Application of cold atmospheric microwave plasma as an adjunct therapy for wound healing in dogs and cats

BACKGROUND

Cold atmospheric plasma is a novel innovative approach for wound care, and it is currently underrepresented in veterinary medicine.

OBJECTIVES

To investigate the efficacy and safety of using cold atmospheric microwave plasma (CAMP) as an adjunct therapy for wound healing in dogs and cats.

METHODS

Wound healing outcomes were retrospectively analyzed using clinical records of client-owned dogs and cats who were first managed through standard wound care alone (pre-CAMP period) and subsequently via CAMP therapy (CAMP period). The degree of wound healing was estimated based on wound size and a modified wound scoring system.

RESULTS

Of the 27 acute and chronic wounds included in the analysis, 81.48% showed complete healing after the administration of CAMP as an adjunct therapy to standard care. Most wounds achieved complete healing in < 5 weeks. Compared with the pre-CAMP period, the rate of wound healing significantly increased every week in the CAMP period in terms of in wound size (first week, p < 0.001; second week, p = 0.012; third week, p < 0.001) and wound score (first week, p < 0.001; second week, p < 0.001; third week, p = 0.001). No adverse events were noted except for mild discomfort and transient erythema.

CONCLUSIONS

CAMP is a well-tolerated therapeutic option with immense potential to support the treatment of wounds of diverse etiology in small animal practice. Further research is warranted to establish specific criteria for CAMP treatment according to wound characteristics.

Effect of argon cold plasma composition on orthodontic bonding-new insights into input parameters and protocols

PURPOSE

Cold atmospheric plasma can functionalize enamel without damaging the substrate morphology. It therefore has the potential to be a gentle alternative to conventional acid etching. To realize the full potential of cold atmospheric plasma in orthodontic bonding, the input parameters and protocols that are most beneficial to surface modification must first be identified. We aimed to clarify how the admixture of oxygen to cold atmospheric plasma and the rewetting of the enamel affect the conditioning properties for orthodontic bonding.

METHODS

First, we illustrated the morphological effects of different plasma compositions on the enamel surface by means of scanning electron microscopy. Then, we measured the shear bond strength resulting from different conditioning techniques on bovine enamel specimens: conventional acid etching; no conditioning; pure argon plasma; argon plasma plus 0.5% oxygen admixture; argon plasma plus 0.5% oxygen and rewetting after plasma application. Brackets were bonded using light cured adhesive; all specimens were subjected to thermocycling. The shear bond strength of each specimen was measured in a universal testing machine and compared using Welch one-way analysis of variance (ANOVA) and Games-Howell post hoc test.

RESULTS

Specimens conditioned with argon plasma plus 0.5% oxygen and rewetting showed a significantly higher shear bond strength than specimens conditioned with conventional acid etching. Conditioning with pure argon plasma and argon plasma plus 0.5% oxygen without rewetting yielded significantly lower shear bond strength.

CONCLUSION

Admixing 0.5% oxygen and rewetting the enamel after plasma application are crucial steps that could help make cold atmospheric plasma a gentle conditioning technique in orthodontic bonding.

Benchtop plasma treatment of titanium surfaces enhances cell response

OBJECTIVE

Modifications to implant surface properties, including topography, chemistry, and wettability, alter immune response, osteoblast differentiation of bone marrow stromal cells (MSCs), and implant integration in vivo. Dielectric barrier discharge (DBD) plasma treatment has been used to sterilize surfaces and remove adsorbed carbon, improving wettability. However, unless it is used immediately prior to placement, ambient atmospheric hydrocarbons rapidly adhere to the surface, thereby reducing its hydrophilicity. Moreover, this method is not practical in many clinical settings. The aim of this study was to evaluate the effectiveness of an on-site benchtop modification technique for implants at time of placement, consisting of a DBD plasma that is used to sterilize implants that are pre-packaged in a vacuum. Effects of the plasma-treatment on implant surface properties and cellular response of MSCs and osteoblasts were assessed in vitro.

