A cone-beam computed tomography evaluation of posterior available space in both arches relative to various skeletal patterns

• Published in: American journal of orthodontics and dentofacial orthopedics Vol. 161; no. 6; pp. 798 - 808
• Main Authors: Kim, Ki-Jun, Park, Jae Hyun, Chang, Na-Young, Seo, Hye Young, Chae, Jong-Moon
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-06-2022
• ISSN: 0889-5406; 1097-6752
• DOI: 10.1016/j.ajodo.2021.01.031

This study aimed to evaluate the posterior available space (PAS) in both dental arches of adult patients with varying skeletal patterns using cone-beam computed tomography.
A sample of 114 adult patients (56 males and 58 females) was divided into 3 groups according to ANB angle and facial height ratio. Using C-mode cone-beam computed tomography images from these patients, maxillary PAS (MxPAS) and mandibular PAS (MnPAS) were measured in the distobuccal and palatal roots of the maxillary second molars and the distal roots of the mandibular second molars, respectively. The planes perpendicular to the tooth axes of the second molars in the coronal views and parallel to the posterior occlusal planes in the sagittal views were set at 3 heights of furcation, middle, and apex of the roots. For each plane, the shortest posterior distances from the roots to the inner and outer cortices were measured parallel to the furcation line connecting the furcations of the molars in the axial views. Posterior cortical bone thickness, defined as the distance from the inner cortex to the outer cortex, was measured.
PAS was significantly greater in males than in females and in the maxilla than in the mandible (P <0.01). All MxPAS gradually increased from the furcation to the apex with significance (P <0.05), but there was no difference in MnPAS. MxPAS was significantly greater (P <0.05) in subjects with Class II and III malocclusion than subjects with Class I malocclusion, whereas MnPAS showed no difference. MxPAS showed no significant differences in facial height ratio, whereas MnPAS was significantly greater (P <0.05) at furcation in normovergent subjects than in others. Posterior cortical bone thickness was greater (P <0.001) in the mandible than in the maxilla.
PAS was different according to sex and skeletal patterns. It would be helpful to evaluate PAS when distalizing the molars in either arch.
•This study was done to evaluate the posterior available space (PAS) using CBCT.•PAS was significantly greater in males than females and in the maxilla than the mandible.•MxPAS gradually increased from furcation to apex but showed no differences in the MnPAS.•MnPAS was greater in normovergent subjects than in hyper- and hypodivergent subjects.•These findings would be helpful to evaluate PAS when distalizing the molars in either arch.