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At least 667 records · Page 37Linked to original sources
PubMed1992

Penetration of the pulp chamber by carbamide peroxide bleaching agents.

Hydrogen peroxide readily penetrates the pulp chamber of freshly extracted teeth. This study was undertaken to determine whether carbamide peroxide also penetrates the pulp chamber. Freshly extracted teeth were sectioned 2 to 3 mm apical to the cementoenamel junction and the coronal pulpal tissue was removed. Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. The coronal portion of each tooth was immersed in either carbamide peroxide gel or gelled hydrogen peroxide at various concentrations for 15 min at 37 degrees C. The buffer was removed, leukocrystal violet was added, and the optical density of the resulting blue solution was determined spectrophotometrically. Amounts of peroxide found in the pulp chamber after 15 min ranged from 3.3 +/- 0.38 micrograms for the 10% sample to 40.4 +/- 3.51 micrograms for the 30% sample.

Carbamide Peroxide↗
PubMed1993

Effect of smear layer removal on the diffusion of calcium hydroxide through radicular dentin.

Forty single-rooted teeth were sectioned transversely through the cementoenamel junction and instrumented to a size #50 K-Flex file at the working length by saline irrigation. Each root was placed in a dilution vial containing 10 ml of normal saline, and the pH and Ca2+ levels were recorded after 24 h. The roots in group 1 then received a final irrigation with 20 ml of normal saline. Group 2 received a final irrigation with 10 ml of 17% ethylenediaminetetraacetic acid followed by 10 ml of 5.25% NaOCl to remove the smear layer. Group 3 was irrigated in the same manner as group 2, but calcium hydroxide (CH) was placed into the root canal. Group 4 was irrigated with 20 ml of NaOCl, and CH was placed into the root canal. The pH and Ca2+ levels were recorded at 1, 3, 5, and 7 days. After 7 days a 3- x 3- x 1-mm external defect was created in the coronal one third of the root surface. The pH and Ca2+ levels were subsequently recorded at 1, 3, and 7 days. Groups 3 and 4 demonstrated significantly higher H+ and Ca2+ levels than did groups 1 and 2 three days after CH placement and at all subsequent intervals. Group 3 demonstrated significantly higher H+ and Ca2+ readings at some but not all intervals. The results demonstrated that CH diffuses from the root canal to the exterior surface of the root and that the removal of the smear layer may facilitate this diffusion.

Analysis of Variance↗
PubMed1995

Microbial induction of dentinal caries in human teeth in vitro.

The ability of Lactobacillus casei, Streptococcus sobrinus, Actinomyces viscosus, and Streptococcus salivarius to induce dental caries was determined in vitro. A class I cavity (depth: 2mm) was prepared in extracted human caries-free premolars to make dentin blocks. The blocks were inoculated with these four bacterial strains in a monoinfective fashion and were incubated under anaerobic conditions. In addition to the monoinfection groups, mixed-infection groups of L. Casei with S. sobrinus or A. viscosus were also prepared. Half of the culture medium was renewed every 3 days, and the pH of the medium was measured. After 4 or 12 wk, these dentin blocks were prepared by Brown-Brenn staining and by contact microradiography for light microscopic observation and for immunohistochemical staining. The final pH of the S. salivarius group was the highest among the experimental groups, at approximately 5.1; that of the others was approximately 4.3. Bacterial invasion into the dentinal tubules was observed in all but the S. salivarius group. Among the monoinfection groups, the S. sobrinus group showed the highest invasion rate, followed by the A. Viscosus group and the L. casei group. The invasion rate was also high in the mixed-infection groups. Immunohistochemical staining revealed invasion only by L. casei, and not by S. sobrinus and A. viscosus. The invasion rate by L. casei was higher in the mixed-infection group with either S. sobrinus or A. viscosus than in the monoinfection groups. These findings suggest that lactobacillus might play an important role in the initiation and progress of dentinal caries, and that this bacterial species might exhibit a cooperative cariogenicity when it coexists with other bacterial species that surpasses its individual cariogenicity.

Actinomyces viscosus↗
PubMed1995

Efficacy of XeCl 308-nm excimer laser in reducing dye penetration through coronal dentinal tubules.

The efficacy of XeCl excimer laser irradiation in reducing dye penetration through human coronal dentinal tubules was studied. The roots of 20 freshly extracted human molars were resected, and the apical aspect of the crowns was ground until the pulp chamber was completely exposed. Following total removal of the pulp chamber and further grinding of the occlusal and apical surfaces up to the intact dentin, the teeth were randomly divided into experimental and control groups of 10 each. The teeth in the experimental group were completely coated with nail polish and then irradiated with XeCl 308-nm excimer laser at a fluence of 0.7 J/cm2 to form an elliptical lased area. The teeth in the control group were also coated with nail polish, but with a similar elliptical spot of exposed dentin corresponding to the irradiated spot created in the lased teeth left uncoated. All specimens were placed in 0.5% methylene blue dye for 48 h, rinsed, and air-dried. The specimens were then ground to reach the experimental area in order and photographed. The total area of penetrated dye was determined by three independent evaluators and then measured with a computerized planimeter. The mean total areas (mm2) measured in the lased specimens were significantly smaller than those in the controls (p = 0.012).

