Photodynamic treatment of endodontic polymicrobial infection in vitro

We investigated the photodynamic effects of methylene blue on multispecies root canal biofilms comprising Actinomyces israelii, Fusobacterium nucleatum subspecies nucleatum, Porphyromonas gingivalis, and Prevotella intermedia in experimentally infected root canals of extracted human teeth in vitro. The 4 test microorganisms were detected in root canals by using DNA probes. Scanning electron microscopy showed the presence of biofilms in root canals before therapy. Root canal systems were incubated with methylene blue (25 microg/mL) for 10 minutes followed by exposure to red light at 665 nm with an energy fluence of 30 J/cm(2). Light was delivered from a diode laser via a 250-microm diameter polymethyl methacrylate optical fiber that uniformly distributed light over 360 degrees. Photodynamic therapy (PDT) achieved up to 80% reduction of colony-forming unit counts. We concluded that PDT can be an effective adjunct to standard endodontic antimicrobial treatment when the PDT parameters are optimized.     

Endodontic photodynamic therapy ex vivo

Introduction

The objective of this study was to evaluate the antimicrobial effects of photodynamic therapy (PDT) on infected human teeth ex vivo.

Methods

Fifty-two freshly extracted teeth with pulpal necrosis and associated periradicular radiolucencies were obtained from 34 subjects. Twenty-six teeth with 49 canals received chemomechanical debridement (CMD) with 6% NaOCl, and 26 teeth with 52 canals received CMD plus PDT. For PDT, root canal systems were incubated with methylene blue (MB) at concentration of 50 μg/mL for 5 minutes, followed by exposure to red light at 665 nm with an energy fluence of 30 J/cm². The contents of root canals were sampled by flushing the canals at baseline and after CMD alone or CMD+PDT and were serially diluted and cultured on blood agar. Survival fractions were calculated by counting colony-forming units (CFUs). Partial characterization of root canal species at baseline and after CMD alone or CMD+PDT was performed by using DNA probes to a panel of 39 endodontic species in the checkerboard assay.

Results

The Mantel-Haenszel χ² test for treatment effects demonstrated the better performance of CMD+PDT over CMD (P = .026). CMD+PDT significantly reduced the frequency of positive canals relative to CMD alone (P = .0003). After CMD+PDT, 45 of 52 canals (86.5%) had no CFUs as compared with 24 of 49 canals (49%) treated with CMD (canal flush samples). The CFU reductions were similar when teeth or canals were treated as independent entities. Post-treatment detection levels for all species were markedly lower for canals treated by CMD+PDT than they were for those treated by CMD alone. Bacterial species within dentinal tubules were detected in 17 of 22 (77.3%) and 15 of 29 (51.7%) canals in the CMD and CMD+PDT groups, respectively (P = .034).

Conclusions

Data indicate that PDT significantly reduces residual bacteria within the root canal system, and that PDT, if further enhanced by technical improvements, holds substantial promise as an adjunct to CMD.     

光动力疗法联合EDTA进行根管消毒的体外研究

目的：探究光动力疗法（photodynamictherapy，PDT）与EDTA联合应用进行根管消毒的效果。方法：选取75颗人单根管离体前磨牙建立感染根管模型，随机均分为5组，A组：PDT处理组；B组：EDTA处理组；C组：PDT联合EDTA处理组；D组：NaCIO阳性对照组；E组：生理盐水阴性对照组。各组处理前、处理后分别用纸尖在根管内取样，进行平板菌落计数。回复实验中在根管内注满无菌液体培养基，培养7d后用纸尖取样，统计检出细菌的根管个数。结果：PDT联合EDTA组杀菌率达100％，明显高于其余4组（P〈0．05）。回复实验中PDT联合EDTA组检出细菌根管数为4个，明显少于其余4组（P〈O．05）。结论：PDT联合EDTA可有效进行根管消毒，有望为临床提高根管消毒效率提供一条新途径。     

