Publications by authors named "Ya Shen"

158 Publications

Micro-computed Tomography Evaluation of Root Canal Filling Quality of Mandibular Molars Obturated for 54 Months.

J Endod 2021 Sep 4. Epub 2021 Sep 4.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Canada.

Introduction: The present study evaluated the percentage volume of voids in root canals of mandibular molars that had been obturated for 54 months.

Methods: Thirty extracted human mandibular molars were instrumented and debrided. The teeth were assigned to three groups (n=10) according to the filling technique and sealer used: single-cone technique using AH Plus sealer (AHS) or EndoSequence BC sealer (BCS), and warm vertical compaction technique using AH Plus sealer (AHW). The specimens were stored at 37 °C and 100% humidity. Micro-computed tomography was used to scan each specimen one day and 54 months after obturation. Data were analyzed using one-way ANOVA and paired t-test.

Results: The percentage volume of voids in the teeth one day after obturation in the AHS group was higher than in the BCS group and AHW group (P < 0.05). After 54 months, the proportion of voids decreased in all groups (P < 0.05). No significant difference was observed between the AHS group and BCS group after 54 months. Teeth in the AHW group contained fewer voids than the AHS group (P < 0.05).

Conclusions: Voids in root canal filling were reduced 54 months after obturation. The warm vertical compaction technique achieved better root canal filling quality in mandibular molars than the single-cone technique when using AH Plus sealer after long-term storage at 100% humidity.
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http://dx.doi.org/10.1016/j.joen.2021.08.015DOI Listing
September 2021

Long-term porosity and retreatability of oval-shaped canals obturated using two different methods with a novel tricalcium silicate sealer.

Clin Oral Investig 2021 Aug 14. Epub 2021 Aug 14.

Division of Endodontics, Department of Oral Biological & Medical Sciences, Faculty of Dentistry, University of British Columbia, 2199 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.

Objective: To evaluate the percentage volume of voids and gaps in oval-shaped canals obturated using two different methods with a tricalcium silicate-based sealer after short- or long-term storage. The long-term effect of storage on the efficiency of removing filling material was also investigated.

Materials And Methods: Forty premolar teeth with oval-shaped canals were instrumented to Reciproc R25 and obturated using single cone obturation (SCO) or warm vertical compaction (WVC) techniques with gutta-percha and HiFlow sealer. The specimens were stored at 100% humidity and 37°C for 2 weeks or 6 months and scanned using micro-computed tomography. Initial retreatment was performed up to a Reciproc R40, and the operating time was recorded. The residual material in the canal received a supplementary procedure using XP-endo Finisher R (XPFR) files. After each retreatment procedure, the specimens were rescanned.

Results: The percentage volume of voids and gaps in the SCO group was higher than that of the WVC group at both 2 weeks and 6 months (P < 0.05). The percentage volume of the filling material removed after initial retreatment and XPFR cleaning was significantly higher in the 6-month group than in the 2-week groups (P < 0.05). The proportion of the residual material decreased significantly when XPFR files were used, compared to the initial retreatment group (P < 0.05) in both storage times.

Conclusion: The efficiency of retreatment in the oval-shaped canal was closely related to the storage time rather than the filling technique using a tricalcium silicate sealer. The XPFR instrument proved effective in the removal of the remaining materials from the oval-shaped canal.

Clinical Relevance: Obturation of the oval-shaped canal with TSBS using the SCO technique in the coronal area needs to be optimized. The retreatment was less efficacious in freshly filled canals than aged filled canals.
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http://dx.doi.org/10.1007/s00784-021-04088-zDOI Listing
August 2021

Effects of dentine surface cleaning on bonding of a self-etch adhesive to root canal sealer-contaminated dentine.

J Dent 2021 Sep 5;112:103766. Epub 2021 Aug 5.

Department of Endodontics, The Dental College of Georgia, Augusta University, Augusta, GA, USA. Electronic address:

Objectives: To compare the effectiveness of different sealer cleaning methods on bonding of a self-etch adhesive to root canal sealer-contaminated dentine.

Methods: Forty-nine extracted molars were divided into seven groups. Dentine surfaces were exposed and cotaminated with a thin layer of epoxy resin-based sealer (AH Plus (AHP)) or zinc oxide eugenol-based sealer (Pulp Canal Sealer (PCS)). Three cleaning protocols were examined: dry cotton pellet, 70% ethanol-saturated cotton pellet or a surfactant-based cleaner (Katana Cleaner (KC), Kuraray Noritake Dental Inc.). Uncontaminated dentine served as control. The dentine surfaces were bonded with a two-step self-etch adhesive and restored with resin composite. Bond strength testing was performed using a microtensile approach. Two teeth from each group were used for scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The pulpal floor of the teeth was covered with sealer and cleaned. The percentage of zinc/zirconium on the dentine surface was detected to indicate the amount of remnant sealer.

Results: Tensile bond strength for uncontaminated dentine control was 46.4±7.3 MPa; bond strength decreased significantly for the dry cotton group (29.6±4.2 MPa for AHP, 24.7±4.7 MPa for PCS, p<0.05). Both ethanol and KC restored bonding performance after cleaning, with no significant difference from the control. Significantly lower MTBS was observed for the ZOE/ethanol subgroup (38.9±5.1 MPa). Cleaner surfaces and less zinc/zirconium elements were identified by SEM/EDX after cleaning with ethanol or KC.

Conclusions: Katana Cleaner decontaminates root canal sealer-smeared dentine surfaces effectively and restores the bonding performance of a self-etch adhesive to dentine.

Clinical Significance: The surfactant-based Katana Cleaner, originally designed for cleaning zirconia surfaces prior to adhesive bonding, may be used as for cleaning dentine that has been contaminated with unset root canal sealers after root canal treatment to restore the bonding strength of a self-etch adhesive to sealer-contaminated dentine.
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http://dx.doi.org/10.1016/j.jdent.2021.103766DOI Listing
September 2021

Comparison of the effects from coronal pre-flaring and glide-path preparation on torque generation during root canal shaping procedure.

Aust Endod J 2021 Jul 20. Epub 2021 Jul 20.

Department of Conservative Dentistry, School of Dentistry, Dental and Life Science Institute, Dental Research Institute, Education and Research Team for Life Science on Dentistry, Pusan National University, Yangsan, Korea.

