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PDT in oral hygiene- a split mouth randomized trial

Nikinmaa S, Meurman J, Moilanen N, Sorsa T, Rantala J, Alapulli H, Kankuri E, Kotiranta A, Auvinen P, Pätilä T. 

The effects of indocyanine green-mediated photodynamic therapy on the development of plaque, plaque bacteriological ecology, and early periodontitis markers - A randomised study 

Abstract: Antimicrobial photodynamic therapy (aPDT) has been introduced as an adjunct method for dental hygiene. Although antibacterial and antiplaque effects resulting from aPDT have already been demonstrated in the literature, effects on bacterial flora diversity or early gingivitis biomarkers have not previously been established. Fifteen healthy adults were assigned to the study. Upper premolars (4. and 5.) were examined on both sides of the maxilla. After meticulous scaling and root planing, the maxillary dental arch was left without any mechanical cleaning for four days. Randomisation of the treatment side of the upper dental arch was performed, and following the initial sample collection, the mouth was rinsed with indocyanine green (ICG), and 100J/cm2 of 810 nm light was subsequently applied for eight minutes. The treatment was repeated daily for four days. ICG localisation after the mouth rinse procedure was measured after each treatment by near-infrared imaging. Plaque area, 16S rRNA bacteriological identification, and gingival crevicular fluid (GCF) matrix metalloproteinase 8 (MMP-8) samples were measured. Fluorescent imaging showed ICG adherence to dental plaque, enabling localised treatment at the target site. Antimicrobial photodynamic therapy resulted in a significant reduction of plaque formation. An analysis of the 16S rRNA sequencing found reduction in the Streptococcus, AcinetobacterialCapnocytophagal, and Rothia bacteria species and a gain in Neisseria and Hemophilus bacteria on the aPDT-treated side. The gain in the latter group of bacteria superseded the relative loss of the former in the plaque, while alpha diversity remained stable. A reduction of the total amount of MMP-8 in the GCF was seen on the treated side, suggesting inhibition of early gingivitis. In conclusion, ICG -based aPDT is effective and reduces the amount of known oral pathogens, with compensated bacterial growth in species associated with good oral health, but without a change in overall bacterial diversity. The treatment can be applied specifically to dental plaque, and the anti-inflammatory effect may prevent the development of early gingivitis. 

Dual light provides a sustained antibacterial effect

Nikinmaa S, Meurman J, Sorsa T, Rantala J, Pätilä T

Daily administered dual light photodynamic therapy provides a sustained antibacterial effect in biofilm and prohibits Streptococcus mutans adaptation 

Introduction: Antibacterial photodynamic therapy (aPDT) and antibacterial blue light (aBL) have been emerging as novel auxiliary treatment methods to mechanical debridement for periodontitis. Single wavelength light application with indocyanine green (ICG) photosensitizer has shown efficacy in several dental in-office-treatment protocols. In this study, we tested the Streptococcus mutans biofilm sensitivity to dual light aPDT, the combined simultaneous exposure of aPDT and aBL, and compared this to their separate application. 

Materials and Methods: Biofilm was grown on the bottom of well plates by adding diluted Streptococcus mutans suspension with growth medium. Well plates were incubated at 36° C, at 5% CO2 atmosphere. Similar amount of light energy was applied at 810nm, at 405nm or their combination, together with ICG. Exposure was given once on a single-day biofilm, once after a 4-day biofilm maturation period of once-daily on a four-days biofilm. Biofilms were scraped, diluted into rations between 1:1 to 1:100 000 and plated. After re-incubation, colony-forming units (CFU) were counted and 3D biofilm imaging was performed. 

Results: On a single-day biofilm, dual-light was significantly more efficient than aBL or aPDT, although all modalities were bactericidal.  On a four-day maturated biofilm, single exposure of aPDT or dual-light aPDT was more efficient than aBL, resulting in a four logarithmic scale reduction in CFUs. Surprisingly, when the same amount of aPDT was given repeatedly, on a daily basis, on the four-day biofilm, a significantly improved bacterial viability was observed. Similar, but milder response was seen after repetitive aBL application. The viability improvement was abolished when dual-light aPDT was applied.   

Conclusion: When aPDT is administered repeatedly to S. mutans-biofilm, a single wavelength-based aBL or aPDT leads to significant biofilm adaptation and increased S. mutans viability. The combined use of aBL light in synchrony with aPDT as dual-light aPDT treatment blocks the adaptation and provides significantly greater antibacterial efficacy, with sustained effect.