Soft tissue sealing around dental implants based on histological interpretation

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.

Development of a Coculture Model for Assessing Competing Host Mammalian Cell and Bacterial Attachment on Zirconia versus Titanium

Objectives: Coculture models are limited by bacteria rapidly outcompeting host mammalian cells for nutrients in vitro, resulting in mammalian cell death. The goal of this study was to develop a coculture model enabling survival of mammalian cells and oral bacterial species to assess their competition for growth on dental implant materials. Methods: Two early colonizing oral bacterial species, Streptococcus mutans or Actinomyces naeslundii, were grown in coculture with primary human macrophages or human gingival fibroblasts for up to 7 days on tissue-culture treated polystyrene or polished titanium and zirconia disks. Chloramphenicol was supplemented in cell culture medium at bacteriostatic concentrations to maintain stable bacterial inoculum size. Planktonic and adherent bacterial growth was assessed via spot plating while mammalian cell growth and attachment were evaluated using colorimetric metabolic assay and confocal fluorescence microscopy, respectively. Results: Macrophages and fibroblasts proliferated in the presence of S. mutans and maintained viability above 70% during coculture for up to 7 days on tissue-culture treated polystyrene and polished titanium and zirconia. In contrast, both mammalian cell types exhibited decreasing proliferation and surface coverage on titanium and zirconia over time in coculture with A. naeslundii versus control. S. mutans and A. naeslundii were maintained within an order of magnitude of seeding inoculum sizes throughout coculture. Significance: Cell culture medium supplemented with antibiotics at bacteriostatic concentrations can suppress bacterial overgrowth and facilitate mammalian cell viability in coculture model systems. Within the study's limitations, oral bacteria and mammalian cell growth in coculture are comparable on polished titanium and zirconia surfaces.

Osseointegration of Anodized vs. Sandblasted Implant Surfaces in a Guided Bone Regeneration Acute Dehiscence-Type Defect: An In Vivo Experimental Mandibular Minipig Model

OBJECTIVES

This controlled preclinical study analyzed the effect of implant surface characteristics on osseointegration and crestal bone formation in a grafted dehiscence defect minipig model.

MATERIAL AND METHODS

A standardized 3 mm × 3 mm acute-type buccal dehiscence minipig model grafted with deproteinized bovine bone mineral and covered with a porcine collagen membrane after 2 and 8 weeks of healing was utilized. Crestal bone formation was analyzed histologically and histomorphometrically to compare three implant groups: (1) a novel, commercially available, gradient anodized (NGA) implant, to two custom-made geometric replicas of implant "1," (2) a superhydrophilic micro-rough large-grit sandblasted and acid-etched surface, and (3) a relatively hydrophobic micro-rough large-grit sandblasted and acid-etched surface.

RESULTS

At 2 and 8 weeks, there was no difference between the amount and height of newly formed bone (NBH, new bone height; BATA, bone area to total area) for any of the groups (p > 0.05). First bone-to-implant contact (fBIC) and vertical bone creep (VBC) at 2 and 8 weeks were significantly increased for Groups 2 and 3 compared to Group 1 (p < 0.05). At 8 weeks, osseointegration in the dehiscence (dehiscence bone-implant-contact; dBIC) was significantly higher for Groups 2 and 3 compared to Group 1 (p < 0.05).

CONCLUSIONS

The amount of newly formed bone (BATA) and NBH was not influenced by surface type. However, moderately rough surfaces demonstrated significantly superior levels of osseointegration (dBIC) and coronal bone apposition (fBIC) in the dehiscence defect compared to the NGA surface at 2 and 8 weeks.

TRIAL REGISTRATION

For this type of study, clinical trial registration is not required. This study was conducted at the Biomedical Department of Lund University (Lund, Sweden) and approved by the local Ethics Committee of the University (M-192-14).

Revolutionizing Dental Implant Research: A Systematic Review on Three-Dimensional In Vitro Models

Dental implants have been clinically used for almost five decades with high success rates. In vitro research models used in implant dentistry are limited to two-dimensional experiments, which are reproducible and well adapted to evaluate a single parameter but do not reproduce the complexity of clinical settings. On the contrary, the in vivo research models using animals offer similar histological and anatomical features to humans, and tissue healing can be close to a clinical situation, but those models are usually accompanied with ethical concerns, and their outcomes could not be extrapolated to humans because of interspecies variabilities. This makes the development of novel in vitro models that recapitulate physiological events occurring during dental implant placement of particular interest for current research in dentistry. Also, such models could be challenged by setting a pathological environment (peri-implantitis) to better understand the disease and eventually serve as a platform to evaluate novel treatment modalities. The aim of this systematic literature review was to cover all the in vitro three-dimensional (3D) complex models available for research in implant dentistry. To accomplish this, a comprehensive search of the literature present on Scopus and PubMed databases was done using specific keywords, as well as inclusion/exclusion criteria. Out of 1334 articles found, we have finally included 27 articles in this review with publication dates between 2001 and 2022. In those articles, the 3D models were designed to study tissue-implant interface behavior in bone or gingival tissue. The articles focused on simulating implant integration, evaluating the effect of different conditions on implant integration, or developing an infection model for the implant integration process. The methods used involved implant material and cells organized in a specific 3D structure. The 3D models developed were able to simulate the process of dental implant osseo- and soft tissue integration and lead to results comparable with conventional in vitro and in vivo models. A relatively limited number of articles were obtained, which indicates that this is an emerging field, highly dependent on progresses made in biotechnologies and tissue engineering, and that further investigation is needed to enhance these 3D in vitro models.

The 50 most cited articles on soft tissue integration of dental implants: A bibliometric analysis

STATEMENT OF PROBLEM

Soft tissue integration helps prevent the bacterial invasion of dental implants, but bibliometric studies on the top 50 most cited articles in the field of soft tissue integration are lacking.

PURPOSE

The purpose of this bibliometric study was to analyze the 50 most cited articles since 1999 to explore global trends and research hotspots.

MATERIAL AND METHODS

A specific search strategy of the Science Citation Index Expanded (Web of Science) was devised, and relevant article-based, journal-based, and author-based parameters were analyzed. Correlation analysis was performed (α=.05).

RESULTS

The number of citations ranged from 71 to 586. Clinical Oral Implants Research was the most cited journal (1722 citations). Berglundh, Tord was the author with the most publications (6 publications) and citations (957 citations). Dental implants and titanium were the keywords with the highest frequency. Switzerland was the country with the highest number of publications (12 publications). Correlation was found between the publication year and average annual citations (P<.001).

CONCLUSIONS

This study determined the scientific progress in soft tissue integration. The surface design of dental implant materials is essential for the soft tissue integration of dental implants. Soft tissue integration has been a focus of interest in the past few years, but many experiments still need to be done to improve soft tissue compatibility with innovative materials.

Clinical efficacy of two vertical soft tissue augmentation techniques for peri-implant crestal bone level stability: A randomized clinical trial

OBJECTIVES

This study aimed to compare the efficacy of two techniques-acellular dermal matrix (ADM) grafting and tenting technique (TT)-for soft tissue height (STH) augmentation simultaneous to implant placement to minimize peri-implant crestal bone level (CBL) changes.

METHODS

Forty patients with a healed single mandibular posterior edentulous site with a thin soft tissue phenotype were enrolled. Twenty patients received simultaneously to implant placement ADM grafting, while the others received submerged healing abutment (TT). Clinical peri-implant soft tissue height and radiographic CBL changes were measured at restoration delivery and 1-year follow-up.

RESULTS

Both techniques effectively increased soft tissue thickness, resulting in a final average STH of 3.4 ± 0.5 mm after augmentation. On average, soft tissue increased by 1.6 ± 0.5 mm in group ADM and by 1.8 ± 0.4 mm in group TT after augmentation. In Group ADM, mesial CBL decreased from 0.4 ± 0.3 mm to 0.1 ± 0.2 mm, and distal CBL decreased from 0.5 ± 0.3 mm to 0.2 ± 0.3 mm over 1 year. In Group TT, mesial CBL remained stable at 0.3 ± 0.2 mm, while distal CBL reduced slightly from 0.5 ± 0.5 mm to 0.3 ± 0.2 mm. Both groups showed minimal changes in CBL, indicating great stability (pmesial = 0.003, pdistal = 0.004). TT was particularly effective in preventing mesial bone loss (pmesial = 0.019). The mesial CBL changes significantly differed between groups (p = 0.019), and not significantly at distal sites (p = 0.944). Neither treatment exhibited significant bone remodeling below the implant shoulder.

CONCLUSION

This study suggests that both techniques were successful in STH augmentation, and they may effectively reduce peri-implant crestal bone level changes, with TT being slightly superior. TT was more prone to post-surgical complications. This RCT was not registered before participant recruitment and randomization.

Roughness affects the response of human fibroblasts and macrophages to sandblasted abutments

BACKGROUND

A strong seal of soft-tissue around dental implants is essential to block pathogens from entering the peri-implant interface and prevent infections. Therefore, the integration of soft-tissue poses a challenge in implant-prosthetic procedures, prompting a focus on the interface between peri-implant soft-tissues and the transmucosal component. The aim of this study was to analyse the effects of sandblasted roughness levels on in vitro soft-tissue healing around dental implant abutments. In parallel, proteomic techniques were applied to study the interaction of these surfaces with human serum proteins to evaluate their potential to promote soft-tissue regeneration.

