Advanced therapeutic options for endodontic biofilms

Development of clobetasol-loaded biodegradable nanoparticles as an endodontic intracanal medicament

AIM

The aim of current study is the development and optimization of biodegradable polymeric nanoparticles (NPs) to be used in the field of Endodontics as intracanal medication in cases of avulsed teeth with extended extra-oral time, utilizing PLGA polymers loaded with the anti-inflammatory drug clobetasol propionate (CP).

METHODOLOGY

CP-loaded nanoparticles (CP-NPs) were prepared using the solvent displacement method. CP release profile from CP-NPs was assessed for 48 h against free CP. Using extracted human teeth, the degree of infiltration inside the dentinal tubules was studied for both CP-NPs and CP. The anti-inflammatory capacity of CP-NPs was evaluated in vitro measuring their response and reaction against inflammatory cells, in particular against macrophages. The enzyme-linked immunosorbent assay (ELISA) was used to examine the cytokine release of IL-1β and TNF-α.

RESULTS

Optimized CP-NPs displayed an average size below 200 nm and a monomodal population. Additionally, spherical morphology and non-aggregation of CP-NPs were confirmed by transmission electron microscopy. Interaction studies showed that CP was encapsulated inside the NPs and no covalent bonds were formed. Moreover, CP-NPs exhibited a prolonged and steady release with only 21% of the encapsulated CP released after 48 h. Using confocal laser scanning microscopy, it was observed that CP-NPs were able to display enhanced penetration into the dentinal tubules. Neither the release of TNF-α nor IL-1β increased in CP-NPs compared to the LPS control, displaying results similar and even less than the TCP after 48 h. Moreover, IL-1β release in LPS-stimulated cells, decreased when macrophages were treated with CP-NPs.

CONCLUSIONS

In the present work, CP-NPs were prepared, optimized and characterized displaying significant increase in the degree of infiltration inside the dentinal tubules against CP and were able to significantly reduce TNF-α release. Therefore, CP-NPs constitute a promising therapy for the treatment of avulsed teeth with extended extra-oral time.

The Evaluation of Anti-Osteoclastic Activity of the Novel Calcium Hydroxide Biodegradable Nanoparticles as an Intracanal Medicament

INTRODUCTION

The aim of this study was to evaluate the anti-osteoclastic activity of calcium hydroxide-loaded poly(lactic-co-glycolic acid) nanoparticles [Ca(OH)2-loaded PLGA NPs] in comparison to calcium hydroxide nanoparticles [Ca(OH)2 NPs].

METHODS

RAW 264.7 cell lines (third-fifth passage) were cultured and incubated with soluble receptor activator of nuclear factor kappa B ligand in triplicate. Subsequently, Ca(OH)2-loaded PLGA NPs and Ca(OH)2 NPs were added for 7 days to evaluate their effects on receptor activator of nuclear factor kappa B ligand-induced osteoclast differentiation of RAW 264.7 cells by tartrate-resistant acid phosphatase activity. Additionally, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to confirm the cytotoxicity of treatments to cells.

RESULTS

Tartrate-resistant acid phosphatase staining showed a significant reduction in the osteoclast number when treated with Ca(OH)2-loaded PLGA NPs compared with Ca(OH)2 NPs (P < .01). In comparison to the control, the number of osteoclasts significantly reduced upon treatment with Ca(OH)2-loaded PLGA NPs (P < .05), but there was no significant difference in Ca(OH)2 NPs. Furthermore, osteoclast morphology in both treatment groups exhibited smaller sizes than the control group. Neither Ca(OH)2-loaded PLGA NPs nor Ca(OH)2 NPs demonstrated cytotoxic effects on RAW264.7 cells.

CONCLUSIONS

Both Ca(OH)2 NPs with and without poly(lactic-co-glycolic acid) have the ability to inhibit osteoclast differentiation. However, Ca(OH)2-loaded PLGA NPs exhibit greater potential than Ca(OH)2 NPs, making them a promising intracanal medicament for cases of root resorption.

Novel Antibacterial and Biocompatible Nanostructured Gels Based on One-step Synthesis as a Potential Disinfectant for Endodontic Infection Control

AIM

The objective of this study was to develop nanostructured gels as biocompatible intracanal disinfectants by one-step microwave radiation-assisted synthesis.

METHODS

Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) were used as a support network, and polyethylene glycol (PEG) was used as a reducing agent. The gels were characterized by measuring the swelling ratio (SR) and rheological properties and by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The antibacterial effects of each gel were evaluated against the endodontic clinical strain Enterococcus faecalis. Then, the viability of the 21-day mature multispecies bacterial biofilm was assessed using confocal microscopy in an ex vivo model, where the biofilm was exposed to the mix of nanogels. The cell proliferation, viability, and morphology of human periodontal ligament (HPDL) cells were quantified using a real-time IncuCyte® S3 Live-Cell System. Viability was measured by confocal microscopy using an ex vivo model exposing a 21-day mature multispecies bacterial biofilm to the mix of nanogels.

RESULTS

The antibacterial activity of the gels coincided with the superficial characterization and the solubility of the gel in the growth medium. Gels with higher viscosity (327.85-980.58 Pa s), higher dissolution (42-70%SR), and lower porosity (no porosity and 611.63 nm) showed excellent antibacterial activity against E. faecalis. Despite their physicochemical characteristics, CuNPs gels showed greater effectiveness against E. faecalis.These nanostructured gels with high PVA concentrations promote HPDL cells proliferation while still exerting antibacterial properties. Mix of nanogels showed an increase non-viable cells biomass from at of application.

CONCLUSIONS

The use of biocompatible polymers influences the physicochemical, bactericidal, and cytotoxic response, making these materials potential disinfectant agents against resistant bacteria with good biocompatibility and improved HPDL cells proliferation.

In vitro comparison to study the antimicrobial effect of silver nanoparticles gel and its various combinants as an intracanal medicament against Enterococcus faecalis

Background

Endodontic infections have been clearly described as biofilm-mediated infections. Bacteria and their by-products have been known to cause these infections. With the introduction of new drugs and the use of nanoparticles in recent times, there has been a significant reduction in the bacterial load in endodontic infections.

Aims and Objectives

The in vitro study focuses on checking the antibacterial efficacy of silver nanoparticles and its combination with other medicaments against the root canal pathogen - Enterococcus faecalis (E. faecalis).

