RELIABILITY OF THE VESTIBULO-OCULAR REFLEX AS AN INDEX OF THE EFFECTS OF HYPNOTIC DRUGS ON THE CENTRAL NERVOUS SYSTEM

The vestibulo–ocular reflex was tested after the administrationof step doses of thiopentone or propanidid in 171 unpremedicatedpatients. The dose of thiopentone (3 mg kg^–1) requiredto induce loss of nystagmus also abolished the response to verbalcommand. The dose required to inhibit the reflex in 95% of patientswas 7.22 mg kg^–1 and prevented adrenergic responses tonociceptive stimulation. The dose of propanidid required toinduce loss of nystagmus was greater than that necessary toabolish response to verbal command. The reflex inhibition rateincreased proportionally to the dose up to 8 mg kg^–1;larger doses exerted a facilitatory effect and reduced the reflexinhibition rate. The vestibulo–ocular reflex is a reliableand sensitive means of demonstrating the different effects exertedby step doses of hypnotic drugs     

Influence of different restorative techniques on marginal seal of class II composite restorations

Objective

To evaluate the gingival marginal seal in class II composite restorations using different restorative techniques.

Material and Methods

Class II box cavities were prepared in both proximal faces of 32 sound human third molars with gingival margins located in either enamel or dentin/cementum. Restorations were performed as follows: G1 (control): composite, conventional light curing technique; G2: composite, soft-start technique; G3: amalgam/composite association (amalcomp); and G4: resin-modified glass ionomer cement/ composite, open sandwich technique. The restored specimens were thermocycled. Epoxy resin replicas were made and coated for scanning electron microscopy examination. For microleakage evaluation, teeth were coated with nail polish and immersed in dye solution. Teeth were cut in 3 slices and dye penetration was recorded (mm), digitized and analyzed with Image Tool software. Microleakage data were analyzed statistically by non-parametric Kruskal-Wallis and Mann-Whitney tests.

Results

Leakage in enamel was lower than in dentin (p<0.001). G2 exhibited the lowest leakage values (p<0.05) in enamel margins, with no differences between the other groups. In dentin margins, groups G1 and G2 had similar behavior and both showed less leakage (p<0.05) than groups G3 and G4. SEM micrographs revealed different marginal adaptation patterns for the different techniques and for the different substrates.

Conclusion

The soft-start technique showed no leakage in enamel margins and produced similar values to those of the conventional (control) technique for dentin margins.     

Baseline Transition Sleep and Associated Sleep Episodes are Related to the Learning Ability of Rats

The EEGs of 18 adult male Wistar rats were recorded during a baseline session lasting 7 h (day 1). The following day, rats were trained for a 2-way active avoidance task in an automated shuttle-box. A retention test was scheduled on the third day. On the basis of the number of avoidances scored during the training and retention sessions, rats were assigned to a fast-learning group (FL; achieving criterion during the training session), a slow-learning group (SL; achieving criterion in the retention test session), and a nonlearning group (NL; failing to achieve criterion). Vigilance states were determined by analyzing EEG data in 5-s epochs and calculating EEG power spectra of consecutive time intervals as short as 1 s. This high-resolution method led to the identification of transition sleep episodes that followed slow-wave sleep (SS) and were followed by waking (TS → W) or by paradoxical sleep (TS → PS). Comparison of the baseline sleep variables of the 3 behavioral groups revealed the presence of several significant differences. These observations were confirmed by the results of correlative analyses between baseline sleep variables and number of avoidances scored during the training and retention sessions. The most reliable indices of the capacity to learn the avoidance task were the amounts of SS preceding the TS → W or the TS → PS sequence, and the amounts of either component of the latter sequence. These variables displayed markedly higher values in FL rats. In addition, the amount of SS preceding TS → W and the amount of TS → (W) were significantly correlated with the number of avoidances scored during the training session. On the other hand, 1. SS → (PS) and (SS) → PS episodes were longer in NL rats than in SL or FL rats, respectively; and 2. the duration of SS → (PS) episodes was inversely correlated with the number of avoidances of the first training period. The data are interpreted to suggest that TS and associated sleep episodes may predict the acquisition of the avoidance task, and the episodes of SS → PS not associated with TS may predict the retention of innate responses, such as freezing or escapes.