Characterisation of the efficacy of endodontic medications using a three‐dimensional fluorescent tooth model: An ex vivo study

The purpose of this study was to establish a three‐dimensional fluorescent tooth model to investigate bacterial viability against intra‐canal medicaments across the thickness and surface of root dentine. Dental microbial biofilms (Enterococcus faecalis and Streptococcus mutans) were established on the external root surface and bacterial kill was monitored over time against intra‐canal medicament (Ca(OH)₂) using fluorescent microscopy in conjunction with BacLight SYTO9 and propidium iodide stains. An Olympus digital camera fitted to SZX16 fluorescent microscope captured images of bacterial cells in biofilms on the external root surface. Viability of biofilm was measured by calculating the total pixel area of green (viable bacteria) and red (non‐viable bacteria) for each image using ImageJ® software. All data generated were assessed for normality and then analysed using a Mann–Whitney t‐test. The viability of S. mutans biofilm following Ca(OH)₂ treatment showed a significant decline compared with the untreated group (P = 0.0418). No significant difference was seen for E. faecalis biofilm between the Ca(OH)₂ and untreated groups indicating Ca(OH)₂ medicament is ineffective against E. faecalis biofilm. This novel three‐dimensional fluorescent biofilm model provides a new clinically relevant tool for testing of medicaments against dental biofilms.     

Antimicrobial effectiveness of grape seed extract against Enterococcus faecalis biofilm: A Confocal Laser Scanning Microscopy analysis

This study evaluated the antimicrobial effectiveness of 6.5% Vitis vinifera grape seed extract (GSE) against Enterococcus faecalis biofilm using confocal laser scanning microscopy (CLSM). Saline solution (SS), 5.25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX) were used for comparison. Dentin discs were inoculated with E. faecalis strain establishing a 3‐week‐old biofilm. Discs (n = 10) were exposed to 5.25% NaOCl, 2% CHX, 6.5% GSE and SS (negative control) for 10 min. Discs were stained with the fluorescent LIVE/DEAD‐BacLight? dye and analysed using CLSM. The proportion of dead cells in biofilm was analysed using one‐way anova and Tukey tests (P < 0.05). A higher proportion of dead cells was found in GSE group compared with CHX and SS (P < 0.05). NaOCl group was associated with the highest proportion of dead cells (P < 0.05). GSE presented antimicrobial activity against E. faecalis; however, NaOCl was the most effective irrigant solution. GSE was more effective than CHX and SS.     

Effect of Different Final Irrigation Methods on the Removal of Calcium Hydroxide from an Artificial Standardized Groove in the Apical Third of Root Canals

Introduction

The aim of this study was to compare the efficacy of conventional syringe, ultrasonic, EndoVac (Discus Dental, Culver City, CA), and Self-Adjusting File (SAF) (Re-Dent-Nova, Ra'nana, Israel) irrigation systems in removing calcium hydroxide (Ca[OH]₂) from simulated root canal irregularities.

Methods

The root canals of 88 extracted single-rooted teeth were prepared using ProTaper rotary instruments (Dentsply Maillefer, Ballagiues, Switzerland) up to size F4. The roots were split longitudinally, and a standardized groove was prepared in the apical part of 1 segment. The root halves were reassembled, and Ca(OH)₂ medicament was placed into the root canals using a Lentulo spiral. The roots were randomly divided into 4 experimental groups and 2 control groups according to the different irrigation systems used: conventional syringe irrigation, continuous passive ultrasonic irrigation (PUI), EndoVac irrigation, and SAF irrigation. Each group was then divided into 2 subgroups (n = 10) according to the irrigation protocol: subgroup 1: 10 mL 2.5% NaOCl and subgroup 2: 10 mL 17% EDTA + 10 mL 2.5% NaOCl. The amount of remaining medicament was evaluated under a stereomicroscope at 30× magnification using a 4-grade scoring system. The influences of the different Ca(OH)₂ medicament removal methods and irrigation protocols were statistically evaluated using 2-way analysis of variance and Tukey post hoc tests.

Results

In the NaOCl-irrigated groups, PUI removed significantly more Ca(OH)₂ medicament than the other techniques (P < .05). There was no significant difference among the other groups (P > .05). In the EDTA/NaOCl-irrigated groups, the SAF and PUI removed significantly more Ca(OH)₂ than the other techniques (P < .05).

