The antibacterial efficacy of photon-initiated photoacoustic streaming in root canals with different diameters or tapers

Comparation of the effectiveness of conventional needle irrigation and photon-induced photoacoustic streaming with sodium hypochorite in the treatment of teeth with apical periodontitis: a randomized clinical trial

Photon-initiated photoacoustic streaming (PIPS) with an Er: YAG laser has been introduced in root canal treatment to improve irrigation and facilitate the removal of bacteria in the root canal system. This study aimed to compare the antibacterial effectiveness of two different root canal irrigation techniques, conventional needle irrigation (CNI) and PIPS, using 1% sodium hypochlorite (NaOCl), in the treatment of teeth with apical periodontitis. Sixty patients with a total of sixty teeth affected by apical periodontitis were included in this study. The teeth underwent root canal therapy, and after mechanical instrumentation, they were randomly assigned to two groups (n = 30) based on the final irrigation protocol: CNI or PIPS with 1% NaOCl. Bacterial suspensions in the root canals were evaluated using Adenosine 5'-triphosphate (ATP) assay kit after mechanical instrumentation and after final irrigation. Then, a follow-up was conducted after 7 days. The results revealed that final irrigation significantly reduced ATP values in both the CNI and PIPS groups (P < 0.001). The ATP values after final irrigation was greater in the CNI group compared to the PIPS group (P < 0.001). After a 7-day follow-up, percussion tenderness and fistula were significantly resolved in both groups (P < 0.05). A multivariate linear regression model was used to identify the factors that influence post irrigation ATP values. The analysis demonstrated that pre-operative percussion tenderness (P = 0.006), the presence of a fistula (P < 0.001) and the method used in the final irrigation (P < 0.001) had a significant impact on the ATP value after final irrigation. These results indicate that employing PIPS with 1% NaOCl as the final irrigation protocol exhibited superior antibacterial effectiveness and has the potential to enhance clinical outcomes in the treatment of teeth afflicted with apical periodontitis.

In vitro efficacy of Er:YAG laser-activated irrigation versus passive ultrasonic irrigation and sonic-powered irrigation for treating multispecies biofilms in artificial grooves and dentinal tubules: an SEM and CLSM study

BACKGROUND

Multispecies biofilms located in the anatomical intricacies of the root canal system remain the greatest challenge in root canal disinfection. The efficacy of Er:YAG laser-activated irrigation techniques for treating multispecies biofilms in these hard-to-reach areas has not been proved. The objective of this laboratory study was to evaluate the effectiveness of two Er:YAG laser-activated irrigation techniques, namely, photon-induced photoacoustic streaming (PIPS) and shock wave-enhanced emission photoacoustic streaming (SWEEPS), in treating multispecies biofilms within apical artificial grooves and dentinal tubules, in comparison with conventional needle irrigation (CNI), passive ultrasonic irrigation (PUI), and sonic-powered irrigation (EDDY). Two types of multispecies root canal biofilm models were established in combination with two assessment methods using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) with the aim to obtain more meaningful results.

METHODS

Ninety extracted human single-rooted premolars were chosen for two multispecies biofilm models. Each tooth was longitudinally split into two halves. In the first model, a deep narrow groove was created in the apical segment of the canal wall. After cultivating a mixed bacterial biofilm for 4 weeks, the split halves were reassembled and subjected to five irrigation techniques: CNI, PUI, EDD, PIPS, and SWEEPS. The residual biofilms inside and outside the groove in Model 1 were analyzed using SEM. For Model 2, the specimens were split longitudinally once more to evaluate the percentage of killed bacteria in the dentinal tubules across different canal sections (apical, middle, and coronal thirds) using CLSM. One-way analysis of variance and post hoc multiple comparisons were used to assess the antibiofilm efficacy of the 5 irrigation techniques.

RESULTS

Robust biofilm growth was observed in all negative controls after 4 weeks. In Model 1, within each group, significantly fewer bacteria remained outside the groove than inside the groove (P < 0.05). SWEEPS, PIPS and EDDY had significantly greater biofilm removal efficacy than CNI and PUI, both from the outside and inside the groove (P < 0.05). Although SWEEPS was more effective than both PIPS and EDDY at removing biofilms inside the groove (P < 0.05), there were no significant differences among these methods outside the groove (P > 0.05). In Model 2, SWEEPS and EDDY exhibited superior bacterial killing efficacy within the dentinal tubules, followed by PIPS, PUI, and CNI (P < 0.05).