Dental Leakage↗
PubMed1995

Ability of bacterial endotoxin to diffuse through human dentin.

An in vitro system was developed to determine whether bacterial endotoxin is capable of diffusing through dentin without the use of filtration pressure. Cavities were prepared in five third molar teeth in order to produce a split chamber device consisting of occlusal and pulpal chambers with 0.5 mm of intervening dentin. Endotoxin was introduced into the occlusal chamber and the effluent in the pulpal chamber was sampled every 30 min for 5 h and at 24 h using the limulus lysate assay. In four specimens the initial appearance of endotoxin in the effluent ranged from 15 min to 4 1/2 h. In two specimens the concentration of endotoxin in the effluent leveled off in 4 1/2 and 5 h, respectively, whereas in another two the concentration continued to increase throughout the experiment. In one specimen no endotoxin was detected. The results indicate that endotoxin is capable of passing through 0.5 mm of dentin.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Scanning electron microscopic evaluation of two compaction techniques using a composite resin as a root canal filling material.

The canals of 20 human dental roots were instrumented using a a step- back technique. The smear layer was removed, and the canals were obturated with composite resin. Two different techniques of compaction were used: either vertical or lateral motions were used to condense composite resin inside the root canal that was then photopolymerized layer by layer using the argon laser (488 nm). The beam was delivered into the root canal by means of an optical fiber 320 micrometers in diameter. Longitudinal and cross-sections of the samples and resin replicas of the root canals were examined using a light and scanning electron microscope. Scanning electron microscopic examination revealed that laterally compacted resin fillings showed fewer voids than those obtained by vertical compaction. In both experimental groups, adhesion of the resin to the dentin walls, pulled-out resin tags, microfailure, and resin fracture, leaving a layer of resin associated with the wall surface were observed.

Argon↗
PubMed1994

Bacterial retention in canal walls in vitro: effect of smear layer.

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 (2-10 ml 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 degrees C in 5% CO2. Cells were harvested by centrifugation and resuspended in fresh media. Serial dilutions were performed to achieve inocula of 10(6) colony-forming units in a 30-microliters volume. Teeth were inoculated and incubated for 2 h in 5% CO2 at 37 degrees 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 (10(4) colony-forming units) versus teeth without smear layer (10(5) 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.

Bacterial Adhesion↗
PubMed1992

Evaluation of internal sealing ability of three materials.

Thirty-six maxillary central incisors were prepared in a manner similar to nonvital bleaching procedures. They were examined with respect to the degree of procion green dye penetration of dentin with and without heating. Cavit, IRM, and zinc phosphate cement were used to evaluate their sealing ability. Cavit and IRM provided better internal sealing of the dentin than did zinc phosphate cement.

Calcium Sulfate↗
PubMed1992

Cervical canal leakage after internal bleaching.

The effects that walking bleach procedures had on root canal filling leakage and the extent of dentinal penetration were studied. Forty teeth were divided into four groups: 1--GP, set sealer, no base; 2--GP, set sealer, 2-mm Cavit base; 3--GP, unset sealer, no base; and 4--GP, unset sealer, 2-mm Cavit base. All were bleached for 7 days, fresh bleach was added for another 7 days, then methylene blue dye was placed for 5 days. The extent of dye penetration apically along the root canal filling and through the dentinal tubules was evaluated. The results indicate that 2 mm of Cavit was sufficient to significantly reduce linear leakage and dentinal penetration. The Cavit should be placed to a level slightly coronal to the facial cementoenamel junction. Teeth with cemental defects demonstrated greater perpendicular dye penetration in the areas of the defects than those with intact cementum. The data from this study suggest the use of a base material over gutta-percha in clinical practice prior to internal walking bleach procedures.

Analysis of Variance↗
PubMed1992

Dentin as inhibitor of bacterial toxicity on pulpal cells in vitro.

Many studies have shown that the major cause of pulpal disease is the presence of bacteria or their by-products in the dentinal tubules. The purpose of this investigation was to develop an in vitro model, simulating the pulp chamber, that would permit the study of the transport of bacterial by-products through dentin and their effect on pulpal cells. Human pulpal cells were cultured in a modified Sykes-Moore chamber and exposed through dentin to sonicated extracts of Porphyromonas gingivalis ATCC 33277. The cell response was evaluated with the thymidine incorporation method. The results were compared with the cell response obtained after direct exposure to the same irritant. It was found that dentin significantly restricts the diffusion of bacterial proteins in a 24-h experimental period. The time needed for the first bacterial protein molecule to cross the dentin barrier was 6 h. The "diffusion velocity" of the bacterial proteins was 0.023 microns/s. The proposed model has further applications in biocompatibility and microleakage research.

