Histological and immunohistochemical evaluation of the peri-implant soft tissues around machined and acid-etched titanium healing abutments: a prospective randomised study

A Microscopy Evaluation of Emergence Profile Surfaces of Dental Custom CAD-CAM Implant Abutments and Dental Implant Stock Abutments

Recently, due to the high demand for dental implants, the use of dental implant stock abutments has increased significantly, especially dental custom CAD/CAM implant abutments milled by dental technicians in their laboratories. The purpose of this study is to analyze the surface quality of the emergence profile of dental custom CAD/CAM implant abutments made by a non-industrial milling machine, compared to original and compatible dental implant stock abutments made by industrial machines. Thirty dental implant abutments were divided into six study lots. Lot 1 (control group): original dental implant stock abutments-industrial machined; lot 2 (study group): compatible dental implant stock abutments-industrial machined; lots 3, 4, 5, and 6 (study groups): compatible custom CAD/CAM dental implant abutments-non-industrial milled with hyperDENT CAM software and Paragon Tools. The Nikon SMZ745T stereomicroscope was used to analyze the emergence profile surface of each dental implant abutment. The structure of the analyzed surfaces did not show significant differences between original and compatible abutments that were industrially machined. As for the customized dental implant abutments, the greatest similarity with the original was obtained for lot 6, and a significant statistical difference was obtained for lot 4. Stepover and Feed Rate parameters of the milling process influenced the surface roughness of the emergence profile for the customized dental implant abutments. The digital technology of non-industrial milling compatible custom CAD/CAM dental implant abutments is reliable and within the correct milling parameters.

Innovative Bioactive Ca-SZ Coating on Titanium Dental Implants: A Multidimensional Structural and Elemental Analysis

The design of new, biomimetic biomaterials is of great strategic interest and is converging for many applications, including in implantology. This study explores a novel approach to improving dental implants. Although endosseous TA6V alloy dental implants are widely used in oral implantology, this material presents significant challenges, notably the prevalence of peri-implantitis. Therefore, in this study, we investigate a new advance in the design of hybrid medical devices. This involves the design of a Ca-SZ coating deposited by PVD on a TA6V substrate. This approach aims to overcome the inherent limitations of each of these materials, namely TA6V's susceptibility to peri-implantitis on the one hand and zirconia's excessively high Young's modulus compared with bone on the other, while benefiting from their respective advantages, such as the ductility of TA6V and the excellent biocompatibility of zirconia, offering relevant prospects for the design of high-performance implantable medical devices. This study integrates characterisation techniques, focusing on the structural and elemental analysis of the Ca-SZ coating by XRD and TEM. The results suggest that this coating combines a tetragonal structure, a uniform morphology with no apparent defects, a clean interface highlighting good adhesion, and a homogeneous composition of calcium, predisposing it to optimal biocompatibility. All of these findings make this innovative coating a particularly suitable candidate for application in dental implantology.

Detection and comparison of neutrophil extracellular traps in tissue samples of peri-implantitis, periodontitis, and healthy patients: A pilot study

OBJECTIVE

The aim of this study was to detect and compare the tissular expression of neutrophil extracellular traps (NETs) in peri-implant and periodontal samples of patients with peri-implantitis, periodontitis, and controls.

MATERIALS AND METHODS

An observational study was performed on patients with peri-implantitis, periodontitis, and controls. Peri-implant and/or periodontal clinical examinations were performed on each participant. Tissue samples were collected during tooth/implant extraction for clinical reasons. Electron microscopy analysis, Picro-Sirius red staining, immunohistochemical (CD15), and immunofluorescence (citrullinated H3 and myeloperoxidase) techniques were performed to detect NET-related structures and the degree of connective tissue destruction, between the study groups.

RESULTS

Sixty-four patients were included in the study: 28 peri-implantitis, 26 periodontitis, and 10 controls, with a total of 51 implants, 26 periodontal teeth, and 10 control teeth. Neutrophil release of nuclear content was observed in transmission electron microscopy. Immunohistochemical analysis showed a greater CD15 expression in both peri-implantitis and periodontitis compared to controls (p < 0.001), and peri-implantitis presented lower levels of connective tissue and collagen compared to both periodontitis (p = 0.044; p < 0.001) and controls (p < 0.001). Immunofluorescence showed greater citH3 expression in peri-implantitis than the one found in both periodontitis (p = 0.003) and controls (p = 0.048).

CONCLUSIONS

A greater presence and involvement of neutrophils, as well as a greater connective tissue destruction were observed in cases of peri-implantitis. A higher expression of NET-related markers was found in mucosal samples of peri-implantitis compared to periodontitis and controls.

The Impact of Peri-Implant Diseases on the General Status of Patients with Cardiovascular Diseases: A Literature Review

BACKGROUND AND OBJECTIVES

The aim of this study is to connect peri-implantitis to cardiovascular diseases, following the association found between periodontitis and cardiovascular conditions in recent years.

MATERIALS AND METHODS

PubMed, Scopus, Web of Science online databases were searched up to June 2023, with the exclusion criteria being research written in a language other than English. The MeSH search items were as follows: ["peri-implant health OR peri-implantitis OR peri-implant mucositis OR peri-implant disease"] AND ["cardiovascular diseases"]. Patient/population (P), intervention (I), comparison (C), outcome (O) framework questions were followed to identify the clinical evidence for the systematic review. Only clinical studies that used a control group to compare the relationship between cardiovascular diseases and peri-implantitis were selected.

