Publications by authors named "Van T Himel"

16 Publications

  • Page 1 of 1

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

Accuracy of Cone-beam Computed Tomographic Image Interpretation by Endodontists and Endodontic Residents.

J Endod 2018 Apr 1;44(4):571-575. Epub 2018 Feb 1.

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

Introduction: Limited field cone-beam computed tomography (CBCT) imaging has become a modality frequently used by endodontists to evaluate the teeth and surrounding tissues of their patients. Accurate image interpretation is vital to obtain needed treatment information as well as to discern coincidental findings that could be present. The goal of this study was to determine the accuracy of CBCT volume interpretation when performed by endodontists and endodontic residents.

Methods: Eighteen deidentified limited field CBCT scans were obtained and evaluated by an oral and maxillofacial radiologist and an endodontist experienced in reading CBCT images. Their collective findings were combined as the "gold standard" of interpretation for this investigation. Using standard CBCT software, 4 practicing endodontists and 5 second-year endodontic residents evaluated each scan and recorded any notable findings and whether or not each scan warranted referral to a radiology specialist. Their interpretations were then compared with the gold standard to determine accuracy and any significant differences among the groups.

Results: The overall accuracy was 58.3% for endodontists and 64.3% for residents. Paired t tests showed no statistically significant differences in accuracy between the 2 groups for findings in teeth or in bone, but residents were significantly better for maxillary sinus findings. Endodontists agreed with the gold standard 38.9% of the time and residents 49.8% of the time on necessity of referral. The Cohen kappa coefficient showed moderate agreement between the groups.

Conclusions: Endodontists and residents had similar accuracy in CBCT scan evaluation. More training and experience are warranted for both groups in order to maximize image assessment accuracy.
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http://dx.doi.org/10.1016/j.joen.2017.12.012DOI Listing
April 2018

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

Methacrylate Resin Adhesion in Root Canals Conditioned with Phosphoric Acid and Ethylenediaminetetraacetic Acid.

Eur Endod J 2017 6;2(1):1-6. Epub 2017 Feb 6.

Department of Biomedical Materials Science, East Carolina University School of Dental Medicine, Greenville, USA.

Objective: The purpose of this study was to determine the ability of a methacrylate resin dentin bonding agent to adhere to the dentin surfaces of prepared and conditioned root canals with either 32% phosphoric acid (PA) or 17% ethylenediaminetetraacetic acid (EDTA).

Methods: Prior to the application of the methacrylate resin, the root canals of 54 intact, caries-free, single- rooted, de-crowned, extracted human maxillary incisor and canine teeth were endodontically prepared and conditioned with either 32% PA or 17% EDTA or with distilled water as the unconditioned control. The resin-treated roots were cross-sectioned at three levels and scanning electron microscope (SEM) imaged for circumferential views of the root canals at 60-90× magnification and site-specific views at 250× magnification, and then randomly coded for independent and blind evaluation by four calibrated examiners. The circumferential surface of the root canals that showed no resin adhesion were digitally measured and subtracted from the digitally measured total root canal circumference, and resin adhesion was expressed as a percentage of the circumference.

Results: The mean percentages of resin adhesion were 97% for the PA group, 94% for the EDTA group, and 76% for the control group. There were statistically significant differences among the PA, EDTA, and control groups.

Conclusion: Root canals conditioned with 32% PA or 17% EDTA had more resin adhesion than unconditioned root canals. Root canals conditioned with 32% PA had more resin adhesion than those conditioned with 17% EDTA.
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http://dx.doi.org/10.5152/eej.2017.17047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7757943PMC
February 2017

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

Evaluation of 4 Commercial Viewing Devices for Radiographic Perceptibility and Working Length Determination.

J Endod 2015 Jul 8;41(7):1120-4. Epub 2015 Apr 8.

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

Introduction: This study compared images displayed on 1 desktop monitor, 1 laptop monitor, and 2 tablets for the detection of contrast and working length interpretation, with a null hypothesis of no differences between the devices.