Conclusions

The use of the SAF system with the combination of EDTA and NaOCl enhanced Ca(OH)₂ removal when compared with the use of only NaOCl irrigation with the SAF. Continuous PUI and SAF were more effective than EndoVac, and conventional syringe irrigation in the removal of the Ca(OH)₂ medicament from an artificial standardized groove in the apical part of the root canal.     

The antimicrobial properties,cytotoxicity, and differentiation potential of double antibiotic intracanal medicaments loaded into hydrogel system

Objective

This study evaluated the antimicrobial properties, cytotoxicity, and mineralization potential of methylcellulose hydrogels loaded with low concentrations of double antibiotic pastes (DAP).

Materials and methods

The direct and residual antibacterial effects of 1, 5, and 10 mg/mL of DAP loaded into hydrogels as well as calcium hydroxide (Ca(OH)₂) were tested against single-species biofilms of Enterococcus faecalis and dual-species biofilms (Enterococcus faecalis and Prevotella intermedia). The effects of DAP hydrogels on proliferation and mineralization of dental pulp stem cells (DPSC) were tested using MTT assays, alkaline phosphate activity (ALP), and alizarin red staining. Fisher’s exact tests, Wilcoxon rank sum tests, and one-way ANOVA were used for statistical analyses (α = 0.05).

Results

All tested concentrations of DAP hydrogels as well as Ca(OH)₂ demonstrated significant direct antibacterial effects against single- and dual-species biofilms. However, only 5 and 10 mg/mL of DAP hydrogels exhibited significant residual antibacterial effects against both types of tested biofilms. Only 1 mg/mL of DAP hydrogels did not have significant negative effects on DPSC viability, ALP activity, and mineralization nodule formation. However, 5 and 10 mg/mL of DAP hydrogels caused significant negative effects on cytotoxicity and mineralization nodule formation of DPSC.

Conclusions

Hydrogels containing 1 mg/mL DAP offered significant direct antibacterial effects against single- and dual-species biofilms without causing significant negative effects on viability, ALP activity, and mineralization nodule formation of DPSC.

Clinical relevance

The methylcellulose-based hydrogel proposed in this study can be used clinically as a biocompatible system to deliver controlled low concentrations of DAP.

     

Combined effect of fluoride varnish to Er:YAG or Nd:YAG laser on permeability of eroded root dentine

ObjectiveThis study evaluated the combined effect of fluoride varnish to Er:YAG or Nd:YAG laser on permeability of eroded root dentine.DesignSixty slabs of bovine root dentine (2 × 2 × 2 mm) were eroded with citric acid 0.3% (pH 3.2) during 2 h and then kept in artificial saliva during 24 h. Specimens were randomly assigned in 6 groups (n = 10), to receive the following treatments: fluoride varnish; fluoride varnish + Er:YAG laser; fluoride varnish + Nd:YAG laser; non-fluoride varnish; non-fluoride varnish + Er:YAG laser; non-fluoride varnish + Nd:YAG laser. The Er:YAG (100 mJ, 3 Hz) and Nd:YAG (70 mJ, 15 Hz) were applied for 10 s. Specimens were subjected to further erosive challenges with citric acid 0.3% 4×/day, during 1 min, for 5 days, remaining in artificial saliva between cycles. Dentin permeability was then assessed. Two-way ANOVA demonstrated no significant interaction between laser and varnish (p = 0.858).ResultsNo effect was also detected for the main factor varnish (p = 0.768), while permeability of eroded root dentin was significantly lower when such substrate was laser-irradiated, no matter the laser source (p < 0.001).ConclusionsThis study concluded that Er:YAG and Nd:YAG lasers can be employed to control the permeability of eroded root dentin, regardless of fluoride varnish application.     

Role of efflux pump inhibitors on the antibiofilm efficacy of calcium hydroxide, chitosan nanoparticles, and light-activated disinfection

Introduction

The purpose of this study was to evaluate the role of efflux pumps in altering the susceptibility of Enterococcus faecalis biofilms to calcium hydroxide (Ca(OH)₂), chitosan nanoparticles, and light-activated disinfection (LAD).

Methods

E. faecalis as 4-day-old biofilms and biofilm-derived cells were tested with aqueous Ca(OH)₂ in concentrations of 25%, 50%, and 100%; chitosan nanoparticles in concentrations of 10 and 20 mg/mL (3, 12, and 24 hours); and methylene blue (MB) mediated LAD at an energy dose range of 2–40 J/cm². An efflux pump inhibitor (EPI) was incorporated into all 3 modalities of treatment. The antimicrobial activity was assessed by determining the colony-forming units.