RESULTS

A total of 118 studies were identified through electronic search of the keywords. After removing duplicates, there were 76 records to be screened. Upon exclusion of ineligible titles and abstracts, 27 studies remained for evaluation. Finally, 23 studies were excluded for not meeting the inclusion criteria, leaving 4 studies to be included in the qualitative analyses.

CONCLUSIONS

This study found there is a linear association between mucosal/gingival inflammation and carotid intima-media thickness test (c-IMT) values. Peri-implant mucosal inflammation could be a contributor to the vascular disease burden of an individual; further specific clinical studies should be performed in order to demonstrate this connection.

Bacterial Adhesion Strength on Titanium Surfaces Quantified by Atomic Force Microscopy: A Systematic Review

Few studies have been able to elucidate the correlation of factors determining the strength of interaction between bacterial cells and substrate at the molecular level. The aim was to answer the following question: What biophysical factors should be considered when analyzing the bacterial adhesion strength on titanium surfaces and its alloys for implants quantified by atomic force microscopy? This review followed PRISMA. The search strategy was applied in four databases. The selection process was carried out in two stages. The risk of bias was analyzed. One thousand four hundred sixty-three articles were found. After removing the duplicates, 1126 were screened by title and abstract, of which 57 were selected for full reading and 5 were included; 3 had a low risk of bias and 2 moderated risks of bias. (1) The current literature shows the preference of bacteria to adhere to surfaces of the same hydrophilicity. However, this fact was contradicted by this systematic review, which demonstrated that hydrophobic bacteria developed hydrogen bonds and adhered to hydrophilic surfaces; (2) the application of surface treatments that induce the reduction of areas favorable for bacterial adhesion interfere more in the formation of biofilm than surface roughness; and (3) bacterial colonization should be evaluated in time-dependent studies as they develop adaptation mechanisms, related to time, which are obscure in this review.

Gelatin-Curcumin Nanocomposites as a Coating for Implant Healing Abutment: In Vitro Stability Investigation

Regarding the importance of preventing peri-implantitis in dental implants, the current study aimed to coat a healing abutment with gelatin−curcumin nanocomposites, and the stability of this coating on the healing abutment was evaluated. A cell viability measuring test was used to determine the cytotoxicity of nanocomposites against dental pulp stem cells. To show the pattern of curcumin release from nanocomposites, drug dissolution apparatus two was applied. Then, 16 healing abutments were examined in vitro. Titanium healing abutments were coated with the gelatin−curcumin nanocomposite. The dip coating method was applied for coating and the consistency of coated cases was evaluated at intervals of one, 30, and 60 days after coating inside the simulated body fluid (SBF) solution. A scanning electron microscope (SEM) was used for investigating the microstructure and morphology of coatings, and an energy dispersive X-ray (EDX) was applied for determining the combination of the coating. Moreover, the healings were weighed before and after coating via an accurate digital scale with an accuracy of 0.0001. Finally, the data were analyzed using SPSS software. The prepared nanocomposite was non-cytotoxic against tested cells. The nanocomposite showed a relatively rapid release pattern in the first 10 days for curcumin. The release of curcumin from the nanoparticles continued slowly until the 30th day. The weight changes were statistically significant (p-value < 0.001) during this time. Based on the post hoc test, the weight between two times immediately after coating and 30 days after coating, and also one day after coating and 30 days after coating, was statistically insignificant. The results revealed that the coating of the gelatin−curcumin nanocomposite on the healing was successful and this consistency was kept for at least one month. It is necessary to investigate more evaluations in different fields of physicochemical, mechanical, and antimicrobial aspects for coated healing abutments.

Introducing Nanozymes: New Horizons in Periodontal and Dental Implant Care

The prevalence of periodontal and peri-implant diseases has been increasing worldwide and has gained a lot of attention. As multifunctional nanomaterials with enzyme-like activity, nanozymes have earned a place in the biomedical field. In periodontics and implantology, nanozymes have contributed greatly to research on maintaining periodontal health and improving implant success rates. To highlight this progress, we review nanozymes for antimicrobial therapy, anti-inflammatory therapy, tissue regeneration promotion, and synergistic effects in periodontal and peri-implant diseases. The future prospects of nanozymes in periodontology and implantology are also discussed along with challenges.

The Potential Role of a Surface-Modified Additive-Manufactured Healing Abutment on the Expression of Integrins α2, β1, αv, and β6 in the Peri-Implant Mucosa: A Preliminary Human Study

The stability of peri-implant soft tissues is essential for long-term success. Integrins play a vital role in biological processes through developing and maintaining cell interactions; however, few studies have evaluated the effects of modifications to abutment surfaces on cell adhesion across integrin expression. Therefore, this pilot study assessed the influence of different surface topographies of titanium healing abutments prepared by additive manufacturing (AM) on the gene expression levels of the integrin subunits α2, β1, αv, and β6 in the human peri-implant mucosa. Thirteen healthy adults were included. Depending on the number of required implants, the subjects were distributed in different groups as a function of healing abutment topography: group 1 (fully rough surface); group 2 (upper machined + lower rough); group 3 (rough upper surface + lower machined); group 4 (fully machined). A total of 40 samples (n = 10/group) of the peri-implant mucosa around the abutments were collected 30 days after implant placement, and subsequently, the gene expression levels were evaluated using real-time PCR. The levels of gene expression of β1-subunit integrin were upregulated for individuals receiving fully rough surface abutments compared with the other surface topographies (p < 0.05). However, the healing abutment topography did not affect the gene expression levels of the α2, αv, and β6 integrin subunits in the human peri-implant mucosa (p > 0.05). This preliminary study suggested that controlled modifications of the surface topography of titanium healing abutments produced by AM may influence the quality of the peri-implant mucosa in the early stages of the soft tissue healing process.

