Search PubMed⌕ Search

Biomedical subjects

F Goldberg

Publications and source records attributed to F Goldberg.

At least 19 recordsLinked to original sources
PubMed2001

Effectiveness of different obturation techniques in the filling of simulated lateral canals.

The purpose of this in vitro study was to evaluate the ability of lateral compaction of gutta-percha and of five thermoplasticized gutta-percha filling techniques to obturate simulated lateral canals. Sixty extracted single-rooted human teeth were instrumented at the working length to a #35 file before creating three simulated lateral canals on the mesial and distal surfaces of the root, one in each third, using a #15 engine reamer. After enlarging root canals to a #45 file, the teeth were randomly divided into six equal groups of 10 and obturated according to the following techniques: lateral compaction of gutta-percha (group A), hybrid technique (group B), Ultrafil (group C), Obtura II (group D), System B + Obtura II (group E), and Thermafil (group F). AH26 was used as the sealer. A greater number of simulated lateral canals were obturated when Ultrafil, Thermafil, and System B + Obtura II were used, in comparison with canals obturated with the hybrid technique, Obtura II, or lateral compaction of gutta-percha. This difference was statistically significant (p < 0.05). No statistically significant differences were found between results obtained in the obturation of simulated lateral canals in the different thirds of the root (p > 0.05).

Gutta-Percha↗
PubMed2000

Comparison of different techniques for obturating experimental internal resorptive cavities.

Forty extracted maxillary central incisors were instrumented at the working length to a #50 file. The roots were sectioned transversely with a diamond disk at 7 mm from the anatomical apex. At the opening of the root canal of each section, hemicircular cavities were drilled with a specially designed bur. The corresponding root sections were cemented with glue, thus obtaining root canals with similar cavities that simulated internal resorptions. Teeth were embedded in plaster casts to facilitate their handling. The specimens were randomly separated into four groups of 10. The following obturation techniques were evaluated: lateral compaction (group A), hybrid technique (group B), Obtura II (group C), and Thermafil (group D). AH26 was used as the sealer. After obturation, the plaster was removed and the teeth were radiographed in buccolingual and mesiodistal directions to evaluate the quality of the obturation at the IRC. The incisors were then cut with a scalpel at the same level as the previous section, to examine, under a stereomicroscope, the type of material that filled the IRC. Obtura II gave the best results and in most of the specimens obturated with this technique, the IRC were filled mainly with gutta-percha. Statistical analysis of the data indicated that the differences between group C and the other groups were significant (P < 0.05).

Bismuth↗
PubMed1999

Nicotinic acetylcholine currents of cultured Kkenyon cells from the mushroom bodies of the honey bee Aapis mellifera.

1. Acetylcholine-induced currents of mushroom body Kenyon cells from the honey bee Apis mellifera were studied using the whole-cell configuration of the patch clamp technique. Pressure application of 1 mM acetylcholine (ACh) induced inward currents with amplitudes between -5 and -500 pA. 2. The cholinergic agonists ACh and carbamylcholine had almost equal potencies of current activation at concentrations between 0.01 and 1 mM; nicotine was less potent. The muscarinic agonist oxotremorine did not elicit any currents. 3. Approximately 80 % of the ACh-induced current was irreversibly blocked by 1 microM alpha-bungarotoxin. Atropine (1 mM) did not block the ACh-induced current. 4. Upon prolonged ACh application the current desensitized with a time course that could be approximated by the sum of two exponentials (tau1 = 276 +/- 45 ms (mean +/- s.e.m. ) for the fast component and tau2 = 2.4 +/- 0.7 s for the slow component). 5. Noise analyses of whole-cell currents yielded elementary conductances of 19.5 +/- 2.4 pS for ACh and 23.7 +/- 5.0 pS for nicotine. The channel lifetimes, calculated from the frequency spectra, were tauo = 1.8 ms for ACh and tauo = 2.5 ms for nicotine. 6. Raising the external calcium concentration from 5 to 50 mM shifted the reversal potential of the ACh-induced current from +4. 6 +/- 0.9 to +37.3 +/- 1.3 mV. The calcium-to-sodium permeability ratio (PCa : PNa) was 6.4. 7. In high external calcium solution (50 mM) the ACh-induced current rectified in an outward direction at positive membrane potentials. 8. We conclude that Kenyon cells express nicotinic ACh receptors with functional profiles reminiscent of the vertebrate neuronal nicotinic ACh receptor subtype.