Methodology

In the present study, 140 extracted human teeth were used. The teeth were sectioned, and biomechanical preparation was done. The root canals of the extracted teeth were inoculated with the culture of E. faecalis. The teeth were divided into six groups based on the intracanal medicament used: Group 1 - Silver nanocure gelGroup 2 - Silver nanocure gel + Cavisept gel (1:1)Group 3 - Silver nanocure gel + Aveu-Cal gel (1:1)Group 4 - Silver nanocure gel + Cavisept gel + Aveu-Cal gel (1:1:1)Group 5 - Positive control (specimens were inoculated with Enterococcus faecalis and left untreated to confirm the presence of infection)Group 6 - Negative control (no bacterial contamination of specimens). The colony-forming units were recorded after 48 h of incubation.

Results

The statistical analysis of the colony-forming units was done using the Kruskal-Wallis tests. Silver nanocure gel + Cavisept gel + Aveu-Cal gel (1:1:1) showed the least colony-forming units.

Conclusion

The present study is an in vitro study, in which we concluded that the combination of all the intracanal medicaments is the best for the elimination of E. faecalis biofilm from the root canal. The above findings need to be tested in vivo also.

Comparative evaluation of antimicrobial efficacy of different combinations of calcium hydroxide against Enterococcus faecalis

BACKGROUND

The study aims to compare the synergistic antibacterial efficacy of different combinations of calcium hydroxide as an intracanal medicament against E. faecalis.

MATERIAL AND METHODS

The current study included four hundred extracted human permanent mandibular premolar teeth. After complete chemo-mechanical preparation, the middle third of the root was sectioned using a rotary diamond disc and a total of 400 samples were obtained. The specimens were inoculated with E. faecalis for 21 days. After that, specimens were divided into five groups (n = 80) based on materials used for the disinfection of samples: Group I, calcium hydroxide alone; Group II, calcium hydroxide + 2% chlorhexidine gel; Group III, calcium hydroxide + 2% chitosan gel; Group IV, calcium hydroxide + 0.02% silver nanoparticle gel; Group V, calcium hydroxide + Bioactive glass S53P4. Dentin shavings from the apical third were obtained from the inner third of dentin were obtained using gates glidden no.1 to the apical depth, followed by no.2, 3, 4 and 5 analyzed for E. faecalis using the culture method. One-way analysis of variance (ANOVA) was used for data analysis, followed by post-hoc Tukey's test for multiple comparisons of means to check the difference in bacterial inhibition between the groups.

RESULTS

ANOVA results revealed a significant reduction of bacterial counts in all the groups compared (p < 0.001). Intergroup comparison showed maximum bacterial reduction (p < 0.001) with calcium hydroxide + bioactive glass S53P4 compared with other groups.

CONCLUSION

Synergistic effect of calcium hydroxide showed better bacterial reduction compared to calcium hydroxide alone. Among the combinations evaluated, calcium hydroxide with bioactive glass, found to be most effective compared to other groups.

Irrigants and irrigation activation systems in Endodontics

Root canal infections are typically polymicrobial and involve strong bacterial interactions. The goal of endodontic treatment is to remove infected content from the root canal system to allow the healing of a pre-existing periapical lesion or to prevent infection of the periradicular tissues. Instrumentation alone is not capable of touching all of the root canal walls. Therefore, the irrigation process is an essential step in the endodontic treatment. However, due to the complex anatomy of the root canal system, this cleaning is very challenging. Although syringe and needle irrigation associated with the use of chemical substances is still the most used method, it does not guarantee optimal cleaning of the root canals. As a result, not only alternative irrigating substances but also numerous activation systems - which are technologies that aim to optimize the action of irrigating substances, both chemically and physically - have been developed. This work aimed to review the characteristics of both classic and current alternatives of irrigating substances and irrigation activation systems.

Silver Nanoparticles and Their Therapeutic Applications in Endodontics: A Narrative Review

The efficient elimination of microorganisms and their byproducts from infected root canals is compromised by the limitations in conventional root canal disinfection strategies and antimicrobials. Silver nanoparticles (AgNPs) are advantageous for root canal disinfection, mainly due to their wide-spectrum anti-microbial activity. Compared to other commonly used nanoparticulate antibacterials, AgNPs have acceptable antibacterial properties and relatively low cytotoxicity. Owing to their nano-scale, AgNPs penetrate deeper into the complexities of the root canal systems and dentinal tubules, as well as enhancing the antibacterial properties of endodontic irrigants and sealers. AgNPs gradually increase the dentin hardness in endodontically treated teeth and promote antibacterial properties when used as a carrier for intracanal medication. The unique properties of AgNPs make them an ideal additive for different endodontic biomaterials. However, the possible side effects of AgNPs, such as cytotoxicity and tooth discoloration potential, merits further research.

Synchronized Microbubble Photodynamic Activation to Disinfect Minimally Prepared Root Canals

INTRODUCTION

The purpose of this study was to evaluate the antimicrobial efficacy of a novel irrigation strategy using synchronized microbubble photodynamic activation (SYMPA) in a minimally prepared single canal.

METHODS

Single-canal mandibular incisors were inoculated with Enterococcus faecalis for 3 weeks and randomly allocated to 4 groups based on the irrigation protocols: (1) control (saline), (2) conventional needle irrigation (CI), (3) ultrasonic-assisted irrigation (UI), and (4) irrigation with SYMPA. The first 3 groups were instrumented to size 25.07v (WaveOne Gold Primary; Dentsply Sirona, Johnson City, TN), and the SYMPA group was minimally prepared to size 20.07v (WaveOne Gold Small, Dentsply Sirona). The apical 5 mm was resected for microbiological assessment using the culture technique (colony-forming unit), adenosine-5'-triphosphate-based viability assay (relative luminescence units), and the percentage of live bacteria using confocal laser scanning microscopy.

RESULTS

Log colony-forming units from the UI (2.37 ± 0.66) and SYMPA (2.21 ± 0.86) groups showed a reduction compared with the control (5.16 ± 0.75) and CI (4.08 ± 1.19) groups. Relative luminescence unit reduction was significant for UI (619.08 ± 352.78) and SYMPA (415.25 ± 329.51) compared with the control (1213.2 ± 880.03) (P < .05). The percentage of live bacteria was significantly lower in the UI and SYMPA groups compared with the control and CI groups. Although higher microbial reduction was observed in SYMPA compared with UI, there was no statistical significance (P > .05).

CONCLUSION

SYMPA in minimally prepared canals showed significant antimicrobial efficacy. The novel irrigation strategy using SYMPA could be an effective disinfection strategy for minimally prepared root canals.