This study aimed to evaluate the effect of glide-path preparation and coronal pre-flaring on torque generation of rotary nickel-titanium files. Sixty mesiobuccal root canals of 3D printed resin teeth (Dentalike) were randomly divided into 4 groups (n = 15) according to the preparation method; Group 1: OneCurve only; Group 2: OneG and OneCurve; Group 3: OneFlare and OneCurve; Group 4: OneFlare, OneG, and OneCurve. During the final canal preparation procedure, the torque generated was recorded. The sum of generated torque and maximum torque were calculated. Statistical analysis was performed with one-way ANOVA and Duncan's post hoc comparison. The summed torque was reduced by glide-path preparation and coronal pre-flaring (P < 0.05), whereas the maximum torque was not reduced by the glide-path preparation (P > 0.05). It will be advantageous to create a glide-path with coronal pre-flaring to reduce the stress and reactive forces to the NiTi file and root dentin.
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http://dx.doi.org/10.1111/aej.12548DOI Listing
July 2021

Effects of Root Canal Curvature and Mechanical Properties of Nickel-Titanium Files on Torque Generation.

J Endod 2021 Sep 5;47(9):1501-1506. Epub 2021 Jul 5.

Department of Conservative Dentistry, School of Dentistry, Dental and Life Science Institute, Dental Research Institute, Pusan National University, Yangsan, South Korea. Electronic address:

Introduction: This study aimed to compare the torque generated by 4 different files in root canals with 4 different curvature angles.

Methods: Four brands of nickel-titanium (NiTi) endodontic files were selected: WaveOne Primary (Dentsply Sirona, Ballaigues, Switzerland), WaveOne Gold Primary (Dentsply Sirona), ProTaper Universal F2 (Dentsply Sirona), and ProTaper Next X2 (Dentsply Sirona). A tempered steel block containing artificial canals with 4 different canal curvatures (15°, 25°, 35°, and 45°) was constructed. Each file was used according to the manufacturer's instructions in the dynamic model, with an added 15 axial up-and-down movements of 4 mm at the end of the canal. The generated torque was recorded, and the total and maximum torque values were measured. Two-way analysis of variance and the Duncan post hoc comparison test were performed at a significance level of 95%.

Results: A significant correlation between the curvature angle and the type of file system was observed (P < .05). As the degree of canal curvature increased, the generated total and maximum torque increased. At 15° and 25°, the NiTi files with reciprocating motion generated a higher total and maximum torque than files with continuous rotation. ProTaper Universal of conventional NiTi alloy showed the steepest increase in the generated total and maximum torque with the increasing curvature angle. The ProTaper Next file had the lowest torque values at the higher canal angles of 35° and 45° (P < .05).

Conclusions: Despite the study limitations, it can be concluded that root canal curvature, design, and heat treatment of NiTi files and file kinematics affect the generated torque during instrumentation.
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http://dx.doi.org/10.1016/j.joen.2021.06.019DOI Listing
September 2021

Efficacy of XP-endo instruments in removing 54 month-aged root canal filling material from mandibular molars.

J Dent 2021 Sep 25;112:103734. Epub 2021 Jun 25.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Canada. Electronic address:

Objective: To investigate the effectiveness of XP-endo Shaper (XPS) and XP-endo Finisher R (XPFR) instruments in removing aged root filling material from root-treated mandibular molars.

Methods: Thirty mandibular molars were instrumented and divided into three groups: single-cone obturation using AH Plus sealer (AHS) or EndoSequence BC sealer (BCS), and warm vertical compaction using AH Plus sealer (AHW). The specimens were stored at 100% humidity and 37 °C for 54 months. Retreatment was performed using XPS and XPFR. Micro-computed tomography was used to scan the specimens after 54 months, after XPS retreatment and after the supplementary approach using XPFR.

Results: The XPS removed more filling material in the BCS and AHS groups, compared with the AHW group (P < 0.05). After supplementary instrumentation XPFR, the proportion of the remaining filling material decreased significantly in all groups (P < 0.05). The XPFR instruments were more efficient in removing filling material in the BCS group than in the AHS or AHW group (P < 0.05). The combined use of XPS and XPFR instruments efficiently removed filling material in the BCS group, followed by the AHS and AHW groups (P < 0.05).

Conclusions: Although the combined use of XPS and XPFR instruments helped remove the bulk of aged root filling material from mandibular molars, material removal from canals filled using warm vertical condensation in the critical apical area remains a concern.

Clinical Significance: Removal of the aged filling materials using XP-endo instruments from the apical area is challenging when instrumented root canals are filled using warm vertical condensation.
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http://dx.doi.org/10.1016/j.jdent.2021.103734DOI Listing
September 2021

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

Odontology 2021 Jun 18. Epub 2021 Jun 18.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, 2199 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.

The purpose is to evaluate the efficacy of different irrigation techniques in the removal of various calcium hydroxide [Ca(OH)] and barium sulfate [BaSO] 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) paste, Ca(OH)-BaSO 8:1 paste, Ca(OH)-BaSO 1:1 paste, pure BaSO 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 BaSO content of the paste. ONI at 15 mL/min removed pure Ca(OH) paste, Ca(OH)-BaSO (8:1) paste, Ca(OH)-BaSO (1:1) completely but could not completely remove pure BaSO 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) and the mixture with BaSO 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.
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http://dx.doi.org/10.1007/s10266-021-00628-xDOI Listing
June 2021

Effectiveness of photon-initiated photoacoustic streaming in root canal models with different diameters or tapers.

BMC Oral Health 2021 06 15;21(1):307. Epub 2021 Jun 15.

Department of Endodontics, Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou Key Laboratory of Basic and Applied Research of Oral Regenerative Medical, Guangzhou, 510182, Guangdong, China.

Background: This study aimed to compare the use of photon-initiated photoacoustic streaming (PIPS) and conventional needle irrigation (CNI) in conjunction with different concentrations of sodium hypochlorite (NaOCl) to remove Enterococcus faecalis (E. faecalis) suspended bacteria and biofilms from root canal systems with different diameters or tapers.

Methods: Artificial root canal samples (n = 480) were randomly divided into three groups (n = 160/group). The canals were prepared to fit file sizes #10/.02, #25/.02, or #25/.06. The size #10/.02 group was incubated for seven days. The size #25/.02 or #25/.06 group was incubated for 2 days. A stable biological model of E. faecalis infection was established. The root canals were washed with distilled water or with 1%, 2%, or 5.25% NaOCl combined with CNI or PIPS. Bacterial suspensions and biofilms were assessed using an ATP assay kit and fluorescence microscopy. Image-Pro Plus was used to analyse the average fluorescence intensity to determine the most suitable root canal irrigation solution.