Animals↗
PubMed1998

Comparative study of retreatment of Thermafil and lateral condensation endodontic fillings.

The aim of the present study was to evaluate the possibility of retreating teeth obturated with: (i) Thermafil with plastic carrier, (ii) Thermafil with metallic carrier and (iii) laterally condensed gutta-percha. The following aspects were analysed: removal of obturation, time required for removal, remaining filling material and apical extrusion during reinstrumentation. Thirty human teeth with a single canal were instrumented up to a size 45 K-type file, divided into three groups of 10 teeth each and obturated with Thermafil with plastic carrier (group 1), Thermafil with metallic carrier (group 2), and laterally condensed gutta-percha (group 3) with AH26 as the sealer. Reinstrumentation was performed manually after 30 days storage using Hedstroem files and xylene as a solvent. The average time needed to remove the obturation was 12 min 1 s for group 1, 14 min 36 s for group 2 and 11 min 26 s for group 3. Although no statistically significant differences were observed between groups 1 and 2, and 1 and 3 (P > 0.05), the differences between groups 2 and 3 were significant (P < 0.05). The amount of remaining filling material was significantly higher in group 2 when compared with groups 1 and 2 (P < 0.01). Although the lowest incidence of apical extrusion during reinstrumentation was found in group 3, the differences among groups were not statistically significant.

Analysis of Variance↗
PubMed1998

Radiographic assessment of simulated external root resorption cavities in maxillary incisors.

Upper central and lateral incisors of three human skulls were used to assess radiographically the possibility of detecting cavities of different sizes and locations, drilled to simulate external root resorptions. The sequence of radiographs was evaluated by three endodontists, who were unaware of the experiment being done, using a 2 x magnifier. The first observation was done without comparing the radiographic images of the different cavities with the preoperative radiograph. For the second round of observation, each sequence was compared with the preoperative X-ray. The results showed that small cavities were more difficult to detect than the medium and large ones. Moreover, cavities located on the proximal surfaces were more easily detected than those located on the buccal surfaces. Finally, when the observers could compare with the preoperative radiographs (second round of observation), the rate of detection was considerably higher.

Chi-Square Distribution↗
PubMed1997

Mammographic density in women on postmenopausal hormone replacement therapy.

BACKGROUND: Studies have suggested that mammographic density and pattern are affected by hormone replacement therapy (HRT) and may influence breast diagnosis. Because 40% of breast cancers diagnosed at our center are mammographically detected while still clinically occult, mammographic sensitivity is crucial. For this reason we studied the effect of HRT on mammographic density. METHODS: During a period of 18 months we studied consecutive women older than 54 years attending for breast screening. We recorded HRT use and dosing regimes. A breast density score (BDS) was developed and applied to all mammograms. RESULTS: Mammograms of 148 HRT users were compared with those of 158 nonusers. HRT users had a significantly higher mean density score (4.7 versus 3.4; p < 0.001). Only 11% of non-HRT users had high scores compared with 37% among HRT users (p < 0.001). The significant difference remained when women were stratified by age. Duration of HRT (longer or shorter than 5 years) did not affect density scores. CONCLUSIONS: HRT is associated with a significant increase in breast density. In turn, density and mammographic sensitivity are related. The possibility that increased breast density will hamper mammographic diagnosis of clinically occult cancers is worrisome.

Age Factors↗
PubMed1997

Disintegration of endodontic cements in water.

The disintegration of three endodontic cements in water was determined quantitatively and qualitatively. The materials studied were Ketac-Endo (KE), Tubli Seal (TS), and AH26 (AH). Specimens were immersed in water for 48 h (GI), 7 (GII) and 45 days (GIII). The solid residue was then determined. For the qualitative analysis three groups of tubes were filled with the materials and stored in water for the same periods. The exposed surface was photographed. Results expressed as percentage of original mass in the quantitative analysis for loss of mass due to dissolution were: GI = KE 2.39 (0.70); TS 3.56 (0.37); AH 4.94 (2.83); GII = KE 2.84 (0.30); TS 2.50 (0.50); AH 0.66 (0.26); GIII = KE 1.60 (0.84); TS 1.03 (0.42); AH 1.22 (0.54). Tukey's least significant difference (0.05) was 2.94. In the qualitative experiment KE disintegration was far more evident than that suffered by other materials. The quantitative results had no correlation with the qualitative observations probably due to the difference in the moment when the materials were immersed.

