Abstract: Objective: To discuss the application of three-dimensional digital technology in diagnostic set-up of orthodontic cases by comparing results’ consistency of tooth extraction or not based on two different therapeutic regimens with or without the three-dimensional digital technology.Methods: 40 orthodontic first-visit cases with complete history information in recent 5 years were selected as the research samples after the preliminary screening by an orthodontist with intermediate certificate in our hospital. All the samples were divided into two groups, and the therapeutic regimens were designed by 6 orthodontists with secondary senior position according to the impression models, X ray examinations, facial & oral pictures and analysis of traditional routine data measurement. Additionally, the three-dimensional digital technology, as an aiding method, was applied in the second group. Results of the therapeutic regimens were divided into tooth extraction, non-extraction and boardline cases. Statistical analysis was applied to compare the results consistency of tooth extraction situation between the two groups. Results: With a standard of completely consistent results of 6 orthodontists，consistency rate of tooth extraction, non-extraction and boardline cases of the first group were 7.50%, 2.50% and 12.93%, respectively with the 22.50% general coincidence rate, and the second group were 42.50%，20.00% and 2.50%, respectively with the 65.00% general coincidence rate. Set value of the extraction case as 1, and boardline case as 0, and non-extraction case as -1.Six doctors separately value the 40 cases ,and then summit every single case with the absolute value of what the doctor evaluates. We performed paired design and analyze the data with Wilcoxon rank test. The coincidence rates of extraction and non-extraction of the second group were higher than the first one, the coincidence rate of boardline cases of the second group was lower than the first one, and the differences were significant based on the statistics analysis.Conclusions: It can offer beneficial reference for tooth extraction or not by aiding three-dimensional digital technology into the design of orthodontic therapeutic regimens.

Key words: Three-dimensional digital technology, Diagnostic set-up, Orthodontic, Treatment planning