Survival of Enterococcus faecalis in root canals ex vivo

AIM: The hypotheses tested in this study were that: (i) Enterococcus faecalis can survive long-term entombment in root filled teeth without additional nutrients, (ii) initial cell density influences the survival of E. faecalis in instrumented root canals and (iii) gelatinase-production capacity influences the survival of E. faecalis in root canals. METHODOLOGY: The root canals of 150 extracted single canal teeth were instrumented to apical size 60 and divided into six groups of 25. Within each group 10 canals were inoculated with either gelatinase-producing E. faecalis OG1-S and the other 10 with its gelatinase-defective mutant E. faecalis OG1-X. Five canals per group were kept as uninoculated controls. The root canals in groups 1 and 2 were inoculated with 10(6) bacteria, incubated for 48 h at 37 degrees C then filled with gutta-percha and zinc-oxide eugenol sealer. Root canals were inoculated with 10(6), 10(5), 10(4) and 10(3) bacteria in groups 3-6, respectively, and left unfilled. All teeth were sealed coronally with glass-ionomer cement. After 6- (groups 1, 3-6) and 12-month (group 2) incubation at 37 degrees C in 100% humidity, root fragments were analysed for presence of E. faecalis, using culture, polymerase chain reaction and histological methods. RESULTS: Viable E. faecalis was recovered from all root filled teeth and from 95-100% of unfilled inoculated teeth. Initial cell density and gelatinase production did not influence the recovery of viable E. faecalis (P > 0.05; chi-square test). Enterococcus faecalis 16S rRNA gene products were present in all inoculated teeth and absent in all noninoculated controls. Dentinal tubule infection was evident under light microscopy in sections from inoculated teeth after 48-h, 6- and 12-month incubation. CONCLUSIONS: Enterococcus faecalis inoculated into root canals maintained viability for 12-months ex vivo. The clinical implications are that viable E. faecalis entombed at the time of root filling could provide a long-term nidus for subsequent infection.     

Detection of bacteria in endodontic samples by polymerase chain reaction assays and association with defined clinical signs in Italian patients

BACKGROUND/AIMS: The presence of selected bacteria (Enterococcus faecalis, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, Treponema denticola) in infected root canals was studied using polymerase chain reaction (PCR) assays, and the association of bacteria with clinical signs of endodontic disease was assessed. The null hypothesis, that no difference could be observed between clinical signs of apical periodontitis and a specific bacterial strain, was tested. METHODS: Microbial samples were obtained from 62 teeth in 54 patients with endodontic disease. For each tooth, clinical data including patient symptoms were collected. Teeth were categorized by diagnosis as having acute apical periodontitis (AAP, teeth with clinical symptoms but no periapical radiolucency, n=22), chronic apical periodontitis (CAP, teeth with radiolucency but no clinical symptoms, n=15) or exacerbated apical periodontitis (EAP, teeth with symptoms and radiolucency, n=25). Seventy-one percent of cases were primary endodontic infections, and 29% were recurrent ('secondary') endodontic infections (failing cases). PCR assays were used to detect the presence of the selected bacteria. RESULTS: T. denticola and E. faecalis were each detected in 15 of 62 samples (24%), P. gingivalis in 8 samples (13%), P. intermedia in 5 samples (8%), and T. forsythensis in 4 samples (7%). T. denticola was detected in 56% of teeth with EAP. E. faecalis was found in 60% of teeth with CAP and in 72% of teeth with secondary infection. Statistical analysis demonstrated an association of CAP and secondary endodontic infection with the presence of E. faecalis. (P<0.01). EAP was associated with the presence of T. denticola (P<0.01). CONCLUSION: T. denticola was associated with symptomatic endodontic disease in the presence of apical bone resorption. E. faecalis was associated with treatment failures. We suggest that these species may play critical roles in endodontic pathology.     

