Newer Aesthetic Materials in Fixed Partial Denturea Review

ABSTRACT

Objective: The increasing demand for aesthetics and durability in fixed partial dentures has driven remarkable advancements in dental material science. This review examines the development of innovative technologies and materials that aim to deliver superior aesthetics, enhanced biocompatibility, and improved clinical outcomes, thereby surpassing traditional options such as porcelain-fused-to-metal.

Overview: Materials such as yttria-stabilized zirconia (YSZ), lithium disilicate, polyether ether ketone (PEEK), and high-impact polymer composites (HIPC) are at the forefront of this transformation. These materials, combined with cutting-edge fabrication techniques such as CAD/CAM technology and additive manufacturing, provide unmatched precision, strength, and lifelike translucency. YSZ exhibits exceptional toughness and aesthetic potential, while PEEK provides a lightweight, metal-free alternative for patients with specific clinical needs. Moreover, 4D and 5D printing technologies promise to revolutionize restorative dentistry by enabling dynamic, patient-specific restorations.

Conclusion: The development of advanced aesthetic materials like ultra-translucent zirconia, PEEK, lithium disilicate, and CAD/CAM composites, alongside innovations like 4D printing, has transformed fixed partial denture restorations. These advancements improve clinical outcomes and patient satisfaction. Ongoing research and clinical integration promise more predictable, patient-focused solutions.

Keywords: Fixed partial dentures, aesthetic materials, yttria-stabilized zirconia, lithium disilicate, polyether ether ketone, HIPC, CAD/CAM technology, additive manufacturing, 4D printing, 5D printing, restorative dentistry.

INTRODUCTION AND BACKGROUND

Advancements in dental materials and digital technology have significantly influenced the pursuit of excellence in fixed partial dentures (FPDs). As patients' aesthetic demands grow, prosthodontic materials have evolved from conventional to esthetically superior alternatives. Fixed partial dentures (FPDs) have long been a cornerstone of prosthodontic rehabilitation, addressing patients' functional and aesthetic needs with partial edentulism.

Historically, porcelain-fused-to-metal (PFM) restorations dominated FPD fabrication due to their durability and ease of use. However, with limitations such as reduced translucency and a risk of marginal discoloration from metal exposure, the need for materials that closely resemble natural dentition with mechanical integrity had to be addressed. This review has highlighted the need for new, more mechanically superior yet lifelike aesthetic materials to enhance the face of FPD fabrication. Additionally, advancements in computer-aided design/computer-aided manufacturing (CAD/CAM) systems have significantly enhanced the precision, efficiency, and visual appeal of FPDs, enabling clinicians to meet patients' growing aesthetic and functional expectations.^8,14,25,26

Zirconia is popular among emerging materials due to its superior strength, biocompatibility and aesthetic properties. Modern advancements, such as ultra-translucent and colored zirconia ceramics, have expanded their application in prosthetic dentistry, offering natural-like esthetics while maintaining mechanical performance.^1,29 Another breakthrough has been the development of hybrid resin nano-ceramics and fiber-reinforced composites, which combine the benefits of ceramics and resins, providing a balance of esthetics, resilience, and ease of fabrication.^11,26

Digital fabrication techniques have also revolutionized prosthodontic materials, enabling the provision of precise and reproducible restorations. Additive manufacturing, such as 3D printing, offers faster production times and greater cost efficiency compared to subtractive techniques. For instance, 3D-printed composite resin restorations have demonstrated comparable fatigue behavior to traditionally milled materials, providing a viable alternative for aesthetic restorations8. Similarly, CAD/CAM technology advancements have allowed for the integration of innovative materials like lithium disilicate and polyether ether ketone (PEEK), which exhibit excellent mechanical and aesthetic characteristics, making them ideal for FPD applications.^4,7

4D printing technology has revolutionized the prosthodontic field. Dynamic materials replace traditional static materials and respond to environmental stimuli time-dependently. This ensures that restorations and prosthetic devices can react to changes in temperature, humidity, or stress variation compared with the traditional static material. The promise of applying this technology in dentistry is phenomenal and it offers new concepts for personalized treatment and greater efficiency in fixed partial dentures.^15,23 High-tech materials integrated with intricate manufacturing techniques make 4D printing a notable breakthrough in achieving aesthetic, functional, and adaptive outcomes in prosthodontics.