Results

E. faecalis biofilms, in contrast to the biofilm-derived cells, were found to persist even after 24-hour treatment with different concentrations of Ca(OH)₂ and chitosan nanoparticles. LAD at an energy dose of 40 J/cm² completely inactivated 4-day-old E. faecalis biofilms. The addition of EPI improved the antibiofilm efficacy of Ca(OH)₂ at lower concentrations (P < .001) and LAD (P < .001). EPI did not influence the antibiofilm effect of chitosan nanoparticles and Ca(OH)₂ at higher concentrations.

Conclusions

E. faecalis biofilms were more susceptible to killing by LAD, when compared with the tested concentrations of Ca(OH)₂ and chitosan nanoparticles. The effect of EPI was more significant with LAD, when compared with Ca(OH)₂ and chitosan nanoparticles. This study highlighted the role of biofilm matrix in providing resistance to antimicrobials.     

Nitric oxide detection in cell culture exposed to LPS after Er:YAG laser irradiation

Aim To evaluate in vitro the effect of calcium hydroxide [Ca(OH)₂] and Er:YAG laser on bacterial endotoxin [also known as lipopolysaccharide (LPS)] as determined by nitric oxide (NO) detection in J774 murine macrophage cell line culture. Methodology Samples of LPS solution (50 μgmL^?1), Ca(OH)₂ suspension (25 mg mL^?1) and LPS suspension with Ca(OH)₂ were prepared. The studied groups were: I – LPS (control); II – LPS + Ca(OH)₂; III – LPS + Er:YAG laser (15 Hz 140 mJ); IV – LPS + Er:YAG laser (15 Hz 200 mJ); V – LPS + Er:YAG laser (15 Hz 250 mJ), VI – Pyrogen‐free water; VII – Ca(OH)₂. Murine macrophage J774 cells were plated and 10 μL of the samples were added to each well. The supernatants were collected for NO detection by the Griess reaction. Data were analysed statistically by one‐way anova and Tukey’s test at 5% significance level. Results The mean and SE (in μmol L^?1) values of NO release were: I – 10.48 ± 0.58, II – 6.41 ± 0.90, III – 10.2 ± 0.60, IV – 8.35 ± 0.40, V – 10.40 ± 0.53, VI – 3.75 ± 0.70, VII – 6.44 ± 0.60; and the values for the same experiment repeated after 1 week were: I – 21.20 ± 1.50, II – 9.10 ± 0.60, III – 19.50 ± 1.00, IV – 18.50 ± 0.60, V – 21.30 ± 0.90, VI – 2.00± 0.20, VII – 6.80 ± 1.70. There was no significant difference (P > 0.05) between the control and the laser‐treated groups (III, IV and V), or comparing groups II, VI and VII to each other (P > 0.05). Group I had significantly higher NO release than group II (P < 0.05). Groups II and VI had similar NO release (P > 0.05). Conclusions Calcium hydroxide inactivated the bacterial endotoxin (LPS) whereas none of the Er:YAG laser parameter settings had the same effectiveness.     

Trauma from instrumentation after non-surgical periodontal treatment with ultrasonic scalers and Nd:YAG laser

Abstract

Objective. Periodontal therapies aimed at altering the progression of periodontal diseases must include meticulous mechanical debridement during both the non-surgical and the surgical phases of periodontal treatment. The aim of this study was to evaluate and compare the immediate effect of trauma from instrumentation on clinical attachment level after non-surgical periodontal treatment with ultrasonic scalers and a Nd:YAG laser. Materials and methods. Twenty-four patients with untreated chronic periodontitis, presenting probing depths of 4–6 mm on anterior teeth, upper and lower, were entered into the study. The selected teeth were probed with a pressure-controlled probe, guided by stents. Each quadrant was randomly allocated in a split-mouth design either to treatment with Nd:YAG laser using an energy of 1W, 100mj, 1064nm (test group) or to periodontal treatment using ultrasonic scalers (control group). Clinical parameters, including plaque index (PI), bleeding on probing (BOP), probing pocket depth (PPD) and probing attachment level (PAL) were acquired prior to and immediately after treatment. Results. Statistical analysis demonstrated no differences between groups at baseline for all parameters (p > 0.05). Immediately after treatment, the control group showed a greater PAL loss than the test group (p < 0.05). For the control group, there were statistically significant differences between PAL immediately before and after treatment (p < 0.05), but not test group (p > 0.05). Conclusions. Within the limits of the present study, it may be concluded that non-surgical periodontal treatment with ultrasonic scalers causes a mean immediate attachment loss of 0.68 mm and that a Nd:YAG laser seems to reduce significantly the trauma the instrumentation produced.     