RESULTS

Grade-5 machined titanium discs (MC) underwent sandblasting with alumina particles of two sizes (4 and 8 μm), resulting in two different surface types: MC04 and MC08. Surface morphology and roughness were characterised employing scanning electron microscopy and optical profilometry. Cell adhesion and collagen synthesis, as well as immune responses, were assessed using human gingival fibroblasts (hGF) and macrophages (THP-1), respectively. The profiles of protein adsorption to the surfaces were characterised using proteomics; samples were incubated with human serum, and the adsorbed proteins analysed employing nLC-MS/MS. hGFs exposed to MC04 showed decreased cell area compared to MC, while no differences were found for MC08. hGF collagen synthesis increased after 7 days for MC08. THP-1 macrophages cultured on MC04 and MC08 showed a reduced TNF-α and increased IL-4 secretion. Thus, the sandblasted topography led a reduction in the immune/inflammatory response. One hundred seventy-six distinct proteins adsorbed on the surfaces were identified. Differentially adsorbed proteins were associated with immune response, blood coagulation, angiogenesis, fibrinolysis and tissue regeneration.

CONCLUSIONS

Increased roughness through MC08 treatment resulted in increased collagen synthesis in hGF and resulted in a reduction in the surface immune response in human macrophages. These results correlate with the changes in protein adsorption on the surfaces observed through proteomics.

Multifunctional and bioinspired titanium surface with multilayer nanofilms for novel dental implant applications

Introduction: Smart multifunctional surfaces targeting intricate biological events or versatile therapeutic strategies are imminent to achieve long-term transmucosal implant success. Methods: This study used dopamine (DA), graphene oxide (GO), and type IV collagen (COL-IV) to construct multilayer nanofilms (DGCn) based on their universal adhesive and biomimetic properties to design a versatile and bioactive titanium implant. The characterization of DGCn on different titanium surfaces was performed, and its loading capacity, release profile, in situ gene delivery, and in vitro biological properties were preliminarily evaluated. Results: Our results demonstrate that hydrogenated TiO2 nanotubes (H) provide a better platform for the DGCn coating than machined Ti and air-TiO2 nanotubes. The H-DGC10 displayed the most stable surface with excellent loading capacity, sustained-release profile, and in situ gene transfection efficiency; this could be due to the high specific surface area of H and GO, as well as the functional groups in H, DA, and GO. Moreover, the H-DGC10 exhibited good biocompatibility for human oral epithelial cells and promoted the expression of integrin β4 and laminin 332, both being hemidesmosome-related proteins. Discussion: Our findings suggest that H-DGCn can be designed as a smart multifunctional interface for titanium implants to achieve long-term transmucosal implant success and aid in versatile therapeutic strategies.

The use of customized 3D-printed mandibular prostheses with pressure-reducing device: A clinical trial

BACKGROUND

Segmental bone defects of the mandible result in the complete loss of the affected region. We had incorporated the pressure-reducing device (PRD) designs into the customized mandible prostheses (CMP) and conducted a clinical trial to evaluate this approach.

METHODS

Seven patients were enrolled in this study. We examined the association among the history of radiotherapy, the number of CMP regions, the number of chin regions involved, and CMP exposure.

RESULTS

We included five men and two women with an average age of 55 years. We excised tumors with an average weight of 147.8 g and the average weight of the CMP was 68.5 g. No significant difference between the two weights was noted (p = 0.3882). Three patients received temporary dentures and the CMP remained stable in all patients.

CONCLUSION

The use of PRD in CMP may address the previous challenges associated with CMP, but further research is necessary.

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.

Experimental models for peri-implant diseases: a narrative review

OBJECTIVES

Peri-implant diseases, being the most common implant-related complications, significantly impact the normal functioning and longevity of implants. Experimental models play a crucial role in discovering potential therapeutic approaches and elucidating the mechanisms of disease progression in peri-implant diseases. This narrative review comprehensively examines animal models and common modeling methods employed in peri-implant disease research and innovatively summarizes the in vitro models of peri-implant diseases.

MATERIALS AND METHODS

Articles published between 2015 and 2023 were retrieved from PubMed/Medline, Web of Science, and Embase. All studies focusing on experimental models of peri-implant diseases were included and carefully evaluated.

RESULTS

Various experimental models of peri-implantitis have different applications and advantages. The dog model is currently the most widely utilized animal model in peri-implant disease research, while rodent models have unique advantages in gene knockout and systemic disease induction. In vitro models of peri-implant diseases are also continuously evolving to meet different experimental purposes.

CONCLUSIONS

The utilization of experimental models helps simplify experiments, save time and resources, and promote advances in peri-implant disease research. Animal models have been proven valuable in the early stages of drug development, while technological advancements have brought about more predictive and relevant in vitro models.

CLINICAL RELEVANCE

This review provides clear and comprehensive model selection strategies for researchers in the field of peri-implant diseases, thereby enhancing understanding of disease pathogenesis and providing possibilities for developing new treatment strategies.

Cementum and enamel surface mimicry influences soft tissue cell behavior

AIMS

To test whether titanium surface roughness disparity might be used to specifically guide the behavior of gingiva fibroblasts and keratinocytes, thereby improving the quality of soft tissue (ST) integration around abutments.

METHODS

Titanium discs resembling the roughness of enamel (M) or cementum (MA) were created with normal or increased hydrophilicity and used as substrates for human fibroblasts and keratinocytes. Adhesion and proliferation assays were performed to assess cell-type specific responses upon encountering the different surfaces. Additionally, immunofluorescence and qPCR analyses were performed to study more in depth the behavior of fibroblasts and keratinocytes on MA and M surfaces, respectively.

RESULTS

While enamel-like M surfaces supported adhesion, growth and a normal differentiation potential of keratinocytes, cementum-emulating MA surfaces specifically impaired the growth of keratinocytes. Vice versa, MA surfaces sustained regular adhesion and proliferation of fibroblasts. Yet, a more intimate adhesion between fibroblasts and titanium was achieved by an increased hydrophilicity of MA surfaces, which was associated with an increased expression of elastin.

CONCLUSION

The optimal titanium implant abutment might be achieved by a bimodal roughness design, mimicking the roughness of enamel (M) and cementum with increased hydrophilicity (hMA), respectively. These surfaces can selectively elicit cell responses favoring proper ST barrier by impairing epithelial downgrowth and promoting firm adhesion of fibroblasts.

Biological Response of the Peri-Implant Mucosa to Different Definitive Implant Rehabilitation Materials

BACKGROUND

Sealing the peri-implant tissue is a determining factor for long-term implant survival. In the transmucosal region, the cervical fraction of the prosthetic crown is in contact with these tissues, so mucointegration will also be influenced by the biomaterial used for the prosthetic restoration. This study aims to compare the tissue response generated by definitive restorative materials and polymeric materials from a histological point of view.

METHODS

This study performed an observational prospective cohort study in which biopsies of the peri-implant mucosa were taken after placement of implant-supported prosthetic restorations made of different materials (zirconium oxide, lithium disilicate, and PMMA).

RESULTS

A statistically significant difference was observed in the increase in the thickness of the non-keratinized epithelium when comparing the definitive materials (zirconium oxide/lithium disilicate) vs. the provisional material (PMMA) and in the number of collagen fibers when comparing zirconium oxide and lithium disilicate.

CONCLUSIONS

This study found that zirconia is the material that presents the most adequate biological response of peri-implant tissues. It shows a lower intensity of inflammatory cellular content, a total normality in the number of collagen fibers (the arrangement of the fibers is normal in 90% of the cases), and vascular proliferation of connective tissue in 83% of the cases. These parameters make it a material with a predictable response. Similarly, only the following slight statistically significant differences between the definitive and provisional materials are observed, indicating that the biological response generated by the provisional material (PMMA) is not very different from that obtained with the placement of the definitive restoration.

Surface Topography Steer Soft Tissue Response and Antibacterial Function at the Transmucosal Region of Titanium Implant

Metallic dental implants have been extensively used in clinical practice due to their superior mechanical properties, biocompatibility, and aesthetic outcomes. However, their integration with the surrounding soft tissue at the mucosal region remains challenging and can cause implant failure due to the peri-implant immune microenvironment. The soft tissue integration of dental implants can be ameliorated through different surface modifications. This review discussed and summarized the current knowledge of topography-mediated immune response and topography-mediated antibacterial activity in Ti dental implants which enhance soft tissue integration and their clinical performance. For example, nanopillar-like topographies such as spinules, and spikes showed effective antibacterial activity in human salivary biofilm which was due to the lethal stretching of bacterial membrane between the nanopillars. The key findings of this review were (I) cross-talk between surface nanotopography and soft tissue integration in which the surface nanotopography can guide the perpendicular orientation of collagen fibers into connective tissue which leads to the stability of soft tissue, (II) nanotubular array could shift the macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) and manipulate the balance of osteogenesis/osteoclasia, and (III) surface nanotopography can provide specific sites for the loading of antibacterial agents and metallic nanoparticles of clinical interest functionalizing the implant surface. Silver-containing nanotubular topography significantly decreased the formation of fibrous encapsulation in per-implant soft tissue and showed synergistic antifungal and antibacterial properties. Although the Ti implants with surface nanotopography have shown promising in targeting soft tissue healing in vitro and in vivo through their immunomodulatory and antibacterial properties, however, long-term in vivo studies need to be conducted particularly in osteoporotic, and diabetic patients to ensure their desired performance with immunomodulatory and antibacterial properties. The optimization of product development is another challenging issue for its clinical translation, as the dental implant with surface nanotopography must endure implantation and operation inside the dental microenvironment. Finally, the sustainable release of metallic nanoparticles could be challenging to reduce cytotoxicity while augmenting the therapeutic effects.

