The photo-activated and photo-thermal effect of the 445/970 nm diode laser on the mixed biofilm inside root canals of human teeth in vitro: A pilot study

Evaluation of tooth color change after a bleaching process with different lasers

The aim of this in vitro study was to evaluate the efficiency of diode laser-activated bleaching systems for color change of teeth. 75 extracted teeth were studied in five different bleaching protocols. Group 1: diode laser 445 nm, 320 µm fiber, 0.5W, continuous wave mode, dose 53 J/cm2. Group 2: diode laser 970 nm, 320 µm fiber, 1W, continuous wave mode, dose 106.10 J/cm2. Group 3: diode laser 940 nm, bleaching handpiece, 7W, continuous wave mode, dose 105 J/cm2. Group 4: diode laser 940 nm, 300 µm fiber, 2W, continuous wave mode, dose 47.16 J/cm2. Group 5: bleaching process without laser activation. In groups 1, 2 and 5, teeth were bleached with Perfect Bleach Office + and in groups 3 and 4, LaserWhite20 bleaching gel was used. Tooth color was determined immediately after the bleaching process using a spectrophotometer. Color change data on the CIE L * a * b* system was analyzed statistically by the one-way ANOVA and Tukey's HSD test. All bleaching procedures resulted in a change of color. All laser groups (∆E * ab > 3) have statistically larger ∆E * ab values than the control group (∆E * ab = 0.73) (p < 0.05). The diode laser 445 nm has the largest ∆E * ab value (∆E * ab = 4.65) and results in a significantly higher color difference than all other groups. In terms of color score difference in VITA Shades, all laser-activated groups lead to a lightening effect while the control group leads to only a slight lightening effect. The diode laser 445 nm produced the greatest color difference. Laser-activated bleaching is more effective than conventional bleaching without light activation. The diode laser 445 nm performs best in this in vitro study.

Medium-term antifungal effects of methylene blue versus flavin mononucleotide in the treatment of moderate toenail onychomycosis

BACKGROUND

Methylene blue (MB) and flavin mononucleotide (FMN)-mediated photodynamic therapy (PDT) have demonstrated local antimicrobial effect, but no direct comparative study has been published so far for the treatment of toenail onychomycosis.

OBJECTIVES

To directly compare the short and medium-term efficacy of MB versus FMN as photosensitizers in PDT for toenail onychomycosis by applying them in a 40% w/w urea cream in two different dye concentrations.

METHODS

Forty toenails with distal and lateral subungual moderate onychomycosis due to dermatophyte fungi were randomised to receive 10 weekly sessions of PDT mediated by four topical formulations including MB or FMN at two different concentrations: Group I: 0.1% w/w MB; Group II: 2% w/w MB; Group III: 0.1% w/w FMN; and Group IV: 2% w/w FMN. Photographs were used for onychomycosis severity index (OSI) estimation allowing clinical assessment at any point of the study. Microscopic and microbiological evaluations were carried out at baseline, 27- and 35-week follow-ups. Side effects were recorded along with patient satisfaction.

RESULTS

At week 27, mycological cure rates were 60%, 30%, 50% and 40% and complete cure rates were 0%, 20%, 10% and 20%, for Groups I, II, III and IV respectively. At week 35, mycological cure rates were 70%, 70%, 70% and 60% and complete cure rates were 30%, 50%, 70% and 30%, for Groups I, II, III and IV respectively. All cream formulations were safe and patients were fairly satisfied.

CONCLUSIONS

Results of the present work confirm PDT as a therapeutic alternative for onychomycosis. Although all cream formulations were safe and effective, with a good degree of satisfaction, higher cure rates were obtained with 2% w/w MB cream and 0.1% w/w FMN cream.