Antibacterial efficiency of adjuvant photodynamic therapy and high-power diode laser in the treatment of young permanent teeth with chronic periapical periodontitis. A prospective clinical study

BACKGROUND

The study aimed at determining antibacterial efficiency of adjuvant photodynamic therapy (PDT) and high-power diode laser (DL) in the treatment of chronic periapical periodontitis (CPP) in young permanent teeth.

METHODS

Forty-four young permanent teeth with CPP were randomly divided into three groups (PDT, DL and control). Each tooth underwent standard chemo-mechanical treatment, while within tested groups was additionally treated by PDT or DL. Bacterial identification and quantification were provided by MALDI-TOF spectrometry and plate counting assay, performed after accessing the canal, following chemo-mechanical preparation, and after PDT or DL procedure where applicable.

RESULTS

Thirty-nine young permanent teeth with CCP (patients age 9.77 ± 1.43) completed the study. Before the treatments, 202 isolates belonging to 13 genera/species, including Streptococcus (36), Actinomyces (34), Peptostreptococcus micros (27), Veillonella (25) and Enterococcus faecalis (22), were recovered. Chemo-mechanical treatment reduced CFU count in the all three groups (p < 0.001), but complete eradication was not observed for any of isolated species. Adjuvant PDT and DL completely eradicated isolates of 8 and 6 bacterial genera/species, resulting in complete bacterial elimination from 53.8% and 30.8% of root canals, respectively. In the rest canals, total Δlog CFUs were 4.71 and 4.58.

CONCLUSION

The results indicated that both PDT and DL could be performed as adjuvants to standard endodontic treatment of the young permanent teeth with CPP.

Nanoparticles in Endodontics Disinfection: State of the Art

Endodontic-related diseases constitute the fourth most expensive pathologies in industrialized countries. Specifically, endodontics is the part of dentistry focused on treating disorders of the dental pulp and its consequences. In order to treat these problems, especially endodontic infections, dental barriers and complex root canal anatomy should be overcome. This constitutes an unmet medical need since the rate of successful disinfection with the currently marketed drugs is around 85%. Therefore, nanoparticles constitute a suitable alternative in order to deliver active compounds effectively to the target site, increasing their therapeutic efficacy. Therefore, in the present review, an overview of dental anatomy and the barriers that should be overcome for effective disinfection will be summarized. In addition, the versatility of nanoparticles for drug delivery and their specific uses in dentistry are comprehensively discussed. Finally, the latest findings, potential applications and state of the art nanoparticles with special emphasis on biodegradable nanoparticles used for endodontic disinfection are also reviewed.

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 statistic 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 ANOVA-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±11.3MPa, 7.9±0.9GPa) compared to TCS (44.5±7.8MPa, 2.1±0.3GPa,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 (444.34N) while CS-HA dentin-conditioning alone (928.28N, p<.05) and CS-HA dentin-conditioning plus CS-HA/TCS resulted in higher fracture resistance (1134.06N, 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.

Root canal cleaning in roots with complex canals using agitated irrigation fluids

The internal topography of the root canal is complex, especially for the mesial root of the permanent first molar. In response to such challenges, enhanced irrigation protocols have been developed, using laser pulses to agitate fluids and enhance the removal of microbial deposits. The aim of this laboratory study was to assess the effectiveness of laser agitation of sodium hypochlorite in removing multispecies biofilms grown in the mesial root of the permanent first molars. The five agitation groups (N = 12 roots for each) were: 940 nm diode laser (superpulsed mode, 50 μs/pulses at 20 Hz using 20 mJ/pulse); 1064 nm Nd: YAG laser (200 μs/pulse at 20 Hz using 20 mJ/pulse); 2940 nm Er: YAG laser (50 μs/pulse at 15 Hz using a 400/14 conical tip in the SWEEPS protocol, with 20 mJ/pulse); passive ultrasonic agitation at 28 kHz (positive control); and irrigation with a 27-gauge side vented needle for 2 min per canal (negative control). Biofilm removal was assessed by confocal microscopic imaging of root slices at 1, 4 and 7 mm from the root apex. None of the tested methods were effective in completely eradicating biofilm from the most confined regions of the root canal system. The greatest challenge was cleaning the isthmus regions. There was a positive correlation between canal cleaning and isthmus cleaning, suggesting that increased effectiveness in cleaning root canal walls is associated with more effective isthmus cleaning. Wider and narrow isthmuses were cleaned better than long and narrow isthmuses.

The Products of Probiotic Bacteria Effectively Treat Persistent Enterococcus faecalis Biofilms

Objectives: Enterococcus faecalis is a Gram-positive commensal bacterium that possesses various survival and virulence factors, including the ability to compete with other microorganisms, invade dentinal tubules, and resist nutritional deprivation. E. faecalis is associated with persistent endodontic infections where biofilms formed by this bacterium in the root canal frequently resist dental therapies. Aseptic techniques, such as the inclusion of sodium hypochlorite, are the most commonly used methods to treat E. faecalis infections within the root canal system. In this work, we assess the effectiveness of probiotic strains to prevent the regrowth of E. faecalis biofilm cells treated by sodium hypochlorite irrigation. Methods: First, methods are presented that evaluate the effects of short-term exposure to sodium-hypochlorite on established E. faecalis. Next, we evaluate the effects of the secreted products of probiotic strains on biofilm cells and planktonic cells. Results: Sodium hypochlorite, the treatment conventionally used to decontaminate infected root canal systems, was extremely toxic to planktonic bacteria but did not fully eradicate biofilm cells. Furthermore, low concentrations of sodium hypochlorite induced eDNA dependent biofilms. Strikingly, conditioned medium from the probiotic bacteria Lactobacillus plantarum and Lactobacillus casei was sufficient to fully prevent the regrowth of treated biofilms while showing reduced potency towards planktonic cells. Conclusion: Sodium hypochlorite irrigations may contribute to the persistence of biofilm cells if used at concentrations lower than 3%. Probiotic strains and their products represent a new reservoir of biofilm therapies for E. faecalis infections formed in the root canal system.

