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At least 1,477 records · Page 82Linked to original sources
PubMed2002

Cyclic fatigue of endodontic nickel titanium rotary instruments: static and dynamic tests.

Endodontic instruments upon rotation are subjected to both tensile and compressive stress in curved canals. This stress is localized at the point of curvature. The purpose of this study was to evaluate the cyclic fatigue of 0.04 ProFile nickel titanium rotary instruments operating at different rotational speeds and varied distances of pecking motion in metal blocks that simulated curved canals. A total of 150 ProFile instruments were made to rotate freely in sloped metal blocks at speeds of 200, 300, or 400 rpm by a contra-angle handpiece mounted on an Instron machine. The electric motor and Instron machine were activated until the instruments were broken in two different modes, static and dynamic pecking-motion. The fractured surfaces of separated instruments were examined under a scanning electron microscope. All data obtained were analyzed by a stepwise multiple regression method using a 95% confidence interval. The results demonstrated that the time to failure significantly decreased as the angles of curvature or the rotational speeds increased. However, as pecking distances increased, the time to failure increased. This is because a longer pecking distance gives the instrument a longer time interval before it once again passes through the highest stress area. Microscopic evaluation indicated that ductile fracture was the major cyclic failure mode. To prevent breakage of a NiTi rotary instrument, appropriate rotational speeds and continuous pecking motion in the root canals are recommended.

Compressive Strength↗
PubMed2002

Endodontic treatment of unusual central incisors.

This report presents an endodontic therapy in an unusual case of a patient who had wide crowns of both permanent maxillary central incisors. The right maxillary central incisor had two separate canals on a fused root and the left had a large root canal within one root.

Adolescent↗
PubMed2002

The effect of rotational speed and the curvature of root canals on the breakage of rotary endodontic instruments.

One of the biggest concerns when working with rotary endodontic instruments is that the instrument might break in the root canal thus compromising the treatment. This study evaluated the effect of rotational speed and the curvature of root canals on the breakage of ProFile rotary instruments to determine whether either causes an increase in instrument breakage. One hundred twenty root canals of extracted molars were divided into two groups according to whether the curvature of the canal was greater or lesser than 30 degrees. Three different rotational speeds (150, 250, and 350 rpm) were then used to carry out the instrumentation of the canals. The curvature of the canals would seem to be the most important factor that increases the risk of instrument breakage.

Dental Instruments↗
PubMed2002

Differential scanning calorimetric studies of nickel titanium rotary endodontic instruments.

Differential scanning calorimetric (DSC) analyses were performed between -130 degrees and 100 degrees C on specimens prepared from nickel-titanium (NiTi) rotary endodontic instruments: ProFile (n = 5), Lightspeed (n = 4), and Quantec (n = 3). The ProFile and Lightspeed instruments were in the as-received condition, whereas the Quantec instruments were randomly selected from a dental clinic and had unknown history. The DSC plots showed that the ProFile and Lightspeed instruments analyzed had the superelastic NiTi property, with an austenite-finish (Af) temperature of approximately 25 degrees C. Differences in DSC plots for the ProFile instruments and the starting wire blanks (n = 2) were attributed to the manufacturing process. The phase transformation behavior when the specimens were heated and cooled between -130 degrees and 100 degrees C, the temperature ranges for the phase transformations, and the resulting enthalpy changes were similar to those previously reported for nickel-titanium orthodontic wires having superelastic characteristics or shape memory behavior in the oral environment. The experiments demonstrated that DSC is a powerful tool for materials characterization of these rotary instruments, providing direct information not readily available from other analytical techniques about the NiTi phases present, which are fundamentally responsible for their clinical behavior.

Calorimetry, Differential Scanning↗
PubMed2002

Survival rate and fracture strength of incisors restored with different post and core systems and endodontically treated incisors without coronoradicular reinforcement.

