OBJECTIVETo discuss through retrospective study associated factors influencing orthodontists to develop orthodontic treatment plans and to calculate constituent ratio of a typical extraction in orthodontic treatment.

METHODSSystematic sampling was performed among 7 344 orthodontic patients, who received orthodontic treatment from April 2012 to March 2014 in the Department of Orthodontics, West China Hospital of Stomatology, Sichuan University. The study included statistical data on factors that may influence development of treatment plans. Samples were used to calculate extraction-ratio and atypical-extraction-ratio. Research focused on associated factors influencing development of treatment plans while evaluating correlation significances of each factor. Finally, treatment outcomes of atypical-extraction were compared with those of typical-extraction.

RESULTSAmong studied patients, 55.31% (406/734) received orthodontic extraction treatment. In orthodontic-extraction-treated patients, typical-extraction accounted for 59.11% (240/406), orthodontists-selected atypical-extraction accounted for 23.15% (94/406), and passive atypical-extraction accounted for 17.73% (72/406). With statistical analysis, we inferred associated factors influencing development of treatment plans as follows: sex and age of patients, sex of orthodontists, accurate condition of specific teeth, Angle's classification, and degree of midline deviation. Tooth loss before treatment also directly influences passive atypical-extraction. Statistically significant factors were not obtained. Significant difference of treatment outcome was not observed between atypical-extraction and typical-extraction-orthodontic treatment (P>0.05).

CONCLUSIONSAbove mentioned factors may influence orthodontists to develop treatment plans. However, orthodontists should also consider expected results of treatment strategies to prepare individual treatment plans on the basis of comprehensive analysis. 
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