The emerging concept of 5D printing opens new frontiers in prosthodontics by combining advanced dimensional capabilities into material fabrication. Unlike traditional 3D and 4D printing, 5D printing allows for simultaneous manipulation of multiple axes, producing stronger, more precise, and adaptable restorations. According to Anas et al. (2021), this technology may revolutionize the fabrication process of fixed partial dentures by offering better structural strength, minimal material waste, and proper customization for patient-specific needs. Future applications of 5D printing may still make clinical workflows more manageable and raise the bar to a higher level in the rehabilitation of prosthodontics.

Besides, advancements in zirconia ceramics with lithium disilicate crowns brought about a new standard of color matching and translucency to achieve harmony in blending with the natural dentition.^18,27 Evaluations made over time concerning the lifespan and patient satisfaction of such materials have ensured their position in the prosthodontics of the present millennium.^14,25 Clinical studies support Their success well, highlighting their long-term stability, fracture resistance, and excellent marginal adaptation.^14,18 These properties make lithium disilicate particularly favorable in achieving natural esthetics in high-demand cases, such as anterior restorations.

Polyether ether ketone (PEEK), a high-performance thermoplastic polymer, represents a groundbreaking advancement in prosthodontic materials. Because of its exceptional wear resistance, chemical stability, and biocompatibility, PEEK is ideal for FPD frameworks and implant-supported restorations. Its light and non-metallic nature makes it highly suitable for those with metal sensitivities or aesthetic concerns. In addition, the unique mechanical properties of PEEK, including shock absorption, elasticity, and intraoral stresses, make it a strong contender for prosthodontic applications intended to last.⁴

Yttria-stabilized zirconia is one of the most promising materials in dentistry. The field favors it for its outstanding mechanical strength, fracture toughness, and aesthetic translucency. The addition of yttria improves the stability of zirconia by stabilizing the favorable tetragonal phase at room temperature, thus enhancing its ability to withstand functional loads. Advanced fabrication techniques in extrusion 3D printing and stereolithography-driven additive manufacturing have further improved the material properties of YSZ. It now becomes possible to make accurate, customized dental restorations. Such advanced fabrication techniques have enabled wide usage in fixed partial dentures and other prosthodontic interventions to meet their aesthetic and functional needs.

Other types of hybrid materials, aside from ceramics, are resin nano-ceramics and fiber-reinforced composites. These materials combine the aesthetic characteristics of ceramics with the strength and reparability of resin-based composites; therefore, they provide a distinct solution to specific clinical situations. For example, fiber-reinforced composites can be used to construct fixed partial dentures due to their superior flexural strength and low weight, making them appropriate for certain patients or trends.¹¹ Concurrently, resin nano-ceramics have enhanced machinability and polishability, ensuring superior aesthetic outcomes with minimal chairside adjustments.²⁶

High Impact Polymer Composite (HIPC) is an innovative material increasingly used in dental prosthetics due to its superior mechanical properties, aesthetic appeal, and biocompatibility. HIPC has excellent wear resistance, color stability, and toughness against fracture. Hence, replacing conventional materials such as porcelain and metal in fixed partial dentures is easy. It is thus ideal for long-term restorations, especially about the resistance against intraoral forces and the natural appearance of the HIPC material. Its versatility in direct and indirect applications increases the clinical applicability in various prosthodontic treatments.