Evaluation of the surface roughness of zirconia ceramics after different surface treatments

Objective. This study aimed to investigate the effects of different mechanical surface treatments of pre-sintered zirconium oxide (ZrO₂) in an attempt to improve its bonding potential. Materials and methods. One hundred and twenty IPS e-max ZirCAD (Ivoclar Vivadent) pre-sintered zirconia blocks (7 mm diameter, 3 mm height) received six different surface treatments (n = 20): Group C was untreated (control); Group E was Er:YAG laser irradiated; Group N was Nd:YAG laser irradiated; Group SB was sandblasted, Group SN was sandblasted and Nd:YAG laser irradiated; and Group SE was sandblasted and Er:YAG laser irradiated. After the surface treatments, the average surface roughness (Ra, µm) of each specimen was determined with a profilometer, then all the specimens were sintered. The surface roughness values were analysed through one-way ANOVA and Tukey's test. Changes in the morphological characteristics of ZrO₂ were examined through scanning electron microscopy (SEM). Results. Sintered sandblasted, Er:YAG laser treatment, sandblasted + Er:YAG laser and sandblasted + Nd:YAG laser irradiation resulted in a rougher surface than the other treatments. Conclusion. Nd:YAG laser irradiation alone was not effective in altering the zirconia surface morphology.     

Efficacy of self‐adjusting file,XP‐endo finisher and passive ultrasonic irrigation on the removal of calcium hydroxide paste from an artificial standardized groove

The purpose of this study was to compare the effectiveness of self‐adjusting file (SAF), XP‐endo finisher (XP), passive ultrasonic irrigation (PUI) and conventional syringe and needle irrigation (SNI) in the removal of Ca(OH)₂ from an artificial groove. Eighty mandibular incisors with single oval canals were prepared to size 40/0.04 and split longitudinally. A standardised groove was prepared in the apical third and filled with Ca(OH)₂. The root halves were reassembled and divided into two control groups (n = 4) and four experimental groups (n = 18) according to the removal methods used. The amount of residual Ca(OH)₂ was evaluated using a four‐grade scoring system. The differences among the groups were analysed using the Kruskal–Wallis test (P < 0.05). SAF, XP and PUI removed significantly more Ca(OH)₂ than SNI (P < 0.001), although there were no significant differences among them (P = 0.209). None of the tested methods could completely clean Ca(OH)₂ from the groove.     

The ability of different irrigation methods to remove mixtures of calcium hydroxide and barium sulphate from isthmuses in 3D printed transparent root canal models

The purpose is to evaluate the efficacy of different irrigation techniques in the removal of various calcium hydroxide [Ca(OH)₂] and barium sulfate [BaSO₄] formulations from three isthmuses in 3-dimensional (3D) printed molar root canal models. 3D printed transparent models were designed, fabricated, and filled with pure Ca(OH)₂ paste, Ca(OH)₂–BaSO₄ 8:1 paste, Ca(OH)₂–BaSO₄ 1:1 paste, pure BaSO₄ paste, all in water, and Diapaste. Open-ended needle irrigation (ONI) at 5 and 15 mL/min, double-side-vented needle irrigation (DNI) at 5 mL/min, the GentleWave system (GW), PiezoFlow (PF), and passive ultrasonic activation (PUI) with distilled water, 0.5% sodium hypochlorite (NaOCl) and 3% NaOCl were used to remove the materials from the isthmuses. Ninety groups (n?=?10) were established. The removal time was recorded from the start of irrigation to the completion of removal. GW and PF were the only methods that removed all tested materials from the isthmuses. PF required 2–3?×?as much time as GW for complete removal, depending on the BaSO₄ content of the paste. ONI at 15 mL/min removed pure Ca(OH)₂ paste, Ca(OH)₂–BaSO₄ (8:1) paste, Ca(OH)₂–BaSO₄ (1:1) completely but could not completely remove pure BaSO₄ paste and Diapaste. PUI with intermittent needle irrigation, ONI, and DNI at 5 mL/min were not able to completely remove any of the materials within 7.5 min. The GW removed all materials faster than PF, whereas other methods failed to remove all materials from the isthmuses. Pure Ca(OH)₂ and the mixture with BaSO₄ paste in the proportion 8:1 were removed in less time than the other mixtures by the GW, PF and ONI systems, the latter only when using 15 mL/min flow rate.

