Bioactive coatings for dental implants: A review of alternative strategies to prevent peri-implantitis induced by anaerobic bacteria

Members of oral bacterial communities form biofilms not only on tooth surfaces but also on the surface of dental implants that replace natural teeth. Prolonged interaction of host cells with biofilm-forming anaerobes frequently elicits peri-implantitis, a destructive inflammatory disease accompanied by alveolar bone loss leading to implant failure. Here we wish to overview how the deposition of bioactive peptides to dental implant surfaces could potentially inhibit bacterial colonization and the development of peri-implantisis. One preventive strategy is based on natural antimicrobial peptides (AMPs) immobilized on titanium surfaces. AMPs are capable to destroy both Gram positive and Gram negative bacteria directly. An alternative strategy aims at coating implant surfaces - especially the transmucosal part - with peptides facilitating the attachment of gingival epithelial cells and connective tissue cells. These cells produce AMPs and may form a soft tissue seal that prevents oral bacteria from accessing the apical part of the osseointegrated implant. Because a wide variety of titanium-bound peptides were studied in vitro, we wish to concentrate on bioactive peptides of human origin and some of their derivatives. Furthermore, special attention will be given to peptides effective under in vivo test conditions.

A micromorphological/microbiological pilot study assessing three methods for the maintenance of the implant patient

OBJECTIVE

The aim of this study was to evaluate and compare the effectiveness of the ultrasonic piezoelectric inserts of EMS Steel Tip A, EMS Peek, and IS-TiP-STS-3E© in reducing peri-implant bacterial load without compromising the surface of implants during professional oral hygiene in the follow-up.

MATERIALS AND METHODS

Thirteen implants were examined (Winsix, Biosafin, Ancona, Italy). The implants were divided into five groups and analyzed with a SEM microscope and microbiological analysis to evaluate the possible modification of structure and the bacterial load reduction.

RESULTS

The control and A, B, and C test groups were initially contaminated in vitro with Streptococcus mutans. Subsequently, the A, B, and C test groups were treated by an only expert operator in standard conditions. Test groups A, B, and C were inoculated for 3 hr and, furthermore, microbiologically analyzed.

CONCLUSION

The gold standard of an implant maintenance is a significant reduction of the bacterial load without becoming aggressive. According to our results, despite the limitations of the study, the authors recommend the least aggressive IS-TiP-STS-3E© , but combined with an antimicrobial agent to reduce the bacterial load, because the IS-TiP-STS-3E© did not show appreciable results versus the EMS Peek in reducing the bacterial load.

The Translation from In Vitro Bioactive Ion Concentration Screening to In Vivo Application for Preventing Peri-implantitis

Peri-implantitis is a typical pathological condition characterized by the destructive inflammation in the soft tissue and the progressive loss of supporting bones. As the current effective treatments and preventive measures are inconsistent and unpredictable, the use of biomaterials as carriers of bioactive ion coatings is a promising approach. However, the translation from lab to large-scale production and clinical applications is difficult due to a technology barrier. Determining the effective dosage of each ion to achieve an in vivo application of the in vitro screening is challenging. Here, we selected zinc and strontium ions to provide multiple effects on antibacterial activity and osteogenesis. The optimal coating with effective release concentrations of the two ions was obtained after the two-step screening from in vitro testing. The results showed that this type of in vivo bioactive ion usage leads to an enhanced osseointegration during the immediate implantation in a periodontitis-affected environment and prevents soft tissue inflammation and bone resorption in an inflammatory environment. The new biologically active ion screening method could verify the effectiveness of this clinical translation and its potential for large-scale production and could determine the effective dosage of each ion for a specific application.

Evaluation of Antimicrobial Effect of Air-Polishing Treatments and Their Influence on Human Dental Pulp Stem Cells Seeded on Titanium Disks

Dental implants are one of the most frequently used treatment options for tooth replacement, and titanium is the metal of choice due to its demonstrated superiority in resisting corrosion, lack of allergic reactions and mechanical strength. Surface roughness of titanium implants favors the osseointegration process; nevertheless, its topography may provide a suitable substrate for bacterial biofilm deposition, causing peri-implantitis and leading to implant failure. Subgingival prophylaxis treatments with cleansing powders aimed to remove the bacterial accumulation are under investigation. Two different air-polishing powders—glycine and tagatose—were assayed for their cleaning and antimicrobial potential against a Pseudomonas biofilm and for their effects on human dental pulp stem cells (hDPSCs), seeded on sandblasted titanium disks. Immunofluorescence analyses were carried out to evaluate cell adhesion, proliferation, stemness and osteogenic differentiation. The results demonstrate that both the powders have a great in vitro cleaning potential in the early period and do not show any negative effects during hDPSCs osteogenic differentiation process, suggesting their suitability for enhancing the biocompatibility of titanium implants. Our data suggest that the evaluated cleansing systems reduce microbial contamination and allow us to propose tagatose as an adequate alternative to the gold standard glycine for the air-polishing prophylaxis treatment.

