Hard and soft tissue changes around implants activated using plasma of argon: A histomorphometric study in dog

Allylamine coating on zirconia dental implant surface promotes osteogenic differentiation in vitro and accelerates osseointegration in vivo

OBJECTIVES

The glow discharge plasma (GDP) procedure has proven efficacy in grafting allylamine onto zirconia dental implant surfaces to enhance osseointegration. This study explored the enhancement of zirconia dental implant properties using GDP at different energy settings (25, 50, 75, 100, and 200 W) both in vitro and in vivo.

MATERIALS AND METHODS

In vitro analyses included scanning electron microscopy, wettability assessment, energy-dispersive X-ray spectroscopy, and more. In vivo experiments involved implanting zirconia dental implants into rabbit femurs and later evaluation through impact stability test, micro-CT, and histomorphometric measurements.

RESULTS

The results demonstrated that 25 and 50 W GDP allylamine grafting positively impacted MG-63 cell proliferation and increased alkaline phosphatase activity. Gene expression analysis revealed upregulation of OCN, OPG, and COL-I. Both 25 and 50 W GDP allylamine grafting significantly improved zirconia's surface properties (p < .05, p < .01, p < .001). However, only 25 W allylamine grafting with optimal energy settings promoted in vivo osseointegration and new bone formation while preventing bone level loss around the dental implant (p < .05, p < .01, p < .001).

CONCLUSIONS

This study presents a promising method for enhancing Zr dental implant surface's bioactivity.

Plasma of Argon Treatment of the Implant Surface, Systematic Review of In Vitro Studies

This paper aims to review the evidence of the cellular activity on titanium samples exposed to Plasma of Argon (PoA) treatment. A systematic review was carried out based on the PRISMA statement by searching the Cochrane Library, PubMed, Web of Science, EMBASE and Scopus, up to October 2020. Papers were selected according to PICOS format that is: Population (P): osteoblasts, fibroblasts, gingival cells; Intervention (I): PoA disinfection treatment; Comparison (C): untreated controls; Outcome (O): cell culture; Setting (S): in vitro assays. The quality assessment was performed according to the CRIS Guidelines (Checklist for Reporting In vitro Studies). A total of 661 articles were found, of which 16 were included. The quality assessment revealed an overall poor quality of the studies analyzed. In vitro studies on the potential of PoA showed a potential effect in promoting higher cell adhesion and protein adsorption in the earliest times (hours). This outcome was not so evident when later stages of cell growth on the surfaces were tested and compared to the control groups. Only one study was conducted in vivo on a human sample regarding abutment cleaning. No meta-analysis was conducted because of the variety of experimental settings, mixed methods and different cell lines studied. PoA seems to be effective in promoting cell adhesion and protein adsorption. The duration of this effect remains unclear. Further evidence is required to demonstrate the long-term efficacy of the treatment and to support the use of PoA treatment in clinical practice.

Clinical and Histological Healing after Maxillary Sinus Floor Elevation

Sinus floor elevation is a surgical procedure that allows for the insertion of the implant in the posterior region of the maxilla in case of insufficient volume of native bone. Several studies have reported a high success rate, and this has helped to spread this surgical procedure around the world. The subject has been extensively studied and this could lead researchers to think that no new scientific evidence can be provided. However, new ideas and discoveries show that research never reaches a conclusion, and that new information can be added all the time. This collection aimed to provide new evidence that could be added to daily clinical work and to provide new ideas for future research.

Influence of cold atmospheric plasma on dental implant materials - an in vitro analysis

Background and objectives

Alterations in the microenvironment of implant surfaces could influence the cellular crosstalk and adhesion patterns of dental implant materials. Cold plasma has been described to have an influence on cells, tissues, and biomaterials. Hence, the mechanisms of osseointegration may be altered by non-thermal plasma treatment depending on different chemical compositions and surface coatings of the biomaterial. The aim of the present study is to investigate the influence of cold atmospheric plasma (CAP) treatment on implant surfaces and its biological and physicochemical side effects.

