Publications by authors named "Ahmed Hieawy"

12 Publications

  • Page 1 of 1

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

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

Acute Vision Loss as an Ophthalmic Complication of Dental Procedures.

Semin Ophthalmol 2021 Apr 27;36(3):75-81. Epub 2021 Feb 27.

Department of Ophthalmology and Visual Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.

Acute vision loss has been previously described as a complication of dental procedures through a variety of mechanisms. The vision loss is typically transient, although permanent loss has been reported. Physicians, including ophthalmologists, typically lack formal education around dental procedures and may be uninformed about the risks to ocular or periocular structures as well as the types of complications that can arise. We aimed to summarize literature describing the various mechanisms by which dental procedures can lead to vision loss in order to equip physicians (primary care, emergency medicine, and ophthalmologists) with a better understanding of the mechanisms by which dental procedures can lead to acute vision loss.  A literature search (1950 to 2020) identified articles discussing acute vision loss as a complication of dental procedures.  Dental procedures can result in a variety of ophthalmological conditions through ischemic, infectious, compressive, and anesthetic-related etiologies.  While the majority of vision loss is transient and requires little management, there are vision and life-threatening complications that can arise and would require assessment and appropriate treatment.
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http://dx.doi.org/10.1080/08820538.2021.1890788DOI Listing
April 2021

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

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

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

Effect of Torsional and Fatigue Preloading on HyFlex EDM Files.

J Endod 2018 Apr 12;44(4):643-647. Epub 2018 Jan 12.

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

Introduction: The purpose of this study was to evaluate the effect of a low amount of torsional preloading on the fatigue life and different degrees of cyclic fatigue on torsional failure of HyFlex EDM (EDM; Coltene-Whaledent, Allstetten, Switzerland) and HyFlex CM (CM; Coltene-Whaledent) instruments.

Methods: EDM and CM files were used. The fatigue resistance was examined in a 5-mm radius and 60° single curve, and the mean number of cycles to failure (N) was recorded. The torque and rotation angles at failure of the instruments were measured according to ISO 3630-1. New files were precycled to 0%, 50%, and 75% of the N, and torsional tests were then performed. Other new files were preloaded at 5%, 15%, 25%, and 50% of the mean rotation angles before the fatigue test. The fracture surfaces of the fragments were examined under a scanning electron microscope.

Results: The fatigue resistance of EDM instruments was higher than that of CM instruments (P < .05). The torque and angle of rotation at fracture of the files were similar. Torsional preloading lowered the N of EDM at 15% preloading (P < .05) and the N of CM at 50% preloading (P < .05). However, the N of EDM files even with 50% torsional preloading was significantly higher than unused CM files (P < .05). Fatigue prestressing even at 75% had no negative effect on the torque and rotation angle of the EDM files. Moderate precycling (50%) of EDM files increased their torsional resistance. The fractographic patterns corresponded to the pattern defined by the last stage test.

Conclusions: A low amount (15%) of torsional preloading reduced the fatigue resistance of EDM files, whereas even extensive (75%) precyclic fatigue was not detrimental to their torsional resistance.
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http://dx.doi.org/10.1016/j.joen.2017.12.002DOI Listing
April 2018

Fatigue Resistance of a 3-dimensional Conforming Nickel-Titanium Rotary Instrument in Double Curvatures.

J Endod 2016 Jun 20;42(6):961-4. Epub 2016 Apr 20.

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

Introduction: Fatigue resistance of ProFile, Vortex Blue, and TRUShape files in artificial single curvature and in 2 different artificial double curvature canals was evaluated.

Methods: Three files (ProFile, Vortex Blue [size 20/.06], and TRUShape [size 20/.06v]) were subjected to fatigue tests in a single curvature (group 1: 60° curvature) and 2 different double curvatures (group 2: 60° and 30° curvatures; group 3: two 60° curvatures). The time to fracture and the total number of cycles to failure were recorded. The fracture surfaces of the fragments were examined with a scanning electron microscope.

