Antimicrobial Capacity and Surface Alterations Using Photodynamic Therapy and Light Activated Disinfection on Polymer-Infiltrated Ceramic Material Contaminated with Periodontal Bacteria

Abstract

This study determined the antimicrobial efficiency of light-activated disinfection (LAD) and photodynamic therapy (PDT) on polymer-infiltrated ceramic network (PICN) material contaminated with three periodontal bacteria and explored if PDT and LAD cause PICN surface alterations. Sixty PICN discs were contaminated with Tannerella forsythia, Porphyromonas gingivalis, and Treponema denticola and randomly divided into five groups (n = 12 samples/each) according to the treatment groups: Group PDT-PDT (630 ± 10 nm diode laser) with methylene blue; Group DL-808 nm diode laser in contact mode without photosensitizer; Group MB-methylene blue without light application; Group CHX-0.12% chlorhexidine digluconate solution and; Group NT-no treatment. Each disc was then placed in tubes containing phosphate buffered saline (PBS) and vortexed for 30 s to remove the remaining bacteria from the discs. A total of 10× serial dilutions were performed followed by plating of 30 μL of suspension on Brucella agar plates. The colony forming units (CFU) were calculated after 72 h. PICN discs with the attached biofilms were used for confocal microscopy investigation for live/dead bacterial viability. A random single sample from each group was selected to study the bacterial adherence and topographical alterations on PICN discs under scanning electron microscope (SEM). The PDT group showed higher reduction for each bacterial species and total counts of bacteria assessed followed by the DL group (p < 0.05). When compared with MB group, the two laser groups were significantly superior (p < 0.05). The MB group did not show significant differences for any bacteria when compared to NT. The bacteria with the CHX group and DL groups appeared dead with few areas of surviving green stained bacteria. The PDT group showed the highest dead cell count (p < 0.05). PDT and DL groups indicate no significant changes on the surface compared to the sterile PICN discs on visual assessment. Photodynamic therapy produced superior periodontal bacteria reduction over the surface of PICN surface. PDT group showed higher reduction for each bacterial species and total counts of bacteria assessed followed by the DL group. Both PDT and DL treatment strategies are effective without producing surface alterations on PICN.

Keywords: bacteria; ceramics; decontamination; laser; photodynamic therapy.

Figure 1

MTT assay showing relative percentage of P. gingivalis, T. forsythia and T. denticola biofilm viability with different treatment groups. Dissimilar letters indicate statistical significance between groups using ANOVA test followed by Tukey’s test.

Figure 2

Representative CLSM images of periodontal bacteria grown on PICN discs are shown. (a) The control specimens with no treatment (NT) and (b) MB specimens are shown as green densely clustered colonies with almost no areas of dead cell; (c) represents data for CHX treated specimens. The bacteria in the CHX and (d) DL groups appeared dead with few areas of surviving green stained bacteria, indicating survivability; (e) Specimen from PDT group before decontamination (control for PDT) and (f) post decontamination indicating the highest dead cell count and destroyed bacteria that could be removed after treatment.

Figure 3

Representative SEM images of: (a) periodontal niche grown on PICN discs showing dense colonies (NT control specimen) (b) The specimen with MB shows no reduction in clustered colonies; (c) represents disc with CHX treatment; (d) DL therapy and; (e) PDT. The specimen (f) is shown to compare the sterile PICN disc (magnification 1500×).