Local immunomodulatory effects of intracanal medications in apical periodontitis

The immune system is an extremely complex biological network that plays a crucial role in the hemostasis of periapical tissue, pathogenesis of apical periodontitis (AP) as well as periapical tissue healing. The successful elimination of microbial infections remains a significant challenge, mostly due to the ever-growing development of antimicrobial-resistant pathogens. The bacterial endurance in the root canal system contributes to features ranging from altered post-treatment healing to exacerbation of chronic periradicular immune response, that compromise the outcome of endodontic treatment. A highly effective strategy for combating infectious diseases and the associated inflammation-mediated tissue damage is to modulate the host immune response in conjunction with antimicrobial therapy. There are several medications currently used in endodontic treatment, however, they suffer various levels of microbial resistance and do not deliver all the required characteristics to simultaneously address both intracanal bacteria and periapical inflammation. Interaction of antimicrobial agents with the immune system can impact its function, leading to immune-suppressive or immune-stimulatory effects. The group of non-conventional antimicrobial medications, such as antimicrobial peptides, propolis, and nanomaterials, are agents that provide strong antimicrobial effectiveness and concomitant immunomodulatory and/or reparative effect, without any host tissue damages. Herein, we provide an overview of local immune modulation in AP and a comprehensive review of the immunomodulatory effect of antimicrobials intracanal medications applied in endodontics with specific emphasis on the antimicrobial nanomaterial-based approaches that provide immunomodulatory potential for successful clinical deployment in endodontics.

The effect of using nanoparticles in bioactive glass on its antimicrobial properties

Objectives

This study addresses the effect of using nanoparticles (np) on the antimicrobial properties of bioactive glass (BAG) when used in intracanal medicaments against Enterococcus faecalis (E. faecalis) biofilms.

Materials and Methods

E. faecalis biofilms, grown inside 90 root canals for 21 days, were randomly divided into 4 groups according to the antimicrobial regimen followed (n = 20; BAG-np, BAG, calcium hydroxide [CaOH], and saline). After 1 week, residual live bacteria were quantified in terms of colony-forming units (CFU), while dead bacteria were assessed with a confocal laser scanning microscope.

Results

Although there was a statistically significant decrease in the mean CFU value among all groups, the nano-group performed the best. The highest percentage of dead bacteria was detected in the BAG-np group, with a significant difference from the BAG group.

Conclusions

The reduction of particle size and use of a nano-form of BAG improved the antimicrobial properties of the intracanal treatment of E. faecalis biofilms

Calcium hydroxide-loaded PLGA biodegradable nanoparticles as an intracanal medicament

AIM

To develop a formulation in which calcium hydroxide (Ca(OH)₂) was successfully loaded into poly(lactic-co-glycolic acid) (PLGA) biodegradable nanoparticles (NPs) to be used in the field of endodontics as an intracanal medicament, including NP optimization and characterization, plus drug release profile of the NPs compared with free Ca(OH)₂. Additionally, the depth and area of penetration of the NPs inside the dentinal tubules of extracted teeth were compared with those of the free Ca(OH)₂.

METHODOLOGY

Ca(OH)₂ NPs were prepared using the solvent displacement method. NPs was optimized with a central composite design to obtain a final optimized formulation. The morphology of the NPs was examined under transmission electron microscopy (TEM), and characterization was carried out using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). The drug release profile of the Ca(OH)₂ NPs and free Ca(OH)₂ was evaluated up to 48 h. Finally, the depth and area of penetration inside the dentinal tubules of extracted teeth were examined for both the Ca(OH)₂ NPs and free Ca(OH)₂ using the Mann-Whitney U test to determine any significant differences.

RESULTS

Utilizing the optimized formulation, the Ca(OH)₂ NPs had an average size below 200 nm and polydispersity index lower than 0.2, along with a highly negative zeta potential and suitable entrapment efficiency percentage. The spherical morphology of the Ca(OH)₂ NPs was confirmed using TEM. The results of the XRD, FTIR and DSC revealed no interactions and confirmed that the drug was encapsulated inside the NPs. The drug release profile of the Ca(OH)₂ NPs exhibited a prolonged steady release that remained stable up to 48 h with higher concentrations than the free Ca(OH)₂. After examination by confocal laser scanning microscopy, Ca(OH)₂ NPs had a significantly greater depth and area of penetration inside dentinal tubules compared with the free drug.

CONCLUSIONS

Ca(OH)₂-loaded PLGA NPs were successfully optimized and characterized. The NPs exhibited a prolonged drug release profile and superior penetration inside dentinal tubules of extracted teeth when compared to Ca(OH)₂ .

Antibacterial effect of silver nanoparticles mixed with calcium hydroxide or chlorhexidine on multispecies biofilms

The purpose is to evaluate the antibacterial effects of the silver nanoparticles (AgNPs) (Nanografi, METU Teknokent, Ankara, Turkey) mixed with calcium hydroxide (Ca(OH)₂) (Ultracal XS, Ultradent, St Louis, US) or chlorhexidine gel (CHX) (Gluco-Chex, Cerkamed, Stalowa Wola, Poland) against a multispecies biofilm, by confocal laser scanning microscopy (CLSM) and culture-based analysis. Dentine blocks were inoculated with Enterococcus faecalis, Streptococcus mutans, Lactobacillus acidophilus and Actinomyces naeslundii for 1 week. Infected dentine blocks were randomly divided into groups according to medication; saline solution (SS), Ca(OH)₂, Ca(OH)₂ + AgNP, 2%CHX gel and 2%CHX gel + AgNP and time of application: 1 and 7 days (all groups, n = 5). Bacterial samples were collected before and after medication to quantify the bacterial load. Biofilm elimination was quantitatively analyzed by Live/Dead BacLight Bacterial Viability staining and CLSM. The addition of AgNPs to Ca(OH)₂ increased the effectiveness of medicament in terms of bacterial reduction in both application times (1 and 7 days) (p < 0.05: ANOVA, Tukey's test) according to culture-based analysis. The CLSM images revealed that mixture of AgNP with CHX killed significantly more bacteria when compared with all other medicaments at 1- and 7-day application times (p < 0.05 and p > 0.05, respectively: Kruskal-Wallis, Dunn post hoc tests). The efficacy of Ca(OH)₂ mixed with AgNPs was superior to Ca(OH)₂ used alone in both application times (p < 0.05) according to CLSM analysis. The present study put forth the potential use of AgNPs mixed with Ca(OH)₂ or CHX on multispecies (Enterococcus faecalis, Streptococcus mutans, Lactobacillus acidophilus and Actinomyces naeslundii) biofilm in 1 and 7day application periods.

Recovery of Oral In Vitro Biofilms after Exposure to Peptides and Chlorhexidine

INTRODUCTION

This study aimed to examine the dynamic recovery of established multispecies biofilms of oral bacteria after an initial treatment by D-enantiomeric peptide DJK-5, L-enantiomeric peptide 1018, or chlorhexidine digluconate (CHX).

