
A recent review revealed that the weighted mean prevalences for peri-implantitis were 9.25% and 19.83% based on implant and subject respectively. Similarly, the weighted mean prevalences for peri-implant mucositis were 29.48% and 46.83% based on implant and subject respectively. The study found that peri-implant diseases were prevalent and the prevalence of peri-implantitis increased over time.1 Traditional treatment approaches involve mechanical debridement using instruments such as curettes, ultrasonic scalers, and air powder abrasion. These methods are often combined with chemical treatments using substances like citric acid, hydrogen peroxide, ethylene-diamine-tetraacetic acid, chlorhexidine gluconate, and local or systemic antibiotics.2-4
However, these treatments may be associated with undesirable outcomes, including implant surface damage, chemotoxicity to surrounding tissues, and the emergence of antibiotic-resistant bacterial strains.3-5 To address these challenges, antimicrobial photodynamic therapy (PDT) has been proposed as an alternative for treating peri-implant diseases, aiming to mitigate the side effects associated with conventional treatment modalities.5 PDT is a non-invasive photochemical treatment modality designed to eliminate periodontal pathogens using low-level laser light (wavelength range: 650 - 940 nm) with a photosensitizer. Photosensitizers absorb specific wavelengths, converting light into energy that generates reactive oxygen species (ROS). ROS exert a cytotoxic impact by damaging DNA, inhibiting cell-wall synthesis, and modifying cell membrane proteins or potassium ions.5 PDT offers several advantages, including the absence of bacterial resistance development, targeted antibacterial efficacy at the treatment site, and minimal damage to adjacent healthy tissues due to its localized effect.6,7
Recommended photosensitizers include toluidine blue, methylene blue, and indocyanine green (ICG), with ICG noted for its optimal peak absorption at 805 - 810 nm.8,9 Some studies have suggested that the mechanism of diode laser with ICG (ICG-PDT) involves not only the photodynamic effect that produces ROS but also the photothermal effect, inducing cell destruction by elevating intercellular temperature.9-11 Bashir et al.11 demonstrated the effectiveness of ICG-PDT in destroying periodontopathogenic cells and improving clinical periodontal parameters in chronic periodontitis.
The sequence of biofilm formation and microbial species involved in implant surface colonization resembles those observed on teeth surfaces.12,13 Surface characteristics, including roughness and surface free energy of implant surfaces, significantly influence biofilm formation.12 Previous studies reported the highest bacterial adhesion on rough implant surfaces, particularly those represented by the sandblasted, large grit, and acid-etched (SLA) surface.14-16
Although several in vitro studies demonstrated the efficacy of ICG-PDT in reducing
Titanium disks (Φ 8.0 mm, height 2.5 mm, Shinhung, Seoul, Korea) underwent sandblasting and acid etching (SLA). These disks were then covered with a putty-type vinyl polysiloxane (GC Corporation, Tokyo, Japan), leaving one surface exposed for biofilm formation. Subsequently, the disks underwent sonication, soaking in 70% ethanol, and autoclaving at 121°C for 15 m.
After 48 h of incubation, disks were gently washed twice with 2 mL phosphate-buffered saline (PBS) and divided into five groups (Table 1). Each group consisted of six disks, and the experiment was repeated twice. The control group underwent a 30 s wash with 100 μL PBS. The chlorhexidine gluconate (CHX) group received a 30 s treatment with 0.1% CHX (Bukwang Pharm. Co., Seoul, Korea), the Tetracycline (TC) group was treated with 50 mg/mL TC (Teracyclin®, Chong Kun Dang, Seoul, Korea) solution for 30 s, the indocyanine green (ICG) group received a 5 m treatment with 1 mg/mL ICG, and the photodynamic therapy (ICG-PDT) group underwent a 5 m treatment with 1 mg/mL ICG activated with infrared diode laser irradiation (Laserland, Hubei, China) at 810-nm wavelength, 300 mW power, 24 J/cm2 energy density, irradiation time of 30 s. Irradiation was performed in the dark under aseptic conditions, and disks were shielded to prevent light transmission. After treatment, disks were washed twice with PBS, and biofilm was dispersed by sonication for 15 s. A 1 : 100 dilution was made using PBS, and two blood agar plates were inoculated. Colony-forming units (CFU) were counted using an automated colony counter (IUL, Barcelona, Spain).
Treatment protocol
Group | Treatment | N |
---|---|---|
Control | PBS only 30 s | 6 |
CHX | 0.1% CHX 30 s | 6 |
TC | 50 mg/mL TC 30 s | 6 |
ICG | 1 mg/mL ICG 5 m | 6 |
ICG-PDT | 1 mg/mL ICG 5 m + laser 30 s | 6 |
PBS: phosphate-buffered saline; CHX: chlorhexidine; TC: tetracycline; ICG: indocyanine green; ICG-PDT: photodynamic therapy using ICG.
