Assessment of shear and tensile bond and rebond strengths of orthodontic brackets using different etching times

This in vitro study is designed to assess and compare the shear and tensile strengths of both bond and rebond strengths of adhesive with the metal brackets when they exposed to different etching times. Sixty sound upper first premolars had been extracted from 13-18 years old orthodontic patients, were divided into two groups, one group was tested for shear bone strength, and the other was tested for tensile bond strength. A new metal brackets were bonded to the buccal surface of the teeth using the same type of adhesive material, each group was subdivided into three subgroups and then etched with 37% phosphoric acid using 15, 60 and 120 seconds for etching, then the results were recorded for shear and tensile bond strengths for the sample. All the brackets were later on debonded and the brackets base with the remnant adhesive material were etched and rebonded to the teeth which were cleaned and prepared to receive etching solution using the previous etching times, then they were tested for the shear and tensile strengths. The results showed that there was a significant regression in the shear and tensile strengths of the rebonded orthodontic brackets than that of the bonded one, and the highest bond and rebond strengths were obtained at the 60 second etching time

Tooth size discrepancy of the permanent dentition in class II div. 1 malocclusion with crowding or spacing

A proper relationship of the total mesiodistal width of the maxillary dentition to that of the mandibular dentition will favor an optimal post treatment occlusion, the purpose of this study is to compare the mesiodistal crown dimension and tooth size discrepancy in subject with class II div.1 malocclusion with spacing or crowding in the upper and lower arches. Sixty pairs of dental casts were obtained [30 crowding, 30 spacing] were measured and analyzed, the results indicates males generally have greater mesiodistal crown dimension than females in both crowding and spacing groups, and there was a significant difference between both groups with greater mesiodistal width for the crowding group, and non significance difference regarding tooth size analysis [Bolton ratio]

Early loss of deciduous teeth and occlusion

This study was designed to observe the percentage of early loss deciduous canines, first and second molars and its effect on the occlusion among children [3-6 years of age] that were examined from urban and rural areas of Baghdad province, the result showed that premature loss of deciduous teeth was more in urban than rural samples and it was more in posterior than anterior regions as well as malocclusion was increased with premature loss of primary teeth