Results: In the CNI and PIPS groups, the ATP value of the 5.25% NaOCl subgroup was the lowest, followed by that of the 2% and 1% NaOCl subgroups. The ATP value of the distilled water subgroup was the highest (P < 0.05). When the root canal taper was 0.02, the ATP value of the #10/.02 + PIPS group was significantly lower than that of the #25/.02 + CNI group (P < 0.05). The average fluorescence intensity of the #10/.02 + PIPS group was lower than that of the #25/.02 + CNI group (P < 0.05). When the apical diameter was #25, the ATP value of the 0.02 taper in the PIPS group was lower than that of the 0.06 taper in the CNI group (P < 0.05), and the average fluorescence intensity of the 0.02 taper + PIPS group was lower than that of the 0.06 taper + CNI group (P < 0.05). PIPS combined with 2% and 5.25% NaOCl effectively improved the long-term antibacterial effect after irrigation and re-culture for 6 h.

Conclusions: Compared with CNI, PIPS has greater ability to remove bacteria in root canals with a small preparation diameter and a small taper. PIPS with 2% and 5.25% NaOCl exhibited superior antibacterial and bacteriostatic effects.
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http://dx.doi.org/10.1186/s12903-021-01671-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8207708PMC
June 2021

Root dentine thickness in C-shaped lower second molars after instrumentation: A CBCT and micro-CT study.

Aust Endod J 2021 Aug 17;47(2):122-129. Epub 2021 Mar 17.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.

Stripping perforation is a possible complication in instrumentation of C-shaped canals. This study evaluated the minimum thickness of the root canal wall in C-shaped teeth after instrumentation. Twelve extracted C-shaped mandibular second molars (four teeth of type I, II and III each) were examined by CBCT (voxel size 90 μm) before and after instrumentation with WOG primary file. Micro-CT scans (voxel size 30 μm) were obtained after instrumentation. Percentage of canal wall area touched by the file and minimum thickness of dentine were measured and compared between CBCT and micro-CT. In type I C-shape canals, less than 10% of the canal wall area was touched by the instrument. In ten teeth, the shortest distance to root surface was from the instrumented area; no perforations occurred. CBCT and micro-CT measurements were in good agreement in ten cases; in two teeth, micro-CT revealed considerably shorter distance to root surface. The two shortest distances were 0.27 and 0.41 mm.
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http://dx.doi.org/10.1111/aej.12509DOI Listing
August 2021

Geometric Analysis of the Distolingual Root and Canal in Mandibular First Molars: A Micro-computed Tomographic Study.

J Endod 2021 May 18;47(5):779-786. Epub 2021 Feb 18.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada.

Introduction: The purpose of this study was to comprehensively assess by micro-computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.

Methods: One hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.

Results: All DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.

Conclusions: The novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.
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http://dx.doi.org/10.1016/j.joen.2021.02.006DOI Listing
May 2021

Effect of apical size on apical pressure during syringe-needle and multisonic negative pressure irrigation.

Odontology 2021 Jul 5;109(3):625-631. Epub 2021 Jan 5.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, 2199 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.

Apical pressure during root canal irrigation is regarded as a key factor affecting the risk of irrigant extrusion. The aim of this study was to examine the effect of apical size on the apical pressure by positive and negative pressure syringe-needle and multisonic negative pressure irrigation. An extracted maxillary first molar with two separate buccal roots, one palatal root and four canals was selected. The roots of the molar were fixed in a specially made apparatus to acquire the apical pressure of the four root canals separately. The apical sizes tested were from sizes 10, 30, 40, 50, 60, 70, 80, 90, 110. Multisonic negative pressure irrigation protocol was as recommended by the manufacturer (45 mL/min), syringe-needle irrigation was done using 30-G side-vented needle 3 mm from the working length at 5 mL/min as a conventional positive pressure irrigation (SNI), and as negative pressure irrigation (NPSNI) using suction. Apical pressure by SNI was measured also at 10 mL/min with an open-ended 30G needle, for the smallest and largest apical sizes. Apical pressures by SNI stayed positive, except when suction was used (NPSNI). The apical pressure by multisonic negative pressure irrigation remained negative in all situations. With increasing apical size, apical pressure by SNI decreased, whereas with multisonic negative pressure irrigation and NPSNI, it was not affected by apical size. Large apical size did not result in higher apical pressure values compared to small apical sizes.
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http://dx.doi.org/10.1007/s10266-020-00586-wDOI Listing
July 2021

The value of high-flow nasal cannula oxygen therapy in treating novel coronavirus pneumonia.

Eur J Clin Invest 2021 Mar 31;51(3):e13435. Epub 2020 Oct 31.

Department of Respiratory and Critical Care Medicine, No. 2 People's Hospital of Fuyang City, Fuyang, China.

Objective: This study aimed to investigate the value of high-flow nasal cannula (HNFC) oxygen therapy in treating patients with severe novel coronavirus pneumonia (COVID-19).

Methods: The clinical data of 22 patients with severe COVID-19 were collected. The heart rate (HR), respiratory rate (RR) and oxygenation index (PO /FiO ) at 0, 6, 24 and 72 hours after treatment were compared between the HFNC oxygen therapy group and the conventional oxygen therapy (COT) group. In addition, the white blood cell (WBC) count, lymphocyte (L) count, C-reactive protein (CRP) and procalcitonin (PCT) were compared before and at 72 hours after oxygen therapy treatment.

Results: The differences at 0 hours between the two groups were not statistically significant. Compared with COT group,in the HFNC oxygen therapy group, HR, RR and PaO /FiO were better at 6 hours after treatment, PaO /FiO was better at 24 and 72 hours. After 72 hours, L and CRP had improved in the HFNC oxygen therapy group compared with the COT group, but the differences in WBC and PCT were not statistically significant. The length of stay in the intensive care unit (ICU) and the total length of hospitalization was shorter in the HFNC oxygen therapy group than in the COT group.

Conclusion: Compared with COT, early application of HFNC oxygen therapy in patients with severe COVID-19 can improve oxygenation and RR, and HFNC oxygen therapy can improve the infection indexes of patients and reduce the length of stay in the ICU of patients. Therefore, it has high clinical application value.
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http://dx.doi.org/10.1111/eci.13435DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7645937PMC
March 2021

Characteristics of the Irrigant Flow in a Simulated Lateral Canal Under Two Typical Laser-Activated Irrigation Regimens.

Lasers Surg Med 2020 Sep 10. Epub 2020 Sep 10.

Department of Endodontics, Beijing Stomatological Hospital, Capital Medical University, Beijing, 100050, PR China.

Background And Objectives: Photon-induced photoacoustic streaming (PIPS) and shockwave-enhanced emission photoacoustic streaming (SWEEPS) are two promising laser-activated irrigation (LAI) methods for root canal irrigation. Their performance in driving irrigant flush in a complex root canal system will be evaluated by microscale particle image velocimetry (μPIV) measurement and will be compared with that of ultrasonic-activated irrigation (UAI).

