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Updated: Oct 7, 2025

Author Spotlight: 3D Movement Assessment of Maxillary Posterior Teeth in Clear Aligner Treatment
Published on: February 23, 2024
Balkwill's angle, occlusal plane, mandibular shape, and curve of Spee
Estelle Casazza1,2,3, Jean-Daniel Orthlieb1,2, Anne Giraudeau1,2
1Aix-Marseille University, School of Dentistry, Marseille, France.
Objective:
This study proposes a cephalometric method to determine an individual radius of the curve of Spee in cases of occlusal prosthetic rehabilitation.
Methods:
A retrospective study was conducted on 469 lateral cephalograms. Statistical analysis was performed. Correlations were computed using simple regression, Z tests, paired t-tests, and one-way repeated measures ANOVA.
Results:
Regression calculations supported a link between the radius of the curve of Spee and occlusal plane inclination, Balkwill's angle, mandibular parameters (MP), with MP = corpus - ramus + Bonwill height. Based on MP, data that are accessible even in the absence of teeth, a regression formula can be proposed to provide an individualized estimation of the radius of the Spee curve (RCS): RCS = 0.624 * MP + 26.583.
Conclusion:
This study proposes an individualized estimation of the RCS from only skeletal mandibular parameters: the length of the ramus, length of the corpus, and the Bonwill height.
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