Significant shear bond strength improvements of a resin-modified glass ionomer cement with a resin coating.

Previous evidence has suggested that resin-modified glass ionomer cements (RMGICs) may be sensitive to temperature and moisture changes for the first 24 hours after photopolymerization. To test the hypothesis that a resin coating placed over the surface of an RMGIC restoration would decrease the susceptibility to moisture and temperature conditions, 44 RMGIC samples were prepared in inverted-cone recesses drilled in epoxy resin plates. After abrasion of all samples with 800-grit silicon carbide paper to simulate a diamond bur finish on the surface, a coat of highly filled resin was applied to the experimental group (n = 22) and cured according to the manufacturer's instructions. The plates were thermocycled 500 times between 5°C and 55°C and then maintained at 37°C with 95% humidity. The thermocycled samples were bonded to a second epoxy resin plate filled with RMGIC and subjected to shear bond strength testing. The resin-coated group had a significantly greater mean shear bond strength than the control group (P < 0.05). The resin coating also appeared to affect the mode of failure by significantly increasing the number of mixed failures (P < 0.05). The results suggest that a resin coating protects RMGIC from moisture- and temperature-induced damage and increases shear bond strength.

Eruption sequence of the permanent maxillary canine: a radiographic review.

This study evaluated the eruption sequence of the permanent maxillary canine in patients to determine if it follows the previously established normal pattern: first premolar, second premolar, and canine. A total of 363 panoramic radiographs of patients 7-12 years of age were evaluated; in 261 (72%) of the patients, the permanent canine erupted after the first and second premolars. Based on the results obtained in this study, the eruption sequence of the permanent maxillary canine followed the historical normal pattern for the majority of patients in this population. The difference in eruption sequence for males versus females was not significant.

Sensory-evoked turning locomotion in red-eared turtles: kinematic analysis and electromyography.

We examined the limb kinematics and motor patterns that underlie sensory-evoked turning locomotion in red-eared turtles. Intact animals were held by a band-clamp in a water-filled tank. Turn-swimming was evoked by slowly rotating turtles to the right or left via a motor connected to the shaft of the band-clamp. Animals executed sustained forward turn-swimming against the direction of the imposed rotation. We recorded video of turn-swimming and computer-analyzed the limb and head movements. In a subset of turtles, we also recorded electromyograms from identified limb muscles. Turning exhibited a stereotyped pattern of (1) coordinated forward swimming in the hindlimb and forelimb on the outer side of the turn, (2) back-paddling in the hindlimb on the inner side, (3) a nearly stationary, "braking" forelimb on the inner side, and (4) neck bending toward the direction of the turn. Reversing the rotation caused animals to switch the direction of their turns and the asymmetric pattern of right and left limb activities. Preliminary evidence suggested that vestibular inputs were sufficient to drive the behavior. Sensory-evoked turning may provide a useful experimental platform to examine the brainstem commands and spinal neural networks that underlie the activation and switching of different locomotor forms.

Processing irrelevant location information: practice and transfer effects in a Simon task.

How humans produce cognitively driven fine motor movements is a question of fundamental importance in how we interact with the world around us. For example, we are exposed to a constant stream of information and we must select the information that is most relevant by which to guide our actions. In the present study, we employed a well-known behavioral assay called the Simon task to better understand how humans are able to learn to filter out irrelevant information. We trained subjects for four days with a visual stimulus presented, alternately, in central and lateral locations. Subjects responded with one hand moving a joystick in either the left or right direction. They were instructed to ignore the irrelevant location information and respond based on color (e.g. red to the right and green to the left). On the fifth day, an additional testing session was conducted where the task changed and the subjects had to respond by shape (e.g. triangle to the right and rectangle to the left). They were instructed to ignore the color and location, and respond based solely on the task relevant shape. We found that the magnitude of the Simon effect decreases with training, however it returns in the first few trials after a break. Furthermore, task-defined associations between response direction and color did not significantly affect the Simon effect based on shape, and no significant associative learning from the specific stimulus-response features was found for the centrally located stimuli. We discuss how these results are consistent with a model involving route suppression/gating of the irrelevant location information. Much of the learning seems to be driven by subjects learning to suppress irrelevant location information, however, this seems to be an active inhibition process that requires a few trials of experience to engage.