The Effect of MTAD on the Coronal Leakage of Obturated Root Canals
Dong Sung Park, DDS, MS, PhD, Mahmoud Torabinejad, DMD, MSD, PhD, and Shahrokh Shabahang, DDS, MS, PhD
The purpose of this study was to evaluate the effect of smear-layer removal using MTAD on coronal leakage of obturated root canals using a dye leakage test. Fifty, extracted, single-rooted, human teeth were cleaned and shaped and divided into 5 equal groups of 10 each. The smear layer in groups 1 to 3 was left intact. The smear layer in groups 4 and 5 was removed using 17% EDTA or MTAD, respectively. After obturation of root canals, the access opening to each canal was filled with India ink for 48 h. The depth of coronal-dye penetration was measured using the Sigmascan software. ANOVA showed statistically significant differences among the groups (p < 0.05). Samples treated with MTAD yielded significantly less leakage than samples treated with sodium hypochlorite. The amount of dye penetration was not statistically different between teeth treated with MTAD or EDTA (p = 0.062).
Real-Time Imaging and Quantification of Bioluminescent Bacteria in Root Canals In Vitro
Christine Sedgley, PhD, Bruce Applegate, PhD, Aaron Nagel, BSc, and Dan Hall, CEM
The detection of microorganisms in root canals is generally limited to qualitative or semiquantitative methods. We describe a new and nondestructive in vitro method to quantify root-canal bacteria over sequential treatment procedures using real-time imaging in conjunction with the bioluminescent reporter strain Pseudomonas fluorescens 5RL. Induced bacterial photon emission can be monitored by sensitive optical photonic imaging and luminometry, providing images as well as spatial and quantitative measurements. Bioluminescence imaging and luminometry determined that the lower limit of detection of bacteria in root canals occurred between 2 × 10² and 2 × 10³ cells, with high correlation between cell counts and detection devices (r ≥ 0.981). A preliminary study assessed the efficacy of sequential irrigation procedures to remove 5 × 106 bacteria from root canals (n = 5; apical size 60) using a 28-gauge, endodontic needle positioned 1 mm from working length; 9.2% ± 3.1% and 8% ± 3.6% of bacteria remained after 3 and 6 ml irrigation, respectively (p = 0.03), corresponding to approximately 4 × 105 bacteria remaining after 6 ml. This method can be used to study the efficacy of sequential endodontic treatment procedures in removing bacteria from root canals.
Chairside Sensor for Rapid Monitoring of Enterococcus faecalis Activity
A. Kishen, BDS, MDS, PhD, N. N. Chen, BDS, MDS, MS, L. Tan, BDS, MSc, and A. Asundi, PhD
In this study, optical spectroscopy was used to monitor a chromogenic, enzyme-substrate reaction for the rapid identification of Enterococcus faecalis. The detection system, comprising a miniature spectrophotometer and an accompanying data acquisition system, was placed in an incubator. During testing, a 3-ml test sample was placed in a cuvette within the spectrophotometer. This permitted online, real-time, and remote analysis of spectral signature needed to monitor the bacteria. It was observed that the absorption peak intensity increased conspicuously 3.5 h after inoculation and through the entire period of testing. A linear regression analysis demonstrated a significant correlation between the increase in absorption peak intensity at 610 nm (r = 0.9389) and 653 nm (r = 0.9387) with the formation of colony-forming units. Optical spectroscopy-based sensing systems can pave the way for rapid, nonlaboratory-based approaches to monitor microbial status quantitatively and qualitatively from clinical samples.
The Benefit of the Operating Microscope for Access Cavity Preparation by Undergraduate Students
Michael E. Rampado, DDS, MSc, FRCD (Canada), Leo Tjäderhane, DDS, PhD, Shimon Friedman, DMD, Stanley J. Hamstra, PhD
Although studies show the operating microscope (OM) provides benefits for endodontists, the benefit to undergraduates has not been evaluated as completely as for specialists. The purpose of this study was to determine whether using the OM would improve students’ performance in endodontic access cavity preparation and canal identification. Thirty-six dental students prepared access cavities and located canals in extracted maxillary molars, before and after training, which varied according to group. The standard group received a lecture and practice in preparation of access cavities. The microscope group received identical instruction using the OM. The control group received lectures only. All groups received equal content and instruction time (2 hr 20 min). Faculty graded preparations according to a multidimensional 5-point rating scale. Using the OM, the microscope group improved significantly in access cavity preparation (p <0.05) and significantly outperformed both standard and control groups in accuracy of identifying canals (p <0.05).
