The Effect of Various Concentrations of Sodium Hypochlorite on the Ability of MTAD to Remove the Smear Layer
Mahmoud Torabinejad, Yongbum Cho, Abbas Ali Khademi, Leif K. Bakland, and Shahrokh Shabahang
Induction of Cyclooxygenase-2 mRNA and Protein Expression in Human Pulp Cells Stimulated with Black-pigmented Bacteroides
Yu-Chao Chang, M Fu-Mei Huang, M Shun-Fa Yang, Chia-Ming Liu, Chung-Chih Lai, You Chan, and Yih-Shou Hsieh
Treponema socranskii in Primary Endodontic Infections as Detected by Nested PCR
José F. Siqueira, Jr., and Isabela N. Rôças
Effects of NaOCI on Bond Strengths of Resin Cements to Root Canal Dentin
Hale Ari, Erdem Yaşar, and Sema Bellí
Three-Dimensional Quantitation of Periradicular Bone Destruction by Micro-Computed Tomography
Dietrich von Stechow, Khaled Balto, Philip Stashenko, and Ralph Müller
Antimicrobial Activity of Endodontic Sealers on Enterococcus faecalis
André K. Mickel, Tuan H. Nguyen, and Sami Chogle
Effectiveness of Stannous Fluoride and Calcium Hydroxide Against Enterococcus faecalis
André K. Mickel, Priya Sharma, and Sami Chogle
The Comparative Sealing Ability of Hydroxyapatite Cement, Mineral Trioxide Aggregate, and Super Ethoxybenzoic Acid as Root-End Filling Materials
C Mangin, C. Yesilsoy, R. Nissan, and R. Stevens
The Effect of Various Concentrations of Sodium Hypochlorite on the Ability of MTAD to Remove the Smear Layer
Mahmoud Torabinejad, DMD, MSD, PhD, Yongbum Cho, DDS, MS, PhD, Abbas Ali Khademi, DMD, MS, Leif K. Bakland, DDS, and Shahrokh Shabahang, DDS, MS, PhD
Various organic acids, ultrasonic instruments, and lasers have been used to remove the smear layer from the surface of instrumented root canals. The purpose of this study was to investigate the effect of various concentrations of sodium hypochlorite (NaOCI) as an intracanal irrigant before the use of MTAD (a mixture of a tetracycline isomer, an acid, and a detergent) as a final rinse to remove the smear layer. Ten operators, using a combination of passive step-back and rotary 0.04 taper, nickel-titanium files, prepared 80 single- and multirooted human teeth. Distilled water, four different concentrations of NaOCI, or MTAD was used as intracanal irrigant. The canals were then treated for 2 min with 5 ml of one of the following solutions as a final rinse: 5.25% NaOCI, sterile distilled water, 17% EDTA, or MTAD. The presence or absence of smear layer and the amount of erosion on the surface of the root canal walls at the coronal, middle, and apical portion of each canal were examined under a scanning electron microscope. The results show that although MTAD removes most of the smear layer when used as an intracanal irrigant, some remnants of the organic component of the smear layer remain scattered on the surface of the root canal walls. The effectiveness of MTAD to completely remove the smear layer is enhanced when low concentrations of NaOCI are used as an intracanal irrigant before the use of MTAD as a final rinse. This regimen does not seem to significantly change the structure of the dentinal tubules.