Study Design/materials And Methods: A μPIV system with 7 μm fluorescent tracer particles was adopted to measure two-dimensional (2D) velocity fields around the junction region, with a size of 1.8 mm × 1.5 mm, between one main canal and one lateral canal in an endodontic training block, which was driven by SWEEPS (Er:YAG laser) operating at 15 Hz and 20 mJ. The flow field driven by PIPS (Er:YAG laser) at the same frequency and energy, as well as by UAI (with non-cutting insert) operating at 40% unit power, was also measured for a direct comparison.

Results: It was found that both SWEEPS and PIPS can activate a so-called "breath mode" during the irrigation. Namely, the induced irrigant flush presented a back-and-forth oscillation along both the main canal and the lateral one. The maximum flow speed in the lateral canal was observed to be up to 10 m/s in the SWEEPS modality, while reduced to around 7 m/s in the PIPS modality. The penetration length in the lateral canal in both modalities was estimated to be larger than 1 mm. In comparison, the flow field induced by UAI was characterized as irregular vortical structures, the maximum flow speed in the lateral canal was 0.15 m/s and significantly lower than LAI (P < 0.01), and the penetration length was less than 300 μm and lower than LAI (P < 0.05).

Conclusion: Compared to UAI, PIPS, and SWEEPS are more capable of delivering the irrigant deeper into the lateral canal. Furthermore, the back-and-forth flush in the breath mode is ideal for removing debris during irrigation. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.
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http://dx.doi.org/10.1002/lsm.23317DOI Listing
September 2020

sp. nov., isolated from the saline Lake Tus in Siberia.

Int J Syst Evol Microbiol 2020 Oct 11;70(10):5586-5593. Epub 2020 Sep 11.

Siberian Federal University, Krasnoyarsk 660041, Russia.

A halotolerant, psychrotolerant and methylotrophic methanogen, strain SY-01, was isolated from the saline Lake Tus in Siberia. Cells of strain SY-01 were non-motile, cocci and 0.8-1.0 µm in diameter. The only methanogenic substrate utilized by strain SY-01 was methanol. The temperature range of growth for strain SY-01 was from 4 to 40 °C and the optimal temperature for growth was 30 °C. The pH range of growth was from pH 7.2 to 9.0, with optimal growth at pH 8.0. The NaCl range of growth was 0-1.55 M with optimal growth at 0.51 M NaCl. The G+C content of the genome of strain SY-01 was 43.6 mol % as determined by genome sequencing. Phylogenetic analysis revealed that strain SY-01 was most closely related to SD1 (97.3 % 16S rRNA gene sequence similarity), and had 95.5-97.2 % similarities to other species with valid names. Genome relatedness between strain SY-01 and DSM 21339 was computed using average nucleotide identity and digital DNA-DNAhybridization, which yielded values of 79.7 and 21.7 %, respectively. Based on morphological, phenotypic, phylogenetic and genomic relatedness data presented here, it is evident that strain SY-01 represents a novel species of the genus , and the name sp. nov. is proposed. The type strain is SY-01 (=BCRC AR10051=NBRC 113166 =DSM 107642).
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http://dx.doi.org/10.1099/ijsem.0.004453DOI Listing
October 2020

Decontamination of rough implant surfaces colonized by multispecies oral biofilm by application of leukocyte- and platelet-rich fibrin.

J Periodontol 2021 06 21;92(6):875-885. Epub 2020 Sep 21.

Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia.

Background: Decontamination of biofilm-infected rough implant surfaces is challenging. Platelet rich blood products have been shown to have anti-microbial properties against periodontal pathogens. Our aim was to investigate the effect of a potential biological implant surface disinfectant, leukocyte- and platelet-rich fibrin (L-PRF), on a mature oral multispecies biofilm on a rough titanium surface.

Methods: Sandblasted, large grit, acid-etched (SLA) titanium disks were inoculated with subgingival dental plaque and cultured anaerobically for 21 days. The L-PRF membranes were collected from 12 donors in three trials (four donors in each trial). The disks were rinsed with 0.9% NaCl and exposed to the cell-rich portion of the L-PRF membranes for 48 hours followed by scanning electron microscope (SEM) analysis immediately or after rinsing with 0.9% NaCl prior to fixation. The presence of platelet factor-4 in the rinse samples was analyzed by Western blotting. Remaining bacteria were quantified from SEM images of the implant surfaces and their numbers statistically compared.

Results: The L-PRF-treated samples without rinsing displayed numerous cells with multiple pseudopodia in immediate contact with bacteria that appeared perforated and increased in size. The cells were identified as platelets based on morphological criteria and by positive reaction for platelet factor-4 by Western blotting. After post-treatment rinsing, the L-PRF-treated disks displayed a significant reduction in bacterial counts (in average 92% reduction).

Conclusion: Application of L-PRF significantly reduced bacterial counts on contaminated SLA titanium surface, most likely through anti-microbial action by platelets.
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http://dx.doi.org/10.1002/JPER.20-0205DOI Listing
June 2021

Resumption of Endodontic Practices in COVID-19 Hardest-Hit Area of China: A Web-based Survey.

J Endod 2020 Aug 18. Epub 2020 Aug 18.

Department of Endodontics, University of Alabama at Birmingham, Birmingham, Alabama.

Introduction: The purpose of this study was to investigate the resumption of endodontic practices in Hubei Province, China 1 month after the end of the lockdown.

Methods: A Web-based survey was sent to 1069 active endodontic specialists and general dentists who provided endodontic care in Hubei Province from May 7 to May 9, 2020. The survey consisted of 18 questions on demographics, the current situation of endodontic practice for the participants, and concerns regarding contracting or spreading the virus in newly opened endodontic practices.

Results: A total of 322 participants completed the survey. Most respondents (62%) were from Wuhan. Almost 83% of the respondents have resumed their endodontic practice partially or fully. Most respondents in practice (99%) would take measures to screen patients before treatment including paid screening measures. More than 93% of the respondents reported having taken special measures for routine endodontic treatment at this stage, with the most common measure taken being wearing an N95 mask. The rubber dam was recognized as efficient in preventing infection by most respondents. Many respondents were concerned about contracting coronavirus disease 2019 (COVID-19) as a result of routine endodontic practice at this stage, and respondents with more than 11 years of endodontic experience were significantly less concerned about infection compared with those with fewer than 5 years of experience (P < .05).