Histologic Evaluation of Soft Tissues around Dental Implant Abutments: A Narrative Review

The basis for dental implant success comes not only with the titanium implant osseointegration but also depends on other factors such as the development of a soft tissue barrier, which protects the peri-implant bone from the oral environment. The characteristics of surfaces in contact with peri-implant soft tissues may affect the capacity of peri-implant mucosal cells to create a tight seal around the implant, thus influencing long-term implant success. Many histological studies on animals have been conducted on different materials to better understand their influence on peri-implant soft tissues, with the limitation that results from animal studies cannot be fully translated in humans. The aim of this review paper was to analyze the literature focusing on histological clinical studies in humans which have examined different materials or different surface treatments and their effects on peri-implant soft tissues. The research was conducted according to the following PICO question: “Do different implant/abutment materials affect peri-implant soft tissues adhesion and health?”. Nine articles were analyzed in this review. The results of this review show the influence of different abutment materials on the peri-implant soft tissues, and the need of further research regarding the effect that abutment materials, surface treatments, and surface properties have on soft tissues.

Human Gingival Fibroblast Adhesion and Proliferation on Hydroxyapatite-Coated Zirconia Abutment Surfaces

Applying antibacterial coatings to dental implant materials seems reasonable but can have negative influences on desired cell adhesion and healing. In this study, zirconia abutment specimens interacting with gingival tissue were used. The aim was to compare the influence of machined or coated zirconia surfaces on the adhesion and proliferation of human gingival fibroblasts (HGF-1). Surface modifications were performed using atmospheric plasma coating with hydroxyapatite, zinc, and copper. Zirconia specimens were divided into four groups: hydroxyapatite, hydroxyapatite with zinc oxide (ZnO), hydroxyapatite with copper (Cu), and an untreated machined surface. After the characterization of the surface conditions, the morphology of adhered HGF-1 was determined by fluorescence staining and subjected to statistical evaluation. The visual analysis of cell morphology by SEM showed flat, polygonal, and largely adherent fibroblast cells in the untreated group, while round to partially flat cells were recorded in the groups with hydroxyapatite, hydroxyapatite + ZnO, and hydroxyapatite + Cu. The cell membranes in the hydroxyapatite + ZnO and hydroxyapatite + Cu groups appeared porous. The results show that HGF-1 adhere and proliferate well on machined zirconia, while plasma coating with hydroxyapatite or hydroxyapatite mixtures does not lead to increased adhesion or proliferation.

Influence of Nano, Micro, and Macro Topography of Dental Implant Surfaces on Human Gingival Fibroblasts

Current research on dental implants has mainly focused on the influence of surface roughness on the rate of osseointegration, while studies on the development of surfaces to also improve the interaction of peri-implant soft tissues are lacking. To this end, the first purpose of this study was to evaluate the response of human gingival fibroblasts (hGDFs) to titanium implant discs (Implacil De Bortoli, Brazil) having different micro and nano-topography: machined (Ti-M) versus sandblasted/double-etched (Ti-S). The secondary aim was to investigate the effect of the macrogeometry of the discs on cells: linear-like (Ti-L) versus wave-like (Ti-W) surfaces. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis showed that the Ti-S surfaces were characterized by a significantly higher micro and nano roughness and showed the 3D macrotopography of Ti-L and Ti-W surfaces. For in vitro analyses, the hGDFs were seeded into titanium discs and analyzed at 1, 3, and 5 days for adhesion and morphology (SEM) viability and proliferation (Cck-8 and MTT assays). The results showed that all tested surfaces were not cytotoxic for the hGDFs, rather the nano-micro and macro topography favored their proliferation in a time-dependent manner. Especially, at 3 and 5 days, the number of cells on Ti-L was higher than on other surfaces, including Ti-W surfaces. In conclusion, although further studies are needed, our in vitro data proved that the use of implant discs with Ti-S surfaces promotes the adhesion and proliferation of gingival fibroblasts, suggesting their use for in vivo applications.

Comparative analyses of the soft tissue interfaces around teeth and implants: Insights from a pre-clinical implant model

AIM

To evaluate the similarities and differences in barrier function of a peri-implant epithelium (PIE) versus a native junctional epithelium (JE).

MATERIALS AND METHODS

A mouse model was used wherein titanium implants were placed sub-occlusally in healed extraction sites. The PIE was examined at multiple timepoints after implant placement, to capture and understand the temporal nature of its assembly and homeostatic status. Mitotic activity, hemidesmosomal attachment apparatus, and inflammatory responses in the PIE were compared against a JE. Additionally, we evaluated whether the PIE developed a Wnt-responsive stem cell niche like a JE.

RESULTS

The PIE developed from oral epithelium (OE) that had, by the time of implant placement, lost all characteristics of a JE. Compared with a JE, an established PIE had more proliferating cells, exhibited lower expression of attachment proteins, and had significantly more inflammatory cells in the underlying connective tissue. Wnt-responsive cells in the OE contributed to an initial PIE, but Wnt-responsive cells and their descendants were lost as the PIE matured.

CONCLUSIONS

Although histologically similar, the PIE lacked a Wnt-responsive stem cell niche and exhibited characteristics of a chronically inflamed tissue. Both features contributed to suboptimal barrier functions of the PIE compared with a native JE.

