Mandibular incisor alveolar housing and incisor-alveolar axis relationship in untreated skeletal Class III malocclusion: A cross-sectional CBCT study
- 1Department of Orthodontics, National Hospital of Odonto-Stomatology Hanoi, Hanoi, Vietnam
- 2Faculty of Dentistry, VNU University of Medicine and Pharmacy, Hanoi, Vietnam
- 3Department of Orthodontics, School of Dentistry, Hanoi Medical University, Hanoi, Vietnam
Abstract
Patients with skeletal Class III malocclusion may have limited alveolar support around the mandibular incisors, but conventional cephalometric measures do not directly describe the root-alveolus relationship. This retrospective cross-sectional study quantified labial and lingual alveolar bone thickness and examined whether signed IA-PAMD indicated apical root position within the symphysis. Pretreatment cone-beam computed tomography and lateral cephalometric records from 80 untreated patients (320 incisors) with signed ANB < 0° were analyzed. Bone thickness was measured at three root levels. Correlations and cluster-robust multivariable models adjusted for tooth, age, sex, signed ANB, GoGn-SN, and incisor mandibular plane angle. Mean labial thickness was 0.36, 0.49, and 2.40 mm at the cervical, middle, and apical levels; corresponding lingual values were 0.59, 1.39, and 4.01 mm. Labial bone was thinner than lingual bone (all P < 0.001), and labial thickness was below 0.5 mm in 80.3% of cervical and 63.4% of middle-root observations. Signed IA-PAMD correlated positively with labial apical thickness, negatively with lingual apical thickness, and not with total apical width. In adjusted models, each 1° increase in signed IA-PAMD was associated with 0.084 mm greater labial apical thickness (95% CI, 0.053–0.115), 0.092 mm lower lingual apical thickness (95% CI, −0.141 to −0.043), and no difference in total apical width (−0.008 mm; 95% CI, −0.082 to 0.065). The mirror-image labial and lingual coefficients, together with the near-zero total-width coefficient, support interpretation of signed IA-PAMD as a measure of root-apex eccentricity within the symphysis rather than aggregate apical bone support. It should not be interpreted as a treatment target or safety threshold, and the absence of a Class I comparator limits conclusions specific to skeletal Class III morphology.
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BibTeX
@article{nguyen2026mandibular,
title = {{Mandibular incisor alveolar housing and incisor-alveolar axis relationship in untreated skeletal Class III malocclusion: A cross-sectional CBCT study}},
author = {Thanh Huyen Nguyen and Huong Ly Nguyen and Thi Dung Dao and Thi Thu Trang Vu},
journal = {PLOS One},
year = {2026},
month = sep,
doi = {10.1371/journal.pone.0358261},
url = {https://doi.org/10.1371/journal.pone.0358261},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Mandibular incisor alveolar housing and incisor-alveolar axis relationship in untreated skeletal Class III malocclusion: A cross-sectional CBCT study
AU - Thanh Huyen Nguyen
AU - Huong Ly Nguyen
AU - Thi Dung Dao
AU - Thi Thu Trang Vu
PY - 2026
DA - 2026/09/15
JO - PLOS One
DO - 10.1371/journal.pone.0358261
UR - https://doi.org/10.1371/journal.pone.0358261
AB - Patients with skeletal Class III malocclusion may have limited alveolar support around the mandibular incisors, but conventional cephalometric measures do not directly describe the root-alveolus relationship. This retrospective cross-sectional study quantified labial and lingual alveolar bone thickness and examined whether signed IA-PAMD indicated apical root position within the symphysis. Pretreatment cone-beam computed tomography and lateral cephalometric records from 80 untreated patients (320 incisors) with signed ANB < 0° were analyzed. Bone thickness was measured at three root levels. Correlations and cluster-robust multivariable models adjusted for tooth, age, sex, signed ANB, GoGn-SN, and incisor mandibular plane angle. Mean labial thickness was 0.36, 0.49, and 2.40 mm at the cervical, middle, and apical levels; corresponding lingual values were 0.59, 1.39, and 4.01 mm. Labial bone was thinner than lingual bone (all P < 0.001), and labial thickness was below 0.5 mm in 80.3% of cervical and 63.4% of middle-root observations. Signed IA-PAMD correlated positively with labial apical thickness, negatively with lingual apical thickness, and not with total apical width. In adjusted models, each 1° increase in signed IA-PAMD was associated with 0.084 mm greater labial apical thickness (95% CI, 0.053–0.115), 0.092 mm lower lingual apical thickness (95% CI, −0.141 to −0.043), and no difference in total apical width (−0.008 mm; 95% CI, −0.082 to 0.065). The mirror-image labial and lingual coefficients, together with the near-zero total-width coefficient, support interpretation of signed IA-PAMD as a measure of root-apex eccentricity within the symphysis rather than aggregate apical bone support. It should not be interpreted as a treatment target or safety threshold, and the absence of a Class I comparator limits conclusions specific to skeletal Class III morphology.
SN - 1932-6203
ER -