Application of Denaturing Gradient Gel Electrophoresis (DGGE) to the Analysis of Endodontic Infections
José F. Siqueira, Jr., DDS, MSc, PhD, Isabela N. Rôças, DDS MSc, PhD, and Alexandre S. Rosado, BS, MSc, PhD
The recent expanding use of cultivation-independent techniques for bacterial identification is reliant on the lack of knowledge of the conditions under which most bacteria are growing in their natural habitat and the difficulty to develop culture media that accurately reproduce these conditions. A molecular method that has been recently used in several areas to examine the bacterial diversity living in diverse environments is the denaturing gradient gel electrophoresis (DGGE). In DGGE, polymerase chain reaction (PCR)-generated DNA fragments of the same length but with different base-pair sequences can be separated. Separation is based on electrophorectic mobility of a partially melted double-strand DNA molecule in polyacrylamide gels, which is decreased when compared with that of the completely helical form of the molecule. Molecules with different sequences may have a different melting behavior and will therefore stop migrating at different positions in the gel. Application of the PCR-DGGE method in endodontic research has revealed that there are significant differences in the predominant bacterial composition between asymptomatic and symptomatic cases. This suggests that the structure of the bacterial community can play a role in the development of symptoms. In addition, new bacterial phylotypes have been disclosed in primary endodontic infections. PCR-DGGE has also confirmed that intra-radicular infections are a common finding in root-filled teeth associated with persistent periradicular lesions. The microbiota in failed cases significantly vary from teeth to teeth, with a mean number of species far higher than previously shown by culturing approaches. Application of the PCR-DGGE technique in endodontic microbiology research has the potential to shed light on several aspects of the different types of endodontic infection as well as on the effects of treatment procedures with regard to infection control.
The Influence of Different Factors on the Survival of Root Canal Fillings: A 10-Year Retrospective Study
Richard Stoll, PD, Dr.med.dent.habil., Kirsten Betke, Dr.med.dent., and Vitus Stachniss, Prof.Dr.med.dent.
The aim of the present study was to determine the survival time of root canal fillings performed in 1990 and 1991 at the Dental School, Philipps University of Marburg, Germany. Data were collected retrospectively from the dental records and control radiographs were evaluated. The survival probability was determined by Kaplan-Meier analysis. Intergroup differences were verified with the log-rank test. The 914 evaluated root canal fillings yielded an overall 10-yr cumulative survival probability of 0.74. The factors baseline periapical condition (p < 0.001), length (p < 0.001), condensation (p < 0.001), vitality (p < 0.001), and pain symptoms (p = 0.005) were found to have a significant influence on the long-term success of root canal fillings. Higher survival rates were recorded for teeth with healthy periapical conditions, root canal fillings of the correct length, homogeneously condensed root canal fillings, root canal fillings in previously vital teeth, and teeth that had been asymptomatic during treatment. A nonsignificant influence was recorded for the parameters operator (p = 0.606) and retreatment (p = 0.196).
A Real Time Quantitative PCR Analysis and Correlation of COX-1 and COX-2 Enzymes in Inflamed Dental Pulps Following Administration of Three Different NSAIDs
Claudia I. Holt, DDS, MS, Max O. Hutchins, PhD, and Roberta Pileggi, DDS, MS
Dental pain is encountered daily by clinicians. Nonsteroidal anti-inflammatory drugs (NSAIDs) commonly used for pain management are traditionally cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) inhibitors, and more recently selective COX-2 inhibitors. This study was designed to identify and quantify COX-1 and COX-2 gene expression level in inflamed rat molar pulps after administration of three NSAIDs: Celebrex, Vioxx, and Advil. Fifty male Wistar rats had their first and second molar pulps exposed and sealed with Cavit for 4 days. Rats were randomly divided into the three drug groups and two control groups. RNA was isolated from the rat pulps. Real Time Quantitative Reverse Transcriptase-Polymerase Chain Reaction assay, a relatively new PCR technique, was used to quantify COX-1 and COX-2 mRNA. Statistical analysis demonstrated no significant differences in COX-1 and COX-2 levels among the drug groups. However, Vioxx and Advil significantly reduced COX-2 expression levels compared to inflamed (positive control) pulps (p < 0.05).
Chelation in Root Canal Therapy Reconsidered
Matthias Zehnder, Dr med dent, Patrick Schmidlin, Dr med dent, Beatrice Sener, and Tuomas Waltimo, Dr odont, Docent
The aim of this study was to assess interactions of EDTA and citric acid (CA) with sodium hypochlorite (NaOCl), the indispensable endodontic irrigant. Other chelators were simultaneously evaluated as possible alternatives: sodium triphosphate (STP), amino tris methylenephosphonic acid (ATMA), and 1- hydroxyethylidene-1, 1-bisphosphonate (HEBP). Available chlorine was titrated in chelator-NaOCl solutions. All chelators other than HEBP and STP caused an almost complete, immediate loss of available chlorine in solution. Atomic absorbtion spectrometry and SEM evaluation of root canal walls of instrumented teeth indicated that NaOCl had no negative effect on calcium-complexing ability of chelators. STP was too weak a complexing agent to warrant further studies. Finally, CA-, EDTA-, and HEBPNaOCl mixtures were evaluated for their antimicrobial capacity. Again, EDTA and CA negatively interfered with NaOCl, while HEBP did not.
