Publications by authors named "Timothy C Kirkpatrick"

24 Publications

  • Page 1 of 1

Vascular Endothelial Growth Factor and/or Nerve Growth Factor Treatment Induces Expression of Dentinogenic, Neuronal, and Healing Markers in Stem Cells of the Apical Papilla.

J Endod 2021 Jun 27;47(6):924-931. Epub 2021 Feb 27.

Department of Endodontics, University of Texas School of Dentistry at Houston, Houston, Texas; Center for Craniofacial Research, University of Texas School of Dentistry at Houston, Houston, Texas. Electronic address:

Introduction: The goal of regenerative endodontic procedures is to preserve and stimulate stem cells from the apical papilla (SCAPs) to develop the pulp-dentin complex using various growth factors and scaffolds. We hypothesized that the treatment of SCAPs with vascular endothelial growth factor (VEGF) or nerve growth factor (NGF) may impact the expression of osteogenic and dentinogenic markers.

Methods: The optimum concentration of VEGF and NGF on SCAP viability was assessed and introduced to SCAPs for 6-24 hours. SCAPs were also challenged with Escherichia coli lipopolysaccharide (LPS). Messenger RNA (mRNA) expression of DSPP, DMP1, TGFB1, OCN, SP7, and TWIST1 was examined via quantitative reverse transcription polymerase chain reaction. Immunohistochemistry was used to verify protein expression. In addition, total RNA from NGF-treated SCAPs in the presence or absence of LPS was extracted for RNA sequencing.

Results: Compared with untreated cells, NGF-treated SCAPs showed markedly higher levels of DSPP, DMP1, and TGFB1 mRNAs (>9-fold change, P < .05), and SCAPs treated with both VEGF and NGF showed a significant increase of DSPP and TGFB1 mRNAs (P < .05). In addition, in LPS-challenged SCAPs, treatment with these growth factors also exhibited increased expression of DSPP, DMP1, and TGFB1 mRNAs, with the most significant change induced by VEGF (P < .05). Immunohistochemistry confirmed increased dentin sialophosphoprotein, dentin matrix acidic phosphoprotein 1, and transforming growth factor beta 1 protein expression in treated SCAPs. RNA sequencing revealed multiple pathways regulated by NGF, including TGF-β and neurogenic pathways.

Conclusions: VEGF- and NGF-induced dentinogenic/neuronal/healing marker expression in SCAPs indicates the potential value of applying these growth factors in regenerative endodontic procedures.
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http://dx.doi.org/10.1016/j.joen.2021.02.011DOI Listing
June 2021

Evaluating the substantivity of silver diamine fluoride in a dentin model.

Clin Exp Dent Res 2020 Dec 8. Epub 2020 Dec 8.

Department of Endodontics, University of Texas Health Science Center, School of Dentistry at Houston, Houston, Texas, USA.

Objectives: The goal of endodontic therapy is to prevent apical periodontitis. This is achieved by biomechanical preparation, microbial control using endodontic irrigants, and complete obturation of the canal space. In order to prevent possible post-obturation complications and for an added antimicrobial effect, substantivity is a desired characteristic of endodontic irrigants. Currently the most commonly used endodontic irrigant that produces an antibacterial substantivity effect is chlorohexidine (CHX). Silver diamine fluoride (SDF) is a topically applied agent for managing dental caries and has shown to stop caries lesion progression. The objective of this study was to compare the antimicrobial substantivity effect of 3.8% SDF against other commonly used endodontic irrigants such as 2% CHX and 6.25% Sodium hypochlorite (NaOCl).

Material And Methods: Using a diffusion disc assay we determined the antimicrobial activities of 38%, 3.8%, 0.38%, and 0.038% of SDF against the bacterium Enterococcus faecalis OG1RF. Subsequently, we compared the levels of colonization of E. faecalis by scanning electron microscopy (SEM) at 1.5- and 3-week time intervals on dentin pretreated with 3.8% SDF, 6.25% NaOCl, 2% CHX or sterile phosphate buffered saline (PBS).

Results: The diffusion disc assay demonstrated that 38% and 3.8% of SDF inhibited the growth of E. faecalis. Moreover, the substantivity of 3.8% SDF (p < 0.01) was comparable to 2% CHX (p < 0.01) and it is significantly greater than 6.25% of NaOCl compared to the PBS treated samples after 1.5 and 3 weeks of incubation.

Conclusions: In this study, we demonstrate that SDF possesses antimicrobial properties against the opportunistic pathogen E. faecalis. Moreover, using a dentin model we show the substantivity of 3.8% SDF is significantly greater than 6.25% NaOCl, but is comparable to 2% CHX.
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http://dx.doi.org/10.1002/cre2.376DOI Listing
December 2020

Shear Bond Comparison between 4 Bioceramic Materials and Dual-cure Composite Resin.

J Endod 2019 Nov 3;45(11):1378-1383. Epub 2019 Sep 3.

Department of Endodontics, Louisiana State University, School of Dentistry, New Orleans, Louisiana.

