Biomedical subjects

G B Pelleu

Publications and source records attributed to G B Pelleu.

At least 19 recordsLinked to original sources

PubMed1992

The effect of slot preparation length on the transverse strength of slot-retained restorations.

An in vitro study was conducted (1) to compare fracture strength of amalgam restorations retained with retentive slots of different lengths when stressed with a transverse force, (2) to determine if beveling the slot preparation resulted in an increase in fracture resistance to a transverse force, and (3) to evaluate the incidence of unrestorable tooth fracture as it relates to slot preparation length. Six groups of 10 specimens were prepared with slots of increasing length, with each specimen receiving four slots of equal length. Slot preparations in group 6 were beveled. Results showed that shorter slot preparations provided statistically equal amounts of resistance to a transverse force as did the longer preparations. Beveling the slot preparation did not significantly increase fracture strength. Specimens restored with longer slot preparations failed unrestorably more often than restorations retained with shorter slot preparations.

Dental Amalgam↗

PubMed1992

Effect of dentinal bonded resin post-core preparations on resistance to vertical root fracture.

An in vitro study was conducted to compare the resistance to failure of two restorative protocols for endodontically treated teeth. Half of 24 specimens received cemented cast post-core restorations and the other half were restored with dentin-bonded composite resin using the ferric oxalate, NTG-GMA, and the PMDM system developed by Bowen. The dentin-bonded resin post-core restorations provided significantly less resistance to failure than the cemented custom cast post-core. The dentin-bonded resin post-core fractured in every instance before the root fractured. A greater force was required to cause failure of the resin post as the cross-sectional area of the post increased.

Acrylic Resins↗

PubMed1991

Wear of human enamel against a commercial castable ceramic restorative material.

This study determined the effect of castable ceramic, with and without shading porcelain applied, on enamel wear. The wear produced by conventional dental porcelain was used as a control. Cusp tips from extracted human third molars were precision-machined into cones of enamel approximately 1 mm long. Three groups of nine cones each were abraded against rotating disks of (1) castable ceramic with shading porcelain, (2) castable ceramic without shading porcelain, and (3) conventional dental porcelain. Enamel wear was calculated from microscopic measurements of the enamel cones before and after abrading. Mean and standard deviation values were 1.220 +/- 0.218 for castable ceramic with shading porcelain, 0.639 +/- 0.218 for castable ceramic without shading porcelain, and 0.785 +/- 0.311 for glazed conventional dental porcelain (all values are X 10(-3) cm3). Significant differences were found between castable ceramic with and without shading porcelain and between conventional dental porcelain and castable ceramic with shading porcelain (p less than 0.001 ANOVA and 0.05 Scheffe's test). These findings suggest that castable ceramic with shading porcelain should not be used in regions that will function against opposing natural teeth.

Ceramics↗

PubMed1991

Effects of an internal escape channel on a castable ceramic crown.

This study evaluated the adaptation and strength of Dicor castable ceramic crowns cemented using an internal escape channel on the axial wall of the preparation. Twenty-eight crown wax patterns were made on 14 machined brass dies. The adaptation of the crowns was evaluated by measuring the combined height of the die and crown. The results revealed a significant difference in the mean and standard deviation of 16 +/- 13 micron in the experimental group and 85 +/- 31 microns in the control group. The differences between the force to fracture of 2155 +/- 1188 N and 1040 +/- 658 N, respectively, was also significant. The findings suggested that having an internal escape channel during cementation significantly improved the fit and strength of Dicor castable ceramic crowns. This technique would be particularly beneficial for cementation of posterior castable ceramics.

Cementation↗

PubMed1991

Halothane and eucalyptol as alternatives to chloroform for softening gutta-percha.

Because chloroform was identified as a potential carcinogen by the Food and Drug Administration, interest has been revived to identify an alternative solvent to soften gutta-percha for removal from obturated root canals. This study compared the effectiveness of halothane, eucalyptol, and chloroform in softening gutta-percha in simulated root canals. One milliliter of a solvent was placed into a small glass funnel whose stem was obturated with a 30-mm column of gutta-percha. After 30 s, softening was evaluated for each solvent by recording the time required to reach a depth of 10 mm by hand filing with a #100 Hedstrom file. The depth of penetration of a #40 finger plugger under constant weight for 15 min was also determined for each solvent. By using a one-way analysis of variance and Scheffe's test, all comparisons were not significant except for the depth of penetration with constant weight between chloroform and halothane (p less than 0.05). The results indicate that halothane and eucalyptol are suitable alternatives to chloroform as gutta-percha softening solvents.

Analysis of Variance↗

PubMed1990

Alternative solvents to chloroform for gutta-percha removal.

