The object of the study was to investigate the behavioural characteristics of orthodontic elastomeric modules with regard to their effect on frictional resistance and their failure load forces, and involved the use of an experimental laboratory-based study. Six cohorts were assembled employing five types of module and two bracket types. Straight lengths of 0.018 x 0.025-inch stainless steel were pulled through the ligated brackets and frictional resistance was measured using an Instron universal testing machine. Recordings were repeated over a 4-week period, during which time the cohorts were placed in a simulated oral environment. Failure load forces of new and used modules were also recorded, and frictional resistance and failure load forces. Analysis of variance revealed that the Minitwin cohort exhibited significantly higher frictional resistance and that the clear modules demonstrated the lowest levels of friction. Time soaked in a simulated oral environment had a variable effect on frictional resistance. A wide range of failure load forces was seen for the five types of module and all types showed a reduction in failure load force following their soaking in the simulated oral environment. There was variation in performance of the different modules both in friction testing and failure load testing.
Dental malocclusion is present in all societies but its prevalence varies. There is a need to identify the occlusal problems, their incidence and the need for treatment so that appropriate manpower arrangements may be made. In this initial survey, patients attending the orthodontic clinic at the Riyadh Armed Forces Hospital were examined for occlusal relationship, crowding, and facial type. There are indications amongst Saudi Arabian patients of a tendency for bimaxillary proclination and a greater proportion of Class III malocclusion, than in Western communities. The need for a comprehensive survey is identified.
The shear forces necessary to remove ceramic brackets from human premolar teeth using mechanical and electrothermal debonding techniques were compared and the post-debond enamel characteristics were evaluated. The temperature rise in the pulp cavity during electrothermal debonding was recorded. The samples were tested sequentially on a shear jig attached to an Instron Universal Testing Machine. The results indicate that removal of ceramic brackets with an electrothermal debonder requires less force than with a mechanical debonding technique. Furthermore, the associated pulp temperature rise appears to be within currently established biologically acceptable limits. However, the indices that are commonly used to define the condition of the enamel surface following debond may not be applicable to electrothermal debonding.
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