Osseointegrable dental implants are biomaterials made of titanium or other alloys mixed with titanium, which have high biocompatibility and allow osseointegration. However, this process can be modulated by changes in the complex mechanisms between microbiota, immune response and host. The present study aims to present how the immune system-microbiota-host interaction influences the osseointegration process of titanium dental implants and its alloys. A literature review was performed through electronic and manual searches in several databases, including PubMed, LILACS, Google Scholar, SciELO and Web of Science for articles published in the last 20 years in English and Portuguese. The formation of a temporary fibrin matrix on the implants surface after implantation implies the recruitment, adhesion and activity of immune cells at this site, with the release of pro-inflammatory molecules and recruitment of neutrophils. In the second moment, monocytes and macrophages (M1) are recruited, producing, in this step, reactive oxygen species. In the later stage of inflammation, macrophages (M2) help in tissue regeneration with expression of anti-inflammatory cytokines. In addition, the implants surface provides a site for microbial colonization mediated by salivary pellicle and topographical features. Thus, in symbiosis the modulation of the immune response will be favorable to osseointegration. However, the dysbiotic process exacerbates the inflammatory progression modulating the immune response influencing abnormal tissue healing or scar and fibrosis formation, compromising osseointegration. Different conditions of the subgingival microbiota will influence different immunological cascades, generating different cellular responses and positive or negative modulation of the osseointegration process.

There has yet to be a consensus among researchers, professionals, companies, regulatory agencies, and technical standards regarding the definition of osseointegration. The divergence is conceptual and occurs due to explanations of the mechanisms of interactions among cells and proteins with the implant. In medicine, osseointegration is assessed visually in radiographic examinations by the absence of implant-bone space or by mechanical stability and absence of pain. In the medical field, it is mentioned that there is osseointegration of cemented orthopedic prostheses, stainless steel prostheses, Co-Cr-Mo alloys, and zirconia. In dentistry, osseointegration occurs only with titanium implants and is characterized by bonding bone cells with the implant surface through proteins. Titanium implants are chemically, physically, and mechanically linked to the bone through proteins adhered to their surface without a fibrous connective tissue interface. The protein-titanium connection has mechanical strength and can withstand functional loads on dental implants. Given the divergences in the understanding of osseointegration of titanium and zirconia implants, concepts are presented that explain the differences in biocompatibility and applications of biomaterials, inflammatory processes, osseointegration, foreign body reaction, and the mechanisms of protein interactions with surfaces of titanium and zirconia implants.

The peri-implant ligament is formed from the interface of bone tissue, through the anchoring of proteins and the surface of the dental implant. In this sense, it is relevant to understand the extent to which this ligament is structured and biomimics the periodontal ligament functions. Aim: The goal of this scoping review is to present and analyze the peri-implant ligament composition and compare the extent to which this ligament is structured and biomimics the periodontal ligament functions. Methods: This scoping review was performed according to the Joanna Briggs Institute methodology for scoping reviews and following the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension for scoping review. Two independent researchers searched Pubmed, Cochrane, Embase, Virtual Health Library, Scielo, Scopus, Web of Science, Brazilian Bibliography of Dentistry, Latin American and Caribbean Literature in Health Sciences, Digital Library of Theses and Dissertations from the University of São Paulo and Portal Capes. Studies published in English, Portuguese and Spanish, over the last 21 years (2000-2021). Results: A total of 330 titles were identified and after applying inclusion and exclusion factors, 27 studies were included in this review. All proteins were identified regarding their tissue function and classified into 6 major protein groups. After that this new protein ligament was compared with the periodontal ligament regarding its function and composition. The main proteins associated with osseointegration, and thus, with the peri-implant ligament are recognized as belonging to the periodontal ligament. Conclusion: This scoping review results suggest evidence of the composition and function of the periimplant ligament. However, variations may still exist due to the existence of several modulants of the osseointegration process.