Effect of photo-activated disinfection on endodontic pathogens ex vivo

AIM: To test the hypothesis that photo-activated disinfection (PAD) has a bactericidal effect on pathogens inoculated in root canals, with emphasis on biofilm formation/destruction. METHODOLOGY: Root canals of extracted teeth (n = 38) were prepared (size 30, 0.10 taper), autoclaved, divided into three groups and two negative controls inoculated (Streptococcus anginosus, Enterococcus faecalis or Fusobacterium nucleatum) and treated (PAD, laser, dye or positive control) according to a cross-sectional design. Resultant colony-forming unit counts were associated with observations of cell structural changes using environmental scanning electron microscopy (ESEM) on inoculated dentinal surfaces (n = 22, two controls) before (1, 2 and 6 days of incubation) and after treatment with PAD. RESULTS: Treatment of root canals with PAD (15 J) caused a significant reduction of the bacterial load, resulting in a 93.8% kill of S. anginosus (P < 0.0001), a 88.4% kill of E. faecalis (P < 0.05) and a 98.5% kill of F. nucleatum (P < 0.0001), but no sterilization. Laser alone had no significant effect on the load nor did the dye without laser. The ESEM experiment showed that individual cells or monolayers were easily eliminated with PAD. But when biofilms were present (2 and 6 days for E. faecalis, 6 days for S. anginosus), bacterial eradication was substantially reduced in deep layers. CONCLUSIONS: Photo-activated disinfection is not an alternative but a possible supplement to the existing protocols for root canal disinfection as the interaction between light (diode laser) and associated dye (TBO) provides a broad-spectrum effect. Some endodontic pathogens that grow as single-species biofilms, however, are difficult to eradicate.     

Sensitivity of oral bacteria to 254 nm ultraviolet light

AIM: To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer. METHODOLOGY: The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm(-2). An experimental model was designed to produce a bacterial multilayer and to study absorption of UV light by bacteria in an outer layer and its effect on the elimination of bacteria in the inner layer. RESULTS: Direct exposure to relatively low doses of UV light (2-7 mJ cm(-2)) effectively eliminated all bacterial strains tested. Furthermore, an Enterococcus faecalis strain, partially resistant to a 24 h exposure to calcium hydroxide, was effectively eliminated within several seconds of exposure to UV light (P < 0.001). UV was absorbed by a multilayer of bacteria. When 4 bacterial cells microm(-2) were present in the light path, the UV light dose had to be increased by a factor of x10 to achieve 100% elimination of the bacteria in an inner layer. CONCLUSIONS: The application of UV light to eliminate endodontic pathogens may be possible. Nevertheless, its absorbance by outer layers of bacteria should be considered and the UV light dose adapted accordingly.     

Ex Vivo Evaluation of the Efficacy of Photodynamic Therapy in Eliminating Enterococcus faecalis from Dentinal Tubules by Confocal Laser Scanning Microscopy

IntroductionThe aim of the present study was to investigate ex vivo by confocal laser scanning microscopy the antibacterial effect of photodynamic therapy (PDT) on dentinal tubules in the apical 5 mm of human mandibular premolars contaminated with Enterococcus faecalis.MethodsThirty-four teeth were standardized to 20 mm and foraminal anatomic diameters using a #20 K-file (Dentsply Maillefer). Samples were contaminated for 21 days and divided into the following 3 experimental groups (n = 10): the PDT group (instrumented canals and PDT), the passive ultrasonic irrigation (PUI) group (instrumented canals and PUI), and the PUI-PDT group (instrumented canals, PUI, and PDT), along with a control group (n = 4) (noninstrumented canals). The canals in the experimental groups were instrumented with ProTaper Next (Dentsply Maillefer) up to X3 and rinsed with EDTA and sodium hypochlorite. The photosensitizer used was 0.01% methylene blue with a preirradiation time of 5 minutes and a diode laser with 4 J energy and a 660-nm wavelength. Cross sections were made 5 mm from the apex of all samples, which were analyzed using confocal laser scanning microscopy. The results were analyzed using the Shapiro-Wilk and Kruskal-Wallis (Dunn) tests.ResultsThere was a lower percentage of live bacteria in the PUI-PDT group, with a statistical difference compared with the control and PDT groups (P < .05). There was no statistical difference in the percentage of live bacteria between PUI-PDT and PUI (P > .05).ConclusionsIt was concluded that the PUI-PDT association was most effective in disinfecting root canals compared with the control group and PDT.     