Radiological Outcomes of Bone-Level and Tissue-Level Dental Implants: Systematic Review

Background: to assess the radiological marginal bone loss between bone-level or tissue-level dental implants through a systematic review of literature until September 2019. Methods: MEDLINE, Embase and other database were searched by two independent authors including only English articles. Results: The search provided 1028 records and, after removing the duplicates through titles and abstracts screening, 45 full-text articles were assessed for eligibility. For qualitative analysis 20 articles were included, 17 articles of them for quantitative analysis counting a total of 1161 patients (mean age 54.4 years) and 2933 implants, 1427 inserted at Tissue-level (TL) and 1506 inserted at Bone-level (BL). The survival rate and the success rate were more than 90%, except for 2 studies with a success rate of 88% and 86.2%. No studies reported any differences between groups in term of success and survival rates. Three studies showed that BL-implants had statistically less marginal bone loss (p < 0.05). Only one study reported statistically less marginal bone loss in TL-implants (p < 0.05). Conclusion: In the most part of the studies, differences between implant types in marginal bone loss were not statistically significant after a variable period of follow-up ranged between 1 and 5 years.

Adjunctive Use of Lasers in Peri-Implant Mucositis and Peri-Implantitis Treatment: A Systematic Review

BACKGROUND

The aim of this systematic review is to compare the effectiveness of lasers in the treatment of implant mucositis and peri-implantitis compared to conventional treatment (non-surgical or surgical: resective or regenerative).

METHODS

Sources of PubMed, Cochrane and Google Scholar search engines were used on articles published from 1997 to 2020 in English, with selected keyword criteria applied. Nine randomized controlled trials (RCTs) were selected.

RESULTS

All included studies were considered of "high quality" according to the quality assessment scale. The comparative assessment of the RCTs was done twice for each RCT based on the type of treatment and according to wavelength. There is strong scientific evidence that, regarding non-surgical treatment, adjunct laser application can provide better results only in the short term (three months). Regarding the surgical approach, the method of decontamination plays a subordinate role. All wavelengths/applications presented similar results.

CONCLUSION

Within the limitations of this study, the adjunctive use of lasers in the treatment of peri-implant inflammation is effective for up to three months; there is no strong evidence regarding the long term benefit compared to conventional treatment.

TLR4 mediates alveolar bone resorption in experimental peri-implantitis through regulation of CD45+ cell infiltration, RANKL/OPG ratio, and inflammatory cytokine production

BACKGROUND

The present study was to determine the role of Toll-like receptor 4 (TLR4) signaling in inflammation and alveolar bone resorption using a murine model of Porphyromonas gingivalis-associated ligature-induced peri-implantitis.

METHODS

Smooth surface titanium implants were placed in the left maxilla alveolar bone 6 weeks after extraction of first and second molars in Wild-type (WT) and TLR4^-/- (TLR4 KO) mice. Silk ligatures immersed with P. gingivalis were tied around the implants 4 weeks after the implant placement and confirmation of osteointegration. Two weeks after the ligation, bone resorption, osteoclastogenesis, cellular inflammatory responses, and gingival mRNA expression levels of cytokines were assessed by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) staining, immunobiological examination and Real-time quantitative polymerase chain reaction, respectively.

RESULTS

In both WT and TLR4 KO mice, the bone resorption around implants was significantly increased in the P. gingivalis/ligation group compared with control group. In P. gingivalis/ligation group, the levels of bone resorption, TRAP+ cell formation, and gingival CD3+ and CD45+ cell infiltration were significantly decreased in TLR4 KO mice compared with that in WT mice. Receptor activator of nuclear factor-kappa B ligand /osteoprotegerin (RANKL/OPG) ratio was significantly increased after P. gingivalis/ligation treatment in WT mice not in TLR4 KO mice. When comparing the P. gingivalis/ligation group with the respective control group, gingival mRNA expressions of IL-1β, IFN-γ, and 1L-17 were significantly increased in TLR4 KO mice.

CONCLUSION

This study suggests that TLR4 mediates alveolar bone resorption in P. gingivalis associated ligature-induced peri-implantitis through regulation of immune B cell infiltration, RANKL/OPG expression ratio, and differential inflammatory cytokine production.

Porphyromonas Gingivalis Load is Balanced by 0.20% Chlorhexidine Gel. A Randomized, Double-Blind, Controlled, Microbiological and Immunohistochemical Human Study

Microbial contamination could compromise the stability of dental implants increasing the risk of inflammatory reactions in the surrounding soft tissues. In this human, randomized, double-blind, clinical study, the presence of Porphyromonas gingivalis on the healing abutment and the inflammatory infiltrate surrounding peri-implant soft tissues were investigated. Experiments were done in order to clarify the effect of 0.20% chlorhexidine (CHX) versus placebo, applied during each rehabilitation stage. Thirty patients (15 per group) were included. The load of adhering P. gingivalis on the healing screw were quantified by quantitative Polymerase Chain Reaction (qPCR) Taq-Man. Immunohistochemical analysis was carried out on the gingival biopsy. Moreover, clinical data were recorded. Analysis of variance and the Holm-Sidak test was used to evaluate differences between groups. The results showed a significant low presence of P. gingivalis load in healing abutments belonging to the 0.20% CHX group. Overall, the differences in terms of P. gingivalis DNA copy number between two groups were statistically significant (p < 0.01). All implants showed very low plaque and bleeding scores, but the placebo group appeared to have the highest expression of inflammation markers for T Lymphocytes, B Lymphocytes and macrophages Cluster definitions (CD3, CD20 and CD68). The use of 0.20% CHX could be recommended in all clinical procedures as it reduces significantly P. gingivalis load and host inflammatory response around implants.

