Rowan, Michael E.2022-06-062022-06-0619711971(OCoLC)16016262b14337332https://hdl.handle.net/2144/44655PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please log in with a valid BU account to access and click Download. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, 1971. (Orthodontics)Bibliography included.The purpose of this investigation was to evaluate the early tissue changes seen in the periodontal tissues with the application of moderate orthodontic forces. A 60 gram tipping force was applied to the teeth of immature dogs for 1, 3, 5, and 7 days. Histological sections of the teeth and their surrounding tissues were evaluated qualitatively. Of particular interest was the sequence of response and the degree of degenerative change. The results were in general agreement with the findings of Reitan. After twenty-four hours, the only visible changes were the distortion of the periodontal fibers and blood vessels. Seventy-two hours produced a localization of differentiated cells, although no obvious increase in cell number, and initial alteration of calcified tissues. These changes were consistent specifically with the theoretical areas of pressure and tension. Application of force for 120 hours produced an increase in differentiated cells and well-defined bone resorption and apposition in areas of pressure and tension. After 168 hours an indirect cellular response, which is necessary to maintain the width of the lamina dura, was also noted. [TRUNCATED]en-USThis work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.PeriodontiumConnective tissueOrthodonticsThesis/Dissertation