Achieving the appropriate primary stability for immediate or early loading in areas with low-density bone, such as the posterior maxilla, is challenging. A three-dimensional (3D) stabilization implant design featuring a tapered body with continuous cutting flutes along the length of the external thread form, with a combination of curved and linear geometric surfaces on the thread’s crest, has the capacity to enhance early biomechanical and osseointegration outcomes compared to implants with traditional buttressed thread profiles. Commercially available implants with a buttress thread design (TP), and an experimental implant that incorporated the 3D stabilization trimmed-thread design (TP 3DS) were used in this study. Six osteotomies were surgically created in the ilium of adult sheep (N = 14). Osteotomy sites were randomized to receive either the TP or TP 3DS implant to reduce site bias. Subjects were allowed to heal for either 3 or 12 weeks (N = 7 sheep/time point), after which samples were collected en bloc (including the implants and surrounding bone) and implants were either subjected to bench-top biomechanical testing (e.g., lateral loading), histological/histomorphometric analysis, or nanoindentation testing. Both implant designs yielded high insertion torque (ITV ≥ 30 N⋅cm) and implant stability quotient (ISQ ≥ 70) values, indicative of high primary stability. Qualitative histomorphological analysis revealed that the TP 3DS group exhibited a continuous bone–implant interface along the threaded region, in contrast to the TP group at the early, 3-week, healing time point. Furthermore, TP 3DS’s cutting flutes along the entire length of the implant permitted the distribution of autologous bone chips within the healing chambers. Histological evaluation at 12 weeks revealed an increase in woven bone containing a greater presence of lacunae within the healing chambers in both groups, consistent with an intramembranous-like healing pattern and absence of bone dieback. The TP 3DS macrogeometry yielded a ~66% increase in average lateral load during pushout testing at baseline (T = 0 weeks, p = 0.036) and significantly higher bone-to-implant contact (BIC) values at 3 weeks post-implantation (p = 0.006), relative to the traditional TP implant. In a low-density (Type IV) bone model, the TP 3DS implant demonstrated improved performance compared to the conventional TP, as evidenced by an increase in baseline lateral loading capacity and increased BIC during the early stages of osseointegration. These findings indicate that the modified implant configuration of the TP 3DS facilitates more favorable biomechanical integration and may promote more rapid and stable bone anchorage under compromised bone quality conditions. Therefore, such improvements could have important clinical implications for the success and longevity of dental implants placed in regions with low bone density.

Trabecular Metal^TM (TM) dental implants comprise a tantalum (Ta)-based biomimetic open-cell structure designed to replicate the structural, functional, and physiological properties of cancellous bone. Yet, the current literature primarily focuses on the evaluation of osseointegration outcomes surrounding TM implants in uncompromised bone environments and/or brief periods of observation in pre-clinical models. In addition, the performance of TM implants in bony defect environments reconstructed with allogenic grafts and bioactive molecules, such as platelet-rich fibrin (PRF), has not been thoroughly investigated. This longitudinal, randomized clinical trial comprised patients presenting with completely edentulous maxillaries. Guided Bone Regeneration (GBR) was performed using a cortico-cancellous allograft/PRF agglomerate. After 26 weeks, bone biopsies were obtained, followed by the insertion of a TM implant, after which patients were allowed to heal for 52 weeks for assessment of osseointegration. Qualitatively, histomicrographs at 26 weeks confirmed the presence of newly formed bone extending from the periphery of defects and along the direct surface of the allograft. TM implant biopsies at 52 weeks demonstrated osseointegration with bone ongrowth and ingrowth at the interconnected, porous trabecular region. These histological characteristics were consistent across all patients. No metal debris was detected, and the TM implants maintained their porous structure throughout the study period. TM implants placed in PRF-augmented allograft-reconstructed maxillae fostered a conducive environment for osseointegration. By leveraging the open-cell Ta structure, robust new bone formation was achieved without signs of adverse tissue reactions.