To assess bacterial cell viability after treatment, a LIVE/DEAD™ BacLight™ Bacterial Viability Kit (Molecular probes Inc. Eugene, USA) was utilized following the manufacturer’s instructions. Samples were visualized using a confocal laser-scanning microscope (CLSM; TCS SP8 STED, Leica Microsystems, Mannheim, Germany). Treatment effects were evaluated by analyzing merged images with an image processing program (LAS X, Leica Microsystems) at a 10× magnification.
Antimicrobial efficacy was determined by dividing the mean CFU value of the experimental group by that of the control group, with bacterial colony count expressed as a log-transformed value. Groups were compared using one-way analysis of variance, followed by Tukey’s HSD test. Statistical analysis was performed using SPSS software (version 28, IBM, Armonk, USA), with the level of significance set at
Table 2 presents the bacterial reduction rates for each group. All treatment groups exhibited a significant reduction in bacterial viability. Notably, the CHX, TC, and ICG-PDT groups demonstrated a bacterial reduction rate exceeding 90%. When comparing groups based on log-transformed values (Fig. 1), there was a statistically significant decrease in bacterial viability in the chemical disinfection groups compared to the control group (
Bacterial reduction rate
Group | Reduction rate (%) | P-value |
---|---|---|
Control | - | - |
CHX | 92.9 | |
TC | 91.9 | |
ICG | 69.4 | |
ICG-PDT | 94.6 |
CHX: chlorhexidine; TC: tetracycline; ICG: indocyanine green; ICG-PDT: photodynamic therapy using ICG.
In CLSM images, live bacteria were stained in green, while dead bacteria were stained in red (Fig. 2). The control group’s image appeared green, indicating a high proportion of live bacteria. In comparison with the control group, all treatment groups exhibited a trend toward a lower proportion of live bacteria and a higher proportion of dead bacteria. Among these groups, the ICG-PDT group’s images revealed a relatively higher number of dead bacteria stained in red compared to the other groups.
This in vitro study aimed to assess the antimicrobial effectiveness of ICG-PDT against
Effective management of peri-implant biofilm is crucial in the treatment of peri-implant disease. Previous studies have shown that ICG-PDT significantly reduces pathogenic bacteria, including Porphyromonas gingivalis, Streptococcus mutans, Enterococcus faecalis, and Aggregatibacter actinomycetemcomitans in vitro.25-27 Moreover, systematic reviews have reported improved clinical periodontal parameters with the adjunctive use of ICG-PDT in non-surgical periodontal therapy for chronic periodontitis.11
In this study, the antimicrobial efficacy of ICG-PDT against
In this study, there was a higher proportion of dead bacteria in the ICG-PDT group in CLSM images. This result might be explained by photothermal effect which penetrate even in deeper layer of biofilm in contrast of CHX, penetrating only limited depth of the biofilm.29 ICG transformed most of the absorbed energy of laser into heat, increasing the penetration depth of effect.30 In previous study, similar result was reported that the antimicrobial effect of ICG-PDT highly penetrated within the mature biofilm despite the comparable CFU values between CHX and ICG-PDT.29
The study also considered the impact of implant macro-design and surface roughness on treatment efficacy. While these factors enhance osseointegration, the rough surface may act as a bacterial reservoir.31,32 An in vitro study reported that implant macrostructure significantly influenced the access of the mechanical decontamination devices and in turn its efficacy.33 Therefore, adjunctive antimicrobial approaches such as antiseptic, or local or systematic antibiotics should be considered to improve the treatment outcomes and to prevent bacterial colonization. Both CHX and TC groups in this study demonstrated a statistically significant reduction in bacterial viability compared to the control group, highlighting the efficacy of chemical decontamination. However, there were no significant differences between CHX and TC groups, suggesting a lack of superiority for one treatment modality over the other.4
The potential complications of implant surface decontamination include mechanical damage, chemotoxicity, and the emergence of resistant bacteria with antibiotics.4 ICG-PDT offers advantages such as low chemotoxicity, ease of handling, rapid elimination, and minimal side effects.10 The generated ROS in ICG-PDT have a limited migration depth, minimizing damage to sound tissue.5 These facts advocate the use of ICG-PDT in treatment of peri-implant disease with less side effect possibility.
Despite its strengths, the study has limitations. The exclusion of other treatment options and the absence of mechanical intervention limit the generalizability of the findings. Moreover, the single bacterial species (
Despite the limitations, the superior effect of ICG-PDT suggests its potential clinical relevance in peri-implant disease treatment. In practice, ICG-PDT could effectively disrupt biofilm with minimized side effects, limiting irradiation to specific areas. Understanding the mechanism of PDT and the etiology of peri-implant disease is essential for effective prevention and treatment.
Within the limitations, ICG-PDT demonstrated effective disruption of
![]() |
![]() |