Topological insight of immune-vascular distribution in peri-implantitis lesions

OBJECTIVE

To characterize the distribution of macrophages, neutrophils, NK cells, and blood vessels in peri-implantitis compared to healthy aged gingiva samples.

MATERIALS AND METHODS

This observational study included eight gingival samples from peri-implantitis and eight from periodontally healthy individuals. By immunofluorescence were identified neutrophils, NK cells, macrophages, and their pro-inflammatory or pro-healing phenotypes, and blood vessels. Two ROIs were designated as zone 1, connective tissue closest to the epithelium and zone 2, connective tissue over 200 microns from the rete ridges. Immune cells and vascular structures were quantified and characterized according to their distribution in both zones.

RESULTS

Two peri-implantitis zones were characterized by unique macrophage phenotypes and blood vessel architecture. Blood vessels were larger in zone 2 in peri-implantitis. A greater number of NK cells and macrophages were found in peri-implantitis compared to healthy aged samples. A higher presence of pro-inflammatory macrophages was found in zone 1 compared to zone 2. A similar proportion of pro-inflammatory and pro-healing macrophages were found in zone 2.

CONCLUSION

A specific distribution for pro-inflammatory macrophages and vascular architecture is observed in peri-implantitis. TNF-α colocalizes with macrophages in the connective tissue near rete ridges. NK cells are more abundant in peri-implantitis than in healthy samples.

Surface modification affects human gingival epithelial cell behavior on polyetheretherketone surfaces

Gingival epithelial attachment to the abutment is important for the prevention of peri-implantitis. Polyetheretherketone (PEEK) has recently gained attention as an alternative material to titanium; however, it is biologically inert, which is disadvantageous for obtaining soft tissue sealing of the transmucosal part of the implant abutment. Therefore, ultraviolet (UV) irradiation, argon plasma irradiation, and buffing were selected as treatments to modify the PEEK surface. None of the treatments had any effect on the material's mechanical strength. The UV and plasma treatments did not significantly affect the surface morphology. Surface elemental analysis showed a decrease in carbon content and an increase in oxygen content and wettability for all treatments. Human gingival epithelial cell adhesion, proliferation, and the expression of adhesion proteins integrin β4 and laminin 332, were increased. Surface modification to PEEK was suggested to enhance cell activity on PEEK.

Highly Ordered Nanotube-Like Microstructure on Titanium Dental Implant Surface Fabricated via Anodization Enhanced Cell Adhesion and Migration of Human Gingival Fibroblasts

Background

Titanium (Ti) surface with nanotubes array via anodization has been used in dental implants to enhance bone regeneration but little research was carried out to evaluate whether the presence of highly ordered or disorderly distributed nanotubes array on titanium surface would have an effect on cell behaviors of gingival fibroblasts.

Methods

The present study fabricated nanotubes arrays with varied topography under different constant voltage of electrochemical anodization in fluorine-containing electrolyte. Human gingival fibroblasts (HGFs) from extracted third molar were harvested and co-cultured with titanium disks with different nanotubes topography. Then cell behaviors of gingival fibroblasts including cell proliferation, adhesive morphology and cell migration were estimated to investigate the influence of titanium nanotubes on cell biology. Besides, gene and protein expression of adhesion molecule (integrin β1/β4/α6, fibronectin, intracellular adhesion molecule-1 and collagen type I) were detected to evaluate the influence of different surfaces on cell adhesion.

Results

Highly ordered arrays of nanotubes with pore diameter of 60 nm and 100 nm were fabricated under 30 and 40 V of anodization (TNT-30 and TNT-40) while disorderedly distributed nanotube arrays formed on the titanium surface under 50 V of anodization (TNT-50). Our results demonstrated that compared with raw titanium surface and disorderly nanotubes, surface with orderly nanotubes array increased cell area and aspect ratio, as well as cell migration ability in the early phase of cell adhesion (p<0.05). Besides, compared with raw titanium surface, gene and protein expression of adhesion molecules were upregulated in nanotubes groups to different extents, no matter whether in an orderly or disorderly array.

Conclusion

Within the limitations of our study, we conclude that compared with raw titanium surface, the presence of nanotubes array on titanium surface could enhance cells adhesion and cell migration in the early phase. And compared with disorderly distributed nanotubes, highly ordered nanotubes array might provide a much more favorable surface for gingival fibroblasts to achieve a tight adhesion on the materials.

Influences of standardized clinical probing on peri-implant soft tissue seal in a situation of peri-implant mucositis: A histomorphometric study in dogs

BACKGROUND

Clinical probing is commonly recommended to evaluate peri-implant conditions. In a situation of peri-implant mucositis or peri-implantitis, the peri-implant seal healing from the disruption of soft tissue caused by probing has not yet been studied. This study aimed to investigate soft tissue healing after standardized clinical probing around osseointegrated implants with peri-implant mucositis in a dog model.

METHODS

Three transmucosal implants in each hemi-mandible of six dogs randomly assigned to the peri-implant healthy group or peri-implant mucositis group were probed randomly in the mesial or distal site as probing groups (PH or PM), the cross-sectional opposite sites as unprobed control groups. Histomorphometric measurements of implant shoulder (IS)-most coronal level of alveolar bone contact to the implant surface (BCI), apical termination of the junctional epithelium (aJE)-BCI, mucosal margin (MM)-BCI, and MM-aJE were performed at 1 day, 1 week, and 2 weeks after probing. Apoptosis, proliferation, proinflammatory cytokines, and matrix metalloproteinases (MMPs) of peri-implant soft tissue were estimated by immunofluorescent analysis.

RESULTS

In the PM group, apical migration of junctional epithelium was revealed by significantly decreased aJE-BCI from 1 day to 2 weeks in comparison to unprobed sites (p < 0.05), while no significant differences were found in the PH group. Immunofluorescent analysis showed higher levels of interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), MMP-1, and MMP-8, together with exaggerated apoptosis and proliferation of peri-implant soft tissue in the PM group.

CONCLUSION

Within the limitations, standardized clinical probing might lead to apical migration of the junctional epithelium in a situation of peri-implant mucositis.

3Y-TZP/Ta Biocermet as a Dental Material: An Analysis of the In Vitro Adherence of Streptococcus Oralis Biofilm and an In Vivo Pilot Study in Dogs

The surface adhesion of bacterial cells and the in vivo biocompatibility of a new ceramic-metal composite made of zirconium dioxide and tantalum were evaluated. Within the framework of an in vitro study using the crystal violet staining and colony counting methods, a relatively similar adhesion of Streptococcus oralis to the 3Y-TZP/Ta biocermet (roughness Ra = 0.12 ± 0.04 µm) and Ti-Al6-V4 titanium alloy (Ra = 0.04 ± 0.01 µm) was found. In addition, in an in vivo preliminary study focused on the histological analysis of a series of rods implanted in the jaws of beagle dogs for a six-month period, the absence of any fibrous tissue or inflammatory reaction at the interface between the implanted 3Y-TZP/Ta biocermets and the new bone was found. Thus, it can be concluded that the developed ceramic-metal biocomposite may be a promising new material for use in dentistry.

Comparative evaluation of gingival fibroblast growth on 3D-printed and milled zirconia: An in vitro study

PURPOSE

The purpose of this study was to analyze the fibroblast growth and proliferation on 3D-printed zirconia in presence and absence of porosities.

MATERIAL AND METHODS

A total of 40 bars (8 × 4 × 3) were included in this study. Thirty 3D-printed and 10 milled zirconia samples were prepared. The 3D-printed samples had different porosities, 0% (PZ0), 20% (PZ20), and 40% (PZ40) with 10 specimens in each group. Milled zirconia samples were used as the control (MZ). Rat gingival fibroblasts were cultured for 48 h, and the proliferation of fibroblasts on each sample in each group (n = 10) was determined by MTT assays. The differences among the four groups were compared by one-way ANOVA. To test the significance of the observed differences between two groups, an unpaired Student's t-test was applied. The significance level was set at p < 0.05. Qualitative analysis for the cell culture was performed using scanning electron microscopy.

RESULTS

One-way ANOVA showed that the numbers of the fibroblasts among the four groups had a statistical difference. Post hoc Bonferroni test revealed that there was no significant difference between PZ0 and MZ; however, all other groups and among groups were significantly different.

CONCLUSIONS

Fibroblasts had a better affinity toward the MZ and PZ0 in a short period of cell culture time.