Pretreatment of Root Dentin Using Photon-Induced Photoacoustic Streaming, Photodynamic Therapy, and Riboflavin with EDTA as a Final Irrigant to Improve Bond Integrity of Glass Fiber Post

Objective: To evaluate the outcome of post space disinfection using Er,Cr:YSGG laser (ECYL), riboflavin photosensitizer (RFP), and photon-induced photoacoustic streaming (PIPS) along with ethylene diamine tetra acetic acid (EDTA) as final irrigant on the bond values of glass fiber post (GFP) to the canal wall. Materials and methods: Forty human mandibular premolars were subjected to root canal treatment after decoronation till the cementoenamel junction. Post space was prepared using a Gates-Glidden drill leaving 4 mm of gutta perch at the apical third of the root section. Random allocation of samples was performed into four groups based on the post space disinfection (n = 10 each): Group 1: 1% RFP and 17% EDTA, group 2: 5.25% sodium hypochlorite (NaOCl) and 17% EDTA (control), group 3: PIPS and 17% EDTA, and group 4: ECYL and 17% EDTA. GFP was luted using Rely X Unicem. A universal testing machine and stereomicroscope were used to assess the push-out bond strength (PBS) and failure mode, respectively. Analysis of variance determined the PBS amid different experimental groups at three root levels. Multiple group comparison using means of tested groups was identified using post hoc Tukey. Results: The coronal third of group 2 (5.25% NaOCl +17% EDTA) demonstrated the highest PBS (8.83 ± 0.11 MPa). However, the lowest bond integrity (4.15 ± 0.52 MPa) was displayed in an apical third of group 1 (RFP +17% EDTA). The intergroup comparison revealed that 5.25% NaOCl +17% EDTA at all three levels demonstrated comparable outcomes of PBS with PIPS +17% EDTA and ECYL +17% EDTA specimens (p > 0.05). However, riboflavin +17% EDTA demonstrated the lowest bond strength (p < 0.05). Conclusions: Er,Cr: YSGG and PIPS in combination with 17% EDTA demonstrated comparable outcomes of bond score with those of conventional gold standard irrigation regime 5.25% NaOCl.

Antimicrobial photodynamic therapy against oral biofilm: influencing factors, mechanisms, and combined actions with other strategies

Oral biofilms are a prominent cause of a wide variety of oral infectious diseases which are still considered as growing public health problems worldwide. Oral biofilms harbor specific virulence factors that would aggravate the infectious process and present resistance to some traditional therapies. Antimicrobial photodynamic therapy (aPDT) has been proposed as a potential approach to eliminate oral biofilms via in situ-generated reactive oxygen species. Although numerous types of research have investigated the effectiveness of aPDT, few review articles have listed the antimicrobial mechanisms of aPDT on oral biofilms and new methods to improve the efficiency of aPDT. The review aims to summarize the virulence factors of oral biofilms, the progress of aPDT in various oral biofilm elimination, the mechanism mediated by aPDT, and combinatorial approaches of aPDT with other traditional agents.

Analysis of Temperatures Generated during Conventional Laser Irradiation of Root Canals-A Finite Element Study

The success of endodontic treatment is dependent on the removal of bacteria. A modern strategy to reduce bacterial load is laser irradiation. During this procedure, there is a local increase in temperature with possible side effects. The aim of this study was to determine the thermal behavior of a maxillary first molar when performing the conventional irradiation technique using a diode laser. For this study, a 3D virtual model of a maxillary first molar was created. The preparation of the access cavity, the rotary instrumentation of the palatal root canal and the laser irradiation protocol were simulated. The model was exported in a finite element analysis program where the temperature and heat flux were studied. Temperature and heat flux maps were obtained, and the temperature increase on the internal wall of the root canal was analyzed. The maximum temperature value exceeded 400 °C and was maintained for less than 0.5 s. The obtained temperature maps support the bactericidal effect of diode laser and the limitation of damage to surrounding tissues. On internal root walls, the temperature reached several hundred degrees Celsius, but for very short durations. Conventional laser irradiation is an adjuvant method of decontamination of the endodontic system.

