PubMed · 9540526
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D D Epstein. 1994. Why overdentures?. https://pubmed.ncbi.nlm.nih.gov/9540526/
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PURPOSE: The purpose of this study was to measure the resistance to displacement in an adult bovine rib mandible model as the vertical dimension of the bone decreases, and to compare the fixation strength of titanium miniplates and reconstruction plates. MATERIALS AND METHODS: Five groups of 6 ribs each were tested based on the vertical dimension of the rib and method of fixation (group 1, 40 mm, miniplate), (group 2, 30 mm, miniplate), (group 3, 20 mm, miniplate), (group 4, 10 mm, miniplate), (group 5, 10 mm, reconstruction plate). In the 4 groups stabilized with a miniplate, a 3-hole-per-segment, 2.0-mm titanium miniplate and 6.0-mm monocortical titanium screws were used. In group 5, a 3-screw-per-segment, 2.4-mm titanium reconstruction plate and 2.4-mm bicortical titanium screws were used for fixation. A 2-dimensional beam model (Class III lever) was established, and an Instron machine was used initially to develop a load-displacement curve to 100 N for each specimen. An osteotomy was then created, and the segments were reduced without preload. The ribs were then loaded to failure in the Instron machine. The load-displacement curve and failure load were recorded. RESULTS: There was no significant difference (P < or = .05) between any of the groups before the osteotomy. At 75 N, groups 1 and 2 were superior to group 5 in resistance to displacement. Group 4 showed significantly less (P < or = .05) resistance to displacement than the other experimental miniplated subgroups. As loads increased, groups 1 and 2 continued to show increased resistance to displacement when compared with groups 3, 4, and 5. Loads to failure for groups 1 and 2 were comparable to group 5. CONCLUSIONS: Decreased resistance to displacement occurs with decreasing vertical dimension of the bovine rib. In fractures of the edentulous mandible, a miniplate is more likely to provide adequate fixation if the mandible is 30 to 40 mm in height (nonatrophic). At higher loads, groups with greater vertical height (30 mm and 40 mm) provided resistance to displacement equivalent to the 10-mm group repaired with a reconstruction plate. Therefore, fractures of the atrophic mandible may be better treated with more rigid techniques.
OBJECTIVE: The purpose of this study was to compare E-speed Plus film and digital imaging with a charge-coupled device (CCD) sensor and a complementary metal-oxide semiconductor active pixel sensor (CMOS-APS) in the detection of periapical bone lesions. STUDY DESIGN: Periapical lesions were created in the cortical and trabecular bone of 10 dried human mandibles. Seventy radio-graphic images and 140 digital images were evaluated by 6 endodontists and 2 radiologists. Receiver operating characteristics curves and analysis of variance were used for statistical analysis.Results. No statistically significant differences were found between film, CCD, and CMOS-APS systems. Lesion detection occurred with significantly greater accuracy in cortical bone than in trabecular bone, as well as when the cortical plate was involved. CONCLUSIONS: That no differences were found between the two sensors lends support for the use of CMOS-APS sensors, which require less system power and may have longer life spans than CCD sensors. Digital imaging required 50% less radiation than film to obtain the same diagnostic information.
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