CONCLUSION

Er:YAG laser-activated irrigation techniques, along with EDDY, demonstrated significant antibiofilm efficacy in apical artificial grooves and dentinal tubules, areas that are typically challenging to access.

Biofilm Removal from In Vitro Narrow Geometries Using Single and Dual Pulse Er:YAG Laser Photoacoustic Irrigation

The disinfection and removal of biofilm from titanium dental implants remains a great challenge in oral medicine. Here we present results of novel photoacoustic irrigation laser modalities for biofilm removal in model geometries mimicking the peri-implant pocket. The efficacy of single pulse (Er:YAG-SSP) and dual pulse (Er:YAG-AutoSWEEPS) photoacoustic irrigation modalities were determined for Enterococcus faecalis biofilm decontamination from titanium surfaces in narrow cylindrical and square gap geometries. The density of bacteria as well as the number of live bacteria were determined prior and after different photoacoustic treatments. Both SSP and AutoSWEEPS photoacoustic irrigation techniques removed at least 92% of biofilm bacteria during the 10 s photoacoustic treatment. The effectiveness of cleaning was better in the narrow square gap geometry compared to the cylindrical geometry. The dual pulse Er:YAG-AutoSWEEPS photoacoustic irrigation showed better results compared to SSP modality. No chemical adjuvants were needed to boost the effectiveness of the photoacoustic irrigation in the saline solution. The results imply that photoacoustic irrigation is an efficient cleaning method for debridement and decontamination in narrow geometries and should be considered as a new therapeutic option for the treatment of peri-implant diseases.

Comparable Effectiveness of Photon-Induced Photoacoustic Streaming with XP-Endo Finisher and Passive Ultrasonic Irrigation on Removing Residual Root Canal Filling Materials from Oval Canals

Objective: This study aimed to evaluate the effectiveness of photon-induced photoacoustic streaming (PIPS), XP-endo Finisher (XPF), and passive ultrasonic irrigation (PUI) for the removal of root canal filling materials from oval root canals. Background: Various adjunctive irrigation techniques following mechanical preparation have been applied to enhance removal of fillings during root canal retreatment. However, whether there is superiority of one approach over others remains controversial. Methods: Thirty extracted single-rooted teeth with oval-shaped canals were instrumented with the ProTaper Next (PTN) system and obturated with the warm vertical compaction technique. After storage at 37°C for 1 month, retreatment was performed with the PTN system up to size X4. The teeth were then randomly assigned into three groups (n = 10) that were, respectively, subjected to supplementary irrigation with different protocols: PIPS, PUI, and XPF, followed by measurement of filling material volumes using high-resolution micro-computed tomography. Results: The PTN preparation resulted in significant reductions in residual filling materials (p < 0.05), whereas PIPS, PUI, and XPF moderately improved the removal of the remnants (p > 0.05). The residual filling materials after supplementary irrigation ranged from 0.384 ± 0.181 to 0.421 ± 0.143 mm³ in oval canals. There was no significant difference in the effectiveness among the PIPS, PUI, and XPF approaches (p > 0.05). Conclusions: Mechanical preparations are useful for removing most root fillings during retreatment in oval-shaped canals. PIPS can reduce residual root-filling materials to the similar extent as PUI and XPF.

Effect of Passive Ultrasonic Irrigation, Er,Cr:YSGG Laser, and Photon-Induced Photoacoustic Streaming against Enterococcus faecalis Biofilms in the Apical Third of Root Canals

PURPOSE

This study aimed to compare the antibacterial effectiveness of passive ultrasonic irrigation (PUI), Er,Cr:YSGG laser (WTL), and photon-induced photoacoustic streaming (PIPS) using an Er:YAG laser against Enterococcus faecalis biofilms in the apical third of root canals.

