The influence of growth medium on the photodynamic susceptibility of Aggregatibacter actinomycetemcomitans to antimicrobial blue light.

The aim of this study was to investigate whether antimicrobial blue light (aBL) can cause the death of Aggregatibacter actinomycetemcomitans (A.a) and to determine the influence of different culture media, specifically brain heart infusion and blood agar, on bacterial survival fraction. An LED emitting at 403 ± 15 nm, with a radiant power of 1W, irradiance of 588.2 mW/cm2, and an irradiation time of 0 min, 1 min, 5 min, 10 min, 30 min, and 60 min, was used. The plates were incubated in microaerophilic conditions at 37 °C for 48 h, and the colony-forming units were counted. The photosensitizers were investigated using spectroscopy and fluorescence microscopy. There was no significant difference between the culture media (p > 0.05). However, a statistical reduction in both media was observed at 30 min (1058 J/cm2) (p < 0.05). The findings of this study suggest that aBL has the potential to kill bacteria regardless of the culture media used. Light therapy could be a promising and cost-effective strategy for preventing periodontal disease when used in combination with mechanical plaque control.

Clinical and microbiologic follow-up evaluations after non-surgical periodontal treatment with erbium:YAG laser and scaling and root planing.

BACKGROUND: This study compared erbium-doped: yttrium, aluminum, and garnet (Er:YAG) laser irradiation (100 mJ/pulse; 10 Hz; 12.9 J/cm(2)) with or without conventional scaling and root planing (SRP) to SRP only for treatment of periodontal pockets. METHODS: Nineteen patients with pockets from 5 to 9 mm were included. In a split-mouth design, each site was allocated to a treatment group: 1) SRPL, SRP and laser; 2) L, laser; 3) SRP, SRP only; and 4) C, no treatment. Clinical parameters of probing depth (PD), gingival recession, and clinical attachment level (CAL) were evaluated at baseline and 1, 3, 6, and 12 months after treatment. Visible plaque index, gingival bleeding index (GI), bleeding on probing (BOP), and subgingival plaque samples were also measured 12 days postoperatively, in addition to the above mentioned months. Intergroup and intragroup statistical analyses were performed (P <0.05). RESULTS: GI decreased for SRPL and increased for L, SRP, and C (P <0.05) 12 days postoperatively and decreased for SRPL and SRP (P <0.05) 3, 6, and 12 months after baseline; BOP and PD decreased for all treated groups (P <0.01) 3, 6, and 12 months after treatment. CAL gain was significant for SRPL, L, and SRP (P <0.05) 3, 6, and 12 months postoperatively. SRPL and L presented a significant reduction in the percentage of sites with bacteria 6 and 12 months after treatment (P <0.05). CONCLUSION: Non-surgical periodontal treatment with Er:YAG laser may be an alternative treatment for reduction and control of the proliferation of microorganisms in persistent periodontitis.

Photodynamic therapy in periodontal therapy: microbiological observations from a private practice.

In recent years, the combination of laser light and photosensitizer known as photodynamic therapy (PDT) has been used in periodontal therapy. However, there are not enough clinical studies to fully evaluate the effects of PDT on the periodontal tissues. This microbiological study examined the effects of PDT on the periodontal bacteria in combination with scaling and root planing (SRP) in the same group of patients by randomly selecting PDT or SRP for use in different quadrants of the mouth. For the present study, PDT was compared with a diode laser (980 nm) and an Nd:YA G laser (1,064 nm). Microbiological samples were examined and evaluated over a period of three months. Significant bacterial reduction has been observed in all cases. The diode laser with SRP presented long-term positive results, while PDT showed a significant bacteria reduction during the entire observation period.

Photodynamic therapy in planktonic and biofilm cultures of Aggregatibacter actinomycetemcomitans.

OBJECTIVE: To evaluate the inactivation of Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), responsible for causing aggressive periodontitis, using photodynamic therapy (PDT) by rose bengal (RB) as a model of a reactive oxygen species (ROS) generator, in planktonic and biofilm cultures. MATERIALS AND METHODS: A. actinomycetemcomitans was grown in planktonic and biofilm cultures using tryptic soy broth medium. The sensibility (dark toxicity) to RB was determined, and its ideal concentration for PDT was established. Concentrations in the range from 0.01 to 50.0 micromol L(-1) RB, with different light potencies and incubation times, were used. An odontological resin photopolymerizer that emits the adequate wavelength for absorption of the RB dye was applied. Bacterial viability was determined by colony- forming units (CFU). RESULTS: RB photosensitizer dye in concentrations up to 0.1 micromol L(-1) did not show toxicity per se toward A. actinomycetemcomitans cells. In a PDT study with photoirradiation (1 min) at 0.1 micromol L(-1), a 55% reduction of A. actinomycetemcomitans viability was obtained in planktonic cultures. Preincubation (30 min) of the bacteria with the dye resulted in a 90% reduction of its viability. It is important to note that, for dye concentrations up to 1 micromol L(-1), in the same experimental conditions, no death effect on gingival fibroblasts was observed. The A. actinomycetemcomitans biofilm was not affected by RB or light alone. After PDT, the reduction in the biofilm (about 45%) is significantly dependant on RB concentration and irradiation time when this dye was used as a ROS generator. CONCLUSION: Photodynamic therapy-generated ROS inactivates A. actinomycetemcomitans both in planktonic and biofilm cultures, even in small concentrations of the photosensitizing agent, and it does not cause damage to fibroblast cells under the same conditions.

Neodymium:yttrium aluminum garnet laser irradiation with low pulse energy: a potential tool for the treatment of peri-implant disease.

Bacterial contamination may seriously compromise successful implant osteointegration in the clinical practice of dental implantology. Several methods for eliminating bacteria from the infected implants have been proposed, but none of them have been shown to be an effective tool in the treatment of peri-implantitis. In the present study, we investigated the efficacy of pulsed neodymium:yttrium aluminum garnet laser irradiation (Nd:YAG) in achieving bacterial ablation while preserving the surface properties of titanium implants. For this purpose, suspensions of Escherichia coli or Actinobacillus (Haemophilus) actinomycetemcomitans were irradiated with different laser parameters, both streaked on titanium implants, and in broth medium. It was found, by light and atomic force microscopy, that Nd:YAG laser, when used with proper working parameters, was able to bring about a consistent microbial ablation of both aerobic and anaerobic species, without damaging the titanium surface.

Sensitization of oral bacteria to killing by low-power laser radiation.

Twenty-seven compounds were screened for their ability to sensitize Streptococcus sanguis to killing by light from a 7.3-mW Helium/Neon (HeNe) laser. Bacteria were mixed with various concentrations of the test compounds, spread over the surfaces of agar plates, and then exposed to light from the HeNe laser for various time periods. The plates were then incubated and examined for zones of inhibition. Those compounds found to be effective photosensitizers were then tested against Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Fusobacterium nucleatum. Toluidine blue O, azure B chloride, and methylene blue at concentrations of 0.005% (wt/vol) were effective photosensitizers of all four species, enabling killing of bacteria following exposure to laser light for only 30 s.