The effect of standoff distance and surface roughness on biofilm disruption using cavitation

Effective biofilm removal from surfaces in the mouth is a clinical challenge. Cavitation bubbles generated around a dental ultrasonic scaler are being investigated as a method to remove biofilms effectively. It is not known how parameters such as surface roughness and instrument distance from biofilm affect the removal. We grew Strepotococcus sanguinis biofilms on coverslips and titanium discs with varying surface roughness (between 0.02-3.15 μm). Experimental studies were carried out for the biofilm removal using high speed imaging and image analysis to calculate the area of biofilm removed at varying ultrasonic scaler standoff distances from the biofilm. We found that surface roughness up to 2 μm does not adversely affect biofilm removal but a surface roughness of 3 μm caused less biofilm removal. The standoff distance also has different effects depending on the surface roughness but overall a distance of 1 mm is just as effective as a distance of 0.5 mm. The results show significant biofilm removal due to an ultrasonic scaler tip operating for only 2s versus 15-60s in previous studies. The technique developed for high speed imaging and image analysis of biofilm removal can be used to investigate physical biofilm disruption from biomaterial surfaces in other fields.

Targeting Pathogenic Biofilms: Newly Developed Superhydrophobic Coating Favors a Host-Compatible Microbial Profile on the Titanium Surface

Polymicrobial infections are one of the most common reasons for inflammation of surrounding tissues and failure of implanted biomaterials. Because microorganism adhesion is the first step for biofilm formation, physical-chemical modifications of biomaterials have been proposed to reduce the initial microbial attachment. Thus, the use of superhydrophobic coatings has emerged because of their anti-biofilm properties. However, these coatings on the titanium (Ti) surface have been developed mainly by dual-step surface modification techniques and have not been tested using polymicrobial biofilms. Therefore, we developed a one-step superhydrophobic coating on the Ti surface by using a low-pressure plasma technology to create a biocompatible coating that reduces polymicrobial biofilm adhesion and formation. The superhydrophobic coating on Ti was created by the glow discharge plasma using Ar, O_2, and hexamethyldisiloxane gases, and after full physical, chemical, and biological characterizations, we evaluated its properties regarding oral biofilm inhibition. The newly developed coating presented an increased surface roughness and, consequently, superhydrophobicity (contact angle over 150°) and enhanced corrosion resistance (p < 0.05) of the Ti surface. Furthermore, proteomic analysis showed a unique pattern of protein adsorption on the superhydrophobic coating without drastically changing the biologic processes mediated by proteins. Additionally, superhydrophobic treatment did not present a cytotoxic effect on fibroblasts or reduction of proliferation; however, it significantly reduced (≈8-fold change) polymicrobial adhesion (bacterial and fungal) and biofilm formation in vitro. Interestingly, superhydrophobic coating shifted the microbiological profile of biofilms formed in situ in the oral cavity, reducing by up to ≈7 fold pathogens associated with the peri-implant disease. Thus, this new superhydrophobic coating developed by a one-step glow discharge plasma technique is a promising biocompatible strategy to drastically reduce microbial adhesion and biofilm formation on Ti-based biomedical implants.

Sealing agent reduces formation of single and dual-species biofilms of Candida albicans and Enterococcus faecalis on screw joints at the abutment/implant interface

The aim of this research was to evaluate the efficacy of a commercial sealing agent at the abutment/implant interface against microleakage of single and dual-species biofilms of Candida albicans and Enterococcus faecalis into external hexagon (EH) and Morse taper (MT) prosthetic connections. A total of 216 samples of implants and their abutments were tested. Six groups (n = 36) were evaluated based on biofilm and period of incubation (7 and 14 days). The implant connections EH and MT (n = 18) were divided according to the use of the material (n = 9) (EH-T and MT-T: with the sealing agent; EH-C and MT-C: control). The biofilms were analyzed by microbial counting (CFU/mL) and SEM analysis and photographs of the material in the screw joints were also taken. Data were analyzed by Student t test, two-way ANOVA and Bonferroni test. For the single-species biofilms, there was a significant reduction in the growth of E. faecalis when compared MT-C and MT-T or EH-C and EH-T at 7 and 14 days. The same was observed for C. albicans biofilms. For dual-species biofilms of E. faecalis and C. albicans, the sealing agent was more effective in preventing microbial infiltration into the MT connection at 14 days, while microbial infiltration did not occur into EH connections even in absence of the sealing agent for both periods of evaluation. Overall, these data suggest that the presence of the sealing agent reduces or eliminates the microleakage of E. faecalis and C. albicans biofilms into the implants regardless of the period of incubation.