     

Efficacy of a combined nanoparticulate/calcium hydroxide root canal medication on elimination of Enterococcus faecalis

The purpose of this study was to evaluate the efficacy of Ca(OH)₂ with or without a silver nanoparticle suspension to eliminate Enterococcus faecalis from root canals. A total of 66 extracted human single‐rooted teeth contaminated with E. faecalis were treated with 10% Ca(OH)₂ alone, Ca(OH)₂ with nanosilver or sterile water (as a negative control). Samples were obtained with paper points and Gates‐Glidden burs at 1 and 7 days after root canal preparation and the number of colony‐forming units (CFU) was determined. The number of CFUs observed after dressing with Ca(OH)₂ + nanosilver was significantly less than the number observed with Ca(OH)₂ alone after 1 or 7 days (P < 0.001, P < 0.001). No differences in antimicrobial properties were observed between the two time points in the Ca(OH)₂ + nanosilver group (P > 0.05). Higher antimicrobial efficacy was observed in the Ca(OH)₂ group after 7 days than 1 day (P < 0.001). This study highlighted the potential advantage of using a mixture of Ca(OH)₂ and nanosilver for intracanal medicament.     

Removal efficacy of various calcium hydroxide/chlorhexidine medicaments from the root canal

Aim To compare the efficiency of removing calcium hydroxide [Ca(OH)₂]/chlorhexidine (CHX) (gel), Ca(OH)₂/CHX (solution) and Ca(OH)₂/saline pastes with the use of instrumentation and irrigation with sodium hypochlorite and ethylene diamine tetraacetic acid (EDTA) solutions. Moreover the role of the patency file in the cleanliness of the apical third of the root canal was evaluated. Methodology Sixty‐four human single‐rooted teeth with straight canals were used. Root canal preparation was performed with a stepback technique using Hedström (H) files. Teeth were randomly assigned to three groups and subsequently filled with one of the pastes: Ca(OH)₂/CHX (gel), Ca(OH)₂/CHX (solution) and Ca(OH)₂/saline paste. The medicaments were removed 10 days later using instrumentation and irrigation with 1% sodium hypochlorite and 17% EDTA, with or without obtaining patency of the apical foramen with a size 10 H‐file. The crowns were removed at the cemento‐enamel junction and the roots were grooved longitudinally and split into halves. Images of all halves were acquired with the use of a flatbed scanner. A scoring system of 1 to 4 was used to assess the amount of residue on the cervical, middle and apical third of the canal. Data were subjected to statistical analysis using Kruskal–Wallis and Mann–Whitney tests, with Bonferroni correction, at 95% confidence level (P < 0.05). Results Remnants of medicament were found in all experimental teeth regardless of the experimental material used and the use of the patency file. When examining the root canal as a whole, Ca(OH)₂/CHX (gel) paste was associated with significantly larger amount of residue, whereas the Ca(OH)₂/CHX (solution) paste was associated with less amount (P < 0.05) than the other two medicaments with or without the use of a patency file. Conclusions None of the techniques used in this study removed the inter‐appointment root canal medicaments effectively; the use of the patency file facilitated removal of more of the medicament in the apical third of those straight canals.     

In vitro evaluation of the antibacterial effect of four root canal sealers on dental biofilms

Objectives

To dynamically evaluate the effect of four root canal sealers on the killing of biofilms within dentinal tubules.

Materials and methods

Dentin blocks were prepared for infection of the dentinal tubules. Enterococcus faecalis VP3-181 and multi-species bacteria from two donors were cultured. After 3 days of incubation, the infected dentin specimens were rinsed with sterile water for 1 min and subjected to treatment. Additionally, multi-species bacteria from donor 1 were incubated for 3 weeks to allow biofilm maturation and then the specimens were subjected to treatment. Gutta-percha-treated dentin specimens comprised the control group. A root canal sealer (bioceramic sealers: EndoSequence BC Sealer, ProRoot Endo Sealer, or GuttaFlow Bioseal; and a traditional silicone-based sealer: Guttaflow 2) was spread onto the canal walls of the dentin. The specimens were examined with confocal laser scanning microscopy at 7, 30, or 60 days.

