The integration of peri-implant soft tissues around zirconia abutments: Challenges and strategies

Surface modification strategies to reinforce the soft tissue seal at transmucosal region of dental implants

Soft tissue seal around the transmucosal region of dental implants is crucial for shielding oral bacterial invasion and guaranteeing the long-term functioning of implants. Compared with the robust periodontal tissue barrier around a natural tooth, the peri-implant mucosa presents a lower bonding efficiency to the transmucosal region of dental implants, due to physiological structural differences. As such, the weaker soft tissue seal around the transmucosal region can be easily broken by oral pathogens, which may stimulate serious inflammatory responses and lead to the development of peri-implant mucositis. Without timely treatment, the curable peri-implant mucositis would evolve into irreversible peri-implantitis, finally causing the failure of implantation. Herein, this review has summarized current surface modification strategies for the transmucosal region of dental implants with improved soft tissue bonding capacities (e.g., improving surface wettability, fabricating micro/nano topographies, altering the surface chemical composition and constructing bioactive coatings). Furthermore, the surfaces with advanced soft tissue bonding abilities can be incorporated with antibacterial properties to prevent infections, and/or with immunomodulatory designs to facilitate the establishment of soft tissue seal. Finally, we proposed future research orientations for developing multifunctional surfaces, thus establishing a firm soft tissue seal at the transmucosal region and achieving the long-term predictability of dental implants.

Effect of ultraviolet treatment on soft tissue healing and bacterial attachment to titania-coated zirconia

Zirconia is the most promising implant abutment material due to its excellent aesthetic effect, good biocompatibility and corrosion resistance. To obtain ideal soft tissue sealing, the implant abutment surface should facilitate cell adhesion and inhibit bacterial colonization. In this study, pre-sintered zirconia was placed in a suspension of titania (TiO2) and zirconium oxychloride (ZrOCl2) and heated in a water bath for dense sintering. A titania coating was prepared on the zirconia surface and subjected to UV irradiation. The surface morphology, elemental composition and chemical state of each group of samples were analyzed by scanning electron microscope, x-ray energy spectrometer, x-ray photoelectron spectroscopy and x-ray diffraction. The responses of human gingival fibroblasts (HGFs) and common oral pathogensStreptococcus mutans(S. mutans) andPorphyromonas gingivalis(P. gingivalis) to modified zirconia were systematically assessed. Our findings demonstrated that the surface of titania-coated zirconia after UV irradiation produced a large number of hydroxyl groups, and its hydrophilicity was significantly improved. Meanwhile, the UV irradiation also greatly removed the hydrocarbon contaminants on the surface of the titania-coated zirconia. The UV-treated titania coating significantly promoted the proliferation, spreading, and up-regulation of adhesion-related genes and proteins of HGFs. Furthermore, the titania coating irradiated with UV could reduce the adhesion, colonization and metabolic activity ofS. mutansandP. gingivalis. Therefore, UV irradiation of titania-coated zirconia can promote the biological behavior of HGFs and exert a significant antibacterial effect, which has broad clinical application prospects for improving soft tissue integration around zirconia abutments.

Unveiling the governing role of 'remodeling triangle area' in soft-hard tissue interface equilibrium for metal implants advancement

Metal implants holds significant promise for diverse fixed prostheses. However, their long-term reliability and broader application are hindered by challenges related to the disequilibrium at the soft-hard tissue interface. By using anti-inflammatory (PDA/IL4) and pro-inflammatory (PDA/LPS/IFNγ) coatings to modulate distinct immune characteristics, we discovered a dynamic bioactive structure at the soft-hard tissue interface around metal implant, which we have named the 'Remodeling Triangle Area' (RTA). We further demonstrate that the RTA can be influenced by the PDA/IL4 coating to favor a phenotype that enhances both innate and adaptive immunity. This leads to stronger epithelial adhesion, the formation of dense connective tissue via IGF1 secretion, and a more balanced soft-hard tissue interface through the OPG/RANKL axis. Conversely, the PDA/LPS/IFNγ coating shifts the RTA towards a phenotype that activates the innate immune response. This results in a less cohesive tissue structure and bone resorption, characterized by reduced IGF1 secretion and an imbalanced OPG/RANKL axis. Over all, our study introduces the novel concept termed the 'Remodeling Triangle Area' (RTA), an immune-rich anatomical region located at the nexus of the implant interface, epithelial, connective, and bone tissue, which becomes highly interactive post-implantation to modulate the soft-hard tissue interface equilibrium. We believe that an RTA-centric, immunomodulatory approach has the potential to revolutionize the design of next-generation metal implants, providing unparalleled soft-hard tissue interface equilibrium properties.