Conclusions: There is a fear of contracting/spreading COVID-19 among endodontic clinicians, the fear is negatively associated with years of practice, and most clinicians believe that rubber dam isolation can protect them and their patients from COVID-19.
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http://dx.doi.org/10.1016/j.joen.2020.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7431398PMC
August 2020

Effect of Curvature Location on Fatigue Resistance of Five Nickel-titanium Files Determined at Body Temperature.

J Endod 2020 Jul 5. Epub 2020 Jul 5.

Faculty of Dentistry, Department of Oral Biological and Medical Sciences, The University of British Columbia, Vancouver, Bitish Columbia, Canada. Electronic address:

Introduction: The purpose of this study was to evaluate the effect of 5 different curvature locations on the fatigue resistance of thermomechanically treated nickel-titanium (NiTi) files and superelastic NiTi files at body temperature and to document the corresponding phase transformations.

Methods: EndoSequence (ES; Brasseler USA, Savannah, GA), EndoSequence CM (ESCM, Brasseler USA), K3 (SybronEndo, Orange, CA), K3XF (SybronEndo), and Vortex Blue (VB; Dentsply Tulsa Dental Specialties, Tulsa, OK) NiTi files (size 25/.04) were subjected to fatigue tests inside customized artificial canals containing a curvature of 60° and a 3-mm radius. There were 5 different canals based on the location of initial curvature; these included groups in which the distance between the canal orifice and the location of the curvature (DOC) was 5, 6, 8, 10, and 11 mm. The model canal was immersed in water at 37°C ± 1°C. The number of cycles to failure (N) was recorded, and the fracture surface of the fragments was examined by scanning electron microscopy. Two unused files of each brand were examined by differential scanning calorimetry.

Results: The N was highest in the 10-mm and 11-mm DOC groups and lowest with the 5-mm and 6-mm DOC groups (P < .05). ESCM files had the highest fatigue resistance followed by the VB, K3XF, K3, and ES files (P < .05). ESCM files had the highest N (P < .05), and ES and K3 files had the lowest N (P < .05) depending on the curvature location. Two endothermic peaks were observed on the heating curve of the heat-treated files (ESCM, K3XF, and VB).

Conclusions: The location of the canal curvature had a significant effect on the fatigue resistance of both heat-treated and superelastic NiTi files. The fatigue life of files in the coronal curve was quite short.
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http://dx.doi.org/10.1016/j.joen.2020.06.041DOI Listing
July 2020

External Cervical Resorption: A Retrospective Case-Control Study.

J Endod 2020 Oct 7;46(10):1420-1427. Epub 2020 Jun 7.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Introduction: The current retrospective case-control study examined the potential systemic and local risk factors in relationship to external cervical resorption (ECR). The study hypothesis stated that both local and systemic risks are associated with higher ECR rates.

Methods: The ECR group included data about 76 patients (98 teeth) diagnosed with ECR at the university graduate endodontics clinic from 2008-2018. An equivalent comparative control group without ECR was composed of the same pool of patients and matched with cases by sex and age. Information about dental and medical history, including potential local risk factors (bruxism, trauma, eruption disorders, extraction of an adjacent tooth, orthodontics, and restorations) and systemic risk factors (medical conditions, medication, and allergies), was collected for both groups. Data were analyzed at tooth and patient levels. The chi-square test or Fisher exact test compared proportions between the 2 study groups.

Results: The overall ECR prevalence among endodontic patients during the 10-year follow-up was 2.3%. ECR was most frequent in maxillary anterior teeth (31.6%), and the Heithersay class 2 was the most frequent (38.8%) ECR diagnosis. Diabetes was the only significant systemic risk factor (P < .05). Trauma, as a local risk factor, was significantly (P < .05) more frequently reported in cases than in controls.

Conclusions: The study hypothesis stating that both systemic and local risk factors were associated with higher ECR rates was partly confirmed, as one systemic (diabetes) and one local (trauma) risk factor were associated with higher ECR rates.
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http://dx.doi.org/10.1016/j.joen.2020.05.021DOI Listing
October 2020

Dynamics of Dissolution, Killing, and Inhibition of Dental Plaque Biofilm.

Front Microbiol 2020 20;11:964. Epub 2020 May 20.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, BC, Canada.

The present study aims to establish a standardized model that makes it possible to evaluate the dynamic dissolution of biofilm, killing of biofilm microbes and inhibition of growth of biofilm by disinfecting solutions. Biofilm was grown from dental plaque bacteria on collagen-coated hydroxyapatite (HA) disks for 3 days or 3 weeks under anaerobic conditions. Biofilms were stained with the LIVE/DEAD viability stain and subjected to sterile water, 2% sodium hypochlorite (NaOCl), 6% NaOCl, or 2% chlorhexidine (CHX) for 32 min. Dynamic change in fluorescence on bacterial cells and extracellular polymeric substance (EPS) during the exposure was analyzed using Alexa Fluor 647-labeled dextran conjugate and a live-cell imaging confocal laser scanning microscopy (LC-CLSM). The biofilm structures after treatments were visualized by scanning electron microscopy (SEM). The treated biofilms on HA disks were collected and subjected to colony forming unit (CFU) counting. Another set of sterile HA disks were coated with CHX prior to the monitoring of plaque biofilm growth for 12 h. The LC-CLSM results showed that NaOCl dissolved biofilm effectively, more so at a higher concentration and longer exposure time. Six percent NaOCl was the most effective at dissolving and killing bacteria (e.g., 99% bacterial reduction in 3-day-old biofilm and 95% bacterial reduction in 3-week-old biofilm in 32 min) followed by 2% NaOCl and CHX. Sodium hypochlorite dissolved over 99.9% of the EPS whereas CHX only slightly reduced the EPS biovolume in 32 min. CFU results indicated that the dispersed biofilm bacteria are more resistant than planktonic bacteria to disinfectants. SEM showed the disruption of biofilm after exposures to CHX and NaOCl. The use of 2% CHX and sterile water did not result in biofilm dissolution. However, prior exposure of the HA disks to 2 and 0.2% CHX for 3 min prevented biofilm from growing on the HA disk surfaces for at least 12 h. This new platform has the potential to aid in a better understanding of the antibiofilm properties of oral disinfectants.
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http://dx.doi.org/10.3389/fmicb.2020.00964DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7251032PMC
May 2020

Effect of canal curvature location on the cyclic fatigue resistance of reciprocating files.

Clin Oral Investig 2021 Jan 2;25(1):169-177. Epub 2020 Jun 2.

Division of Endodontics, Faculty of Dentistry, The University of British Columbia (UBC), 2199 Wesbrook Mall, Vancouver, V6T1Z3, Canada.

Objectives: To determine the effect of the location of the canal curvature on the fatigue resistance of WaveOne (WO), WaveOne Gold (WOG), Reciproc (Rec), and Reciproc Blue (RecB) files, and to examine the phase transformation behaviors of the reciprocating file systems.