The demand for aesthetic excellence in fixed prosthodontics extends beyond the intrinsic properties of the materials perse. Factors such as shade matching, translucency, surface texture, and optical properties are crucial in achieving natural-looking restorations. Recent innovations have focused on refining these aspects, with materials like colored zirconia ceramics and high-translucency monolithic restorations setting new benchmarks for aesthetic integration.^1,29 Similarly, advances in shade-matching technologies and digital tools have enabled clinicians to replicate complex color gradients and optical effects seen in natural teeth.¹⁸

Despite significant advancements, the selection of materials for fixed partial dentures (FPDs) must carefully balance aesthetic appeal with functional performance to ensure long-term clinical success. Restorations in high-load areas, for example, require materials with adequate fatigue resistance, wear resistance, and fracture toughness, alongside superior translucency and patient-centered outcomes. Comparative studies on materials like zirconia and lithium disilicate have provided valuable insights into their mechanical properties and clinical suitability in various scenarios.^14,25 Cost, ease of fabrication, and chairside efficiency remain critical considerations for clinicians, especially when increasing access to advanced restorative options.⁸

This narrative review discusses how aesthetic materials used for fixed partial dentures have changed, considering characteristics, clinical applications, technological improvements, and possible influence on future practice. It has synthesized information from the new and current literature to equip clinicians with a comprehensive, evidence-based understanding of these materials' advantages and disadvantages. This review aims to guide the selection and utilization of newer aesthetic materials, ultimately producing superior patient outcomes and achieving aesthetic, functional, and patient-centered restorations.

SEARCH METHODOLOGY

In December 2024, we searched articles through PubMed and Google Scholar using keywords such as aesthetic materials, PEEK, HIPC, colored zirconia, and nanoceramics. We also collected articles from our parental article references. We used the advanced search for 2023 to 2024 and the English language. With these above filters, we collected relevant articles using inclusion and exclusion criteria.

AESTHETIC MATERIALS

1. Ultra-Translucent Zirconia

Zirconia has been one of the most important materials in prosthodontics because of its excellent mechanical properties and biocompatibility. However, due to its opacity, it was limited to highly aesthetic zones. Ultra-translucent zirconia now overcomes this limitation.

Properties:

The article by Ban S. (2023) concluded that ultra-high translucent zirconia improved optical properties while maintaining adequate mechanical strength for clinical applications. The study highlights the potential of these zirconia materials in achieving superior aesthetics for dental restorations, especially in the anterior region.

Vijan et al. (2024) highlighted the ultra-translucent zirconia as a significant advancement in dental materials, offering enhanced aesthetics compared to conventional zirconia. Its improved translucency makes it more suitable for anterior restorations where a natural, lifelike appearance is crucial. Despite its aesthetic benefits, the article emphasizes that clinicians must carefully consider the reduction in strength associated with ultra-translucent zirconia and select it appropriately based on the specific clinical scenario.

2. Polyether Ether Ketone (PEEK):

Polyether Ether Ketone (PEEK) is a high-performance thermoplastic polymer with exceptional mechanical properties, including high strength, stiffness, and dimensional stability. Its melting temperature is 343°C, making it suitable for high-stress applications. With repeating ether and ketone groups, PEEK's chemical structure provides excellent chemical resistance and thermal stability, making it particularly durable in the harsh oral environment. Additionally, PEEK is biocompatible, has low cytotoxicity, and is radiolucent, which does not interfere with radiographic imaging.²⁵

In prosthodontics, PEEK offers several advantages. Its aesthetic appeal is a key benefit, as it can be processed to match natural tooth color closely, making it an ideal material for cosmetic dental restorations.¹⁶ PEEK is versatile, used in partial dentures, implant abutments, crowns and temporary restorations, offering strong mechanical properties and wear resistance.⁴ It also reduces stress on surrounding tissues and implants, as its mechanical properties are similar to natural bone.⁶ Furthermore, PEEK is compatible with CAD/CAM technologies, enabling efficient and precise restoration fabrication.¹⁶

However, PEEK has some limitations. It lacks the translucency of materials like zirconia, which may limit its aesthetic potential, especially for anterior restorations.¹⁶ Bonding PEEK to other materials can be challenging due to its inert nature, requiring surface treatments like sandblasting or primers.²⁵ Additionally, PEEK can be more expensive than traditional materials, which may affect widespread adoption.⁴