Enterococcus faecalis affects the proliferation and differentiation of ovine osteoblast-like cells

Enterococcus faecalis (E. faecalis) is a Gram-positive bacterium, mostly recovered from root-filled teeth with persistent periapical lesions. Bacterial contamination of root canals inevitably results in interaction between E. faecalis and periapical tissues during the dynamic process of periapical inflammation. This study investigated the impact of heat-inactivated endodontic E. faecalis on the proliferation and the differentiation of ovine osteoblast-like cells, in an attempt to elucidate its putative enhanced pathogenicity mechanisms. Therefore, two different concentrations of a heat-inactivated endodontic E. faecalis isolate (2 × 10(6) or 2 × 10(8) CFU/ml) were incubated with ovine osteoblast-like cells for 7 and 14 days, respectively. Cells without antigen served as control. The effects of antigen on cell growth were evaluated by a proliferation assay (EZ4U). Furthermore, the assessment of alkaline phosphatase (ALP) activity, calcium deposition, and osteocalcin (OCN) gene expression through quantitative real-time PCR determined the degree of osteogenic cell differentiation. Scanning electron microscopy (SEM) was also performed to detect alterations in cell morphology. Interestingly, although highly concentrated E. faecalis increased cellular reproduction after 14 days, ALP activity and OCN gene expression decreased in an antigen concentration-dependent and incubation time-independent way. SEM images revealed E. faecalis adhesion on cells, a fact that might contribute to its virulence. These results suggest that E. faecalis stimulated cell multiplication, whereas it likely restrained cell differentiation of ovine osteoblast-like cells. In conclusion, the presence of E. faecalis in root canals may negatively affect periapical new bone formation, and thus, the healing of periapical lesions.     

Augmenting the antibiofilm efficacy of advanced noninvasive light activated disinfection with emulsified oxidizer and oxygen carrier

In this study, we tested the hypothesis that the inclusion of an oxidizer and oxygen carrier in the photosensitization formulation would facilitate comprehensive disinfection of matured endodontic biofilm by light-activated disinfection (LAD). Photosensitizing formulations containing methylene blue (MB) and an oxygen carrier alone (perfluorodecahydronaphthalene) (PF1) or in combination with oxidizer (H(2)O(2)) (PF2) or their emulsions formed with triton-X100 (Bio-Rad Laboratories, Hercules, CA) in different proportions (PF3 and PF4) were tested for photochemical properties and damage to the biofilm structure using confocal laser scanning microscopy. Conventional chemomechanical preparation, LAD using MB in water, and LAD using MB in emulsion (PF4) were also conducted on 10-week-old Enterococcus faecalis biofilm within root canals. MB in emulsion (PF4) was overall the most effective photosensitizer formulation for photooxidation, generation of singlet oxygen (p = 0.001), and in disinfecting biofilm bacteria. Advanced noninvasive LAD using a photosensitizer formulation containing oxidizer and oxygen carrier disrupted the biofilm matrix and facilitated comprehensive inactivation of biofilm bacteria. This modified photosensitizer formulation will have potential advantages in endodontic disinfection.     

Loop-mediated isothermal amplification method for the rapid detection of Enterococcus faecalis in infected root canals

INTRODUCTION: Enterococcus faecalis is a major pathogen in the etiology of apical periodontitis after root canal treatment. A loop-mediated isothermal amplification method, which amplifies DNA with high specificity, efficiency and rapidity under isothermal conditions using a set of four specially designed primers and a DNA polymerase with strand-displacement activity, was developed for the rapid detection of E. faecalis in clinical specimens from root canals. METHODS: Primers for detecting E. faecalis from the azoA gene were designed. The specificity of this assay was evaluated using various oral bacteria and the sensitivity was evaluated using serially diluted E. faecalis chromosomal DNA. In addition, loop-mediated isothermal amplification assays were applied to the rapid detection of E. faecalis from endodontic samples. RESULTS: The loop-mediated isothermal amplification products amplified with the primer set were specific for E. faecalis. To confirm the specificity of the amplicon, the amplified products were digested with the restriction endonuclease Sau3AI. The lower detection limit of the E. faecalis primer set without the loop primer set was 10 microg/tube for a 50-min loop-mediated isothermal amplification reaction. Using loop primers increased the detection sensitivity by several orders of magnitude. Furthermore, E. faecalis was detected with the loop-mediated isothermal amplification assay in four root canals from 18 individuals and the detection results were consistent with those of conventional polymerase chain reactions. CONCLUSION: These results indicate that the loop-mediated isothermal amplification assay is very useful for rapid detection of E. faecalis and diagnosis of endodontic infection.     

