Abstract: Objective Todiscuss two kinds of orthodontic technology that caused the gingival invagination and the influence on its occurrence.Methods 75 cases that used straight wire application system (with the first premolar extracted) and 22 cases that used invisible application system were selected and the incidence rate of gingival invagination was compared between two groups.Logistic regression analysis was done with regard to such factors as gender,age,closing the extraction space and the treatment time.Results There was no significant difference inthe occurrence rate of gingival invagination in these two systems.Gender,the time of closing the extraction space and the size of extraction space did not influence the occurrence of gingival invagination while age had the positive correlation with gingival invagination.Conclusions The gingival invagination is not influenced by different methods of orthodontic technology.It might have correlation with age.

Key words: invisible orthodontics, gingival invagination, extraction treatment, periodontium