Photothermal-promoted multi-functional gallic acid grafted chitosan hydrogel containing tannic acid miniaturized particles for peri-implantitis

Peri-implantitis, a leading cause of implant failure, currently lacks effective therapeutic strategies. Given that bacterial infection and reactive oxygen species overabundance serve as primary pathogenic and triggering factors, respectively, an adhesive hydrogel has been created for in-situ injection. The hydrogel is a gallic acid-grafted chitosan (CS-GA) hydrogel containing tannic acid miniaturized particles (TAMP). This provides antibacterial and antioxidant properties. Therefore, this study aims to evaluate the potential role of this hydrogel in preventing and treating peri-implantitis via several experiments. It undergoes rapid formation within a span of over 20 s via an oxidative crosslinking reaction catalyzed by horseradish peroxidase and hydrogen peroxide, demonstrating robust adhesion, superior cell compatibility, and a sealing effect. Furthermore, the incorporation of TAMP offer photothermal properties to the hydrogel, enabling it to enhance the viability, migration, and antioxidant activity of co-cultured human gingival fibroblasts when subjected 0.5 W/cm2 808 nm near-infrared (NIR) irradiation. At higher irradiation power, the hydrogel exhibits progressive improvements in its antibacterial efficacy against Porphyromonas gingivalis and Fusobacterium nucleatum. It attains rates of 83.11 ± 5.42 % and 83.48 ± 6.855 %, respectively, under 1 W/cm2 NIR irradiation. In summary, the NIR-controlled CS-GA/TAMP hydrogel, exhibiting antibacterial and antioxidant properties, represents a promising approach for the prophylaxis and management of peri-implantitis.

Accuracy of digitally coded healing abutments: A systematic review

The aim of this systematic review was to evaluate the in vitro accuracy of dental implant impressions taken using digitally coded healing abutments (CHAs) compared with impressions taken with conventional techniques (CI) and/or within the CHA group at varying degrees of angulations for multiple implant units. Two independent reviewers conducted a systematic electronic search in the MedLine, PubMed, Google Scholar, Cochrane Library, Web of Science, and Scopus databases. Some of the employed key terms, combined with the help of Boolean operators, were: "digitally coded healing abutments", "encode healing abutment", "dental implants", "impression accuracy", "digital impression", and "conventional impression". Publication dates ranged from January 2010 to November 2022. A total of 7 articles fulfilled the inclusion criteria: 6 studies compared the accuracy of CHA with conventional pick-up impression techniques, and one study only used CHAs at different angulations and heights to compare accuracy within the group. The results were divided into Group A (elastomeric impression of CHA) and Group B (CHA + Intraoral scanner). According to the results of this systematic review, elastomeric impression of CHA performed poorly when compared to CI for multiple implants, although an intraoral scan of CHA appears to be more accurate. Within the CHA group, the angulation and visible height of CHA play a significant role in impression accuracy. However, more studies are needed before CHA can be recommended for all non-parallel multiple implant-supported restorations.

A Dual-Antioxidative Coating on Transmucosal Component of Implant to Repair Connective Tissue Barrier for Treatment of Peri-Implantitis

Since the microgap between implant and surrounding connective tissue creates the pass for pathogen invasion, sustained pathological stimuli can accelerate macrophage-mediated inflammation, therefore affecting peri-implant tissue regeneration and aggravate peri-implantitis. As the transmucosal component of implant, the abutment therefore needs to be biofunctionalized to repair the gingival barrier. Here, a mussel-bioinspired implant abutment coating containing tannic acid (TA), cerium and minocycline (TA-Ce-Mino) is reported. TA provides pyrogallol and catechol groups to promote cell adherence. Besides, Ce3+ /Ce4+  conversion exhibits enzyme-mimetic activity to remove reactive oxygen species while generating O2 , therefore promoting anti-inflammatory M2 macrophage polarization to help create a regenerative environment. Minocycline is involved on the TA surface to create local drug storage for responsive antibiosis. Moreover, the underlying therapeutic mechanism is revealed whereby the coating exhibits exogenous antioxidation from the inherent properties of Ce and TA and endogenous antioxidation through mitochondrial homeostasis maintenance and antioxidases promotion. In addition, it stimulates integrin to activate PI3K/Akt and RhoA/ROCK pathways to enhance VEGF-mediated angiogenesis and tissue regeneration. Combining the antibiosis and multidimensional orchestration, TA-Ce-Mino repairs soft tissue barriers and effector cell differentiation, thereby isolating the immune microenvironment from pathogen invasion. Consequently, this study provides critical insight into the design and biological mechanism of abutment surface modification to prevent peri-implantitis.

Effects of abutment materials on peri-implant soft tissue health and stability: A network meta-analysis

PURPOSE

This systematic review aimed to evaluate the effect of the abutment material on peri-implant soft tissue health and stability.

STUDY SELECTION

An electronic and hand search was conducted until February 2022. Only prospective randomized trials (RCTs) and controlled clinical trials (CCTs) comparing titanium abutments with abutments made of different materials, with a follow-up of at least 6 months, were selected by two independent reviewers. Data on marginal bone loss (MBL) and peri-implant tissue indexes, i.e., plaque index (PI), bleeding on probing (BOP), probing depth (PD), and recession (REC), were collected. The risk of bias for RCTs and non-RCTs was evaluated according to the tool reported in the Cochrane Handbook for Systematic Reviews of Interventions and the ROBINS-I tool, respectively. Both pairwise and network meta-analyses (NMA) were performed.

RESULTS

We included 18 relevant studies from 1,437 identified studies. Overall, 612 patients were treated, and 848 abutments were inserted. Five studies presented a low risk of bias. Pairwise meta-analysis showed that, as compared to titanium, zirconia abutments presented a significantly reduced MBL (0.20 mm, 95% Confidence Interval CI [0.14-0.26], P < 0.00001). No significant differences were found for the other outcomes. In the NMA, zirconia abutments demonstrated an 83.3% probability of achieving the highest rank in PI, an 87.0% in BOP, and a 65.0% in PD outcome, suggesting that zirconia abutments generally performed better than titanium and alumina abutments.

CONCLUSIONS

Within the limits of the present study, zirconia abutments seem a viable alternative to titanium ones.

CREB3L2 Regulates Hemidesmosome Formation during Epithelial Sealing

The long-term success rate of dental implants can be improved by establishing a favorable biological sealing with a high-quality epithelial attachment. The application of mesenchymal stem cells (MSCs) holds promise for facilitating the soft tissue integration around implants, but the molecular mechanism is still unclear and the general application of MSC sheet for soft tissue integration is also relatively unexplored. We found that gingival tissue-derived MSC (GMSC) sheet treatment significantly promoted the expression of hemidesmosome (HD)-related genes and proteins in gingival epithelial cells (GECs). The formation of HDs played a key role in strengthening peri-implant epithelium (PIE) sealing. Further, high-throughput transcriptome sequencing showed that GMSC sheet significantly upregulated the PI3K/AKT pathway, confirming that cell adhesion and HD expression in GECs were regulated by GMSC sheet. We observed that the expression of transcription factor CREB3L2 in GECs was downregulated. After treatment with PI3K pathway inhibitor LY294002, CREB3L2 messenger RNA and protein expression levels were upregulated. Further experiments showed that overexpression or knockdown of CREB3L2 could significantly inhibit or promote HD-related genes and proteins, respectively. We confirmed that CREB3L2 was a transcription factor downstream of the PI3K/AKT pathway and participated in the formation of HDs regulated by GMSC sheet. Finally, through the establishment of early implant placement model in rats, we clarified the molecular function of CREB3L2 in PIE sealing as a mechanical transmission molecule in GECs. The application of GMSC sheet-implant complex could enhance the formation of HDs at the implant-PIE interface and decrease the penetration distance of horseradish peroxidase between the implant and PIE. Meanwhile, GMSC sheet reduced the length of CREB3L2 protein expression on PIE. These findings elucidate the potential function and molecular mechanism of MSC sheet regulating the epithelial sealing around implants, providing new insights and ideas for the application of stem cell therapy in regenerative medicine.

Influence of surface nanotopography and wettability on early phases of peri-implant soft tissue healing: an in-vivo study in dogs

BACKGROUND

It is well established that nanotopography and wettability of implant surfaces contribute to osseointegration and long-term implant success. However, the effects of a hydrogenated surface with nanotubular and superhydrophilic properties on peri-implant soft tissue remain unclear. This study was designed to study the impact of a modified abutment surface on early soft tissue integration compared with a machined surface.

METHODS

Thirty-six implants were placed at the bone level in the bilateral mandible of six beagles, followed by healing abutments belonging to the standard machined Ti-6Al-4V alloy abutments (TC4-M), anodized abutments with nanotubes (TC4-Nano), and hydrogenated abutments (TC4-H/Nano) groups, which were randomly screwed to the implants. After two and four weeks of wound healing, the animals were euthanized for histological evaluation.

RESULTS

A superhydrophilic nanotubular surface developed on the hydrogenated abutment. Histological and histometric analyses revealed similar peri-implant soft tissue healing and dimensions for the three types of abutments at two and four weeks. Connective tissue (CT) length was longer around TC4-H/Nano abutments compared with standard abutments; however, the differences were not statistically significant. Moreover, collagen fibers in the TC4-H/Nano group extended and were attached perpendicularly to the superhydrophilic surface.

