A Study on Application of Silicone-based Materials for Sports Mouthguards - Mechanical Properties of Various Activation Modes of Microwave Vulcanizations-

松本歯科大学大学院歯学独立研究科博士（歯学）学位申請論

日本成人女性における前歯部配列の理想的な切歯のプロポーションに関する検討

The goal of dental esthetic treatment is to restore mastication and esthetics. Dental esthetic treatment differs from prosthodontic treatment due to the fact that the former considers the relationship between the anterior teeth and the entire facial configuration, especially around the mouth, to provide a beautiful smile. Rufenacht, in his textbook “Fundamental of Esthetics” in 1₉₉0, advocated 10 factors to create a beautiful smile. One of the factors states that “The shape of the anterior teeth has to be in Golden Proportion”. Although the factors make sense, the factor regarding the golden proportion raises a question. Hence, we measured the width of the maxillary anterior teeth and compared them to the ʻgolden proportionʼ. A total of 162 Japanese female, with an average age of 31 years old were examined. They were treated by orthodontists who are boardcertified by the Japanese Orthodontic Association. The subjects underwent orthodontic treatment with an initial diagnosis of Angle class 1, ANB2 to 4 malocclusions with no skeletal involvement.Photographs of the maxillary anterior after orthodontic treatment were used for measurements. Three dentists with more than 5 years of clinical experience measured the width of the maxillary anterior from the photos enlarged by 3.8 times. The crown width obtained from the two–dimensional photographs was 32.48 ± 1.01 mm for central incisors, 23.83 ± 0.8₉ mm for lateral incisors, and 1₉.₉0 ± 1.04 mm for cuspids. The average width of central incisor was 1.36 and the cuspid was 0.84 with the lateral incisor as 1. It is common that the width of the tooth increases from lateral incisor followed by the cuspid, and the central incisor. However, the harmony of anterior teeth should not be based on the actual width of each tooth, but on the two–dimensional tooth proportion viewed from the anterior, which can be affected by the shape of the dental arch, the angle of each tooth, and so on. According to our results, the ratio of the central to the lateral incisor did not coincide with the golden ratio of 1:1.618 but rather to the silver ratio of 1: √2 (1.414), a traditional beautiful proportion in Japanese culture. To compare of results, we used the textbook “Anteriores”, by Dr. Jan Hajto and examined the two–dimensional measurement of the maxillary anterior teeth in 32 European female. We concluded that the ideal incisor proportion before and after orthodontic treatment in Asian women is closer to the silver ratio. Even for European female, the ideal incisor proportion is not necessarily the golden ratio, contrary to popular belief

Dental exchange class in the 2018 introduction to dentistry practice impressions analysis of junior high school students and dental university students

Summary[Purpose]In the introduction to dentistry practice in 2018, the first–year students of Matsumoto Dental University (MDU) had the opportunity to participate in the dental exchange class with students from junior high schools and elementary schools in Shiojiri City. Among them, the MDU students received a report on the class from the first and sec ond graders of Koryo Junior High School. The MDU students returned the impressions of the class to the junior high school students. The class was a valuable experience for the students and the teachers of MDU. We thought we should analyze the students’ impressions and use them for future reference.[ Methods ] The number of the students’ impressions was 131 for the first–year, and 149 for the second–year students of Koryo Junior High School, while the number of MDU students’ impressions was 56 for the first–year students and 50 for the second–year students.Based on these impressions, (1) we selected the main words of the impressions as keywords,counted them, and organized them into items based on our subjective opinion. (2)The impressions were text–mined and multivariate analysis was performed. (3) Visualizationwas attempted by cooccurrence network analysis.[Results] The result of (1), the key words were 354 words for the first–year students of junior high school and 353 words for the second–year students. The MDU students had 144 words for the first–year students and 154 words for the second–year students. The importanceof the key words and the frequency of their occurrence were found in (2). The importance of the key word “tooth” was the most important and thefrequency of its appearance in the first year of junior high school, while “understanding” was the most important and “tooth” was the most frequent in the second year of junior high school. The MDU students gave the highest importance and frequency of occurrence of “presentation” to both the first and second–year students. In task (3), we connected the key words in the network and visualized the relationship between the words.[Discussion] By looking at the number of key words, it can be inferred that the first and second–year students were able to understand the task. The investigation implies that theMDU students might have gained valuable experience from this exchange class.[Conclusion] Throughout the exchange class,1. The first and second–year students of Koryo Junior High School gained professional knowledge of dentistry.2. Students at Koryo Junior High School gained a better understanding of the MDU.3. First year students of the MDU gained valuable experience as presenters by understanding, preparing and devising class assignments

Evaluation of educational effectiveness of Oral Implantology programs in prosthodontics hands–on course

Summary Matsumoto Dental University has been offering lectures on oral implantology to fourth– year dental students since 2007 and a hands–on program since 2019 as part of it’s under graduate program. In order to evaluate the educational effects of oral implantology and identify areas for improvement, 85 fourth–year dental students (59 males and 26 females) in the 2020–2021 academic year and 78 fourth–year dental students (54 males and 24 females) in the 2021–2022academic year were enrolled as subjects, and questionnaires were administered after the hands–on training.The questionnaire surveyed the interest in this program, the level of understanding, and the usefulness of implant treatment for their future. As statistical analysis,anindependent sample t–test was used to examine the questionnaire results of the years at a significance level of 5%.There was no significant difference in any of the items.The level of understanding and interest in content was high in both years.These results suggest that this hands–on program will help teach students oral implantology