Effects of Multiple Dentinal Lesions on the Rat Pulp
R. B. Johnson, DDS, PhD
The purpose of this study was to compare the effects of single and multiple dentinal lesions on the dental pulps of rats. ³H-proline was used to measure pulpal reactionary dentin deposition, and ³H-thymidine was used to measure pulpal cell proliferation by radioautography. Data were compared by factorial analysis of variance and a post-hoc Tukey test. A significant increase in radiolabeled collagenous proteins within reactionary dentin and pulpal cell labeling indices were evident coincident to single dentinal injuries, compared with controls (p < 0.001). After double injuries, the radiolabeled collagenous proteins within reactionary dentin and the pulpal labeling indices remained significantly greater than in controls (p < 0.01); however, each was significantly less than after single injuries (p < 0.05). These data suggest that pulpal cell proliferation and collagenous protein deposition into reactionary dentin are decreased subsequent to a previous dentinal injury. Thus, the healing potential of the dental pulp could be decreased by recent tooth cavity preparation.
C-shaped Canal System in Mandibular Second Molars: Part I—Anatomical Features
Bing Fan, DDS, MS, PhD, Gary S.P. Cheung, BDS, MDS, MSc, Mingwen Fan, DDS, James L. Gutmann, DDS, PhD, FACD, FICD, FADI, and Zhuan Bian, DDS, MS, PhD
The purpose of this study was to investigate the anatomical features of C-shaped root canal system in mandibular second molars using micro-computed tomography (µCT). Fifty-eight extracted mandibular second molars with fused roots were collected from a native Chinese population. The teeth were scanned into layers of 0.5-mm thickness by µCT and measurements were made at eleven levels. The ratio of the depth of the deepest part of the groove to the buccal-lingual thickness of the cross-section of the root was calculated for each tooth. The canal shapes of the scanned cross-sections were assessed and classified according to a modified Melton’s method. Results were subject to the Kruskal-Wallis test. Of the 58 molars, 54 had a C-shaped canal system with a mean groove-to-thickness ratio of 47.96%; the four teeth without a C-shaped canal had a mean ratio of 14.82%. Most orifices (98.1%) were found within 3 mm below the cemen to enamel junction. Of teeth with a C-shape canal system, a majority demonstrated an orifice with an uninterrupted “C” configuration. Seventeen canals divided in the apical portion, most of which did so within 2mmfrom the apex. The cross-sectional shape varied drastically along the length of the canal. Teeth with a high groove-to thickness ratio had at least one section with C1, C2, or C3 configuration. The canal shape in middle and apical thirds of C-shaped canal systems could not be predicted on the basis of the shape at the orifice level. Section 2 of this paper addressed the correlation between the radiographic appearance and these µCT images.
Optimal Positioning for a Dental Operating Microscope During Nonsurgical Endodontics
Yoshifumi Kinomoto, DDS, PhD, Fumio Takeshige, DDS, PhD, Mikako Hayashi, DDS, PhD,
Shigeyuki Ebisu, DDS, PhD
The most comfortable positioning for a dental operating microscope (DOM) during nonsurgical endodontics for operators was investigated. Operators were categorized into 3 groups according to height. We recorded the time taken to obtain magnified images, and the angles of binoculars, microscope body, and the mirror to floor surfaces. For the group of shorter operators, observations were also made with an angled optics or a short objective lens (200 mm). It took longer to observe the mandibular molars than maxillary in every group. Although the differences in angles among each group were not remarkable for maxillary observation, we confirmed significant differences for the mandibular. Shorter operators had to adopt a strained position for mandibular observation in a standard setup but were more comfortable using angled optics or a short objective lens. By understanding the proper position, operators could learn to perform microendodontics more efficiently.
