Appropriate Electrode Placement Site for Electric Pulp Testing First Molar Teeth
Jack Lin, BDS, Nicholas Chandler, BDS, MSc, PhD, David Purton, BDS, MDS, Brian Monteith, BChD, MChD
Twenty volunteers with first molars free of restorations and caries were recruited. One molar from each arch was selected, and rubber dam was applied. Seven sites on each crown were electric pulp tested 4 times with an Elements Diagnostic Unit, and lowest threshold responses were recorded. Data were analyzed with one-way analysis of variance and the Tukey test at the .01 level. The lowest response for both the maxillary and mandibular teeth was with the probe on the mesiobuccal cusp tip. Other sites showed an increase in level from the mesiobuccal cuspal surface, mesiobuccal gingival surface, and the center of the supporting cusps (palatal of maxillary molar, buccal of mandibular molar). No significant difference in responses was found between male and female subjects; however, male subjects responded at higher thresholds than female subjects on all test sites except the mesiobuccal cusp tip. The optimum site for pulp testing first molars is the mesiobuccal cusp tip.
Localized Increases in Corticotropin-releasing Factor Receptors in Pulp after Dental Injury
J. Carson Rutz, MS, DMD, John F. Hatton, DMD, Charles Hildebolt, MA, DDS, PhD, Jason E. Wells, PhD, Kevin C. Rowland, PhD
Corticotropin-releasing factor (CRF) binds to membrane-bound CRF receptors (CRF-Rs). Among the actions mediated by activated CRF-Rs is β-endorphin (END) release from immune cells, increasing peripheral antinociception. For assessment of inflammatory regulation of CRF-R expression, rats underwent pulp exposure of left, first mandibular molars and recovered for 6 days. Control pulpal tissue consisted of contralateral, uninjured molars and left, first mandibular molars of uninjured animals. Pulp tissue specimens were incubated with antibodies directed against CRF-R (both isoforms), neurofilament, CD45, and END. We observed (1) increases in pulp CRF-R immunoreactivity after injury, (2) increased CRF-R immunoreactivity expressed in 3 distinct zones in relation to the injury, and (3) increased CD45 and END immunoreactivity in regions surrounding the pulpal abscess. CRF-Rs might provide an additional target for novel analgesics to treat pulpal pain.
Clinical Efficiency of 2% Chlorhexidine Gel in Reducing Intracanal Bacteria
Ching S. Wang, DDS, Roland R. Arnold, PhD, Martin Trope, DMD, MS, Fabricio B. Teixeira, DDS, MS, PhD
This study evaluated the clinical efficacy of 2% chlorhexidine (CHX) gel on intracanal bacteria reduction during root canal instrumentation. The additional antibacterial effect of an intracanal dressing (Ca[OH]2 mixed with 2% CHX gel) was also assessed. Forty-three patients with apical periodontitis were recruited. Four patients with irreversible pulpitis were included as negative controls. Teeth were instrumented using rotary instruments and 2% CHX gel as the disinfectant. Bacterial samples were taken upon access (S1), after instrumentation (S2), and after 2 weeks of intracanal dressing (S3). Anaerobic culture was performed. Four samples showed no bacteria growth at S1, which were excluded from further analysis. Of the samples cultured positively at S1, 10.3% (4/39) and 8.3% (4/36) sampled bacteria at S2 and S3, respectively. A significant difference in the percentage of positive culture between S1 and S2 (p < 0.001) but not between S2 and S3 (p = 0.692) was found. These results suggest that 2% CHX gel is an effective root canal disinfectant and additional intracanal dressing did not significantly improve the bacteria reduction on the sampled root canals.
