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.

Color Blindness In Dental Students And Staff- An Obstacle In Shade Selection For Restorations .

Dentists having defective color vision may be unaware of their defect or may have problems in perceiving color as normal vision dentists do. People who are "color vision defective" tend to be missing some of the color-sensitive cones, so these colors will appear darker. The aim of the present study is to 1. estimate the number of dental students/ personnel having problems in color discrimination based on a color blindness test 2. To refer the students/ personnel to a specialist for confirmative diagnosis. 3. To provide alternate options for shade selection to the same. Dental students, dental teachers and dental technicians/ dental auxiliaries were randomly selected for the study, with a sample size of 400 with age range of 17 to 35 out of which 200 were males and 200 females. An Ishihara color blindness test (numbers made up of color dots) was conducted to screen the dental personnel for color defective vision in the same room and in the same light source. 5% of the male and 0% of female dental personnel/ students were found to be color vision defective. Counseling to such students and personnel required to take assistance in appointments of shade selection / matching.

Evaluation of shade matching practices among nigerian dentists / Avaliação dos procedimentos de determinação de cor de restaurações entre dentistas niegerianos

OBJECTIVES: To assess tooth shade matching practices among Nigerian Dentists. MATERIALSAND METHODS: The data was collected by paper questionnaire mailed at random to dentists insome Nigerian Teaching Hospitals and General Hospitals. The questionnaires comprised of two aspectsthat inquired about their biographical data and basic methods of shade selection. About 95% of thequestionnaires were retrieved and analyzed. RESULTS: 160 (83, males; 77 females) dentists participatedin the study. 71% performed tooth shade matching often, with restorative dentists (100%) mostlyinvolved than other specialists. 67% agreed that shade matching should be done in consultation withothers. However, only 40.6% actually consults others during shade selection. Also, 85% of the dentistsresponded correctly that shade matching should be done under natural lights. However in their clinicalpractice, majority (97%) selected their teeth under dental lights. CONCLUSION: The study revealedthat majority of the dentists practicing in the Nigerian Teaching and State Dental Hospitals are involvedin shade matching practices. Majority of the dentists performed tooth matching procedure withoutconcurrence from others and under dental light source. However few dentists reported complaintsfrom their patients. Emphasizing color science in dental curriculum and teaching new shade matchingsystems could be essential for improved restorative outcomes.

OBJETIVOS: Determinar os procedimentos de determinação de cor entre dentistas nigerianos.MATERIAIS E MÉTODOS: Os dados foram coletados por meio de questionários em papel,enviados aleatoriamente a dentistas em alguns hospitais de ensino e hospitais gerais. Osquestionários compreenderam dois aspectos de questões sobre dados biográficos e métodos básicosde seleção de cores. Em torno de 95 % dos questionários foram recuperados e analisados.RESULTADOS: 160 dentistas (83 homens, 77 mulheres) participaram do estudo. 71% executamescolha de cores, sendo que 100% dos dentistas restauradores o fazem, em número bem maior doque as demais especialidades. 67% concordam que escolha da cor deve ser feita em conjunto comoutras pessoas. Entretanto, somente 46,6 % realmente consultam uma segunda opinião durantea seleção de cores. Também 85% dos dentistas responderam que a escolha da cor deve ser feitasob luz natural. Entretanto, em sua prática clínica a maioria seleciona a cor sob luz de refletores.CONCLUSÃO: O estudo revelou que a maioria dos dentistas atuantes nos centros pesquisadospraticam a seleção de cores dentárias. A maioria procede sem consultar segunda opinião e sobluzes de refletores. Entretanto, poucos dentistas relataram queixas de pacientes. A ênfase daciência da cor no currículo dental e ensino de novos sistemas de escolha de cores poderia seressencial para a melhora dos resultados restauradores.