Titanium abutment surface modifications and peri-implant tissue behavior: a systematic review and meta-analysis

OBJECTIVES

To evaluate the effect of various titanium abutment modifications on the behaviour of peri-implant soft tissue healing, inflammation and maintenance.

MATERIAL AND METHODS

An electronic database research until 30 April 2019 was performed. A meta-analysis (MA) for each outcome parameter was performed by using the random-effects models with the DerSimonian-Laird estimator.

RESULTS

Ten studies were included in the present review. Four studies with a long follow-up (5-6 years) reported the outcomes in a heterogeneous way and were suitable for MA. Six studies (4 RCT, 2 CCT) including 118 patients and 182 implants dealing with a modified healing abutment surface and short follow-up were selected for MA. The MA for PI and BoP as outcome showed no significant differences between surfaces (PI: P = 0.091; BoP: P = 0.099). The MA for PD as outcome showed no significant differences between surfaces (P = 0.488). No statistical significance was found by evaluating each mixed-effects model for potential moderators (type of study, study design, number of implants, follow-up length). The other four studies with a longer follow-up (5-6 years) reported contradictory results depending on the surface treatment investigated.

CONCLUSIONS

Within their limits, the present findings suggest that peri-implant soft tissue may not be affected by the surface treatment of titanium abutments on the short term. Contrasting results are reported in longer follow-up periods depending on the technique used to modify the abutment.

CLINICAL RELEVANCE

Clinicians should carefully evaluate the use of a modified titanium surface in their practice. Even if no differences in terms of inflammation are present at short term, these findings need to be validated in long-term studies.

Surface treatments on titanium implants via nanostructured ceria for antibacterial and anti-inflammatory capabilities

Peri-implantitis is the most common risk factor for dental implant failure. Nanostructured ceria (nano-CeO₂) has anti-inflammatory and antibacterial functions, and different shapes of ceria enclosed by specific crystal planes could be an effective approach to enhance intrinsic catalysis. In the present study, the authors developed a novel implant surface-modification strategy by coating different shapes of nano-CeO₂ onto titanium (Ti) surfaces to enhance their antibacterial and anti-inflammatory properties. The objectives of the study were to: (1) develop novel Ti surfaces modified with different shapes of nano-CeO₂ (nanorod, nanocube and nano-octahedron) for peri-implantitis prevention; (2) investigate and compare the inhibition efficacy of different shapes of CeO₂-modified surfaces against biofilms of peri-implantitis-related pathogens; and (3) evaluate the different CeO₂-modified surfaces on cell inflammatory response in vitro and in vivo. The results showed that nanorod CeO₂-modified Ti had more bacteria attachment of Streptococcus sanguinis in the early stage, compared with other CeO₂-modified Ti (p < 0.05). They all exhibited similarly substantial CFU reductions against peri-implantitis-related biofilms (p > 0.1). Nanocube and nano-octahedron CeO₂-modified Ti exerted much better anti-inflammatory effects and ROS-scavenging ability than nanorod CeO₂in vitro (p < 0.05). In vivo, the mean mRNA expression of TNF-α, IL-6 and IL-1β in the tissues around Ti was decreased by the three shapes of nano-CeO₂; nano-octahedron CeO₂ showed the strongest anti-inflammatory effect among all groups (p < 0.05). In conclusion, all three types of CeO₂-modified Ti exerted equally strong antibacterial properties; nano-octahedron CeO₂-modified Ti had the best anti-inflammatory effect. Therefore, CeO₂-modified Ti surfaces are highly promising for enhancing antimicrobial functions for dental implants. Novel nano-octahedron CeO₂ coating on Ti had great therapeutic potential for alleviating and eliminating peri-implantitis. STATEMENT OF SIGNIFICANCE: Peri-implantitis is the most common risk factor for dental implant failure. Nanostructured ceria (nano-CeO₂) has anti-inflammatory and antibacterial functions, and different shapes of ceria enclosed by specific crystal planes could be an effective approach to enhance intrinsic catalysis. In the present study, we developed a novel implant surface-modification strategy by coating different shapes of nano-CeO₂ onto titanium surfaces to enhance their antibacterial and anti-inflammatory properties for dental implants. In addition, we found that the nano-octahedron CeO₂ coating on titanium would have great therapeutic potential for alleviating and eliminating peri-implantitis.

Is Peri-Implant Probing Causing Over-Diagnosis and Over-Treatment of Dental Implants?

Pocket probing depth (PPD) and bleeding on probing (BOP) measurements are useful indices for the assessment of periodontal conditions. The same periodontal indices are commonly recommended to evaluate the dental implant/tissue interface to identify sites with mucositis and peri-implantitis, which, if not treated, are anticipated to lead to implant failure. The aim of the present narrative review is to discuss the available literature on the effectiveness of probing at dental implants for identification of peri-implant pathology. There is substantial clinical evidence that PPD and BOP measurements are very poor indices of peri-implant tissue conditions and are questionable surrogate endpoints for implant failure. On the contrary, the literature suggests that frequent disturbance of the soft tissue barrier at implants may instead induce inflammation and bone resorption. Moreover, over-diagnosis and subsequent unnecessary treatment may lead to iatrogenic damage to the implant-tissue interface. Despite this, the recommendations from recent consensus meetings are still promoting the use of probing at dental implants. For evaluation of implants, for instance at annual check-ups, the present authors recommend a clinical examination that includes (i) a visual inspection of the peri-implant tissues for the assessment of oral hygiene and the detection of potential redness, swelling, (ii) palpation of the peri-implant tissues for assessment of the potential presence of swelling, bleeding, suppuration. In addition, (iii) radiography is recommended for the assessment of crestal bone level for comparison with previous radiographs to evaluate potential progressive bone loss even if there is a need for more scientific evidence of the true value of the first two clinical testing modes.

