In-vitro effects of novel periodontal scalers with a planar ultrasonic piezoelectric transducer on periodontal biofilm removal, dentine surface roughness, and periodontal ligament fibroblasts adhesion.

OBJECTIVES: To compare ultrasonic scaler prototypes based on a planar piezoelectric transducer with different working frequencies featuring a titanium (Ti-20, Ti-28, and Ti-40) or stainless steel (SS-28) instrument, with a commercially available scaler (com-29) in terms of biofilm removal and reformation, dentine surface roughness and adhesion of periodontal fibroblasts. MATERIALS AND METHODS: A periodontal multi-species biofilm was formed on specimens with dentine slices. Thereafter specimens were instrumented with scalers in a periodontal pocket model or left untreated (control). The remaining biofilms were quantified and allowed to reform on instrumented dentine slices. In addition, fibroblasts were seeded for attachment evaluation after 72 h of incubation. Dentine surface roughness was analyzed before and after instrumentation. RESULTS: All tested instruments reduced the colony-forming unit (cfu) counts by about 3 to 4 log10 and the biofilm quantity (each p < 0.01 vs. control), but with no statistically significant difference between the instrumented groups. After 24-hour biofilm reformation, no differences in cfu counts were observed between any groups, but the biofilm quantity was about 50% in all instrumented groups compared to the control. The attachment of fibroblasts on instrumented dentine was significantly higher than on untreated dentine (p < 0.05), with the exception of Ti-20. The dentine surface roughness was not affected by any instrumentation. CONCLUSIONS: The planar piezoelectric scaler prototypes are able to efficiently remove biofilm without dentine surface alterations, regardless of the operating frequency or instrument material. CLINICAL RELEVANCE: Ultrasonic scalers based on a planar piezoelectric transducer might be an alternative to currently available ultrasonic scalers.

Reduction of microorganisms in carious dentin by photodynamic therapy mediated by potassium iodide added to methylene blue and red laser.

OBJECTIVE: To evaluate the effect of the association of potassium iodide to antimicrobial photodynamic therapy on human carious dentin produced with a microcosm biofilm model. METHODS: A microcosm biofilm model was used to generate a caries lesion on human dentin. Pooled human saliva diluted with glycerol was used as an inoculum on specimens immersed on McBain artificial saliva enriched with 1 % sucrose (24 h at 37 °C in 5 % CO2). After refreshing culture media for 7 days, the dentin specimens were divided in 5 groups (3 specimens per group, in triplicate; n = 9): C (NaCl 0.9 %), CX (2 % chlorhexidine), PKI (0.01 % methylene blue photosensitizer+50 mM KI), L (laser at 15 J, 180 s, 22.7 J/cm2), and PKIL (methylene blue + KI + Laser). After the treatments, dentin was collected, and a 10-fold serial dilution was performed. The number of total microorganisms, total lactobacilli, total streptococci, and Streptococcus mutans was analyzed by microbial counts (CFU/mL). After normality and homoscedasticity analysis, the Welch's ANOVA and Dunnett's tests were used for CFU. All tests used a 5 % significance level. RESULTS: CX and PKIL groups showed significant bacterial decontamination of dentin, compared to group C (p < 0.05) reaching reductions up to 3.8 log10 for CX for all microorganisms' groups and PKIL showed 0.93, 1.30, 1.45, and 1.22 log10 for total microorganisms, total lactobacilli, total streptococci, and S. mutans, respectively. CONCLUSION: aPDT mediated by the association of KI and methylene blue with red laser reduced the viability of microorganisms from carious dentin and could be a promising option for cavity decontamination.

Assessment of multispecies biofilm growth on root canal dentin under different radiation therapy regimens.

OBJECTIVES: To assess the growth of a multispecies biofilm on root canal dentin under different radiotherapy regimens. MATERIALS AND METHODS: Sixty-three human root dentin cylinders were distributed into six groups. In three groups, no biofilm was formed (n = 3): NoRT) non-irradiated dentin; RT55) 55 Gy; and RT70) 70 Gy. In the other three groups (n = 18), a 21-day multispecies biofilm (Enterococcus faecalis, Streptococcus mutans, and Candida albicans) was formed in the canal: NoRT + Bio) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. The biofilm was quantified (CFUs/mL). Biofilm microstructure was assessed under SEM. Microbial penetration into dentinal tubules was assessed under CLSM. For the biofilm biomass and dentin microhardness pre- and after biofilm growth assessments, 45 bovine dentin specimens were distributed into three groups (n = 15): NoRT) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. RESULTS: Irradiated specimens (70 Gy) had higher quantity of microorganisms than non-irradiated (p = .010). There was gradual increase in biofilm biomass from non-irradiated to 55 Gy and 70 Gy (p < .001). Irradiated specimens had greater reduction in microhardness after biofilm growth. Irradiated dentin led to the growth of a more complex and irregular biofilm. There was microbial penetration into the dentinal tubules, regardless of the radiation regimen. CONCLUSION: Radiotherapy increased the number of microorganisms and biofilm biomass and reduced dentin microhardness. Microbial penetration into dentinal tubules was noticeable. CLINICAL RELEVANCE: Cumulative and potentially irreversible side effects of radiotherapy affect biofilm growth on root dentin. These changes could compromise the success of endodontic treatment in oncological patients undergoing head and neck radiotherapy.