Introduction: Bioceramic materials have shown biologic and physical properties favorable for regenerative treatment. A key to treatment success is an adequate restoration to prevent microleakage; however, research is limited regarding the bond strength between restorative and bioceramic materials used in regenerative procedures. This study compared the bond strength between 4 bioceramic materials and a dual-cure composite resin.

Methods: Eighty wells in Teflon (ePlastics, San Diego, CA) blocks were filled with bioceramic materials representing 4 groups: White ProRoot mineral trioxide aggregate (MTA) (Dentsply Tulsa Dental, Tulsa, OK), Biodentine (Septodont, Saint Maur des Fosses, France), EndoSequence Root Repair Material Fast Set Putty (Brasseler USA, Savannah, GA), and NeoMTA (Avalon Biomed Inc, Houston, TX). After allowing samples to set according to the manufacturers' instructions, exposed surfaces of the bioceramic materials were prepared using ClearFil SE Bond (Kuraray America, Inc., New York, NY) followed by restoration with ClearFil DC Core Plus (Kuraray America, Inc.). To test shear bond strength, each block was secured in a universal testing machine, and the crosshead was advanced at 0.5 mm/min until fracture. Newton peak force was recorded and megapascals calculated followed by data comparison.

Results: The mean shear bond strengths between ClearFil DC Core Plus and the bioceramic materials were as follows: White ProRoot MTA, 7.96 MPa; Biodentine, 9.18 MPa; EndoSequence Root Repair Material Fast Set Putty, 4.47 MPa; and NeoMTA, 5.72 MPa. White ProRoot MTA and Biodentine were statistically similar, with a higher stress bond strength than NeoMTA, which had a statistically greater bond strength than EndoSequence Root Repair Material. All these values were lower than typical bond strengths shown for dentin-composite resin bonding.

Conclusions: The choice of which bioceramic material to use in regenerative procedures should be based on factors other than the bond between that material and the overlying coronal resin restoration.
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http://dx.doi.org/10.1016/j.joen.2019.07.008DOI Listing
November 2019

The Effects of Irrigants on the Survival of Human Stem Cells of the Apical Papilla, Including Endocyn.

J Endod 2018 Feb 8;44(2):263-268. Epub 2017 Dec 8.

Department of Cell Biology and Anatomy, Louisiana State University, School of Dentistry, New Orleans, Louisiana. Electronic address:

Introduction: Endocyn, a pH-neutral solution of hypochlorous acid and hypochlorite has been developed for use as an endodontic irrigant. The purpose of this study was to evaluate the effect of Endocyn on human periodontal ligament (PDL) fibroblasts, rat osteosarcoma cells (UMR-106), and stem cells of the apical papilla (SCAP) compared with other commonly used endodontic irrigants.

Methods: To determine cytotoxicity, cells were exposed to various concentrations of Endocyn, 6% sodium hypochlorite (NaOCl), 17% EDTA, and 2% chlorhexidine for 10 minutes, 1 hour, or 24 hours. Cell survival was measured fluorescently using calcein AM. Endocyn also was tested for its ability to inhibit SCAP proliferation and alkaline phosphatase activity. Finally, SCAP transcript expression was examined via reverse-transcriptase polymerase chain reaction.

Results: Endocyn was no more toxic to PDL and UMR cells than water for up to 24 hours. Endocyn concentrations of 50% were toxic to SCAP after 1 hour of exposure. Endocyn concentrations of >20% inhibited SCAP proliferation, whereas concentrations of ≥10% inhibited alkaline phosphatase activity. Exposure of SCAP to 10% Endocyn for 3 days did not alter most transcript expression, but did significantly reduce the expression of alkaline phosphatase, fibromodulin, and osteomodulin.

Conclusion: Endocyn was significantly less cytotoxic to PDL, UMR-106, and SCAP cells compared with other commonly used endodontic irrigants. High concentrations of Endocyn did inhibit some transcript expression and alkaline phosphatase activity, indicating a potential reduction in the osteogenic potential of stems cells exposed to Endocyn.
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http://dx.doi.org/10.1016/j.joen.2017.09.001DOI Listing
February 2018

A Comparison of Coronal Tooth Discoloration Elicited by Various Endodontic Reparative Materials.

J Endod 2016 Mar 24;42(3):470-3. Epub 2015 Nov 24.

Louisiana State University, New Orleans, Louisiana.

Introduction: The purpose of this study was to evaluate coronal tooth discoloration of ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN), white ProRoot MTA, EndoSequence Root Repair Material (Brasseler USA, Savannah, GA), MTA Angelus (Angelus Solucoes Odontologicas, Londrina, Brazil), and Biodentine (Septodont, Saint Maur des Fosses, France) when used in an ex vivo pulpotomy model.