The Outcome of Endodontic Treatment: A Retrospective Study of 2000 Cases Performed by a Specialist
Noboru Imura, MS, DDS, Ericka T. Pinheiro, PhD, MS, DDS, Brenda P.F.A. Gomes, PhD, MS, DDS, Alexandre A. Zaia, PhD, MS, DDS, Caio C.R. Ferraz, PhD, MS, DDS, Francisco J. Souza-Filho, PhD, MS, DDS
The purpose of this study was to evaluate the treatment outcome of initial endodontic treatment and nonsurgical retreatment performed by an endodontic specialist in his private office. A total of 2,000 teeth were examined clinically and radiographically and the results were analyzed statistically by Pearson or Fisher’s Exact test and multivariate logistic regression. The multivariate analysis evaluated joint associations among various factors, using logistic regression models. The dependent variable for this analysis was the dichotomous outcome: healed versus disease. The overall endodontic success rate was 91.45%, and the healed rate was significantly higher for initial endodontic treatments than for nonsurgical retreatments; teeth without lesion than for those with lesions; teeth treated without complications than for those with complications; recall period of 18-24 months than for other periods, and teeth with final coronal restoration than for those without. Of the 1376 teeth treated in the initial endodontic treatment sample, the success rate was 94.0%. Multivariate analysis identified the presence of procedural complications (file breakage, perforation and flare-up), as well as the absence of the restorations at follow-ups as the significant predictors of outcome, showing lower rates of success. Of the 624 teeth in the nonsurgical retreatment sample, 85.9% were successful. Stepwise logistic regression analysis revealed that preoperative radiolucency was a strong statistically significant factor to determine lower rates of success than in its absence. Two additional variables (age and tooth type) were found to have a significant influence on the outcome of the retreatment sample. A higher healed rate was observed for the 50-59 years age groups than others, while multirooted (molars) teeth revealed a significantly lower percentage of success than pre-molars and anterior teeth.
Evaluation of the Surface Characteristics of Used and New ProTaper Instruments: An Atomic Force Microscopy Study
Ugur Inan, DDS, PhD, Cumhur Aydin, DDS, PhD, Ozgur Uzun, DDS, PhD, Ozgur Topuz, DDS, PhD, Tayfun Alacam, DDS, PhD
The purpose of this study was to evaluate the topography of new and used ProTaper rotary nickel-titanium (NiTi) instruments by using atomic force microscope. Four new and four used size S1, S2, F1, and F2 instruments were selected for this study. New and used instruments were analyzed on 11 points along a 3-mm section at the tip of the instrument. Quantitative measurements according to the topographic deviations (root mean square) were recorded. Data were analyzed by paired samples t test. Mean root mean square values for used ProTaper instruments were higher than the new ones, and the difference between them was statistically significant. The results of this study showed that used ProTaper instruments demonstrated more surface deformation and wear.
Comparison of the Area of Resin-based Sealer and Voids in Roots Obturated with Resilon and Gutta-Percha
Kamran Gulsahi, DDS, PhD, Zafer C. Cehreli, DDS, PhD, Emel O. Onay, DDS, PhD, Fugen Tasman-Dagli, DDS, PhD, Mete Ungor, DDS, PhD
The aim of this study was to compare the cross-sectional area of sealer plus voids of Epiphany sealer surrounding root fillings completed with Resilon cones and laterally compacted gutta-percha. The root canals of extracted human mandibular premolars were prepared to a final size of 40 (0.06 taper). The teeth were then randomly assigned into 2 groups (n = 12/group) for the filling procedures in conjunction with Epiphany sealer: group 1, Resilon cones, and group 2, gutta-percha. Horizontal sections were obtained every 1 mm up to 5 mm from the apical foramen. The sections were digitally photographed under magnification, and the cross-sectional area of the root canal and the area occupied by the sealer and voids were calculated, after which statistical comparisons were made. No differences were found between the sealer plus void or void area of Resilon or gutta-percha groups at any level of sectioning (P > .05). Comparisons within each obturation group showed that there was no significant difference between any level of sectioning with regard to the ratio of sealer plus void area or void area to that of the root canal (P > .05). Within the experimental conditions of the present study, both obturating techniques with the Epiphany sealer exhibited similar amounts of sealer and void area, regardless of the apical level of sectioning compared.