Antimicrobial action, cytotoxicity and erosive potential of hypochlorous acid obtained from an electrolytic device compared with sodium hypochlorite.

OBJECTIVES: This study aimed to compare the antimicrobial action, cytotoxicity, cleaning ability, and erosion of dentine of hypochlorous acid (HClO) obtained from an electrolytic device at two different concentrations (Dentaqua) and three concentrations of sodium hypochlorite (NaOCl). METHODS: Microbiological test-The root canals of sixty single-rooted extracted human teeth were inoculated with Enterococcus faecalis and divided into 6 groups (n = 10), according to decontamination protocol: DW (control); 1% NaOCl; 2.5% NaOCl; 5.25% NaOCl; 250 ppm HClO and 500 ppm HClO. The colony-forming units were counted to evaluate the decontamination potential of each group, calculating the reduction in bacterial percentage. Cytotoxicity test-Cytotoxicity was evaluated after inoculation of the same tested protocols in fibroblastic cells for 3 min, calculating the cell viability percentages. Specifical statistical analysis was performed (α = 5%). Cleaning ability and erosion-Fifty-six single-rooted bovine lower incisors were divided into seven groups of 8 roots each, being the test groups 1% NaOCl; 2.5% NaOCl; 5,25% NaOCl; 250 ppm HClO and 500 ppm HClO, and a negative and positive control. Negative control was not contaminated, and the other groups were inoculated with Enterococcus faecalis. SEM images were ranked as from the cleanest to the least clean. Erosion was also assessed, being ranked from the least to the most eroded dentine. RESULTS: The highest bacterial reduction was observed in experimental groups, with no statistical differences between them (p > 0.05). The highest number of viable cells was observed in control group, followed by 250 ppm HClO and 500 ppm HClO groups, with statistical differences between them (p < 0.05). 1% NaOCl; 2.5% NaOCl; 5.25% NaOCl and 500 ppm HClO displayed the cleanest areas. All sodium hypochlorite groups displayed erosion with higher ranks with greater concentration, while hypochlorous acid did not display any erosion regardless the concentration. CONCLUSIONS: It is possible to conclude that HClO obtained from an electrolytic device presented high antimicrobial activity and low cytotoxicity in both tested concentrations. 500 ppm HClO did not display erosion and showed great cleaning ability. CLINICAL RELEVANCE: The use of 500 ppm hypochlorous acid may reduce unfavorable behavior of sodium hypochlorite whilst maintaining its antimicrobial action.

Lipopeptide biosurfactant as a potential root canal irrigation agent: Antimicrobial and anti-biofilm evaluation.

OBJECTIVES: Lipopeptide Biosurfactant (LB) is a bacteria derived compound able to reduce surface tension between water and hydrophobic substances and exhibit antimicrobial and anti-biofilm properties. This study aimed to investigate the antimicrobial and anti-biofilm effect of a Lipopeptide Biosurfactant (LB) on Enterococcus faecalis, and its potential use in root canal treatment, either as a standalone irrigation solution or in conjunction with sodium hypochlorite (NaOCl). METHODS: LB was extracted from Bacillus clausii isolate and the dry extract was diluted in deionized water. The antimicrobial effect of LB against planktonic E. faecalis was evaluated by determining the Minimal Inhibitory Concentration (MIC50). The anti-biofilm effect was evaluated by Minimal Biofilm Inhibitory Concentration (MBIC50) and Minimal Biofilm Eradication Concentration (MBEC50) assays on biofilm grown on dentin specimen surface. To evaluate the effectiveness of LB as a single irrigation solution and as a pre-irrigation prior to NaOCl, live and dead bacterial cells were quantified using Confocal Laser Scanning Microscopy (CLSM), and cell biomass was assessed. RESULTS: LB exhibited an MIC50 and MBIC50 of 100 ppm, with an MBEC50 of 1000 ppm, resulting in 52.94 % biofilm inhibition and 60.95 % biofilm eradication on dentin specimens. The effectiveness was concentration-dependent, at 500 ppm, LB demonstrated comparable antimicrobial efficacy to 2.5 % NaOCl. Pre-irrigation with LB resulted in lower biofilm biomass compared to NaOCl alone. CONCLUSION: Pre-irrigation with LB enhanced the antimicrobial effect when followed by NaOCl irrigation. Consequently, LB shows promise as both a standalone root canal irrigation solution and as an adjunct to NaOCl in root canal treatment. CLINICAL SIGNIFICANCE: The study highlights the potential of Lipopeptide Biosurfactant (LB) as an environmentally friendly irrigation solution for root canal treatment, demonstrating potent antimicrobial and anti-biofilm properties against Enterococcus faecalis. LB exhibits concentration-dependent efficacy comparable to 2.5 % NaOCl and can be used as a standalone irrigation solution or in conjunction with NaOCl.