Methods: Freshly extracted mandibular third molars were collected and stored in 1% chloramine-T solution. Teeth were randomly assigned into 6 groups (n = 15) and stored individually in phosphate buffered saline at 37 °C in 100% humidity. A standardized endodontic access was made in 5 groups. A 3-mm-thick increment of reparative material was placed on the pulpal floor, covered by glass ionomer, and the access opening restored with composite. Color (Commission Internationale de l'eclairage L*a*b*) was recorded with the Vita Easy Shade spectrophotometer (VITA Zahnfabrik, Bad Säckingen, Germany) on the midbuccal surface at baseline; after access preparation; after material placement; and then after 1, 7, 30, and 60 days. Changes in Commission Internationale de l'eclairage L*a*b* were measured for each experimental group and compared with ProRoot MTA (positive control) and no treatment (negative control) using the following equation: ΔE = ([Li - L0*]2 + [ai - a0*]2 + [bi - b0*]2)(1/2). The mean results were analyzed within each group and between groups using the Friedman 2-way analysis post hoc test (P < .05).

Results: There were no significant differences between white ProRoot MTA, MTA Angelus, and the positive control group. EndoSequence Root Repair Material and Biodentine produced significantly less discoloration than white ProRoot MTA, MTA Angelus, and ProRoot MTA.

Conclusions: Under the conditions of this study, EndoSequence and Biodentine had significantly less discoloration compared with white ProRoot MTA, MTA Angelus, and ProRoot MTA. The potential for discoloration may or may not correlate when materials are used clinically.
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http://dx.doi.org/10.1016/j.joen.2015.10.013DOI Listing
March 2016

Evaluation of 4 Different Irrigating Systems for Apical Extrusion of Sodium Hypochlorite.

J Endod 2015 Sep 2;41(9):1530-4. Epub 2015 Jul 2.

Louisiana State University, New Orleans, Louisiana.

Introduction: The aim of this study was to evaluate NaOCl apical extrusion by using negative apical pressure (EndoVac), sonic agitation (EndoActivator), side-vented needle (Max-i-Probe), and photon induced photoacoustic streaming (PIPS 10 mJ and PIPS 20 mJ) laser irrigation in an in vitro gel model.

Methods: Extracted mandibular and maxillary central incisors (n = 18) were prepared to size 35/.04 and 55/.04, respectively. Teeth were mounted in transparent containers with clear acrylic and suspended in a color-changing pH-sensitive gel, creating a closed system. By using a crossover design, each tooth was sequentially irrigated by using 6% NaOCl with each device following manufacturers' recommendations. Each tooth served as its own control. Pre-irrigation and post-irrigation buccal and proximal view photographs served to measure the longest distance of extrusion and were analyzed with ImageJ software. Mean results were analyzed by using Kruskal-Wallis and Dunn post hoc test (P < .05).

Results: There were no significant differences between EndoVac, EndoActivator, and the passive extrusion groups. The EndoVac and EndoActivator groups produced significantly less extrusion than PIPS irrigation. Max-i-Probe extrusion results were more variable than those of EndoActivator but had no significant difference. Across all irrigation systems, there were no significant differences with respect to apical preparation size.

Conclusions: Under the in vitro conditions of this study, no difference was found between the 10 mJ and 20 mJ PIPS laser groups. EndoVac demonstrated significantly less potential for apical extrusion than PIPS and Max-i-Probe, whereas apical preparation size did not significantly affect extrusion of irrigant. The potential for apical extrusion of endodontic irrigants should be a consideration when selecting a system for final irrigation.
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http://dx.doi.org/10.1016/j.joen.2015.05.007DOI Listing
September 2015

The effect of 8.25% sodium hypochlorite on dental pulp dissolution and dentin flexural strength and modulus.

J Endod 2015 Jun 17;41(6):920-4. Epub 2015 Mar 17.

Wilford Hall Department of Endodontics, Joint Base San Antonio-Lackland, Texas and Keesler Medical Center Department of Endodontics, Keesler Air Force Base, Biloxi, Mississippi.

Introduction: The purpose of this study was to evaluate the effect of various concentrations of sodium hypochlorite (NaOCl), including 8.25%, on dental pulp dissolution and dentin flexural strength and modulus.

Methods: Sixty dental pulp samples and 55 plane parallel dentin bars were retrieved from extracted human teeth. Five test groups (n = 10) were formed consisting of a pulp sample and dentin bar immersed in various NaOCl solutions. The negative control group (n = 5) consisted of pulp samples and dentin bars immersed in saline. The positive control group (n = 5) consisted of pulp samples immersed in 8.25% NaOCl without a dentin bar. Every 6 minutes for 1 hour, the solutions were refreshed. The dentin bars were tested for flexural strength and modulus with a 3-point bend test. The time until total pulp dissolution and any changes in dentin bar flexural strength and modulus for the different NaOCl solutions were statistically analyzed.

Results: An increase in NaOCl concentration showed a highly significant decrease in pulp dissolution time. The pulp dissolution property of 8.25% NaOCl was significantly faster than any other tested concentration of NaOCl. The presence of dentin did not have a significant effect on the dissolution capacity of NaOCl if the solutions were refreshed. NaOCl concentration did not have a statistically significant effect on dentin flexural strength or modulus.