Evaluation of the Photoactivation Effect of 3% Hydrogen Peroxide in the Disinfection of Dental Implants: In Vitro Study

Photoactivation of 3% hydrogen peroxide with a 445 nm diode laser represents a relatively new, insufficiently researched antimicrobial method in the treatment of peri-implantitis. The purpose of this work is to evaluate the effect of photoactivation of 3% hydrogen peroxide with a 445 nm diode laser, and to compare the obtained results with 0.2% chlorhexidine treatment and 3% hydrogen peroxide treatment without photoactivation, in vitro, on the surface of dental implants contaminated with S. aureus and C. albicans biofilms. Previously, 80 infected titanium implants with S. aureus and C. albicans cultures were divided into four groups: G1-negative control (no treatment), G2-positive control (0.2% chlorhexidine), G3 (3% hydrogen peroxide), and G4 (photoactivated 3% hydrogen peroxide). The number of viable microbes in each sample was determined by the colony forming unit (CFU) count. The results were statistically processed and analyzed, showing a statistically significant difference across all groups compared to the negative control (G1), and the absence of a statistically significant difference between groups G1-G3. The new antimicrobial treatment, according to the results, could be worthy of further analysis and research.

Disinfection of polyvinyl siloxane impression material using ozone gas, 0.1% riboflavin, glutaraldehyde, and microwave irradiation and their effect on physical properties

AIM

To assess the antimicrobial effect of ozone gas (OG) 0.1% riboflavin (RF), glutaraldehyde (GaH), and microwave irradiation (MI) on Polyvinyl siloxane impression material formerly colonized with E. coli, P. Aeruginosa, E. faecalis, and S.aureus and their effect on the physical properties MATERIAL AND METHODS: One hundred disk-shaped specimens (diameter 10 mm and thickness 3 mm) were developed by using polyvinylsiloxane impression material and inoculated by the American Type Culture Collection (ATCC) of E. coli, P. aeruginosa, E. faecalis, and S.aureus in an in-vitro setup. The samples were arbitrarily isolated into five groups and subjected for 3 min to the designated disinfection modality. Group 1 Control, group 2: GaH, group 3: 0.1% RF, group 4: MI, and group 5 OG. Following decontamination, the physical properties (contact angle, strain-in-compression, and tear strength) of impression materials were evaluated. Statistical analysis for CFU/mL (log10) for exposed E. coli, P. aeruginosa, E. faecalis, and S.aureus was performed by using analysis of variance (ANOVA) and Tukey's multiple comparison tests at a p-value of less than 0.05.

RESULTS

The most effective antimicrobial efficacy for impression disinfection against all scrutinized microbial colonies were displayed by group 5 OG and the lowest disinfection effectiveness was unveiled by the control group with no treatment. The intragroup comparison revealed that impression disinfection with GaH, MI, and ozone corroborated analogous antimicrobial efficacy(p > 0.05). The disinfecting capacity of the impression material with 0.1% RF was significantly less than MI, GaH, and OG (p < 0.05).

CONCLUSION

Disinfection of polyvinyl siloxane impression material with ozone gas, microwave irradiation, and glutaraldehyde demonstrated reasonable antimicrobial efficiencies against E. coli, P. aeruginosa, E. faecalis, and S.aureus with no detrimental effects on the physical properties of impression material. More studies are advocated to extrapolate the findings of the present study.

A Novel Technique for Disinfection Treatment of Contaminated Dental Implant Surface Using 0.1% Riboflavin and 445 nm Diode Laser—An In Vitro Study