Sodium hypochlorite against Enterococcus faecalis biofilm in dentinal tubules: effect of concentration, temperature, and exposure time.

This study aimed to evaluate the effectiveness of two sodium hypochlorite concentrations at different exposure times and temperatures against Enterococcus faecalis biofilms of varying ages in human dentinal tubules. Dentin blocks were infected with E. faecalis for either 3 days or 3 weeks of incubation. Subsequently, the samples were exposed to sterile water, 2%, and 5.25% sodium hypochlorite for 3 and 10 min at 20 °C and 60 °C . Viability staining and confocal laser scanning microscopy were used to assess the proportion of killed bacteria in the dentinal tubules after exposure. There are no significant differences in the efficacy of E. faecalis killing between 2% sodium hypochlorite at 60 °C for various exposure times and 5.25% sodium hypochlorite at different temperatures or exposure times (P > 0.05). When both solutions were compared at the same temperatures with a 10-min exposure time, no significant differences in the effectiveness of E. faecalis killing between 2% and 5.25% sodium hypochlorite were observed (P > 0.05). To optimize the effectiveness of sodium hypochlorite in killing E. faecalis while minimizing potential damage to root dentin and soft tissue, clinicians should prioritize increasing the temperature or exposure time of sodium hypochlorite, rather than raising its concentration.

Tracing of Microbes in Prepared Cavity Following Different Minimally Invasive Caries Removal Protocols.

AIMS: The conventional caries removal technique has been replaced with minimally invasive (MI) techniques to preserve healthy natural teeth and to provide durable dental restorations. Each of these MI caries removal protocols is reported to be favorable in dealing with different caries conditions. The current study aimed to trace the residual bacteria that may remain in a prepared cavity following a visual-tactile (VT), caries detection dye (CDD), and chemo-mechanical caries removal (CMCR) protocol. MATERIALS AND METHODS: A total of 29 extracted human molar teeth with visible caries lesions were randomly divided into three groups. The cavity preparation and caries removal of each group was accomplished following one of the MI caries removal protocols. Swab samples (one from each specimen) were taken and inoculated onto a blood agar plate and incubated for 48 hours. The growth of the bacterial colony was observed under a microscope and the specific genome of the bacteria was identified by polymerase chain reaction (PCR) test. RESULTS: The maximum number of traceable bacteria was observed following the chemo-mechanical caries removal group followed by the caries detection dye group and the least in the visual-tactile group. The PCR test revealed the presence of Streptococcus mutans in all the observed colonies; however, Streptococcus sobrinus was absent completely. The Chi-square test reveals a statistically insignificant (p = 0.646) difference among the tested groups. CONCLUSION: All of the MI caries removal protocols used in this study showed a trace of microbes in certain teeth. The cavity prepared following a visual tactile protocol showed the least amount of traceable bacteria in the prepared cavity. CLINICAL SIGNIFICANCE: Cavity that is prepared following individual MI protocol has a risk of leaving microbes in it.

Presence of host and bacterial-derived collagenolytic proteases in carious dentin: a systematic review of ex vivo studies.

