RESUMO
BACKGROUND: Implant denture is a kind of dental restoration with excellent retention, support and stability. However, the phenomenon of dental fillings after implantation is a common phenomenon that troubles the majority of patients with dental defects. OBJECTIVE: The finite element analysis method was used to analyze the food impaction after planting denture by biomechanical numerical simulation, and find the quantitative relationship between the food impaction and relative width, relative height, relative angle of the denture. METHODS: To study fully relative teeth under the conditions of different widths, heights and angles influence on food embedded plug, we designed different width groups of the upper structure of the denture (5 subgroups: 5.6, 5.7, 5.8, 5.9, 6.0 mm), different height groups of the upper structure of the denture (5 subgroups: 6.6, 6.8, 7.0, 7.2, 7.4 mm), different planting angle groups of the denture (5 subgroups: 92°, 91°, 90°, 89°, 88°), different width groups of natural crowns (5 subgroups: 5.6,5.7, 5.8, 5.9, 6.0 mm), different height groups of natural crowns (5 subgroups: 6.6, 6.8, 7.0, 7.2, 7.4 mm), and different natural tooth growth angle groups (5 subgroups: 92°, 91°,90°, 89°, 88°) as a 4-teeth partial denture model. Each subgroup was designed by changing the relative position of the third dental component, with the same remaining conditions. The numerical simulation of food impaction was carried out for all dentition models, and the deformation of the teeth was analyzed. The tooth gap width curves were compared before and after stress between each group. RESULTS AND CONCLUSION: (1) After force, the total horizontal displacement of the denture was slowly reduced with the increase of the width of the upper part of the denture. When the width of the upper structure was between 5.9 and 6.0 mm, the interdental space of the natural tooth was rapidly reduced after the deformation of the tooth. The effect of food impaction was closer to the food impaction condition in the case of natural teeth. (2) When the height of the upper structure of the denture was lower than that of the adjacent teeth, with the increase of the height of the upper structure of the denture, the gap between the teeth increased first and then decreased. When the denture was lower than the adjacent tooth and the height was between 6.8 and 7.0 mm, the tooth space decreased rapidly after the force was applied. (3) The total horizontal displacement decreased slowly with increasing planting angle. (4) The results show that to reduce food impaction, the interdental distance of the implant denture and adjacent teeth should be less than 0.05 mm. The height of the implant denture should be less about 0.2 mm than adjacent teeth, and the planting angle should be about 90°.
RESUMO
To improve the precision of image registration based on corner detection, a relative position function between multiple points to determine matching points accurately. First the corners in images are detected using Harris detector, and clustering method is used to eliminate most wrong matches after coarse screening. Then the proposed relative position function is used as a criterion of precise matching. Finally the image registration process is accomplished by affine transformation. Results show that the proposed algorithm is more effective and accurate than conventional registration algorithm.