This in vitro study evaluated the survival rate and fracture resistance of maxillary central incisors restored with different post and core systems. The post and core systems investigated were a prefabricated high precious metal post with cast core (group A), zirconia post with a prefabricated bonded ceramic core (group B), and a resin-ceramic interpenetrating phase composite post (experimental) with a prefabricated bonded ceramic core (group C). The all-ceramic copings were cemented using Panavia 21 TC. In the group without coronoradicular reinforcement, the access cavity was closed with a light-cured composite in combination with a dentine-bonding agent (group D). Each specimen was intermittently loaded and thermocycled before final stress tests in a Zwick machine. The survival rates after 1,200,000 cycles in the artificial mouth were 90% (group A), 80% (group B), 60% (group C), and 100% (group D). Statistically significant differences were found between all groups with the exception of A and B, when failure during cyclic loading was included (Kruskal-Wallis multiple comparisons test). Samples restored with a cast post and core demonstrated more vertical root fractures. It was concluded that the preservation of both internal and external tooth structure is of utmost importance when restoring endodontically treated teeth.

Cementation↗
PubMed2002

Apical healing of an endodontically treated tooth with a temporary restoration.

A 35-yr-old, healthy male presented to the graduate endodontic clinic at Indiana University School of Dentistry for treatment of tooth #26. Two and one-half yr after treatment, the patient returned to the dental school for comprehensive treatment. The canal access opening had been restored with an intact interim restorative material restoration. The tooth was asymptomatic, and radiographic examination showed evidence of apical healing. In this article, a review of the literature concerning crown-down leakage is presented. A case report is given in which healing occurred after the tooth was restored with only an interim restorative material for an extended period of time.

Adult↗
PubMed2002

Fatigue resistance of engine-driven rotary nickel-titanium endodontic instruments.

A comparative study of the fatigue resistance of engine-driven nickel-titanium endodontic instruments was performed, aiming to access the influence of the cutting flute design and of the size of the files that reach the working length in curved canal shaping. Geometrical conditions similar to those found in practice were used. Series 29 #5 ProFile, together with #6 and #8 Quantec instruments, were tested in artificial canals with a 45-degree angle of curvature and 5-mm radius of curvature. It was observed that the size of the instrument, which determines the maximum strain amplitude during cyclic deformation, is the most important factor controlling fatigue resistance. The effect of heat sterilization on the fatigue resistance of the instruments was also examined. The results obtained indicate that the application of five sterilization procedures in dry heat increases the average number of cycles to failure of unused instruments by approximately 70%.

Dental Alloys↗
PubMed2002

Differential scanning calorimetric studies of nickel-titanium rotary endodontic instruments after simulated clinical use.

Differential scanning calorimetric (DSC) analyses have been performed between -130 degrees and 100 degrees C on single-segment specimens obtained from ProFile and Lightspeed nickel-titanium rotary endodontic instruments in the as-received condition and after one, three, and six periods of simulated clinical use in extracted teeth. The DSC analyses showed that both brands of instruments were always in the superelastic condition, although the enthalpy values for the transformation from martensitic NiTi to austenitic NiTi were much smaller for the Lightspeed instruments. Simulated clinical use had no evident effect upon this transformation for both brands, which is attributed to insufficient mechanical deformation of the instruments. There were substantial differences in the enthalpy change associated with the transformation from martensitic NiTi to austenitic NiTi for test segments from different positions along the shafts of the instruments and for as-received instruments from two different batches that were analyzed in this study and a previous study. These differences are attributed to variations in work hardening along the shaft during instrument fabrication and to processing differences during production of the two batches of each instrument brand.

Calorimetry, Differential Scanning↗
PubMed2002

The cellular compatibility of five endodontic sealers during the setting period.