Introduction and aim: The presence of host collagenases in the degradation of the protein matrix at later stages of carious dentin lesions development, as well as the potential involvement of bacterial collagenases, have been suggested but lack conclusive evidence. This study aims to conduct a systematic review to comprehensively assess the profile of host and bacterial-derived collagenolytic proteases in both root and coronal dentin carious lesions. Methods: The search was performed in eight databases and the grey literature. Studies evaluating ex vivo dentin, extracted teeth, or biofilms from natural caries lesions were included. The methodological quality of studies was assessed using the Joanna Briggs Institute tool. Synthesis of the results and the certainty of evidence were performed following the Synthesis without Meta-analysis (SWiM) checklist and GRADE approach for narrative synthesis, respectively. Results: From 935 recovered articles, 18 were included. Although the evidence was very uncertain, it was possible to suggest that 1) MMP-2, MMP-9, MMP-13, and CT-B may be increased in carious dentin when compared to sound dentin; 2) there is no difference in MMP-2 presence, while MMP-13 may be increased in root when compared to coronal carious dentin; 3) there is no difference of MMP-2 and MMP-9 expression/activity before and after cavity sealing; 4) MMP-8 may be increased in the dentin before cavity sealing compared to dentin after cavity sealing; 5) there is no difference of MMP-20 in irradiated vs. non-irradiated carious dentin. MMP-20 probably reduces in carious outer dentin when compared to carious inner dentin (moderate certainty). Genes encoding bacterial collagenolytic proteases and protein-degrading bacteria were detected in coronal and root carious lesions. Conclusion: Trends in the direction of the effect were observed for some collagenolytic proteases in carious dentin, which may represent a potential target for the development of new treatments. (Protocol register-PROSPERO: CRD42020213141).

Dentin disinfection and adhesive bond strength using modified photoactivated carbon nanoparticles.

AIMS: The present study aimed to investigate the bond integrity and disinfection efficacy of Methylene blue(MB) alone, MB-PDT (Photodynamic therapy), MB@ carbon nanoparticles (CP)-PDT, and Cr, Cr: YSGG (ECL) against lactobacilli in Caries-affected dentin (CAD) MATERIAL AND METHODS: Methods consisted of Shear bond strength (SBS), Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), methods of disinfection, and failure analysis. CAD samples were prepared and biofilm formed on the specimens randomly allocated into five groups based on disinfection. Group 1: CHX; Group 2: MB; Group 3: MB-PDT: group 4: MB@CP-PDT and group 5: ECL. After disinfection Colony forming units were measured and specimens were restored and positioned under a universal testing machine (UTM). Failure analysis was performed using a stereomicroscope. The difference in survival rate was assessed using the Kruskal-Walis test. Mean and standard deviation for bond values after different methods of disinfection was evaluated using analysis of variance (ANOVA) and Post Hoc Tukey. The significance level was p<0.05 RESULTS: Morphological analysis revealed that CPs under SEM are flat discs with edged irregular shapes. EDX analyses show a spike indicating carbon particles by more than 95%. MB@CP-PDT displayed the highest reduction in lactobacillus levels in comparison to the other disinfection methods. The highest SBS was exhibited by the CAD sample disinfected with ECL. The lowest SBS values in CAD specimens after cavity cleansing with MB alone. The predominant failure type in CAD disinfected with MB alone, ECL CHX, MB-PDT, and MB@CP-PDT was adhesive. CONCLUSION: The use of MB@CP-PDT showed high antibacterial potency against lactobacillus but demonstrated bond values similar to CHX. Use of Er, Cr: YSGG showed considerable effectiveness against lactobacillus along with the highest bond values.

Overexpression of proinflammatory cytokines in dental pulp tissue and distinct bacterial microbiota in carious teeth of Mexican Individuals.

The prevalence of dental caries in the Mexican adult population aged 20 to 85 years is around 93.3%, and 50% in Mexican children and adolescents. Worldwide, it is the most common non-communicable disease. One of the main etiological factors for dental caries is the oral microbiome and changes in its structure and function, with an expansion of pathogenic bacteria like Streptococcus mutans. The exposed dental pulp tissue triggers an innate immune response to counteract this bacterial invasion. The relation between oral dysbiosis and innate immune responses remains unclear. We aimed to understand the relationship between innate immune response and the oral microbiota by quantifying the expression of Toll-like receptors (TLRs) and proinflammatory markers (cytokines and a chemokine) in dental pulp tissue, either exposed or not to carious dentin, and to correlate this information with the oral microbiome found in healthy teeth and those with moderate caries. RNA was purified from pulp tissue, subjected to RT-qPCR and analysed with the ΔΔCt method. Supragingival dental plaque of non-carious teeth and dentin of carious teeth were subjected to 16S targeted sequencing. Principal coordinate analysis, permutational multivariate ANOVA, and linear discriminant analysis were used to assess differences between non-carious and carious teeth. Correlations were assessed with Spearman´s test and corrected for multiple comparisons using the FDR method. The relative abundance (RA) of Lactobacillus, Actinomyces, Prevotella, and Mitsuokella was increased in carious teeth; while the RA of Haemophilus and Porphyromonas decreased. Olsenella and Parascardovia were only detected in carious teeth. Significant overexpression of interleukin 1 beta (IL1 ß), IL6, and CXCL8 was detected in pulp tissue exposed to carious dentin. IL1ß correlated positively with TLR2 and Actinomyces; yet negatively with Porphyromonas. These findings suggest that immune response of pulp tissue chronically exposed to cariogenic microbiome is triggered by proinflammatory cytokines IL1ß and IL6 and the chemokine CXCL8.