Importance of Mast Cells in Human Periapical Inflammatory Lesions
Constantino Ledesma-Montes, PhD,* Maricela Garcés-Ortíz, PhD,* Gilberto Rosales-García, DDS (Oral Path),† Juan Carlos Hernández-Guerrero, PhD‡
The role of mast cells (MCs) in periapical inflammatory lesions is not well understood. The objective of this work was to quantify MC numbers in human periapical lesions with the aim to clarify their role in the pathogenesis of these lesions. We analyzed the slides of 64 human periapical inflammatory lesions stained with pH 8.0 toluidine blue technique, quantified the number of MCs, and evaluated any correlation with age, gender, size, and location. The results of this study suggest that MCs were more numerous in females (p < 0.01); MC numbers were higher in biopsies from granulomas with proliferating epithelium and lower in biopsies from chronic apical abscesses; MC counts did not correlate with patients’ age or size. MCs were observed more commonly in areas containing inflammatory infiltrate and degranulation was a frequent finding in these zones. Our results suggest that MCs play an active role in the pathogenesis of the periapical inflammatory lesions. The potential role of MCs related with the initiation, development, and persistence of the periapical inflammatory process are discussed.
Simultaneous Detection of Dialister pneumosintes and Filifactor alocis in Endodontic Infections by 16S rDNA-directed Multiplex PCR
José F. Siqueira, Jr., DDS, MSc, PhD, and Isabela N. Rôças, DDS, MSc, PhD
Dialister pneumosintes and Filifactor alocis have been recently considered as candidate endodontic pathogens. In this study, we devised a 16S rDNAdirected multiplex PCR protocol for simultaneous detection of these two bacterial species in endodontic infections. Samples were taken from infected root canals associated with asymptomatic periradicular lesions as well as from cases of acute periradicular abscesses. DNA extracted from the samples was used as template for simultaneous detection of D. pneumosintes and F. alocis through a multiplex PCR assay. Two fragments of the expected sizes, one specific for D. pneumosintes and the other for F. alocis, were simultaneously amplified from amixture of reference genomic DNA containing DNA from both species. Clinical samples that were positive for the target species showed a single band of the predicted size for each species. D. pneumosintes was detected by multiplex PCR in 11 samples (7 asymptomatic and 4 abscesses) and F. alocis was identified in 9 cases (6 symptomatic and 3 abscesses). Six samples (3 asymptomatic and 3 abscesses) shared the two species. Data from the present study confirmed that D. pneumosintes and F. alocis are common members of the microbiota present in primary endodontic infections and thereby may participate in the pathogenesis of periradicular lesions. The proposed multiplex PCR assay is a simple, rapid, and accurate method for the simultaneous detection of these two candidate endodontic pathogens.
Comparative Study of White and Gray Mineral Trioxide Aggregate (MTA) Simulating a One- or Two-Step Apical Barrier Technique
Gary D. Matt, DDS, MS, Jeffery R. Thorpe, DDS, James M. Strother, DDS, MS, and Scott B. McClanahan, DDS, MS
This study investigated the use of Mineral Trioxide Aggregate (MTA) as an apical barrier by comparing the sealing ability and set hardness of white and gray MTA. Forty-four root segments were prepared to simulate an open apex. Apical barriers of white and gray MTA were placed to a thickness of 2 mm or 5 mm. The samples were obturated immediately (one step) or after the MTA set for 24 h (two-steps). After placement in methylene blue dye for 48 h, the samples were sectioned for leakage analysis and microhardness testing of the barrier. Gray MTA demonstrated significantly less leakage than white MTA (p < 0.001), and the two-step technique showed significantly less leakage than one-step (p < 0.006). The 5-mm thick barrier was significantly harder than the 2 mm barrier, regardless of the type of MTA or number of steps (p < 0.01). Results suggested that a 5 mm apical barrier of gray MTA, using two-steps, provided the best apical barrier.