Results: All files had significantly higher fatigue resistance in a single curvature canal than in the double curvature canals. In a single curvature group, the time to fracture of TRUShape and ProFile was longer than in Vortex Blue files. In both double curvature groups, TRUShape had the longest time to fracture among all files. The fatigue resistance (the time to fracture and number of cycles to failure) of ProFile and Vortex Blue was lower in group 3 than in group 2 (P < .05). However, there was no significant difference in fatigue resistance of TRUShape in the double curvature groups. The length of the fragment of TRUShape was longer than in Vortex Blue and ProFile files in group 3 (P < .05).

Conclusions: The fatigue performance of TRUShape is different in double curvature canals, compared with conventional nickel-titanium rotary files. The fatigue resistance of TRUShape was superior to ProFile and Vortex Blue in double curvature canals.
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http://dx.doi.org/10.1016/j.joen.2016.02.012DOI Listing
June 2016

Physical properties and hydration behavior of a fast-setting bioceramic endodontic material.

BMC Oral Health 2016 Feb 20;16:23. Epub 2016 Feb 20.

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

Background: To investigate the physical properties and the hydration behaviour of the fast-setting bioceramic iRoot FS Fast Set Root Repair Material (iRoot FS) and three other endodontic cements.

Methods: iRoot FS, Endosequence Root Repair Material Putty (ERRM Putty), gray and white mineral trioxide aggregate (G-MTA & W-MTA), and intermediate restorative material (IRM) were evaluated. The setting time was measured using ANSI/ADA standards. Microhardness was evaluated using the Vickers indentation test. Compressive strength and porosity were investigated at 7 and 28 days. Differential scanning calorimetry (DSC) was employed for the hydration test.

Results: iRoot FS had the shortest setting time of the four bioceramic cements (p < .001). The microhardness values of iRoot FS, ERRM Putty and MTA increased at different rates over the 28 days period. At day one, ERRM Putty had the lowest microhardness of the bioceramic cements (p < .001), but reached the same level as MTA at 4, 7 and 28 days. The microhardness of iRoot FS was lower than that of W-MTA at 7 and 28 days (p < .05). The porosity of the materials did not change after 7 days (p < .05). The compressive strength values at 28 days were significantly greater for all bioceramic groups compared to those at 7 days (p < .01). ERRM Putty had the highest compressive strength and the lowest porosity of the evaluated bioceramic cements (p < .05), followed by iRoot FS, W-MTA, and G-MTA, respectively. DSC showed that iRoot FS hydrated fastest, inducing an intense exothermic reaction. The ERRM Putty did not demonstrate a clear exothermic peak during the isothermal calorimetry test.

Conclusions: iRoot FS had a faster setting time and hydrating process than the other bioceramic cements tested. The mechanical properties of iRoot FS, G-MTA and W-MTA were relatively similar.
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http://dx.doi.org/10.1186/s12903-016-0184-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4761215PMC
February 2016

WaveOne Rotary Instruments after Clinical Use.

J Endod 2016 Feb 2;42(2):186-9. Epub 2015 Dec 2.

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

Introduction: The purpose of this study was to evaluate the incidence and mode of WaveOne (Dentsply Tulsa Dental Specialties, Tulsa, OK) instrument defects after single use at different endodontic clinics.

Methods: A total of 438 WaveOne instruments were collected after clinical use from the 4 specialist clinics over a 12-month period and from 1 graduate program over a 20-month period. The incidence and type of instrument defects were analyzed. The lateral surfaces of part of the defective instruments and fracture surfaces of fractured files were examined using scanning electron microscopy. Unused and clinically used files were examined by a nanoindentation test.

Results: Of the 438 WaveOne instruments collected, 42 (9.6%) had defects: 40 (9.1%) were distorted and 2 (0.5%) files had fractured, 1 Small and 1 Primary file. Clear differences in the frequency of defects were found among the 3 file sizes; the occurrence of distortion and fracture were highest with the Small file (21.2% and 0.7%, respectively) followed by the Primary file (4.4% and 0.4%, respectively) (P < .05). No defects were detected on the Large file. The cause of the 2 fractures was shear stress. Instruments from various clinics showed no significantly different occurrence of instrument deformation. Unwinding occurred at 1.2-3.1 mm from the tip. No significant difference in nanohardness was detected among unused and used instruments.