A modified dentine infection model with fluorescent lipopolysaccharide and lipopolysaccharides sampling technique to compare XP-Endo finisher and passive ultrasonic irrigation.

AIM: The lipopolysaccharides-dentine-infection (LPS-dentine-infection) models and sampling techniques frequently used to evaluate LPS disinfection have limitations. In this study, a LPS-dentine-infection model was devised using fluorescent conjugate LPS. Secondly, a sampling technique using cryogenic grinding for intraradicular LPS analysis was evaluated. Thirdly, the effectiveness of the XP-endo Finisher (XP-EF) was compared with passive ultrasonic irrigation (PUI) in removing LPS from root canal system. METHODOLOGY: Sixty-nine mandibular premolars were submitted to dentine pretreatment and inoculated with fluorescent LPS conjugate (Alexa Fluor® 594). Twenty-three teeth were analysed under confocal laser scanning microscopy (CLSM) to validate this modified LPS-dentine-infection model. Forty-six teeth were randomly divided into two experimental groups: XP-EF (n = 23) and PUI (n = 23). All teeth were instrumented with XP-endo shaper (XPS; FKG Dentaire) and 2.5% NaOCl. The root canals were sampled with paper points before (s1) and after (s2) instrumentation and after supplemental treatment (s3) with XP-EF and PUI. After s3, all roots were cryogenically ground for intraradicular LPS analysis (s4). Limulus amebocyte lysate assay was used for LPS quantification. The Friedman test was used for differences in LPS among four time-points (s1, s2, s3, and s4). Dunn's test was used for pairwise testing of time-points. The significance level was set at 5% (p < .05). RESULTS: Fluorescent LPS conjugate was detected in 100% of the samples under CLSM with a penetration depth of approximately 400 µm into dentine. Chemo-mechanical preparation using XPS files significantly reduced LPS levels (p < .05). Both the XPS and PUI improved the LPS disinfection (p < .05), with no difference between them (p > .05). LPS was recovered from all samples after cryogenic grinding. The residual amount of LPS detected using the cryogenically sampling technique at s4 was approximately three times greater than with the paper-point sampling technique at s3. CONCLUSION: This study established a modified LPS-dentine-infection model using fluorescent conjugate LPS, and validated a LPS sampling technique for using cryopulverization intraradicular LPS analysis. Moreover, both the XP-EF and PUI further improved LPS disinfection from the root canals, and the innovative XP-EF was as effective as PUI.

Impact of Dentin Conditioning and Sealer Modification With Chitosan-Hydroxyapatite Nanocomplexes on the Antibacterial and Mechanical Characteristics of Root Dentin.

INTRODUCTION: This study aimed to characterize the effectiveness of dentin conditioning with bio-mineralizable chitosan-hydroxyapatite precursor (CS-HA) nanocomplexes alone or associated with tricalcium silicate sealer (TCS/CS-HA) on the mechanical property and antibiofilm efficacy in root dentin. METHODS: Flow tests were performed following ISO6876:2012 specifications. Solubility was measured. Micromorphology was assessed using scanning electron microscopy (SEM). Nanohardness/elastic modulus were also determined. Fracture resistance was determined on lower premolars that were prepared, and randomly distributed among 7 groups (n = 8/group), including the control, CS-HA dentin-conditioning, and root canal-filled groups. Similar canal preparation/distribution procedure was followed to test the antibacterial effect on Enterococcus faecalis-infected roots. Descriptive statistics was used to report SEM findings. Flowability results were analyzed using paired t test. Multiple comparisons from solubility, fracture, and antibacterial assays were assessed by one-way analysis of variance-Tukey's tests. RESULTS: TCS/CS-HA showed optimal flow and no effect on solubility after immersion for 4 weeks (P > .05). TCS/CS-HA significantly increased nanohardness and elastic modulus (210 ± 11.3 MPa, 7.9 ± 0.9 GPa) compared with TCS (44.5 ± 7.8 MPa, 2.1 ± 0.3 GPa, P < .05). SEM revealed needle-shaped mineralized structures resulting in fewer voids and a well-adapted sealer-dentin interface in the TCS/CS-HA groups. NaOCl-EDTA irrigation resulted in reduced fracture resistance (444.34 N), whereas CS-HA dentin conditioning alone (928.28 N, P < .05) and CS-HA dentin-conditioning plus CS-HA/TCS resulted in higher fracture resistance (1134.06 N, P < .05). CS-HA dentin conditioning also reduced bacteria by 2.04 log (4.50 ± 0.43) from the initial bacterial load (6.54 ± 0.07, P < .05). There was further bacterial reduction when CS-HA-conditioned root canals were filled with TCS or TCS/CS-HA (0.00 to 0.98 ± 0.57, P > .05). CONCLUSION: Dentin modification with CS-HA increased the fracture resistance of root dentin, and decreased the residual bacterial burden. TCS/CS-HA potentiated the nanomechanical and physical properties of TCS.