Antibiotic resistance gene transfer between Streptococcus gordonii and Enterococcus faecalis in root canals of teeth ex vivo

Multiple bacterial species coexisting in infected root canals might interact, but evidence for interspecies gene transfer is lacking. This study tested the hypothesis that horizontal exchange of antibiotic resistance can occur between different bacterial species in root canals. Transfer of the conjugative plasmid pAM81 carrying erythromycin resistance between 2 endodontic infection-associated species, Streptococcus gordonii and Enterococcus faecalis, was investigated in an ex vivo tooth model. Equal numbers of each species (one with pAM81 and the other plasmid-free) were combined in prepared root canals of sterilized teeth and incubated at 37 degrees C. At 24 and 72 hours, bidirectional interspecies antibiotic resistance gene transfer was evident in microorganisms recovered from teeth; average transfer frequencies from S. gordonii to E. faecalis were 10(-3) transconjugants per donor and from E. faecalis to S. gordonii were 10(-6) and 10(-7) transconjugants per donor at 24 and 72 hours, respectively. Microbial accumulations were observed on root canal walls with scanning electron microscopy. Horizontal genetic exchange in endodontic infections might facilitate adoption of an optimal genetic profile for survival.     

The influence of root canal sealer on extended intracanal survival of Enterococcus faecalis with and without gelatinase production ability in obturated root canals

Enterococcus faecalis can survive for extended periods in obturated root canals. In this study, the hypotheses tested were that long-term survival of E. faecalis is dependent on (1) the type of endodontic sealer and (2) the capacity for microbial gelatinase activity, a potential "virulence" trait identified previously in clinical isolates. Root canals of extracted human canines (n=95) were inoculated with either E. faecalis OG1RF or its gelatinase-negative mutant E. faecalis TX5128. After 48 hours of incubation at 37 degrees C, canals were obturated with gutta-percha and either the epoxy-resin-based AH-Plus (Dentsply, De Trey, Konstanz, Germany), the silicone-based RoekoSeal (Coltène/Whaledent, Langenau, Germany), or zinc oxide eugenol-based Roth's sealer (Root Canal Cement Type 801; Roth International Ltd, Chicago, IL). Access cavities were sealed. After 8 months of incubation at 37 degrees C, viable E. faecalis was recovered from more teeth sealed with RoekoSeal (95%) compared with AH-Plus (40%) (p=0.0004, Fisher's exact test) and Roth's sealer (45%) (p=0.0012, Fisher's exact test). In the RoekoSeal groups, viable counts of E. faecalis OG1RF were higher than E. faecalis TX5128 (p=0.03, Mann-Whitney U test) suggesting that gelatinase activity plays a role in long-term survival of E. faecalis in obturated root canals.     

Effect of endodontic procedures on enterococci, enteric bacteria and yeasts in primary endodontic infections

AIM: To detect enterococci, enteric bacteria and yeast species from the canals of teeth with primary endodontic infections before and after canal preparation and to test the antibiotic susceptibility of enterococcal strains isolated from infected root canals. METHODOLOGY: Twenty-five single-rooted teeth with pulp necrosis, intact pulp chambers and periradicular lesions were selected for study. Samples were collected from canals before and after instrumentation. Amongst isolated microorganisms from infected root canals only enterococci, enteric bacteria and yeasts were identified by biochemical tests. The in vitro antimicrobial susceptibility of isolated enterococci strains was evaluated by the Etest system. RESULTS: Microorganisms were isolated from 92% of the samples following intracoronal access, 22% were enterococci, enteric bacteria or yeast species. After biomechanical preparation, these species were no longer detected. After 7 days without intracanal dressing, 100% of the canals contained microorganisms, 52% of which were target species. However, after using paramonochlorophenol [PRP (2.0 g), Rinosoro and polyethylene glycol (400 equal parts up to 100 mL)] as an intracanal dressing for 7 days, enteric bacteria and yeasts were not detected; only enterococci were still present. All strains of enterococci were susceptible to ampicillin, but exhibited variable susceptibility to rifampin and ciprofloxacin. CONCLUSIONS: Enterococci, enteric bacteria and yeasts were present in primary endodontic infections. Enterococci, particularly Enterococcus faecalis and E. faecium were resistant to removal by root canal preparation followed by intracanal dressing.     