Background: Antimicrobial photodynamic therapy (PDT) has been introduced as a potential option for peri-implantitis treatment. The aim of this study is to evaluate the antimicrobial effect of a novel technique involving a combination of 445 nm diode laser light with 0.1% riboflavin solution (used as a photosensitizing dye) as applied on a bacterial–fungal biofilm formed on implants and to compare the performance of this technique with that of the commonly used combination of 660 nm diode laser with 0.1% methylene blue dye. Methods: An in vitro study was conducted on 80 titanium dental implants contaminated with Staphylococcus aureus (SA) and Candida albicans (CA) species. The implants were randomly divided into four groups: negative control (NC), without surface treatment; positive control (PC), treated with a 0.2% chlorhexidine (CHX)-based solution; PDT1, 660 nm (EasyTip 320 µm, 200 mW, Q power = 100 mW, 124.34 W/cm2, 1240 J/cm2) with a 0.1% methylene blue dye; and PDT2, 445 nm (EasyTip 320 µm, 200 mW, Q power = 100 mW, 100 Hz, 124.34 W/cm2, 1.24 J/cm2) with a 0.1% riboflavin dye. Results: The PDT1 and PDT2 groups showed greater reduction of SA and CA in comparison to the NC group and no significant differences in comparison to the PC group. No statistically significant differences between the PDT1 and PDT2 groups were observed. Conclusions: A novel antimicrobial treatment involving a combination of 445 nm diode laser light with riboflavin solution showed efficiency in reducing SA and CA biofilm formation on dental implant surfaces comparable to those of the more commonly used PDT treatment consisting of 660 nm diode laser light with methylene blue dye or 0.2% CHX treatment.

Power Output of Two Semiconductor Lasers: An Observational Study

The objective of this study was to evaluate the power output of two dental devices. The study examined two semiconductor lasers, namely, SIROLaser Blue (445 nm, 970 nm) and Picasso (810 nm). The power output performance was studied at the maximum output power of the devices. The study compared the preset power output measured by a power meter in a continuous-wave mode and in pulsed mode at 50% duty cycles. Ten 60 s measurements were performed for each setting. The largest difference between the stipulated and the actual output power at continuous-wave (D-cw) and pulsed (D-p) modes was calculated. Moreover, the percentage variations in the mean output power at continuous-wave (%D-cw) and pulsed (%D-p) modes were calculated. The D-cw values for 445 nm, 970 nm, and 810 nm lasers were 0.7 W, 0.5 W, and −0.3 W, respectively, and %D-cw values were 21%, 23%, and −8%, respectively. The D-p values for 445 nm, 970 nm, and 810 nm lasers were 1.1 W, 0.5 W, and −0.1 W, respectively, whereas the %D-p values were 37%, 26%, and −3%, respectively. This study found that the actual power is not necessarily lower but can be higher than the displayed power output. Clinicians are recommended to calibrate the laser output by using a power meter before use.

Antibacterial Effects of the Novel Blue Laser and Erbium Chromium Laser on Enterococcus Faecalis in Root Canal Dentin with Different Thicknesses

The aim of this study was to investigate the antibacterial effects of 445 nm blue diode lasers and erbium chromium lasers on the biofilm of Enterococcus faecalis in root canal dentin with different thicknesses. Dentin slices with thicknesses of 300, 500, and 1,000 microns were prepared; and after the biofilm formation, they were randomly divided into four groups: group A : Er, Cr:YSGG laser radiation; group B: 445 nm diode laser radiation; group C : laser radiation in three cycles; and control group D: 5 samples of each thickness were selected as a positive control group. Er, Cr:YSGG and diode lasers alone did not significantly reduce the number of bacteria in any of the thicknesses. Only in 1 mm thick sections, the group exposed with the both Er, Cr:YSGG laser and 445 nm diode laser (66%) significantly reduced the number of bacteria. There was a significant difference in a thickness of 0.3 mm compared to a thickness of 1 mm, indicating that these lasers had a better effect at a thickness of 0.3 mm than at 1 mm parts (P-value < 0.008). It seems that these lasers can be used as an adjunct to conventional chemical methods in cleaning infected canals.