METHODS

Oral biofilms from 2 donors were grown on collagen-coated hydroxyapatite disks for 3 weeks and exposed to DJK-5, 1018, and 2% CHX for 3 minutes. Immediately after treatment and 1, 2, 3, 5, 7, 8, and 12 weeks after exposure, the biofilm volume and the volume ratio of dead and live bacteria in biofilms were assessed by confocal laser scanning microscopy using a live/dead viability stain. Results were examined by 1-way analysis of variance and post hoc multiple comparisons to determine significance at a P < .05 significance level.

RESULTS

DJK-5 killed almost 80% of biofilms in 3 minutes and maintained this high level of dead bacteria for 1 week. The proportion of viable bacteria in DJK-5-treated biofilms returned to the pretreatment level after 12 weeks. The biovolume of DJK-5-treated biofilm remained significantly lower than that of biofilms after CHX and no treatment throughout the 12-week follow-up period (P < .001). The proportion of dead bacteria was higher in biofilms exposed to DJK-5 than with 1018 or CHX for 8 weeks after the exposure (P < .001). The proportion of dead bacteria almost doubled to 46%-52% during the first 7 days after the 3-minute exposure to CHX and peptide 1018. The timeline of biofilm recovery was slow but similar after exposure to CHX and the 2 peptides.

CONCLUSIONS

ecovery time after exposure to DJK-5 was longer than that after exposure to 1018 and CHX. Peptide 1018 showed a delayed, continued antibacterial effect similar to that of 2% CHX against the biofilm microbes.

Antimicrobial activity and inhibition of biofilm formation in vitro and on human dentine by silver nanoparticles/carboxymethyl-cellulose composites

OBJECTIVE

To evaluate the antimicrobial activity of a silver nanoparticles/carboxymethyl-cellulose (AgNPs/CMC) composite on in vitro and dentine disc heterogeneous biofilms.

DESIGN

AgNPs/CMC composite effect on normal human gingival fibroblast cells (HGF) viability was determined by the MTT reduction assay. In addition, we evaluated the antimicrobial effect of AgNPs/CMC composite on Candida albicans, Enterococcus faecalis, and Fusobacterium nucleatum growth in vitro and heterogeneous biofilms, as well as dentine disc biofilms.

RESULTS

Quasi-spherical AgNPs/CMC composites, with a mean 22.3 nm particle-size were synthesized. They were not toxic to HGF cells at concentrations tested that were antimicrobial, however they caused significant cytotoxicity (89 %, p <  0.05) at concentrations > 15 μg/mL. In vitro, they inhibited up to 67 %, 66 %, and 96 % C. albicans, E. faecalis, and F. nucleatum growth at concentrations ranging from 1.2 μg/mL to 9.6 μg/mL, as compared with untreated control. We also demonstrated significant (p <  0.05) 58 % biofilm reduction by 4.8 μg/mL AgNPs/CMC composite on human dentine discs.

CONCLUSION

AgNPs/CMC composite showed anti biofilm activity on monocultures, heterogenous cultures, and dentine discs, resulting a potentially effective alternative to prevent and eliminate infections after endodontic treatment.

Detection, treatment and prevention of endodontic biofilm infections: what's new in 2020?

Endodontic disease, a biofilm infection of the root canal space, is a significant cause of dental morbidity worldwide. Endodontic treatment, or root canal treatment, as it is commonly known is founded on the ability to eradicate microbial biofilm infection and prevent re-infection of the highly complex root canal space. Despite many "advances" in clinical endodontics we have seen little improvement in outcomes. The aim of this critical review paper is to provide a contemporary view of endodontic microbiology and biofilm polymicrobiality, provide an understanding of the host response, and how together these impact upon clinical treatment. Ultimately, it is intended to provide insight into novel opportunities and strategies for the future diagnostics, treatment, and prevention of endodontic disease.

Efficacy and potential use of novel sustained release fillers as intracanal medicaments against Enterococcus faecalis biofilm in vitro

Background

Enterococcus faecalis is a bacterium frequently isolated after failed root canal therapy. This study analyzed the antibacterial and antibiofilm effects in vitro of sustained-release fillers (SRF) containing cetylpyridinium chloride (CPC) against vancomycin resistant E. faecalis.

Methods

First, the solidification capability was tested by introducing liquid SRF into phosphate buffered saline, followed by 30 s of vortexing. The antimicrobial effects of SRF-CPC against static monospecies biofilms were analyzed with a metabolic assay. Inhibition of biofilm formation was tested by exposing daily refreshed E. faecalis suspensions to SRF-CPC for 9 weeks. To evaluate the effects of SRF-CPC against preformed biofilms, biofilms were grown for 1, 3 and 7 days, and then treated with SRF-CPC for 24 h. Biofilm kill time was tested by applying SRF-CPC to a 3-day-old biofilm and measuring its viability at different time points. All experiments were compared to Placebo SRFs and to untreated control biofilms. Data were analyzed with two-way ANOVA followed by Tukey’s test. Results were considered significant at P < 0.05.

Results

The liquid SRF solidified within seconds and no structural changes were observed after 30 s of vortexing at maximum speed. SRF-CPC inhibited E. faecalis biofilm formation for 7 weeks and significantly reduced its viability in weeks 8 and 9. Mature biofilms grown for 1, 3 and 7 days were destructed by SRF-CPC in less than 24 h. Fifty percent of a 3-day-old biofilm was destructed in 2 h and complete destruction occurred in less than 12 h. (P < 0.05 in all cases, compared to SRII-Placebo).

Conclusions

SRF-CPC’s physical properties and long-lasting anti-biofilm effects make it a promising coadjuvant medication for endodontic therapy.

Electronic supplementary material

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Sustained-Release Fillers for Dentin Disinfection: An Ex Vivo Study

Enterococcus faecalis is the most commonly recovered species from failed root canal treatments. In this study, we tested the capability of a novel intracanal sustained-release filler (SRF) containing cetylpyridinium chloride (CPC) to disinfect dentinal tubules of segmented human tooth specimens. Human dental root specimens were infected with E. faecalis V583 for 3 weeks in a static environment. The tested intracanal medicaments were SRF-CPC and calcium hydroxide (CH). Each medicament was introduced into the canal of the dental specimen and incubated for 7 days. The bacteriological samples were taken by shaving the dentine surrounding the root canal with dental burs ranging in size from ISO 014-020. The obtained dentine powder was collected in test tubes containing phosphate-buffered saline, sonicated, and plated on agar plates. Colony-forming units were counted after 48 h of incubation. Random specimens were also examined under confocal laser scanning microscopy and scanning electron microscopy. A statistical difference was found in the bacterial counts obtained from all layers of infected dentin between the control and the SRF-CPC groups. CH reduced bacterial viability significantly only in the first layer of the infected dentin, up to 150 μm into the dentinal tubules. CLSM images showed that SRF-CPC killed most bacteria throughout the infected dentin up to 700 μm of penetration. SEM images demonstrated the adhesion ability of SRF-CPC to the dentinal wall. In conclusion, SRF-CPC is a potential intracanal medicament for disinfecting dentinal tubules.