Dentin Demineralization When Subjected to BioPure MTAD: A Longitudinal and Quantitative Assessment
Gustavo De-Deus, MD, Claudia Reis, MS, Sandra Fidel, PhD, Rivail Fidel, PhD, Sidnei Paciornik, PhD
In the present study, the demineralizing ability of BioPure MTAD (Dentsply/Tulsa, Tulsa, OK), 17% EDTA, and 5% citric acid on radicular dentin was quantitatively and longitudinally analyzed. 3 mm thick disks were obtained at the root cervical third from 9 maxillary human molars, and a standardized smear layer was produced. Cosite images of the dentin surface were obtained after several cumulative demineralization times. Sixteen images were obtained in each dentin sample for each experimental time, at 1000× magnification. An image processing and analysis sequence measured sets of images, providing data of area fraction for thousands of tubules over time. Thus, it was possible to follow the demineralization phenomenon and quantitatively analyze the effect of the various substances. The nonparametric Kruskal-Wallis H-test was used to analyze the data. Based on the present results, it can be concluded that the demineralization kinetics promoted by both 5% CA and BioPure MTAD was significantly faster than by 17% EDTA.
An In Vitro Evaluation of the Contents of Root Canals Obturated With Gutta Percha and AH-26 Sealer or Resilon and Epiphany Sealer
Brian L. James, DDS, MSD, Cecil E. Brown, DDS, MS, Joseph J. Legan, DDS, MS, B. Keith Moore, PhD, Mychel M. Vail, DDS, MSD
The purpose of this study was to compare the contents of root canals obturated with gutta percha and AH-26 sealer (Dentsply, Tulsa, OK) to canals obturated with the Resilon and Epiphany (Pentron, Wallingford, CT) system. Canal contents were assessed by determining the percentage of canal space occupied by core material, sealer, voids, and debris. Forty extracted human maxillary anterior teeth were instrumented, and the teeth were randomly assigned to either the gutta percha/AH 26 group or the Epiphany/Resilon group. Canals were obturated, and the teeth were subsequently embedded in resin and sectioned horizontally at 2, 4, and 6 mm from the anatomic apex. Sections were photographed by using a low vacuum scanning electron microscope. Image-J (Wayne Rasband; National Institute of Health, Bethesda, MD) software was used to quantify the proportion of core material, sealer, voids, and debris in each canal. Percentages and statistical comparisons for each method were compared. There were no significant differences found among the two groups in terms of the percentage of core (p = 0.9), sealer (p = 0.58), debris (p = 0.999), or voids (p = 1.00). Additionally, there were no differences in the percentage of core material, sealer, debris, or voids at any of the examined levels (2, 4, or 6 mm).
Root Canal Adhesive Filling in Dogs’ Teeth with or without Coronal Restoration: A Histopathological Evaluation
Mario Roberto Leonardo, DDS, PhD, Frederick Barnett, DMD, Gilberto J. Debelian, DMD, PhD, Regina Karla de Pontes Lima, DDS, Léa Assed Bezerra da Silva, DDS, PhD
The purpose of this study was to evaluate in vivo the response of the periradicular tissues after endodontic treatment and root filling with Epiphany/Resilon (Penntron Clinical Technologies, LLC, Wallingford, CT) or gutta percha and new Sealapex (SybronEndo, Glendora, CA) in dogs’ teeth with or without coronal restoration. Teeth without coronal restorations were used to assess the influence of continuous exposure to the oral environment on the periradicular tissues. Sixty root canals with vital pulps in three dogs were instrumented and obturated in a single session and randomly assigned to one of four groups as follows. group 1: root canal filling with Epiphany/Resilon with coronal restoration, group 2: root canal filling with Sealapex sealer and gutta percha with restoration, group 3: root canal filling with Epiphany/Resilon without restoration, and group 4: root canal filling with Sealapex sealer and gutta percha without coronal restoration. After 90 days, the animals were euthanized, and the maxillas and mandibles were removed and submitted for histologic processing. Longitudinal sections were obtained and stained with hematoxylin and eosin, Mallory’s trichrome, and Brown and Brenn stains and examined under light microscopy. There were significant differences found between the four groups (p < 0.05). The results showed that roots canals filled with Epiphany/Resilon, with coronal restoration, had significantly less periradicular inflammation than roots canals filled with gutta percha and Sealapex, with coronal restoration (p = 0.021). No significant difference was observed in the intensity of inflammation between roots canals filled with Epiphany/Resilon with no restoration and roots filled with gutta percha and Sealapex with restoration (p = 0.269). Roots canals filled with gutta percha and Sealapex sealer without coronal restoration showed the greatest degree of periradicular inflammation.