Assessment of dental caries lesion activity status using quantitative parameters obtained from the quantitative light-induced fluorescence method and difference of microbial distribution in primary molars.

BACKGROUND: This study aimed to assess differences in quantitative measures obtained from the quantitative light-induced fluorescence method and microbial composition of carious dentin and saliva according to the activity status of caries lesions in primary molars. METHODS: A total of 34 teeth from 34 children were evaluated in this study. The activity status of carious lesions was classified using the International Caries Classification and Management System criteria (active or inactive). Images of the carious lesions were captured using a quantitative light-induced fluorescence device for quantitative analyses. Carious dentin and saliva were collected to detect and quantify selected bacterial species (S. mutans, S. sobrinus, Lactobacillus species, F. nucleatum, P. nigrescence, P. intermedia) and C. albicans by quantitative polymerase chain reaction. Mann-Whitney U tests were performed to evaluate differences in quantitative measures from quantitative light-induced fluorescence, the microbial composition of carious dentin, and saliva according to the activity status of carious lesions. RESULTS: Red fluorescence values (∆R, ∆Rmax) from the quantitative light-induced fluorescence method were significantly higher in active lesions (∆R, p = 0.009; ∆Rmax, p = 0.014). The quantitative mean levels of Lactobacillus species (p = 0.010) in carious dentin and S. sobrinus (p = 0.017) in saliva were significantly higher in the active-lesion group. CONCLUSIONS: Quantitative measures related to red fluorescence from the quantitative light-induced fluorescence method, levels of Lactobacillus species from carious dentin, and levels of S. sobrinus from saliva were associated with caries lesion activity.

Influence of acidic pH on antimicrobial activity of different calcium silicate based-endodontic sealers.

OBJECTIVE: To investigate the antibacterial activity of calcium silicate-based sealers (CSBSs) against Enterococcus faecalis biofilm in a neutral or acidic condition. MATERIALS AND METHODS: Dentin cylinders (4 mm length) were prepared and infected with 3-week-old E. faecalis. The samples were filled with BioRoot RCS (BR), EndoSequence BC (ES), and NeoMTA Plus (NMTA) and incubated in either neutral or acidic conditions for 7 days (n=10/group). Sterile or infected samples alone were used as the positive and negative control. The root canal sealers were removed after 7 days, and the remaining bacteria on dentinal walls were determined by colony-forming units (CFUs/ml), and three samples from each group were visualized under a confocal laser scanning microscope (CLSM). The pH was also measured (n=3/group) after 4 h and 7 days of incubation at 37°C in both conditions. RESULTS: In the neutral condition, all sealers significantly decreased the log-CFU values (p<0.05), while in the acidic condition, the log-CFU reduction was less for ES and NMTA, but a higher reduction was observed in BR (p<0.05). The antibacterial activity of CSBSs was similar in neutral conditions (p>0.05), and BR showed a greater antibacterial effect than ES and NMTA in the acidic condition (p<0.05). The pH of BR, ES, and NMTA ranged from 8.2 to 8.8 in the neutral condition in the presence of dentin after 7 days. However, acidic conditions reduced the pH values to 7.8 for BR, 6.0 for ES, and 5.8 for NMTA. CONCLUSIONS: All CSBSs showed similar antibacterial activity in neutral conditions, while acidic pH had a reducing antibacterial effect on CSBSs. CLINICAL RELEVANCE: Inflammatory pH decreased the antibacterial properties of CSBSs depending on the sealer type.

Effect of high-fluoride dentifrice on root dentine and bacterial composition in a multispecies biofilm model.

The present study evaluated the effect of high-fluoride dentifrice on dentine demineralization and bacterial composition in a multispecies biofilm model in vitro. A seven-organism bacterial consortium was grown on bovine dentine discs in a high-throughput active attachment model. The biofilms were submitted twice per day to the following dentifrices treatments: 5,000 ppm F, 1,100 ppm F, with placebo as a negative control. After 5 days of biofilm growth, dentine samples were assessed by transversal microradiography, the biofilm was collected for bacterial counts and the pH of the media was determined. Lower integrated mineral loss values were observed when 5,000 ppm F-treatment was used compared to the other treatments. Overall microbiological counts decreased with increasing F-concentration as well the pH of the media throughout the experiment. The 5,000 ppm F-treatment caused a shift in microbial composition and reduced dentine demineralization in the in-vitro experimental model.