Materials and methods

Dental implant discs from titanium and zirconia with different surface modifications were treated with CAP at various durations. Cell behavior and adhesion patterns of human gingival fibroblast (HGF-1) and osteoblast-like cells (MG-63) were examined using scanning electron microscopy and fluorescence microscopy. Surface chemical characterization was analyzed using energy-dispersive X-ray spectroscopy (EDS). Quantitative analysis of cell adhesion, proliferation, and extracellular matrix formation was conducted including real-time PCR.

Results

CAP did not affect the elemental composition of different dental implant materials. Additionally, markers for cell proliferation, extracellular matrix formation, and cell adhesion were differently regulated depending on the application time of CAP treatment in MG-63 cells and gingival fibroblasts.

Conclusions

CAP application is beneficial for dental implant materials to allow for faster proliferation and adhesion of cells from the surrounding tissue on both titanium and zirconia implant surfaces with different surface properties.

Clinical relevance

The healing capacity provided through CAP treatment could enhance osseointegration of dental implants and has the potential to serve as an effective treatment option in periimplantitis therapy.

Pre-Clinical Models in Implant Dentistry: Past, Present, Future

Biomedical research seeks to generate experimental results for translation to clinical settings. In order to improve the transition from bench to bedside, researchers must draw justifiable conclusions based on data from an appropriate model. Animal testing, as a prerequisite to human clinical exposure, is performed in a range of species, from laboratory mice to larger animals (such as dogs or non-human primates). Minipigs appear to be the animal of choice for studying bone surgery around intraoral dental implants. Dog models, well-known in the field of dental implant research, tend now to be used for studies conducted under compromised oral conditions (biofilm). Regarding small animal models, research studies mostly use rodents, with interest in rabbit models declining. Mouse models remain a reference for genetic studies. On the other hand, over the last decade, scientific advances and government guidelines have led to the replacement, reduction, and refinement of the use of all animal models in dental implant research. In new development strategies, some in vivo experiments are being progressively replaced by in vitro or biomaterial approaches. In this review, we summarize the key information on the animal models currently available for dental implant research and highlight (i) the pros and cons of each type, (ii) new levels of decisional procedures regarding study objectives, and (iii) the outlook for animal research, discussing possible non-animal options.

Argon Bioactivation of Implants Installed Simultaneously to Maxillary Sinus Lifting without Graft. An Experimental Study in Rabbits

Background: The treatment of the surface of titanium implants with argon plasma improved its hydrophilicity and cell adhesion, resulting in higher bone apposition on implant and graft surfaces. The spontaneous perforation over time of the sinus mucosa after sinus augmentation has been documented in experimental studies at both implants and graft particles. The aim of the present study was to evaluate the influence of plasma argon treatment of the implant surface on bone apposition and on the rate of sinus mucosa perforations. Methods: A sinus lifting procedure was performed bilaterally in sixteen rabbits, and implants, either treated with argon plasma or left without treatment (control), were placed simultaneously without grafts. After 8 weeks, histological analyses were carried out. Results: A collapse of the sinus mucosa was observed at all implants. Twenty-four out of thirty-two implants presented sinus mucosa perforations at the apex. Several perforations were also found at the threads. Thinned mucosa sites (width < 40 µm) were found around almost all implants. About 2.6–2.9 mm of the apical regions of the implant did not present signs of osseointegration and about 1.3 mm were exposed to the sinus cavity. No statistically significant differences were found between plasma and control sites. Conclusions: In conclusion, the sinus mucosa was damaged and perforated by direct contact with treated and non-treated implant surfaces. The treatment of the implant surface with argon plasma did not affect the outcomes.

Microscopic Characterization of Bioactivate Implant Surfaces: Increasing Wettability Using Salts and Dry Technology

The surface topography of dental implants plays an important role in cell-surface interaction promoting cell adhesion, proliferation and differentiation influencing osseointegration. A hydrophilic implant leads to the absorption of water molecules and subsequently promotes the adhesion of cells to the implant binding protein. Dried salts on the implant surfaces allow one to store the implant surfaces in a dry environment while preserving their hydrophilic characteristics. This process has been identified as “dry technology”. The aim of the present study is to describe from a micrometric and nanometric point of view the characteristics of this new bioactivated surface obtained using salts dried on the surface. Topographic analysis, energy-dispersive X-ray spectroscopy, and contact angle characterization were performed on the samples of a sandblasted and dual acid-etched surface (ABT), a nanosurface (Nano) deriving from the former but with the adding of salts air dried and a nanosurface with salts dissolved with distilled water (Nano H₂O). The analysis revealed promising results for nanostructured surfaces with increased wettability and a more articulated surface nanotopography than the traditional ABT surface. In conclusion, this study validates a new promising ultra-hydrophilic nano surface obtained by sandblasting, double acid etching and surface salt deposition using dry technology.