Bismuth↗
PubMed1997

Comparison of three instruments in the preparation of curved root canals.

The transportation produced in the apical and middle areas of 30 mesiobuccal root canals of human mandibular molars was evaluated after circumferential instrumentation using stainless steel K-files (group A), nickel-titanium K-files (group B), and clockwise/counterclockwise file rotation using Flexogates (group C). The canals were instrumented with files #15 to #35 in size. Apical transportation was assessed radiographically while that occurring in the middle area was studied microscopically in cross-sections. Although apical transportation was greatest in the canals of group A, this difference was not statistically significant (P > 0.05). With respect to the middle area of the root canal, considerable transportation was observed in 7 of the 30 instrumented roots. Of these, five belonged to group A and two to group B, a difference which was not statistically significant (P > 0.05). The best results for transportation in the middle area of the canal were obtained in group C, in which no transportation occurred. This difference was significant when compared with the transportation observed in group A (P = 0.02) but not with that in group B (P > 0.05).

Dental Alloys↗
PubMed1997

[Health and violence as perceived by young people, a study of the Parisian region].

We know better the violences made by the youngs than those they suffer from. The purpose of this study is to assess, as for a city surrounding Paris, the prevalence of the violences they felt and its relation with the psychic uneasiness. Some 344 youngs (from 15 to 25 years old) selected in the city, have filled in an autoquestionnaire. It has shown that 61.6% of them have already suffered from violences, among them 44.5% from adults and what is more from institutional adults. 13.7% of the selected youngs were victims of regular violences in school sphere and 12.8% in urban environment. The expression of a psychic uneasiness is linked to the previous violences they have felt. The feeling of call for help by a psychologist or a psychiatrist is in relation with the past psychic discomfort and not with the past suffered violences.

Adolescent↗
PubMed1995

Apical sealing ability of a new glass ionomer root canal sealer.

This study compared the sealing ability of Ketac Endo with and without smear layer and Tubli Seal. Thirty upper central incisors and canines with straight canals were instrumented and randomly divided into three equal groups of 10. All teeth were obturated with laterally condensed gutta-percha. An additional group of five teeth with unobturated++ root canals served as positive controls. The sealers were Tubli Seal (group A), Ketac Endo (group B), and Ketac Endo preceded by the removal of the smear layer (group C). The teeth were immersed in India ink for 7 days, centrifuged for 5 min at 3000 rpm, cleared, and then examined under a light microscope at X 50 magnification. The mean value of ink penetration for group A was 0.14 mm, for group B 0.24 mm, and for group C 0.48 mm. No statistically significant differences were observed among groups (p > 0.05).

Acrylic Resins↗
PubMed1995

Comparison of the sealing capacity of three endodontic filling techniques.

This study compared the sealing capacity of three different endodontic gutta-percha filling techniques. Forty-seven upper central incisors with straight canals were instrumented and randomly divided into three equal groups of 14. An additional group of five teeth with unobturated canals served as positive controls. The following gutta-percha filling techniques were evaluated: Trifecta (group A), lateral condensation (group B), and a combination of SuccessFil gutta-percha and lateral condensation (group C). Tubli-Seal was used as a sealer. The teeth were radiographed in mesiodistal and bucco-lingual directions to study the quality of the filling. Afterward, the teeth were immersed in India ink and subsequently cleared. The maximal depth of penetration was measured using a light microscope. The mean value of ink penetration for group A was 1.073 mm, for group B was 0.522 mm, and for group C was 0.765 mm. No statistically significant differences were seen among groups (p < 0.05).

Dental Leakage↗
PubMed1994

Interval breast cancers in the Screening Mammography Program of British Columbia: analysis and classification.