Commensal and pathogenic biofilms differently modulate peri-implant oral mucosa in an organotypic model

The impact of oral commensal and pathogenic bacteria on peri-implant mucosa is not well understood, despite the high prevalence of peri-implant infections. Hence, we investigated responses of the peri-implant mucosa to Streptococcus oralis or Aggregatibacter actinomycetemcomitans biofilms using a novel in vitro peri-implant mucosa-biofilm model. Our 3D model combined three components, organotypic oral mucosa, implant material, and oral biofilm, with structural assembly close to native situation. S. oralis induced a protective stress response in the peri-implant mucosa through upregulation of heat shock protein (HSP70) genes. Attenuated inflammatory response was indicated by reduced cytokine levels of interleukin-6 (IL-6), interleukin-8 (CXCL8), and monocyte chemoattractant protein-1 (CCL2). The inflammatory balance was preserved through increased levels of tumor necrosis factor-alpha (TNF-α). A. actinomycetemcomitans induced downregulation of genes important for cell survival and host inflammatory response. The reduced cytokine levels of chemokine ligand 1 (CXCL1), CXCL8, and CCL2 also indicated a diminished inflammatory response. The induced immune balance by S. oralis may support oral health, whereas the reduced inflammatory response to A. actinomycetemcomitans may provide colonisation advantage and facilitate later tissue invasion. The comprehensive characterisation of peri-implant mucosa-biofilm interactions using our 3D model can provide new knowledge to improve strategies for prevention and therapy of peri-implant disease.

Research: Recovery of Microorganisms in Nonsterile, Reusable, Loaned Orthopedic Implants

Currently, there are two orthopedic implant types: (1) Sterile implants (e.g., joint prostheses) are distributed in a ready-for-use sterile fashion, and (2) nonsterile implants (e.g., plates, screws, Schanz pins, intramedullary rods) are processed by a healthcare facility's central sterile service department (CSSD). The current study evaluated processed implants for presence of coagulase-negative staphylococci, which was observed in 30% of the cortical screws, spongy screws, and Schanz pins (37 total samples) processed by a CSSD. Some samples were resistant to antimicrobial agents, thereby demonstrating that risk exists in the current methods used in the processing of nonsterile implants. Also of important note, nonsterile implants are commonly loaned worldwide. Loaned implantable materials should not be processed in the same manner as materials routinely prepared in the CSSD, as it is not possible to know the quality of the cleaning performed before the materials are returned to the loaning company. It is not uncommon for hospitals to receive loaned materials with organic residues.

Keratinocytes protect soft-tissue integration of dental implant materials against bacterial challenges in a 3D-tissue infection model

The soft-tissue seal around dental implants protects the osseo-integrated screw against bacterial challenges. Surface properties of the implant material are crucial for implant survival against bacterial challenges, but there is no adequate in vitro model mimicking the soft-tissue seal around dental implants. Here, we set up a 3D-tissue model of the soft-tissue seal, in order to establish the roles of oral keratinocytes, gingival fibroblasts and materials surface properties in the protective seal. To this end, keratinocytes were grown on membrane filters in a transwell system, while fibroblasts were adhering to TiO₂ surfaces underneath the membrane. In absence of keratinocytes on the membrane, fibroblasts growing on the TiO₂ surface could not withstand challenges by commensal streptococci or pathogenic staphylococci. Keratinocytes growing on the membrane filters could withstand bacterial challenges, but tight junctions widened to allow invasion of bacteria to the underlying fibroblast layer in lower numbers than in absence of keratinocytes. The challenge of this bacterial invasion to the fibroblast layer on the TiO₂ surface negatively affected tissue integration of the surface, demonstrating the protective barrier role of keratinocytes. Streptococci caused less damage to fibroblasts than staphylococci. Importantly, the protection offered by the soft-tissue seal appeared sensitive to surface properties of the implant material. Integration by fibroblasts of a hydrophobic silicone rubber surface was affected more upon bacterial challenges than integration of more hydrophilic hydroxyapatite or TiO₂ surfaces. This differential response to different surface-chemistries makes the 3D-tissue infection model presented a useful tool in the development of new infection-resistant dental implant materials. STATEMENT OF SIGNIFICANCE: Failure rates of dental implants due to infection are surprisingly low, considering their functioning in the highly un-sterile oral cavity. This is attributed to the soft-tissue seal, protecting the osseo-integrated implant part against bacterial invasion. The seal consists of a layer of keratinocytes covering gingival fibroblasts, integrating the implant. Implant failure involves high patient discomfort and costs of replacing an infected implant, which necessitates development of improved, infection-resistant dental implant materials. New materials are often evaluated in mono-culture, examining bacterial adhesion or tissue interactions separately and neglecting the 3D-structure of the tissue seal. A 3D-tissue model allows to study new materials in a more relevant way, in which interactions between keratinocytes, gingival fibroblast, bacteria and materials surfaces are accounted for.

