Effect of Hydrogen Peroxide and Sodium Perborate on the Microhardness of Human Enamel and Dentin
Lewinstein, Hirschfeld, Stabholz, and Rotstein
Apical Sealing Ability of Thermafil following Immediate and Delayed Post Space Preparations
Rybicki and Zillich
Indirect Longitudinal Cytotoxicity of Root Canal Sealers on L929 Cells and Human Periodontal Ligament Fibroblasts
Araki, Suda, and Spångberg
In Vitro Attachment of Streptococcus sanguis to the Dentin of the Root Canal
Calas, Rochd, and Michel
Relationship between Clinical Symptoms and Enzyme-Producing Bacteria Isolated from Infected Root Canals
Hashioka, Suzuki, Yoshida, Nakane, Horiba, and Nakamura
Bacterial Retention in Canal Walls In Vitro: Effect of Smear Layer
Drake, Wiemann, Rivera, and Walton
Effect of Smear Layer Removal on the Diffusion Permeability of Human Roots
Galvan, Ciarlone, Pashley, Kulild, Primack, and Simpson
Presence of Secretory IgA in Human Periapical Lesions
Torres, Torabinejad, Matiz, and Mantilla
Retreatment Efficacy 3 Months after Obturation Using Glass Ionomer Cement, Zinc Oxide-Eugenol, and Epoxy Resin Sealers
Moshonov, Trope, and Friedman
Effect of Hydrogen Peroxide and Sodium Perborate on the Microhardness of Human Enamel and Dentin
Israel Lewinstein, DMD, PhD, Zvia Hirschfeld, DMD, Adam Stabholz, DMD, and Ilan Rotstein, CD
The effect of 30% hydrogen peroxide and a paste of sodium perborate mixed with hydrogen peroxide at different temperatures and time intervals on the microhardness of human enamel and dentin was examined. Intact extracted human teeth were sectioned, embedded in acrylic resin, polished, and divided into four test groups related to surface treatment. The groups were 30% hydrogen peroxide at 37° C, 30% hydrogen peroxide at 50° C in an illuminated chamber, a paste of sodium perborate mixed with hydrogen peroxide at 37° C, and a paste of sodium perborate mixed with hydrogen peroxide at 50° C in an illuminated chamber. Teeth treated with distilled water at either 37° C or 50° C served as controls. The results indicated that treatment with 30% hydrogen peroxide reduced the microhardness of both enamel and dentin. This reduction was statistically significant after 5-min treatment for the dentin and after 15-min treatment for the enamel (p < 0.05). Treatment with sodium perborate mixed with hydrogen peroxide did not alter the microhardness of either the enamel or dentin at the tested temperatures and time intervals. It is therefore suggested that the use of high concentrations of hydrogen peroxide for bleaching purposes should be limited. Sodium perborate appears to be a less damaging bleaching agent.
Apical Sealing Ability of Thermafil following Immediate and Delayed Post Space Preparations
Robert Rybicki, DDS, and Richard Zillich, DDS, MS
Sixty extracted human teeth were prepared in a step-back flare method. Forty-five were obturated with plastic Thermafil and 15 were filled with lateral condensation. The Thermafil filled teeth were divided into three groups consisting of no post preparation, immediate post preparation, or delayed post preparation. Post preparations were not performed (controls) on the laterally condensed specimens. After 10 days of exposure to methylene blue dye, the specimens were decalcified in nitric acid for 72 h. A volumetric analysis measuring absorbance was then performed on each specimen. Within the testing parameters, no significant differences in leakage were observed among the tested groups.
Indirect Longitudinal Cytotoxicity of Root Canal Sealers on L929 Cells and Human Periodontal Ligament Fibroblasts
Kouji Araki, DDS, PhD, Hideaki Suda, DDS, PhD, and Larz S.W. Spångberg, DDS, PhD
The cytotoxicity of two root canal sealers was evaluated in vitro. The powder components of both sealers, mainly zinc, were the same. The liquid for one sealer, Canals, was clove oil (included eugenol in more than 80%) and other materials. For the other, Canals-N, the liquid was composed of higher fatty acids and glycol. The experiments included two cell lines, heteroploid L929 mouse fibroblasts and diploid human periodontal ligament fibroblasts. Cytotoxicity was assessed using the radiochromium release method with 4-h exposure time. The assay involved using insert chambers in multiwell arrays to produce indirect contact of materials with the cell monolayer at a controlled distance of approximately 1 mm. This model also allowed for the longitudinal study of the same material sample to assess time-dependent changes in toxicity.
Freshly mixed Canals was highly toxic (p < 0.01) to both cell lines. On and after 24 h of setting no toxicity was detected. At no time could cytotoxicity be observed when experimenting with Canals-N. These results indicate that both materials have a low content of water diffusible toxic components. Substituting eugenol can further decrease the toxicity of the sealer.
In Vitro Attachment of Streptococcus sanguis to the Dentin of the Root Canal
Paul Calas, DCD, DSO, Tarik Rochd, and Georges Michel
The adhesion of a strain of Streptococcus sanguis (NCTC 7863) to the root canal dentin of bovine incisors was evaluated. Samples (104) were prepared and smear layer was created on the root canal surface with a tungsten carbide bur. The samples were divided into four groups, one of them serving as a control sample and the other three each receiving a different treatment: 6% citric acid for 2 min (group 3), 6% citric acid for 2 min + 6.25% sodium hypochlorite for 1 min (group 2), 6% citric acid for 10 min (group 4). After sterilization, they were incubated, and adhesion was assessed by direct examination using a scanning electron microscope. The use of irrigation solutions significantly reduced the adhesion in the latter two groups only, with a reduction of 15% (group 2) and 18.7% (group 4) in the number of bacteria.