Immunohistochemical Evaluation of Peri-Implant Soft Tissues around Machined and Direct Metal Laser Sintered (DMLS) Healing Abutments in Humans

Background: Direct metal laser Sintering (DMLS) is an additive manufacturing technique that allows fabrication of dental implants and related components with a highly porous surface. To date, no human studies have investigated the soft tissue adhesion and presence of inflammatory infiltrate with porous DMLS healing abutments (HAs), nor have they compared these with the classic machined ones. Purpose: To evaluate the degree of cell adhesion (integrin expression) and the quantity/quality of inflammatory infiltrate, on HAs with different surfaces; full DMLS, full machined, and hybrid (half DMLS and half machined). Methods: Fifty implant patients were randomly assigned to receive one of these different Has: T1, full DMLS (11 subjects); T2, machined in the upper portion and DMLS in the lower one (10 subjects); T3, DMLS in the upper portion and machined in the lower one (19 subjects); T4, full machined (10 patients). Thirty days after placement, circular sections of soft tissues around HAs were retrieved for immunohistochemical evaluation. Results: With regard to the adhesion molecules, the samples showed different intensity of integrin expression, with a statistically significant difference (p < 0.001) between T1 and the other groups. All the samples were positive for the different clusters related to the inflammatory infiltrate (T lymphocytes, CD3; B lymphocytes, CD20; and macrophages, CD68), but a lower infiltrate was found in T1, with statistically significant differences (p < 0.001) among the groups. Conclusions: The HA surface seems to influence the degree of cell adhesion and the inflammatory infiltrate of the surrounding soft tissues.

Oral microbiome and peri-implant diseases: where are we now?

Peri-implant infective diseases (PIIDs) in oral implantology are commonly known as peri-implant mucositis (PIM) and periimplantitis (PI). While PIM is restricted to the peri-implant mucosa and is reversible, PI also affects implant-supporting bone and, therefore, is very difficult to eradicate. PIIDs in clinical outcome may resemble gingivitis and periodontitis, as they share similar risk factors. However, recent study in the field of proteomics and other molecular studies indicate that PIIDs exhibit significant differences when compared to periodontal diseases. This review aims to elucidate the current knowledge of PIIDs, their etiopathology and diversified microbiology as well as the role of molecular studies, which may be a key to personalized diagnostic and treatment protocols of peri-implant infections in the near future.

Transforming growth factor-β, interleukin-17, and IL-23 gene expression profiles associated with human peri-implantitis

OBJECTIVES

The mRNA expression profiles of IL-23/Th17 and the Treg-associated cytokine TGF-β in peri-implantitis are currently under research. This study characterized the IL-17, IL-23, and TGF-β gene expression levels in healthy and diseased peri-implant tissues and correlated these data with radiographic bone loss.

MATERIAL AND METHODS

Peri-implant soft tissues from 40 subjects (20 healthy controls with mean age of 59.4 ± 6.3, and 20 with peri-implantitis with mean age of 56.6 ± 5.5) were enrolled in this study, and real-time PCR (RT-PCR) was used to define the profile of IL-17, IL-23, and TGF-β gene expression.

RESULTS

Higher levels of TGF-β mRNA were observed in biopsies taken from healthy controls, and the IL-23 mRNA levels were significantly increased in the peri-implantitis group (P < 0.0001). No differences in IL-17 mRNA levels were observed between the two groups (P > 0.05).

CONCLUSIONS

Data presented in this report demonstrated a predominant Th17 response in peri-implantitis subjects based on the higher levels of IL-23 and lower levels of TGF-β detected.

Foreign bodies associated with peri-implantitis human biopsies

BACKGROUND

Peri-implantitis is an inflammatory condition that can lead to implant loss. The aim of this descriptive retrospective study is to describe the histopathologic findings in soft tissue biopsies of implants with peri-implantitis.

METHODS

Thirty-six human peri-implantitis biopsies were analyzed using light microscopy (LM) and scanning electron microscopy (SEM). The composition of foreign materials found in the tissues was assessed using an energy dispersive x-ray spectrometer.

RESULTS

At the LM level, the inflammatory lesion of peri-implantitis was in most cases a mixture of subacute and chronic inflammation dominated by plasma cells. At the SEM level, radiopaque foreign bodies were identified in 34 of the 36 biopsies. The predominant foreign bodies found were titanium and dental cement. These foreign materials were surrounded by inflammatory cells.

CONCLUSIONS

At present, the exact mechanism for introduction of these materials and their role in peri-implantitis is unknown. Further research is warranted to determine their etiology and potential role in pathogenesis.