METHODS

Titanium-aluminum-vanadium implant surfaces were grit-blasted (GB) or grit-blasted and acid-etched (AE), and packaged under vacuum. AE surfaces were also plasma-treated using the benchtop device (GB + AE) and then removed from the vacuum. GB surface morphology was altered with AE but AE microroughness was not changed with the plasma-treatment. Plasma-treatment increased the surface wettability, but did not alter surface atomic concentrations of titanium, oxygen, or carbon.

RESULTS

MSCs and osteoblast-like cells (MG63 s) produced increased concentrations of osteocalcin, osteopontin, and osteoprotegerin after plasma-treatment of AE surfaces compared to non-plasma-treated AE surfaces; production of IL6 was reduced and IL10 was. Aging GB + AE surfaces for 7 days after plasma-treatment but still in the vacuum environment reduced the effectiveness of plasma on cellular response.

SIGNIFICANCE

Overall, these data suggest that application of benchtop plasma at the time of implant placement can alter the surface free energy of an implant surface without modifying surface chemical composition and enhance the differentiation and activity of MSCs and osteoblasts that are in contact with these implant surfaces.

Safety evaluation of atmospheric pressure plasma jets in in vitro and in vivo experiments

Purpose

The atmospheric pressure plasma jet (APPJ) has been introduced as an effective disinfection method for titanium surfaces due to their massive radical generation at low temperatures. Helium (He) has been widely applied as a discharge gas in APPJ due to its bactericidal effects and was proven to be effective in our previous study. This study aimed to evaluate the safety and effects of He-APPJ application at both the cell and tissue levels.

Methods

Cellular-level responses were examined using human gingival fibroblasts and osteoblasts (MC3T3-E1 cells). He-APPJ was administered to the cells in the experimental group, while the control group received only He-gas treatment. Immediate cell responses and recovery after He-APPJ treatment were examined in both cell groups. The effect of He-APPJ on osteogenic differentiation was evaluated via an alkaline phosphatase activity assay. In vivo, He-APPJ treatment was administered to rat calvarial bone and the adjacent periosteum, and samples were harvested for histological examination.

Results

He-APPJ treatment for 5 minutes induced irreversible effects in both human gingival fibroblasts and osteoblasts in vitro. Immediate cell detachment of human gingival fibroblasts and osteoblasts was shown regardless of treatment time. However, the detached areas in the groups treated for 1 or 3 minutes were completely repopulated within 7 days. Alkaline phosphatase activity was not influenced by 1 or 3 minutes of plasma treatment, but was significantly lower in the 5 minute-treated group (P=0.002). In vivo, He-APPJ treatment was administered to rat calvaria and periosteum for 1 or 3 minutes. No pathogenic changes occurred at 7 days after He-APPJ treatment in the He-APPJ-treated group compared to the control group (He gas only).

Conclusions

Direct He-APPJ treatment for up to 3 minutes showed no harmful effects at either the cell or tissue level.

Antimicrobial and protective effects of non-thermal plasma treatments on the performance of a resinous liner

OBJECTIVE

Overcoming substantial shortcomings of soft liners as physico-chemical changes and liner-biofilm-related infections remains a challenge in the rehabilitation treatment. In this study, protective non-thermal plasma (NTP) treatments were developed on the soft liner surface to improve its surface and physico-chemical properties and to reduce fungal colonization after biofilm inhibition challenge.

METHODS

Resinous liner specimens (Coe-Soft) were prepared and distributed in 3 groups according to the surface treatments: (1) untreated (control); (2) treated with sulfur hexafluoride-based NTP (SF₆); and (3) treated with hexamethyldisiloxane-based NTP (HMDSO). To test the NTP stability and their protective and antimicrobial effect on the liner surface over time, the morphology, chemical composition, roughness, water contact angle, shore A hardness, sorption and solubility were evaluated before and after the specimens were exposed to dual-species biofilm of Candida albicans and Streptococcus oralis for 14 days. Colony forming units and biofilm structure were assessed. Data were submitted to ANOVA and Tukey tests (α = 0.05).

RESULTS

Both treatments modified the surface morphology, increased hydrophobicity and roughness of the liner, and were effective to reduce C. albicans adhesion without affecting the commensal health-associated S. oralis. HMDSO presented chemical stability and lower hardness in both periods, whereas SF₆ exhibited higher initial hardness than control and the highest sorption; contrarily, similar solubility was noted for all groups.