Conclusions: Dilution of NaOCl decreases its pulp dissolution capacity. Refreshing the solution is essential to counteract the effects of dentin. In this study, NaOCl did not have a significant effect on dentin flexural strength or modulus.
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http://dx.doi.org/10.1016/j.joen.2015.01.028DOI Listing
June 2015

Effect of repeated simulated clinical use and sterilization on the cutting efficiency and flexibility of Hyflex CM nickel-titanium rotary files.

J Endod 2015 May 3;41(5):725-8. Epub 2015 Mar 3.

Department of Endodontics, Louisiana State University, New Orleans, Louisiana.

Introduction: Recent nickel-titanium manufacturing processes have resulted in an alloy that remains in a twinned martensitic phase at operating temperature. This alloy has been shown to have increased flexibility with added tolerance to cyclic and torsional fatigue. The aim of this study was to assess the effect of repeated simulated clinical use and sterilization on cutting efficiency and flexibility of Hyflex CM rotary files.

Methods: Cutting efficiency was determined by measuring the load required to maintain a constant feed rate while instrumenting simulated canals. Flexibility was determined by using a 3-point bending test. Files were autoclaved after each use according to the manufacturer's recommendations. Files were tested through 10 simulated clinical uses. For cutting efficiency, mean data were analyzed by using multiple factor analysis of variance and the Dunnett post hoc test (P < .05). For flexibility, mean data were analyzed by using Levene's Test of Equality of Error and a general linear model (P < .05).

Results: No statistically significant decrease in cutting efficiency was noted in groups 2, 5, 6, and 7. A statistically significant decrease in cutting efficiency was noted in groups 3, 4, 8, 9, and 10. No statistically significant decrease in flexibility was noted in groups 2, 3, and 7. A statistically significant decrease in flexibility was noted in groups 4, 5, 6, 8, 9, 10, and 11.

Conclusions: Repeated simulated clinical use and sterilization showed no effect on cutting efficiency through 1 use and no effect on flexibility through 2 uses.
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http://dx.doi.org/10.1016/j.joen.2015.01.011DOI Listing
May 2015

A panoramic survey of air force basic trainees: how research translates into clinical practice.

J Endod 2014 Sep 16;40(9):1332-7. Epub 2014 Jul 16.

Keesler Medical Center Department of Endodontics, Keesler Air Force Base, Biloxi, Mississippi.

Introduction: The purposes of this study were to examine the following in young adults residing in the United States: (1) the prevalence of teeth with root canal therapy (RCT) and teeth in need of RCT, (2) how frequently treatment practices associated with success as cited in the literature are found in posterior teeth with RCT, and (3) which treatment practices are associated with periradicular pathology.

Methods: Panoramic radiographs taken of all basic trainees entering the US Air Force in 2011 were evaluated in a 2-part review. A general survey of all radiographs was performed to determine the prevalence of teeth with and teeth in need of RCT. All panoramic radiographs that showed a posterior tooth with RCT were evaluated in detail to consider the presence and quality of cuspal coverage restorations, the quality of RCT, and the presence of periradicular pathology.

Results: A total of 35,811 panoramic images were evaluated. Ten percent of basic trainees had existing RCT, whereas 5% showed a need for RCT. The total number of posterior teeth with RCT was 3,455. Nearly half of these teeth had either no cuspal coverage or an unacceptable cuspal coverage restoration. Almost one third of the existing RCT was considered inadequate based on best treatment practices. Approximately 25% of teeth with RCT had periradicular pathology present. A strong correlation was found between the quality of RCT and the absence of periradicular pathology. Of RCT teeth deemed hopeless, 97.5% had no cuspal coverage restoration present.

Conclusions: Factors cited in the literature as being associated with success are lacking in the dental treatment of young adults residing in the United States.
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http://dx.doi.org/10.1016/j.joen.2014.05.016DOI Listing
September 2014

Healing of apical periodontitis through modern endodontic retreatment techniques.

Gen Dent 2013 Mar-Apr;61(2):19-23

USAF Academy, Colorado, USA.

The presence of apical periodontitis in teeth which have undergone initial root canal treatment is largely attributed to bacteria residing in or invading from the apical root canal space. Bacteria-associated apical periodontitis will not heal spontaneously, nor will systemic antibiotics eradicate the infection. Only endodontic retreatment, endodontic surgery, or extraction will control the bacterial etiology. Modern retreatment is an effective means of addressing apical periodontitis. A mandibular premolar with apical periodontitis, apical root resorption, and overfilled gutta percha was retreated with post removal, retrieval of gutta percha from beyond the apex, ultrasonic irrigation and disinfection, and placement of a collagen internal matrix to facilitate a well-controlled MTA apical fill. The magnification and illumination imparted by the operating microscope was integral to achievement of treatment objectives. The patient's symptoms were resolved and complete osseous healing occurred. During treatment planning, clinicians should consider the capability of modern endodontic techniques to overcome technical challenges, often allowing the natural dentition to be preserved and restored to function days after retreatment.
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April 2014

In vitro canal and isthmus debris removal of the self-adjusting file, K3, and WaveOne files in the mesial root of human mandibular molars.