Novel endodontic sealer with dual strategies of dimethylaminohexadecyl methacrylate and nanoparticles of silver to inhibit root canal biofilms

OBJECTIVE

Endodontic treatment failures and recontamination remain a major challenge. The objectives of this study were to: (1) develop a new root canal sealer with potent and long-lasting antibiofilm effects using dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg); (2) determine the effects of incorporating DMAHDM and NAg each alone versus in combination on biofilm-inhibition efficacy; and (3) determine the effects on sealer paste flow, film thickness and sealing ability, compared to a commercial control sealer.

METHODS

Dual-cure endodontic sealers were formulated using DMAHDM mass fractions of 0%, 2.5% and 5%, and NAg mass fractions of 0.05%, 0.1% and 0.15%. The sealing ability of the sealers was measured using linear dye penetration method. Colony-forming units (CFU), live/dead assay, and polysaccharide production of biofilms grown on sealers were determined.

RESULTS

The sealer with 5% DMAHDM and 0.15% NAg yielded a flow of (22.18 ± 0.58) which was within the range of ISO recommendations and not statistically different from AH Plus control (23.3 ± 0.84) (p > 0.05). Incorporating DMAHDM and NAg did not negatively affect the film thickness and sealing properties (p > 0.05). The sealer with 5% DMAHDM and 0.15% NAg greatly reduced polysaccharide production by the biofilms, and decreased the biofilm CFU by nearly 6 orders of magnitude, compared to AH Plus and experimental controls (p < 0.05).

SIGNIFICANCE

A therapeutic root canal sealer was developed using 5% DMAHDM with biofilm-inhibition through contact-mediated mechanisms, plus 0.15% of NAg to release silver ions into the complex and difficult-to-reach root canal environment. The novel root canal sealer exerted potent antibiofilm effects and reduced biofilm CFU by 6 orders of magnitude without compromising sealer flow, film thickness and sealing ability. This method provided a promising approach to inhibit endodontic biofilms and prevent recurrent endodontic infections.

Novel Activated Microbubbles-based Strategy to Coat Nanoparticles on Root Canal Dentin: Fluid Dynamical Characterization

INTRODUCTION

Activated microbubbles (MBs) have the potential to deliver nanoparticles in complex microspaces such as root canals. The objective of the study is to determine the fluid dynamical parameters associated with ultrasonic, sonic, and manual activation of MBs in simulated root canals and to assess the effectiveness of surface coating formed by delivering chitosan nanoparticles using activated MBs within root canals in extracted teeth.

METHODS

In stage 1, polydimethylsiloxane models were fabricated to determine the physical effects of MBs agitated manually (MM), sonically (MS), and ultrasonically (MU). Spherical tracer particles were used to visualize and record the fluid motion using an inverted microscope linked to a high-speed camera. The velocity, wall stress, and penetration depth were analyzed at regions of interest. In stage 2, 35 extracted human incisors were divided into 7 groups to evaluate the effectiveness of chitosan nanoparticle delivery using activated MBs (MM, MS, and MU groups). Field emission scanning electron microscopy and energy-dispersive X-rays were used to characterize the nanoparticle coating on root canal dentin and the degree of dentinal tubule occlusion.

RESULTS

In stage 1, velocity, wall stress, and penetration depth increased significantly in the MB groups compared with the control (P < .01). In stage 2, 70% of the dentin surface was coated, and 65% of the dentinal tubule was occluded with nanoparticle-based coating in the MM, MU, and water ultrasonic groups. Element analysis displayed the presence of dentin smear on the root canal surface for the MU and water ultrasonic groups.

CONCLUSIONS

Activated MBs enhanced fluid dynamical parameters when compared with water in simulated root canal models. Manual activation of MBs resulted in uniform and significant nanoparticle-based surface coating and tubule blockage in root canal dentin without dentin smear formation.

Synergistic Effect of Newly Introduced Root Canal Medicaments; Ozonated Olive Oil and Chitosan Nanoparticles, Against Persistent Endodontic Pathogens

This study was conducted to investigate the antimicrobial-biofilm activity of chitosan (Ch-NPs), silver nanoparticles (Ag-NPs), ozonated olive oil (O3-oil) either separately or combined together against endodontic pathogens. While testing the antimicrobial activity, Ch-NPs showed the least minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values exerting eightfold higher bactericidal activity than O3-oil against both Enterococcus faecalis and Streptococcus mutans as well as fourfold higher fungicidal activity against Candida albicans. Antimicrobial synergy test revealed synergism between O3-oil and Ch-NPs against the test pathogens (FIC index ≤ 0.5). Ch-NPs was superior at inhibiting immature single and mixed-species biofilm formations by 97 and 94%, respectively. Both of O3-oil and Ch-NPs had a complete anti-fibroblast adherent effect. The safety pattern results showed that O3-oil was the safest compound, followed by Ch-NPs. The double combination of Ch-NPs and O3-oil reduced the mature viable biofilm on premolars ex vivo model by 6-log reductions, with a fast kill rate, indicating potential use in treating root canals. Therefore, the double combination has the potential to eradicate mature mixed-species biofilms and hence it is potent, novel and safe.

Antimicrobial Photodynamic therapy enhanced by the peptide aurein 1.2

In the past few years, the World Health Organization has been warning that the post-antibiotic era is an increasingly real threat. The rising and disseminated resistance to antibiotics made mandatory the search for new drugs and/or alternative therapies that are able to eliminate resistant microorganisms and impair the development of new forms of resistance. In this context, antimicrobial photodynamic therapy (aPDT) and helical cationic antimicrobial peptides (AMP) are highlighted for the treatment of localized infections. This study aimed to combine the AMP aurein 1.2 to aPDT using Enterococcus faecalis as a model strain. Our results demonstrate that the combination of aPDT with aurein 1.2 proved to be a feasible alternative capable of completely eliminating E. faecalis employing low concentrations of both PS and AMP, in comparison with the individual therapies. Aurein 1.2 is capable of enhancing the aPDT activity whenever mediated by methylene blue or chlorin-e6, but not by curcumin, revealing a PS-dependent mechanism. The combined treatment was also effective against different strains; noteworthy, it completely eliminated a vancomycin-resistant strain of Enterococcus faecium. Our results suggest that this combined protocol must be exploited for clinical applications in localized infections as an alternative to antibiotics.

