Bactericidal Efficacy of Cold Plasma at Different Depths of Infected Root Canals In Vitro

Objectives: Cold plasma (CP) has been shown to be effective even against multiresistant microorganisms. As previous investigations on the effect of CP in root canals showed promising results, the aim of the present study was to analyze the bactericidal efficacy of CP in different depths of infected dentin. Methods: 32 standardized root canals of human mandibular premolars were infected with Enterococcus faecalis and incubated for one week. Specimens were randomly selected for one of four disinfection methods: control (5mL NaCl), 5mL chlorhexidine (CHX), CP alone (CP), and a combination of 5mL CHX and cold plasma (CHX+CP). CHX was ultrasonically activated for 30s, while cold plasma was used for 60s in the root canals. Dentin samples at depths of 300, 500 and 800 µm were obtained and diluted serially. Colony forming units (CFUs) were counted on agar plates after 24h of incubation. Results: The highest overall logarithmic reduction factors (RF) were obtained from CHX+CP (log RF 3.56 p<0.01; Mann-Whitney U test), followed by CP (log RF 3.27 p<0.01) and CHX alone (log RF 2.65 p<0.01) related to the control. All disinfection methods showed significantly lower CFU counts compared to the control group in 300 µm and 800 µm (both p<0.01, Kruskal-Wallis test). Discussion: The adjuvant use of CP might be beneficial in highly infected root canals to improved disinfection. However, the disinfection effect against Enterococcus faecalis of CP is comparable to ultrasonically activated CHX

Cold atmospheric plasma in the elimination of therapy-resistant microorganisms as an adjuvant therapy of medication-related osteonecrosis of the jaw