J Endod 2012 Aug;38(8):1140-4

Department of Endodontics, Wilford Hall Ambulatory Surgical Center, Lackland Air Force Base, Texas 78236, USA.

Introduction: The purpose of this study was to compare the effectiveness of debris removal between the Self-Adjusting File (SAF), WaveOne, and K3 file systems in the mesial roots of mandibular molars. In addition, the SAF was tested as a potential adjunct after instrumentation with other systems.

Methods: The mesial roots of 30 extracted mandibular molars were mounted in resin by using the K-Kube, sectioned at 2 and 4 mm from working length, and randomly placed into 3 groups: K3 group, sequential preparation with K3 files to an apical size of 35/.04; WaveOne group, preparation with WaveOne primary file; and SAF group, preparation with SAF. Images were taken before instrumentation, after instrumentation, after final irrigation, and after SAF adjunct irrigation. A cleanliness percentage was calculated by using interactive software. Comparisons between groups were analyzed with repeated-measures analysis of variance and post hoc tests (P < .05).

Results: There was no significant difference in canal cleanliness among the groups, but the WaveOne was significantly worse for isthmus cleanliness. Use of the SAF as an adjunct only significantly improved canal cleanliness in the K3 group at the 2-mm level by an average of 1.7%.

Conclusions: There was no difference in canal cleanliness between the 3 file systems; however, the SAF and K3 files performed significantly better than the WaveOne with respect to isthmus cleanliness. When used as a final irrigation adjunct device after instrumentation, the SAF provided a significant improvement only in a subset of the K3 group.
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http://dx.doi.org/10.1016/j.joen.2012.05.007DOI Listing
August 2012

Reinforcement of simulated immature roots restored with composite resin, mineral trioxide aggregate, gutta-percha, or a fiber post after thermocycling.

J Endod 2011 Oct 19;37(10):1390-3. Epub 2011 Aug 19.

Department of Endodontics, Wilford Hall Medical Center, Lackland Air Force Base, Lackland, Texas 78236, USA.

Introduction: The purpose of this study was to evaluate the fracture resistance after thermocycling of simulated immature teeth restored with composite, a fiber post, mineral trioxide aggregate (MTA), or gutta-percha.

Methods: Eighty-four primary bovine mandibular incisors were divided into 7 groups (n = 12). Negative controls received no treatment. Teeth in all other groups were prepared to an internal diameter of 1.75 mm. After placement of 4-mm apical barrier of MTA, the canals were filled with their respective test materials to the facial cementoenamel junction. For the fiber post group, a fiber post was fitted to extend from the MTA barrier to 2 mm below the incisal edge and was cemented with Build-It FR. The positive controls were left unfilled. The access openings were filled with BisFil II composite. All teeth were then thermocycled for 500 cycles at 5 °C and 55 °C with a 30-second dwell time and 5-second transfer time. Each root was horizontally fractured through the test material by using an Instron Universal Testing Machine, and the peak load to fracture was recorded. The data were analyzed with analysis of variance and Tukey post hoc tests (P < .05).

Results And Conclusions: Thermocycled composite was not significantly stronger than gutta-percha and MTA. The only material that significantly strengthened the simulated immature teeth was the fiber-reinforced composite with a fiber post.
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http://dx.doi.org/10.1016/j.joen.2011.07.001DOI Listing
October 2011

Comparison of debris removal with three different irrigation techniques.

J Endod 2011 Sep 25;37(9):1301-5. Epub 2011 Jun 25.

Department of Endodontics, Wilford Hall Medical Center, Lackland Air Force Base, Texas 78236, USA.

Introduction: The purpose of this study was to compare the effectiveness of debris removal between EndoVac, PiezoFlow, or needle irrigation (Max-i-Probe) in mandibular molars.

Methods: The mesial roots of 30 extracted mandibular molars were mounted in resin by using the K-Kube and then sectioned at 2 and 4 mm from the apex. The specimens were reassembled and instrumented to size 40/0.04. A standard irrigation protocol was used during instrumentation in the PiezoFlow and Max-i-Probe groups. During instrumentation of teeth in the EndoVac group, the manufacturer's recommendations for irrigation were followed. Images of the canals and isthmuses were taken before final irrigation. The percentage of cleanliness for each canal and isthmus was calculated by using interactive software. The specimens were reassembled for final irrigation with EndoVac, PiezoFlow, and Max-i-Probe by using similar volumes of irrigants. Images were again used to calculate cleanliness. Comparisons of canal and isthmus cleanliness before and after final irrigation were made by using paired t tests, and the groups were compared with repeated-measures analysis of variance (P < .05).

Results: There were no statistically significant differences in canal and isthmus cleanliness among all 3 groups at 2 and 4 mm from working length before or after final irrigation. Canal and isthmus cleanliness significantly improved at all levels after the final irrigation regimen in each group.

