OBJECTIVES: To examine tooth root length and root volume in cone beam computed tomography (CBCT) images in patients with skeletal Class II and III anomalies who have undergone single-jaw (SJ) and double-jaw (DJ) orthognathic surgery, and to compare the changes between jaws with and without osteotomy. MATERIALS AND METHODS: This study was conducted on the archive records of a total of 60 adults: 36 women and 24 men with an average age of 21.1 ± 3.1 years, whose CBCT images were recorded just before orthognathic surgery and within 6-12 months after surgery. The sample was divided into four groups with 15 individuals in each: Class II SJ (mandibular advancement only), Class II DJ (maxillary advancement and impaction with mandibular advancement), Class III SJ (maxillary advancement and impaction), and Class III DJ (maxillary advancement and impaction with mandibular setback). RESULTS: Within groups, statistically significant decreases in root length and root volume were found in the period between preorthognatic and postorthognathic surgery (P <
.05). No statistically significant differences were found in comparisons between groups (P >
.05). CONCLUSIONS: Regardless of the type of skeletal anomaly in the sagittal direction and the orthognathic surgery performed, a statistically significant but clinically insignificant decrease was found in tooth root length and root volume during the postorthognathic surgery period, both in jaws with and without osteotomy.