Invasive Cervical Root Resorption: Treatment Rationale with an Interdisciplinary Approach
Ami Smidt, DMD, MSc, Eyal Nuni, DMD, David Keinan, DMD, MSc
Invasive cervical resorption (ICR) is a significant and often aggressive pathologic process that, unfortunately, might lead to tooth loss. The presence of such a lesion in the cervical area is always a clinical challenge. This article presents an ICR case in which successful treatment was achieved by combining 4 disciplines: endodontics, orthodontics, periodontics, and prosthetics. Forced eruption combined with fiberotomy was used in this case for pulling the root rapidly from within the alveolar socket, thus exposing sound and healthy tooth material beyond the affected zone suitable for crown preparation. The presented interdisciplinary technique is offered for the prudent clinician as a solution in ICR cases of severe destructive nature.
Calcium Phosphate Phase Transformation Produced by the Interaction of the Portland Cement Component of White Mineral Trioxide Aggregate with a Phosphate-containing Fluid
Franklin R. Tay, BDSc(Hons), PhD, David H. Pashley, DMD, PhD, Frederick A. Rueggeberg, DDS, MS, Robert J. Loushine, DDS, R. Norman Weller, DMD, MS
The bioactivity of mineral trioxide aggregate (MTA) has been attributed to its ability to produce hydroxyapatite in the presence of phosphate-containing fluids. It is known that stoichiometric hydroxyapatites do not exist in biological systems and do not contribute to the osteogenic potential of calcium phosphate–based biomaterials. Because Portland cement is the active ingredient in white MTA, we have characterized the calcium phosphate phases produced when set white Portland cement was immersed in phosphate-buffered saline using pH and turbidity measurements, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, electron diffraction, x-ray diffraction, and Fourier transform-infrared spectroscopy. An amorphous calcium phosphate phase was initially formed that transformed to an apatite phase, with the latter consisting of calcium-deficient, poorly crystalline, B-type carbonated apatite crystallites. Amorphous calcium phosphate is a key intermediate that precedes biological apatite formation in skeletal calcification. Thus, the clinical manifestations of bioactivity with the use of MTA may at least be partially attributed to the mineralization induction capacity of its Portland cement component.
Influence of Deep Dry Cryogenic Treatment on Cutting Efficiency and Wear Resistance of Nickel–Titanium Rotary Endodontic Instruments
Thilla Sekar Vinothkumar, MDS, Revathi Miglani, MDS, DNB, Lakshmikanthanbharathi Lakshminarayananan, MDS
This study tested the effect of cryogenic treatment on nickel-titanium (NiTi) endodontic instruments. Ten rotary NiTi instruments (ProFile 30, 0.06; Dentsply Maillefer Instruments SA, Baillegues, Switzerland)) were subjected to deep dry cryogenic treatment at liquid nitrogen temperature (−185°C) (group A) and compared with that of nontreated instruments (group B). Root canals of 30 extracted permanent mandibular premolars were prepared to size 25 using ProFile 0.04 taper rotary NiTi instruments. Each instrument was used in 4 root canals for a total of 240 seconds. Cutting efficiency in rotary motion was assessed from weight loss of tooth samples after instrumentation. Wear resistance was assessed from surface defects on cutting heads pre- and postinstrumentation using scanning electron microscope. The weight loss was significantly higher in group A (p < 0.05, Student t test). The presence of surface defects after use was higher in group B. Deep dry cryogenic treatment increases the cutting efficiency significantly but not the wear resistance.