METHODS

Root canals of 70 single-rooted human teeth were instrumented and infected with E. faecalis for 3 weeks to form biofilms. The samples were randomly divided into five groups as follows: (i) PUI + 3% NaOCl (n = 16); (ii) Er,Cr:YSGG laser (n = 16); (iii) PIPS + 3% NaOCl (n = 16); (iv) positive control group (n = 10); and (v) negative control group (n = 10). The bacterial content in the root canal was sampled using (a) the paper-point sampling method before (S1) and after (S2) treatment and (b) pulverising the apical 5 mm of the root. The number of bacteria recovered from each group was counted as colony-forming units (CFUs). The amount of reduction between the groups was compared with the Kruskal-Wallis test and post-test Dunn's multiple comparisons tests. The significance level was set at 5% (p < 0.05).

RESULTS

The samples from the paper-point sampling method showed that the amount of bacteria before (S1) and after treatment (S2) was significantly different between PIPS and WTL, as well as between the PUI and WTL groups. In contrast, no significant difference was found between the PIPS and PUI groups. From the pulverised samples, the results indicated no significant difference among all experimental groups in the amount of bacterial reduction in the apical 5 mm of the root.

CONCLUSIONS

PUI and PIPS showed a significantly greater reduction in bacterial content within the main root canal compared with the WTL. There was no difference among all experimental groups in the apical third of the root.

The evolution of cavitation in narrow soft-solid wedge geometry mimicking periodontal and peri-implant pockets

In periodontology and implantology, laser-induced cavitation has not yet been used to treat biofilm-related problems. In this study we have checked how soft tissue affects the evolution of cavitation in a wedge model representing periodontal and peri-implant pocket geometry. One side of the wedge model was composed of PDMS mimicking soft periodontal or peri-implant biological tissue, the other side was composed of glass mimicking hard tooth root or implant surface, which allowed observations of the cavitation dynamics with an ultrafast camera. Different laser pulse modalities, PDMS stiffness, and irrigants were tested for their effect on the evolution of cavitation in the narrow wedge geometry. The PDMS stiffness varied in a range that corresponds to severely inflamed, moderately inflamed, or healthy gingival tissue as determined by a panel of dentists. The results imply that deformation of the soft boundary has a major effect on the Er:YAG laser-induced cavitation. The softer the boundary, the less effective the cavitation. We show that in a stiffer gingival tissues model, photoacoustic energy can be guided and focused at the tip of the wedge model, where it enables generation of secondary cavitation and more effective microstreaming. The secondary cavitation was absent in severely inflamed gingival model tissue, but could be induced with a dual-pulse AutoSWEEPS laser modality. This should in principle increase cleaning efficiency in the narrow geometries such as those found in the periodontal and peri-implant pockets and may lead to more predictable treatment outcomes.

Current Applications and Future Directions of Lasers in Endodontics: A Narrative Review

The utilization of lasers has been regarded as a novel technique for the purposes of clinical use in the dental field. Recently, numerous studies have been conducted on the potential applications of laser therapy in endodontics. Moreover, due to their ablation, penetrability, and disinfection capabilities, lasers have performed well with respect to endodontic treatments, including root canal treatment, vital pulp therapy (pulp capping and pulpotomy), dentinal hypersensitivity treatment, and management of dental pain related to pulp and periradicular disease. In particular, the superiorities of laser-aided pulp therapy are emphasized through condensed clinical controlled trials, and histological studies, in this review. Moreover, the ingenious use of laser applications with respect to aiding in the acceleration of root development and the extraction of foreign matters (i.e., broken files and fiber posts) in canals has quickly become the cutting-edge trend of current research. This review offers a summary and discussion of the current literature on all the aforementioned laser applications. Moreover, the characteristics of laser devices, including erbium lasers, neodymium-doped lasers, CO2 lasers, and diode lasers, are detailed and discussed here, providing useful references for laser application in endodontics. We also focus on the different wavelengths with respect to the lasers that are applied in endodontics. High-power lasers perform well as operative instruments; in addition, low-level lasers lead to the regulation of pulp inflammation, and the promotion of pulp healing. This narrative review provides a summary of the advanced applications of lasers in conjunction with various devices in the practice of endodontics, and aims to inspire innovative perspectives on lasers in the context of the treatment of dental diseases, especially pulp diseases, in the future.

Efficacy of chitosan paste as intracanal medication against Enterococcus faecalis and Candida albicans biofilm compared with calcium hydroxide in an in vitro root canal infection model

Background

Enterococcus faecalis and Candida albicans are frequently found in persistent endodontic infection and could remain in dentinal tubules despite intracanal medication with calcium hydroxide (Ca(OH)₂), a commonly used medication. Thus, an effective and safe antimicrobial medication against such refractory infection is necessary in endodontic retreatment, so we aimed to test the efficacy of chitosan paste against these microorganisms compared with Ca(OH)₂ in root canals of extracted human teeth.

