CAM milled provisional resin materials. Specifically, these 3D-printed materials exhibited higher fracture strength, flexural strength, elastic modulus, peak stress, and wear resistance. This suggests that 3D printing technology offers substantial advantages in the mechanical performance of provisional dental restorations when compared to traditional mill-ing techniques and conventional resin materials.³⁶

Furthermore, 3D-printed zirconia crowns exhibit superior aesthetic colour and contour matching to adjacent natural teeth when compared to milled crowns. Both milling techniques and 3D printing consistently yield crowns with internal and marginal fits meeting clinical acceptability standards.³¹

Limitations

1. Limited focus on clinical outcomes: The article primarily discussed the technological advancements and benefits of 3D printing; however, it places relatively little emphasis on detailed clinical outcomes and long-term studies assessing patient results.

2. Scope of included studies: Although the review utilized established scientific databases, it may have excluded relevant studies published in non-English languages or those not indexed in major databases, potentially limiting the comprehensiveness of the findings.

Conclusion

Incorporating 3D printing into restorative dentistry offers advantages such as reduced material wastage and the ability to reproduce multiple copies of objects. However, challenges like cost, lack of trained personnel, and limited material options exist. Further studies are needed to establish 3D printing as a reliable technology in restorative dentistry. Studies should focus on clinical treatment outcomes, the mechanical properties of printed materials, and the effects of processing methods. Despite challenges, the digital workflow in dentistry shows promise for creating clinically acceptable results, from diagnostics to restorative aspects. Additive manufacturing presents opportunities for more predictable and cost-effective treatment pathways. Long-term research is crucial to understand the behavior of 3D-printed materials and optimize their use in clinical settings. In conclusion, although 3D printing in restorative dentistry still encounters certain challenges, continuous research and technological progress offer promising potential for transforming dental care by enhancing both outcomes and efficiency.

Financial support and sponsorship

Nil

Conflicts of interest

There are no conflicts of interest