The Ability of Optical Coherence Tomography to Characterize the Root Canal Walls
Hagay Shemesh, DMD, Gijs van Soest, PhD, Min-Kai Wu, PhD, Lucas W.M. van der Sluis, PhD, Paul R. Wesselink, PhD
A detailed understanding of the complexity of root canal systems is imperative to ensure successful root canal therapy. The aim of this study was to evaluate the ability of an optical coherence tomography (OCT) system in imaging root canal walls after endodontic preparation and to correlate these images to histologic sections. Ten extracted mandibular incisors were prepared to size 50 with K-files and Gates Glidden drills. A three-dimensional OCT scan was made with a rotating optical fiber probe inside the root canal. All teeth were sectioned at 5 and 7 mm from the apex and viewed through a microscope. Histologic sections were compared with the corresponding OCT output. All oval canals, uncleaned fins, risk zones, and one perforation that was detected by histology were also imaged by OCT. OCT proves to be a reliable method to image root canals and root dentin in a nondestructive way. This technique holds promise for full in vivo endodontic imaging.
Variation in the Expression of Insulin-like Growth Factor-1 in Human Pulp Tissue According to the Root-development Stage
Javier Caviedes-Bucheli, DDS, MSc, Patricia Angel-Londoño, DDS, Alberto Díaz-Perez, DDS, María Patricia Orozco, DDS, José Luis Álvarez, DDS, Nelson Lombana, MSc, Eduardo Díaz, MSc, Hugo Roberto Muñoz, DDS, MSc
Insulin-like growth factor-1 (IGF-1) plays an important role in cell proliferation and differentiation. It actively participates during odontogenesis and mineralization of dental hard tissues. The purpose of this study is to use a radioimmunoassay (RIA) to determine whether there are differences in the expression of IGF-1 in human pulp from teeth having incomplete or complete root development. Twenty-six pulp samples were obtained from freshly extracted human third molars, half of them from teeth with incomplete root development. All of the samples were processed and labeled using an IGF-1 RIA kit. Results showed IGF-1 presence in all human pulp samples with a statistically significant higher expression in pulps having complete root development. The present findings are consistent with the hypothesis that IGF-1 contributes toward forming and mineralizing dental tissues in teeth with incomplete root development as well as in pulp-repairing process in teeth with complete root development.
The Ability of Portland Cement, MTA, and MTA Bio to Prevent Through-and-Through Fluid Movement in Repaired Furcal Perforations
This study assessed the ability of Portland cement, white Angelus–mineral trioxide aggregate (MTA), and MTA Bio to seal furcal perforations in extracted human molar teeth. Fifty-five human mandibular molar teeth were accessed, and the canal orifices were located. The roots were horizontally sectioned in the middle third. Resin composite was used to fill the root canal orifices and the apical end of the root. Perforations were created in the center of the pulp chamber floor by using a size 3 round bur. The teeth were divided into 3 groups (n = 15), and an additional 10 teeth served as controls. In G1, the perforation defects were repaired with MTA, whereas in G2 and G3, MTA Bio and Portland cement were used, respectively. Each tooth was assembled in a hermetic cell to allow the evaluation of fluid filtration. Leakage was measured by the movement of an air bubble traveling within a pipette connected to the teeth. Measurements of the air bubble movement were made after 10 minutes at a constant pressure of 20 cm H2O. Kruskal-Wallis H test was applied to the fluid flow data to detect differences between the experimental groups (P < .05). Leakage existed in every sample and was very variable in all the experimental groups, ranging from 0.098–0.51 μL/min. Kruskal-Wallis H-test results showed that there was no significant difference in mean fluid flow between the experimental groups (P = .874). The sealing ability promoted by the 3 cements was similar; no cement was able to produce a fluid-tight seal.