Laser-fluorescence assessment of sodium hypochlorite quenching reversal agents on human dentine.

BACKGROUND: Laser-fluorescence diagnostic technology for real-time clinical assessment of residual bacteria could help assist in determining the endpoints for root canal debridement. Sodium hypochlorite (NaOCl) can however quench fluorescence and lead to false low reading. This study aims to evaluate various antioxidant for their ability to recover quenched fluorescence in dentine treated with NaOCl. METHODS: Human dentine fluorescence was measured using 655 nm laser at baseline and again after a 2 min application of 4% NaOCl. The putative recovery agents were then applied, and the fluorescence measured after 5, 10, 20, 30 and 60 min. Recovery from quenching was also assessed using laser confocal scanning microscopy (CLSM) with a bound tetracycline fluorophore using 488 nm excitation. RESULTS: A 5 min application of vitamin E oil or buffered 2% lignocaine solution (1:80,000 adrenaline) was effective in regaining quenched fluorescence within the following 5 mins. Distilled water, sodium thiosulfate, unbuffered 2% lignocaine with 1:80000 adrenaline and phosphate buffered saline were less effective, and of equal performance. Ascorbic acid and butylated hydroxyanisole were not effective and had deleterious effects on the levels of dentine fluorescence. CLSM provided confirmation of recovery from quenched fluorescence using vitamin E oil. CONCLUSION: Based on these findings, reversal agents should be employed when assessing the fluorescence of dentine that has been exposed to NaOCl or other quenching agents.

Modified photoactivated methylene blue-incorporated quartz particles for dentin disinfection: A scanning electron microscope and spectroscopic analysis.

The aim of this study was to synthesize methylene blue-incorporated quartz particles (MB@QP) and to investigate its anti-bactericidal properties. Methylene blue was incorporated inside QP and characterized for morphology and chemical structure using scanning electron microscope (SEM) and Fourier transformed infrared spectroscopy (FTIR). Specimens were randomly divided into experimental and control groups (n = 9/groups). The dentin specimen infected with Enterococcus faecalis was treated using different treatment modalities: Control groups: treatment with 5.25% of sodium hypochlorite (NaOCl) for 60 s; MB: treatment with 1 ml MB solution and incubated for 60 s; MB-PDT (photodynamic therapy): treatment with 1 ml MB solution followed by irradiation using diode laser for 60 s; MB-QP-PDT: specimens treated with MB@QP and irradiated by the diode laser for 60s, and Er,Cr:YSGG laser alone. MB@PDT therapy showed the highest efficacy in reducing the survival rate of E. faecalis (0.49%) in comparison to control NaOCl (0.78%) and Er,Cr:YSGG laser treatment (2.17%). Encapsulating MB into QP followed by the PDT significantly improved the bactericidal capacity and significantly reduced the bacterial survival rate to 0.11% (p < .05) compared to other groups. The combination of MB incorporated into QP and PDT could be an alternative treatment modality to conventional disinfection method for eliminating bacteria from the tooth dentin. RESEARCH HIGHLIGHTS: Quartz particles are potent in delivering the photosensitizer. Photoactivated MB@QP has a higher efficacy in eliminating bacteria from tooth dentin.

Visualization of initial bacterial colonization on dentin using fluorescence activating headlight for fluorescence enhanced theragnosis.

