13 生理学生理学.pdf

. 1, What is dental crowding 2, Etiology of dental crowding 3, Diagnosis of dental crowding 4, Therapeutics of dental crowding Crowding of the teeth, the most common type of malocclusion at present, undoubtedly is related in part to the continuing reduction in jaw and tooth size in human evolutionary development. Its clinical manifestations include teeth dislocation or rotation. 1, Evolution factor: Due to the changes in environment and refined food structure, the function of chewing organs are gradually degraded. 2, Heredity factors: The shape and size of the teeth and jaw are affected by the family members. 3, Environmental factors: During the mixed-dentition process, the abnormal eruption or exfoliation time may lead to crowded teeth. Besides, long- term biting of the lower lip, mouth-breathing and other oral habits may lead to crowded dentition. Evolutionary factors SHORT MODERATE LONG Environmental factors nDental habits: mouth-breathing, lip-sucking nDisturbances of Dental Development: Ectopic eruption, early loss of primary teeth and so on nImbalanced pressure environment: lips, cheek, Tongue and fingers can influence tooth position 1、Grading of dental crowding Mild Crowding: 2-4mm Moderate Crowding: 4mm -8mm Severe Crowding: 8mm Mild Crowding: 2-4mm Moderate Crowding: 4mm -8mm Severe Crowding: 8mm Principle ：balance the amount of bone and teeth 1, Increase the “amount of bone” ( 1) Expansion of arch length (2) Expansion of arch width 2, Decrease the “amount of teeth” ( 1) Decrease the number of teeth (2) Decrease the size of teeth Molar distalization Expansion of arch length Tilt the incisors labially