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Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition
Published on: February 23, 2024
Lower incisor dentoalveolar compensation and symphysis dimensions among Class I and III malocclusion patients with
Núria Molina-Berlanga1, Jaume Llopis-Perez, Carlos Flores-Mir
1a Clinical Instructor, Department of Orthodontics, School of Dentistry, Universitat Internacional de Catalunya, Sant Cugat del Vallés, Barcelona, Spain.
Objective:
To compare lower incisor dentoalveolar compensation and mandible symphysis morphology among Class I and Class III malocclusion patients with different facial vertical skeletal patterns.
Materials And Methods:
Lower incisor extrusion and inclination, as well as buccal (LA) and lingual (LP) cortex depth, and mandibular symphysis height (LH) were measured in 107 lateral cephalometric x-rays of adult patients without prior orthodontic treatment. In addition, malocclusion type (Class I or III) and facial vertical skeletal pattern were considered. Through a principal component analysis (PCA) related variables were reduced. Simple regression equation and multivariate analyses of variance were also used.
Results:
Incisor mandibular plane angle (P < .001) and extrusion (P = .03) values showed significant differences between the sagittal malocclusion groups. Variations in the mandibular plane have a negative correlation with LA (Class I P = .03 and Class III P = .01) and a positive correlation with LH (Class I P = .01 and Class III P = .02) in both groups. Within the Class III group, there was a negative correlation between the mandibular plane and LP (P = .02). PCA showed that the tendency toward a long face causes the symphysis to elongate and narrow. In Class III, alveolar narrowing is also found in normal faces.
Conclusions:
Vertical facial pattern is a significant factor in mandibular symphysis alveolar morphology and lower incisor positioning, both for Class I and Class III patients. Short-faced Class III patients have a widened alveolar bone. However, for long-faced and normal-faced Class III, natural compensation elongates the symphysis and influences lower incisor position.
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