CONCLUSIONS

Our results revealed that the soft tissue interface adjacent to the hydrogenated abutment is comparable to that of the machined abutment. A tendency of increased CT length and perpendicular collagen fibers was observed around the modified abutment. This study suggests that nanotubular/superhydrophilic surfaces could be a promising modification to enhance soft tissue sealing. However, comprehensive studies should be conducted to evaluate the peri-implant soft tissue around the modified abutment immunohistochemically, histopathologically, and clinically.

In Vitro Characterization of an Anodized Surface of a Dental Implant Collar and Dental Abutment on Peri-Implant Cellular Response

The purpose of this paper was to determine the effect of anodization on the in vitro proliferation and adhesion of immortalized human keratinocytes (HaCats) and mouse bone marrow-derived mesenchymal stem cells (BM-MSCs) in Titanium Grade 23 (Ti6Al4V ELI) discs and to describe the surface topography, roughness, and composition of dental implants (body and collar) and abutments submitted to an area-specific anodization process. HaCat cells and BM-MSCs were seeded onto discs with three different surface treatments: machined, area-specific anodization for abutments, and area-specific anodization for implant collars. Cell proliferation was assessed using a resazurin-based fluorescent dye on days 1, 3, and 7, while cell adhesion was examined using scanning electron microscopy (SEM). Surface topography, roughness, and composition were evaluated for six implant bodies with an anodized rough surface, six anodized implant smooth collars, and six anodized prosthetic abutments. Both HaCats and BM-MSCs showed increased viability over time (p < 0.001) with no statistically significant differences among the different surfaces (p = 0.447 HaCats and p = 0.631 BM-MSCs). SEM analysis revealed an enhanced presence and adhesion of HaCat cells on the anodized surface for the implant collars and an increased adhesion of BM-MSCs on both the anodized and machined surface abutments. The topography characteristics of the treated implants and abutments varied depending on the specific implant region. Chemical analysis confirmed the presence of oxygen, calcium, phosphorus, and sodium on the anodized surfaces. The area-specific anodization process can be utilized to create variable topography, increase the specific surface area, and introduce oxygen, calcium, phosphorus, and sodium to dental implants and abutments. While BM-MSCs and HaCat cells showed similar adhesion and proliferation on anodized and machined surfaces, a positive interaction between anodized Ti6Al4V ELI surfaces and these two cell lines present in the peri-implant mucosa was observed. Due to the limitations of the present study, further research is necessary to confirm these findings.

Mucosal bleeding correlates with submucosal microbial dysbiosis in peri-implant mucositis of patients with periodontitis

OBJECTIVES

This study aimed to investigate the relationship between microbial communities and the severity of peri-implant mucosal bleeding in peri-implant mucositis.

MATERIALS AND METHODS

Submucosal plaque samples were collected from 54 implants divided into the healthy implant (HI) group, peri-implant mucositis (PM) group, and peri-implantitis (PI) group. Sequencing of 16S rRNA was performed using the Illumina MiSeq platform. Alpha diversity (i.e., Shannon and Chao index) and beta diversity were used to measure microbial diversity within and between microbial communities, respectively. Differences in microbial taxa between groups were assessed via linear discriminate analysis effect size. Correlation between the modified sulcus bleeding index (mSBI) and microbial dysbiosis index (MDI) was examined using Spearman correlation analysis and linear models.

RESULTS

The submucosal bacterial richness (Chao index) was positively correlated with the mean mSBI in the PM group. As the mean mSBI increased in the PM group, the beta diversity became closer to that of the PI group. In the PM group, the abundances of 47 genera were significantly correlated with the mean mSBI, and the MDI was positively associated with the mean mSBI. Fourteen of the forty-seven genera were discriminative taxa between the HI and PI groups, and the abundances of these biomarkers became closer to those in the PI group in the progression of peri-implant disease.

CONCLUSIONS

A higher mSBI value corresponded to a higher risk of microbial dysbiosis in peri-implant mucositis. The biomarkers identified may be useful for monitoring the progression of peri-implant disease.

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

Stable soft tissue integration around the implant abutment attenuates pathogen penetration, protects underlying bone tissue, prevents peri-implantitis and is essential in maintaining long-term implant stability. The desire for "metal free" and "aesthetic restoration" has favored zirconia over titanium abutments, especially for implant restorations in the anterior region and for patients with thin gingival biotype. Soft tissue attachment to the zirconia abutment surface remains a challenge. A comprehensive review of advances in zirconia surface treatment (micro-design) and structural design (macro-design) affecting soft tissue attachment is presented and strategies and research directions are discussed. Soft tissue models for abutment research are described. Guidelines for development of zirconia abutment surfaces that promote soft tissue integration and evidence-based references to inform clinical choice of abutment structure and postoperative maintenance are presented.

Behaviour of the Peri-Implant Soft Tissue with Different Rehabilitation Materials on Implants

(1) Background: Mucointegration seems to gain interest when talking about success in the maintenance of dental implants. As we well know, collagen fibres cannot be inserted due to the lack of root structure on the implant surface, so the structural integration of peri-implant tissues that provide a firm seal around implants seems to be of interest when it comes to ensuring the survival of dental implants. To achieve a good epithelial barrier, the physicochemical characteristics of the surfaces of the restorative materials are of vital importance; therefore, the objective of this study is to analyse the histological behaviour of the peri-implant soft tissues in three different restorative materials. (2) Methods: Histological analysis of biopsied peri-implant keratinised mucosa, inflammatory epithelium and connective tissue in contact with a reinforced composite (BRILLIANT Crios), a cross-linked polymethylmethacrylate (TELIO CAD), and a hybrid ceramic (Vita Enamic), restored on a customised Atlantis-type abutment (Dentsply Sirona) between 60 and 180 days after restoration. (3) Results: A greater number of cells per mm2 of keratinised epithelium is observed in the reinforced composite, which could indicate greater surface roughness with greater inflammatory response. In this way, the greater number of lymphocytes and the lateral cellular composition of the inflammatory cells confirm the greater inflammatory activity towards that material. The best material to rehabilitate was hybrid ceramic, as it shows a better cellular response. (4) Conclusions: Knowing the limitations of the proposed study, despite the fact that greater inflammation is observed in the reinforced composite relative to the other materials studied, no statistically significant differences were found.

Optimized titanium dioxide nanotubes for dental implants: Estimation of mechanical properties and effects on the biological behaviors of human gingival fibroblasts and oral bacteria

The long-term successes of implant restorations rely on both appropriate osseointegration and robust soft tissue integration (STI). Numerous studies have reported that titanium dioxide nanotube (TNT) arrays formed by electrochemical anodization (EA) can promote early osteogenesis, but the mechanical stability of such modifications is often ignored and remains underexplored. In addition, relatively little research has been done on their effects on soft tissues integration. In this study, we developed mechanically robust TNT arrays using an optimized EA system. Subsequently, we immobilized a peptide, specifically D-amino K122-4, onto the anodized TNTs via polydopamine (PDA) films to enhance their mechanical properties. Surface morphology and composition were characterized by scanning electron microscopy (SEM), atomic force microscopy, and X-ray photoelectron spectroscopy. Mechanical properties, including the elastic modulus and hardness of TNTs modified Ti surfaces, were assessed using the nano-indention test. The adhesive strength of TNTs films to the substrate was measured using the nano scratch test. Furthermore, we evaluated the adhesion, spreading, and proliferation of human gingival fibroblasts (HGFs) and periodontal pathogenic bacteria such as Streptococcus mutans (S.m) and F. nucleatum (F.n) on the surface. Results showed that the elastic modulus, hardness, and adhesive strength of anodized TNTs were significantly enhanced by the incorporation of the D-amino K122-4 peptide. Live-dead staining and SEM observation suggested a decreased surface colonization by both bacterial species. The antibacterial rate of S.m and F. n was 81.5% and 71.7%, respectively, evaluated by colony counting method. Additionally, results of CCK8 assay showed that modified TNTs slightly stimulated HGFs attachment and proliferation while producing enhanced fluorescence of integrin β1 and F-actin, confirmed by laser confocal microscopy observation. Thus, D-amino K122-4 biofunctionalized TNTs present significantly improved mechanical properties, and the mechanically robust structures modulate HGFs proliferation and alignment, resulting in decreased bacteria growth. This novel strategy has the potential to create a surface coating for implants that exhibits superior mechanical robustness and enhanced surface-to-implant interactions.