Endodontic Implications of Bisphosphonate-Associated Osteonecrosis of the Jaws: A Report of Three Cases
Harmon Katz, DDS
Bisphosphonates are commonly used in medicine to maintain bone density in patients with certain nonneoplastic diseases or cancers. A serious adverse effect of bisphosphonates that has substantial dental significance is osteonecrosis that appears to uniquely affect the mandible and maxilla without occurring in other bones of the skeleton. Patients with bisphosphonate associated osteonecrosis of the jaws may present with pain and exposed necrotic bone. This has substantial clinical implications because surgical procedures (including extractions or endodontic surgical procedures) are contraindicated in the jaws of these patients and the presenting pain may mimic pain of odontogenic origin. This report describes three patients with bisphosphonate associated osteonecrosis and emphasies the endodontic implications of managing these patients.
An Objective Evaluation Comparing The Physical Properties of Two Brands of Stainless Steel Endodontic Hand Files
Gregory J. Dearing, DMD, Reza B. Kazemi, DMD, and Roy H. Stevens, DDS, MS
The purpose of this study was to evaluate the physical properties of a flexible stainless steel K-type hand file recently introduced by Brasseler USA (F-Style files; Brasseler USA, Savannah, GA), in comparison to those of a well-studied instrument (Flex-o-files; Maillefer- Dentsply, Ballaigues, Switzerland), that has been on the market for more than 20 yr. The physical properties measured included torque at failure, angular deflection at failure, flexibility, and consistency of diameter at 3 mm from the cutting tip; and the evaluations were carried out on size #10 through #50 files of each of the two brands being tested. The results indicated that the Brasseler instruments were inherently more flexible, but had smaller diameters, lower torque, and angular deflection values at failure, than those of the Maillefer files.
Comparison of the Cutting Efficiency of Two Ultrasonic Units Utilizing Two Different Tips at Two Different Power Settings
Ernesto Paz, DMD, James Satovsky, DDS, MS, and Ivan Moldauer, DDS, MS
The objective of this in vitro study was to set up a testing protocol and utilize it to evaluate and compare the cutting efficiency of ultrasonic units. Evaluation of two ultrasonic units utilizing two different tips was done by measuring the weght of a dentin specimen before and after ultrasonic treatment for set time periods. The difference in weight was the amount of dentin removed. The ultrasonic units tested were the P5 Booster (Staelec, France) and the Spartan (Obtura-Spartan, Fenton, MO) machines. The tips tested were the CPR-2D and ETD20 types. The units were tested at maximum and medium power. All the experimental variables, ultrasonic unit type, power setting and tip type were found to have an effect on the cutting efficiency (P < 0.0001). The P5 ultrasonic unit was more effective at dentin removal than the Spantan ultrasonic unit at both power settings. The ETD-20 tip was more effective at dentin removal than the CPR-2D tip on both units at both power settings.
Erbium:YAG Laser versus Ultrasonic in Preparation of Root-End Cavities
Zoran Karlovic, Sonja Pezelj-Ribaric, Ivana Miletic, Silvana Jukic, Josko Grgurevic, and Ivica Anic
The aim of this in vitro study was to compare the sealing effectiveness of the Erbium:YAG laser to the sealing effectiveness of an ultrasonic device in the preparation of similar retrograde cavities using different retrograde filling materials. After root-canal instrumentation and filling, apices of 60 single-rooted teeth were resected. Retrograde class I cavities 3 mm deep were prepared using an ultrasonic device (group A) and Er:YAG laser (group B). An ultrasonic unit was used with CT-5 retrotip at the frequency of 32 KHz. Laser beam parameters were a pulse of very short duration (100 _s), energy of 280 mJ, and repetition rate of 10 Hz. Cavities of each group of 10 samples were filled with mineral trioxide aggregate (MTA), Super-EBA, and IRM. Microleakage was measured using a fluid transport model. The results showed that cavities prepared with Er:YAG laser have significantly lower microleakage for all tested materials.
An In Vitro Assessment of Iodoform Gutta-Percha
Sami Chogle, BDS, DDS, MSD, André K. Mickel, DDS, MSD, S. Kirk Huffaker, and Benjamin Neibaur
The purpose of this study was to test the ability of a commercially available iodoform gutta-percha, to delay infiltration of Enterococcus faecalis using a microleakage model. Seventy extracted single-rooted teeth were decoronated and biomechanically prepared using hand and rotary instruments. Thirty roots were obturated laterally with iodoform gutta-percha and another 30 with regular gutta-percha. Both groups were suspended in sterile BHI broth. An inoculum of E. faecalis suspension was placed at the coronal end of each root, incubated and replenished daily. The apical broth was observed for turbidity, indicating bacterial microleakage. Samples were observed for 32 days, and data was analyzed to compare microleakage between the two groups. The results showed no significant difference between the iodoform and regular gutta-percha samples in delaying microleakage of E. faecalis (p > 0.05).