[STRESS AS A PREDICTOR OF PERI-IMPLANTITIS DEVELOPMENT (REWIEV)]

In the era of modern technology is becoming increasingly popular implantation. This method is one of the leading methods in prosthetics of dental patients. Implantation solves a number of problems both aesthetic and functional. However, the percentage of complications, such as peri-implantitis and mucositis, leading to a violation of the chewing function of the dentition, is steadily increasing. To date, the etiology and pathogenesis of post-implantation complications have not been definitively clarified. One of the leading predictors is psychoemotional stress. On the basis of the literature analysis method to study stress, its impact on the development of periimplantitis, is laser Doppler flowmetry, allows you to quickly assess the state of microcirculation of the oral cavity at the stage of diagnosis, prior to the commencement of pharmacotherapy and in the dynamics of treatment and to adjust treatment regimen to prevent postoperative complications. The obtained LDF-grams allow to reflect the state of the regulatory systems of the body, and therefore it is possible to use LDF for the diagnosis of psychological stress.

Antimicrobial efficacy of copper-doped titanium surfaces for dental implants

The aim of this in vitro study was to quantify the antibacterial effect of a copper-deposited titanium surface as a model for dental implants on the peri-implantitis-associated strain Porphyromonas gingivalis (DSM 20709). A spark-assisted anodization method in a combined deposition-anodization process was applied to deposit copper on discs made of titanium. This method allows the deposition of different concentrations of copper on the surface by varying the process time. Conventional culturing was used to investigate the adhesion of P. gingivalis onto the discs over 2, 4, and 6 h as well as to study the antibacterial effect of copper released in solution. The viability of the bacterial cells is strongly inhibited on copper-deposited discs and reaches a CFU reduction of 3 log-units after 6 h in comparison to the reference. The copper released in solution causes a reduction of 4 log-units after a 6 h incubation time. With a 6 h incubation time, the CFU count decreases with increasing copper concentrations on the disc (by 2% for the 1.3 µg/disc; 32% for the 5.6 µg/disc; and 34% for the 9.5 µg/disc). However, at a higher copper concentration of 17.7 µg/disc, after 6 h, the decrease in the CFU count is less pronounced than that observed in solution, where a further decrease is observed. In conclusion, copper-functionalized titanium significantly reduces the survival of adhered bacteria and decreases the viable bacterial count in the environment surrounding the titanium. Thus, the area surrounding implants is being protected by copper released from the surface, forming a "safe zone" for improved implant healing.

The role of implant-abutment connection in preventing bacterial leakage: a review

Osseointegration can be affected by oral conditions; in particular, the micro gap at the implantabutment-connection (IAC) represents a site for dental plaque aggregation favoring bacterial leakage that can increase inflammatory cells at the level of the IAC, causing peri-implantitis. This micro gap, once early colonized, may constitute a bacterial reservoir that could subsequently contaminate fixture's surroundings and interfere with peri-implant tissues health. The aim of this review is to describe, according to the most recent literature, the different kind of implant-abutment connection and their ability to reduce bacterial leakage and thus preventing peri-implantitis. The following database were consulted: Pubmed (n=26), Scopus (n=90), Research gate (n=7) and 123 articles were found. Duplicates were excluded and after reading abstract and titles, those articles that were off topic were also excluded. The remaining ones (n=24) were assessed for full-text eligibility. We excluded 5 articles because they were case reports, 2 because there was no clear reference to the relationship between IAC and bacterial leakage and 2 because they were not pertinent to the argument. Fifteen articles were included in the review. From the review, it is clear that a relationship between the IAC and bacterial leakage exists. All the connections presented an amount of micro-gap and bacterial micro-leakage but conical and mixed connection systems seem to behave better. Moreover, both connections seem to have a better load distribution and the mixed one has anti-rotational properties, very useful during the positioning of the prosthesis.