Induction of Cyclooxygenase-2 mRNA and Protein Expression in Human Pulp Cells Stimulated with Black-pigmented Bacteroides
Yu-Chao Chang, DDS, MMS, PhD, Fu-Mei Huang, DDS, MMS, Shun-Fa Yang, MS, Chia-Ming Liu, DDS, Chung-Chih Lai, DDS, You Chan, DDS, PhD, and Yih-Shou Hsieh, PhD
Cyclooxygenase-2 (COX-2) is induced after the activation of cells by a variety of proinflammatory agents. Recently, evidence has shown that COX-2 may play a role in the pathogenesis of pulpal inflammation. However, little is known regarding the mechanism of pulpal inflammation at the site of bacterial infection. The purpose of this study was to determine the effects of the supernatants from black-pigmented Bacteroides (Porphyromonas endodontalis, Porphyromonas gingivalis, and Prevotella intermedia) on the COX-2 expression in primary human pulp cells in vitro. Investigations of the time dependence of COX-2 mRNA expression in black-pigmented Bacteroides-treated human pulp cells revealed a rapid accumulation of the the transcript, a significant signal first detectable after 1 h of exposure. In addition, black-pigmented Bacteroides also up-regulated COX-2 protein expression in human pulp cells. Data from our in vitro experiment showed that black-pigmented Bacteroides were capable of stimulating COX-2 expression in human pulp cells. These results indicate that black-pigmented Bacteroides species may play an important role in the pathogenesis of pulpal inflamation. The activation of COX-2 may be one of the distinct host degradative pathways in the pathogenesis of microbial-induced pulpal/periapical inflammation.
Treponema socranskii in Primary Endodontic Infections as Detected by Nested PCR
José F. Siqueira, Jr., DDS, MSc, PhD, and Isabela N. Rôças, DDS, MSc
Spirochetes have been frequently observed in root canal infections, but they were rarely identified. The purpose of this study was to investigate the prevalence of Treponema socranskii in primary endodontic infections using a species-specific nested polymerase chain reaction assay. Samples were collected from 60 teeth having carious lesions, necrotic pulps, and different forms of periradicular diseases. DNA extracted from the samples was initially amplified using universal 16S rDNA primers. A second round of amplification used the first polymerase chain reaction products to detect a specific fragment of T. socranskii 16S rDNA. T. socranskii was detected in 11 of 28 asymptomatic cases (39.3%), five of 12 root canals associated with acute apical periodontitis (41.7%), and five of 20 cases diagnosed as acute periradicular abscesses (25%). There was no relationship between the presence of T. socranskii and the occurrence of symptoms. In general, this spirochete was detected in 21 of 60 samples of endodontic infections (35%). Findings suggest that T. socranskii can be involved in the pathogenesis of different forms of periradicular lesions.
Effects of NaOCI on Bond Strengths of Resin Cements to Root Canal Dentin
Hale Ari, DDS, PhD, Erdem Yaşar, and Sema Bellí, DDS, PhD
Microleakage occurs due to the lack of sealing ability of root sealing materials or adhesive cements used to lute post-core materials. This may cause premature failure of endodontic treatment. The purpose of this study was to evaluate regional bond strengths of four adhesive systems to root canal dentin. Sixteen extracted human single rooted teeth were used. After removing the crowns and the pulp tissues, the root canals were then instrumented and irrigated with or without 5% NaOCI. The root canal dentin walls were then bonded with C&B Metabond, Panavia F, Variolink II, or Rely-X. Microtensile bond strengths to root canal dentin were then measured using an Instron machine. The bond strength data were recorded and expressed in MPa. Statistically significant differences were found among the NaOCI treated and nontreated groups (p < 0.05). C&B Metabond gave the highest bond strength compared with others in the control group (p < 0.05). C&B Metabond also had significantly higher bond strength compared with Variolink II and Panavia F groups when the canals were irrigated with NaOCI (p < 0.05).
Three-Dimensional Quantitation of Periradicular Bone Destruction by Micro-Computed Tomography
Dietrich von Stechow, MD, Khaled Balto, DDS, Philip Stashenko, DMD, PhD, and Ralph Müller, PhD
We have previously shown that two-dimensional, high-resolution, micro-computed tomography is a rapid, reproducible, and noninvasive method for measuring periradicular bone resorption in mice, giving results virtually identical to histology. In this study, we determined whether a three-dimensional volumetric quantitation of bone resorption could be achieved and whether this correlates with two-dimensional measurements. Periradicular lesions were induced in the lower first molars of mice by pulp exposure and infection; unexposed teeth served as controls. Mandibles were harvested on day 21 and subjected to: (a) three-dimensional micro-computed tomography imaging; and (b) conventional histology. Using a three-dimensional model and a semiautomatic contouring algorithm, we determined three-dimensional void volume, void surface, void thickness, and the standard deviation of the thickness distribution. The results showed a significant correlation between lesion void volume and two-dimensional lesion area by histology (r2 = 0.73), as well as high correlations between void volume and void thickness (r2 = 0.86) and standard deviation of the void thickness (r2 = 0.87), but no relationship with void surface. These results show that three-dimensional analysis of micro-computed tomography images is highly correlated with two-dimensional cross-section measures of periradicular lesions. Nevertheless, micro-computed tomography allows assessment of additional microstructural features as well as sub-regional analysis of lesion development.