Impact of Adjunctive Laser Irradiation on the Bacterial Load of Dental Root Canals: A Randomized Controlled Clinical Trial

Successful root canal treatment depends on the adequate elimination of pathogenic bacteria. This study evaluated the effectiveness of a novel 445-nm semiconductor laser in reducing bacteria after chemomechanical root canal treatment. Microbiological specimens from 57 patients were collected after emergency endodontic treatment, in the following sequence: 1, removal of the temporary filling material; 2, chemomechanical treatment; 3, rinsing with sodium hypochlorite (3%) along with one of three adjuvant protocols (n = 19 in each group). The adjuvant procedures were: (a) sodium hypochlorite rinsing alone (3%); (b) laser irradiation; (c) combined sodium hypochlorite rinsing and laser irradiation. The diode laser was set to 0.59 W in continuous-wave mode (CW) for 4 × 10 s. After the flooding of the root canal with saline, specimens were collected using paper points and analyzed microbiologically. Statistically significant reductions in the bacterial load were observed in all three groups (p < 0.05): 80.5% with sodium hypochlorite rinsing alone and 58.2% with laser therapy. Both results were lower than with the combination of sodium hypochlorite rinsing and 445-nm laser irradiation, at 92.7% (p < 0.05). Additional disinfection of the root canal can thus be achieved with 445-nm laser irradiation after conventional chemical disinfection with sodium hypochlorite solution.

Antimicrobial action of photodynamic therapy on Enterococcus faecalis biofilm using curing light, curcumin and riboflavin

The aim of this study was to assess the effect of antimicrobial photodynamic therapy (aPDT) with curcumin and riboflavin on three-week Enterococcus faecalis biofilm. At first the 15-mm root canals of 65 single rooted extracted human teeth (including maxillary incisors, mandibular and maxillary canines and mandibular premolars) were separated from the crown and were prepared with ProTaper instruments. After autoclave sterilisation, samples were inoculated with E. faecalis suspension, and incubated for three weeks. After ensuring biofilm formation by scanning electron microscopy (SEM) in two teeth, the remaining 63 teeth were randomly divided into seven groups (n = 9): aPDT + curcumin, aPDT + riboflavin, LED, curcumin, riboflavin, 5.25% NaOCl (positive control) and no intervention (negative control). For light source a LED unit with 390-480 nm wavelength (peak of 460 nm), power density of 1000 ± 100 mW cm^-2 and mean energy density of 60 J cm^-2 was used. The roots were horizontally sectioned into coronal, middle and apical thirds each with 5 mm thicknesses. Dentin chips with equal weight (1 ± 0.005 g) were collected from the root canal walls with Gates Glidden drills and were transferred into microtubes containing 1 mL of sterile saline and vortexed for 30 s. Next, 10 µL of the contents of each tube was serially diluted and eventually, 10 µL of each solution was cultured on BHI agar. The number of colony-forming units was determined. Data were analysed using the Kruskal-Wallis and Friedman tests. The colony reduction was not significantly different between NaOCl and either riboflavin + LED or Curcumin + LED. The 5.25% NaOCl group showed maximum reduction in colony count, compared with the negative control (P = 0.00). Groups with aPDT with Curcumin + LED (P = 0.005), and with riboflavin + LED (P = 0.011) showed significant reduction in colony count in all three canal thirds (P < 0.05) without any difference with one another. With significant reduction of E. faecalis colony count, aPDT with Curcumin and riboflavin can serve as an adjunct to routine root canal disinfection method.

Photodynamic antimicrobial chemotherapy (PACT) using riboflavin inhibits the mono and dual species biofilm produced by antibiotic resistant Staphylococcus aureus and Escherichia coli

PURPOSE

Multispecies biofilms play a significant role in persistent infections. Furthermore, by interspecies transfer of antibiotic resistance genes, multispecies biofilms spread antibiotic resistance. The purpose of this study was to investigate the effect of Photodynamic Antimicrobial Chemotherapy (PACT) using riboflavin on mono and multi species biofilms.

METHODS

For this we used two clinically relevant opportunistic pathogens species E. coli and S. aureus as mono-species and multispecies biofilms. We did broth dilution assay for antibacterial, crystal violet assay for biofilms and fluorometric study for reactive oxygen species (ROS) and extracellular polymeric substance (EPS) production by phenol-HCl method.