The purpose of this study was to evaluate new or previously identified solvents for effectiveness in dissolving gutta-percha. The solubility of a standardized weight of gutta-percha was tested in 5-ml quantities of 32 solvents. Ten samples of 30 solvents were tested at both 22 and 37 degrees C for 15 min. If the gutta-percha samples dissolved within 15 min, the times were recorded and statistically analyzed. There was no significant difference (p greater than 0.05, one-way analysis of variance and Scheffe's test) between dissolving times of chloroform and trichloroethylene at 22 and 37 degrees C. At 22 degrees C, three solvents dissolved the gutta-percha sample, whereas at 37 degrees C, nine solvents dissolved the gutta-percha. At 37 degrees C, halothane (Fluothane) was twice as effective as cineole and demonstrated many favorable working qualities. An important finding from the experimentation with halothane was the discovery of a potential obturating material, which was termed "halopercha".

Chloroform↗

PubMed1989

Bacteriological comparison of ultrasonic and hand instrumentation of root canals in dogs.

This study compared the effectiveness of hand and ultrasonic instrumentation for removing a standardized inoculum of pigmented Serratia marcescens from the root canal system of premolars in dogs. Forty-four premolars from nine beagle dogs were divided into two experimental groups of 20 and 24 teeth, respectively. The experimental teeth were inoculated with approximately 10 colony-forming units of S. marcescens. After the bacterial were allowed to colonize for 1 wk, the experimental teeth were instrumented with either hand instruments or the Cavi-Endo device. The teeth were extracted, crushed, and assayed for recoverable colony-forming units of S. marcescens. Statistical comparisons of the ratio of inoculated to recovered colony-forming untis were made. The results indicated that the difference between the positive controls and the experimental groups was significant. There was no significant difference between the two instrumentation groups.

Animals↗

PubMed1989

Vertical root fractures in curved roots under simulated clinical conditions.

The purpose of this study was to determine the incidence of vertical root fractures in the mesial roots of extracted human mandibular molars that were endodontically prepared by hand or ultrasonic instrumentation and obturated with laterally condensed gutta-percha and sealer using finger and hand spreaders. One-hundred twenty mesiofacial canals were prepared by hand or ultrasonic instrumentation. After placing the teeth in a simulated alveolus, they were obturated by laterally condensing gutta-percha and sealer with B-finger or D11T hand spreaders. Teeth were obturated using forces in the range of 1 to 3 kg or 4.5 to 7.5 kg. Three teeth obturated with the D11T hand spreader using 7.0 to 7.3 kg of force demonstrated vertical root fractures. The results suggest that in vitro the range of forces reported as most commonly used by endodontists to laterally condense gutta-percha (1.0 to 3.0 kg) and those of a higher magnitude up to 4.9 kg are safe and will not result in vertical root fractures of mesial roots of mandibular molars.

Dental Pulp Cavity↗

PubMed1989

A comparison of four root canal filling techniques.

This study compared the apical seal produced by four obturation techniques. Sixty-four extracted human teeth were prepared and obturated using lateral condensation of gutta-percha that was either unmodified or was dipped in chloroform, eucalyptol, or eucapercha paste. After storage in normal saline and 0.02% azide solution at 37 degrees C for 200 days, the teeth were immersed in India ink for 48 h. The most coronal extent of leakage of India ink into the canal was then determined. Significantly more apical leakage occurred in the eucapercha group than in the other three groups. All other comparisons were equivalent. The results suggest that modification of the gutta-percha master cone with solvent does not improve the apical seal in vitro. If modification is desired, then dipping the master cone in either eucalyptol or chloroform produces an apical seal superior to that achieved with eucapercha.

Chloroform↗

PubMed1989

Effects of sonic instrumentation on the apical preparation of curved canals.

This study compared apical transportation produced in curved (45- to 60-degree) molar canals instrumented with two MM-3000 Sonic Air test files (Rispi-Sonic and Trio-Sonic) with apical transportation from instrumentation with conventional K-type files. Seventy-five extracted human permanent mandibular molars were equally divided into three groups. Results showed that 92 (61%) of 150 measurements demonstrated no transportation, and only 7 (5%) had transportation between 0.25 and 0.5 mm. Most of the transportation was 0.25 mm or less, and no file produced transportation greater than 0.5 mm in a buccolingual or mesiodistal direction. Statistical analysis (chi-square test and analysis of variance) showed no significant difference (p greater than 0.05) in the amount of apical transportation in canals prepared with the Kerr K-type, Rispi-Sonic, or Trio-Sonic files.

Dental Pulp Cavity↗

PubMed1988