Three solutions of EDTA--a 15% concentration of the alkaline salt, a 15% concentration of the acid salt, and a 25% concentration of the alkaline salt--were evaluated for smear layer removal in root canal systems. All solutions were adjusted to pH 7.1 using either NaOH or HCl. When the EDTA solutions were alternately used for root canal irrigation with 5.25% NaOCl, they completely removed the smear layer in the middle and coronal thirds of canal preparations, but were less effective in the apical third. None of the EDTA solutions by themselves were effective at completely removing the smear layer at any level. The alkaline tetrasodium salt, pH adjusted with HCl, is more cost effective and performed equally as well as the more commonly used disodium salt.
Coronal leakage has been recognized as a cause of pulpal and periradicular disease. Although cleaning and shaping of the root canal system is considered paramount, obturation of the system is an important step in endodontic success. The purpose of this study was to evaluate coronal bacterial leakage in teeth obturated with the System B continuous wave of condensation technique, followed by an Obtura II backfill, versus teeth obturated using the lateral condensation technique. Sixty single-rooted bilaterally matched teeth were evaluated in this study. An anaerobic bacterial leakage model was used. Results indicate that microbial coronal leakage occurs more quickly using lateral condensation than with the System B continuous wave of condensation and Obtura II backfill. This difference was statistically significant (p < or = 0.05). However, there was no statistical difference between groups 1 and 2 in the numbers of teeth that demonstrated bacterial leakage at the end of the study.
The purpose of this work was to investigate the relation between the sensations of pain and 'pre-pain' evoked by stimulation of teeth in human subjects. Electrical pulses of progressively increasing amplitude, generated by a computer-controlled stimulator, were applied to 1 or 2 teeth, and the subjects responded by indicating the nature of the resulting sensation. Pre-pain and pain could be readily and rapidly distinguished by all 11 subjects (response latency about 0.4 sec). Both sensations had stable thresholds with relatively small variance (S.D. 10-15% of threshold value) for a given subject. Subjects characterized the stimuli as indifferent or unpleasant, localized, and brief. By using special stimulation strategies (termed 'optimal trajectories') for exciting 2 teeth simultaneously, spatial summation for pre-pain was demonstrated in most subjects and for pain in almost all subjects. Spatial summation of pre-pain resulted in pain rather than in more intense pre-pain. These results are consistent with both the dual modality (separate afferent fibers for pre-pain and pain) and the single modality hypotheses (single type of afferent fibers) of tooth pulp sensibility, but favor single modality innervation.
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