Material And Methods: The instruments were subjected to fatigue testing in five artificial canals with a curvature of 60° angle and a 3-mm radius. The location of the curvature was unique for each canal. Each file was inserted 16 mm into the canal and operated until fracture occurred. The time to fracture was recorded and the length of the fragment was measured. Differential scanning calorimetry was used to characterize the thermal behavior of the files. The number of cycles to failure was analyzed using two-way analysis of variance and the post hoc Tukey test. The Kruskal-Wallis test was used to compare the mean fragment lengths between groups.

Results: The instruments had significantly lower fatigue resistance in canals with curvatures in the middle and coronal canals compared with those with apical curvatures (p < 0.05). At all tested curvature locations, RecB had superior fatigue resistance compared with WO and Rec (p < 0.05). There were no significant differences between WOG and Rec in canals with curvatures in the middle and coronal canals. The DSC thermograms for RecB exhibit a single exothermic peak during cooling but double endothermic peaks during heating indicating that a two-step phase transformation from martensite to R-phase to austenite takes place.

Conclusions: The reciprocating instruments experience decreased cyclic fatigue resistance when operated in canals with coronal- and middle-third curvatures when compared with curvatures in the apical-third. Instrumenting coronally positioned curvatures with reciprocating files needs to be performed with caution.

Clinical Relevance: The location of the root canal's curvature influences the fracture resistance of rotary files that are used with reciprocating movements. Therefore, caution needs to be exercised when using reciprocating instruments in canals with coronal or middle curvatures.
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http://dx.doi.org/10.1007/s00784-020-03348-8DOI Listing
January 2021

Follow-up study on pulmonary function and radiological changes in critically ill patients with COVID-19.

J Infect 2021 Jan 27;82(1):159-198. Epub 2020 May 27.

Department of Biological Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, Jiangsu, 215123, China. Electronic address:

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http://dx.doi.org/10.1016/j.jinf.2020.05.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7251349PMC
January 2021

Characteristics of Endodontic Emergencies during Coronavirus Disease 2019 Outbreak in Wuhan.

J Endod 2020 Jun 10;46(6):730-735. Epub 2020 Apr 10.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, British Columbia, Canada.

Introduction: In late 2019, an outbreak of a new coronavirus named severe acute respiratory syndrome coronavirus 2 was detected in Wuhan, China. A great percentage of patients with this disease developed symptoms of dry cough, malaise, and a high fever. During this time, several patients requiring assessment and treatment of endodontic emergencies were directed to the School and Hospital of Stomatology at Wuhan University, Wuhan, China. We examined the characteristics of these patients.

Methods: A total of 96 patients with a mean age of 42.24 ± 18.32 years visited the general and emergency department of the School and Hospital of Stomatology at Wuhan University because of endodontic emergencies during the peak period of February 22 to March 2, 2020. Patient information was collected and organized by date of visit, sex, age, and systemic disease history. Body temperature was measured and acquired for each patient, a coronavirus disease 2019 (COVID-19) epidemiologic investigation questionnaire was given to each patient, an endodontic diagnosis was determined for the offending tooth, and a verbal numerical rating scale (VNRS) was used to record pain levels.

Results: Of the total patient visits during this period, 50.26% of visits were for endodontic treatment. No patients had a fever (>37.2°C). One patient with a confirmed COVID-19 history was admitted after recovery. Three admitted patients had been exposed to confirmed or suspected COVID-19 patients. Twelve admitted patients (12.5%) with a mean age of 62.42 ± 13.77 years had a history of systemic diseases. The most common age group for endodontic emergencies was 45-64 years (30.21%), and patients of this group showed a significantly higher mean VNRS score compared with that of the 6- to 19-year age group and the 20- to 34-year age group (P < .05). The majority of endodontic emergency diagnoses were diseases of symptomatic irreversible pulpitis (53.10%). Patients who were diagnosed with symptomatic irreversible pulpitis, symptomatic apical periodontitis, and acute apical abscess showed a significantly higher mean VNRS score than that of other groups (P < .05).

Conclusions: Endodontic emergencies, with symptomatic irreversible pulpitis being the most common, consist of a much higher proportion of dental emergencies in a COVID-19 high-risk area than normally. Vital pulp therapy can advantageously reduce treatment time, resulting in a reduced risk of infection for vital pulp cases. Rubber dams, personal protective equipment, and patient screening are of great importance during the COVID-19 outbreak in protecting clinicians.
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http://dx.doi.org/10.1016/j.joen.2020.04.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7151235PMC
June 2020

Effects of Litterfall on the Accumulation of Extracted Soil Humic Substances in Subalpine Forests.

Front Plant Sci 2020 5;11:254. Epub 2020 Mar 5.

Long-Term Research Station of Alpine Forest Ecosystems, Key Laboratory of Ecological Forestry Engineering, Institute of Ecology and Forestry, Sichuan Agricultural University, Chengdu, China.

Plant litter is one of the main sources of soil humus, but which can also promote primary humus degradation by increasing microbial activity due to the higher availability of energy released, resulting in a confusing relationship between litterfall and soil humus. Therefore, an incubation experiment was carried out in three subalpine forests (coniferous, mixed and broadleaved forests) on the eastern Qinghai-Tibetan Plateau. We set up two treatments. One that allowed litterfall to enter the soil normally and the other prevented litterfall to enter the soil. Soils were sampled in October (the end of the growing season), January (the onset of the freezing season), March (the end of the freezing season), and May (the start of the growing season) from May 2017 to May 2018. By assessing the litterfall production, the content of total extracted humus, humic acid (HA) and fulvic acid (FA) in the topsoil (0-20 cm) in each incubation period, we determined the impact of litterfall on the content of humus extracted from the soil during the freezing and the growing season. Over 1-year incubation, soil total extracted humus and HA showed considerable decreases in the treatment of retained litterfall in the mixed forest but not in the coniferous or broadleaved forests. Moreover, litterfall significantly reduced the contents of soil total extracted humus and HA during the growing season in all three forests, while only reduced soil HA content in the broadleaved forest in the freezing season. The relationship between litterfall and soil extracted humic substances was greatly regulated by the seasonal dynamics of litter types and litter production in all forest types. The larger the amount of litterfall was, the more litterfall could promote the reduction of soil extracted humic substances. Compared with a single type of broadleaf or needle litter, mixed litterfall could promote a higher degradation of soil humic substances. However, broadleaf litter might lead to much greater decreases in soil humic substance than needle litter because it is more decomposable. These results indicate that the effect of litterfall on soil humic substances are mainly regulated by litter types and litter production. Moreover, the effects of litterfall on soil humic substances are more significant during the growing season than winter. This suggests that the longer growing season and a shorter winter caused by ongoing global warming may alter the relationships between litterfall and extracted humic substances, further disrupting the carbon balance of forest ecosystems in the subalpine forests.
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http://dx.doi.org/10.3389/fpls.2020.00254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7066323PMC
March 2020

Cytotoxicity and the Effect of Temperature on Physical Properties and Chemical Composition of a New Calcium Silicate-based Root Canal Sealer.

