Alveolar Bone Thickness May Impact Orthodontic Treatment Time

Objectives: Three-dimensional imaging technology has allowed correlations between bone thickness and rate of tooth movement to be explored. No in-depth assessment of these correlations has been reported. The aim of this study was to assess the relationship between bone thickness across and size of the premolar extraction site and time to end of orthodontic treatment (TTEOOT).
Methods: Twenty-three patients received orthodontic treatment, underwent premolar extractions, and received three-dimensional Cone-Beam Computer Tomography (CBCT) scans prior to treatment. Utilizing CBCT images, cortical bone widths (CBW), maxillary/mandibular bone widths, and mesio-distal widths of the to-be-extracted teeth were measured at levels 5mm and 8mm apical to the alveolar crest (AC) and at the apex of the premolars. Comparisons were made between right and left halves of the arches and between varying distances from the AC along the axis of the tooth. Relationships between bone thickness, size of extraction site, and TTEOOT were assessed.
Results: This study comprised of 18 females and 5 males with a mean age of 19.46 years. Survival analysis showed individuals with <10mm maxillary alveolar bone width 5mm apical to the AC had a shorter TTEOOT.^{(HR=3.62,p-value=0.018)} Survival analysis revealed individuals with a <3mm mesio-distal width of the to-be-extracted tooth at a level 5mm apical to the AC had a shorter TTEOOT.^{(HR=3.6,p-value=0.047)} There was no statistically significant association between CBW and TTEOOT.^{(p-value>0.05)} T-tests presented no statistically significant difference (SSD) between bone widths in the right versus left halves of the maxilla/mandible.^{(p-value>0.05)} ANOVAs revealed no SSD between CBWs at levels 5mm and 8mm apical to the AC, and at the apex of the premolars.^{(p-value>0.05)}
Conclusions: Patients with thicker alveolar bone and larger extraction sites may experience slower rates of tooth movement. CBW is relatively homogenous 5mm apical to the AC through the apex of the premolars as well as between right and left halves of the maxilla/mandible.