CONCLUSION

HMDSO-based film showed improved physico-chemical properties and inhibited C. albicans biofilm. Thus, it has potential for use to control candida-related stomatitis and improve liner's stability even after being exposed to biofilm inhibition challenge.

Changes in surface properties of dental alloys with atmospheric plasma irradiation

Chemical transitions after atmospheric pressure plasma irradiation were investigated by evaluating intermolecular attractions and atomic and molecular reactions. Gold, titanium and stainless-steel alloy samples were ground with #800 grit SiC waterproof paper and nitrogen gas atmospheric plasma irradiation was conducted. The surface free energies of the treated alloys were calculated and compared statistically. X-ray photoelectron spectroscopy analysis was performed.The surface free energies of all metal surfaces treated by plasma irradiation were 1.5-times higher than those of the untreated metals. The energy of the hydrogen bonding component increased, and all alloy surfaces were coated with metal oxide after only a short period of plasma irradiation. The surfaces oxidized by plasma exhibited a high active energy, mainly due to an increase in the hydrogen bonding component. Reactions with oxygen in the air were promoted on the clean surfaces with exposed reactive elements.

[Application of plasma sprayed zirconia coating in dental implant: study in implant]

Objective: To investigate the osseointegration of a novel coating-plasma-sprayed zirconia in dental implant. Methods: Zirconia coating on non-thread titanium implant was prepared using plasma spraying, the implant surface morphology, surface roughness and wettability were measured. In vivo, zirconia coated implants were inserted in rabbit tibia and animals were respectively sacrificed at 2, 4, 8 and 12 weeks after implantation. The bond strength between implant and bone was measured by push-out test. The osseointegration was observed by scanning electron microscopy (SEM), micro CT and histological analyses. Quantified parameters including removal torque, and bone-implant contact (BIC) percentage were calculated. Results: The surface roughness (1.6 µm) and wettability (54.6°) of zirconia coated implant was more suitable than those of titanium implant (0.6 µm and 74.4°) for osseointegration. At 12 weeks, the push-out value of zirconia coated implant and titanium implant were (64.9±3.0) and (50.4±2.9) N, and BIC value of these two groups were (54.7±3.6)% and (41.5±3.6)%. All these differences had statistical significance. Conclusions: The surface characters of zirconia coated implant were more suitable for osseointegration and present better osseointegration than smooth titanium implant in vivo, especially at early stage.

Photofunctionalization and non-thermal plasma activation of titanium surfaces

OBJECTIVE

The aim of this study was to compare UV light and non-thermal plasma (NTP) treatment regarding the improvement of physical material characteristics and cell reaction on titanium surfaces in vitro after short-term functionalization.

MATERIALS AND METHODS

Moderately rough (Ra 1.8-2.0 μm) sandblasted and acid-etched titanium disks were treated by UV light (0.05 mW/cm² at λ = 360 nm and 2 mW/cm² at λ = 250 nm) or by NTP (24 W, -0.5 mbar) of argon or oxygen for 12 min each. Surface structure was investigated by scanning electron microscopy, confocal microscopy and X-ray photoelectron spectroscopy (XPS). Hydrophilicity was assessed by dynamic contact angle measurement. Cell attachment, viability, cell proliferation and cytotoxicity were assessed in vitro using murine osteoblast-like cells.

RESULTS

UV irradiation or NTP treatment of titanium surfaces did not alter the surface structure. XPS analysis revealed a significantly increased oxidation of the surface and a decrease of carbon after the use of either method. NTP and UV light led to a significant better cell attachment of murine osteoblasts; significantly more osteoblasts grew on the treated surfaces at each time point (p < 0.001).

CONCLUSIONS

UV light as well as NTP modified the surface of titanium and significantly improved the conditions for murine osteoblast cells in vitro. However, results indicate a slight advantage for NTP of argon and oxygen in a short time interval of surface functionalization compared to UV.

CLINICAL RELEVANCE

UV light and NTP are able to improve surface conditions of dental implants made of titanium.