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As an alternative to the conventional fixed appliance that uses orthodontic brackets, a simple round tube without a bonding base can be bonded to the tooth surface by covering the tube with flowable resin. In this technique, bent wires cannot be inserted into the simple tubes; therefore, repositioning of the simple tubes is often required for adjustments. To reduce repositioning of simple tubes, a dome-shaped resin covering of the simple tube can be designed with a customized in-and-out compensation, using three-dimensional computer-aided design software based on digital simulation of orthodontic tooth movement. In the present case, the use of simple tubes bonded with customized resin coverings in a Class I nonextraction case is described in a 17-year-old male, in whom moderate crowding of the anterior teeth was treated over an 8-month period. This case shows that simple tubes can be used as an alternative to brackets in some Class I nonextraction cases, with the potential benefit of reducing decalcification.

The aim of this study was to evaluate cortical bone formation on the mandibular condyle using cone-beam computed tomography (CBCT) in asymptomatic adolescents and young adults and to evaluate the relationship between age and sex. CBCT images that can evaluate the shape of the mandibular condyle were selected from asymptomatic patients aged 13–25. The degree of cortication on the mandibular condyle (CMC) was evaluated using CBCT images reconstructed in the axial, sagittal, and coronal planes. CBCT data of 829 patients (413 males, 416 females) were selected and then the left and right images of all patients were acquired; consequently, a total of 1658 temporomandibular joint-related images were evaluated in this study. The degree of CMC was correlated with age in men and women (p < 0.05). The frequency of CMC 0 disappeared in woman aged 20 years and in men aged 21 years. Cortical bone formation of the mandibular condyle was completed at age 22 years in women and 24 years in men. The degrees of cortical bone formation of the mandibular condyle between men and women showed significant differences between the ages of 15–19 and 22 years. This difference can be interpreted as a different mandible growth period between the sexes.

This study evaluated the effect of repetitive prestretching on hysteresis and abrupt force drops during the initial unloading phase (1-mm-unloading/peak force ratio) of elastomeric chains. Thirty samples of closed-type elastomeric chains were tested for each group of generation II power chain, energy chain, and memory chain. Elastomeric chains were elongated to a 100% extension from their original length of 12.5 mm and unloaded. Forces during the five loading and unloading cycles were determined. The memory chain showed significantly lower hysteresis than the generation II power chain and energy chain. Both loading and unloading forces were decreased significantly with repetitive prestretching. However, unloading forces decreased less than the loading force, thereby reducing the hysteresis. All three products showed the greatest hysteresis in the first cycle, which decreased significantly following repeated prestretching. The 1-mm-unload/peak ratio increased significantly until the 4th cycle, the cycle after triple prestretching. Conclusively, repetitive prestretching of elastomeric chains further decreased hysteresis and abrupt force drop during the initial 1-mm unloading, up to triple prestretching.