J Endod 2020 Apr 18;46(4):531-538. Epub 2020 Feb 18.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada. Electronic address:

Introduction: The suitability of EndoSequence BC Sealer (BC Sealer; Brasseler USA, Savannah, GA) for warm vertical compaction has been questioned. The aim was to evaluate the cytotoxicity and the effect of heating on the physicochemical properties of a new calcium-based root canal sealer (EndoSequence BC Sealer HiFlow [HiFlow]) in comparison with EndoSequence BC Sealer.

Methods: Human periodontal ligament fibroblasts were incubated for 1, 2, or 3 days with material extracts of different concentrations, and cell viability was evaluated by Cell Counting Kit-8 (Enzo Life Sciences Inc, Burlington, Ontario, Canada). The setting time, flow, film thickness, microhardness, radiopacity, and radiopacity of the 2 sealers were measured according to ISO 6786/2012. The continuous changes in viscosity were tested by a stress-controlled rheometer at shear rates ranging from 0.01-10 s and different temperatures, and chemical composition was assessed by Fourier-transform infrared spectroscopy.

Results: Cell viability was significantly decreased on day 3 for the 1:4 diluted extract from both materials. The setting time, microhardness, and solubility of HiFlow were similar to BC Sealer at 37°C and 100°C. HiFlow had significantly higher flow and radiopacity than BC Sealer at room temperature (P < .05), and when heated, HiFlow retained its higher flow and lower film thickness (P < .05). Both sealers showed decreasing viscosity with increasing shear rate, and at a shear rate of 0.01 and 0.1 s, HiFlow exhibited lower viscosity than BC Sealer at all temperatures measured. The chemical composition of the 2 sealers was not changed by heating.

Conclusions: HiFlow showed better performance on flow/viscosity and film thickness, especially under high temperatures, which are generated by the commonly used warm vertical compaction technique.
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http://dx.doi.org/10.1016/j.joen.2019.12.009DOI Listing
April 2020

Epidermal growth factor receptor signaling suppresses αvβ6 integrin and promotes periodontal inflammation and bone loss.

J Cell Sci 2019 12 5;133(5). Epub 2019 Dec 5.

Faculty of Dentistry, Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, BC V6T 1Z3, Canada

In periodontal disease (PD), bacterial biofilms cause gingival inflammation, leading to bone loss. In healthy individuals, αvβ6 integrin in junctional epithelium maintains anti-inflammatory transforming growth factor-β1 (TGF-β1) signaling, whereas its expression is lost in individuals with PD. Bacterial biofilms suppress β6 integrin expression in cultured gingival epithelial cells (GECs) by attenuating TGF-β1 signaling, leading to an enhanced pro-inflammatory response. In the present study, we show that GEC exposure to biofilms induced activation of mitogen-activated protein kinases and epidermal growth factor receptor (EGFR). Inhibition of EGFR and ERK stunted both the biofilm-induced suppression and stimulation. Furthermore, biofilm induced the expression of endogenous EGFR ligands that suppressed and stimulated expression, indicating that the effects of the biofilm were mediated by autocrine EGFR signaling. Biofilm and EGFR ligands induced inhibitory phosphorylation of the TGF-β1 signaling mediator Smad3 at S208. Overexpression of a phosphorylation-defective mutant of Smad3 (S208A) reduced the β6 integrin suppression. Furthermore, inhibition of EGFR signaling significantly reduced bone loss and inflammation in an experimental PD model. Thus, EGFR inhibition may provide a target for clinical therapies to prevent inflammation and bone loss in PD.
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http://dx.doi.org/10.1242/jcs.236588DOI Listing
December 2019

Effect of Long-term Exposure to Peptides on Mono- and Multispecies Biofilms in Dentinal Tubules.

J Endod 2019 Dec 9;45(12):1522-1528. Epub 2019 Oct 9.

Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Introduction: The aim of this study was to evaluate the antibiofilm effectiveness of 2% chlorhexidine (CHX) and peptides 1018 and DJK-5 used either alone or in a mixture (peptide and 2% CHX) against Enterococcus faecalis and multispecies biofilms in dentin canals after short-term and long-term exposure.

Methods: One hundred eighty dentin blocks were prepared and filled with E. faecalis or multispecies bacteria by centrifugation. Three-week-old biofilms in dentin were subjected to 2% CHX, DJK-5 (10 μg/mL), 1018 (10 μg/mL), DJK-5 + 2% CHX, or 1018 + 2% CHX for short-term (1 or 3 minutes), short-term exposure after 24 hours, and long-term exposure (24 hours of exposure). The antibacterial efficacy was determined by live/dead bacterial viability staining and confocal laser scanning microscopy.

Results: Peptide DJK-5 with or without CHX was the most effective agent against all the biofilms (P < .05), killing 77% of biofilm bacteria in 1 minute. No significant difference in bacterial killing was detected between the first 3 minutes of exposure (>81%) and after 24 hours of exposure (83%) to DJK-5 or DJK-5 + CHX. Chlorhexidine and peptide 1018 had a weaker antibiofilm effect than DJK-5, and their effect was time dependent (P < .05) with a maximum killing of 60% after 24 hours of exposure.

Conclusions: Peptide DJK-5 alone and together with CHX had a rapid antibacterial effect against dentin infection. An additional antibacterial effect by CHX and peptide 1018 was achieved after a 24-hour long-term exposure.
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http://dx.doi.org/10.1016/j.joen.2019.09.003DOI Listing
December 2019

Removal of calcifications from distal canals of mandibular molars by a non-instrumentational cleaning system: A micro-CT study.

Aust Endod J 2020 Apr 11;46(1):11-16. Epub 2019 Oct 11.

Division of Endodontics, Department of Oral Biological & Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada.