OBJECTIVE: To evaluate accuracy of caries detection and the application-sensitivity of the new Designs for Vision's REVEAL™ utilizing a fluorescence activating headlight for excitation purpose. MATERIALS AND METHODS: REVEAL dental fluorescence loupes and headlight system were used. Occlusal enamel was removed, and mid-coronal dentine was exposed. Carious artificial lesion was created. Streptococcus mutans, Actinomyces naeslundii, and Streptococcus sanguis were used. The assessment was performed using two diagnostic methods: naked eye and Design for Vision Glasses with inter examiner blinding using two calibrated examiners. After 7 days, Raman measurements were made on dentin disc specimens with 785 nm wavelength. The bacterial counts in colony-forming units (CFU) were used to examine the growth kinetics of biofilms. The collagen fibril structure within the discs was performed using Transmission Electron Microscope. Scanning Electron Microscope was used to image samples at various magnifications. FISH was performed with specimens fixed in 4% paraformaldehyde in phosphate-buffered saline. Reproducibility was measured by Cohen kappa scores, values of which range from 0 for less than chance agreement to 1 for almost perfect agreement (p < 0.05). RESULTS: A significant kappa score of 0.706 showing significant reproducibility for the given diagnostic techniques, as all the teeth included in the study were spotted with the lesions. Most bacteria were detected using the CFU technique. The Raman bands scanned across the dentin surface at 960 cm-1 (P-O peak) are assigned to hydroxyapatite phosphate vibrations. FISH identified nearly all stained bacteria as days and time and dental hard tissue had a significant impact on the number of adherent bacteria. Scanning electron micrographs of polished cross sections of demineralized and non-demineralized specimens with perpendicular each tubule orientation (zone of demineralized dentin inset. CONCLUSION: Fluorescent enhanced theragnosis through Reveal vision glasses can ensure constant monitoring and diagnosis of caries progress . This may allow for a better clinical outcome.

The dentine-sealer interface: Modulation of antimicrobial effects by irrigation.

AIM: Assess whether sodium hypochlorite (NaOCl) or chlorhexidine (CHX) and two irrigation protocols may alter the antibacterial properties of dentine and three endodontic sealers using a novel ex vivo tooth model. METHODOLOGY: Prior to antibacterial testing, the tooth model was validated by means of scanning electron microscopy (SEM) to evaluate the separation between dentine and sealer surfaces. Root blocks prepared from extracted human roots were pre-treated with 17% EDTA + 0.9% saline and subsequently treated with 1% NaOCl (G1), 2% CHX (G2) or no irrigant (G3). Two irrigation protocols were further investigated, "1% NaOCl + 17% EDTA" (P1) and "1% NaOCl + 17% EDTA + 2% CHX" (P2). Following irrigation, the root blocks were either filled with AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS), or left empty. All groups were incubated for 1, 7 and 28 days. Direct contact tests for planktonic E. faecalis and 48 h E. faecalis biofilms were performed at the level of dentine and sealer surfaces. Statistical analysis was performed on the bacterial survival between irrigants (G1, G2 and G3) and between irrigation protocols (P1 and P2); p < .05. RESULTS: The model was considered reproducible as SEM examination of dentine samples indicated consistent separation between dentine and sealer surfaces. Irrigation with CHX (G2) and irrigation protocol P2 enhanced the antibacterial properties of dentine without sealer application as well as dentine in contact with all three sealers tested, especially against planktonic E. faecalis. G2 and P2 also improved the antibacterial effect of AH Plus surfaces for all three incubation times. No irrigation groups (G1, G2) or irrigation protocols (P1, P2) altered the antibacterial properties of BioRoot RCS surfaces against planktonic bacteria or biofilms. Only BioRoot RCS surfaces eliminated the planktonic E. faecalis in all irrigation groups (G1, G2, G3) and protocols (P1, P2) investigated whilst PCS surfaces eliminate E. faecalis in biofilms in all groups up to 7 days. CONCLUSIONS: The tooth model was reproducible. CHX improved the antibacterial activity upon both sealer and dentine surfaces. Amongst sealers, BioRoot RCS was less affected by NaOCl and CHX, and exhibited high antibacterial properties regardless the irrigation applied.

Depth of Penetration and Antimicrobial Activity of 5% and 10% Bamboo Salt, 2% Chlorhexidine Gel and Calcium Hydroxide Against Enterococcus faecalis - An In Vitro Study.

OBJECTIVE: E. faecalis is one of the most commonly found species in persistent and secondary infections associated with endodontic failure. This in vitro study aimed to evaluate the depth of penetration and antimicrobial efficacy of 5% and 10% bamboo salt (BS), 2% chlorhexidine gel (CHX) and calcium hydroxide (CH) against E. faecalis. METHODS: E. faecalis was inoculated in dentine blocks for 21 days following which the antibacterial efficacy of the experimental medicaments were quantatively assessed by harvesting the dentinal debris from depths of 200 µm and 400 µm from the block lumen on the 2nd and 7th day. The depth of penetration of the medicaments was measured using LIVE/DEAD BacLight stain under CLSM. RESULTS: Results showed that the medicaments had varying degrees of antimicrobial efficacy and depth of penetration. Among the medicaments, CHX showed the highest antimicrobial activity on both the time intervals (P<0.05), followed by 10% BS, 5% BS and the least efficacy was observed in CH group. CHX and 10% BS exhibited the highest depth of penetration, which was proximate to the penetration of E. faecalis. CONCLUSION: It can be concluded that 10% bamboo salt can serve as a viable natural antimicrobial in endodontic therapy.