Methods: Three aluminum blocks, with milled circles of varying depth, were radiographed at various exposure levels to create 45 images of varying radiographic density. Six observers viewed the images on 4 devices: Lenovo M92z desktop (Lenovo, Beijing, China), Lenovo Z580 laptop (Lenovo), iPad 3 (Apple, Cupertino, CA), and iPad mini (Apple). Observers recorded the number of circles detected for each image, and a perceptibility curve was used to compare the devices. Additionally, 42 extracted teeth were imaged with working length files affixed at various levels (short, flush, and long) relative to the anatomic apex. Observers measured the distance from file tip to tooth apex on each device. The absolute mean measurement error was calculated for each image. Analysis of variance tests compared the devices. Observers repeated their sessions 1 month later to evaluate intraobserver reliability as measured with weighted kappa tests. Interclass correlation coefficients compared interobserver reliability.

Results: There was no significant difference in perceptibility detection between the Lenovo M92z desktop, iPad 3, and iPad mini. However, on average, all 3 were significantly better than the Lenovo Z580 laptop (P values ≤.015). No significant difference in the mean absolute error was noted for working length measurements among the 4 viewing devices (P = .3509).

Conclusions: Although all 4 viewing devices seemed comparable with regard to working length evaluation, the laptop computer screen had lower overall ability to perceive contrast differences.
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http://dx.doi.org/10.1016/j.joen.2015.02.027DOI Listing
July 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 novel GuttaFlow sealer supports cell survival and attachment.

J Endod 2014 Feb 15;40(2):231-4. Epub 2013 Oct 15.

Department of Cell Biology and Anatomy, Louisiana State University Health Science Center, Center of Excellence in Oral and Craniofacial Biology, School of Dentistry, New Orleans, Louisiana. Electronic address:

Introduction: The purpose of this in vitro study was to compare the biocompatibility of a novel formulation of a silicone-based endodontic sealer GuttaFlow 2 (GF2; Coltène/Whaledent, Langenau, Germany) with the original (GFO) and fast-set (GFF) formulations of GuttaFlow and with an epoxy resin sealer, AHPlus Jet (AH+J; Dentsply, York, PA).

Methods: Sealers were set into 3 × 5.5 mm discs. Cell culture media was used to extract leachable products at 24 hours and 1, 2, and 4 weeks. Primary human periodontal ligament fibroblasts were incubated with sealer elutes for 24 hours and evaluated using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay and the calcein AM assay. Cell attachment was evaluated on set sealer that was either rinsed or unrinsed with cell media for 1 week. Statistical analysis was performed using the Student t test.

Results: Both calcein and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assays revealed that periodontal ligament cell viability was reduced on AH+J at 1, 2, and 4 weeks compared with all GuttaFlow sealers. There were no differences in cell viability between the GuttaFlow samples, and all displayed high rates of cell survival at all time periods. After 2 hours, cell attachment to the rinsed GFO and GFF samples exceeded the control, and at 24 hours cell attachment on all GuttaFlow samples exceeded the control. AH+J sealers supported significantly less cell attachment when compared with all GuttaFlow sealers. Cell attachment to set sealers showed better cell attachment when rinsed compared with unrinsed.

Conclusions: GuttaFlow sealers were more biocompatible than AHJ in vitro. The novel GF2 displayed comparable biocompatibility with GFF and GFO.
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http://dx.doi.org/10.1016/j.joen.2013.08.029DOI Listing
February 2014

Shaping ability of three nickel-titanium endodontic file systems in simulated S-shaped root canals.

J Endod 2012 Dec 18;38(12):1618-21. Epub 2012 Oct 18.

Department of Endodontics, Keesler Medical Center, Keesler Air Force Base, Mississippi 39534, USA.

Introduction: The purpose of this study was to determine the shaping ability of 3 nickel-titanium (NiTi) endodontic file systems by measuring canal transportation.

Methods: Seventy-two S-shaped canals in resin blocks were randomly allocated into 3 groups (n = 24): the Self-Adjusting File (SAF; ReDent Nova, Ra'anana, Israel) group, the Typhoon group (Typhoon rotary files with Controlled Memory Wire; DS Dental, Johnson City, TN), and the Vortex group (ProFile Vortex rotary files with M-Wire NiTi; Dentsply Tulsa Dental Specialties, Tulsa, OK). Blocks were secured in a jig for imaging standardization and instrumentation stabilization. Gates Glidden and PathFile drills (25 mm/.02 taper) were used to prepare the glide paths. For the Typhoon and Vortex groups (25 mm/.04 taper), canals were flooded with sterile water and instrumented using a crown-down technique from sizes 40 to 20/.04 and then apically enlarged to size 30/.04. The SAF group (25 mm) was instrumented with constant sterile water irrigation in a light-pecking, transline motion. Pre- and postinstrumentation images were taken at 40× magnification and layered, and canal transportation was measured.