Clinical Outcome of Teeth Treated Endodontically with a Nonstandardized Protocol and Root Filled with ResilonDeborah A. Conner, DDS, MS, Daniel J. Caplan, DDS, PhD, Fabricio B. Teixeira, DDS, MS, PhD, Martin Trope, DMD
The purpose of this study was to evaluate the clinical outcomes of root canal treatment in private practice and filled with Resilon. Immediate postoperative radiographs were compared to follow-up radiographs of at least 1 year in 82 randomly selected primary endodontic cases treated according to a nonstandardized protocol but root-filled with Resilon. The Periapical Index (PAI) and the Clinical Impression of Healing (CIH) quantification procedures were used to determine the status and change in the condition of the teeth. The PAI evaluation revealed that 90% of the teeth that were healthy at the initial reading (PAI, 1or 2) maintained the condition at follow-up evaluation. Of those teeth that were unhealthy (PAI, 3–5) at the initial reading, 73.3% were judged healthy (50%) or improved (23.3) at the last evaluation. In contrast, the proportion of healthy or healing with the CIH evaluation was 89.4%. The findings of this study support the contention that regardless of treatment protocol, healing rates for Resilon-filled teeth in private practice were within the range of success rates for studies with uniform treatment techniques mostly in university settings with gutta-percha root filling.
Effects of Root Canal Sealers on Lipopolysaccharide-induced Expression of Cyclooxygenase-2 mRNA in Murine Macrophage Cells
Dong Hee Lee, PhD⁎, Na Ryoung Kim, BS, Bum-Soon Lim, PhD, Yong-Keun Lee, DDS, PhD, Kyu-Kye Hwang, PhD, Hyeong-Cheol Yang, PhD
Cyclooxygenase-2 (COX-2) is a useful biomarker of the inflammatory potential of biomaterials in vitro. In this study we investigate the effects of soluble extracts from 3 selected root canal sealers (AH26, Sealapex, and N2 Universal) on COX-2 mRNA expression in cultured murine macrophage cells. Root canal sealers and the addition of lipopolysaccharide (LPS) both produced significant increases in COX-2 mRNA expression in RAW 264.7 macrophages. In addition, both Sealapex and N2 Universal produced a synergistic 6- to 8-fold increase in COX-2 mRNA expression, whereas AH26 did not demonstrate synergy with LPS. These results suggest that LPS and certain root canal sealers have a synergistic effect on the inflammatory responses of macrophages. Under the conditions of this in vitro study, the results suggest that one potential mechanism of periapical inflammatory reactions might be the synergistic effects of certain root canal sealers on LPS-induced COX-2 expression by macrophage cells.
The Antimicrobial Effect of Biopure MTAD on Eight Strains of Enterococcus faecalis: An In Vitro Investigation
Bradley M. Newberry, DDS, Shahrokh Shabahang, DDS, MS, PhD, Neal Johnson, PhD, Raydolfo M. Aprecio, OD, Mahmoud Torabinejad, DMD, MSD, PhD
The purpose of this investigation was to determine the antimicrobial effect of MTAD as a final irrigant on eight strains of Enterococcus faecalis (E. faecalis) and to measure the minimum inhibitory concentration (MIC) and the minimum lethal concentration (MLC) of MTAD. The roots of 240 extracted human teeth were instrumented using 1.3% NaOCl and 17% EDTA. The roots were divided into eight groups and contaminated with one of eight strains of E. faecalis. After irrigating with 1.3% NaOCl, the root canal and the external surfaces were exposed to MTAD for 5 minutes. Roots or dentin shavings were cultured to determine the growth of E. faecalis. The results showed that this treatment regimen was effective in completely eliminating growth in seven of eight strains of E. faecalis. The MIC/MLC tests showed that MTAD inhibited most strains of E. faecalis growth when diluted 1:8192 times and killed most strains of E. faecalis when diluted 1:512 times.