Implant connection and abutment selection as a predisposing and/or precipitating factor for peri-implant diseases: A review

Peri-implant mucosal integration is becoming a critical aspect for long term implant health and can be triggered the selection of implant components. The aim of this review is therefore to investigate the evidence concerning implant connection and abutment characteristics (abutment materials, design, handling) as predisposing or precipitating factor for peri-implant mucositis and peri-implantitis. Although the evidence that these features can directly predispose/precipitate peri-implant diseases is limited, there are -few- studies showing a potential role of the implant connection, trans-mucosal configuration, and handling in the development of early bone loss and/or peri-implantitis. With bone level implants, conical internal connections (with inherent platform switching) might be preferred over internal flat-flat and external connections to decrease the risk of early bone loss and potentially the risk of peri-implant disease. Moreover, there is a trend suggesting moving the prosthetic interface coronally (to the juxta-mucosal level) as soon as possible to reduce the number of disconnections and to limit the risk of cements remnants. This can be achieved by choosing a tissue-level implant or to place a trans-mucosal abutment (one abutment-one time approach) to optimize the peri-implant soft tissue seal. In absence of evidence for the biocompatibility regarding several restorative materials, biocompatible materials such as titanium or zirconia should be preferred in the trans-mucosal portion. Finally, higher implants (≥2mm) with an emergence angle below 30° seem more favourable. It should however be noted that some of this information is solely based on indirect information (such as early bone loss) and more research is needed before making firm recommendations about abutment choice. [Correction added on 13 March 2023, after first online publication: 'longer implants (≥2mm)' was changed to 'higher implants (≥2mm)' in this version.].

Fit and forget: The future of dental implant therapy via nanotechnology

Unlike orthopedic implants, dental implants require the orchestration of both osseointegration at the bone-implant interface and soft-tissue integration at the transmucosal region in a complex oral micro-environment with ubiquitous pathogenic bacteria. This represents a very challenging environment for early acceptance and long-term survival of dental implants, especially in compromised patient conditions, including aged, smoking and diabetic patients. Enabling advanced local therapy from the surface of titanium-based dental implants via novel nano-engineering strategies is emerging. This includes anodized nano-engineered implants eluting growth factors, antibiotics, therapeutic nanoparticles and biopolymers to achieve maximum localized therapeutic action. An important criterion is balancing bioactivity enhancement and therapy (like bactericidal efficacy) without causing cytotoxicity. Critical research gaps still need to be addressed to enable the clinical translation of these therapeutic dental implants. This review informs the latest developments, challenges and future directions in this domain to enable the successful fabrication of clinically-translatable therapeutic dental implants that would allow for long-term success, even in compromised patient conditions.

Soft tissue dimensional change using customized titanium healing abutment in immediate implant placement in posterior teeth

BACKGROUND

The morphologic and dimensional alveolar bone is significant for resorption in the first 3 months after tooth removal because they restrict treatment outcomes with respect to function and esthetic. Following teeth extraction, the width and height of the alveolar ridge contour are reduced in both the horizontal and vertical dimensions. Following implant placement, the gingival morphology should be changed minimally compared to pre-extraction. Surrounding natural-like tissue is also an ultimate goal of the dental implant treatment, which is correlated with the cervical third contour on the anatomical tooth, for comfortable cleansing, food impaction avoidance, and esthetics.

PURPOSE

To evaluate the peri-implant soft tissue changes after immediate implant placement (IIP) with the use of a customized titanium healing abutment in the posterior teeth.

METHOD

Digital impressions using the intraoral scanner (MEDIT i500) were taken from 30 patients. Customized titanium healing abutments were designed and milled before extraction. Flapless extractions were done using surgical guides, 32 immediate implants placement were done in posterior areas, and healing abutments were placed. Soft tissues were scanned during pre-operation, and post-surgery during the 1st, 3rd, and 6th months. A 3D analysis program (Final Surface) evaluated the gingival margin distance, height, contour width, and volume in each period. SPSS was used to analyze the data with a p-value = 0.05. The between-time interval comparisons were done and the analysis was done using a Multivariate test.

RESULTS

Customized titanium healing abutments used in immediate implantation maintained optimal peri-implant mucosa. In intermittent periods, there was no significant reduction in all aspects of the margin distances and heights. During the entire period, the margin height reduction on the buccal, lingual, mesial, and distal was 0.63 mm, 0.93 mm, 0.08 mm, and 0.24 mm, respectively, and contour width reduction on the buccal, lingual, and buccolingual was 0.59 mm, 0.43 mm, and 1.03 mm, respectively. There was a significant reduction in the total buccolingual contour width in the 1st month and total volume in the 3rd to 6th months.

CONCLUSIONS

Immediate implant placement with customized titanium healing abutment can achieve the optimal peri-implant mucosa and this protocol is an alternative for soft tissue management.

Built-up sodium alginate/chlorhexidine multilayer coating on dental implants with initiating anti-infection and cyto-compatibility sequentially for soft-tissue sealing

Soft-tissue sealing at transmucosal sites is very important for preventing the invasion of pathogens and maintaining the long-term stability and function of dental implants. However, the colonization of oral pathogens on the implant surface and surrounding soft tissues can disturb the early establishment of soft-tissue sealing and even induce peri-implant infection. The purpose of this study was to construct two antibacterial coatings with 5 or 10 sodium alginate/chlorhexidine bilayers on titanium surfaces using layer-by-layer self-assembly technology to promote soft-tissue sealing. The corresponding chemical composition, surface topography, wettability and release behaviour were investigated to prove that the resultant coating of sodium alginate and chlorhexidine was coated on the porous titanium surface. In-vitro and in-vivo antibacterial results showed that both prepared coatings inhibited or killed the bacteria on their surfaces and the surrounding areas to prevent plaque biofilm formation, especially the coating with 10 bilayers. Although both coatings inhibited the initial adhesion of fibroblasts, the cytocompatibility gradually improved with coating degradation. More importantly, both coatings achieved cell adhesion and proliferation in an in-vitro bacterial environment and effectively alleviated bacteria-induced subcutaneous inflammation in-vivo. Therefore, this study demonstrated that the multilayered coating could prevent implant-related infections in the initial stage of implant surgery and then improve soft-tissue integration with implant devices.

Construction of a Localized and Long-Acting CCN2 Delivery System on Percutaneous Ti Implant Surfaces for Enhanced Soft-Tissue Integration

Soft-tissue integration (STI) plays an essential role in the long-term success of percutaneous Ti implants since it acts as a biological barrier that protects the soft and hard tissue around implants. Surface modification of Ti implants with drug-release properties to achieve soft-tissue regeneration has been proven to be effective in STI. However, the short-acting effect caused by the uncontrolled drug release of the topical delivery system limits long-term STI enhancement. Herein, a long-acting protein delivery system for Ti implants that involved micro-arc oxidation of Ti surfaces (MAO-Ti) and localized immobilization of cellular communication network factor 2 (CCN2) bearing mesoporous silica nanoparticles (MSNs) on MAO-Ti was prepared, namely, CCN2@MSNs-Ti. The CCN2 release study of CCN2@MSNs-Ti demonstrated a sustained-release profile for 21 days, which was able to maintain long-term stable STI. In addition, in vitro cell behavior evaluation results indicated that CCN2@MSNs-Ti could promote the STI-related biological response of human dermal fibroblasts via the FAK-MAPK pathway. More importantly, the system could effectively enhance STI after 4 weeks and proinflammatory factors in the soft tissue decreased significantly in a rat model of implantation. These results denote that CCN2@MSNs-Ti showed an appealing application prospect for enhanced STI around transcutaneous Ti implants, which would ultimately result in an increased success rate of percutaneous Ti implants.

Optimization of stress distribution of bone-implant interface (BII)

Many studies have found that the threshold of occlusal force tolerated by titanium-based implants is significantly lower than that of natural teeth due to differences in biomechanical mechanisms. Therefore, implants are considered to be susceptible to occlusal trauma. In clinical practice, many implants have shown satisfactory biocompatibility, but the balance between biomechanics and biofunction remains a huge clinical challenge. This paper comprehensively analyzes and summarizes various stress distribution optimization methods to explore strategies for improving the resistance of the implants to adverse stress. Improving stress resistance reduces occlusal trauma and shortens the gap between implants and natural teeth in occlusal function. The study found that: 1) specific implant-abutment connection design can change the force transfer efficiency and force conduction direction of the load at the BII; 2) reasonable implant surface structure and morphological character design can promote osseointegration, maintain alveolar bone height, and reduce the maximum effective stress at the BII; and 3) the elastic modulus of implants matched to surrounding bone tissue can reduce the stress shielding, resulting in a more uniform stress distribution at the BII. This study concluded that the core BII stress distribution optimization lies in increasing the stress distribution area and reducing the local stress peak value at the BII. This improves the biomechanical adaptability of the implants, increasing their long-term survival rate.

Clinical and immunological evaluation of peri-implant tissues around ultra-polished and conventionally-polished zirconia abutments. A 1-year follow-up randomized clinical trial

PURPOSE

This is a randomized clinical trial to compare the clinical and immunological performance of ultrasmooth versus conventionally-smooth zirconia abutments placed subgingivally after a period of 1 year.

MATERIALS AND METHODS

Sixty-two bone level platform-switched implants (NobelParallel CC) were placed epicrestally in the mandibular molar or premolar region in 62 patients. After osseointegration, implants were restored with auto polymerizing acrylic resin crowns and subsequently randomly allocated to two groups according to the type of screw-retained zirconia crown prescribed. The control group received custom zirconia restoration with the subgingival zirconia part conventionally polished, whereas the test group implants were restored with ultra-polished zirconia abutments. Periodontal parameters (PD, PI, and BOP) and marginal bone level changes (MBLC) were recorded for each implant 2 months after insertion (T0), 1 month after final delivery of the crown (T2), and at the 1-year follow-up (T3). Immunological mediators from gingival crevicular fluid (IL-1α, IL-1ra, and TNF-α) were inspected at 1 month after provisional (T1) and accordingly at T2 and T3. Data was analyzed statistically, and significance level was set to α = 0.05.