Efficacy of a new chemical device to minimize microbial contamination along implant-abutment connection: an in vitro study

Osseointegrated dental implants showed elevated success rates on the long-term treatment in the last ten years. However, the risk of peri-implantitis and implant failure is the main complication of implantology. The presence of a micro gap at the implant-abutment connection (IAC) allows microorganisms to penetrate and colonize the inner part of the implant leading to biofilm accumulation and consequently to peri-implantitis development. Some chemical devices (CD) has been studied to reduce bacterial penetration at IAC level but no one have been demonstrated to be effective for this purpose. Aim of the present study is to evaluate the effectiveness of a new chemical formulation STCX-1, placed in the internal part of dental implants for killing bacteria present in the IAC. To identify the antibacterial power of SXTC-1 at interface between implant-abutment connection, the passage of genetically modified Escherichia coli across IAC was evaluated. A total of eight implants were used (Edierre Implant System, Edierre SpA, Genova, Italy). The inner side of four out of the eight implants were firstly contaminated with few microliters of pure bacteria, subsequently were treated with SXTC-1 for few second and finally, the antibacterial was replaced with Lysogeny Broth (LB) and antibiotics without bacteria. The remaining four implants were not treated with SXTC-1 and just filled with LB with antibiotics. Bacteria viability was determined by measuring their Optical Density (OD) at 600nm. The analysis revealed that, in untreated implants, bacteria grew (internally and externally) for the first 48 hours, but subsequently they started to dye. In treated implants, instead, bacteria grew just in the space surrounding the device suggesting that, even if bacteria were able to get into, they immediately died thanks to the presence of SXTC-1. The STCX-1 liquid formulation have been demonstrated to be an adjuvant CD effective for prevention of of bacterial colonization at IAC level.

Which Parameters Affect Biofilm Removal with Acoustic Cavitation? A Review

Bacterial biofilms are a cause of contamination in a wide range of medical and biological areas. Ultrasound is a mechanical energy that can remove these biofilms using cavitation and acoustic streaming, which generate shear forces to disrupt biofilm from a surface. The aim of this narrative review is to investigate the literature on the mechanical removal of biofilm using acoustic cavitation to identify the different operating parameters affecting its removal using this method. The properties of the liquid and the properties of the ultrasound have a large impact on the type of cavitation generated. These include gas content, temperature, surface tension, frequency of ultrasound and acoustic pressure. For many of these parameters, more research is required to understand their mechanisms in the area of ultrasonic biofilm removal, and further research will help to optimise this method for effective removal of biofilms from different surfaces.

Biology of teeth and implants: Host factors - pathology, regeneration, and the role of stem cells

In chronic periodontitis and peri-implantitis, cells of the innate and adaptive immune systems are involved directly in the lesions within the tissues of the patient. Absence of a periodontal ligament around implants does not prevent a biologic process similar to that of periodontitis from affecting osseointegration. Our first focus is on factors in the biology of individuals that are responsible for the susceptibility of such individuals to chronic periodontitis and to peri-implantitis. Genetic factors are of significant importance in susceptibility to these diseases. Genetic factors of the host affect the composition of the oral microbiome in the same manner that they influence other microbiomes, such as those of the intestines and of the lungs. Our second focus is on the central role of stem cells in tissue regeneration, in the functioning of innate and adaptive immune systems, and in metabolism of bone. Epithelial cell rests of Malassez (ERM) are stem cells of epithelial origin that maintain the periodontal ligament as well as the cementum and alveolar bone associated with the ligament. The tissue niche within which ERM are found extends into the supracrestal areas of collagen fiber-containing tissues of the gingivae above the bony alveolar crest. Maintenance and regeneration of all periodontal tissues involves the activity of a variety of stem cells. The success of dental implants indicates that important groups of stem cells in the periodontium are active to enable that biologic success. Successful replantation of avulsed teeth and auto-transplantation of teeth is comparable to placing dental implants, and so must also involve periodontal stem cells. Biology of teeth and biology of implants represents the biology of the various stem cells that inhabit specialized niches within the periodontal tissues. Diverse biologic processes must function together successfully to maintain periodontal health. Osseointegration of dental implants does not involve formation of cementum or collagen fibers inserted into cementum - indicating that some stem cells are not active around dental implants or their niches are not available. Investigation of these similarities and differences between teeth and implants will help to develop a better understanding of the biology and physiologic functioning of the periodontium.

Relevance of Topographic Parameters on the Adhesion and Proliferation of Human Gingival Fibroblasts and Oral Bacterial Strains

Dental implantology allows replacement of failing teeth providing the patient with a general improvement of health. Unfortunately not all reconstructions succeed, as a consequence of the development of infections of bacterial origin on the implant surface. Surface topography is known to modulate a differential response to bacterial and mammalian cells but topographical measurements are often limited to vertical parameters. In this work we have extended the topographical measurements also to lateral and hybrid parameters of the five most representative implant and prosthetic component surfaces and correlated the results with bacterial and mammalian cell adhesion and proliferation outcomes. Primary human oral gingival fibroblast (gum cells) and the bacterial strains: Streptococcus mutans, Streptococcus sanguinis and Aggregatibacter actinomycetemcomitans, implicated in infectious processes in the oral/implant environment were employed in the presence or absence of human saliva. The results confirm that even though not all the measured surface is available for bacteria to adhere, the overall race for the surface between cells and bacteria is more favourable to the smoother surfaces (nitrided, as machined or lightly acid etched) than to the rougher ones (strong acid etched or sandblasted/acid etched).