MTA Obturation of Pulpless Teeth with Open Apices: Bacterial Leakage as Detected by Polymerase Chain Reaction Assay
Metello Leiss de Leimburg, DDS, Alessandra Angeretti, PhD, Paola Ceruti, DDS, Mario Lendini, DDS, Damiano Pasqualini, DDS, and Elio Berutti, MD, DDS
Polymerase chain reaction (PCR) followed by reverse dot blot was used to detect Enterococcus
faecalis leakage through mineral trioxide aggregate (MTA) apical obturations of pulpless teeth with open apices. Prepared root canals of 34 extracted teeth were given a standard apical foramen opening and received orthograde apical obturation with MTA; three groups had 1-, 2-, or 3-mm thickness. Sterilized specimens were inoculated with E. faecalis and incubated in sterile medium. DNA extracted from the specimens was amplified by polymerase chain reaction, which yielded a specific segment of E. faecalis 16S rDNA. On day 10 of incubation, no specimens were contaminated. On day 50, almost 17% of specimens were contaminated, with no statistically significant difference between groups (Chi-square = 0.48; df = 2; p = 0.787). Therefore, MTA provides an adequate seal even in cases of orthograde apical obturation of pulpless teeth with open apices.
Peroxide Penetration into the Pulp from Whitening Strips
Osman Gökay, Arzu Müjdeci, DDS, PhD, and Evren Algın, MSD
It was observed that externally applied bleaching gels may penetrate into the pulp chamber. This study was conducted to evaluate the peroxide diffusion from two whitening strips into the pulp chamber. Twenty-four, human, extracted, maxillary central teeth were separated into three groups (n = 8). All teeth were sectioned 3-mm apical to CEJ, the intracoronal pulp tissue was removed, and the pulp chamber was filled with acetate buffer. Vestibuler crown surfaces of teeth in the experimental groups were subjected to whitening strips; the teeth in the control group were exposed only to distilled water. The acetate buffer solution in each tooth was transferred to the tube. Leucocrystal violet and enzyme horseradish peroxidase also were added to the tube. The pulpal peroxide was determined spectrophotometrically. The results indicated that the whitening strip containing 14% hydrogen peroxide presented a higher pulpal peroxide penetration than 6.5 % hydrogen peroxide (p < 0.001).
Effect of Sodium Hypochlorite on Dentin Microhardness
Iris Slutzky-Goldberg, DMD, Manal Maree, DMD, Reuven Liberman, DMD, and Ilana Heling, DMD, MSc
This study was designed to evaluate the effect on root dentin microhardness of 2.5% and 6% sodium hypochlorite solutions for various irrigation periods. Forty-two bovine roots were divided into seven groups. The control group was irrigated with saline. The experimental samples were continuously irrigated with 2.5% or 6% NaOCl for 5, 10, or 20 min. Microhardness was measured at depths of 500 µm, 1000 µm, and 1500 µm from the lumen. A decrease in microhardness was found at 500 _m between the control and samples irrigated with 6% NaOCl and 2.5% NaOCl (p = 0.352, p = 0.084 respectively) at all irrigation periods. There also was a significant difference in groups irrigated for 10 or 20 min (p = 0.001, p < 0.001 respectively). At all distances, the decrease in microhardness was more marked after irrigation with 6% NaOCl than 2.5% NaOCl.
C-Shaped Canal System in Mandibular Second Molars: Part II—Radiographic Features
Bing Fan, DDS, MS, PhD, Gary S.P. Cheung, BDS, MDS, MSc, Mingwen Fan, DDS, James L. Gutmann, DDS, PhD, FACD, FICD, FADI, and Wei Fan, DDS, MS, PhD
The purpose of this study was to investigate the relation between the radiographic features of Cshaped mandibular second molars and the crosssectional shapes of their root canal system. Fifty eight extracted mandibular second molars with fused roots were collected from a native Chinese population. The teeth were scanned at 0.5-mm interval thickness by micro-computed tomography (µCT) and observed at 11 levels. The 54 teeth that possessed a C-shaped canal system were further examined. Their radiographic appearances were classified into three types according to discernible radiographic features. The results were subject to the Kruskal-Wallis statistical test. In these 54 molars, 16 teeth (29.63%) showed a type I radiographic image, 22 (40.74%) type II, and 16 (29.63%) type III. In the type I category, the C1 and C4 canal configurations were mostly found in the apical area. Categories C2 and C3 were the main configurations in the middle and apical areas in type II and III. The type III had more C2 canals in middle area than type II. These results suggested that it was possible to predict the presence and the configuration of C-shaped canal system by the radiographic appearance.