Biological characterization of implant surfaces - in vitro study

<title>Abstract</title><sec><title>Objective</title><p>Evaluate the biological performance of titanium alloys grade IV under different surface treatments: sandblasting and double etching (Experimental surface 1; Exp1, NEODENT); surface with wettability increase (Experimental surface 2; Exp2, NEODENT) on response of preliminary differentiation and cell maturation.</p></sec><sec><title>Material and method</title><p>Immortalized osteoblast cells were plated on Exp1 and Exp2 titanium discs. The polystyrene plate surface without disc was used as control group (C). Cell viability was assessed by measuring mitochondrial activity (MTT) at 4 and 24 h (n = 5), cell attachment was performed using trypan blue exclusion within 4 hours (n = 5), serum total protein and alkaline phosphatase normalization was performed at 4, 7 and 14 days (n = 5). Data were analyzed using one-way ANOVA and Tukey test.</p></sec><sec><title>Result</title><p>The values of cell viability were: 4h: C– 0.32±0.01^A; Exp1– 0.34±0.08^A; Exp2– 0.29±0.03^A. 24h: C– 0.43±0.02^A; Exp1– 0.39±0.01^A; Exp2– 0.37±0.03^A. The cell adhesion counting was: C– 85±10^A; Exp1- 35±5^B; Exp2– 20±2^B. The amounts of serum total protein were 4d: C– 40±2^B; Exp1– 120±10^A; Exp2– 130±20^A. 7d: C– 38±2^B; Exp1– 75±4^A; Exp2– 70±6^A. 14 d: C– 100±3^A; Exp1– 130±5^A; Exp2– 137±9^A. The values of alkaline phosphatase normalization were: 4d: C– 2.0±0.1^C; Exp1– 5.1±0.8^B; Exp2– 9.8±2.0^A. 7d: C– 1.0±0.01^C; Exp1– 5.3±0.5^A; Exp2– 3.0±0.3^B. 14 d: C– 4.1±0.3^A; Exp1– 4.4±0.8^A; Exp2– 2.2±0.2^B. Different letters related to statistical differences.</p></sec><sec><title>Conclusion</title><p>The surfaces tested exhibit different behavior at dosage of alkaline phosphatase normalization showing that the Exp2 is more associated with induction of cell differentiation process and that Exp1 is more related to the mineralization process.</p></sec>

Definition, etiology, prevention and treatment of peri-implantitis--a review

Peri-implant inflammations represent serious diseases after dental implant treatment, which affect both the surrounding hard and soft tissue. Due to prevalence rates up to 56%, peri-implantitis can lead to the loss of the implant without multilateral prevention and therapy concepts. Specific continuous check-ups with evaluation and elimination of risk factors (e.g. smoking, systemic diseases and periodontitis) are effective precautions. In addition to aspects of osseointegration, type and structure of the implant surface are of importance. For the treatment of peri-implant disease various conservative and surgical approaches are available. Mucositis and moderate forms of peri-implantitis can obviously be treated effectively using conservative methods. These include the utilization of different manual ablations, laser-supported systems as well as photodynamic therapy, which may be extended by local or systemic antibiotics. It is possible to regain osseointegration. In cases with advanced peri-implantitis surgical therapies are more effective than conservative approaches. Depending on the configuration of the defects, resective surgery can be carried out for elimination of peri-implant lesions, whereas regenerative therapies may be applicable for defect filling. The cumulative interceptive supportive therapy (CIST) protocol serves as guidance for the treatment of the peri-implantitis. The aim of this review is to provide an overview about current data and to give advices regarding diagnosis, prevention and treatment of peri-implant disease for practitioners.

Controlled-release of bone morphogenetic protein-2 from a microsphere coating applied to acid-etched Ti6AL4V implants increases biological bone growth in vivo

A central clinical challenge regarding the surgical treatment of bone and joint conditions is the eventual loosening of an orthopedic implant as a result of insufficient bone ingrowth at the bone-implant interface. We investigated the in vivo effectiveness of a coating containing recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded microspheres applied to acid-etched Ti6Al4V cylinders for implantation. Three groups of rabbits (24 per group) were used for implantation: (1) acid-etched Ti6Al4V implants coated with a mixture of rhBMP-2-loaded microspheres (125 ng rhBMP-2/mg microspheres) and α-butyl cyanoacrylate; (2) acid-etched, uncoated implants; and (3) bare, smooth uncoated implants. After implantation, 12 rabbits from each group were used for bone ingrowth determination at 4, 5, 6, 7, 8, and 12 weeks (2 rabbits per time point), while the remainder were used for histological analysis and push-out testing at 12 weeks. Scanning electron microscopy showed significant improvement in bone growth of the rhBMP-2 microspheres/α-butyl cyanoacrylate group compared with the other groups (p<0.01). Histological analysis and push-out testing also demonstrated enhanced bone growth of the rhBMP-2 group over that in the other two groups (p<0.01). The rhBMP-2 group showed the most significant bone growth, suggesting that coating acid-etched implants with a mixture of rhBMP-2-loaded microspheres and α-butyl cyanoacrylate may be an effective method to improve the osseointegration of orthopedic implants.

Soft tissue integration versus early biofilm formation on different dental implant materials

OBJECTIVE

Dental implants anchor in bone through a tight fit and osseo-integratable properties of the implant surfaces, while a protective soft tissue seal around the implants neck is needed to prevent bacterial destruction of the bone-implant interface. This tissue seal needs to form in the unsterile, oral environment. We aim to identify surface properties of dental implant materials (titanium, titanium-zirconium alloy and zirconium-oxides) that determine the outcome of this "race-for-the-surface" between human-gingival-fibroblasts and different supra-gingival bacterial strains.

METHODS

Biofilms of three streptococcal species or a Staphylococcus aureus strain were grown in mono-cultures on the different implant materials in a parallel-plate-flow-chamber and their biovolume evaluated using confocal-scanning-laser-microscopy. Similarly, adhesion, spreading and growth of human-gingival-fibroblasts were evaluated. Co-culture experiments with bacteria and human-gingival-fibroblasts were carried out to evaluate tissue interaction with bacterially contaminated implant surfaces. Implant surfaces were characterized by their hydrophobicity, roughness and elemental composition.

