Time-dependent reactive oxygen species inhibit Streptococcus mutans growth on zirconia after a helium cold atmospheric plasma treatment

Nonthermal Atmospheric Pressure Plasma Treatment of Endosteal Implants for Osseointegration and Antimicrobial Efficacy: A Comprehensive Review

The energy state of endosteal implants is dependent on the material, manufacturing technique, cleaning procedure, sterilization method, and surgical manipulation. An implant surface carrying a positive charge renders hydrophilic properties, thereby facilitating the absorption of vital plasma proteins crucial for osteogenic interactions. Techniques to control the surface charge involve processes like oxidation, chemical and topographical adjustments as well as the application of nonthermal plasma (NTP) treatment. NTP at atmospheric pressure and at room temperature can induce chemical and/or physical reactions that enhance wettability through surface energy changes. NTP has thus been used to modify the oxide layer of endosteal implants that interface with adjacent tissue cells and proteins. Results have indicated that if applied prior to implantation, NTP strengthens the interaction with surrounding hard tissue structures during the critical phases of early healing, thereby promoting rapid bone formation. Also, during this time period, NTP has been found to result in enhanced biomechanical fixation. As such, the application of NTP may serve as a practical and reliable method to improve healing outcomes. This review aims to provide an in-depth exploration of the parameters to be considered in the application of NTP on endosteal implants. In addition, the short- and long-term effects of NTP on osseointegration are addressed, as well as recent advances in the utilization of NTP in the treatment of periodontal disease.

Decontaminative Properties of Cold Atmospheric Plasma Treatment on Collagen Membranes Used for Guided Bone Regeneration

Background cold atmospheric plasma (CAP) is known to be a surface-friendly yet antimicrobial and activating process for surfaces such as titanium. The aim of the present study was to describe the decontaminating effects of CAP on contaminated collagen membranes and their influence on the properties of this biomaterial in vitro. Material and Methods: A total of n = 18 Bio-Gide^® (Geistlich Biomaterials, Baden-Baden, Germany) membranes were examined. The intervention group was divided as follows: n = 6 membranes were treated for one minute, and n = 6 membranes were treated for five minutes with CAP using kINPen^® MED (neoplas tools GmbH, Greifswald, Germany) with an output of 5 W, respectively. A non-CAP-treated group (n = 6) served as the control. The topographic alterations were evaluated via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Afterward, the samples were contaminated with E. faecalis for 6 days, and colony-forming unit (CFU) counts and additional SEM analyses were performed. The CFUs increased with CAP treatment time in our analyses, but SEM showed that the surface of the membranes was essentially free from bacteria. However, the deeper layers showed remaining microbial conglomerates. Furthermore, we showed, via XPS analysis, that increasing the CAP time significantly enhances the carbon (carbonyl group) concentration, which also correlates negatively with the decontaminating effects of CAP. Conclusions: Reactive carbonyl groups offer a potential mechanism for inhibiting the growth of E. faecalis on collagen membranes after cold atmospheric plasma treatment.

Antifungal efficiency and cytocompatibility of polymethyl methacrylate modified with zinc dimethacrylate

Objectives

Considering the high incidence rates of denture stomatitis, research that providing dental biomaterials with antifungal property are essential for clinical dentistry. The objectives of the present study were to investigate the effect of zinc dimethacrylate (ZDMA) modification on the antifungal and cytotoxic properties, as well as the variance in surface characteristics and other physicochemical properties of polymethyl methacrylate (PMMA) denture base resin.