Micro-Raman Spectroscopy Reveals the Presence of Octacalcium Phosphate and Whitlockite in Association with Bacteria-Free Zones Within the Mineralized Dental Biofilm

Through a correlative analytical approach encompassing backscattered electron scanning electron microscopy (BSE-SEM), energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy, the composition of the mineralized biofilm around a dental implant, retrieved due to peri-implantitis, was investigated. The mineralized biofilm contains two morphologically distinct regions: (i) bacteria-containing zones (Bact+), characterized by aggregations of unmineralized and mineralized bacteria, and intermicrobial mineralization, and (ii) bacteria-free zones (Bact-), comprised mainly of randomly oriented mineral platelets. Intramicrobial mineralization, within Bact+, appears as smooth, solid mineral deposits resembling the morphologies of dental plaque bacteria. Bact- is associated with micrometer-sized Mg-rich mineral nodules. The Ca/P ratio of Bact+ is higher than Bact-. The inorganic phase of Bact+ is carbonated apatite (CHAp), while that of Bact- is predominantly octacalcium phosphate (OCP) and whitlockite (WL) inclusions. Compared with native bone, the inorganic phase of Bact+ (i.e., CHAp) exhibits higher mineral crystallinity, lower carbonate content, and lower Ca/P, C/Ca, Mg/Ca, and Mg/P ratios. The various CaPs found within the mineralized dental biofilm (CHAp, OCP, and WL) are related to the local presence/absence of bacteria. In combination with BSE-SEM and EDX, micro-Raman spectroscopy is a valuable analytical tool for nondestructive investigation of mineralized dental biofilm composition and development.

Effect of Bioactivation on Traditional Surfaces and Zirconium Nitride: Adhesion and Proliferation of Preosteoblastic Cells and Bacteria

PURPOSE

The aim of this vitro study was to reproduce and evaluate the response of bone and bacteria to traditional and innovative implant surfaces with difference wettability.

MATERIALS AND METHODS

Two hundred fifty-two samples made of grade 4 titanium with different coating (machined [MAC]; double-etched, Ti-AE; zirconium nitride [Ti-ZrN]) were used for this in vitro study. Disks were divided into test (bioactivated using plasma of argon) and control group (untreated). To assess the surface morphology of the specimens, representative images were acquired via scanning electron microscopy (SEM). Murine preosteoblasts (MC3T3-E1) were used to study the biologic response in vitro, while the quantification of protein adsorption was achieved through the incubation of the titanium samples in a 2% solution of fetal bovine serum (FBS) in phosphate-buffered saline (PBS). The sterilized titanium disks were then colonized by bacterial species from a single sputum sample obtained from a healthy volunteer. For every analysis, 24 disks were used (12 for each group).

RESULTS

SEM and topographic analyses demonstrated a Sa value of 0.33 (Ti-ZrN), 0.34 (MAC), and 0.62 (Ti-AE). Compared with the control groups, plasma treatment significantly increased the protein adsorption level on all the different titanium surfaces (5.88 ± 0.21 vs 7.85 ± 0.21, 7.13 ± 0.14 vs 9.74 ± 0.65, 4.41 ± 0.62 vs 6.13 ± 0.52, respectively, for MAC, Ti-treated, and Ti-ZrN). Similar behavior was described for cell adhesion (27.67 ± 2.03 vs 58.00 ± 20.13, 116.67 ± 12.02 vs 159.33 ± 8.09, 52.00 ± 4.73 vs 78.33 ± 4.67, respectively, for MAC, Ti-treated, and Ti-ZrN). Plasma treatment significantly augmented the number of CFU only in MAC and ZrN samples.

CONCLUSION

With the limitations of this in vitro study, the following conclusions could be drawn: (1) rough implant surfaces present a higher adhesion and proliferation of preosteoblastic cells and bacterial biofilm; (2) rough implant surfaces benefited the most by the plasma of argon treatment.

In vitro evaluation of a multispecies oral biofilm over antibacterial coated titanium surfaces