Conclusions: Final irrigation by using EndoVac, the PiezoFlow, or Max-i-Probe with similar volumes of irrigants significantly improved canal and isthmus cleanliness.
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http://dx.doi.org/10.1016/j.joen.2011.05.008DOI Listing
September 2011

The effects of dentin debris on the cyclic fatigue resistance of several nickel titanium rotary systems.

Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011 Sep 4;112(3):390-5. Epub 2011 May 4.

Department of Endodontics, Wilford Hall Medical Center, Lackland AFB, TX 78236, USA.

Objective: The aim of this study was to compare the effects of impacted dentin debris on the cyclic fatigue resistance of a traditional ground file, an electropolished file, and a thermally treated twisted file.

Study Design: One hundred thirty-five files were rotated against bovine dentin or a highly polished surface at the manufacturers' recommended rotation speed with a continuous 5-mm axial movement of 1 cycle per second. The files were equally divided into 3 groups: group 1, contacting dentin for 500 cycles and then metal to failure; group 2, contacting metal only to failure; group 3, contacting dentin only to failure. Cycles to failure were analyzed using analysis of variance (P < .05).

Results: K3 and Twisted Files outperformed EndoSequence files in the dentin-only group. No difference was found between the metal and dentin-metal groups.

Conclusions: In the presence of dentin, the electropolished surface of the EndoSequence NiTi rotary files did not increase the files' cyclic fatigue resistance compared with K3 or Twisted Files of the same tip size and taper.
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http://dx.doi.org/10.1016/j.tripleo.2011.01.032DOI Listing
September 2011

In vitro comparisons of debris removal of the EndoActivator system, the F file, ultrasonic irrigation, and NaOCl irrigation alone after hand-rotary instrumentation in human mandibular molars.

J Endod 2010 Aug 13;36(8):1367-71. Epub 2010 May 13.

Department of Endodontics, 10th Dental Squadron, United States Air Force Academy, Colorado, USA.

Introduction: The purpose of this in vitro study was to compare the debris removal efficacy of the EndoActivator system, the F file, ultrasonic irrigation, or 6% NaOCl irrigation alone in human mandibular molars after hand-rotary instrumentation.

Methods: A custom brass cube (K-Kube) was used to create a sealed canal system, allowing each tooth to serve as its own control. Forty extracted mandibular molars were randomly divided into 4 equal experimental groups. Each tooth was mounted, sectioned at 1, 3, and 5 mm from the working length, and then reassembled into the K-Kube, and the mesial roots were similarly prepared by using hand-rotary instrumentation. For final debridement, group 1 used F file for 30 seconds, group 2 used EndoActivator system for 30 seconds, group 3 used ultrasonic irrigation for 30 seconds, and group 4 used irrigation with 6% NaOCl within 1 mm of working length. All groups received a final irrigation with 6% NaOCl in each canal. Specimens were evaluated at 1, 3, and 5 mm from the working length for cleanliness by capturing a digital image with a stereomicroscope. All specimens had the percent cleanliness for each canal and isthmus calculated both before and after final debridement. Statistical analysis was completed by using a repeated-measures analysis of variance with Tukey post hoc tests.

Results And Conclusions: The results showed no statistically significant difference in canal or isthmus cleanliness among the 4 groups, but there was a statistically significant difference (P < .001) in canal cleanliness between the 1-mm level versus the 3-mm and 5-mm levels for all of the groups.
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http://dx.doi.org/10.1016/j.joen.2010.03.022DOI Listing
August 2010

Case report: Diagnosis and treatment of a botryoid odontogenic cyst found in the maxillary anterior region.

J Endod 2010 Apr;36(4):751-4

Department of Periodontics, 1st Dental Squadron, Langley Air Force Base, VA, USA.

Introduction: The botryoid odontogenic cyst (BOC) is a multicompartmentalized variant of the lateral periodontal cyst (LPC) that is typically found in the premolar-canine region of the mandible.

Methods: A 60-year old man was referred for evaluation of a radiolucent lesion discovered on a routine examination. Radiographs revealed a unilocular radiolucency between the roots of teeth #10 and #11. Clinically, the site appeared normal with minimal probing depths, and there were no signs of swelling, bleeding, or mobility of the adjacent teeth. The pulps of both teeth responded to cold without lingering. After patient consent, the lesion was accessed by a mucoperiosteal flap, curetted from its bony cavity, and submitted for biopsy. The site was then treated with a bone allograft and a collagen membrane.

Results: The diagnosis of a BOC was made based on location and the histopathological findings of multiple cystic spaces lined by nonkeratinized stratified squamous epithelium. The 22-month follow-up revealed a normal clinical appearance with evidence of radiographic bone fill at the site of the lesion.

Conclusion: This case shows an unusual presentation of a BOC in both location and radiographic appearance and emphasizes the importance of a microscopic examination of unilocular lesions when associated with teeth having normal responding vital pulps. The relatively high recurrence rate for the BOC warrants periodic follow-up.
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http://dx.doi.org/10.1016/j.joen.2010.01.013DOI Listing
April 2010

Comparison of nonsurgical root canal treatment and single-tooth implants.