RESULTS

After 1 year, there were no significant changes in PD control-2.18 ± 0.89 mm and test-2.5 ± 0.72 mm (p = 0.073). PD between T2 and T3 dropped significantly in the test group (p = 0.037) and remained stable in the control group. PI was not different in both groups at T0 (p = 0.518) and T2 (p = 0.817). At T3, the test group (0.9 ± 1.01) had a significantly lower PI than the control group (1.55 ± 1.23) (p = 0.035). There was no difference in BOP positive cases between groups after 1 year (control-61.3%, test-51.7%, and p = 0.455). The amount of IL-1ra decreased significantly in the test group (41.75 ± 57.58) (p = 0.001) but not in the control group (59.59 ± 70.43) (p = 0.177). MBLC for the control and test groups after 1 year were 0.68 ± 0.7 and 0.94 ± 0.65 mm (p = 0.061).

CONCLUSIONS

PD dynamics, PI, BOP, and IL-1ra revealed better outcomes around ultra-polished zirconia abutments than around conventionally polished zirconia abutments.

Enhanced Corrosion Resistance and Local Therapy from Nano-Engineered Titanium Dental Implants

Titanium is the ideal material for fabricating dental implants with favorable biocompatibility and biomechanics. However, the chemical corrosions arising from interaction with the surrounding tissues and fluids in oral cavity can challenge the integrity of Ti implants and leach Ti ions/nanoparticles, thereby causing cytotoxicity. Various nanoscale surface modifications have been performed to augment the chemical and electrochemical stability of Ti-based dental implants, and this review discusses and details these advances. For instance, depositing nanowires/nanoparticles via alkali-heat treatment and plasma spraying results in the fabrication of a nanostructured layer to reduce chemical corrosion. Further, refining the grain size to nanoscale could enhance Ti implants' mechanical and chemical stability by alleviating the internal strain and establishing a uniform TiO₂ layer. More recently, electrochemical anodization (EA) has emerged as a promising method to fabricate controlled TiO₂ nanostructures on Ti dental implants. These anodized implants enhance Ti implants' corrosion resistance and bioactivity. A particular focus of this review is to highlight critical advances in anodized Ti implants with nanotubes/nanopores for local drug delivery of potent therapeutics to augment osseo- and soft-tissue integration. This review aims to improve the understanding of novel nano-engineered Ti dental implant modifications, focusing on anodized nanostructures to fabricate the next generation of therapeutic and corrosion-resistant dental implants. The review explores the latest developments, clinical translation challenges, and future directions to assist in developing the next generation of dental implants that will survive long-term in the complex corrosive oral microenvironment.

Generating bioactive and antiseptic interfaces with nano-silver hydroxyapatite-based coatings by pulsed electrochemical deposition for long-term efficient cervical soft tissue sealing

Infections related to osseointegrated implants have sparked the interest in studying titanium modification for long-term effective soft tissue sealing. Constructing a silver (Ag)-hydroxyapatite (HA) coating is regarded as an effective strategy for integrating antibiosis with osteanagenesis; however, the outcome for long-term cervical soft tissue sealing in vivo is compromised. It is challenging to construct an Ag-HA coating for long-term efficient soft tissue integration that instills a maximum antibacterial effect while retaining favorable bioactivity to normal gingival mesenchymal cells in vivo. In this study, we employed gradient concentrations of Ag/CaP by pulsed electrochemical deposition to fabricate optimal Ag-HA nanocoatings. By physicochemical analyses, these uniform coatings were mainly formed with spherical metallic and hydroxyapatite nanoparticles, which facilitated good hydrophilicity, moderate rough surfaces and corrosion protection. Furthermore, the nanocoating of the 1.5Ag/CaP group exhibited superior performances in dental follicle cells' proliferation, osteogenic differentiation and antibacterial properties mainly through direct contact inhibition and partially through sustained silver ion release, which resulted in functional cervical soft tissue sealing in beagles lasting for one year. Our investigations provide a feasible strategy to balance the long-term antibacterial demand and bioactive induction around osseointegrated implants for long-term efficient cervical soft tissue sealing.

Optimization of Lactoferrin-Derived Amyloid Coating for Enhancing Soft Tissue Seal and Antibacterial Activity of Titanium Implants

A poor seal of the titanium implant-soft tissue interface provokes bacterial invasion, aggravates inflammation, and ultimately results in implant failure. To ensure the long-term success of titanium implants, lactoferrin-derived amyloid is coated on the titanium surface to increase the expression of cell integrins and hemidesmosomes, with the goal of promoting soft tissue seal and imparting antibacterial activity to the implants. The lactoferrin-derived amyloid coated titanium structures contain a large number of amino and carboxyl groups on their surfaces, and promote proliferation and adhesion of epithelial cells and fibroblasts via the PI3K/AKT pathway. The amyloid coating also has a strong positive charge and possesses potent antibacterial activities against Staphylococcus aureus and Porphyromonas gingivalis. In a rat immediate implantation model, the amyloid-coated titanium implants form gingival junctional epithelium at the transmucosal region that resembles the junctional epithelium in natural teeth. This provides a strong soft tissue seal to wall off infection. Taken together, lactoferrin-derived amyloid is a dual-function transparent coating that promotes soft tissue seal and possesses antibacterial activity. These unique properties enable the synthesized amyloid to be used as potential biological implant coatings.

The burden of diabetes on the soft tissue seal surrounding the dental implants

Soft tissue seal around implant prostheses is considered the primary barrier against adverse external stimuli and is a critical factor in maintaining dental implants' stability. Soft tissue seal is formed mainly by the adhesion of epithelial tissue and fibrous connective tissue to the transmembrane portion of the implant. Type 2 diabetes mellitus (T2DM) is one of the risk factors for peri-implant inflammation, and peri-implant disease may be triggered by dysfunction of the soft tissue barrier around dental implants. This is increasingly considered a promising target for disease treatment and management. However, many studies have demonstrated that pathogenic bacterial infestation, gingival immune inflammation, overactive matrix metalloproteinases (MMPs), impaired wound healing processes and excessive oxidative stress may trigger poor peri-implant soft tissue sealing, which may be more severe in the T2DM state. This article reviews the structure of peri-implant soft tissue seal, peri-implant disease and treatment, and moderating mechanisms of impaired soft tissue seal around implants due to T2DM to inform the development of treatment strategies for dental implants in patients with dental defects.

Strontium-loaded hydrogel scaffolds to promote gingival fibroblast function

Dental implant clinical success is dependent on effective peri-implant tissue attachment to the trans-mucosal portion following placement. Modification of transmucosal implant surfaces can improve cellular adhesion and function leading to formation of an effective soft-tissue seal during healing, of which gingival fibroblasts are prominent cells to migrate to repair wounds and crucial for the development of a collagen rich connective tissue. Biocompatible loaded scaffold materials have been developed to allow local release of molecules with effective biological activity. Our previous studies indicate that strontium can promote gingival fibroblast metabolism, decrease apoptosis and support adhesion to titanium healing abutments. In this study, we developed a strontium-loaded alginate hydrogel scaffold which can be easily personalized to fit over any size and shape of implant transmucosal collar or healing abutment. Results indicate that biologically active strontium ions are effectively released from loaded alginate hydrogel material to promote fibroblast viability and migration to repair in vitro wounds similar to that of strontium citrate solution. Overall, this novel strontium-loaded alginate scaffold device displays good biocompatibility and functionality, demonstrating high potential as a system to provide local delivery of strontium to improve peri-implant mucosal healing following implant placement and clinical success.

Plasma polymerized bio-interface directs fibronectin adsorption and functionalization to enhance "epithelial barrier structure" formation via FN-ITG β1-FAK-mTOR signaling cascade

BACKGROUND

Transepithelial medical devices are increasing utilized in clinical practices. However, the damage of continuous natural epithelial barrier has become a major risk factor for the failure of epithelium-penetrating implants. How to increase the "epithelial barrier structures" (focal adhesions, hemidesmosomes, etc.) becomes one key research aim in overcoming this difficulty. Directly targeting the in situ "epithelial barrier structures" related proteins (such as fibronectin) absorption and functionalization can be a promising way to enhance interface-epithelial integration.

METHODS

Herein, we fabricated three plasma polymerized bio-interfaces possessing controllable surface chemistry. Their capacity to adsorb and functionalize fibronectin (FN) from serum protein was compared by Liquid Chromatography-Tandem Mass Spectrometry. The underlying mechanisms were revealed by molecular dynamics simulation. The response of gingival epithelial cells regarding the formation of epithelial barrier structures was tested.

RESULTS

Plasma polymerized surfaces successfully directed distinguished protein adsorption profiles from serum protein pool, in which plasma polymerized allylamine (ppAA) surface favored adsorbing adhesion related proteins and could promote FN absorption and functionalization via electrostatic interactions and hydrogen bonds, thus subsequently activating the ITG β1-FAK-mTOR signaling and promoting gingival epithelial cells adhesion.