Peri-implantitis is an infectious disease that affects the supporting soft and hard tissues around dental implants and its prevalence is increasing considerably. The development of antibacterial strategies, such as titanium antibacterial-coated surfaces, may be a promising strategy to prevent the onset and progression of peri-implantitis. The aim of this study was to quantify the biofilm adhesion and bacterial cell viability over titanium disc with or without antibacterial surface treatment. Five bacterial strains were used to develop a multispecies oral biofilm. The selected species represent initial (Streptococcus oralis and Actinomyces viscosus), early (Veillonella parvula), secondary (Fusobacterium nucleatum) and late (Porphyromonas gingivalis) colonizers. Bacteria were sequentially inoculated over seven different types of titanium surfaces, combining different roughness level and antibacterial coatings: silver nanoparticles and TESPSA silanization. Biofilm formation, cellular viability and bacterial quantification over each surface were analyzed using scanning electron microscopy, confocal microscopy and real time PCR. Biofilm formation over titanium surfaces with different bacterial morphologies could be observed. TESPSA was able to significantly reduce the cellular viability when compared to all the surfaces (p < 0.05). Silver deposition on titanium surface did not show improved results in terms of biofilm adhesion and cellular viability when compared to its corresponding non-coated surface. The total amount of bacterial biofilm did not significantly differ between groups (p > 0.05). TESPSA was able to reduce biofilm adhesion and cellular viability. However, silver deposition on titanium surface seemed not to confer these antibacterial properties.

Peptide coatings enhance keratinocyte attachment towards improving the peri-implant mucosal seal

There is a critical need for preventing peri-implantitis as its prevalence has increased and dental implants lack features to prevent it. Research strategies to prevent peri-implantitis have focused on modifying dental implants to incorporate different antimicrobial agents. An alternative strategy consists of barring the expansion of the biofilm subgingivally by forming a long-lasting permucosal seal between the soft tissue and the implant surface. Here, we innovatively biofunctionalized titanium with bioinspired peptide coatings to strengthen biological interactions between epithelial cells and the titanium surface. We selected laminin 332- and ameloblastin-derived peptides (Lam, Ambn). Laminin 332 participates in the formation of hemidesmosomes by keratinocytes and promotes epithelial attachment around teeth; and ameloblastin, an enamel derived protein, is involved in tissue regeneration events following disruption of the periodontium. Lam, Ambn or combinations of both peptides were covalently immobilized on titanium discs. Successful immobilization of the peptides was confirmed by contact angle goniometry, X-ray photoelectron spectroscopy and fluorescent labelling of the peptides. Additionally, we confirmed the mechanical and thermochemical stability of the peptides on Ti substrates. Proliferation and hemidesmosome formation of human keratinocytes (TERT-2/OKF-6) were assessed by immunofluorescence labelling. The peptide-coated surfaces increased cell proliferation for up to 48 h in culture compared to control surfaces. Most importantly, formation of hemidesmosomes by keratinocytes was significantly increased on surfaces coated with Ambn + Lam peptides compared to control (p < 0.01) and monopeptide coatings (p < 0.005). Together, these results support the Ambn + Lam multipeptide coating as a promising candidate for inducing a permucosal seal around dental implants.

Plasma of Argon Increases Cell Attachment and Bacterial Decontamination on Different Implant Surfaces

PURPOSE

This in vitro study tested the effects of argon atmospheric pressure dielectric barrier discharge (APDBD) on different implant surfaces with regard to physical changes, bacterial decontamination, and osteoblast adhesion.

MATERIALS AND METHODS

Seven hundred twenty disks with three different surface topographies-machined (MAC), titanium plasma-sprayed (TPS), and zirconia-blasted and acid-etched (ZRT)-were tested in this experiment. Bacterial adhesion tests were performed repeatedly on a simplified biofilm of Streptococcus mitis. Bacteria were incubated in the presence of the samples, which were subsequently either left untreated as controls or treated with APDBD for 30, 60, and 120 seconds. Samples were then metalized, prior to the recurring acquisition of images using a scanning electronic microscope (SEM). Protein adsorption, surface wettability, and early biologic response were determined for both treated (120 seconds) and untreated implant surfaces. For depicting the eukaryotic cell behavior, preosteoblastic murine cells were used. Cells were conveniently stained, and nuclei were counted. Cell viability was assessed by a chemiluminescent assay at 1, 2, and 3 days.

RESULTS

On all treated samples, values of the contact angle measurements were lower than 10 degrees. The untreated samples showed values of contact angle of 80, 100, and 110 degrees, respectively, for MAC, TPS, and ZRT. The protein adsorption on TPS and ZRT was significantly increased after the plasma of argon treatment. However, no significant effect was noted on the MAC disks. The number and the cell spreading area of adherent osteoblasts significantly increased in all treated surfaces. Nonetheless, argon treatment did not influence the osteoblast proliferation and viability at different time points. Bacteria adhesion was significantly reduced, even after 60 seconds of argon treatment.

CONCLUSION

Preliminary data showed that argon atmospheric pressure dielectric barrier discharge disinfected the implant surface, with potential to promote osteoblast attachment and spreading, suggesting this may be a possible approach to clean a peri-implantitis-contaminated implant surface.

Association Between Clinical and Microbiologic Cluster Profiles and Peri-implantitis

PURPOSE

The correlation between associated local factors and peri-implantitis remains unknown. The aim of this study was to investigate the association between the clinical and microbiologic profiles and peri-implantitis to eventually categorize different groups of this disease.