Die Therapie Medikamenten-assoziierter Knochennekrosen stellt Kliniker vor umfangreiche Herausforderungen, insbesondere vor dem Hintergrund der Superinfektion dieser Areale. Die bakterizide Wirkung von kaltem atmosphärischen Plasma (CAP) auf der Haut ist in zahlreichen Studien belegt worden. Im Mund-, Kiefer-, Gesichtsbereich fehlen zum Teil noch geeignete Methoden zur Biofilmbeherrschung. Im Rahmen dieser Arbeit sollte die Wirkung von CAP auf komplexen dentalen, ossären und alloplastischen Strukturen in vitro überprüft werden. Zunächst erfolgte die Herstellung von Modellen aus porcinem Knochen, Implantaten und Wurzelkanälen mit anschließender Kultivierung von Biofilmen auf deren Oberflächen. In der ersten Versuchsreihe wurde die bakterizide Wirkung von CAP in verschiedenen Knochentiefen untersucht. Je drei infizierte Knochenproben wurden vertikal gestapelt und anschließend behandelt (Kontrollgruppe: Spülung mit 5 ml 0,9% NaCl, CHX- Gruppe: Spülung mit 5 ml Chlorhexidindigluconatlösung (CHX), CAP-Gruppe: CAP- Anwendung für 60 s). Die zweite Versuchsreihe bestand in der Behandlung von inkubierten Implantaten. Auch hier wurden die Implantate mit verschiedenen Dekontaminationsmethoden (Kontrollgruppe: Spülung mit 5 ml 0,9% NaCl, Laser- Gruppe: Behandlung der Proben mit einem Dioden-Laser für 60 s, CAP-Gruppen: CAP-Anwendung für 60 s bzw. 120 s) behandelt. Ziel der letzten Versuchsreihe war die Wirkung von CAP in verschiedenen Tiefen infizierter Dentintubuli. Es erfolgte die Behandlung der Wurzelkanäle in der Kontrollgruppe (Spülung mit 5 ml 0,9% NaCl), der CHX-Gruppe (Spülung mit 5 ml CHX), der CAP-Gruppe (CAP- Anwendung für 60 s) sowie einer Kombinationsgruppe (CAP+CHX). Die quantitative Auswertung erfolgte mittels Auszählung Kolonie bildender Einheiten (CFUs). Insgesamt waren die logarithmierten medianen CFU/ml-Werte in allen Versuchen (Knochen: 0-9000 µm, Implantate, Wurzelkanäle: 0-800 µm) im Vergleich zu den Kontrollgruppen signifikant niedriger (p ≤ 0,05, Mann-Whitney U / Kruskal- Wallis Test). Ergebnisse zeigten signifikante Unterschiede in der mittleren Knochenschicht (3000-6000 µm), bei Vergleich der CAP-Gruppe zu den anderen Gruppen (CAP vs. CHX: p = 0,007, CAP vs. C: p = 0,035). Auch in der tiefen Schicht (6000-9000 µm) zeigten sich signifikante Unterschiede (CAP vs. CHX: p = 0,027). Die Ergebnisse der Implantatversuche zeigen eine signifikante Keimreduktion der CAP-Gruppen gegenüber der Kontrollgruppe (CAP60 vs. C: p = 0,012, CAP120 vs. C: p = 0,024). Letztlich waren die Werte der Kombinationsgruppe (CAP+CHX) in der oberflächlichen (0-300 µm) und tiefen Dentinschicht (500-800 µm) signifikant effektiver als die, der restlichen Gruppen (p ≤ 0,01). In allen anderen Gruppen zeigten sich keine signifikanten Unterschiede. CAP stellt eine vielversprechende Ergänzung in der Dekontamination komplexer Oberflächen im Mund-, Kiefer-, Gesichtsbereich dar und sollte daher in klinischen Studien weiter untersucht werden.The therapy of medication-related osteonecrosis remains a challenge for clinicians, especially regarding superinfection of affected areas. The bactericidal efficacy of cold atmospheric plasma (CAP) on skin has been proven in many studies. In the oral and maxillofacial region, appropriate methods for biofilm control are still missing. The aim of this work was to evaluate the effect of CAP on complex surfaces of the oral cavity in vitro. Specimen of porcine bone, implants, root canals were produces and biofilms were cultivated on their surfaces. The aim of the first investigation was to study the bactericidal efficacy of CAP in different depths of bone. Three samples were vertically stacked and subsequently treated (control group: rinsing with 5 ml 0,9% NaCl, CHX group: rinsing with 5 ml Chlorhexidine digluconate (CHX), CAP group: CAP application for 60 s). In the second study infected implant surfaces were treated with different decontamination methods (control group: rinsing with 5 ml 0,9% NaCl, Laser group: diod laser applicaton for 60 s, two CAP groups: CAP application for 60 s and 120 s). In the third study the effect of CAP in different depths of infected dentinal tubules was examined. The infected root canals were treated in different groups (control group: rinsing with 5 ml 0,9% NaCl, CHX group: rinsing with 5 ml CHX, CAP group: CAP application for 60 s, combination group: rinsing with 5 ml CHX and 60 s CAP application). Colony-forming units were counted to estimate bacterial reduction. Overall, log median CFU/ml of CAP were significantly lower in all experiments (bone: 0-9000 µm, implants, root canals: 0-800 µm) when compared to the control groups (p ≤ 0,05, Mann-Whitney U / Kruskal-Wallis Test). In the mid bone layer (3000-6000 µm), the results of the CAP group were significantly different compared to the other groups (CAP vs. CHX: p = 0,007, CAP vs. C: p = 0,035). Also the deep layer (6000-9000 µm) showed significant differences compared to the CHX group (CAP vs. CHX: p = 0,027). The results of the implant trials revealed a significant bacterial reduction compared to the control group (CAP60 vs. C: p = 0,012, CAP120 vs. C: p = 0,024). Significant differences in the results of the root canal trial in the superficial (0-300 µm) and deep layer (500-800 µm), compered to the other groups, (p ≤ 0,01) were observed. Among the other groups, no significant differences were observed. CAP appears to be a promising approach in the decontamination of complex surfaces in the oral and maxillofacial region. Therefore, CAP should be further investigated in clinical trials

Bactericidal Efficacy of Cold Plasma at Different Depths of Infected Root Canals In Vitro

OBJECTIVES: Cold plasma (CP) has been shown to be effective even against multiresistant microorganisms. As previous investigations on the effect of CP in root canals showed promising results, the aim of the present study was to analyze the bactericidal efficacy of CP in different depths of infected dentin. METHODS: 32 standardized root canals of human mandibular premolars were infected with Enterococcus faecalis and incubated for one week. Specimens were randomly selected for one of four disinfection methods: control (5mL NaCl), 5mL chlorhexidine (CHX), CP alone (CP), and a combination of 5mL CHX and cold plasma (CHX+CP). CHX was ultrasonically activated for 30s, while cold plasma was used for 60s in the root canals. Dentin samples at depths of 300, 500 and 800 µm were obtained and diluted serially. Colony forming units (CFUs) were counted on agar plates after 24h of incubation. RESULTS: The highest overall logarithmic reduction factors (RF) were obtained from CHX+CP (log RF 3.56 p<0.01; Mann-Whitney U test), followed by CP (log RF 3.27 p<0.01) and CHX alone (log RF 2.65 p<0.01) related to the control. All disinfection methods showed significantly lower CFU counts compared to the control group in 300 µm and 800 µm (both p<0.01, Kruskal-Wallis test). DISCUSSION: The adjuvant use of CP might be beneficial in highly infected root canals to improved disinfection. However, the disinfection effect against Enterococcus faecalis of CP is comparable to ultrasonically activated CHX