Mechanical properties and biocompatibility of titanium with a high oxygen concentration for dental implants

In order to improve the strength of commercially pure Ti (CP-Ti) for oral implants, the high oxygen content Ti (HOC-Ti) was prepared via powder metallurgy. Its composition and mechanical properties were then characterized. After surface treatment by sandblasting and acid etching (SLA), the surface morphology, wettability and roughness of the HOC-Ti and CP-Ti sample were examined. In an in vitro test that followed an evaluation of the protein adsorption capacity of HOC-Ti, the mouse preosteoblast cells were inoculated onto the specimens to evaluate their biocompatibility, in comparison with those of CP-Ti. The oxygen concentration of the HOC-Ti increased to 0.62 wt%, which is higher than the 0.26 wt% of the CP-Ti, while their compositions and microstructures were very similar. The tensile and compressive yield strength of the HOC-Ti (800 MPa) was improved significantly in comparison to that of the CP-Ti (530 MPa). After surface treatment, a unique structure of micropores with a diameter of 380 nm was observed on the entire surface of the HOC-Ti that facilitates cell adhesion and proliferation. The wettability of the HOC-Ti was obviously superior (p < 0.05). The in vitro study showed that the MC3T3-E1 cells inoculated on the surface of HOC-Ti exhibited a homogeneous microstructure, and the viability was higher than that of the control group on days 4 and 7 (p < 0.05). In addition, the number and differentiation activity of cells that adhered to the surface of the HOC-Ti increased significantly on day 7 (p < 0.05). The experimental results showed that, in view of its mechanical properties and biocompatibility, HOC-Ti is superior to CP-Ti and is promising for oral implant applications.

Photo and Plasma Activation of Dental Implant Titanium Surfaces. A Systematic Review with Meta-Analysis of Pre-Clinical Studies

Background: Ultraviolet (UV) and non-thermal plasma functionalization are surface treatment modalities that seem able to improve osseointegration. The aim of this systematic review and meta-analysis is to assess the effect of the two methods and possible differences. Materials and Methods: The systematic research of pre-clinical animal studies was conducted up to May 2020 in the databases PubMed/Medline, Scopus and the Cochrane Lybrary. A meta-analysis was performed by using the DerSimonian–Laird estimator in random-effects models. Results: Through the digital search, 518 articles were identified; after duplicate removal and screening process 10 papers were included. Four studies evaluating UV treatment in rabbits were included in the meta-analysis. The qualitative evaluation of the included studies showed that both UV photofunctionalization and non-thermal plasma argon functionalization of titanium implant surfaces might be effective in vivo to improve the osseointegration. The meta-analysis on four studies evaluating UV treatment in rabbits showed that bone to implant contact values (expressed as standardized mean differences and raw mean differences) were significantly increased in the bio-activated groups when follow-up times were relatively homogeneous, although a high heterogeneity (I² > 75%) was found in all models. Conclusions: The present systematic review and meta-analysis on pre-clinical studies demonstrated that chair-side treatment of implants with UV or non-thermal plasma appear to be effective for improving osseointegration. This systematic review supports further clinical trials on this topic.

New bone ingrowth into β-TCP/HA graft activated with argon plasma: a histomorphometric study on sinus lifting in rabbits

BACKGROUND

In a previous experimental study, new bone was found growing within granules of HA/β-TCP. In vitro and experimental studies have shown increased protein adsorption and cell adhesion graft material bioactivated with Argon plasma. The aims of the present experiment were to study new bone ingrowth into β-TCP/HA granules used as filler material for sinus lifting and the influence on the healing of the bioactivation of the graft with argon plasma.

METHODS

Sinus lifting was carried out in 20 rabbits using 60% HA and 40% β-TCP as filler material either bio-activated with argon plasma (plasma group) or left untreated (control group). The antrostomies were closed with collagen membranes. Biopsies representing the healing after 2 and 10 weeks were collected, and ground sections were prepared for histomorphometric analyses. Various regions of the elevated space were analyzed both around (outer bone; OB) and inside (interpenetrating bone network, IBN) the graft particles.

