Auditory P300 development from an active, passive and single-tone paradigms.

The P300 (P3) event-related brain potential (ERP) was elicited with auditory stimuli in order to compare three different tasks and to assess the effect of ageing from childhood to adolescence. Seventy-two subjects, ranging in age from 6 to 14 divided into three age groups, were selected for this study. In the active task, the subject was required to discriminate between standard and target tones (oddball); in the passive task condition, the subject did not respond to either the standard or target stimulus; in the single task, a target but not a standard tone stimulus was presented and the subject was required to react to the target tone. Our results show that the passive sequence and the single-tone paradigm yielded similar P300 waveform to those obtained from the active task. Separate age/ERP component latency and amplitude linear regression were computed. A significant negative correlation between age and P3 latency was found. The event-related potential P3 wave shows consistent and significant age-related changes in human cerebral function, regardless of the methodology used. These findings suggest that the passive and single-tone paradigms can be a useful way to elicit the P3 ERP component.

[Scanning electron microscopic studies on the efficacy of irrigated, hand root canal preparation]. / Rasterelektronenmikroskopische Untersuchungen zur Effektivität der feuchten manuellen Wurzelkanalaufbereitung.

The effectiveness of hand preparation and irrigation of 48 root canals of upper anterior teeth was evaluated by scanning electron microscopy. Independently of instrument (K reamer or combination K reamer and H file), irrigating solution (sodium chloride) and root canal dressing a similar degree of preparing and cleaning effectiveness of root canals was detected. In all groups a homogeneous or inhomogeneous smear layer of different thickness and extent dominated. A scale of preparing and cleaning effectiveness is recommended.