Upper incisor intrusion: an anatomical analysis via CBCT

To verify, via CBCT, the existence of a definable distance for bodily intrusion of maxillary incisors, and its correlation to age, sex and/or facial biotype.

The sample consisted of sagittal sections obtained from 79 CBCTs of 220 maxillary incisors correctly aligned on their osseous base (maxillary plane/long axis between 105° and 115°). The same sagittal sections were then used to measure the distance between the root apex and upper internal cortical bone of the jaw at each incisor, along the extension of the long axis. The patient sample was divided into three distinct subgroups based on the degree of divergence; it was also subdivided by gender and by age.

The mean distances between the apex and upper internal cortical bone were higher than 5mm for the four maxillary incisors. Statistically significant differences were evidenced between the two age groups in the means measured for the right lateral incisor, left central and lateral incisor. The mean of the distance measured for the right lateral incisor in the hyperdivergent patients was significantly greater with respect to that of the hypodivergent patients.

The CBCT data obtained permitted identification of the alveolar anatomy and quantification of the intrusion possible. In the older age group, potential intrusion was significantly greater for teeth 12, 21 and 22. Furthermore, a directly proportional relationship between the measurements pertaining to each tooth in a single patient was noted.