Comparison of Two Protocols for the Treatment of Class 2 Malocclusion

Purpose: The purpose of this study was to compare the outcomes of the treatment with the twin block and modified twin block appliances in growing patients with Class 2 malocclusion. Materials and Methods: A cephalometric analysis was performed in 51 patients. The twin block sample consisted of 23 patients, 10-girls and 13-boys (mean age 10.46±0.71 years at the start of treatment, T1, and 12.84±0.78 years at the end of active treatment, T2). The modified twin block sample consisted of 28 patients, 18 girls and 15 boys (mean age 11.78±0.91 years at T1, and 13.32±0.56 years at T2). The twin block activators were used during the day, except for eating time, and the modified ones were used only at night. Duration of the treatment was 16-20 months. The changes from T2 to T1 and the differences between the groups were compared with the analysis of variance. Results: SNB angle in the twin block group showed 1.25±1.39 degrees change and in the modified twin block group, it exhibited 3.69±1.01 degrees change. Overjet in the group with twin block decreased 4.58±1.59 mm, and in the group with modified twin block it decreased 4.43±1.41 mm. In the modified twin block group, there was more retrusion of upper incisors in comparison with the twin block group. Accordingly, under the effect of modified twin block, retrusion of the upper lip was observed. Conclusion: Through modifying the twin block appliance, it is possible to ensure the comfort of the patients by reducing the daily usage, to reposition the mandibula forward and to correct overjet and sagittal dento-skeletal relationships without increasing facial height and to improve positions of upper incisors and lips.

Influence of pulsive pressure waves on liquid penetration into wood in semi-opened container

The purpose of this paper was to confirm the influence of pulsive pressure waves on the liquid penetration into wood in the semi-opened container. Wood block sample was irradiated by the pulsive pressure waves in the semi-opened container filled with water used as a liquid. The irradiation was also performed in the closed container for the comparison. The water penetration into the sample was promoted by the pressure-wave irradiation. There was little difference in the degree of the penetration between the closed and the semi-opened containers. It was presumed from the measured hydraulic pressure that the pressure-wave energy irradiated on the sample in the closed container was higher than that in the semi-opened container. It was also presumed that the cavitation generation was promoted in the semi-opened container. This indicates that the cavitation as well as the pressure waves themselves affected the liquid penetration into wood. The compressive deformation of the sample irradiated in the semi-opened container was slightly smaller than that in the closed container. This indicates that the pulsive pressure-wave irradiation in the semi-opened container promoted the liquid penetration into wood with less compressive deformation.