RESULTS

Biofilm formation occurred on all implant materials, and neither roughness nor hydrophobicity had a decisive influence on biofilm formation. Zirconium-oxide attracted most biofilm. All implant materials were covered by human-gingival-fibroblasts for 80-90% of their surface areas. Human-gingival-fibroblasts lost the race-for-the-surface against all bacterial strains on nearly all implant materials, except on the smoothest titanium variants.

SIGNIFICANCE

Smooth titanium implant surfaces provide the best opportunities for a soft tissue seal to form on bacterially contaminated implant surfaces. This conclusion could only be reached in co-culture studies and coincides with the results from the few clinical studies carried out to this end.

Microbiological and immuno-pathological aspects of peri-implant diseases

Peri-implant diseases are a cluster of "contemporary" oral infections in humans that have emerged as a result of the routine application of osseointegrated dental implants in clinical practice. They are characterized by the inflammatory destruction of the implant-supporting tissues, as a result of biofilm formation on the implant surface. Peri-implant mucositis and peri-implantitis are analogous to gingivitis and periodontitis that affect natural teeth. The aim of this comprehensive review was to provide insights into the infectious aetiology and immuno-pathology of peri-implant diseases, and to identify similarities and differences with periodontal diseases. The microbial composition of peri-implantitis-associated biofilms is mixed, non-specific and very similar to that of periodontitis. A considerable exception is the frequent presence of high numbers of staphylococci and enteric bacteria in peri-implantitis. The sequence of immuno-pathological events and the qualitative composition of the immune cells in peri-implant infections are similar to that of periodontal infections. The lesions are characterized predominantly by neutrophils, macrophages, T- and B-cells. Nevertheless, compared to periodontitis, peri-implantitis is marked by a more extensive inflammatory infiltrate and innate immune response, a greater severity of tissue destruction and a faster progression rate. This could well account for the structural differences between the two tissue types, predominantly the lack of periodontal ligament and Sharpey's fibres around implants. In order to support the early diagnosis and prevention of peri-implantitis, it is crucial to explain its fast progression rate by elucidating the underlying molecular mechanisms. This could be achieved, for instance, by utilizing the non-invasive collection and analysis of peri-implant crevicular fluid.

Crestal bone reactions to immediate implants placed at different levels in relation to crestal bone. A pilot study in Foxhound dogs

OBJECTIVES

The aim of the present study was to evaluate bone-to-implant contact (BIC) and bone remodeling dynamics after immediate implant placement at different levels in relation to the crestal bone.

MATERIALS AND METHODS

The mandibular second, third, and fourth premolars of six Foxhound dogs were extracted bilaterally. Randomly, three implants were immediately placed in the hemi-arches of each dog, crestally or 2 mm subcrestally. Three dogs were allowed an 8-week submerged healing period, and the other three at 12-week submerged healing period. The animals were sacrificed at 12 weeks and samples were obtained. Biopsies were processed for ground sectioning. Histomorphometric analysis was carried out to compare BIC, bone neoformation, and bone remodeling.

RESULTS

All implants osseointegrated clinically and histologically. Healing patterns examined microscopically at eight and twelve weeks for both groups (crestal and subcrestal) yielded similar qualitative bone findings. The Total BIC mean value for the crestal group 44.52% at 8 weeks and 39.50% at 12 weeks, and for the subcrestal group was 47.33% at 8 weeks and 53.85% at 12 weeks%. There was less bone resorption in the subcrestal group (test) than in crestal group (control).

CONCLUSIONS

Within the limitations of this study, our findings suggest that apical positioning of the top of the implant does not jeopardize bone crest and peri-implant tissue remodeling. However, less resorption of the lingual crest may be expected when implants are placed 2 mm subcrestally. Moreover, higher BIC values were found in implants placed subcrestally.

Osteoblastic and cytokine gene expression of implant-adherent cells in humans

OBJECTIVES

Implant surface topography is a key determinant affecting osteoblastic differentiation and cell-cell signaling of implant-adherent cells.

MATERIALS AND METHODS

To assess the early osteoinductive and cell-cell signaling events in adherent cells, commercially pure titanium implants (2.2 × 5 mm) with nanotopography (HF-treated TiO2 grit-blasted) were compared with micron-scale topography TiO2 grit-blasted (micron-scale, control) implants in vivo. Six implants (n = 3/surface) were placed in 10 systemically healthy subjects and removed by reverse threading at 1, 3, and 7 days. Gene expression profiles of adherent cells were interrogated using low-density RT-PCR arrays.

RESULTS

Osteoinduction was not observed at day 1 on either surface. At 3 days, elevated levels of BMP6, osteopontin, and osterix (OSX) were observed in RNA of cells adherent to both micron-scale and nanotopography surfaces. Both surfaces supported osteoinductive gene expression at 7 days; however, modest elevations of most mRNAs and significantly higher OSX mRNA levels were measured for cells adhered to nanotopography implants. Further, chemokine and cytokine profiles including CXCL10, CXCL14, IL-9, IL-22, and TOLLIP were upregulated on nanotopographic surfaces as compared with microtopographic surfaces.

CONCLUSIONS

Implants with superimposed nanoscale topography generate a greater induction of genes linked to osteogenesis and cell-cell signaling during the early phases of osseointegration.