Methods

Thirty-six sterilized human root samples prepared from extracted premolars and upper maxillary incisors were infected with E. faecalis for 14 days, while 32 were infected with C. albicans for 48 h, for mature biofilm formation. The samples were assigned to 6 groups of intracanal medications: Group 1: no medication (negative control); Group 2: 20% Polyethylene glycol (PEG); Group 3: 20% Propylene glycol (PG); Group 4: Ca(OH)₂; Group 5: Chitosan + PEG; and Group 6: Chitosan + PG. After 7 days, intracanal surface dentin was harvested using Protaper next, resuspended, serially diluted and spread on Brain–Heart-Infusion agar (for E. faecalis) and Yeast Extract-Peptone-Dextrose agar (for C. albicans) for colony count. Antimicrobial efficacy was determined as percentage of remaining colony forming unit (CFUs) relative to negative control and analyzed using One-way ANOVA and post-hoc Games-Howell test. The significance level was set at 0.05.

Results

For E. faecalis, chitosan + PG had significantly higher antibacterial activity than Ca(OH)₂ (P = 0.039). Chitosan + PEG and chitosan + PG medication significantly reduced viable bacteria compared with negative control, PEG and PG (P = 0.001, 0.003, 0.024, respectively for chitosan + PEG; P = 0.002, 0.003, 0.014, respectively for chitosan + PG). For C.albicans, chitosan + PEG and chitosan + PG were not significantly different from Ca(OH)₂. However, Chitosan + PEG and chitosan + PG, but not Ca(OH)₂, showed a significantly lower level of remaining CFUs compared with negative control (P = 0.013 and 0.005, respectively).

Conclusion

Chitosan paste showed better efficacy in reducing viable E. faecalis biofilm when compared to Ca(OH)₂ after 7-day intracanal medication in this in vitro root canal model. It could also significantly reduce viable C. albicans, but was not significantly different from Ca(OH)₂.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02385-x.

Bactericidal Efficacy of Photon-Induced Photoacoustic Streaming-Erbium:Yttrium-Aluminum-Garnet Laser Combined with Irrigation Solution on Enterococcus faecalis in Curved Root Canals: An In Vitro Study

Objective: This experiment aimed to study the bactericidal effect of photon-induced photoacoustic streaming (PIPS)-erbium:yttrium-aluminum-garnet (Er:YAG) laser on Enterococcus faecalis in curved root canals. Materials and methods: Sixty-two molars with moderately curved roots (10°-20°) and 62 molars with severely curved roots (25°-40°; one root was selected in each tooth) were assigned to group A and group B, respectively. A curved root canal model with E. faecalis infection was established. Four samples were used for sterility test, and 20 samples were used for testing if the modeling was valid. The remaining 100 samples were randomly divided into 5 subgroups (A1/A2/A3/A4/A5 and B1/B2/B3/B4/B5, n = 10) and treated as follows: A1/B1: PIPS-Er:YAG laser +5.25% sodium hypochlorite (NaOCl); A2/B2: passive ultrasonic irrigation +5.25% NaOCl; A3/B3: PIPS-Er:YAG laser+normal saline (NS); A4/B4: two-hole root canal irrigator +5.25% NaOCl; A5/B5: two-hole root canal irrigator+NS. After treatment, bacterial culture counts and scanning electron microscopic (SEM) observations were carried out for each subgroup, and the bacterial clearance rate of each subgroup was calculated. SPSS 23 software package was used for statistical analysis of the data, and a single-factor analysis of variance was used to compare the subgroups. Results: The bacterial clearance rate in group A was higher than that in group B; however, in each group, A or B, there were significant differences between the subgroups (p < 0.001) except for subgroups 1 and 2 (p > 0.05). SEM revealed that the antibacterial and smear layer removal effect of root canal in subgroups 1 and 2 was better than that in subgroups 3, 4, and 5. Conclusions: PIPS-Er:YAG can significantly enhance the bactericidal effect of NaOCl on E. faecalis in moderately and severely curved root canals.