TGF-β1 Enhances the Expression of α–Smooth Muscle Actin in Cultured Human Pulpal Fibroblasts: Immunochemical and Ultrastructural Analyses
Elizabeth F. Martinez, DDS, MSc Vera C. Araújo, DDS, PhD, Suzana O.M. Sousa, DDS, PhD, Victor E. Arana-Chavez, DDS, PhD
Transforming growth factor–beta 1 (TGF-β1) has been related to induce the expression of α–smooth muscle actin (α-SMA) in fibroblasts during repair. Because pulpal fibroblasts seem to be somewhat different from other fibroblasts, the present study investigated in vitro whether TGF-β1 enhances the expression of α-SMA in human pulpal fibroblasts. TGF-β1 was added in doses between 5–10 ng/mL to cultures of both dental pulp and gingival human fibroblasts. The expression of α-SMA was analyzed by immunofluorescence and Western blotting, whereas the ultrastructure was evaluated by electron microscopy. In addition, the expression of tenascin, osteonectin, and vimentin was also investigated. Both cell types were immunoreactive for α-SMA even without TGF-β1. When TGF-β1 was added to cell cultures, the expression of α-SMA increased dramatically in pulpal fibroblasts, independent of the concentration used. It was confirmed by the Western blotting analysis. Ultrastructure revealed myofilaments and indented nuclei in both fibroblasts treated with TGF-β1. Tenascin and osteonectin were only immunolabeled in pulpal fibroblasts treated or not with TGF-β1. Both fibroblast types were positive for vimentin. The present findings showed that TGF-β1 up-regulated the expression of α-SMA, thus inducing pulpal fibroblasts to acquire the myofibroblast phenotype.
Impact of Irrigant Sequence on Mechanical Properties of Human Root Dentin
Monika Marending, Dr med dent, Frank Paqué, Dr med dent, Jens Fischer, Dr med dent, PD, Matthias Zehnder, Dr med dent, PhD, PD
To get the root canal system free of organic debris and the smear layer, it has been recommended to irrigate with a NaOCl solution during instrumentation, followed by a rinse with a chelating agent such as ethylenediaminetetraacetic acid (EDTA) and a final irrigation with NaOCl. However, both hypochlorite and EDTA weaken dentin through dissolution of its organic and inorganic components, respectively. EDTA exposes the organic dentin matrix, which could then be attacked more easily by hypochlorite. It was the aim of this study to assess the impact of different irrigation sequences of NaOCl (2.5% w/v; total exposure time, 24 minutes) and EDTA (17%; 3 minutes) on the elastic modulus and flexure strength of standardized human root dentin bars (n = 11 per group). Exposures to solely EDTA (3 minutes), NaOCl (24 minutes), and water were used as control treatments. Specimens were subjected to 3-point bending tests; modulus of elasticity and flexure strength values were compared between groups with one-way analysis of variance followed by Fisher probable least-squares difference test. The alpha-type error was set at .05. The 24-minute exposure to the hypochlorite solution caused a significant drop in flexure strength compared with water- or EDTA-treated controls (P < .05), whereas the elastic modulus remained unaffected. In contrast, the short exposure to EDTA as is clinically recommended did not affect the mechanical dentin parameters under investigation, regardless of the irrigant sequence that was used.
Proinflammatory Cytokine Expression in Cyclooxygenase-2–deficient Primary Osteoblasts
Jianing He, DMD, PhD, Rosamond Tomlinson, BS, David Coon, DDS, Ajay Gulati, BDS, MSc, Cameron Cowan, BS
Many of the proinflammatory effects of interleukin (IL)-1β and tumor necrosis factor-α (TNF-α) are mediated through cyclooxygenase-2 (COX-2)-dependent prostaglandin E2 (PGE2). The purpose of this study was to examine the expression of IL-1β and TNF-α in COX-2–deficient osteoblasts during inflammation. Primary osteoblasts prepared from wild-type (WT) and COX-2 knockout (K/O) mice were exposed to lipopolysaccharide (LPS) and endodontic obturation materials. An enzyme-linked immunosorbent assay was used to measure cytokine levels. LPS treatment led to a significant upregulation in IL-1β and TNF-α levels in both WT and K/O cells. TNF-α upregulation in response to LPS was much more pronounced in K/O cells compared with WT cells (p < 0.05). All materials tested except for gutta percha caused an increase in IL-1β expression. In conclusion, there appears to be a positive feedback regulation between TNF-α and COX-2–dependent PGE2 during LPS-induced inflammatory reactions.
