Genetic effects on dentofacial form and limitation of orthodontic treatment

Research Project

Project/Area Number	62480415
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	小児・社会系歯学
Research Institution	Kyushu University
Principal Investigator	TAKAHAMA Yasuhide Kyushu University, Dentistry, Professor, 歯学部, 教授 (20037518)
Co-Investigator(Kenkyū-buntansha)	ABE Kiyosi Kyushu University, Dentistry, Instructor, 歯学部, 助手 (90167932) SUZUKI Akira Kyushu University, Dentistry, Instructor, 歯学部, 助手 (20037542) MATUDA Masato Kyushu University, Dentistry, Instructor, 歯学部, 助手 (90108754) 一ノ瀬元史九州大学, 歯学部, 助手 (30150460) AKIYAMA Youichi Kyushu University, Dentistry, Instructor (50037537)
Project Period (FY)	1987 – 1989
Project Status	Completed (Fiscal Year 1989)
Budget Amount *help	¥6,200,000 (Direct Cost: ¥6,200,000) Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000) Fiscal Year 1988: ¥900,000 (Direct Cost: ¥900,000) Fiscal Year 1987: ¥4,500,000 (Direct Cost: ¥4,500,000)
Keywords	Orthodontic treatment / Relapse / Cephalogram / Dental cast / Genetics / Correlation analysis / 矯正治療の後戻り / 咬合の遺伝 / 切歯歯軸の変化 / 顎顔面形態 / 頭部X線規格写真法 / 歯科矯正治療 / 歯軸傾斜
Research Abstract	Ninety-eight orthodontic patients whose orthodontic treatment had finished and their parents were selected as subjects. Cephalograms and dental casts were taken before treatment (A), after treatment (B) and after retention (C). Correlation analyses of skeletal and dental variables were performed between each stage A and B, B and C, A and C and between families. 1. Skeletal variables taken from lateral cephalograms showed small changes either after orthodontic treatment and retention. Patients seem to maintain their original skeletal growth pattern. 2. Labio-lingual inclinations of incisors, especially upper incisors of crowding and maxillary protrusion cases and lower incisors of anterior cross-bite cases, changed both after treatment and retention. The relapse of incisor inclination were observed in every case 10 - 20 % in degree. 3. Correlationship between patients and their parents became larger with their growth. This may be a result of that the adult presented his genetic phenotype su … More fficiently or that there is any heritability between parents's forms and the patient's stable state which was obtained after orthodontic treatment. However, the genetic influences on incisor inclinations seem to be smaller than on skeletal structures. Orthodontic treatment is considered to contribute to changealveolar bones and the positions of teeth only. If soft tissue does not adapt to the new circumstance after treatment, any kinds of relapse must be resulted. 4. Summations of distances between contact points on upper and lower anteriors were estimated on dental casts. The small values mean well teeth alignment without rotation or labial-lingual discrepancy of teeth. After treatment, upper anteriors showed larger relapse than lower anteriors did. 5. Upper and lower normal molar intercuspal relationship is considered to be important to avoid possible relapses. But the posters-anterior changes of upper and lower dental arches after retention were contrary to the changes with orthodontic treatment. This might be relapse in part or the growth in part. The conventional orthodontic diagnosis were erroneous. Orthodontic treatment applied to young patients without considering genetic influences of their parents should not be real therapeutics but cosmetics. Less