The purpose of this study was to evaluate the cellular compatibility of five endodontic sealers in the first 24 h after mixing. Specimens of N2, Endomethasone, Apexit, AH Plus, and Ketac Endo were extracted with cell culture medium 0, 1, 5, and 24 h after mixing. Eluates were tested for cytotoxicity with immortal 3T3 cells and primary human periodontal ligament fibroblasts using XTT-assays. Data were analyzed for statistically significant differences by means of Dunnett's t tests (p < 0.05). All extracts of N2 completely inhibited cell metabolism (p < 0.05). Similar effects were provoked by the first three eluates of Endomethasone, but the 24-h extract irritated cells significantly less (p < 0.05). Severe cytotoxicity was also observed with all Ketac Endo extracts (p < 0.05). A significant inhibition of mitochondrial activity was induced by the first (3T3) or the first and second eluate (periodontal ligament fibroblasts) of AH Plus (p < 0.05). The subsequent eluates of this sealer and all extracts of Apexit did not reveal any cytotoxic potency.

3T3 Cells↗
PubMed2002

In vitro cytotoxicity evaluation of endodontic sealers exposed to heat before assay.

During warm-vertical condensation of gutta-percha, endodontic sealers are exposed to temperatures that potentially alter their cytotoxicity profiles. This study investigated the effects of heat on sealer toxicity by using the CyQuant assays for cell adhesion and proliferation of human gingival fibroblasts. Seven sealers were exposed to one of the following temperatures for 10 min before assay: 23 degrees C, 43 degrees C, or 100 degrees C. Adhesion data were used to determine percentage of cells bound, and proliferation data were used to determine percentage of change in cell number from 24 to 72 h, for each sealer at each temperature. The temperatures of 23 degrees C, 43 degrees C, and 100 degrees C were significantly different in both the adhesion and proliferation assays. Sealer type and temperature were significant variables in both assays. The changes in toxicity measured by adhesion and proliferation for each sealer were not always similar. Roth 801 and Roth 811, after exposure to 100 degrees C, showed enhanced adhesion but not proliferation, whereas Kerr PCS and Dentalis, after exposure to 100 degrees C, showed decreased adhesion but enhanced proliferation. AH Plus and AH26 showed an increase in adhesion and proliferation after heat exposure, whereas Sealapex remained virtually unaffected.

Adhesiveness↗
PubMed2003

The effect of endodontic solutions on resorcinol-formalin paste.

This study determined if any of four endodontic solutions would have a softening effect on resorcinol-formalin paste and if there were any differences in the solvent action between these solutions. Resorcinol, formalin, and zinc oxide were mixed and allowed to set for 30 days. The solutions tested were 0.9% sodium chloride, 5.25% sodium hypochlorite, chloroform, and Endosolv R. Seven samples per solution were tested and an additional seven samples served as controls. Each sample was saturated with one of the solutions and the depth of penetration was tested at 1, 2, 5, 10, and 20 min using a dial strain gauge. At 2 min, sodium hypochlorite and sodium chloride had significantly greater penetration than the other groups (p < 0.0010). Sodium hypochlorite was superior to all other groups after 5 min. This study showed that both sodium chloride and sodium hypochlorite exhibited a significant softening effect within 2 min.

Analysis of Variance↗
PubMed2003

In vitro inhibitory effect of EGTA on macrophage adhesion: endodontic implications.

Ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) is an specific calcium ion chelator proposed as endodontic irrigant. This study investigates the effect of EGTA on substrate adherence capacity of rat inflammatory macrophages. Inflammatory macrophages were obtained from Wistar rats and resuspended in RPMI-1640 medium. Substrate adherence capacity assays were carried out in Eppendorf tubes for 15 min of incubation at 37 degrees C in a humidified atmosphere of 5% CO2. The adherence index was calculated. Results showed that EGTA decreased substrate adherence capacity of inflammatory macrophages in a time- and dose-dependent manner. The EGTA concentration that caused half-maximal inhibition (IC50) was 202 +/- 32 mM (p < 0.01). EDTA was more potent than EGTA in inhibiting macrophage adherence (IC50 = 185 +/- 22 mM). Calcium chloride (10 mM) decreased the EGTA inhibitory effect on adherence index by 60.2% (p < 0.01). We conclude that EGTA significantly decreased substrate adherence capacity of macrophages.

