Purpose: Accurate space discrepancy evaluation is important in treatment planning. Straight-line segments and brass wire method are the most common methods in arch length assessment. However, using segments causes underestimation, while more reliable brass wire method shows lower reproducibility. The aim of our study is (1) to compare the difference between conventional segmental distance method (SD) and a new method, ideal arch form (IA), and (2) to assess the reproducibility and reliability of two methods by means of digital models. Materials and methods: Thirty sets of digital dental models presented full permanent dentition and Angle’s Class III malocclusion were included. The dental arch length was assessed with two methods: SD method and IA method. Paired-t test was used to compare two methods; Pearson’s correlation coefficient was used to analyze the correlated variables with inter-group difference; and interclass correlation coefficient was used to evaluate the reproducibility. Result: Arch length in IA group was 1.86 and 0.86 mm larger than SD group in upper and lower arch, respectively (pr= -0.39, pr= 0.40, pConclusion:The SD method showed high consistency but low reliability in short upper arches and crowding lower arches. On the other hand, the IA method can represent the real arch length regarding to the basal bone, and simply be constructed and measured with digital software with high reproducibility.

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Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.