Pulpal calcifications can present problems in endodontic treatment. This micro-CT study examined the removal of calcifications by a multisonic cleaning system in uninstrumented mandibular molar distal canals. The teeth were accessed and distal canals located and their patency ensured. Micro-CT images were obtained, and 15 teeth with distal canal calcifications were selected. The volume of distal canals and calcifications were calculated from the micro-CT images before and after cleaning with the GentleWave system. Calcifications were observed in all thirds of the canals. Attached and free calcification were detected. Root canal volumes were slightly increased after GentleWave treatment, whereas the calcifications were completely or partially removed in all canals. Mean reduction percentage of calcification was 86.4 ± 3.9%, in individual canals from 60% to 100%. Calcifications in the distal canals of mandibular molars could be partially or completely removed by the multisonic cleaning system without instrumentation.
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http://dx.doi.org/10.1111/aej.12376DOI Listing
April 2020

Doxycycline release and antibacterial activity from PMMA/PEO electrospun fiber mats.

J Appl Oral Sci 2019 7;27:e20180663. Epub 2019 Oct 7.

The University of British Columbia, Faculty of Dentistry, Department of Oral Health Sciences, Vancouver, Canada.

Objective: To investigate the use of polymethyl methacrylate (PMMA) electrospun fiber mats containing different amounts of polyethylene oxide (PEO) as a doxycycline delivery system and to test antibacterial activity against an oral pathogen.

Methodology: PMMA powders or PEO (mol wt 200 Kd) (10,20,30% w/w/) were dissolved in N, N-dimethylformamide (DMF) to obtain a final polymer concentration of 15% in DMF (w/v). 2% Doxycycline monohydrate was added to the solutions and submitted to vortex mixing. The solution was transferred to a plastic syringe and fit into a nanofiber electrospinning unit. The parameters applied were: voltage at 17.2 kV; distance of 20 cm between the needle tip and the collector plate; target speed at 2 m/min; and transverse speed at 1cm/min. Syringe pump speed was 0.15 mm/min. The drug release analysis was performed by removing aliquots of the drug-containing solution (in PBS) at specific periods. Doxycycline release was quantified using RP-HPLC. Fiber mats from all groups had their antibacterial action tested against S. mutans based on inhibition halos formed around the specimens. The experiments were performed in triplicate. Gravimetric analysis at specific periods was performed to determine any polymer loss. Morphological characterization of the electrospun fibers was completed under an optical microscope followed by SEM analysis.

Results: The addition of PEO to the PMMA fibers did not affect the appearance and diameter of fibers. However, increasing the %PEO caused higher doxycycline release in the first 24 h. Fibers containing 30% PEO showed statistically significant higher release when compared with the other groups. Doxycycline released from the fibers containing 20% or 30% of PEO showed effective against S. mutans.

Conclusion: The incorporation of PEO at 20% and 30% into PMMA fiber mat resulted in effective drug release systems, with detected antibacterial activity against S. mutans.
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http://dx.doi.org/10.1590/1678-7757-2018-0663DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6768291PMC
October 2019

Fatigue resistance of ProTaper gold exposed to high-concentration sodium hypochlorite in double curvature artificial canal.

Bioact Mater 2019 Dec 9;4:245-248. Epub 2019 Sep 9.

Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.

This study aimed to evaluate and compare the fatigue resistance of ProTaper Gold (PTG) and ProTaper Universal (PTU) in artificial single and double curvature canals in 5% sodium hypochlorite (NaOCl) at body temperature (37 °C). PTG and PTU files (size F1) were subjected to fatigue tests in two different artificial ceramic canals. The single curvature model had a 60° curvature angle with a 5 mm radius. The double curvature model had a 60° curvature angle with a 5 mm radius and a second 30° curvature with a 2 mm radius. A file segment was introduced into the artificial canal and immersed in water or 5% NaOCl at 37 °C. The total number of cycles to fracture (NCF) was recorded. Data were analyzed using -test and linear regression analysis. The NCF of all files was significantly influenced by the type of NiTi metal alloy ( < .01), canal curvatures ( < .01), and the environmental conditions ( < .05). PTG had higher fatigue resistance than PTU files in both single and double curvature canals ( < .05). The NCF of PTU files in 5% NaOCl was shorter than that in water ( < .05). The mean length of broken PTG was significantly shorter than those of PTU files in both single and double curvature canals ( < .01). The fatigue performance of PTG is better than that of PTU in both single and double curvature. Environmental conditions may affect the fatigue behavior of PTU files with single curvature.
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http://dx.doi.org/10.1016/j.bioactmat.2019.07.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739284PMC
December 2019

Quality of Root Filling after Obturation with Gutta-percha and 3 Different Sealers of Minimally Instrumented Root canals of the Maxillary First Molar.

J Endod 2019 Aug 8;45(8):1030-1035. Epub 2019 Jun 8.

Faculty of Dentistry, Division of Endodontics, Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, BC, Canada. Electronic address:

Introduction: The aim of this study was to compare the quality of root fillings completed by a modified single-cone (MSC) technique with 3 different sealers after minimal instrumentation and multisonic cleaning of root canals of maxillary first molars.

Methods: Root canals of 18 maxillary first molars were instrumented to size 15/.04 taper using rotary files. Sodium hypochlorite 5.25% was used during instrumentation; the final cleaning was performed by the GentleWave System (Sonendo Inc, Laguna Hills, CA). The specimens were allocated into 3 groups and root filled by the MSC technique using a size fitted gutta-percha master cone and GuttaFlow Bioseal (Coltene Whaledent GmBH + Co KG, Langenau, Switzerland), GuttaFlow 2 (Coltene Whaledent GmBH + Co KG), and MTA Fillapex (Angelus Industria de Produtos Odontológicos S/A, Londrina, PR, Brazil) sealers. Micro-computed tomographic scans were obtained before and after instrumentation, post-GentleWave, and after obturation. Reconstructed images were analyzed for the volumetric percentage of filling materials. Mesiobuccal roots of the selected teeth were sectioned at 0.5-mm increments starting at the apex of the root. The cross sections were further examined using a light microscope.

Results: The 3 groups had 90%-99% of the canal space filled with the root filling material. The mean volume of the filling material was higher in the GuttaFlow Bioseal and GuttaFlow 2 groups than in the MTA Fillapex group (P < .05). There was no significant difference among the apical, middle, and coronal thirds. The cross-sectional images showed no obvious gaps or voids in the GuttaFlow groups. After instrumentation, 49 of the 189 canal thirds (25.9%) had hard tissue debris in the root canal system. After GentleWave cleaning, only 4 of 63 canals (6.3%) and 4 of the 189 canal thirds (2.1%) still had debris.

Conclusions: The MSC method with GuttaFlow 2 and GuttaFlow Bioseal sealers after multisonic cleaning of minimally instrumented molar canals resulted in high-quality root fillings. Multisonic cleaning of minimally instrumented molars seems to be effective in debris removal.
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http://dx.doi.org/10.1016/j.joen.2019.04.012DOI Listing
August 2019
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