Bacterial Proteins↗
PubMed1991

Effect of cementum defects on radicular penetration of 30% H2O2 during intracoronal bleaching.

Bleaching pulpless teeth with 30% hydrogen peroxide has been reported to cause external cervical root resorption. It has been hypothesized that H2O2 penetrating through open dentin tubules can initiate an inflammatory reaction which could result in root resorption. Extracted human premolars were treated endodontically and bleached intracoronally using the thermocatalytic technique. The teeth were divided into three groups; one group with no cementum defects at the cementoenamel junction, one group with artificial cementum defects at the cementoenamel junction, and another group with artificial cementum defects at the middle third of the root. The radicular penetration of 30% hydrogen peroxide in the three groups was assessed directly and compared using an in vitro model. Radicular penetration of hydrogen peroxide was found in all of the groups tested. The penetration of hydrogen peroxide was significantly higher in teeth with cementum defects at the cementoenamel junction than in those without defects.

Dental Cementum↗
PubMed1991

Dye leakage in retrofilled dog teeth and its correlation with radiographic healing.

In a previous study in beagle dogs, statistically significant differences in healing were observed radiographically 6 months after apicoectomy and retrofilling with amalgam and varnish, glass ionomer cement, or a composite resin. The purpose of this study was to compare the leakage of these retrofilling materials and to correlate leakage data with healing. After the dogs were sacrificed, 48 roots were extracted. Half of the roots had been irradiated with a CO2 laser on the bevelled root surface after retrofilling. The roots were coated with nail polish, except for their bevelled surface, and were suspended together with positive and negative controls in 2% methylene blue for 8 h. After the specimens were longitudinally split, they were ranked according to the severity of dye penetration, as observed with a dissecting microscope. The differences in dye leakage among the three retrofilling materials were not statistically significant. Consequently, dye leakage did not correlate with the previously assessed healing. Dye penetrated into the root through the bevelled root surface, regardless of CO2 laser exposure of that surface.

Animals↗
PubMed1989

The penetration of smear material into dentinal tubules during instrumentation with surface-active reagents: a scanning electron microscopic study.

Thirty freshly extracted, single-rooted anterior teeth were used. They were divided into three groups and instrumented conventionally with #10 to 50 K files. During instrumentation, the K files in the first group were moistened with saline solution, in the second group with 50% sodium dodecylbenzenesulfonate solution, and in the third group with Sulfapon (sodium salt of sulfonated condensation product of ethylen oxide with a fatty acid) solution. After the experimental procedure the specimens were examined in a scanning electron microscope to observe packing of smear material into dentinal tubules. Results showed the surface-active reagents cause the deeper penetration of the smear material into the dentinal tubules. These findings support the hypothesis that the phenomenon of the packing of smear material into the dentinal tubules is by capillary action and fluid dynamics.

Benzenesulfonates↗
PubMed1989

Systemic distribution of 14C-labeled formaldehyde applied in the root canal following pulpectomy.

The systemic distribution of 14C-labeled formaldehyde which had been placed in the root canals of the canines of cats following pulpectomies was studied using liquid scintillation counting and wholebody autoradiographic technique. Radioactive 14C which had been placed in the canals was found in the plasma 30 min after the root canal procedure. The recovery of systemic 14C radioactivity increased with time. In addition, it seemed that approximately 3% of the dose placed in the teeth was excreted in the urine within 36 h. Whole-body autoradiograms indicated extensive concentration of 14C radioactivity in tissues other than those analyzed with the liquid scintillation technique.

Animals↗
PubMed1996

Microleakage of human saliva through dentinal tubules exposed at the cervical level in teeth treated endodontically.

This study investigated the possibility of saliva recontamination occurring between the root canal wall and sealer through dentinal tubules exposed after the cementum was removed at the cervical level by root planing and treatment with citric acid. Thirty-four extracted human maxillary anterior teeth were randomly placed into five groups after chemomechanical preparation and obturation with gutta-percha and sealer; the sealer was allowed to set for 48 h. A ring 3 mm high, at the cervical level, was subjected to root planing, with complete removal of the cementum. All specimens were coated with two layers of nail polish and two layers of sticky wax, except for the ring subjected to root planing that was treated with citric acid for 30 s. The specimens were exposed to human whole saliva for 20 to 80 days and then immersed in dye to determine microleakage. Specimens were cleared and measurements made to the maximum point of dye penetration. All of the specimens exposed to saliva showed leakage except for the negative control, wherein no dye penetration was seen. Where leakage was found, the dye penetrated between the canal walls and the sealer to increasing depths, proportional to the time of exposure to the saliva. Statistical analysis confirmed these data, evidencing a difference between the means, which was highly significant for all pairs.

Analysis of Variance↗