Photothermal modulation of gingival fibroblasts via polydopamine-coated zirconia: A novel approach for promoting peri-implant soft tissue integration

Achieving robust soft tissue integration around dental implants is crucial for long-term clinical success, as it forms a protective biological seal against bacterial invasion. However, the soft tissue attachment to implants is relatively deficient compared to natural teeth, particularly in the connective tissue region lacking sufficient gingival fibroblasts and collagen fiber alignment. This study proposed an innovative strategy to enhance peri‑implant soft tissue integration by modulating gingival fibroblast behavior via photothermal conversion. Zirconia surfaces were coated with polydopamine (PDA), a melanin-like polymer exhibiting near-infrared (NIR) absorption for photothermal conversion. Under NIR irradiation, the PDA coating enabled mild hyperthermia (42-43 °C) on the zirconia surface. Remarkably, this mild photothermal stimulation significantly promoted human gingival fibroblast proliferation, adhesion, and collagen production compared to unmodified zirconia in vitro. By utilizing the photothermal properties of PDA coatings to modulate cellular behaviors beneficial for connective tissue formation, this approach provides a promising avenue to achieve improved soft tissue integration and long-term stability of dental implants. The findings highlight the innovative potential of combining biomaterial surface engineering with photothermal therapy for applications in implant dentistry.

Silk fibroin microgrooved zirconia surfaces improve connective tissue sealing through mediating glycolysis of fibroblasts

The use of zirconia has significantly enhanced the aesthetic outcomes of implant restorations. However, peri-implantitis remains a challenge to long-term functionality of implants. Unlike the perpendicularly arranged collagen fibers in periodontal tissue, those in peri-implant tissue lie parallel to the abutment surface and contain fewer fibroblasts, making them more prone to inflammation. Studies have shown that microgroove structures on implant abutments could improve surrounding soft tissue structure. However, creating precise microgrooves on zirconia without compromising its mechanical integrity is technically challenging. In this study, we applied inkjet printing, an additive manufacturing technique, to create stable silk fibroin microgroove (SFMG) coatings of various dimensions on zirconia substrates. SFMG significantly improved the hydrophilicity of zirconia and showed good physical and chemical stability. The SFMG with 90 μm interval and 10 μm depth was optimal in promoting the proliferation, alignment, and extracellular matrix production of human gingival fibroblasts (HGFs). Moreover, the in vitro results revealed that SFMG stimulated key glycolytic enzyme gene expression in HGFs via the PI3K-AKT-mTOR pathway. Additionally, the in vivo results of histological staining of peri-abutments soft tissue showed that SFMG promoted the vertical alignment of collagen fibers relative to the abutment surface, improving connective tissue sealing around the zirconia abutment. Our results indicated that SFMG on zirconia can enhance HGF proliferation, migration and collagen synthesis by regulating glycolysis though PI3K-AKT-mTor pathway, thereby improving connective tissue sealing.

Advances in zirconia-based dental materials: Properties, classification, applications, and future prospects

OBJECTIVES

Zirconia (ZrO2) ceramics are widely used in dental restorations due to their superior mechanical properties, durability, and ever-improving translucency. This review aims to explore the properties, classification, applications, and recent advancements of zirconia-based dental materials, highlighting their potential to revolutionize dental restoration techniques.

STUDY SELECTION, DATA AND SOURCES

The most recent literature available in scientific databases (PubMed and Web of Science) reporting advances of zirconia-based materials within the dental field is thoroughly examined and summarized, covering the major keywords "dental zirconia, classification, aesthetic, LTD, applications, manufacturing, surface treatments".

CONCLUSIONS

An exhaustive overview of the properties, classifications, and applications of dental zirconia was presented, alongside an exploration of future prospects and potential advances. This review highlighted the importance of addressing challenges such as low-temperature degradation resistance and optimizing the balance between mechanical strength and translucency. Also, innovative approaches to improve the performances of zirconia as dental material was discussed.

