Young, Shawn Jonathan2020-03-042020-03-0419951995(OCoLC)41428627b22398594https://hdl.handle.net/2144/39777PLEASE 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, Henry M. Goldman School of Graduate Dentistry, 1995 (Periodontology).Includes bibliographical references: (leaves 80-87).This thesis describes a quantitative study of periodontal defects produced in a skull model using subtraction images obtained with RadioVisioGraphy. Analysis using RadioVisioGraphy was compared to changes in weight and volume determined by physical measurements. Four types of Periodontal defects were studied: two walled defects, three walled defects, crater defects and furcation defects. All defects were fabricated on posterior teeth in alveolar bone and done with triplicate samples. Defects were made progressively larger in approximately 1mm steps allowing examination of defects ranging from 1mm to 5mm. Radiographic images before and after each step were obtained with a RadioVisioGraphy system and subtracted. Changes in weight and defect volume were also recorded and compared to the results obtained after each step from the digital subtraction. For each defect type, a regression analysis was performed to compare changes in bone mass determined by weight with calculated bone loss determined by subtraction radiography or by volume measurements. When the calculated bone losses were compared to the true bone losses it was evident that the subtraction method underestimated the lesion sizes. For all lesions the average underestimation was 22%. The largest underestimation occurred with furcation lesions where the measured bone loss was underestimated on average by 67%. Two walled lesions were underestimated by 30%, three wall lesions by 3% and crater lesions were overestimated by 10%. This study indicates that the software program used in this study should be modified to compensate for the non-linear exposure response of the RVG system. At present, the imaging system is not sufficiently accurate to establish absolute determinations of the bone loss, but would be clinically useful in determining relative changes in bone loss or gain after treatment.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.Radiography, dentalThesis/Dissertation