MATERIALS AND METHODS

Subjects with at least one implant presenting signs of peri-implantitis were selected. The clinical, radiographic, occlusal, and microbiologic profiles of these infected implants were collected. Cases were classified into five peri-implantitis groups according to potential disease-triggering factors: surgically, prosthetically, biomechanically, purely plaque-associated, and a combination of them. Generalized estimating equations models were used to study differences among the potential risk factors. Cluster analyses were applied to investigate the correlation between clinical and microbiologic profiles and diseased implant samples.

RESULTS

Overall, 110 diseased and 121 healthy implants were included. The biomechanically associated group showed higher levels of microbiologic contamination inside the connection; however, the plaque-associated group had a higher level of microbial variety in the peri-implant sulcus. Cluster analyses demonstrated a significant ability to predict the associated factor of peri-implantitis. Moreover, radiographic marginal bone loss and implant width demonstrated the largest influence on the model.

CONCLUSION

While peri-implantitis represents a plaque-induced inflammatory condition, certain local factors might be associated with this biologic complication, as they imply plaque retention. Therefore, disease classification could be further implemented with the associated surgical, prosthetic, and biomechanical factors to better target the etiology.

Biofilms Developed on Dental Implant Titanium Surfaces with Different Roughness: Comparison Between In Vitro and In Vivo Studies

Microbial biofilms developed on dental implants play a major role in perimplantitis' pathogenesis. Many studies have indicated that surface roughness is the main feature favoring biofilm development in vitro, but its actual influence in vivo has still to be confirmed. In this study, the amount of biofilm formed on differently treated titanium surfaces, showing distinct roughness, has been examined both in vivo and in vitro by Confocal Laser Scanning Microscopy. In vitro studies availed of biofilm developed by Pseudomonas aeruginosa or by salivary bacteria from volunteer donors. In vivo biofilm production was obtained by exposing titanium discs to the oral cavity of healthy volunteers. In vitro experiments showed that P. aeruginosa and, to a lesser extent, salivary bacteria produce more biomass and develop thicker biofilms on laser-treated and sandblasted titanium surfaces with respect to machined ones. In vivo experiments confirmed that bacterial colonization starts on sites of surface unevenness, but failed to disclose biomass differences among biofilms formed on surfaces with different roughness. Our study revealed that biofilm developed in vitro is more easily influenced by surface features than biofilm formed by complex communities in the mouth, where the cooperation of a variety of bacterial species and the presence of a wide range of nutrients and conditions allow bacteria to optimize substrate colonization. Therefore, quantitative differences observed in vitro among surfaces with different characteristics may not be predictive of different colonization rates in vivo.

Antimicrobial efficacy of photodynamic therapy and light-activated disinfection on contaminated zirconia implants: An in vitro study

BACKGROUND

We aimed to evaluate the antimicrobial efficacy of photodynamic therapy (PDT) and light-activated disinfection (LAD) on zirconia dental implants contaminated with three bacterial species and investigate if the PDT and LAD cause implant surface alterations.

METHODS

Seventy-two zirconia dental implants were contaminated with a bacterial suspension of Prevotella intermedia, Actinomyces actinomycetemcomitans, and Porphyromonas gingivalis. The implants were subsequently randomly divided into four groups (n = 12 dental implants/each) according to the decontamination protocol: Group 1 (PDT1) - PDT (660 nm, 100 mW) with toluidine blue; Group 2 (PDT2) - PDT (660 nm, 100 mW) with phenothiazine chloride dye; Group 3 (LAD) - light emitting diode (LED) with toluidine blue; and Group 4 (TB) - toluidine blue without the application of light. Implants in the positive control (PC) group were treated with a 0.2% chlorhexidine-based solution, and implants assigned to the negative control (NC) group did not undergo any treatment. Each implant was then placed in tubes containing phosphate buffered saline (PBS) and vortexed for 60 s to remove the remaining bacteria from the implant surface. After 10-fold serial dilutions, 30 μl of the suspension was plated on Brucella agar plates. After 72 h, the colony forming units (CFU) were counted. Distinctive colonies were confirmed with MALDI Biotyper. The implants were analyzed using scanning electron microscope (SEM) to evaluate the possible surface alterations due to PDT or LAD.

RESULTS

All study groups had significant reductions in the number of CFUs compared with the NC (p < 0.05). PDT1, the PDT2, and the LAD groups had the largest bacterial reduction with respect to each bacterial species separately and the total bacterial count, and they were more efficient compared with the TB group (p < 0.05). SEM analysis did not reveal any alterations of the implant surface after the treatment procedures.

CONCLUSION

Both PDT protocols and LAD showed high and equal effectiveness in decontamination of zirconia dental implants.