Results

In the 3-day-old biofilm group, the proportion of killed bacteria decreased significantly from the first 7 days of treatment to 60 days of treatment for all sealers (p?<?0.05). In the 3-week-old biofilm group, 60 days of exposure to bioceramic sealers resulted in more significant dead bacteria than 7-day exposures of the biofilms (p?<?0.05). Bioceramic sealers were more effective in killing bacteria than the GuttaFlow 2 sealer (p?<?0.05).

Conclusions

Calcium silicate–based sealers showed good antimicrobial effects against biofilms within dentinal tubules, especially in the first week in young biofilms. There is no substantive antibacterial activity observed for the examined root canal sealers against young dentinal tubule biofilms.

Clinical relevance

The bioceramic root canal sealers examined demonstrate minimal additional antibacterial effects after long-term exposure to young biofilms.

     

A comparison of hydroxyl ion diffusion through root dentine from various calcium hydroxide preparations

Different calcium hydroxide [Ca(OH)₂] formulations are available. The aim was to assess differences in hydroxyl ion release with different formulations. Sixty-six teeth were divided one control (n = 6) and four experimental (n = 15) groups: (i) Pulpdent Paste; (ii): DT Temporary Dressing; (iii): Ca(OH)₂ powder/saline; (iv): Ca(OH)₂ points; (v): no medicament. pH was measured in inner dentine and outer dentine cavities over 12 weeks. Inner dentine pH rose rapidly for all groups except the points and controls. Peak pH was reached by day 2 before dropping and stabilising (8.0–9.2). Outer dentine pH rose steadily until day 21 for aqueous solutions and then stabilised (8.0–8.5). The points had minimal pH increase for the entire period. There were no significant differences in hydroxyl ion release between the aqueous solutions. Type of paste base did not affect release and diffusion of hydroxyl ions which continued for 84 days.     

Impact of combined CO2 laser irradiation and fluoride on enamel and dentin biofilm-induced mineral loss

Objectives

The caries-protective effects of CO₂ laser irradiation on dental enamel have been demonstrated using chemical demineralization models. We compared the effect of CO₂ laser irradiation, sodium fluoride, or both on biofilm-induced mineral loss (∆Z) and Streptococcus mutans adhesion to enamel and dentin in vitro.

Materials and methods

Ground, polished bovine enamel, and dentin samples were allocated to four groups (n = 12/group): no treatment (C); single 22,600-ppm fluoride (F) varnish (5 % NaF) application; single CO₂ laser treatment (L) with short pulses (5 μs/λ = 10.6 μm); and laser and subsequent fluoride treatment (LF). Samples were sterilized and submitted to an automated mono-species S. mutans biofilm model. Brain heart infusion plus 5 % sucrose medium was provided eight times daily, followed by rinses with artificial saliva. After 10 days, bacterial numbers in biofilms were enumerated as colony-forming units/ml (CFU/ml) (n = 7/group). ∆Z was assessed using transversal microradiography (n = 12/group). Univariate ANOVA with post hoc Tukey honestly-significant-difference test was used for statistical analysis.

Results

Bacterial numbers were significantly higher on dentin than enamel (p < 0.01/ANOVA). On dentin, LF yielded significantly lower CFUs than other groups (p = 0.03/Tukey), while no differences between groups were found for enamel. The lowest ∆Z in enamel was observed for L (mean/SD 2036/1353 vol%×μm), which was not only significantly lower than C (9642/2452 vol%×μm) and F (7713/1489 vol%×μm) (p < 0.05) but also not significantly different from LF (3135/2628 vol%×μm) (p > 0.05). In dentin, only LF (163/227) significantly reduced ∆Z (p < 0.05).

Conclusion/clinical relevance

CO₂ laser irradiation did not increase adhesion of S. mutans in vitro. Laser treatment alone protected enamel against biofilm-induced demineralization, while a combined laser-fluoride application was required to protect dentin.

     

Anticaries effect of toothpaste with nano-sized sodium hexametaphosphate

Objective

To evaluate the effect of a fluoride toothpaste containing nano-sized sodium hexametaphosphate (HMPnano) on enamel demineralization on the biochemical composition and insoluble extracellular polysaccharide (EPS) in biofilm formed in situ.