Bacteriophages induced from lysogenic root canal isolates of Enterococcus faecalis

Introduction:  Bacterial viruses play crucial roles in the pathogenesis of many systemic diseases. They are known to inhabit the oral cavity, both as free virions and as prophages in lysogenic bacterial strains; however, there has been no report of bacteriophages in endodontic infections. In this study, we sought to detect, isolate, and describe temperate bacteriophages harbored by Enterococcus faecalis strains isolated from endodontic infections.
Methods:  Ten E. faecalis strains were isolated from root canals of teeth undergoing retreatment following unsuccessful endodontic therapy. Mitomycin C was used to induce any prophages present in the bacterial isolates. The induced phages were purified and examined using electron microscopy. The DNA extracted from one of the phage isolates was subjected to restriction endonuclease digestion and agarose electrophoresis analysis.
Results:  Lysogeny was demonstrated in 4 of the 10 E. faecalis strains. Three of the lysogenic strains yielded phages exhibiting a Siphoviridae morphology, with long, non-contractile tails 130 nm in length, and spherical/icosahedral heads 41 nm in diameter. The virus induced from the fourth lysogenic E. faecalis strain had a contractile tail characteristic of Myoviridae. Restriction endonuclease analysis of Nsi I and Nde I DNA fragments from one of the Siphoviridae phage isolates (phage φEf11) indicated a genome size of approximately 41 kbp.
Conclusion:  This is the first report of lysogenic bacteria and their inducible viruses in infected root canals.     

Prevalence of Enterococcus faecalis at multiple oral sites in endodontic patients using culture and PCR

There are conflicting data on the occurrence of Enterococcus faecalis in the oral cavity of endodontic patients. This study investigated the prevalence of E. faecalis in multi-site oral samples (n = 136) from 41 endodontic patients using culture and polymerase chain reaction (PCR). Additionally, culturable strains were investigated for virulence traits. Overall, E. faecalis was detected in at least one tongue, oral rinse, or gingival sulcus sample in 68% of patients and in the root canals only in 5% of patients. In 21 patients from whom samples were obtained from all four sites, E. faecalis was detected in more tongue than gingival sulcus, oral rinse, and root canal samples (43, 14, 10, and 10%, respectively; p = 0.0148, chi(2)), and in proportionally greater numbers of patients with gingivitis/periodontitis compared to healthy periodontium (73% versus 20%; p = 0.03, Fisher's exact test). PCR was more sensitive than culture in detecting E. faecalis in oral samples (32% and 4%, respectively; p < 0.0001, McNemar's test). Multiple virulence traits were identified in culturable strains.     

Evaluation of photodynamic therapy using a light-emitting diode lamp against Enterococcus faecalis in extracted human teeth

Introduction

Photodynamic therapy (PDT) with high-power lasers as the light source has been proven to be effective in disinfecting root canals. The aim of this study was to evaluate the antimicrobial effect of PDT using toluidine blue O (TBO) and a low-energy light-emitting diode (LED) lamp after the conventional disinfection protocol of 6% NaOCl.

Methods

Single-rooted extracted teeth were cleaned, shaped, and sealed at the apex before incubation with Enterococcus faecalis for 2 weeks. Roots were randomly assigned to five experimental groups and three control groups. Dentin shavings were collected from the root canals of all groups with a #50/.06 rotary file, colony-forming units were determined, and the bacterial survival rate was calculated for each treatment.

