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Biomedical subjects

M L Hicks

Publications and source records attributed to M L Hicks.

51 records · Page 3Linked to original sources
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↗
PubMedDate not supplied

Electron microscope comparison of freeze-substitution and conventional chemical fixation of undecalificied human dentin.

Within the stated limits of cell fine structure preservation and within the observed anatomical limits specified in the Results and Discussion sections, a freeze-substitution method using an ethylene glycol-Hank's solution eutectic mixture with a glutaraldehyde additive can be used to effectively prepare undecalcified human dentin for electron microscopy. The ultrastructual appearance of the odontoblast cell body and the odontoblastic process subjected to freeze-substitution differs from that seen with conventional chemical fixation. Artifacts produced by freeze-substitution differ in appearance and frequency of occurrence from those produced by glutaraldehyde-osmium tetroxide sequential double fixation. The cellular component of dentin shows greater structural preservation of protein when it is subjected to freeze-substitution that when it is prepared by conventional chemical fixation. The absence of ice crystal defects in the odontoblastic process in calcified dentin and the presence of ice crystal defects in the odontoblast cell body suggest that intracellular water in the odontoblastic process in the calcified dentin may exist in a more highly structured state than intracellular water in the odontoblast cell body. If intracellular water exists in a more highly structured state in the odontoblastic process of the calcified dentin than in the cell body, the ratio of protein molecules to cytoplasmic volume may be greater in the odontoblastic process than in the cell body. After glutaraldehyde-osmium tetroxide sequential double fixation, the use of graded alcohol dehydration obtained cell fine structure preservation and artifact control superior to that obtained by use of ethylene glycol cryodehydration. Further refinements of the freeze-substitution technique, as it applies to the preparation of undecalcified human dentin, are necessary to increase the amount of cellular preservation, to decrease the number of ice crystal artifacts, and to improve the overall quality of cell fine structure preservation.

Adolescent↗