J Endod 2009 Oct 28;35(10):1325-30. Epub 2009 Aug 28.

Wilford Hall U.S.A.F. Medical Center, Lackland Air Force Base, Texas 78236, USA.

Introduction: The aim of this review was to compare the differences between nonsurgical root canal treatment and single-tooth implants. With the emerging field of implant dentistry gaining acceptance, the choice to retain a diseased tooth through the use of root canal therapy or extract it and replace the tooth with an implant-supported crown has become controversial. Many practitioners consider the single-tooth implant as a reasonable alternative to the preservation of a diseased tooth.

Methods: An extensive search of the dental literature was accomplished to identify publications related to the differences in root canal therapy and dental implants. Several comparative studies were also considered.

Results: The treatment modalities were reviewed with respect to outcome measures and study design, success/failure, functional rehabilitation and psychological differences, complications related to treatment, cost differences, and factors influencing treatment planning considerations.

Conclusions: With the reviewed information in hand, the practitioner should be better prepared to determine which treatment option is most appropriate for each individual patient.
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http://dx.doi.org/10.1016/j.joen.2009.07.003DOI Listing
October 2009

pH changes in external root surface cavities after calcium hydroxide is placed at 1, 3 and 5 mm short of the radiographic apex.

Dent Traumatol 2009 Oct 26;25(5):470-4. Epub 2009 Aug 26.

USAF, DC, Endodontic Resident, Wilford Hall Medical Center, Lackland AFB, TX 78236, USA.

The purpose of this study was to test the null hypothesis that there is no difference in the pH on the external apical dentin surface when the canal is completely filled with calcium hydroxide or when it is placed 3 or 5 mm short of the apical foramen in extracted human teeth. The root canals of single-rooted anterior human teeth were cleaned and shaped after decoronation. Cavities about 0.50 mm deep and 1.0 mm wide located at 1, 3 and 5 mm from the radiographic apex were prepared on the external root surface and the teeth were randomly divided into four groups. The roots were filled with calcium hydroxide at 1, 3 and 5 mm from the radiographic apex, and the control group was left empty. pH readings were obtained at intervals over a 28-day study. The roots which were filled within 1 mm of the radiographic apex had the greatest increase in pH in each of the cavities. These results demonstrate that the greatest pH change on the external root surface near the apex is obtained when the canal is more completely filled with calcium hydroxide.
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http://dx.doi.org/10.1111/j.1600-9657.2009.00806.xDOI Listing
October 2009

Cyclic fatigue resistance of two variable-taper rotary file systems: ProTaper universal and V-Taper.

J Endod 2009 Apr;35(4):555-8

Wilford Hall U.S.A.F. Medical Center, Lackland Air Force Base, TX 78236, USA.

The cyclic fatigue resistance of ProTaper Universal (Dentsply Tulsa Dental Specialties, Tulsa, OK) and V-Taper (Guidance Endo, Albuquerque, NM) files was measured while rotating files around a 5-mm radius curve with 90 degrees of maximum flexure. The files were rotated at 250 rpm with a continuous axial oscillation of 4 mm at 1 Hz. The number of cycles to failure was calculated and analyzed by using univariate analysis of variance and the Tukey HSD posthoc test with results confirmed by nonparametric Kruskal-Wallis and Mann-Whitney U tests with a Bonferroni correction. The fracture faces of representative files were imaged with a scanning electron microscope to confirm cyclic fatigue as the mode of fracture. For the instruments tested, the ProTaper files appeared to resist fracture better than the V-Taper files. At each tip size tested, the ProTaper files either outperformed or were not statistically different than V-Taper files.
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http://dx.doi.org/10.1016/j.joen.2009.01.002DOI Listing
April 2009

Clinical outcomes of artificial root-end barriers with mineral trioxide aggregate in teeth with immature apices.

J Endod 2008 Jul;34(7):812-7

Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA.

The purpose of this retrospective study was to evaluate the clinical outcomes of ProRoot mineral trioxide aggregate used as an artificial apical barrier in teeth with immature apices. Twenty teeth from 19 patients were included in this study. A healed diagnosis was based on periapical index scores of 1 or 2 and no clinical signs or symptoms at recall examinations. Eighty-five percent (17/20) of these teeth were healed, and improvements in periapical index scores at recall appointments were shown to be statistically significant (P < .001, Wilcoxon signed-rank test). Chi-square test indicated that age, gender, primary treatment versus retreatment, presence of preoperative lesion, and differences in recall times did not significantly influence healing outcome. Overall, these results indicated that the mineral trioxide aggregate apical barrier technique is a successful method for obturating teeth with immature apices.
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http://dx.doi.org/10.1016/j.joen.2008.04.003DOI Listing
July 2008

Cyclic fatigue of EndoSequence and K3 rotary files in a dynamic model.