Recent research has focused on improving PEEK’s properties. Surface modifications, such as plasma or laser treatments, have been explored to enhance bonding with other materials.²⁵ Reinforced PEEK, incorporating fibers like carbon or glass, has improved its mechanical strength and reduced brittleness.⁴ CAD/CAM technology advances have also made PEEK restorations more precise and clinically acceptable.¹⁶

Clinical studies have shown that PEEK performs well in dental applications, particularly for implant abutments, offering durability, comfort, and aesthetic benefits. Despite its limitations, PEEK remains a promising material in prosthodontics due to its strength, biocompatibility, and versatility.^6,25

3. High-Impact Polymer Composites (HIPC):

High-impact polymer Composite (HIPC) is a thermoplastic polymer known for its excellent impact resistance, optical clarity, and good mechanical properties. When modified to enhance its impact strength, HIPC becomes a durable material suitable for demanding dental applications. It is biocompatible, has minimal adverse effects on tissues, and exhibits moderate thermal stability, making it safe for use in the oral environment.²⁵ HIPC is highly transparent, mimicking natural teeth, making it ideal for aesthetic dental restorations like temporary crowns and bridges.²⁶

HIPC offers several advantages in prosthodontics. Due to natural translucency, its aesthetic properties make it suitable for temporary crowns, bridges, and denture bases, providing both strength and durability.²⁵ The material is also cost-effective compared to ceramics or metals, which makes it a favorable choice for patients and dental professionals.²⁶ HIPC can be easily processed using conventional techniques like injection molding and CAD/CAM technology.¹⁶

However, HIPC has limitations, such as lower wear resistance than zirconia or metals, making it less suitable for long-term applications.²⁶ It is also prone to chemical degradation over time, which may reduce its longevity.¹⁶ Moreover, HIPC may not provide sufficient strength for high-load applications like full-mouth rehabilitation or implant-supported restorations.²⁶

Recent studies have focused on enhancing HIPC’s properties. Reinforcement with fibers or nanoparticles has improved its strength and wear resistance, while surface treatments have enhanced its bonding with other materials.²⁵ Advances in CAD/CAM and 3D printing technologies are also being explored to improve the precision and customization of HIPC restorations.¹⁶

Clinical studies indicate that HIPC performs well for temporary crowns, dentures and orthodontic appliances, offering good clinical outcomes. Despite its wear limitations, HIPC remains a valuable, cost-effective option in prosthodontics for aesthetic and functional restorations.²⁶

4. Lithium Disilicate Ceramics:

Lithium disilicate ((Li2Si2O5) is a highly aesthetic and durable glass-ceramic material widely used in prosthodontics for restorations like crowns, veneers, inlays, onlays and bridges. Composed of lithium oxide and silica, it undergoes crystallization to form a dense ceramic that combines strength and translucency.¹⁴ Lithium disilicate has notable properties such as high flexural strength, typically ranging from 350 MPa to 500 MPa, making it suitable for anterior and posterior restorations.²² Its translucency closely mimics natural tooth enamel, ideal for aesthetic applications.¹⁴ Additionally, lithium disilicate demonstrates excellent durability, superior to traditional feldspathic porcelain, and has minimal adverse effects in the oral environment, ensuring biocompatibility.¹⁸

In prosthodontics, lithium disilicate is preferred for its aesthetic excellence and versatility in fabrication, using methods such as CAD/CAM systems, manual waxing, and pressable techniques.²² It is ideal for anterior crowns, veneers, inlays, onlays, and implant-supported restorations due to its strength, translucency, and minimal tooth preparation.¹⁴ Despite its advantages, lithium disilicate has limitations, including potential fracture under excessive masticatory forces, especially in patients with bruxism.¹⁸ It also requires precise preparation and bonding techniques, and its higher cost may make it less accessible for some patients.¹⁴

Recent research focuses on enhancing its strength and durability for high-load applications, especially in patients with heavy occlusion or bruxism.¹⁸ Innovations in CAD/CAM systems, digital impressions, and surface treatments improve fabrication precision and bond strength.¹⁴ Clinical studies have confirmed lithium disilicate's longevity and success, with survival rates of up to 97.3% over five years.¹⁴ Although it may not be suitable for high-stress posterior areas, its combination of aesthetics, strength, and biocompatibility makes it a leading material in modern prosthodontics.²²