Interfacial Strength of Resilon and Gutta-Percha to Intraradicular Dentin
Andrea Gesi, Ornella Raffaelli, Cecilia Goracci, David H. Pashley, Franklin R. Tay, and Marco Ferrari
Strengthening of Resilon-filled roots via an adhesive interface should be reflected by improvement in the interfacial strength and dislocation resistance between the root fillings and intraradicular dentin. This study compared the interfacial strengths of Resilon/Epiphany and gutta-percha/AH Plus using a thin-slice push-out test design. Failure modes of root slices after push-out testing were examined with environmental scanning electron microscopy. The gutta-percha group exhibited significantly higher interfacial strength than the Resilon group, when premature failures that occurred in Resilon root slices were included in the statistical analysis. The gutta-percha root slices failed exclusively along the gutta-percha/sealer interface. The Resilon root slices failed predominantly along the sealer/dentin interface with recognizable, fractured resin tags. Detachment of the Resilon from the Epiphany sealer was also surprisingly observed in some specimens. The similarly low interfacial strengths achieved with both types of root filling challenges the concept of strengthening rootfilled teeth with the new endodontic material.
Fibroblast Growth Factor-2 Stimulates Hyaluronan Production by Human Dental Pulp Cells
Yoshio Shimabukuro, Maki Ueda, Tomoo Ichikawa, Yoshimitsu Terashi, ma, Satoru Yamada, Yutaka Kusumoto, Masahide Takedachi, Mami Terakura, Akira Kohya, ma, Tomoko Hashikawa, and Shinya Murakami
Hyaluronan (HA), is a high molecular mass extracellular matrix constituting connective tissue and plays a critical role in not only homeostasis but also inflammatory and wound-healing responses. In this study, we investigated the effect of fibroblast growth factor (FGF)-2 on the production of HA by human dental pulp cells (HDPC). An inhibition binding-protein assay showed that FGF-2 increased HA production by HDPC. In addition, expression of mRNA of hyaluronan synthase (HAS) 1 and HAS 2, both of which are related to the production of high molecular mass of HA, but not HAS 3, was enhanced in FGF-2-stimulated HDPC. These results provide new evidence for the involvement of FGF-2 in the regulation of HA production by HDPC possibly through HAS 1 and HAS 2.
The Effect of Endodontic Therapy on Periapical Exudate Neutrophil Elastase and Prostaglandin-E₂ Levels
Nilgun Ozlem Alptekin, DDS, PhD, Hale Ari, DDS, PhD, Seyfullah Haliloglu, VMD, PhD, Tuncay Alptekin, DDS, PhD, Behic Serpek, VMD, PhD, and Tamer Ataoglu, DDS, PhD
This study aimed to investigate periapical exudate neutrophil elastase (NE) and prostaglandin E₂ (PG E₂) levels and their relationships with clinical symptoms, and to determine the changes of their levels following first treatment visit. Periapical exudate samples were collected from the canals of 34 nonvital single-rooted teeth at two sequential treatment visits. Periapical exudates NE and PGE₂ levels were found to be higher in the presence of clinical symptoms (pus discharge, swelling) (p < 0.05). The canals of teeth with larger periapical radiolucent area (≥1 cm) contained more PGE₂ levels than with smaller ones (<1 cm) (p < 0.05). Periapical exudate NE levels were significantly correlated with PGE2 levels (p < 0.05), and their levels at first treatment visit did not change following root canal therapy (p > 0.05). The periapical exudate NE and PGE2 levels may regulate periapical disease expression, but the results of this study were unable to reveal this association.
A Comparative Study of Three Different Root Canal Curvature Measurement Techniques and Measuring the Canal Access Angle in Curved Canals
Mahir Günday, DDS, PhD, Hesna Sazak, DDS, PhD, and Yýldýz Garip, DDS, PhD
In the first part of this study the Schneider (S), Weine (W), and Long-Axis (LA) techniques are used for comparing the measurement of canal curvature. One hundred mandibular first and second molar teeth were selected. Radiographs were taken after inserting size 10 K-files into the mesiobuccal root canals. The radiographic findings were digitized on a computer, and the three different curvature angles were measured from drawings of the same root canal and compared statistically. ANOVA showed that there were significant differences between the curvature angle values determined using each technique (p < 0.001). In the second part of this study the term “canal access angle” (CAA) was introduced and it was defined by examining the morphology of canal curvature. Canal length, curvature distance (y), curvature height (x), Schneider angle, and the newly defined CAA were evaluated statistically. Using a multiple regression analysis, the CAA was significantly related to x (p < 0.001) and y (p < 0.005). There was a positive correlation (r = 0.74) between the CAA and curvature height (x). The results indicated that the CAA is a more effective way of evaluating the root canal curvature.