RESULTS

After 2 weeks of healing, 8.2% and 9.3% (n = 10; p = 0.635) of total new bone (OB + IBN) was found in the plasma and control groups, respectively. Small fractions of IBN were found, spreading from the periphery inward of the graft particles. After 10 weeks of healing, the total new bone was 34.0% in the plasma and 31.3% in Control groups (n = 9; p = 0.594). The respective fractions of IBN were 18.0% and 16.0%. New bone was penetrating from the peripheral regions inside the remnants of graft particles, where it was forming a network of bridges in continuity to the remnants of biomaterial through its porosities. The biomaterial decreased in proportion between 2 and 10 weeks from 52.1 to 28.3% in the plasma group, and from 52.5% to 31.9% in the control group.

CONCLUSION

The bio-activation with argon plasma on a synthetic graft composed of 60% HA and 40% β-TCP used as filler material for sinus lifting showed a tendency to improve bone formation; however, the difference with the control group was neither statistically significant nor clinically relevant.

The Emerging Role of Cold Atmospheric Plasma in Implantology: A Review of the Literature

In recent years, cold atmospheric plasma (CAP) technologies have received increasing attention in the field of biomedical applications. The aim of this article is to review the currently available literature to provide an overview of the scientific principles of CAP application, its features, functions, and its applications in systemic and oral diseases, with a specific focus on its potential in implantology. In this narrative review, PubMed, Medline, and Scopus databases were searched using key words like “cold atmospheric plasma”, “argon plasma”, “helium plasma”, “air plasma”, “dental implants”, “implantology”, “peri-implantitis”, “decontamination”. In vitro studies demonstrated CAP’s potential to enhance surface colonization and osteoblast activity and to accelerate mineralization, as well as to determine a clean surface with cell growth comparable to the sterile control on both titanium and zirconia surfaces. The effect of CAP on biofilm removal was revealed in comparative studies to the currently available decontamination modalities (laser, air abrasion, and chlorhexidine). The combination of mechanical treatments and CAP resulted in synergistic antimicrobial effects and surface improvement, indicating that it may play a central role in surface “rejuvenation” and offer a novel approach for the treatment of peri-implantitis. It is noteworthy that the CAP conditioning of implant surfaces leads to an improvement in osseointegration in in vivo animal studies. To the best of our knowledge, this is the first review of the literature providing a summary of the current state of the art of this emerging field in implantology and it could represent a point of reference for basic researchers and clinicians interested in approaching and testing new technologies.

Single-cell adhesion of human osteoblasts on plasma-conditioned titanium implant surfaces in vitro

OBJECTIVES

This study aimed to demonstrate the effect of treating titanium-implant surfaces with plasma from two different sources on wettability and initial single-cell adhesion of human osteoblasts and to investigate whether aging affects treatment outcomes.

METHODS

Titanium disks with sandblasted and acid-etched (SLA) surfaces were treated with atmospheric pressure plasma (APP) and low-pressure plasma (LPP). For wetting behavior of the specimens after plasma treatment, the water contact angle was measured. The single-cell detachment force and amount of work of detachment of human osteoblasts were determined with single-cell force spectroscopy (SCFS). To evaluate the aging effect in APP-treated specimens, SCFS was conducted 10 and 60 min after treatment.

RESULTS

Significantly higher hydrophilicity was observed in the APP and LPP treatment groups than in the control group, but no significant difference was observed between the APP and LPP groups. No significant difference in cell-detachment force or work of detachment was observed, and there were no significant differences according to the conditioning mechanisms and storage time.

SIGNIFICANCE

Conditioning of the titanium surfaces with APP or LPP was not a significant influencing factor in the initial adhesion of the osteoblasts.

Surface bio-functionalization using plasma of argon could alter microbiological and topographic surface analysis of dental implants?

BACKGROUND

Plasma of argon was demonstrated to improve protein and cell adhesion on implant surface. On the other hand, increased surface energy and hydrophilicity could potentially amplify the risks of implant surface contamination during clinical phases, risks that have not yet been evaluated in Literature. The aim of the present in vitro study was to verify if Plasma treatment could alter the implant surface characteristics and its ability to remain sterile.