Relationship between Clinical Symptoms and Enzyme-Producing Bacteria Isolated from Infected Root Canals
Kazuko Hashioka, DDS, PhD, Kazuyoshi Suzuki, DDS, Tsutomu Yoshida, DDS, Akinobu Nakane, DDS, PhD, Naoki Horiba, DDS, PhD, and Hiroshi Nakamura, DDS, PhD
The object of this study was to determine the correlation between clinical symptoms and the activity of enzymes such as collagenase, chondroitinase, and hyaluronidase produced by bacteria isolated from infected root canals. The materials examined consisted of 28 teeth with apical periodontitis from 25 patients. Bacteria producing collagenase or chondroitinase and hyaluronidase were found to be significantly related to subacute clinical symptoms involving percussion pain. The frequency of bacteria producing collagenase was higher in isolates from root canals with a radiolucent area over 5 mm in diameter than in those from canals having a radiolucent area less than 5 mm in diameter.
Bacterial Retention in Canal Walls In Vitro: Effect of Smear Layer
David R. Drake, MS, PhD, Alfred H. Wiemann, DDS, MS, Eric M. Rivera, DDS, MS, and Richard E. Walton, DDS, MS
When dentin is planed by endodontic instruments, a smear layer forms. Whether this layer should be removed is unknown and controversial. This study was conducted to assess the effect of the smear layer on retention of bacteria using an in vitro root canal bacterial colonization model. Canals of 26 extracted human canines were step-back prepared using 2.5% NaOCl. Teeth were then randomly divided into two groups based on the type of high volume final flush: 1-20 ml of sterile saline (0.85% wt/vol) or (2-10ml of 17% EDTA followed by 10 ml of 2.5% NaOCl which removes smear layer. Streptococcus anginosus (milleri) was cultured in trypticase soy broth supplemented with 0.5% yeast extract at 37°C in 5% CO2. Cells were harvested by centrifugation and resuspended in fresh media. Serial dilutions were performed to achieve inocula of 106 colony-forming units in a 30-µl volume. Teeth were inoculated and incubated for 2 h in 5% CO2 at 37° C. Following incubation, teeth were split and processed for microbiological analysis. Numbers of colonizing bacteria were determined by a spiral-plating system. Enumeration of the numbers of bacteria revealed a reproducible, order of magnitude difference (p = 0.0002) between teeth with smear layer (104 colony-forming units) versus teeth without smear layer (105 colony-forming units). This suggests that smear layer produced during root canal therapy may inhibit bacterial colonization of root canals. One suggested mechanism is that smear layer may block bacterial entry into dentinal tubules.
Effect of Smear Layer Removal on the Diffusion Permeability of Human Roots
David A. Galvan, DDS, MS, Alfred E. Ciarlone, DDS, PhD, David H. Pashley, DMD, PhD, James C. Kulild, DDS, MS, FICD, Patrice D. Primack, DMD, MS, and Mark D. Simpson, BS
Ten human maxillary incisors, extracted because of periodontal disease or nonrestorable caries, were obtained and instrumented to a size #70 K-Flex file at the working length using a standard stepback technique. Tritiated water (3H2O) was placed in the root canals and allowed to diffuse to the external surface of the roots until it reached a constant rate. The smear layer in each of the experimental roots was then removed using 0.5M EDTA followed by 5.25% sodium hypochlorite (NaOCl). The constant rate diffusion of 3H2O was remeasured. The roots were then stored in deionized H2O for 2 months and the constant rate diffusion of 3H2O was remeasured. A statistically significant difference was noted between all three groups. A decrease in the diffusion permeability of the root to 3H2O was noted immediately after smear layer removal and the highest permeability was recorded after storage in the deionized water for 2 months.
Presence of Secretory IgA in Human Periapical Lesions
Jorge Orlando Cortes Torres, DDS, Mahmoud Torabinejad, DMD, MSD, Rene Alejandro Rodriguez Matiz, DDS, and Enrique Gomex Mantilla, DDS
The concentration of secretory IgA in fluids present in the canals of 33 teeth was determined by the rocket immunoelectrophoresis technique. Except for the presence or absence of communication between the oral cavity and the root canals of the affected teeth, no other clinical finding showed significant statistical correlation with the presence of secretory IgA. The canals which were open to the oral flora had significantly higher concentrations of secretory IgA. Leaving canals open to the oral cavity may result in formation of periapical cysts.
Retreatment Efficacy 3 Months after Obturation Using Glass Ionomer Cement, Zinc Oxide-Eugenol, and Epoxy Resin Sealers
Joshua Moshonov, DMD, Martin Trope, DMD, and Shimon Friedman, DMD
The efficacy of ultrasonic retreatment, 3 months after obturation, in conjunction with Ketac-Endo, Roth's 801, and AH26 sealers was evaluated. Seventy-two root canals were prepared and obturated with gutta-percha and one of the sealers mentioned above. After 90 days, the canals were retreated by an ultrasonic technique and the retreatment time was recorded. The roots were split and the amount of debris that remained on the canal walls in three separate levels was scored. Compared by one-way and two-way analysis of variance, the mean scores of remaining debris at the different canal levels for the three sealer groups, as well as for each group, were not significantly different. The only significant difference was found in retreatment time for which Ketac-Endo was significantly slower to retreat than the other two sealers (p < 0.002). Thus, the results of this study showed that the amount of debris remaining on the root canal walls following retreatment 3 months after obturation is similar for Ketac-Endo, Roth's 801, and AH26 sealers, but the retreatment time for Ketac-Endo is significantly longer.