Methods

PMMA with various mass fraction of ZDMA (1 wt%, 2.5 wt% and 5 wt%) were prepared for experimental groups, and unmodified PMMA for the control. Fourier-transform infrared spectroscopy (FTIR) was applied for characterization. Thermogravimetric analysis, atomic force microscopy and water contact angle were performed to investigate the thermal stability and surface characteristics (n=5). Antifungal capacities and cytocompatibility were evaluated with Candida albicans (C. albicans) and human oral fibroblasts (HGFs), respectively. Colony-forming unit counting, crystal violet assay, live/dead biofilm staining and scanning electron microscopy observation were performed to assess antifungal effects, and the detection of intracellular reactive oxygen species production was applied to explore the possible antimicrobial mechanism. Finally, the cytotoxicity of ZDMA modified PMMA resin was evaluated by the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay and live/dead double staining.

Results

The FTIR analyses confirmed some variation in chemical bonding and physical blend of the composites. Incorporation of ZDMA significantly enhanced the thermal stability and hydrophilicity compared with unmodified PMMA (p < 0.05). The surface roughness increased with the addition of ZDMA while remained below the suggested threshold (≤ 0.2 µm). The antifungal activity significantly improved with ZDMA incorporation, and cytocompatibility assays indicated no obvious cytotoxicity on HGFs.

Conclusions

In the present study, the ZDMA mass fraction up to 5 wt% in PMMA performed better thermal stability, and an increase in surface roughness and hydrophilicity without enhancing microbial adhesion. Moreover, the ZDMA modified PMMA showed effective antifungal activity without inducing any cellular side effects.

Influence of Cold Atmospheric Plasma on Surface Characteristics and Bond Strength of a Resin Nanoceramic

The purpose of this study was to investigate the effect of cold atmospheric plasma (CAP) treatment on resin nanoceramic (RNC) surface state and its bond strength with resin cement. RNC with different surface treatments were prepared: control, sandblasting treatment (SB), hydrofluoric acid etching (HF) and plasma treatment of helium gas (CAP-He) and argon gas (CAP-Ar). The prepared samples were measured by SEM, Ra, Rz, contact angle goniometer, and XPS for surface characteristics. The shear bond test of RNC was examined in nine groups: SB + saline coupling agent (SL), HF + SL, CAP-He/Ar, CAP-He/Ar + SL, SB + CAP-He/Ar + SL, and control. The bond strength between RNC and resin cement was compared using shear bond strength test, before and after thermocycling. After CAP irradiation, the surface topography maintained, while the surface water contact angle was significantly reduced to 10.18° ± 1.36° (CAP-He) and 7.58° ± 1.79° (CAP-Ar). The removal of carbon contamination and inducing of oxygen radicals was detected after CAP treatment. The bond strength was improved by CAP treatment, but varied on CAP gas species and combination methods. CAP of Ar gas had better SBS than He gas. After thermocycling, CAP-Ar + SL showed the maximized shear bond strength (32.38 ± 1.42 MPa), even higher than SB + SL group (30.08 ± 2.80 MPa, p < 0.05). In conclusion, CAP treatment of helium and argon can improve the bonding properties of RNC by improving surface wettability, and CAP of argon gas combined with silane coupling agent shows the highest bond strength.

Application Effect of New Material after Surface Modification of Zirconia Ceramics and Analysis of Patient Evaluation

Objective

To explore the application effect of new material after surface modification of zirconia ceramics and patient evaluation.

Methods

A total of 60 patients with tooth defect treated in our hospital from April 2020 to April 2021 were selected as the study subjects and randomly divided into the control group and experimental group, with 30 cases each. The patients in the control group were treated with glass-ceramics, and those in the experimental group received LiSi surface treatment, so as to compare the application effect and patients' evaluation between the two groups.

Results

Between the two groups, no obvious differences in surface loss, adhesive strength, and transmittance at 3 months, 6 months, and 1 year were not observed (P > 0.05); and after intervention, the score on dental aesthetics, hardness value, and occlusal force were obviously higher in the experimental group than in the control group (P < 0.001).

Conclusion

The new material enables forming an acid etchable coating on the zirconia surface, increases the adhesive strength, and achieves an aesthetic degree that is welcomed by the patients; meanwhile, after grinding, the edge is defect free and the tightness is higher. Further research will help to establish a better solution for patients.