Class III Decompensation Moved Point A Back and Thinned Palatal Bone

Edited by Orthotown staff

Premolar-extraction presurgical decompensation in skeletal Class III patients moved the maxillary incisors, alveolar bone, and point A posteriorly, and was frequently accompanied by palatal alveolar bone thinning. The finding comes from a cone-beam computed tomography study published online Oct. 3 in the American Journal of Orthodontics and Dentofacial Orthopedics.

Investigators analyzed CBCT data from 40 patients before and after decompensation. They used 3D cephalometric analysis along with surface-based registration and voxel-based analysis.

Angular measurements all decreased (P < .001):

• SNA by 1.22°

• FH-NA by 0.99°

• U1-SN by 9.43°

• U1-NA by 7.06°

Every landmark moved posteriorly:

• point A by 1.07 mm

• superior prosthion by 3.87 mm

• the incisal midpoint of the maxillary central incisor by 5.28 mm

• the root apex by 2.26 mm

Bodily movement accounted for an average of 41% of anterior retraction, and tipping for 59%.

The maxillary anterior teeth showed partial root resorption, averaging 1.11 to 1.97 mm. Palatal alveolar bone thinned significantly in the cervical and middle thirds, while labial bone volume increased apically. Point A retraction showed weak correlations with SNA, incisor inclination, and the proportion of bodily versus tipping movement, but Bonferroni correction substantially reduced the significance of those correlations.

The authors concluded that remodeling from tooth position and point A changes should be built into initial treatment planning to individualize the mode and amount of maxillary incisor retraction. They said this is critical for Class III patients who are ineligible for bimaxillary surgery or who need only mandibular surgery.

The study was conducted at Fujian Medical University and its First Affiliated Hospital in Fuzhou, China.

Measurements spanned the start to the end of presurgical decompensation, so the study does not address remodeling after surgery or during retention.

Sources:
American Journal of Orthodontics and Dentofacial Orthopedics, “Three-dimensional analysis of maxillary alveolar bone and point A remodeling after premolar-extraction decompensation in patients with skeletal Class III malocclusion,” published online Oct. 3, 2026: doi.org/10.1016/j.ajodo.2026.07.016
PubMed, PMID 42828532: pubmed.ncbi.nlm.nih.gov/42828532