CLINICAL SIGNIFICANCE

This review provides a better understanding of zirconia-based dental biomaterials for dentists, helping them to make better choice when choosing a specific material to fabricate the restorations or to place the implant. Moreover, new generations of zirconia are still expected to make progress on key issues such as the long-term applications in dental materials while maintaining both damage resistance and aesthetic appeal, defining the directions for future research.

Comparison of Peri-Implant Soft Tissue Around Zirconia and Titanium Abutments in the Aesthetic Zone: A Narrative Review

This narrative review compares the peri-implant soft tissue responses around zirconia and titanium abutments in the aesthetic zone, emphasizing their mechanical, biological, and aesthetic properties. Titanium abutments, known for their excellent mechanical strength and fatigue resistance, have traditionally been the standard in dental restorations but face challenges in aesthetic integration due to their metallic appearance and potential for higher inflammatory responses. Zirconia abutments, emerging as a promising alternative, offer superior aesthetic outcomes, reduced plaque accumulation, and lower inflammatory responses, making them ideal for use in visible areas with thin soft tissue biotypes. However, zirconia's mechanical properties, such as lower fracture resistance, necessitate careful clinical application. The review also highlights rare instances of titanium allergies, underscoring the importance of individualized treatment planning and regular monitoring to ensure the longevity and success of implant restorations.

Soft and Hard Tissue Integration around Percutaneous Bone-Anchored Titanium Prostheses: Toward Achieving Holistic Biointegration

A holistic biointegration of percutaneous bone-anchored metallic prostheses with both hard and soft tissues dictates their longevity in the human body. While titanium (Ti) has nearly solved osseointegration, soft tissue integration of percutaneous metallic prostheses is a perennial problem. Unlike the firm soft tissue sealing in biological percutaneous structures (fingernails and teeth), foreign body response of the skin to titanium (Ti) leads to inflammation, epidermal downgrowth and inferior peri-implant soft tissue sealing. This review discusses various implant surface treatments/texturing and coatings for osseointegration, soft tissue integration, and against bacterial attachment. While surface microroughness by SLA (sandblasting with large grit and acid etched) and porous calcium phosphate (CaP) coatings improve Ti osseointegration, smooth and textured titania nanopores, nanotubes, microgrooves, and biomolecular coatings encourage soft tissue attachment. However, the inferior peri-implant soft tissue sealing compared to natural teeth can lead to peri-implantitis. Toward this end, the application of smart multifunctional bioadhesives with strong adhesion to soft tissues, mechanical resilience, durability, antibacterial, and immunomodulatory properties for soft tissue attachment to metallic prostheses is proposed.

Biocompatible Nanostructured Silver-Incorporated Implant Surfaces Show Effective Antibacterial, Osteogenic, and Anti-Inflammatory Effects in vitro and in Rat Model

Introduction

Titanium (Ti) and its alloys are widely utilized in endosseous implants. However, their clinical efficacy is marred by complications arising from bacterial infections owing to their inadequate antibacterial properties. Consequently, enhancing the antibacterial attributes of implant surfaces stands as a pivotal objective in the realm of implantable materials research.

Methods

In this study, we employed sequential anodization and plasma immersion ion implantation (PIII) technology to fabricate a silver-embedded sparsely titania nanotube array (SNT) on the near-β titanium alloy Ti-5Zr-3Sn-5Mo-15Nb (TLM) implants. The surface characteristics, antimicrobial properties, biocompatibility, and osteogenic activity of the silver-nanomodified SNT implant (SNT Ag) surface, alongside peri-implant inflammatory responses, were meticulously assessed through a combination of in vitro and in vivo analyses.

Results

Compared with polished TLM and SNT, the silver-embedded SNT (SNT Ag) surface retained the basic shape of nanotubes and stably released Ag+ at the ppm level for a long time, which demonstrated an effective inhibition and bactericidal activity against Staphylococcus aureus (SA) while maintaining ideal cytocompatibility. Additionally, the subtle modifications in nanotubular topography induced by silver implantation endowed SNT Ag with enhanced osteogenic activity and mitigated inflammatory capsulation in soft tissue peri-implants in a rat model.

Conclusion

Incorporating a silver-embedded SNT array onto the implant surface demonstrated robust antibacterial properties, impeccable cytocompatibility, exceptional osteogenic activity, and the potential to prevent inflammatory encapsulation around the implant site. The Silver-PIII modification strategy emerges as a highly promising approach for surface applications in endosseous implants and trans-gingival implant abutments.