The purpose of the this study was to develop a practical approach for transverse analysis using cone beam computed tomography (CBCT) to assist practitioners in diagnosis and treatment planning.
Methods:
The CBCT scans of 86 patients with or without posterior crossbite were selected to obtain coronal sections at the level of first molars. Among various measurements, the widths of the jaws were measured as the distance between centroids of the left and right basal bones; and the inclination of the teeth were measured as the inner angle between occlusal plane and the long axis of the tooth. Skeletal and dental measurements were compared between the crossbite and non-crossbite groups.
Results:
Transverse analysis of non-crossbite group revealed that it can be divided into three subgroups: 1. Control group (molar inclinations within 1SD of the mean); 2. Superior convergent group (maxillary molar inclinations below 1SD of the mean and/or mandibular molar inclination above 1SD of the mean); 3. Inferior convergent group (maxillary molar inclinations above 1SD of the mean and/or mandibular molar inclination below 1SD of the mean). Significant differences were found in maxillary width (42.74±2.79mm vs. 44.82±3.30mm vs. 43.30±2.28mm, p<0.05) and mandible-maxilla differential (6.31±2.60mm vs. 2.05±3.98mm vs. 3.42±3.40mm, P<0.01) among the three groups. Compared to the control group, significant decreases in maxillary width (41.04±2.40mm vs. 43.31±2.28mm, p<0.01) and maxillary dental width (43.06±2.74 vs. 45.25±3.10mm, p<0.05) and significant increase in mandible – maxilla differential (6.53±4.78mm vs. 3.42±3.40mm, p<0.05) were found in the crossbite groups. No significant differences in these measurements were found between bilateral and unilateral crossbite groups.
Conclusions:
Significant skeletal transverse discrepancy occurred not only in patients with posterior crossbite, but also in non-crossbite patients with dental compensation. The centroid of the basal bone is a valid and reliable skeletal landmark that represents the transverse relationship, without relying on external landmarks.