RESULTS

Antibacterial study revealed that photo-illuminated riboflavin shows bactericidal effect against each bacteria and their mix culture. E. coli was found to be little more resistant than S. aureus. Crystal violet assay revealed photo-illuminated riboflavin shows anti-biofilms activity against both mono and mix species biofilms. But mix species biofilms were more resistant to PACT than mono species biofilms. Further study revealed this may be due to the interaction between different EPS production, hence in mix species biofilms EPS production is less affected after PACT than mono species biofilms. We found photo-illuminated riboflavin increased the intracellular ROS production.

CONCLUSION

Photo-illuminated riboflavin shows bactericidal and anti-biofilms effect against each bacteria and their mix culture. Photo-illuminated increased intracellular ROS production, which may induce the oxidative stress and destroy the respiratory system of bacteria.

Biofilm Inactivation using Photodynamic Therapy in Dentistry: a review of literature

Introduction: Photodynamic therapy (PDT) is a therapy involving light and a photosensitising chemical substance, used in conjunction with molecular oxygen in order to elicit cell death (photo-toxicity) and thus ability to kill microbial cells, including bacteria, fungi and viruses. Photodynamic therapy is an alternative method of biofilm disruption and it is considered a new way of microorganism inactivation. It is also an additional procedure to reduce the infection rate in patients, caused by the increasing antimicrobials resistance of bacteria. The aim of this literature review was to evaluate the specific effects and the antibacterial effectiveness of photodynamic therapy using different types of photosensitizers (Erythrosine, Rose Bengal, Toluidine blue, Methylene blue, Ozone, Riboflavin, Curcumin, Chlorhexidine, SAPYR) and a visible light of a specific wavelength for each photosensitizer and to reveal the applications of PDT in periodontics, endodontics, prosthodontics and dental caries. Methods: A research of literature was performed in an attempt to find all the articles published on this topic in the last 10 years. The articles was searched by using a certain combination of different keywords (photodynamic therapy ) and (diode laser ) and (teeth) in PubMed database. Results: A total number of 83 articles were found. After applying inclusion and exclusion criteria, 35 articles were taken into consideration for our study and among them 4 were a manuscript, 3 was a review of literature, 1 was an in vivo evaluation and 27 were in vitro studies. Conclusion: Considering that none of the disinfection methods can completely remove the biofilm, PDT is a therapeutic tool complementary to conventional disinfection, with great applicability in dentistry. PDT showed significantly efficacy in reduction of biofilms. Exposure to light in the presence of a photosensitizing chemical substance helps in the reduction of microbes and the protocols could be recommended for clinical usage, but only together with ‘classic ‘ disinfection.

The effect of laser-activated bleaching with 445 nm and 915 nm diode lasers on enamel micro-hardness; an in vitro study

BACKGROUND

The appearance of the teeth is of great importance to patients, particularly tooth color. In recent years, tooth whitening has been one of the most popular ways to restore tooth color. Bleaching gels can be affected by heat, light or laser, which can improve its effects. This study intends to examine the effects of two different wavelengths of diode laser (445 & 915 nm) after the bleaching process, on the enamel micro-hardness.

METHODS

A total of 65 caries-free humans third molars were randomly divided into five groups (N = 13): first group: bleaching gel activated with 915 nm diode laser (1.5 W), second: bleaching gel activated with 915-nm (2.5 W), third: bleaching gel activated with 445-nm (1 W), fourth: bleaching gel activated with 445-nm (1.5 W), fifth (control group): bleaching gel without laser activation. Micro-hardness test (Vickers test) was performed before and after the treatment. The data were submitted to repeated measurement ANOVA and Tukey's HSD post hoc test (α = 0.05).

RESULTS

Enamel micro-hardness did not change significantly in groups 3 and 4 but decreased in groups 1 and 2. Group 2 showed the most reduction in micro-hardness. There were no significant changes in the control group.

CONCLUSION

According to the results of this study, 445 nm Diode laser did not reduce enamel micro-hardness, making it suitable for bleaching treatments. However, more studies are required to consider other factors, such as color changes and pulp temperature.