OBJECTIVE: Interval cancers in an annual mammography screening program are defined as cancers detected within 12 months after a mammographic screening in which findings are considered normal. Our objective was to analyze interval cancers for histologic type, tumor size, staging, and histologic grade. A classification for interval cancers is presented. Detection of interval cancers is an integral part of quality control and is required for the establishment of sensitivity rates for screening mammography, a necessary part of implementing the recommendations for breast cancer screening. MATERIALS AND METHODS: A total of 47,583 mammographic screening examinations of 38,219 women were available for review for the period of July 1988 to March 1991. Linkage with the provincial population-based cancer registry provided identification of all interval cancers of the breast. Histologic analysis of breast cancers was provided by an internationally recognized breast cancer pathologist who interpreted the specimens twice. RESULTS: A total of 207 breast cancers were detected at mammographic screening (true-positive cancers) during the first 33 months of the program, and 37 interval cancers were identified during the 33 months of screening plus a 12-month interval. Blinded review by three radiologists experienced in screening mammography resulted in classification of 21 of 37 cases as true interval cancers and 16 cases as misses. No interval cancers were missed because of poor mammographic technique. The sensitivity of screening mammography was 85%, 63% for patients less than 50 years old and 89% for patients more than 50 years old. The specificity was 93% for all patients (both younger and older than 50 years). CONCLUSION: The availability of a population-based cancer registry in the province of British Columbia makes an accurate determination of interval cancers and sensitivity rates possible. These data are essential for quality analysis, program planning, and education of radiologists in screening mammography. There were more true interval cancers than misses, and histologic analysis demonstrated that the majority of interval cancers were in stages I and II.

Adult↗
PubMed1993

Evaluation of the dimensional stability of different thermoplasticized gutta-percha fillings using simulated glass root canals.

The dimensional stability of different thermoplasticized gutta-percha fillings was analyzed using simulated glass canals. For comparison, gutta-percha fillings obtained with the cold lateral condensation technique was used. The evaluation was done at 0 min, 2 min, 5 min, and 30 min after the filling was completed. The general analysis showed statistically significant differences between 0 min and 5 min-30 min recordings. No significant differences were found between 0 min and 2 min, and between 2 min, 5 min, and 30 min. Although warm lateral condensation resulted in a poor obturation, it was the only thermoplasticized technique analyzed that did not produce significant volumetric changes between 0 min and 30 min. All the other thermoplasticized filling techniques showed important shrinkage during cooling.

Analysis of Variance↗
PubMed1991

SEM study of surface architecture of gutta-percha cones.

The apical third of 60 standardized, gutta-percha cones obtained from six different manufacturers were analyzed by scanning electron microscopy. Despite the fact that the majority of the commercial gutta-percha cones showed rather uniform and smooth surfaces, some displayed morphologic variations such as gross protuberances or deeply cratered areas containing numerous free or entrapped crystal-like particles.

Gutta-Percha↗
PubMed1991

Surface architecture of a low-temperature thermoplasticized gutta-percha.

The surface characteristics of two Ultrafil materials, Regular set (RS) and Firm set (FS) were analyzed by scanning electron microscopy (SEM). The samples of Ultrafil were obtained from both RS and FS cannules which were pre-heated to 70 degrees C. Another RS and FS samples were obtained at room temperature from un-heated cannules. Samples of standard gutta-percha points obtained from the same manufacturer were studied for comparative purposes. RS samples obtained from pre-heated and un-heated cannules exhibited rough surfaces containing randomly distributed crystal-like structures. Heated and un-heated FS samples featured smoother surfaces with fewer crystal-like structures. The gutta-percha points also exhibited smooth surfaces and absence of crystal-like structures. The consequence of the possible release of these structures from Ultrafil in a biological system is discussed.

Gutta-Percha↗
PubMed1990

Periapical tissue response to two calcium hydroxide-containing endodontic sealers.

One-hundred twenty root canals of dog teeth were cleaned, shaped, and obturated with gutta-percha and sealers using a lateral condensation technique. The sealers used were Sealapex, CRCS, and zinc oxide-eugenol. The animals were killed after 30 or 180 days and the specimens were examined histologically. Sealapex and CRCS caused a periapical tissue response similar to that found with the zinc oxide-eugenol. An ingrowth of connective tissue infiltrated with chronic inflammatory cells was noticed in cases where the filling material reached the apical stops. Regardless of sealer used, deposition of new hard tissue along the apical root canal walls was observed, which caused the partial closure of the apical opening. In the Sealapex and CRCS groups, sealer particles were found at a considerable distance from the apices. All overfilled specimens caused chronic inflammatory reactions in the periapical tissues.

Animals↗