Assessment of four cephalometric measurements utilized in evaluation of the mandibular position

This study was conducted to assess and correlate four cephalometric measurements utilized in evaluating the mandibular position in the anteroposterior direction. The four measurements used were, the SNB angel, Downs facial angle, Bjork's facial angle, and modification of Koski's ratio. Lateral cephalometric radiographs of forty seven adults [20 males and 27 females] with age ranged from 18-20 years were selected for this purpose. All had accepted normal occlusions, normal skeletal relationship and balanced profiles. Statistical analyses were performed to assess these four measurements. The results revealed no significant difference between the norms of males and females in the four measurements. Downs and Bjork's facial angles presented more sysmmetrical normal distribution than SNB angle and Kosk's ratio. A low and non significant correlation was found between Downs and Bjork's facial angles. Therefore, their conjunctive use would be recommended. Finally, a high and significant correlation was found between Bjork's facial angle and SNB angle. Accordingly these two measurements could be interchangeable

Evaluation of anchorage using nance and modified holding arches

The present study was conducted to evaluate the effects of modified Nance holding arch [tranpalatal arch soldered to Nance holding arch] as anchorage unit during canine retraction. Fourteen patients with Class I crowding sheared in this study. They were divided into two equal groups. All patients had orthodontic fixed appliance. In the first group, Nance holding arch was used for anchorage. On the other hand, a modified form of Nance holding arch [transpalatal arch soldered to Nance holding arch] was utilized for anchorage in the second group. Maxillary canines were retracted by power chain. For all patients cephalometric x-ray films and study casts were taken before and after canine's retraction. The results of this study revealed that; the modified Nance holding arch [transpalatal arch soldered to Nance holding arch] proved a very effective anchorage device. On the other hand, there was significant anchorage loss in the first group [Nance group] as there was mesial movement of the maxillary first permanent molars during canine's retraction. In addition there was no significant molar rotation in either group. Finally, the followings were concluded; the modified Nance holding arch provided an effective anchorage device than the Nance holding arch during canines retraction. Also, both Nance holding arch and the modified Nance form proved a very effective anchorage control against molar rotations during canines retraction

Bond strength of esthetic brackets to esthetic substrates

This study was carried out to compare the shear bond strength of esthetic brackets [composite and ceramic] to enamel surface and to two esthetic restorative materials [millable composite blocks [MZ 100] and machinable ceramic blocks [Vita Mark II] using the Bistite II DC adhesive luting agent. This study was classified into three groups, two test groups [millable composite blocks [MZ 100, machinable ceramics [Vita Mark II] and control group [natural teeth extracted upper first premolars] [n=16]. The control group [upper first premolars] was extracted during routine orthodontic treatment. The teeth were washed then stored in 0.1% thymol solution. Small area on the buccal surface was ground flat then, polished with wet 400 and 600-grit silicon carbide abrasive paper. The second group was formed of sixteen blocks of millable composite [MZ 100]]. In addition, the third group was formed of sixteen blocks of machinable ceramics [Vita Mark II]. Each group was divided into two subgroups [A and B] according to the brackets type [composite or ceramic brackets] [n=8]. Adhesive bonding agent [Bistite II DC] was used for bonding of brackets to different substrates of the main three groups. All specimens were stored in water bath at 37 C for 45 days followed by thermal cycling for 500 cycles. Results; There was significant difference between composite brackets bonded to ceramic substrate and composite brackets bonded to composite substrate and vice versa, ceramic brackets bonded to ceramic substrate showed significant higher shear bond strength compared with ceramic brackets bonded to composite substrate. The clinical implication of this study is that the Bistite II DC adhesive can be used clinically for bonding esthetic brackets to esthetic substrates. Moreover, it is preferable to use ceramic brackets in case of ceramic restorations and composite brackets in case of composite restorations to get the highest shear bond strength regardless to the other characteristics of their designs