5. 4D and 5D printing:

The advent of 4D and 5D printing technologies represents a giant leap in prosthodontics, especially for producing fixed partial dentures (FPDs). The studies by Javaid et al. and Perambudhuru et al. demonstrated that 4D printing technology is superior to traditional 3D printing technology because it utilizes smart materials that respond adaptively to environmental stimuli, such as temperature, humidity, or light. This innovation enables the development of adaptive dental prostheses for adjustment according to physiological changes and those that have occurred in tissues over time to contribute to improved clinical outcomes and higher patient satisfaction.

5D printing, which utilizes additional axes of motion within the fabrication procedure, can thus produce complex and highly defined restorations. According to Daher et al. and de Lima Gomes et al., this new technology can produce restorations with excellent mechanical properties, ideal translucency, and improved structural stability. The capability to create complex zirconia-based and composite resin frameworks with high precision is one of the promises 5D printing holds for realizing aesthetic appearance and functional efficiency.

Such advanced additive manufacturing techniques open unprecedented opportunities for customization and biocompatibility, redefine material innovation and clinical workflows in prosthodontics, and can significantly elevate the standards of care for fixed prosthetic restorations.

6.CAD/CAM composites:

CAD/CAM composites have been a subject of great interest in prosthodontics, especially their use in fixed partial dentures (FPDs). The materials combine the benefits of accurate engineering with improved physical and aesthetic properties, which makes them highly popular for modern prosthetic restorations. Jovanovi? et al. (2021) and Cevik et al. (2022) highlight that advanced subtractive methods produce CAD/CAM composites with high accuracy and homogeneity.

Compared with traditional restorative materials, CAD/CAM composites provide the advantages of improved flexural strength, increased wear resistance, and higher biocompatibility. Excellent marginal adaptation and fracture resistance in posterior FPDs can be achieved with such composites, as shown by research from Daher et al. (2024) and Emam and Metwally (2023). Li et al. (2024) demonstrated that these composites offer advanced translucency and color-match capabilities, allowing a highly accurate reproduction of the natural dentition's appearance.

CAD/CAM composites are cost-effective and time-efficient, thus decreasing chairside adjustments and laboratory processing time. The introduction of CAD/CAM technology into prosthodontic workflows is bound to improve clinical outcomes through the seamless integration of durability and esthetics in FPDs. Further development will undoubtedly redefine the horizon of restorative materials in fixed prosthodontics.

7. Fiber- Reinforced Composite:

Fixed partial dentures (FPDs) have increasingly utilized fiber-reinforced composites (FRCs) because of their outstanding mechanical properties and high aesthetic qualities. FRCs consist of reinforcing fibers within a polymeric matrix, giving the material enhanced flexural strength and improved resistance to fracture. According to Garoushi and Vallittu (2006), FRCs play a significant role in prosthodontics. They can resist functional loads and remain lightweight.

Adding fibers, glass, or polyethylene can enhance mechanical properties. Khalesi et al. (2020) research indicates that FRCs possess higher interfacial fracture toughness than conventional composite resins and are, hence, suitable for high-stress fixed prosthodontic regions, especially in fixed partial dentures. Moreover, FRCs offer better biocompatibility and versatility, enabling clinicians to perform minimally invasive restorative treatments more easily.

FRCs produce impressive aesthetic results, especially due to their translucency and ability to mimic natural tooth structures. Jovanovi? et al. (2021) underlined the use of FRCs in CAD/CAM technology, which allows for accurate fabrication of durable and aesthetically pleasing prosthetic frameworks. In addition, their adaptability to different clinical situations makes them a versatile option in modern prosthodontics.

Fiber-reinforced composites combine mechanical strength with aesthetic appeal, thus offering a reliable choice for long-term effectiveness in fixed prosthodontic restorations.