J Endod 2007 Dec;33(12):1469-72

Department of Endodontics, Wilford Hall Medical Center, Lackland AFB, Texas 78236, USA.

The cyclic fatigue resistance of K3 and EndoSequence files was compared by rotating files against a highly polished surface inclined at 15 degrees to the horizontal. For each brand, files with a 25 tip in .04 and .06 taper and files with a 40 tip in .04 and .06 taper were tested at both 300 and 600 rpm. A 3-mm axial movement simulated a clinical pecking motion at 1 cycle per second. The number of rotations to failure was calculated and analyzed by using analysis of variance and Independent Student's t tests, with results confirmed by nonparametric Mann-Whitney U tests with a Bonferroni correction. At both 300 and 600 rpm, K3 files exhibited statistically significantly more cycles to fracture than their EndoSequence counterparts with the same tip size and taper. Scanning electron microscopy images demonstrated surface features consistent with fracture due to cyclic fatigue. In this model, file design appeared to be the most important determinant of cyclic fatigue resistance.
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http://dx.doi.org/10.1016/j.joen.2007.07.041DOI Listing
December 2007

Effects of pH and mixing agents on the temporal setting of tooth-colored and gray mineral trioxide aggregate.

J Endod 2007 Aug 23;33(8):970-3. Epub 2007 May 23.

Department of Endodontics, Wilford Hall Medical Center, Lackland AFB, TX 78236-5346, USA.

The purpose of this study was to test the compressive strength of white mineral trioxide aggregate (WMTA) and gray mineral trioxide aggregate (GMTA) when mixed with sterile water or local anesthetic and exposed to an acidic environment. A total of 248 samples of WMTA and GMTA were mixed and placed in phosphate-buffered saline (PBS), at pH 5.0 or 7.4, for a period of 7 or 28 days. When WMTA and GMTA were mixed with local anesthetic, the following were observed: 1) pH 5.0 caused a significant decrease in compressive strength (p<0.0001); 2) WMTA was significantly stronger than GMTA (p<0.0001); and 3) more time in PBS (total 28 days) caused a significant decrease in compressive strength (p<0.001). There were no consistent differences in compressive strength for WMTA or GMTA when mixed with sterile water. Variability of results suggests both types of MTA be mixed with sterile water in acidic and neutral environments.
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http://dx.doi.org/10.1016/j.joen.2007.01.024DOI Listing
August 2007

The anti-microbial effect against enterococcus faecalis and the compressive strength of two types of mineral trioxide aggregate mixed with sterile water or 2% chlorhexidine liquid.

J Endod 2007 Jul 18;33(7):844-7. Epub 2007 May 18.

Department of Endodontics, Wilford Hall Medical Center, Lackland AFB, Texas 78236-5346, USA.

The purpose of this in vitro study was 2-fold: First, to compare the antimicrobial effect of gray and tooth-colored mineral trioxide aggregate (MTA) when mixed with sterile water or 2% chlorhexidine. Second, to compare the compressive strengths of the MTA/chlorhexidine versus MTA/sterile water samples. The antimicrobial effect test was accomplished by placing freshly mixed MTA samples on agar plates inoculated with Enterococcus faecalis and comparing the zones of inhibition at 24 hours. In the compressive strength test, MTA pellets were allowed to set for 72 hours and then compressed to fracture by using an Instron testing machine. Values were recorded and compared. In the antimicrobial effect experiment, the zones of inhibition were significantly larger for samples mixed with 2% chlorhexidine. In the compressive strength study, statistical evaluation showed no significance due to variability. However, data revealed that MTA mixed with sterile water always had higher compressive strengths than MTA mixed with chlorhexidine.
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http://dx.doi.org/10.1016/j.joen.2007.04.006DOI Listing
July 2007

Fracture resistance of simulated immature teeth filled with resilon, gutta-percha, or composite.

J Endod 2007 Apr 22;33(4):480-3. Epub 2007 Jan 22.

Department of Endodontics, Wilford Hall Medical Center, 2450 Pepperell Street, Lackland AFB, TX 28236, USA.

The purpose of this study was to evaluate the fracture resistance gained by filling root canals of simulated immature teeth with either Resilon, gutta-percha, a self-curing flowable composite resin (BisFil 2B), or a self-curing hybrid composite resin (BisFil II). Seventy-two sheep incisors were divided into six groups of 12 teeth each. Negative controls received no treatment. Teeth in all other groups were prepared until a size 120 LightSpeed LSX instrument could be passed out the apex. After apical placement of a mineral trioxide aggregate (MTA) barrier, the canals were filled with their respective test material to the facial CEJ. The positive control canals were left unfilled. The access openings (including positive controls) were restored with BisFil II. Each root was horizontally fractured through the test material using an Instron. The mean peak loads to fracture were recorded. The hybrid composite resin (BisFil II) was the only material significantly more fracture resistant than positive controls (p < 0.017).
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http://dx.doi.org/10.1016/j.joen.2006.11.014DOI Listing
April 2007
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