Shade comparative analysis of natural tooth measured by visual and spectrophotometric methods / 대한치과보철학회지

STATEMENT OF PROBLEM: A clinically successful color match is one of the important factor to get an esthetic dental restoration. Dental shade guides are commonly used to evaluate tooth color in restorative procedure. But numerous reports have indicated that common shade guides do not provide sufficient spectral coverage of the natural tooth colors. To address issues associated with the shade guide, distinct avenues have been pursued objective spectrophotometric / colorimetric assessment. PURPOSE: This study compared the accuracy of tooth color selection of spectrophotometer with that of human visual determination. Three main factors were investigated, namely, the effect of light, the individual variation and the experience of the observer. MATERIAL AND METHODS: At the first experiment, on ten patients, one operator independently selected the best matching shade to the unrestored maxillary central incisor, using a Vita Classical Shade Guide in the morning, at noon and in the afternoon. The same teeth were measured by means of a reflectance spectrophotometer. At the second experiment, on ten patients, ten operators (5 experts, 5 novices) selected and measured by the same method above at noon. At the third experiment, the results of the second experiment were divided into two groups, expert and novice, and analyzed. RESULTS: 1. There was significant difference between visual and spectrophotometric assessment (mean delta E values) in experiment 1, 2, 3 (p < .05). 2. There was no significant difference between experts and novices group, when comparing with each visual and spectrophotometric assessment (mean delta E values). CONCLUSION: Spectrophotometer could be used to analyze the shade of natural tooth objectively. Thereby, this method offers the potential tominimize considerably the need for corrections or even remakesafter intraoral try-in of restoration. Furthermore, to achieve its advantage, both the shade-matching environment and communication between dentist and technician should be optimized with use of visual and instrumental shade-matching systems.

Shade analysis of anterior teeth using digital shade analysis system / 대한치과보철학회지

STATEMENT OF PROBLEM: A scientific examination and understanding of overall aspects of the natural dentition is the first step involved in making a satisfactory selection in the shade of an aesthetic prosthesis. Proper natural shade selection of the prosthetic restoration that is in harmony with the remaining dentition is as important aesthetically, as harmony of form and function in the anterior dentition. Clinically, the most commonly applied method of shade selection has been visual, but because of the subjective nature inherent to this method, shade selection results are variable and can be influenced by such factors as the technician, the type of shade guide used, and the type and intensity of the lighting. PURPOSE: The purpose of this study was to develop a more objective and scientific approach to examining and understanding the shade of teeth, which has in turn lead to the development of a number of shade analysis devices that present a more objective method of shade analysis. MATERIAL AND METHOD: In this study, the shades of healthy anterior teeth were examined and analyzed using the recently developed digital shade analysis of the ShadeScan(TM) System. The study examined 80 individuals in their twenties, 40 males and 40 females, presenting 6 healthy, unrestored maxillary anterior teeth. Tooth brushing and oral prophylaxis were performed prior to evaluation. The ShadeScan handpiece was used to acquire images of the 6 maxillary anterior teeth. These images were analyzed using the Vita/Classical mode of the ShadeScan(TM) Software, and shade maps of each tooth were acquired and divided into cervical, middle, and incisal thirds. The shade distribution of each third, left and right symmetry, and gender differences were investigated and analyzed. RESULTS: The results of the study are as follows: 1. An overwhelming majority of the examined teeth were found to possess shades belong to Group A, with the greatest variations occurring at the middle and cervical thirds of the maxillary central and lateral incisors, in both male and female subjects. 2. Canines of both male and female subjects showed left and right symmetry with uniform shade distribution of A4 and C4, while the lateral and central incisors showed left-right symmetry of the incisal 1/3 with a uniform shade distribution of A2 and A3 shades. 3. No significant differences in shade distribution were seen between genders in maxillary canines, whereas maxillary central and lateral incisors showed differences at the middle and cervical thirds between male and female subjects. The results of this study show that with the exception of maxillary canines, maxillary anterior teeth display a diverse shade distribution as well as gender differences. CONCLUSION: Clinically, when making a shade selection using the existing shade guide, one must consider the fact that even a single tooth consists of a variety of shades. The results of this study show that when selecting a shade from a number of groups is difficult, shades from A group are the most consistent with the natural shade of maxillary anterior teeth.