Animals↗
PubMed2003

Antimicrobial activity of endodontic sealers on Enterococcus faecalis.

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 degrees C. The zones of inhibition were measured at 24 and 48 h. Analysis using a one-way ANOVA and Tukey 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.

Analysis of Variance↗
PubMed2003

Resorcinol-formaldehyde resin "Russian Red" endodontic therapy.

Resorcinol-formaldehyde resin is a material used in endodontic therapy in many foreign countries. With immigration to the United States increasing, American dentists need to become familiar with resorcinol-formaldehyde therapy. It contains two potentially toxic components, formaldehyde (liquid) and resorcinol (powder). Zinc oxide or barium sulfate may be used for radiopacity. When 10% sodium hydroxide is added to the mixture, polymerization occurs, which can form a brick-hard red material that has no known solvent. Several variations in technique exist. The catalyst can be mixed in before insertion into the tooth, added after the mixture is inserted, or not used. Providers believe pulp tissue will be fixed and bacteria destroyed apical to the level of resorcinol-formaldehyde resin placement. Canals are frequently not instrumented or obturated to their full length. Few success-failure studies have been published and results are contradictory. Consequently, providers have little guidance regarding when to retreat or for predicting the difficulty of retreatment.

Drug Combinations↗
PubMed2003

Calibrated latex microspheres percolation: a possible route to model endodontic bacterial leakage.

Endodontic therapy is conducted to effectively seal the root canal system. In vitro methods are used to estimate the quality of the seal, generally by measuring any microleakage that allows the tracers to penetrate along the obturated root canal. The use of bacteria as tracers seems to give the most clinically relevant demonstration of microleakage associated with a root canal system. Many bacterial strains have been used to evaluate marginal leakage, but results are sometimes contradictory, probably because they may depend on the bacterial strain used. In the studies described in this article, the percolation of both calibrated latex microspheres equivalent in diameter (0.4-9.5 microm) to bacteria and three bacterial strains (Actinomyces odontolyticus, Lactobacillus acidophilus, and Pseudomonas fluorescens) was compared in teeth filled using noncompressive and compressive techniques. The depth (d) to which the microspheres and bacteria penetrated varied over the time (t) of contamination according to a logarithmic relation. The slope (S) and the intercept (I, corresponding to penetration after 1 month) of the d = f(In t) plots can serve to quantify penetration over time. Statistical analysis of I by the Newman-Keuls procedure, which couples the tracers and filling techniques, showed that A. odontolyticus and L. acidophilus behave like 4.8-microm particles and P. fluorescens like 2.2-microm particles (corresponding approximately to their size in length) and that noncompressive techniques are less hermetic than compressive techniques. S and I are in direct relation and this relation is independent of the filling technique. Moreover, for the calibrated particles, both I and S varied linearly with the inverse of the square root of the particle diameter, indicating that their displacements are governed solely by Brownian movements and the penetration over time is caused by diffusion phenomena. The size of the tracer is the predominant factor governing its penetration. Inert particles mimic bacterial percolation into the marginal hiatus and can thus be used to model this percolation and establish a relative scale of the behavior of different bacteria during percolation.

Actinomyces↗
PubMed2003

Occurrence of Actinomyces in infections of endodontic origin.