Results: After adjusting for the level and canal wall side, the mean transportation was significantly higher for the Typhoon (P < .001) and Vortex (P = .005) groups compared with the SAF group. Additionally, the mean transportation was significantly higher for the Typhoon group versus the Vortex group (P < .001).

Conclusions: Under the conditions of this study, SAFs showed less canal transportation than ProFile Vortex and Typhoon files in simulated S-shaped root canals.
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http://dx.doi.org/10.1016/j.joen.2012.09.011DOI Listing
December 2012

Tennessee smiles: the UT grassroots oral health outreach initiative.

J Tenn Dent Assoc 2011 ;91(4):20-9; quiz 30-1

Department of Restorative Dentistry, University of Tennessee Health Science Center, College of Dentistry, Memphis, USA.

Access to and awareness of oral healthcare in the United States have been highlighted in the mass media and discussed among diverse populations. The current surge to provide access to oral healthcare for citizens springs from this quagmire of oral healthcare issues which affects global to local (grassroots) communities. Publications by the World Health Organization's (WHO) Health for All and the United States' Healthy People have set into motion an agenda by which institutions, healthcare professionals and governments can develop action plans to foster and nurture grassroots organizations to address these issues. An initiative has been undertaken by members of the faculty, student doctors and staff of the University of Tennessee Health Science Center, College of Dentistry (UTHSC CoD) and its partners. This cadre of volunteers has implemented grassroots efforts for the citizens of western Tennessee to date as the flagship of Tennessee Smiles: UT Grassroots Oral Health Outreach Initiative (Tennessee Smiles). By participation in health fairs, school programs and other cultural events, these volunteers have made a difference in the lives of thousands of Tennessee citizens who need exposure to information regarding their oral health care needs. The authors discuss the basis for the Tennessee Smiles organization, their successes and challenges. Future plans and the need for support of the organization are emphasized.
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February 2012

Comparison of autoclaving effects on torsional deformation and fracture resistance of three innovative endodontic file systems.

J Endod 2011 Nov 9;37(11):1572-5. Epub 2011 Sep 9.

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

Introduction: Recent innovative manufacturing techniques have produced nickel-titanium (NiTi) rotary instruments with reports of superior properties compared with standard NiTi files. These include Profile Vortex made from M-Wire (PV), Twisted Files (TF), and 10 Series files made from CM Wire (CM). Sterilization is recommended before use and is repeated if files are reused and/or carried forward between cases. The purpose for this study was to compare the effects of multiple autoclaving cycles on the torsional load resistance of these 3 new rotary endodontic files.

Methods: PV, TF, and CM files (n = 100; size 25/.04) were divided into 5 groups (n = 20). Files were steam autoclaved for 1, 2, 3, and 7 sterilization cycles. A control group was not subjected to autoclaving. Files were tested in a torsiometer in general accordance with ISO 3630-1 standards. Torsional load and degrees of rotation to failure were recorded. Mean data were analyzed by using Kruskal-Wallace/Dunn post hoc tests (P < .05).

Results: Autoclave cycles had no significant overall effect on file performance for any of the instrument systems tested. PV and CM displayed significantly greater resistance to torsional load than TF (P < .001) but were not different from each other (P > .05). Angular deflection values for TF and CM were significantly higher than for PV (P < .001), with TF demonstrating greater rotational distortion than CM (P < .05).

Conclusions: Under the conditions of this study, repeated steam autoclaving did not affect torsional resistance for unused files of the systems evaluated. In addition, CM Wire files might have a combined advantage of greater torsional strength and high deformation before failure.
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http://dx.doi.org/10.1016/j.joen.2011.07.008DOI Listing
November 2011

Dens evaginatus: literature review, pathophysiology, and comprehensive treatment regimen.

J Endod 2006 Jan;32(1):1-9

Department of Biologic and Diagnostic Sciences, University of Tennessee Health Science Center, College of Dentistry, 875 Union Avenue, Memphis, TN 38163, USA.

