Application of optical illusion in stomatological aesthetics / 口腔疾病防治

@#Optical illusion refers to the phenomenon in which the scene observed by the human eye is not completely consistent with the objectively presented scene. Optical illusions in stomatology, as well as their clinical application, are demonstrated in this paper in terms of shade, shape and aesthetic design. Shade is not only affected by the optical illusions with which it is associated, such as color metamerism, color constancy and the Chevreul illusion, but also influenced by the surroundings. It is suggested that the surrounding lighting during veneering should be the same as that during color matching in the clinic. As indicated by the Poggendorf illusion and the Leaning Tower illusion, the practice should be conducted and checked from multiple perspectives to compensate for the limitation of human eyes, such as intraoral scanning. Other digital technologies, including digital facial scanning and cephalometric measurement, could be used to reduce the subjective influence of observation. In terms of esthetic design, the interaction of the part and the whole, suggested by Ebbinghaus illusion, should be considered: an individual harmony smile should be designed considering the characteristics of the personality and the features of the face, lips, teeth and gingiva of the patient. Furthermore, personal information, such as gender and age, should be taken into consideration in beautification presentation. Further research should be focused on the influence of optical illusions in stomatology in more details. More communication among doctors, technicians and patients is needed. Clinicians should be aware of the impact of optical illusions to reduce subjective bias in clinical standardized operations and further take advantage of optical illusions to create beautification presentations of dental restorations and smiles.

Analysis of crown size and morphology, and gingival shape in the maxillary anterior dentition in Korean young adults

PURPOSE: The aim of this investigation was to analyze the dimensions of clinical crowns and to classify the crown and the gingival type in the anterior teeth in Korean young adults. MATERIALS AND METHODS: Casts were obtained from 50 subjects ranging in age from 24 to 32. Measurements of length and width were made on the casts using a pair of digital calipers on the entire dentition. Crown thickness and papilla height were also measured and MDW/CL (mesiodistal width to clinical length) and CW/CL (cervical width to clinical length) ratios of the maxillary anterior teeth were calculated. The K-clustering method was used for CW/CL to classify the anterior tooth shape into three groups (tapered, ovoid, and square), and one-way analysis of variance and Duncan's post-hoc comparison were used to evaluate statistical significance between the groups. Pearson's correlation analysis was performed between tooth shape and papillary height (PH) to demonstrate the correlation between tooth shape and gingival morphological characteristics. RESULTS: The average length of the maxillary central incisors was 9.89 mm; the mesio-distal width was 8.54 mm; and the ratio of width/length was 0.86 in Korean young adults. The average bucco-palatal thickness of the central incisor was 3.14 mm at the incisal 1/3 aspect. Ovoid type was the most common tooth shape (48%), followed by square type (29%) and taper type (23%) in the central incisors of Korean young adults. Tooth shape and gingival type were correlated with each other. CONCLUSION: New reference data were established for tooth size in Korean young adults and the data show several patterns of tooth shape and gingival type. Clinicians should diagnose and treat based on these characteristics for better results in the Korean population.

Relationship between the shape of the upper central incisors and the facial contour in dental students: Lima, Peru / Relación entre la forma de los incisivos centrales superiores y el contorno facial en estudiantes de odontología: Lima, Perú

Determine the relationship between the shape of the face and the shape of the upper right central incisor according to “The law of harmony” proposed by Williams. Materials and methods: This was an observational, analytic and cross-sectional study. A sample of 124 subjects, male and female students between 17 and 28 years old, was selected for the research. Their facial biotype and the shape of their upper right central incisor were determined by means of direct and photographic methods. Height and facial width were clinically evaluated using the direct method, and the proximal contours of the incisors were evaluated using a Vernier digital caliper. Images were downloaded to a computer and analyzed by means of the photographic method using Adobe Photoshop 5.0. Results: The relationship between the shape of the face and the shape of the incisor was positive in 43.5 percent of the sample (p=0.006) in the direct method. In the photographic method, the relationship between the shape of the face and the shape of the incisor was positive in 41.1 percent of the sample (p=0.037). The most frequent facial biotype in the direct and photographic methods was the dolichofacial with 61.3 percent and 71 percent respectively. The most frequent shape of the tooth with the direct and photographic methods was the ovoid with 55.6 percent and 51.6 percent respectively. Conclusion: Results do not confirm “The law of harmony” proposed by Williams, therefore when choosing the most suitable anterior tooth, experience and criteria of the dentist as well as the opinion of the patient should be taken in account in order to achieve a good aesthetic result...

Determinar la relación entre la forma de la cara y la forma del incisivo central superior derecho según la “ley de la armonía” propuesta por Williams. Materiales y métodos: Este estudio fue observacional analítico de tipo transversal, se seleccionó una muestra de 124 estudiantes de ambos sexos entre 17 y 28 años de edad, a los cuales se determinó el biotipo facial y la forma del incisivo central superior derecho, por medio de un método directo y otro fotográfico. Por el método directo se evaluó clínicamente la altura y el ancho facial así como también los contornos proximales del incisivo utilizando un Vernier digital y por el método fotográfico se realizaron trazos en las imágenes tomadas utilizando el software de Adobe Photoshop 5.0 Resultados: Por el método directo la relación entre la forma de la cara y la forma del incisivo fue positiva en un 43.5 por ciento de la muestra (p= 0.006). Por el método fotográfico la relación entre la forma de la cara y la forma del incisivo fue positiva en un 41.1 por ciento de la muestra (p=0.037). El biotipo facial con mayor frecuencia por el método directo y fotográfico fue el dolicofacial en un 61.3 por ciento y 71 por ciento respectivamente. La forma del diente con mayor frecuencia por el método directo y fotográfico fue el ovoide en un 55.6 por ciento y 51.6 por ciento respectivamente. Conclusión: Los resultados no confirman la “ley de la armonía” propuesta por Williams, por lo tanto al momento de seleccionar el diente anterior más adecuado, se debe tener en cuenta la experiencia y el sentido crítico del profesional así como los deseos del propio paciente con el fin de alcanzar un buen resultado estético...