The Induction of Heme Oxygenase-1 Modulates Bismuth Oxide-induced Cytotoxicity in Human Dental Pulp Cells
Kyung-San Min, DDS, MS, Hoon-Sang Chang, DDS, MS, Ji-Myung Bae, DDS, PhD, Sang-Hyuk Park, DMD, PhD, Chan-Ui Hong, DDS, PhD, Eun-Cheol Kim, DDS, PhD
The aim of this study was to investigate the cytotoxic and nitric oxide (NO)-inducing effects of bismuth oxide (Bi2O3)–containing Portland cement (BPC) on human dental pulp cells. We also assessed whether heme oxygenase-1 (HO-1) is involved in BPC-induced cytotoxicity in dental pulp cells. Cytotoxicity and NO production induced by BPC were higher than those induced by Portland cement at 12 and 24 hours, and the former gradually decreased to the level observed for PC. HO-1 and inducible nitric oxide synthase messenger RNA expressions in the BPC group showed maximal increase at 24 hours, and it gradually decreased with increasing cultivation time. Hemin treatment reversed the BPC-induced cytotoxicity, whereas zinc protoporphyrin IX treatment increased the cytotoxicity. These results suggested that NO production by BPC correlates with HO-1 expression in dental pulp cells. Moreover, BPC-induced HO-1 expression in dental pulp cells plays a protective role against the cytotoxic effects of BPC.
Effect of Application Technique of Luting Agent on the Retention of Three Types of Fiber-reinforced Post Systems
Camillo D’Arcangelo, DDS, Maurizio D’Amario, DDS, Francesco De Angelis, DDS, Simone Zazzeroni, DDS, Mirco Vadini, DDS, Sergio Caputi, MD, DDS
The aim of this study was to evaluate retentive strengths of three adhesive/resin cement/fiber post systems to the apical third of post-space dentin varying the application method of the luting agent. ENA post (Micerium, Avegno, Genova, Italy), FRC Postec Plus (Ivoclar Vivadent, Schaan, Liechtenstein), and Anatomical Post (Dentalica, Milano, Italy) were luted in prepared root canals using the adhesive system and resin cement provided by the respective manufacturer. Each group was randomly divided into three subgroups (n = 10) according to the technique used to place the luting agent into post space: using a lentulo spiral, applying the cement onto the post surface, and injecting the material with a specific syringe. A push-out test was performed on sections from the post-space apical part of each specimen. All fractured specimens were observed using a stereomicroscope. Bond strength values were not significantly affected by the application technique of the luting agent (p > 0.05). The ENA post system showed the highest retentive strengths. The other two post groups exhibited similar bond strengths to each other. Microscopic analysis revealed a prevalence of post/cement and mixed failures.
Effect of an Estrogen-deficient State and Alendronate Therapy on Bone Loss Resulting from Experimental Periapical Lesions in Rats
Haofei Xiong, DDS, PhD, Bin Peng, DDS, PhD, Lili Wei, DDS, PhD, Xiaolei Zhang, DDS, PhD, Li Wang, DDS, PhD
The aim of the research was to evaluate the impact of an estrogen-deficient state and alendronate (ALD) therapy on bone loss resulting from experimental periapical lesions in rats. Periapical lesions were induced on ovariectomized (OVX) and sham-ovariectomized (Sham) rats. After sample preparation, histologic and radiographic examination for periapical bone loss area and an enzyme histochemical test for tartrate-resistant acid phosphatase (TRAP) were performed. The results showed that OVX significantly increased bone loss resulting from periradicular lesions. After daily subcutaneous injection of ALD, the bone loss area and the number of TRAP-positive cells (osteoclasts) were reduced. These findings suggested that alendronate may protect against increased bone loss from experimental periapical lesions in estrogen-deficient rats. Given recent recognition of adverse effects of bisphosphonates, including an increased risk for osteonecrosis, the findings from this study should not be interpreted as a new indication for ALD treatment. However, they may offer insight into understanding and predicting outcomes in female postmenopausal patients already on ALD therapy for medical indications.