Effects of nanosilver and nanozinc incorporated mesoporous calcium-silicate nanoparticles on the mechanical properties of dentin

Mesoporous calcium-silicate nanoparticles (MCSNs) are advanced biomaterials for drug delivery and mineralization induction. They can load silver and exhibit significantly antibacterial effects. However, the effects of MCSNs and silver-loaded MCSNs on dentin are unknown. The silver (Ag) and/or zinc (Zn) incorporated MCSNs (Ag-Zn-MCSNs) were prepared by a template method, and their characterizations were tested. Then the nanoparticles were filled into root canals and their effects on the dentin were investigated. Ag-Zn-MCSNs showed characteristics of mesoporous materials and sustained release of ions over time. Ag-Zn-MCSNs adhered well to the root canal walls and infiltrated into the dentinal tubules after ultrasound activation. Ag-Zn-MCSNs showed no significantly negative effects on either the flexural strength or the modulus of elasticity of dentin, while CH decreased the flexural strength of dentin significantly (P<0.05). These findings suggested that Ag and Zn can be incorporated into MCSNs using a template method, and the Ag-Zn-MCSNs may be developed into a new disinfectant for the root canal and dentinal tubules.

The effect of sodium hypochlorite concentration and irrigation needle extension on biofilm removal from a simulated root canal model

To investigate the effect of sodium hypochlorite concentration and needle extension on removal of Enterococcus faecalis biofilm, sixty root canal models were 3D printed. Biofilms were grown on the apical 3 mm of the canal for 10 days. Irrigation for 60s with 9 mL of either 5.25% or 2.5% NaOCl or water was performed using a needle inserted either 3 or 2 mm from the canal terminus and imaged using fluorescence microscopy and residual biofilm percentages were calculated using imaging software. The data were analysed using analysis of covariance and two-sample t-tests. A significance level of 0.05 was used throughout. Residual biofilm was less using 5.25% than with 2.5% NaOCl. Statistically significant biofilm removal was evident with the needle placed closer to the canal terminus. A greater reduction of available chlorine and pH was noted as the concentration increased. One-minute irrigation was not sufficient for complete biofilm removal.

Eradication of Enterococcus faecalis Biofilms on Human Dentin

Objectives: This work assesses different methods to interfere with Enterococcus faecalis biofilms formed on human dentin slabs.

Methods: First, methods are presented that select for small molecule inhibitors of biofilm targets using multi-well polystyrene biofilm plates. Next, we establish methodologies to study and interfere with biofilm formation on a medically relevant model, whereby biofilms are grown on human root dentin slabs.

Results: Non-conventional D-amino acid (D-Leucine) can efficiently disperse biofilms formed on dentin slabs without disturbing planktonic growth. Cation chelators interfere with biofilm formation on dentin slabs and polystyrene surfaces, and modestly impact planktonic growth. Strikingly, sodium hypochlorite, the treatment conventionally used to decontaminate infected root canal systems, was extremely toxic to planktonic bacteria, but did not eradicate biofilm cells. Instead, it induced a viable but non-culturable state in biofilm cells when grown on dentin slabs.

Conclusion: Sodium hypochlorite may contribute to bacterial persistence. A combination of the methods described here can greatly contribute to the development of biofilm inhibitors and therapies to treat Enterococcus faecalis infections formed in the root canal system.

Antibiofilm efficacy of photoactivated curcumin, triple and double antibiotic paste, 2% chlorhexidine and calcium hydroxide against Enterococcus fecalis in vitro

Root canal disinfection is one of the most important factors governing success of root canal treatment, especially when regenerative strategies are used. This study evaluated the efficacy of 5 intracanal medicaments against mature biofilms of Enterococcus fecalis in vitro: Light activated curcumin, triple antibiotic paste (TAP), double antibiotic paste (DAP), chlorhexidine, calcium hydroxide. Untreated teeth with biofilms served as controls. Confocal microscopy was used to analyse the biofilm mass and percentage of live/dead bacteria within the root canal as well as dentinal tubules. Dentinal shavings obtained from the root canal walls (at 200 and 400 microns depth) were used to quantify the colony forming units/mL. The results showed that light activated curcumin and triple antibiotic paste brought about complete disruption of the biofilm structure (P < 0.05) while chlorhexidine and calcium hydroxide were not significantly different from the control (P > 0.05). Light activated curcumin brought about the highest percentage of dead cells at both depths, but this was not significantly different from triple antibiotic paste (P > 0.05). Curcumin, TAP and DAP brought about a significant reduction of CFU/mL at both depths compared to the control and other groups (P < 0.05). Light activated curcumin brought about a 7 log reduction of bacteria at both depths.

New Technologies to Improve Root Canal Disinfection

Abstract Effective irrigant delivery and agitation are prerequisites to promote root canal disinfection and debris removal and improve successful endodontic treatment. This paper presents an overview of the currently available technologies to improve the cleaning of the endodontic space and their debridement efficacy. A PubMed electronic search was conducted with appropriate key words to identify the relevant literature on this topic. After retrieving the full-text articles, all the articles were reviewed and the most appropriate were included in this review. Several different systems of mechanical activation of irrigants to improve endodontic disinfection were analysed: manual agitation with gutta-percha cones, endodontic instruments or special brushes, vibrating systems activated by low-speed hand-pieces or by sonic or subsonic energy, use of ultrasonic or laser energy to mechanically activate the irrigants and apical negative pressure irrigation systems. Furthermore, this review aims to describe systems designed to improve the intracanal bacterial decontamination by a specific chemical action, such as ozone, direct laser action or light-activated disinfection. The ultrasonic activation of root canal irrigants and of sodium hypochlorite in particular still remains the gold standard to which all other systems of mechanical agitation analyzed in this article were compared. From this overview, it is evident that the use of different irrigation systems can provide several advantages in the clinical endodontic outcome and that integration of new technologies, coupled with enhanced techniques and materials, may help everyday clinical practice.