Antimicrobial Activity of Endodontic Sealers on Enterococcus faecalis
André K. Mickel, DDS, MSD, Tuan H. Nguyen, DDS, and Sami Chogle, BDS, MSD
Enterococcus faecalis has been shown to be highly resistant once established in the root canal system and may play an important role in endodontic failures. The purpose of this study was to evaluate the antimicrobial activity of four root canal sealers on E. faecalis. Seventeen blood-agar plates were inoculated with E. faecalis using the Lawn technique. Five discs were placed on each plate, four with sealers-Sealapex, Roth 811, Kerr EWT, and AH-Plus-and an ampicillin disc as the control. The plates were incubated at 37°C. The zones of inhibition were measured at 24 and 48 h. Analysis using a one-way ANOVA and Turkey test showed a statistically significance difference (p < 0.05) between all four groups of sealers. Roth 811 showed the largest zone of inhibition (1.1 mm), followed by Sealapex (0.8 mm) and Kerr EWT (0.5 mm), whereas AH-Plus had no antimicrobial activity. There was no difference in the zones of inhibition between the 24- and 48-h time periods.
Effectiveness of Stannous Fluoride and Calcium Hydroxide Against Enterococcus faecalis
André K. Mickel, DDS, MSD, Priya Sharma, BDS, and Sami Chogle, BDS, MSD
The objective of this study was to evaluate the antimicrobial activity of stannous fluoride, calcium hydroxide, or the two in combination against Enterococcus faecalis. Fifteen Mueller-Hinton agar plates were used to conduct a disc diffusion susceptibility test. The plates were inoculated with E. faecalis. The groups tested were: (a) stannous fluoride (Stanimax); (b) calcium hydroxide; and (c) a combination of stannous fluoride and calcium hydroxide. Three filter paper discs, each soaked with one of the groups, were placed along with an antibiotic control (ampicillin) on each agar plate. The plates were then incubated at 37°C. The zones inhibition were measured at 24 and 48 h. One-way ANOVA revealed a statistically significant difference (p < 0.05) between the three groups. Stannous fluoride displayed the widest zone (1.7 mm), followed by the combination of stannous fluoride and calcium hydroxide (1.1 mm), whereas calcium hydroxide by itself displayed a minimal zone of inhibition (0.05 mm).
The Comparative Sealing Ability of Hydroxyapatite Cement, Mineral Trioxide Aggregate, and Super Ethoxybenzoic Acid as Root-End Filling Materials
C Mangin, DMD, C. Yesilsoy, DMD, MS, R. Nissan, DMD, and R. Stevens, DDS, MS
A comparison was made of the ability of hydroxyapatite cement, mineral trioxide aggregate, and super ethoxybenzoic acid to prevent the leakage of bacteria from root canals, when used as root-end filling materials. The materials were tested in a double-chamber device in which a root segment connects the upper (delivery) chamber and the lower (receiving) chamber. The root segment was prepared by having the root canal instrumented to a #45 file, and a 3-mm-deep, root-end preparation placed at the apical foramen. The canal of each root segment was filled with gutta-percha, and the root-end preparation was filled with one of three test materials, mixed according to the manufacturer’s directions. Negative controls were constructed with sticky wax sealing the apical foramen. A tittered suspension of radioactively (3H-thymidine)-labeled bacteria (Enterococcus faecalis) was placed into the delivery chamber, and sterile saline was placed into the receiving chamber such that the apical third of each root section was immersed. At various time points, samples were taken from the receiving chamber, and measured for 3H activity. The results indicated that (a) all the test materials leaked significantly compared with the negative controls; and (b) there was no significant difference found between the leakage rates of the three materials tested.