Article

The approach to an attractive smile in dentistry : examination of changes in the distance around the mouth

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Abstract

Recently, interests in health and oral health have been increasing both individuals and society. We evaluated changes in the distance between ten reference points around the mouth during smiling to analyze the face. Twentyfive young Japanese adults (10 women, 15 men; Mean±S.D. 21.0±1.9) were participated. Digital facial images for 7 patterns (normal face, 4 types of smiles, and the pronunciation of "E" and "E-" sounds) were acquired using a digital camera. The distances between the points were measured using Photoshop CS4 (Adobe Systems, Japan). When the subjects were smiling, the distance between the labial commissures increased, and upper lip width and the distance between nasion and cheilion (Na-Ch) decreased compared with the normal face. However, the lower lip width and the distance between nasion and gonion (Na-Go) did not change. As the method to analyze the change of face, to measure the relative difference between reference points on the normal face and variation of smiles or the pronunciation of "E" using captured static photos was found be useful. These findings suggest that the upper lip, which is located near the greater zygomatic muscle, is affected more strongly than the lower lip by the action of this muscle. Based on these results, it was suggested that the patient pronouncing "E" may simulate an attractive smile.

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As the public becomes increasingly concerned with looking younger and healthy, aesthetic considerations will become increasingly more relevant in dental treatment planning. As such, dentists must define the basic tenets of an aesthetic smile - extending that vision beyond simply "pretty teeth" to a concept whereby total dentofacial harmony is developed. Aesthetics is not simply a matter for restorative dentists - it uses restorative dentistry as one of the disciplines, but it is about beauty. The same rules that apply for a denture are therefore pertinent for crown and bridge and/or implants and must be applied in all aesthetic endeavors.
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The normal growth, development, and aging of facial soft tissues was studied by three-dimensional (3D) computerized mesh diagram analysis. The 3D coordinates of 50 soft-tissue landmarks were collected from 591 healthy white northern Italians (351 males, 240 females) 6-40 years of age. For each gender and age class, mean values were computed, and a standardized mesh of equidistant horizontal, vertical, and anterior-posterior lines was constructed. Within each age group, male meshes were superimposed on female meshes. For each gender, the 6-year-old reference mesh was superimposed on the reference mesh of each age group. The global (size plus shape) difference was evaluated by calculating the relevant displacement vectors for each landmark. Consequently, a size normalization was carried out and the shape difference was evaluated by calculating new relevant displacement vectors for each landmark. Growth and development were different along the three spatial planes: the largest increment was observed in the vertical dimension, with major modifications in the soft-tissue profile. The vertical dimension in males increased even after 30 years of age: ear dimensions increased, trichion moved superiorly and posteriorly, and pogonion, menton, and gonion moved anteriorly and inferiorly. In all age groups, size-standardized shape differences were found in the forehead, lower-third facial profile, eyes, cheeks, and ears. In each age class, male dimensions were larger than female dimensions. During childhood, gender differences in size were limited; shape differences were even less manifest. Overall, the profile was more anterior and inferior, the gonia were more inferior and more lateral, the forehead was more anterior, and the ears were larger in males than in females of corresponding age.
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