Substantivity of Ag-Ca-Si mesoporous nanoparticles on dentin and its ability to inhibit Enterococcus faecalis

The main purpose of this study was to investigate the substantivity of Ag-Ca-Si mesoporous nanoparticles (Ag-MCSNs) on dentin and its residual antibacterial effects against Enterococcus faecalis. Ag-MCSNs were fabricated and characterized, ion release profile and pH were tested, and the ability to inhibit planktonic E. faecalis as well as the cytotoxicity was evaluated. Dentin slices were medicated with Ca(OH)2 paste, 2 % chlorhexidine gel and Ag-MCSNs paste for 7 days and then irrigated. Dentin slices were then immersed in E. faecalis suspension for 6 days and then transferred to fresh brain heart infusion solution. The optical density value within 10 h after immersing and transferring were measured and compared among groups. Results indicated that Ag-MCSNs showed high pH, sustained Ag(+)-Ca(2+)-SiO3 (2-) ion release, and high substantivity on dentin. The Ag-MCSNs exhibited strong antibacterial effects against planktonic E. faecalis and much better residual inhibition effects against E. faecalis growth on dentin than Ca(OH)2 paste (P < 0.05). The Ag-MCSNs showed excellent antibacterial ability against E. faecalis and high substantivity on dentin, which might be developed to a new effective intra-canal medicament for human teeth.

Ag-loaded mesoporous bioactive glasses against Enterococcus faecalis biofilm in root canal of human teeth

Ag-loaded mesoporous bioactive glass (Ag-MBG) powders were synthesized and characterized. The ions release of Ag-MBGs in Tris-HCl and the pH stability of simulated body fluids after immersing Ag-MBGs were tested. Root canals were inoculated with Enterococcus faecalis for 4 weeks, and the antibacterial activity of MBGs, Ag-MBGs and calcium hydroxide against E. faecalis biofilm were evaluated. Results showed that Ag-MBGs possessed highly ordered mesoporous structure with silver nanoparticles deposited in the mesopores, which enabled a sustained Ag ions released. The biofilms treated with Ag-MBGs showed a significant structural disruption compared with MBGs. These results indicated that Ag-MBGs possess a potent antibacterial effect against E.faecalis biofilm in root canal, and the antibacterial activity was induced by the release of Ag ions from Ag-MBGs.

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.

Effects of different sonic activation protocols on debridement efficacy in teeth with single-rooted canals

OBJECTIVES

The effects of different EndoActivator® (EA) sonic activation protocols on root canal debridement efficacy were examined.

METHODS

Root canals in 48 single-rooted teeth were instrumented, irrigated initially with NaOCl and divided into 6 groups (N=8) based on the application time of QMix (antimicrobial calcium-chelating irrigant), and the time and sequence of EA irrigant activation - Positive Control: 90s QMix; Negative Control: 90s saline; Group 1A: 15s QMix+15s QMix with EA-activation; Group 1B: 30s QMix+30s of QMix with EA-activation; Group 2A: 15s QMix with EA-activation+15s QMix; Group 2B: 30s QMix with EA-activation+30s QMix. Split roots were examined with scanning electron microscopy for assignment of smear and debris scores in locations along the coronal, middle and apical thirds of the canals. The overall cleanliness of pooled canal locations in the Positive Control and the 4 experimental groups were compared with chi-square tests.

RESULTS

Significant differences were detected among the 5 groups (P<0.001). Post hoc pairwise comparisons indicated that the overall canal cleanliness was in the order (from best to worst): 1B=2B>2A>1A>Positive Control. Completely clean canals could not be achieved due to the absence of continuous irrigant flow for EA to clear intraradicular debris.

CONCLUSIONS

Irrespective of the sonic activation sequence, irrigant activation for 30s during a 60-s period of QMix application appears to maximise the smear layer and debris removal potential of the EndoActivator® system.

CLINICAL SIGNIFICANCE

Sonic activation of root canal irrigants produces cleaner root canals and reduces the time required for final delivery of a canal wall smear later-removing irrigant when compared to the use of needle irrigation alone.

Antibiofilm efficacy of photosensitizer-functionalized bioactive nanoparticles on multispecies biofilm

INTRODUCTION

Newer disinfection strategies based on antibacterial nanoparticles and photodynamic therapy (PDT) aim to eliminate residual biofilm bacteria during root canal treatment. The aim of the current study was to test the newly developed rose bengal-functionalized chitosan nanoparticles (CSRBnps) for their interaction/uptake with monospecies bacteria/biofilm and assess their antibiofilm efficacy on a multispecies biofilm model in vitro.

METHODS

The interaction of CSRBnps with bacterial cells was conducted using atomic force microscopy. Their membrane-damaging effect was determined by measuring the absorbance at 260 nm (OD260nm) using Enterococcus faecalis. The penetration of CSRBnps into E. faecalis biofilms was evaluated using confocal laser scanning microscopy (CLSM). Multispecies biofilms of Streptococcus oralis, Prevotella intermedia, and Actinomyces naeslundii were grown on dentin sections for 21 days to assess the antibiofilm efficacy. The biofilms were subjected to PDT (60 J/cm(2)) using CSRBnps and rose bengal. The treated/untreated biofilms were examined under scanning electron microscopy and CLSM.

RESULTS

The CSRBnps synthesized were 60 ± 20 nm and showed absorption spectra similar to rose bengal. Atomic force microscopy showed adherence of CSRBnps to bacteria, roughening of cell surface, and cell disruption after PDT. CSRBnp treatment resulted in significantly increased bacterial membrane damage (P < .05). CSRBnps exhibited deeper penetration into the biofilm structure. Scanning electron microscopy and CLSM confirmed the complete disruption of multispecies biofilm with a reduction in viable bacteria and biofilm thickness (P < .05).

CONCLUSIONS

These novel photosensitizer functionalized bioactive nanoparticles with increased affinity to bacterial cell membrane, higher penetration into biofilm structure, and enhanced ability to eliminate clinically relevant multispecies bacterial biofilm present a potential antibiofilm agent for root canal disinfection.

Regeneration of the dentine-pulp complex with revitalization/revascularization therapy: challenges and hopes

The concept of regenerative endodontics has gained much attention in clinical endodontics in the past decade. One aspect of this discipline is the application of revitalization/revascularization therapies for infected and/or necrotic immature pulps in permanent teeth. Following the publication of a case report (Iwaya et al. ), investigators have been rigorously examining the types of tissues formed in the canals as well as exploring strategies to regenerate the pulp-dentine complex in revitalized teeth. This review will provide an update on the types of tissues generated in the canals after revitalization/revascularization therapy in both animal and human studies. The understanding of the role of stem cells and microenvironment in the process of wound healing resulting in either regeneration or repair will be thoroughly discussed. Stem cells and microenvironmental cues introduced into the canal during revitalization/revascularization procedures will be examined. In addition, requirement of a sterile microenvironment in the canal and vital tissue generation in revitalization/revascularization therapy will be emphasized. The challenges that we face and the hopes that we have in revitalization/revascularization therapy for regenerative endodontics will be presented.