Conclusions: The risk of WaveOne fracture is very low when files are singly used by endodontists and residents. Unwinding of the files occurred most frequently in the Small file. The frequency of defects of WaveOne instruments were not influenced by the operator.
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http://dx.doi.org/10.1016/j.joen.2015.10.008DOI Listing
February 2016

Cyclic Fatigue of ProFile Vortex and Vortex Blue Nickel-Titanium Files in Single and Double Curvatures.

J Endod 2015 Oct 31;41(10):1686-90. Epub 2015 Jul 31.

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

Introduction: The aims of this study were to determine the flexibility of ProFile Vortex (VX) and Vortex Blue (VB) files (Dentsply Tulsa Dental Specialties, Tulsa, OK) and then to evaluate and compare their fatigue resistance in artificial single curvature and 2 different artificial double curvature canals.

Methods: Flexibility of the files (size 25/.04) in bending was assessed according to ISO 3630-1. Both files were subjected to fatigue tests inside artificial canals with a single curvature (group 1: 60° curvature, 5-mm radius) and with 2 different double curvatures (group 2: first [coronal] curve of 60° curvature and 5-mm radius and the second one [apical] of 30° curvature and 2-mm radius and group 3: first curve of 60° curvature and 5-mm radius and the second one of 60° curvature and 2-mm radius). The number of cycles to fracture (NCF) was recorded, and the fracture surface of all fragments was examined with a scanning electron microscope.

Results: The bending load was significantly lower for VB files than VX files (P < .05), and the 2 types of files followed different trajectories in identical canals. In group 1, the 2 files had significantly higher NCF than in groups 2 and 3 (P < .05). Both files had significantly higher NCF in group 2 than in group 3 (P < .05). In group 1, VB files had fatigue resistance superior to VX files (P < .05), whereas in groups 2 and 3 their fatigue resistance was not statistically different from each other. The crack initiation of a vast majority of files that fractured in double curvature canals (groups 2 and 3) was localized on either 1 of 2 of the 3 cutting edges.

Conclusions: Double curvature canals represent a much more stressful and challenging anatomy than single curvature canals, and, in them, fatigue resistance may be affected by the degrees and the radii of curvatures as well as by the bending properties of the files.
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http://dx.doi.org/10.1016/j.joen.2015.06.012DOI Listing
October 2015

Phase Transformation Behavior and Resistance to Bending and Cyclic Fatigue of ProTaper Gold and ProTaper Universal Instruments.

J Endod 2015 Jul 1;41(7):1134-8. Epub 2015 Apr 1.

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

Introduction: The purpose of this study was to compare the flexibility and cyclic fatigue resistance of ProTaper Universal (PTU; Dentsply Tulsa Dental Specialities, Tulsa, OK) and ProTaper Gold (PTG; Dentsply Tulsa Dental Specialities, Tulsa, OK) instruments in relation to their phase transformation behavior.

Methods: Sizes S1, S2, F1, F2, and F3 of PTU and PTG instruments were subjected to rotational bending at a curvature of 40° and a radius of 6 mm. The number of cycles to fracture (NCF) was recorded. The fracture surface of all fragments was examined with a scanning electron microscope. Flexibility was determined by 45° bending tests according to the ISO 3630-1 specification. Unused and fractured instruments were examined by differential scanning calorimetry.

Results: PTG had a cyclic fatigue resistance superior to PTU in all sizes (P < .001). The NCF of the nickel-titanium files of sizes S1 and S2 was significantly higher than those of sizes F1 to F3 (P < .001). No significant difference in the NCF of PTU instruments was detected between F1 and F2. The fractured files of both PTU and PTG showed the typical fracture pattern of fatigue failure. The bending load values were significantly lower for PTG than for PTU (P < .05). The differential scanning calorimetry analyses showed that each segment of the PTG instruments had a higher austenite finish temperature (50.1°C ± 1.7°C) than the PTU instruments (21.2°C ± 1.9°C) (P < .001). PTG instruments had a 2-stage transformation behavior. There was no significant difference in the austenite finish between unused files and instruments subjected to the fatigue process.

Conclusions: PTG files were significantly more flexible and resistant to fatigue than PTU files. PTG exhibited different phase transformation behavior than PTU, which may be attributed to the special heat treatment history of PTG instruments. PTG may be more suited for preparing canals with a more abrupt curvature.
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http://dx.doi.org/10.1016/j.joen.2015.02.030DOI Listing
July 2015
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