Results

The bacterial survival rate of the NaOCl/TBO/light group (0.1%) was significantly lower (P < .005) than the NaOCl (0.66%) and TBO/light groups (2.9%).

Conclusions

PDT using TBO and a LED lamp has the potential to be used as an adjunctive antimicrobial procedure in conventional endodontic therapy.     

Influence of irrigation regimens on the adherence of Enterococcus faecalis to root canal dentin

Enterococcus faecalis is frequently associated with post-treatment endodontic infections. Because adherence of bacteria to a substrate is the earliest stage in biofilm formation, eliciting the factors that links adherence of this bacterium to dentin would help in understanding its association with treatment-failed root canals. This investigation aimed to study the effects of endodontic irrigants on the adherence of E. faecalis to dentin. The bacteria adherence assay was conducted by using fluorescence microscopy, and the adhesion force was measured by using atomic force microscopy. There were significant increases in adherence and adhesion force after irrigation of dentin with ethylenediaminetetraacetic acid (EDTA), whereas sodium hypochlorite (NaOCl) reduced it. With the use of chlorhexidine (CHX), the force of adhesion increased, but the adherence assay showed a reduction in the number of adhering bacteria. The irrigation regimen of EDTA, NaOCl, and CHX resulted in the least number of adhering E. faecalis cells. This study highlighted that chemicals that alter the physicochemical properties of dentin will influence the nature of adherence, adhesion force, and subsequent biofilm formation of E. faecalis to dentin.     

Bacterial examination of endodontic infections by clonal analysis in concert with denaturing high-performance liquid chromatography

BACKGROUND/AIMS: The aim of this study was to examine the diversity of bacterial species in the infected root canals of teeth associated with endodontic abscesses by cloning and sequencing techniques in concert with denaturing high-performance liquid chromatography. METHODS: Samples collected from five infected root canals were subjected to polymerase chain reaction (PCR) with universal 16S ribosomal DNA primers. Products of these PCRs were cloned and sequenced. Denaturing high-performance liquid chromatography (DHPLC) was used as a screening method to reduce the number of clones necessary for DNA sequencing. RESULTS: All samples were positive for the presence of bacteria and a range of 7-13 different bacteria were found per root canal sample. In total, 48 different oral clones were detected among the five root canal samples. Olsenella profusa was the only species present in all samples. Porphyromonas gingivalis, Dialister pneumosintes, Dialister invisus, Lachnospiraceae oral clone, Staphylococcus aureus, Pseudoramibacter alactolyticus, Peptostreptococcus micros and Enterococcus faecalis were found in two of the five samples. The majority of the taxa were present in only one sample, for example Tannerella forsythia, Shuttleworthia satelles and Filifactor alocis. Some facultative anaerobes that are frequently isolated from endodontic infections such as E. faecalis, Streptococcus anginosus and Lactobacillus spp. were also found in this study. CONCLUSION: Clonal analysis of the microflora associated with endodontic infections revealed a wide diversity of oral species.     

Photodynamic therapy: An adjunct to conventional root canal disinfection strategies

Although chemical‐based root canal disinfectants are important to reduce microbial loads and remove infected smear layer from root dentin, they have only a limited ability to eliminate biofilm bacteria, especially from root complexities. This paper explores the novel photodynamic therapy (PDT) for antimicrobial disinfection of root canals. The combination of an effective photosensitizer, the appropriate wavelength of light and ambient oxygen is the key factor in PDT. PDT uses a specific wavelength of light to activate a non‐toxic dye (photosensitizer), leading to the formation of reactive oxygen species. These reactive oxygen molecules can damage bacterial proteins, membrane lipids and nucleic acids, which promote bacterial cell death. In, addition PDT may enhance cross‐linking of collagen fibrils in the dentin matrix and thereby improving dentin stability. The concept of PDT is plausible and could foster new therapy concepts for endodontics. The available knowledge should enable and encourage steps forward into more clinical‐oriented research and development. This article discusses PDT as related to root canal disinfection, including its components, mechanism of action, reviews the current endodontic literature and also highlights the shortcomings and advancements in PDT techniques.