CONCLUSION

This study offers an effective perspective to overcome the current dilemma of the inferior interface-epithelial integration by in situ protein absorption and functionalization, which may advance the development of functional transepithelial biointerfaces. Tuning the surface chemistry by plasma polymerization can control the adsorption of fibronectin and functionalize it by exposing functional protein domains. The functionalized fibronectin can bind to human gingival epithelial cell membrane integrins to activate epithelial barrier structure related signaling pathway, which eventually enhances the formation of epithelial barrier structure.

Cell Type-Specific Effects of Implant Provisional Restoration Materials on the Growth and Function of Human Fibroblasts and Osteoblasts

Implant provisional restorations should ideally be nontoxic to the contacting and adjacent tissues, create anatomical and biophysiological stability, and establish a soft tissue seal through interactions between prosthesis, soft tissue, and alveolar bone. However, there is a lack of robust, systematic, and fundamental data to inform clinical decision making. Here we systematically explored the biocompatibility of fibroblasts and osteoblasts in direct contact with, or close proximity to, provisional restoration materials. Human gingival fibroblasts and osteoblasts were cultured on the "contact" effect and around the "proximity" effect with various provisional materials: bis-acrylic, composite, self-curing acrylic, and milled acrylic, with titanium alloy as a bioinert control. The number of fibroblasts and osteoblasts surviving and attaching to and around the materials varied considerably depending on the material, with milled acrylic the most biocompatible and similar to titanium alloy, followed by self-curing acrylic and little to no attachment on or around bis-acrylic and composite materials. Milled and self-curing acrylics similarly favored subsequent cellular proliferation and physiological functions such as collagen production in fibroblasts and alkaline phosphatase activity in osteoblasts. Neither fibroblasts nor osteoblasts showed a functional phenotype when cultured with bis-acrylic or composite. By calculating a biocompatibility index for each material, we established that fibroblasts were more resistant to the cytotoxicity induced by most materials in direct contact, however, the osteoblasts were more resistant when the materials were in close proximity. In conclusion, there was a wide variation in the cytotoxicity of implant provisional restoration materials ranging from lethal and tolerant to near inert, and this cytotoxicity may be received differently between the different cell types and depending on their physical interrelationships.

Junctional epithelium and hemidesmosomes: Tape and rivets for solving the "percutaneous device dilemma" in dental and other permanent implants

The percutaneous device dilemma describes etiological factors, centered around the disrupted epithelial tissue surrounding non-remodelable devices, that contribute to rampant percutaneous device infection. Natural percutaneous organs, in particular their extracellular matrix mediating the "device"/epithelium interface, serve as exquisite examples to inspire longer lasting long-term percutaneous device design. For example, the tooth's imperviousness to infection is mediated by the epithelium directly surrounding it, the junctional epithelium (JE). The hallmark feature of JE is formation of hemidesmosomes, cell/matrix adhesive structures that attach surrounding oral gingiva to the tooth's enamel through a basement membrane. Here, the authors survey the multifaceted functions of the JE, emphasizing the role of the matrix, with a particular focus on hemidesmosomes and their five main components. The authors highlight the known (and unknown) effects dental implant - as a model percutaneous device - placement has on JE regeneration and synthesize this information for application to other percutaneous devices. The authors conclude with a summary of bioengineering strategies aimed at solving the percutaneous device dilemma and invigorating greater collaboration between clinicians, bioengineers, and matrix biologists.

Strong adhesive and drug-loaded hydrogels for enhancing bone-implant interface fixation and anti-infection properties

The bonding strength of the bone-titanium (Ti) implant interface is critical for patients undergoing joint replacement. However, current bone adhesives used in clinic have shortcomings, such as biological inertness, cytotoxicity, and lack of osteogenic ability. In this study, a simple and low-cost hydrogel-based bone adhesive was prepared to improve the osseointegration ability and anti-infection ability of the bone-implant interface. A multifunctional hydrogel was prepared by incorporating nano-hydroxyapatite (HA) on polyethyleneimine (PEI) and polyacrylic acid (PAA) (PEI/PAA-HA). It was shown that PEI/PAA-HA hydrogel exhibited good self-healing and strong adhesive ability. The adhesive strengths of bone-Ti and Ti-Ti were measured as 2.30 ± 0.15 MPa and 1.07 ± 0.07 MPa, respectively. Vancomycin (VAN) was loaded into the PEI/PAA-HA hydrogel (PEI/PAA-HA-VAN) via a simple immersion method. The PEI/PAA-HA-VAN showed excellent antibacterial effect by sustained release of VAN. In addition, the PEI/PAA-HA-VAN hydrogel exhibited excellent cytocompatibility promoting the expression of osteogenic genes and the deposition of mineralized matrix. Collectively, this strong adhesive hydrogel showed great potential in enhancing bone-implant interface fixation.

Inspired by the Periodontium: A Universal Bacteria-Defensive Hydrogel for Preventing Percutaneous Device-Related Infection

Percutaneous device-related infection has greatly shortened the service period of devices and seriously reduced the quality of life of patients. Bacteria are one of the main pathogenic factors and cannot be effectively and conveniently eradicated by traditional strategies (e.g., construct coatings and introduce antibiotics), due to the complex interface among medical devices, surrounding tissue, and colonizing bacteria. Inspired by the periodontium, a universal bacteria-defensive hydrogel adapting to the complicated interface is fabricated by introducing phenol-amine chemistry to a polymeric matrix of N-hydroxyethyl acrylamide (HPC hydrogels). The HPC hydrogels with excellent toughness (2.1 MJ/m3), adhesion (10.2 and 13.2 kPa for pigskin and Ti-6Al-4V alloy, respectively), and antibacterial property (up to 99.9% for both Escherichia coli and Staphylococcus aureus) contributed to the innate microbe barrier via sealing the tissue-device interface and adaptive defense to eradicate bacteria. Meanwhile, bacterial invasion experiments demonstrate HPC hydrogels possess both a bacteria-defensive property (up to 24 h) and cell-protecting function at the same time. Furthermore, the biocompatibility of HPC hydrogels is verified in tests for in vitro cytotoxicity and in vivo irritation. Hence, the designed HPC hydrogels are considered as an emerging and universal candidate for preventing bacterial infection and can protect the deep tissue around a percutaneous device.

Preventing Peri-implantitis: The Quest for a Next Generation of Titanium Dental Implants

Titanium and its alloys are frequently the biomaterial of choice for dental implant applications. Although titanium dental implants have been utilized for decades, there are yet unresolved issues pertaining to implant failure. Dental implant failure can arise either through wear and fatigue of the implant itself or peri-implant disease and subsequent host inflammation. In the present report, we provide a comprehensive review of titanium and its alloys in the context of dental implant material, and how surface properties influence the rate of bacterial colonization and peri-implant disease. Details are provided on the various periodontal pathogens implicated in peri-implantitis, their adhesive behavior, and how this relationship is governed by the implant surface properties. Issues of osteointegration and immunomodulation are also discussed in relation to titanium dental implants. Some impediments in the commercial translation for a novel titanium-based dental implant from "bench to bedside" are discussed. Numerous in vitro studies on novel materials, processing techniques, and methodologies performed on dental implants have been highlighted. The present report review that comprehensively compares the in vitro, in vivo, and clinical studies of titanium and its alloys for dental implants.

Benchmark performance of anodized vs. sandblasted implant surfaces in an acute dehiscence type defect animal model

OBJECTIVES

Crestal bone formation represents a crucial aspect of the esthetic and biological success of dental implants. This controlled preclinical study analyzed the effect of implant surface and implant geometry on de novo crestal bone formation and osseointegration.

MATERIALS AND METHODS

Histological and histomorphometrical analysis was performed to compare three implant groups, that is, (1) a novel, commercially available, gradient anodized implant, (2) a custom-made geometric replica of implant "1," displaying a superhydrophilic micro-rough large-grit sandblasted and acid-etched surface, and (3) a commercially available implant, having the same surface as "2" but a different implant geometry. The study applied a standardized buccal acute-type dehiscence model in minipigs with observation periods of 2 and 8 weeks of healing.

RESULTS

The amount of newly formed crestal bone (BATA) around control groups (2) and (3) was significantly increased when compared to the test group (1) at the 8 weeks of healing time point. Similar results were obtained for all parameters related to osseointegration and direct bone apposition, to the implant surface (dBIC, VBC, and fBIC), demonstrating superior osseointegration of the moderately rough, compared to the gradient anodized functionalization. After 2 weeks, the osseointegration (nBIC) was found to be influenced by implant geometry with group (3) outperforming groups (1) and (2) on this parameter. At 8 weeks, nBIC was significantly higher for groups (2) and (3) compared to (1).

CONCLUSIONS

The extent (BATA) of de novo crestal bone formation in the acute-type dehiscence defects was primarily influenced by implant surface characteristics and their ability to promote osseointegration and direct bone apposition. Osseointegration (nBIC) of the apical part was found to be influenced by a combination of surface characteristics and implant geometry. For early healing, implant geometry may have a more pronounced effect on facilitating osseointegration, relative to the specific surface characteristics.