MATERIALS AND METHODS

Implants from 9 brands were collected (n=11). One implant for each company was used for SEM surface analysis. To perform the microbiological analysis, ten implants from each company were used and randomly split by allocation either in test or control group. To replicate the surgical work flow, both test and control samples were left 60s in clinical environment. Bacterial growth analysis was performed. Optical density at 600nm was measured as readout of bacterial growth and colony forming unit (CFU) after 24h was evaluated. Statistical analysis was performed by using the Wilcoxon Mann Whitney test. A p-value lower than 0.05 was considered significant.

RESULTS

SEM analysis revealed different categories of implant surface roughness. The optical density confirmed a readout of bacterial growth between 4 and 7 with no significant differences within groups. The number of CFU/ml for each measured sample (test and control) was lower than 102 and failed to present significant differences.

CONCLUSION

Surface activation using plasma of argon did not affect the degree of implant contamination, allowing to maintain a substantial sterility of the implant independently of its morphology. This may allow in the next future the use of bioactivation through plasma of argon to exploit the superhydrophilicity deriving from this biophysical process.

Is maxillary diastema an appropriate site for implantation in rats?

Background

Implantology or implant dentistry is growing fast during last four decades. Facing the growing demand of implant treatment, there are extreme challenges to clinicians and researchers. First is peri-implantitis with remarkable prevalence. Though investigators have revealed that the etiology of the peri-implant infection is similar to periodontitis, clinically there is no effective treatment. Second, implantation in patients with severe systemic conditions, i.e., severe diabetes, lupus, osteoporosis, organ transplant, and cancer with intensive radiotherapy and/or chemotherapy, is another challenge to implant treatment for lack of scientific research data. Animal models are crucial to help investigators reveal the mechanisms underlying these disorders. Murine models are used most commonly. Rats are the better subject in dental implant research, due to mice could not provide clinical compatible and macro-level measurable data for implant osseointegration and peri-implantitis in oral cavity for lacking enough cancellous bone to support an implant more than 1 mm in length.

Objective

Our aim of this research is to find a clinical comparable rat dental implant model.

Methods

Six male Sprague-Dawley rats with body weight more than 500 g were used in the experiment. Each rat received two implants. One implant was placed at maxillary diastema in each side. Seven weeks after the implantation, only one implant successfully osseointegrated without movement and inflammation. Implant success and failure rate is analyzed by using Clopper-Pearson’s exact method at 95% confidence interval.

Results

The present data indicate that the true success rate of implantation in maxillary natural diastema in rat is less than 38.4% at a confident level of 95%. Meanwhile, Micro-CT indicates maxillary first molar position will be a promising site for implantation.

Conclusion

Maxillary nature diastema may not be an appropriate site for implantation research for its low successful rate, but maxillary first molar position could be a candidate for implantation research. Further researches are required to illustrate the details.

Effect of Plasma of Argon Treated Implants on Bone Density: A Randomized, Controlled, Histomorphometric Study in Dogs

Background:

Altering surface characteristics by increasing its energy and hydrophilicity will accelerate the interaction between cells and implant surface. Energy and hydrophilicity tend to disappear over a short time. The implant surface may be reactivated by the use of argon plasma

Objective:

To assess bone density at cleaned and activated titanium implants using argon plasma.

Methods:

Mandibular premolars and first molars were extracted bilaterally in eight Beagle dogs. After three months, four implants, two treated with argon plasma (test; plasma) and two left without treatment (control), were randomly installed in one side of the mandible. Abutments were applied on the implants and a non-submerged healing was allowed. After one month, the same surgical procedures were adopted on the opposite side of the mandible. The animals were euthanized after one month and ground sections representing the healing after 1 and 2 months were obtained for histological examination.

Results:

No statistically significant differences were found between test and control sites (p < 0.05). After 1 month of healing, new bone was 32.5 ± 12.2% and 33.8 ± 8.8% at the plasma and control sites, respectively. After 2 months, the respective values were 50.8 ± 21.5% and 47.6 ± 15.6%.

Conclusion:

The treatment of the implant surface with argon plasma did not have a significant effect on bone density around implants.