| The esthetics of smile,as the dynamic reflection of facial esthetics, has been regarded as one of the most important goals of orthodontic treatment for patients with variable malocclusions . The observation,recording,measurement and analysis will be performed by orthodontists in their common practice,which have great significance for orthodontic diagnosis, treatment planning and evaluation. Different appearances are often shown because of different nationalities and ethnic groups. Therefore, the quantitative studies of smile features of Chinese adults are sure to offer guidance for orthodontic clinical work in our country and to approach the aim of harmony,stability and esthetics. This research aims to conduct some preliminary study in this field,including three parts below:Part I: Development of computerized analysis system for studying smile featuresObjective To develop a comprehensive and practical computer-assisted measuring analysis system for studying smile characteristics and to provide a powerful tool for orthodontic clinical work and studies. Methods Frontal photographs of face for each patient were taken during rest and smile postures with a digital camera; the program was written in Microsoft C++6.0 under the Windows 2000 Professional system. Results Landmarks could be located on the photograghs by the program, 10 points in rest posture,21 points in smile posture,and then 29 items of smilecharacteristics were obtained automatically; the program was proved to be reliable. Conclusion Following advantages can be found in this system: accuracy of measurements,profusion of measuring items,convenience for clinical use,comprehensiveness of management and compatibility of functions. This system may show some significance in the orthodontic practice and be useful for the research of smile characteristics of Chinese. Part II: The study of computerized measurement on smile featuresof Chinese young adults with normal occlusion Objective To study the smile characteristics of normal occlusion youth of Chinese Han-nationality and give references to orthodontic clinical work. Methods By means of a cephalostat, frontal photographs of face for 112 subjects(60 males,62 females) aged from 18-23 were taken during rest and smile postures with a digital camera, analysis was performed by a self-developed program Smile 1.0 and 29 items about smile characteristics were obtained. Results There were significant differences between genders in soft tissue features and few differences in soft tissue dynamic changes; Significant differences were also shown between male and female in three items about lip-teeth relationship: the distance between lower lip and upper incisal edge, smile line ratio and clinical crown length of upper left incisor ;A sexual dimorphism was found in smile types. Conclusion The posed smile is a standard posture for the study of smile characteristics; Some items of smile characteristics are quite different between two genders so the following study should be carried out separately; the average smile of female of Chinese Han-nationality can be regarded as the ideal smile relatively. Part III:The study of computerized measurement on smile features of Chinese young adults with deep overbite occlusion... |
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