Species of Actinomyces have been associated with endodontic treatment that failed to heal. In this study polymerase chain reaction was used with a pair of universal primers for Actinomyces and species-specific primers to evaluate the contents of infected root canals and aspirates from abscesses or cellulitis for the presence of Actinomyces israelii, A. naeslundii, and A. viscosus. DNA was extracted from 131 clinical samples. DNA from 2 of the original 131 samples was not available for polymerase chain reaction with the universal primer for Actinomyces and A. naeslundii. DNA reacting with the universal primer for Actinomyces was detected in 72 of 129 (55.8%) clinical samples. Of those 41 of 51 (80.4%) were from infected root canals, 22 of 48 (45.8%) were from abscesses, and 9 of 30 (30%) were associated with cellulitis. A. viscosus was detected in 42 of 131 (32.1%) clinical samples. Of those 31 of 52 (59.6%) were from infected root canals, 6 of 43 (14%) were from abscesses, and 5 of 36 (13.9%) were associated with cellulitis. A. israelii was detected in 31 of 131 (23.7%) clinical samples. Of those 14 of 52 (26.9%) were from infected root canals, 11 of 43 (25.6%) were from abscesses, and 6 of 36 (16.7%) were associated with cellulitis. A. naeslundii was detected in 11 of 131 (8.5%) clinical samples. Of those 7 of 51 (13.7%) were from infected root canals, 2 of 48 (4.2%) were from abscesses, and 2 of 30 (6.7%) were associated with cellulitis.

Actinomyces↗
PubMed2003

Cytotoxicity testing of endodontic sealers: a new method.

The purpose of this study was to compare ISO standards versus a new technique for in vitro evaluation of cytotoxicity of root canal sealers. The cytotoxicity of AH Plus, Cortisomol, and Sealapex was first recorded according to ISO standards on L 929 fibroblasts by the MTT assay. In parallel, 30 single-rooted teeth were cut at the cementum enamel junction (CEJ), and the roots were prepared and sterilized before filling with the lateral condensation using one of three sealers (n = 10). The apexes of the roots were dipped into 1 ml of minimum essential medium for 1, 2, and 30 days renewing the medium every other day. After 24-h contact between the medium and the filled roots, the medium was used to measure the cytotoxicity on L 929 with the MTT assay. ISO standards always gave a statistically higher cytotoxicity than the root-dipping technique (p < 0.0001), whatever the sealer and the exposure time. The ISO standards showed statistically significant differences among the sealers (p < 0.0001). AH Plus was noncytotoxic, Cortisomol showed a high cytotoxicity decreasing over time (p < 0.001), and Sealapex displayed a high cytotoxicity that did not decrease over time (NS). The new technique showed statistically significant differences among the sealers (p = 0.001), but the differences were so small that they were likely not clinically relevant. The high cytotoxicity of Sealapex decreased over time but the cytotoxicity of AH Plus and Cortisomol did not. The results show that the ISO standards may strongly over-evaluate the cytotoxicity of the endodontic sealers, emphasize the difference among the sealers, and may clinically correspond to a large overfilling. The new technique reduces the discrimination of the test and may clinically correspond to a classical filling. Therefore, both methods might be considered as clinically relevant, corresponding to classical and overfilling conditions.

Analysis of Variance↗
PubMed2003

Incidence of flare-ups and evaluation of quality after retreatment of resorcinol-formaldehyde resin ("Russian Red Cement") endodontic therapy.

The purpose of this retrospective study was to evaluate the quality of treatment and incidence of flare-ups when teeth with resorcinol-formaldehyde resin are retreated in a postgraduate endodontic clinic. Fifty-eight cases were included in this study. Obturated and unfilled canal space was measured on radiographs. Forty-eight percent of the total canal space was filled before retreatment; 90% was filled after retreatment. After retreatment, obturations were rated as optimal in 59%, improved in 33%, unchanged in 6%, and worse in 2%. Seven patients (12%) had postretreatment flare-ups. Data were statistically analyzed using the Cochran-Armitage Test for Discrete Variables. No statistical difference in the incidence of flare-ups was found in teeth that before treatment had more than half the canal space filled compared to teeth with less than half, cases with pre-existing periradicular radiolucencies compared to cases with normal periradicular appearance, symptomatic cases compared to asymptomatic cases, or cases with optimal fillings after retreatment compared to less than optimal cases. It was concluded that teeth with resorcinol-formaldehyde fillings might be retreated with a good prognosis for improving the radiographic quality, but a higher than normal incidence of flare-ups may occur.

Acute Disease↗