Methods

This crossover double-blind study consisted of four phases (7 days each), in which 12 volunteers wore intraoral appliances containing four enamel bovine blocks. The cariogenic challenge was performed using 30% sucrose solution (6×/day). Blocks were treated 3×/day with the following toothpastes: no F/HMP/HMPnano (Placebo), conventional fluoride toothpaste, 1100 ppm F (1100F), 1100F + 0.5% micrometric HMP (1100F/HMP), and 1100F + 0.5% nano-sized HMP (1100F/HMPnano). The percentage of surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), and enamel calcium (Ca), phosphorus (P), and fluoride (F) were determined. Moreover, biofilms formed on the blocks were analyzed for F, Ca, P, and insoluble extracellular polysaccharide (EPS) concentrations. Data were analyzed using one-way ANOVA, followed by Student–Newman–Keuls’ test (p < 0.001).

Results

1100F/HMPnano promoted the lowest %SH and ΔKHN among all groups (p < 0.001). The addition of HMPnano to 1100F significantly increased Ca concentrations (p < 0.001). The 1100F/HMPnano promoted lower values of EPS when compared with 1100F (~ 70%) (p < 0.001) and higher values of fluoride and calcium in the biofilms (p < 0.001).

Conclusion

1100F/HMPnano demonstrated a greater protective effect against enamel demineralization and on the composition of biofilm in situ when compared to 1100F toothpaste.

Clinical relevance

This toothpaste could be a viable alternative to patients at high risk of caries.

     

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.     

High-level laser therapy versus scalpel surgery in the treatment of oral lichen planus: a randomized control trial

Objective

To compare the clinical effectiveness of various types of high-level laser therapy (HLLT) toward scalpel excision for the surgical treatment of erosive oral lichen planus (OLP).

Materials and methods

The total number of 128 individuals were enrolled in the study. The 35 did not meet the inclusion criteria due to malignancy signs and presence of diabetes mellitus. In total, 8 were lost to follow-up, and 10 were excluded from the analysis, due to analgesics intake. This way 75 patients with the erosive form of OLP were analyzed in three intervention groups (Er:YAG, n = 19; Nd:YAG, n = 15; Er:YAG + Nd:YAG combination, n = 20) and one control group with scalpel excision (n = 21). The therapy effectiveness has been assessed based on the comparison of salivary interleukin (IL)-1β, IL-6 and interferon (IFN)-γ preoperative levels to 14, 30 days, and 2 years postoperation, as well as pain level and time of epithelization.

Results

All HLLT groups demonstrated a significantly (p > 0.05) higher IL-1β, IL-6, IFNγ and pain level reduction and quicker epithelization toward the control group on the 30th day, except Nd:YAG in case of IFNγ level. The highest IL-1β, IFNγ and pain level reduction and quicker epithelization on the 30th day was observed in Er:YAG group, followed by Er:YAG + Nd:YAG combination, Nd:YAG respectively. However no significant difference was observed between the HLLT groups with regard to IL-6 level reduction. After a 2-year follow-up, no significant difference was observed between all study groups with regard to all variables.

Conclusion

HLLT yields a superior clinical outcome compared to the scalpel excision for the surgical treatment of oral lichen planus, whereby the Er:YAG has been proposed as the most effective laser type at the end of the first postoperative month.

Clinical relevance

For the surgical treatment of erosive OLP the Er:YAG laser may be a preferable treatment option compared to Nd:YAG and scalpel surgery.

Trial registration

The present trial was registered retrospectively in the German Clinical Trials Register, as a member of WHO international clinical trials registry platform, on the 18.03.2020 with the following number: DRKS00020986

     

Dentin strain induced by laser irradiation

The purpose of this study was to investigate the strain and temperature change in dentin induced by laser irradiation of human root canals with or without water cooling. Twenty-eight palatal roots of extracted human maxillary first molars were used. The strain in dentin was measured using strain gauges fixed on the apical third of the buccal root surface. The temperature change of the root dentin was monitored using thermocouples embedded into dentin near the apex. The root canal was irradiated with Er:YAG or Nd:YAG laser at an output of 1 W (100 mJ, 10 pps) for 5 s. The tip of the irradiation fibre was located 2.0 mm from the root apex. With water cooling, the mean maximum strain induced by Er:YAG laser was significantly lower than that by Nd:YAG laser (P < 0.05). However, without water cooling, no significant difference between the two lasers (P > 0.05) was found. The results suggest that the strain induced by Er:YAG laser irradiation in dentin with water cooling may be minimal, but there still might be a risk of root micro-fracture if cooling is not sufficient.