Dens evaginatus (DE) is an uncommon dental anomaly, having been well documented since 1925. It occurs primarily in people of Asian descent and is exhibited by protrusion of a tubercle from occlusal surfaces of posterior teeth, and lingual surfaces of anterior teeth. Tubercles have an enamel layer covering a dentin core containing a thin extension of pulp. These cusp-like protrusions are susceptible to pulp exposure from wear or fracture because of malocclusion, leading to pulpal complications soon after eruption. Endodontic intervention of permanent teeth with immature roots is unpredic for inflamed pulps, and leaves a tooth with compromised root structure when treating necrotic pulps. Efforts to ensure root maturity have involved preventive or prophylactic treatment with varying degrees of pulp invasiveness. Treatment options have changed as technology and materials have improved. The goal is to review the literature and pathophysiology regarding DE, and present a new comprehensive treatment regimen, including a truly prophylactic approach without pulpal invasiveness. A case study of a mestizo with DE is documented. Treatment of four affected mandibular premolars exhibiting three distinct diagnostic categories will illustrate various aspects of the treatment protocol presented, and tooth morphology of the anomaly is shown to aid clinical recognition.
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http://dx.doi.org/10.1016/j.joen.2005.10.009DOI Listing
January 2006

The effect of insertion rates on fill length and adaptation of a thermoplasticized gutta-percha technique.

J Endod 2003 Aug;29(8):505-8

Department of Biologic and Diagnostic Sciences, College of Dentistry, University of Tennessee Health Science Center, Memphis 38163, USA.

The purpose of this in vivo study was to determine the effect of the insertion rate of a thermoplasticized gutta-percha obturation technique (Thermafil Plus) on the quality of the root canal obturation. A calibrated practitioner obturated the tooth in each of three groups with insertion rates of 18, 6, and 3 mm/s, respectively. The quality of the obturation was assessed by measuring the length of fill and the replication of induced canal irregularities, consisting of dimples and grooves. All measurements were made on a single tooth, with a working length of 18 mm from the canal orifice, embedded in a split mold, with 20 measurements for each insertion rate. Measurements were made under a low-power microscope, with the images recorded on videotape. The length of fill decreased with decreasing the insertion rate, from a mean overextension of +0.88 mm (SD 1.12 mm) for the 18 mm/s rate to a mean underfill of -0.13 mm (SD 1.03 mm) for the 3 mm/s rate. A trend of decreasing fill with decreasing insertion rate was observed, with the difference between the insertion rates of 18 mm/s and 3 mm/s being statistically significant at p < 0.05 using a single comparison test. Replication of dimples decreased with decreasing the insertion rate from a mean reproduction of 99% for the 18 mm/s rate to a mean reproduction of 90% for the 3 mm/s rate. The replication of grooves also decreased with decreasing the insertion rate from a mean reproduction of 100% for the 18 mm/s rate to a mean reproduction of 88% for the 12 mm/s rate. Statistical analysis of the data for both the dimples and the grooves using a paired comparison post hoc Scheffe test found these differences are significant at p < 0.05.
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http://dx.doi.org/10.1097/00004770-200308000-00004DOI Listing
August 2003

Use of nickel titanium instruments for cleaning and shaping root canal systems.

J Tenn Dent Assoc 2003 ;83(2):29-33

Department of Biologic and Diagnostic Sciences, University of Tennessee Health Science Center, College of Dentistry, Memphis, USA.

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September 2003

Use of nickel titanium instruments for cleaning and shaping root canal systems.

Tex Dent J 2003 Mar;120(3):262-8

Department of Biologic and Diagnostic Sciences, University of Tennessee Health Science Center, College of Dentistry, USA.

Rapid and significant changes in goals, techniques, instrument design, and type of metals used to manufacture endodontic instruments have been made over the last few years in an attempt to overcome canal preparation errors. Although techniques change, basic treatment objectives remain the same. Schilder has stated that "root canal systems must be cleaned and shaped: cleaned of their organic remnants and shaped to receive a three dimensional hermetic filing of the entire root canal space." The goal of root canal instrumentation is to obtain a continuously tapering funnel from the coronal access to the apex that flows with the shape of the original canal (1). The ability to prepare the canal without weakening the remaining dentin or perforating the root is essential for proper obturation and subsequent long-term success (2, 3). Procedural errors occurring during the instrumentation phase include apical zipping, instrument separation, canal transportation, ledging, and strip perforation (4-6).
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March 2003
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